L I E) HA R.Y OF THE U N I VERS ITY or ILLINOIS ?%1 Digitized by the Internet Archive in 2015 https://archive.org/details/textbookofscientOOpend TEXT-BOOK OF SCIENTIFIC AGRICULTUHE: WITH PRACTICAL DEDUCTIONS. INTENDED FOR THE USE OF COLLEGES, SCHOOLS, AND PEIVATE STUDENTS. BY E. M. PENDLETON, M. D. PROPESSOR OP AGRICULTURE AND HORTICULTURE IN TKB UNIVERSITY OF GEORGIA. NEW YORK: A. S. BARNES & COMPANY, 1875. Entered, according to Act of Congress, in the year 1874, by B. M. PENDLETON, M. D. in the Office of the Librarian of Congress at Washington. PKEFAOE. When the author entered upon his duties two years ago, as Agricultural Professor in the University of Georgia, he found no text-book, embracing what he deemed a legiti- mate Agricultural course, to recommend to his students. He had to gather from various old works, and a few new ones, as well as from his own observations and experience, such facts and inferences as seemed to him best calculated to elucidate Agricultural Science. From these lectures he has systematized a Text-Book of Scientific Agriculture, for the use of his own classes, or any teacher or private student who may choose to adopt it. He has not attempted a practical treatise on Agricul- ture; giving the processes of planting, cultivating, and saving different crops ; but has endeavored to teach the great truths of Agricultural Science, the foundation of all that is valuable in the art. For while much has been ac- complished empirically, it has been done imperfectly, and at a heavy cost. Thus while the agricultural art has brought millions from the soils of the South, it has been at the sacrifice of the principal, rather than the interest, of the landed estates. Science will ultimately restore these soils, but it will take millions more to do it, which must be charged to the blunders of empiricism. The science of Yeo-etable ISTutrition, the most intricate B3896 11 PREFACE. as well as the moi presented in the clearest possible light, with the latest discoYcries and the best established theories. A number of recent experiments conducted by the author will add much interest, he trusts, to this department, and throw no little light on Southern agriculture especially. He has avoided as far as possible mere theories; and proceeded entirely on the inductive system ; leaving in doubt what has not been demonstrated, for future experi- ments to determine, and placing in bold relief the great truths of Agricultural Science as established upon un- doubted authority. Although prepared especially for Southern students, the work is what it professes to be, a Compend of General Agricultural Science^ and adapted to every section of the country, making always such necessary distinctions as may result from different climates, soils, and products. The first part of the book is devoted to the Physics of Agriculture, being adapted to students not so far advanced; while the latter part embraces the more intricate subject of Agricultural Chemistry, for the higher classes, who are versed in scientific nomenclature. The author has aimed at systematic arrangement, terseness of style, and simplicity of expression ; avoiding technicalities, except when absolutely essential to the knowledge of the student. How far he has succeeded must be left for an impartial public to decide. University of Georgia, November 9, 1874. OOI^TEIfTS. PAET I. AISTATOMY AND PHYSIOLOaY OF PLANTS. CHAPTER 1. PAGE 1. Agriculture Defined. 2. Basis of Agricultural Science. 3. Relation of Botany to Agriculture 13 CHAPTER II. 4. Vegetable Cells. 5. One-celled Plants. 6. Vegetable Tis- sues 17 CHAPTER III. 7. Organs of Plants. 8. Roots. 9. Spongioles. 10. Root Hairs, etc. 11. Offices of the Roots 20 CHAPTER IV. 12. Of the Stem. 13. Structure of the Stem. 14. Endogenous Stems. 15. Exogenous Stems. 16. Offices of the Stem . 25 CHAPTER V. 17. Of the Leaves. 18. Offices of Foliage. 19. Of the Stomata. 20. Of Buds , 30 CHAPTER VI. 21. The Flower. 22. Fructification. 23. Of the Fruit. 24. Of the Seed T. 33 iv CONTENTS. CHAPTER VII. PAGE 25. Germination of Seed. 2G. Plant Growth. 27. Nutrition of the Plantlet. 38 CHAPTER VIII. 28. Formation and Growth of Wood. 29. Character and Dura- tion of Plants 44 CHAPTER IX. 80. Absorption of Water. 31. Exhalation of Water. 32. Cir- culation of Sap. 33. Theory of Electrical Force 46 PAET II. AGRICULTURAL METEOROLOGY. CHAPTER T. 84. Description of the Atmosphere. 35. Its Relation to the Vegetation. 36. Its Height. 37. Pressure of the Atmo- sphere. 38. The Barometer. 39. Moisture of the Atmo- sphere. 40. Evaporation. 41. Hygrometer 59 CHAPTER II. 42. Temperature. 43. The Thermometer. 44. Fogs. 45. Dew. 46. Frost. 47. Snow. 48. Hail 66 CHAPTER III. 40. Formation of Clouds. 50. Height of Clouds. 51. Original Clouds. 52. Combined Clouds. 53. Causes of Rain. 54. Amount of Rain-fall at Different Stations. 55. The Rain Gauge. 56. Sources of Rain 76 CHAPTER IV. 57. Electricity. 58. Sunlight. 59. Air in Motion. 60. Lunar Influence 86 CONTENTS. V PAET III. SOILS AS RELATED TO PHYSIOS. CHAPTER L PAGE 61. The Earth. 62. The Eocks. 63. Geology of Georgia. 64. Disintegration. 65. Mechanical Action, or Waste. . . 94 CHAPTER II. 66. Geological Division of Soils. 67. Agricultural Division of Soils. 68. Silicious Soils. 69. Clay Soils. 70. Calcare- ous Soils. 71. Vegetable Moulds 100 CHAPTER in. 72. Physical Qualities, as Distinguished from Chemical. 73. Weight of Soils. 74. Absorptive Power of Soils for Gases. 75. Power to Remove Salts from Solutions. 76. Adhesiveness of Soils. 77. Divisibility of Soils. ^ 78. Shrinking of Soils 105 CHAPTER IV. 79. Temperature of Soils. 80. Capacity of Soils for Heat. 81. Retentive Power of Soils for Heat. 82. Permeability to Water in Soils. 83. Hygroscopic Power for Water. 84. Retentive Power for Water Ill CHAPTER V. 85. Water, its Mode of Existence in Soils. 86. Of Hydrostatic Water. 87. Capillary Water. 88. Hygroscopic Water. 89. Supply of Water to Plants. 90. How Plants Absorb Water. 91. Requisite Amount of Water in Soils for Plants 120 CHAPTER VL 92. Of Drainage. 93. Underdraining. 94. Drainage at the South. 95. Of Trenching 128 vi CONTENTS. CHAPTER Vll. PAGE 96. Of Ploughs. 97. Benefits of Ploughing. 98. Subsoiling. 99. Horizontal culture 133 PAET IV. CHEMISTRY OF THE ATMOSPHERE. CHAPTER I. 100. Composition of the Atmosphere. 101. Oxygen, O. 102. Ozone — Condensed Oxygen. 103. Sources of Ozone. 104. Amount of Ozone in the Atmosphere. 105. Rela- tion of Ozone to Vegetation 141 CHAPTER II. 106. Hydrogen, H. 107. Carbon, C. 108. Carbonic Acid, CO2. 109. Qualities and Tests of Carbonic Acid. 110. Esti- mates of Carbonic Acid in the Atmosphere 146 CHAPTER III. 111. Nitrogen, N. 112. Nitric Acid, NO3H. 113. Nitric Per- oxide, NO2. 114. Generation of Nitric Acid in the Atmo- sphere. 115. Nitrates and Nitrites. 116. Nitric Acid in Rain Water 150 CHAPTER IV. 117. Ammonia, NH3. 118. Ammonia in the Atmosphere. 119. Ammonia in Rain Water. 120. Relation of Atmo- spheric Ammonia to Vegetation. 121. Steam, or Vapor of Water. 122. Other Atmospheric Ingredients. 123. Or- ganic Matters of the Atmosphere 154 CONTEOTS. vii PAET V. CHEMISTRY OF PLANTS. CHAPTER I. FAOB 124. Organic and Inorganic Constituents. 135. Relative Amount of each in Plants. 126. Organism of Plants. 127. The Four Organic Elements in Plants. 128. Oxygen in Plants. 129. Effect of Light on the Transmission of Oxygen. 130. Hydrogen in Plants. 131. Nitrogen in Plants. 132. Plants do not Absorb or Emit Nitrogen 160 CHAPTER II. 133. Carbon in Plants. 134. Decomposition of Carbonic Acid by Solar Light. 135. Fixation of Carbon in Plants. 136. Exhalation of Carbonic Acid in Diffused Light, 137. Supply of Carbonic Acid. 138. Carbonic Acid from the Soil, 139. Carbonic Acid as a Solvent. 140. Changes in Vegetable Tissues. 141. Tabular View of the Rela- tion of Atmospheric Ingredients to Plant Life 168 CHAPTER III. 142. Inorganic Elements and their Importance. 143. Alumina, AI2 O3. 144. Manganese, Mn. 145, Iodine, I. 146. Iron, Fe. 147. Silica, Si,O==60 177 CHAPTER IV. 148. Phosphorus, P=31. 149. Sulphur, S=32. 150. Potas- sium, K=39.1. 151. Sodium, Na=23. 152. Calcium, Ca=40. 153, Magnesium, Mg=24. 154. Chlorine, Cl= 35.5 184 CHAPTER V. 155. Proximate Principles of Plants. 156. Albuminoids. 157. Albumen. 158. Casein. 159. Fibrin. 160. Other Ni- trogenous Compounds. 161. Composition of Albumi- noids. 162. Albuminoids in Crops 190 viii CONTENTS. CHAPTER VI. PAGE 163. Carbo-liydrates. 164. Cellulose. 165. Ligniii. 166. Starch. 167. Inulin. 168. Dextrin. 169. The Gums 196 CHAPTER VII. 170. Cane Sugar — Saccharose. 171. Grape Sugar — Glucose. 172. Fruit Sugar— Fructose. 173. Milk Sugar— Lactose. 174. Other Saccharine Substances. 175. Alcohol a Pro- duct of Sugar. 176. Pectin. 177. Changes in Proximate Principles 201 CHAPTER VIII. 178. Vegetable Acids. 179. Malic Acid. 180. Tartaric Acid. 181. Citric Acid. 182. Oxalic Acid. 183. Tannic Acid. 184. Acetic Acid. 185. Vinegar. 186. Prussic Acid. 187. Vegetable Oils. 188. Volatile Oils. 189. Fixed Oils. 190. Saponification. 191. Phosphorized Fats. 192. Fat in Vegetable Products 209 CHAPTER IX. 193. The Alkaloids. 194. Nicotine. 195. Caffeine. 196. Theo- bromine. 197. Coloring Matters of Plants. 198. Chloro- phyl..... 217 CHAPTER X. 199. Density and Course of the Sap. 200. Ascending and De- scending Sap. 201. Chemical Composition of the Sap. . . 221 PAKT YI. CHEMISTRY OF SOILS. CHAPTER I. 202. American and European Soils Contrasted. 203. Consti- tuents of Plants Exhausted from Soils. 204. Of Seed and Plant Constituents 224 CONTENTS. CHAPTER 11. PAGE 205. Plant Constituents in Minerals. 206. Mineral Constituents per Acre, and their Period of Exhaustion. 207. Other Requisites of Fertility 228 CHAPTER III. 208. Coarse and Fine Soils— Soluble and Insoluble. 209. Of Soluble Matters in Soils. 210. Exhaustion of Soils 231 CHAPTER IV. 211. Water Chemically Considered. 212. Water, Gaseous, Liquid, Solid. 213. Chemical Absorption of Soils 235 CHAPTER V. 214. Sources of Nitrogen. 215. Organic Nitrogen in Soils. 216. Compounds of Nitrogen in Soils. 217. Ammonia in Soils. 218. Nitric Acid in Soils. 219. Nitrous Acid in Soils 239 CHAPTER VI. 220. Analysis of Soils a Dubious Test of Fertility. 221. New Method of Soil Analysis. 222. Deductions from M. Gran- deau's Experiments 246 CHAPTER VII. 223. M. Grandeau's Theory Tested. 224. Organic Matter a Means of Solubility. 225. Solubility a Test of Fertility. 250 CHAPTER VIII. 226. Humus in Soils. 227. Influence of Climate on Organic Matter in Soils. 228. Humic Acid 255 CHAPTER IX. 229. Decay. 230. Putrefaction. 231. Eremacausis. 232. Fer- mentation. 233. Organic Matter Essential to Fertility. 234. Benefits of Humus 259 X CONTENTS. PAET YII. FERTILIZERS AND NATURAL MANURES. CHAPTER L ] 235. The Subject Introduced. 236. Fertilizers, how Divided. 237. Special Fertilizers. 238. Effect of Fertilizers in Hastening Maturity. 239. Nitrogen as a Fertilizer. 240. Forms in which Nitrogen enters Plants. 241. Ammonia and Nitric Acid in Plants. 242. Amount of Nitrogen re- quired by Crops 265 CHAPTER IL 243. Nitrification. 244. Conditions Essential to Nitrification. 245. Ammonia a Principal Source of Nitric Acid. 246. Im- portance of Nitric Acid as a Fertilizer 271 CHAPTER III. 247. Formation of Ammonia in Soils. 248. Escape of Ammo- nia from Soils. 249. Loss of Ammonia Applied to Crops. 250. Ammonia not Efficient by Itself. 251. Ammonia Superior to the Nitrates. 252. Ammonia as a Solvent... 276 CHAPTER IV. 253. Phosphoric Acid, P2O5. 254. Sources of Phosphoric Acid. 255. Relation of Phosphoric Acid to Plants. 256. Origin of Mineral Phosphates. 257. Composition of Mineral and other Phosphates 283 CHAPTER V. 258. Manufacture of Superphosphates. 259. Hydrus Sulphuric Acid, SO3HO. 260. Composition of Superphosphates. 261. Bi-Phosphate of Lime, CaO^HO, PO5. 262. Home- made Superphosphates. 263. Effect of Liquid Bi-Phos- phate of Lime as a Fertilizer. 264. Precipitated Phos- CONTENTS. xi PAGE phate of Lime. 265. Reduced Phosphates. 260. Experi- ments with Reduced and Unreduced Phosphate. 267. Am- moniated Superphosphate 289 CHAPTER VI. 268. Potassa, Ko. 269. Chloride of Potassium. 270. Soda, Na20. 271. Lime, CaO. 272. Sulphate of Lime, CaO, SO32HO. 273. Magnesia, MgO. 274. Sulphuric Acid as a Fertilizer. 275. Chlorine, CI. 276. Chloride of Sodium as a Fertilizer j 303 CHAPTER VII. 277. Natural Manures. 278. Stable Manure. 279. Composi- tion of Stable Manure. 280. Saving and Composting Manures. 281. Chemical Changes in Manure Heaps. 282. Night Soil. 283. Hurdling System. 284. Cotton Seed as a Manure. 285. Experiments with Cotton Seed. 286. Wood Ashes , 312 CHAPTER VIII. 287. Green Manures. 288. Value of Mineral Substance in Or- ganic Matter. 289. Absorption and Oxidation of Nitrogen by Carbonaceous Matters. 290. Rotation of Crops. 291. Plants Differently Constituted. 292. Benefit of Resting Lands. 293. Best Rotation in Cotton Culture. 294. De- ductions from Experiments 326 PAET YIII. ANIMAL NUTRITION. CHAPTER I. 295. Experiments in Germany. 296. Proximate Composition of Animal Substances. 297. Flesh Formers and Fat Form- ers. 298. Proportion of Different Foods Digested by Animals. 299. Mixing Carbo-hydrates and Albuminoids as Food. 300. Laws which Govern Flesh Building 341 Xll CONTENTS. CHAPTER II. PAGE 801. Respiration Apparatus. 302. Digestion of Crude Fibre. 303. Experiments on the Production of Milk. 304. Ex- periments in Butter-Making. 305. Preservation and Con- densation of Milk 348 CHAPTER III. 806. Fuel and Food for the Animal System. 307. Importance of Mixing Cattle Foods. 308. Nutritiousness of Wheat Bran. 309. Cotton-Seed Meal. 310. Fodder Corn. 311. Relative Value of Cattle Foods as Provender 353 APPENDIX. 1. The Cotton Plant. 2. Indian Corn. 3. Wheat. 4. The Oat. 5. The Grasses. 6. The Tobacco Plant. 7. The Cryp- togams. 8. Water Culture. 9. Tables of Agricultural Products 359 ACKNOWLEDGMENTS. In consulting authorities, it is difficult for an author always to distinguish between what is original and what is borrowed. In science, many ideas have no paternity, and are adopted as the common property of mankind. In this work the author has endeavored to give credit to every one known to be original. He feels particularly indebted to the two able works of Prof. Johnson, How Crops Grow, and How Crops Feed, for much valuable information compiled from late European authorities on vegetable Physiology and Nutrition, as well as the Chemistry of Plants and Soils. Also to Prof. Morfit's new and valuable book, Pure Fertilizers. For the more recent contributions to agricultural science, now being demon- strated at the Experimental Stations of Germany, France, and England, the author is under special obligations to the Monthly Reports of the Department of Agriculture at Washington. Besides these, the following works have been consulted by him with profit : American Farmer's Encyclopcedia, Liebig's Agricultural Chemistry, Johnston''s Agricultural Chemistry, CaldwelVs Agricultural Chemical Analysis, Liebig''s Laws of Husbandry, StockhardVs Agricultural Chemistry, Gray'' s Field Book of Botany, Wood's Botanist and Florist, Graham's Chemisti^, Fresenius'' Chemical Analysis, BoussingaulV s Rural Economy, Liebig's Modern Agriculture, Sibson's Agricultural Chemistry, Barbee's Cotton Question, Harris's Insects Injurious to Vegetation, Al- len' s American Farm Book, Hilgard's Agriculture and Geology of Mississippi, Ken- tucky Geological Reports, Ville's High Farming without Manure, Shepard's Min- eralogy, Brockelsby's Meteorology, Tenney's Geology, White's Statistics of Georgia, American Weeds and Useful Plants, Smithsonian Reports, Southern Cultivator, {published at Athens, Georgia,) Rural Carolinian, {Charleston, South Carolina,) and American Farmer, Baltimore, PHILIP S. CHAPPELL, Esq., OF BALTIMOKE, THIS WORK IS RESPECTFULLY DEDICATED, AS A TOKEN OF ESTEEM, AND A TRIBUTE TO HIS KINDLINESS, LIBERAI.ITY, AND INTEGRITY, BY THE AUTHOR. PAET L ANATOMY AND PHYSIOLOGY OF PLANTS. CHAPTEK I. ! ■ I /LGEICULTUKE DEFIXED. — BASIS OF AGRICULTURAL SCIENCE. \'i RELATION OF BOTANY TO AGRICULTURE. 1. Agriculture Defined, Agriculture is the art or science of cultivating the -^^oil ; the term being derived from the Latin ciger^ a field, I and cultura^ cultivation. Ifi its widest scope it embraces [jtiot only the cultivation of the soil and the chemistry and physiology of farm plants, but the natural history of all iomestic animals ; the best mode of utilizing their labor md food, as well as their flesh, milk, tallow, hides, etc. ; md the climatic, atmospheric, and telluric influences afiect- mg plant life. An agriculturist is one learned in the principles of agricultural science. A farmer, husbandman, or culti- vator 23ursues the art simply as an occupation. The same distinction exists between the machinist and the factory )perative. The one understands the science of mechanics, ^md can repair and reconstruct the machinery ; the other iSGS the tools and applies the art. So does the farmer ; .rvhile the agriculturist is supposed to understand all the orocesses of fertilizing and restoring worn soils, and utiliz- |ng the labor and culture of a farm. 14 ANATOMY AND PHYSIOLOGY OF PLANTS. Agriculture then may be taught both as a science and art. The former teaches a man why it is necessary to plough; the latter, the process of ploughing. The art teaches how to jDlant, cultivate, and husband crops ; the science, of what they are composed, and how they are de- rived from the soil and atmosphere. The effect of the art is to wear out the soil by constant cropping ; science will restore it to its pristine fertility. The agricultural art has been pursued by all enlight- ened nations since the curse was pronounced "by the sweat of thy face shalt thou eat bread." The Egyptians and the Jews were the earliest nations which fostered it. The Greeks and Romans improved much upon them, and advanced it almost abreast with the German and English methods of the last century. Up to near its close the whole process of cultivation was empirical. About that period several eminent agricultural scientists made their appearance, as Bergen, Thaer, De Saussure, and Dundon- ald. Sir Humphry Davy delivered the first course of lec- tures on agricultural chemistry at London, in 1812. Baron Liebig improved upon him, and during a long lifetime accomplished much for agricultural science. Agriculture is not a pure. science, like mathematics ; but a mixed science, like medicine, made up from a number of collateral sciences. Among these, the most prominent are Botany, Physiology, Chemistry, Physics, Meteorology, Mineralogy, and Geology. All of these, and some others, such as Zoology, Entomology, Rural Architecture, and Me- chanics, are involved to some extent in making up what is termed Agricultural Science. In fact, so many of the physical sciences are interblended with agriculture, and collateral to it, that it may be con- sidered in its most extended bearing as a comprehensive system of Natural Science. BASIS OF AGEICULTURAL SCIENCE. 15 2. Basis of Agricultural Science. The science of Agriculture (indeed, all 1^^'atural Science) has to do with Matter and the Forces which move matter. The distinct forces now recognized in nature, are either physical, chemical, or physiological. Ph3i^ical forces are those which change matter as to its situation without affecting its qualities. Chemical force changes the nature and qualities of matter by composition or decomposition. Physiological or organic force develops the life, growth, I and sustenance of living organisms. The Physical forces may be divided into the loichictive : ■Light, Heat, Electricity, and Magnetism. The Cosmical: ■ Gravitation. The Molecular: Crystallization, Cohesion, Adhesion, Solution, and Osmose. Although several of these are the result of chemical j action, yet there is but one well-defined chemical force, I viz.: Affinity. There is also but one jDhysiological force, Vitality. All matter then is either organic or inorganic. Oiganized bodies differ from inorganic in possessing the vital force, through which they grow by the absorption of food, and by which they reproduce themselves. , Plants, like animals, are organized bodies, and have ^ their anatomical and physiological relations. 3. Relation of Botany to Agriculture, The science of Botany comprehends all that relates to 'she vegetable kingdom ; and whatever of it that has a ilirect or indirect bearing on Agriculture, maybe jDroperly :ermed Agricultural Botany. This embraces the Struc- ture of Plants, Vegetable Physiology, and so much of systematic Botany as describes all plants which are culti- • ated and deemed useful to man. 16 ANATOMY AND PHYSIOLOGY OF PLANTS. In what is termed the Natural System, all plants are divided into two Series : 1st. Phenogams^ flowering plants, producing seeds. 2d. Cryptogams^ plants without flow- ers, reproducing their species by sporeSy which are mostly single cells. In this Series is embraced mushrooms, lichens, ferns, sea-weeds, mosses, liverworts, moulds, algaa, and fungi. Series are divided into Classes, by the germ, the stem, the leaves, and the flowers : they are the Exogens^ or out- side growers^ and the Endogens^ or inside groioers. Classes are divided into Families or Orders, which contain groups agreeing in many points, but yet essentially different, as the okra, the hollyhock, and cotton. Orders embrace Genera, which have the same charac- ters in common distinguishing them from all other plants ; thus all the oaks belong to the same genus. Species bring them still nearer together, in w^hich animals or plants, though of different varieties or sub-species^ possess in com- mon the power of reproduction. 'Varieties occur in the same species from numerous causes, such as scarcity or abundance of nutriment (by which dwarfs or giants are made), difference in, climate, etc. ; but often they are beyond explanation. Some plants, as the cereals, beans, peas, etc., may be reproduced fron: their seed ; while others, as apples, grapes, etc., are betteii perpetuated as to variety from cuttings, layers, or grafts This may be owing to unavoidable contact wdth the j^ol 1 len of other varieties, but doubtless in some cases there exists inherent disability. Hybrids are sometimes produced in plants as well a^ animals ; the pollen of one species fertilizing the ovule of another. The limit of hybridization is very narrow, fecun dation taking place only in species which are very closel} allied. Mere mixing of different kinds of corn, melons etc., does not amount to hybridization. Botany requires two names for a plant, one to indicate the genuSy the other the species. Thus in Quercus albd VEGETABLE CELLS. 17 J (the white oak), the first name indicates the genus, the V . second the species. The names of some families are derived from the form or arrangement of the flower ; thus the pulse family, in- cluding clover, the bean, pea, and vetch, is called FapiliO' ,naceous, because their flowers resemble the butterfly. The mustard family, also embracing the radish, turnip, and cabbage, are called Cruciferoics, because their flowers have four petals resembling the four arms of a cross. Composite plants are so called when their flowers are arranged on an expanding stem, side by side, in great numbers; as the sunflower, artichoke, thistle, etc. The Coniferous embrace the fir, pine, larch, etc. ; their flowers being arranged in conical receptacles. Tlmldliferous plants have the flowers radiating from a centre, like the ribs of an umbrella, as the caraway, car- rot, parsnip, etc. CHAPTER II. VEGETABLE CELLS.— ONE-CELLED PLANTS.— VEGETABLE TISSUES. 4. Vegetable Cells, The microscope has revealed that all organized struc- tures, whether animal or vegetable, originate in minute vesicles or cells. The cell structure is an aggregation of ^ little globular vesicles, more or less filled with liquid or solid substances. ^ Cell formation is very rapid in some cases ; most strik- .ing in the mushroom family. Some as large as a peck measure are produced in one summer night, at the rate as estimated of several hundred millions of cells in one hour. ^ Buds, leaves, and flowers, and the tip of roots in a grow- ling state, show very distinctly, ^the process of cell forma- . tion under the microscope. 18 ANATOMY AND PHYSIOLOGY OF PLANTS. The protoplasm^ a semi-fluid mucilaginous substance, is the formative layer of the cell. From it is developed the nucleus and nucleolus. The m^cleus is a small rounded body within, and sur- rounded by the protoplasm which lines the cell. The nucleolus is a minute globe within the nucleus. The cell wall consists of a substance called cellulose^ which is composed chiefly of carbon. In some cases there are no cell walls, but the cells consist of the protoplasm and nucleus. The protoplasm and matters dissolved in the juices of the plant are transformed, and result in the production of solid substances. The processes of plant development may be observed under the microscope, such as the formation and growth of starch grains and the matters which give color to leaves and flowers. At first there are no solid matters except the nucleus and protoplasm. Then appear green grains of chlorophyl, completely hiding the nucleus. Then these grains lose their green color and assume the character of starch. As the seed hardens, the microscope reveals the change of the starch grains into cellulose. The nucleus disappears, and more starch grains appear ; which in their turn become converted into smaller grains of aleurone, which completely occupy the cells at the maturity of the seed. Similar transpositions take place reversely in the sprouting of the seed. The nucleus again appears, the aleurone is dissolved, and even the cellulose is converted into soluble food for the seedling. These facts were ob- served from experiments with the common nasturtium (Tropoeolum majus) by Hartig. Vegetable cells are quite variable in dimensions. A marine plant (Caulerpa prolifera) has a single cell some- times a foot in length. In most cases, however,- they are less than of an inch in diameter ; many of them much OXE-CELLED PLAXTS. 19 smaller. The pulp of an orange is a fine example of cell tissue on a large scale, it8 cells being about one-fourth of an inch in length. Every fibre of cotton is a distinct cell. Wood cells are mostly elongated, tapering at both ends. In the bark of many trees, and stems and leaves of grasses, they are rec- tangular. Although cells show no apertures under the strongest microscope, they are known to be permeable to liquids. A thin slice of potato immersed in water, if touched with a drop of iodine solution, will exhibit a rapid transfusion of the iodine through all the unbroken cells. 5. One-celled Flcints, Some plants of the lower orders are known to exist with a single cell, while others are constituted of cells through every stage of their existence. What is known as red siioic of the Arctic regions, is common snow colored with a one-celled microscopic plant. The flocculent mould which gathers in the solutions of certain salts, as those of sulphate of soda and magnesia, are seen to be under the microscope, vegetation of one cell, rapidly formed. And this is true of brewer's yeast, some of which has only a few, and some but one. Mushrooms, sea-w^eeds, the mould of damp walls, old cheese, etc., constitute similar developments of vegetable life. While some of the fungi and parasites wdiich prey upon plants are also produced in the same way. In one-celled plants the new cell buds out from the parent cell and becomes detached from it. In higher plants no separation takes place, save the adhering tissue formed between the cells. 6. Vegetable Tissues, In the higher order of plants, where the cells cannot be well separated, they form a coherent mass, attached 20 AXATOMY AND PHYSIOLOGY OF PLANTS. more or less firmly, known as vegetahle tissue, A large number have been named by vegetable anatomists, based upon their different forms or functions ; the principal of which are Cellular Tissue, Vascular Tissue, Woody Tissue, and Bast Tissue. Cellular Tissue is the base of all vegetable structure, and is constituted of globular or polyhedral cells. This is the only form of tissue in the simpler kinds of plants. Cell tissue and parenchyma are synonymous terms. Wood tissue consists of long, spindle-shaped cells, taper- ing at each end. They overlap each other^ constituting the tough fibres of wood. They are often thickened by cel- lulose, lignin, and coloring matters. Vcfscular Tissue is formed from a simple transposition of cellular tissue, and embraces the tubes and ducts of the higher kinds of plants. These ducts are dotted^ ringed, angular, and spiral. Bast Tissue is so named because it is found only in the hast or inner bark. It resembles w^ood tissue, but is more flexible and delicate. Linen, hemp, and all flexible mate- rial except cotton, is constituted of this tissue. Bast cells are to the rind what wood cells are to the wood. All elongated cells like the two last are called prosenchyma. CHAPTEE III. ORGANS or PLANTS. ROOTS. SPONGIOLES. — ROOT HAIRS. OFFICES OF THE ROOTS. 'Z. Organs of Plants, The Compound Organs of Plants are divided into Vegetative and Reproductive. To the vegetative belong the Roots, the Stems, and the Leaves. To the reproduc- tive, the Flower, and the Fruit, which embraces the Seed. ROOTS. 21 8. Boots. The Root is properly the desceiiding axis of the plant, as the Stern is its ascending axis. The roots grow downward into the soil and seek a moist medium. They can develop fully in light, though it is unfavorable to them. They increase mostly by elongation. About \ of an inch from the tip is in the formative grow- ing state. When this is cut off, the root does not extend, but branches off. Dicotyledonous plants^ or Exogens^ have tap roots descending vertically into the ground. Sometimes these roots are very long, having two lateral branches ; others short, being smaller than their side roots. The pine and fir tree, cotton j^lant, radish, carrot, etc., are examples of the tap root. Trees of this species draw their nourish- ment from many feet below the surface. Tap roots throw out lateral roots from their base to their extremities, which again subdivide into branches. The lateral roots near the surface, Avhicli permeate the tilth (as of the cotton plant) are much larger, and liave many more rootlets than lower down. Monocotyledonoiis plants^ or Endogens^ have what are termed crown roots, which branch directly from the base of the stem. The cereals, grasses, and Indian corn, are examples. Tlie Fibrils^ also called Feeders, are small thread-like rootlets which branch out in many directions from the older I'oots. They are the last formed, are only a few * inches in length, and permeate in some cases (as in cotton S and corn) the whole surface of the ground in quest of food. E They generally extend as far from the plant as the height 1 of the stem. ' 9. Spongioles. ^ The tips of the rootlets are called spongioles^ or sponge- lets. They do not suck up the food from the soil, as their 22 AXATOMY AXD PHYSIOLOGY OF PLANTS. name indicates, but merely protect the true end of the root, being formed of detached cells like an elastic cushion. They soon perish when this office is fulfilled. They are filled with air instead of sap. This air cap is much larger in diameter than the true root is, w^hich shrinks as it matures. 10. Hoot Hairs^ etc. Some plants, the mustard for instance, have root hairs on their roots, scarcely visible, which absorb their food. These hairs are more numerous in poor than in rich soils. Other plants, as the onion, which have no root hairs, absorb food by the delicate texture and greater number of rootlets. The contact of root hairs and rootlets wdth the soil is very intimate, and often inseparable. Roots may further be divided according to the medium in which they grow; as soil roots, w^ater roots, and air roots. Soil roots, which are common to all agricultural plants, perish in air and rot in water. The roots of aquatic plants flourish in water, and die when removed from it, or from earth saturated with it. Air roots are common only to tropical plants. Indian corn is an exception, which throws out brace roots through the air from the lower joints into the soil. The banyan of India sends down roots from its branches to the earth ; and other tropical plants, as the Orchids, send out roots into the air which never penetrate the water or the soil. The Zamia spiralis throws out lateral air roots from the crown of its tap root, which sends branches down into the earth and others up into the air. Some plants, as rice, may be termed amphibious, hav- ing roots which luxuriate either in water or soil. So of j willow and alder trees ; parts of their roots do well in water, and part equally well in soil comparatively dry. ! Roots vary as to the relative amount of the whole | plant, according to the age and character of the plant. | Schubart found the roots of wheat, as comjDared to the I OFFICES OF THE ROOTS. 23 # entire plant, to be 40 per cent, the last of April. Peas 44 per cent, four weeks after sowing — Avhen in bloom, 24 per cent. The length of roots also varies according to the char- acter and fertility of soil. Hellriegel estimated the length of the roots of a vigorous barley stalk in a porous garden soil at 128 feet, an oat plant 158 feet. In a coarse com- pact gravel soil, the barley plant had but 80 feet of roots. The internal structure of the roots corresponds with that of the stem, and will be described under that head. 11. Offices of the Boots, Roots have three offices : 1st, to fix the plant or tree in the earth and maintain its upright position ; 2d, to absorb nutriment from tlie soil ; 3d, to hold it for future use. The brace roots of maize seem to have but little else to do than to hold up the plant; while the tap roots of the tur- nip, carrot, and beet act as store-houses for sugar, pectose, etc., with Avhich to supply the stem, flower, and seeds the second year; hence their value in fattening stock. The older and larger roots act as vehicles for the fibrils to convey the food taken up by them to the stems and leaves. Roots are variously constructed, so as to absorb food from the soil. All of the young and delicate parts of the roots are engaged in this work except the extreme ends. Old roots, es23ecially of perennial plants, become hard and lose this quality. The amount of absorbing surface de- pends largely upon the rapidity of extension and length of the rootlets. This is due to several contingencies, as the* moisture and fertility of the soil. In a poor soil, the absorbing surface would be much less than in a fertile soil. And so of a dry, compared to a moist soil. Nobbe proved by experiments in glass cylinders with a poor clay soil manured near the surface, that the roots would form there in thick masses, while very few extended 24 ANATOMY AND PHYSIOLOGY OF PLANTS. ! into the poor soil beneath. The manure being placed in the bottom of the cylinder, the whole thing was reversed. Long slender roots put out through the i^oor soil, till they reached the manure, and then formed a perfect network of fibrils in quest of food, which greatly invigorated the plant. The first root branches are sent out bv the visror of the plant itself, without reference to the soil they penetrate, j Afterward, they increase and extend according to the fer- tility of the soil. When there is no nourishment they soon perish. The office of the air roots is in doubt. Duchartre denies tlieir power to absorb moisture, w^hich is sustained in the fact that they only grow in humid air where the plants have plenty of water. De Candolle contended that plants have excretory roots to throw off substances injurious to them. Dr. Gyde trans- planted to water healthy plants, w^hich imparted sub- stances to it similar to their sap, and hence inferred excre- j tive powers. This may have resulted from disorganized I root hairs, produced by the change of the medium. It is not probable that healthy plants excrete at all. Henrici made experiments with a young raspberry, to prove that plants sent out roots after water. It was put in a glass funnel filled with soil, on a jar containing water. In several w^eeks, four strong roots penetrated the paper stopper of the funnel, and pushed down into the water, Avhere they threw oat many lateral roots, apparently to supply water to the plant. Some plants, as the bean, squash, and maize, after being itairly sprouted, will develop without soil if the roots are kept in water and supplied with soluble food. Such plants will soon perish transplanted to a common arable soil. And the roots of soil plants placed in water will also die, new roots putting forth adapted to water. A sudden change will produce the death of the plant. (Dr. Sachs.) Nobbe could discover no structural difference between the OF THE STEM. 25 roots of buckwheat which grew in water and those which grew in soil. Sachs found that roots die from a change of medium from mechanical injury to the fibrils. When the roots are preserved intact the plants do not die. CHAPTEE IV. OF THE STEM. — ITS STEUCTURE. ENDOGENOUS STEMS. EXOGENOUS STEMS. OFFICES OF THE STEM. 12. Of the Stem, The Stem makes its appearance soon after the seed germinates and the rootlets appear. It has an upward direction at first, which some retain, while others are horizontal. Some are recumbent, as if too weak to stand, like the sanfoin ; others procumbent, or trailmg, as the Bermuda grass ; others creeping or climbing, as the pea, cucumber, ivy, grape; others twine, coiling themselves around pillars, trees, etc., as the morning glory, poison oak (Rhus toxicodendron), hop vine, etc. Runners^ as in the strawberry, and layers^ as in the currant, are horizontal stems, which branch out and take root and serve for propagation. The tillering of wheat and other small grain is similar to layering ; the branch- ing stems in some cases producing 50 or 60 grain-bearing culms from one seed. The cereals and grasses have unbranched stems called culms. Their leaves clasp the stems at the base of each joint, which is a thickened knot called the node. The internode is the stem between the nodes. Other agricul- tural plants have branching stems, as well as all trees of temperate zones. They have also side stems, which are again subdivided into branchlets. 2 26 ANATOMY AND PHYSIOLOGY OF PLANTS. kStems also exist under ground. The peanut is a striking instance. As soon as the bloom falls, the liower-stems lengthen, penetrate the earth, ripening their fruit in the soil. Hoot stocks are stems which creep under the soil, put- ting out fresh roots at each node. The bloodroot (San- guinaria Canadensis) and quack grass are examples. The raspberry, rose, and cherry have suckers springing out from the centre root similar to the root stock. Tubers of the Irish potato and artichoke are enlarge- j ments of underground stems. They serve vv^ell for propa- j gation, each eye forming the germ of a new plant. J^ulbs j are also examples of thickened stems, as the onion, the dahlia, etc. 13. Structure of the Stem, The structure of the stem is complicated. The rudi- • mentary stem found in the seed consists of cellular tissue, an aggregation of cells, which multiply rapidly during the active growth of the plant. In the lower plants, as mushrooms, lichens, etc., the stems are purely cellular. In flowering plants this gives way to vascular tissue, con- sisting of ducts and tubes which are in close connection, arranged in bundles, and are in fact the fibres of the stem. They give strength and solidity to the stem. Herbaceous stems have but little wood in them, and are of soft texture, dying down annually, while those of shrubs and trees (arborescent) are woody, and seem to differ mainly in the size and height. 14. Endogenous Stems, Endogenous stems have no distinct outer bark that may be stripped off, and no central pith of cell tissue free from vascular chords. They are covered with a skin or epidermis composed of layers of flattened cells. The fibres grow toward the centre, tlie outer fibres being older and Larder ; liciice the name, Avhich signifies inside groiccr. In EXOGENOUS STEMS. 27 some trees of this tribe, as the palm, the outer portion becomes so hard as to admit of no further expansion, and it elongates simply, or dies from the choking up of the central fibres. In herbs, however, the soft stem admits of indefinite growth. The rushes have a central pith composed entirely of cell tissue, while the reeds and grasses are hollow. In the maize, the bast and wood cells are the same in appear- ance. In most plants they difier ; the bast cells occupy- ing the exterior and the wood cells the interior of the plant. Between the cells is a delicate tissue called the cam- hiiim. It is constituted of a number of newly formed cylindrical cells of delicate tissue. It exists only during the growth of the vascular bundles which it forms. It then grows away from it to form another. In a corn stalk the cellular tissue is the first to rot, leaving the vascular bundles unimpaired. They form a plexus or network at each node, and may be torn oul like strings. In cutting across one of these stalks the ducts may be seen permeating the whole surface. 15. Exogenous Stems, Exogenous plants are outside groicers^ their stems en- larging in diameter from the exterior. Their seeds have two cotyledons. Most forest trees belong to this class. Of agricultural plants, we have the potato, beet, turnip, bean, ]Dea, clover, flax, etc. The ducts and fibrils of cell tissue form just within the epidermis. They are not scattered as in the endogens, but form a circle. The structure of the root being similar to the stem, a beet root cut across afi*ords a fine example of the concentric layers of vascular tissue. The pith is the centre of the stem. In young and growing stems, it is full of juices ; in old ones it becomes 28 ANATOMY AND PHYSIOLOGY OF PLANTS. dead and sapless. The pith cells are filled with starch in potato tubers. The Rind is occupied with cells of unusual length, termed bast cells. These, with their ducts, form the bast fibres which grow on the interior of the rind next to the wood. The rind, by age and development of these fibres, becomes harh in trees ; which gets its peculiar toughness from the bast cells. All textile materials, as flax, hemp, etc., except cotton, are bast fibres. The external bark, as in fo- rest trees, becomes dead and sapless from age and falls away. Cork is a peculiar formation of the epidermal cells on the cork oak, potato tuber, and other plants. Pith rays are cells which interpose between the fibres and connect the pith with the rind. In the oak and maple they are known as silver grains. They are also termed medullary rays. The camhimn of the exogens exists between the bark and wood, from which wood and bast fibres develop. In spring-time the new cells of the cambium are very delicate and easily broken, hence the bark may be stripped from the w^ood without difficulty. The sieve cells^ which originate from the cambium, and constitute an independent set of ducts, act in transmitting the nutritive juices of the growing plant. These cells are extremely delicate, their transverse walls perforated like a sieve, so as to communicate with each other. It is be- lieved that the nutriment organized in the leaves passes downward through these ducts, to supply the stems and even roots with food. 3Iilk ducts also exist in the sweet potato, dandelion, milkweed, etc., through which flow milky juices to nourish these plants. The water w^hich comes from the cambial ducts sup- plies the interior of the leaf, and the surplus passes out of the thickened walls of the epidermal cells. Their cavities, however, are chiefly filled with air. A smaller portion of OFFICES OF THE STEM. 29 vajDor passes directly through the stomata, which seem to regulate exhalation to a large extent, by closing up when rapid evaporation takes place in dry weather. Thus they prevent too rapid a loss of water to the plant, and thereby save it from perishing till perchance the rain comes. While there are new cells only in the cambium, the alburnum or sap Avood adjoining carries on the living processes with much activity, constituting a vehicle for the flow of the nourishing juices of the plant. The heart wood does, not fulfil any office of this kind, but receives depositions of sap through these channels, thereby becoming more compact, dense, and durable, and better fitted for industrial purposes. A striking example between the alburnum and heart wood is seen in the pine. The sap rotting away and leav- ing the heart or light wood standing for many years. This durability is owing to the cells being filled with resin so as to make the wood impermeable to water. The herbaceous stems of exogenous annual plants, usual- ly have but one ring of woody tissue, with a central pith and external bark. The woody stems of perennial exogens of temperate zones have a series of rings, equal to the number of years of their growth. This is owing to the finer woody cells formed in autumn, at the cessation of growth, being more compact than the larger and more vigorous cells of spring- time, by which a distinct mark is made, easily perceptible to the eye in the oak and other trees. The cone-bearing trees, as pines and firs, have no ducts, but visible pores to answer the purpose of sap and air chan- nels, through which different cells communicate laterally, their contents passing directly from one to another. 16. Offices of the Stem. The stem bears the leaves, flowers, and seeds of the so ANATOMY AND PHYSIOLOGY OF PLANTS. plant. Some plants, as the cacti, have no leaves, the stems jDerforming their office. The stem conveys nourishment to the leaves and flow- ers, and supports them mechanically, and acts as a vehicle for the ascending sap from the soil, and the descending, gathered in part from the atmosphere to sustain the plant. The stem forms the principal part of forest trees by weight, subserving important purposes for fencing, fire- wood, lumber, etc. OHAPTEE Y. OF THE LEAVES. THEIR OFFICES. STOMATA. BUDS. 1 7. Of the Leaves. The Leaves of plants issue from the stems and limbs, and spread out a broad thin membrane (the Blade), so as to present an extensive surface to sunshine and air. This membrane is connected with a network of ducts and fibres. It seems to be an expansion of the cambium of the stem. The veins or ribs are a continuation of the vascular bun- dles of the stem. Leaves are covered on both sides with an epidermis, ; which has thick-walled cells, generally devoid of liquid. I In some cases, as in the nettle, it has hairs or glands filled with an acid liquid. | The stems and leaves of the grasses difier but little in t structure, though easily distinguishable from each other, t In trees, however, the difierence is very striking. The leaves of plants are essential to the vitality of roots i except during winter, in the case of deciduous trees. 1 Some few plants, as the prickly pear (cactus), have no leaves. While the structure of leaves is very diverse, their in- ternal arrangement is quite simple. The active cells con- THE STOMATA. 31 tain all the principles of plants — also the chlorophyl or leaf green. Other cells and interspaces contain air simpl}-. Leaves of sandy soils in warm climates have several layers of cell walls, which are also quite thick. Nearly all vigorous leaves have some shade of green. This is true of young stems, also showing their close relation to each other. When leaves of deciduous trees mature in autumn, they gradually lose their green color and drop off. A few plants, mostly cultivated by florists for this peculiarity, have leaves of white, brown, and red tints. Their cells, however, contain chlorophyl, though its peculiar green tint is masked by other colors. 18. Offices of Foliage, The main office of the leaves is to put the plant in com- munication with air and sunshine. They regulate the escape of water, which enters by the roots, charged with organic and inorganic food for the plant, and absorb from the air, gases which supply a considerable part of the nourishment of the plant. They are quite as essential to the building up the vegetable organism as the roots. 19. Of the Stomata, All plants have pores or mouths called Stomata^ by which they inhale carbonic acid gas and exhale water and oxygen. Hence they are called hreathing pores. They exist mostly on the under surface of ordinary leaves. Each stoma has two curved cells, with an opening be- tween them. This orifice undergoes frequent changes. In damp weather they curve outward and the orifice enlarges. In dry air they straighten up and it is nearly closed. In strong light they are also enlarged, which is one reason why sunlight is so beneficial to plants. ^ In aquatic plants, the stomata are wanting in all leaves ^ except those which float ; the surface exposed to the air only having them. They arc very sparse on the upper 32 ANATOMY AXD PHYSIOLOGY OF PLANTS. leaves of land plants, but numerous on the lower surface. In plants occupying damp and shady situations, they are more numerous and occur on both sides. The stomata are very variable in number, some leaves having not more than eight hundred to the square inch of surface, while others have one hundred and seventy thou- sand. There are twenty-four thousand mouths on the under surface of every square inch of the apple leaf; on the plum and cherry about ninety thousand, on the vine leaf thirteen thousand six hundred, on the yucca (Adam's needle) forty thousand, and on the misletoe only four hundred. (Darby.) The leaves of all plants during their healthy existence are constantly absorbing or exhaling gaseous substances through their stomata. These connect with spaces between the cells, which are generally filled with air, and the ducts continue from them, ramifying throughout the veins, ter- minating in the vascular bundles of the stem. There are cracks or pores in the bark or woody stems, through which the air communicates with the longitudinal ducts. These facts were demonstrated by Sachs with a simple apparatus, by which the pressure of a column of mercury forced the water through the stomata of the leaf, the inter- cellular spaces, veins, and ducts, into the ducts of the leaf stem, where it escaped in minute bubbles. A simple demonstration of the air passage may be made by taking a section of a corn stalk: immerse one end in water and blow through the other, and small bubbles of escaping air will be seen on its surface. 20. Of Buds, Buds are undeveloped leaves and stems. Leafhuds have embyro leaves folded into each other, all united at the base, which is the tip of the stem. The flovm^ hud is similar in structure, only the embryo fruit may be seen in many buds on cutting them open. THE FLOWER. 33 Trees have latent hicds^ which form and lie dormant till the succeeding summer, unless the active buds have been destroyed by frost or pruned by the gardener. Adven- titious buds also spring out from the bark where there are no latent buds, when trees are cut down, as is seen in the maple and chestnut. Flower buds prepare for the reproductive organs. They resemble the leaf buds at first, but later, are larger in size and dilFer in shape and color. CHAPTEK YL OF THE KEPRODUCTIVE ORGANS. — FLOWERS. FRUIT, SEED. 21. TheFloxoer. BoTAis^iCALLY Speaking, the flower has four difierent sets of organs, the Calyx, Corolla, Stamens, and Pistils. The calyx or cup is the outermost envelope of the flower. It is sometimes red or white, but generally green. Its leaves are called sejmls. The corolla or crown is one leaf, or may be composed of several small leaves within the calyx, called petals. The stamens are thread-like organs which emerge from within the corolla ; they are terminated by an oblong sack, called the anther. This latter encloses the pollen, a fine brown or yellow dust, which has an important ofiice to fill. The pistil or pistils emerge from the centre of the flower ; they vary in form, having the seed vessels, or ovaries, at their base. The ovides (little eggs), which are the rudimentary seeds, occupy the ovaries. The end of the pistil has no skin or epidermis upon it, and is called the stigma. In some plants, termed 7nonoerious, the stamens and 2* 34 ANATOMY AKD PHYSIOLOGY OF PLATs^TS. pistils are in separate flowers, as the oak and birch trees, Indian corn, melon, squash, cucumber, and straAvberry. In maize, the tassels are the staminate, and the silk the pistillate flowers. Every fibre of the silk has an ovary at its base, which develops to a grain when impregnated by the pollen from the tassel. The staminate are called the male or sterile, the pistil- late the female or fertile flow^er. Dioecious plants have the male and female in separate individuals, as the willow, persimmon, hemp, and hop vine. 22. Fructification, Fructification is the grand function of reproduction in flowers. In order to this the pollen must touch the naked tip of the pistil. Here it sends out a slender tube, seen under the microscope down in the interior of the pis- til, till it reaches the seed sack and touches the ovule, which becomes fertilized, and begins to grow. The corolla and stamens now gradually wither, and the ovules increase in size until the seeds are ripe. The pollen is carried by winds or insects to pistillate plants, and seem to be quite sufiicient in every case, as artificial fecundation has not seemed to be of any special advantage. It is believed that the wheat crop sometimes fails from the pollen being washed ofl* by heavy rains. This is pro- bably true, as much rain about the blooming of wheat seems to lighten the crop. 23. Of the Fruit. The Fruit succeeds the flower. The ovary becomes the pericarp, or seed vessel, and the ovules become the seeds. Stone fruity or Drupe, is a nut enveloped by a fleshy coat, as the peach, cherry, and hickory nut. Blackberries, raspberries, etc., are clusters of small drupes. Dome is a term npiJied to such fruits as the apple, THE SEED. 35 pear, etc., the coi'e being the true seed vessel, and the tiesh)^ edible part constituting a thickened calyx. A Berry is a many-seeded fruit, as the grape, tomato, huckleberry, etc. The Kilt has a hard or leathery shell, as the acorn, chestnut, hazelnut, etc. Gourd fruits have a hardened rind and soft fleshy in- terior, as the melon, squash, cucumber, etc. Pods are dry seed vessels, which open and scatter their seeds when ripe, as the touch-me-not. The Legume is a pod which splits in two halves, like the bean or pea. The pulse family are termed legumi- nous, from the shape of their fruit. Grains^ as of the cereals, are properly fruits, of which the bran is the seed vessel. The Akene is a plant with a single seed in its dry en- velojje, as the sunflov/er. 24. Of the Seed, The Seed properly consists of its coats and its kernel. It has generally two coats. In the cotton seed the fibre seems to answer for the outer and the hull for the inner coat. The Kernel lies within, and consists of the embryo and endosperm or cdhumen. The Embryo is the chit or germ of the plant, having root, stem, leaves, and bud in a state of incipient develop- ment. It contains the radicle, the plumule, and the cotyledon. By soaking a grain of corn for a few days in water, the embryo can be easily separated from the endosperm, and all three of its parts plainly exhibited. The liadicle is tlie rootlet or point from which the root \ starts downward. , The Plumade is the central bud from which the stem is developed. 36 ANATOMY AND PHYSIOLOGY OF PLANTS. The Cotyledon is the leaf-like structure which clasps the plumule in the embryo, and appears above ground as the first leaves in many plants. Endogenous plants have but one cotyledon, while the exogens have two. The pine, and others of its species, have often five or ten small cotyledons arranged in a circle ; they are called polycotyledonous. In some plants, as the horse bean and pea, the cotyle- dons never form leaves, but remain in the soil, decay, and feed the young plant. The seeds of nearly all agricultural plants of this class have no endosperm, such as the legu- minosa, crucifera, and ordinary fruits; also the gourd family and some trees, as the oak, elm, maple, etc. The embryo of the seed, after its maturity, kept in a dry state, lies dormant, losing its vitality at various peri- ods. Willow seed, for instance, will not germinate longer than two weeks after maturing. Of agricultural j^lants, the leguminous seeds remain uninjured for a long period. Girardin, it is said, sprouted beans over a century old ; and Grimstone produced peas from a seed taken from a sealed vase of an Egyptian sarcophagus believed to be nearly 3,000 years old. Coffee berries lose their germinating powers more rapidly than most other seeds ; hence it is very difiicult to get them to germinate after they are transj)orted to this country. They should be planted as soon as taken from the bush. Yet it is remarkable that when steeped in a weak solution of carbonate of ammonia, or sal ammoniac, their vitality seems to return, and many of them will sprout readily. Doubtless seeds kept free from exposure to atmospheric vicissitudes, especially moisture, may be kept for centuries. In agriculture, as a general rule, new seeds are the best, though some practical planters think otherwise. Loudet experimented with wheat one, two, and three THE SEED. 37 years old. One hundred seeds, one year old, produced 404 heads. Those two years old, 365 heads ; and three years old, 269 heads. Haberlandt found that eight per cent, of wheat seed germinated which were six years old, but none older. Barley twenty-four per cent, six years old ; oats sixty per cent, eight years old ; and maize seventy-six per cent, six years old. Of seeds two years old, 100 of maize germi- nated, eighty of oats, ninety-two of barley, forty-eight of rye, eighty-four of wheat. Rye failed entirely the third year. Melon seeds kept for several years produce more fruit than new seeds, which are more disposed to run to vine. Old flower seeds produce weak plants, but better flowers, and in some instances double flowers have been produced by seeds several years old. Unripe seed of cereals, when the kernel is soft, and be- fore starch is formed, will germinate in some instances, but not produce as good a crop, especially on poor land. Siegart says that unripe seeds of peas will produce early varieties. Some flowers, as the gilliflower, will also pro- duce double blossoms from the unripe shrivelled seed. Experiments of Muller and HeHreigel prove that light grains will sprout quicker than full, heavy grains; but not germinate as surely, and produce weaker plants. Practi- cal planters have found this out. Some of them throw their seed across a barn floor, and gather up those at the extreme end, as the heaviest, for planting. Liebig says " the strength and number of the roots and leaves formed in the process of germination (as regards the non-nitrogenous constituents) are in direct proportion to the amount of starch in the seed." He says further that " poor and sickly seeds will produce stunted plants, which will again yield seeds bearing in a great measure the same character." Boussingault says that seed sown in sterile soil will produce perfect seed, though diminutive ; sown in a fer- 38 AIS-ATOMY AND PHTSIOLOGY OF PLANTS. tile soil, these seed will produce plants of a natural size. Frof. Church, of the Royal College of Cirencester, Eng- land, made a number of experiments in 1863-4 on the germinating qualities of wheat seed, particularly as to their density. He came to the following conclusions : 1. Seed wheat of the greatest density produced the densest seed, and yielded the greatest amount of dressed corn. 2. Seed of medium density produced more ears, but of a poorer quality, and also the largest number of fruiting plants. 3. Wheat grains, which sink in water, but float in a liquid (salt water, for instance) which has a specific gravity of 1.247, are of very low value, yielding on an average 34.4 lbs. of dressed grain for every 100 yielded by the densest seed. Church found the densest not always the largest seed. From the above facts too much care cannot be used by farmers in the selection of ripe, healthy seeds, to 23revent depreciation in the quality and quantity of farm products. At the same time, Schubert says truly that " the vigor of plants depends far less on the size and w^eight of the seed than upon the depth to which it is covered in the earth, and the stores of nourishment which it finds in its first period of life." This indicates not only the importance of having land well fertilized, but having plenty of soluble food for the crop put under the seed to give the plant a vigorous start. OHAPTEE VIL PROCESSES OF PLANT LIFE. 25. Germination of Seed. The first process of vegetable life is germination. It is produced in agriculture by burying the seed a proper depth in the earth, thereby securing warmth, moisture, and uiodified light. GERMIXATIOi^' OF SEED. 39 The seed first absorbs a large amount of water, and swells and softens; the germ enlarges beneath the seed coat, which bursts, and the radicle first appears, pushing down- ward in the soil; and next the plumule, which ascends, bursting through the soil, seeking air and light. The endosperm, where any exists, as in the cereals, remains to nourish the plant; as does the cotyledon in some instances, as in the pea, maize, and barley ; while in others, as the buckwheat, squash, and radish, the cotyledons push up with the plumule forming the first pair of leaves. The radicle of the seeds goes downward into the soil, and divides and subdivides into new roots; and the plu- mule, ascending upward, spreads into new branches and leaves, and thus a perfect phant is formed. Seeds require heat, moisture, and oxygen gas to pro- duce germination. Goeppert found that no seeds would sprout below 39^ F. In Sachs' exj)eriments some sprouted at 41^, others required 55^. Some would not germinate at a higher temperature than 102^, others 116^. The vitality of the seed is preserved below the minimum and killed above the maximum. The point of rapid germina- tion is between the two extremes, 70° to 93°. The following table presents the special temperatures for six field and garden plants : Lowest. Highest. Most rapid. Wheat 41^ F.. . 104^ F . ....84^ F. Barley ....41 ... ...104 .. , . ,84 Pea 44.5... ...102 .. , , 84 . ,, 48 ... ...115 .. ....93 49 ... ...Ill .. . ,..79 54 ... ...115 .. ....93 Doubtless plants in frigid zones will germinate much lower (probably near the freezing point), and in inter- tropical climates much higher. The cocoanut, it is said, requires a soil of 120°'F. 40 ANATOMY AND PHYSIOLOGY OF PLANTS. Sachs observed that the temperature of seed germina- tion has much to do with the health, vigor, and product of the plant — low temperature retarding the growth of the root buds and leaves, while high temperature makes them too rapid. A medium is the best. While a proper temperature is deemed essential for the germination of plants, Koppen concludes, from experiments made, that variations in temperature are always prejudicial to the growth of the germ, even when amounting to only a few degrees, and within the limits favorable to energetic growth. Thus germination proceeds more rapidly at a low but uniform temperature than at a high and varia- ble temperature. Cool nights and warm days are more unfavorable than cloudy days with moderately warm nights. Seeds will not germinate without moisture, and even when half sprouted, if deprived of it, the process ceases. The absorption of water puts in motion the contents of the germ cells by expansion. Excess of water is, however, injurious to land plants, causing them to rot. Saussure proved that free oxygen, as contained in the atmosj^here, was also essential to the growth of the embryo, being excited by its presence. Johnston taught that light was opposed to germination. Prof. S. W. Johnson dissented. He says that " the seeds of common agricultural plants will sprout when placed on moist sand or sawdust, with apparently no less readiness than wlien buried out of sight." In twenty-four experi- ments, Hoffman came to the conclusion that light had no appreciable influence on the germination of seeds. The time of germination is very variable with different seeds. Beech, maple, and ash require one or two years, while several weeks is all required by the pine, walnut, and larch. The willow seed will sprout in 12 hours after it strikes the ground. Common agricultuial plants, as PLANT GROWTH. 41 corn, cotton, and oats, sprout in from three to five days. Seeds in thick, hard envelopes, as the okra and beet, re- quire much longer time than others. Oily seeds are slower than thin-skinned starchy seeds. It took 22 days for a sugar beet to sprout at a tempera- ture of 41^ F. (according to Haberlandt), and 4 days for rye. The time was shortened one-half at a temperature of 51^. Indian corn, at this temperature, sprouted in 11 days, and at 61"^ in 3 days. The process of germination lasts from the time the root- let appears until the seed is exhausted of its nutriment. Smaller seeds will germinate sooner than larger ones, be- cause the supply of nutriment is less. Covering seed in the soil seems to be only essential to supply proper warmth and moisture. It also protects from birds and freezing out in the winter. Porous, light soils require deeper planting than close, compact soils. According to Prof. Johnson, the Indians of Colorado plant their corn at a depth of 12 to 14 inches, as it will not sprout in their dry and sandy soils nearer the surface, for lack of moisture. HolFman found no seeds to sprout at 12 inches on light loamy land, out of 24 kinds which he tried. At 10 inches, none but peas, vetches, beans, and maize sprouted. At 8, besides these, wheat, millet, oats, barley, and colza. At 6 inches, buckwheat, the beet, and winter colza. At 4, besides all the preceding, mustard, red and white clover, flax, horse-radish, hemp, and turnips ; and at 3 inches, lucerne. The deep-planted seed sprouted 1 first, and no difierence appeared in the plants from deep and shallow planting by the time of blooming. Gronven found difierent results on a difierent soil. The character of the soil, the temperature, the relative mois- ture will require difierent depths ; hence no general rule ' can be laid down. • 42 ANATOMY AND PHYSIOLOGY OF PLANTS. 26. Plant Groioth, All plants possess in common so many features of resem- blance, that a complete study of one gives a very good knowledge of the whole. Difierences are rather incidental than radical, either as to their structure or functions. In all seeds the plantlet exists in one form or another before germination begins. The stem seeks the light, the root avoids it. Why, we cannot tell. They grow in opposite directions ; the stem upward, the root downward. They also grow in a different way. The stem produces joints, each growing upon the summit of its predecessor, and elongating, as the stem lengthens, until the plant is fully grown, each bearing one or more leaves on its summit. The root has no joints or nodes, and lengthens only from its extremity. The stem has a length to begin with in the embryo ; the root has none, but begins a new formation at the base of the stemlet, and lengthens by accretion, the parts formed not elongating afterward. But for this wise arrangement the lateral roots would be broken, as their fibrils would branch out and become attached to the solid earth, and their base be drawn forward in the process of elongation after the parent root. Traube proved the elongation of the stem by fastening the cotyledons of a young pea plant to a rod, the stem and rod both being marked at equal intervals with a mixture of indigo and oil. The spaces on the stem widened be- tween the lines, w^hich, when compared with those on the rod, showed that no growth took place at the distance of near an inch from the base of the terminal bud. 27. Nutrition of the Plantlet, The nourishment of the germinating plantlet is pro- vided beforehand by the parent plant, and stored up either NUTRITION OF THE PLANTLET. 43 ill or around the embryo. There is just enough of this to begin the root, and push it out in the soil to seek more, and to bring up the seed leaves to the surface, where they may unfold and begin to absorb nutriment from the air. Hence if the seed is planted so deep as that the food gives out before the stem reaches the light, the planllet dies. In some cases, however, a larger supply of nourishment is provided, and the plant is not thrown upon its own re- sources quite so early, as in the pea and the horse-chestnut. The squash or pumpkin has scarcely anything but the two seed hairs within, but yet they are themselves very rich in food, which causes them to grow rapidly and have very- long stems before leafing. And so of the peach, almond, and plum. In other cases the food is deposited outside of the embryo, a good example of which is the convolvulus, or morning glory. This store of food thus deposited around the germ was first called albumen, a name which it still retains from its resemblance to the white of the egg enclosing the yolk. Plants sometimes lay up their food in underground stems, as the artichoke and Irish potato. These thickened ends are called tubers. They are not roots. In some cases, as the house-leek, the nourishment for the next year's growth is laid up in the leaves. In shrubs and trees, much of the nutritive substance made the previous summer is preserved in the young wood, bark of the shoots, trunk, and roots, for them to feed on the next spring. By this means they shoot forth vigorously, and clothe the forests in rich foliage in a few days. 44 ANATOMY AND PHYSIOLOGY OF PLANTS. CHAPTER VIII. PEOCESSES OF PLANT LIFE — (CONTINUED.) 28. Formation and Groioth of Wood. The theory of the French botanists, in reference to the formation and growth of wood, is tliat it begins in the leaves or leaf buds, and descends continuously to the roots, so that the united mass of wood in the stems and roots emanate from the leaves of the plants. An objection to this theory, however, is found in the fact that the stumps of pines and other coniferous trees often increase in diameter, forming new woody layers for several years. Dutrochet mentions the instance of a stump of a Pinus picea, wdiich was felled in 1821, being still alive in 1836, having fourteen new thin layers of wood ; and one felled in 1743 was still alive, having formed ninety-two thin layers of w^ood ; one for each year. - Goeppert investigated this subject as early as 184-3, and found a union of the roots of the fallen trees with the roots of living trees, growing in the immediate vicinity ; yet this does not explain why the sap, which is thus robbed from the roots of living trees, in passing up the usual channels, does not overiiovv^ tlie top of the stump, as in the case of a grape vine or a deciduous tree, when cut during the ascent of the sap. And as the growth of new wood in exogenous trees is from the cambium, and the theory makes the cambium the sap, which has been elaborated in the leaves, from w^hence does the cambium of these stumps originate ? These facts certainly prove, if they prove anything, that wood formation is independent of the descending sap elaborated in the leaves, at least under certain circum- Btances; and that vegetable physiologists must look further CUARACTER AND DURATION OF PLANTS. 45 than the theory of the French botanists for an explanation of this subject. The vegetable cells constitute the formative state of all the tissues of the plant, each of which may be considered an independent body. The extension of the wood of the tree in any direction is through the cell growth ; and where- ever the cellular tissue is in a state of vitality, and the sap is brought in contact with it from whatever source, there will be cell multiplication and material growth. 29. Character and Duration of Plants. Plants are divided into Herbs, Shrubs, and Trees. The first class are short-lived, some existing only for a few weeks; while trees are known to endure for centuries. Herbs are Annual, Biennial, and Perennial. Annuals generally come up from the seed in the spring, and die in the autumn. Our common agriculturial plants, corn, cotton, and peas, are familiar examples. Some, as wheat, oats, and barley, spring up in the fall, and mature and die in the early summer. Biennials live for two years, bloom the second year, and die when they ripen their seeds. The turnip, carrot, and beet are examples. They have a bud on their roots, which is an embryo stem, in which nourishment is depos- ited for the next season's growth. When this bud is cut out the roots may continue to grow, but the prospective stem is destroyed. Perennials are ever-living plants, to which class belong all shrubs and trees and many herbs. Perennial herbs, however, generally die down to the ground on the approach of winter. Climate has much to do with the character and dura- tion of plants. The cotton plant, for instance, is an annual here, but in Central America assumes the character of a 46 ANATOMY AXD PHYSIOLOGY OF PLANTS. shrub or small tree. We occasionally see it even here live through a mild winter, and ratoon the next spring from the living roots, and rarer from the stems. CHAPTER IX. CIRCULATION OF FLUIDS IN PLANTS. 30. Absorption of Water, Formerly it was supposed that plants had the power to absorb vapor of water as well as to imbibe liquid water from the atmosphere. This theory, however, has been ex- ploded. Duchartre found that when plants were excluded from the air, and their roots allowed to receive moisture, they increased rapidly in weight ; while they lost in air nearly as possible saturated with water, where the roots were excluded from it. Sachs established, by a number of interesting experiments, that even the roots are incapable of taking watery vapor. More recently, M. Cailletet has found that while the leaves of plants neither absorb water nor vapor of water, when there is a sufficient supply of water in the soil to fur- nish the roots, yet when there is a deficiency of this im- portant principle, the leaves do absorb liquid water, but under no circumstances do they imbibe watery vapor. This explains the fact that certain plants are able to maintain a healthy condition without any contact w^ith the soil, as in the case of water culture. The absorptive force by which roots imbibe water is very great. Hales, who experimented one hundred and forty years ago with a grape vine, found in one instance that the pressure was equal to the support of a column of mercury 32^ inches high, equal to 36|- feet of water. Hof- ABSOEPTION OF WATEK. 47 meister made the force of the vine 29 inches, a beau 7 inches, and nettle 14. This power resides in the surface of the young roots, and is greater the less the length of the stem (Dutrochet) ; a long stem resisting the rise of the liquid more than a short one. The seat of the absorbing power is near the extremities, but not at them. (Ohlerts.) The absorbent force is more vigorous when the rootlets are in active development. The forcible imbibition of water into plants sometimes causes its exudation on its foliage. Instance, a drop of water on the tip of the leaves of young corn. Also, the bleeding of the grape vine when severed while young. The stumps of large trees when cut down in spring-time are often full of water exuding from the cut surface. The amount of water taken up by the roots is increased by an elevated temperature and decreased by a low tem- perature in the soil. Sachs observed an entire cessation of absorption when the temperature was reduced to 41^ F. On a morning in November, when the thermometer had fallen to this point, he observed that some tobacco and squash plants in his room (which were growing in a soil nearly saturated with water), hung down their leaves like wet cloths, as if wilted by the heat of the sun. On Avarming the soil, the leaves returned to their natural tur- gidity. He found by further experiments, that plants would wilt in a few hours by surrounding them with snow, showing that a cold soil would so contract the roots as to completely prevent absorption. Pie also found that certain salts added to a soil, as phosphate and silicate of potash, sulphates of lime and magnesia, would produce the same effect, retarding the transpiration from 10 to 90 per cent., while a diluted solution of free nitric acid would accelerate it correspondingly. Boehm has come to the conclusion, from recent experi- ments, that transpiration of water through plants actually 48 ANATOMY AND PHYSIOLOGY OF PLAKTS. ceases when the surrounding atmosi^liere is saturated with watery vapor. So that tlie dryness of air has much to do with this process. Hesse found that a beet leaf, gathered at evening, after several days of dry sunshiny weather, con- tained 85.74 per cent, of water, while a similar one, pulled the next morning after a heavy rain, yielded 89.57 per cent. The difference of 3.8 per cent, between the two leaves (which other observations corroborated), shows clearly that the wilting in dry weather is caused by a more rapid exhalation than absorption of w^ater by plants. The absorptive power of plants is weakened by cold and increased by w^armth. At 41^ F., Sachs found it to cease in the squash and tobacco plant, but quickly re- new^ed when plunged in w^arm water. In a moist as com- pared with a dry soil, the quantity would be greater, but the imbibing power the same. New roots and scions springing from a stump will cause the water to sink in a pressure gauge. (Hofmeister.) Plants wilt in dry w^eather because there is a lack of moisture in the soil to supply as much as is exhaled by the leaves. More in fact is required, as a portion of the water is fixed in the plant as nutrition, where its oxygen and hydrogen are needed to supply by chemical affinities these important elements. Although it has for a long time been believed that the exhalation of water from plants is indispensable to their life and nutrition, as thereby room is made for the upw^ird flow of nutritive matters held in solution by water imbibed by the roots, yet there is strong reason, as Prof. Johnson says, for believing that the current of water which ascends through a plant is independent of soluble matters within or without it, and that soluble matters may be taken up from the soil even without an aqueous current. Thus in the confined atmosphere of green-houses, where the air is saturated with vapor, and transpiration ceases almost en- tirely, they seem to grow^ as well as in the open air, where EXHALATION OF WATER. 49 this process reaches its maximum. And thus, during rainy- weather, plants grow rapidly when there is but little if any exhalation, quite as much as in dry weather, w^hen trans- piration is constantly going on. And yet this process cannot be considered accidental or unimportant. Sachs found that a bean, whose roots were in an atmosphere saturated with aqueous vapor, while the branches had fresh air, did not grow any while in this condition, although it remained healthy. Knop also found that several kinds of plants died w^hen confined in a vessel over water. Other causes may have conspired to this end. While it is probably true, that transpiration of water from plants is not essential to their health and growth, its entrance into them, so as to keep up a due sup- ply of hydrogen, is a well-established fact. Some plants haA^e a much greater power of absorbing water from soils than others. The eucalyptus tree, from Australia, is the most remarkable instance, growing with great rapidity in regions unsuitable for the growth of forest vegetation. In marshy lands it has a very decided effect m draining them of the superincumbent water, and in freeing the surrounding atmosphere from malarial influ- ences. 31. Exhalation of Water, Water exhales freely from growing plants in the form of invisible vapor. The amount is often very great. If you will cover a plant exposed to the light of the sun w^ith a bell glass, you Avill soon see the inner surface of the glass covered with dew, and then with little drops which come from the leaves. An experiment made by Hales (more than a century ago) showed that a sunflower having 39 square feet of foliage exhaled 3 lbs. of water in 24 hours. A cabbage, whose leaves had 19 square feet of surface, exhaled nearly as much. In the same length of time Schubler found that 50 ANATOMY AND PHYSIOLOGY OF PLANTS. 1 square foot of pasture grass exhaled 5^ lbs. of water. A recent experiment made by Knop showed that a dwarf bean exhaled, in 23 days in September and October, 13 times its weight of Avater. He further established the fact, that a grass plant will exhale its own weight of water in 24 hours in the hot dry days of summer ; and that a maize plant exhaled 36 times its own weight of water from May 2d to Sept. 4th. During rainy weather, or damp days and dewy nights, this exhalation almost entirely ceases, while in dry weather it is rapid and copious. Other things affect more or less the quantity of water exhaled, as the age, texture, and number of breathing pores of the plant, as well as the temperature of the soil. Young plants also lose more water than older ones, as ascertained by Lawes and Knop. Exhalation is not essential to the life of the plant, and may be reduced to its minimum without affecting its growth. Only when the water exhales faster than it is imbibed by the roots, is the plant injured; then it wilts and will die, if the drought continues too long. Von Fettenkofer ascertained that transpiration of Avater in an oak tree increased gradually from May to July, and then decreased till October. The number of the leaves on the tree were estimated at 751,600, and the total amount of evaporation for the year at 539 cubic centimeters of Avater for the Avhole area of the leaves. The average rain-fall for the same period Avas only 65 centimeters, the amount of evaporation being 8^ times greater than the rain-fall. The excess must be drawn up by the roots from a great depth. The inference is very clear, that trees prevent the gradual drying of a climate, by restoring moisture to the air Avhich Avould otherwise be carried of by drainage. After a number of experiments to ascertain the pro- cesses of plant exhalation, M. Barthelemy concludes that aqueous exhalations may result from plants in three ways CIRCULATION OF SAP. 51 1. By insensible exhalation from the entire surface of the cuticle by means of a true gaseous dialysis. 2. By sudden emission of saturated gases which escape from the stomata when the plant is submitted to a rapid elevation of temperature, especially when enclosed. 3. By accidental exudation, resulting from a defect in the equilibrium between the absorptive action of the roots and the work of the parts exposed to the atmosphere, in fixing carbon combined with the elements of water, work which ceases with the disappearance of light. We know that it is also right to conclude that heat exercises a strong influence upon this function, and that at equal temperatures carbonic acid in presence of light has the effect of diminishing the evaporation. 32. Circulation of Sap. The roots of plants are endowed with a peculiar quality, by which they are enabled to suck up the moisture which comes in contact with them. And every part of a plant has a force which brings into play the suction power of the roots. Thus a root deprived of its spongioles, a sec- tion of a stem, or a leaf, exerts this suction powder when plunged into water. The true cause which produces the ascent of sap, has not been discovered, although several theories have been presented. This force seems to be independent of any known law of hydrostatics. We can conceive how the roots might imbibe water by capillary attraction, but not how this force could operate with such rapidity to the remotest leaves. Atmospheric pressure has been suggested ; but from experiments made by Hales, it is evident that a much greater force is employed than this can bring to bear in a simple vacuum. He found that the pressure exerted by the escaping sap, upon the mercury in a reversed siphon, caused it to rise in one of the arms, and remain stationary 52 ANATOMY AND PHYSIOLOGY OF PLANTS. at a height of thirty-eight inches above its original level. The descending sap is conveyed by some other force than mere gravity, as has been proven by tying a cord round a limb in the upright and another in the depending position. In one case below and in the other above the cord, there was a thickening of the integuments, doubtless from the accumulation of the obstructed sap. Hales supposed that the motion of the sap in plants depends upon exhalation. Liebig admitted his theory in part, but contended that it was aided by some powerful force from without, as atmospheric pressure. But after all the experiments that have been made, and all the theories advanced, we have to fall back upon the old notion of the vitcd force^ which we know exists, and but little more in reference to it. Since the time of Hales, who experimented a century and a half ago, but little advance has been made in inves- tigating this interesting subject, so much so that Liebig asserted, that nothing had been developed in addition to his experiments. We have now, however, to record the re- sult of an interesting series of experiments during the last year, 1873, conducted by Prof. Peabody of the Massachu- setts Agricultural College, assisted by Profs. Stockbridge and Goessman. We condense from President Clark's re- port the following summary of facts. They prepared six mercurial gauges to determine the pressure of the sap of different trees. About sixty spe- cies of trees and shrubs were tapped, and it was found that the great majority do not bleed from wounds in the wood at any season, and the few species which do so to any considerable extent, only do it when deprived of their leaves. No reason for this has been found in their struc- ture or habits. Of those which bled, each species had their own time to awake from their winter's repose, the flow steadily CIRCULATIOX OF SAP. 53 increasing in quantity and force, until it reached its max- imum, and then gradually declined ; the composition of the sap differing remarkably according to the date of the flow and the time of its beginning. ''This singular peri- odicity," says the report, peculiar to every species, de- monstrates that the absorption of water by the rootlets is not caused by osmose, or any other mere physical force, but is the result of the specific life which imparts to every plant its distinctive characteristics." The sugar maple begins to flow in October; maximum, 1st of April ; ceases early in May. The black bircli begins the last of March, has its maximum last of April, and ceases middle of May. The summer grape begins first of May, reaches its greatest flow and pressure about the 2oth of the same month, and ends early in June. The principal ingredient of maple sap was found to be cane sugar ; that of birch sap, grape sugar, and of vine sap, vegetable mucilage or gum. These three carbo-hy- drates are believed to be formed out of the starch a> hich descended and was deposited in tlie root the previous season ; these transformations probably occurring in the sap after it begins to flow in the spring, thus : the insolu- ble is changed into soluble gum, the gum into uncrystal- lizable grape sugar, and this becomes cane sugar, under favorable circumstances. The reason why the maple sap is changed into cane sugar, while the birch only makes grape sugar, as inferred by the report, is, that more time is allowed for the proper chemical changes to take place in the one case than in the other. The maple being fall of sap for six months, between the fall of the leaf and the beginning of growth in the spring, is the only tree that can develop the grape sugar. The beginning of vegetable growth in the vine is attended by the rapid exhaustion of water, which assimilates the guu- which is transformed into cellulose. This ordinarily occurs with plants at the beginning of their spring growth. 54 ANATOMY AN^D PHYSIOLOGY OF PLANTS. These experiments further show that the weather affects the dally and hourly flow, although the general flow corre- sponds with the season, rising to a maximum and then declining, till it ceases entirely. Steady cold weather, or uniformly warm, foggy weather, was the most unfavorable for the flow of sap ; while freezing nights, succeeded by sunshiny days, were the best. Biot, in France, on the poplar, and Nevins, in Ireland, on the elm, found that freezing weather forced the sap from the alburnum into the heart wood of these trees. Absorption going on as usual under ground, it is natural to infer that there would be a rush of sap to the surface, and consequently an increased flow, as soon as the warmth of the sun expands the tubes of the sap wood. A piece of gas pipe being introduced into the heart wood, the flow of sap was regular and long continued, although not so abundant as from the alburnum. This proves that the heart wood, as well as the sap wood, is fllled with the sap during the spring. The flow from the heart continued eleven days longer than from the sap of another tree, but the amount from the sap wood was twelve pounds greater than from the heart. The north side of a tree yielded twice as much as the south side, although from the latter the flow continued two wrecks longer. A healthy tree, tapped near the ground, bled six pounds and two ounces of sap in seven hours ; while a limb, Avhicli was cut thirty-five feet above the ground, did not bleed a single drop. Other experiments showed that the sap flowed more freely twelve feet from the ground, while above that height it decreased rapidly. This fact seems to indicate that there is an absorbent power of the roots which forces the sap upward, as the force is weaker the higher it ascends. It is also inferred from the fact that the sap only rises CIRCULATION OF SAP. 55 about twenty feet in the maple tree; that developments of leaf and flower above that point result from other causes than the flow of sap by mechanical force from below. Their vitality is doubtless stimulated by the genial sun- shine, and their growth caused by organic substances accumulated during the previous season, and the absorp- tion of gases from the atmosphere. Experiments also proved that the sap of the roots of maple also contained sugar, and that it flowed from both ends of a cut root. The largest flow of sap from one tree, during the spring, occurred 'March 23d, amounting to ten pounds and three ounces from two sprouts. On the 16th of December fol- lowing, a similar tree bled from two orifices sixteen pounds and seven ounces. In November the sap was found to contain not more than half the percentage of sugar as that obtained in March. It is not believed that loss of the sap from tapping or pruning in the spring has any appreciable efiect upon the growth or vigor of the tree or vine. Dr. Jabez Fisher selected fifty grape vines in his vineyard, and pruned one every day, beginning the first of May, until the young shoots were well grown. He found it made no difierence so the pruning was done before the new growth was devel- oped. The mercurial gauge used in these experiments w^as made of an inverted siphon, the lower end being inserted into the sap wood, near the ground, with a stop-cock attached. The mercury being poured into the upper end settles down in the first bend, until both tubes are filled up to a certain point. This is the zero point, and the scale may be graded from this. When the sap rises and passes over the first bend down upon the mercury in the left-hand tube, it falls in that, and rises in the right-hand tube. When the suction toward the tree takes place, it rises in 66 ANATOMY AND PHYSIOLOGY OF PLANTS. the left and falls in tlie right, and thus the pressure and motion both may be easily ascertained. Observations were made daily from 1st of April to 20th of July. The following facts were elicited : 1st. The mer- cury generally stood below^ zero in the morning, and would then rise rapidly with the sun until the outward pressure was sufficient to sustain a column of water many feet in height." At seven o'clock, April 21st, there was suction in the tree sufficient to sustain a column of water 25.90 feet. The mercury began to rise very rapidly as soon as the sun began to shine on the tree, so that by fifteen min- utes after nine a.m. the pressure outward would have sus- tained a column of water 18.47 feet high, equal to a force sufficient to sustain 44 feet of water. The next day the oscillation was still more remarkable, representing 47.42 feet of water. No explanation is given of the probable cause of these fluctuations. 2d. The maximum pressure of the sap was equal to sustaining a column of water 31.73 feet high. This was April 11th. After the 29th the mer- cury remained below zero day and night. During the month of May the mercury remained below zero at a point equal to the pressure of a column of eight feet of water, probably caused by exhaustion from the exhausting leaves. Its uniformity, however, could not be accounted for. In June it gradually decreased, and finally the mercury settled permanently at zero for the season. Two gauges attached to a black birch on the 20th of April, one 30.20 feet above the other, showed the next morning a difierence of pressure between them of 29.92 feet of water, corresponding almost exactly as if connected by a tube. The pressure on the lower gauge was 56.65 feet of water; on the upper, 26.74. The upper gauge, raised twelve feet higher, showed the same correspond- ence. At 12.30 P.M., a hole bored directly opposite to the lower gauge, showed a diminished pressure in both gauges, CIECULATION OF SAP. 57 while the sap flowed freely from the orifice. In fifteen minutes one pound of sap escaped ; both gauges had fallen 19.27 feet of Avater. On closing the hole, the sap rose in ten minutes to its former level. This illustrates very clearly that the whole system of sap circulation is closely and delicately connected, and also that the roots absorb from the soil, and carry with great rapidity, the nutritive substances requisite for the support of the tree, which are carried forward with equal celerity through the whole network of ducts and tubes to every part of the tree. By inserting a stop-cock in the hole opposite the lower gauge, it was found that the communication between the two gauges was almost instantaneous, showing that the tree was filled with sap, pressing as freely in all directions as if it stood in a cylindrical vessel sixty feet in height. On the 11th of May the sap pressure in the birch repre- sented a column of water 84. 7 7 feet in height, the highest ever before recorded. The sap now began to diminish and the buds to shoot forth, the upper gauge ceasing its pressure on the 14th, and the lower one on the 27th of May. In order to determine whether any of the supposed forces of exhalation, dilatation, contraction, caj)illarity, or oscillation, had anything to do in causing the sap to rise, a large root of a birch, situated in a shady ravine, was followed ten feet from the trunk, and carefully cut one foot below the surftice, a piece being removed between the cut and the tree. To the end thus detached, measuring about one inch in diameter, was attached a mercurial gauge on the 26th of April. The pressure began to rise, which continued with slight fluctuations till noon of the 30th ; it had attained a height of 85.80 feet of water. This de- stroyed completely the idea of exhalation, capillarity, or any of the forces, save the vital force known to exist in the root. 3* 58 ANATOMY AND PHYSIOLOGY OF PLANTS. The experiment of Rev. Stephen Hales, conducted on the vine one hundred and fifty years ago, was repeated, . the mercury rising to 49.52 feet, six and a half feet higher than was observed by him. The report concludes very wisely, that " we may as well admit that life is still a special force, and not to be resolved into any sort or combination of attractions or repulsions, whether called electricity or osmose, or any other name." 33. Theory of Electrical Force, As to one of the forces mentioned above, the electrical by contractility^ it is well known that in higher animals the muscles and nerves are possessed of electrical currents, flowing in definite directions, which produce these con- tractile movements. Very recently. Dr. Sanderson has established very clearly that two plants at least, the dionsea (Venus's fly-trap), and the mimosa (sensitive plant), are endowed witli similar currents and contractile tissues, which are subject to the same laws as those of animals. The dionose grows only in sandy bogs near Wilmington, North Carolina, and is remarkable for its contractile movements, by which it catches insects that alight upon it, and, it has been supposed, is nourished in part by them. Might it not be possible that electrical currents have something to do with carrying on the movement oi" fluids in vegetable as well as animal life, since at least two species are now known to possess it ? PAET 11. AGRICULTURAL METEOROLOGY. CHAPTER I. THE ATMOSPHERE. DESCRIPTION. — RELATION TO VEGETA- TION. HEIGHT. — PRESSURE. THE BAROMETER. MOIS- TURE. — HYGROMETER. 34. Description of the Atmosphere. To the untaught mind, the atmosphere seems to be a vacuum — space without any substance whatever. A sim- ple illustration will convince us of its substantial quality. Take a glass jar with an open mouth, invert it, and press it down into water ; you observe that the water does not enter it until turned to one side so as to admit the escape of air. Then it begins to fill, as shown by the bubbles of air which escape. For every volume of air that escapes, an equal volume of water enters the jar, until it is filled. Upon this principle the diving-bell is constructed, by which a man may descend to the bottom of the ocean, and live and breathe until the oxygen of the air is nearly consumed. This proves very satisfactorily that the air is a real substance, although invisible. Then the atmosphere is composed of a layer of light matter, surrounding the earth and resting upon it, which envelops everything we see on or near its surface. It is not only invisible, but transparent, elastic, destitute of taste or smell, and movable in every direction. It has a slight CO AGEICULTURAL METEOKOLOGY. blue tint when viewed in masses at a distance. It has been compared to a vast aerial ocean, surrounding the earth on every side and extending to a great height. The natural constituents of the air are gaseous. Liquids and solids do sometimes exist in it, as rain-water, hail, snow, sleet, and impalpable dust ; but they are extraneous to it, and do not exist in a pure atmosphere. The vajDors which float in the air are properly gases, i We become acquainted with solids and liquids through the | sight, but know but little of the gases by this method, as they are mostly invisible, and transparent like the atmo- ^ phere. Gases are much lighter than liquids and solids. Some of them are considerably heavier than the atmo- sphere; others lighter. While most of them are colorless, some possess beautiful colors ; as green, red, and violet. Many are without smell, while others are possessed of the most pungent, disagreeable, and even poisonous odors. 35. Its Relation to Vegetation. \ The atmosphere is very closely related to vegetation, as it furnishes much the largest portion of the food of all plants. This is done by the absorption of nutritive gases through the stomata of their foliage, which is freely per- meable to them. Carbonic acid, and perhaps ammonia, are thus absorbed, and appropriated by the cells, and the structure of the plant built up. The atmosphere, however, has a natural limit, which art cannot improve as to vegetable nutrition. Unlike the soil, which may become exhausted of certain elements, and have them reapplied by art, the atmosphere recuperates as fast as the plant exhausts it of its appropriate food. When the carbonic acid surrounding the foliage is taken up, more flows in by the law of diffusion, and an increasing supply is thus furnished by day and night. The atmo- sphere then, while of interest, is only of secondary import- HEIGHT OF THE ATMOSPHERE. 61 ance to the practical agriculturist, when contrasted with the soiL The common properties of the atmosphere are weight, fluidity, and eLasticity. Its pressure depends upon its weight and fluidity. Its weight is owing to gravitation or the centripetal force. Air is 810 times lighter than water, when the ther- mometer stands at 62°. The bulk of the atmosphere varies with the temperature ; being heavier in cold, and lighter in warm weather. 36. Its Height, Some philosophers have estimated the height of the atmosphere to be at least one hundred miles, inasmuch as the combustion of meteors has been known to take place that far from the earth. It is believed that one-half of the whole of its bulk is found within the distance of 3f miles of the earth, and one-third beneath the level of the Rocky Mountains. If the atmosphere had a uniform density, it would be 5.208 miles in height ; but its density being proportional to its pressure, diminishes with its elevation. It is sup- posed to have a sensible density for about 45 miles in height, founded upon the phenomena of refraction. At 2^-^ miles above the earth, it is just half as dense as at the surface; one volume expanding into two. At the same height above this, it is again halved ; ex- panding into four volumes. At 16^ miles above the level of the sea, it would be divided into 64 volumes; that is, it would be 64 times thinner and lighter than at the earth. Although some suppose that the atmosphere is illimitable, existing, though very rare, throughout the planetary system, yet it is probable that the earth's atmo- sphere has a true surface and an exact limit. 62 AGEICULTURAL METEOEOLOGY. 37. Pressure of the Atmosphere, As the atmosphere extends many miles upward, al- though it becomes thinner and lighter, it must press with considerable weight upon the earth. This has been found to be equal to the pressure of thirty-two feet of water, if the whole earth was covered at. this depth, or about thirty inches of quicksilver. The actual pressure of the atmo- sphere upon the earth's surface is about 15 lbs. on every square inch. We do not feel this pressure, because of the mobility of the air, or its power to move in any direction. Thus, the downward pressure is relieved by pressing upon every side, as well as upward, and the force is thus coun- terbalanced. If a complete vacuum could be produced around a man, he would be crushed to the earth by the weight of the atmosphere suddenly pressing down upon him. The weight or pressure of the atmosphere may be il- lustrated thus : Take a hollow globe of glass and divide into two hemispheres, the edges of which are made to fit very tightly so as to exclude the air. Take a piece of paper and wet in alcohol and burn within the globe so as to produce a vacuum: the hemispheres placed together, having a handle to each, cannot be separated by two powerful men, because the whole pressure of the atmo- sphere is upon them. 38. The Barometer, The barometer, an instrument invented by Toricelli, an Italian philosopher, indicates the pressure of the atmo- sphere. It is made of a glass tube about three feet long, filled and then connected with a vat of mercury at its open end. Tlie tube thus filled is inverted with the finger upon the open end, which is thus placed in the vat of mercury. The column of quicksilver fails and leaves a vacuum. The vat of mercury is held in a leather pouch beneath, so that the atmosphere can press upon it from below. At the level MOISTURE OF THE ATMOSPHERE. 63 of the sea on a clear day, the mercury in the column will stand at 30 inches above the bottom of the vat of mercury. This is the standard for the barometrical scale, which is so graded as to indicate the hundredth part of an inch. In clear weather the barometer ranges high, indicating that the pressure is great, and that there is but little mois- ture in the air, and no prospect of rain. If it falls slowly and continuously for several days, it indicates a long spell of rain. A rapid fall early in the morning betokens even- ing showers. A very rapid and low fall forebodes a storm. The barometer is well adapted for measuring the height of mountains. For every 87 feet in altitude, it will fall y^^- of an inch. This varies a little as between cold and hot weather, owing to the contraction and expansion of the atmosphere, as well as the mercury, which, however, is very slight. The barometer might be made of use to every practical farmer who will take the trouble to become versed in its changes and indications. By it he wnll be able to judge, to a considerable degree, of the condition of the atmo- sphere around him, and what it is likely to be for the next day or two ; a knowledge of which is very important, especially as to impending rains, as indicating the kind of woi'k necessary to be performed — the sowing of seed, the gathering of hay and fodder, the cutting of grain, and the ploughing of low or uplands. Every intelligent farmer should become versed in what are termed the natural signs of the weather, especially those which foretell rain. The study of the barometer (a science almost within itself) would be a great help to hira in this regard. 39. Moisture of the Atmosphere, Water exists in the atmosphere as steam. This, of course, is not liquid water, but vapor of water, as the for- mer is not volatile, and cannot rise in the air. 64 AGRICULTURAL METEOROLOGY. A body whose temperature is far lower than the at- mosphere, will condense vapor from the air. Thus a tum- bler of ice-water on a warm day gathers dew on the out- side. And from the same cause, on calm summer nights, the ground, grass, and other bodies where the temperature suddenly falls from the abstraction of the sun's rays, is covered with dew. In the same way, invisible vapor issu- ing from a steam boiler into the cold air, forms a cloud, which is composed of minute drops of water. And thus, by the rapid evolution of the air from any cause, fogs and clouds are produced. When the change is very rapid, the minute droplets aggregate into full drops of water in the form of rain, and fall to the ground in showers. The properties of the atmosphere are modified to a considerable extent by the quantity of vapor in it, which is always limited by temperature, and is deposited sooner or later as dew or rain ; returning to the seas, rivers, and soil, from whence it came. We must not confound the dampness or relative hu- midity of t 'le atmosphere with its absolute humidity. The relative humidity indicates the proximity of the atmosphere to saturation or condensation ; a state dependent on the mutual influence of absolute humidity and temperature. From numerous experiments of Kaemtz on the shores of the Baltic, the relative humidity is highest in the morning be- fore sunrise, and lowest at the hour of the greatest diur- nal heat. This corresponds with results obtained in this country. 40. Evaporation, If, on a dry day, you pour water in an open shallow vessel, you will soon perceive that it gradually disappears. It has risen in the form of vapor, and mingles with the atmosphere. This process is called evaporation. Even snow and ice of a cold day will thus suffer loss. There are three circumstances which govern the spon- iiygkomi:teh. 65 taneous evaporation of water, viz. the dryness oi the air, its warmth, and its mobility by currents. Water emits double the quantity of vapor at 60° that it does at 40°. Hence humid, hot air contains much more moisture than when it is cold ; and this, moved by rapid currents of air as on a windy day, will cause a much more rapid escape of vapor than in calm weather. Evaporation, then, is constantly going on from oceans, seas, and lakes, as w^ell as the land, wherever there is mois- ture in the earth. This passes upward in vapor, gathers in clouds, and falls again to the earth in rain. Water may also exist as a liquid in the atmosphere, but it is only when rain is formed from vapor. The amount of vapor in the atmosphere is very variable, ranging from a half to three and a half per cent., and aver- aging about three per cent When the air is very damp it becomes saturated, and is deposited on window glass and other cool surfaces. When dry, it is always capable of taking up more moisture; hence, evaporation goes on at a rapid rate. 41. Hygrometer. The hygrometer is another useful instrument to the agriculturist. It indicates the amount of humidity in the atmosphere ; and of course where there is most moisture there is a greater prospect of rain, all other things being equal. This instrument has been variously constructed, both in form and principle. The hygrometer of Prof. Daniel (considered the best, because it involves the principle of condensation) is con- structed as follows : A glass tube is bent twice at right angles and suspended on a pillar, having a bulb at each end. One of these bulbs is partially filled with ether, into w^hich a delicate thermometer dips, being inserted within the tube, from which the air is entirely expelled, and it contains nothing but the ethereal vapor. The other bulb is covered with a thin piece of muslin. The pillar hns a thtrmometer GG AGEICULTURAL MFTEOKOLOGY. attached to it, which indicates the temperature of the exter- nal air. The amount of m.oisture in the atmosphere at a given time, is obtained by placing the instrument in an open window, or in some place to communicate with the exter- nal air, and a few drops of pure ether poured on the muslin covering one of the bulbs. The ether evaporating rapidly, causes a fall of temperature in the tube, condenses the ethe- real vapor within, and evaporates the ether in the other bulb. A consequent reduction of temperature takes place in the enclosed thermometer. Soon the atmospheric vapor will be seen gathering in a ring upon the glass. At the moment this transpires, Avhich is called the dew point, note the difference between the two thermometers. If the ex- ternal stands at 65^, and the internal at 60^, the dryness of the atmosphere is indicated by 5^. If the external ther- mometer is 75°, and the internal 60°, the indication of dry- ness is 15^, showing less humidity by 10°. In England, which is a damp climate, the dew point seldom reaches 30° F. ; while in the hot, dry clime of Italy, a difference has been noticed of 61°, the internal thermome- ter running down from 90° to 29°. CHAPTER II. TBMPERATURE OF THE ATMOSPHERE. — THE THERMOMETER. FOGS. — DEW. — FROST. SNOW. HAIL. 42. Temperature, The temperature of the atmosphere regulates that ol the soil ; and it has been found that different seeds will geraiinate in any climate, when the sum of all the means of the thermometer reaches a certain point — some requir- ino- more heat than others. 1 doubt not this would be TEMPEKATURE. 61 exactly true in the same class of soils. But as soils are so variable as to warmth, moisture, etc., an approximation is all that could be expected. True isothermal lines might thus be established, as to the cultivation of different plants, as well as the best time for the deposition of seeds in the soil. The lower strata of air near the earth is warmed in two ways : by the luminous beams of the sun, and by the radiation of heat from the earth itself. Kaemtz and Martin state that the atmosphere absorbs nearly half of the daily amount of the heat emitted by the sun, even when the sky is perfectly serene. The remaining portion strikes the earth, and elevates its temperature, which sends back in- visible rays of heat to the lower strata of the atmosphere by radiation. Modern researches show that all bodies ab- sorb more of the non-luminons rays of heat. The radiation of heat from the earth is effected by cli- mate and local causes. Though there is much more heat during the whole year at New Orleans than at Montreal, for instance, there is more received durins; the three summer months at the latter than at the former place, owing to the greater amount of radiated heat. The atmosphere trans- mits the penetrating rays of tlie sun to the earth, which absorbs them, and radiates other rays of heat not so pen- etrating, which are retained in the atmosphere near the earth, and add to its warmth. Thus w^e see, that in com- paring the agricultural capacity of different latitudes, we must remember to allow for the radiation of heat from the earth, as well as the direct rays of the sun. There is much greater radiation of heat shown in dry places like African deserts, where the days are very hot and the nights cold, than under other circumstances. Colonel Emory observed a difference of 60^ between day and night on some of the Western plains. From actual experiments made it has been ascertained 68 AGRICULTUKAL METEOROLOGY". that air expands 1.491 parts of its bulk above the freezmg point, for every degree of heat. Heated air is therefore specifically lighter, and its tendency is constantly to ascend. Every pound of air, according to Dalton, contains an equal amount of heat; and as it is more expanded in the higher regions, it is of course cooler. The amount of vapor in the atmosphere, as well as its density, modifies the heat. It has been ascertained that for every 352 feet of ascent, the temperature rises one degree. This is owing to two principal causes: 1st, the fact that air becomes colder by expansion; 2d, that the atmosphere derives its heat mostly from the earth. The surface of the earth is much more heated by the sun than that of the ocean ; inasmuch as the rays of heat enter the ground but little more than half an inch during a long summer day; while in the same length of time they jDenetrate the ocean many fathoms deep. Thus the surface of the earth is heated many times more than that of the sea. This has much to do with the aerial currents. For as the heated strata above the continents are continually rising, the cooler atmosphere of the ocean moves to fill up the partial vacuum thus produced. This is the cause of the sea breeze, which is ever blowing from the land to the sea, or vice versa, 43. The Thermometer. The thermometer^ as you all know, is the instrument which indicates the temperature of the atmosphere. The one commonly used in this country and England is Fah- renheit's, the scale of which begins at zero, 32^ below the freezing point. The centigrade thermometer, used prin- cipally in France, has it zero at the freezing point, and numbers 100 degrees between that and boiling. The same points are divided into 180^ in Fahrenheit's, so that one degree centigrade is equal to If Fahrenheit. This instrument consists of a small glass tube, termi- FOGS. 69 nated by a bulb, which is filled with mercury, having enough in the tube to stand at a mark indicating 32^ when sur- rounded by ice. The tube itself, having previously been made a vacuum by heat, and the pressure of the mercury, is inverted and hermetically sealed. For frigid climates, the thermometer is graded to 40^ below zero, the point at which mercury freezes. Below that point, a spirit ther- mometer has to be used. Tlie thermometer is an important instrument to agri- culturists, and even practical farmers. The daily mean temperature, kept for years, would be of great value in a given locality. This can be approximated by noting the temperature during the morning twilight, at 2 p.m., and one hour after sunset each day. The three added together and averaged, would about equal the sum of all the hours, day and night, taken separately and divided by 24. For scientific observations, a simple exposure to the external air for the morning and evening hours will suffice, but at 2 r.M., Avhen the sun is shining, more care must be taken in locating the instrument. A place exposed to the general warmth of an external atmosphere must be selected, without the slightest reflection from ground or wall. A bay window with blinds, on the shady side of the house, or a similar structure under an umbrageous tree, would sub- serve the end. 44. Fogs, According to Scripture, there was no rain before the flood; "but there went up a mist from the earth and watered the whole face of the ground." This mist seems to have been produced very much like our dews, though much heavier, as it sufficed for vegetation. The difference, however, between our mist and dews, is that the one is visible, the other invisible. Fogs or mists are visible vapors floating near the sur- face of the earth, and are always the result of a slight 10 AGIUCULTURAL METEOKOLOGY. precipitation of moisture. The only difference between mist and rain is that the one falls from a thin cloud near the surface of the earth, being composed of the smallest drop- lets of water; while the other falls from a dense cloud at a distance from the earth formed by a copious precipitation of moisture ; the cloud itself being a thick mist of drop- lets, which mingling in their fall become smaller or larger drops of rain, according to circumstances, before they reach the earth. Saussure and Kratzenstein found that mists were com- posed of minute globules of water, which they supposed to be hollow, as they possessed rings of prismatic colors like soap bubbles, which could only exist in globules of w^ater without air. Fogs are not common in hot climates, or during the hottest part of the day in temperate latitudes. They fre- quently occur, however, in the latter, but to a small extent compared with the polar regions. There, at the approach of w^inter, the whole surface of the ocean steams with va- por, csillecl frost sinoJce, It disappears, however, when the cold weather sets in. These i3olar fogs are caused by the warm air of the ground during summer, mingling with cold air of the ice- bound shores. According to Simpson, the thermometer sometimes rises to 71^ on the land, while the shores are lined with ice of immense thickness. These dense fogs cause it to be so dangerous to navigate the polar seas. The fogs which rise from rivers are produced by the much more rapid radiation of heat, during the day, from the banks than from the running stream. As soon as the tem- perature is equalized by the morning sun, they disappear. Mountains and high hills are more subject to fogs than level plains, from the mingling of the warm air of the vales with their summits. Dense forests produce fogs, and even light showers of rain, when the cool air of their shady DEW. recesses rises and mingles with the heated air of their sunny- tops. Mists are always beneficial to growing crops in our hot summer weather, to the extent that they deposit moisture on the surface of the earth, as it increases the hygroscopic water of the soil, especially in clay soils and vegetable moulds. Indeed, we cannot appreciate the value of even the invisible vapors, which float near the earth during long summer droughts, as the thirsty soil absorbs enough moisture from them to sustain life in the plant till the rain comes. This is one reason why soils abound- ing in clay and organic matter prolong the health and life of plants for days after they have succumbed in hot sandy lands. 45. Dew, DeiL\ another important source of moisture to plants in certain seasons, is spontaneously deposited during clear, calm nights, on the surfaces of all bodies exposed to the atmosphere. During the day, the earth as well as the lower strata of air, becomes heated by the direct rays of the sun ; as night approaches, it loses its heat very rapidly by radiation, and falls as fast in temperature. But the earth loses its heat more rapidly than the air, there being sometimes as much as 15*^ difference. Thus the stratum of air immediately in contact Avith the earth is cooled down rapidly, its vapor condensed, and deposited as dew upon the earth, and substances^lying upon its surface. A body, then, must be colder than the contiguous at- mosphere before the dew can be deposited upon it, and the greater the difference in temperature, other things being equal, the greater the amount of dew. Dew can be formed only when the atmosphere is calm and clear; hence it is not deposited on cloudy or windy nights. The clouds reflect back the radiated heat of the earth, and keep the intermediate atmosphere of an equable 12 AGRICULTURAL METEOIICLGGY. temperature, so that it cannot be formed. Dr. Wells demon- strated this, as follows : On a clear night, a thermometer laid upon the grass stood at 32^. The sky being suddenly overcast with clouds, it rose in twenty minutes to 39^ ; and in the same length of time sank down to 32*^ again when the sky became serene. When there is wind no dew is formed, because a vol- ume of air cannot remain long enough in contact with the cold surface of the earth for its moisture to be con- densed. A slight agitation, however, will prove favorable rather than otherwise to the deposition of dew. As the substance bedewed must be colder than the sur- rounding atmosphere, it is easily perceived how bodies which rapidly lose their heat, and slowly acquire it from others, are more affected than others. Thus glass, and bodies of a porous texture, such as wool and silk, are copi- ously bedewed, while metals and rocks are not, because the warm soil below easily and rapidly restores their lost heat. Dew is sometimes formed just before sunset, in conse- quence of the earth losing more heat than it receives from the rays of the declining sun. And so in shady places after sunrise, the same effect may be produced where the low temperature of the earth, which has been gradually cooling during the night, is not immediately influenced by the w^armth of the rising sun. Most dew will always be formed when there is most humidity in tlie air. The heavy dews of September, the driest month of the year, supply to a large extent the needful moisture to the cotton plant, and keep it in a thrivins: condition with but little rain. 46. Frost. Hoar frost is frozen dew, and of course results from tlie same causes, only it requires the temperature of the earth to be below tlie freezing point, while the atmosphere a IS few feet from it is several degrees liiglier. The formation of frost is arrested by anything which prevents the radia- tion of heat. Hence plants situated under trees are not so liable to be frozen. Ploughed land is much more subject to frost than that which has not been recently disturbed, as the radiation of heat is much more rapid, owing to the many angular points of surface it presents. We once ploughed a few rows of corn on a cold evening of spring : the next morning it was cut down by the frost, while the adjoining rows were unhurt. ♦ Frost, as before stated, is very beneficial to land in pulverizing the soil by the force of expansion, uj)on a principle in nature which seems to have been specially instituted for a benevolent purpose ; wdiile cold contracts everything else, it causes water to expand when con- gealed. But for this, ice would sink to the bottom of rivers and oceans, and accumulate in such masses as to freeze the earth into an icicle. Sometimes, frost is very disastrous to gardens, orchards, and crops. We may protect tender plants in a small way by covering them so as to prevent radiation. Vine-yards have been saved by building fires, and enveloj^ing them in smoke during the night. Late planting is the best pro- tection against frost ; and a judicious farmer can gene- rally tell from the budding of forest trees, when the ground is warm enough for seeds to germinate rapidly, and plants to grow healthily. Once in a lifetime, under such circumstances, the frost might kill them, but it would be very rare indeed. , 47.. Snoio, Snow is frozen moisture that descends from the atmo- sphere in the form of white crystals or flakes, when the 4 ?4 AGRICULTURAL METEOROLOGY. temperature of the air at the earth's surface is near the freezing point. When the air abounds in vapor, large flakes form ; the reverse causes fine snow. The crystals of snow contain air, which prevents the transmission of of light; otherwise they would be transparent like other pure crystals. The needle-like crystals of snow often differ very much in the arrangement of their spiculse ; but those of the same storm are said to be always alike. The bulk of snow is ten or twelve times greater than the water of which it is composed. Red and i^reen snow have been observed in northern latitudes, existing in some instances in large quantities. They are produced by microscopic plants, which are capable of existing at very low temperatures, and are said to flourish with remarkable vigor. They are formed of globules which vary in diameter from one thousandth to three thousandths of an inch. The cells are red, which is believed to be their natural color, the green tint result- ing from exposure to air and light. Snow is useful, agriculturally, in preserving the internal warmth of the earth by preventing the radiation of heat, and in this way acts beneficially on grain crops. Oftentimes in a temperate climate, wheat is winter-killed; when it is protected in higher latitudes by a covering of snow. Ammonia also is held in the soil and appropriated to the benefit of the plants, which would otherwise be volatil- ized by sunshine and winds. Even the temjDcrature of the tropics is modified and improved by the wind from the snow-capped mountains, which are the natural refrigera- tors of southern climes ; and thus far plants as well as animals are benefited, and enabled to better Avithstand the burning heat of a vertical sun. HAIL. 75 48. Hail. Hall is water frozen in the upper regions of the atmo- sphere, whicli usually falls in summer during the hottest part of the day. It is very destructive at times to grow- ing crops, but is generally confined to very narrow limits. Its origin has been a vexed question with meteorologists. Volta attributed it to the cold produced by electricity. Hence in France, where hail-storms are very disastrous to crops, they erected hail-rods to draw off the electricity^ This theory, however, proved to be fanciful, and the rods ineffectual. Olmstead's theory of warm currents from the tropics and cold ones from the polar regions being suddenly brought together by the force of storms and whirlwinds, causins; sudden condensation and freezino; of the atmo- spheric vapors, is certainly more logical ; particularly as the temperate regions, where such currents meet, are al- most exclusively visited by hail-storras. Hail, though produced by cold, occurs only in summer in warm climates and seldom at night. An ascending cur- rent of humid air could, by rarefraction (having an upward velocity), be capable of sustaining the falling hail-stones until they are sometimes very large. Hail-storms are always attended with thunder or electrical discharges; hence the origin of the idea that thunder-rods might protect from their devastations. (Graham.) The formation of hail is a blessing even to the farmer ; for in its freezing into solid ice, the rain is prevented from falling in chilling torrents, which passing through currents near the freezing point would seriously injure the crops. Besides, the latent heat of the rain becomes sensible heat, which being cariied off by the cold current, causes its temperature to rise, and thus it falls in warm, genial showers, even during a hail-storm. 10 AGRICULTUP.AL METEOROLOGY. CPIAPTER III. CLOUDS AND RAIX. 49. Formation of Clouds, Clouds are collections of vapor, which float above the earth, most generally at a lofty height. Tlie only differ- ence between them and fogs is in their elevation. When warm and cold air unite in the upper regions, the combining volumes having a slight excess of humidity, clouds are formed. As evaporation takes place from the earth, warm currents of humid air are continually ascend- ing, and as they meet the colder atmosphere above, clouds form. The higher they ascend, and the colder the at- mosphere above, the larger and more numerous will the clouds be. They redissolve, however, into invisible vapor when they meet with warm currents of air, as they ascend or descend nearer the earth, where the temperature is always warmer during sunshiny weather. It is only when the excess of moisture is small that clouds are formed, from the ever-changing currents of warm and cold air which float at various heights and in different directions many thousand feet above the earth. Of clear summer mornings there are no clouds ; but to- ward noon, as the heated air near the earth begins to rise and mingle with the cooler air above, saturation takes place, and clouds form. If there is humidity enough, rain will fall after the heat of the day. Hence nearly all our summer rains are in the afternoon. 50. Height of Clouds. Clouds vary much in altitude. Peytier and Hossard, two French engineers stationed on the Pyrenees, estimated the lower surface of forty-eight different clouds to range in OFwIGIXAL CLOUDS. I^ight from 1,476 to 8,200 feet. Daltoii states that two- fifths of all the clouds observed in England for five years averaged more than 3.150 feet above the surface of the earth. Gay-Lussac in 1804 ascended in a balloon 23,000 feet, and beheld clouds floating above him at a much greater height. According to Kaenitz, who had collected many obser- vations on the subject, clouds range in height from 1,300 to 23,000 feet. It is certain, however, that they float higher than this estimate, as Chimborazo is 21,840 feet above the sea, and they have been seen floating above the summit of this mountain. Clouds were observed by Peytier and Hossard to be as mucli as 2,788 feet thick, or more than half a mile. Others were only 1,476 feet, on another day. 51. Original Clouds, Meteorologists divide clouds into seven diflerent kinds. Three original, viz. .cirrus, cumulus, and stratus ; and four combined, viz. cirro-cumulus, cirro-stratus, cumulo- stratus, and nimbus. Cirrus clouds are so named from the Latin word sig- nifying a curl^ because it frequently assumes the form of a lock of hair. It is of a light fleecy appearance and light structure, and is capable of assuming a variety of forms. After a fine spell of weather cirrus are generally the first precursors of a change. They stretch across the sky as white slender filaments, thready, and arranged in parallel bands, sometimes spreading out like the tail of a horse, called by the sailors wind trees or mares' tails^ which to them denote stormy weather. The cirrus soars above all the other clouds. Kaemtz, at Halle, Germany, estimated them to be frequently 21,300 feet above the earth. He came to the conclusion that they were entirely composed of snowflakes. This is no IS AGRICULTURAL METEOROLOGY. doubt true in some cases, as the elevated regions they occupy must often be far below the freezing point. Cumulus, the Latin word for a heap, has been applied to that class of clouds which are piled up one upon an- other. They are usually in the form of a hemisphere, resting upon a horizontal base. This is properly the day cloud, as it is rarely seen at night, unless after the evening twilight, and seldom early in the morning or during the winter. These clouds are produced by the ascending cuiTents of warm air caused by solar heat. In the clear open weather of summer, about noontide or before, small specks of these clouds may be seen, generally in the northwest, rising toward the zenith. As they approach they become thicker and larger, during the heated portion of the day, but disappear toward nightfall. This is frequently re- peated for several days, the clouds becoming larger and more numerous until rain comes, or they are dissipated by the winds. Cumulus clouds float lower of a morningf, increasino; in altitude with the ascending currents of heat, and then de- scend again as the heat of the day declines. Meteorolo- gists stationed on high mountains, have observed these clouds below them in the morning, around and above them during the heat of the day, and then descending again to the vale below in the cool of the evening. Saussure attributed their rounded figure to their mode of formation. When one fluid flows through another at rest, the outline of the figure formed always represents a curve. This is illustrated by a drop of milk or ink falling into a glass of water, or a cloud of steam issuing from a steam boiler. The stratus is properly a night cloud, from the Latin, a covering. It generally forms about sunset, increases in density during the night, and disappears early in the morn- ing. It is caused by the vapors which have been exhaled COMBINED CLOUDS. 79 during the clay, settling toward night nearer the earth, around the horizon. To the same class belong those light elongated clouds, Avhich gather over the meadows and vales toward a summer's eve: this jDhenomenon is regarded by the common people as the settling of smoke, and is a popular sign of approaching rain. 52. Combined Clouds. The eiri'O' stratus cloud is a combination of the cirrus and stratus. It is generally remarkable for its length in proportion to its thickness; but assumes a variety of forms — sometimes appearing in a streak, broad at the middle and narrow at both ends, and then like a number of parallel bars, and again in sriiall rows of diminutive clouds parallel to each other. In another form it overspreads the whole sky Avith a thin, gauze-like appearance, through which the sun struggles with a feeble light. The cirro-cumulus presents a number of forms and shapes, and is sometimes very thin and fleecy, then in dense, well-rounded masses. They generally arise from a change in the cirrus and cirro-stratus, and then fall back into the same forms. This class of clouds, as well as the cirro-stra- tus, float at a lofty height, next to the cirrus. The cumido-stratus combines the features of the two classes after which it is named. Its base generally as- sumes the form of the stratus, while its summit resembles that of the cumulus. When a number of them assumins: large proportions are driven together by the winds, they presage the approach of a thunder-storm ; and are termed thunder-heads by the common people. The Latin term nimbus^ meaning dar'kj rainy ^ has been appropriated as the name for the rain-cloud. When first formed, it generally assumes a dark, threatening aspect, especially if the sun shines against it. This changes into a grayisli watery appearance when the rain begins to fall. It is formed from a combination of several of the clouds 80 AGKICULTURAL METEOROLOGY. described, having at first tiie fringed edges of the cumulus type. As they blend together and increase in density, they lose their simple forms and merge into the well-defined rain-cloud, so easily distinguished from all others. The morning rain-clouds generally come from the cumulo-stratus. The stratus clouds of the evening pre- vious are often seen lino-erino; around the horizon about sunrise, assuming the cumulo-stratus form, and tlien, be- coming thicker and darker, change to the nimbus, which soon precipitates in showers of rain. The afternoon show- ers, especially during summer, originate in vapors which rise from the heated lower strata of air, forming at first cumulus clouds, and then changing into nimbus. The study of clouds is of interest to the practical agri- culturist, as they indicate the approach of rain ; and he may often tell by their appearance a day or two in advance, what the changes in the weather are likely to be. Clouds are not simply useful as the harbingers of rain, but their shade often saves the tender plants from the burning sun, and prolongs their existence during the days of protracted drought. 53. Causes of Rain. There are several causes which operate in the conden- sation of vapor into drops of water, as mentioned by Prof Graham. 1. The ascent of the heated air from the earth, and consequent rarefaction, which produces cold. This is ob- served frequently on the summits of mountains, where clouds and mists appear to settle and remain stationary; the wind, passing over the plain below, strikes the moun- tain and ascends, producing the effect mentioned. 2. The mixing of hot and cold currents, both saturated with humidity, first demonstrated by Dr. Hutton, that two volumes of air thus mixing and attaining a mean tempera- ture are incapable of sustaining the same amount of vapor. CAUSES OF EAIX. 81 3. The contact of air in motion with the cold surface of the earth. This is the most usual cause of its coldness and condensation of vapors, and consequently precipitation of rain. To illustrate : the air being at a temperature of 34°, at Avhich it frequently stands in the winter-time even in this climate, a southwest wind setting in will cause it to rise 20° in 36 or 48 hours. Now this air, being probably satu- rated with humidity at 54° on its first arrival, mingling with the current at 34°, would produce a condensation of the vapors and precipitation of rain. Graham illustrates it thus : Tension of vapor at 54° 0.429 inch. 34° 0.214 Condensed 0.215 " The following illustration by Prof. Brocklesbey is to the point : " Four thousand cubic inches of air at the tem- perature of 86° F. can contain no more than 31-2- grains of moisture, and an equal volume at 32° only 7|- grains. Now if the two volumes are mingled together, their average temperature will be 59°, and the weight of moisture they unitedly possess will be 39f grains. But at this tempera- ture 31-2- gi'ains is all the moisture that 8,000 cubic inches of air can possibly retain ; since the first portion by its union with the second diminishes its capacity one-half, Avhile that of the latter is only doubled. The excess there- fore of grains will be condensed and descend in the form of water." This condition of things grows out of a law of nature by Avhich the capacity of the air for moisture increases at a faster rate than the temperatui-e : the latter advancing arithmetically, the former by geometrical progression. Rain will happen often er where the w^inds are variable and shifting, as they are the natural agents by which the combinations of cold and warm air are effected. Constant 4* 82 AGRICULTURAL METEOROLOGY. winds blowing for a long period over an atmosphere of uniform temperature, as the deserts of Sahara, will never bring rain, until they meet with some object, as the slope of a mountain, to change the current and mix the hot air with the cold. After a general fall of rain, the atmosphere is clear and unclouded, and comparatively free from watery vapor ; there is also less heat generated, and of course the temper- ature is cooler. When, however, evaporation begins to take place, the warmth of the air increases as well as its humidity. A cold and warm current of air meeting would only form clouds or fogs at first; but when the atmosphere becomes so full of humidity as to approach saturation, the overplus of the two currents would be converted into rain by their not being able to hold the same amount of mois- ture when combined, for reasons before stated. Vapors rising from the surface of the ocean, are con- densed in the upper and cooler regions of the atmosphere, and carried by the winds to different parts of the earth, being a prolific source of rain over the continents. The heated air which ascends at the equator especially, is satu- rated with moisture in passing over the Northern and Southern oceans ; and as it ascends higher and spreads over the temperate zones, and meets with colder currents of atmosphere, it is condensed and falls in extensive rains over vast sections of the earth. 54. Amoimt of Rain- fall at Different Stations, As air becomes more humid when its temperature in- creases, it is natural to infer that there would be more rain in the tropics than toward the poles. This is not merely theoretically true, but has been established by facts ; as the rain kept at seven stations beginning at Grenada, at IS'' north of the equator, and ending at Uleaburg, 65^ AMOUNT OF EAIX-FALL. 83 north latitude, showed a gradual falling off in the quantity. At the first station it was 126 inches, at the next 120, then 81, 39, 25, 15, and at the last 13| inches. Notwithstand- ing this uniformity, however, there are great differences in the same latitude owing to local causes. At San Luis, Maranham, 2° 30' south latitude, the annual fall of rain has reached as high as 280 inches. At Vera Cruz, Mexico, 278 inches fell in one year. The heaviest rainfall on record occurred at the Hima- laya mountains : 660 inches in one year. The average fall at Athens, Georgia, for five years, kept by Prof. McCay, was 37.53 inches ; while at Augusta during the same period it was 40.27 inches. This difference may be accounted for in part from the lower altitude of Augusta, being 160 feet above tidewater, and Athens 782. At Sparta, Georgia, 550 feet altitude, the average fall for five years, kept by the authoi', ending in 1869, was 57.49 inches. In 1868, the largest amount recorded in any one year, the rain-fall was 78.32, while the next year it was not half so much, being only 37.43 inches. The heaviest fall for one month was in August, 1867, being 17.15 inches. There seems to be two sliding scales for the year in this climate, one embracing the four crop months, of which August is the climax. Thus, the average fall for the five years at Sparta was for May 3.38 inches, June 3.52, July 4.29, August 7.04. There was also a regular scale for the eight cooler months, April being the climax, thus: Sep- tember 2.61, October 3.47, November 3.77, December 4.79, January 5.22, February 5.46, March 6.65, and April 7.54. Prof. Phillips found that a very moderate elevation would affect the fall of rain. Thus, on the top of York Minster, 242 feet high, the annual rain-fall was 15.910 inches. On the roof of the Museum, 73 feet in height, 20.461 inches. On the surface of the ground, 24.401 inches. This would seem to indicate that rain is produced mostly 84 AGKICULTUK AL M ETE OROLOG Y. by the last cause mentioned : viz. that the strata of air near the ground being more rapidly cooled could deposit more humidity. 55. The Rain Gauge, The Rain Gauge, or Pluviometer, is the instrument used for measuring rain. Any vessel Avith perpendicular sides, set out in an open sj^ace where the rain might fall into it would indicate the amount by measuring its depth with a rule. But this would not be an exact method, es|)ecially for small showers. In order to do this, we have a cylindrical zinc funnel, which is set out in the open weather, day and night, and catches all the rain that falls, conveying it into a vessel beneath. After a rain, the water thus caught is poured into a graduated glass tube several feet long and several inches in diameter, which has been graded to the circum- ference of the zinc funnel. When the water rises to 100 on this graduated tube it indicates one inch, so that the one- hundredth of an inch can be easily estimated by it. liegular observations kejDt by this instrument in a given locality may be made very useful in practical fjirming. It is difficult always to tell whether rain enough has fallen upon the crop from mere observation. This instrument gives the amount with mathematical precision, and, other things being equal, will indicate whether a sufficient quan- tity has fallen for a good season. This, how^ever, is very variable, one crop requiring more than another, and so of different classes of soils. Much less rain also will answer, when it falls at night or late in the evening, than during the morning or at noon, when the hot sun shines down upon it, producing rapid evaporation. Rains that fall at night cannot be w^ell estimated as to their amount; and yet much depends ujDon knowing this fact as indicative of the proper work of the day, Avhether to plough or hoe, or engage in other work : with the rain gauge, this fact is easily ascertained. SOURCES OF HAIN, 85 From observations made during a series of years, vre found that a half inch of rain will suffice for cotton when it begins to suffer, while corn requires three-fourths to an inch, and sv/eet potatoes still more than this. Land that has been subsoiled, needs much less rain than common plough land, and its effects will last longer by the rising of capillary water through the porous subsoil. Observations of the rain-fall and other meteorological phenomena compared with the crop production, would form a pleasant recreation to the agriculturist, and kept for a series of years, would not only prove of benefit to himself and his section, but add sometlnng to the progress of agricultural science. 56. Sources of JRain, Most of the heavy summer rains which fall in the Cotton States are doubtless generated by the heated waters of the Gulf of Mexico, which always contain so much heat that tliey give off an immense amount of vapor, which spreads for many miles over the continent. Thus, when a southerly wind sets in and blows for 36 or 48 hours, we are almost sure to have rain. It is different, however, with our Avinter rains, owing to the difference in the temperature between the land and ocean. In cold weather they are more general, lasting frequently for several days, and extending over a large scope of country. They are mostly from the east, showing that they originate from the Atlantic Ocean. In summer, the Gulf of Mexico condenses moisture much more rapidly than the ocean, owing to the greater heat of the air above it; while in winter, the land being generally colder than the water, there is no cause for southerly winds or rains from that quarter. The colder atmosphere of the ISTorth Atlantic and Avarmer waters of the Gulf, mingling on our coast, produce condensation 86 AGEICULTUPvAL METEOEOLOGY. and rain, and as the atmosphere becomes colder than that of the land, easterly winds set in, and drift the rain clouds over the continent. CHAPTEE IV. OF ELECTRICITY. SUNLIGHT. AIR IN MOTION. LUNAR INFLUENCE. 57. Electricity. Electricity at one time was thought to be greatly instrumental in the germination of seeds and the growth of plants. The old idea that turnips sown at particular changes of the moon would do better than at other times, has been accounted for on the supposed electrical condition of the moon and earth at those particular phases. It is known that nitric acid is produced during thun- der-storms by electricity, and believed to form a nitrate with the amm-onia of the atmosphere, which falling to the earth either with the rain water or by its own gravitation, aids to a small extent the growing summer crops. Ozone, also believed to be a powerful agent in vegetable germina- tion especially, is generated by electricity. Davy found that corn sprouted much more rapidly in w^ater positively electrified by the voltaic instrument, than when in a negative state. As water, when evaporated from the earth, as well as condensed into rain, becomes posi- tively electrified, it is probable that this condition is one reason why rain water is so much better a fertilizer tlian fountain water. From experiments of Pouillet, it appears that when seeds first sprout, plants become positively electrified, leaving the earth in a negative state. The same results SUXLIGHT. 87 might possibly occur during the growth of the plant. It is well known that the vegetable kingdom suj)plies the air with a large amount of electricity. It rises with the carbonic acid which exhales daring the night from all grow- ing plants. M. Becquerel, the elder, states that the atmosphere and earth are constantly in two dissimilar states of elec- tricity ; the former having an excess of positive electricity, the latter of negative. These two excesses becoming neutralized by means of the conducting substances found at the surface of the earth, especially plants; colored vegetable tissues are affected by electrical discharges in a peculiar manner, producing three distinct actions upon the colors of leaves and flowers of plants: First, the color- ing matters, which are in a state of solution in the cellules are easily absorbed or filtered in cold water after being electrized. This is particularly true of red and blue colors. Second, when the electrization is prolonged a dis- coloring action is produced on those colors in the plant. Third, infiltration, or a transfer of the coloring matter takes place under the preceding influences. It would thus seem that electricity has much to do with colorization in plants, which, as is well known, is closely connected with their health and growth. 58. Sunlight, The influence of light upon vegetation is a fact well known for centuries. Plants growing in the shade, under trees or in inverted vessels, are recognized by the most careless observer as being inferior in general appearance, more diminutive, and of a lighter green color than others. In fact, some plants cannot long survive without direct sunlight. In 1873 we fixed a movable cover with three planks, and placed it over a section of a row of cotton, after it had 88 AGRICULTURAL METEOROLOGY. begun to leaf, so as to exclude from it the direct rays of the sun. It was not removed for three weeks, except to receive, in common with the other plants, the showers of rain. It began at once to weaken and shrivel up, and soon ceased to grow, and one after another the leaves died and fell off the stalks, and at the end of the time above speci- fied every plant was literally dead. Ingenhouz and Sennebier found that seeds germinate quicker in the absence of light. Bertholin attributed this to deficient moisture, as sunlight would cause it to evapo- rate. Sennebier, however, conducted some exact experi- ments, adding more moisture to the plants in sunlight, and arrived at the same conclusion as before. Saussure contended that the heat associated with the light retarded germination, and when this was obstructed, light had no appreciable influence over germination. This seems now to be the conclusion of modern scientists. Late experiments appear to establish the fact that it is necessary to exclude seeds from the luminous rays of the solar spectrum in order for their healthy germination ; while the chemical or actinic rays are indispensable to the process. As these latter penetrate much deeper into the soil than the luminous rays, both of these ends may be ob- tained by planting seed a proper depth in the earth. Seeds then do not fail to grow when buried too deeply, for the lack of oxygen simply, but also because of the exclusion of the chemical rays. Solar light affects the direction of plant growth. If you place plants in a window they instinctively turn to the light, and seem to grow more rapidly in ihat direction, as if they received more nourishment from that source. Knight observed that branches of trees shaded by others did not flourish like those enjoying more sunlight. This may be seen in roads passing through forests ; the limbs of the trees extending over the road are much more vigorous, AIR IN MOTION". 89 and grow larger than those on the forest side. In some instances, as the ivy and mistletoe, they turn from the light. The young stems of nasturtium incline to it, the old ones turn from it. Priestley first investigated the chemical action of sun- light on vegetation. It is now very satisfactorily ascer- tained by chemists that carbonic acid gas, being absorbed from the atmosphere by the leaves, is decomposed by sun- light, the oxygen emitted, and the carbon appropriated to the building up the structure of the plant. More of this hereafter. 59. Air in Motion. It is proper to say someting of the icind^ air in motion^ as it in several ways comes within the scope of agricul- tural meteorology. Anything which disturbs the repose of the atmosphere, as the fall of an avalanche, may be con- sidered a cause of wind. A change of temperature, and by consequence of density, is the usual cause. Rarefication of atmosphere, produced by heat, will cause the contiguous column of cooler air to flow into the rarefied column, and thus wind is induced. The old theory that magnetism and electricity were the principal causes of the currents has been exploded. The latter has doubtless something to do with them, but, accord- ing to Prof. Henry, is more a consequence than a cause. It has been well established that terrestrial magnetism does not afi*ect materially meteorological phenomena. The air, not being naturally magnetic, of course could not de- velop that power until magnetized. ' The true theory of the currents of wind, as first estab- lished by Prof. Espy, is that they are owing to the amount of heat generated by the condensation of vapor into rain. This process in the equatorial regions evolves an astonish- I ing power in the form of heat, as the vapor condenses and ^ ascends. The impulse given by the solar rays to the 90 AGRICULTURAL METEOROI-OGY. atmosphere is the remote cause of its agitation. These doubtless produce, through secondary causes, the moving currents, from the gentle breeze to the violent storm. From data well substantiated by experiments, it has been proven that every cubic foot of rain which falls on the surface of the earth, leaves in the air Avhen it descends heat enough to produce an expansion of at least 6,000 cubic feet in the space of the surrounding atmosphere, beyond that occupied by the vapor itself. (Henry.) Counter currents are constantly going on in nature on a large scale, like those illustrated by Franklin between a cold and warm room. A door opened between them will show by a lighted candle that the current flows into the warm room from below, and out of it from above. Thus we frequently see clouds blown by currents above, directly oj)posite to the wind on the surface of the earth. The velocity of the wind is estimated by an instrument called the anemometer. It is simply a small windmill, to which is attached an index, by which the number of revo- lutions per minute is noted. It may be graduated thus : One of these instruments taken on a still day on a raih'oad car going at the rate of twenty miles an hour, and the number of revolutions counted and divided by 60, will give its velocity per minute. The higher aerial currents may be estimated by the speed with which the shadow of a cloud passes over the earth's surface. Winds may be properly divided into three classes : con- stant, periodical, and variable. The trade loiiid is the most remarkable instance of the first class. The monsoons and sea breezes are periodical winds. Northwestern winds generally indicate clear weather ; southern and southwest- ern, foul weather. Easterly winds are generally damp and not good for invalids. They prevail mostly in the fall and winter, and are accompanied with long spells of rain. Gen- erally when the wind-vane settles due north, a calm ensues. LUNAR INFLUENCE. Winds veer from north to east, south, and west : very rarely do they ever change in a westerly direction. Cold winds in the spring-time are very damaging to young cotton and other plants ; and during the summer, crops are seriously injured by being twirled about by vio- lent gusts of w^ind. In autumn much cotton is destroyed by being blown out when open, daring rain-storms. Winds, however, have their agricultural uses: they enable the far- mer to plough much sooner after long spells of rain, pre- vent killing frosts of cold nights, and add to the health, vigor, and muscular power of laborers during our long, hot summers. Winds also prevent the settling of pestiferous vapors in cities and around habitations, wdiich would be a con- tinued source of the most malignant diseases. The car- bonic oxides are deadly poisons, and are being constantly generated from the decay of animal and vegetable sub- stances, and, as they are heavier than the atmosphere, tend to settle near the earth during calm spells of weather. The winds dissipate them, and j^i'event disease and death. 60. Lunar Influence. The influence of the moon upon the germination of seeds and growth of plants has been believed for ages past. If it has such a powerful attraction for the waters of the ocean at certain phases, as to produce the tides, might it not be potent in other respects ? And as it is clearly established that the direct rays of the sun have such a powerful eiFect on vegetation, as that some plants cease to grow, and die without them, might not the reflected light of the moon have a similar though modified effect ? It is probable that exact experiments would show that the electrical conditions of the moon at certain periods, as well as its increased light when at its full and its decrease when in the wane, ]iave a marked effect on vegetation, I 92 AGRICULTURAL METEOROLOGY. As to lunar influence upon the weather, although many observations have been taken, no satisfactory conclusions have been reached. Experiments made in England by Dr. Laycock as to the amount of rain-fall at different phases of the moon, show but little if any difference. We instituted similar experiments for a number of months in Sparta, Georgia, with like results. The amount of rain at new and full moons, at each of the quarters as well as the intermediate days, was very nearly the same. For ten years, at Montpellier, in France, there were nine rainy days in the growing to eleven in the waning moon. At Munich, in Germany, this was reversed ; the number of rainy days on its increase being 845, against 696 on its decrease ; showing that local causes have more to do with rain than lunar influence. From March, 1873, to April, 1 874, at this experimental station (Athens, Georgia), there were 55 rainy days on the increase, and 50 on the decrease of the moon. The amount of rain, however, which fell on the decrease was more than double the other, being 30.16 inches against 14.71. It is to be regretted that other exi:>e- rimenters did not note the amount of rain as well as the rainy days. It has long been a popular belief that the full moon in April of each year was hazardous to vegetation because of frost. Herschel and others held that the full moon generally brings cool weather with it. This has been accounted for by scientists ui3on the fact, that at the full moon the earth receives not only the sun's heat, but the reflected heat of the moon also; and as it is known that the more heat existing in the atmosphere the greater the capacity for its absorption, it is reasonable to infer that the vapor would be dissipated, and the skies rendered clearer at the full than at other phases of the moon. Clear and calm nights, then, are apt to bring cool mornings during the spring-time, and hence frost is dreaded by gardeners LUNAR INFLUENCE. 93 and fruit-growers about the full moon in April, as the last one that could possibly bring cool weather with it. M. P. Charbonnier noticed the increased growth of cryptogamic vegetation on the sides of an aquarium dur- ing the time of full moon : it being much more luxuriant than at the new moon. Other observations being made, it was found that aquatic vegetation was affected favorably under the influence of lunar light. PAET IIL SOILS AS RELATED TO PHYSICS. CHAPTER L the earth. — the rocks. geology of georgia. formatio^nt of soils. 61. The Earth, The science which treats of the earth is called Geology. This relates to its physical form and what it contains, as loam, sand, clay, bowlders, solid rocks, and the fossils imbedded in them. It also teaches much of the earth's history, of its soils and minerals, and their utility to man. Many of its speculations are, however, dubious, and its chronological data uncertain and unreliable. Its well- established facts corroborate, in a remarkable degree, the divine record in the first chapter of Genesis. One-fourth of the earth is solid land, containing about 52,500,000 square miles. About three-fourths of this lies north of the equator, which has been called the Land Hemi- sphere, as the other has been termed the Water Hemi- sphere. The surface of the earth has been divided into loidands ov plains^ which rise less than 1,000 feet above the level of the sea ; and plateaus or table lanch^ which rise above these another thousand feet ; and mountains^ whose altitude varies from 2,000 to 29,000 feet, the height of Mount Everest, the tallest peak of the Himalayas. THE ROCKS. 95 The mean height of the land surface of the earth is is about 1,000 feet ; the mean depth of the ocean about 15,000 feet. The highest mountains generally lie nearest the deepest oceans, leaving the continents basin-shaped. In proportion to the two bodies, an orange is much rougher than the earth. The highest mountain is as 1 to 1,600, or the thickness of one sheet of paper to 1,600 sheets. The temperature of the earth is not uniform. The sun affects it about the depth of 100 feet. For every 50 feet below that the temperature rises about one degree. This would reduce the whole of the interior of the earth to a molten fluid, leaving a crust of some 50 miles in thickness, but for counteracting agencies. Recently Prof. Le Conte has announced an opinion that the whole theory of geology must be reconstructed upon the basis of a solid earth. 62. The Books. The rocks which compose the earth are divided into two great classes, the stratified and unstratified. Stratified rocks exist in layers and strata, and are termed aqueous^ because they are believed to have origi- nated in the settling of sediment at the bottom of rivers and oceans. Unstratified rocks are not in layers, but massive, reg- ular, irregular, or crystalline, according to the minerals of which they are composed. They are called also igneous^ as they appear to have resulted from the cooling of molten matter. The Primary or lowest rocks, called Plutonian, doubt- less originated from fire, and existed long before the crea- tion of organized matter, animal or vegetable. By far the larger portion of the rocks have evidently been dissolved and stratified by the action of water. The oldest of these (though more recent than the igneous) have 96 SOILS AS RELATED TO PHYSICS. 110 fossils, and doubtless constituted that long chaotic period, when "the earth was without form, and void (empty of inhabitants), and darkness dw^elt upon the face of the deep." lletamorphic rocks are those which have apparently been acted on by both fire and water. Unstratified rocks maybe classed as Granite, Syenite, Greenstone, Basalt, Trachyte, Amygdaloid, and modern Lavas. Stratified rocks, as Gneiss, Mica Slate, Clay Slate, Hornblende Slate, Talcose Slate, Quartz Rock, Sandstone, Conglomerate, and Limestone. The most common of these rocks are Granite, Gneiss, Mica Slate, Clay Slate, Quartz Rock, Sandstones, and Lime- stones. The principal minerals entering into them are Quartz, Mica, Feldspar, Oxide of Iron, Carbonate of Lime, Talc, Hornblende, Tourmaline, and Epidote. Most soils are composed of the disintegration of rocks w^hich underlie them. The earth was probably at one time a molten mass, and when cooled, a solid rock without soil. But by chemical agencies put into action by the great Architect of the Universe, the rocks were disinte- grated and rendered soluble, and fitted for vegetable life. The character of a soil may generally be determined by the rocks which underlie it. Thus, if lime rocks crop out, the soil is calcareous ; if quartz predominate, it is silicious, and so on. There are exceptions to this rule, however, as the coal-fields of some countries, and most alluvial soils ; especially the deltas of large rivers, w^hich are composed of the debris of the different soils through which they flow. The depth of soils on the surface of the rocks varies from one inch to two hundred feet. Their average depth on mountains and high lands is much below that on plains GEOLOGY OF GEORGIA. 97 and in valleys. After a certain de^Dtli the solid rock is always found, which crops ont in contiguous places, con- stituting mines, quarries, and clilTs. 63. Geology of Georgia, The geology of the State of Georgia may be stated thus : In the extreme northwestern counties, extending as low down as the Allatoona Mountain, we have the older fos- siliferous rocks, in w^hich are the petrified remains of species of shell-fish long since extinct, showing that coral reefs once existed in these now elevated regions, which w^ere then the bottom of the ocean. In this same region the carhonifer- ous system crops out to a small extent. Here coal-beds exist. Then comes the Primary region, extending from the Tennessee line down the Savannah River to Augusta, thence southwest to Columbus. Thence up the Chattahoochee River to near Cedartow^n, and easterly to Canton and north- erly to the junction of the Tennessee and North Carolina line. The north v>^estern belt of this extensive system con- stitutes the Gold region, and a narrow strip running south- Avesterly through Habersham, Hall, and Gwinnett counties, forms the elastic sandstone (itacolumite), which is regarded as the matrix of the diamond. All this vast region is Primart, except a few spots in Gilmer, Hall, and Habersham counties, where the blue limestone crops out, and very good marble has been quar- ried. Most of this region is underlaid by stratified rocks, as micaceous, fel spathic, and syenite gneiss, and talcose and hornblende schist. Granite ledges, which are unstra- tified and crystalline, crop out on the lower border in Hancock and other counties, and again in De Kalb, as presented in the majestic Stone Mountain. The Cretaceous system embraces several counties and parts of counties, forming a triangle between Columbus 5 98 SOILS AS RELATED TO PHYSICS. and Knoxville, and the mouth of Pataula Creek on the Chattahoochee River, several miles above Fort Gaines. Again it occurs in a small place near Sandersville, where clypeasters and shark's teeth are found. All the lower portion of the State not described belongs to the Tertiary system, and presents some interesting fea- tures as to its fossils. The rocks are mainly sandstones, with rotten limestone, silicified shells and buhrstone, which makes good millstones for grinding corn. The soil is silicious, and in some places marly ; not rich in potash like the middle belt, except in sections which have a clay sub- stratum. This really constitutes some of the best cotton lands in the State. Yast sections (embracing a number of counties in this region generally known as the wire-grass), are composed of a silicious soil deficient in important elements and covered in many j^laces by stunted pines. Generally in this Tertiary region, the lands are valu- able where the pines are large; as the spines of these trees abound in potash, which has been brought up as the work of ages, by their tap roots from the subsoil beneath, and spread upon tlie surface to form a rich loam, as they accumulate and decay. The underlying rocks in this section are devoid of potash ; hence this substance must have come from the Primary region above, and the organic remains of the marine animals which inhabited the vast Eocene sea once covering it. 64. Disintegration. The term waste has been applied by chemists to the effects of mechanical forces upon rocks, as that oi disinte- gration is said to denote chemical action. Disintegration is effected by oxygen, carbonic acid, and water. It is a gradual but effective process. Perhaps in the lifetime of an individual but little is accomplished. MECHANICAL ACTION, OR WASTE. 99 yet what poets call the " tooth of time" will eat its way in the lapse of ages. Protoxide of iron is an ingredient of many of the com- mon rocks, as basalt and clay slate ; and having a great tendency to absorb oxygen from the atmosphere and be- come converted into a higher oxide known as the per- oxide, by this process the^e rocks are gradually broken down and become converted into rich ferruginous soils. And this is true to a limited extent of other minerals, as their ingredients are susceptible of entering into union with oxygen. Thus the metallic sulphurets are gradually converted into sulphates. The decomposition of silica from its alkaline bases is effected by the action of carbonic acid and water, and in this way many rocks as (felspar, containing silicate of pot- ash) are broken down and converted into soil. Large beds of porcelain clay (decomposed felspar), Avhich are found on the line of the Primary and Tertiary formations of South Carolina and Georgia, have been thus disintegrated and mingled with the soil. Water seems to be essential to the proper action both of oxygen and carbonic acid in the decomposition of rocks, although it is difficult to say exactly what that action is. The influence of these three agents upon rocks is clearly seen in the silver mines of South America, which led to their discovery by huntsmen and herdsmen. This metal, being invulnerable to these agencies, while the rocks associated with it have been dissolved away, stands out in tooth-like proportions in many instances from the surface of the boAvlders and jutting cliffs. 65. Mechanical Action^ or Waste. Mechanical as well as chemical forces are constantly at work in breaking dowui the rocks and forming soils. Rocks are thus worn by glaciers, snow-drifts, and i"ain- 100 SOILS AS RELATED TO PHYSICS. Storms; and immense beds of their debris are formed in the bottoms of rivers, to be washed out by the floods, forming rich alluvial lands. Extremes of heat and cold, the alternate freezing and thawing of water, have in many cases much to do with these processes. Dense limestone is sometimes acted on by the frost of a single night so effectually as to render turbid the waters that wash over it the next day. Prof. Agassiz supposes that glaciers of ice have done more to grind the rocks to pieces, and thus prepare the soil for vegetation, than every other agency put together. The stones and rocks ground and polished by the glaciers are easily distinguishable from those scratched by running water. The angular bowlders found in meadows and ter- race of rivers not reached by water can be accounted for only in this way. CHAPTER 11. CLASSIFICATION OF SOILS, GEOLOGICAL AND AGRICULTURAL. 66. Geo log ical Div Ision of So Us. The geological division of soils embraces the Sedentary and Transported. Sedentary soils are those which are supposed to remain in situ^ having never been removed by geological agencies. The rocks which underlie them give a good idea of their composition and agricultural value. This class of soils usually has but little depth. Most of the soils of Middle Georgia are of this character. Transported soils are those which have been drifted by glaciers or floods from their original position, and de- posited as sediment. These have again been divided into Drift, iVUuvial, and CoUuvial soils. AGRICULTURAL DIVISION OF SOILS. 101 Drift soils are generally without stratification, and have fragments of rocks rounded by friction, of all sizes from small pebbles to large rounded bowlders. Geologists believe that these drift soils were formed during what they term the Glacial Epoch, by moving bodies of ice. There are many evidences of drift soil in the counties bordering on the Primary and Tertiary regions of this State. Alluvial soils are simply the deposits of running waters, rivers, and tides. They are more or less stratified, and have no large masses of rocks, as currents of water cannot move them any great distance. These deposits are formed in every land and during every period. Valleys contain them drifted down from mountains and hills. Lakes and gulfs and sometimes seas are filled with silt by the attrition oi' ages, and recede, leaving alluvial deposits. The lowlands and deltas of all rivers and running streams are constantly forming them by freshets and floods. Colluvial soils consist of both drift and alluvium, have sharp angular fragments of rocks, and seem to have been transported bu,t a small distance from their original posi- tion, if not formed in place. 67. Agricultural Division of Soils, Soils are classified agriculturally, according to the pre- ponderance of certain substances. Thus, w^here silica pre- vails, it is called a sandy soil ; where alumina abounds, it is a clay soil ; the preponderance of lime gives calcareous and mar/y soils ; of organic matter, a vegetable mould ; and where there is a due admixture of all, a loamy soil. The upper crust of the soil, varying from an inch to six or eight inches in depth, is called the surface soil, or tiltJi^ wRich is stirred by the plough, and acted upon directly by the chemical agencies of the atmosphere. Here seeds germinate and plants send out their roots in search o\ 102 SOILS AS RELATED TO PHYSICS. food, and here they decay and blacken the soil, being con- verted into humus. The subsoil is the stratum immediately beneath the surface soil, or, in a more extended sense, all that underly- ing portion of the soil down to the solid rock upon which it rests. Tap-rooted trees and plants receive much of their nourishment from this substratum, in some instances for many feet below the surface. 68. Silicious Soils. Sandy or silicious soils contain from 70 to 90 per cent, of sand. They are light and porous, not retentive of mois- ture, and by consequence suffer quickly from a drought. They do not, however, possess much of the fertilizing elements, are more easily exhausted of them, hence wear out much sooner; and when soluble fertilizers are applied to them, they leach out more readily by the heavy spring rains. They are much more friable, permeable to water, and easier to cultivate than clay soils. Deep ploughing is much easier achieved, and wider ploughs may be used, so that one mule can cultivate many more acres of land, and, on soils equally fertile, with more profit. The only way to permanently improve such soils is to add clay to them, which will not pay in this country, where lands are so cheap. This, however, is common in Europe, as is also the application of liquid manures to this class of lands, which is said to pay well. 69. Clay Soils, Clay soils are cold and dense, and termed " heavy " because they require much more labor, strength, and mo^ey to cultivate them successfully than other soils. Up to a certain percentage the retentive quality of clay for moisture is a great benefit. By this quality water is held and let off slowly to plants in dry weather, and CALCAREOUS SOILS. 103 ammonia and other salts retained for future use. Too much clay, however, renders the soil so compact and re- tentive of water as to submerge the roots and cause ob- struction to nutrition, as well as to prevent proper aeration. Such soils require much labor to j^lough, and are apt to break up in clods. All soils which have a pij^e-clay substratum are of this class, and in this country are generally laid aside as un- productive. Cotton will always rust upon them, from the inability of the tap root to penetrate and find proper nour- ishment, and corn will take the " yellows," as farmers say, from the superincumbent moisture. The most effectual remedy is drainage, which costs too much for our cheap lands. Burning and liming are also used to advantage in the old countries, where it will pay to reclaim such soils. When reclaimed they are among the most fertile of all soils, and will last longer than others, from the quantity of potash and other mineral food with which they abound. 70. Calcareous Soils, Calcareous or lime soils exist extensively in many sec- tions of Europe and the United States, but are not very prevalent in the South. All soils containing twenty per cent, and more of car- bonate of lime are classed as calcareous. This embraces every degree of fertility, from the character of the rocks from which they originate. The great majority are classed as thin, poor soils, while those resting on the lower chalk formation are said to be quite fertile. Lime soils are light and easy to work, and are particularly adapted to clover, peas, and other leguminous crops. Marly soils consist of a due admixture of clay and lime, and their qualities are intermediate between the two — having from five to twenty per centum of lime. They are 104 SOILS A3 RELATED TO PHYSICS. generally quite fertile, owing to the fact that they have, in addition to other mineral substances, more than a usual quantum of phosphoric acid. There are besides clay marls, chalk marls and sandy marls. They are used with good effects as manures on other classes of soils. 71. Vegetable Moulds, Vegetable moulds embrace soils which have a large quantity of organic matter, either as humus or in some other form. Garden soils and fresh forest lands are in- cluded in this variety— the organic matter existing from five to ten per cent. These are classed as among the most fertile of soils. Peaty or boggy soils contain frequently a much larger amount of vegetable matter, sometimes as high as seventy per cent. This renders it unproductive, owing to the gen- eration of acids and the absence of soluble plant-food. Burning and liming is the proper treatment for the reduc- tion of such soils. But while an overplus of vegetable matter becomes injurious, a certain percentage is always requisite to make a fertile soil: as not only does it add to the physical im- provement of most soils by the admission of air and the retention of moisture, but the decomposition of vegetable debris constantly going on, keeps on hand a rich supply of soluble food for plants. Loamy soils consist of a mixture of sand, clay, lime, and organic matter, and they rank in fertility next to the fertile vegetable moulds. They are subdivided into clay loams, sandy loams, etc. They combine most of the ad- vantages of every other class of soil, without their dis- advantages, being sufficiently retentive of moisture, with- out too much coldness — having enough clay to absorb and retain valuable manures, and enough sand and organic matter to make the land friable and cultivation easy. WEIGHT OF SOILS. 105 Some soils are termed ferruginous^ in which iron ahounds, as oxides or silicates. They are brown, red, or yellowish in color. Gravelly soils are termed so from the number of small stones they contain. Soils of this character, however rich in mineral food, are generally infertile, from their coarse- ness and difficult assimilation. CHAPTER III. PHYSICAL QUALITIES OF SOILS. 72. As Distinguished from ChemicaL The soil is possessed of both physical and chemical pro- perties. Its physical properties are very important, though subordinate to the chemical. They relate simply to the mechanical condition and arrangement of the visible par- ticles of the soil, to each other, to air, Avater, temperature, and gravitation. A deficiency in physical properties will retard vegetable growth and minify the product of a soil, but still perfect plants are produced. A deficiency in chem- ical properties is fatal to the very existence of vegetation. 73. Weight of Soils. Different kinds of soils vary in weight. A cubic foot of dry earth of diflferent kinds, according to Schubler, will weigh as follows : Silicious or Calcareous earth. . . 110 lbs. Half clay and half sand 95 " Common arable land 80 to 90 " Pure agricultural clay 75 " Rich garden mould 70 " Peaty soil 30 to 50 " Sandy soils will weigh something over 4,000,000 lbs. 106 SOILS AS RELATED TO PHYSICS. per acre, a foot in depth. Clay soils less this. An average of arable loamy soil will be about 4,000,000 lbs. Sandy soils are termed ^' light" because of their lack of adhesive qualities, yielding readily before the plough ; and clay soils heavy " because of their adhesive qualities and resistance to the plough. They are lighter than any exce23t> vegetable moulds. These are light in both senses. Sandy soils being so much heavier than clay soils, having an equal percentage of nutritive elements, would have a more fertile tilth, because a greater number of pounds of soil in the same depth. The porosity of a soil has much to do with its weight. When thd air is excluded, all soils, except those abound- ing in humus, have nearly the same density. The specific gravity of a soil is its weight in bulk, com- pared to the same bulk of water. A cubic foot of water weighs 62|- lbs. The weight of soils above given does not apply to solid soils, but relates to soils in a natural state, including the atmospheric air in their interspaces. 74. Absorptive Power of Soils for Gases, Not only do certain soils have the power of absorbing, but at the same time of condensing gases into smaller spaces. This power is called the force of adhesion. Charcoal affords a good illustration of this force, ab- sorbing ninety times its bulk of ammonia. Experiments of Reichardt and Blumtritt show that 100 grains of moist garden soil yielded 14 cubic centimetres of gas, while the air-dried yielded 38. Nitrogen is nearly always absorbed in greater proportion than oxygen by soils, and is greatly condensed in some cases. A fine dry soil will completely absorb all the offensive matters of human ordure, as in the case of the earth closet now" in use among many families. Nothing but an earthy amnioniacal smell appears to result from its decomposition. POWER TO REMOVE SALTS FROM SOLUTIONS. 107 It is now admitted by chemists, that but little volatile matters escape even from dung scattered over the surface of the earth, so powerful is its absorbing power on these gases. Some soils possess this power much more than others ; as those abounding in clay and humus, while sandy soils have it only in proportion to the percentage of these substances present. From a series of experiments instituted by Reichardt, the following conclusions have been reached as to. the power of soils to absorb gases : 1. Clay purified by hydrochloric acid and dried at a temperature of 212^, absorbs carbonic acid very slightly when compared with that which contains hydrated oxide of iron. 2. Sand treated in the same manner absorbs only slight traces of carbonic acid ; and so of mixtures of clay and sand in a dry condition : but much larger quantities when in a moist condition. Moisture favors the absorption of nitrogen rather than oxygen. Soils lose what they absorb when exposed to the sun, and gradually regain it again in the shade. The amount absorbed is very small, however, in all the soils tried, except that containing hydrated oxide of iron, which seems to add much to the absorptive power. The amount of carbonic acid in a soil also corresponds to its per centum of this oxide. The action of the sun's heat is to drive out a large part of the carbonic acid existing in all soils, especially when moist. The amount of car- bonic acid is less of an evening, owing to the elFects of the sun, and more of a morning, as the soil regains it during the night. 75. Poirer to JRemove Salts fro^n Solutions, The power of soils to remove salts from their solutions is a remarkable quality, possessed especially by simple 108 SOILS Aa RELATED TO PHYSICS. sand. Lord Bacon referred to this power, known even in his day, in which holes dug in the sand on the sea-shore, at low tide, would have pure fresh water at high tide flow into them. Dr. Stephen Hales also mentions, that sea water may be made pure by filtering through stone cisterns ; the first being quite free from brackishness, and then becoming gradually as salt as usual. Berzelius found the same thing true in filtering salt water through sand ; and Matteuci found similar results in experimenting with other salts. Thus, while sandy soils are very deficient in the power to absorb and hold water and gases, they are compensated somewhat for its loss by possessing the power to remove solid saline substances from solutions, which otherwise would be wholly lost to them by drenching rains. Heiden also found a similar quality to be possessed by humus. Solutions of chloride of potassium and ammonium, when brought into contact with peat, were thus deprived of a portion of these salts and made perceptibly weaker. Schumacher also found that prepared humus made of sugar absorbed about two per cent, of sulphate of soda and ammonia, about four of sulphate of potash, and ten of i:)hosphate of soda. He also found that humic acid, satu- rated with sulphate of ammonia, would be replaced by sul- phate of soda. Free water would readily dissolve the salts of the humic acid. Clay and humus possess this power in a remarkable degree as to ammonia, phosphoric acid, and certain nutrient salts which are very soluble in water. It seems that the finer constituents of the soil possess this property, partly by capillary attraction and partly by chemical transmission and exchange, by which they are rendered less soluble in water, but only so much so that they can only be extracted again, very slowly, by the long- continued a''-tion of water. ADHESIVENESS OF SOILS. 109 On this principle putrescent and offensive liquids are taken up when filtered through a soil, especially clay and huraus soils, which lose their fertility more slowly than sandy soils. This may be easily demonstrated by. filling a jar or bottle, having a small hole in the bottom, with fine river sand or garden earth: pour in a strong lye, made by the solution of stable manure in water, which is very high colored and quite offensive to the smell at first ; it will trickle out below perfectly purified and sweet, having left all of its offensive matters in the soil contained in the jar. 76. Adhesiveness of Soils, The adhesiveness of a soil depends to a considerable extent on its dryness. Thus vegetable moulds and sili- cious and calcareous soils have very little adhesiveness when dry, but considerable when in a moist state. A clay soil, when thoroughly dried and pulverized, has but little adhesive power, and scarcely more resistance to the plough than a sandy soil. When saturated with water it runs together, and becomes very hard and heavy after drying off. It is difticult to plough, and breaks up in lumps, requiring repeated harrowings to have it properly pulverized for the planting of seed. Particularly is this the case when ploughed too soon after a rain. The effect of subsoiling on such lands, seemingly important, will last but a short time. In Europe, where every class of soil is worked, they use thorough drainage, deep tillage, and the application of sand, with advantage. The same purpose is accomplished, and more effectually, by burning, as practised in England, which is said to cause the clay to lose permanently its tenacious quality. Liming and the incorporation of vege- table matter also have a good effect on this class of soils. The freezing and thawing of water in the soil in cold climates has a fine effect in separating the particles and 110 SOILS AS BELATED TO PHYSICS. overcoming its adhesiveness. As water expands when it solidifies, a great jDower is thus brought to bear upon it. Schubler estimated that immediately after the frost disappears from lands in spring-time, there is one-third less resistance in clay loams than previously. One advantage of fall ploughing is that the frosts of winter have a better effect in pulverizing soils, by which, also, more nutrition is secured to plants in soluble forms. The absorbing power of the soil seems to be in direct proportion to its adhesiveness. Sandy soils, possessing this quality in a less degree than dry soils, do not hold nutri- ent salts so tenaciously; hence practical agriculturists have learned to apply soluble manure in smaller quantities and more frequently to such lands, as it will not pay to apply them in large quantities, as upon more tenacious soils. 77. Divisibility of Soils, The divisibility of a soil, or its capability of being divided into coarser or finer particles, is a very imj)ortant quality. All fertile soils have a large percentage in an extremely fine condition. This not only causes a much greater surface to be exposed to the fibrils of the plant, but also to solvents both of the atmosphere and soil, by which a much larger amount of soluble food may be prepared. There are exceptions to this rule, where soils of a cemented structure may become too compact from their extreme fineness. In coarse, gravelly soils, soluble food must be added in order to insure anything like remunerative crops. Land buyers have learned the unproductiveness of this class of soils, and always avoid them. The importance of comparative divisibility in soils may be illustrated by a block of granite on which mosses and lichens will grow. Broken up into coarse gravel, a higher order of weeds will spring up and grow ; and reduced to a fine dust, the cereals and finer plants will flourish in it. TEMPEEATURE OF SOILS. Ill YS. Shr inking of Soils. The shrinking of soils, effected by their becoming dry after heavy rains, as well as by frost, thus changing their bulk, is a matter of much practical import. This also pertains mostly to clay soils. Thus constant changes are going on ; they expand when wet and shrink when dry, presenting in some cases quite a cracked surface. Heavy clays will lose one- tenth of their volume on dry- ing, which acts injuriously on plants by rupturing the rootlets in long dry spells, thus adding to the severity of the drought. In this respect sandy soils have an advan- tage, as they do not cake or shrink by wet and dry weather, but remain friable and of equal bulk. CHAPTEE ly. PHYSICAL QUALITIES OF SOILS AS TO HEAT AND WATER. ^79. Temperature of Soils. The mean annual temperature of the soil is about that of the air. During^ the summer it is warmer durino- the day and cooler at night. At a depth of three feet from the surface it is unchanged from day to night, and seventy- five feet below the surface the thermometer never varies. In tropical regions the point of unvarying temperature is reached about one foot from the surface. There are two sources of heat to the soil : one external, from the solar rays, the other internal, produced by the chemical process of oxidation or decay. The warmth of the soil which favors the growth of plants is due mainly, if not entirely, to the sun. The earth has a heat within itself, which keeps up a high temperature in its interior, 112 SOILS AS RELxiTED TO PHYSICS. bat it escapes so rapidly from its surface that there would be eternal winter but for the genial sunshine. The temperature of the soil is affected by its color. A black soil absorbs and retains more heat than a gray or white soil. The latter, however, radiates the solar rays back upon the growing crops, so as to often prove disas- trous to them, producing the death of the corn tassels and young cotton bolls. When the humus is exhausted from a sandy soil by cultivation, it generally assumes a whitish color, and the only way to restore it is by resting for a number of years until it becomes dark again from the vegetable mould. Experiments have been made by Lampodius and others, by which good crops were made on a white soil by the application of charcoal over the surface. Prof. Johnson, on a July day at noon, tested the tem- perature of the soil, the air being 90^. A thermometer placed at the depth of one inch below the surface, gave the following results : The angle at which the sun strikes a soil has great influence upon its temperature, as has been observed in cold climates. A difference of 8^ has been noted between hillsides with a southern exposure, and level lands which receive the rays of the sun obliquely. Such soils, all other things being equal, might be planted much earlier, and would be more productive. Schubler made experiments with a number of soils as to the effect of color and moisture upon their temperature. Quartz sand Crystalline lime soil Garden soil , Yellow sand-clay. . . Pipe-clay Chalk soil , ,126^ 115 114 100 .94 .87 RETENTIVE POWER OF SOIL FOK HEAT. 113 The average temperature of soils whitened by magnesia was 108.5. Of those blackened by lampblack 121.4. Wet. Dry. Gray plough land 97.7^ 111.7^ Heavy clay soil, yellowish gray 99.3 112.3 Garden mould, blackish gray 99.5 113.5 Humus, brownish bJ ack 103.6 1 17. 3 80. Capacity of the Soil for Heat. M. Becquerel has made some interesting experiments in reference to the capacity of different kinds of soil for heat. That is, the same degree of heat, natural or artificial, that would bring a calcareous sand to 100^ would bring a silicious sand to 95.6, etc. The following will show the capacity of several different soils for heat: Calcareous sand 100.0 Silicious sand 95.6 Argillaceous earth 68.4 Calcareous earth 61.8 Mould 49.0 Thus a sandy soil is warmer than a clay soil, while a vegetable mould has less capacity for heat than any other earth. In a warm climate, tlien, humus is a refri- gerator of the soil, which renders it useful in hot, dry weather. In more northerly latitudes, this might be a disadvantage, as they require heat rather than moisture. 81. Retentive Power of Soils for Heat, As a general rule, the larger and denser the particles of a soil, the slower it parts with its heat. Thus a soil covered with gravel cools much more slowly than a fine sand. This is the prime reason why such soils are so well adapted to grapes in a cold climate. They have but small 114 SOILS AS RELATED TO PHYSICS. deposits of dew on tlieir surface, owing to their slowness in radiating heat. M. Becquerel tested this quality in several different classes of soils, as follows. He took a cube of 18 solid feet of each different kind of soil, and heated it up to 144^, noting the time it took to be reduced to 70^, the surround- ing air being 61*^. Result : Hours. Min. Mould 1.... Thus a vegetable loam will radiate heat at the close of a hot summer day, twice as fast as a sandy soil, inducing a much greater deposition of dew, which in the dry, hot days of summer must be very advantageous to growing crops. And when it is remembered that the interspaces of the soil for 12 inches or more are filled with air contain- ing more or less vapor which deposits moisture in the same way, the value of mould in time of drought cannot well be estimated. These conditions apply especially to the leading crops of the South, corn and cotton, which leave the soil, when properly cultivated, comparatively naked. Soils covered with vegetation, as by clover and the grasses, are not so much concerned in these processes, as their temperature is much more uniform. 82. Permeability to Water in Soils. One of the most important physical qualities of a soil IS its permecihility to water^hj ^\\\\Q\\ the two great func- tions of imbibition and capillary power are manifested. A soil may have all other physical qualities as well as chemical, its salts being abundant and in soluble forms, and PER^IEABILITY TO AVATER SOILS. 115 yet, deprived of this, obstruction and death would ensue to the plant; indeed, germination could never take place. The degree of permeability of a soil depends upon the size of its pores. Coarse gravelly soils have but few pores, but they are very large, and water percolates through them. This is a disadvantage, as soluble matters are thus carried off too rapidly. Soils composed of finer particles of clay, sand, and organic matter, have many minute pores, which let the water in slowly, and hold it to saturation. These soils have great capillary power or surface attrac- tion. This peculiar force may be illustrated by a small vial partly filled with water. The liquid will adhere to its sides and the water present a concave surface. In a very narrow tube, the water will rise to a considerable height; the surface attraction overcoming the power of gravitation. On this principle water rises in the pores of a sponge, or in a lump of sugar or salt. Where a soil is so compact (as in some clays) as to run together and become cemented, not only does a great dis- advantage accrue by its loss of power to absorb water, but also the air is precluded to a large extent; and plants do not germinate well in such soils, owing to a lack of free oxygen. In 1873 we experimented in two barrels, one a surface soil having organic matter and being porous, the other a subsoil with but little organic matter. The cotton seed in the former came up and the plant grew finely. In the other, not a seed germinated until the third planting; for in applying the water to give the soil moisture, it would become so cemented as to prevent the free access of air even ; and to this physical defect we attribute more the non-fertility of the soil, than to any deficiency in nutritive matters. The diffusibility of water in a soil depends upon its 116 SOILS AS RELATED TO PHYSICS. capillary and imbibing powers to a great extent. A good illustration is the burning of a lampwick saturated with oil. As the oil is consumed in the upper portion of the wick it is supplied from below by capillary attraction. So when the surface of a soil is rendered dry by the sun's rays and the winds, the moisture rises from the subsoil and supplies to a large extent the evaporated moisture. Thus, during the intense droughts of summer, some soils well adapted by the size of their pores to capillary force, are constantly receiving supplies of moisture from below, while on others the crops soon wither up and die for the lack of this power. And thus nature furnishes supplies of water in the heavy rains of winter, by saturating the subsoil, to fur- nish through this beneficent power a supply when the clouds refuse them in the heat of summer. When the surface soil becomes more moist than the subsoil, as after rain, the capillary force ceases to bring the water up, and rather aids gravity to carry it downward in the soil. In regions like California, where rains fall period- ically, the rising of water to the surface during the long- dry season causes soluble salts to come up with the water, and thas incrustations are formed on the surface, to be dissolved and carried down again by the first rain. Soils in Bengal thus saturated with nitre during the dry season, produce luxuriant crops when the I'ain sets in. The immense beds of carbonate of soda and other salts in the deserts of Utah, and the nitrate of soda-beds in Peru, are supposed to have originated thus. This latter salt is brought from its deposits and used exten- sively in this country and Europe to mix with fertilizing compounds. Thus water charged with carbonic acid and oxygen is constantly circulating up and down through the soil, acting upon the silica, lime, phosphoric acid, and potash, HYGROSCOPIC POWER FOR WATER. Ill rendering them soluble, and supplying them directly to the feeders of the plants. 83. Hygroscopic Power for Water, The liygroscopic or absorptive power of soils is an- other and very essential quality. This is the power to imbibe vapor from the air and condense it in its pores. There can be no upward movement of water in the soil without evaporation. The absorbing power of soils for the watery vapor of the atmosphere opposes evapora- tion ; hence this process is influenced not only by the sun and winds, but also by the soil. Liquid water is also im- bibed and held by some soils more tenaciously than others. In the following table, from experiments by Schubler, the first column shows the percentage of liquid water absorbed by a dry soil, and the second the amount of water that evaporated from them in four hours after com- plete saturation. Quartz sand 25 88.4 Clay soil (60 per cent, clay) 40 52.0 Loam 51 45.7 Plough land 52 32.0 Heavy clay (80 per cent, clay) 61 34.9 Garden mould 89 24.3 Humus 181 25.5 Thus we perceive that the soil which imbibes the most water holds it most tenaciously, and vice versa. Contrast quartz sand and garden mould. One absorbs just as much as the other lets off in both instances. Soils which have this imbibing and retaining power for water are, other things being equal, much the best for a warm climate. It will thus be perceived that the power of a soil to imbibe water depends greatly on its percentage of clay, and that this power is greatly increased by the addition of humus. Sandy soils are in themselves dry and arid. 118 SOILS AS RELATED TO PHYSICS. and it is of the utmost importance for such soils to be furnished with organic matter. The rapidity of absorption is always increased when the air is moist. Knop has shown that the amount is always determined by the temperature, i. e. at a given tem- perature, the same quantity of moisture will be absorbed by a dry soil, but it will take longer to do it. A soil possessing this hygroscopic power may be greatly benefited in time of drought, by imbibing during the cool night-time much of the moisture lost in the hot day, and imparting thereby nutriment and strength to perishing plants. From experiments made by Sir H. Davy, on a number of soils of different degrees of productiveness, he found that the most fertile soils always possessed these qualities in a higher degree than the less fertile. Zenger made experiments on soils as to the effect of their state of division on their power of imbibing water. He proved that porous soils w^ould lose this power in the ratio of their being made fine; while those more cemented in structure would acquire greater powers of absorption. In the following table, the imbibing power of each soil is presented in the two classes of soils, one of equal coarseness, and the other reduced to extreme fineness by pulverization. Coarse, Fine. Quartz sand 28.0 53.5 Marl 30.2 54.5 Brick clay 66.2 57.5 Moor soil 104.5 101.0 Aim soil 178.2 102.5 Peat dust 377.0 268.5 84. Hetentive Poiver for Water. The power of retaining or holding water in its pores is another quality to be considered. Water poured upon EETEXTIVE POWEK FOR WATER. 119 a lump of pipe-clay or other soil drop by drop, will ulti- mately saturate it so it can hold no more. Experiments made by Schubler established the follow- ing facts : That 106 pounds of different kinds of soils will absorb the number of pounds of water stated as follows: Calcareous sand 29 lbs. Loamy soil 40 '* English chalk 45 " Clay loam 30 " Pure clay TO While this is a valuable quality in warm climates, in keeping up moisture and reducing the temperature of a soil, it might prove disadvantageous in a northern climate, where they have to husband warmth and sunshine, rather than moisture and a reduced temperature. A porous soil, with tubes sufficiently large to suck up the water like a sponge, upon the principle of capillary attraction, possesses the power of holding water more than other soils: too much porosity will, however, act reversely. Some soils have such small apertures as to prevent the access of water to such an extent, as to render them unfit for cultivation. Another advantage of soils which retain water, is that they hold soluble matters, applied as fertilizers, or natu- rally produced, for the benefit of plants. Good arable soils are able to hold from 40 to 70 per cent, of their weight of water. Under 40 per cent, reduces them below the point of remuneration, while above 70 makes them cold and unproductive. Farmers learn by experience places in their fields which dry soonest after rain, as they can always plough them first ; they also suf- fer earliest from dry weather. These soils are always deficient in clay and humus. Soils possessed of a medium retentive power are the 120 SOILS AS RELATED TO PHYSICS. most fertile. While those which are deficient in this im- portant quality are unfruitful to the degree of the defi- ciency. Those possessing too much, as some clay soils, will, especially after heavy rains, and in temperate lati- tudes, produce a coldness adverse to fruitfulness. CHAPTEE V. "WATER AS A PHYSICAL AGENT IN THE SOIL, 85. Its Modes of Existence, Water has much to do with the physical character of the soil. It has been noticed as existing under three con- ditions, viz. hydrostatic^ capillary^ and hygroscopic. Water also exists in the soil chemically combined, as in zeolites, kaolin (true clay), the oxides of iron, quartz, etc. As this w^ater requires a very high heat to ex]Del it from its combinations, it can never be of any service to plants, or have any special influence on the soil itself, only so far as it is connected with the substances in which it exists. 86. Of Hydrostatic Water, Hydrostatic loater relates to that which flows through the soil, may be seen by the eye, and is free to move about by the laws of gravity or any other force. This is always more abundant after rains, melting of snows, etc. The pores of the soil at these times become surcharged with this hydrostatic water, until it is carried off by evaporation or sinks down into lower situations to unite with drains and currents many feet below the surface. This is called bottom loater^ which rises and falls with wet and dry seasons. After long-continued rains, and especially in low situations, this bottom water ajDpears neai HYGROSCOPIC WATER. 121 the surface and acts very disastrously, by submerging the roots of the growing crops. This frequently results in level lands during wet springs, to the serious detriment of crops. In table-lands such a condition is not to be apprehended, only in valleys and low places. When this bottom water is but a few inches from the earth's surface, we have bogs and swamps, not fit for any- thing but water plants, such as reeds and rushes. When it exists from two to three feet from the surface, and the soil is of an open texture, the grasses and some other plants will grow well u^on it. When it is not more than six or eight feet, and the soil light and loamy, it is favorable for all classes of vegetable growth, on account of the constant supply of water afibrded the roots by capillary attraction, especially in dry seasons. 87. Capillary Water, Cajnllary water is properly the moisture in a soil, which cannot be seen by the naked eye as water, yet when exist- ing to any great extent is easily discernible as a moist or wet soil. Being no longer subject to hydrostatic law, capillary water is held by this peculiar force, adhering with consid- erable tenacity to the particles of earth. When a soil saturated with water is air-dried, the escaping moisture is properly what is termed capillary; although it is difficult to draw a distinct line between that and hygroscopic water. As a general rule, the finer the pores of a soil, the greater its capillary power. It exists in greater or less abundance for some distance above the line of bottom water, according to the size of the pores in the soil. 88. Hygroscopic Water. Hygroscopic loater is closely blended with the particles 6 122 SOILS AS RELATED TO PHYSICS. of the soil ; so much so that the eye cannot detect its pre- sence. It is only ascertained by the loss or increase of organic weight, as the soil is deprived of it, or acquires it. When a soil is air-dried it loses all of its capillary water. One hundred grains of this kept at about the boiling point for several hours will lose its hygroscopic water. The amount of this water in the soil is very variable, being reduced as low as -J per cent, in dry weather, and rising to 40 per cent, after rain, in some soils. It increases during the night, being imbibed from the atmosphere or deposited as dew, and diminishes during the day by evapo- ration. The distinctions between hydrostatic, hygroscopic, and capillary water, are not absolute in their character, but simply relate to the degree in which the water exists in the soil, and serves a good purpose in this way. There can be no precise boundary l^etween hydrostatic and capil- lary water, for instance, especially where the soil has minute pores. 89. Supply of Water to Plants, Hydrostatic water rarely serves as nourishment for plants, but on the contrary olFers obstructions to their pro- per nutrition. In rare cases, however, some plants send out their roots in fountains and drains for food. As a general rule, agricultural plants get their nourish- ment from the soluble matters of capillary and hygroscopic water. And as plants are known to exhale large quan- tities of water from their leaves, and even their roots, the amount of water thus taken up by the fibrils must be in correspondence with the amount exhaled. The healthiness of plants and their very existence de- pend on a proper supply of water, surcharged with nutri- tive substances ; as their food must be held in solution by it and can only penetrate their cells and tissues through HOW PLANTS ABSORB WATER. 123 this as a menstruum. Other solvents, as carbonic acid and ammonia, have to be diluted with water before the sub- stances dissolved by them can be appropriated as plant- food. Sachs proved, in an experiment with a young bean j^lant, that the water exhaled from its leaves was sui^plied by the hygroscopic moisture of a soil, which it absorbed from the damp air surrounding it. The foliage of the plant was allowed free access to fresh dry air, while the pot of soil containing the roots was confined in an atmosphere satu- rated with vapor of water. He also showed, in other experiments, that roots not in contact with the soil lose water continually, and cannot obtain it from damp air ; thereby demonstrating that soils (especially clay and humus) condense vapor in their pores, holding it as hygroscopic water for the benefit of plants. Then, the soil is the medium through which plants receive their water, nor can the roots, much less the leaves, obtain it in appreciable quantities from the atmosphere. When a plant begins to wilt, it is evident that the soil is exhausted of the water which it can absorb from it. Sachs took advantage of this fact, and found in one soil, that it held 8 per cent, of water, unapjDropriated by a to- bacco plant. This soil was capable of absorbing 52.1 per cent, of water. Thus it had the power of furnishing 44.1 per cent, of its weight of water to plants. A coarse sand was found to absorb 20.8 per cent, of watei*, and yield all but 1.5 per cent, to a tobacco plant. A mixture of humus and sand held 46 per cent, of capillary water, and furnished all but 12.3 per cent, to the plant before wilting. 90. Hoio Plants absorb Water. An interesting question is. How do plants take up water from the soil? Dead plants retain much water, and after being dried, are capable of absorbing a portion of it 124 SOILS AS RELATED TO PHYSICS. again. Wheat straw and corn stalks, when thoroughly air- dried, retain 12 to 15 per cent, of water, and absorb much more in a moist atmosphere. One hundred parts of the following substances (experi- ments by Trommer), when dry, absorbed from a damp at- mosphere, as follows : 12 hours. 24 hours. 48 hours. 72 hours. Barley straw 15 24 34 42 parts of water. Rye " 12 20 27 29 " White paper 8 12 17 19 " The term hygroscopic implies an attraction for water. This attractio7i is called adhesion, or adhesive attraction. A law of attraction is that distance weakens its force. It only acts intensely then at small distances. A lump of dr}^ clay will absorb water rapidly by its external pores ; more feebly and slowly nearer the centre, until it ceases entirely at a certain distance from the surface. Two hygroscopic bodies, one dry, the other saturated with water, placed in contact, would form an equilibrium as to the amount of water on their surfaces at least, the dry absorbing from the moist ; on the same principle, the active roots of plants would easily take up water from a moist soil in contact with them. As water evaporates from the leaves, or is decomposed within the plant and appropriated, the vacuum produced absorbs water from the adjacent tubes below, and thus a constant current is established down to the extremities of the roots, which in their turn (being eminently hygroscopic) suck up water from a com- paratively dry soil. (Johnson.) The supply and waste of water to a plant may be une- qual to a certain extent, without detriment ; but when the exhalation is more rapid than the supply for a length of time, owing to a dry soil, the plant wilts and becomes un- healthy, although it may possess a larger percentage of HOW PLANTS ABSORB WATER. 125 water than the soil. Some plants contain 80 per cent, of water, while soils hold, according to Sachs, from 1.5 to 12.3 per cent, of water. Vegetable matter, fully air-dried, will hold from 13 to 15 per cent. Average soils do not retain more than 2 or 3 per cent. This shows conclusively that ])lants are much more hygroscopic than soils. From experiments made by Sachs, it is admitted that the foliage as well as stems and roots of plants absorb, to a small extent, water from the atmosphere, but the absorp- tion of liquid water from the soil proceeds at least one thousand times more rapidly than from the air, which may be considered as the only real source of supply. The amount of root surface to that of the soil in which a plant grows is very small. Boussingault found that a dwarf bean spread its roots in 51 pounds of soil ; a potato plant in 190 pounds ; a tobacco plant 470 pounds, and a hop plant 2,900 pounds, equal to 50 cubic feet. This shows that even if roots did not possess a greater power of absorption than water, they possess much greater capa- city for its imbibition. The quantity of water in vegetation is always influ- enced by the amount in the soil. Thus De Saussure found that plants growing in a moist loam contained more water than those in a dry lime soil. So, of a wet summer, grass and weeds are more succulent, and the green crop heavier than of a dry summer. The hay, however, when dried, loses so much more water, that the amount may be nearly the same. Ritthausen, in 1854, gave the produce of two crops of clover from a loamy soil, as follows : WEIGHT m POUNDS PER ACRE. Fresh. Air-dry. Water lost in drying. 1. Manured with ashes 14.903 5.182 9.721 Unmanured 12.380 5.418 6.962 2. Manured with gypsum.. . .22.256 4.800. 17.456 Unmanured 18.815 5 . 190 13 . 625 126 SOILS AS RELATED TO PHYSICS. It is a singular fact that tlie immanured plots produced more hay than those manured, notwithstanding the bulk was much in favor of the latter. The water constituted the dilierence. The stems of the unmanured clover were much more compact than the other. 91. liequisite Amoimt of Water in Soils for Plants, The quantity of water supplied to a soil has, as we all know, much to do with its production. A dry year always cuts off the crop of corn and cotton, w^hile too much rain is equally injurious, especially to cotton. Ikenhoff made experiments on buckwheat as to the amount of water requisite for a maximum crop. He filled pots with garden earth, of the same size, and placed them in a southern exposure. The plants in pot No. 1 received ^ litre of water each time, being a little less than an Eng- lish pint. No. 2, ^ litre ; No. 3, \ litre ; No. 4, and No. 5, litre. The plants were watered 17 times in 67 days. The following shows the product of each pot : Straw. Water used, in litres. No. 1. Ill seeds, weighing 1.68 grammes. . ..4.52... 25.0 No. 2. 282 " 5.47 ..8.47... 12.5 No. 3. 93 " 1.73 ..4.55... 6.25 No. 4. 37 " 0.52 ..0.30... 3.12 No. 5. 12 " 0.09 . ..0.30... 1.56 This experiment teaches that the amount of water in a soil has much to do with the production of plants. It should not, however, be taken as a rule for all soils. In fact no general rule can be given as to how much is requi- site, some soils, as some crops, demanding more than others. Hellriegel experimented with wheat, rye, and oats in sand mixed wdth a sufficiency of plant-food furnishing from 2^ to 20 per cent, of water: 10 to 15 per cent, of water REQUISITE AMOUNT OF WATER FOR PLANTS. 127 produced n maximum crop of rye — wheat and oats requir- ing a little more. Wilting never took place except when the percentage of water was reduced below 2^. Above this the growth was stunted more or less up to 10 per cent. Groven found in fourteen experiments in the open field, in various parts of Germany and Austria, on sugar beets, that the eight best crops received, from the time of plant- ing to gathering, 140 Paris lines of water in depth ; the six poorest 115 lines, equal to about 37 inches. There is no fact better established than that water is the most essential factor in the production of a crop. Perhaps temperature is equally so, as nothing can vege- tate without proper warmth. An abundant supply of water, when needed, will produce good crops even on poor soils, while the richest will utterly fail without it. The physical offices of water are very important. All the nutritive matters that circulate in the plant are held in solution by this agent, and carried forward to its extreme parts. Not only are the solid matters brought up through the roots thus distributed, but the gases imbibed by the leaves also impregnate the sap, and are carried and depo- sited wherever needed. The very force of absorption has a tendency to enlarge the cells and expand the tubes, and thus add to the growth of the plant, while a deficiency of this vital fluid will produce smaller cells and a stunted growth. The solid matters of the soil are also dissolved by water, especially when surcharged with carbonic acid and ammonia, and doubtless through this agency, chemical actions are constantly going on in the soil, by the moving of hygroscopic and capillary waters through the solid strata of insoluble matter. 128 SOILS AS RELATED TO PHYSICS. CHAPTER VL MECHANICAL IMPROVEMENT OF SOILS. 92. Of Drainage, Among the mechanical means for the improvement of the soil, so important in older countries, drainage stands preeminent. This process is practised at the North and in Europe very extensively, even on uplands. This is done in order to get clear of the moisture as much as possi- ble, and thereby make the land warmer and hasten the growth of crops; for it is known that too much water makes land cold and retards vegetation. This system of drainage is the very thing for cold countries, as it improves the climate, so to speak, by relieving the soil of the chilly moisture and letting in the genial sunshine. It acts also unquestionably very favor ably in aiding the decomposition of insoluble substances, both of organic and inorganic matters of the soil. Air is indispensable to the soil to prepare food for plants by the chemical action of oxygen and carbonic acid ; as well, it may be, to supply nitrogen to the interspaces of the soil, by which it may be charged and made soluble food for plants. A soil, then, in a healthy condition, is full of pores and crevices by which the air is let into it, and the gases escaping from decomposing organic sub- stances may circulate in it and act chemically upon its insoluble substances. But when bottom water rises in the soil it prevents the access of air, as well as the capillary water, to a large extent, from rising in the surface soil, when but a few feet intervene. In stagnant waters many compounds are formed inju- rious to vegetation as well as to the health of man. When OF DRAINAGE. 129 a shower of rain falls on a porous soil the water presses the air through to lower depths, which is followed by a fresh supply from the atmosjDhere, and thus chemical action is readily carried on : the ammonia and carbonic acid of the rain water are thus secured to plants. But in compact soils not properly underdrained, the particles run together by the influence of rain, and the water runs off the surface, or is carried off by evaporation ; it becomes also impervi- ous to air. Hence the valuable constituents of rain water as well as of the atmosphere are lost to the soil. All soils saturated with water are necessarily cold. Steam, whether natural or artificial, always contains a large quantity of heat; hence the evaporation of water, which process is carried on by the conversion of it into steam or vapor, always produces heat. Hence the heat produced by the solar rays on wet ground, is lost to the soil by being absorbed by the vapor which is constantly passing off from such a soil in dry, sunshiny, or windy weather. Miasma is also generated in the steam of stagnant waters, where drainage is neglected, producing malarial fevers. If you mix earth and water in an open vessel, and let it stand several weeks in warm weather, an offensive effluvia will arise, clearly proving the injurious effects of stagnant water upon animals as well as plants. Thus, by draining, the soil is made more porous and productive, and a greater depth obtained for the roots of plants; insuring, also, a protection from drought, especially over the underdrains, and for some distance each side, by the rise of capillary water; for the surface attraction of the water is toward the ditches as well as to the surface, at least until the soil in them becomes as compact as that between them. Another great benefit of draining is the rapidity with which the soil dries off after rain; thus fitting the land for 6* 130 SOILS AS RELATED TO PHYSICS. ploughing and the reception of seed much sooner after long spells of rainy weather. It often happens that bottom lands are wholly lost for a whole crop by continuous spring rains. But a proper system of drainage would make them as susceptible of cul- tivation as most uplands. Another very important effect of draining lands inclined to be sobby is, that fertilizers will act much better in a soil moderately dry than one saturated with water. Too much water in a soil prevents its circulation, and thus far deprives roots of solvent matters held by water, which they would otherwise receive. The moving waters of a soil may be compared to a bird feeding her young. When there is a deposit of rich food, the roots near by have a plenty, but those below are suffer- ing, it may be, until a shower comes; the water which passes this deposit becomes charged with soluble matter, and in sinking by gravitation, carries down to the lower roots, especially the tap roots, as of cotton, a good supply of food. As soon as the rain is over, the wind and sun- shine begin to dry off the surface soil by evaporation, Avhich is supplied by capillary attraction from below, and thus from the same rich deposit, which the hydrostatic water carried down to the lower roots, the capillary water now loads itself with soluble food, and brings it to the upper roots. These waters also supply, to a considerable extent, the roots laterally, upon the principle of diffusibility already noticed. The free circulation of the air through the soil also aids the effects of fertilizers, by supplying, when needed, oxygen, nitrogen, and carbonic acid, and thus forming the exact combinations which are needed by plants. Soils too much saturated w^ith water will prevent this, and all the advantages growing out of the combinations and chemical changes above stated. Thus we see the importance of DEAmAGE AT THE SOUTH. 131 artificial drainage in all soils disposed to hold too much water, 93. Under draining, Underdraining is a work requiring much practice and skill, and if not done well, had better not be done at all. We have no faith in any of the processes in common use among farmers, such as j)ine logs, stones, brickbats, etc. The manufacture of tiles for this purpose is much better, and any farmer having a bed of clay on his land, should establish a tile factory, and make and burn them for his own use, and to sell to others. Drain tiles are made in various forms: the two mostly used, and the best, are the round, and the half circle, or horse-shoe. This latter is in two parts, one long and flat, which is laid on the bottom of the ditch; the other, a half circle, as if a hollow tube had been split in two from end to end. This lies upon the flat bottom piece, which forms a half circle for the water to pass through. The round tile is much the most convenient, being about three feet in length, larger at one end than the other, which acts as a sheath for the small end of its fellow, while the other end penetrates a third, thus forming a continuous tunnel through the ditch. The water percolates into the joints, and through crevices in the tile at difierent points made pervious by the action of the fire. The ditches for underdrains should be constructed jDar- allel to each other, from 20 to 40 feet, according to the character of the soil, the number of springs, etc. They should be four or five feet deep, wide at the top and narrow at the bottom. 94. Drainage at the South, There is but one class of soils at the South that will pay for draining: lowlands which are surcharged with bot- tom water. The object here is not to improve the climate or aid chemical action, so much as to get clear of the super- 132 SOILS AS RELATED TO PHYSICS. incumbent water, which acts mechanically as an obstrnc* tion to the nutrition of plants. Much of this ditching^ as termed at the South, was per- formed before the war; but since, owing to the paucity of labor, the ditches have not been kept open, many valuable bottoms lost to cultivation, and malarial fevers have become much more prevalent ; for one great advantage of draining a country is, that it adds to the salubrity of the climate and health of the inhabitants. In every cultivated field, much of the valuable hillside soil, as well as manurial substances, are washed down by rains into the wet bottoms; and where there is much water, the land is but little improved, as the soil has no absorbing j^ower, being already saturated. Drainage would be of great benefit in this regard ; and also wliere there is not much water, but still too much for cultivation, and the val- leys have been enriched by the accumulation of ages. These lands once well ditched and properly underdrained, would pay better for the investment than any portion of the farm. Because the uplands need an annual outlay of money for manures, more than the ditching would cost. When once done as it should be, it will last an age with- out fertilizers. While it is true, as stated, that it would hardly pay to drain uplands, where, in most cases, there is a scarcity of water during the summer, yet there are many soils, even among this class, that would be benefited, because of their compactness and impermeability to air and water. Many of the flat lands might be greatly improved by drainage, but we must wait for an increase in their value before much money can be expended in this way, as there is quite as much land to be obtained at cheap rates (having every natural advantage) as there is labor to cultivate them. 95. Of TrencMng, Trenching and spading are very useful in some of the OF PLOUGHS. 133 older countries, where land is high and human muscle can be used to much greater advantage than with us. There are two valuable ends obtained by trenching which it is proper to state : making the soil porous for a greater depth than can be attained by the plough, and bringing up from the subsoil soluble matters that have been washed away for ages, and depositing them on the surface. The practical tests of it in this country, in gardens and vineyards, have 2:)roven very clearly that it will not pay. The physical benefit to the soil lasts but a short time, as our heavy rains cause our clay soils soon to assume their former compactness, and the immense outlay required pre- cludes all hope of remuneration. Hence the system in this country has been abandoned for the cheaper, if not more efficient, processes of the plough. CHAPTER VII. PLOUGHS. PLOUGHING. SUBSOILING. HORIZONTAL CULTUKE. 96. Of Ploughs, Of all the mechanical means of improving the soil, ploughing is the most important and efficient. In order to do this it is very essential to have good tools properly constructed. Simplicity in mechanical construction, so iniportant in everything else, is especially so in reference to ploughs. For turning rough lands, such as we have at the South, being often rocky and rooty and stumpy, the common turning shovel is the best implement. It breaks deep, and turns very well. This followed by a good subsoiler 134 SOILS AS EELATED TO PLANTS. will prepare land well either for corn or cotton; and, as is the case in most instances where there is no time to subsoil, this plough can be constructed so as to go very- deep as well as turn under the top soil at the same time with two horses attached. The principal objects to be obtained by ploughing, are to turn over tlie soil, to subsoil, to pulverize, to open for planting, to cover the seed, and to cultivate the plant. Here are six different objects, all of which require a dif- ferent iinjDlement. There are so many manufacturers of ploughs, and so many good ploughs in market, and such a diversity of opinions as to which is the best, that we leave the subject, adding nothing to the general suggestions given above. 97. Benefits of Ploughing, There are two good reasons why land should be turned over at least once a year. This should be done during the autumn or winter. You bring up and place on the surface soluble matters that have leached down too low for the feeders to reach, and you cover in the soil the weeds, grass, and stubble of the gathered crops, where they will undergo decomposition, and be in the right place for the rootlets to feed upon. The tilth is deej^ened also, and if some of the clay subsoil is thrown on top it becomes much more exposed to the action of carbonic acid and oxygen, which disintegrates it more effectually, and ren- ders its particles so fine as that solvents may act upon them much more readily. We say that this operation should be performed dur- ing fall or winter, as thereby the action of frost upon the clods is secured. The moisture in them freezes into ice, which expands and separates the particles of soil, leaving them, when the spring opens and the moisture dries out, much better pulverized than could be effected by mechan- BENEFITS OF PLOUGHING. 135 ical means, and in a finer condition for absorbing and retaining ammonia and other gases. Besides, the organic matter turned in and lying all winter, will be so decom- posed as to furnish considerable nitrogenous and mineral food for the next summer crops. It will always be advisable to cut down the stalks of corn and chop them in two before the plough, and beat down the cotton stalks, thereby scattering the burs, and having them covered that they may rot during the win- ter. There is no telling the amount of available food which may be acquired in this way. Turning over land in the spring is of doubtful utility, especially if the soil is thin. We have seen land injured for the growing crop by having the surface soil buried so deep, and so much of the hard subsoil put on top, after the w^inter is over, that the plants could not get the benefit of what little soluble matters existed in the soil. Spring ploughing should be conducted with reference to mixing thoroughly the soil and subsoil of the autumn ploughing, letting it remain in place, and deepening as far as possible the tilth beneath. Lands should be well pulverized in order for plants to obtain the available food already in the soil, or that wdiich is applied as manure. One great reason why stable ma- nure itself is often so ineffective, and even injurious in time of drought, is because it is not fine enough. So well convinced are the venders of fertilizers in Europe of tlie importance of pulverizing soils, that they often with their manures furnish ploughs and harrows gratis, that they know will well accomplish this end. Clay lands that have been trodden very hard, or are ploughed too soon after a rain, are apt to break up cloddy. A heavy harrow, if pro- perly used, will pulverize the land and relieve this difficulty. In sandy soils this implement is rarely needed. It is very important sometimes to bed up lands in 136 SOILS AS RELATED TO PLANTS. order to keep them dry and warm during cold, wet springs. This is especially true of cotton. The common rooter subserves a good purpose to lay off the rows, the shovel to open for the deposition of fertilizers, and then the rooter to cover, and the turning shovel to finish the bed. A small harrow with two teeth or a bull tongue are the best implements for covering seed; and the cotton sweep the best cultivator for corn or cotton, where land has been properly prepared. With it much more land can be culti- vated than with ordinary ploughs, with much less damage to the growing crop ; as the grass is effectually ploughed up, and the surface soil stirred, and the crust broken for the admission of air, while the roots of the plants are left, for the main part, uninjured. Another great benefit of ploughing, not heretofore noticed, is the much greater surface of soil which it exposes to the action of the atmosphere. A smooth, un- ploughed, compact soil presents but one surface to the air. A sod well broken exposes every side, or nearly so, of every particle of soil as deep as the tilth goes. All the interspaces are filled with atmospheric air, which goes to work in its disintegrating and solvent action, and very much more is accomplished than when a soil has been unbroken. For a similar reason it is requisite to plough most crops after every rain, when the surface soil is more or less beaten down and rendered almost impervious to air. By this process fresh air is let down to the roots, and the benefit obtained is perceptible to the most casual observer. Very few crops are ploughed suflficiently. As a general rule, those are the most productive which are ploughed the most. True, great caution must be used, especially in the latter stages of corn, and after the fruit begins to form on cotton, but the ground must be kept stirred to produce a maximum crop. We are satisfied from actual SUBSOILIXG. 137 experiments that corn will recuperate much more readily from injury to the roots by deep ploughing than cotton. A good rule for both is to plough deep the first and second time, and use the surface plough in all the after cultiva- tion. 98. Suhsoiling, Several advantages grow out of breaking land very deep, or what is generally called subsoiling. The roots are enabled to penetrate much deeper in quest of food, a greater amount of atmospheric air (and consequently nitro- gen and carbonic acid) is held in the soil ; for as the plough passes on, the atmosphere presses into every inter- space behind it, and a soil well broken twelve inches deep will have twice as much of these valuable gases as that only broken six inches. Besides, it causes heavy rains to sink rapidly, preventing too much water from injuring the plants, and at the same time saves rolling lands from washing into such ugly gullies as so often disfigure our hillsides. Again, subsoiling lands is a great prevention to drought, by holding in store a better supply of hygroscopic and capillary waters, enabling the latter to move more freely through a deeper and more porous tilth. In 1873 we instituted a practical test of the advantages of subsoiling land botli for corn and cotton. For the lat- ter we planted one-fourth of an acre, subsoiled 12 inches deep, 4 feet wide, using at the rate of 300 lbs. of am- moniated phosphate. It produced at the rate of 1,227 lbs. per acre. The same amount, not subsoiled, by its side, pro- duced 1,012 lbs. The first paid for the fertilizer and made a clear profit of $16.38 per acre. The last made a profit of $7.03. Subsoiling land for corn was tested as follows: One- half acre was planted and cultivated precisely the same Avay, with a small amount of ammoniated superphosphate 138 SOILS AS EELATED TO PLANTS. applied in each hill. The corn was planted in rows six feet wide by three in the drill: one-fourth acre was sub- soiled 12 inches deep just previous to planting. The sub- soiled plat produced at the rate of 19.70 bushels to the acre. That not subsoiled, 17.34 bushels. The overplus of corn made, about paid for the extra labor. A dry year it would doubtless have paid more. 99. Horizontal Culture, One of the greatest difficulties in the cultivation of roll- ing lands, is the washing olf of the surface soil, and the formation of gullies, especially where corn and cotton are the principal crops. The best remedies are deep plough- ing, hillside ditching, and horizontal culture, which may be thus described : Beginning at the summit of a hill, the guide rows must be run some twenty or thirty paces apart, according to its steepness or irregularity. Where they begin on a decliv- ity, and end on a gentle slope, they must be run much nearer than where there is more or less uniformity in the steepness of the hill. The points of departure, or hedge roios^ must be as few as possible, and well selected. On hills running out into a valley, like a promontory, the crest of the hill from its summit to its base must be the hedge row. The hollow between the hills should form another, and so of all rapid curves on hills or in valleys. A straight ditch should be opened in every considerable hollow, to carry off the waters of heavy showers, as it is impossible to construct long horizontal rows around such sharp curves and protect the land from washing. In old fields, gullies are already formed where such ditches are required. They should be straightened and deepened, how- ever, as this will prevent much valuable soil from being carried off. nORIZONTAL CULTURE. 139 As a general rule, guide rows, and, of course, the corn or cotton rows between them, should be run on a perfect level. Rows thus constructed hold all the water of mod- erate rains, and prevent any washing of the land. Cotton beds thus saturated with water from a considerable shower will retain moisture for da^'s, while those inclining down the hill would carry off the falling rain in the furrows between, and leave the bed dry and the cotton to suffer. On long slopes, where washes begin and form small gullies, after heavy showers, the first hillside ditch should be constructed. Below this run the rows on a level as above, and where the break begins run another ditch. By this means the rows will all be run on a level, and compa- ratively few hillside ditches be needed, while the corn or cotton will suffer much less from drought, the beds hold- ing all the water that falls upon the land, except in super- abundant showers, when it will not be necessary to retain all. In a few cases (which a practical eye will soon detect) it may be necessary to run the rows with a slight fall to each, in order to stop the formation of gullies, and prevent the land from being washed away. It then becomes a question whether the hillside ditches should not be in- creased and enlarged, and the rows still run upon a level,' because of the great benefit resulting from holding all the water and saturating the beds during a dry season. As economy of time and labor are the first requisites in every good system of agriculture, it becomes necessary to adopt some plan for levelling the rows much more expedi- tious than the plumb-line level, as used in the construction of hillside ditches. The old plan was to take a stand at one hedge row with a spirit level, and sight round the hill, causing stakes to be placed at prominent points, as a guide to the ploughman. But this process, though much shorter than the other, is too tedious and laborious. 140 SOILS AS RELATED TO PLANTS. The best plan is to level with the eye in the following manner : Go ahead of the ploughman, either on foot or horseback, keeping your eye intently fixed on the ground some eight or ten steps in advance. A practical eye can soon learn to keep on a level round the hill in this way ; at least near enough for all practical purposes. When the guide row is completed, while the ploughman is laying oli one by its side, you can go down the hill and ride round below the guide row, and ascertain by keeping your eye fixed on the point above you in a direct line, and looking backward and forward, whether the row is level or not. By practising this plan a short time, any person may lay oflf a field horizontally almost as perfectly as with a level, and in one-tenth the time, and with no labor whatever, only the walking or riding. The guide rows being thus laid off on a level, or nearly so, the other ploughs follow and fill up the interstices be- tween them, with corn or cotton rows as the case may be. The plan is to lay ofi" half by the guide row from above, and half by the guide row from below, filling out with short rows in the middle, which should be a little narrower at the ends, and the very last ones wdder in the middle. When short rows are run to fill out a place thrown off of a line by irregular slopes, always have two or four in- stead of one or three, as this will be found to save time and prevent lifting the plough back to the starting point, both in laying off rows, and in ploughing three or five furrows to the row. This plan of horizontal culture is particularly adapted to larger plantations, by which time and labor are both economized. It will be found, doubtless, with some modi- fication, adapted to smaller farms wherever lands are dis- posed to wash. PAET IT. CHEMISTRY OF THE ATMOSPHERE. CHAPTER I. COMPOSITION OF THE ATMOSPHEKE. OXYGEN. OZONE, 100. Composition of the Atmosphere, The atmosphere, Avhen pure, is composed of two gases, oxygen and nitrogen, in about the following proportions: By Weight. By Volume. Oxygen 23,17 20.95 Nitrogen 76.83 79.05 Other substances, as w^ater, carbonic acid, and am- monia, occur in small quantities, of which we will speak more fully hereafter. Tlie two gases of which the atmosphere is mainly com- posed are combined mechanically, and not chemically, as many have been led to suppose. There is a general, though not exact, uniformity existing between these gases, as well as the amount of carbonic acid, which is owing doubtless to the even balance kept up between the life, growth, and decay of animal and vegetable substances. Another remarkable fact is, that these gases are mixed in uniform proportions, without reference to their specific gravity. This is owing to a law of nature called the dif- fusion of gases. Whenever two gases, although of dif- erent Aveights, are brouglit together in a confined space, it 142 CHEMISTRY OF THE ATMOSPHERE. will be found that they gradually intermingle, until they are both uniformly diffused throughout the place. If a volume of hydrogen gas is introduced into an inverted jar, it will rise at once to the upper portion, press- ing out the atmospheric air as it is so much lighter. Now introduce a volume of carbonic acid below the hydrogen gas, which is fifteen times lighter than the other; in a few days it will be found that the two gases have become uniformly mixed. There are some gases which seem to be an exception to this rule, as the carbonic anhydride (olefiant gas), which settles at the bottom of old w^ells, and is very deleterious to animal life. 101. Oxygen^ O. As we have already seen, oxygen constitutes about one- fifth of the air, and exists more largely in all living plants than any other element. In fact, it is the most abundant body in nature — forming in combination with other bodies about one-third of all the soils and rocks as well as plants and animals of the globe, and eight-ninths of the water of its rivers, lakes, and oceans. There are, in fact, but few chemical compounds in which it is not an ingredient. Oxygen forms new compounds with other bodies, hav- ing a universal tendency to this kind of union. Some of these combinations are called acids^ as with carbon it forms carbonic acid ; others are oxides, as the oxide of iron. In the processes of combination, decay, putrefac- tion, fermentation, and respiration, it is being constantly set free — forming new compounds by its chemical affini- ties with other bodies. Although oxygen exists in the atmosphere in an un- combined state, it is impossible to obtain it pure, except from some of its compounds, as chlorate of potash, which, when exposed to heat, melts, and this gas escapes in abun- dance. This is the most common source for obtaining it. OZONE — CONDENSED OXYGEN, 143 As oxygen gas is a great supporter of combustion, it will increase the tlame of a lighted splinter when placed in it, and instantly restore it when blown out. This is a good test for it. The burning of all bodies is attended with a chemical union of the oxygen of the air and the body being con- sumed. The increase of a flame depends upon an increase of oxygen. The reason why a coal of fire may be blown into a flame, is because of the increased amount of oxygen added to it, and not from any supposed virtue in the force of the wind. Bodies which unite slowly with oxygen are said to oxidize, as the decay of wood and rust of iron. This is a species of combustion, and has been termed by Liebig eremacausis (slow burning). Free oxygen has been termed vital air^ as animals and plants will perish in its absence. It is introduced into the lungs and blood by the act of breathing, and thence carried throughout the system. Thus the animal heat is kept up, and the waste of the structure replenished. 102. Ozone — Condensed Oxygen, Ozone, according to Faraday, is oxygen in an active state under the influence of electricity or in combination with it. It has never been obtained pure, but is always found mixed with several times its weight of air and oxygen. A molecule of ozone, as demonstrated by Andrews, Babo, and Loret, contains more atoms than ordinary oxy- gen gas, which shows that this element diminishes in volume when electrized. Ozone is therefore condensed oxygen, ■This disposition of elements to occur in two or more forms is called allotropism.. Thus carbon is found as dia- mond, plumbago, and charcoal; and phosphorus exists in 144 CHEMISTRY OF THE ATMOSPHERE. two forms, red and colorless, which are very distinct from each other, the latter, like ozone, having much more vigor- ous tendencies than the other. A mixture of oxygen and ozone has been prepared by Babo and Glaus, containing 6 per cent, of the latter. It is insoluble in water, irritating to the lungs, and destructive of insect life. A moderate heat will destroy it. 103. Sources o f Ozone. The principal sources of ozone, as far as know^n, are atmospheric electricity, combustion, and slow oxidation. If it be true that it is also produced by the exhalation of all plants in sunlight, it Avould seem that this should con- stitute its principal source. But however rapidly or con- tinuously produced, the quantity must be very small, as it is constantly uniting with other bodies and disappearing, and cannot manifest its peculiar properties only as it is reproduced. Oxygen is converted into ozone under the influence of electricity, when jDcrfectly pure ; and enclosed in a glass tube containing moist metallic silver. By long-continued electrical discharges, the oxygen is made to entirely dis- appear, by its conversion into ozone and union with the silver, which gives it a black color. On heating the silver afterward, the same quantity of oxygen is reproduced. The white vapor which rises from colorless phosphorus when half covered with tepid water is produced by the formation of ozone mingling with other substances; as not only is the odor manifest, but the air of the vessel will give to iodide of potassium starch paper the blue color w^hich indicates ozone. The vigor of this principle is manifest when it is known that when thus formed by the oxidation of phosphoi-us, only Y^Vo ^^^^ weight of the air is composed of it ; and yet all of its reactions are fully seen. (Johnson.) RELATION OF OZONE TO VEGETATION. 145 M. Boillot found that one litre of pure oxygen treated with electric discharges produced seven milligrammes of ozone, while the same amount of air gave thirty-seven milligrammes of ozone. 104. Amount of Ozone in the Atmosphere, Schonbien, who made a number of interesting experi- ' ments with this principle, says that its peculiar odor is distinctly apparent when it constitutes only one-millionth of the Aveight of the air. This of itself would indicate that it must exist in very minute proportions, as it is very rare that its odor is perceptible. Efforts to ascertain the amount by Zinenger, Pless, and Pierre, as a constant quantity, have varied from 13 to 65 million parts of air to one of ozone. Atmospheric ozone is most abundant in winter, as the electrical conditions which produce it are the greatest at that period, and in more northern climates the snow hides from it many bodies, with which it would otherwise unite and oxidize. 105. Relation of Ozone to Vegetation. As to the effect of ozone upon vegetable nutrition we are as yet almost entirely at sea. What we think we know is only inference and theory at most. If it be true, how- ever, that it is constantly the result as well as an active agent of oxidation, we can easily perceive how it is con- nected with the processes which keep up vegetable nutri- tion and growth, as this principle of oxidation is going on by day and by night in all soils and plants. Prof. S. W. Johnson has a favorite theory of vegetable nutrition, from experiments made by Schonbien and others, that free nitrogen can in no case be made to unite with water, but that it does enter such combinations by the action of ozone, and in this way may be made to play an important part in vegetation. 7 146 CHEMISTRY OF THE ATMOSPHEEB. CHAPTEE II. OF HTDEOGEN. — CARBO^^^. — CARBONIC ACID. 106. Hydrogen^ H. Hydrogen gas is the lightest of all known substances, being fourteen and a half times lighter than atmospheric air. It is destitute of taste, color, or smell. It constitutes one-ninth part of water, and never exists free in nature, except w^here it is developed from pools and stagnant waters, volcanoes and boiling springs, and some kinds of rocks and limestones, by natural chemical action. Hydrogen exists rarely in the mineral world except in combination w^ith water. It is, however, a constant ingre- dient of plants and animals, and of most substances which enter into organic life. Hydrogen is prepared by abstracting oxygen from water by substances which have no special affinity for it : as so- dium, metallic iron, and zinc. Owing to its extreme levity it is used for filling bal- loons, which causes them to ascend. Although incapable of supporting combustion by itself, hydrogen inflames when brought in contact with a lighted taper, becoming intensely hot, though scarcely luminous. The air in contact with the hydrogen, keeps up the flame, which results in the forming of jDrotoxide of hydrogen, which is the universally diffused substance, water. With carbon, hydrogen forms a number of compounds, as oil of turpentine, oil of lemons, the volatile oils, etc. The hydrocarbons constitute the principal illuminating ingredient of defiant gas, kerosene, benzine, and paraffine. 107. Carbon, C. Carbon in one of its purest forms is nothing more than CAEBON. 147 charcoal, which you know is produced by burning wood in a kiln so as to prevent the oxygen of the air from unit- ing with the carbon and escaping as carbonic acid gas. Charcoal generally contains, besides carbon, a slight admix- ture of earthy and saline matters. The diamond also is carbon in its purest form, which, though very different in its physical features and value from the other substances, is identical in a chemical sense, all yielding carbonic acid gas upon combustion. The black smoke produced in the burning of kerosene, lampblack, anthracite, and black lead (plumbago), are other forms of carbon. Animal charcoal or bone-black is also an impure car- bon mixed with phosphate of lime. It is produced by heat- ing bones in closely covered iron pots, and is used for refining sugar ; after w^hich, it is appropriated to the man- ufacture of superphosphates, on account of the phosphoric acid left in it. Porous carbonaceous substances have a great absorbing power for gases, and because of this are good disinfectants. Charcoal will absorb 90 per cent, of its volume of ammo- niacal gas. This element is universal in all vegetable and animal substances ; in fact no organism could be complete with- out it. Hence it may be deemed, in the language of Prof. Johnson, as "the characteristic ingredient of all organic compounds." When uncombined, carbon is solid, and can only be taken up as plant food, or volatilized by union with oxygen. This combination readily takes place when burned in the open air. Hence, you observe that ashes are always white which are exposed to the air ; while those parts of the wood which are consumed under a bed of ashes make charcoal, because of the absence of oxygen to form the carbonic acid gas. 148 CHEMISTRY OF THE ATMOSPHERE. 108. Carbonic Acid^ COg. Garhonic acid results from the union of carbon and oxygen, and is one of the most important principles in na- ture, especially in its relations to vegetable life. Twelve grains of pure carbon heated to redness in 32 grains of oxygen gas, will unite and form 44 grains of car- bonic acid ; being one equivalent of carbon and two of oxygen — hence the formula, COg. Whenever any organic body decays or is burned, car- bonic acid is formed by the oxidation of carbon. Carbonic acid exists very extensively in nature. Forty- four per cent, of this acid united to lime, constitutes all the marble, chalk, and common limestones of the earth, under the different forms of carbonate of lime. There are other carbonates, as of potash (saleratus) and soda, so extensively used in making bread : also carbonate of ammonia, which exists in the atmosphere, and is brought down by the rains, constituting an important fertilizer to the growing crops. Carbonic acid exists to a small extent in all fountain and river waters, and also in rain water. One reason why cold spring water is so refreshing is owing to its presence. 109. Qualities and Tests of Carbonic Acid. Carbonic acid is invisible, having a slight pungent odor, is half heavier than atmospheric air, and nearly one- half heavier than oxygen gas. It is the colorless gas which causes beer and soda water to effervesce and sparkle, and produces the frothing of por- ter and ale. It has a sour taste, and reddens vegetable blues. It is very soluble in water, which dissolves more than its bulk of this acid as 106 is to 100. As carbonic acid is so much heavier than the air, it can CARBONIC ACID IN THE ATMOSPHERE. 149 be poured from one vessel into another like a fluid. At a temperature below 72^, it becomes solid, forming white crystals similar to ice. Carbonic acid is very deleterious to animal life. The fumes of burning charcoal in a close room have often proved fatal to persons sleeping in them, by this gas dis- placing the oxygen and thus producing a poisonous air. When it reaches 15 to 20 parts in 1,000, it produces the distressing efiects of headache, giddiness, stupor, and sufib- cation, and will result in death if relief is not alforded. Its presence may be easily demonstrated, by fixing a jar of lime water Avith an open mouth, thus exposing it to the air. A film will soon form upon it, which results from the combination of the carbonic acid of the atmosphere with the lime held in solution. Another way to test the presence of carbonic acid is, to insert a reed or quill into lime w^ater and blow the breatli through it ; a milky cloud will form at once where the carbonic acid of the breath meets with the lime in the water, forming carbonate of lime. It is thrown ofi* by the respiration of animals, as is proven by breathing into lime water, as in the experiment above mentioned. The burning of fuel of any kind, and the decay of all animal and vegetable substances, also pro- duce it in immense quantities. 110. Estimates of Carbonic Acid in the Atmosphere, In 300 analyses of the atmosphere, the carbonic acid ranged from 46 to 86 parts by weight in 100,000. In round numbers, it has been estimated at one part in 12,000. Though this is a small amount in comparison with the whole bulk of the atraosphere, it is nevertheless immense when taken in the aggregate, furnishing an un- failing supply of carbon to plants, and oxygen to animals. Prof. Shultz, of Rostock, by recent experiments finds 150 CHEMISTEY OF THE ATMOSPHERE. rather less carbonic acid than heretofore indicated by most observers. He detected only about 2.9 of the acid in 10.000 volumes of the air, being less than one-third per cent. While he found no variations as to the time of day or year, meteorological phenomena had undoubted influ- ence. Thus a snow-fall would increase the amount, while rain would cause a decrease. Northwest winds invari- ably augmented the amount, while southwest winds dimin- ished it. These facts led Prof. Shultz to infer that while the average percentage was kept up by volcanic exhalations, animal respiration, processes of decomposition and com- bustion, and some minor causes, the sea Avas itself a con- stant absorbent of carbonic acid from the atmosphere. The professor is now engaged in endeavoring to learn to what this absorptive power of- sea water is due ; having already ascertained that w^hen it boiled it absorbs scarcely one-fourth part as much as sea water which has lost its carbonic acid by the action of hydrogen. CHAPTER III. NITROGEN AND ITS OXIDES. 111. Nitrogen^ N. Nitrogen^ as we have seen, constitutes about 80 per cent, of the atmosphere, but, without a proper admixture of oxygen, instantly extinguishes flame and destroys human life. It is therefore neither a supporter of combustion nor respiration. Its office in the atmosphere seems to be to dilute and temper the oxygen. Nitrogen may be obtained by the abstraction of oxy- NITRIC ACID. 151 gen from the atmosphere by any body which is very com- bustible and unites readily with oxygen, as phosphorus for instance. This gas when free possesses very little activity, being characterized by its chemical indifference to most other bodies. It was formerly called azote (against life), because animals perish when confined in it. It is very difficult to make it unite with other bodies. With oxygen it forms nitric acid, and with hydrogen am- monia, both of which are powerful fertilizers. At a high heat, it unites with carbon, forming cyanogen^ which is found in Prussian blue. Although nitrogen constitutes so large a portion of the air, it is of no direct benefit to vegetation as such ; nei- ther is it even convertible into ammonia by the direct union with hydrogen, escaping from any substances con- taining: it. 112. Nitric Acid.^O^. Nitric acid is composed of one equivalent of nitrogen, three of oxygen, and one of hydrogen. When pure it is colorless, but generally is a yellow liquid, sold in the shops as aquafortis. It has a sour, burn- ing taste, penetrating, suffocating odor, and is a very pow- erful corrosive poison. It is volatile, and evaporates when exposed to the air, not as rapidly as water, however. It is 50 per cent, heavier than its own bulk of water. Having a strong affinity for water, it condenses mois- ture, and hence when its vapors rise they appear in white fumes or clouds. Nitric acid is a powerful oxidizing agent. By this process it loses oxygen, and is reduced to other compounds, having less nitrogen ; as nitric oxide, nitric peroxide, and nitrous acid. Boussingault, Cloez, and De Luca have abundantly proved the existence of nitric acid in the air by causing 162 CHEMISTRY OF THE ATMOSPHERE. large volumes of it to pass through solutions of potash, or over bricks and pumice-stone saturated with it. These absorbents in this way gradually acquire small quantities of it. And to make the results more conclusive, Cloez and De Luca first washed the air of its ammonia with sulphuric acid. 113. Nitric Peroxide^ NOo. Nitric peroxide (hyponitric acid) is formed from free nitrogen in the atmosphere by electrical ozone. This was demonstrated by Schonbien and Meissner by experiments showing that a discharge of electricity through dry air would cause the oxygen and nitrogen to unite. This explains experiments made by Cavendish as early as 1784, that electric sparks transmitted over a solution of potash in moist air would produce nitrate of potash. 114. Generation of Nitric Acid in the Atmosphere, Formerly it was believed that nitric acid was present in the atmosphere only during thunder-storms. Way and Boussingault, however, have proved by analytical investi- gation, that this principle is not increased by visible or audible discharges of electricity, the rains without these manifestations being equally as rich in nitric acid as others. In fact, Babo and Meissner have demonstrated that there is more of it developed in silent electricity than when at- tended with flashes and detonation. Meissner has also shown that the electric fluid produces a copious formation of nitric peroxide in its path by reason of the heat which accompanies it. This increases the en- ergy of the ozone simultaneously produced, causing it to expand into the oxidation of nitrogen. Another method by which free nitrogen of the atmo- sphere is made to form compounds with oxygen and hydro- gen, is by the processes of combustion and slow oxidation. Saussure first noticed that nitric and nitrous acid were NITRATES AND NITRITES. 153 formed by burning a mixture of oxygen and hydrogen together in the air. Subsequently he discovered that the water resulting from this process contained ammonia. Kolbe also produced reddish-yellow vapors of nitric j)eroxide, by a jet of burning hydrogen communicating with an open bottle containing oxygen. This was pro- duced freely as soon as atmospheric air mingled with the burning gases. Schonbien was the first to observe that nitric acid might be formed at ordinary temperatures. By adding carbonate of potash to the liquid resulting from the slow oxidation of phosphorus, he obtained nitrate of potash. 115. Nitrates and Nitrites, The nitrates are admitted to be among the most efficient means through which plants receive their nitrogen. But although generated to some extent in the atmosphere, they are never imbibed as plant food by the leaves, but have necessarily to pass into the soil, and are taken up by the roots. We will therefore defer what we have to say of them, as well as ammonia, until we come to speak of fertilizers. There is generally an excess of ammonia over nitric acid in the atmosphere; there being a strong affinity be- tween them, doubtless most of the nitric acid as soon as produced unites with the ammonia, forming nitrate of am- monia, which contains more soluble nitrogen than any other substance. As the nitrate of ammonia is not volatile like the car- bonate, it is probable that this salt may be held in a state of mechanical solution until it is brought down by the rains, when it is doubtless soon appropriated as plant-food. The nitrates and nitrites are convertible into each other, and are both of them instantly oxidized by ozone. By pro- longed action both of these classes of salts may be trans- formed into ammonia. 154 CHEMISTRY OF THE ATMOSPHERE. 116. Nitric Acid in Rain Water, Inasmuch as a small bulk of rain washes a large volume of air, it is reasonable to suppose that the rain water con- tains much more nitric acid than the air itself. Liebig first found nitrates in rain water, and the subsequent investiga- tions of Boussingault, 1856-8, amply confirmed the previous announcement of Barral, that nitric acid in combination is almost invariably present in fog, dew, rain, hail, and snow. In 180 rains, snows, dews, etc., Boussingault found only 16 in which he could not detect nitric acid. The total quantity of nitric acid detected in rains at Rothemstead, England, by Lawes, Gilbert, and May, amounted in 1855 to 2.98 lbs., and in 1856, 2.80 lbs. per acre. At Insterburg, Pincus and Rollig found in the rains which fell the year ending March 1865, 7^ pounds of nitric acid. Bretschneider found in 488 gallons of rain water, eleven pounds of nitrogen, equal per acre for one year, 9.93 of ammonia, and of nitric acid nearly one pound. CHAPTER lY. AMMONIA, YAPOR OF WATER, AND OTHER INGREDIENTS OP THE ATMOSPHERE. 117. A7nmonia^ NHo. Ammonia is a colorless gas, having a strong pungent odor. It is condensible into a liquid form, under a pressure of six and a half atmospheres at a temperature of 60^ F. It is composed by weight of hydrogen 8, nitrogen 14 ; by measure, three of hydrogen to one of nitrogen. It is AMMONIA IN EAIN WATEK. 155 alkaline in its character, and denominated by the early- chemists the volatile alkali. Liquor ammonia, according to Faraday, freezes at a temperature of 75^ F. into a colorless solid, heavier than the liquid itself. Water dissolves seven hundred times its volume of this gas. De Saussure says that boxwood charcoal absorbs ninety- eight times its volume of ammonia. This takes place, how- ever, according to Stenhouse, by cooling hot charcoal in mercury or a vacuum. It escapes P9 rapidly that in a short time only minute traces of it are found. 118. Ammonia, in the Atmosphere, Ammonia may be considered as a permanent ingre- dient of the air, as it is constantly escaping from the earth, being generated by the decaying bodies of dead animals, as well as the urine and excrement of living ones, and also from the decay of vegetable substances. Some chemists have estimated the average amount of ammonia, as existing in the atmosphere, at fifty-two mil- lionths. The quantity, however, is necessarily variable, as every rain brings down all that exists between the clouds and the earth, and, for the time being, leaves that part of the atmosphere bereft of it. It is soon, however, resupplied on the principle of dilFasibility. Some idea may be given of the small amount of am- monia existing in the atmosphere by a calculation of Lie- big. He estimates, that if all the ammonia of the air was brought to the surface and compressed into one stratum, it would not be one-fourth of an inch in thick- ness. 119. Ammonia in Rain Water, The results of all the investigations made by Boussin- gault. Way, Knop, and others, as to the amount of ammonia in rain water, make it range from 1 to 33 parts in ten mil- 156 CHEMISTRY OF THE ATMOSPHERE. lion. This applies more particularly to country places. In cities; much larger estimates have been obtained. Summer showers have much more ammonia in them than the long-continued winter rains, as they occur fre- quently and over small extents of country ; the atmosphere being resupplied not only by evaporation, but by difFusi- bility. Upon this j^rinciple the amount of ammonia would be nearly equal in what are termed local showers, and thus the amount of ammonia which a crop receives from the rain may be estimated according to the amount of rain w^ater precipitated. The first portion of a shower of rain that comes down contains more ammonia than the last. Boussingault found 66 parts of ammonia in the first tenth of a slow-falling rain, to tqn million of water ; and in the last three tenths, only 13 parts. The total amount of rain-fall at Rothemstead, England, in 1855, as estimated by Lawes and Gilbert, and analyzed by Way, contained 7 pounds of ammonia for an acre of surface ; and in 1856, 9^ pounds. The estimated amount of rain water being respectively 663,000 and 616,000 gal- lons. Pincus and RoUig found 6.38 lbs. of ammonia per acre for the rain-fall at Insterburg, in 1865; and Bretschneider at Ida-Marienhutte, the same year, estimated 12 lbs. of ammonia for each acre of surface. 120. Relation of Atmospheric Ammonia to Vegetation. The ammonia of the atmosphere, although of small Bignificance ^s to amount, is doubtless of much benefit to vegetation. Escaping as free ammonia from so many different sources, it unites with the carbonic acid of the at- mosphere, forming carbonate of ammonia, which is volatile also, and remains until absorbed and brought down by rain water. STEAM OR YAPOR OF WATER. 167 It is well known by agricultural chemists that ammonia (nitrogen) has the peculiar effect of imparting a rich green color to foliage when it occurs in notable quantity. The change produced in the blades of Indian corn after summer showers is so marked in this regard, that it is clearly infer- able that it does not result exclusively from rendering soluble ammoniacal matters already in the soil, but by furnishing ammonia directly to them brought down by the atmospheric waters. Liebig attributes (very properly we think) the good effect of a top-dressing of plaster on clover to ammonia which has been absorbed from the atmosphere by dews, mists, and rain. The ammonia, having a stronger affinity for the sulphuric acid than lime, takes it from it, and forms sulphate of ammonia ; which is a fixed salt and very solu- ble, being carried down by each succeeding rain to the roots of the plants. 121. Steam or 'Va2^07' of Wate7\ Steam is composed of two volumes of hydrogen and one of oxygen, condensed into two volumes, its specific grav- ity being 0.625. It is volatile, and rises in the air, and in a vacuum, according to the same law by w hich gases diffuse through each other. Dalton discovered that the evapora- tion of water has the same limit in air as in a vacuum. Hence, in order to determine the quantity which rises in a vacuum, it is only necessary to determine the quantity which rises in air. Evaporation is not simply an escape of liquid water, as many suppose. Into the air, inasmuch as water, as such, cannot remain in the air. It would fall by its own gravity. But in the act of evaporation a chemical change takes place ; the w^ater is converted into vapor, three volumes being condensed into two; and thus it becomes a part of the atmosphere. 158 CHEMISTRY OF THE ATMOSPHERE. Steam exists in the atmosphere in an average of about one per cent.; although it is quite variable, being sometimes found as high as three and a half per cent. Yapor is beneficial to vegetation only as it is absorbed by the soil, and enters through the roots ; as there are no well-authenticated facts to prove that it is ever imbibed by the leaves of agricultural plants. Certain air plants (epiphytes), which have no connec- tion with the soil, are known to imbibe moisture from the atmosphere. Mosses and lichens also, which are dry and crisped when there is but little moisture in the air, become pliable, and show signs of vigor and growth, as soon as the atmospheric vapors are known to increase. 122. Other Atmospheric Ingredients, Quite a number of other ingredients have been men - tioned by authors as being contained in the atmosphere. Among them are Marsh Gas, Carbonic Oxide, Nitrous Oxide, Hydrochloric Acid, Sulphurous Acid, Sulphydric Acid, Organic Vapors, and suspended solid matters. (How Crops Feed, p. 91.) None of these, however, if we except the last, occur in such quantities as to be of any interest to the agriculturist. In fact they may be all put down as existing accidentally, not constantly, in the atmosphere. 123. Organic Matters of the Atmosphere, Solid matters suspended in the atmosphere assume some interest under recent investigations made by M. Tissandier, wlio analyzed rain water which fell in Paris on the 1st and 8th of July, 1870, and found that a litre of water contained 0.0658 grams of dry solid residue; containing insoluble mineral matters, 0.0108 grams ; insoluble organic matter, 0.034 grams ; soluble salts, 0.021. This rain water was found to contain 0.02 grams of OKGANIC MATTERS OF THE ATMOSPHERE. 159 nitrate of ammonia. As this salt contains 35 per cent, of nitrogen, it follows that 10 millimetres of rain-fall carried down 70 grams of nitrogen to one hectare of land, besides the organic matter. If this analysis represents rain water generally, the old idea of its being approximately pure, and answering for distilled water in many cases, is exploded. Its value as a fertilizer also is greatly enhanced. Barral and Robinet also profess to have discovered phosphoric acid in rain water in 1862. Luca obtained the same result from w^ater taken from near the surface of the earth, but at a height of 60 or more feet found none. It is supposed that these organic matters are small par- ticles of impalpable dust, carried by the winds to such a height that they are not influenced by gravitation. It is believed that these substances impart the whitish hazy appearance to the sky so often seen in dry windy weather. And when it assumes its deep blue color, it is evident that these organic particles have become saturated with watery vapor and fallen to the earth. This is confirmed in the fact, that such a change in the color of the sky generally precedes rain, being an evidence of greatly increased mois- ture in the atmosphere. PAET Y. CHEMISTRY OF PLANTS. CHAPTER I. ORGANISM OF PLANTS. HYDROGEN AND NITROGEN IN THEM. 124. Organic and Inorganic Constituents, All plants are composed of two classes of substances — • the first, combustible and volatile ; the second, incom- bustible and'fixed. When any vegetable product is subjected to a high heat, that portion which disappears in invisible gases ris- ing and mingling with the atmosphere, is called combus- tible ; that which remains as ash, incombustible. They have also been termed organic and inorganic, because the organic matters which constitute the vital growth and organization of plants and animals are mostly combustible; and the inorganic, which constitute the bases of all minerals, rocks, and salts, are incombustible. In a very just sense, the whole of a plant, embracing the mineral elements as well, constitute its organism. It is only then in a restricted sense that the mineral portion is called inoi-ganic. They constitute so small a portion of plants, that the early chemists regarded them as rather accidental than otherwise. With the exception of very minute portions of sulphur and phosphorus, they exist outside of the true organic compounds, or proximate prin- ciples of plants. OUGANISM OF PLANTS. 161 The organic and inorganic parts of plants may be dis- tinguished from each other, thus : 1. Fire destroys the organic, but cannot affect the inorganic. 2. The first decompose under the influence of warmth and moisture ; while the latter retain their elementary integrity. 3. Organic compounds cannot be made out of simple elements by chemists, while they can build up the most complex and beautiful crystals out of inorganic material. 125. Relative Amount of each in Plants, It is estimated that organic substances, including water, constitute about ninety-five per cent, of all living plants, leaving from one to five per cent, of ash. While the actual amount of these substances found in plants differs essentially, according to their age, the season in which they grow, and the character of the plant ; yet an approximation to the general average may be arrived at by comparing a number of estimates. Wolff and Knop give the following percentage from all the trustworthy analyses made of agricultural plants; all of them air-dried, except the last : Water Organic * water. Matter. Average of all the grasses 14.3 79.9 5.8 " of grains and seeds . . . 14.2 83. 3 2.5 of straw 14.4 80.2 5.4 of chaff and hulls . . . .13.7 77.7 8.6 of roots and tubers. . .85.7 13.4 0.9 of green fodder 79.5 18.8 1.7 126. Organism of Plants, Organic matter may be either structural (made up of cells, fibres, and tubers, as wood and flesh) ; or non-struc- tural — mere results of the nutritive processes of animal and vegetable life, as sugar and fat. 162 CHEMISTRY OF PLANTS. While combastion and decay will disorganize organic substances and render them inorganic, vegetable growth will reorganize these substances, and render them organic again. Thus, when a piece of wood is burned at a high heat, the carbon which constitutes the principal part of its bulk unites with oxygen and flies off into the atmo- sphere, becoming an inorganic gas. It may be again appropriated, however, by plants, and become solid organic w^ood or flesh, in proper combinations. There are many bodies which are organic, but do not enter properly into the structural organism of plants, that leave no ash when burned ; such as dextrine, sugar, and oxalic acid. 127. The Four Organic Elements in Plants, If the invisible gases which escape ii'om burning w^ood and other vegetable substances are gathered in a retort and analyzed, they will be found to consist of four simple elements, viz. Carbon, Hydrogen, Nitrogen, and Oxygen. Carbon, being solid, never enters the roots or leaves of plants except in combination with oxygen as carbonic acid gas. As hydrogen exists in the atmosphere only in vapor, and never in the soil in an uncombined state, it does not enter the roots or leaves of plants in a free state, but in combination as water or ammonia. It is a well-established fact, that oxygen enters plants in carbonic acid both from the soil and the atmosjDhere. It is not believed that nitrogen is ever appropriated by plants as a simple element, but always in combination as ammonia or nitric acid. Oxygen is present also in the ash of plants, associated with phosphorus, sulphur, and iron. Carbonic acid also exists in certain carbonates, as it OXYGEN IN PLANTS. J 63 takes the place of some of the organic acids during the jDrocess of combustion. Hydrogen is never present in the ash of plants, where the burning has been complete and perfect. Nitrogen occurs under certain conditions united with carbon as a cyanide in the ash of plants. In order to effect this the temperature must be very high, and the carbon in excess. Potassium or calcium are the bases with which the union most generally takes place. This combination occurs naturally in only one common plant, viz. the oil of mustard. All of the nitrogen and hydrogen, and much of the oxygen and probably carbon of plants, are furnished them directly from the soil. For while it is true that solid mineral substances do not exist in the atmosphere, owing to their ponderosity, it is equally true that all of the atmospheric elements exist in large quantities in the soil. It may then be safely estimated, that at least one-half of all the substances of which the vegetable world is com- posed comes directly from the earth. 128. Oxygen in Plants, Oxygen is found in the ash as well as in the volatile parts of plants, uniting with all the inorganic elements which enter into living plants, except chlorine. Experiments made by Traube show that free oxygen is essential to the growth of the seedling plant, exciting the plumule, and the parts which are in the act of elonga- tion. It is probable that oxygen is the principle which starts the vital jDrocess in the germ, when moisture and heat expand and burst the capsule. De Saussure proved that oxygen gas was consumed by the buds of trees in the following manner: He took willow and apple twigs with fresh buds and placed them under ^ bell-glass set in water, so as to cut off the outer air, Sub- 164 CHEMISTRY OF PLANTS. sequent analyses proved that the oxygen was consumed by the buds. In a mixture of nitrogen and hydrogen gas, they decayed without any signs of vegetable grov^^th. He also found that free oxygen w^as absorbed by tlie roots of a young horse-chestnut which was carefully taken from the earth and placed in a bottle partly filled with water, and then hermetically sealed around the stem. The plant flourished for three weeks, as did two others similarly treated ; while other plants, placed separately in carbonic acid, nitrogen, and hydrogen, perished. Flower buds consume in twenty-four hours many times their bulk of oxygen gas. Free oxygen does not simply act as food for plants, but also aids in assimilating other substances, which the roots absorb or the leaves organize for the tissues of growing plants. Traube found in the germination of seed, that when the tip of the plumule an inch in length was coated with oil thickened with chalk, so as to cut off a supply of free oxy- gen, the seedling stopped growing at once, withered, and perished. As a further proof that free oxygen must have access to the growing part of a plant, Traube varnished one side of the stem of a young pea vine. The uncoated side contin- ued to enlarge and extend, while the other ceased to grow — which produced a curvature in the stem. 129. Effect of Light on the Transmission of Oxygen, It has been proved by experiments that the leaves and green parts of plants absorb and exhale oxygen during their exposure to light. If you invert a glass funnel, and fill it wnth fresh lecves, placing it in a wide glass vessel containing water, so that it is completely immersed, having expelled the air from its interior by agitation, and making the neck of the funnel IIYDKOGEA^ IN PLANTS. 165 air-tight with a cork, then pour off a portion of the water from the outer vessel, and expose the leaves to a strong sunlight; minute bubbles of air will soon gather on the leaves, which will graduall}^ increase in size and detach themselves, so that in an hour or two enough gas wdll accumulate in the neck of the funnel to enable you to demonstrate that it is pure oxygen. This can be done by bringing the w^ater inside and out- side the neck of the funnel to a level, having the end of a pine splinter glowing hot, but not in a flame, inserted into the gas upon the removal of the cork. The gas will at once become inflamed, and burn much more brightly than in atmospheric air. De Saussure and Grischow found that green plants emit carbonic acid in the dark, and at the same time absorb and appropriate oxygen. During this process, it has been ascertained that the volume of air undergoes diminution; which shows that the quantity of ox3'gen gas absorbed must be greater than the volume of carbonic acid separated. In no case has it been known that oxygen gas has been exhaled from plants in the absence of light. It is a known fact that the leaves of plants absorb oxy- gen during the night ; and it has been proven by actual experiments that both oxygen and carbonic acid are ab- sorbed by their roots. This can be demonstrated by par- tially filling a bottle w^ith water, saturated with carbonic acid gas, and inserting the roots of a growing plant in it. The carbonic acid of the water, as well as the oxygen of the atmosphere in the bottle, will gradually diminish. While if the atmospheric air is substituted by the carbonic acid, or by nitrogen or hydrogen, the plants will speedily die, showing the importance of oxygen to their vitality. 130. Hydrogen in Plants, It is doubtless through water that plants receive most 1G6 CHEMISTRY OF PLANTS. of their hydrogen. In the interior of plants, this water is constantly undergoing decomposition, and in this way hydrogen is supplied to them. Another source of hydrogen to plants is ammonia, which is a combination of hydrogen and nitrogen, and one of the most powerful fertilizers known. While this is owing, no doubt, to the nitrogen it contains, its hydrogen is also appropriated we doubt not. Light carburetted hydrogen gas contains about one- fourth of its weight of this element, and is known to be freely evolved from the decay of vegetable matter in the soil. This probably may be another source, both of carbon and hydrogen, to plants, as their roots are known to take up gaseous substances in the soil. 131. Nitrogen in Plcmts, Nitrogen is a constant ingredient of all plants, and of the muscles, tendons, nerves, etc., of animals; hence all nutritive food has in it larger or smaller quantities. It will not average in plants more than from two to three per cent, and yet no plant can exist without it. Notwithstanding the atmosphere is the great store- house of nitrogen, yet plants never imbibe it from the air; it only reaches them through the soil, and then never as nitrogen, but either as nitric acid or ammonia. Deherain, having conducted a number of experiments in reference to the relation of the nitrogen of the atmo- sphere to vegetation, arrives at the following conclusions : "First, that in the course of the slow combustion of organic matter, the nitrogen of the atmosphere enters into combination, j^robably to form nitric acid, which, in con- tact with an excess of carbonized matter, is reduced and then gives up nitrogen to the organic matter. " Second, that every plant which throws off refuse mat- ter upon the soil which sustains it, furnishes the occasion of PLANTS DO yOT ABSOEB OR EMIT XITEOGEX. IG7 a greater or less tixation of nitrogen. This reaction, con- tinued for many years, ultimately produces the accumula- tion, in soils left to themselves, of a quantity of nitrogen sufficient to maintain a large crop of cereals.*' Xitric acid and ammonia are both formed in the atmo- sphere in minute quantities, and brought down to the earth by rains, and thus appropriated as food for plants. The average fall of nitrogen in atmospheric waters, allowing that all should be retained and appropriated by the crop, would suffice to make about one-half a crop of wheat, and one-third of a crop of cotton. But when it comes to high farming, this amount would have to be tripled and cpiadrupled. For nine years, at six difierent stations in Prussia, the average fall was 9.06 lbs. per acre. On this basis, the amount of nitrogen contained in an average crop of wheat, say 9^ bushels and 1 cwt. of straw, would be 15.11 lbs. In the whole of the cotton plant, to make 500 lbs. of seed cot- ton per acre, which may be put down as a fair average crop according to the best analyses we have (which are very imperfect), the amount of nitrogen would be 2Tf lbs. 132. Plants do not Absorb or Enut Xltrogen. As early as 1779, Dr. Priestly gave it as his opinion that plants absorbed nitrogen from the atmosphere. Twenty years later, De Saussure experimented on the subject and arrived at a differeiU conclusion. In 1S51 it was satisfac- torily demonstrated by Boussingault that plants received no nitrogen as food in this way. M. Vilie, however, about the same time experimented on a larger scale, and came to a difierent conclusion. In 1S54, Boussingault repeated his experiments with moi'e satisfactory results than before. Subsequently, 31. Cloez, who was employed by the French Academy to supervise a repetition of the experi- ments of M. Ville, found that o. quantity of arnntonia icas 163 CHEMISTKY OF PLANTS. either generated or introduced into the apparatus^ which vitiated cdl his results. If any doubts had remained of the correctress of Bous- singault's conclusions, they were entirely removed by the researches of Lawes, Gilbert, and Pugh, in 1857 and '58, at Rothemstead, England. They conducted twenty-seven experiments on graminaceous and leguminous plants, and on buckwheat; and confirmed the fact previously demon- strated by Boussingault, that plants do not absorb nitro- gen from the atmosphere. These experiments, curious and interesting in themselves, may be found in an elaborate memoir prepared by them in the Philosophical Transactions for 1861. Another error entertained by some of the early vege- table physiologists, that nitrogen is emitted in small quan- tities by plants, was clearly proven to be untrue by Cloez and Boussingault as late as 1863 and 1865. CHAPTER XL RELATION OF CARBON AND CARBONIC ACID TO PLANTS, ETC. 133. Carhon in Plants, Carbonic Acid is found in the ash of plants, combined with bases which were united in the living plant wdth or- ganic acids. These liavingbeen expelled by the heat, are replaced by this more incombustible acid. The amount of it found in ash depends on the temperature produced in the analysis. It occurs in many other plants as a car- bonate of lime. In 1840, Boussingault proved that the foliage of plants absorbed carbonic acid from the atmosphere, and was nourished thereby. He caused a current of air with about EFFECT OF SOLAR LIGHT. IGO rAu carbonic acid to pass into a vessel having three tubes, one of them containing the branch of a living vine which had borne twenty leaves, the tube being sealed round the stem so as to admit uo air. This air, after passing into one tube over the leaves ac the rate of fifteen gallons an hour, passed out at a third tube into an arrangement for collecting and weighing the carbon/ " acid gas. It was found that in sunlight, the leaves consumed three-fourths of the carbonic acid. Plants purify the air by taking up carbonic acid, and throwing off oxygen. Animals, on the other hand, inhale and appropriate oxygen, and throw off carbonic acid ; thus they are promotive of each other's health, and depend the one upon the other for their very existence. 134. Deconipositioii of Carbonic Acid hy Solar Light, De Saussure found that when the atmosphere was aug- mented from tlie natural amount of carbonic acid in it (being about ^Vo" bulk) to -^^^ plants thrived more rapidly in the sunshme : but beyond this it acted dele- teriously. In the shade, however, any increase over the natural quantity proved injurious to plants. As early as the middle of the eighteenth century, Charles Bonnet of Geneva established the fact, as he sup- posed, that the green portion of plants under the action of solar light decomposes the carbonic acid taken into them by their roots, when carried to their leaves, assimi- lating the carbon and rejecting the oxygen. This was a remarkable approximation to the truth for that early period. Ingenhouz, a German physician, subsequently demon- strated that thic:, Bmi'^.al action was the result of sun- light purely, and that t he coloring matter of the plant had nothing to do with it ; that the sun does not begin to perform this function until it is some distance abnye the 8 170 CHEMISTHY OF PLANTS. horizon, and ceases it entirely during the darkness of the night; that plants shaded by high buildings, or other plants, do not perform this function, and hence, instead of purifying the air of the noxious carbonaceous vapors, really render it poisonous around our dwellings ; that all plants corrupt the surrounding air during the night, while, aided by sunlight, they purify it by retaining the carbon and emitting only oxygen. De Saussure established by experiment, that young peas in sunlight would endure an atmosphere for some days, containing 50 per cent, of carbonic acid. When increased to 66 per cent, however, they soon died. When reduced to -^^ part of the acid, they flourished better than in pure atmospheric air, increasing 11 grains in eight or ten days; while in the natural atmosphere, the increase was only 6 grains. He also found that the foliage of plants could not long exist in air exposed to direct sunlight, bereft of carbonic acid. This was done by covering young plants in a bell- glass, and exposing them to the action of moist, caustic lime, which would rapidly absorb the carbonic acid. The leaves soon turned yellow, and dropped off in two or three weeks. In the dark, however, they flourished all the better, by having the carbonic acid taken up by the lime. Boussingault also demonstrated that pure carbonic acid was not decomposed by the leaves of plants in sunlight, as when mixed with oxygen, nitrogen, and hydrogen. From experiments by De Saussure, and later, by linger and Knop, it has been proven that the oxygen exhaled in sunlight is nearly equal in volume to the carbonic acid absorbed. As the free oxygen occupies the same bulk as the carbonic acid, most of the carbon is retained by the plant. The amount of carbonic acid absorbed, however, is FIXATION OF CARBOX IN PLANTS. 171 much greater by daylight, than that exhaled during the night. The colza, bean, raspberry, and sunflower, in 15 or 20 minutes of direct sunlight, absorbed as much carbonic acid as they exhaled during a whole night. Corinwinder also found that a colza plant took up in one sunshiny day more than two quarts of gas, the carbon of which was retained. Boussingault found that a square surface of oleander leaves decomposed in one horn of sunlight, sixteen times as much carbonic acid as the same surface of leaves exhaled in the dark in the same length of time. 135. Fixation of Carbon in Plants, It is believed that the grains of chlorophyl in the stems and leaves of plants has an intimate relation with the fixation of carbon from the carbonic acid of the atmo- sphere. Microscopic observations of the developments of some of the carbo-hydrates, especially starch, which begins its organization in the chlorophyl grains, as well as some experiments made by Gris, in the withholding iron from plants, have led to this conclusion. This chemist found that when iron was withheld from plants, the leaf would attain a certain development, but chlorophyl not being formed, the plant would soon die. Prof. Johnson also states that experiments show that oxygen is given off, carbonic acid decomposed, and carbon fixed, only where the microscope reveals the presence of chlorophyl. The unfolded leaves of plants imbibe carbonic acid and decompose it, fixing the carbon through chlorophyl, the oxygen being set free. This process transpires only under the influence of sunlight, which produces decom- position. The carbo-hydrates whicli result from the carbon thus fixed, are believed to be formed in the chloro- phyl cells of the leaf. 172 CHEMISTRY OF PLANTS. Carbon is also fixed in the plant under the influence of light, as first discovered by Ingenliouz as early as 1779. When a seed germinates in the absence or light, it loses its weight by slow oxidation from the consumption of carbon and hydrogen. Boussingault proved this in an experiment with two beans; one being placed in dark- ness and the other in ordinary light for 26 days. The gain and loss of dry w^eight of carbon is thus estimated: 136. Exhalation of Carbonic Acid in Diffused Light, It was early demonstrated by De Saussure and others that carbonic acid is exhaled from plants during nights and cloudy days, in the absence of solar light. Senncbier found that the oxygen which was exhaled by sunlight, was produced by the decomposition of car- bonic acid, while the carbon was appropriated to the plant, and it is believed that carbonic acid is not absorbed and decomposed by the plant in total darkness, but only produced in and exhaled from it. Either oxygen or carbonic acid may be exhaled from plants in preponderating quantities, of cloudy days and in diffused light, according to circumstances. Corinwinder discovered an exhalation of carbonic acid in this diffused light from several plants, as tobacco, cabbage, sunflower, etc. Under similar conditions he observed the evolution of oxygen from the lettuce, pea, violet, and fuchsia. In one experiment the bean exhaled neither gas. Plants when quite young evolved carbonic acid better than when old; when quite old they ceased it altogether. In later investigations in 1861, Coi in winder found Gain in light. LosB in darkness. Carbon . . . Hydrogen Oxygen . . 0.1926 0.0200, .0.1591 0.1598 0.0332 0.1766 SUPPT-Y OF CARBONIC ACID. 173 lliat buds and young leaves absorb oxygen, and exhale carbonic acid even in bright, sunshine. He also found that all leaves exhale carbonic acid by day as well as by night, when placed in the diffused light of a room Avhich is illuminated only from one side. A plant which in full light yields no carbonic acid from its foliage, immediately gives off this gas when placed in such an apartment, and ceases to do it when removed from it. Garreau in 1851, and Corinwinder in 1858, I'eviewed the whole subject of the relation of carbonic acid tu plants, confirming former conclusions, and adding more facts to those already ascertained. They found that there are constantly going on in tlie plant two opposite pro- cesses ; the first, the exhalation of carbonic acid and evolution of oxygen ; this process corresponding* to the respiration of animals ; the other process being the fixa- tion of carbon in plants. The absorption of oxygen and exhalation of carbonic acid seem to be independent of solar light, and go on during every hour of day and night. But although car- bonic acid is constantly produced under the influence of the solar rays, the absorption of carbonic acid and exhala- tion of oxygen take place with greater rapidity, so that the first result is completely masked to the experimenter. The preponderance then of the latter process over the for- mer is all that we can estimate. 187. Supply of Carbonic Acid, Although carbonic acid forms so Fmall a part of the weight of the atmosphere (about ^oIto')? J^^j estimated in its entire height in the air surrounding the globe, there are in round numbers 3,400,000,000,000 tons; amounting to about 28 tons for every acre of the earth's surface. Chavendier estimated that an acre of beech forest would consume annually 1950 lbs. of carbon, equal to 3^ tons of 174 CHEMISTRY OF PLANTS. gas. Thi-s would in about eight years consume all the car- bonic acid of the atmosphere, if every acre of vegetation destroyed as much, and there were no processes of restora- tion going on. (How Crops Feed, p. 47.) But when we remember that not more than one-fourth of the earth's surface is land, and the general average of consumption must be much below that of a thrifty forest, as Prof. Johnson says, we are warranted in the assumption that there is now existing enough for one hundred years' growth without any replenishing. But then, as we have already stated, this ingredient of the atmosphere is resupplied as fast as appropriated to vegetation, by the oxidation of carbon from decay of or- ganized bodies, both animal and vegetable, the combustion of fuel, and the respiration of animals. 138. CarhoiiiG Acid from tJie Soil, Although it is belicA^ed that about one-third of the car- bon of plants is supplied them through the roots from the soil, yet it is equally true that some plants may grow to a normal standard without receiving any carbon from the soil. Boussingault developed full-sized sunflowers in this w^ay, which received no carbon from the soil except what the seed contained. Prof. S. W. Johnson did the same with buckwheat, and others have produced perfect plants of maize and oats in weak saline solutions without car- bon. Recent experiments by Hellriegel have led him to infer that the atmospheric supply of carbonic acid is probably sufficient for the jDroduction of a maximum crop under all circumstances, as an artificial supply to the soil had no eflect to increase the crop. We think, however, that this needs fiirther demonstration, as there are many facts which tend to prove that plants receive a good portion of carbon CHAXGES IN THE VEGETABLE TISSUES. 175 through their roots ; not the least of which is, that the sap of plants is little else than carbonated water. 139. Carbonic Acid cts ci Solvent. Carbonic acid does not only furnish food directly to plants, but is one of the best solvents in nature for the pre- paration of other insoluble substances, not otherwise capa- ble of being appropriated as plant-food. In union with water it not only attacks the insoluble phosj^hates of the soil and renders them soluble, but granite, limestone, and magnesia rocks, which are by slow processes disintegrated and crumbled into fine powder, and made available food for plants. By uniting with the ammonia of the atmosphere, and the potash and soda of the earth, carbonic acid forms three alkaline carbonates, all of which have the power of dissolv- ing silica, which enters very largely into the straw of the cereals and some other vegetable organisms. The three minerals of which granite is composed, quartz^ feldspar, and mica, all contain a large amount of silica, and are slowly attacked by these carbonates, and rendered sol- uble, and by union with the potash made available as plant- food. 140. Changes in the Vegetable Tissues. Lawes, Gilbert, and Pugh made some interesting expe- riments to estimate the changes which transpire in the vegetable tissues. They found that the atmospheric air in plants, wdien removed from sunlight, had, in an average of three experiments, nitrogen, 74.08, oxygen, 7.37, and car- bonic acid, 18.56 per cent. While in sunlight it had of nitrogen, 33.4, oxygen, 26.02, and carbonic acid, 5.56 per cent. Thus at night the air of plants contained 41.04 more nitrogen than under the solar rays, 18.65 less of oxygen, and 13.00 less of carbonic acid. Admitting, as we must, that the atmospheric air freely .176 CHEMISTRY OF PLANTS. penetrates the vegetable tissues, we can easily perceive what changes are going on in them day and night. In sunlight the carbonic acid undergoes decomposition, the oxygen being set free, while the carbon remains to form the solid constituents of the plant. In darkness the oxygen of the air in the plant takes carbon from the vegetable tis- sues, and forms carbonic acid with comparative rapidity, so that the oxgen is reduced from its normal standard 21, down to 7.37, on an average, and in one of the experiments as low as 3.75 : while in others not here estimated it is re- duced to less than one per cent. (How Crops Feed, p. 46.) 141. Tahidar View of the delation of Atmospheric Ingredients to Plant Life, The following tabular view of the relation of the atmo- spheric ingredients to the life of plants, is given by Prof. Johnson. (How Crops Feed, page 98.) ABSORBED BY PLANTS. Oxygen, \>j roots, flowers, ripening fruit, and by all growing parts. Carbonic acid, by foliage and green j^arts, but only in the light. Ammonia, as carbonate, by foliage, probably at all times. Water, as liquid through the roots. Nitrous acid, \ united to ammonia and dissolved in through the Nitric acid, S roots. i Ozone, , , . ' \ uncertani. Marsh gas, ) NOT ABSOKBED BY PLANTS. Nitrogen. Water in vapor. Oxygen, ) foliage and green parts, but only in the light. Ozone, ) EXHALED BY PLANTS. Marsh gas is transferred by aquatic plants Y Water as mjyor, from surface of plants at all times Carlonic acid, from the growing parts at all times. INOKGANIC ELEMENTS AND THEIR IMPORTANCE. 177 CHAPTER III. MINERAL ELEMENTS OF PLANTS.— THOSE DEEMED ACCIDENTAL. THOSE ABUNDANT IN SOILS. 142. Inorganic Elements and their Importance, The mineral or inorganic constituents of plants are alumina, manganese, iodine, iron, silicium, sulphur, phos- phorus, chlorine, potassium, sodium, calcium, and magne- sium. Of these, alumina, manganese, and iodine, are deemed to be rather accidental than essential ; while iron and silica are so abundant in nature that tliey are never exhausted from a soil, or needed as a fertilizer. None of these inorganic elements are capable of enter- ing the structure of plants, as they exist in soils or rocks in a solid state, however minute they may be made ; and with the exception of sulphur, are rarely found in an un- combined state, but most generally combined with oxy- gen, occasionally with one another, and with carbonic acid. Metallic oxides exist in every plant, and may be de- tected in their ashes after incineration, and the organic acids existing in the juices of vegetables are generally combined with these metallic oxides, or the inorganic bases. The following, among other considerations which might be mentioned, w^ill show the importance of the inorganic elements to plant-life : 1. On whatever soil a healthy plant is grown the quantity and quality of the ash is nearly the same. 2. While each species shows about the same quantity of the same elements, distinct species show very diiFerent results, both as to kind and quantity; and the more remote 178 CHEMISTRY OF PLAIS'TS. the natural affinity of the species, the wider the differ- ence. 3. No perfect plant can be produced in a soil where one of the more important elements is absent, as phos- phorus, potassium, sulphur, calcium, magnesium, etc= 4. Soils which have been reduced to a very low state of fertility by constant cropping, and carrying off their elements in the crops, have been at once restored to their original fertility by a reapplication of these mineral ele- ments. 143. Alumina^ AL^Og. Alumina is the only known oxide of aluminum. It is isomorphous, with sesquioxide of iron, and so intimately as- sociated with the peroxide, that they, together with silica, form the red clay hills of all primary regions. The hydrate of alumina combines with certain kinds of organic matter so intimately as to extract their coloring matters and thus form the i^igments which are termed lakes. Thus its intimate association and combination with the vegetable matters of the soil have important offices in agricultural production. Alumina combined with silica forms clay which con- stitutes the basis of porcelain and earthenware. This is a most essential ingredient of all fertile soils, improving their physical qualities and holding moisture and ammonia, with other salts, as food for plants. The sulphate of aluminum and potassium (common alum) is known to possess fertilizing powers; and possibly by this means plants are furnished with the small amount of alumina which exists in them. The phosphates of alumina occur in such inappreciable quantities in most clay soils, as to elude the common pro- cesses of analysis; and yet they are believed by chemists to constitute a trace of all clay soils. Being insoluble, how- MANGANESE. 179 ev'er, tliey can only furnish food for plants after changing their form. Pure alumina is nearly white, and has 48.70 of oxygen, and 53.30 of the metal aluminum. This metal was first discovered by Sir H. Davy, and occurs in a pure state in some rare minerals, as corundum, the sapphire, and the ruby. Although alumina forms a large portion of the ci'ust of the globe, it contributes but liftle to the direct nourish- ment of plants. It performs, however, a very important agency in agriculture, and constitutes an essential part of all productive soils. Hence it is important that its phys- ical and chemical qualities should be well understood by the agricultural student. According to De Saussure, Sprengel, and the older chemists, alumina is found in small quantities in straw and grains of most agricultural plants. In the ash of wheat, Sprengel found in one analysis 1.90 per cent. Modern chemists, however, ignore it as not essentiah 144. Manganese^ Mn. Manganese is found generally but sparsely in all soils, mostly associated with iron, which it resembles in many of its properties. It is not, however, used to any extent in the arts. Oxide of Manganese is found in most plants in small quantities, either as peroxide, MnO, MngO.,, or sesquioxide, MrioO.^. The former is the black manganese of commerce, called by mineralogists pyroto^V^. The salts of manganese exist in much less quantities in plants than iron, and as neither of the oxides is soluble, they must first be changed into other and more soluble forms, as the chloride, cai'bonate, and sulphate. J. A. Vs'anklyn, in investigating the value of different leaves for tea, found that beech leaves contained so much 180 CHEMISTRY OF PLANTS. rnanganese as to cause it to show a decided green color in the dry state, and upon treatment with ^vater it exhibited the characteristic red solution of permanganate of potash. It may thus be essential to certain trees and plants, as the beech, and aid in giving fragrance to tlie tea; but in com- mon agricultural plants it is not deemed an essential ingre- dient. It has lately been ascertained also, that beech-nuts con- tain a large percentage of manganese, although the soil in which they are grown may exhibit no appreciable trace of this metal. 145. Iodine^ I. Iodine exists in sea water in small quantities as an iodide of sodium. It is poisonous both to animals and plants. It has been found as a constituent in the Fucus lami- naria, and other marine plants, but has never been detected in crops usually raised for food. It is slightly soluble in water, and affords a striking test for starch, by the beautiful blue color it imparts to this substance when brought in contact with it. Iodide of potassium has been applied to certain plants, causing them to thrive. It is, however, of no special inter- est to the agriculturist, although it may be true that cer- tain marine j^lants cannot exist without it. 146. /ro/?., Fe. Iron is known to be of great importance to plant-life, although it is found in them in very small quantities. The peroxide, Fe^O., is the form in which it generally exists in plants. It occurs abundantly in nature, more so than any other simple element except siliciuni and aluminum. As indi- cated by the table, it has 30.66 per cent, of oxygen, and is insoluble except in water containing acid in solution. 181 It has the power of absorbing ammonia from the atmo- sphere, as well as from soils, when deposited in fertilizers, or by rain water, and thus retain it for the benefit of plants. In iron soils abounding in humus, this oxide is de- prived of one-third of its oxygen by the carbon of the decaying vegetable matter, and thrown back into a pro- toxide, which, being made soluble by the acids it comes in contact with, is taken up by plants and proves deleterious to them. A good practical suggestion may here be made ; red irony soils should be stirred as frequently as possible, so that the oxygen of the air may unite wiili the bLack oxide, and prevent its deleterious elFects upon the growth of plants. The tendency of the black oxide is to unite with moi'e oxygen and form the red oxide. This is constantly tran- spiring in chalybeate waters. When they first rise they are tinctured witli the protoxide, but upon exposure to air they change, and the stream is found lined with a reddish sedi- ment of insoluble peroxide. Both of these oxides are insoluble except in water containing acids in solution. The black oxide is much more soluble, however, in the same weight of acid, and in boggy lands often proves injurious to vegetation. Carbonate of iron is another form which exists in our soils, especially as bog iron ore, in low marshy places. Being wholly insoluble in water as a carbonate, it cannot as such prove deleterious to plants, but is first converted into a peroxide, and then back into a jjrotoxide, which is very soluble, and easily taken up by plants. As iron is a constant constituent of all plants (though ofttimesin mere traces), it must have some important office to perform in the v(>getable organism, as it has in the animal, where we know without it the blood corpuscles could never be formed, and death would soon ensue from 182 CHEMISTRY OF PLANTS. anemia. Liebig thinks that the action of iron is so im- portant to the function of jDlants, that the absence of it would endanger their existence. As iron is a necessary constituent of the food of ani- mals, they must die without it in their food. Hence, as men live and thrive on vegetable diet, it is inferable that vegetables intended for nutritious food would have iron in them. Prince Salm-Hostmar planted grass and colza in a soil destitute of iron, and they became chlorotic; but when iron was put in the soil the chlorosis disappeared. In 1849 Eusebe Gris first considered chlorosis of the leaves due to a want of iron. M. Boussingault has recently shown that the white blood of the invertebrates has almost as much iron as red blood ; and plants destitute of green coloring matter, as mushrooms, have as much as those which are colored. 147. Silica, Si2O=60. Silica occurs as rock crystal, or in massive quartz. When pure it is perfectly transparent and colorless, ap- proaching in hardness the precious stones. Native Silica is insoluble in water, and in all the acids except the hydrofluoric. It has the power, however, when finely divided, of uniting with bases. Common glass, and other artificial forms of silica, are much more easily acted upon by solvents than the native crystals. If an excess of hydrochloric acid be added to a dilute solution of an alkaline silicate, the silica is dissolved. A solution of hydrate of silica may be thus obtained, con- taining five per cent, of silica in cold water. This may be concentrated up to 14 per cent, by boiling down in a flask. There are two forms of hydrate of silico, one of which, very white and light, occurs naturally and abundantly in SILICA. 383 beds at the base of the chalk formation. This forms sili- cate of calcium when united with slaked lime. All spring and river waters contain traces of soluble silica, as tineiy divided sand is dissolved by the alkaline carbonates. The silica is deposited in the insoluble form upon evaporation. Where the water is of high tempera- ture, as the boiling springs of Iceland, the dissolved silica occurs in large quantities, as is seen deposited in petrifac- tions exposed to the stream. A class of minerals called zeolites, also contains silica in soluble forms, as hydrated siliceous compounds. Thus we see that processes are constantly going ou in nature to prepare this hard and insoluble mineral, which occurs so lai'gely in the cereals and other agricul- tural plants to be assimilated by them. Xotwithstanding recent experiments in water culture in Germany seem to indicate that silica is not essential as a constituent of plant food, yet we cannot believe that a substance enterinsj so lars^elv and constantlv into aori- cultural plants could be merely acci*lental. Thus, as will be seen by our tables, two-thirds of the ash of wheat straw is composed of silica, 46.4 per cent, of the ash of oat grain, and 27.2 of barley; while the ash of the grain of millet with the husk, is more than one-half silica. The silicates occur abundantly in nature. Clay, fel- spar, mica, hornblende, and a large number of other min- erals, are compounds of this character. Many of these are double silicates, and of complex composition. Silicic acid has a very feeble acid character. The ordinary vegetable acids, as the acetic, oxalic, and tartaric, separate it from its combinations with the alkalies ; and the same purpose is effected by a current of carbonic acid, or its gradual absorption from the atmosphere. 184 CHEMISTRY OF PLANTS. CHAPTER lY. OF MINERAL ELEMENTS ESSENTIAL TO VEGETATION AND NOT ABUNDANT IN SOILS. 148. PhosrjlioTiis, P=31. Phosphorus was discovered by Brandt in 1669. It never occurs in nature uncombined, and only in small proportions as a phosphate of calcium, in the primitive and volcanic rocks. By gradual decay it passes into the soil, where, being dissolved by carbonic acid, and thus rendered soluble, it accumulates in organic matters, being extracted by plants, and thus becomes sparsely but uni- versally diiiused even in soils which have none in their underlying rocks. Phosphorus is a colorless waxy-looking substance, and becomes hard and brittle at low temperatures. It is exter- nally inflammable, takes fire in the open air at a tempera- ture but little above its freezing point, and emits white vapors of an alliaceous odor. It is insoluble in water, slightly soluble in ether, oil of turpentine, and the fixed and essential oils. This important element seems to be essential to the exercise of the higher functions of animals, as it always exists in the brain and nerves. It also forms the principal part of the earthy constituent of their bones. Phosphorus furnishes four compounds with oxygen, two of them anhydrous : Phosphorus anhydride, P2O3=110. Phosphoric anhydride, P205=142. It forms also three oxidized acids, which are monobasic, dibasic, and tribasic, in proportion as the oxygen increases. Thus we have : suLriiuR. 185 Ilypophosphorous acid (monobasic), IIPII.,Oi). Phosphorus acid (dibasic), H.PHOs. Phosphoric acid (tribasic), PI8PO4. When the oxide of phosphorus represented by P2O5 is acted on by water, it forms phosphoric acid, a most essen- tial constituent of all plants, especially of the seed, and the most important of all compounds used to fertilize soils. 149. SulpJiur, S=32. Suljyhur is found, native or uncombined, in amorphous masses, or in transparent yellow crystals. It is presented in commerce in round sticks, called roll sulphur, or hrim- stone ; also in a harsh yellow powder, known flowers of s\dplim\ It is insoluble in water, tasteless, and is a bad conductor of heat. Most of the sulphur used in this country is obtained from Sicily, where it occurs, uncombined, in a blue clay forma- tion, stretching for a number of miles between Mount Etna and the southern coast. It forms many compounds in na- ture, which are more or less abundant, as the sulphides of iron, copper, lead, and zinc. Iron pyrites (bisulphide of iron) is extensively used in the manufacture of oil of vitriol. Sulphur exists also very extensively in an oxidized con- dition as sulphuric acid in combination with various earths; of these, the sulphates of calcium, magnesium, barium, and strontium are the most abundant. Sulphur is an essential ingredient of many bodies of organic origin, both animal and vegetable ; it is a neces- sary constituent of muscular tissue in animals, enters into the composition of several volatile oils, and is always found in the albumenoids. There are tvro anhydrous oxides of sulphur : sulphurous and sulphuric. The acids resulting from them are exten- sively used in the arts. The sulphuric acid especially is 186 CHEMISTRY OF PLANTS. important to the agriculturist in many ways which will be treated of in another part of this work. 150. Potassium, K=39.1. Potassium is a bluish white metal, brittle, having a cr3^s- talline fracture at 32°. It has a specific gravity of 0.865, being light enough to float on water. Oxygen has a powerful attraction for potassium, which decomposes nearly all the gases containing it, if heated when in contact. Three well-defined oxides of potassium are formed by these combinations, the most important of which in agriculture is potash, K20=94.2. Hydrate of potash, or caustic potash, KHO, is prepared by dissolving pearlash, an impure variety of carbonate of potash, in ten or twelve times its weight of water, and add- ing caustic lime equal to half its weight. This is an indis- pensable reagent to the chemist, and has been used in cer- tain combinations as a fertilizer. Potash is an indispensable constituent of all fertile soils, and is found in a considerable per cent, wherever felspa- thic and micaceous rocks have become disintegated. It ex- ists largely in all agricultural plants, as will be seen from the tables in this work. Chloride of potassium and magnesium has been found in extensive beds of clay in the neighborhood of Stassfurt, in Prussia, lying immediately above a bed of rock salt 100 feet in thickness. It is used extensively as a fertilizer in Europe, and is now combined with most of the fertilizers for cotton and tobacco in this country. This bed contains the sulphates and chlorides of potassium, sodium, and mag- nesium, and is believed to have been formed by the drying up of an inland sea, the common salt crystallizing out first and sinking to the bottom. Nearly one-fourth of the mine is made up of the chloride of potassium. CALCIUM. 187 151. Sodium^ !N'a=23. Sodium has a bluish white color, and resembles potas- sium in most of its qualities, being somewhat more volatile. It forms two well-known oxides of sodium, common soda and the peroxide of sodium y the latter contains twice as much oxygen as the former. Besides these, a blue suboxide appears also to exist. Sodium occurs in several minerals, as albite, a species of felspar, cryolite, and the double fluoride of sodium and aluminum. Borate of sodium (common borax), is also a native compound. But common salt, existing in extensive mines and in sea water, is the great source from which the sodium of commerce is derived. Chloride of sodium, as such, occurs in plants, as has been noticed under chlorine. Recent experiments in water cul- ture seem to indicate that soda is not an essential consti- tuent of plants. It is very satisfactorily jDroven by experiments made in 1874 by the author, in flower-pots containing river sand, out of which all soluble matters had been washed, that soda is at least essential to the cotton plant. The pot containing all the elements except sodium, produced a diminutive, sickly plant, only a few inches high, with no branching stems or any forms for fruit, much less the fruit itself. 152. Calcium J Ca=40. Calcium is a very abundant and important constituent of soils and plants. It is the metallic basis of lime, from whence it derives its name, calx^ lime. It is found in nature in combination with fluorine, but more frequently as a carbonate and sulphate. Calcium has the color of gold alloyed with silver, has an intermediate hardness between lead and gold, and melts at a red heat. Water is rapidly decomposed by it, hydro- 188 CHEMISTRY OF PLANTS. gen being evolved, and ?iydrate of lime formed. It has only one oxide, lime, wliich will be described under the head of special fertilizers, with other of its compounds deemed useful in agriculture. It is a very essential constituent of plants. It exists in the ash of some of the grasses from 10 to 12 per cent., and in clover and fodder plants from 30 to 60 per cent. It constitutes 10.5 per cent, of the ash of corn stalks and 37.9 of pea vines. In cereal grains it ranges from two to four per cent. 153. Magnesium^ Mg=24. Magnesium is a malleable, ductile metal, having the color of silver : it is susceptible of a high polish, but is slowly oxidizable in moist air. It has been classed with those metals the oxides of which form the alkaline earths; but is now deemed by chemists to be more analogous to zinc in its properties. It is an abundant ingredient of the crust of the earth, and occurs in large quantities as a double carbonate with calcium, forming dolomite or the magnesian limestone. It exists in all agricultural plants, as an oxide or some of its compounds, and next to phosphoric acid and potash is the most abundant constituent of seeds. In the small grain cereals it ranges from 8 to 12 j^er cent., and in Indian corn runs up as high as 14.6 per cent. 154. Chloriyie, Cl=35.5. Chlorine is a transparent gas of a greenish-yellow color. It is much heavier than air, is not combustible, and does not combine directly with oxygen. It is found abundantly in nature in combination with sodium, with which it forms our common table salt. Chloride of sodium is the most abundant saline body found in sea water ; and many beds of it exist in various CHLOEINE. 189 parts of the world. Chloride of potassium also exists in minute quantities in the waters of the ocean, and has been found in extensive mines at Strassfurt, Prussia. Chlorine is a rare constituent both of plants and soils. As it is found as chlorides of sodium ai;id calcium in vege- tation, it is probable that it enters plants in such com- binations. And as green leaves under the influence of the sun have the power of decomposing common salt, it is probable that whatever of chlorine is admitted into plants more than is proper to their nourishment is thus given off. The same may be true of other chlorides, as of magnesium and potassium; and when the chlorine is evolved their bases may be retained by the plant as appro- priate nourishment. The chlorides are no doubt very injurious in overdoses both to animal and vegetable life in the soil. The famous Dead Sea (Lake Asphaltis) of the East, is a striking me- mento of this fact, as vegetation is destroyed on its shores and for miles around. It was a custom among the ancients when they wished utterly to destroy a city, to plough it up and sow it with salt, as this was known to effectually kill vegetation for many years. Dr. Kedzie, of the Michigan Agricultural College, says that a vigorous sassafras tree on the college grounds, had inadvertently poured around it, a quantity of strong brine, which formed near by, a stagnant pool. The salt was absorbed, unchanged, by the roots in immense quantities which, entering the circulation, left a white crystalline deposit on the surface of the leaves. The tree withered and died in a short time. 190 CHEMISTRY OF PLANTS. CHAPTER V. PROXIMATE ORGANIC PRINCIPLES. — ALBUMINOIDS. • 155. Proximate Principles of Plants, The proximate organic principles of plants are certain organisms existing within them composed of two or more of the four organic elements. A few of them have also sulphur and phosphorus in minute proportions. Similar compounds exist in the animal structure, but blinder very different arrangements, although the chemical constituents are very near the same. These principles may be divided into albuminoids, carbo-hydrates, vegetable acids, vegetable oils, alkaloids, and coloring matters. Water, in one sense, enters into vegetable and animal structure as an organic compound, but as it exists abun- dantly in nature outside of organic matter, it cannot pro- perly be classed with them. The proximate principles of plants are very numerous. Hundreds are already known to chemists : only a few, how- ever, constitute the bulk of plants. Many plants contain some organic principle peculiar to themselves, in the form of oils, acids, bitter principles, resins, coloring matters, etc. Thus we have nicotine from tobacco, thein from tea and coffee, quinia from the cin- chona tree, and salacin from the willow. In the orange arc found three different oils : one in the flowers, one in the leaves, and another in the rind of the fruit. We shall only treat of those substances which are deemed to be of interest to the agricultural student. 156. A Ihitmin o ids. The Albuminoids differ from all other proximate prin- ALBUMEN. 191 ciples in having all the organic elements existing in them with minute traces of sulphur, and in some cases phos- phorus. The albuminoids are called protein bodies, from a notion of Mulder that they were composed of various hypothetical compounds of sulphur and phosphorus, with a common in- gredient which he termed lyrotein. Others supposed that they were identical in composition, only the atoms were arranged differently, as in cellulose and starch. While the arrangement of these bodies cannot be pro- perly accounted for, they are sufficiently distinct in com- position to be readily distinguishable by analysis, and yet their differences cannot be deemed essentiaL There are three albuminoids existing in animal and vegetable substances properly distinguishable from each other, though very nearly related, viz. albumen, fibrin, and casein. Others have been mentioned, as gliitine and legumine. The former was described by Dumus and Cahours as a pul- taceous substance resulting from crude gluten, which Bous- singault, however, considered a compound substance con- sisting of fibrin and casein, with a little starch and fat. JLegumine exists in the pod-bearing plants, and though de- scribed by some of the early chemists as a distinct albu- minoid, is now classed with casein. 157. Albumen, Vegetable albumen exists in its purest form in the white of an egg. It is a peculiar thick, glairy substance, has neither color, taste, nor smell, is insoluble in water or alcohol; but dissolves in vinegar, caustic potash, and soda. It exists sparingly in the seeds of plants, but occurs large ly in the fresh juices of many plants, as cabbage leaves, turnips, etc. The albumen is readily separated from the juices of these plants, by being heated. If the water which remains after gluten is prepared 192 CHEMISTRY OF PLAXTS. from wheat, is heated, white films or particles of albumen will separate, which may be easily collected. The stench emitted by the putrefaction of the albumen of eggs, is owing to the escaping sulphuretted hydrogen gas; and it is this in cooked eggs which possesses the qual- ity of blackening silver and other metals. Albumen also exists in the muscles, bones, and nerves of animals. 158. Casein, Casein is the purified curd of milk, and the basis of cheese. It is held in solution in milk, and constitutes its most nourishing portions. It exists dissolved to the ex- tent of 3 to 6 per cent, of fresh milk, is not coagulated by heat like albumen, but by acids and rennet (the membrane of a calf's stomach); also with salts of magnesia and lime, when heated to boiling. When it stands for some time the casein of milk coagu- lates spontaneously. It has recently been detected in the brain of animals. Vegetable casein is found in wheat, and largely in le- guminous plants, (17 to 19 per cent.). It closely resembles milk casein, in all respects. Those foods are always the most nutritive w^hich con- tain the most casein. It may be considered as the stand- ard of food, furnishing all that is essential to the growth and nutrition of animals. 159. Fibrin, Fibrin occurs in a state of solution in the blood of ani- mals, and with albumen, forms the basis of muscle. When blood cools, it coagulates spontaneously, separat- ing from the watery part or serum. The white, stringy particles of this coagulum, which adhere together and form a network, is pure fibrin. When w^ashed in water the red coloring matter disappears, leaving W'hite masses of fibrin. It is quite flexible and elastic when moist. COMPOSITION OF ALBUMINOIDS. 193 When dried it loses about 30 per cent, of water, and be- comes horny, brittle, and semi-transparent. It is perfectly insoluble in cold water. When burned, a strong odor of sulphuretted hydrogen gas escapes, leaving considerable ash. Vegetable fibrin is found in the seeds of the cereals, accompanied with starch. It has no fibrous structure lil^e that of animals, but forms when dry, a tough horny sub- stance. 160. Other Isfitrogenous Compounds, Aleurone is the name given by Hartig to organized granules of plants which are a mixture of the difierent albuminoids, ablumen, casein, and fibrin, the two latter largely predominating. These grains sometimes assume the form of crystals, and are called crystalloid aleurone. It is found as cubes in the outer part of the potato tuber. It is also found abundantly in the Brazil nut, according to Maschke, as a compound of casein with an unknown acid. Two other albuminoids have been found in crude wheat gluten; gliadin or vegetable glue, which is very soluble in water and alcohol ; and miieidin^ insoluble in water, and sparsely soluble in alcohol. It is found in rye grain. Ceraline a new principle found in wheat by the Messrs. Deveaux, consists of the compact layer just inside the bran, and is generally removed with it in the process of bolting. It is highly nitrogenized, containing also phosphoric acid. This principle is said to stimulate digestion, and is used in the treatment of dyspepsia by the faculty of Paris. The valuable properties of bran-meal in the celebrated Graham bread are thus accounted for in the treatment of such cases. 161. Composition of Albuminoids, The following table arranged by Johnson will show the 9 194 CHEMISTRY OF PLANTS. composition of the albuminoids, animal and vegetable. He did not include phosphorus, for the reason that its quantity, if not its very presence, is deemed uncertain. Voelcker and Norton claimed to have found from 1.4 to 2.3 per cent, of phosphorus in casein, and other chemists have claimed to have found less quantities in albumen and fibrin. (How Crops Grow, p. 102.) Carbon. Hydrogen. Nitrogen. Oxygen. Sulphur. Vegetable albumen ...53.4.. ..7.1.. ..15.6.. ..23.0.. ..0.9 ...52.6.. ..7.0.. ..17.4.. ..21.8.. 1 2 Wheat fibrin , ...54.3.. ..7.2.. ..16.9.. . .20.6. . 1.0 Vegetable casein ...50.5.. ..6.8.. . .18.0. . ..24.2,. ..0.5 Gluten casein ^ , ...51.0.. ..6.7.. ..16.1.. . ,25.4. . ..0.8 Gliadin > Wheat . . ..52.6.. . .7.0.. .,18.1.. ..21.5.. .,0.8 Mucidin ) ...54.1.. ..6.9.. ..16.6.. ,,21.5.. . .09 From this it will appear that there is but little differ- ence between animal and vegetable albuminoids, as to their composition. The average is as follows: Carbon. Hydrogen. Nitrogen. Oxygen. Sulphur. Animal 53.45. . . .7.10. . . .16.15. . , .22.05. . . .1.22 Vegetable 52.65. , , .6.95. , , .16.88. , . .22,70. . . .0.82 162. Albuminoids in Crops. As it is a very difficult and uncertain process to sepa- rate the albuminoids from the other organic principles, some chemists have adopted the plan of simply estimating their amount by the content of nitrogen found in the plant. This is near enough for all practical purposes. As the albuminoids contain on an average about 16 per cent, of nitrogen, and all the nitrogen of plants exists in the albu- minoids, it is easy to calculate their amount when the per- centage of nitrogen is known. From the table given by Professors Wolf and Knop, ALBUMINOIDS IN CROPS. 195 we select the most interesting agricultural plants, and parts of plants, as to their content of albuminoids : Average of the grasses 9.5 Peas in blossom 14.3 Lucerne " 14.4 Red clover " 13.4 Rice, grain 7.5 Wheat " 13.0 Oats " 12.0 Maize " 10.0 Millet " 14.5 Buckwheat, grain 9.0 Peas " 22.4 Field Beans " 25.5 Acorns 5.0 Corn fodder (green) 1.0 Pea vines " 3.2 Wheat straw 2.0 Rye " 1.5 Barley 2.0 Oat " 2.5 Pea " 6.5 Bean " 10.2 Corn-stalks , . . .3.0 " cobs 1.4 Pea hulls 8.1 Bean " 10.5 Wheat chatf 4.5 Potato (Irish) 2.0 Turnip (Ruta Baga) 1.6 Beet 1.1 Pumpkin 1.3 This table is of great interest to the agriculturist, when it is remembered that an article is nutritious according to the amount of albuminoid in it. All of these substances were thoroughly air- dried, except those marked green. It thus appears that pea vines have about three times the nutriment of corn-fodder, while peas themselves have more 196 CHEMISTRY OF PLANTS. than twice as much as Indian corn. Our corn-field pea is classed as a bean, which is still more nutritious than the pea. THE CAEBO-HYDRATES. — CELLULOSE. LIGNIN. — STARCH. AND THE GUMS. The Carho-liydrates are composed of carbon, hydrogen, and oxygen, without nitrogen ; hence their name. They have been divided by some authors into the Cel- lulose and Pectose groups. We think the following a more natural division, founded upon their physical as well as chemical differences. Woody Fibre^ Cellulose, and Lignin. The Starch Groiip^ Starch, Inulin, and Dextrin. The Gums^ Arabin, Cerasin, and Vegetable Mucilage. The Sugars^ Saccharose, Levulose, Glucose, and Lactose. The Jellies^ Pectin, Pec- tic Acid, and Metapectic acid. Cellulose constitutes the skeleton or framework of plants, and next to water is the most abundant substance in the vegetable world. The fibres of cotton, flax, and hemp are nearly pure cellulose ; in fact, nearly every part of every plant contains it, as it forms the outer coating of all the cells. Wood fibre is constituted of long cells com- posed principally of cellulose with lignin. Cellulose exists in various vegetable matters when air- dried, in the following proportions: CHAPTER YI. 163. Carbo-hydrates, 164. Cellidose, Potato tuber . . . Wheat kernel. Per cent. ...1.1 ...3.0 STARCH. 197 Per cent. Maize kernel 3.5 Barley " 8.0 Oat " .....10.3 Clover hay... .....34.0 Maize cobs .38.0 Oat straw 40.0 Wheat straw 48.0 Eye " 54.0 165. Xiignin. It is now well ascertained that woody fibre is composed of cellulose, already described, which constitutes the skele- ton or frame-work of this fibre, and lignin^ which is much denser, and covers it. It is also known that while cellu- lose is largely digestible, lignin is almost entirely indi- gestible. Lignin is more solid and compact than cellulose, and contains more carbon, which amounts to 52.53 accord- ing to Gay-Lussac and Thenard; the hydrogen and oxygen making up the remaining per cent, in the same proportions found in water. 166. Starch, Starchy next to cellulose, is the most abundant of all the vegetable principles, being found in all classes of plants except the fungi. It is a tine white powder without taste or smell, and is insoluble in alcohol, ether, and cold water. It exists abundantly in wheat, maize, potato, and arrow- root ; occurring in the interior of vegetable cells in the form of transparent granules. It is also found in the wood of all trees, more abundantly during the autumnal and winter months. The sago-palm (Metroxylon Rumphii), a tree of the Malay Islands, produces it in such abundance that one tree is said sometimes to yield 800 lbs. The Irish potato (Solanum tuberosum) has about 20 per cent, of starch, which may be separated from it by the fol- 198 CHEMISTRY OF PLANTS. lowing simple process: The potatoes are reduced to a pulp by being grated, the starch grains are thus released from the broken cells. The pulp being placed on a fine sieve, is agitated, while a stream of water is teemed upon it, which carries through a milky fluid, containing the starch, while the cellulose is held by the sieve. The milky fluid is poured into vessels, and allowed to settle, when the water is decanted, leaving the starch, w^hich is fit for use when dried. The corn starch of commerce, useful as a bland diet for invalids, is prepared from maize, by dissolving out the al- buminoids with a weak solution of caustic soda. The bran and starch are then separated by adding water, which causes the former to settle ; the water containing the starch is poured ofl*, which is deposited and dried. Starch is a very important ingredient of food for man and domestic animals, and is said to be dissolved by their saliva at blood heat, and converted into sugar. The liquids of the large intestine perform this ofiice much more promptly. (Johnson.) The chemical composition of starch and cellulose are identical, being composed as follows : Carbon 44.44 Hydrogen 6.17 Oxygen 49.39 167. Iiiulin, Inulin was first obtained by Rose from a decoction of the roots of inula helenium, or elecampane, and is very much like starch. It forms the greater part of Jerusalem artichoke, and dahlia, which contain no starch. It is soluble in boiling water. It seems to replace starch in the natural family (compositse), but does not occur in grains as starch, but in the liquid form, separating from the juice after standing some time in white granular particles. The DEXTRIN. 199 dahlia tuber, according to Bouchardat, contains 8 per cent, of this substance. Inulin maybe converted into a saccharine matter called levulose^ by boiling in diluted acids. The same result is accomplished by hot water, only it requires a much longer time. As nutriment it has about the same value as starch. Its composition is the same as starch and cellulose. 168. -Dextrin, Dextrin is a light brown substance, found by Busse in old potato tubers and unmatured wheat plants. As it may be made artificially from starch, and has not been found in young potatoes, it is probable that it results in old ones from the transformation of starch. When exposed to the heat of an oven for some hours, starch is readily converted into dextrin, the grains swelling and bursting by the intense heat. It has been found in but few plants, and then in small quantities. Von Bibra says that what was supposed to be dextrin in bread grains, by the early chemists, is nothing but gum. When biscuit are steamed, the crust often presents a glazed surface ; this is due to dextrin. In fact, the very process of baking bread changes a portion of the starch into this substance, amounting often to ten per cent. Under the name of British gum, prepared from starch, it is used extensively in the arts, particularly in printing calicoes, being cheaper than gum arable, and answering the same purpose. It dissolves readily in cold water, and when the solution is mixed with alcohol, it separates in white flocks. Commercial dextrin is changed into a fine purplish color by iodine ; but pure dextrin is not affected by it. Dextrin is also formed from starch and cellulose by acids and fermentation. It is composed identically as starch, cellulose, and inulin. 200 CHEMISTRY Or PLANTS. 169. The Gums. The Gums found in the vegetable kingdom are very extensive, and of several types. One is found in gum arabic, called arabin ^ one in gum tragacanth and Bas- so ra gum, called hassorin / that in the plum and cherry, cerasin^ and vegetable mucilage found in the comfrey and mallow roots, and quince and flax seeds. There are others, but these constitute the principal gums. Gum arabic leaves about 3 per cent, of mineral matter, upon incineration, carbonates of lime and potash ; the re- mainder being arabic acid. This latter contains 100 parts, carbon 42.12, hydrogen 6.41, oxygen 51.47. The gum found on the peach, cherry, and plum trees, is a mixture of arabin and cerasin. Cold water will dis- solve out the former and leave the latter a swollen mass of jelly, which is composed principally of metarabic acid. JBassorin has much similarity to vegetable mucilage, if not identical with it. It is insoluble in cold water, but forms a paste with it, which was formerly used by druggists for labelling. Vegetable mucilage is found in nearly all plants, and may be produced in a pure state by soaking flax seed in cold water, boiling it, and then strain and evaporate. Al- cohol will then cause it to separate in tenacious threads. The external cells of the flax seed contain the mucilage, Avhich being soaked in water, swell and burst, which causes it to exude. The inner bark of the slippery elm (ulmus fulva), so extensively used in the South as a mucilaginous drink in fever cases, also contains a large percentage of it. The gums are converted into grape sugar (glucose) by long boiling in water. They are generally thought to be indigestible and devoid of nutritive qualities. We satis- fied ourselves, years ago, that this was a mistake, as we have fed children upon gum arabic exclusively for weeks, CAXE SUGAR — SACCHAROSE. 201 both as food and medicine, when emaciated with summer complaint, and it improved them in flesh and strength. Eecently Grouven has satisfactorily demonstrated that gum arabic is digestible by animals. Yon Bibra gives the following percentage of gum in various substances air-dried. Wheat kernel 4.50 Wheat flour 6.25 Rye flour 7.25 Barley flour 6.33 Oatmeal 3.50 Bice flour 2.00 Wheat bran 8.85 Bye kernel 4.10 Millet flour 10.60 Corn meal (maize) 3.05 Buckwheat flour 2.85 Spelt flour 2.48 Such a large percentage of soluble gum in the bread grains is doubtless appropriated at least in part to the nourishment of animals, being possibly first converted into sugar by acids through processes peculiar to digestion. CHAPTER YII. CARBO-HYDRATES, CONTIXUED. — THE SUGARS. PECTIN. CHANGES IN PROXIMATE PRINCIPLES. IVO. Cane Sugar — Saccharose, Sugar occurs in several forms, the principal of which are cane sugar, fruit sugar, grape sugar, and milk sugar. Cane Sugar or Saccharose^ so called because it was first found in the sugar cane (Acer saccharinum), con- stitutes the sugar of commerce. It crystallizes in small rhombic prisms, and when pure is of a white color. Some 9* 202 CHEMISTRY OF PLANTS. of its crystals in rock candy are an inch or more in length. It is also found in the beet, sugar maple, sorghum, maize, sweet potato, and a great many other vegetables. The following table will show the average percentage of saccharose in the juice of several plants. (How Crops Grow, p. 13.) Sugarcane 18 percent Peligot. Sugar beet 10 " " " Sorghum OJ^ " Goessman. Indian corn, in tassel .. " " Ludersdoff. Sugar-maple sap 2^ " Liebig. Red maple 2^ " Cane sugar will be converted into equal parts of grape and fruit sugar, by the action of yeast or heated diluted acid. Its composition is nearly identical with that of arable acid; viz. in 100 parts, carbon 42.11, hydrogen 6.43, oxygen 51.46. 171. Grape Sugar — Glucose, Grape Sugar or Glucose^ exists in the juices of many plants, and constitutes the crystals which form in honey; also the granular sweet masses found in raisins and old dried fruits. It crystallizes in cubes or square tables. It is only half as sweet by weight, as cane and fruit sugar. Glucose is formed from starch in the malting of grain, and from dextrin, by hot diluted acids. The prolonged action of these acids, it is said, will convert cellulose into it, and even sawdust by this process will form an impure syrup, from which alcohol may be produced. The composition of grape sugar is as follows: Carbon 40.00, hydrogen 6.6, oxygen 53.33. Grape sugar occurs in a number of trees connected with bitter principles, as tannin found in the oak, salacin in the willow bark, phloridzin from the apple-tree root, and others found in the almond, peach kernel, horse-chestnut, MILK SUGAK. 203 etc. These bitter principles are called glucosides^ and some of them are nsed as medicines. By heating with dilute acids, glucose is obtained from them. 172. Fruit Sugar — Fructose, Fructose^ or Fruit Sugar ^ called also Levulose^ exists generally in combination with other sugars, in honey, molasses, and most acidulous fruits. It is equal in sweet- ness to cane sugar, but does not granulate or crystallize, being generally found in the form of syrup. Its composi- tion in 100 parts is as follows: Carbon 40.00, hydrogen 6.67, oxygen 53.33. The composition of fructose is identical with that of glucose. Crystallizable sugar has been made from molasses by Dubrunfaut, by treating with a concentrated solution of baryta. When the carbonate of baryta which is formed subsides, the saccharine liquid is drawn off, and submitted to the ordinary processes of evaporation and crystallization. 173. 3IUk Sugar — Lactose. Milk Sugar — Lactose^ crystallizes in four-sided prisms, . and has less sweetening power than grape sugar. It is found only in the milk of animals. It contains exactly the ele- ments of carbonic acid and alcohol, minus one atom of wa- ter ; and as neither of tl^ese compounds exist in sugar, they must be produced by a different arrangement of atoms, and by their union with the elements of water. It is largely pre- pared for commerce in Switzerland, from the whey of milk. The composition of milk-sugar, is carbon 42.10, hydro- gen, 6.40, oxygen, 47.00. 174. Other Saccharine Substances. Other sugars are found in plants in small quantities, 204 CHEMISTRY OF PLANTS. but are not deemed of sufficient importance to require l^articular notice. Among them, Prof. Johnson mentions the following : (How Crops Grow, p. 78.) Mannite^ CeHuOe, occurs in the bark of several species of ash, found in the south of Europe and the East, as the Fraxinus ornus, and rotundifolia. It is found also in edible mushrooms, and the sap of some of our fruit trees. Quercite^ CgHisOs, found in the acorn in colorless crys- tals. My cose J found in the ergot of rye, and Finite^ which exudes from the bark of a Californian and Australian pine. Honey, sorghum, syrup, and molasses, generally con- tain cane sugar, grape sugar, and fruit sugar. The reason why saccharose is obtained from sorghum with difficulty, is because of its being so easily changed into other forms on the heating of its solution. The fructose in molasses pre- vents the crystallization of the other forms into solid sugar. The honey dew which we find on the leaves of the honeysuckle, lime, and other trees, is a mixture of these three different sugars with gum. The saccharine matter of the bread grains, supposed by Vauquelin and other early chemists to be crystallizable sugar, is also composed of this mixture, as has been recently established by Von Bibra. He found in the flour of dif- ferent grains, the following quantities of sugar ; some par- taking of the character of saccharose, and others of glucose and fructose: % Per Cent. Wheat flour 2.33 Wheat bran 4.30 Rye flour 3.46 Rye bran 1.86 Maize meal 8.71 Barley meal 3.04 Barley bran 1.90 Oat meal 2.19 Rice 0.39 Buckwheat meal 0.91 PECTIN. 205 175. Alcohol^ a Product of Sugar, Alcohol^ so extensively used in the arts, is a product of sugar, when mixed with water and a ferment, at a cer- tain temperature. The water gives fluidity — the ferment, heat — which begins and keeps up the chemical changes. In this process the sugar disappears, part of which is con- verted into the tissue of a microscopic plant, and a part into alcohol. The temperature ranges from 60 to 90^. Sugar is not the only substance which produces alcohol; as rice, potatoes, and other starch plants produce it by a similar process of vinous fermentation. This is done, how- ever, by the starch being first converted into sugar by spontaneous action. Absolute Alcohol^ Anhydrous^ has the following for- mula : C4H5O0. It combines with water in all propor- tions ; is entirely combustible, burning without leaving any residuum. It exists in all fermented wines from 6 to 25 per cent.; and in the ardent spirits of commerce, from 50 to 55 per cent. It is a pure difiiisible stimulant, with but little, if any nutritive functions ; a good medicine, when properly used, and a most seductive and fatal poison. Restricted to its uses in the arts, it would be a blessing to mankind. 176. Pectin, Pectin, vegetable jelly, forms the gelatinous princi- ple of certain plants — was discovered by M. Braconnot, and plays a very important part in the 2:)henomena of vegetable life. Pure pectin is quite insipid, and when dried, is in membranous semi-transparent pieces, resem- bling isinglass. M. Fremy supposes that pectin results from pectose, a substance which occurs associated with cellulose, in the flesh of unripe fruits, and the roots of beets, turnips, etc. \ 206 CHEMISTRY OF PLANTS. With pectic and metapectic acid, pectin constitutes a a class of carbo-hydrates called the Pectose group. These bodies are found in pumpkins, squashes, many berries, fruits, and root crops. They constitute an imjDortant part of the food of man and domestic animals. Pectin results from pectose by the action of heat, acids, and ferments. The pectose of unripe fruits is changed by the influence of acids existing in them into pectin. The viscid gummy substance which exudes from baked apples or pears is an aqueous solution of pectin. When fruits ferment, pectin is changed into pectosic, and subsequently into pectic acid. The fruit jellies are composed of these acids. Pectosic acid is soluble in boil- ing water, but pectic acid is not. Neither of them is soluble in cold water. When fruit jellies are kept too long, and decay, the pectic and pectosic acids are changed into another form, metapectic acid^ which is very soluble and quite sour. The pectin of decayed fruits is also changed into it, and it has also been found in beet molasses. This acid contains, according to formulae of Fremy, CgHioO^ with two equiva- lents of water. Pectin has been prepared by Grouven on a large scale, from beet-root cake, which remains after the sugar has been extracted from it. This is effected by digesting with dilute chlorhydric acid, then precipitating and wash- ing with alcohol. Pectin and pectic acid have each in 100 parts, as follows : The pectin prepared by Grouven is almost identical with the pectic acid analyzed by Fremy. It is believed that cellulose passes into pectose and Pectin. .40.67. ..5.08. .54.25. Pectic Acid. Carbon . . Hydrogen Oxygen. . 42.29 .4.84 52.87 CHANGES IN PROXIMATE PRIXCIPLES. 207 pectin in the living plant. But the pectin bodies are not convertible into sugar, as was formerly supposed. 177. Changes in Proximate Principles, Constant changes are transpiring during the growth of plants in the different proximate principles. Deherain says, that they migrate from the older to the newly formed leaves, and that this migration is associated with a trans- formation of glucose into cane sugar ; that when the seed is formed the cane sugar is converted into starch, and the albumen into gluten, both insoluble. The accumula- tion of substances in the seed, and the conversion of solu- ble into insoluble principles are thus accounted for. He demonstrates this by taking a porous vessel filled with distilled water, placed in another vessel containing a solution of sulphate of copper (bluestone). The salt pene- trates into the inner vessel by diflfusion. To which if a few drops of baryta water be added, the salt is precipi- tated, the equilibrium disturbed, and a new portion of the bluestone diffuses into the inner vessel. The precipi- tation again transpires on the application of the baryta water, until the whole of the sulphate of copper has passed and becomes precipitated. The carbo-hydrates are remarkable for the facility with which they may be changed into each other. Thus in ger- mination, the starch of the seed is converted into dextrin and glucose, and in this form passes into the embryo to nourish theplantlet. Here, again, it changes into cellulose and starch. In the sugar beet (which is destitute of starch, ut contains 10 to 14 per cent, of sugar), in certain dis- eased conditions, the sugar is transformed into starch. The cereals sometimes show dextrin, upon analysis, instead of sugar or gum, which is more common. In the animal economy, similar transformations take place during the process of digestion. Cellulose, starch, 208 CHEMISTRY OF PLANTS. dextrin, and the gums, are converted into sugar (glucose). Many of these changes which take place in nature may be produced by the action of chemical agents — as heat, acids, and ferments. Thus, cellulose and starch are convertible into dextrin and glucose, by boiling in dilute acids. Cot- ton or paper may be gradually changed into sugar, by strong chlorhydric acid (spirit of salt.) Cellulose and starch into dextrin, by nitric acid. A singular fact noticed by Prof. Johnson is, that while these changes are produced by physical and chemical agen- cies in one direction, they can only be accomplished in the reverse manner, under the influence of life. Thus, chem- istry may reduce a higher organism to a lower or simpler one ; but not the reverse. In nature, however, these changes take place Avith perfect facility either way. All of the carbo-hydrates represented by cellulose and starch contain 12 atoms of carbon united with 20 to 24 of hydrogen and 10 to 12 of oxygen. Their change then into each other can be easily effected by the abstraction or ad- dition of a few molecules of water. It is a singular fact in chemistry, that certain bodies containing precisely the same elements, are very different in physical qualities and appearance. These are termed isomeric bodies, which can be accounted for only in the fact, that the same quality and kinds of elements are ar- ranged in different proportions, upon the same principle that an architect can construct out of the same material, very different kinds of structures. Thus, cellulose and dextrin being isomerical bodies, must have the carbon, oxygen, and hydrogen of which they are composed, very differently arranged; a fact which is clearly inferable, but which chemistry fails to reveal. MALIC ACID. 209 CHAPTEE VIII. VEGETABLE ACIDS, AND VEGETABLE OILS. 178. Vegetable Acids. The Vegetable Acids exist in great numbers in all classes of plants. They are better characterized than the other carbo-hydrates, being generally obtained in the crystallized state, and are consequently, more nearly assimilated to in- organic bodies. They have also the general characteristics of mineral acids, forming salts by uniting with bases, etc. With potash, soda, and ammonia, they form salts soluble in water, and with other bases, they form salts either solu- ble or insoluble, according to the kind of acid. Only a few of these acids are of special interest to the agriculturist, although many of them are of great impor- tance in the economy of vegetation. Among these we mention acetic, malic, oxalic, tartaric, citric, and tannic acids. Acids, in a general sense, are sour to the taste. They are better characterized as substances capable of uniting chemically with bases. These latter are the opposite of acids. When acids and bases unite, they are termed salts. Thus, phosphate of lime is a salt, produced by the chemi- cal union of phosphoric acid and lime. 179. Malic Acid. Malic acid, C^HgO^ is found in apples, strawberries, plums, cherries, and other fruits ; but always in a combined condition. Thus in tobacco leaves and the sugar maple, it occurs as a malate of potash. It succeeds tartaric acid in the mountain ash, where it is found as a lime salt ; the 210 CHEMISTRY OF PLANTS. tartaric acid losing a part of its oxygen, is converted into malic acid. Malic acid never occurs pure in nature, but may be found in the shops in white crystalline masses, being ex- tremely soluble as well as sour. 180. Tartaric Acid. Tartaric acid^ C4H6O6, occurs abundantly in the grape as the bi-tartrate of potash, and is frequently found de- posited on the sides of wine casks, as argol^ produced by fermentation. When purified, this substance is known in commerce as Cremor tartar ; from which the acid may be easily extracted. It is a valuable medicine, and the acid is an ingredient of the famous Seidlitz powders. 181. Citric Acid. Citric acid^ CgHgO^, is found in a free state in the juice of lemons, oranges, currants, and unripe tomatoes. It is used medicinally, and in the arts; for which large quantities are extracted from the lemon and the lime. It is found in small quantities combined with lime in tobacco leaves, artichokes, beets, coffee berries, and the bulbs of onions. 182. Oxalic Acid. Oxalic acid^ C2H2O4, 2H2O, exists largely in the wood sorrel, as a binoxalate of potash. It exists free in the bases of the chick pea, and is found in many other plants, generally in a state of combination. It may be seen in the shops in colorless transparent crystals, resembling Epsom salts so closely, that fatal mistakes have been made by using it in the place of that medicine, as it is a rank poison. It is a powerful acid, having such a remarkable affinity for lime, that it takes it even from sulphuric acid. Oxalate ACETIC ACID. 211 of lime is insoluble in water, but exists dissolved in the cells of living plants while in a growing state. 183. Tannic Acid. Tannic acid (tannin), is the bitter principle found in the bark of the oak, hemlock, sumach, and many other plants. It is used extensively in the arts for tanning leather, having the remarkable property of rendering the hides of animals insusceptible of putrefaction. It is also a useful medicinal astringent. Sir Humphry Davy found it to exist in the Bombay catechu as high as 54.3 per cent., and in nut-galls 27.4. Dr. SchifF has lately arrived at the conclusion, that tannic acid is an ether which bears the same relation to gallic acid, that ordinary ether does to alcohol. The difference between tannic and gallic acid being merely in the elements of water. He thinks that some practical results might be reached with regard to the processes of tannin, if some method could be discovered by which these elements could be displaced. Recently, Dr. McMurtie, chemist of the Department of Agriculture, has analyzed several kinds of wood, and found in the heart of the mesquite (Algarobia glaudulora), G.21 of tannic acid; in the heart of the Osage orange (Madura aurantica), 5.87 per cent. This is nearly equal to many barks used in tanning, and in some sections, and especially in the Southwest, where these trees grow abun- dantly, they may be successfully introduced in this branch of industry. 184. Acetic Acid, Acetic acid^ HC2H3O2, although found in very small quantities in the juices of plants, and in animal fluids, is of such importance in agriculture, that we cannot well omit it in this place. It results as vinegar from the fer- mentation of all acid fruits, and the action of air on alco* 212 CHEMISTRY OF PLANTS. holic liquors; and is found among the products of the destructive distillation of organic matters. It is well known that when sweet wine or cider is ex- posed to the influence of the atmosphere, it becomes sour. This change is owing to the production of acetic acid. A mixture of sugar and water will produce the same result. When deprived of water and all impurities, acetic acid contains, according to analysis of Berzelius, carbon 46.83 ; oxygen 46.82; hydrogen 6.85. M. Vauquelin found this acid in the sap of various trees, and in the chick pea. It has also been found in the date, palm, and in the elderberry, by Scheele. It exists in many plants as acetates of lime and potassa, and with other bases. 185. Vinegar, Vinegar^ which is diluted acetic acid with some im- purities, is the oldest of known acids. Reference is made to its chemical action on nitre [natron^ soda), by Solomon, showing that this substance would destroy its sharpness and neutralize its acid. Mixed in the proportion of one part of brown sugar to seven of water, with a little yeast, in a cask, the bunghole being bound with a thin piece of gauze to keep out the insects, and exposed to the atmo- sphere and sun for several weeks, a good vinegar for domestic use will be produced. The German method of acetification will produce good vinegar in 24 to 36 hours. Take one part of alcohol, graded at 80 per cent., four to six of Avater, with one-thou- sandth of honey to act as ferment. This mixture must be made to trickle through beech shavings previously steeped in vinegar, and placed in a deep oaken tub. This vessel must have a wooden diaphragm near the top, perforated with a number of holes loosely filled with pack-thread tied in a knot to prevent its falling through. The liquid, heated T5 to 83"^, is poured on, slowly percolates through these PEUSSIC ACID. 213 holes, and thus becomes minutely divided, and exposed to the atmosphere. There must be also holes bored in the sides of the tub, for the admission of air. To make strong vinegar, the liquid should be passed through three or four times, and the temperature made to rise to 100 and 104^ during the process. The contact of air promotes acetifica- tion, which consists in oxidation of the alcohol. During acetous fermentation, there is a miscroscopic vegetable growth produced, which Pasteur has shown to be a cryptogam of the micraderma. This formation is essential to the progress of acetification. It is doubtless similar to the California moss (only much more minute), which was used so extensively in making beer some years since; and which had the remarkable properties of indefi- nite increase, and changing water in which it was placed into a palatable acid beverage in a few hours. 186. Prussic Acid. There are a number of other acids found in different plants, but of minor importance. They all consist of defi- nite proportions of carbon, hydrogen, and oxygen, vary- ing but little in composition, with one exception, viz. pimssic {hydrocyanic) acid. It contains 48 per cent, of hydrogen, and 52 of nitrogen, without a particle of oxygen, and is the most powerful poison in nature. It is found in the bark and leaves of the cherry and peach, as well as in their kernels and fruit, and constitutes a considerable percentage of the fruit and bark of the wild cherry; the value of which, as a medicine in lung-affections, is supposed to depend upon this acid. Its extreme dilu- tion in nature renders it comparatively harmless; but even here, it sometimes produces bad effects. One single drop of Scheele's concentrated solution, placed upon the tongue of a cat, will produce instant death. 214 CHEMISTRY OF PLANTS. 187. Vegetable Oils. TJie Vegetable Oils are divided into the fatty or fixed oils, and essential or volatile oils. They exist to a consid- erable extent in many plants. Boussingault extracted about 40 per cent, of fatty oil from the colewort seed. An equal quantity is found in the kernel of the cotton seed after being deprived of its hull. Walnuts contain from 40 to 70 per cent., and castor beans (Palma Chrysti) as high as 62. The common bayberry and tallow tree of Nicaragua have their fat of a solid consistence at ordinary tempera- tures, which has to be extracted by heat. This is an ex- ception to the general rule ; as in most, if not all other known plants, the fats exist in a liquid state. Oil exists in the vegetable cells in minute transparent globules. The grains of the cereals, especially oats and maize, contain it in appreciable quantities ; and this is probably the reason why Indian corn is considered a very heating food for horses, as the fat of vegetables is known to be productive of heat in the animal economy. 188. Volatile Oils, Volatile Oils may be divided into three classes : those composed entirely of carbon and hydrogen ; those con- taining carbon, hydrogen, and oxygen, and those which have an addition of sulphur ; one of them, oil of mustard seed, containing nitrogen also. This latter class consti- tute the Essential Oils^ which exist in aromatic plants. The volatile oils generally have a strong aromatic odor, and leave no stain or grease-spot on white paper. The reverse is true of the fatty or fixed oils. They have certain properties in common, however, as insolubility in water, inflammability, and solubility in ether and alcohol. SAPONIFICATION. 215 Camphor is combined with essential oils in many plants of the labiate family. According to M. Dumas, this substance contains carbon, 79.2; hydrogen, 10.4; oxygen, 10.4. Resin and wax also exist in solution with essential oils, making them viscid and sticky. The balsams which exude from certain trees are nothing but solutions of resin in essential oils. The resin remains in a solid state when the oils are evaporated. The resins are inodorous, fusible, extremely inflammable, and non-volatile. Tallow, olive oil, and butter are the three most abun- dant fats used as food for man. They consist of three substances, viz. stearin, palmitin, and olein. Stearin is the most abundant, and is the principal in- gredient of tallow. Palmitin exists largely in butter and beeswax, and the tallow of the bay berry. It is named from the palm oil of Africa, of which it is a principal ingredient. Olein is the liquid part of fats existing abun- dantly in all oils. It is obtained by bringing olive oil down to the freezing point ; the stearin and palmitin be- come solid, and the olein is poured off in a liquid state. The fat formerly called Margarin has been found to be a mixture of stearin and palmitin. The following table gives the centesimal composition of these elementary fats : (How Crops Grow, p. 92.) 189. Fixed Oils, Carbon . . . Hydrogen Oxygen . . Stearin. ..76.6. ..12.4. ..10.0. Palmitin. ..75.9.. . .12.2. . 11.9 Olein. .77.4 .11.8 .10.8 190. Saponification, When the fats are heated with strong potash or soda- lye, or brought under the influence of strong acids, or 216 CHEMISTEY OF PLANTS. heated with water to a high temperature — nearly 400^ — they are decomposed ; changed into fatty acids and gly- cerine. These acids, stearic, palmitic, and olein, combine with the alkalies, making soap. Soft soap is a combination of potash with these acids, mixed with water and glycerine. Hard soap is the soda compound with these acids, free of glycerine. Stearin candles, so called, are a mixture of stearic and palmitic acid. Glycerine^ which is simultaneously produced with the acids, is a kind of liquid sugar, and is found in the shops as a sweetish, colorless syrup. 191. Phosphor ized Fats, Von Bibra first discovered the existence of a phospho- rized fat in the brain and spinal cord of animals, and in the yolk of eggs. The amount of phosphorus in this ani- mal fat, ranged from 1.21 to 2.53 per cent. A similar fat was found by Knop to exist in the sugar pea and other plants. It contained in 100 parts, carbon, 66.25 ; hy- drogen, 9.52 ; oxygen, 22.38 ; phosphorus, 1.25. Topler afterward found phosphorus at a less percentage in the oils of the lupine, horse-bean, vetch, horse-chestnut, wheat, barley, rye, and oats. Liebreich, according to Hoppe Seyler, discovered, in 1864, a white crystallized body in the brain, which he termed JProtagon, Its composition is as follows : carbon, 67.2; hydrogen, 11.6; nitrogen, 2.7; phosphorus, 1.5; oxygen, 17.0. It is found also in the nerves of animals, and in the oil of maize. 192. Fat in Vegetable Products, The oil or fat of plants results from the transforma- tion of starch and cellulose, as starch is always found in seeds not matured, which disappear and give place to oils when THE ALKALOIDS. 217 matured. When there is a small percentage of sugar in the sugar cane, there is a larger percentage of wax ; more sugar lessens the quantity of wax. When germination takes place, the oil of the seeds is changed back into sugar and starch to nourish the plantlet. The proportion of fat in certain vegetable products is given by Wolf and Knop, as follows : Maize fodder (green) 0.5 Red clover (green) 0.7 Cabbage 0.4 Pea fodder (dry) 2.0 Clover hay 3.2 Wheat straw 1.5 Average of all the grains 2.6 Potato (Irish) 0.3 Turnip 0.1 Indian corn 7.0 Wheat 1.5 Rice 0.5 Oats 6 0 Peas 2.5 Barley 2.5 Winter rye 2.0 Pumpkin 0.1 Beet ...0.1 CHAPTER IX. THE ALKALOIDS, AND COLORING MATTERS OF PLANTS. 193. The Alkaloids. The vegetable alkalies, or alkaloids, formed in the course of vegetation, always contain a certain quantity of nitrogen. They have the general characteristics of alka- lies. They constitute salts by uniting with acids, and 10 218 CHEMISTRY OF PLANTS. restore the "blue color of reddened tincture of turnsole; and like ammonia combine with the hydrates of the oxacids. All the vegetable alkalies are soluble in alcohol, and generally insoluble in water. In elementary composition they are very much alike, having definite proportions of carbon, from 50 to 75, hydrogen from 6 to 12, oxygen 8 to 27, and azote 16 to 35 per cent. The alkalies doubtless perform important functions, existing as they do in the juices of plants with vegetable acids. Liebig thinks that they constitute one step in the organization of starch, sugar, oil of turpentine, and other valuable bodies extracted from plants. Thus the union of the constituents of water with carbonic acid, forms a sub- stance becoming gradually poorer in oxygen, the carbon assuming the form of citric, malic, and other organic acids, before being changed into sugar, lignin, starch, etc. This furnishes a simple explanation, the necessity of alkaline bases in vegetable life, and constitutes a strong inferential evidence of their uses in the organism of plants. Sertuerner, in 1804, first indicated the existence of mor- phine in opium, and is entitled to the credit of discovering the vegetable bases. We will describe several of these alkaloids which are of interest to agriculturists. 194. Nicotine, Nicotine exists in tobacco in combination with malic and citric acids. It is derived from a concentrated solid oil found in the tobacco plant, called nicotianine. It is a narcotic poison, so deadly that a single drop has proven fatal to a large dog. When pure, it is an oily, colorless liquid, has a strong odor of tobacco, and is A^ola- tile and inflammable. It has no oxygen, and contains 17.3 per cent, of nitrogen. Some grades of French tobacco COLORING MATTERS OF PLAXTS. 219 have from 7 to 8 per cent.; Virginia, 6 to 7 percent., and Havana, about 2 per cent, of nicotine. Its centesimal composition is as follows : carbon, 74.07; hydrogen, 8.64; nitrogen, 17.32. 195. Caffeine, Caffeine is found when pure in white crystals, in tea and coffee united with tannic acid. It occurs in tea, some- times as high as 6 per cent. ; in coffee, only one-half per cent. It is the same as theine. Its composition is as follows: carbon, 49.48 ; hydrogen, 5.15; nitrogen, 28.86; oxygen, 16.48. 196. Theobromine. Theobromine is found in the cacao bean, out of which chocolate is made. It has very nearly the same chemical composition as caffeine, and resembles it in its physical characters. Its composition is : carbon, 46.66 ; hydrogen. 4.40 ; nitrogen, 31.11, oxygen, 17.22. 197. Coloring Ma tiers o f Plan ts. The coloring matters of plants very seldom exist in an isolated condition, but are generally allied with some of the immediate principles, which are themselves frequently colored. They present great diversity of shades, but are generally derived from green, yellow, and red. They are solid; inodorous, and have but little taste. Some are solu- ble in water, and others dissolve only in ether and alcohol. Several of them unite with acids, and all combine with alkalies, which have the effect to modify their tints. Many blues, for instance, become green or yellow under the action of the alkalies, and red under the agency of acids. The color of flowers depends to a certain extent on the 2^0 CHEMISTRY OF PLANTS. soil m which they grow. Yellow primroses transplanted from a poor to a rich soil, will bear flowers of an intense purple. Charcoal deepens the tints of dahlias, hyacinths, and petunias. Carbonate of soda reddens hyacinths, and phosphate of soda changes the hues of certain plants in many ways. It is a well-known fact that maize and other plants receive a much deeper tint of green, by the application of ammonia to the soil. This color is always enhanced after a rain succeeding a long dry spell, which is probably owing to the ammonia brought down by the showers, as well as that rendered soluble in the soil. 198. Chlorophyl. Chlorophyl (leaf green) though occurring in very mi- nute quantities, is nevertheless deemed to be very impor- tant to vegetation. It constitutes the green coloring matter of the leaves and young stems of all living j^lants, having about the same relation to them in quantity, that the particles of dye have to colored fabrics. Berzelius supposes that the largest trees will not contain more than 100 grains. It is of the nature of the vegetable waxes; but often decomposes before it melts. Hydrochloric and sulphuric acids will dissolve it, imparting to their liquids an intense green color. Fremy says chlorophyl may be easily decomposed into two coloring matters — one yellow, zanthopliyl^ and the other blue, cyariophyL A mixture of hydrochloric acid and ether will efiect this. It is probable that the yellow color of autumnal leaves is owing to zanthophyl; the cyanophyl having been dissolved out. According to Sachs, those parts of plants which are not green, but capable of becoming so, have a transparent substance, leitcophyl^ which is converted into chlorophyl DENSITY AND COURSE OF THE SAP. 221 in contact with oxygen. This possibly accounts for the fact that leaves growing in the shade and just emerging from the soil, as the young cotton plants, are white, or of a very light green, owing to the lack of decomposition of the carbonic acid by sunlight and consequent appropria- tion of oxygen by the plant. Thus the bleaching of celery and endive, by covering with the soil, excludes the oxygen, and leaves the leucophyl in their stems. An impure chlorophyl obtained from grass, upon analy- sis by Pfaundler, had the following composition : carbon, 60.85; hydrogen, 6.39; oxygen, 72.78. (^.HAPTER X. THE SAP. — ITS DENSITY, COURSE, AND CHEMICAL COMPOSITION. 199. Density and Course of the Sap, In botany, sap is defined as the fluid which is absorbed by the roots of plants from the earth, and performs the first action of vital chemistry toward their organism. As soon as the sap has penetrated the spongioles of the roots, very important changes take place in it, for chemi- cal combinations are found which could not have existed as such in the water that moistened the soil. It increases also very rapidl}?- in density, as Mr. Knight found by experiment that the Acer platanoides, at the level of the ground had a density of 1.004, at 6^ feet above it was 1.008, and at 13 feet 1.012. Mr. Knight concludes that this increased density is oc- casioned by the sap taking up nutritive matter deposited in the cellular tissues. We think a more rational conclusion is that it oomes from the appropriation of hydrogen in the 222 CHEMISTRY OF PLANTS. plant, and exhalation of water through the pores of the stem. By this simple process of evaporation the sap be- comes concentrated not only in the leaves, but to a cer- tain extent before it reaches the leaves. That which remains is surcharged more heavily with important nutri- tive principles, and being now acted upon by sunlight and air, and receiving heavy supplies of carbonic acid, is elimi- nated and transformed into such salts as are needed for the growth of the plant. The course of the sap is at first through the tissue in- cluded in the bark, as long as it is permeable ; the central part of the stem or heart of trees especially, soon becomes chocked up or solidified by deposits of matter in the tissue, and the outer part of the wood (alburnum) only remains free and open for the circulation of the sap. The woody tubes (pleurenchyma) contained in this part of the tree oiFer the most constant means for the conveyance of the sap until the plant reaches maturity. 200. Ascending and Descending Sap. The ascending sap consists of carbonated water and mi- nute portions of all the salts entering into plant structure. What is termed the descending sap seems to be, from recent experiments, as of doubtful significance; as when the plant is in full growth the juices are held in equilibrium, rising or falling by hydrostatic law as in a cistern, only as the vital force, and the power of selection, changes the soluble atoms to whatever points they are needed. The carbonic acid of the air seems to be imbibed by the leaves, absorbed by the juices, and decomposed by the sun- light for the special building up of the leaf organism. It is probable that the carbon which builds the growing structure of the stem comes mainly from the soil. For if the sunlight decomposes the carbonic acid in the leaf and fixes the carbon, how can the insoluble carbon be conveyed CHEMICAL COMPOSITION OF THE SAP. 223 hy the juices of the plant to its base ? If so carried, it must be as carbouic acid united with the sap, and of course could not have been decomposed and fixed by sunlight. 201. Chemical Composition of the Sap, It is very evident from all the investigations that have been made, that the chemical qualities of the sap are very diverse in different plants and trees, as well as different seasons of the year, and the stages of maturity of the plant when the analysis is made, as w^ell as the part of the plant in which the sap exists. The sap of the elm was found to be at the beginning of April, mucilaginous, of a yellow color and sweetish taste. Its analysis is as follows : Water 1027.90 Acetate of potash 9.23 Organic matter 1.06 Carbonate of lime 0.80 So that water constituted about 988 in 1000 lbs. of sap. M. Regimbeau found in the sap of the vine, bi-tartrate of potash, tartrate of lime, mucilage, and free carbonic acid. M. Biot found no free carbonic acid in his experi- ments. Sugar has been found in considerable quantities in the sap of the maple tree, and Liebig and Will detected am- moniacal salts in the sap of maple and birch trees. Some trees and plants exude a milky sap, as the paw- paw, the cow tree, the ^^lumeria, and the poppy. In the latter, upon analysis, was found, besides morphine, fatty matters, gum, ulmine, and a woody substance, mineral salts with a basis of lime, magnesia, and potash. PAET YL CHEMISTRY OF SOILS. CHAPTER 1. HOST IMPOKTANT CONSTITUENTS OF SOILS. — EUROPEAN AND AMERICAN SOILS CONTRASTED. PLANT CONSTITUENTS EXHAUSTED FROM SOILS. 202. American and European Soils Contrasted. Agricultural chemists have laid it down as a rule, that the ingredients that are rarest in a worn soil, are the first exhausted and most needful to be replaced. This axiom will do, if we add to it as well, that those taken up most abundantly as plant-food, and existing most sj^arsely in soils, will be the first exhausted. Applying these two rules we shall be able, by getting an average analysis of soils, and knowing the amount of each element in plants, to arrive at a just estimate of the exhaustion of each from cj^ltivated soils. We present a table of 129 analyses of European and American soils, from the most reliable sources, giving the average of the seven most important constituents of plant-food, the only ones, in fact, ever needed to be ap- plied as fertilizers. We have separated the American from the European, because we Avished to ascertain the relative amount of potash, as European agriculturists have generally placed it in the front rank, superior, if anything, to phosphoric acid in importance, while we AMERICAN AXD EUROPEAN SOILS CONTRASTED. 225 have found that it was far less valuable than the latter substance; and that most of our worn soils have plenty of potash, if we can get nitrogen and phosphoric acid. It is proper to state that 63 of these analyses are of Kentucky soil, by Prof. Peter, and 12 by Prof. Hilgard, of Mississippi, taken from the Geological Reports of those States. The remaining 28 are by other chemists, and divided between different States, as follows: Ohio, six; Maryland, five; Mississippi, four; Connecticut, four; Canada, three ; Georgia, two ; and one each from Virginia, New York, Arkansas, and South Carolina. Table showing the average amount of the seven most important plant constituents in 101 American, and 28 European soils. American. European. Araa4. Potash 0.865 0.064 0.718 Lime 0.626 0.713 0.644 Magnesia 0 . 801 0.507 0 . 747 Soda 0.256 0.054 0.216 Phosphoric Acid 0 . 200 0 . 055 0 . 173 Sulphuric Acid 0 . 139 0 . 079 0 . 128 Chlorine 0 . 052 0 . 009 0 . 032 This table shows that European soils have been ex- hausted of their mineral ingredients to a much larger extent than American, with the exception of one single constituent, viz. lime : a thing to be inferred from the long period during which they have been under cultiva- tion ; and yet there seems to have been no reference made to this fact by any agricultural writer. Lime being still more abundant in European soils after the cultivation of a thousand years, shows the fact that their soils are much more calcareous than ours. It is also a fact well known, that they apply lime profusely as a fertilizer, not as food for plants, but as a decomposer of 10^^ 226 CHEMISTRY OF SOILS. organic matter which abounds in all soils cultivated in clover and small grain. As to potash, we find it existing in American soils as 13-|- to one of European. Magnesia nearly two to one; soda nearly five to one ; phosphoric acid nearly four to one; sulphuric acid nearly two to one, and chlorine nearly six to one. Since potash is so largely appropriated by plants, it is easy to perceive why European agriculturists are so loud in their praises of its virtues, and yet phosphoric acid is still more sparse even in their soils, although taken up very nearly in the same proportion by agricultural plants. 203. Constituents of Plants Exhausted from Soils, Carrying out the axiom above announced in reference to the value of constituents of plant-food in accordance with their sparsity in soils, chlorine would be the most important in European soils, and then successively, soda, phosphoric acid, potash, sulphuric acid, magnesia, and lime. In American soils it would stand, chlorine, sul- phuric acid, phosphoric acid, soda, lime, magnesia, and potash. But when we take into the account the percentage in which these substances exist in plants and are carried off by cropping, we find quite a change necessary to be made in our estimates. And with a view to have all the light thrown upon this subject possible, we select from the valu- able tables of Wolff and Knop, analyses of the leading agricultural crops in Europe and this country. The following table will show the average of the seven most important ingredients in the ash of agricultural plants, from all the most trustworthy analyses made. SEED AND PLANT CONSTITUENTS. 227 Potash. Soda. Magne- sia. Lime. Phos- plioric Acid. Sulphu- ric Acid. Chlor- ine. XT JVlGa.QOw tlay , . . . /CO . u . 7 0 4.9. .11 .6. 9 5.1 . Red. Clover. , . . . . . Otc . O . 1 i. . U . 19, 9 . Otc . V . Q Q ^ 0 .O.I Turnips . . Oo . o . 10 4- 1.^ ^ 14- ^ 4 1 Wlie3it Strsiw. . . 9 fi fi 9 5.4. . 2.9. V/OiL OllttW 22.0. 5.3. 4.0. 8.2. 4.2. 3.5. ST Kia V ilic>s .21 .8. 5.3. 7.7. .37.9. 7.8. 5.6. .6.1 Vr xlcctt 3.5. . .12.2. 1 . . 46 . 2 . 2.4. Oaf e V/clLb.. . o . o . . 4 . O . . o . o . 90 7 1 Maize ...27.0. . 1.5. ..14.6. . 2.7. ..44.7. . 1.1. Peas ..40.4. 3.7. .. 8.0. . 4.2. ..36.3. . 3.5. .2.3 Cotton Seed. . . ..32.8. 1.6. ..13.7. . 7.1. ..32.8. . 4.8. .0.6 Cotton Lint.. . . ...3t.2. . 2.1. .. 9.3. .16.6. .. 6.8. . 3.3. .1.7 The last two items are an average of two recent analy- ses, one each by Professors White and Land. 204. Of Seed and Plant Constitueiits. From this table it appears that only three constituents enter more largely into the ash of seeds than other parts of the plants. These may be well classed as seed consti- tuents, viz. phosphoric acid, potash, magnesia. The table would stand thus: Per cent, in Seed. Per cent, in Plant, Phosphoric acid 36.1 Potash 27.4 Magnesia 11.1 Lime - .4.1 Soda 2.8 Sulphuric acid 2.6 Chlorine 1.9 Potash 26.5 Lime 17.8 Phosphoric acid 10.7 Magnesia 6.3 Sulphuric acid 5.4 Soda 5.1 Chlorine 3.3 As the seed is the most valuable part of the plant, and that part which is most commonly taken from the land in cropping, it may safely be estimated that elements entering largely into the composition of seed are of the most importance, agriculturally speaking. This would make the first column represent the grade of the value of the different constituents, placing phosphoric acid first, and chlorine last. 228 CHEMISTRY OF SOILS. CHAPTER II. PLANT CONSTITUENTS IN MINERALS, AND MINERAL CONSTITUENTS IN SOILS. 205. Plant Constituents in Minerals. It is a remarkable fact that phosphoric acid, though SO valuable a constituent of plants, is found very rarely in minerals or rocks underlying all Primary regions. True, minerals and fossils exist in many localities containing this substance; and in such places as the phosphatic beds of South Carolina, it exists in a much larger percentage than any other soil constituent. We have taken the pains to investigate the subject by an analysis of all the minerals found commonly existing in Middle Georgia, and give the result in a table below. What is true of this region, will be true of all others with the same geological formation. Table showing the percentage of the different organic oxides found in the common minerals of the Primary and Metamorphic regions of Georgia : Minerals. SiO. Al^Og. KO. MgO. FeO. CaO. NaO. MnO. S. Quartz 100 Felspar 67.. 19... 14 Mica 46... 14... 10... 10... 20 Hornblende 59 20... 7... 14 Augite 53 8... 17... 22 Epidote 37... 27 17... 14 Talc 29... 17 12... 27... 3 Chlorite 26... 18... 2... 8... 43 Tourmaline 35... 35 1...18,.. 1... 2... 1 Albite 70... 18 trace.. 1 .. .10. .trace.. . . Garnet 44... 8 12... 33 trace.... Iron Pyrites 47 53 MINERAL CONSTITUENTS. 229 From this exhibit all the inorganic elements that enter plants exist in the rocks of Middle Georgia, except phos- phoric acid and chlorine. These are found but sparsely in the soils, and are doubtless the first exhausted in most soils, especially the former. 206. Mineral Constituents per Acre, and their Period of Exhaustion. Estimating that an acre of soil one foot deep contains 4,000,000 pounds, we have in American soils one-half foot deep, of plant constituents, as follows : Potash 17,333 lbs. Lime 12,500 " Magnesia 16,000 " Soda 6,000 " Sulphuric acid 3,400 " Phosphoric acid 3,080 " Chlorine 500 " Should a crop of cotton be continuously planted on an acre of ground, producing a half bale equal to 250 lbs. of cotton fibre, it would take many years to exhaust an average American soil of these mineral ingredients. The follow- ing taJDle shows the number of years required for each substance. The estimate is made both of the seed and fibre taken from the soil. Phosphoric acid 465 years. Potash - 2,595 Lime 4,671 Magnesia 6,413 Soda 6,090 Sulphuric acid 4,000 Chlorine 943 There is no need that the available mineral elements should ever be exhausted from any soil. If all the cotton seed, and wheat and oat straw is returned to the land, and 230 CHEMISTRY OF SOILS. the corn and cotton stalks left to rot upon it, there would be much less of these principles extracted from the soil, and it would require but a A^ery small annual application 01 them to keep our soils in good heart, and even improve them in their mineral wealth, as well, as actual production. 207. Other Requisites of Fertility, If the fertility and value of soils depended mainly on the amount of mineral matter in them, we would suppose that their fertility would remain unimpaired for centuries to come. But it must be remembered that there is another element more easily exhausted than any of them, without which, a soil would be perfectly barren. We refer to nitrogen. It is also equally true that these mineral elements must be in a soluble form or they are not available. A soil might have enough phosphoric acid in it to supply the crops for a thousand years, and yet if not made soluble by natural or artifical processes, the soil would remain barren, though all the other mineral constituents, and nitrogen too, were in abundance, and in soluble forms. And if all these were present with soluble phosphoric acid, the soil might yet be utterly worthless from the absence of organic matter, to act physically upon it, in opening it, rendering it cool and moist, by absorbing and retaining water, as well as ammonia. This is particularly true of soils in warm climates. It is thus perceived that the fertility of a soil depends upon a number of contingencies, all of which must trans- pire in order for a soil to be productive. COARSE AND FINE SOILS. 231 CHAPTEE III. SOLUBILITY OF SOILS. EXHAUSTION OF SOILS. 208. Coarse and Fine Soils, — Soluble and Insoluble, If a sample be taken from common arable soil, and thoroughly dried, and sifted in a fine sieve, it will be found that much the larger portion will remain as fragments of roclvS, coarse pebbles, and small grains of sand. These pebbles when properly disintegrated will be quite as valu- able as the silt or finer particles, and an analysis would doubtless show all the constituents of plant food in good proportions. They may be considered as the reserved forces, held in store for future use. They have no agri- cultural value however, only prospectively and in the far future. The finer particles of soil which escape through the sieve, are of much higher value, being the part from w^liich crops have to draw upon for nutriment. And even this, how^ever fine, is divisible into three parts; the first soluble in water, the second in acids, and the third insoluble. The portion soluble in w^ater is that upon which the present crops feed, and find sustenance. This is generally in the finest atomic condition. In fact some chemists incline to the opinion that mineral substances may be reduced to such impalpable atoms, as that they may be appropriated as plant food without any change in their form. We can- not think so, however. We do not believe, for instance, that the tribasic phosphate of lime could be rendered fit food for plants by mere mechanical fineness. That con- dition renders it in a much better state to become soluble by ammonia, carbonated water, or solution of chloride of 232 CHEMISTRY OF SOILS. sodium in the soil. But the form is changed by these solvents and thus it becomes fit food for plants. 209. Of Soluble Matters in Soils, Prof. Johnson gives an interesting estimate made of various soils, as to the amount of matters in those soluble in water. (How Crops Feed, p. 311.) Seventeen different analyses show an average of the following substances in 100,000 parts of various soils: Lime 38.3 Sulphuric acid 35.9 aesia 7.9 Silica 14.1 Potash 8.8 Oxide of iron 7.5 Soda 40.2 Organic matter 80.2 Phos. acid 0.9 Total soluble 303.9 Chlorine 51.3 Of lime, every soil had 1 part or more. Of magnesia one soil had only a trace, and one other under ^, Of potash only one had less than one part, having -J. Of soda one soil was a salt marsh having 476 parts. The others ranged from 1 to 24. Of phosphoric acid four soils had not a particle soluble in water; five others only a trace, one other of one part, another -J, the remaining six ranging from 1 to 5 parts. How clearly this shows the value above all others of phos- phoric acid as a fertilizer, and the need of its being ren- dered soluble by the intervention of science. The same remark is true of chlorine, as of soda, the saft marsh running up to 407, all the others, (except five which had only a trace) ranging from 1 to 7|^. Of sulphuric acid one soil had 302, another salt meadow 144, two others a trace, the remainder ranging from 1 to 18. Of silica three soils had only a trace ; the others ranging from 1 to 58. Of oxide of iron, four soils had none, the rest of them ransjino^ from 1 to 77. EXHAUSTION OF SOILS. 233 Of organic matters, the lowest was 10, the highest 44.9. Take the 17 different soils, the one lowest in soluble matters was 39| parts, the highest 1393, equal to 1.393 per cent. The quantity of soluble matters was as a general rule greatest in damp soils abounding in organic matters. I^ext in fertile soils, either natural or made so by manures, and the least in poor sandy soils. 210. Exhaustion of SoUs. We now propose to notice a little more in detail the exhaustion of soils by cropping. We have seen that nitro- gen is supplied to plants by their roots, and that it is the only organic element needed to be supplied to soils, or that can be exhausted from them. Then the nitrogen of plants is furnished at the expense of the soil. With this excep- tion, certain mineral elements, constitute the entire amount of matters taken up by croj^s, which produce the exhaustion of soils. Then the mineral theory of Liebig must be re- ceived with this much modification, that the nitrogen fur- nished by organic matters in the soil, or applied to them in fertilizers is quite as essential as the minerals, inasmuch as the atmosphere cannot supply it directly. We have seen that the mineral substances of most im- portance to plants, are phosphoric acid, potash, magnesia, lime, soda, sulphuric acid and chlorine. These exist in the sparsest quantities, and all of them may, under certain cir- cumstances, become exhausted from soils, so as to require replenishing. This, we believe, is never true of silica, alumina, manganese and iron. Mineral substances can only be exhausted from a soil, by cropping, if we except soluble matters, Avhich are some- times leached out of certain soils, and carried beyond the reach of plants. All cultivated soils lose more or less by crops that are carried off from them. When the entire 234 ClIEMISTEY OF SOILS. plant is returned to the soil, it rather enriches than im- poverishes it, by increasing the amount of organic matter taken from the atmosphere, and increasing the amount of available mineral food. We now present a statement of the amount of the most important mineral substances, as well as of nitrogen carried off by different field crops. A crop of 750 lbs. of seed cotton will carry off from one acre of land 23.25 lbs. of nitrogen, and 35.3 lbs. of ash; of which there will be of the most important mineral elements, Potash 8.30 Magnesia 5.05 Sulph. acid... 0.50 Soda 3.20 Chlorine 0.30 Plios. acid . ..7.20 Lime 0.83 A crop of 8^ bushels of wheat and an equal quantity by weight of straw, will carry off from an acre of land, in pounds, Nitrogen 11.50 Magnesia 0.74 Lime 0.46 Soda 0.31 Sulphuric acid 0.26 Chlorine trace Phos. acid. . . .2.57 Potash 2.12 Total ash. . . .35.15 A crop of Indian corn in the ear equal to nine bushels of the grain, will carry off from an acre of land, in pounds, Nitrogen 9.00 Magnesia 0.76 Lime 0.18 Soda 0.09 Sulphuric acid 0.09 Chlorine trace Phos. acid 2.27 Potash 2.13 Total ash 7.94 A crop of oats, grain and straw, allowing that the weight of the straw is double that of the grain, the crop being 12 bushels per acre, will carry off of Nitrogen 12.0 Lime 1.62 Phos. acid. . . .2.27 Magnesia . . .12.0 Soda 1.52 Sulph. acid. . .0.59 Chlorine trace Potash 4.72 Total ash . . .32.76 A crop of peas, consisting of the seed, equal to nine bushels per acre, will carry off the following amount of nitrogen and mineral substances : Nitrogen 16.50 Magnesia 0.40 Lime 0.21 Soda 0.18 Sulphuric acid 0.17 Chlorine 0.11 Phosph. acid .1.81 Potash 2.02 Total ash . . .14,05 WATER CHEMICALLY CONSIDERED. 23e5 Here, then, we have the principal field crops in the South rated at about their average annual production. Nitrogen, phosphoric acid, and potash, being confessedly the most valuable substances, will be exhausted from the soil by cotton in four successive crops, per acre, as follows: Nitrogen, 92.80 lbs.; phosphoric acid, 28.80; potash, 33.20. A rotation of crops, 1st cotton, 2d wheat, 3d coi'u and peas, 4th oats, will abstract of nitrogen, 72.25; of phos- phoric acid, 15.12 ; of potash, 19.29. Thus it will be seen that running land in cotton exclu- sively for four years, will leave the land poorer in nitrogen by 20.55 lbs.; in phosphoric acid by 12.78, and in potash by 13.91, than to have the rotation of five crops above men- tioned, in four years. These amounts taken mostly from the surface soil, not more than six inches deep, seem very small in comparison with the whole amount of these substances found in most soils, but when subtracted from the available nitrogen, phosphoric acid, and potash of even the richest soils, it produces, as our experience too well teaches us, a most rapid deterioration. CHAPTER ly. WATER AS A CHEMICAL AGENT IX SOILS. CHEMICAL ABSORPTION OF SOILS. 211. Water Chemically Considered, We have now^ treated of all the constituents of soils useful to vegetation, except water, and that is by no means the least important. In fact it is of such impor- tance that no germ could sprout, and no vegetation sub- sist without it. 236 ClIEMISTKY OF SOILS. In chemical language, water is the 23rotoxide of hydro- gen. The old formula was, H0=9, one equivalent of hydrogen, and one of oxygen. Under the new regime it is H.^0=18, two atomic weights of hydrogen and one of oxy- gen. Its centesimal composition is Oxygen 88.88 Hydrogen 11.11 100.00 By measure, water has one volume of oxygen to two of hydrogen. Water may be formed by the burning of hydrogen gas. It is first mingled with vapor of water in a suitable appa- ratus, and made to stream slowly through a wide tube, filled with fragments of dried chloride of calcium, which cause its dessication. After the displacement of the air, the gas is ignited at the upper end of the tube, and a bell-glass suspended over the flame, on which water will be collected as dew, and soon flow down in drops into a vessel placed beneath. Water exceeds any other liquid in nature as a solvent. It combines with saline substances, as water of crystalliza- tiorij forming liydrates by chemical union with other sub- ijtances. This is generally attended with heat, as when lime is slaked, by which a hydrate of lime is formed, 212. 'Water ^ Gaseous^ Liquid^ Solid. Water occurs in nature under three forms : gaseous, liquid, and solid. The first is the watery vapor of the at- mosphere ; the second, limpid, fluid water; the third, frozen water, or ice. When pure, water is colorless, transparent, and without taste or odor. And yet there is something so refreshing in a cool draught of water, that it is very grateful to the palate. CHEMICAL ABSOPvPTIOX OF SOILS. 237 It freezes at 32^ F. when slightly agitated, but when perfectly at rest, at a lower temperature. Its densest point is 40°, boils at 212°, and evaporates at all inferior tem- peratures. In the construction of ice, which is lighter than Avater (having a specific gravity of 0.918), we can see the wisdom of an Infinite mind so clearly portrayed, that even the materialist must acknowledge in it an intelligent design. It is a general law of nature that all gaseous and liquid substances in becoming solid, become more dense. lee is an exception to this rule. Should it have been differ- ently constructed, it would, as fast as congealed at the surface of tlie northern lakes and rivers, have sunk to tlie bottom never to rise again, and never to be thawed, Tlius would not only all the northern regions have become frozen, but it would have extended the line of perpetual winter to the temperate and even torrid zones. The great value of water to soils, not only by furnish- ing hydrogen and free water to plants, but by rendering soluble all nutrient elements taken up as plant-food, as well as its effects as a physical agent in the soil, have already been fully discussed in this work. 213. Chemical Absorption of Soils. Soils have a power which has been termed chemical absorption, by which they imbibe and retain from the atmosphere and fertilizers applied to them, the most valua- ble salts, which will be needed for plant-food. This power is possessed by aluminous soils to a liigher degree than silicious soils. An excess of soluble matters may thus be appropriated and reserved for a time of want. From various experiments made by Liebig, Yoelcker, Eichhorn and others, the following facts have been elicited in reference to this absorptive power of soils on different salts. 238 CHEMISTRY OF SOILS. Oxide of iron and alumina absorb ammonia and hold it in a slightly soluble state. Free ammonia and its carbonate, are retained by the organic acids in a non-volatile form. The sulphate, hydrochlorate and nitrate of ammonia, are decomposed by the soil, the ammonia retained, and the acids united to lime. Phosphoric and silicic acid are also retained, and sul- phuric and hydrochloric acids are also said to be liable to absorption. In no case, however, has nitric acid been ab- sorbed and fixed. Salts of lime, especially when added alone to the soil, ro to a soil rich in lime, are said not to be absorbed. The carbonate of lime, however, and lime itself are held by the organic acids of the soil as humic, crenic, etc. In a dilute solution of chloride of ammonium for ten days, the mineral took up 3.83 per cent, of ammonia; and in twenty-one days it yielded 6.94 per cent, with a loss of water. These and similar experiments have established with- out doubt, that the hydrous double silicates in all soils determine the absorption and retention of potash, ammonia, etc., from solutions of their salts. It is known also, that insoluble phosphates and sili- cates are formed with oxide of iron, alumina, lime, and magnesia, under certain conditions. Sulphuric acid also forms insoluble combinations with iron and alumina. We are justified then in the conclusion that all clay soils are capable of imbibing and fixing all the ammonia, potash, and phosphoric acid, that is likely to be brought into the soil by any means w^hatever. This cannot be true of sandy soils ; nor are clay soils so retentive of am- monia in southern as in northern climates. It is also probable that these bodies are never com- pletely removed from the most dilute solution ; and thjit SOURCES OF NITKOGEX. 239 when a soil has become saturated with them, it lets them off slowly to i^iire water, or acid solution, by which means plants receive their food. CHAPTER V. NITROGEN IN SOILS. 214, Sources of Nitrogen, Nitrogen exists in three forms in soils, viz. nitrogen, ammonia, and nitric acid. Nitrogen gas is developed sometimes from the ground in certain localities, but rarely, owing, as is supposed, to the decomposition of air in cavernous rocks. The nitrogen and oxygen uniting to form nitric acid, a large excess of nitrogen is thus left and evolved from the soil. (Shepard.) It is also evolved from many well-known springs, as Cheltenham and Ilarrowgate. Nitrogen exists in all kinds of soils, and in mineral^ which were never in contact with organic substances. But its principal source in soils, we doubt not, is from the decay of vegetable and animal organisms. When we remember how many human beings are buried beneath the ground, how many worms, insects, and reptiles, also die and decay in the soil, as well as the nu- merous birds and beasts that rot upon its surface, from whose carcases more or less of the nitrogen, as ammonia or nitric acid, is imbibed; we see what a continued supply is being furnished from these sources. The urine and excrement also of every living being, is constantly imparting nitrogen in one of these three forms to the soil. We have a notable instance of these sources of nitro- 240 CHEMISTRY OF SOILS. gen in the Chincha, Guanape, and other islands of Peru, where a species of sea fowl have been wont for ages to congregate. Carrying thither the fishes of the sea upon which they prey, and then in their turn sicken and die; fish and fowl, flesh and bones and excrement, all com- mingling, form the most powerful fertilizer known, with just about as much silica as the gizzards of these birds would require to aid in digesting their food. These rich deposits contain from 4 to 18 per cent, of nitrogen. In the same country, in the district of Tarapaca, im- mense beds of the nitrate of soda have been found, which is transported to this country and Europe for fertilizing purposes. 215. Organic Nitrogen in Soils. Boussingault has shown conclusively that nitrogen exists largely in many soils in an insoluble form. This organic nitrogen, however, may be made assimilable in two ways : first, by oxidation, which converts the nitrogen into nitric acid, through heat, moisture, and vegetable putrefaction ; second, the application of lime and alkalies, which reduces the nitric acid by a rapid putrefactive de- composition to ammonia. A soil saturated with water, thus excluding the air, would favor this reduction, but as the soil becomes dry, nitric acid would form again, rapidly. The albuminoids probably furnish most of the organic nitrogen of soils. Natural humus is never destitute of nitrogen. The acids of humus, crenic, apocrenic, humic, and ulmic, them- selves free from nitrogen, are naturally combined with ammonia ; but this is so fixed as to be difficult of separa- tion. Carbon and hydrogen evolve more rapidly from decaying organic matter than nitrogen; hence the nitrogen in humus is relatively larger than the carbon. Kroker analyzed 22 diiferent soils, and found nitrogen COMPOUNDS OF NITROGEN IN SOILS. 241 ill all of them in considerable quantities. An unfruitful sand contained a hundred times more nitrogen than is necessary for a good crop. In all arable soils there were present 500 to 1,000 times more nitrogen than was neces- sary. Schmid found a black soil of Prussia to contain 0.99 per cent, of nitrogen. Nitrogen exists mostly in the surface soil, which is denominated the tilth, gradually diminishing the deeper you go down ; so that below the depth of 10 inches, it exists in infinitesimal quantities, if at all. This is prima facie evidence that the atmosphere is its principal, if not only source. When it is known that soils rich in organic matter have from 5,000 to 35,000 lbs. of inert nitrogen, how im- portant to learn the cheapest process to convert this nitro- gen into soluble forms, rather than spend so many millions to bring it from Peru. 216. Compounds of Nitrogen in Soils, Salts of ammonia, nitrates, and nitrites, as far as known, are the only compounds of nitrogen existing in soils, and these in minute quantities. Where humus abounds, the amount of nitrogen is greatly increased. In 32 specimens of peat free from earthy matters, Prof. Johnson found the average 2.6 per cent. ; in some cases as high as 4.31. Most of this belonged to the humus as nitrogen; a mi- nute portion only was in the form of ammonia, or the nitrates. Nitrogen accumulates in rich soils, but is mostly insol- uble. Boussingault found only four per cent, in such soils existini^ as nitrates or ammonia, the remainder beino; unavailable to plants. He also analyzed a number of soils w^ith reference to the amount of ammonia, nitrate of potash, 11 242 CHEMISTRY OF SOILS. and nitrogen. We select several analyse? of different classes of soils, as follows : Soils, Ammonia. Nitrate of Potash. Nitrogen at the depth of one foot. Lbs. per acre. Lbs. per acre. in combination. Light garden soil 100 875 12,970 Wheat field, clay 45 75 6,985 Rich past ure 300 230 25 .650 Heavy forest clay 183 5 5,955 Fine sand, prairie 190 5 3,440 Loam, near Amazon. ..... .210 none 9,100 Rich leaf mould 2,875 none 34,250 From this table, ammonia is generated largely, more in the rich leaf mould than elsewhere, while of nitric acid there is none. This was probably owing to constant nloisture — a state adverse to nitrification. Boussingault found in 100 parts of rich garden mould, that had been cultivated for many years. Nitrogen 0.261 Ammonia , 0.0022 Nitric acid 0.00034 This distinguished experimenter found that only the ammonia and nitric acid were of present use to vegetation. The remainder being for the time inert. So variable is the assimilable nitrogen of a soil, that no estimate can be made of it as a constant quantity. Bretschneider experimented during the growing months to ascertain this fact. He found that ammonia decreased rapidly from April to September in porous soils and slowly in compact soils. That nitric acid obtained its maximum in June, and fell to nothing in September. The oat plot had 59 of ammonia in April, and only seven in September, the reduction being, gradual; the uncultivated plot falling from 59 to 23. The nitric acid in the oat plot fell from 66 to naught, and the same in the vacant plot ; but in June the latter had 108, the former only 57. The total nitrogen of the soil in the uncultivated plot AMMONIA IN SOILS. 243 increased from April to September from 4,652 to 6,525, show- ing that the latter gathered nitrogen more rapidly from the atmosphere in some way. Also that ploughed lands will increase more rapidly in nitrogen than those lying fallow. This, however, requires further demonstration. Ammonia and nitric acid are the exclusive sources of nitrogeneous food for plants — the organic nitrogen hav- ing to be converted into one of these forms before it is available. Boussingault experimented with his own gar- den soil, which contained 26 per cent, of nitrogen, equiva- lent to 7 tons of ammonia per acre. This soil in small quantities, when shielded from rain and dew did not de- velop plants but little farther than a barren sand. In eight trials the crops weighed on an average four times as much as the seed, while in sand and burned soils containing no nitrogen, the crops weighed three times more than the seed. The available nitrogen in this garden soil was as 19 to 2,610 unavailable. It is believed that under peculiar circumstances, the nitrogen of ammonia and of tlie nitrates may pass into organic coml)ination in the soil, forming an amide — like sub- stance w^ith the humus. Knop demonstrated that ammonia kept in close vessels with humus would entirely disappear in the course of several months. Other experiments of Hunt, Dusart, and Thenard prove that ammonia as a car- bonate in prolonged contact with cellulose and humic acid forms combinations which may be reproduced by the action of the alkalies and lime. 217. Armnoiiia in Soils, Ammonia exists, to a limited extent, in all soils that have any productive capacity, though Knop asserts that clay is the only ingredient of soils which absorbs ammonia, and that all carbonate of ammonia found in soils, adheres to clay. 244 CHEMISTRY OF SOILS. The quantity of ammonia in a soil is small and variable, always increased by dew and rain, as well as by the appli- cation of manures ; and decreased by evaporation. It is most probably true, that ammonia as such, is re- tained by the alumina of a soil, its humus and the hygro- scopic water existing in it. And besides its combining with acids foi*ming sulphates, phosphates, carbonates, etc., it undergoes the process of nitrification. Soils boiled with solutions of potash, yield ammonia for a long period. Lime incorporated with soils at a common temperature increase its ammonia. In one experiment a quantity of soil with lime and water, confined for eight months, increased from 11 to 303 milligrames of ammo- nia. (Boussingault.) Ammonia is a constant constituent of minerals contain- ing iron. Hematite and common iron ore are said to con- tain one per cent, of ammonia, and also soils containing oxide of iron and clay have more or less of this salt. Bonis says that the peculiar odor emitted by moisten- ing minerals containing alumina originates in part irom ammonia. This is always discernible in the first fall of summer showers after a dry spell on the impalpable dust of a street or well-trodden road. Humfield found the carbonate and nitrate of ammonia in the springs at Eldena in Germany, and pharmaceutical chemists have often detected it in well water. 218. Nitric Acid in Soils, Nitric acid exists in soils as a very inconstant quantity, undergoing rapid changes, being formed from ammonia and then uniting with bases forming nitrates. The nitrates are very soluble, and leach out of soils by heavy rains. In 100 analyses of lake, river, spring, and well water, Boussingault found nitric acid in every case — the quantity being the largest in cities and fertile regions. NITROUS ACID IN SOILS. 245 Thus the Seine had six times as much nitrate of potash as the Rhine, and the Nile four times as much. He esti- mated that the Rhine and its tributaries carried to the sea 220 tons of saltpetre daily, the Seine 270, and the Nile 1,100. Nitric acid exists also in minerals in combination with lime, magnesia, potash, and soda. This latter forming large beds in some localites. We will treat of this subject more fully when we come to natural fertilizers under the head of Nitrification. 219, Nitrous A cid in jSoils. Chabrier ascertained by analysis that all tilled soils contained nitrous acid. The soils were powdered very fine, passed through a sieve, and then bleached in order to make the determination. It is well known that nitric acid is acumulated in dry weather in the superficial strata of the earth ; the reverse being true of nitrous acid. Hence it would seem that the soluble nitrites ascend by capillarity in the soil during dry weather, where they are transformed into nitrates, and then washed out by the rain. One part of nitrous acid to 25,000 parts of water is gen- erally found in soil water ; never more than one part in 5,000. Fields which have not been ploughed for some time contain much nitric, and but little nitrous acid j while the reverse is true of forest lands. Clay soils which have been submerged contain no nitrous and but little nitric acid. Nitric acid, though occurring in such a small percentage, is of importance, especially in the early stages of vegeta- tion. 240 CHEMISTRY OF SOILS. CHAPTER VI. ANALYSIS OF SOILS A DUBIOUS TEST OF FERTILITY. NEW METHOD OF SOIL ANALYSIS. 220. Analysis of Soils a Dubious Test of Fertility, ITeeetofore chemistry has never been able to define exactly the laws which govern fertility. Liebig, who de- voted a long life to agricultural chemistry, in one of his last works says, " Chemical analysis gives but rarely a correct standard by which to measure the fertility of different soils, because the nutritive substances therein contained, to be really available and effective, must have a certain form and condition, which analysis reveals but imperfectly." All the chemical constituents of which plants are formed may be present in a soil, and yet it be unproductive. They must be in certain soluble and available forms which chem- istry cannot fully define. And even soils having less of these available matters may be more productive than others having more of them, owing to certain physical defects existing in the one from which the others are free. As illustrative of this general principle, you may take a stiff clay soil and a sandy loam, and have them analyzed. The leading principles of plant-food exist more abundantly in the clay than in the sand. You may now take 50 per cent, of the sand and add to the clay. Upon analysis the mixed soil will have less of nutriment than the clay soil, but put them both in cultivation, and it will be found that the mixed soil will be the most fertile, owing to the fact, that there is a much greater surface afforded the plants than before for obtaining the nutritive substances of the soil. It does not follow by any means, that there is no bene- fit derived from analysis. On the contrary, an ultimate 5^EW METHOD OF SOIL ANALYSIS. 24Y analysis of a soil, together with its soluble matters elimi- nated and properly characterized, and its physical qualities also developed, would throw much light upon its compara- tive fertility. A chemist may tell a soil that is wholly barren, by the absence of any essential constituent; but where all are present, its fertility depends upon so many contingencies that the problem becomes very difficult. 221. jVew Method of So il A n alysis, M. Grandeau, who has charge of one of the experimental stations in France, concludes that the black matter which is dissolved out of the humus of the soil, by ammonia water, contains in an assimilable form, the veritable food of plants. He proposes a new method of analysis of soils to deter- mine their fertility, founded upon the actual amount of humus in them in combination with inorganic matter, especially lime. He gives the following as an example of his method. He took two soils, one known to be fertile without ma- nure for a long series of years, and the other only equally fertile with the application of 10 tons of stable manure to the acre. The ultimate analysis of these soils gave the following results : 1,000 parts air-dry son. phoric Potash. Lime. ^If^^' Nitre. Matter. ^^^^ sia. Naturally fertile soil... 71 .0. . .2.00. . . 2.50. . .5.20. . .0.5 ..2.60 I Artificially fertile soil ..110.0...2.10...11.30...1.00...4.10..3.00 Here we perceive the first, or fertile soil, has less organic matter, less phosphoric acid and nitrogen, and much less potash and magnesia. And only in the lime has the as- cendency. Any chemist would have pronounced in favor I of the second soil as being the most fertile. M. Grandeau, struck with the great difierence between 248 CHEMISTRY OF SOILS. the two soils as to fertility, and the failure of an ultimate analysis in determining that difference, instantly set about an investigation of the two soils in a more philosoj)hical light. He established another method of analysis, which was crowned with success. This analysis was founded upon the assumption that, in its wider sense, humus is a combination of organic and inorganic matter, that it contains not only water and car-^ bon, but phosphoric acid and potash, and all the other essential elements of plant-food in soluble conditions, and that the minerals tlius associated with humus or in humus, are the veritable plant-food. His analysis of the two soils upon this method gave the following results : No. 1. NATrKx\LLY Fertile Soil, from Russia. 1 000 r)art<3 ) Lime 53J<^...75 ...62 ...43 ...180 ...675 Superphosphate 533^ . . 101 ... 86 ... 50 ... 287 ... 887 No manure 56 ...65 ...47 ...168 ...600 From the above experiment it is seen that while the lime by itself increased the product over the natural soil twelve ounces, it reduced the amount made by the super- phosphate 37 oz. by throwing it back into the tri-basic 300 FERTILIZEES AND NATURAL MANURES. form. This teaches very clearly that lime and superphos- phates are incompatible, and that it will not pay to apply the latter to soils abounding in lime. 267. Ammo7iiated Superphosphate, We have seen that nitrogen and phosphoric acid are the first principles exhausted from the soil; hence, when ap- plied in soluble conditions, they act as powerful fertilizers. In order, however, for them to act efficiently, .they must be applied together. Nitrogen by itself, or phosphoric acid by itself, will produce only partial results, especially in the production of seeds. Combine them, and marked results will follow. In 1867, we applied superphosjohates alone on cotton, at the rate of 178 lbs. to the acre, and 75 lbs. of Peruvian guano, combined with as much superphosphate. The for- mer produced 633 lbs. of seed cotton, the latter 907. In 1869 we used the sulphate of ammonia and super- phosphate, each alone, and then the two combined, at a cost of $10 each per acre, with the following result: l^t 2d 3d 4th ,p , , Increased Picking. Picking. Picking. Picking. product. Ammonia 20 47 35 6 108 19}^ lbs Superphosphate 21 62 37 7. ... ,129 393^ " Combined 57 83 11 1 152 75 " The last column indicates the increased production ovei the natural soil, showing that a combination of nitrogen and phosphoric acid is much more powerful in the production of cotton at least, than when taken separately. In 1870 we applied the same fertilizers to cotton in similar proportions, in rows 70 yards long ; the ammo- niated phosphate made 287, the superphosphate alone 204 oz., the natural soil 118 oz. The following table of an experiment in 1873, shows still further the effect of combination, though not so marked am:moxiated superphosphate. 301 as some of the other experiments. The cotton was planted m rows seventy yards long. The natural soil is the average of six rows on each side of the plot. Amount per Acre. 1st Pick- 2d Pick- 3d Pick- 4th Pick- Total. Lbs. per acre. ing. ing. ing. ing. Pure Ammonia, 22 lbs.. . 46 oz, . .97 oz. . 54 oz . . 8oz. .205 oz. .750 lbs. Pure Bi-pliospliate of Lime, 66 lbs 20 . ..90 . .78 . .14 . .202 . .742 Six lbs. Ammonia, 42 lbs 56 , .119 . .60 . . 6 . .231 . .866 14 . .65 . .60 . .15 . .154 . .562 The ammonia was used in the form of sulphate, and of course had sulphuric acid besides the pure ammonia. The bi-phosphate was used as a superphosphate, and the com- pound had ammonia potential and actual, combined with superphospliate. The bi-phosphate cost something less than the other two per acre. Peruvian guano, which has proven to be so powerful a fertilizer for all agricultural crops in every soil and climate, is itself a remarkable combination of nitrogen and phos- phoric acid, while the latter is to a large extent insoluble as found in the dry guano. When, however, it becomes moist in the soil, a decomposition takes place through the agency of the sulphate of ammonia, by which the bone phosphate of lime is transposed into oxalate of lime and phosphate of ammonia. The phosphoric acid then becomes soluble, diffusing itself through the soil, and forming solu- ble combinations of potash, phosphate of soda, and phos- phate of ammonia. (Liebig.) This substance then, is the most remarkable of all combinations, natural or artificial as to fertilizing qualities. The advantage of manipulated fer- tilizers over it, is because they contain the minimum of ammonia, and are cheaper and less heating, requiring less rain for the crops. A good formula would embrace about three per cent. 302 FERTILIZERS AND NATURAL MANURES. of ammonia and nine of soluble phosphoric acid, equal to 19.50 of bi-phosphate of lime. The remainder of the hundred pounds being made up of alkaline salts, insoluble phosphate, sulphate of lime, organic matter, and a small percentage as necessary concomitants of alumina, iron, and silica. While most commercial fertilizers are of a lower grade than this, there are no well-established houses who would attempt to palm off a spurious article on the farmers. It would take but one year for such an article to be condemned by experiments in the field, to say nothing of the labora- tory. ^ CHAPTER YI. POTASH, SODA, AND LIME, AND THEIR COMPOUNDS, MAGNESIA, SULPHURIC ACID, CHLORINE. 268. Potassa^ KO. Next to phosphoric acid, potash or potassa is the most valuable inorganic ingredient. Its symbol is KO, having one equivalent of potassium (kalium) and one of oxygen. Potassa is the technical, potash the commercial name. The potash of commerce is a hydrated oxide of potas- sium, and is not valued much as a fertilizer. Twenty years ago, agricultural chemists were much concerned about using potash in some form, as they thought Peruvian guano would exhaust the soil of this important substance ; and yet it could not be used in conjunction with ammonia or superphosphate, causing the one to escape and the other to be thrown back into a neutral phosphate. Hence a pre- paration was made and sold in Baltimore, by Mr. Samuel Sands, of plaster and potash, containing 10 per cent, of the latter. We tested it in 1867, applying 187 lbs. per acre, at a CHLORIDE OF POTASSIUM. 303 cost of $4.20, in rows of cotton 70 yards long, on a clay soil. It produced at the rate of 646 lbs. of seed cotton, against 578 of natural soil, not making enough within 60 c. to pay for its purchase. The second year, however, it did much better in the same rows, having, as we suppose, been converted into a carbonate by the action of carbonic acid in the soil, as well as by reducing the organic and mineral substances of the soil to an assimilable condition. 269. Chloride of Potassium, The chloride of potassium shipped from Germany, is now the cheapest and most reliable form in which potash is used. Especially is it considered valuable in the pro- duction of tobacco on the worn soils of Virginia. In 1870, we made an experiment with this substance on a poor clay soil, near Sparta, and also with the dung salt, a German compound, containing potash, soda, sulphuric acid, chlorine, magnesia, and lime. Both of these preparations produced considerable weed, giving the promise of a bountiful har- vest, so that a casual observer would have pronounced it a success, but the result was, of the chloride of potassium, 373 lbs.; dung salt, 352 lbs.; natural soil, 348 lbs. of seed cotton per acre. In 1873, we instituted the following experiment on a worn clay soil: 53^ ounces of each of the salts below were applied to a row of cotton 70 yards in length. Six rows on each side with natural soil averaged 162 oz. The salts produced above this the following amounts: Sulph. soda. . . .39 oz. Nit. potash 11 oz. Sulph. lime 39 " Sulph. magnesia. .8 " Nit. soda 15 Chloride potassa. .6 " All combined . .49 " Chloride sodium. .1 " less. Another experiment, in which a formula containing superphosphate, ammonia, animal matter, and chloride of sodium was used in the one row, with 6f oz. chloride of 304 FERTILIZERS AND NATURAL MANURES. potash added, and in an adjoining row the same, only an equal quantity of sulphate of soda was added, with the following results : Formula with potash 211 oz. " soda 194 Natural soil 131 " In this case, the muriate of potash in combination beat the sulphate of soda, but its cost being more than double, still renders it an unsafe investment. In another experiment on the poorest spot in the farm, we applied under rows of cotton 54 yards long, 40 ozs. superphosphate, and 12 of sulphate of ammonia, adding for one row 12 oz. of muriate of potash, and for the other row 12 oz. sulj^hate of soda, with the following results : Formula with mur. potash 211 oz. sulph. soda 162 " Natural soil 62 " From this experiment, we infer that a sufficiency of ammonia and phosphoric acid greatly enhances the value of potash on very poor soil in the production of cotton. 270. Soda, Na-0. Soda is not very abundant in soils, but is generally present in sufficient quantities to supply the demand. Even where it is partially absent, it is believed that pot- ash will supply its place, as they are both alkalies, and possess in common the same properties. It has been surmised by some that soda is not indispen- sable to plant life, and that its presence in plants is only accidental. Herdpath found in tAVO analyses of asparagus and beet as follows : Wild asparagus Potash. .18.8 Soda. .16.2 Cultivated'' 50.5.... " ..trace Field beet, No. 1 "....57.0.... " ...7.3 No. 2 " 21.0 " . .34.1 SODA. 305 Here, there is 15 per cent, more of alkalies in the culti- vated than in the wild asparagus, which must have been accidental, as both were perfect plants; and the ]30tash and soda vary considerably in both the asparagus and beet, showing that they are to a large extent interchangeable ; and as in one instance there is a trace of soda, ^v^here it replaces the potash it must be accidental; and the replaced potash must also be accidental, or the soda answers the same end of the potash. Evidently, the quantities of al- kalies taken up by plants, depend to a large extent on the amount assimilable in the soil. From experiments of Salm-Horstmar, Knop, and Schre- ber, they conclude that soda cannot entirely replace potash, the latter being indispensable to plant life. Cameron has satisfied himself from a series of experiments, that soda can partially replace potash in plants. The range of alkalies is very great in plants. Thus in 79 analyses of wheat kernel, the highest percentage of soda was 15.9, the lowest 0.0 per cent. In 21 analyses of rye, the highest was 20.8 ; the lowest 0.0. In barley, 43 ana- lyses, the highest was 8.9 ; the lowest 0.6. In 14 analyses of Indian corn, the highest 13.2 ; the lowest 0.0. Although soda is put down as absent in most of these cases, it does not appear that the specimens were all perfect seed, or that it was absent from the entire plant. Under the older modes of analysis it was difficult to separate traces of soda from potash, and it is possible that in all cases it is present. From the most recent analyses made by experts, soda exists in the ash of certain plants as follows : Asli of wheat kernel Potato tuber . . . " Barley kernel . . " Sugar beet " Turnip root .... ,0 to 5 per cent. 0to4 " ItoG " 4.7 to 29.8 per cent. 7.7 to 17.1 " 306 FERTILIZERS AND NATURAL MANURES. The result of all the investigations shows very clearly, that while soda may not exist in some cereals and tubers in a weighable quantity, yet all plants have traces of it, and that it is indispensable to plant life. The newly dis- covered spectral analysis by which yo~ooV o o o o ^ grain of soda may be detected, shows that it exists in everything in nature, however minute. From a number of experiments, Salm-Horstmar con- sidered soda not essential in the early stages of plants, but important to their perfection, though in small quantities. The following conclusions seem to be legitimate from all the experiments made: 1. That soda is never entirely ab- sent from plants. 2. That it exists in variable proportions from very minute to large quantities. 3. That only minute amounts are requisite. 4. That when it exists in consider- able amounts, it is rather accidental than otherwise. While some of the German experimentalists have satis- fied themselves, that soda is not essential to buckwheat, and other plants, we have in an experiment the present year (1874), not yet completed, satisfied every one who has seen it, that at least soda is very essential. In flower-pots of river sand out of which all soluble matters had been thoroughly washed in shoaly water, the pot minus the soda was inferior to all others except the ones without phosphoric acid and potash ; and compared with the one having all the salts, was as a pigmy to a giant. 271. Lime, CaO. Lime has one equivalent of calcium = 20, one of oxygen = 8. It is then an oxide of calcium, having in 100 lbs. 71.43 of lime, and 28.57 of oxygen. It exists in all soils and in all plants. Lime is found abundantly in nature as a carbonate, from the coarsest limestones to the finest marble. This is taken and burned in kilns, the carbonic acid escaping, LIME. 307 leaving the lime as a hot caustic substance, in hard, concrete masses. Take a lump of quicklime and pour water upon it, and it hisses, swells and cracks, and falls into a white pow- der, under high heat. The Avater unites chemically with the lime, forming a hydrate. When caustic lime slowly acquires moisture from the atmosphere, and falls to a fine powder, it is said to be air-slaked. It acquires carbonic acid also, losing much of its caustic properties, assuming its original form as a carbonate of lime, only in a pulveru- lent state. Carbonate of lime is very insoluble in water, and not valued much as a fertilizer. Very few soils are so deficient in lime as to require it to be added as food for plants. In that case the most economical method is to use it as a bi-phosphate, the phosphoric acid of which is always in demand. Quicklime is a valuable application for turfy, boggy soils, otherwise unfit for agricultural purposes. It dis- integrates the soil, decomposes the organic matter, and neutralizes the acid which has accumulated for years in the luxurious beds of humus. It has the effect of opening the dense cemented structure of clay soils, by which the atmosphere is able to reach a much greater surface, and the water to penetrate deeper. In many cases it also destroys worms and insects hurtful to vegetation. In Europe, where liming lands constitutes an impor- tant part of good farming, caustic lime is carried to the fields, put up in heaps, and covered with earth. A few weeks will suffice for it to become air-slaked, and fall to pieces, thus being made fit for use. We have doubted the utility of applying caustic lime to our worn soils, already denuded of organic matter by our system of clean cotton culture. At the North and in Europe, where organic matter accumulates so rapidly, lime is essential as a corrective and solvent. Even there, 308 FEPwTILIZEES AND NATURAL MANURES. objections have been raised in some instances, because lands are said to become jDOorer and poorer, under the constant application of lime. A small experiment on a worn soil, deficient in organic matter, has made us think moie favorably of it. In a row of cotton 70 yards long, we put 10 lbs. of caustic lime under the seed ; in another, 42 lbs. of well-rotted chip manure ; in a third, the same quantity of lime and chip manure; and in a fourth, quad- ruple the quantity of chip manure. The product of each row was as follows: Chip manure, 218 oz. ; air slaked lime, 236 ; lime and chip manure, 260 ; chip manure quad- rupled, 292 ; no manure, 182. The lime by itself increased considerably the produc- tion over the natural soil, showing its solvent action mainly on the mineral matter of the soil. The chip ma- nure doubtless was enhanced in value, by nitrogenous par- ticles accumulated about the wood-yard. The silicate and nitrate of lime occur sparsely in nature, and are believed to act well as fertilizers ; but we are satis- fied that no form of this important substance need ever be applied as mere food for plants, except the superphos- phate. This embraces the soluble bi-phosphate and the sulphate — the one very soluble, and united to the most im- portant of all the mineral substances needed in fertiliza- tion ; and the other a good absorbent of ammonia. 272. Sulphate of Lime, CaO,S032HO. Sulphate of lime, or gypsum, known in commerce as plaster of Paris, is a very cheap and useful form for appli- cation, under some conditions. It exists in nature in many localities, amorphous and crystallized, and is found in the ashes of many plants, as clover, beans, etc. The water is driven out by burning, forming plaster of Paris. Ii exists very sparsely in soils, and is but slightly soluble in water. It is found in superphosphates from 40 to 50 SULPHURIC ACID AS A FEETILIZEE. 309 per cent., and this is much the cheapest form for its appli- cation. It is used very extensively in some sections for clover, and is believed to be very nsefal. Liebig attributes its special virtue as a top dressing to the fixation of ammonia, which being brought down by dew and rain, displaces the lime, forming a sulphate of am- monia — its carbon uniting with the lime. This salt being very soluble and not volatile as the carbonate, is carried down to the roots of the clover by the rains. 213. 3Iagnesia^ MgO. Magnesia, the oxide of magnesium, occurs in the shops as calcined magnesia, and is found in the ashes of all plants ; and is universally difiused through all soils. Magnesia exists largely in the grain of the cereals and other agricultural plants, standing next to phosphoric acid and potash. This shows its importance. Arandt found that it is translated from the lower to the upper organs in the oat, and that it increases constantly in the fruit. Liebig states that the bran of flour contains a large quantity of ammoniacal jDhosphate of magnesia. This salt often forms large crystalline concretions in the large intestines of horses belonging to millers ; and ammonia mixed with beer causes a white precipitate of the same salt. Sulphate of magnesia, the only form in which we used it on cotton in the present year in rows 70 yards long, only increased the product from 160 natural soil, to 170 oz. Nevertheless, we think a complete fertilizer should have a small quantity in it for most of our worn soils. 274. Sulphuric Acid as a Fertilizer, Sulphuric acid has already been described. It is an essential element of plant-food, although not existing largely in them, yet on account of its sparsity in all soils 310 FERTILIZERS AND NATURAL MANURES. should be introduced in all first-class fertilizers. Luckily, for agriculturists, it exists in very cheap forms, as sul- phate of soda, sulphate of lime, sulphate of iron, etc. Sulphuric acid forms an important class of salts called sulphates, some of which exist as such in the ash of plants. From experiments made on the oat plant, Arandt came to the conclusion that sulphuric acid is formed in the upper part of the plant by the oxidation of sulphur. The albuminoids cannot be produced without it, as sulphur is a necessary constituent of them, and sulphuric acid is the only form in which it can be introduced into plants. Cer- tain oils found in onions, mustard, horse-radish, turnips, etc., always contain sulphur. The highest percentage of sulphuric acid found in the ash of wheat in 79 analyses was 2.4, the lowest 0.0. In 21 analyses of rye, the highest was 3.0, loAvest 0.5. In 43 analyses of barley, the highest was 4.0, the lowest 0.2. In 11 of maize, the highest was 5.5, the lowest 0.0. As there is always a sufficiency of sulphuric acid in superphosphates for all fertilizing purposes, there is no need of applying it except in this form, which costs abso- lutely nothing ; as it is a necessary concomitant of the phosphoric acid so important to be applied at almost any cost. 275. Chlorine, CI. Chlorine exists very sparingly in soils and in jjlants, but is nevertheless deemed to be important. A weak solution of chlorine, Humboldt asserts, wdll fa- cilitate the sprouting of seeds. As suggested by Johnson, no doubt a reaction takes place by which water is decom- posed and oxygen set free, which is doubtless the real agent in exciting the sleeping germ. Chloride of potassium is present in the juices of all plants as well as their ashes, especially sea-w^eeds ; and is CHLORIDE OF SODIUM AS A FERTILIZER. 311 never absent from fertile soils. The same is essentially true of chloride of sodium. And yet some scientists seem to doubt whether it is indispensable to the life and perfec- tion of plants. Salm-Horstmar, Nobbe, and Siegert consider it essen- tial to the production of wheat. Knop excludes it from maize, and considers its importance to buckwheat as doubt- ful. Leydhecker, from recent investigations, regards it, however, as indispensable to buckwheat. Birner and Lu- canus conclude that it is not necessary to the oat plant. The weight of the crop w^as increased by chloride of potas- sium, the foliage and stem by chloride of sodium, while chloride of magnesium proved deleterious to the plant. Lucanus raised a perfect crop of clover without chlorine, and when added the result was not increased. While it is true that chlorine is always present in plants, much that appears in the foliage and succulent parts is ac- cidental. Nevertheless, until more conclusive experiments have been made, we must conclude that it is essential, though in minute quantities, to most agricultural plants. In 70 analyses of wheat, the highest was 6.1, the lowest .0 43 barley, " 5.2, " .2 21 rye, 2.5, " .0 21 oat, " 1.6, " .0 11 maize, " 4.5, " .0 31 pea. 6.5, " .0 3 cotton seed, " 4.8, " .5 276. Chloride of Sodium as a Fertilizer. Prof. Voelcker is of opinion that common salt has the power of liberating ammonia from soils that have been manured with Peruvian guano, stable manure, etc. This is true especially in sandy soils where the ammonia exists in fertile combinations. The chloride of sodium acts upon the ammoniacal salts by forming soda in the soil, and chlo- 312 FERTILIZERS AND NATURAL MANURES. ride of ammonia, which passes into solution and then be- comes an active fertilizer. This throws light on the use of salt as a fertilizer. It is known that on poor lands devoid of humus and ammo- nia, it is a very indifferent manure, while on better lands, w^here ammonia has been stored in the clay or humus, it acts well by eliminating the ammonia and placing it in combinations suitable for plant nutriment. Salt is also beneficial in soils as fertilizers, by aiding in rendering insoluble phosphates soluble. We suppose chlorhydric acid is set free, which dissolves the bone phos- phate and transforms it into a soluble by phosphate of lime. CHAPTER YII. NATURAL MANURES. — STABLE MANURE. NIGHT SOIL. COTTON SEED. WOOD ASHES. 277. Natural 3Ianures. We shall embrace in what we term natural manures all those substances produced on a farm, which by proper treatment and application aid in the growth of plants and the improvement of the land ; as well as those resulting from processes in nature known to the intelligent agricul- turist, which subserve the same end. To the first class properly belong farm-yard manure, night soil, and cotton seed: to the last,. green manures and rotation of crops. 278. Stable Manure, Farm-yard or stable manure is a powerful fertilizer, owing mainly to the amount of ammonia it contains. It nevertheless has all of the other important elements and co:viPOsrnox of stable maxure. 313 salts, though in undue proportions. It is especially defi- cient in phosphoric acid, so essential to the grains of the cereals, and the seed of cotton. It is also very heating in its character, requiring in our warm climate more rain than generally falls. Hence it should always be composted and modified when applied to crops. This important manure consists of the urine and solid excrements of domestic animals mixed with various kinds of litter. The most valuable part is the urine, which con- tains most of the nitrogen of the food of animals ; hence the importance of having materials mixed with it which will hold it for future use. When urine decomposes in a dung heap or bed of litter, its ammonia does not escape as under ordinary circumstances. As the nourishing quality of food depends greatly on the amount of nitrogen in it, so to a large extent is the value of manures enhanced by the amount of nitrogen in them. The nitrogen present in urine exists as urea, uric acid, and hippuric acid, but these compounds, by sponta- neous decay, all form ammonia, which will escape unless proper means are taken to prevent it. Hence ammonia has been found always existing in the atmosphere of stables. Other compounds are also present in urine of great value, especially phosphoric acid and potash, which exist to a large extent in soluble forms. In 1,000 parts of urine from the stable there are 890 of water, 16 of ammonia as nitrogen, and 1.20 of phosphoric acid. In solid horse-dung there are 760 of water, 6.10 of ammonia as nitrogen and 3.48 of phosphoric acid. 279. Composition of Stahle Manure. The following table will show the analysis of two fair samples of farm-yard manure, by Voelcker. 14 814 FERTILIZERS AND NATURAL MANURES. Fresh. Rotted. Water 66.17 75.42 SoluWe organic matter, * 2.48 3.71 Insoluble organic matter, f 25.76 12.82 Soluble salts 1.54 1.47 Insoluble mineral matters 4.05 6.58 100.00 100.00 * Containing nitrogen t Free ammonia . . . Amnion iacal salts ,0.149, .0.494 ,0.340. 0.880. ,0.297 .0.309 0.046 0.057 The fresh manure contains 0.299 soluble phosphate of lime, and the rotted 0.832. Of potassa, the first contains 0.573 soluble, and 0.446 insoluble. In addition, they have also lime, silica, soda, chlorine, sulphuric acid and carbonic acid, soluble and insoluble. In 100 lbs. then of good farm-yard manure, we have when fresh, 1.863 lbs. of nitrogen. As 14 of nitrogen is equal to 17 of ammonia, the actual ammonia in fresh stable manure is 2.001, in rotted manure 0.839. Of course it varies greatly, according to the kind of food used, and the process of saving it. The great virtue of stable manure is in its nitrogen, and we perceive that a great loss is sustained by the rot- ting process, more than one-half of the ammonia having escaped. How can this be saved to the farmer, so as to secure the greatest profits ? There is no question that for immediate action, well-rotted manure is the best, though having less nitrogen. 280. Savi7ig and Composting 3Ianures. In a cotton country, Avhere stock is a secondary object, we cannot expect to depend much on farm-yard manure^ and yet enough might be made for the near fields, by proper economy, from the mules and milch cows of a cot- SAVING AXD COMPOSTING MANURE. 315 ton plantation. In order to this, have comfortable covered and separate stalls for all of your stock. Cover the floor for several inches thick with dry chip manure, pine straw, oak leaves, or other litter. As it becomes saturated with urine and excrement, add more, so as to keep a dry bed for the cattle to stand or lie on. Occasionally, it is proper to reverse the position of the central and saturated portions, and the untrodden outside part. Much litter also accumu- lates in the course of the year, from the refuse of the fodder, straw, cobs, etc. The stalls should never be touched until after Christ- mas, as they accumulate and hold most of the valuable salts by this process. Then break up and chop into small pieces the accumulated mass, and make your compost heaps, as follows: A layer of stable manure six inches thick, with a good sprinkling of superphosphate over it ; then a layer of cotton seed three inches thick {previously saturated with water), and then another sprinkling of superphosphate, say half an inch thick ; then a layer of stable manure, and so on until the heap is completed, which should be conical in form. Over the whole heap, when sufficiently large, apply several inches of dry clay soil, if you choose, which will absorb every particle of the escap- ing ammonia. If, however, this crust should become so saturated as to allow it to escape, you can easily deter- mine the fact by moistening a piece of red litmus paper, and holding over the surface at different points; the smallest escape of ammonia will change the red to blue, and an additional coating of soil can be applied. The heaps should be put up soon after Christmas, and not touched till ready to put into the corn or cotton beds in March and April. In the mean time the stalls should be replenished, and not touched again for twelve months, only in the way indicated above. When the manure is hauled out, every layer in the heaps should be chopped 316 FERTILIZERS AND NATURAL MANURES. down and well mixed and pulverized. It should be taken from wagons and carefully applied in baskets at the rate of five or six hundred pounds to the acre, at the bottom of a shovel furrow and then bedded on immediately. Th6 best results would follow^ This is the best process known to manufacture farm- I yard manure, as adapted to our circumstances. By this you save all of the valuable elements of dung and urine, converting the nitrogen into ammonia for prompt and efficient action the first year, and relieving the manure to a lg,rge -extent of the heavy masses of water found in this class of manures. You also kill the germ of your cotton ^^eed, and have its nitrogen converted into ammonia in- stead of lying out exposed to the leaching rains and evap- orating winds of winter. Enough soluble phosphoiic acid is also added to supply a deficiency in 'both of the other manures. We are satisfied that such a mixture will pay better than any other for the same cost. And the whole plan is adapted to scarcity of labor, as there is the least possible expense attending it, being handled but once before it is ready to be carted to the fields. Where much litter is applied, it might be necessary in some in- stances, to compost every six months, but we believe the other plan the most economical of the two. Manures should not lie long in the heap after decom- ])Osition has taken place. As they become weaker gra- dually from further decay, the humus which absorbs the ammonia, itself decays slowly, losing its carbonic acid vrhich unites with the ammonia, forming a very volatile 8:ilt ; and in several other ways this deterioration may be carried on ; hence it is important to apply it early to the soil, which will hold it much better than the compost lieap. In fact, so tenacious are clay soils of ammonia and other salts, that it is probable that well rotted manure might be spread on the top of the ground, and CHEMICAL CHANGES IX MANUKE HEAPS. SI*? lose little more than water and carbonic acid by evapora- tion ; all of the valuable salts being absorbed by the soil or leached out by the rains into it are ttius as safely stored as if the whole of the manure were buried. In silicious soils, however, these valuable salts are soon carried down beyond the reach of the rootlets, hence their application should be made at the latest period possible in such cases. Farm-yard manure, kept in open yards, will in the , course of tv\^elve months lose two-thirds of its valuable salts, leaving little else than stVaw and undecomposed organic matter. This loss is mainly produced by the leaching of the rains ; though the w^inds and sun carry off some of the valuable volatile matters. 281. \jhemical Changes in Manure Heaps, Chemically considered, farm-yard manure is a very va- riable and uncertain mixture, as it depends on so many contingencies ; such as the age and number of the animals, their breed, condition and species, the quantity and qual- ity of their food, and of the litter used in their stalls. The dung of a poor grass-fed cow or horse would be of little value compared with one fed on highly nutritious hay and grain. A great degree of uniformity, however, might be attained on a single farm, by a continuous and regular process as to feeding, etc. Until recently, the chemical changes which take place in the manufacture of farm-yard manure were but little understood. Dr. Yoelcker found, upon analysis, that the prmcipal difference between fresh and well rotted manure lies in the amount of soluble matters contained in them. An average specimen of each kind (one fourteen days, and the other six months old) exhibited the following re- sults : 1 i'ERTILIZEES A5^D NATURAL MAXUEES. Freeh. Rotted. Soluble organic matter .2.48 perct... . . . 3.71 per ct. Containing nitrogen .0.149 ... , ., ,2.97 E(j[ual to ammonia .0.181 " ... , , , . 8 60 Soluble inorganic matter . . . .1.54 " , . . , . ,1.47 t€ Of whicL, phosphate of lime .0.299 . . .0.382 Potash .0.573 " ... 2 pounds more of straw. Then for every bushel of grain made on the broadcast system, there is carried off 137 pounds of wheat straw, while for the same amount of grain w^hen drilled, there is carried off 99 pounds of straw. This, then, involves considerably more labor in cutting, reaping, hauling, and thrashing for the amount of grain obtained ; and takes off about 35 per cent, more of all the valuable substances making up agricultu- ral plants. 17 386 APPENDIX. Eecent experiments in England show that thin sowing ol wneat in drills is much more productive than thick sowing. By special culture on small plots, having one grain in the hill, a crop at the rate of 108 bushels per acre has been produced, and another of 162 bushels. 5. Fertilizers for Wheat. While ammonia is an essential fertilizer for wheat, yet it has to be used judiciously, as too much of it, especially on poor land, will produce much straw at the expense of the grain. Hence stable manure, cotton seed, and Peruvian guano should be used sparingly, and in conjunction with lime, ashes, superphosphate, potash, and other mineral fertilizers. Lime acts well on wheat, not only as food, but as a solvent, developing the inert nitrogen of the organic matter into ammonia, as well as eliminating silica from its insoluble combinations, and preparing silicate of lime, so abundant in wheat straw. Thus, where lime is deficient and other fertilizers are abundant, the wheat lodges, as it is termed, falling from weakness, and produces but little grain. Ashes will act like lime, having much of its caustic properties, and possessing as it does, not only lime and silica in available forms, but other essential mineral substances. 6. Chemical Composition of Wheat. In 1,000 pounds of the grain of wheat air-dried (Wolif and Knop), there is of nitrogen 20.8 pounds, and of ash 17.7 pounds; of which there is of Potassa. 5.5 Soda 0.6 Lime 0.6 Magnesia 2.2 Phosphoric acid 8.2 Sulphuric acid 0.4 Silicic acid 0.3 In 100 pounds of winter wheat there was 2.0 of ash, 14.4 of water, and 83.6 of organic matter; which had of Albuminoids 13.0 Carbo-hydrates 67 . 6 Crude fibre 3.0 Fat, etc 1.5 APPENDIX. 387 Wheat grown in a warm climate lias more nitrogen (gluten), according to the per cent, of starch, than that grown in a cold cli- mate. Hence Georgia wheat commands a better price in New York tlian northern raised wheat. Starch being largely composed of carbon and oxygen, is a generator of heat, and hence food of this character is better adapted to a cold climate. A grain of wheat cut crosswise will show the outer coat com- posed of cellular tissue, or bran ; the next layer to this is the gluten, and the central portion the starch, which constitutes the largest part of the kernel. Much of the gluten (which is a mixture of albumi- noids, with a little starch and fat) is lost by the process of grinding flour. In the manufacture of a barrel of flour, sixty to seventy pounds are lost with the bran, when there should be only about ten pounds. The plan of cutting wheat before it i« fully ripe, while it whitens the flour, decreases somewhat the quantity and deteriorates the quality. A sample of Narbonne wheat, cut eighteen days before being fully ripe, had only six per cent, of gluten, while that which remained and matured had tw^elve per cent. 7. Bust in Wheat, Pnccinia Graminas. As early as 1867, Fontana published an account of this destructive pest : and since then botanists have pui'sued the investigation with much interest and assiduity. It is i\ow admitted by all scientists to be a microscopic fungus, to which the name of Puccinia graminas has been given. It attacks both stems and leaves and glumes of all kinds of grain, having at first an orange colored appearance (resembling rust of iron, hence the common name) ; it afterwards assumes a deep chocolate color. One stoma on a straw will produce from twenty to forty fungi, and each of them it is believed will produce at least one hundred spores, or reproductive particles, so that the progeny of a single stoma will be enough to infest a whole plant. The period of germination is supposed to be about one w^eek. The spores, being very light, are wafted about in the air, lighting upon adjacent stems, and will germinate under the influence of warm, damp w^eather, and prove more or less destructive, according to the favorableness of the weather for their increase and growth. Plants have pores which are closed in dry weather, and op*en and expand in warm, moist weather. It is supposed that these pores are 388 APPENDIX. thus made receptacles of the spores of this parasitic fungus, where they immediately take root, intercepting the nourishment intended for the grain ; as it has been ascertained by analysis that these fungi contain very much the same constituents as the flower. Some kinds of wheat are more affected by rust than others, and in northern climates, fall wheat suffers more than that sown in spring. Farmers in England affirm that wheat sown in the neighborhood of the barberry bush seldom escapes the blight, as it is supposed that the spores are generated and preserved on these bushes. It is believed that the spores may be perpetuated from undecom- posed straw carried out into the fields as manure. If this be true, farmers should be careful in this matter, as well as in destroying all grasses, in fields producing rusted wheat. 8. Smut, Wheat Fungus. The smut is a dark brown fungus, which takes possession of the grain, and converts all of the nutritive juices into a most offensive and poisonous substance. This parasitic fungus is undoubtedly propagated by spores; and when wheat once becomes infested with it, it is difficult to extirpated- it. It seems to attack the weaker grains which have but little vital- ity and power of resistance ; hence it is believed that a very effec- tive remedy is to plant only the perfect sound grains, and let the others be separated from the seed by methods above indicated. Bluestone seems to be the effectual remedy. It probably acts by killing the germ in all the faulty grains, which possess feeble vitality. Salt brine acts perhaps, not so much by killing the germs, as by causing more of the weaker grains to float on the surface, which can be skimmed off and separated from the healthy seed. 9. Insects Injurious to Wheat. These are very numerous ; some of them preying upon the grow- ing plant, others sucking out the juices of the grain before its ma- turity, and others preying upon the matured grain after it is housed. Among those which we cannot describe particularly in this work, (but are fully described in Harris's Insects Injurious to Vegetation), we mention the Thrips cerealium. This is similar to the small white wo^^ii found in wheat (wheat maggot). It is supposed to suck the juices out of the seed. Wheat caterpillars, probably oflfspring of the species Noctua, de- APPENDIX. 3S9 your the grains of wheat while growing and after being harvested. Another species of worm similar to those of Europe which are the product of the grain moth (Tinea granella), infest granaries, gnaw- ing the ends of the wheat and other grains, and spinning a thin web uniting a number together, and thus producing considerable damage. The joint worm (produced from a moth belonging to the genus Eurytoma) has produced considerable damage in Virginia and other States. They infest the straw of wheat and barley, sucking its juices and cutting ofif the supply of nutriment to the grain. The European wheat fly (Cecidomyia tritici), a very small gnat, produces a little worm which preys upon the pollen, and afterwards the germ of the fruit, and is in some seas.ons very destructive to the wheat crop. A similar grain worm has been observed for several years in the Northern and Eastern States. 10. The Chinch Bug, Lygoeus Leucoptevus. This insect is said to resemble the bed-bug, both in color and scent. Its eggs are laid in the ground where its young have been found in great numbers, at the depth of an inch. They make their appearance early in the summer, but some of them continue alive in their places of concealment during the whole winter. They prevail mostly in the Western States, south of the fortieth degree of latitude, and commit extensive depredations on the corn and wheat fields. They travel like locusts in immense columns from field to field, destroying everything before them. They make their appearance on wheat about the middle of June, and though very destructive to it, are by no means confined to it ; but appear in their various stages of growth on all kinds of grain, corn, and grass, during the whole summer. (Flarris.) 11. Hessian Fly, Cecidomyia Destructor. This far-famed insect obtained its common name from the fact that it was first seen in the wheat-fields about the time the Hes- sians landed in this country, under the command of Sir William Howe, during the Revolutionary War. It was supposed that the straw that they brought with them was infested by it. Its botanical name was given by Mr. Say. Upon subsequent investigation it was said that no such insect could be found in Germany ; but one answering its description, and 390 APPENDIX. of exactly the same habits, had long been known in the vicinity of Geneva. In 1833 the wheat crops of Austria and Hungary were seriously injured by an insect of the same kind. From the point of Lord Howe's debarkation on Staten and Long Islands, the insect seemed to spread at the rate of about thirty miles a year, until tlie whole country had been infested by it. Every species of small grain, and even timothy grass was attacked by them ; and in some places their ravages in the larva state were so great that the cultivation of wheat had to be abandoned. Mr. Llarris, in his book on Insects Injurious to Vegetation, thus describes the Hessian fly. The head, antennae, and thorax are black. The hind body is tawny, more or less widely marked with black on each wing, and clothed with fine grayish hairs. The egg tube of the female is rose colored. The wings are blackish, except at the base ; the legs pale or reddish, and the feet black." According to Mr. Herrick (who has studied the habits of this in- sect) two broods are brought to maturity during the year, one in the spring and the other in the autumn. From the egg to the winged state they live about one year. The flies lay their eggs on the young plants long before the grain is ripe. As soon as the wheat comes up in the fall, and begins to show a leaf or two, the flies appear, pair off* and begin to lay their eggs, which occupies several weeks. They appear as minute red specks in the longitudinal cavities of the blades, the number being often twenty or thirty on a single leaf. The eggs hatch out in about four days, producing a maggot of a pale red color. As soon as hatched, the maggot crawls down the leaf, till it comes to a joint of the main stalk a little below the surface of the ground* where it fixes its abode with its head toward the root of the plant. Here they remain till all their metamorphoses are completed. They do not penetrate the stalk, nor feed upon it, but are nourished by the juices of the plant, which they appear to take up by suction. One maggot could not destroy a single plant, but when several are fixed in this way around the stem it is impoverished, becomes weak- ened, and withers and dies. These insects continue to increase in size, and obtain their full growth in five or six weeks, when they measure three-twentieths of an inch in length. After lying in the chrysalis state during the winter, when the weather becomes warm in the spring, in April or May, according to the climate, they emerge from their winter quar- APPENDIX. 331 ters by breaking througli one end of their shells, being now trans- % formed into files. Various suggestions have been made to prevent the ravages of the Hessian fly, as the selection of seed wheat from localities not infested by them, soaking it in strong brine, sowing on clean, culti- vated lands, etc., all of which may be advantageous, but none perhaps entirely effectual. A most efficient remedy has been found in the Southern States, adopted years ago, which seems to have rid the country of this pest ; we know not how it will apply to regions fur- ther north. It was found that the fly always disappeared after the first cold spell, having destroyed the early crops. Farmers at once quit sowing what are called late varieties of wheat, as the Big White, Blue Stem, etc., and sowed early varieties, as the Little White, Medi- terranean, etc., which would produce good crops by sowing in Novem- ber and December. It was found that the fly never attacked these crops, and of late years there has been but little complaint of this once dreaded insect. 12. The Fly Weevil, Butalis Cerealella. The name weevil is given to six different kinds of insects in this country ; two of which are flies, two moths, and two beetles. One of these, the fly weevil, called also Angoumois, grain moth, is a great pest to granaries in the Southern States. It is a small moth of a pale cinnamon-brown color, with narrow fringed hind wings of a leaden color, with two tapering feelers turned over its head. It lays sixty or ninety eggs in clusters of twenty or more on a single grain. These eggs hatch out a diminutive worm not thicker than a hair, each of which selects a grain of wheat to itself, and burrows in the softest part, eating out all the substance, leaving nothing but a shell behind. (Harris's Insects, p. 500.) The ravages of this fly weevil have been effectually checked by kiln drying the wheat. It is stated that twelve hours of heat equal to 167° t. has effectually killed every vestige of the insect in a badly infested grain. Many farmers in the South have adopted the plan of wheat houses with movable roofs, with good effect. A few days hot sun, and keeping the wheat well stirred, will kill out this moth. Some also adopted the plan of keeping their wheat in very cool, dry apartments, which seems to prevent the hatching of the eggs. This is particularly true, when kept in small bulk as in sacks where a heating process cannot take place. 392 APPENDIX 13. The Black Weevil, Calandra Oryzm, This is tlie rice weevil of the Southern States, but it is we]l known a.mong wheat raisers as a very destructive insect in their granaries. It is a slender black beetle, very similar according to Harris, to the wheat weevil of Europe (Calandra granaria), only this is of a pitchy red color. The black weevil bores a hole in a grain of rice or wheat, in which it deposits a single egg, and thus continues from grain to grain until all her eggs are laid. She then dies, leaving the grain however well stocked for a future harvest of weevil grubs. After the eggs hatch, the grub lives securely and unseen in the centre of the grain, feeding upon it, and thus deteriorating both the quantity and quality of the rice or wheat as the case maybe. When fully grown it escapes at one end, leaving a little hole, which it artfully closes with particles of flour. This generally occurs during the winter when they are changed into the pupa state. In the following spring they are transformed into beetles and come out of the grains, when by winnowing and sifting they may be separated from the grain and destroyed. This weevtl also depredates upon Indian corn, but is perhaps more destructive to rice than either wheat or corn. IV. THE OAT. AVENA SATIVA. 1. Climatic and Botanical Relations The oat now so extensively cultivated in this country was brought from the Old World. There are several varieties cultivated, as the black oat (Avena nigra), skinless oat (Avena nuda), horse mane oat (Avena secunda), bearded oat (Avena strigora), etc. The common cultivated oat contains two or three seeds in one inflorescence. It has a loose panicle of large drooping spikelets, the florets investing the grain, one flower with a large twisted awn on the back, the other awnless. (Gray.) APPENDIX. 393 The oat is a native of cold climates. It flourishes, however, in temperate latitudes ; but degenerates as you approach the equator. It has been cultivated in Bengal as low as the twentv-fifth degree latitude. It is cultivated successfully in the United States from Maine to Florida. 2. Its Uses and Habitudes. Oatmeal is the principal bread food of the working classes in the northern part of Great Britian. It is quite nutritive, the Scotch oat having, according to analysis, 743 parts in 1000 of soluble nutritive matter. Next to maize it is the great stock food of the Southern and Western States, but it is rarely used in this country as food for man except as a porridge in the northern cities. The oat is a coarse feeder, and is not very dainty in its selection of soil in which to grow. Unlike wheat, it grows on stubble land without being reploughed, and will even produce three very good crops in succession from its own seeding on good laud. This is termed volunteer oats. On this account it is well adapted to the scarce labor and loose methods of Southern farming. It is a thirsty plant, however, and luxuriates in low lands -where its roots can get a good supply of w^ater from the soil. Fall oats always succeed well when a stand is obtained, because of the season- able winter rains. Spring oats frequently fail in the South, on account of dry weather, hence no farmer should rely on this crop exclusively. The most successful plan is to have tw^o or three sowings from October to January. 3. The Oat as an Exhauster of the Soil. A general opinion prevails among farmers, that the oat is very exhausting to land ; so much so, that some are prejudiced against it as a leading crop. Many of these traditional notions are well founded, although resulting from empiricism rather than science, and should be carefully investigated. In comparing the analysis of the oat with the other cereals, there is no remarkable difference between them only in reference to silica. In fact, the more important constituents, as phosphoric acid and potash, existing more sparingly in it, than in w^ieat or Indian corn. In 100 parts of the oat grain, there is 3.07 of ash. Of this, 46.4 is silica. Of the straw, there is 5.12 per cent, of ash ; 48.7 of w^iich 17* 39i APPENDIX. is silica. This would carry off from an acre, in a crop of 15 bushels, 6.83 pounds of soluble silica in the grain, and 16.20 pounds in the straw, equal to 23 pounds. A crop of ten bushels of wheat would carry off only about 15 pounds, and all the other cereals less than this. As the stalk of Indian corn is left on the field, the amount carried off by the grain would be a very small fraction. While silica is not deemed an important constituent of fertilizers, because of its abundance in all soils, yet, when exhausted in such quantities as by the oat crop, taken in connection with the general impression of practical farmers that it is an exhausting crop, it be- comes a matter worthy of investigation. For while it is true that silica abounds in all soils, it is not true that soluble silica does. But while the oat crop, on account of the soluble silica it carries off from a soil, might be detrimental for a succession of cereal crops, it would not in a rotation with cotton, peas, or turnips, as neither of these demands silica as a prime ingredient. We have long been con- vinced that oats and cotton form the best rotation for the Southern States, and this investigation confirms us in the opinion. 4. Diseases of the Oat. The oat is a hardy plant, and not subject to many diseases. It however, is sometimes injured by the black blast, a parasite which destroys the entire head. Also a similar rust to that which attacks wheat. Both of these diseases are, we doubt not, aggravated by imperfect seed ; for no crop seems to suffer more from this cause than the oat crop. If more pains were taken in the selection of vigorous, healthy seed, by similar plans recommended in reference to wheat, we would hear but little of rust and blast in the oat crop. Good seed, good cultivation, and good fertilizers will go far toward relieving any of our crops from the diseases which commonly infest them. APPENDIX. 395 V. THE GEASSES. BoTANiCALLY Speaking, tlie grasses belong to the order Gramineae, but in agriculture, the term embraces plants of other orders. In fact, all the herbage of the field upon which cattle feed, either as pasturage or forage, is embraced under this general term. We shall only treat of such as are of great interest to the agriculturist. There are said to be 130 distinct native species and varieties of grasses in Great Britain ; and probably more than double that many in the United States. Botanists have described over 300 varieties. As to the nutrient qualities of the grasses, Mr. G. Sinclair says, that grasses with culms, having swollen joints, thick and succulent leaves, and flowers with downy husks, contain more sugar and mucilage than others ; while those having culms with numerous joints, smooth and succulent leaves, flowers in a close panicle, and large blunt florets, contain more gluten and mucilage. 1. Bed Clover, Trifolium Pratense. This, the most valuable of what are termed grasses in agriculture, belongs to the Leguminosae. It is useful in American husbandry, not only as a pasturage and forage crop, but as an improver of the soil. Its climatic preferences restrict it to the Northern and Middle States, and the mountainous districts of the Southern States. The plain country of the Cotton States seems to be too dry and hot for it, although even here it succeeds very well on low, rich, moist lands. But it cannot be relied upon as a field crop in the South. The red clover ameliorates the soil in several ways. It has a tap root which penetrates deeper than most plants, and thus brings up nutriment to the stems and leaves, without exhausting so much the the surface soil. Even after the hay is cut and removed, the roots which remain, not only loosen the soil by their ramifications, but add much to its nutriment, especially in the important element of nitrogen. The proximate analysis of red clover is given in this work, under the article of Indian corn, showing that as a cattle food it is equal 396 APPENDIX. to any of the forage plants ; and as a milk and blood producing article, excels all others except lucerne (itself a species of clover), and the Hungarian millet. 2. Timothy or Cafs-tail Grass, Phleum Pratense. This is one of the most valuable grasses known to American farmers. It is perennial, and a native of Great Britain. It was named in honor of Timothy Hanson, Esq., who first introduced the seeds into Maryland. It is called herd's grass in New England, a name given to the Agrotis vulgaris, or red top, in the Middle and Southern States. Its analysis (the cured hay), shows 7.01 per cent, of mineral mat- ter, of which there is 35.6 of silica, 28.8 of potash, and 10.8 of phos- phoric acid ; being the three principal constituents of the ash. The proximate analysis has of albuminoids 9.7, carbo-hydrates 48.8, and fat, 3.0. It flourishes in the Northern and Middle States, but will not produce well in the Cotton States. 3. Lucern, Medicago Satlva. This a perennial plant, and one of the best, if not the very best, for the Southern States. It may be used green, or as dry forage. Sowed on good land, two and a-lialf feet apart, it, will make several tons of the most nutritious hay jDor acre. One seeding, properly cared for, will last ten or fifteen years. It should never be depas- tured, however, as the destruction of the crown of the plants, by grazing and tramping of the cattle, causes the plants to die. Lucern is green every month in the year, except the three winter months. It begins to put forth its leaves late in February, and is ready to cut several weeks before the red clover. Three or four cuttings may be made in a year, on rich land, either for soiling or forage. It is the most nutritious of all the grasses, the hay of the young plants having 19.7 per cent, of albuminoids, carbo-hydrates 32.9, and fat, 3.3. The per cent, of ash, amounts to 7.14, of which there is 25.3 of potash, and 48.0 lime. 4. Crab Grass, Digitaria Sanguinalis. This is a well-known annual of the Southern States, which comes up freely on the cotton beds, and is a great pest to the APPENDIX. 397 farmer. It is, however, a good grass for hay, being very nutritious, admitting of several cuttings on good lands, of a seasonable year. There is no need of ever sowing the seed, as there always seems to be enough on ploughed land, to produce a good crop of hay. If a farmer designates a portion of land for hay, he has Only to give it a thorough ploughing and manuring, if poor ; and should a crop of weeds come up, give it the second or even a third ploughing ; there will then in most cases be a plenty of seed for a good crop of hay. Of wet summers, a good crop may be thus secured after small grain. A principal reason why crab-grass hay is not valued highly at the South, is because it is generally gathered and sold by negroes as their own crop ; and it is frequently over-ripe, and not properly cured, the dew being allowed to fall upon it. If cut in the blossom, and put up in cocks at night, so as to prevent the damage by dew, and then spread out for another day's sun, and housed or stacked that evening, it makes as sweet and nutritious hay as any of the northern grasses. 5. Blue Grass, Poa Pratensis. This, the far-famed Kentucky blue grass, is perhaps the most valuable grass in America. It delights in calcareous soils, and grows spontaneously in the rice limestone lands of the West. It grows very well in woodlands, but luxuriates in fields on which the sun exerts full power. Horses and cattle become fatter on this grass without grain than any other pasturage grass. The blue grass, sown on a soil adapted to it, will soon expel every other species of grass. It should be sown in September or October, but will do very well sown in the spring, if the season is favorable. That grown in open land is much more abundant and nutritious than that on woodland, and will keep a larger amount of stock on the same area of land. 6. Bermuda Grass, Digitaria Dactylon. This valuable grass was introduced into Georgia, from the island of Bermuda, in the early part of the present century, by Hon. Thomas Butlar King, or Mr. Couper. It is familiarly known throughout the south as wire-grass. The generic name Digitaria dactylon is by Elliot. The Bermuda grass, according to Mr. Spalding, is identical with douh grass of India (Cynodon dactylon) ; but there seems to be some 398 APPENDIX. difference, as the fact tliat the Bermuda has no seed, while the doub grass has. They no doubt belong to the same species, as does an- other variety of creeping wire-grass at the South, which can not be distinguished from it without close inspection. It has no seed, and is propagated entirely by layers, each joint answering for one and taking root readily. It is in fact so tenacious of life and so difficult of extirpation, that it is deemed a great pest by most planters. Indeed it would be the extremest folly for any farmer to plant it indiscriminately in his fields. Many of the best bottom lands in some sections of Georgia are so usurped by it as to be entirely useless for cultivation. It will not grow on sandy land, but demands a stiff tenacious clay for its propagation. Hence it luxuriates on the red clay hills of the South, and if properly attended to, would soon intercept the washes, and restore these worn out gullied slopes into fine pastur- age lands. From a recent analysis of Dr. Ravanel, it has 14 per cent, of albu- minoids, which places it in the first rank of pasturage grasses. On rich lands it makes a luxuriant crop of hay, of the most nutritive character. On common uplands, however, it rarely grows tall enough for the sickle. Cows, sheep, and all kinds of stock, will leave all other herbage for it, and it is prospectively the grass of the South. If a planter should devote his hills to this grass, and his level lands to corn and cotton, adopting a mixed husbandry, the country would not only be enriched but beautified. For on the hills, where the soil is not very rich, he could every few years have a rotation in corn, cotton, or oats, which would well repay him, not only for the crop produced, but the subsequent value of the pastarage. It is beyond all question the grass to renovate the worn-out hilly lands of the Cotton States. The roots penetrate a considerable depth, and produce a large amount of organic matter which opens and en- riches the soil. Wherever Bermuda grass fields have been culti- vated, the grass being properly subjected, the product has been re- markable, owing no doubt mainly to the increase of nitrogen. After pasturing for several years, a farmer can prepare a grass sward for a cultivated crop as follows : Run a coulter plough through it, and cross plough it so as to admit a turning shovel. The roots turned up to the frost will soon be killed, and several plougliings of this character during the winter, will prepare the APPENDIX. 399 land for cultivation in peas or corn. A good crop of oats might be produced the next winter, and the grass left for pasturage again. While the Bermuda is not a winter grass, yet in the mild winters of the South, it affords a luxuriant pasturage, properly managed. The field or lot intended for winter use, should not be touched dur- ing the year, until the frost comes, and kills the tops. Then the cattle might browse upon it, and lastly the sheep, who, with their narrow mouths, would eat the green stems into the very ground, which had been protected by the thick coating of grass. In this way, the Bermuda might be made subservient as a pasture for ten months of the year. The only effectual mode of extirpation is repeated ploughings and rakings, and even, then unless carefully watched in after culti- vation, a field will soon be re-set with it. The only plant that has effectually mastered it, so far as our observation goes, is the Japan clover (Lespedeza striata), which has spread over the Southern States during the last ten or twelve years, supposed to have been introduced in a vessel from Japan, as it was first discovered on the commons of Charleston. Many Bermuda grass fields have been superseded by this new species of clover. VI. THE TOBACCO PLANT. NICOTIANA TABACUM. This narcotic, now so extensively used, is a native of North America. John Nicot, who was ambassador of the King of France to Portugal, procured some seeds from a Dutchman, who brought them from Florida. Nicot presented the first plant to Catherine de Medicis ; and botanists honored him with the generic name. The common name was derived from the Island of Tobago, West Indies, whence it was originally brought. It was known in Europe, according to Linnseus, as early as 1560. Tobacco is a powerful narcotic, and a soothing stimulant to the nervous system. It has on this account become an extensive article of commerce, and an important item of agricultural production in this country. 400 APPENDIX. Tobacco is an annual plant, and may be brought to maturity in any clime ; even in Russia and Sweden ; but it does not obtain sufficient size for successful culture, nor is the flavor as good as when grown in a more genial clime. In this country it is cultivated successfully in the Connecticut valley ; but the principal tobacco States, are Virginia, North Caro- lina, Kentucky, and Missouri. Not only is the soil well adapted, but the inhabitants, from long use, are better versed in its culture and preparation for market. For the proper culture of tobacco plants, beds are always neces- sary. New ground, which has never been exhausted by cropping, is the best. After removing all the grubs, brush heaps are piled upon it during the winter, and burned off in the early spring. This furnishes a good supply of potash, so much needed by the tobacco plant. The young plants, after taking good root, are transplanted to the fields after a rain, in hills three to four feet apart each way. The land, if not rich, should be well fertilized, and cultivated with the plough and hoe, very much like corn or cotton. The analysis of the tobacco plant is remarkable for the amount of ash or mineral matter indicated by it. The average of seven anal- yses shows 24.08 per cent, of ash, of which in 100 pounds there would be Potash 27.4 Soda 3.7 Magnesia 10.5 Lime 37.0 Phosphoric acid 3.6 Sulphuric acid 3.9 Silica 9.6 Chlorine 4.5 From this it would seem that potash and lime are rapidly ex- hausted from soils by the tobacco crop ; and it has been found that fertilizers containing them, are very important to be applied to the old tobacco lands of Virginia and Maryland. APPENDIX. 401 VII. THE CEYPTOGAMS. This series embraces quite a number of fungi, and microscopic plants of considerable interest in agriculture. We will speak of them as tliey come up incidentally, in their relations to other plants or their products, as some of them are very active as parasites and ferments. Several of them have been used as food for man, and on that ac- count demand a brief description here. The common mushroom (Agaricus campestris), the truffle (Tuber cibarium), and morel (Morchella esculenta), are considered delicacies with many people. Thirty-three different fungi are eaten by the Russians. Some of this class, however, are very poisonous, and it is important to know how to distinguish them. Dr. Christison says, those which have a warty cap, with fragments adhering to their upper surface, are gen- erally poisonous. Those which are heavy as to weight, and have an unpleasant odor, and emerge from a vulva or bag, are also hurtful. Those also should be avoided which are moist on the surface, and grow in woods and shady places ; as well as those which grow in tufts or clusters from stumps and trunks of trees. A pungent odor and styptic taste he regards as sure tests for poisonous mushrooms ; and those which become blue as soon as cut, are invariably poison- ous. Also, those which have a rose-red color, a corky texture, and a membranous collar around the stem. The easiest mode, how- ever, of testing the quality of fungi, is to introduce a silver spoon or coin into the vessel in which they are boiling; if the silver assumes a bluish black, it is evidence of the presence of poisonous I fungi. An edible fungus (Scleroticum cocos,) called tuckahoe or " Indian bread " by the early settlers, is found in the South. It grows under- ground, and was formerly often ploughed up by the negroes, and ^ used by them also, in some instances, as well as by the aborigines, as bread. The following analysis of a specimen from Virginia, by Dr. Torrey, shows it to be rather deficient in nutritive qualities. It 402 APPENDIX. had glucose, 0.93 ; gum (Arabin), and pectin 2.60 ; and pectose, 17.84 ; the remainder was cellulose, insoluble nitrogenous matter, water, and ash. vm. WATER CULTURE. In order to ascertain exactly " the role which the mineral ingre- dients of plant food play in the vital processes of cultivated plants," the expedient of water culture has been adopted in the experimental stations of Germany, under the direction of Dr. Nobbe. It was be- lieved that not all of the mineral elements found in plants, were essential to their growth and full development, and to ascertain which were the accidental or superfluous, if any, these investigations were made. No soil could be /ound, or made so free from these in- gredients, as to make a safe and satisfactory solution of the question It was found that after seeds have germinated in moist sand or cot- ton, and then suspended with their roots in water, they would thrive if the necessary food was held in solution by the water. Thus, by adding all the essential elements but one (potash or soda for instance), it could be ascertained which of these were most essential to plant life. German chemists, as Knop, Sachs, Nobbe, Siegart, Wolfi, and Kuehn, have carried water culture to very successful results for the last few years, and determined some very interesting facts. Plants have been raised in this way as large, healthy, and well-grown, as in the soil. Nobbe obtained a Japanese buckwheat plant, nine feet high, weighing, air-dry, 4,786 times more than the seed, and bearing 796 ripe, and 108 imperfect seeds. And Knop has a young oak, which has thus far grown normally, with its roots only in aqueous solution. While this species of culture is outside of all of our precon- ceived notions of agriculture, as an art or a science, we may hope for one practical result from it, which if accomplished, will be bene- ficial, viz., the exact formula for the proper support and nourish- ment of each plant. Thus, if it be established that soda is not essential to the production of buckwheat (as these experiments APPENDIX. 403 teach), it may always be left out in a fertilizer for buck wli eat, and 60 on through the whole list of plants. Much can also be ascertained as to the relative amount of the elements needed for each plant. Thus far, some very strange results have been reached ; as for instance, that silica which enters so largely into the composition of the cereals, especially, seems not to be an essential ingredient in the most commonly cultivated plants. That chlorine is needful to some, as buckwheat and vetches ; while soda, if essential at all, is so in the most minute quantities. That in addition to the four organic elements, potash, lime, magnesia, iron, phosphoric and sul- phuric acids, are the only ingredients absolutely essential for the life and normal growth of agricultural plants. This upsets all of our preconceived notions of the chemistry of plants ; as it has always been supposed that silica and soda, which enter so largely into most agricultural plants, were among the most essential and important ; while iron, which has been found only in minute quantities, was deemed altogether accidental. Xow, the observations made by Gris, in 1843, have since been substantiated by numerous experimenters, that iron is important in the proper development of chlorophyl in the leaves of plants. 2s obbe has also shown that chlorine, existing as it does so minutely in most plants, is necessary to the normal formation of the seeds of buckwheat; that w^ithout it, the transfer of starch from the leaves when it is elaborated to the flower and the fruit is prevented ; and the leaves and st-em become diseased. These results have been corroborated by experiments of Beyer. From a series of experiments with maize, buckwheat, cress, oak, and horse-chestnut, in solutions free from chlorine, Knop concluded that this element was not essential to the perfection of these plants. With a view to ascertain the function of potash in vegetable life, two series of experiments were entered into, under the direction of Nobbe, one with buckwheat, and the other with rye. In the normal solutions, the plants grew several feet in height, and seemed to be perfect in development. Without potash they were only a few inches in height ; and micro-chemical investigations showed no starch in the leaves, which obviously caused their stunted growth. The inference is that without the cooperation of potash in the chlorophyl grains, no starch is formed. Of the different salts of potash, the chloride was the most eflacient form for the buckwheat plant. The nitrate stood next. 404 APPENDIX. Tlie sulphate and phospliate seemed to produce a disease, wliich was due to tlie fact that the starch formed in the chlorophyl grains, accumulates passively in the leaves, instead of being taken up to be utilized in the development of the plant. It was also concluded that potassium could not be replaced physiologically, by sodium or lithium. While the sodium was deemed harmless, it was useless ; the lithium, however, had a positively injurious effect on the plant tissues. Experiments on summer rye produced similar results. The potassium seems to be essential for the building up of starch, in the chlorophyl grains. The experiments at least proved this to be one of the offices of potash. While these experiments are very interesting, and may serve to teach us several important truths, it should be remembered that they are not of universal application. Other plants may fail to appropriate nutrition without the natural medium of the soil, and may show a very different behavior as to elements rejected by these. Experiments made the present year (1874), at the experimental station, at Athens, Georgia, show very conclusively that so far as the cotton plant is concerned, soda is about as important as potash. We took river sand from shoaly water, out of which all the sol- uble matters had been com]3letely washed, and put in flower-pots. In one which had all the plant constituents except soda ; the plant was very sickly and diminutive, showing no disposition to produce fruit by the formation of a flower-bud. That without potash had hardly so healthy a foliage, but produced a very minute fruit-germ. The one minus the phosphoric acid, developed a pigmy stalk, with two small leaves ; and when the phosphoric acid existing in the pabulum of the seed was exhausted, it then ceased to grow altogether. One fact in reference to the nitrates, as contrasted with albumi- noids as fertilizers, is worthy of note. Our results corresponded with experiments in Germany and France, as to the superior effect of the nitrates in flower-pots and sand. In the one containing nitrate of soda, the cotton plant grew more rapidly than in those containing ammonia and animal matter representing organic nitro- gen. The latter was considerably behind the others at first, but gradually gained upon them, and came out nearly equal. In the open field just the reverse was true. Two rows of cotton, each 35 yards long, were fertilized with different nitrogenous ma- nures, each of them combined with 27 ounces of superphosphate. APPENDIX. 405 and containing severally as follows : Guanape 203^ ounces, equal to about two ounces of nitrogen as ammonia : Nitrate of soda, 13^^ ounces, equal to 7 ounces nitrogen : Sulphate of ammonia, IB}^ ounces, equal to 3 ounces of nitrogen : Cotton-seed cake, 54 ounces, equal to 33^ ounces nitrogen : dried blood, 27 ounces, equal to four and a half ounces of nitrogen ; and animal matter, 27 ounces, equal to 3 ounces of nitrogen. The following is the result from the two first pickings of cotton : Guanape 135 ozs. Seed cotton Nitrate of soda 54 " " Sulphate of ammonia 114 " Cotton- seed cake 141 " " Dried blood 150 " Animal matter, (dried flesh) . . . 136 " " It will thus be perceived, that nitrogen in the form of a nitrate, and at about an equal cost, is far behind ammonia and organic ni- trogen, as albuminoids in the substances used. This shows conclusively that experiments of an abnormal cha- racter, as water culture, and in flower-pots of sand, cannot be relied upon in the elucidation of agricultural science. In order for this, the open field with a natural soil, and usual cultivation ; the sun- shine, winds, and rains ; day and night ; the processes of decay in the soil, and evaporation from it ; of nitrification, absorption, and elimination ; the action of clay and sand ; of humus, and all the soluble salts in the soil, with their play of chemical afiinities; the sinking of hydrostatic, and the rising of capillary waters, all these, and others that might be mentioned, which are entirely or partially excluded from abnormal processes, are essential in order to de- termine the value of plant constituents, or the laws which govern vegetable life, growth, and nutrition. 406 APPENDIX. IX. TABLES OF AGEICULTUEAL PEODUCTS. Table I. Composition of Agricultural Plants and Products, air-dry, taken from all the reliable analyses compiled by Wolff and Knop, up to August, 1865, witli several recent ones by American cliemists. The table shows the amount of volatile matter, and each mineral sub- stance in 1000 parts. Substance. Volatile Matter. Potash. 03 O W. Magnesia. Lime. Phosphoric Acid. Sulphuric Acid. Silica. Chlorine. 980 20 6 25 0.70 2 44 0 62 9.24 0.48 0 34 . ..* 986 14 3 78 0.21 2 04 0 37 6.25 0.15 0 30 970 30 4 77 1.14 2 19 1 14 6.21 0.48 13 92 Rice 995 5 1 16 0.24 0 .67 0 14 2.55 0.03 0 15 Rye 980 20 6 18 0.36 2 18 0 54 9.50 0.46 0 30 975 25 5 58 0.71 2 .11 0 63 8.36 0.58 6 93 986 14 2 66 0.81 2 60 7.50 0.21 Buckwheat 990 10 2 31 0.62 1 34 6 33 4.80 0.36 6 ii o'.oi 972 28 11 24 1.03 2 24 1 17 10.16 0.98 0 25 0.64 Yield beans 965 35 14 17 0.42 o .34 1 82 13.72 1.78 0 42 1.01 963 37 11 24 1.44 5 .01 3 84 12.17 1.39 0 39 0.61 987 13 4 22 1.06 1 .14 3 02 1.30 0.62 0 18 0.90 945 55 19 41 0.66 3 02 5 77 4.45 2.88 21 90 Wheat straw 950 50 5 75 1.45 1 30 3 10 2.70 1.45 33 15 Corn cobs 972 28 13 39 0.33 1 14 0 95 1.23 0.52 7 50 952 48 8 97 1.58 1 48 3 69 2.25 0.91 27 88 943 57 12 42 3.02 4 38 21 61 4.44 3.19 3 24 3 '.47 Barley straw. . . . 949 51 11 01 2.29 1 22 3 37 2.19 1.88 27 43 929 71 31 52 2.69 5 51 16 40 4.97 0.14 3 83 9 '.79 760 240 65 76 8.88 25 20 88 80 8.64 9.36 13 04 10.80 949 51 11 22 2.70 2 04 4 18 2.14 1.78 24 83 923 67 23 11 1.07 8 17 22 78 6.83 2.01 1 80 2*. 47 Lucern 973 71 17 95 0.78 4 11 34 08 6.03 4.33 1 42 1.35 Potato (Irish)... 963 37 22 12 0.59 1 60 0 75 7.06 2.44 0 85 1.03 932 68 36 10 10.06 3 46 3 12 6.42 2.24 2 24 4.48 Rutabagas 923 77 39 42 5.15 2 00 7 46 11.78 6.46 0 38 3.92 White turnips.. . 928 72 36 43 2.73 1 51 9 64 12.52 4.32 0 79 4.60 Linseed cake 938 62 14 44 0.86 9 85 5 33 21.88 2.10 4 03 0.37 Wheat bran 936 64 15 36 0.38 10 75 3 00 33.15 0 70 Rape cake 934 66 16 03 0.08 7 59 7 19 24.35 2.17 5 74 6.13 Cotton-seed cake 930 70 24 78 3 01 3 22 33.81 0.77 2 80 * In a number of analyses chlorine was not estimated, as the dots indicate, t This is probably the garden pea, as our field pea is, botanically speaking, a bean, and the analysis of the field bean represents more nearly our cow pea. APPENDIX. 401 Table IL Showing the Proximate Composition of Agricultural Plants and Products, embracing the average of water, albuminoids, carbo- hydrates, crude fibre, fat, etc., and of nitrogen, 1000 parts, by Profs. Wolff and Knop. Substance. Water. Organic Matter. 1 Albuminoids. Carbo-hydrates. Crude fibre. * Fat, etc. t 1 Nitrogen. Wheat 144 836 130 676 30 15 20.50 144 835 100 680 55 70 16.00 Oats 143 827 120 609 103 60 19.20 146 849 75 765 9 5 12.00 Rye 143 837 110 692 - 35 20 17.60 143 834 90 659 85 25 14.40 140 830 145 621 64 30 13.20 i3iickwheat 140 836 90 596 150 25 14.40 143 832 224 523 92 25 35.84 Beans (field) 145 820 255 455 115 20 40.80 143 802 20 302 480 15 3.20 143 825 15 270 540 13 2.40 143 802 20 298 484 14 3.20 143 807 25 382 400 20 4.00 143 817 65 .352 400 20 10.40 173 777 102 335 340 10 16.28 140 820 30 390 400 11 4.80 Pea hull 143 797 81 366 350 20 12.90 103 832 105 295 370 20 16.80 780 203 37 86 80 8 5.92 740 240 45 70 125 7 7.20 950 241 20 21 11 3 3.20 880 111 11 91 9 1 1.76 870 120 16 93 11 1 2.56 915 77 8 59 10 1 1.28 131 818 140 500 178 38 22.40 115 806 283 413 110 100 45.28 126 867 118 741 7 12 18.88 * Crude fibre represents impure cellulose. t Fat, etc., includes with fat, wax, chlorophyl, and in some cases the resins. t The field bean of Europe probably approaches nearer our field pea than the European pea. 408 APPENDIX. Table III. Average composition, per cent, and per ton, of various kinds of produce, with tlieir estimated value as manure, from amount of nitrogen, phosphoric acid, and potash, taken from a table prepared by John B. Lawes, of Rothamstead, England. Substance. Per Cent. Pounds per every Ton. Value as manure, in dollars and cents. Mineral Matter. Phosphoric Acid, estimated as Phosphate of Lime. Potash. Nitrogen. Dry Matter. Mineral Matter. Phosphate of Lime. Potash. Nitrogen. 7.00 4.92 1.65 4.75 1.971 156.8 110.2 37.0 106.4 *19.72 tOotton seed cake. 8.00 7.00 3.12 6.50 1.994 179.2 156.8 70.0 145.6 27.86 3.00 2.20 1.27 4.00 1.882 67.2 49.3 28.4 89.6 15.75 2.40 1.84 0.96 3.40 1.893 53.8 41.2 21.5 76.2 13.38 Indian meal 1.30 1.13 0..35 1.80 1.971 29.1 25.3 7.8 40.3 6.65 Wheat 1.70 1.87 0..50 1.80 1.904 38.1 42.0 11.2 40.3 7.08 2.20 1.35 0.55 1.65 1 882 49.3 30.2 12.3 37.0 6.32 Oats 2.85 1.17 0.50 2.00 1.926 63.8 26.2 11.2 44.8 7.70 6.60 7.95 1.45 2.55 1.926 147.8 178.1 32.5 57.1 14.59 7.50 1.25 1.30 2.50 1.882 168.0 28.0 29.1 56.0 9.64 Bean straw 5.55 0.90 1.11 0.90 1.848 124.3 20.2 24.9 20.2 3.87 Meadow hay 6.00 0.88 1.50 1.50 1.882 134.4 19.7 33.6 33.6 6.43 5.00 0.55 0.65 0.60 1.882 112.0 12.3 14.6 13.4 2.68 Barley straw 4.50 0.37 0.63 0.50 1.904 100.8 8.3 14.1 11.2 2.25 5.50 0.48 0.93 0.60 1.859 123.2 10.7 20.8 13.4 2.90 1.00 0.09 0.25 0.25 .280 22.4 2.0 5.6 5.6 1.07 0.68 0.13 0.18 0.22 .246 13.4 2.9 4.0 4.6 91 0.68 0.11 0.29 0.18 .179 15.2 2.5 6.5 4.0 86 1.00 0.32 0.43 0.35 .537 22.4 7.2 9.6 7.8 1.50 * These values are based upon the prices of guanos and superphosphates in England. They are 25 per cent, higher in the United States. t This article of Southern production has more phosphoric acid, more potash, and more nitrogen than any other, and is worth considerably more in dollars and cents. APPENDIX. 409 ^ : 'A ^1 13 :m ^ ?; 5 r; :t s s ^ ^ g - 5 3 z — ^ ^ ^ Z^, -fi ^ o 5 ^ ^ 5 ^§ :m c 1- Ci -1 — — :m t= i: ?5 H r-. o i-t c-t i-- H ^ ;^ ^ ^ £i ?i ^ ^ ^ 21 18 I i I J 1 J 1 ■I H 410 APPENDIX. TABLE V. Fruits arranged according to the proportion of Acid, Sugar, Pectin (jelly), and Gum ; averages from Fresenius ; acid being 1 : Acid. Sugar. irectiii auQ. Gum. 1 1.6 3.1 1 1.7 6.4 1 2.3 11.9 Raspberries . .... 1 2.7 1.0 1 3.0 0.1 1 3.7 1.2 1 4.3 0.4 1 4.4 0.1 1 4.9 0.8 1 4.9 1.1 1 6.9 1.4 1 7.0 4.4 1 11.2 5.6 1 17.3 2.8 1 20.2 2.0 1 94.6 44.4 TABLE VI. Standard weight, per bushel, for grain, seed, etc., in most cases established by law in a number of the States of the Union : Pounds. Peas 60 Irish potatoes 60 Onions 60 Clover seed 60 Timothy seed 44 Flax seed 56 Dried apples 23 Dried peaches, 83 Sweet potatoes 55 Pounds. Indian corn 56 Wheat 60 Eye 56 Oats 33 Barley 48 Buckwheat 48 Beans 63 Cotton seed 28 Corn on the cob 70 Table VII. Showing the amount of different kinds of wood and coal required to throw out a given amount of heat, demonstrated by experiments of Marcus Bull, of Philadelphia. Cords. Hickory Wood. 4 White Oak 4| Hard Maple 6| Soft Maple 74 Cords. Pitch Pine 91. White Pine 9^ Anthracite Coal 4 tons. Bituminous Coal 5 PAGE Absorbent power of soils 105, 109 " clay 107 " " sand 107 Absorption of soils 237 " , water 46 Aceiic acid 210 Acetification 212 Acid, acetic 210 " carbonic 14S citric 210 " huraic 257 '* hydrochloric 158 " hydrous sulphnric 290 malic 209 " nitric 151 " oxalic 210 metapectic 196 '* pectic 193 " prussic 213 Acids 142 " and bases 2C9 " vegclable 2:>9 Acid silicic 183 " sulphuric Z03 " sulphurous 15S ' " sulphydric 15S | " tannic 210 | " tartaric 210 Adhesive attraction 124 j Adhesiveness of soils 109 i Agricultural division of soils 101 ' Agriculturist 13 Agriculture as a science 14 " an art 14 j defined 13 | " basis of 15 Air expansion by heat 63 , PAGE Air in motion 89 roots 22 Akene, the 35 Albuminoids 190 composition of 193 " animal 1&4 " in crops 194 " vegetable 194 Alburnum 29 Albumen 191 Alcohol, product of sugar 205 Aleurone 193 Alkalies 218 Alkaloids 217 Allotropism 143 Alluvial soils 101 Alumina 178 Ammonia 154, 276 Ammoniated phosphates 300 Ammonia and nitric acid in plants. . 270 Ammonia and phosphoric acid com- bined 300 Ammonia as a solvent 282 " escape of from soils 277 from nitric acid 274 formation of in soils 276 " in atmosphere 155 in soils 242, 243 '* in rain-water 155 *' loss of in soils 279 " not efficient by itself 279 relations to vegetation . . '155 nitrate of 277 superior to the nitrates. . 280 held by snow 74 Anemometer 90 Animal charcoal 147 412 INDEX. PAGE - Animal albumen 192 " heat 343 *' nutrition 341 substances, composition of. 341 Analysis of cotton seed 333 soils 225 " '* new method 247 Annuals 45 Anther 33 Apatite 284 Aqua fortis 151 Arabin 200 Artifical milk 352 Argol 210 Ascending and descending sap 222 Ashes 325 Ash in plants 161 Atmosphere, chemistry of 141 absolute humidity G4 " composition of 141 *' density of 61 " pressure of 62 properties of 61 '* as related to vegetation 60 " weight of 61 " description of 59 ** moisture of 63, 6G ** temperature of 66 Atmospheric ingredients 158 •* tabular view of 176 Attraction 124 Bark 28 Barometer 62 Bassorin 200 Barley seed 37 Bast tissue 20 Benefit of resting lands 334 Benefits of humus 263 Berry, the 35 Best rotation in cotton 336 Biennials....- 45 Bi-phosphate of lime 292 solution of 295 Blade, the 30 Bone black 147, 284 Bone phosphate of lime 285 Botany, agricultural 15 Bottom water 120 Bread grains, sugar in 204 Breathing pores 31 Buds 32 " adventitious 33 " latent 33 Bulbs 23 Butter making 351 Cactus 30 Cambium 27, 23 Calcium 187 Capillary water 120, 121 Carbon 146, 162 " fixation in plants 171 " in plants 168 Calcareous soils 101 Calyx 33 Carbonates , 148 Carbonic acid 148 " *' amount of 149 " decomposition of 169 '* " exhalation of 172 " *' as a solvent 175 " " supply of 173 " " from the soil 174 Carboniferous system 97 Carbonic oxide 158 Caffeine 219 California moss 213 Camphor 215 Cane sugar 201 Carbo-hydrates ICS Casein 192 Cattle foods 344 " " analysis of 358 " as provender 357 Caustic potash 186 Causes of rain 80 Cereals, unripe seed 37 Cellular tissue 20 Cellulose 196, 18 Ceraline 193 Cerasine 200 Chemistry of the atmosphere 141 plants 160 " " soils 224 Chemical qualities of soils 205 " changes in manure heaps . 317 Changes in vegetable tissues 175 INDEX. 413 PAGE Chlorine 188, 310 Chlorides 189 Chloride of sodium 188, 311 potassium 186, 3C3 Chlorophyl 220 Cirro-cumulous clouds 79 Cirro-stratus " 79 Cirrus '* 77 Citric acid 210 Circulation of sap 51 Classes 16 Clay soils 101 '* " absorption of 238 absorptive power of 107 Climate, effect on humus , 256 Clouds, combined 79 " formation of 76 '* original 77 Cocoanut 39 Coarse and fine soils 231 Coffee berries. 36 Colluvial soils 101 Coloring matter of plants 219 Color of plants by electricity 87 " " soils 112 Composite plants 17 Composition of the atmosphere 141 Composting manures 314 Condensed milk 353 *' oxygen 143 Constituents of plants 226 " *' " in minerals... 228 " seeds 227 Contractility 58 Coprolites' 284 Cork 28 Corn, exhaustion by 234 " starch 198 Corolla 33 Cotton, best rotation with 336 *' exhaustion by 234 seed analysis of 323 " " as a manure 323 " " meal 355 Cotyledon 36 Cremor tartar 210 Cretaceous system 36 Crops, rotation of 235, 330 PAGE Cruciferous famiJy 17 Crucif era , 36 Crude fibre, digestion of 349 Cryptogams 16 Culms 25 Culture, horizontal... 138 Cumulo-stratus 79 Cumulus clouds 78 Cyanogen 157 Cyanophyl 220 Decay 259 Deductions from experiments 337 Density and course of sap 221 Dew 71 Dextrine 1G9 Diastase 261 Diffused light, effect of 172 Digestion of crude fibre 340 Dioecious plants 34 Disintegration C8 Ditching 131 Divisibility of soils 110 Drainage , 128 at the South 131 Drain tiles 131 Drift soils 101 Drupe 34 Earth closets 320 division of 94 " how warmed 67 " temperature of 95 Elastic sandstone 97 Electrical force 58 Electricity aids germination 86 effect on colors 87 Elements, inorganic, in plants 177 Embryo, the 35 Endogens 16, 36 Endosperm 35 Eocene sea G8 Epidermis 26 Eremacausis 143, 260 Essential oils 214 Evaporation 64 Excretory roots 24 Exhalation of carbonic acid 172 " Avater 49 Exhaustion of soils 233 V INDEX. 414 PAGE Exogens 16 Experiments in 1873 337 " " Germany 341 " with cotton seed 324 " " fertilizers 281 " with reduced phosphates 299 "Families ; 16 Farmer 13 Farm-yard manure 317, 318 Fat former.^ 342 Fat in vegetables 216 Fattening animals 347 Feeders 21 Fermentation 261 Ferruginous soils 105 Fertility, dubious tests of 246 " other requisites of 230 tests of 251, 254 " organic matters essential. . 262 Fertilizers and natural manures 265 " hastening maturity 268 " how divided 266 Fibrils 21 Fibrin 192 Fixation of carbon 171 Fixed oils 213, 214 Flesh building, laws of 346 Flesh formers 342 Flower buds .. 32, 33 Flower, the 33 Flowers of sulphur 185 Fluids, circulation of 46 Fodder corn 356 Fogs 69 Foliage, offices of 31 Forces 15 Frost 72, 100 Frost smoke 70 Fructose ..203 Fructification 34 Fruit, of the 34 Fruit sugar 203 Fuel and food of animals 353 Full moon, elfects on weather 92 Gas light carburetted hydrogen 166 Gases 60 Genera 16 Geology 94 PAGE Geology of Georgia 97 Geological division of soils 100 Germination 38 Gilliflower 37 Glaciers 100 Gliadine 193 Glucose 202 Glucosides 203 Glutine 191 Glycerine 216 Gourd fruits 35 Grains 35 Gravelly soils 105 Grandeau's experiments 248 " theory tested 250 Green manures > 326 Grape sugar 202 Granite 175 Gums, the 196, 200 Hail 75 Heart wood 29 Heat, radiation of 67 Herbs 45 Honey dew 204 Home-made superphosphates 293 Horizontal culture 138 Humic acid 257 Humus in soils 255 " benefits of 263 " absorbing power of 108 Hurdling system 331 Hybrids 16 Hydrochloric acid 158 Hydrogen 146, 102 " in plants 165 Hydrocyanic acid 213 Hydrostatic water 120 Hygroscopic water 120, 121 " power of soils 117 Hygrometer 65 Hypo-phosphoric acid 185 Ice, law of 237 Importance of mineral elements 177 Inside growers 26 Inorganic elements in plants 177 Inulin 198 Iodine - 180 Iron, carbonate of 181 INDEX. PAGE Iron peroxide of 180 " protoxide of 99 " importance to plants 180,182 Isomeric bodies 208 Jellies 196 Kernel, the 35 Lactose 203 Land hemisphere 94 " plaster on clover 157 Laws of flesh building 346 Leaf buds 32 Leaves 30 Legume, the 35 Leguminosa 36 Legumine 191 Leucophyl 20 Levulose 199 Light, lunar 93 " eifect on oxygen 164 " on vegetation 87 Lignin 197 Lime CaO 306, 187 in soils 225 soils 103 sulphate of 308 " carbonate of 307 Lingula 287 Loamy soils 101, 104 Lunar influence 91 Magnesium 188 Magnesia, MgO 308 Malic acid 209 Mannite 204 Manures, composting 314 " heaps, changes in 317 " natural 312 Manganese 179 Margarin 215 Marsh gas 158 Marls 104 Marly soils 101 Maize seed 37 Melon seeds 37 Metallic oxides in plants 177 Mechanical action 99 Mercurial gauge 55 Meteorology, agricultural 59 Metapectic acid 196, 206 PAGE Milk sugar 203 " production of 349 " artificial 352 " ducts 28 Minerals, in organic matter 327 in plants 177,328 value of 329 " exhausted by crops 234 " plant constituents in .... 228 " period of exhaustion 229 " constituents per acre 229 " phosphates, origin of 286 " composition of 287 Mineral theory 233 Miasma 129 Mists 69, 71 Mixing cattle foods 345, 354 Monoecious plants 33 Monocotyledenous plants 21 Moon, influence of 91 Mountains, height of 94 Mucidine 193 Mucilage, vegetable SOO Mycose 204 Natural manures 312 '* system 16 Nevasa guano 288 Nicotine 190,218 Nimbus clouds 79 Nitric acid 157 " "by electricity 86 generation of 142 " " in rain water 154 'Mn soils 242, 244 " "its importance 275 Nitrification 271 " conditions essential ... 273 Nitric peroxide 152 Nitrates 153 Nitrate of soda 116 Nitre beds 274 Night soil 319 Nitiites 153 Nitrogen 150, 162 " in rain water 159 " in ash of plants 163 " in plants 165 " not absorbed by plants — 167 416 INDEX. PAGE Nitrogen exhausted by crops 234 " iu soils 239, 241 " as a fertilizer 269 '* amount requisite 271 *' forms of in plants 269 " absorption of 329 Nitrof,'eneous compounds 193 Nitrous oxide , . . 158 Nodes 25 Nucleolus 18 Nucleus 18 Nut, the * 35 Nutritiousness of wheat bran 355 Oats, exhaustion by 234 ' ' volunteer 332 Offices of roots 23 Oil of vitriol • 291 Oils, vegetable 214 " essential 214 *' fixed 215 " volatile, 214 Olein 215 Orchids 22 Orders 16 Organs of plants 20 Organic and inorganic parts 161 " matters in air 158 " elements in plants 162 Organism of plants 161 Organic nitrogen in soils 240 matter, solubility by 253 " " climate on 256 " " essential to fertility 262 Outside growers 27 Oxalic acid 210 Oxide of magnesium 188 Oxides 142 Ovaries 33 Ovules 33 Oxygen 142, 162 " in plants 163 " transmission of 164 Ozone 143 " relations to vegetation 145 " by electricity 86 Palmatin 215 Papilionaceous family 17 Petals 33 PAGE Peas, exhaustion by 234 Peaty soils 104 Peruvian guano 240, 301 Pecticacid 190 Pectin 196, 205, 206 Pectose group 196, 206 Perennials 45 Finite 204 Pistils 33 Pith 27 " rays 28 Phenogams. 16 Phosphate of lime, precipitated 296 Phosphates, ammoniated 300 '* reduced 297 " composition of . . . . 287, 288 Phosphoric acid 185, 283, 285 " sources of 283 " anhydride 184 Phosphorous acid 185 " anhydride 184 Phosphorus 184 Physical qualties of soils 105 Phosphorized fats 216 Phloridzin 202 Plants, coloring matters of 219 " supply of water 122 " absorption of water 123 " chemistry of 160 " oxygen in 163 " hydrogen in 165 " carbon in 168 " nitrogen in 166 character and duration of . . 45 " differently constituted 333 " one celled 19 Plant life, processes of 44 Plains 94 Plantlet, growth and nutrition 42 Plaster of Paris 308 Plateaus 94 Ploughing, benefits of 134 Ploughs 133 Pluviometer 84 Plumule 35 Pods 35 Pollen 33 Polar fogs 70 I PAGE Pome 34 Porcelain clay 99 Polycotj'ledons 36 Potash, hydrate of 186 Potassa, KO 302 Potassium 186 chloride 303 Potato, Irish 197 Poiidrette 320 Preface 9 Precipitated phosphate of lime 299 Protein 191 Protagon 216 Proximate principles 190 *' changes in 207 Protoplasm 18 Prosenchyma 20 Proximate composition of animals. 341 Provender, relative value 357 Pruning 55 Prussic acid 213 Pyrolusite 179 Quartz 182 Qucrcite 204 Quicksilver 307 Quinia 190 Radicle 35 Rain, causes of 80 " gauge 84 *' sources of 85 *• fall, amount of 82 Red snow 19 Reduced phosphates 297, 299 Requisites of fertility 230 Rennet 192 Reproductive organs 20 Resin ; 215 Respiration apparatus 348 Resting lands, benefits of 334 Retentive power of soils 118 Rind 28 Rotation of crops 330, 335 " " seeds 333 Rock crystal 182 Rocks, stratified, etc 95 Root hairs 22 Roots 21 Root stocks 26 18* 417 PAGB Runners 25 Rye seed 37 Saccharine substances 203 Saccharose 201 Saleratus 148 Salt, common 311 Salts, absorbed by soils 107 Sap, ascending and descending 222 " density and course 221 " chemical composition of 223 " circulation of 51 Salacin 190, 202 Saponification 215 Sand, absorptive power of 107, 108 Sandy soils 101 Sea breese 68 Sea water 150 Serum 192 Scries 16 Sepals 33 Seeds 35, 37 " germination of 37, 38 " depth for planting 41 " and plant constituents 227 " rotation of 333 Sensitive plant 58 Sheep husbandry 321 Sprinkling of soils 110 Shrubs 45 Sieve cells 28 Silica 182 Silicates .\. 183 Silicic acid 1S3 Silica, decomposition of 99 Silicious soils 103 Silver grains 28 " mines 99 Snow 73 Soils, classification of 100 " absorptive power of 106, 108 " chemical qualities of 105 " alluvial 101 " agricultural 101 " adhesiveness of 109 " drift 101 " divisibility of 110 " depth of 96 ** geological division 100 418 INDEX. PA GE Soils, coarse and fine 118 *' color of 112 " capacity for heat 113 " hygroscc pic power of ,.. 117 " ab' to heat Ill calcareous — 101 " as related to physics 94 " loamy 101, 104 " power to absorb salts 107 " clay 101, 102 " colli! vial 101 " specific gravity of 106 " peaty 104 sedentary 101 " as to water Ill " marly 101. 103 " sandy 101 " transported 100 physical qualities of 105 " silicious 102 " weight of 105 permeability to water 114 " retentive power of 118 " " for heat 113 " hygroscopic power of 117 " shrinking of Ill " American and European 224 " analysis of 225, 246 " plant constituents in 226 " coarse and fine 231 " „ exhaustion of 233 " soluble and insoluble 231 " analysis, new method 247, 251 " ammonia in 243 " chemical absorption of 237 " soluble matters in 232 nitrogen in .239,240 " nitrogen compounds in 241 nitric acid in 244 " nitrous acid in 245 " rich and poor 251 Soda essential to plants 187 " carbonate of 116 " common 187, 304 " nitrate of 116 Sodium, peroxide of 187 chloride of 187 Soil roots 22 , IA.GE Solar light or carbonic acid . . . 239 Solubility by organic matter. . . 253 a test of fertility .. , 196, 197 63, 157 .... 29 of the .... 26 . 26,29 .... 26 " " composition of . . 313, 318 .... 33 .... 26 87, 170 " efiect on carbonic acid .... 89 . . . . 99 ... 308 .... 309 Superphosphates, composition of . . 292 " home-made ... 293 " manufacture of . . 289 ... 158 ... 115 ... 94 " atmospheric ingredients , ... 176 ... 194 Tannic acid ... 210 ... 202 ... 210 r INDEX. 419 Temperature *' of soils Ill " in germination 39 Tertiary system ••• 98 Theine '^^^^ Theobromine Thermometer 68 Thunder heads Tiles for drainage 131 Tilth 101 Trade winds 90 Trenching 132 Trees Tubers Turnips, experiments on 321 Umbelliferous plants 17 Under-draining 131 Yapor of water 03, 157 Vascular tissue 20 Varieties Vegetable acids 209 albumen 191 casein 192 " cells 17 " fibrin 193 moulds 101,104 " mucilage 200 oils 214 " ' tissues 19 " changes in 175 Vegetable organs 20 Venus' s fly trap ^8 Vinegar. 212 Vital force 57 Volatile alkali 155 PAGE Volatile oils 214« Waste 98,99 Water, absorption of 46 " amount in plants 125, 126 bottom 120 " exhalation 49 capillary 120 " chemistry of 235 " hemisphere 94 how formed 236 " how plants absorb 122 hydrostatic 120 " hygroscopic 120 gaseous, liquid, solid 236 in the soil 120,126,130 " of crystallization 236 " physical offices in plants ... 127 " supply to plants 122 Wax 215 Weathering 335 Weight of soils 105 Wheat bran, nutritiousness of 355 flour, analysis of 355 " seeds 36, 38 Wind, cause of 89 velocity of.... 90 Wood ashes 325 " tissue 20 growth of 44 Woody fibre 196 Yeast fungus 261 Zamia spiralis 22 Zanthophyl 220 , Zeolites 138 I J i I