a New York State Qollege of Agriculture At Cornell University Dthaca, N. BY. Library 482.M2 “mit THE TREE BOOK OF THE WOODS SY S A DELICATE GIP E BIRCH I HIT THE W THE TREE BOOK BY INEZ N. McFEE Author of “Boys and Girls in Many Lands,” “American Heroes from History,” ete. WITH FIFTEEN ILLUSTRATIONS FROM PHOTOGRAPHS NEW YORK FREDERICK A. STOKES COMPANY PUBLISHERS Copyright, 1919, by Frreperick A. StoKES CoMPANY All Rights Reserved “A man who plants a tree and cares for it, has added at least his mite to God’s creation.’’ —Lucy Larcom FOREWORD Iw this little volume the author has brought together an interesting fund of information concerning the life history of the common spe- cies of American trees, and such foreign species that have been acclimated here, as one may or- dinarily meet in garden and forest, together with the folk-lore and poetic fancies associated with them. In The Infe and Work of the Trees, the sug- gestions for interpreting the sign language of the trees lead the young student into the open to gather all manner of interesting facts con- cerning the hopes and disappointments of the trees about him, the trouble with their neigh- bors, the secrets of age, how they prune them- selves, and how they take care of cuts, bruises and broken limbs. How the trees grow, and the record of the year’s work from the stirring of the sap and the coming of the first fruit and leaf buds, to blossom-time, and on to seed-time and sowing, the falling leaves, and the sleep of the trees, is most fascinatingly told. The reader travels from the nethermost root to the Vii Vill FOREWORD tip-top leaf laboratory, taking in all the wonders along the way, and it is a marvelous journey! He can but feel at its close how truly wonderful are the trees, and how little most people appre- ciate their real worth and beauty. Why trees die, and what we may do to help protect and save them, is explained in the section, ‘‘Some Enemies of the Trees.’’ The student is led to see that trees are like men. They have their prime and their decadence. They are subject to a host of natural enemies and to diseases and infirmities which gradually bring about their downfall, in spite of the fact that each year their working forces are made new, and that they have within themselves the symbol of immor- tality. In the second part of the work, ‘‘The Kinds of Trees,’’ all the important tree families are con- sidered. The principal individuals are intro- duced in such a way as to make them lasting friends, and there is a fund of legend and folk- lore which is most interesting. The third and last part, ‘‘The Forester and His Work,’’ differs slightly in treatment from what has gone before. It is hoped that the inti- mate study of the trees will lead young readers to entertain a personal feeling for them. Per- chance there may be some who will wish to be- FOREWORD ix come champions of their forest friends and to take up some day the study of forestry in real earnest. If so, this chapter will answer many preliminary questions. It gives an idea of the breadth and scope of the great subject of for- estry and shows in brief the life and work of the forester. A hint is also given concerning the interesting details of tree botany, and of the sci- entific possibilities in laboratory work. CONTENTS I THE LIFE AND WORK OF THE TREES CHAPTER PAGE I WaHat tHE TREES ARE. . . ... 38 II Reapine Signs . . .... . . 40 III How Trees Grow ..... . . 19 IV Fruir anp Lear Bups. ... . . 2 V Buossom-TIME ..... . . . 86 VI Basy Leaves. . ...... . 49 VIL Seep-Time anp Sowing. . . . .. . 88 VIII Seepuinecs anp SHOOTS. . .. . . 67 IX Faunce Leaves. . .... . . 88 X Tue SLEEP OF THE TREES . . . . . 95 XI Soms ENEMIES OF THE TREES. . . . 102 II THE KINDS OF TREES I Tue Micoty Oak . .... . . 123 TI Tae Maptzs. ....... . 182 III Tae Eum Fammy ...... . 189 IV WILLows AND Popuars. . . . . . 146 V Tue Beech . . ..... . . 154 VI Waunuts AnD Hickorms . . . . . 162 x1 xi CONTENTS CHAPTER VII VIII IX x XI XII XIII XIV Locusts AND OTHER PoD-BEARERS . THE BIRCHES . THE ASHES a a CHESTNUTS AND CHINQUAPINS . Tue Basswoops or LINDENS . EVERGREENS THE MULBERRY . Hotty AND MISTLETOE . Tit THE FORESTER AND HIS WORK Tur FORESTER AND His WORK . PAGE . 169 . 178 . 186 . 198 . 200 . 204 . 213 . 215 . 221 Acknowledgment is made to The United States Department of Agriculture, Forest Serv- ice, Washington, D. C., for use of photographs of trees reproduced in this volume. LIST OF ILLUSTRATIONS The White Birch is a delicate elpsy of the woods ae oe . . Frontispiece FACING PAGE The Black Oak is a large, loosely headed species 34 The Red Oak has a rounded, dome-like top. . 35 The Shell-bark Hickory has rough, shaggy bark 68 The White Ash is found in aoe well-watered places . 69 The American Elm as it grows in Maseachusetts 98 Weeping Willows along the Potomac River. . 99 The Red Maple is called ‘‘The a of the Forest’? .. 5 . 134 The Sugar Maple is a tavorite Sine is: . . 185 The American Beech is known by. its smooth, sil- ‘very bark . . . . 166 A Black Walnut tree believed to fe a venta: old 167 The Horse Chestnut possesses the streets in many of our towns . ...... . . 198 The Basswood or American Linden is a amely tree. . , é . 199 The Balsam Fir — a iene -green n foliage wit a silvery under surface . . . 222 Among the pines the White Pine is the fallent stateliest and best-known. . . . . 223 THE TREE BOOK I THE LIFE AND WORK OF THE TREES THE TREE BOOK I WHAT THE TREES ARE Tus trees are among the very best gifts of God, but they are so common that we do not half appreciate their worth. We accept their shade and beauty as a matter of course. Occasionally some poet reminds us that: Each breeze a message brings,— “‘Be brave,’’ from Oaks and Cedars, “‘Look up,’’ the Pine tree sings, ‘Oh, earth is fair,’’ the Elm calls, ‘And Heaven is just above!’’ “‘Do good,’’ the Maples whisper, All chorus, ‘‘God is love.”’ The oak tree is pointed out as an example of rugged strength; the pine typifies constancy; the beech, with its low, wide-spreading branches, is a picture of hospitality; the birch, in its wrap- pings of silver gray, ‘‘shows that beauty needs 3 4 THE TREE BOOK not to make gorgeous display’’; the ash teaches resistance in every strong fiber: and soon. Be- yond this we are not apt to go. The real uses of the trees in providing shelter, food, and rai- ment, and their value in the economic plan of Nature are as nothing. For instance, how many know that if the for- ests were cut down our country would soon be- come a desert? The roots of the trees, extend- ing deep into the earth, are constantly bringing up water and discharging it into the air as mois- ture. It is said that the largest steam boiler in use, kept constantly boiling, could not evaporate more water than one large elm would in the same time. We have been in the habit of thinking that the clouds get most of their moisture for rainfall from the vast ocean. But they do not. By far the better part of it is drawn up from the soil through the trees and plants. Here is a little experiment which you may try in proof of this: Take two glasses of equal size and fill them with water. Place them in the direct sunlight in the © open air. Into one put a few cuttings of grow- ing plants with their leaves; let the other stand idle. In a few hours the water will disappear from the glass containing the plants, while that in the other glass will scarcely be diminished. WHAT THE TREES ARE 5 If you were to keep the glasses going, no doubt the one containing the cuttings would throw off gallons of water, before a single gill would evap- orate from the other glass. So you see that the proportion of moisture exhaled from any given surface of ground is vastly greater when cov- ered with trees and plants, than when covered with standing water. Thus we come to one of the first great uses of trees: they are the most important agents of Nature for conveying the moisture of the earth into the air. If a, few cuttings will evaporate a half-pint of water in twelve hours, how much more would be exhaled by a tree! And what would a grove of trees accomplish! Over a forest, as over a lake, there rests always, in calm weather, a stratum of invisible moisture. This moisture is a good conductor of electricity, and may be the direct . means of bringing down a shower. Electricity is always of more or less importance in the clouds. A cloud is made up of millions of little vaporous particles suspended in the air and held apart by a law of electricity which allows them to come nearly together but will not allow them to touch. The effect of the electric current is lessened by cold and increased by heat. So that, in summer, when earth and air are both heated, and drought has prevailed for some 6 THE TREE BOOK time, electricity plays a very important part in- deed in the clouds. It holds the little vapor particles apart, and the clouds float hither and yon till the electricity gets a chance to escape. This is where the trees sometimes help. A forest of trees, with their multitude of tiny branches, is like so many lightning-rods, pre- senting their millions of points both for the dis- charge and absorption of electricity. When the cloud reaches the damp stratum of air above the trees, its electricity is attracted by the numerous vegetable points below; the electricity eagerly seizes the conductor offered; the particles of vapor rush together, and the whole comes down in a copious shower. Thus, trees may be the direct agents in producing rain. As there is a layer of moisture above the woods, so there is a layer of dry, heated at- mosphere above the plains. Sometimes a rain cloud, floating toward the dry section, is drawn out of its course—attracted by the stratum of damp air, above the woods along a river valley, and this section gets the rain which the plains really need far more. Again a dense electric cloud will pass over our heads, without shedding a drop of rain, until it reaches the ocean, when the cool, moist air above the waves, acting as a conductor, causes the cloud to part with its elec- WHAT THE TREES ARE 7 tric fluid, and to fall in heavy rain at the same moment. Trees and groves are considered a protection to buildings near them. But it is not safe for men and animals to take refuge under a tree in the open plain. Lightning is supposed to be conducted by the water passing down on the sur- face of the branches and trunk, rather than by the tree itself. Ifthe tree acted as a conductor, the lightning would pass through the trunk into the ground, and the tree, like a true lightning rod, would be a protection to objects near, so long as they do not touch it. Some trees are thought to be more exempt from lightning than others. Hugh Maxwell, an American writer, says: ‘‘Lightning often strikes the elm, the chestnut, the oak, the pine, and less frequently the ash: but it always evades the beech, the birch, and the maple.’’ Pines are said to be safe when growing among oaks. Tiberius, the cruel and lawless Emperor of early Rome, used to don a crown of laurel leaves when a thunder storm threatened, under the belief that lightning never touched the leaves of this tree. Not only are the trees a safeguard against drought, but they are a considerable protection against floods and overflow. In Holland, Bel- gium, France, and Germany willows are planted 8 THE TREE BOOK as a protection to river banks. In our country they plant themselves. Their long, rigid roots are invaluable in binding together the loose shifting soil of sand dunes and bars. Their foliage decays and helps to form a soil in which other trees and plants can live and thrive. Trees everywhere are great makers of soil. You will understand this better if you dig up a little soil in the forest or grove. Under the loose dry leaves you will find leaves in all stages of decay: lower, you will find a dark soil, called leaf mold; below this is a loam made by filter- ings from the leaf mold; and lastly the soil of that particular locality. Trees, planted upon a hill-side, fertilize and irrigate the lands below and protect them from winds. Trees are of untold value in purifying and renovating the atmosphere. Trees take in the deadly carbonic acid gas, which is produced in immense quantities by the decay of animal and vegetable matter, by the breath of animals, and by all fires in which wood, gas, coal, or petrol- eum is burned; and by some process, recorded only in the closed book of Mother Nature’s se- crets, decomposes it and gives forth pure atmos- pheric air. Of course, the plants, too, aid in this process of purification: but as all the plants united are not equal in bulk to the trees, it is WHAT THE TREES ARE 9 safe to say that if the forests should be de- stroyed the world would be sadly crippled in its supply of life-giving oxygen, nay more, the atmosphere would be without a source for re- generation. Men and animals, every form of life, would perish from the face of the earth. Trees are also of immense importance in af- fording shelter to birds and beasts of the forest, and in the many productions which they furnish. to mankind. These productions or ‘‘Gifts’’ are too numerous to be mentioned here. Suppose you pause a moment and see how many of them you can name off-hand. It is possible to write a list as long as your arm, and then the half will not have been recorded! But at any rate you will have additional proof of the inestim- able value of the trees. The industry of forestry is second to agri- culture in the number of people and amount of capital employed and in value of product. IT READING SIGNS Trees speak a sign language, which is easily understood if one has the patience to study it, and from it we may gather all manner of in- teresting facts concerning their hopes and dis- appointments, the trouble with their neighbors, the secret of age, how they prune themselves, how they take care of cuts and bruises and broken limbs, and their struggle with the long catalog of tree diseases, most of which are as catching as the measles or the whooping-cough. The best way to study this sign language is among the trees themselves. So let us hurry away to the woods! Here we find the trees jostling each other, like rude boys in a crowd, the big fellows conquering the weaker ones and pushing them aside. All are eagerly reaching upward and outward for the sunlight which makes life possible. Close at hand our sharpened eyes detect a smooth spot on the rough bark of an oak. What does it mean? That spot marks a place Io READING SIGNS 11 where once a limb projected. For some reason, probably from lack of light and leaf, due to crowding neighbors, the limb died, decayed, and broke off near the trunk of the tree. Nature patched the rent. The bark is smoother than the other, only because it is younger. Hach year the bark of the tree grows thicker and heavier. A little farther on is a tree with a large knot hole. As we look at it wondering, an incautious woodpecker backs out and flies off with a startled ker-r-ruck. Did he make the hole? No. At least he did not begin it, though he may possibly have drilled it a little deeper. It, too, marks the place of a former limb. This limb was slower in dying than the other, and it broke off so far from the tree that Nature could not possibly cover the stub. So, as the years have passed, the limb has gone on decaying deeper and deeper into the trunk of the tree. Over here is a branch, dead but not fallen. Let us find what steps Nature has taken to prune this. Ah! See here is a sort of collar around the base of the dead branch. Next spring, when the tree wakens to active growth, a new layer of young wood will be spread all over the living trunk and branches. About the ill-fated branch no new wood can form, because 12 THE TREE BOOK the cambium layer, which promotes the new growth, is dead. New wood, however, will be added to the collar which encircles it. This will go on year after year, unless some outside force intervenes; the collar will grow tighter and tighter and the pressure of the young wood will become so strong that the old dead wood will be pinched and ready to snap at the first chance. A gust of wind, a heavy fall of snow, or even its own weight may break it off finally. Each new year’s layer of wood will build around the ring encircling the dead stump, until finally its disk will be covered by a patch of smooth bark, such as we noted on the first tree. In the course of a few years this, too, will vanish, and the record of the dead branch will be buried forever, unless perchance the tree is felled and the action of saw or axe brings the stump disk to light. Here is a great, lengthwise scar on the trunk of a towering old monarch of the forest. What does it mean? Surely it is not an example of Nature’s pruning? No, indeed. It is the work of Jack Frost. See, it is on the southwest side of the tree. Probably after a succession of warm days, the tree was deceived into thinking spring at hand: the rootlets began to drink thirstily, and the water they absorbed moved READING SIGNS 13, upward through trunk and branches. Then, suddenly, winter came howling back and the “‘sap’’ froze, making a great ugly split or wound in the tree. Probably that was years ago, when the tree was young and vigorous. Nature set to work at once to grow new wood over the wound. In time the scar will probably entirely disappear. Should such an accident happen to-day, the tree would, no doubt, be too old to repair the damages, and the wound would become a point of attack and way of en- trance for a horde of insect: enemies, which would soon bring death in their wake. Let us look about a little and find the stump of a tree cut recently. Note that it appears to be made up of numerous rings, one within an- other. Begin in the center and count outward. Forty-seven rings! A ring for each year. A study of the rings close to the pith or center shows them to be very close together. Prob- ably the little seedling was shaded by older neighbors growing near it, possibly, too, they greedily robbed it of water and soil nourish- ment. At the seventeenth ring the circles begin slowly to widen. Something evidently in- creased the tree’s vigor, possibly some of its nearest.neighbors were cut down: it gives every proof of having started to grow lustily. The 14 THE TREE BOOK rings go on showing increase in width to the very last—a mute record that the tree fell in the very prime of life. On stumps with a greater record of rings, we find the circles get- ting nearer together on the outward side, show- ing that trees, like people, lose their vigor as they grow old. Trees usually cease to grow rapidly in height after their fiftieth year. It is not always necessary to cut down a tree in order to tell its age. Each twig and branch bears a record of years, written in the scars of bud scales and leaves. A branch finishes its year by forming buds. In the spring it starts to grow by casting off the scales that protected the buds from the cold. The scales leave a little group of scars to mark their place. So the length between each two groups of scale scars represents a year of growth. Beginning with any little tree you can easily count its age from tip to base. The oldest branches are a year younger than the main stem. Every branch, large or small, must be a year younger than the stem that bears it. The youngest wood bears buds in winter: in summer all the leaves are borne directly upon shoots that grew from the winter buds. With these clews in mind, test your knowl- edge. Here is a certain stem you think is five READING SIGNS 15 years old. Cut it off and see if you can count five rings around its pith. If so, your judg- ment is correct. It would be well to try this experiment a few times; then you are ready for older trees. A twig that gets the most light and air shows the lustiest growth, and hence is easier to read. And remember bud scales al- ways mean winter or a year of growth. Frequently we find branches that tell a story of poverty and woe most plainly. Here is a tiny twig that grew in the shadow. It is small and weak. It did not have enough to eat or drink. Probably it could not even breathe freely. It was crowded and jostled all season. It made a very short growth and scarcely in- creased at all in diameter. A most unhappy little twig in the midst of others that fairly shouted freedom and independence! Verily want and plenty, misery and happiness, exist side by side, even in the realms of the tree tops! Their trail is a pathway of tragedy and cun- ning, for always there is battle and murder in the heart of the buds. And the survival is to the fittest here, as in any other walk of life. Each leaf bud set on the twigs is a branch in miniature. Naturally it opens with high hopes to become a leafy shoot. Should all the buds 16 THE TREE BOOK achieve their ambition, what would be the re- sult? Let us figure a moment. Here is a twig with three shoots rising from a common point. Each bears side buds, scattered along, less than an inch apart; and a cluster of stronger ones at the tip. Last summer a leaf marked «the place of each side bud. And they were not too close. But suppose each bud increases this year to a spray of ten leaves? It would mean about three hundred leaves on a two year old branch scarcely twelve inches long! Naturally, the plans of a large percentage of these minia- ture sprays or twigs must be ‘‘nipped in the bud.’’ Some are too weak ever to enter the con- test. The others contend in a silent, continuous strife for room, for food, and for sunshine. We may learn whole volumes in ethics by just keeping an eye on them, for truly they have a patience and courage almost sublime, and an eye quick to perceive their opportunity. Those farthest out have the best chance. They quickly attain full size, and shade and starve out the unfortunate strugglers beneath them, so that vigor and a favorable situation are the magic keys. Usually death to the side shoots and the persistence of one or two of the terminal ones is the rule. Always Nature shapes to serve the best interests of the whole tree. And she has READING SIGNS 17 a sort of life insurance plan that is most ideal. Among the buds sacrificed, a few are kept dor- mant, that is asleep for a year or two, waiting for any emergency that may arise. If an acci- dent cuts off the shoot above them, they spring into action and carry on the business of that particular branch, which is to keep itself ever growing toward light and space, lest some envi- ous neighbor outdistance it and ‘‘throw it in the shade.’’ Because of their craving for light, trees have a tendency to grow straight toward the zenith, no matter on what slope they may find them- selves. Look about you for the crippled trees —those bent by storms or partially uprooted by accident. They tell some wonderful stories of perseverance and fortitude, in their efforts to attain the upright. A little study of the trees in any region plainly shows the strength and direction of the prevailing winds. Knowledge of this enables the forester to make a compass of the tree tops. The soft, tapering top-most shoots of the pines and hemlocks, bowing be- fore the breeze, are guides more trustworthy than brass-buttoned policemen. All this is but a beginning in the interesting study of sign language. One skilled in the art says: ‘‘It has the fascination of detective 18 THE TREE BOOK work. After your first successes, you find your- self questioning every tree you meet... . The old apple tree by the roadside challenges you to make out the story of its eventful life. You can learn to read the record of last year’s crop. You can tell exactly how many fruits a particu- lar branch has ever borne, and even whether they reached maturity or were picked green. The promise of next year’s crop is revealed to you, though you cannot foretell whether the flowers will be frosted. The veteran recites to you its past successes and failures, declares the year it came into full bearing, the time of the big wind or the ice storm that broke so many large limbs, and you can even give a shrewd guess as to whether the tree has been a profitable in- vestment or not. It is as if the owner kept an account with each individual tree and opened up to you his book of record for this one.’’ Iii HOW ‘TREES GROW A TREE is made up of three important parts— the roots, the trunk or stem, and the leaves. Altogether it is a combination of earth elements, water, and buoyant, invisible gases—the latter comprising about one-half. If we burn a stick of wood in the open air, those parts akin to it pass off in the form of gas: the water goes up in invisible steam; that which is left, the ashes, is of the earth earthy. The ashes never comprise more than one-tenth the weight of the dry timber. All the rest is but a vapor and a breath! Think of it. The alchemist that magically constructed a strong and mighty tree of these primary ele- ments is the leaves. No fairy tale is so won- drous as the work they do. Besides serving as lungs for the tree, each leaf is a tiny laboratory in itself, devoted principally to the manufac- ture of starch. It obtains raw materials from the air and from the soil. The sun furnishes the power. The machinery is the soft green leaf-pulp. 19 20 THE TREE BOOK The watery parts of the wood, which pass off as vapor when it burns, come into the tree by way of the tiny root hairs which reach out in every direction to find plant food. Much of the gases which go up in flame and smoke have en- tered by the same lowly door, as elements of the soil water. All must be worked over in the leaf laboratories before it can be used to build new tissue. There are regular avenues leading from the roots to the leaves and back again. Raw material travels in one: elabor- ated, life-giving sap in the other. The upward route is by way of the youngest fibers of the sap wood. The return trip is made through the inner bark or cambium, by way of slender, thin- walled tubes, of most delicate tracery. Given the proper elements, leaves can make ‘‘not only wood, but cork, the tender petals of flowers, the flesh of fruits, and a large number of gums, oils, essences, and perfumes, which have become indispensable in art, manufactures, and medicine.’? How wondrous must be the machinery compressed between the thin leaf walls! Let us see what we can find out about it, with the aid of a compound microscope. First: We note that the leafy skeleton—the - veins and arteries—divides and subdivides into the tiniest capillaries, a perfect network of HOW TREES GROW 21 woody threads. The leaf veins connect with larger tubes in the leaf stalk and these in turn are joined to tubes in the branch. Second: Filling in the spaces between the network, is a green pulp, which somewhat re- sembles honey comb in arrangement. It is made up of rows of cells. Each cell is a little bag of delicate transparent skin, filled with colorless jelly. This jelly is called protoplasm —‘‘the thing first made’’—and looks very much like the white of an egg. We are told that it contains six ingredients: oxygen, hydrogen, car- bon, nitrogen, phosphorus, and sulphur. The proportion varies according to the supplies taken in. Third: Wenote that, though the protoplasm, or cell jelly, is itself clear, it is so full of float- ing specks of vivid green, that these give their color to the whole leaf. These specks are called chlorophyll bodies. Chlorophyll forms only in the direct light of the sun. Baby leaves, just peeping from the bud scales, appear in various colors. They have, as yet, little or no chlor- ophyll. As one authority puts it: ‘‘The sun has not yet given them their working outfit.’’ Fourth: Over network and cells stretches a protective transparent leaf skin, or epidermis. The thickness of this skin varies to suit climatic 22 THE TREE BOOK conditions, the object being to prevent the sun from drying up the leaf juices. The India-rub- ber tree, of the East Indies, has a leaf skin com- posed of three layers of cells. Always the leaf skin must be thin enough for the water which constantly streams up from below to evaporate readily, otherwise the starch factory would soon be submerged! Fifth: To aid in this work of evaporation, the lower leaf-skin is full of little pores, for the easy passage of air and vapor. Some leaves have such pores on the upper surface too, and they are found on green stems and young branches less than a year old, and also on green fruit. These little pores or mouths are called stomata. It is through the leaf stomata that the great quantity of vapor, which we have al- ready spoken of, rises from the trees. The lit- tle mouths swell up whistle-shape in wet weather and collapse in times of drought. So smooth and polished is the leaf-skin that, in a rain storm, most leaves shed water like tiny um- brellas. On a bright summer day, the leaves of a good sized tree will make over a pound of starch. To do this several hundred pounds of soil water must be taken in, sorted, and passed off in vapor. Starch is the vital food for all plant HOW TREES GROW 23 life. It is made up of carbon, hydrogen, and oxygen. The carbon is drawn from the car- bonic-acid gas absorbed by the leaves; the hy- drogen comes from the soil water soaked up by the roots; some of the oxygen comes in by way of the roots, the balance is breathed in by the green stems and the foliage. Miss Going, in her book With the Trees, tells us that: ‘‘The newly made starch in leaves appears in tiny grains inside the chlorophyll bodies or close beside them. It does not re- main there and grow into larger starch grains, but with the withdrawal of sunlight it seems to melt away. It has been changed into fluid glu- cose, and this travels slowly along, passing through cell wall after cell wall, till it reaches some growing part of the tree, where it is used at once, or some resting place where it is turned into starch again, and stored away to meet the needs of the future. In spring all the starch which the leaves can make is changed to glucose, and used immediately, for growth. But in lat- ter summer the tree puts it by. It may be saved in wood or pith to feed next spring’s blossoms and shoots, or it may be packed into seeds and support the tree’s children during their in- fancy.’’ The wood of a tree is not active. Neither is 24, THE TREE BOOK the bark. But between wood and bark, from root tip to twig end is the cambium, through which, you remember, the sap avenues descend. This is the important factor in the life of the tree proper—the carpenter, if you please. It builds new root and bark, lengthens branches and roots, and adds to the girth of the tree, using the material supplied by the leaves. The cambium is made up of millions of cells. Always the cells have a disposition to increase in size and divide in two parts. This division goes on so long as the food supply lasts. Thus one cell may increase to two, four, eight, sixteen, thirty-two, sixty-four, ete. A new layer of woody tissue and one of bark is formed by the cambium each year, adding to the tree’s thickness just that much. The cam- bium never adds to its own width, but remains always a thin layer of dividing cells, ambitious only to add to the bark on one side and the wood on the other.