aoe University Library QK 47.K il text-book of elementary botany. A il mann LIBRARY Department of Floriculture and Ornamental Horticulture New York STATE CoLLEGE of AGRICULTURE at CORNELL UNIVERSITY ITHACA, N.Y. silat te Date Jone (443 ‘ NEW YORK STATE COLLEGE OF AGRICULTURE DEPARTMENT OF FLORIGULTURE AND ORNAMENTAL MORTIGULTURE CORNELL UNIVERSITY ITHACA, N. Y. TEXT-BOOK OF ELEMENTARY BOTANY. BY W. A. KELLERMAN, Pz. D., PROFESSOR OF BoTANY, OHIO STATE UNIVERSITY. PHILADELPHIA: ELDREDGE & BROTHER, No. 17 North Seventh Street. 1897. O98. 4, & ed Entered, according to Act of Congress, in the year 1897, by ELDREDGE & BROTHER, in the Office of the Librarian of Congress, at Washington. yy, ss $99 ee WESTCOTT & THOMSON, ELECTROTYPERS, PILILADA,. ee Tuis book has been prepared for use in schools in which elementary Botany is taught during the last half or last third of the school year. It is believed that a course in Botany which is designed for those who are taking their first lessons in the subject and most of whom will not have opportunity to pursue it farther, ought to afford opportunity for scientific training as well as for obtaining some general information concerning the vege- table kingdom, particularly in relation to the growth and development of plants, their relationships, their uses, etc. Accordingly, directions for practical work, observation, and performing experiments have been offered throughout, but in immediate connection with the paragraphs of the text that pertain to the subject in hand. This has not interrupted the proper symmetry and logical arrangement of the topics that should be included in an elementary course for high schools. The practical work indicated need not and should not be a verification of the text; that, it is true, would be an im- provement over mere text-book work, but it lacks the very spirit and essential feature of scientific work. The observa- tion and experimentation must be made to find out the facts in the case. This will afford scientific training and, besides, real knowledge will be gained. Whether all the practical exercises that are called for, can be carried out, will depend on the length of time at the disposal of pupils, but every 4 4 PREFACE. course, however short, should include some work of this cha- racter. The physiology of plants is given more attention than usual in school text-books, and some representatives of the important classes of vegetable products are included—innova- tions whose importance obviates the necessity of an apology. The equipment for the experiments will doubtless be at hand in schools where physics or chemistry is taught. When that is not the case, a mere trifle in the outlay will be suffi- cient. A good pocket lens should be carried by every pupil, for use both in the class-room and in the field. Since each pupil cannot be furnished with a compound microscope, no special directions are given for practical work in histology, though when an instrument is available the teacher should use it constantly in demonstration. Most of the figures have been heretofore used in the author’s Elements of Botany, where their source is explained. Men- tion should be made that several of the experiments and a few figures have been given essentially as found in Oel’s Pflanzenphysiologische Versuche. I have had the assistance of my wife in the preparation of the entire book, and to her, equally with myself, the credit, if any, should be awarded. W. A. K. Outo SrarE UNIvERsIty, \ Columbus, Ohio. INTRODUCTION. PAGES WHEN AnD How to Stupy Borany: Specimens in hand—Plants available at all seasons—Knowledge direct, not second-hand—Use of the note-book—Drawings—Preservation of specimens . 7-9 CHAPTER I. SEEDLINGS: Parts of the plant—Germination—Caulicle—Cotyledons —Dicotyls—Monocotyls— Plumule—Radicle—Cotyledons a sur- vival of the earlier foliage . Seteryita + as -« . 10-18 CHAPTER II. Roots: Functions—Root-hairs—Food—Entrance into the soil—True roots—Primary roots—Reservoirs of food — Duration — Adventi- tious and aérial roots... .. eh Lae ge eee G 14-18 CHAPTER III. THE Stem: Herbaceous—Woody—Culm—Stolons—Runners — Ten- drils—Spines—T horns— Rhizome—Tuber—Bulb — Corm — Mono- cotyledonous type—Dicotyledonous type—Medullary rays—Wood —Bast—Cambium—Buds - © — ....... 19-22 CHAPTER IV. Tue Lear: Function — Foliage—Modified forms —Arrangement— Radical—Cauline—Spiral arrangement—Parts—V enation—Shapes —Base—A pex—Margin—Compound—Surface—Stipules. . . . 23-33 CHAPTER V. THE INFLORESCENCE: Indeterminate—Raceme—Corymb—Umbel— Spike—Spadix—Catkin—Head—Panicle—Determinate—Cyme . 34-36 CHAPTER VT. Tue Firowrr: Modified branch—Peduncle—Pedicel—Bract—Spathe —Involucre— Receptacle — Function—Parts—Essential organs— Plan—Arrangement of parts—Cohesion—Forms of Corolla—Adhe- sion—Stamen—Pistil—Placenta—Angiosperms—Gymnosperms . 37-45 5 6 CONTENTS. CHAPTER VII. PAGES PoLLINATION AND Fecunpaton: Agencies—Anemophilous—Ento- mophilous — Proterandrous— Dimorphism — Papilionaceous — Or- chids—Cleistogamous—Fecundation—Embryo . ..... 46-56 CHAPTER VIII. Tae Fruit: Purpose—Dry fruits—Dehiscent—Follicle—Legume— Capsule—Silique—Silicle—Samara—A kene—N ut—Fleshy fruits— Drupe—Pome—Berry— Seed dispersion. . io Re - 57-61 CHAPTER IX. THE CELL AND TissuE: Cells—Shape—Size—Parts—Protoplasm— Cell-wall— Chlorophyll—Starch—Cell-multiplication — Epidermis —Stomates—Fibro-vascular bundles—Fundamental tissue—Grow- ing point . : — & in Se . . 62-73 CHAPTER X. THE PuysioLocy or PLants: Water—Transpiration—Root-pressure —Water-cultures—Food elements—Photo-synthesis—Function of chlorophyll—Metaholism—lInsectivorous plants—Plastic material —Reserve material—Respiration—Temperature—Growth—Move- ments . ; ae . . 74-86 CHAPTER XI. Systematic Botany: Species—Variety—Sport—Genus—Family— Order—Binomial nomenclature—Groups of plants—Slime Moulds Bacteria— Yeast plant—Spirogyra—F ungi—Rusts—Lichens—Bry- ophytes—Mosses— Pteridophytes See —Angio- sperms ..... : . . 87-108 CHAPTER XII. GEOLOGICAL AND GEOGRAPHICAL DISTRIBUTION: Fossils—Plants of the Geologic Ages—Migration—Barriers—Botanical divisions of the Globe S48 eo eee ‘ . 109-118 CHAPTER XIII. Economic Botany: Resins—Turpentines—Gums—Caoutchouc—Gutta percha— Opium — Aloes—Oils — Camphor — Starches — Fibres — Cork—Tanning barks— Cinchona — Timber — Turmeric—Ginger —Calamus—Tea—Tobacco—Cloves— Coffee — Chocolate—Vanilla —Cereals—Fruits a wa » 119-132 INDEX .. ; - 183-136 ELEMENTARY BOTANY. INTRODUCTION. WHEN AND HOW TO STUDY BOTANY. ——00$f,0-e——_. 1. Tur study of Botany is the study of plants. The be- ginner should therefore have specimens before him. It is not necessary to wait till spring or summer, since plants can be obtained at any season of the year. Fewer specimens can be obtained in midwinter, though the native trees and shrubs and cultivated plants are always available and therefore suf- ficient material is never wanting. 2. The common flowering plants and the Ferns with their allies (the Clubmosses and Equiseta or Horsetails), numerous as they are, by no means comprise the entire Vegetable King- dom. The Mosses, Lichens, Fungi (e. g. Toadstools, Mush- rooms, Rusts, Smuts, Moulds, Mildews, etc.) and Algz include a very large number of species. There is scarcely a season of the year when numerous specimens of many of these groups are not obtainable in good condition for satisfactory study; besides, many kinds of material can be collected at the proper stage of development, dried, and laid away for winter study. The specimens can then be moistened and thus made pliant, when their form and structure can be ex- amined, often as satisfactorily as when they were first col- lected. Some material can be kept, ready for use at any time, in alcohol or in a one to two per cent. solution of formalin. 8. Although collecting and identifying plants when in bloom is both interesting and profitable work—having also the addi- 8 ELEMENTARY BOTANY. tional merit of serving in numberless instances to incite to further study—it must be remembered that this in itself, in- cluding the preparative study of descriptive terminology, is a very inconsiderable portion, or perhaps it should not be con- sidered a part, of real Botany. On the other hand, the mere study of a botanical text-book, though it may be made a drill in memorizing, or used as a basis of instruction in etymology or language lessons, cannot be properly designated a study of the science of Botany. This should comprise rather a direct study of the plants themselves; an examination of both their general or gross structure and their minute anatomy; an in- vestigation of their general physiology and the functions of the several parts, also their affinities to each other, their rela- tion to other objects in nature, their embry ological development, their evolution through geologic time, and their past and pres- ent distribution; and finally a study of the application of the facts and principles of the science to every-day life. 4, It should be remembered that the paramount object in the study of Botany is as far as possible to obtain knowledge directly from the plants themselves. These must therefore be handled and carefully observed—the text-book and teacher be- ing guides to systematic observation, and, where possible, to experimentation. The study of the text-book should in all cases follow, not precede, the study of the material and the exe- cution of the experiments. It has seemed preferable to have the directions for practical work follow the paragraph or por- tion of the text devoted to the subject in hand, rather than to precede it; but the order of study of the material and the experimentation, and of the study of the text, should always be as suggested above. To attempta complete examination of all the parts that are presented by any plant should not be attempted in the first lesson. If, for example, a leafless branch collected in winter is at hand, a study of the leaf- scars alone could advantageously occupy some length of time. It should inciude also a comparison of the leaf-scars of other species; the work would thus occupy many hours. The buds, their arrangement, size, shapes, coverings, struc- INTRODUCTION. 9 ture, function, etc. could be taken up and somewhat exhaus- tively studied ; the general characters of the twigs and branches of various shrubs and trees, the Lichens obtainable in open weather, Mosses which may be found in fruit at almost any time in the year, or still other objects, could be the first mate- rial for study. If the work be commenced in spring or sum- mer, plants without number can be obtained, and the study could be commenced equally well with either roots, stems, leaves, flowers, or fruit. If the material needed can be ob- tained in sufficient abundance, it will be well to take up the several subjects in the logical order presented in the following pages. 5. One of the valuable, if not essential, aids to careful and systematic study is the making of an outline or tabulation of the points observed and the information gained from the mate- rial under examination. The note-book should always be at hand and judiciously used. To both pupil and teacher it should furnish evidence daily of increase of knowledge and growing ability to discern. No less important is it to repre- sent by outline drawings all the parts studied. This necessi- tates a close and detailed examination which otherwise would in very many cases not be made. The pocket lens should be daily called into requisition whenever its use might be advan- tageous. Preservation of representative specimens of every- thing studied is also recommended. This will enable one at any time to review or re-examine that which has been pre- viously subjected to complete or partial investigation. Besides, it is a convenient record of the labor performed. The Flora, constituting the last portion of this book, or any other manual of plants, can, after a few weeks of such study, be satisfactorily used in identifying the native plants of the region. CHAPTER. i, SEEDLINGS. ——+.0205, 00 ——_ 1. Numerous seedlings of the common plants should be examined by the beginner. An outline sketch of one or more specimens should be made to insure a careful inspection of every detail. Like the mature plants, the seedlings have three evident parts or organs; namely, root, stem and leaves. These present numerous variations in form and mode of growth, which may be seen by examining specimens repre- senting many different species of plants. They should be studied in the early stages of germination, and also observed at intervals until the ordinary foliage leaves appear upon the stem. This can be conveniently done if the following direc- tions are heeded. Germinator.—Provide a shallow box of sand (or soil or sawdust, but if sawdust is used, that of the Oak and Chestnut must be avoided), and in this plant a number of different kinds of seeds. Any or all of the following may be used :! Bean, Pea, Castor Bean, Mustard, Coreopsis, Maple, Radish, Lark- spur, Sunflower, Phlox, Squash, Four-o’ clock, Mallow, Touch-me-not, Morn- ing Glory, Eschscholtzia, Wild Cucumber, Onion, Corn, Wheat and Pine. Keep sufficiently warm and moist to insure quick germination. Use the seedlings for study in connection with the paragraphs that follow. The ger- minator should be kept in the class-room or other convenient place. It should be so ample that each pupil may have all the specimens desired for each lesson. In case of large classes several boxes should be used. 2. Shortly after the seeds have been subjected to a proper degree of temperature and moisture, the embryo or plantlet (popularly called the “ germ”) begins to grow. A slender 1If all the seeds named are used, all of the conspicuous variations in coty- ledons, etc., will be shown; but the Bean, Morning Glory, Corn, Wheat and Pine might be taken as desirable examples, if but a few can be used. 10 SEEDLINGS. 11 stem, or Caulicle, breaks through the coverings of the seed, and grows downward to form the root. In case of some spe- cies but one root develops directly from the seed. In others two or more appear almost simultaneously ; these are really branches from the caulicle. When the development of the embryo is so far advanced that the testa (covering) of the seed is thrown off, or that the stem appears above ground, many peculiarities present themselves. For the investigation of these the germinator if properly managed will furnish ample material. 3. It will be seen that in many cases there are two seed- leaves (for example, the two halves into which a pea or bean splits) called Cotyledons. All plants having two cotyledons belong to the group called Dicotyls. In these, great varia- tion is seen in the form of the seed-leaves ; some are narrow, others are broad; in a few cases they are unequal; some are sessile—i. ¢. without a stem to the blade or broad part; others are on long petioles (leaf-stems). They generally have an en- tire margin, but some are scalloped or lobed, or they may be notched at the apex or even two-cleft or three-cleft. Some cotyledons are lifted above the surface of the soil by the lengthening of the caulicle, expand more or less and become green so that they strongly resemble ordinary foliage leaves. In other cases they do not increase in size, but remain within the seed-covering underground; they do not then become green, nor have any resemblance to leaves, and they soon disappear. The seedlings from the germinator will show these variations if they are studied at the proper time. They should be examined and sketched in detail, by each pupil before a recitation is called for, or before the text is studied. This will require many hours’ work and should form several les- sons. The specimens should be saved, when possible, for subsequent refer- ence. The pupil should also collect for illustration seedlings from the woods, fields, etc., during the growing season. Such specimens can be dried between folds of paper under pressure, and then glued to sheets of card- board, or thick white paper, of uniform size—eight and one-quarter by eleven and one-half inches (this being just half the size of standard sheets for botan- ical specimens). 12 ELEMENTARY BOTANY. 4, Those seedlings which instead of two (opposite) cotyle- dons, have but one, as the Lily, Onion, Corn, Wheat, Barley, etc., belong to the group of plants called Monocotyls. The seed- leaf of the Monocotyls seldom resembles a foliage leaf. It is aérial in the Lily family, and in case of some other plants of this group, but it remains mostly underground in or at- tached to the seed, making its real nature difficult to deter- mine. In seedlings of members of the Pine family the number of cotyledons varies in different genera and species, often also in different individuals of the same species. Some- times there are only two, but often four to six, or even as many as ten, forming a whorl at the top of the caulicle. In botanical classification the Pine family is not included in either of the two groups, Dicotyls and Monocotyls, but forms a separate class (Gymnosperms) whose characteristics will be explained later. 5. In some seeds the leaves are thick and said to be fleshy. These together with the caulicle may occupy the entire cavity within the seed-covering. They are distended by reason of the nourishment with which they are gorged. It is at the expense of this reservoir of food that the embryo or seedling is developed. When the seed-leaves are thin or small the nourishment is stored up around but yet in contact with them. This they absorb for food during the early period of the de- velopment of the seedling. This stage is called Germination. When nearly or quite all the nourishment has been drawn from the seed and seed-leaves, the latter disappear. By this time roots and leaves in sufficient number have been devel- oped to provide food for the plant. 6. There may be seen between the two cotyledons in case of the bean and many other seeds, a small though conspicu- ous bud. This is called the Plumule. It is present, though usually minute, in every germinating seed; a lens should be used in its examination. It terminates the upper end of the axis (caulicle); the opposite (root) end of this axis has a different structure and it is called the Radicle. The develop- ment of the plumule results in the production of the stem SEEDLINGS. 13 and leaves of the plant. The leaves that first appear are almost invariably quite unlike the cotyledons. They are usually the typical or ordinary foliage leaves of the species. In some cases, however, they are mere scales, as seen in the Pea, Oak, etc. The first one or few leaves that appear are usually simpler than those developed later. They may be simple if the typical leaves are trifoliate, or trifoliate if the foliage is pinnate, etc. If the species has lobed or palmate leaves, the first one or more developed are usually entire or heart-shaped. Of as simple type or pattern as the first leaves generally are, they are by no means so nearly uniform in shape and appearance as the seed-leaves. In reference to the latter a writer has said that “Cotyledons are a survival of the universal foliage of deciduous trees in olden geologic days, ere time had differentiated them into their present varied forms.” B CHAPTERII. ROOTS. 0300 —_ 1. THE Roots serve the double purpose of fixing the plants securely in the soil, and of absorbing the nourishment which is largely contained in solution in the soil-water. They branch irregularly, and subdivide repeatedly, finally ending in a mul- titude of very small rootlets. A portion, near the tip only, of each rootlet is thickly covered with very small hairs. These absorb the soil-water. As the rootlet elongates new hairs are produced, the older ones quickly dying and leaving no scar. Both the rootlets and hairs are most abundantly developed in fertile soils that contain a moderate amount of moisture. The hairs are not developed at all when the roots grow in water. The older roots and older portions of the rootlets are destitute of hairs and they do not perform the function of absorption, or to an inconsiderable extent only. In the resting or dormant (winter) stage of plants, when no new roots nor root-hairs -are being developed, but little absorption takes place. At this time transplanting can be done with less injury than if done during the growing season. Numerous plants should be pulled or dug up and their roots examined. The germinator previously described, if provided early enough, will furnish a variety of examples. Also make a root-cage by tying together two panes of glass, kept one-fourth inch apart by narrow strips of wood placed near the edges on three sides. Fill the space between the panes of glass with fine sand or soil and plant a seed of Sunflower or Corn (or other plants) near the upper open edge ; supply moisture, keep at a proper temperature, and watch the root-development from day to day. Make sketches and notes of the observations. 2. The Root-hairs (called rhizoids) apply themselves very closely to the minute particles of which the soil is composed, 4 ROOTS. 15 Each of the soil particles has a very thin adherent film of moisture, and this it is that the root-hairs absorb. In this manner the dissolved mineral food is conveyed into plants to be converted into organic (vegetable) matter for building up all their parts. Solid particles are not taken up by the plant. However, the tip of the root-hairs is often acid—as test with litmus paper will demonstrate—and the hairs are therefore capable of dissolving to some extent the mineral particles to which they aflix themselves. Plage a number of seeds, as Corn or Wheat and Bean or Sunflower (previously soaked in water), on the surface of wet sand in a shallow box or tray—first covering one-half of the area with a thin sheet of white paper. Cover the box with a pane of glass to prevent evaporation. The seeds which germinate on the paper will in two or three days furnish good examples of root-hairs visible to the unaided eye, but seen more satisfac- torily with a pocket lens. The roots of the other seedlings, not prevented from penetrating the soil, when pulled up will have a mass of particles cling- ing to them, some of which can scarcely or not at all be washed off (soak for a few moments and then use a camel’s-hair brush)—showing that the hairs have taken firm hold on the minute mineral particles. 3. Though granite, limestone and other rock-materials are usually said to be insoluble, yet the rain water, percolating through the soil and there becoming more or less charged with carbon dioxide and alkalies, does slowly dissolve even these refractory mineral matters. While each root-hair ab- sorbs but a tiny drop of this soil-water, the countless myriads combined, take up for the plant a stream that furnishes the food-material required from the soil. That rootlets can dis- integrate mineral matter is shown experimentally by their perceptible corrosion of a piece of polished marble with which they may come in contact. Place a small piece of marble, with one face polished, near the bottom of a box or pot of soil. Plant seeds so that the roots of the seedlings will touch and spread over the polished face as they grow. After an interval of time (fifteen to thirty days) remove the piece of marble and see the corroded lines where the roots have been in contact. Rubbing the surface with ver- milion will render the corroded parts more conspicuous. 4. Since all soils are porous—even the finest clay has space 16 ELEMENTARY BOTANY. between its particles—the roots find entrance and force their way vertically and laterally with but little hindrance. The point of growth and elongation is situated near the tip, which is therefore continually thrust forward. The tissue forming the root-cap, though suffering loss by abrasion against the soil-par- ticles, protects the delicate growing portion, and by the latter it is constantly renewed. In case of contact with a solid par- ticle, growth is not impeded on the side that is free; hence the rootlet, by the continued growth on one side, becomes curved and passes around the obstacle. Darwin showed in his ex- periments with the radicles that “if the tip perceives the air to be moister on one side than on the other it transmits an influence to the upper adjoining part, which bends toward the source of the moisture.” Presently the roots contract longi- tudinally—the central portion shortening so much, that folds or irregularities on the surface, or in the cortical portion, may be seen. This contraction, amounting sometimes to ten per cent. of the length, has the same effect as tightening the ropes to a ship’s mast, and therefore anchors the plant more securely in its position. 5. The higher plants, such as the common herbs, shrubs and trees, and the ferns, have true roots, the growing point being covered by a root-cap. But in the Mosses, Liverworts, Lichens, Fungi, and Algze true roots are wanting. Rhizoids (root-hairs) are present in the Mosses and in the Liverworts, and they perform the same functions as true roots. 6. The primary (first) root often persists and remains con- spicuous instead of being soon lost in branching. In this case it is called the tap-root. It may become enlarged or fleshy as in the Turnip, Carrot, etc. The branches that some- times proceed from the radicle in place of, or accompanying the primary root, are often designated as multiple primary roots though really they are secondary. In the Sweet-potato, Dahlia, etc. they become enlarged, serving, like the tap-root, as reservoirs of plant food; they are in this case said to be tuber- ous. In Grasses and many other plants the roots are fibrous; that is, numerous and thread-like, ROOTS. 17 7. In case of many plants, the so-called annuals, the roots and other parts live but one season. The roots of biennials, such as the Carrot, Teasel, ete. live through two seasons. Per- ennial roots continue to live from year to year, though the stem in some cases dies down at the end of each season. Sec- ondary roots may arise from different parts of the plant— stems and branches—whether above or below the ground. Such are called adventitious roots. They are common in creeping plants, especially at the joints, and their production is usually favored by contact with moist soil. In the Trumpet Creeper, Poison Ivy, etc., they assist the plant in climbing, and since they do not grow into the ground they are called aerial roots. In some rare cases the aerial root is a tendril, as in Vanilla aromatica. In some species of Jussizea (swamp plants) some of the adventitious roots develop into floats. 8. Aerial roots are more common in moist tropical coun- tries, especially in deep forests where the light is partially ex- cluded—it being unfavorable to their development. A notable example is furnished by the Banyan-tree of India, and some other Fig-trees. Their outstretched branches send down adven- titious roots, that grow into the soil and thus become support- ing columns. The Screw-pine is sometimes lifted up by roots that are exposed some distance from the ground. The Sugar- cane produces aerial roots from many joints similar to those near the base of Indian Corn. The seeds of the Mangrove of the West Indies sprout before falling from the tree, and send along root down into the mud, in which these trees grow, thus gaining a foothold before severing their connection with the parent tree. 9. Aerial roots, whose function is somewhat different from the above, are found in Air-plants, or epiphytes (Gr. epi, upon ; phyton, plant). They generally grow on other plants, as their name signifies, but their roots serve merely to give the plant attachment, and the food is derived wholly from the air. Many of the beautiful Orchids of the tropics are of this na- ture. The Epidendron, or Tree Orchis (growing on a species of Magnolia), and the Tillandsia, or Spanish Moss (hanging in 2 18 ELEMENTARY BOTANY. tufts or festoons from trees) of the Southern States, are epi- phytes. 10. Certain plants not only fix themselves to other plants, but also draw their nourishment from them. Such are Para- sites. They send their roots, or what corresponds function- ally to them, into the tissue of their host and absorb the nourishment which the latter had prepared for its own use. True parasites are destitute of the green substance in leaves, which is called chlorophyll. When this is present the plant can in sunlight convert the inorganic matter into plant food. 11. The Fungi (as Rusts, Smuts, Blights, Moulds, etc.) are either parasitic on living plants or draw their nourishment from decaying substances. The leafless Cuscuta, or Dodder, is a slender yellow flower-bearing parasite of peculiar nature. The seeds sprout in the ground, and the plantlet, as soon as it appears above the surface, seeks for a support around which to twine; if unsuccessful it soon dies, but if it finds a proper host-plant, it closely entwines the same producing suckers by means of which it absorbs sufficient nourishment for its growth and development. The lowest portion of the stem of the parasite then dies, and thus severs its connection with the soil. 12. The Mistletoe of Europe and the False Mistletoe of this country have chlorophyll in their leaves, and are therefore capable of converting inorganic into organic (vegetable) mat- ter; that is, of preparing their own food. Yet they do this only in part. They draw a portion of their food from the trees on which they grow, and to that extent are parasitic. The nature of the yellowish or whitish leafless plants, as the Indian-pipe and Cancer-root, which are fixed to the ground, should not be misunderstood. They do not draw their nourishment from the soil, but from underground roots on which they are parasitic. Neither should all subterranean parts of plants be regarded as roots, since stems sometimes grow underground. Stems, however, are easily recognized by the buds and scales (modified leaves) which they produce, and by the presence of a pith which may be seen by examin- ing a transverse section; in roots no pith is formed. CHAPTER III. THE STEM. ——0.0 $F,0-2—___ 1. Brsrpes the distinction of stems based on their duration —as annual, biennial and perennial—they may also be desig- nated as herbaceous and woody. [Illustrations of woody stems are seen in all shrubs and trees. Herbaceous stems are composed of soft or succulent tissue. They are usually green and contain no wood except in the slender and often in- distinctly distinguishable woody strands. A few stems and branches have special names, as culm, which is the jointed, often hollow stem of the Grass and Sedge families; stolons and runners, which are slender, trailing, rooting branches; tendrils, which are slender, elongated, twining branches; spines and thorns, which are the hardened, pointed, some- times merely stunted branches. Collect illustrative specimens of the various kinds of stems for examina- tion in the class-room. Draw outline figures of each kind. In case of the woody stems, the leaf-scars should receive attention. Make an outline figure giving the exact shape, which will be uniform for each species of plant. Note the dots regularly distributed in the scar. These are the ends of the severed woody strands that passed from stem to leaf. Note the numerous but somewhat indistinct scars, very close together, situated at a considerable dis- tance from the end of the twig. The portion beyond this point is the growth of the last season. The scars indicate the position of the bud-scales of the terminal bud of that season. 2. Underground stems sometimes resemble roots, but they are distinguished by having nodes (joints) and scales. The latter represent leaves, above which, or in whose axils, buds may be detected. They are also terminated by a bud. Rhi- zome is the name applied to the elongated slender form, and tuber to the short and much thickened stem. The under- 19 20 ELEMENTARY BOTANY. ground stems of the Mint illustrate the former, and the Trish Potato the latter. A bulb is a very short stem or root-stock, covered by bases of leaves in the form of thickened scales, and bearing roots below. A corm is likewise short and thick, bearing roots below, but destitute of scales. The Onion is a familiar example of a bulb ; the Indian Turnip and Cyclamen furnish examples of the corm. These thickened stems and scales are reservoirs of nourishment. 3. Some stems, as the corn-stalk, have woody strands scat- tered irregularly through the whole interior and commingled with the pith (Fig. 1). Such strands are found, though not always so easily recognized, in stems of the Lily, Spiderwort, the Orchids, Solomon’s Seal, Asparagus, Flag, Palms and many others. The plants with stems of this kind are, with very few exceptions, Monocotyls ‘—that is, they have but one cotyledon or seed-leaf to each seed. When the woody strands attain their full development, there is no further increase in the thickness of the stem (except in Palms and a few others), though the plant may continue to live for some time. This is clearly seen for example, in the stems of Lily, Asparagus, Corn, etc., where the thickness of the stem when a few inches or a few feet high has reached its limit and thereafter the diameter re- mains the same. The strands in such stems are, as shown by microscopic examination, composed of only two kinds of tissue, namely, wood and bast. 4. If a transverse section of a stem of Bean, Bindweed, Mint, Sunflower, Nightshade, Buttercup, Dock, ete., be made and examined with a lens, a central pith will invariably be found, though sometimes it is torn, making the stem hollow. Surrounding the pith but often indistinctly seen, are the iso- lated woody strands, usually few in number, forming a circle (Fig. 2). Dicotyls (with but few exceptions) have such stems.’ 1 Tn older books the terms endogenous (‘‘inside-growing’’) and exogenous (‘‘outside-growing’’) have been erroneously used to designate the mono- cotyledonous and dicotyledonous stems, THE STEM. 21 In many cases during the middle and latter part of the season, the strands become numerous and join each other so as to make a continuous ring or cylinder. This is always true of shrubs and trees. 5. The strands in stems of the Dicotyls con- sist of wood and bast with a thin intervening layer of delicate tissue, called cambium. The woody portion of each strand is next to the pith, and the bast portion is always toward the surface of the stem. Therefore when the strands become numerous and large enough to join, their fusion will neces- sarily result in the formation of a woody ring next to the pith, a thin ring of cambium next to the wood, and a ring of bast outside the cambium. The cambium layer will, each suc- ceeding year, grow and produce an additional layer (or ring) of wood—the annual rings thus revealing the age of the tree. The bast is also constantly renewed by the cambium—the out- ermost portion gradually dying, becoming furrowed, withering away, or exfoliating as dead bark. Fia, 2. Select some twigs and branches of any common tree, say the Linden, and make thin transverse sections. Those from twigs of one year’s growth will have the pith in the centre, a ring of wood adjoining, then a ring of bast, with the original epidermis and cortex exterior to the bast. The sections from stems of two years’ growth will show the pith and two distinguishable though cohering rings of wood. Likewise the age of the others will be indi- cated by the number of rings of wood-growth. Notice the narrow radiating lines of tissue, some of them beginning at the pith. These are the Medul- lary Rays. Use the pocket lens. Draw enlarged figures of the sections. Make sections of twigs of various other species and compare the relative size, shape and color of the pith, the distinctness of the annual rings and the differences in the medullary rays. 6. The Buds on twigs and branches are disposed regularly, either at points opposite—rarely in a whorl of three or more —or but one at a node (joint). They are at approximately regular intervals and there is a terminal bud to each stem or twig. Below each of the lateral buds will be seen a scar (leaf- scar), indicating that each was developed just above (that is, in the axil of) the leaf; the buds are therefore axillary and 22 ELEMENTARY BOTANY. have the same arrangement on the stem as the leaves have. In a few cases, as in the Soft Maple, etc., there are accessory buds, that is, one or more buds added to the side of the axil- lary bud. When the buds develop at irregular places they are said to be adventitious. 7. When a bud is carefully dissected it is seen to consist ex- ternally of scales, usually numerous and overlapping each other in an imbricate manner. These scales are really small leaves. They cover and protect the central portion of the bud, which is the delicate growing end of the branch. Often the outer scales are covered with resin or varnish or the inner scales bear woolly hairs, protecting the growing point very effectually against rain and the extremes of temperature. The following season some of the buds—especially the upper- most and afew of the lateral ones—develop into branches. The others remain dormant, or in some cases may be forced later into development. The buds referred to in this para- graph are sometimes spoken of as leaf-buds in contradistinc- tion to flower-buds, or those which develop directly into flowers. Short twigs of the common shrubs and trees should be collected in the early spring to illustrate the arrangement of the buds and to show the varia- tions in shape, size and other characters. Draw outline figures of each. For preservation the twigs can be attached to a sheet of cardboard by thread or by means of narrow gummed paper strips or narrow strips of court plaster. The name of the plant from which each twig is taken should be written under the specimen. Large buds (as the Lilac, etc.) should be selected for dissec- tion and for slicing vertically (from below upward) through the centre to ex- hibit the growing point surrounded by the scales. Use the lens and make an outline figure showing all the parts. Make drawings also of separate bud-scales. CHAPTERIV. THE LEAF. 01400 — 1. Tux leaves of plants ordinarily present a large surface expansion. They are perforated by minute pores, called Sto- mates. Through these oxygen and carbon-dioxide enter the leaf, and water in the form of vapor escapes from it. Nearly all of the water that is taken up by the roots, thence conveyed through the stem and branches to the leaves, passes out through the stomates. The leaf retains the minerals that were dissolved in the water. It also decomposes the carbon- dioxide (CO,) which it takes from the atmosphere, retaining the carbon but liberating the oxygen. These several elements of inorganic matter are formed into organic or vegetable material, which the plant uses in building up all its parts. The leaf, then, has evidently very important functions to per- form, for which it is specially adapted by its structure. Only the ordinary foliage leaves fully perform these functions ; they may be said to exhibit the typical form. Besides these, there are many modified forms, some of which have departed so far from the type that their true nature can be understood only when we see all the intermediate forms or gradations connect- ing the two extremes. Such are cotyledons, scales, spines, tendrils, pitchers and fly-traps. Tllustrations of everything (or with few exceptions) to which reference is made in this chapter can be obtained everywhere and in great abundance. The pupils should examine, compare, make outline figures and thoroughly study this illustrative material, which of course will be work for many days. Then the text can be studied to advantage. 2. The two halves into which a pea, bean, etc., readily divide are called the Cotyledons, or seed-leaves. If they be observed 23 24 ELEMENTARY BOTANY. in the case of the Pumpkin and certain other plants, some time after germination it will be found that they have changed their shape somewhat and become green, like ordinary leaves. As a rule, however, the cotyledons change but little, and simply furnish the nourishment for the plantlet during germination. In the bulb-scales is stored up food for the early growth of the plant the following season. This nourishment is consumed in such bulbous plants as the Hyacinth, etc., by the produc- tion of flowers early in the season, or in advance of the leaves. 3. The leaves of underground stems are generally reduced to mere scales. The Bud-scales, which protect the tender parts within, are modified leaves. A gradual transition be- tween them and the first foliage leaves may often be traced, as in the Lilac, Hickory, etc. When spines occupy the place of leaves, they are modified forms of the latter. In the Bar- berry all gradations may be seen on a single shoot. The leaf, or a portion of it, may become changed into a tendril for climbing, as in the Pea, Vetch, etc. (Fig. 3.) 4, Very interesting modifications of leaves are furnished by Stipules Fig, 3. Fig. 4. the Pitcher-plant (Sarracenia), Sundew (Drosera), and Ve- nus’s Fly-trap (Dionewa). The leaves of Sarracenia are hollow cups or tubes (Fig. 4) inwardly covered with hairs directed THE LEAF. 25 downward. They are generally half full of a liquid into which insects may fall and become macerated, and their juices are then absorbed by the plant. The Drosera is also carniv- orous, feeding on small insects which alight on and are held fast by the viscid tentacles on the upper side of the leaf. Fie. 5. The leaves of Dioncea (Fig. 5) have at the top, two or three lobes furnished with a marginal row of stout bristles, and three or four slender ones on the upper surface. When the bristles on the upper surface are touched by a small insect, Fie. 7. Fie. 8. the lobes suddenly close in upon it and the prisoner is then digested and consumed. 5. The leaves are said to be alternate (Fig. 6) when there is a single leaf at each node or joint of the stem. Examples C 26 ELEMENTARY BOTANY. of this arrangement are very numerous, as the Apple, Oak, Elm, Willow, Dock, ete. If two leaves occur at each node, they are said to be opposite (Fig. 7), as the Maple, Ash, Pepper- mint, Catnip, etc. Sometimes there are three or more leaves at each joint, as in Cleavers (Galium), Trumpet-weed (Eupato- rium purpureum), etc. In this case the leaves are said to be verticillate (Fig. 8). In the Pines and Larch the needle- shaped leaves are in clusters, that is, they are said to be fas- ciculate. If leaves grow from the base of a stem, but appear to come out of the ground, they are radical (Lat. radix, root). Those leaves inserted in the stem are cauline (Lat. cwulis, stem). 6. On a straight, leafy shoot of an Elm, Cherry, Apple, Oak, Willow, etc., pass a thread from the lowest leaf to the one next above, and continue it around the stem in the same direction to the successive leaves above. The thread will be seen to take a spiral course; the leaves are therefore spiral in their arrangement on the stem. In the Elm the third leaf stands directly over the first, and to reach it the thread has passed once around the stem, or, as is usually said, the cycle is complete when the third leaf is reached, and it is expressed by the fraction 4. The numerator denotes the number of turns; the denominator the number of leaves en- countered. Experimenting in a similar manner with Alder, the fraction 4 is obtained, and with the Cherry 2. In the lat- ter case the stem would be encircled twice before a leaf is found (the sixth), which is inserted directly over the first, and five leaves are contained in the cycle. In a similar man- ner the fraction # with the Flax, ;3; with the Flea-bane, .§ with the Houseleek, 43 with cones of some Pines would be obtained. 7. A leaf may have three parts, namely; the Blade or Lamina, which is the expanded portion; the Petiole, which is the stem of the leaf; and Stipules, which are the append- ages at the base of the petiole (Fig. 9). The stipules are very often wanting, in which case the leaf is said to be exstipulate. If the blade is inserted directly on the stem (which is the case THE LEAF. 27 when the petiole is absent), the leaf is said to be sessile. The blade consists of a frame-work of veins or skeleton of woody tissue, and the soft, green tissue between the veins, called parenchyma. When one central vein surpasses the others in size it is called the midrib; its branches are the veins, and the branches from the veins are the veinlets. When the venation of alarge number of different kinds of leaves is examined, three types are found to prevail. In most of our common Fern-leaves the veins | are separate their entire length and have free | ends, though they are often forked one or more times. In the other two types the smaller vein- lets (and sometimes the veins) anastomose. One is represented by the leaves of most Monocotyls, as the Lily, Flag, Grass, Corn, Wheat, etc. In these a number of conspicuous veins extend ‘Stipules from the base to the apex of each leaf, approxi- Fie. 9. mately parallel to each other, and this fact has suggested the name parallel-veined (Fig. 10). The term striated may be used instead. The third type is seen mostly in Dicotyls, as the Oak, Elm, Maple, Catnip, Mallow, Dock, ete.; the veins om es Zs a eh CATS Petiole - Fie. 10. : Fie. 11, and veinlets here form a conspicuous network, and are said to ‘be netted-veined, or reticulated. Of the latter, there are two sorts: the veins may branch from a midrib (Fig. 9), when they are pinnately-veined (Lat. pinna, feather); or they may branch from 3, 5,7 or more ribs (Fig. 11), in which case they -are palmately-veined (Lat. palma, palm). 28 ELEMENTARY BOTANY. 8. The principal terms used to designate the shape of the leaves are :—linear, narrow, long, and of the same breadth throughout (Fig. 12); lanceolate, long and narrow, tapering upwards and downwards (Fig. 13); oblong, twice or thrice as long as broad (Fig. 14); elliptical, oblong with a flowing iN) Oe Fie. 12. 13. Fie. 16. Fig. 17. outline (Fig. 15); oval, broadly elliptical (Fig. 16); ovate shaped like an egg, the broader end downwards (Fig. 17); orbicular, circular in outline, or nearly so (Fig. 18) ; oblance- olate, like lanceolate, except with the more tapering end down- wards (Fig. 19); spatulate, shaped like a spatula, that is, Fig. 18. Fig. 19. 20. 21. 22, round above and narrow below (Fig. 20); obovate, ovate, with the narrow end downwards (Fig. 21); cuneate (Lat. cunea, wedge), shaped like a wedge (Fig. 22). 9. As to the base, leaves may be:—cordate, heart-shaped (Fig. 23) ; reniform, kidney-shaped (Fig. 24); auriculate (Lat. auricula, little ear), with ears or blunt projections (Fig. 25); sagittate (Lat. sagitta, arrow), with pointed projections down- wards (Fig. 26); hastate (Lat. hasta, spear), with pointed pro- THE LEAF. 29 jections outwards (Fig. 27); peltate (Lat. pelta, shield), when the petiole is attached to the under surface near the middle Fie. 23. Fia. 24, (Fig. 18). The apex of leaves may be:—acuminate, ending in a prolonged point (Fig. 28); acute, ending in an acute Va a Fie. 25. Fria. 26. Fie. 27. angle (Fig. 29); obtuse, with a blunt point (Fig. 30); trun- cate, with the end as if cut square off (Fig. 81); emarginate, notched at the end (Fig. 32); obcordate, with a deep notch, ANSE Fie. 28. 29. or inversely heart-shaped (Fig. 33); cuspidate (Lat. cuspis, point), tipped with a sharp stiff point (Fig. 34) ; aristate (Lat. arista, awn), with a long bristle or awn. 10. The margin of leaves may be :—entire, that is, the edge 30 ELEMENTARY BOTANY. is an even line without any notches or teeth; serrate (Lat. serra, saw), With teeth like a saw projecting towards the apex (Fig. 35); dentate (Lat. dens, tooth), with teeth pointing out- Fig. 35. 36. 3 38. 39. ward instead of forward (Fig. 86); crenate (Lat. crena, scal- lop), scalloped (Fig. 37); undulate (Lat. undula, wave), wavy (Fig. 38) ; incised, when the edge is cut and jagged (Fig. 39). When leaves are.deeply cut, the divisions are called lobes. If the incisions extend more than half-way from the margin to Leaflet -.. Fia. 40. Fig. 41. the midrib, the leaf is said to be cleft; the number of segments is indicated hy the terms bifid (two-cleft), trifid (three-cleft), multifid (many-cleft), ete. If the incisions ex- tend almost to the midrib, the leaf is.said to be parted; if THE LEAF. 31 they extend quite to the midrib, the leaf is divided; and thus a single leaf, or one with a lamina ina single piece, is con- verted into a compound leaf—that is, one with the blade divided into several parts (Fig. 40). Each of the divisions is called a leaflet. 11. Corresponding to the pinnate and palmate type of vena- tion, there are pinnately and palmately compound leaves. The pinnate leaves have the leaflets or pinne arranged on each side of the rachis. If the leaflets are in pairs through- out, the leaf is said to be abruptly pinnate (Fig. 41); [i if a single leaf terminates the (W4/ rachis, the leaf is said to be odd-pinnate (Fig. 40). Pal- mate leaves (sometimes called digitate) have the leaflets borne on the extreme end of the leaf-stalk (Fig. 42). 12. The primary divisions of the blade may be again divided, which is expressed by the terms bi-pinnate (Fig. 43), or tri- pinnate (thrice divided). When the leaf is several times Fie, 44, Fie. 45. compound, it is said to be de-compound. Of numerous other forms not yet mentioned, the following are conspicuous. Perfoliate (Lat. per, through ; folium, leaf), in which the stem 32 ELEMENTARY BOTANY. appears to pass through the leaf near its base (Fig. 44), as in. the Uvularia. In Honeysuckles the opposite leaves are sometimes united at their bases, rendering them connate-per- foliate (Fig. 45). Several kinds of leaves have no distinction of blade and petiole; as the sword-shaped, ensiform (Lat. ensis, sword), leaves of the Daffodils; the needle-shaped, acic- ular (Lat. acus, needle), leaves of the Pine; and the scale- shaped, squamose (Lat. squama, scale), leaves of the Junipers. The surface of leaves differs in various species of plants. It may be glabrous (smooth), or scabrous (rough); it is often hairy, indicated by such terms as pubescent (with short hairs), hirsute (with stiff hairs), villous (with long, soft hairs), lanose (woolly). 13. The Stipules are sometimes free, leaf-like appendages, as in the Pea (Fig. 46), and perform the ordinary function of Stipules Fria. 46. ‘Bee 47. the leaves; ordinarily, however, they are very much reduced in size, as in the Bean; sometimes they take the shape of bristles or prickles, as in the Locust. In the Smilax they have the shape of tendrils. When united to the base of the petioles, as in the Rose and Clover, they are said to be adnate. THE LEAF. 33 The stipules of the Tulip-tree serve as bud-scales, falling off soon after the leaves unfold. In some plants, as the Dock, the Buckwheat, etc., they unite and form a sheath around the stem. The sheath of the Grasses represents the petiole, for it bears the blade at its summit; the small appendage com- monly found at the top of the sheath, called a ligule (Fig. 47), is of the nature of a stipule. Specimens should be collected to illustrate all the points mentioned in the chapter, and figured, as suggested above. Illustrative specimens for preserv- ation should be pressed till dry, and then mounted on cardboard or heavy white paper. They can be attached by means of liquid glue, or by using strips of gummed paper or white court plaster. Opposite or below each the points illustrated should be indicated by the appropriate term. 3 CHAPTER V. THE INFLORESCENCE. —0295 00——— 1. Tus term Inflorescence indicates the mode of flowering, or the situation and arrangement of the flowers on the plant. That this is quite various in different species of plants can be seen by noting the numerous examples to be found any time during the growing season. If the flowers develop from lateral buds the inflorescence is said to be indeterminate, since the shoot, terminated by a leaf-bud, may continue to grow in length. Collect specimens of numerous flower-clusters of both native and culti- vated plants, securing as many forms and variations as possible. Compare these in detail, and arrange so as to show affinities. Make a diagrammatic figure of one of each kind. As noted elsewhere, all illustrative specimens should be saved for use in review ; in this case, after drying under pressure, attach to cardboard or to thick sheets of white paper. 2. If the flowers develop from terminal buds the inflor- escence is determinate, so-called because the length of the axis is thereby determined; it cannot grow longer. The in- determinate inflorescence is also centripetal, that is, the outer- most flowers (when the cluster is level-topped) or the lowest on the stem open first, and those higher follow in regular suc- cession, until finally the one in the centre or at the top ex- pands. Examples are furnished by the Lily of the Valley, Currant, Plantain, Shepherd’s Purse, etc. The determinate inflorescence is centrifugal, inasmuch as the flowering begins in the centre or at the top and proceeds outward or down- ward. This is exhibited in the Chickweed, Dianthus, Hy- drangea, etc. 34 THE INFLORESCENCE. 35 3. The following are varieties of indeterminate inflorescence : raceme, corymb, umbel, spike, spadix, catkin, head and pani- cle. The raceme has the pedicellate flowers scattered on an elongated axis (Fig. 48). The corymb is the same as a ra- ceme, with the lower pedicels elongated so as to make the flower-cluster level-topped (Fig. 49). In an umbel the axis Fie. 48. Fie. 49. is reduced, and all the pedicels proceed from a common point (Fig. 50). The spike is similar to a crowded raceme, with Fie. 50. Fie. 51. Fia4. 52. the flowers sessile (Fig. 51). Two forms of the spike have spe- cial names: the spadix (Fig. 56), which is fleshy and com- 36 ELEMENTARY BOTANY. monly surrounded by a modified leaf, called the spathe; and the catkin or ament, which is scaly. The head differs from a spike in that the axis is reduced, crowding the flowers into a head-like cluster (Fig. 52). A panicle is an open or more or less compounded raceme or corymb (Fig. 53). 4. The cyme is a determinate or definite flower-cluster, with a flat or convex top. It resembles the corymb some- what, except that in the latter the flowering is centripetal, while in the cyme it is centrifugal (Fig. 54). A crowded cyme is called a fascicle. Many of the clusters are often com- pound, as compound umbels, compound cymes, etc. The two classes of inflorescence may be represented in one and the same plant; thus the Mint family has cymes or fascicles, which are centrifugal in their flowering, but these are gene- rally composed of spikes or racemes, which are centripetal in their order of flowering. CHAPTER VI. THE FLOWER. —0a400—_ 1. Ira leafy shoot be reduced in length, the leaves will be brought close together ; if the internodes (portions of the stem between the joints) are wanting entirely, the leaves will be in whorls, or form a rosette. If now these leaves undergo certain changes in form and function, a Flower will be formed. This change or modification of one part or organ into another is called metamorphosis. The flower is a meta- morphosed branch, and the different parts are modified leaves. Proofs of this are found in the partial or complete reversion of floral organs back into ordinary leaves. For example, in almost any “ double” flower, as a rose, holyhock, etc., stamens (the slender bodies near the centre) may be found that have partly reverted to petals (the showy parts); often other parts have become changed from their usual form, so as to resemble more or less closely the ordinary foliage leaves. On the other W Fig. 55. hand numerous intermediate forms may be found which ex- hibit a gradual transition from foliage leaf to the most highly D 37 38 ELEMENTARY BOTANY. modified organ (pistil). The flower of the Water-Lily is a partial illustration (Fig. 55). There can be no lack of easily obtained material for direct study of what is outlined in the following paragraphs. The order in which the several topics of the chapter are given need not be scrupulously followed in the prac- tical work of the class-room ; though all of them should be brought out by a study of abundant and suitable material before the text is assigned for class recitation, or review. The note-book should be daily used, the lens called into requisition when desirable, and drawings made directly from the speci- mens to illustrate all the structures that beginners should see. The advan- tage of preserving illustrative specimens can here, as elsewhere, be seen. 2. The stem or stalk, which supports a flower-cluster or a solitary flower, is called the peduncle. If the peduncle is wanting, the flower is inserted directly on the stem, and is said to be sessile. When the peduncle arises from the ground it is called a scape. The minute branches of the peduncle, or slender stalks which support the individual flowers, are called pedicels. The bracts are generally diminutive leaves which subtend the flower-cluster, or from whose axil the flower-stem proceeds. When a single enlarged bract encloses the flower-cluster, it is called a spathe (Fig. 56). If the bracts are numerous and form a conspicuous cup under the flowers, Spathe or an imbricated covering around a head of flowers, they form an involucre (Fig. 57). The term receptacle (Fig. 57) is ap- THE FLOWER. 39 plied to the axis of a flower-cluster when it is disk-like or short, so that the flowers are crowded into a head. 3. The purpose of the flower is the production of seed. Four distinct parts may be present, each having a distinct function to perform. In a flower such as the Buttercup, Crab- Apple, Morning Glory, Phlox, etc. there will be found as the outermost part, a calyx, or cup-like portion. This consists of several parts, either distinct or united, which more or less re- semble ordinary foliage leaves. Each leaf or portion of the calyx is called a sepal. Within this whorl of leaves forming the calyx is a second whorl, either of distinct or more or less united parts, called the corolla. This is commonly the most showy part of the flower. Its component parts are called petals, and they usually depart farther from the ordinary form and texture of foliage leaves than do the sepals. 4, Within the corolla are slender bodies called stamens. They sometimes revert to petals or sepals, showing that they are also modified leaves. These organs are sometimes exces- sively numerous; and when few are rarely less in number than the parts of the corolla or calyx. Within these and occu- pying the central part of the flower, are the pistils; in the lower enlarged part of which, called the ovary, the seeds are produced. The pistils, like the stamens, may be numerous, but are very often fused together or reduced to one. There can be no production of seed without both stamens and pistils, and for this reason they are together called the essential organs of the flower. The calyx and corolla may or may not be present without directly influencing the production of seed. They are called the perianth (Gr. peri, around ; anthos, flower), a term that is used especially when the sepals and petals more or less closely resemble each other. 5. A flower with the four parts present is called a complete flower; but if one or more of the parts are absent, the flower is said to be incomplete. If the essential organs are present it is called a perfect flower. Those with stamens but no pis- tils, called staminate flowers, and those with pistils but no stamens, called pistillate flowers, are imperfect. If the several 40 ELEMENTARY BOTANY. parts are exactly alike, that is, all the sepals alike in shape and size, all the petals alike in shape and size, and all the stamens alike in shape and length, the flower is said to be regular. If this likeness in shape, size, etc. does not obtain in any one or more of the organs, the flower is said to be irregular. If the petals, sepals and stamens are of the same number, or the latter may be twice or thrice as many, the flower is said to be symmetrical ; but if the number is differ- ent in different whorls, the flower is said to be unsymmetrical. 6. When the relative insertion of the floral parts is exam- ined, two types are found to prevail. In one case each petal is inserted directly in front of, or within, asepal, and each stamen directly in front of, or within, a petal; the parts are then said to be opposite. But in the other case the petals are in front of, or directly within, the spaces between, that is, alternate with the sepals, and the stamens alternate with the petals; then the parts of the flower are said to be alternate. When the parts of the flower, especially of the calyx and corolla, are each three in num- ber, the flower is said to be three-parted. Monocotyls generally have three-parted flowers. If the parts are each four or five in number, the flowers are respectively four- or five-parted ; the five-parted flowers are generally characteristic of Dicotyls. 7. When the sepals are free or distinct from one another, the calyx is said to be chorisepalous (Gr. choris, asunder), and when the petals are free, the corolla is choripetalous. The terms polysepalous and polypetalous, instead of the preceding, have generally, though incorrectly, been used in descriptive botany. The sepals may be united edge to edge, so that only their upper ends are free, by which the number forming the cup or calyx may be determined. The calyx in such ease is said to be gamosepalous (erroneously called monosepalous). When the petals are united the corolla is gamopetalous (Fig. 58). The term monopetalous is erroneously used with the same signification. This union of similar parts, or cohesion, gives rise to a variety of forms of the calyx and corolla, prominent among which are :—rotate, salverform, campanu- late, faunnelform, tubular, labiate and ligulate. THE FLOWER. 41 8. A rotate (Lat. rota, wheel), or wheel-shaped calyx or co- rolla, is one in which the tube is very short or wanting, and the lobes spread at once (Fig. 58). In the salverform corolla, the Fie. 58. Fig. 59. Fie. 60. spreading limb or border is raised on a narrow tube, and forms a right angle with the latter (Fig. 59). The campanulate (Lat. campanula, bell) denotes a bell-shaped calyx or corolla (Fig. 60). The tubular form spreads above but little. The two upper petals may unite closely and form a kind of upper lip, and the three lower ones unite to form a lower lip, In such case the corolla is labiate (Lat. labiwm, lip). The calyx may also be labiate, or two-lipped. 9. Examine a flower-head of a Sunflower; it will be seen to consist of numerous florets, with tubular corollas interspersed with the bristles or chaff. There will also be found a row of marginal flowers, called ray flowers. These have strap-shaped corollas, which are said to be ligulate (Lat. ligula, tongue). In the Dandelion all of the florets are ligulate. A curious shape is presented by the Pea or Bean. The corolla is choripetalous, very irregular, with a vague resemblance to a butterfly, and for this reason it has received the name papilionaceous (Lat. papilio, butterfly); the upper and larger petal is called the banner, the two side petals are called the wings, and the two anterior ones, generally cohering slightly and enclosing the stamens and pistil, are called the keel. The flowers of the Cress, Mustard, Cabbage, etc. have four petals, arranged two and two opposite, somewhat like a Greek cross, and they are said to be cruciform (Lat. cru, cross). 42 ELEMENTARY BOTANY. 10. A conspicuous irregularity in the flower is caused by the production of appendages of various kinds. One petal in the Violet is prolonged so as to form a spur; this organ is tubular and generally contains nectar, or sweet substance se- creted by the flower. Some species of Dicentra are two-spurred. All the petals of the Columbine have spurs. Sometimes there is only a gentle swelling or blunt outward projection (as in Adlumia), which is denoted by the word saccate. Sometimes sepals or petals are eared or crested; or they have, like the pink, a projection (corona) at the point where the claw or narrow part of the petal joins with the spreading lobe or limb. 11. When there is no adhesion or growing together of the calyx and corolla, the former is plainly inserted below the points of insertion of the corolla, stamens and pistils. In such cases (Fig. 61) the calyx is said to be free or inferior; or Pistil the calyx and corolla are said to + Nee be hypogynous (Gr. hypo, under ; gyna, pistil). The cohesion may Fie. 61. Fig. 62. Fie. 63. be to the extent shown in Fig. 62, where the petals and stamens are inserted on the calyx-tube. The petals are then said to be perigynous, though the calyx is free. The calyx-tube may be consolidated with the lower part of the pistil or ovary; the calyx is then adherent or superior; in this case the parts appear to be inserted upon the pistil (ovary), and are there- fore said to be epigynous (Fig. 63). Ifthe adhesion does not extend so far up (half-way), the calyx is said to be half-superior. 12. The stamens consist of two parts, namely, the filament (Lat. filum, thread), or slender stem; and the anther, or en- THE FLOWER. 43 larged upper end. That portion of the filament between the anther-lobes is called the connective. The filament is not an essential part, and when wanting the anther is said to be ses- sile. When the filaments are united into a tube surrounding the pistil, as in the Mallow, they are said to be monadelphous. If they are united into two sets, as in Dicentra, they are dia- delphous; if in three sets, triadelphous, and so on. The an- thers are united into a tube (syngenesious) in the Composite (Sunflower, Dandelion, etc.). Make a transverse section of the anther ; two or four cavities may be seen with the aid of a lens, and these are filled with a yellow dust, which on ex- amination with the microscope proves to be small, round bodies, called pollen. The opening, dehiscence, of the an- ther at maturity for the discharge of the pollen commonly takes place along a line the whole length of each cell. But in the Sassafras, Barberry, etc. the opening is by a lid or valve. In the Azalea, Pyrola, etc. the pollen escapes by a pore at the top of the anther. 13. The number of stamens may vary from one to many in the flowers of different species. They are, however, definite and few in number in the majority of cases. Their size, length and place of insertion may also vary. In the Mint family often two of the stamens are long and the other two short; they are then said to be didynamous (Gr. di, two; dynami, power, strength). In the Mustard family four of the stamens are long and two are short (Fig. 64), called tetradyn- amous (Gr. tetra, four). As regards the insertion of the stamens, they are hypogynous when attached below the pistils; perigynous when attached to the calyx tube surrounding the pistil; and epigynous when situated with the sepals on the ovary. They are epipetalous when attached to the corolla. 14. The pistil (Fig. 65) consists of three parts— namely, the ovary or lower enlarged part which contains the ovules or seeds; the style or slender part above the ovary ; and the stigma, the more or less enlarged upper end of the style. The style may be want- 44 ELEMENTARY BOTANY. ing, which renders the stigma sessile. According as the pistil (or “ carpel,” as it is sometimes called) is formed of a single carpellary leaf or of several leaves, it is simple or compound. In a simple pistil, formed by a single leaf folded edge to edge, the seeds are borne on the part of the inner wall which corre- sponds to the line of union of the edges. This seed-bearing line or part is called the placenta. If two placentas are present, they must have re- sulted from the union of two leaves, edge to edge ; if three placentas, from the union of three leaves, etc. There- fore the presence of two or more placentas is proof of a com- pound pistil. The number of styles often corresponds to the number of leaves entering into the formation of the carpel. 15. Compound pistils may have a single seed-cavity, or locu- lus, or they may have many cavities (loculi). When the car- pellary leaves have united with each other, edge to edge (Fig. 66) there will be but one cavity. The placentas, or seed-bearing lines, will be situated on the ovary wall, as in the simple pistil; that is, they will be parietal. If each sepa- Stigma Fie. 66. Fie. 67. Fic. 68. rate carpellary leaf unites edge to edge, and then all the carpels join (Fig. 67) the ovary will have as many cavities as there were carpellary leaves; the seed-bearing lines will be crowded to the centre and form central placentas. The walls which separate the cavities from one another in case of a multi- locular ovary may become obliterated, leaving the seed-bear- ing column in the centre of a continuous or monolocular cavity, and thus a free central placenta is formed (Fig. 68). Examples of this are found in the Purslane, Chick- weeds, Pinks, etc. THE FLOWER. 45 16. The ovary and calyx-tube may be united with each other as already explained. The ovary is then said to be inferior, and the calyx-tube adherent. If the adhesion extends halfway up, the ovary is said to be half-inferior. If there is no adhesion of the ovary with other parts, it is said to be free or superior. The ovules or small bodies which are to become seeds, are enclosed by the pistil; the latter is, therefore, said to be angiospermous (Gr. angios, vessel; sperma, seed). In the Pine family the ovules lie exposed in the cone, gn the upper surface of the base of the scales. The scale is, there- fore, to be regarded as the pistil. This condition is indicated by the term gymnospermous (Gr. gymnos, naked; sperma, seed). ChAT) ERY Ti. POLLINATION AND FECUNDATION. ——0504 00-—— 1. Iv is necessary that the ripe pollen, which is produced in the anther, be deposited upon the mature stigma ; otherwise no seeds will be produced. The transference of the pollen is called Pollination,’ a process that is effected by several agen- cies and aided by numerous contrivances. When both the essential organs (stamens and pistils) are contained in one and the same flower, as the Rose, Lily, Buttercup, Mint and Grass, it is called a hermaphrodite flower. Many plants possess, either in the same cluster or on different branchlets, both fer- tile (or pistillate) and sterile (or staminate) flowers, and they are said to be monescious (Gr. monos, one ; otkos, house) ; such are the Oaks, Hickories, Alder, Corn, Nettle, etc. Others have the fertile and sterile flowers on different trees, as the Willows, Poplars, Ash, Hemp, etc., and they are described as dicecious (Gr. di, two; otkos, house). In moneecious and dicecious plants it is evident that the transport of the pollen from the staminate to the pistillate flowers must in some way be effected in order to accomplish fecundation. Even in hermaphrodite flowers it is rarely the case that the pollen, wholly unaided, falls on the stigma of the same flower. The topics treated in this chapter call for observation in the field, as well as careful study at the table in the class-room. The structures that are directly or indirectly concerned in pollination must not only be studied anatomically 1The term “ fertilization’? has been used to indicate the transference of pollen as well as to denote the fecundation which follows. To fertilize is to fur- nish nourishment and it is best to use the word only in that sense. For the terms self-fertilization and cross-fertilization used in Darwin’s writings and elsewhere, the words self-pollination and cross-pollination may be substituted. 46 POLLINATION AND FECUNDATION. 47 (for which no additional directions need be here repeated), but also be seen by each pupil when the agencies are in actual operation. Therefore make daily observation at various hours, carefully state the results in the note- book and report in the class-room. The behavior of the various insects vis- iting the flowers, their mode of obtaining nectar, and their agency in trans- ferring pollen and incidentally depositing some of it on the stigma, should be especially observed. The flowers whose pollination is effected by the wind as well as those pollinated through the agency of insects, should be critically studied. The teacher can prolong this phase of the work accord- ing to disposable time and opportunity for visiting blooming plants in suf- ficient variety. 2. When the pollen from the anthers of a perfect flower is applied to the stigma of the same flower the process is called self-pollination, or close-pollination. But if the pollen of one flower is applied to and germinates on the stigma of a different flower, it is called cross-pollination. It would naturally be expected that in hermaphrodite, 7. e. perfect flowers, self-pol- lination would almost invariably obtain. But it is known that cross-pollination is the rule and self-pollination the exception. In fact, there is in the majority of cases something in the structure of the flower to prevent self-pollination. Some plants, however, as the Oxalis, Violet, etc. have two sets of hermaphrodite flowers—a showy form, in which cross-pollina- tion occurs, and an inconspicuous form where self-pollination necessarily takes place. 3. When the transport of the pollen is effected by the wind, the flowers are said to be anemophilous (Gr. anemos, wind ; philos, loving). Such are the Pines, Oaks, Hickory, Walnut, Alder, Grasses, Sedges, Hemp, Hops, etc. They are character- ized by the production of an enormous quantity of pollen. This insures the contact with the stigma of at least a small portion of the pollen. It is light, dry, incoherent, and readily transported great distances. The flowers are mostly greenish, or of dull colors and inconspicuous. The stigmas are gener- ally large, often furnished with hairs or dissected into plumes, for the retention of the grains that may come in contact with them. The anthers are often suspended on capillary filaments so as to be more directly exposed to the action of the wind. 48 ELEMENTARY BOTANY. 4, When pollination is effected by insects, the flowers are said to be entomophilous (Gr. entomon, insect ; philos, loving). In these the amount of pollen produced is not so great, there being but little waste as compared with the loss when trans- ported by the wind. It is not so dry and incoherent as in the anemophilous flowers ; the grains are generally moist or slightly viscid, often provided with projections or entangling threads. In the Orchids and Milkweeds the pollen is in masses, sup- plied with viscid pedicels. All these contrivances tend to in- sure the adherence of the pollen grains or masses to the head, legs, or usually hairy body of the insects which visit the flowers, and thus incidentally effect the transportation of the pollen to the stigmas of other flowers. Such flowers are fur- ther characterized by the possession of a large colored corolla or other showy parts of (or adjacent to) the flower, or of odor, or by the secretion of nectar ; they are often gamopetalous and frequently irregular; or they may furnish all these attractions combined. 5. Of the special adaptations in hermaphrodite flowers to insure cross-pollination, dichogamy is an important one; it means that the stamens and pistil of the same flower do not come to maturity at the same time, hence self-pollination is impossible. The flower is proterandrous (Gr. protos, first; andres, stamens) when the anthers ripen and discharge the pollen before the stigma reaches maturity. If the stigma is in a receptive condition before the pollen escapes, the flower is proterogynous (Gr. protos, first; gyna, pistil). Among the anemophilous flowers the common Plantain furnishes an ex- ample of proterogyny. The long, slender, hairy stigmas may be seen protruding from the unopened perianth while the an- thers are yet enclosed. Only pollen from other flowers, there- fore, can effect the pollination. Later the stigmas wither, and the corolla expands; the four anthers now appear supported on long, delicate filaments and their pollen is carried to stigmas of other Plantain flowers which may have a synchronous maturity. 6. A proterogynous example among entomophilous flowers POLLINATION AND FECUNDATION. 49 is furnished by the Fig-wort (Scrophularia). The flowers are visited by bees for the nectar, which is secreted by glands at the bottom of the corolla. The lower lobe of the irregular corolla serves as a landing-place for the bees. The mature pistil projects (Fig. 69) when the flower first opens; and pol- lination now takes place, the pollen coming from another flower of the same sort. The position of the unripe stamens at this time is not =; seen, for the filaments are curved and the unripe anthers are deep down in the co- rolla. A day or two later, the anthers, now mature, appear at the mouth of the corolla (Fig. 70). By this time the stigma previously pollinated is no longer in a receptive condition, and lies half-withered on the lower petal. Bees visiting the flower, would come in contact with the an- thers, and the pollen grains that adhered to them would be carried to the next Fig-wort (Scrophularia) visited by them. The pistil, if ripe, would retain some of the grains, and pol- lination would thus be accomplished. 7. As an example of a proterandrous flower, may be mentioned “Clerodendron thompsoniz,” a verbenaceous, tropical Fie. 72. Fig. 71. African climber, now common in conservatories. The adapta- tions in this flower are exquisite. The crimson corolla and bright, white calyx in combination, are very conspicuous. The 4 E 50 ELEMENTARY BOTANY. long filiform filaments and style, upwardly enrolled in the bud, straighten and project when the corolla opens; the stamens re- main straight, but the style proceeds to curve downward and backward, as in Fig. 71. The anthers are now discharging pollen ; the stigmas are immature and closed. Fig. 72 represents the flower on the second day, the anthers effete and the fila- ments recurved and rolled up spirally, while the style has taken the position of the filaments, and the two stigmas, now separated and receptive, are in the very position of the an- thers the previous day. The entrance, by which the proboscis of a butterfly may reach the nectar at the bottom, is at the upper side of the orifice. The flower cannot self-pollinate. A good-sized insect flying from blossom to blossom and plant to plant, must transport pollen from the one to the stigma of the other.” (Gray.) 8. The composite flowers, such as the Rudbeckia, Heliopsis, Sunflower, etc., are additional examples of proterandry. The an- thers are united so as to form a tube, the pollen being early dis- charged within. Itis pushed out of the tube by the elongating pistil, which is not as yet in a receptive condition. Moreover the pollen cannot be applied to the stigmatic surfaces, for they are on the inner sides of the forks or branches of the tip of the style. They do not spread until the pistil has acquired its full length, and then curving outward, the adjacent pollen is still prevented from access to the stigma. The conspicuous ray-flowers doubtless serve for the attraction of the many vis- iting insects, and they, by their more or less hairy bodies, con- vey the adhering pollen from some of the flowers to the ex- posed stigmas of others; and thus cross-pollination is effected. Other proterandrous flowers are the Gentians, Epilobium, Campanula, Parnassia, Lobelia, etc. The stamens in Lobelia are like those in the Sunflower family, that is, united by their anthers and forming a tube around the upper portion of the style. The pollen is discharged while the style is yet so short as to be concealed deep down in the tube (Fig. 73). As the stigma approaches maturity, the style elongates and pushes the pollen out before it; the mouth of the tube is so situated POLLINATION AND FECUNDATION. 51 that insects entering the throat of the corolla, for the purpose of getting nectar, would necessarily brush the pollen on to Stigma Fig. 73. Fic. 74. Fig. 75. Fic. 76. their bodies from the end of the protracted stigma (Fig. 74). The stigmatic surface finally becomes exposed (Figs. 75, 76). It is evident that self-pollination is impossible; and cross- pollination by the insects, which transport the pollen from flowers in the first stage of maturity to those in the second stage, must take place. 9. Dimorphism (Gr. di, two; morphe, form) denotes the ex- istence of two kinds or forms of hermaphrodite flowers of the same species. It is often an adaptation for intercrossing. An example is furnished by the Houstonia. One set of flowers has long stamens and a short pistil (Fig. 77), and the other set has short stamens and a long pistil (Fig. 78). A bee visiting the different flowers would brush some part of its body against Mf Fig. 77. Fig. 78. the anthers of the long stamens, and another part against the anthers of the short stamens; and these same parts (which, of course, would have pollen adhering to them) coming in 52 ELEMENTARY BOTANY. contact with long and short pistils respectively, the pollen of one flower would in each case be applied to the stigma of an- other flower ; or, in other words, cross-pollination would neces- sarily result. It is found, besides, that the pollen grains of the two sets of stamens are of different sizes, and each less active upon its own stigma than upon the stigma of another flower. In some genera three sets of flowers with stamens and pistils of differing lengths exist (trimorphism), evidently designed for intercrossing. 10. There are other adaptations for cross-pollination besides dichogamy and dimorphism. . An interesting case is furnished by papilionaceous flowers ; for example, the Pea (Figs. 79-81). Fie. 80. The ten stamens and single pistil are enclosed within the keel. There are hairs on the style below the stigma, and these loosely retain the pollen which is discharged early by the an- thers, the latter remaining in the keel. When a bee alights on the wings and keel of the flower, they are together pressed downward, and the pistil protrudes in consequence. The stigma strikes the abdomen of the bee, and the style also brushes against it. When the bee visits the next flower, the stigma of that one strikes the abdomen as before, but it has been dusted with pollen from the previous flower, and of course a portion of it is retained by the stigma, thereby effecting cross- pollination. In like manner pollen from that tlower is car- ried to the next, and so on. POLLINATION AND FECUNDATION. 53 11. A slight variation from the foregoing is seen in the Bean blossom, where the keel is coiled into asnout. Within this are the stamens, also the pistil with an oblique stigma and a hairy style, the latter loosely retaining the early discharged pollen. When a bee, in alighting to search for nectar, presses the wing-petals downward, the stigma and hairy style loaded with pollen protrude, striking the front part or side of the in- sect. Therefore, visiting a succession of flowers, the bee trans- ports pollen from one to another. In the Mountain Laurel (Kalmia) the anthers of the ten stamens are lodged in cavities in the corolla, and the filaments are curved backward as the flower expands (Fig. 82). Bumble-bees, hovering over the Fie. 82. Fie. 83. flowers, searching for nectar, liberate the stamens by occa- sional contact, which, in springing back straight, discharge the pollen from pores (Fig. 83) at the top of the anthers. Some of the pollen-grains which strike the under side of the bumble- bee and adhere to it, will, when the next flower is approached, be deposited on its stigma, thus bringing about cross-pollination. 12. The most varied and wonderful contrivances for cross- ing are found in the family of Orchids (Fig. 84). The stamens are generally reduced to one and this is united in a column with the pistil, indicated by the term gynandrous (Gr. gyna, pistil ; andres, stamens). In case of some of the species the pollen in each anther-cell is united into a mass, and furnished 54 ELEMENTARY BOTANY. with a little stem, or caudicle, which has a very viscid disk. These two disks are so placed that when an insect visits the flower and thrusts its proboscis into the spur for the nectar, they will touch and adhere to its head, and be dragged from their place when the insect departs. The pedicels dry quickly and curve downward ; when, therefore, the insect approaches another flower of the same kind, the pollen masses, or pol- linia as they are called, strike against its viscid stigma, and a portion of the pollen is retained. The pollinia of this flower are in the same manner transferred to the next vis- ited, and so on. When access to insects is prevented, no seeds are produced, showing that self-pollination is impossible. 13. Many tropical plants cultivated in the conservatories invariably fail to produce seed. The cause of this is to be found in the fact that the tropical insects which alone can effect their pollination are not present. It is not at all seldom that only a certain species, or at most, only a few species, of insects can pollinate a particular kind of flower. Thus in case of the Yucca, a certain minute insect (Pronuba), after in- serting its eges in the ovary, ascends the stamens and pro- cures pollen ; it then mounts the pistil and deposits the pollen on the stigma. In the absence of this species of insect no seeds are formed. Many of the adaptations for crossing, it should be remembered, do not absolutely prevent self-pol- lination, so that if insects fail to visit the flowers a few seeds may, nevertheless, be produced. When the flowers are evi- dently arranged to favor self-pollination and prevent crossing, they are said to be cleistogamous (Gr. Aleistos, closed ; gamos, union). But no known species is altogether cleistogamous. 14. Examples of cleistogamy are furnished hy one set of flowers of Viola, Oxalis, some Grasses, etc. “ Their petals are rudimentary, or quite aborted; their stamens are often re- duced in number with anthers of very small size, containing very few pollen-grains, which have remarkably thin, trans- parent coats, and generally emit their tubes while still en- closed within the anther-cells; and, lastly, the pistil is much reduced in size, with the stigma in some cases hardly at all POLLINATION AND FECUNDATION. 55 developed. These flowers do not secrete nectar, or emit any odor ; from their small size, as well as from the corolla being rudimentary, they are singularly inconspicuous ; consequently insects do not visit them, nor could they find an entrance if they did. Such flowers are, therefore, self-pollinated yet they produce an abundance of seed. In several cases the young capsules bury themselves beneath the ground, and the seeds are there matured.” (Darwin.) 15. The pollen that has been deposited on the mature stigma absorbs some of the moisture that is present, and immediately germinates. The outer and more brittle layer in the covering is ruptured; the inner and more delicate layer protrudes in the form of a tube (Fig. 85). This grows downward through the style, absorbing nourishment from the loose tissue through which it passes. It finally reaches the ovule, or organ in the ovary that is to become the seed. The ovule is at this time an oval or roundish body—being an outgrowth from a portion (the pla- centa) of the interior of the ovary. It is enclosed in one or two coats (integu- ments) that have grown up over it from the base. The integuments do not unite at the top, but leave a small orifice— designated by a term having this mean- ing, namely, micropyle. It is through the micropyle that the pollen-tube passes into the interior of the ovule and reaches the enlarged cell or sac called the embryo-cell (Fig. 85). The protoplasmic contents of the pollen- grain pass into and down the pollen-tube. A nucleus from the pollen-tube fuses with a nucleus contained in the embryo- cell. This process is called Fecundation.' As a result of fecundation a course of development begins which results in 1 The less appropriate term “ fertilization ’ has generally been used in text- books. 56 ELEMENTARY BOTANY. the formation of an embryo, or minute plantlet. This gradu- ally encroaches upon the tissue within the ovule, absorbing a part or all of it for its own growth. In some species the embryo at maturity is comparatively small ; in others it occu- pies the entire volume of the mature seed, covered only by the testa or seed-coat. 16. The embryo consists of a slender stem, or caulicle, hay- ing at one end a bud called the plumule, and at the other a root-tip called the radicle; it also has one or more seed- leaves called cotyledons. The nourishment which is stored up in the seed to nourish the plantlet during germination, may be largely in the tissue of the seed that surrounds the embryo; or it may be wholly deposited in the cotyledons, which in that case are much thickened or fleshy. The number of cotyledons is constant for the two large groups of plants, as their names indicate, Monocotyls and Dicotyls. As already pointed out, the plants constituting the group called Monocotyls have generally the following associated characters :—(1) One cotyledon, (2) woody strands irregularly scattered through the pith, (8) par- allel-veined leaves, and (4) usually three-parted flowers. The Dicotyls have (1) two cotyledons, (2) woody strands or a woody cylinder encircling the pith, (8) netted-veined leaves, and (4) mostly five-parted flowers. But few exceptions to the preceding statements occur in our flora. All the points enumerated in the last two paragraphs cannot be fully studied without the aid of the compound microscope. If the teacher can exhibit prepared microscopic specimens, the statements of the text can be more sat- isfactorily understood and appreciated. CHA PTEE RE. ViItIi. THE FRUIT. —050% oo ——_ 1. Tue first great purpose of the plant is to attain its own development as an individual organism. The second, equally important, is the production of seeds, or reproduction of its kind. The seeds with the ovary which surrounds them, and any additional adnate parts that may be present, con- stitute the Fruit. The ripened ovary with the enclosed seeds form the fruit in a very large number of our com- mon plants, as the Buttercups, Bean, Larkspur, Tulip, Wheat, etc. In the apple and similar fruits the calyx-tube which adheres to the ovary becomes very much enlarged and juicy. The fruit in this case consists of the ripened ovary and adnate calyx. The strawberry consists mainly of the enlarged and juicy end of the stem—which is called the torus. In case of the Rose, the fruit— called the Aip—is a hollow torus containing the ovaries, being al- most closed at the top. The fig is a similar fruit, but within the torus were many flowers instead of a single one (Fig. 86) as in the Rose. The pineapple, mulberry, pine-cone, etc. also result from the union of several flowers. Such are designated as multiple fruits. A search for fruits of the native plants will result in a collection of rep- resentatives of all the kinds mentioned in this chapter. These should be carefully studied in the class-room and properly arranged. Figures of the various kinds of appendages designed for assistance in the dispersion of 57 58 ELEMENTARY BOTANY. seeds, should be made. In short, practical work of the kind mentioned in previous chapters should also here be faithfully carried on. Fruits and seeds should as far as possible accompany herbarium specimens of the species of plants (see last part of Chapter XI.). They can be enclosed in paper pockets, which are to be glued to the species sheet. 2. Many of the dry fruits are dehiscent, that is, break open at maturity. Examples of such are those of the Columbine, Shepherd’s Purse, Pea, etc. Indehiscent fruits, or those that remain closed at maturity, are seen in case of the Maple, Thistle, Gourd, Apple, Grape, ete. This class includes both dry and fleshy fruits. Very many kinds of fruits have special names, only the most common being here mentioned. Two monolocular dehiscent fruits that are formed of a simple pistil are the follicle and legume. The follicle ruptures at maturity along one side only—that which corresponds to the united edges of the carpellary leaf (Fig. 87). The fruit of the Peony, Larkspur, etc. are examples of the follicle. The legume splits into two parts at maturity—one line of separation correspond- ing to the united edges, and the other to the mid-rib, of the carpellary leaf (Fig. 88). The pods of the Pea, Honey-locust, Redbud, Clover, etc. represent the lezume. 3. The term capsule denotes a dehiscent fruit or pod of any compound pistil, as of Purslane, Violet, etc. A modifi- cation of this is seen in the fruit of the plants of the Mustard Fig. 88. Fie. 89. Fie. 90. family, where the pod has two parietal placentas, from which the two valves forming the wall separate; it is called a THE FRUIT. 59 silique (Fig. 89). A very short silique like that of the Shep- herd’s Purse, Pepper-grass, etc. is called a silicle (Fig. 90). A winged one-seeded indehiscent fruit is called a samara (Fig. 91). The fruit of the Elm, Ash and Wafer-Ash are examples; that of the Maple is a double samara. In the Sunflower, Dan- Fig. 91. Fia. 92. delion, Wild Lettuce, Anemone, etc. the fruit is dry, mono- locular, one-seeded and very much resembles a seed itself; such a fruit is called an akene. The nut, as the hazelnut, acorn, hickory, is like an akene but larger and is often en- closed or surrounded by a kind of involucre called a cupule (Fig. 92). 4. The most common fleshy fruits that have received spe- cial names are the drupe, pome and berry. The drupe is illustrated by examples like the peach and the cherry; the outer part is fleshy and the inner is hard or stony. The pome has several carpels of parchment-like or stony texture surrounded by a fleshy covering. The apple, pear, quince, and Hawthorn fruit are familiar examples. The berry is a fruit which is fleshy throughout, as the grape, tomato, cur- rant, cranberry, banana, etc. 5. Very many fruits are furnished with appendages which are important organs for their dissemination. Conspicuous among these may be mentioned the membranous wings seen in the Maple, Box-Elder, Elm, Ash, etc. Fruits furnished with such an appendage will be readily transported, by the wind, often to considerable distances. The fruits of the Thistle, Dandelion, etc. are still better equipped for such transporta- 60 ELEMENTARY BOTANY. tion. Their light dissected parachute or fluffy ball is the modified form of the calyx, called the pappus. The wing- like bract doubtless renders the fruit cluster of the Basswood more buoyant and transportable by the wind. Many fruits have barbs, hooks or prickles by which they lay hold of ani- mals or the clothing of man and in this manner are often car- ried great distances. Such are the fruits of the Beggar-ticks (Bidens), Tickseed (Coreopsis), Tick-trefoil (Meibomia), Bur- grass (Cenchrus), etc. In the Burdock the involucral scales are hooked and the whole head of fruit is often carried from the plant on which it grew. The prickly fruit of the Cockle- bur also represents an involucre and its assistance in distribu- tion is similar and very effectual. 6. Fleshy and edible fruits are, it is true, often eaten and wholly destroyed; it might therefore seem that the produc- tion of an edible part would be a detriment to seed-disper- sion. But in very many cases the seeds escape uninjured. Indeed the importance of such fleshy or edible portions in effecting the distribution of the seed is such that we may regard that as their proper and only function. Many seed- coats are so firm as to resist for along time the action of water. The seeds may therefore germinate after being trans- ported long distances by river and ocean currents. In several cases, for example, Witch Hazel and Touch-me-not, the pods burst in such a way as to throw the seeds some distance. 7. The seeds of pods that break open at maturity are in some cases furnished with appendages that aid in the dissem- ination. Those of the Trumpet Creeper and Catalpa have conspicuous thin wings. In the former these entirely sur- round the seed; in the latter they extend mainly from the two ends and terminate in a hairy fringe. In the Milkweed and Epilobium each seed is surmounted by a tuft of long deli- cate hairs which are very efficient aids to its distribution. The Cotton plant produces in a dehiscent pod, seeds that are completely covered with very long hairs, which constitute the cotton of commerce, and which for the plant are important contrivances for seed distribution. Seeds often lie dormant THE FRUIT. 61 for a long time and then finally germinate when favorable conditions obtain. It is estimated that a large Elm produces upward of half a million and a single Tobacco plant and many other weeds ten to forty thousand seeds, numbers which are small in comparison with those of the spores (cor- responding functionally to seeds) produced by Puff-balls and other Fungi. This great fecundity should be borne in mind when considering the dispersion of plants. The spores of the lower plants are extremely small, and they can be readily transported by the slighest breeze. They are found literally everywhere, as the universal occurrence of Moulds, Mildews, Blights, etc. testifies. F CHAPTER. LX, THE CELL AND TISSUE. 03300 —_ 1. Sections taken from the various parts of the plants are shown by the aid of the microscope to consist of small sac- like bodies (Fig. 93). These structural units are called Cells. Those which are isolated, as pollen grains, spores of Smut, etc. are nearly or quite globular; so also are the cells of pith. Fig. 94. But in stems they are usually crowded closely together, and become many-sided by mutual pressure; they are often also much elongated. In leaves the outer layer of cells is com- pact; in the interior they are sometimes nearly globular, or often quite irregular in shape; there are comparatively large spaces between them. Occasionally cells are star-shaped, as in the tissue of the Rush (Fig. 94). Sometimes they are very irregular and branching, as in the common Moulds. While a laboratory and compound microscopes are indispensable for a full and satisfactory study of cells and tissue (which, however, belongs to an ad- vanced course in Botany), yet by the aid of figures in the text, and the help of a good pocket lens, the essentials of this portion of the subject may 62 THE CELL AND TISSUE. 63 be profitably studied. The work can be made much more valuable, if a compound microscope can be used for the exhibition of prepared mounts that illustrate the parts of the cell, the cell-contents and the various kinds of tissue, etc. 2. The cells in the tissues of common plants are, with few exceptions, microscopic in size. The majority of them are between one-hundredth and one-thousandth of an inch in diameter. In bast tissue they are much larger. Plant hairs often consist of a single cell and are usually large enough to be detected by the unaided eye. Sometimes they are very long, as some Alge, the milk-vessels in some Spurges, and the cotton, which consists of unicellular hairs from the seeds of the Cotton-plant. Many cells, on the other hand, are extremely small. The unicellular plants called Yeast and Bacteria are examples of such. The transparent, nearly round Yeast-cells are about three ten-thousandths of an inch in diameter. The Bacterium termo, or common fungus which causes putrefaction, consists of a cell about nine hundred-thousandths of an inch long and little more than half as wide. 8. The vegetable cell usually consists of four parts which are readily distinguishable, namely, protoplasm, nucleus, cell- wall and cell-sap (Fig. 95). The Protoplasm is a nearly Nucleus Protoplasm Fre. 95, ; Fia. 96. transparent, more or less granular, usually semifluid sub- stance. A denser small globular portion within, called the nucleus, is usually visible. The protoplasm is the essential part of the cell. In it,all the vital activities are manifest and 64 ELEMENTARY BOTANY. when it disappears the cell is dead. It is very complex both in structure and composition. Its constituents are albumin- oids (containing oxygen, hydrogen, carbon and nitrogen), a variable amount of water, and a small quantity of ash or mineral constituents. 4. The protoplasm secretes the cell-wall. This consists of cellulose, which is composed of carbon, hydrogen and oxygen (but no nitrogen), also water and ash, or mineral constituents. The cell-sap is a watery fluid containing plant food in solu- tion. It fills the apparent vacant spaces, called vacuoles, in the cell and also permeates the protoplasm. The cell has no wall or covering in the earlier stage of its existence. In a few cases none is ever formed, at least in the vegetative stage or that preceding the reproductive period. The free protoplasm can in such case swim about, as the so-called Swarm-spores (Fig. 96) are seen to do. Or it may creep about, as do the Fig. 97, Fie. 98. Slime-Moulds. When the protoplasm is enclosed in a wall it may yet manifest movements. In some cases there are slen- der streams moving about in various directions, mostly from the central to the parietal portions and in the reverse direc- THE CELL AND TISSUE. 65 tion. This is called the circulation (Fig. 97) of the proto- plasm. In other cases it moves as a broad stream around the cell-wall. This movement is called the rotation (Fig. 98). 5. The cell wall often remains quite thin. In some of the bast-cells, in wood-cells and many others, it becomes very thick; but its growth in thickness is not uniform. Only a spiral band becomes thickened in very many cases; occasion- ally a thickened ring or annular band is formed. Sometimes the whole wall except small circular areas here and there at- tains a considerable thickness. Simple pits in the wall result from such growth. Bordered pits are formed in the wood- cells of the Pine family. The sides of the pit arch over as growth in thickness proceeds—the upper margin thus making the inner ring, and the bottom of the pit the outer ring, when re Sena ° Shee log C2 ‘feRACHe fokeg a “Jokes . (oka 42 q A Blo) Nav aye co AS B ORS AZ - (OheZ 44 JoketeLki2 PSA Ve Fig. 99. viewed on the side of the cell. In some cells the thickened portions are at the angles and extend across at short and regu- lar intervals, being thus scalariform, that is, like a stairway or slightly resembling the rounds of a ladder. Occasionally the 5 66 ELEMENTARY BOTANY. thickening has a reticulate or net like form (Fig. 99). In the case of isolated cells, like pollen grains and spores, spines, papille, or ridges are occasionally developed. 6. The important substance called leaf-green, or chlorophyll (Gyr. chloros, green ; phyllon, leaf), is found in many cells of the common plants. It is a green coloring matter which is solu- ble in alcohol, ether, chloroform, etc. When it is removed by these solvents a protoplasmic grain remains. Chlorophyll de- velops in cells exposed to sunlight or electric light. Plants with chlorophyll will gradually lose their color if placed in the dark. The importance of this substance in plant nutri- tion is evident from the fact that only in cells containing chlorophyll is mineral, or inorganic, matter changed—while exposed to light—to organic, or vegetable material. Those plants which are destitute of chlorophyll, for example the Fungi and a few other plants, as Indian Pipe, Dodder, etc., cannot live on mineral matter but must absorb their digested food from living plants or decaying material. Such plants can grow in the dark. Put in a vial of alcohol some bits of green leaves and in a day or two note the solution of the chlorophyll. Cover up some green plants with soil or put them in a dark room, or put a board over the grass, and after several days note the bleaching, or disappearance of chlorophyll. Let potatoes sprout in the cellar and the stems will remain white. 7. Starch is formed in the chlorophyll-bearing cells. It is always in the form of grains (Fig. 100). These are oval in the potato, elliptical in the bean, elongated and very irregular in Euphorbia splendens. They are very small in corn, wheat, rice, ete. The starch grains of the potato are distinctly visible with a good lens. The average or commonest size, as well as the shape, is constant in each species of plant, but they vary exceedingly in both these respects in different species. When Fia. 100. THE CELL AND TISSUE. 67 starch is examined under the microscope a nucleus is seen in the larger grains and around it are numerous concentric layers. Starch after its formation in the chlorophyll becomes dissolved, and is transported to growing parts and at once consumed in the formation of the vegetable fabric; or it reappears in the form of starch in reservoirs, stored up for future use, as in seeds, tubers, bulbs, roots, stems, etc. Other products are formed in cells, as oils, organic acids, alkaloids, resing, salts, sugars, etc. Scrape the freshly cut and moist surface of a potato, bean or grain of wheat or corn and a quantity of starch will be obtained. Add to it a drop of dilute iodine solution (made by dissolving a bit of potassium iodide in a little water and adding a very small grain of metallic iodine, till a cherry-red solution is obtained) and note the deep-blue coloration. This is the test for the presence of starch. Examine also with the lens. Make with a sharp blade very thin slices of various tissues, as potato-tuber, bean, twigs, etc., put them under the lens and then add a little of the iodine solution. Some- times the stem of the Oxalis, Begonia or other plants have also crystals that can be seen with the lens when very thin sections are examined. 8. Though each plant begins its existence as a single cell, or simple mass of protoplasm in the embryo cell, all but the unicellular species very soon become many-celled. This mul- tiplication of cells is brought about by the division of the first cell into two. Each of these after increasing in size divides into two, or four in all. The resultant four divide into eight and so on indefinitely. A microscopic study of the process of division shows it to be very complicated, and its elucida- tion will not be attempted here. Suffice it to state that the nucleus takes the initiative; after it divides into two portions, the protoplasm becomes separated into two masses, a new cell- rall being formed between them and two distinct cells are the result. The increase in the size of plants is then due to an increase in the number of cells. Countless millions are to be found even in a plant of moderate size. It has been de- monstrated that though the protoplasm is surrounded in each case, and apparently isolated, by a cell-wall, yet minute pro- toplasmic threads reach from each mass through the walls to 68 ELEMENTARY BOTANY. adjacent ones. By this continuity of protoplasm an intimate union of all parts of the individual plant is established. 9. The cells in the very early development of the plant, and those in simple plants, are nearly or quite alike. Later they may take on different shapes and functions. Several kinds of tissue can then be recognized. In our common her- baceous and woody plants there may be found three distinct systems, namely, the epidermal, the woody strands, and the fundamental tissue. The first of these includes the epider- mis, the hairs and scales, and the stomates. The epider- mis (Fig. 101) is the external compact layer of cells, pro- tecting the more delicate tissue ee —r below. Outgrowths of the epi- TT Tn dermal cells form hairs. These may be one-celled or they may Cre 1 SETA become several-celled ; they may Le iets : be simple or become branched; co ee cde Bh sometimes they are glandular at the tip. The general function of the hairs is to protect the parts on which they grow, but in special cases they have other duties to perform ; for example, the rhizoids (root-hairs) absorb food from the soil. Scales are composed of many cells, and like the hairs, they represent modified epidermal cells. 10. The stomates are very small openings through the epi- dermis. They are popularly spoken of as ‘* breathing pores,” since the oxygen, as well as other gases, passes through them. One of their very important functions is to convey from the interior of the leaf the excessive amount of moisture which the roots absorb in taking up the necessary mineral matter for food. Examination with the microscope shows that the sto- mate is an opening between two cells, which are called guard- cells. These are very different in outline from the other epi- dermal cells. Each is nearly half-moon shaped, the two joined together being broadly oval or spherical (Fig. 102). They con- tain chlorophyll, which is not usually present in the other epi- dermal cells. In section also they appear different from the Fig. 101. THE CELL AND TISSUE. 69 other cells (Fig. 103). Immediately below each stomate is an air-cavity and from this there is communication with the large spaces between the cells in the interior of the leaf. Though the size is small yet the number of the stomates is enormous. Fie. 102. For example, in the leaf of the Anemone there are about 43,000 to the square inch on the under side, none on the upper. On the upper side of the leaves of the Indian Corn there are about 60,000 and on the lower surface about 102,000 Fie. 103. to the square inch. In the leaf of the Sunflower there are about 112,000 stomates above and about 209,000 below. In the leaves which float on the water stomates occur only on the upper side. They are wholly wanting in submersed leaves. 11. The woody strands (called also fibro-vascular bundles) can be easily separated from the other tissue in the stems of Indian Corn, of the Plantain leaf, etc., but microscopic ex- amination is necessary to determine their structure. In one 70 ELEMENTARY BOTANY. type of strands, that from the monocotyledonous stems (Fig. 104), there are two kinds of tissue, namely, the wood and the bast. These are shown in Fig. 105. In the other type, that from the dicotyledonous Strand Fie. 104. Fie. 105. stems, the strand consists of wood, cambium, and bast (Figs. 106 and 109). The cambium cells are thin-walled, rich in Fie. 106. Fia. 107. protoplasm and capable of division. If microscopic sections are not available, an inspection of the figures given may convey a general idea of the structure of the strands and the development of the woody stems and tissue of the tree trunks. THE CELL AND TISSUE. 71 12. Two of the strands begin development simultaneously on the opposite sides of the pith (Fig. 107), in case of the dicotyledonous stem. Later two others appear (Fig. 108), and Bast Cambium Fie. 108. Fie. 109. very soon numerous strands are present which together form a continuous ring (Fig. 109; other parts of this figure, also of Figs. 107 and 108, are the pith, the cortex, and the epidermis). As the wood in each strand is on the pith side, the fusion of the strands results in the formation of a ring of wood adja- cent to the pith. It is evident also that a continuous ring of cambium would be formed, and outside of this a ring of bast. In the following season the cambium renews its growth, the cells are multiplied, and those next to the wood formed the first year are changed to wood cells; on the opposite side some of the cambium cells become bast. The cells of wood formed in the early spring are usually larger than those formed in the latter part of the growing season, and hence the rings or cylinders of growth for each year are distinctly seen in most trees (Fig. 110). The entire portion exterior to the cambium: may be designated as bark. In the outer por- tion of the bast, corky plates or corky layers are developed ; these and the external lifeless bast cells form the dry, often furrowed, dead bark. 13. The original tissue, or that from which the epidermis and woody strands are developed, is called the fundamental 72 ELEMENTARY BOTANY. tissue. The pith and cortex belong to this, as do also the cells in the medullary rays. The latter are seen as radiating lines in the woody stems (Fig. 111). Some of them extend from the pith. These had their origin in the compressed tis- Medullary rays Fre. 110. Fig, 111. sue between the encroaching woody strands. The cells of the medullary rays are longer in the radial direction, whereas the other lignified cells of the trunk have their vertical diameter Growing point TO ‘Root-cap Fig. 112. Fia. 113. much longer than their other dimensions. In lumber where they are especially conspicuous, as in Oak, etc., the medullary rays are called the “silver grain.” The milky juice (latex) is THE CELL AND TISSUE. 73 contained in special elongated cells called the laticiferous ves- sels. Cork tissue is composed of cells whose walls are thin and impermeable to liquids and gases. 14. The growing point of stems and roots is composed of delicate cells, thin-walled and rich in protoplasm. By their multiplication the stems and roots are lengthened. The scales (leaves) of the bud cover the growing point of the stem (Fig. 112).