Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924000575484 ‘ie BOTANY ALL THE YEAR ROUND A PRACTICAL TEXT-BOOK FOR SCHOOLS BY E. F. ANDREWS HIGH SCHOOL, WASHINGTON, GEORGIA NEW YORK -:. CINCINNATI -:. CHICAGO AMERICAN BOOK COMPANY c &! kK’ uf 7 A St Cs ‘ia / CopyYRIGHT, 1903, BY E, F. ANDREWS. ENTERED AT STATIONERS’ Hatt, Lonpon. ANDREWS’S BOTANY. W.P.tT Csr, 4) PREFACE Most of the recent text-books of botany, excellent as many of them are, fail to meet the conditions of the average public school, where expensive laboratory appli- ances are out of the question, and time to make a proper use of them is equally unattainable. It is one of the anomalies of our educational system that the study of plants, if provided for at all, should be confined mainly to city schools, where it is necessarily carried on under disad- vantageous conditions, while it is almost entirely neglected in the country, where the great laboratory of nature stands invitingly open at every schoolhouse door. The writer believes that this neglect is largely due to the want of a text-book suited to general use, in which the subject is treated in a manner at once simple, practical, and scientific. It is with a desire to meet this need and to encourage a more general adoption of botanical studies in the public schools that the present work has been under- taken. It aims, in the first place, to lead the pupil to nature for the objects of each lesson; and in the second place, to provide that the proper material shall be always avail- able by so arranging the lessons that each subject will be taken up at just the time of the year when the material for it is most abundant. In this way the study can be carried on all the year round, a plan which will be found much better than crowding the whole course into a few weeks of the spring term. In order to provide for this all the year round course it has been necessary to depart somewhat from the usual order of arrangement, but years of experience have convinced the writer that the advantages to be gained by having fresh 3 4 PREFACE material always at hand are sufficient to outweigh other considerations that might be advanced in favor of estab- lished methods. The leaf has been selected as the starting point mainly because it is the most convenient material at hand in September, when the schools begin; and it is such an important and fundamental part of the plant that a thorough acquaintance with its nature and functions will clear the way to an understanding of many of the problems that will face the student later. It is not expected that all the work outlined in the book will be done just as it is written, and much of it may even have to be omitted altogether. Each teacher can select such parts as are suited to the circumstances of his school, passing lightly over some topics, giving more attention to others, as material and opportunity may suggest. The study of botany is necessarily sectional to some extent, because nature is so, but the method here outlined is of universal application and every teacher can select his own specimens in accordance with the directions given in the body of the book. Prominence is given to the more familiar forms of vegetation presented by the seed-bearing plants, as the author believes that for ordinary purposes the best results are to be obtained by proceeding from the familiar and well known to the more primitive and obscure forms. The reverse order may be better for the trained investigator; the other is simpler and more attractive, and for ordinary purposes the only practicable one. The average boy and girl will learn more of what it concerns them to know about stem structure, for instance, from a cornstalk, and a handful of chips, or even from the graining of the timber out of which their desks are made, than from the most elaborate study of the xylem and the phloem and the collenchymatous tissues. For we must bear in mind that the object of teaching botany in the common schools is not to train experts and investigators but intelligent observers. In giving the botanical names of plants the terminology of Gray’s handbooks is adhered to, partly because they PREFACE 5 are at present the most generally available for school use, and more especially because the new terminology is in such an unsettled state that nobody can say what it will be to-morrow or next day. Hence, while recognizing the desirability of some of the changes proposed, the author does not think it advisable to confuse the beginner by introducing him to a system that is undergoing a period of transition. After all, this is a mere matter of names, and does not affect the point that ought to be kept in view — the hereditary relationships of plants. The experiments described are for the most part very simple, requiring no appliances but such as the ingenuity of the teacher and pupils can easily devise, as will be seen by a glance at the list on pages 12 and 13 of the text. Teachers trained in normal schools, where all the material needed for their work is furnished by the State, and ample time allowed them, are often completely at a loss when transferred to country schools, where no provi- sion is made for laboratory work, and the patrons grumble if called upon to buy so much as a drawing book or a hand lens. Too often they can think of no other resource than to drop botany from the curriculum altogether rather than depart from what they have been taught to consider the only scientific method. Itis hoped that the present volume may suggest a better way out of the difficulty, and also that it may be a help to those who have not enjoyed the advantage of a technical training. The writer would not underrate the value of histological studies or the advantages of a well equipped laboratory, but since these are at present clearly out of the reach of the great majority of the school population, and more especially of that very class to whom the study of plants is of the greatest practical importance and into whose lives it would bring the greatest amount of pleasure and of intellectual enlargement, it has been made the aim of this book to show that botany can be taught to some pur- pose by means within the reach of everybody. It has also been the author’s aim to keep constantly in view the 6 PREFACE intimate relations between botany and agriculture. The practical questions at the end of each section, it is hoped, will have the effect of bringing out these relations more clearly and at the same time of leading the pupil to reason for himself and draw his own inferences from the common phenomena about him. The author takes pleasure in acknowledging here the many obligations due to Dr. C. O. Townsend of the United States Department of Agriculture for his very effective assistance in revising the manuscript of this work ; also to Professor Charles Wright Dodge of the University of Rochester, and Professor W. F. Ganong of Smith College for valuable criticisms and suggestions. Acknowledg- ments are also due to Messrs. D. Appleton and Company, for permission to use illustrations from Coulter’s “ Plant Relations” and ‘“ Plant Structures,” copyright, 1899, and to the owners of Gray’s Botanies, to Professor William Trelease of the Missouri Botanical Garden, to Mr. Gifford Pinchot of the United States Department of Agriculture, and to Mr. W. S. Bailey of the Chautauqua Bureau of Publication, for permission to reproduce illus- trations from their publications. Quite a number of the figures used are from original drawings by pupils of the Washington, Ga., High School. II; III. IV. Vi. VI. VIII. CONTENTS . INTRODUCTION . THE LEAF: ITS USES— Transpiration; Respiration and Food Production; The Typical Leaf and its Parts; Veining; Branched Leaves; Phyllotaxy, or Leaf Ar- rangement; Leaf Adjustment; Transformations of Leaves; Field Work Fruits — Fleshy Fruits; Dry Fruits; Indehiscent; Dry Fruits; Dehiscent Fruits; Accessory, Aggregate, and Collective Fruits; Field Work SEEDS AND SEEDLINGS — Monocotyledons and Polycoty- ledons; Dicotyledons; Forms and Growth of Seed; Germination; Seedlings; Growth; Field Work ROOTS AND UNDERGROUND STEMS — Function and Struc- ture of Roots; Fleshy Roots; Sub-aérial Roots; Underground Stems; Plant Food; Field Work THE STEM PROPER — Stem Forms and Uses; Stems of Monocotyledons; Stems of Dicotyledons; Movement of Water through the Stem; Wood Structure; Field Work : ‘ : ‘ : Bups AND BRANCHES — Branching Stems; Buds; Inflor- escence; Field Work THE FLOWER— Hypogynous Monocotyledons ; Epigynous Monocotyledons ; Dicotyledons ; The Corolla; Suppres- sions, Alterations, and Appendages; Nature and Office of the Flower; Pollination; Field Work . EcoLtocy — Ecological Factors; Plant Societies; Field Work PAGE 15 63 87 120 142 173 8 CONTENTS X. SEEDLESS PLANTS — Their Place in Nature; Fern Plants ; Study of a Bryophyte; The Alge . XI. Funci— Their Classification; Mushrooms; Rusts; Field Work SYSTEMATIC BOTANY . APPENDIX INDEX . PAGE 250 271 286 289 297 BOTANY ALL THE YEAR ROUND —-c- 094 00—_ I. INTRODUCTION 1. General Statement.— Botany is the science which treats of the vegetable kingdom, but the subject is so com- prehensive that it has been divided into many branches, each of which is a science in itself. For instance, there are Mycology, the study of mushrooms and other fungi; Bacteriology, the study of the microscopic forms con- cerned in the process of fermentation, and in the pro- duction of disease; Paleobotany, the study of fossil plants —and many others, with which we have no concern at present. Each of these studies may be viewed under various aspects, and these in turn have given rise to still other divisions of the subject, such as, — 2. Morphology, or Structural Botany, the study of the different organs or parts of plants in regard to their form and uses and the various changes and adaptations they may undergo. 3. Histology, or Plant Anatomy, the microscopic study of the minute structure of plant organs. This can not be carried on well without the use of the compound micro- scope and other appliances not obtainable in many schools. Something, however, may be learned from a few simple ex- periments, accompanied by intelligent observation with a hand lens, and it is only in so far as it can be carried on by ordinary means like these, that this branch of the sub- ject is touched upon in the present work, 9 10 INTRODUCTION 4, Vegetable Physiology, the study of the action of liv- ing plants and their organs, their mode of growth and re- production, and their various movements for adjustment to their surroundings, as the attraction of roots toward moisture and of leaves toward light. 5. Ecology, the study of plants in their relations to ex- ternal conditions, or, to use a more convenient term, their environment. This is one of the most interesting and important of all the departments of botany, and presents many points of direct practical concern to the farmer. 6. Taxonomy, called also Systematic or Descriptive Botany, the study of plants in their relationships to one another. Its work is to note their resemblances and differ- ences, and by means of these to classify or distribute them into certain great groups called families or orders, and these again into lesser groups of genera and species. This work of classification was formerly considered the chief end of the study of botany, which thus too often de- generated into a mere mechanical drill in hunting down plants and labeling them with hard names. The ten- dency at present is to ignore this part of the subject altogether, which is nearly as great a mistake as the old- fashioned error of thinking that the study of botany con. sisted merely in learning a string of hard words. One of the chief pleasures to be derived from botanical studies, for most of us, consists in being able to know and recog- nize the various plants we meet with. The first thing we all ask on seeing a new shrub or flower is, ‘“‘ What is it ?” and this question can be answered satisfactorily only by referring each to its proper class or order. 7. Learn to know the Common Plants. — These five sub- divisions make up the study of botany, as generally taught in the schools. They apply to all plants, and the only practicable way for most of us to learn them is by a study of the common vegetable life about us. INTRODUCTION it 8. Definitions. — “Organ” is a general name for any part of a living thing, whether animal or vegetable, set apart to do a certain work, as the heart for pumping blood, the lungs for breathing, or the stem and leaves of a plant for conveying and digesting the sap. By “function” is meant the work or office that an organ has to perform. 9. The Cell. — In its strictly scientific sense this word is applied to the smallest portions of organized matter that go to make up a living body, whether vegetable or animal. It usually consists of a tiny membra- nous sac lined with a living semifluid substance called protoplasm, which ordinarily has one portion of denser consistency than the rest, called the nucleus. Nithin the protoplasmic lining are contained various watery fluids known as cell sap. These little sacs are packed together to build up the vegetable or animal structure as bricks are in building a wall. They 1.—Typical cells: 2, nu- are of various sizes and shapes. The ase i ee containing membrane is called the cell wall. Cells can exist, however, without any wall, as mere specks or globules of protoplasm, but these are not common in vegetable structures. The essential part of every cell is the protoplasm with its nucleus. This sub- stance, so far as we know at present, constitutes the physi- cal basis of all life, and if the protoplasm loses its vitality, the cell dies and can no longer perform its functions of absorbing and retaining liquids. Slice a fresh beet in a vessel of water and a boiled one in another; how is the liquid affected in each? Account for the difference. The name “cell” is also applied to the compartments into which the fruits and seed vessels of many plants are divided. This double meaning of an important term is unfortunate, but the context will always show in which sense it is to be taken, so that no confusion need result. 12 INTRODUCTION 10. Tissue is a term used to denote any animal or vege- table substance that is composed of a particular kind of material and that performs a particular office or function. Thus, for instance, we have bony tissue and muscular tissue in animals; that is, tissue made of bone substance and of muscle substance and doing the work of bone and muscle respectively. So in plants, we have woody tissue, or tissue made of woody substance, and vascular tissue, or tissue made up of little conducting vessels, which have their especial functions to perform. 11. Appliances needed for General Use.— The only appli- ances necessary for the study of this book, besides the material furnished by the: woods and fields about us, are so few and simple that there can be no difficulty in pro- viding them. The following list comprises about all that are essential :— Half a dozen glass jars; preserve jars or wide-mouthed bottles will answer. Half a dozen soup plates or other shallow dishes for germinators. Some good-sized bits of window glass for covering jars and dishes. : A garden trowel. A good hatchet for use when the study of timber is taken up. A very sharp knife—a razor is better, if it can be obtained — for making sections. A small whetstone for sharpening knives. A vial of tincture of iodine. A pint of red ink; or, if preferred, a good coloring fluid can be made by purchasing an ounce or two of eosin from the druggist and mixing it with water. A pot of photograph paste. If a yard or two of India rubber tubing, a common bulb thermometer, and a pair of druggist’s scales are added to the above list, the number of experiments that can be per- formed will be considerably increased. INTRODUCTION re 12. Appliances for Individual Use.— In addition to the general outfit for the school, each pupil should be pro- vided with — A good penknife. A drawing book (or drawing paper) and a blank book for taking notes. A book for dried specimens, made by sewing together two or three sheets of unsized paper, such as newspapers are printed on; this can be purchased from a printer. Two well-pointed pencils, one hard, the other medium. A pair of dissecting needles; wax-headed steel pins will do, but better ones can be made by running the heads of ordinary sewing needles into handles of soft wood and gluing them in. Two bits of glass, not larger than a visiting card, as thin and clear as can be obtained, for inclosing specimens that must be held up to the light for examination. The glass plates sold for photograph negatives serve well for this purpose. A good hand lens. The glasses known as “linen testers”? can be purchased for twenty-five cents apiece, and make very good magnifiers. A special place ought to be provided in the schoolroom for storing all these articles, and the strictest order exacted in the care of them. They should always be ready when wanted, and never used for any other purpose. 13. Living Material. — A number of potted plants should always be kept in the schoolroom, especially in cities, for observation and experiment. Among those recommended for this purpose are the following : — One or two ferns. A calla lily, or other arum. A young India rubber tree (Ficus elastica). A pot of “wandering Jew” (Zebrina pendula). The plain, green-leaved varieties are best. Some kind of prickly cactus. The common prickly pear (Opuntia) and the Mamillaria make good specimens. 14 INTRODUCTION A sedge; the umbrella plant (Cyperus alterntfolius) or the Egyptian paper plant (C. papyrus), so common in greenhouses, will either of them do very well, though our native wild plants are always preferable when they can be obtained. Healthy plants of oxalis and tropzolum. A twining vine; hop, morning glory, kidney bean, etc. A glass jar with one or two water plants, such as pond- weed (Potamogeton), hornwort (Ceratophyllum), bladderwort (Utricularia), or pickerel weed (Pontederia), etc. TOT LT eae eee 10 4 3.—A comparative ENGLISH SCALE, METRIC SCALE, seale of the Centigrade Four INCHES TEN CENTIMETERS and Fahrenheit ther- : mometers. On the Cen- z.—A comparative scale of the English and tigrade scale o = the metric systems of length measure. One decimeter temperature of melting = Io centimeters = 100 millimeters = approximately ice, and 100° = that of 4 inches. boiling water. II. THE LEAF: ITS USES TRANSPIRATION MATERIAL. — Freshly cut sprigs of various kinds, bearing healthy leaves ; a leaf of the white garden lily (Z. candidumz) or of the wander- ing Jew (Zebrina pendula); two hermetically sealing preserve jars; a little beeswax or tin foil; a bit of looking glass; a number of empty bottles with perforated stoppers or rubber cloth covers. Norte. — In order to avoid cumbering the pages of the text with tech- nical nomenclature, botanical names of specimens mentioned will be given only: First, in the case of foreign or little known species; Second, where the popular name is local or provincial, or where the same term is applied to several different plants; and Third, where special accuracy of designation is required. 14. Why Leaves wither.— Dry two self-sealing jars thoroughly, by holding them over a stove or a lighted lamp for a short time to prevent their “sweating.” Place in one a freshly cut leafy sprig of any kind, leaving the other empty. Seal both jars and set them in the shade. Place beside them, but without covering of any kind, a twig simi- lar to the one in the jar. Both twigs should have been cut at the same time, and their cut ends covered with wax or vaseline, to prevent access of air. At the end of six or eight hours look to see if there is any moisture de- posited on the inside of either jar. If there is none, set them both in a refrigerator or other cool place, for half an hour, and then examine them again. On which jar is there a greater deposit of dew? . How do you account for it? Take the twig out of the jar and compare its leaves with those of the one left outside; which have withered most, and why? 15. Transpiration. — We learn from experiments like the foregoing that one office of leaves is transpiration, or 15 16 THE LEAF the giving off of moisture, just as animals do through the pores of the skin.! Now, we all know what happens to us if the perspiration glands of our body get stopped up, and hence we need not be surprised if hedgerows can not be ‘kept vigorous and healthy by dusty roadsides, nor if even sturdy trees and shrubs take on a sickly look when the summer rain delays too long to give them their accus- tomed bath. 16. Stomata.— The transpiration pores of leaves are called stomata (sing. stoma) from a Greek word meaning “mouths.” Generally they are too small to be seen with- out a compound microscope, but their presence can be made manifest by a simple experiment. Place a bit of looking glass against your cheek or your arm on a warm day, and it will soon be covered with a film of moisture from the skin. Next, place the glass in contact with the under side of a healthy growing leaf for thirty to forty-five minutes, and see if you can detect any moisture on it. The deposit will probably be fainter than that from the skin, but the presence of any at all will show that the leaf transpires. There are a few plants, such as the white lily of the gardens (L. candidum) and the wandering Jew, in which the stomata are large enough to be seen with *a hand lens. 4.—Portion of the he common iris also epidermis of the gar- shows them, though -den balsam, highly ted magnified, showing the not so distinctly. very sinuous walled Strip off from the epidermis cells and ‘ three stomata (after under side of such a 5, 6.—Stomata of GRAY). leaf a portion of the white lily leaf: 5, closed ; ; . ; . §, open (GRAY), epidermis, or outer covering. Place it between two bits of glass with the outside uppermost, and 1 Transpiration, though similar in external effects to the perspiration of ani- mals, must not be confounded with it, as the two functions are physiologically quite different. TRANSPIRATION 17 examine it with a good lens. Hundreds of little eye-shaped dots will be seen covering the surface, which can easily be recognized, by comparison with the accompanying Fig- ures, as stomata. Examine a portion of the epidermis from the upper side of the leaf ; are the 7.—Stomata of an oak leaf: A, a small piece stomata distributed (highly magnified) with under epidermis removed nT both sid to show stomata, g, and minute hairs, 4. B, a equa yon oth si €S, stoma in vertical median section, cut across its and if not, on which Jonger axis; a, intercellular space; g, guard cell; i 5, orifice of stoma. are they thickest? Which side of the epidermis seems to be most active in the work of transpiration ? 17. Distribution of Stomata.— While stomata are gen- erally most abundant on the under side of leaves, where they are protected from excessive light and heat, this is not always the case. Similar openings occur also on young stems, and are called /exticels. In vertical leaves, like those of the iris, which have both sides equally ex- posed to the sun, stomata are distributed equally on both sides. In plants like the water lily, where the under sur- face lies upon the water, making transpiration in that direction impossible, they occur only on the upper side. Succulent leaves, as a general thing, have very few, be- cause they need to conserve all their moisture. Submerged leaves have none at all; can you tell why? ‘18. Protection of Stomata. — In addition to their function of transpiration, stomata permit the entrance to the interior of the plant of atmospheric air containing carbon dioxide, a gaseous substance used by them in the formation of food. If they become choked up with water or other obstruction, the leaves can neither exhale their superfluous moisture nor take in air; hence these pores are protected by hairs, wax, and other water-shedding appendages. Plunge ANDREWS’S BOT. — 2 18 THE LEAF a sprig of the dwarf St. John’s-wort (Hypericum mutilum) or of wandering Jew into water and notice the silvery appearance of the leaves, especially on the under side. In the iris it is the same on both sides; why? Remove the sprig from the water, and the leaves will be perfectly dry. In the wandering Jew, as may be seen with a good hand lens, this is due to the air imprisoned by little mem- branous appendages which surround the stomata and pre- vent the water from entering. In other cases, as cabbage, hypericum, etc., a coating of wax protects the transpiration pores, and it is the reflection of the light from the air entangled in these protective coverings that gives the leaves their silvery appearance under water. 19. Amount of Transpiration. — Few people have any idea of the enormous amount of water given off by leaves. It has been calculated! that an oak may have 700,000 leaves and that 111,225 kilograms of water (about 244,695 Ibs.) may pass from its surface in the five active months from June to October, and 226 times its own weight of water may pass through it in a year. If this seems an extravagant estimate, we can easily make one for our- selves. Fill three bottles with water, and cover them tightly with rubber cloth to prevent evaporation. Mark the point at which the water stands in the bottles, make a small puncture through the covers, and insert into one bottle the end of a healthy twig of peach or cherry, into the second a twig of catalpa, grape, or any other large-leaved plant, and into the third, one of magnolia, holly, or other thick, tough-leaved evergreen, letting the stems of all reach down well into the water. Care must be taken to select twigs of the same age, as the absorbent properties of very young stems are more injured by cutting and exposure than those of older ones. All the specimens should be cut under water if possible, as even an instant’s exposure to the air will greatly diminish the activity of the cutsurface. Peach 1 See Marshall Ward, “ The Oak.” TRANSPIRATION 19 is an excellent plant to experiment with, as its woody twigs are not greatly affected by cutting, and it absorbs water almost as rapidly as it transpires. At the end of twenty- four hours note the quantity of liquid that has disappeared from each glass. This will represent approximately the amount absorbed by the leaves from the twigs to replace that lost by transpiration. Which twig has transpired most? Which least? Note the condition of the leaves on the different twigs; have they all absorbed water as rapidly as they have lost it? How do you know this? Pluck the leaves from each twig, one by one, lay them on a flat surface that has been previously measured off by the aid of a rule, into a square of about thirty centimeters (twelve inches) to a side, containing nine hundred square centimeters (one hundred forty-four square inches), and thus form a rough estimate of the area covered by each specimen. Measure the amount of water transpired by filling up each bottle to the original level, from a common medicine glass, or if this cannot be obtained, use a table spoon, counting two spoonfuls to the ounce. Make the best estimate you can of the number of leaves on each tree, and calculate the number of kilograms (or pounds) of water it would give off at that rate ina day. In one experiment a peach twig containing thirty-one leaves gave off three- quarters of an ounce of water in twenty-four hours; how many pounds would that be for the tree, estimating it to. bear eighteen thousand leaves? As the tissues of a grow- ing plant are much more active than those of a severed branch, calculations of this kind are not likely to exceed the truth, even when we take into consideration the fact that the twig in the experiment has unlimited water, which the roots of a growing plant have not always. These experiments may be varied at the option of the teacher as time and opportunity may permit, so as to test the absorbing and transpiring properties of any number of plants or of the same plant at different stages of growth. They will succeed best in dry, warm weather, as the work of transpiration is then most active, 20 THE LEAF 20. Practical Effects of Transpiration. — Where does all this moisture come from? If the water in the last experi- ment is colored with a little eosin or with red ink, its course can be traced through the stem into the leaves. In growing plants the earth takes the place of our tumbler of water, and from it the moisture is drawn up by the roots and conveyed through the stem to the leaves. Thus we see that trees are constantly acting as great pumps, drawing up water from the lower strata of the soil and distributing it to the thirsty air in summer. As the water given off by transpiration is in the form of vapor, it must draw from the plant the amount of heat necessary for its vaporization, and hence it has the effect of making the leaves and the air in contact with them cooler than the surrounding medium. 21. The Cause of Transpiration.— The reason why plants exhale such large quantities of water is because they get part of their food from mineral and other substances dissolved in the water of the soil, but this food is in such a diluted state that enormous quantities of the liquid contain- ing it must be taken up in order to give the plant the nour- ishment it requires. This liquid travels through the stem as sap, and after all the food substance has been extracted, the waste water is exhaled by the leaves. Sometimes the roots absorb moisture faster than the leaves can transpire it; the water then exudes through the stomata and settles in drops on the blade, causing the leaves to sweat, just as our bodies do under similar conditions. Sometimes, on the other hand, the leaves transpire faster than the roots can absorb, and then the plant wilts. PRACTICAL QUESTIONS 1. Do you see any connection between the facts just stated and the stories of “weeping trees” and “rain trees” that we sometimes read about in the papers? (Section 21.) ; 2. Can you explain the fact sometimes noticed by farmers, that in wooded districts, springs which have failed or run low during a dry spell sometimes begin to flow again in autumn when the trees drop their leaves, even though there has been no rain? (19, 20.) RESPIRATION AND FOOD PRODUCTION 21 3. Other things being equal, which would have the cooler, pleasanter atmosphere in summer, a well-wooded region or a treeless one? (20.) 4. Could you keep a bouquet fresh by giving it plenty of fresh air? (14.) 5. Why does a withered leaf become soft and flabby, and a dried one hard and brittle? (9, 14.) 6. Why do large-leaved plants, as a general thing, wither more quickly than those with small leaves? (14-19.) 7. Is the amount of water absorbed always a correct indication of the amount transpired ? Explain. (20, 21.) 8. Why must the leaves of house plants be washed occasionaily to keep them healthy? (15-18.) 9g. Why is it so hard to get trees to live in a large manufacturing town? (15, 18.) RESPIRATION AND FOOD PRODUCTION MATERIAL. — A green aquatic plant of some kind in a glass of water ; two wide-mouthed glass jars; a bent glass or rubber tube, and a shallow dish of water; boiled bean or tropzolum, or other green leaves; a half pint of alcohol; some tincture of iodine; a strip or two of tin foil. 22. Leaves give off Oxygen. — Place in a glass of water a green aquatic plant of any kind; the common brook silk (Spzrvogyra) found in almost every pool will answer. Set it in the sunlight and place beside it another similar vessel containing nothing but water, and also a third ves- sel containing a piece of the same plant immersed in water from which the air has been expelled by boiling. After a time bubbles will be seen rising from the first vessel. Air bubbles will usually form on the bottom and sides also, but these are caused by the expansion of gases contained in the liquid, as will be evident on comparing them with similar phenomena in the jar containing only water, and must not be confounded with the gas given off by the plant. Remove the vessel from the light, and the bubbles will soon cease to appear, but will begin to form again if restored to the sunshine, thus showing that their produc- tion can take place only in the light. Do any bubbles at all appear in the glass with the boiled water? It has been proved by chemical analysis that these bubbles are oxygen, which the plant has been separating ( 22 THE LEAF from the gases mixed with the water, and giving off. It is even more active in separating oxygen from the air, but the process is not visible to the eye, because we cannot see a gas except in the form of bubbles. Water is used not as an aid to the plant in the performance of its function, but in order to enable us to see the result. 23. Leaves as Purifiers of the Atmosphere. — Fill two tumblers with water, to expel the air, and invert in a shallow dish of water, having first introduced a freshly cut sprig of some healthy green plant into one of them. Then by means of a bent tube blow into the mouth of each tumbler till all the water is expelled by the impure air from the lungs. Set the dish in the sunshine and leave “g.Experiment for showing it, taking care that the end of the how leaves purify the atmos- cutting is in the water of the dish. phere. : After forty-eight hours remove the tumblers by running under the mouth of each, before lift- ing from the dish, a piece of glass well coated with vase- line (lard will answer) and pressing it down tight so that no air can enter. Place the tumblers in an upright position, keeping them securely covered. Fasten a lighted taper or match to the end of a wire, plunge it quickly first into one tumbler, then into the other, and note the result. It is an established fact that a light will not burn in an impure atmosphere; this is why well cleaners send down a lighted candle before going into a well themselves. What are we to infer from the effects observed as to the action of the plant upon the atmosphere ? This experiment will not succeed unless performed very carefully, and the air must be absolutely excluded from the tumblers until the instant the taper is plunged in. 24. Leaves as Food Makers.—It thus appears that plants are constantly reversing the effects of animal res- piration by giving off oxygen and absorbing carbon dioxide from the air. Besides acting as digestive and assimilating RESPIRATION AND FOOD PRODUCTION 23 organs, leaves are the laboratories in which plant food is manufactured out of the crude materials brought up from the soil by the sap, and those absorbed through the stomata from the gases of the atmosphere. Carbon di- oxide taken from the atmosphere is somehow used up in this operation, and the oxygen, which is not needed by the plant, is given back to be consumed by animals. This is the most important work the leaf has to do, and because it can take place only in the light, has been named by botanists Photosynthesis, a word which means “ building up by means of light,” just as photography means “ drawing or engraving by means of light.” 25. Why Leaves are Green.— Has the color of the leaf anything to do with this function? It will help to a correct answer if we remember that herbs grown in the dark, and parasites like the dodder and Indian pipe (Monotropa), which steal their food ready made from the tissues of other plants, and so have no need to manu- facture it for themselves, always lose their green color. Place a seedling of oats or other rapidly growing shoot in the dark for a few days and note its loss of color. Leave it in the dark indefinitely, and it will lose all color and die. Hence we may conclude that there is some intimate con- nection between the action of light and the green coloring matter of leaves. This green matter is called Chlorophyll, a word meaning “‘leaf green,” and physiologists tell us that through its agency the crude substances brought up from the soil in the sap and the carbon dioxide of the air are converted into nourishment. 26. Starch as Plant Food.—It is the office of chloro- phyll to manufacture a particular class of plant foods known as carbohydrates. The commonest and most impor- tant of these is starch, the presence of which can generally be detected without much difficulty. Boil a few leaves of bean or sunflower, tropzolum, etc., for about fifteen min- utes, and soak them in alcohol until all the chlorophyll is dissolved out. Rinse them in water, and soak the leaves f 24 THE LEAF thus treated, in a weak solution of iodine for half an hour ; then wash them and hold them up to the light. Iodine turns starch blue; hence if there are any blue spots on the leaves, what are you to conclude? Other food substances can be detected by proper tests, but none of them so readily as starch. hoi, y it 27. Necessity of Light and Air. — Exclude the light from parts of healthy leaves on a growing plant of tropzeolum, bean, etc., by plac- o.—Leaf arranged with a ing bands or patches of tin foil disk of tin foil to exclude light over them. Leave in a bright win- from a portion of the surface. dow, or preferably out of doors, for twenty-four to forty-eight hours, and then test for starch as in the last experiment; do you find any in the shaded spots? Cover the lower side of several leaves with vaseline or other oily substance_so as to exclude the air, and after a day or two test as before. From these experiments we learn that leaves can not do their work without light and air. The particular element of the atmosphere used by them in the process of food making is carbon dioxide, a poisonous gas that is being constantly produced by the decay of vegetable and animal matter, by the respiration of animals, and by combustion of all sorts. It constitutes about one fourth of one per cent of our atmosphere, and when the proportion rises much above this, the air becomes unfit to breathe, so that the work of plants in eliminating it is a very important one. 28. Respiration. — The leaf is also an organ of respira- tion; that is, it is always taking in oxygen and giving off carbon dioxide, just as animals do, but in such small quan- tities that the process is entirely obscured during the day by the much more active function of photosynthesis, or food making, which goes on at the same time. For this RESPIRATION AND FOOD PRODUCTION 25 reason it was formerly believed that respiration, or the absorption of oxygen by plants, took place only at night, and some people were led to imagine from this that it is unwholesome to have potted plants in a bedroom; but the quantity of oxygen absorbed by green plants is so small as to be scarcely appreciable. While the leaf is the principal organ of respiration, this function is carried on in other parts of the plant also, else it could not survive during the leafless months of winter. It goes on at all times, in all living parts, and the other leaf functions also are carried on, to some extent, in all green tissues. 29. Relation of Respiration to Other Functions. — The functions of photosynthesis and respiration are mutually complementary and interdependent, the one manufacturing food, and the other using it up, or rather marking the activity of those life processes by which it is used up. In this respect it is strictly analogous to the respiration of animals. The more we exert ourselves and the more vital force we expend, the harder we breathe, and hence respiration is more active in children than in older persons, and in working people than in those at rest. It is just the same with plants; respiration is always most energetic in germinating seedlings and young leaves, in buds and flowers, where active work is going on; hence such organs consume propor- tionately large quantities of oxygen and liberate correspondingly large quantities of carbon dioxide. Fill a glass jar of two liters’ capacity (about two quarts) with germinating seeds, or with flower buds or unfolding leaf buds arranged in layers alternating with damp cotton batting or blotting x : paper; close it tightly and leave it for 10.— Arrangement of twelve to twenty-four hours. If the Pparatus to show that ‘ ‘ . carbon dioxide is given jar is then opened and a lighted taper off by growing seedlings. 26 THE LEAF plunged in, it will be extinguished as quickly as in the empty tumbler in the experiment described in Section 23, thus showing that the process of respiration is more active in this case than the opposite function of taking in carbon dioxide and liberating oxygen. Insert a thermometer bulb and note the difference in temperature. In some of the arums, — calla lily, Jack-in-the-pulpit, elephant’s ear (Co/o- casta), etc., —where a large number of small flowers are brought together within the protecting spathe, the rise of temperature is sometimes so marked that it may be perceived by placing a flower against the cheek." 30. Metabolism. — The total of all the life processes of plants, including growth, waste, repair, etc., is summed up by botanists under the general term Metabolism. It is a constructive or building-up process when it results in the making of new tissues out of the food absorbed from the earth and air, and consequent increase of the plant in size or numbers. But, as in the case of animals, so with plants, not all the food provided is converted into new tissue, a part being decomposed and excreted as waste. In this sense, metabolism is said to be destructive, and, like other destructive processes (combustion, for in- stance), is alwaysaccompanied by the liberation of energy, — heat, as we have seen, being an invariable accompaniment. The waste in healthy plants is always, of course, less than the gain, and a large portion of the food material is in all cases laid by as a reserve store. For this reason, photosynthesis, which is a constructive process, is usually more energetic than respiration, which is the measure of the destructive change of materials that attends all life processes. It is evident also, from what has been said, that growth and repair of tissues can take place only so long as the plant has abundant oxygen for respiration, since the food material manufactured by it must be decomposed into the 1 See Sachs, “ Physiology of Plants.” THE TYPICAL LEAF AND ITS PARTS 27 various substances required by the different tissues before it can be appropriated by them. PRACTICAL QUESTIONS Why do gardeners bank up celery to bleach it? (25.) Why are the buds that sprout on potatoes in the cellar white? (25.) 3. Why does young cotton look so pale and sickly in long-continued wet or cloudy weather? (25.) 4. Why do parasitic plants generally have either no leaves or very small, scalelike ones ? (25.) 5. The mistletoe isan exception to this; can you tell why? (184.) 6. Could an ordinary self-supporting plant live without green leaves? (26, 27.) 7. Are abundance and color of foliage any indication of the health of a plant? (24, 26.) 8. Is the practice of lopping and pruning very closely, as in the process called “ pollarding,” beneficial to a tree under ordinary con- ditions ? (18, 21, 24, 26.) g. Why is it wise to trim a tree close when we transplant it? (20, 21.) 10. Why should transplanting be done in winter or very early spring, when the leaves are off ? (19, 20.) 11. Name some plants of your neighborhood that grow well in the shade. 12. Compare in this respect Bermuda grass and Kentucky blue grass; cotton and maize; horse nettle (Solanum carolinense) and dandelion; beech, oak, red maple, dogwood, pine, cedar, holly, mag- nolia, etc. 13. Why are evergreens more abundant in cold than in warm climates? (19, exp.) 14. Is it wholesome to keep blooming plants in a bedroom ? Leafy om ones ? 15. Why, in each case? (23, 28.) THE TYPICAL LEAF AND ITS PARTS MATERIAL. — Leaves of as many different kinds as can conveniently be obtained, showing their various modes of attachment, shapes, tex- ture, etc. For stipules, leaves on very young twigs should be sought for, as these bodies often fall away soon after the leaves expand. The rose, Japan quince (Pyrus japonica), willow, strawberry, pansy, pea, and young leaves of apple. peach, elm, oak, beech, tulip tree (Zzrzodendron), India rubber tree (/2cws edastzca), magnolia, etc., furnish good exam- ples of stipules. 28 THE LEAF 31. Parts of the Leaf. — Examine a young, healthy leaf of apple, quince, elm, etc., as it stands upon the stem, and notice that it consists of three parts: a broad expansion called the d/ade,; a leaf stalk or petiole that attaches it to the stem; and two little leaflike, or bristlelike bodies at the base, known as stipules. Make a sketch of any leaf provided with all these parts and label them respectively blade, petiole, and stipules. 2 s 11. — A typical leafand . its parts: 4, blade; 4, peti 32. Stipules.— These ae aes three parts make up a perfect or typical leaf, but as a matter of fact, one or more of them is usually want- PA ing. The office of stipules, when present, is generally to subserve in some way the pur- poses of protection. In many cases, as the fig, 12:—Spiny stipules of Clotbur. elm, beech, oak, magno- lia, etc., they appear only as protective scales that cover the bud during winter, and fall away as soon as the leaf ex- pands. When perszstent, that is, en- during, they sometimes take the form of spines and thorns, as in the black i Siieatinestaules locust and spiny clotbur (Yanthium of “prince's feather” (Po- spznosum). The sheathing stipules of bgonum orientale) (GRA) the smartweeds and bindweeds ( Polygo- num) serve to strengthen the stem at the joints (Fig. 13), and the adnate stipules (Fig. 14) of the rose, clover, strawberry, etc., may serve either as water holders or as shields against climbing insects. In the smilax and some other vines they appear as tendrils for climbing, while in other cases, as the garden pea and pansy, they become large and leaflike, or may even usurp the place of THE TYPICAL LEAF AND ITS PARTS 29 the leaves altogether, as in the Lathyrus aphaca (Fig. 17), 14.— Adnate stipules of clover. 16. — Leafy stipules of Japan quince. 15.— Leaves of smilax, show- ing stipular tendrils. a near relative of the sweet pea, where they function as foliage. But under whatever form they occur, their true nature may be recognized by their position on each side of the base of the petiole, and not in the axz/, or angle formed by the leaf with the stem. 33. Petioles. — The normal use of , i . 17.—Leaf of Lathyrus the petiole is to secure a better apsaca, reduced to a pair light exposure for the leaves, but re te oneal like other parts of the leaf, it is subject to modifications. In some vines, such as the jas- mine nightshade and tropzolum of the gardens, it is twisted into a tendril for climbing. Occasionally the leaf blade disappears altogether and the leaf stalk takes its place, as in some of the Australian acacias frequently seen in greenhouses. Simulated leaves of this kind can gen- erally be distinguished by their edgewise position, the blades of true leaves being usually horizontal. Other instances occur, such as the onion, jonquil, hyacinth, etc., where the distinction, if any exists, is difficult to make out. 30 THE LEAF In the sycamore, the base of the petiole is hollowed out into a socket to protect the bud of the season (Fig. 20). 34. Leaf Attachment.— When the petiole is wanting altogether, as is often the case, leaves are said to be sesszle, that is, seated on the stem, and their bases are described by various terms suggestive of the mode of attachment. You can frame your own definition of these terms by an inspection of the accompanying figures, or better still, of some of the sample plants named in connection with each. Clasping (Fig. 21): Wild lettuce (Zactuca), chicory, sow thistle (Sonchus), poppy, stem leaves of turnip, mustard, etc. Decurrent (Fig. 22): Thistle, sneezeweed (Helenium autumnale), comfrey (Symphytum). Connate (Fig. 23): The upper leaves of boneset (Ewpa- torium perfoliatum) and trumpet honeysuckle (Lovicera SeMpervlrens ). Perfoliate (Fig. 24): Bellwort (Uvularia perfoliata). Peltate, or shield-shaped (Fig. 25): Castor oil plant, tropeolum, May apple (Podophyllum), water pennywort (Hydrocotyle). Equitant (Fig. 26): Iris, sweet flag (Acorus calamus), blackberry lily (Belamcanda chinensis). 35. The Use of Botanical Language. — These terms and those which follow are not to be learned by heart, but are given here merely for convenience of reference. Botanists have invented a number of useful terms for describing things briefly and accurately, and while they are not to be regarded as of any importance in themselves, it is impos- sible to get along without some knowledge of them; for besides furnishing a sort of universal vocabulary, intelli- gible to botanists everywhere, they enable us to say in two or three words what it would otherwise require as many lines or perhaps paragraphs to express. In other words, they are a sort of labor-saving device which every botanist must learn how to use, as no good workman can afford to be ignorant of the tools of his profession. THE TYPICAL LEAF AND ITS PARTS 31 25. 18-26.— Petioles, and leaf attachment: 18, petioles of jasmine nightshade (Solanum jasminoides) acting as tendrils; 19, acacia, showing petiole transformed to leaf blade; 20, petiole of sycamore hollowed out to protect the bud of the season ; 21, clasping leaf of lactuca; 22, decurrent leaf of thistle; 23, connate leaves of honeysuckle; 24, perfoliate leaves of uvularia; 25, peltate leaf of tropwolum; 26, equitant leaves of iris. (18, 20, 23, 24, 25, and 26, a/fer GRAY.) a9 THE LEAF 36. Shape and Texture of Leaves. — Examine a number of leaves of different kinds and see how they differ from each other in regard to — General Outline: whether round, oval, heart-shaped, lanceolate, etc. (Figs. 27-33). 32 33 27-33.— Shapes of leaves: 27, lanceolate; 28, spatulate; 29, oval; 30, obovate; 31, reniform, or kidney-shaped; 32, deltoid; 33, lyrate. (27-31, after GRAY.) Base: tapering, obtuse, truncate, cordate, etc. (Figs. 34-38.— Bases of leaves: 34, cordate; 35, sagittate; 36, oblique; 37, auricled; 38, hastate, ws h WANS Y oe: = AV oY See 39 45 46 39-47. Apexes of leaves: 39, acuminate; 40, acute; 41, obtuse; 42, truncate; 43,44, emarginate; 45, obcordate; 46, cuspidate; 47, mucronate (GRAY). Apex: acute, acuminate, emarginate, etc. (Figs. 39-47). THE TYPICAL LEAF AND ITS PARTS 33 Margins: some being unbroken or entire, others variously toothed and cut (Figs. 48-53). 53 AL’. 48-53. — Margins of leaves: 48, serrate; 49, dentate; 50, crenate; 51, undulate; 52, Sinuate; 53, runcinate leaf of dandelion. (48-52, after GRAY.) Symmetry: that is, whether the two halves are alike, so that if folded over on each other they would coincide. Texture: whether thick or thin, fleshy and soft, hard and brittle, or tough and leathery (coriaceous). Surface: smooth and shining (glabrous); wrinkled (ra- gose); hairy (pubescent); covered with a bloom (glaucous) ; moist and sticky (viscid, or glandular). PRACTICAL QUESTIONS 1. Tell the nature and use of the stipules in such of the following plants as you can find: tulip tree; fig; beech; apple; willow; pansy; garden pea; Japan quince (Pyrus japonica) ; sycamore; rose; paper mulberry (Broussonetia). 2. State what differences and resemblances you observe between the leaves of the elm, beech, birch, alder, hackberry, hornbeam. Between the hickory, ash, common elder, walnut, ash-leaved maple (Negundo), ailanthus, sumac. Between the persimmon, black gum, buckthorn, papaw (Aszmzna), sourwood (Oxydendron arboreum). Between chinquapin, chestnut, and chestnut oak. Any other sets of leaves may be substituted for those named, the object being merely to form the habit of distinguishing readily the dit- ferences and resemblances between leaves that bear some general like- ness to one another. Notice that the general resemblances are not confined to plants of closely related species: what other causes may influence them ? ANDREWS’S BOT. — 3 cy THE LEAF VEINING MATERIAL. — A specimen of each of the different kinds of veining. For parallel veining any kind of arum, lily, or grass will do ; for net veining, ivy, maple, elm, or peach, etc. Classes in cities can use leaves from potted plants of wandering Jew (Zedrina pendula), calla lily, and other easily cultivated specimens, or blades of grass, plantain, and vari- ous parallel and net veined weeds can be picked up here and there, even in the largest cities. Have a number of leaves placed with their cut ends in red ink from three to six hours before the lesson begins. 37. Parallel and Net Veining. — Com- pare a leaf of the wandering Jew, garden lily, or any kind of grass, with one of cot- ton, maple, ivy, etc. Hold each up to the light, and note carefully the veins or little threads of woody substance that run through it. Make a drawing of each so as to show plainly the direction and manner of veining. Write under the first, Parallel veined, and under the 54.—Paralleveinea SCCONd, Met verned. This distinction of leaf of lily of the valley leaves into parallel and net veined cor- ee ee responds with another important differ- ence in plants, existing in the seed, and is used by botanists in distinguishing the two great classes into which seed-bearing plants are divided. 38. Pinnate and Palmate Vein- ing. — Next, compare a leaf of the canna, or of any of our common garden arums, with one of the elm, peach, cherry, etc., 55-— Palmately net-veined leaf of or with a leaflet of the rose or ERS clover. Hold both up to the light and observe carefully the veins and reticulations. What resemblance do you notice between the two? What difference? Which is parallel veined and which is net veined? Make a drawing of each, and compare with the first two. Notice that VEINING 45 in the last, the petiole seems to be continued in a large central vein, called the Mzdrib, from which the secondary veins branch off on either side just as the pinne of a feather do from the quill; whence such leaves are said to be pinnately, or feather veined. In the cot- ton, maple, ivy, etc., 56. — Pinnately paral- on the other hand, _lel-veined leaf of cala lily 57.—Pinnately net- the petiole breaks up er Baer veined leafofawillow. at the base of the leaf (Fig. 55) into a number of primary veins or ribs, which radiate in all direc- tions like the fingers from the palm of the hand; hence, such a leaf is said to be palmately veined. 39. Ribbed Leaves. — Net-veined leaves are sometimes ribbed in a way that might lead an inexperienced observer to confound them with parallel-veined ones. Compare, for instance, a leaf of the wild smilax (often improperly called bamboo), or of the common plantain, with one of the kind represented in Figure 54. A little inspection will show that in both the ribs all proceed from the same point at the top of the petiole, as in other leaves of the palmate kind, of which they are varieties, but the reticulations between the ribs in the smilax and plantain show that they belong to the net-veined division. 58.— Ribbed leaf of plantain. 40. Parallel-veined and Straight-veined Leaves. — In some pinnate leaves, like the elm, beech, birch, dogwood, etc., the secondary veins are so straight and regular that beginners are apt to confound them with the parallel kind represented in Figure 56, but this mistake need never occur 36 THE LEAF if the reticulations of the smaller veinlets are noted. Then, too, it must be observed that in a pinnately parallel- veined leaf the secondary veins do not separate from the midrib in such sharp, clear-cut angles as we see in the beech and elm, but seem to flow into s9.— Straight-veined leaf it and mingle gradually with it, so that of dogwood. ack the midrib has the appearance of being made up of the overlapping fibers of the smaller veins, as in Figure 56. 41.. Use of the Veins. — Hold up a stiff, firm leaf of any kind, like the magnolia, holly, or India rubber, to the light, having first scraped away a little of the under surface, and examine it with a lens. Compare it with one of softer tex- ture, like the peach, maple, grape, cotton, clover, etc. In which are the veins closest and strongest? Which is most easily torn and wilted? Tear a blade of grass longitudi- nally and then crosswise; in which direction does it give way most readily? Tear apart gently a leaf of cotton, maple, or ivy, and one of elm or other pinnately-veined plant; in which direction does each give way with least resistance? What would you judge from these facts as to the office of the veins? 42. Effect upon Shape.— By comparing a number of leaves of each kind, it will be seen that the feather-veined ones tend to assume elongated outlines (Figs. 16, 33, 53), while the palmate veining produces more broad and rounded forms (Figs. 25, 55, 61). Notice also that the straight, unbroken venation of parallel-veined leaves is generally accompanied by smooth, unbroken margins, while the irregular, open meshes of net-veined leaves are favorable to breaks and indentations of all kinds. 43. Veins as Water Pipes. Examine a leaf that has stood in red ink for two or three hours. Do you see evi- dence that it has absorbed any of the liquid? Cut across the blade and examine with a lens. What course has the BRANCHED LEAVES 37 absorbed liquid followed? What use does this indicate for the veins, besides the one already noted ? We thus see that the veining serves two important pur- poses in the economy of the leaf; first, as a skeleton, or framework, to support the expanded blade; and second, as a system of supply pipes, or waterworks for conveying the sap out of which its food is manufactured. The microscope shows us that the veins are made up of clusters or bundles of woody fibers, mixed with long, tubu- lar cells that serve as vessels for conducting the sap; hence they are called fdvovascular bundles; which means bun- dles composed of fibers and conducting vessels. In this way the veins get both their hardness and their water- conducting power. The tough, stringy threads that pro- trude from the petiole of a plaintain leaf when broken are made of fibrovascular bundles that supply the leaf blade. PRACTICAL QUESTIONS 1. In selecting leaves for decorations that are to remain several hours without water, which should you prefer, and why: Smilax or Madeira vine (Bousstngaultia)? Ivy or Virginia creeper? Magnolia or maple? Maidenhair or shield fern (Aspzdéunz)? (41, 43.) 2. Should you select very young leavés, or more mature ones, and why? 3. Can you name any parallel-veined leaves that have their margins lobed, or indented in any way? 4. Which are most common, parallel-veined or net-veined leaves? 5. Why do the leaves of corn and other grains not shrivel length- wise in withering, but roll inward from side to side? (41.) 6. Can you name any palmately-veined leaves in which the secondary veins are pinnate? Any, pinnately-veined ones in which the secondary veins are palmate? 7. Account for the difference. BRANCHED LEAVES MATERIAL. — Lobed and compound leaves of various kinds. Many good examples can be found among the weeds growing on vacant lots in cities. 44. Lobing.— Compare the outline of a leaf of maple or sweet gum with one of oak or chrysanthemum. Do 38 THE LEAF you perceive any correspondence between the manner of lobing or indentation of their margins, and the direction of the veins?) To what class would you refer each one? The lobes themselves may be variously cut, as in the 60. — Pinnately lobed leaf of an oak. 61.— Palmately lobed leaf of grape. fennel and rose geranium, thus giving rise to twice-cleft, thrice-cleft, four-cleft, or even still more intricately divided leaves. Where the divisions are very deep it may some- times be a little puzzling to decide whether they are not 62.— Pinnately divided leaf 63. — Palmately parted leaf of tall butter- of a buttercup. cups. separate leaflets, but if there is the merest thread of green connecting the segments, as in Figures 62 and 63, it is con- sidered a simple lobed leaf. 45. Compound Leaves. —Compare with the specimens just examined a leaf of horse-chestnut, clover, or Virginia BRANCHED LEAVES 39 creeper, etc., and one of rose, black locust, vetch, or other pinnate leaf. Notice that each of these last is made up of entirely separate divisions or leaflets, thus