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ELEMENTARY PLANT BIOLOGY 
 
THE MACMILLAN COMPANY 
 
 NEW YORK . BOSTON CHICAGO 
 DALLAS SAN FRANCISCO 
 
 MACMILLAN & CO., LIMITED 
 
 LONDON BOMBAY . CALCUTTA 
 MELBOURNE 
 
 THE MACMILLAN CO. OF CANADA, LTD. 
 TORONTO 
 
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 - 
 
 View in the Hemlock Forest, New York Botanical Garden. (Courtesy 
 of New York Botanical Garden.) 
 
ELEMENTARY PLANT BIOLOGY 
 
 BY 
 
 JAMES EDWARD PEABODY, A.M. 
 
 1 1 
 
 HEAD OF THE DEPARTMENT OP BIOLOGY, MORRIS HIGH SCHOOL 
 BRONX, NEW YORK CITY, AUTHOR OF "STUDIES IN PHYSI- 
 OLOGY " AND " LABORATORY EXERCISES IN ANATOMY 
 AND PHYSIOLOGY " 
 
 AND 
 
 ARTHUR ELLSWORTH HUNT, Pn.B. 
 
 HEAD OF THE DEPARTMENT OF BIOLOGY, MANUAL TRAINING 
 HIGH SCHOOL, BROOKLYN, NEW YORK CITY 
 
 gorfe 
 
 THE MACMILLAN COMPANY 
 1912 
 
 All rights reserved 
 
BIOLOGY 
 
 LIBRARY 
 
 G 
 
 COPYRIGHT, 1912, 
 BY THE MACMILLAN COMPANY. 
 
 Set up and electrotyped. Published February, 1912. 
 
 
 Nortooorj 
 
 J. 8. Cushing Co. Berwick & Smith Co. 
 Norwood, Mass., U.S.A. 
 
TO 
 THE MEMORY OF 
 
 MARTHA FREEMAN GODDARD 
 
 WHOSE DEVOTED INSTRUCTION IN BIOLOGY IS A LASTING 
 
 INFLUENCE FOR GOOD IN THE LIVES OF HUNDREDS 
 
 OF BOYS AND GIRLS AND WHOSE RARE SKILL 
 
 IN LEADERSHIP IS AN INSPIRATION TO 
 
 EVERY TEACHER WHO KNEW HER 
 
 THIS BOOK IS DEDICATED 
 
 BY THE AUTHORS 
 
PREFACE 
 
 ALL the activities of a plant, of an animal, or of man may 
 be grouped in three classes. One class embraces the func- 
 tions relating to the life of the individual organism. These 
 functions have to do with the processes of eating, digest- 
 ing, assimilating, taking in of oxygen, producing of energy, 
 and excreting of waste matters. These may be called the 
 nutritive functions, if the term is used in its broadest sense. 
 To the second group of activities belong the functions that 
 have to do with the perpetuation of the animal or plant 
 species, and these are known as the reproductive functions. 
 Living organisms, whether plant, animal, or human, may, in 
 the third place, be considered in their relations to one another 
 and especially to the general welfare of mankind. Thus we 
 may discuss the beneficial or injurious effects, so far as man 
 is concerned, of different kinds of insects or of various types 
 of bacteria ; we may learn of the activities of individual men 
 or of groups of individuals which promote or retard the 
 advance of human society ; or we might, if we were to carry 
 the study still farther, even seek to learn the ways by which 
 the higher thoughts of mankind, as expressed in poetry, 
 music, and religion, affect the development of the human 
 race. 
 
 In the preparation of this text, the authors have sought 
 to keep continually in mind these three classes of activities, 
 and to unify the study of plant, animal, and human biology 
 by choosing those topics for laboratory work or text descrip- 
 tion that have to do in a broad sense with one or the other of 
 the three great groups of functions of living things to which 
 
 vii 
 
viii PREFACE 
 
 we have just referred. In doing this, they are conscious 
 that many subjects have been slighted or altogether omitted 
 which might well be treated in a year's work in either botany, 
 or zoology, or human physiology. 
 
 Again, in the treatment of a given subject, for example, 
 stems, fishes, or circulation, special emphasis might be laid 
 on structure, on function, or on the relation of the given topic 
 to human life. Books both interesting and scientifically 
 worth while could be prepared along any one of these lines, 
 or, if time permitted, all three phases might be equally em- 
 phasized. But when we remember that less than two hun- 
 dred school periods will probably be devoted by the average 
 student to the study of biology, the necessity for adhering 
 pretty consistently to some one plan is obvious. 
 
 In the judgment of the authors the kind of biology most 
 worth while for the average boy or girl of fourteen years 
 of age is not one based primarily on structure. Young stu- 
 dents are naturally more interested in activities or func- 
 tions than they are in mere form or structure. Hence, if we 
 wish to work with, rather than " against the grain," we must 
 put function in the foreground of our discussion. Every boy 
 and girl knows, too, that both plants and animals as well as 
 human beings must have food and drink, and that they grow 
 and reproduce their kind. It is relatively much easier, 
 therefore, to unify a course like this along physiological lines 
 than on the basis of morphology, or of homologies of structure, 
 many of which are far too complicated to be made clear to 
 young students. 
 
 If properly outlined and presented, there is probably no 
 subject in the school curriculum that can be made of more 
 service to a growing youth than can biology. Biological 
 problems confront him at every turn, and if he is a normal 
 being, he will have asked himself question after question 
 
PREFACE ix 
 
 which an elementary knowledge of biology ought to help him 
 to answer. Some of these questions may be the following : 
 Whence comes the food and oxygen supply used by man? 
 Why are food and oxygen needed in our bodies? Why are 
 some substances beneficial to the body and others injurious? 
 What is the cause of disease, and how is disease transmitted? 
 And if we were to tabulate the biological questions that occur 
 spontaneously to the average pupil in the first year in the 
 high school, we should doubtless find that a great proportion 
 of these questions had to do with the relation of the living 
 world to human life. Is it not clear, therefore, if we are to 
 outline a course in biology that will best fit the interests of 
 the " live material/' i.e. the boy or girl who is to take the 
 course, that the central idea or factor must be man ; that all 
 the various functions considered must have some relation to 
 human life ; and that the course, to be of practical importance, 
 must suggest to the youth better ways of carrying on his own 
 life and of helping to improve the surroundings in which he 
 lives ? 
 
 In order, however, to treat intelligently such a function, for 
 example, as respiration or digestion, it is of course necessary 
 to know something of the machinery by which each of these 
 processes is carried on, and so there must be at least a mini- 
 mum consideration of the structure of plants, animals, and 
 the human body. In every case, however, the authors have 
 called attention only to those details which seem to be abso- 
 lutely essential for an interpretation of the function under 
 consideration. Whenever names in common use are suffi- 
 ciently accurate for descriptions, these are chosen in prefer- 
 ence to scientific terms. Frequently the latter are neces- 
 sarily used, and so, whenever their meaning is made clearer 
 by referring to their derivation from Latin or Greek, these 
 derivations are indicated in parentheses. 
 
X PREFACE 
 
 The sections in coarse type contain the material that seems 
 to the authors most essential for any clear understanding of 
 the subject as a whole, while in fine type we have put addi- 
 tional laboratory work and text description which we believe 
 to have an important bearing on the various topics discussed. 
 If both coarse and fine print on animal, or plant, or human 
 biology are used, sufficient material for a half-year course in 
 either elementary botany, zoology, or human physiology will 
 be provided. 
 
 In the judgment of the authors, plant biology should always 
 be considered first and human biology last in the course for 
 the following reasons : (1) Plants lend themselves far more 
 readily to close observation and especially to experiments 
 than do animals, and so fundamental processes which apply 
 to all living things can be demonstrated scientifically from 
 plant material. (2) Plants are the final source of all the food 
 supply of animals and man, and if the composition and manu- 
 facture of the nutrients are taught early in the course, a solid 
 foundation is laid for all subsequent study of nutrition in 
 animals and man. (3) The purpose of the animal study is 
 largely that of showing the adaptations of animal structure 
 to functions and the relations of the animals studied to 
 human welfare. (4) And finally, if human biology comes 
 last in the course, it may be presented in such a way as to 
 review, sum up, and give real significance to many of the 
 facts learned earlier in the course. In fact, as the work 
 proceeds, comparisons will constantly be made between 
 plants, animals, and man to show that the essential differ- 
 ences in the three kinds of organisms consist not in the dif- 
 ferences in the functions which they carry on, but in the 
 organs by which the functions are performed. 
 
 So far as the order of individual topics under plant, ani- 
 mal, and human biology is concerned, the instructor should 
 
PREFACE . xi 
 
 plan the sequence that best fits the season. In fact, the last 
 use that a good teacher will make of any laboratory manual 
 or text-book is that of following it slavishly. It is the hope 
 of the authors, however, that the laboratory guides and the 
 text descriptions which follow may be sufficiently sugges- 
 tive to help some teachers to work out improved methods 
 in biological instruction. In Appendix II will be found a 
 suggested order of topics which the authors have found 
 satisfactory. 
 
 Living organisms are to a large extent to be regarded as 
 chemical engines so constructed as to liberate different kinds 
 of energy. No one, of course, knows in any ultimate sense 
 how even the simplest functions are performed by the sim- 
 plest animals or plants. But it is utterly useless to attempt 
 to teach biological functions without first presenting some of 
 the elementary principles involved in physical and chemical 
 phenomena. For this reason the first chapter in Plant 
 Biology is devoted to the study of the Composition of Lifeless 
 and Living Things. In Chapter III is a brief discussion of 
 the structure of a common plant, and since cells are funda- 
 mentally alike in structure and functions in all living or- 
 ganisms, emphasis is laid early in the course on the essential 
 characteristics of these cellular elements in plants. Another 
 topic which necessarily recurs throughout plant, animal, and 
 human biology is the principle of osmosis and its applica- 
 tions. The authors have inserted experiments which in their 
 experience have helped to fix in mind this important principle 
 and which demonstrate the necessity of digestion in plants 
 and animals. 
 
 After this brief consideration of the fundamentals of plant 
 composition, structure, and processes, Chapters V, VI, and 
 VII are devoted to the study of the adaptations of plants 
 for performing nutritive and reproductive functions. In 
 
xii PREFACE 
 
 Chapter VIII are grouped experiments and descriptions 
 the aim of which is to show various ways in which plants 
 are propagated. This treatment presents only the briefest 
 statement of underlying principles, since any extended dis- 
 cussion of this topic belongs to a course in agriculture. 
 
 In Chapters IX (Plants in their Relation to Human Wel- 
 fare) and X (Plant Classification) the method of presentation 
 is strikingly different from that adopted in the rest of the 
 book, particularly so in the treatment of the spore-bearing 
 plants. The authors believe that every pupil should be 
 taught something of these simpler forms (especially bacteria), 
 and that he should get as many of these facts as possible by 
 observation. But to expect much laboratory work from young 
 students on difficult microscopic forms like many of these 
 cryptogams, is, we are confident, quite out of the question. 
 We have, therefore, frankly abandoned the inductive method 
 of study and have suggested that the laboratory work be 
 largely in the nature of demonstrations. It is, of course, 
 understood that if these forms are studied, the drawings and 
 descriptions will be prepared from material in the hands of 
 the student. 
 
 In our judgment there are few if any biological topics 
 which are more important in their practical bearings than is 
 that of bacteria. As commonly studied the disease-pro- 
 ducing effects of these organisms are emphasized so much that 
 boys and girls do not appreciate that all the work of the 
 higher plants depends ultimately upon the activity of these 
 low forms of fungi. In order to bring out this aspect of the 
 work of bacteria and for other obvious reasons the structure, 
 physiology, and economic benefit of these organisms are con- 
 sidered in the chapter on the relation of plants to human 
 welfare, while their pathogenic effects are reserved for dis- 
 cussion in human biology. 
 
PREFACE Xlii 
 
 In the preparation of this book the authors have received 
 a great many suggestions from the teachers in their own 
 departments and those of other schools. Our thanks are due 
 to Miss M. Helen Smith of the Manual Training High School, 
 Brooklyn, N. Y. for several laboratory outlines which formed 
 the basis of corresponding studies in the following pages. 
 The authors have been especially fortunate in securing the 
 constructive criticism of Dr. C. Stuart Gager, Director of 
 the Brooklyn Botanic Garden of the Brooklyn Institute of 
 Arts and Sciences. He has carefully read all of the manu- 
 script and the page proofs. 
 
 We are indebted to Dr. H. J. Webber, Professor E. O. 
 Fippin, and others at Cornell University, for valuable ma-* 
 terial and illustrations for the chapter on Plant Propagation. 
 We wish, also, to express our hearty appreciation of the 
 generous permission of Henry Holt & Co. to use some of the 
 material published in Peabody's " Laboratory Exercises in 
 Anatomy and Physiology." We are fortunate, too, in secur- 
 ing from the New York Botanical Garden photographs for 
 the frontispiece, and for several fine cuts in the text, and from 
 Professor E. M. East of Harvard University the cut for Fig. 
 52. Miss Mabelle Baker, Miss Clara Lang, Miss Margaret 
 Cutler, and Miss Grace Gamble, students in our first-year 
 classes, have kindly prepared for us the figures on which 
 their several names appear. 
 
 Cost prices for the items on the list of laboratory appara- 
 tus and equipment were kindly furnished us by Bausch & 
 Lumb, Kny-Scheerer, and O. T. Louis; from these prices the 
 estimates on pp. 173 to 177 were prepared. 
 
 J. E. P. 
 A. E. H. 
 
 January 31, 1912. 
 
TABLE OF CONTENTS 
 
 PACK 
 
 PREFACE vii 
 
 CHAPTER 
 
 I. GENERAL INTRODUCTION 1 
 
 II. COMPOSITION OF LIFELESS AND LIVING THINGS . . 5 
 
 I. Elements, Compounds, and Oxidation . . 5 
 
 II. Definitions .12 
 
 III. A Study of the Food Substances ... 13 
 
 IV". Manufacture of the Food Substances by Plants . 22 
 
 ^ III. THE GENERAL STRUCTURE OF PLANTS ... 26 
 
 IV. OSMOSIS AND DIGESTION 32 
 
 V. ADAPTATIONS OF THE NUTRITIVE ORGANS OF PLANTS 39 
 
 I. The Structure and Adaptations of Roots . . 39 
 
 II. The Structure and Adaptations of Stems . . 45 
 
 III. The Structure and Adaptations of Leaves . . 52 
 
 VI. RESPIRATION AND THE PRODUCTION OF ENERGY IN 
 
 PLANTS 64 
 
 VII. REPRODUCTION IN PLANTS 70 
 
 I. The Structure and Adaptations of Flowers . 70 
 
 II. The Structure and Adaptations of Fruits . . 89 
 
 VIII. PLANT PROPAGATION 97 
 
 I. Seeds and their Development into Plants . . 97 
 II. (Optional.) Other Methods of Plant Propaga- 
 tion .105 
 
 III. Conditions Essential for the Growth of Plants . 108 
 
 IV. (Optional.) The Struggle for Existence and its 
 
 Effects 114 
 
 V. (Optional.) The Improvement of Plants by Man 119 
 
xvi TABLE OF CONTENTS 
 
 CHAPTER PAGE 
 
 IX. PLANTS IN THEIR RELATION TO HUMAN WELFARE . 126 
 
 I. Some of the Uses of Plants to Man . . . 126 
 
 II. The Uses of Forests and Forest Conservation . 132 
 
 III. Fungi and their Relation to Human Welfare . 139 
 
 X. PLANT CLASSIFICATION 154 
 
 I. (Optional.) Common Methods of Classification . 154 
 
 II. (Optional.) Scientific Methods of Classification . 158 
 
 APPENDIX 
 
 I. Laboratory Equipment 171 
 
 II. Order of Topics . . , , . . .. . 178 
 
 III. Biology Note-books . 181 
 
 IV. Review Topics in Plant Biology . . . . . 188 
 V. List of Suggested Books of Reference in Biology . 197 
 
ELEMENTARY PLANT BIOLOGY 
 
PLANT BIOLOGY 
 
 CHAPTER I 
 GENERAL INTRODUCTION 
 
 1. Lifeless Things and Living Things. As we look about 
 us, we find that the world in which we live is wholly composed 
 of two classes of things, which we commonly speak of as 
 living things and lifeless things. Soil, air, and water, for 
 example, we know to be lifeless. Water is probably the 
 simplest of these three so far as its composition is concerned. 
 Soil, on the other hand, is very complex in composition, being 
 formed of nearly all the substances known to the scientist. 
 Enveloping the earth is a mixture of gases called the atmos- 
 phere which extends outward in every direction for a dis- 
 tance of about fifty miles. Everybody knows, too, that over 
 the surface of the earth, in the water, and even in the air 
 are countless numbers of living things which we designate 
 as either plants or animals. 
 
 One might think that it would be an easy matter to set 
 down the characteristics by which living things are dis- 
 tinguished from those that are lifeless. And such is the case 
 when we compare a rock in a field with a horse that is feeding 
 beside it. Unlike the animal, the lifeless rock is unable to 
 move itself, it neither eats nor breathes, and it gives no 
 evidence of feeling or of will power. 
 
 But suppose we select for comparison a railroad locomotive 
 and a horse. Both move ; both need a plentiful supply of air ; 
 
2 PLANT- BIOLOGY 
 
 both develop heat and power to do work ; and both give off 
 certain waste matters. The horse, we may say, requires food, 
 but so does the engine ; for coal and water are as necessary 
 for the development of heat and power in the engine, as food 
 and water are for a similar purpose in the horse. 
 
 When we try to state characteristics that will distinguish 
 all plants from all lifeless objects, we find the task still more 
 difficult ; for most plants do not move about from place to 
 place, it is difficult to realize that they give off heat, and they 
 do not give evidence that they have conscious feelings as 
 do the common animals. In spite, however, of these simi- 
 larities, we are usually able to distinguish living from life- 
 less objects at least by the three following characteristics. 
 
 2. Growth of Living Things. In the first place living 
 things use some of the food they eat for growth. No one ever 
 heard of an engine or other lifeless object beginning as a small 
 machine, and then slowly growing larger until it comes to 
 have many times its former weight. 1 Yet this is what hap- 
 pens to all plants and all animals. The average child, for 
 instance, at birth weighs seven to eight pounds ; while a man's 
 weight is over twenty times as great. And if we try to com- 
 pare the weight of an oak tree with that of an acorn from 
 which it started, the amount of increase we find to be enor- 
 mous. 
 
 3. Repair of Living Things. In the second place, parts 
 of a locomotive or of any other lifeless machine by continual 
 use become worn or broken, and the engine must be sent to 
 the machine-shop for repairs. Our bodies, too, are being 
 constantly worn away ; for every time we make a motion of 
 
 * While it is true that icicles and other crystals apparently grow, 
 this kind of growth is brought about wholly by the addition of mate- 
 rial to the outer surface. 
 
GENERAL INTRODUCTION 3 
 
 any sort, some of our living muscle is used up ; every time 
 we think or exert our will power, some of the living brain 
 substance is probably changed into dead waste material. 
 But in contrast to lifeless machines, our bodies are self-repair- 
 ing. The food we eat not only goes to increase the size of 
 the body ; it also furnishes material to make good the wear 
 and tear of everyday life. This power of self-repair is like- 
 wise present in all animals and in plants as well. 
 
 4. Reproduction of Living Things. A third character- 
 istic that distinguishes living things from those that are life- 
 less is the fact that they produce seeds (in the case of plants) 
 or eggs (in the case of animals), which in turn come to form 
 plants or animals like those by which these seeds or eggs 
 were produced. No lifeless object can do this. We shall 
 find in our laboratory study that, while there are a great 
 many different methods of producing these new organisms, 
 still in their essential features these various methods of repro- 
 duction are much the same from the lowest plants to the 
 highest animals. 
 
 5. Summary. In brief, then, we may say that all liv- 
 ing things have the power of growth from within, of self-repair, 
 and of the reproduction of their kind; but that so far as we know 
 lifeless objects possess none of these powers. 
 
 6. Science and its Subdivisions. Ever since the dawn of 
 history we find that mankind has been seeking to learn the 
 secrets of living and lifeless matter. During the past century 
 our knowledge has increased so rapidly that many sciences 
 have been completely rewritten. The discoveries, for ex- 
 ample, of the characteristics of radium and of X-rays have 
 revolutionized much of what was formerly believed as to the 
 properties of lifeless matter. In the same way our increased 
 knowledge regarding germs and other microscopic plants and 
 
4 PLANT BIOLOGY 
 
 animals has made possible the scientific treatment of disease, 
 and what is more important, the prevention of disease. As 
 our knowledge of the living and lifeless world has increased, 
 it has become necessary to divide this knowledge into a great 
 many different branches, some of which are physics, chemis- 
 try, geology (a study of the earth), mathematics, psychology 
 (a study of mind), and biology. 
 
 7. Biology (from Greek, bi'os = life + lo'gos = discourse) is 
 the general name given to the study of all living things. 
 Hence, this science treats of both animals and plants. If we 
 confine our study to the structure and activities of plants 
 alone, we call this part of the science plant biology, or botany. 
 Animal biology, or zoology, on the other hand, treats of ani- 
 mals. So-called human physiology (better known as human 
 biology) discusses man, the highest type of the animal king- 
 dom ; hence, it is a branch of the science of zoology, which in 
 turn is one of the subdivisions of the study of biology. 
 
CHAPTER II 
 COMPOSITION OF LIFELESS AND LIVING THINGS 
 
 8. Introduction. For a great many years scientists 
 have been studying plants and animals, and from this 
 study they have learned that the bodies of all living organ- 
 isms, including human beings, are made from substances 
 found in the water, soil, and air, and that when plants and 
 animals cease to live, their bodies are changed into the 
 chemical substances of which soil, air, and water are com- 
 posed. We are now to learn by experiments the charac- 
 teristics of some of these materials found in lifeless things, 
 and some of the combinations of these materials in plants 
 and animals. 
 
 I. ELEMENTS, COMPOUNDS, AND OXIDATION 
 
 Materials: Splinters of wood and pieces of carbon; starch, 
 sugar, egg, meat; potassium chlorate, oxid of manganese, pieces of 
 marble, zinc, hydrochloric acid, lime water (see below) ; elements for 
 demonstration (e.g. phosphorus, sulphur, iron, magnesium) ; com- 
 pounds for demonstration (e.g. magnesium sulphate, sodium nitrate, 
 potassium nitrate, calcium phosphate, calcium carbonate); test 
 tubes, thistle tube, apparatus stand, tray for collecting gases, de- 
 livery tube, cylindrical graduate or glass jar. (All of the materials 
 named above will be found in the chemical or physical laboratory 
 of almost every high school.) 
 
 Preparation of lime water : Put into a large bottle a good handful 
 of lime (freshly slaked in water, if possible ; air-slaked lime may be 
 used, however). Fill the bottle with water, shake the mixture, and 
 
 5 
 
6 PLANT BIOLOGY 
 
 allow it to stand until needed. Then pour some of the liquid through 
 a funnel in which is a filter paper. Collect the filtered lime water 
 in a bottle, and keep it stoppered. As soon as it becomes cloudy, 
 throw it away and obtain some more clear liquid by filtration as di- 
 rected above. The large bottle can be kept indefinitely as a stock 
 solution if it is kept filled with water. 
 
 9. Carbon (symbol, C). Laboratory Study No. 1. Sug- 
 gested as home work. 
 
 1. Prepare some charcoal by lighting a long splinter of wood 
 
 or a match and then blowing out the flame. (Pre- 
 pared charcoal may be used.) Charcoal is nearly 
 pure carbon. 
 
 a. Tell what you have done. 
 
 6. Is carbon (charcoal) a solid, a liquid, or a gas ? What 
 is its color ? 
 
 c. Of what substance does this experiment prove that 
 wood is partly composed ? 
 
 2. Hold the tip of the carbon (charcoal) in a hot flame, 
 a. State what was done. 
 
 6. Does any of the carbon disappear ? 
 
 c. Will carbon burn ? How do you know ? 
 
 3. State three characteristics of carbon (charcoal) that you 
 
 have learned from these experiments. 
 
 4. Hold your hand over the glowing charcoal with your eyes 
 
 closed. How can you still tell that the carbon is 
 burning ? 
 
 10. Oxygen (symbol, O). Laboratory Study No. 2. 
 Demonstration . 
 
 Preparation of oxygen: Thoroughly mix a teaspoonful of po- 
 tassium chlorate with about one-fourth as much black oxid of man- 
 ganese. Put the mixture in a large test tube. Close the mouth of 
 the test tube with a stopper through which passes a delivery tube, 
 the other end of which runs beneath the surface of water in a tray. 
 Support the test tube in a slanting position on an apparatus stand, 
 and heat the mixture gently with a gas or an alcohol flame, until 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 7 
 
 the oxygen begins to be given off. Fill three or four bottles with 
 water, cover each with a piece of glass or cardboard, and invert the 
 first one over the mouth of the delivery tube, removing the cover 
 when the mouth is under water. Continue to heat the mixture 
 until the bottle is full of oxygen, then cover it under water with the 
 glass plate or cardboard, and stand it right side up on the table. 
 In the same way fill as many jars as are needed for the experiments 
 with oxygen. (Fig. 1.) 
 
 FIG. 1. Preparation of oxygen. 
 
 Prepare several bottles of oxygen as directed and allow them to 
 stand until all fumes have settled, before answering the following 
 questions. 
 
 1. Examine a bottle of oxygen. 
 a. State what you have done. 
 
 6. Do you find oxygen to be a solid, a liquid, or a gas ? 
 c. State whether or not oxygen has color. 
 
 2. Heat some charcoal (carbon) till it glows and thrust it 
 
 into a bottle of oxygen. 
 
 a. Tell what was done and describe what happens. 
 6. Does carbon burn better in air (which is a mixture of 
 
 oxygen and other gases) or in pure oxygen ? 
 
 3. State the three characteristics of oxygen which you have 
 
 learned. 
 
 11. Carbon dioxid (formula, CO 2 ). Laboratory Study 
 No. 3. Demonstration. 
 
8 
 
 PLANT BIOLOGY 
 
 ~7 
 
 Preparation of carbon dioxid: Into a flask put some pieces 
 of marble, and insert a stopper through which passes a thistle 
 
 tube and a delivery tube like that 
 used in the preparation of oxygen. 
 Pour into the thistle tube diluted 
 hydrochloric acid until the lower 
 end of this tube is covered. Col- 
 lect a bottle of carbon dioxid in 
 the same way that oxygen is col- 
 lected, keeping the mouth of the 
 bottle closed with a glass plate or 
 cardboard. (Fig. 2.) Prepare a 
 V \\ /?* / Bottle of carbon dioxid as directed, 
 \ N^T^ / and allow it to stand till all fumes 
 of carbon nave disappeared, before answering 
 dioxid or of hydrogen. the following questions. 
 
 1. Examine a bottle of carbon dioxid and state whether it 
 
 is a solid, a liquid, or a gas. Compare this gas 
 and oxygen as to color. 
 
 2. Light a splinter of wood and thrust it into the bottle of 
 
 carbon dioxid. 
 
 a. Tell what was done and describe the effect of the carbon 
 
 dioxid upon the burning splinter. 
 
 b. How was the burning splinter or carbon affected by 
 
 oxygen? 
 
 3. Generate some carbon dioxid as suggested above and pass 
 
 it through the delivery tube into a test tube of 
 clear lime water. Tell what was done and describe 
 the effect of carbon dioxid on lime water. (Carbon 
 dioxid is the only gas that affects lime water in this 
 way; hence the latter is a reliable test for carbon 
 dioxid.) 
 
 4. State the four characteristics of carbon dioxid which you 
 
 have learned from these experiments. 
 
 5. Place in a bottle of pure oxygen a piece of glowing 
 
 carbon, and allow it to burn as long as it will. 
 When the carbon ceases to burn, quickly remove 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 9 
 
 it, and pour in some clear lime water, cork the 
 
 bottle, and shake. 
 a. Tell what was done and describe the change that takes 
 
 place in the lime water. 
 6. What substance is evidently formed when carbon 
 
 burns in oxygen? 
 
 6. When carbon is burned in oxygen, the two unite to 
 
 form a new substance entirely different from 
 either carbon or oxygen. This new substance is 
 called carbon dioxid, because it is composed of one 
 part of carbon and two of oxgyen. 
 
 a. Describe the composition of carbon dioxid. 
 
 b. State the method by which carbon dioxid was pro- 
 
 duced in this experiment. 
 
 7. (Optional.) By means of a glass tube blow the breath from the 
 
 lungs into a test tube of lime water, 
 a. What change do you notice in the lime water ? 
 6. What do you therefore conclude to be contained in the breath 
 
 from the lungs ? 
 
 12. Hydrogen (symbol, H) and water (formula, H 2 O). 
 Laboratory Study No. 4. Demonstration. 
 
 Preparation of hydrogen (see Caution below) : Into a flask put 
 some pieces of zinc. (See Fig. 2.) Insert a stopper with two holes. 
 Through one of the holes pass the lower end of a thistle tube until 
 it nearly touches the bottom of the test tube, and through the other 
 run a short piece of glass tubing. To the upper end of the latter 
 attach by means of a piece of rubber tubing a delivery tube that will 
 reach beneath the surface of a tray of water such as that used in 
 collecting oxygen and in the preparation of carbon dioxid. Pour 
 through the thistle tube enough diluted hydrochloric acid to cover 
 the lower end of the thistle tube. (If hydrogen does not come off 
 rapidly enough, put into the flask a bit of copper sulphate.) After 
 the hydrogen has been given off for several minutes, collect a bottle 
 over water in the same manner as in the oxygen experiment. Re- 
 move the bottle, holding it upside down, and place it on the desk 
 in this position. Allow the bottle to stand till fumes disappear. 
 
10 PLANT BIOLOGY 
 
 Caution : If in 3 below an explosion occurs, collect another bottle 
 of hydrogen before answering the questions, for an explosion indi- 
 cates that oxygen is mixed with the hydrogen, and such a mixture 
 is dangerous to experiment with. 
 
 1 . Examine a bottle of hydrogen, and state whether hydrogen 
 
 is a solid, a liquid, or a gas. Compare its color with 
 that of oxygen and carbon dioxid. 
 
 2. Thrust a lighted stick up into the mouth of an inverted 
 
 bottle of hydrogen. (This experiment will be more 
 satisfactory if the room is darkened.) 
 
 a. State what was done and tell how the hydrogen af- 
 
 fected the burning stick. 
 
 b. How does the burning stick affect the hydrogen? 
 
 c. What is one difference between oxygen and hydrogen ? 
 
 d. What is one difference between hydrogen and carbon 
 
 dioxid ? 
 
 3. If hydrogen is not being given off from the delivery tube 
 
 in sufficient quantity, pour into the thistle tube 
 some hydrochloric acid. Detach the delivery tube 
 from the rubber tube of the hydrogen apparatus 
 and insert in its place a piece of glass tubing, the 
 upper end of which is drawn out to a small diameter. 
 Collect some of the gas in a test tube by displacement 
 of air and light it. When it burns with only a slight 
 puff, apply a lighted match to the hydrogen escap- 
 ing from the drawn-out tube. 
 
 Hold over the flame a bottle which is clean and dry. 
 
 a. Describe the preparation of this experiment. 
 
 6. What do you find on the inside of the glass? 
 
 c. What, therefore, is formed when hydrogen burns ? 
 
 4. When hydrogen burns, it unites with the oxygen of the 
 
 air and forms oxid of hydrogen, more commonly 
 known as water (formula, H 2 0). 
 
 a. In what respect does hydrogen differ from oxid of 
 
 hydrogen (water) in its most common form ? 
 
 b. State how oxid of hydrogen was formed. 
 
 c. In what respects is the method of producing oxid of 
 
 hydrogen (water) the same as that of producing 
 oxide of carbon (carbon dioxid) ? (See 11,5 above.) 
 
 5. Name five characteristics of hydrogen. 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 11 
 
 13. Nitrogen (symbol, N) and the composition of the air. 
 Laboratory Study No. 5: Demonstration. 
 
 Fasten a candle to a piece of cardboard and float the latter on a 
 tray of lime water. Light the candle, and cover the flame with 
 an inverted wide-mouthed bottle, bringing the latter slowly down 
 until the edge rests on the bottom of the tray. Allow the candle 
 to burn as long as it will. Then turn the bottle right side up, cover- 
 ing the mouth with the cardboard, keeping inside the bottle the lime 
 water that has risen to take the place of the oxygen. Shake the 
 contents of the bottle, to make the lime water absorb the carbon 
 dioxid, and allow it to stand till the upper part of the jar is clear. 
 Keep the bottle covered to prevent the mixing of air with the 
 nitrogen. 
 
 1. Examine a bottle of nitrogen. Is it a solid, a liquid, or a 
 
 gas ? What is its color ? 
 
 2. Thrust a burning splinter of wood into the nitrogen. 
 
 a. Tell what was done. Does the wood continue to 
 
 burn? 
 
 b. Does the nitrogen burn? 
 
 c. In what respect does nitrogen differ from oxygen? 
 
 3. State four characteristics of nitrogen. 
 
 4. Why does carbon burn faster in oxygen than in air? 
 
 5. Air consists principally of oxygen and nitrogen. The 
 
 water in the bottle represents the amount of oxygen 
 there was in the bottle of air, and the nitrogen 
 occupies the rest of the space. 
 
 a. About what fractional part of the air in the bottle was 
 oxygen ? 
 
 6. What fractional part of the air in the bottle is nitro- 
 gen ? 
 
 6. Expose to the air of the room for a half hour or more a 
 
 dish with some clear lime water, 
 a. Describe the experiment, stating the effect on the lime 
 
 water. 
 6. What substance does this experiment prove to be 
 
 present in air? 
 
12 PLANT BIOLOGY 
 
 II. DEFINITIONS 
 
 14. A chemical element is a ..substance that has never 
 been separated into two or more different kinds of matter. 1 
 Over seventy of these elements are known at the present time, 
 and of these seventy, twelve are found constantly in the liv- 
 ing substance of plants and animals. The most common of 
 these twelve elements are carbon (symbol, C), hydrogen 
 (H), oxygen (0), nitrogen (N), sulphur (S), phosphorus (P), 
 iron (Fe), and calcium (Ca), which is found in lime. 
 
 [In addition to the elements already studied (C, 0, H, N), 
 the others mentioned should be shown to students; and if 
 time permits, some of these elements may be burned or oxi- 
 dized in oxygen and the characteristics of the oxids thereby 
 formed may be discussed.] 
 
 15. A chemical compound is a substance formed by the 
 union of two or more chemical elements. Two of the im- 
 portant compounds considered in biology are carbon dioxid 
 (formula CO 2 ) , which means that it is composed of one part 
 of carbon and two parts of oxygen, and water (formula H 2 O), 
 which means that it is composed of two parts of hydrogen and 
 one part of oxygen. 
 
 16. A mixture differs from a compound in the fact that 
 the elements or compounds of which the former is composed 
 are not chemically united. In air, for instance, the oxygen 
 and nitrogen are not chemically combined, but are simply 
 put together as one might mix pepper and salt. Again, when 
 sugar is dissolved or mixed with water, the two compounds 
 are mingled so closely that the sugar disappears; it may 
 easily be obtained unchanged in its composition by evaporat- 
 ing the water. 
 
 1 There are, however, exceptions to this statement, but they are 
 too technical for discussion in an elementary text-book. 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 13 
 
 17. Oxidation is the chemical union of oxygen with some 
 other substance. It may take place slowly, as when carbon 
 is made to glow in the air ; or it may take place rapidly, as 
 when carbon burns in oxygen. But whenever oxidation takes 
 place, (1) an oxid is formed, (2) a certain amount of heat is 
 produced, and (3) if the process is sufficiently rapid, a flame 
 is seen. 
 
 III. A STUDY OF THE FOOD SUBSTANCES 
 
 18. Introduction. The food substances needed by plants 
 and animals may be divided into five classes, namely : 
 (1) carbohydrates (i.e. starches and sugars) ; (2) fats and oils; 
 (3) proteins, 1 which are also known as albuminous or nitrog- 
 enous substances (e.g., white of egg, lean meat, gluten of 
 wheat) ; (4) minerals (e.g. common salt, saltpeter, phosphate 
 of lime) ; (5) water. 
 
 19. To determine the chemical composition of starch. 
 
 Laboratory Study No. 6. Suggested as home work. 
 
 Warm some starch in an old cooking spoon in order to 
 drive off any water that may be in it, but do not allow it 
 to burn. To determine when the starch is free from water, 
 hold the heated starch under a dry, cold tumbler, and if no 
 moisture collects upon the tumbler, the starch contains no 
 water. Now set the starch on fire, and hold a cold, dry 
 glass over the burning starch. 
 
 1. Tell what you have done and state what is formed on the 
 
 inside of the tumbler by the burning of the starch. 
 
 2. What is the only chemical element that could possibly 
 
 form water by burning (i.e. by uniting with oxygen) ? 
 
 3. What chemical element, therefore, must have been pres- 
 
 ent in the starch in order to have produced water when 
 dry starch is burned? 
 
 1 The term protein is used throughout this book instead of proteid, 
 because of the unanimous recommendation in favor of the former 
 term by the American Society of Biological Chemists and the 
 American Physiological Society. See Science, April 3, 1908. 
 
14 PLANT BIOLOGY 
 
 4. What substance is left in the cooking spoon after the 
 
 flame goes out? 
 
 5. Name two chemical elements present in starch. 
 
 6. Starch also contains oxygen. Name now the three chem- 
 
 ical elements of which this nutrient is composed. 
 
 20. To determine the chemical composition of sugar, 
 fat, and protein. Laboratory Study No. 7. (Optional.) 
 
 1. Test sugar in the same way as directed in Laboratory Study 
 
 No. 6, 1-5 (above). 
 
 a. Describe each of the experiments, giving results and con- 
 
 clusions. 
 
 b. Sugar, like starch, has oxygen also in its composition. Name 
 
 now all the chemical elements of which sugar is com- 
 posed. 
 
 2. In a similar way test a fat (e.g. lard, or the fat of meat). 
 
 a. State what you do, what you see, and what you conclude. 
 b: Fat, like starch and sugar, has oxygen in its composition, but 
 
 in a different proportion. State, therefore, the three 
 
 elements present in fat. 
 
 3. (Demonstration.) Secure a vegetable protein (e.g. gluten) 
 
 and test it as directed above. 
 
 a. Describe your experiments and give your results and con- 
 clusions. 
 
 6. Besides the two elements you have shown to be present, 
 protein also contains oxygen, nitrogen, sulphur, phos- 
 phorus, and often other elements. State, now, the 
 chemical elements of which this food substance is com- 
 posed. 
 
 21. Summary. The carbohydrates, as we have learned 
 and as their name implies, are composed of the chemical ele- 
 ments carbon, hydrogen, and oxygen. The same three chemi- 
 cal elements are likewise present in fats and proteins, but in 
 different proportions. Proteins, however, in addition to the 
 carbon, hydrogen, and oxygen, contain at least three other 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 15 
 
 chemical elements, namely, nitrogen, sulphur, and phos- 
 phorus; in fact, proteins are the most complex of all chemical 
 substances known. 
 
 Following is the composition of the various nutrients stud- 
 ied thus far : 
 
 Starch, composed of C, H, (in the proportion of C 6 Hi 5 ). 
 
 Sugar, composed of C, H, O. (Grape sugar = C 6 H 12 6 .) 
 
 Fat, composed of C, H, O. 
 
 Protein, composed of C, H, 0, N, S, P (and sometimes of 
 other elements). 
 
 22. Tests for the food substances. Having demon- 
 strated that the various food substances are chemical com- 
 pounds, each composed of several chemical elements, we are 
 now to carry on experiments by which it will be possible to 
 test for each of these food substances. By this means we 
 shall be able to prove the presence or absence of starch, grape 
 sugar, protein, fat, mineral matters, and water in the foods 
 used by plants, animals, and man. 
 
 23. To test foods for starch. Laboratory Study No. 8. 
 
 Materials: Corn starch, grape sugar, white of egg, fat or oil, 
 salt, water; various foods in the home kitchen; iodine solution 
 (see below) ; test tubes; gas burner or alcohol lamp. 
 
 Preparation of iodine solution: A quart (1000 cc.) of iodine solu- 
 tion is made by dissolving in 5 teaspoonfuls (40 cc.) of water, one- 
 half teaspoonful (4 grams) of potassium iodide, and one-fourth 
 this amount of iodine (1 gram). This solution, when thoroughly 
 mixed, should be diluted to make one quart (1000 cc.). In a clean 
 bottle this mixture will keep indefinitely. 1 
 
 1. Put a small amount (size of a pinhead) of corn starch 
 in a test tube, add water, shake the mixture, and boil 
 it over a gas flame. Pour into the starch mixture 
 
 1 From Peabody's " Laboratory Exercises." Henry Holt & Co. 
 
16 PLANT BIOLOGY 
 
 thus formed a few drops of iodine. What color is 
 produced ? 
 
 2. Try the effect of iodine on each of the other food sub- 
 
 stances as follows : Put a small amount of grape sugar 
 into a test tube; into a second tube put some white 
 of egg (protein) ; into a third some fat or oil ; into a 
 fourth some mineral matter (salt) ; and into a fifth some 
 water. Add a little water to each and boil as in 1 
 above to cook each nutrient. Add a drop or two of 
 iodine solution to each test tube. 
 
 Do any of the colors thus produced resemble at all the 
 color resulting from the addition of iodine to starch ? 
 
 3. From the preceding, state how you can determine whether 
 
 or not a substance contains starch. 
 
 4. (Optional home work.) Test as many foods as you can (e.g. 
 
 oatmeal, flour, raw meat, milk, parsnip, potato, onions, ap- 
 ples, beans, rice, pepper) in the following way : Put a small 
 amount of a given food into a test tube or in a sauce pan, add 
 a little water, and boil to cook each food, then add a few 
 drops of iodine. Before making each test make sure that the 
 test tube or saucer is clean. Prepare in your note-book a 
 table like the following, and fill in under each head the names 
 of the foods you have proved to contain or to be without 
 starch. 
 
 STARCH PRESENT 
 
 STARCH ABSENT 
 
 
 
 24. To test foods for grape sugar. Laboratory Study 
 No. 9. 
 
 Materials : Grape sugar, corn starch, white of egg, fat or oil, salt, 
 water ; various food substances common in home kitchen ; Fehling's 
 solution (see below) ; test tubes, gas burner or alcohol lamp. 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 17 
 
 Preparation of Fehling's Solution: To make Fehling's solution 
 dissolve 3 teaspoonfuls (34.64 grams) of pure pulverized copper sul- 
 phate (blue vitriol) in a little less than a half-pint of water (200 cc.). 
 Make a second solution by dissolving in a pint (500 cc.) of water 
 twelve heaping teaspoonfuls (150 grams) of Rochelle salt and 3 (5- 
 inch) sticks of caustic soda (50 grams). Fehling's solution does not 
 keep for any great length of time, and hence must be made up fresh 
 a short time before it is needed. To do this, thoroughly mix two 
 volumes of the copper sulphate solution and five volumes of the 
 solution of Rochelle salt and caustic soda, and dilute the mixture 
 with an equal volume of water. It is more convenient to prepare 
 it in small quantities from the tablets that may be obtained of 
 druggists. Before making any tests boil a small quantity of the 
 Fehling's solution in a clean test tube. If it retains its transparent 
 blue color, it is ready for use; otherwise a fresh supply must be 
 prepared. 1 
 
 1. Dissolve a small amount of grape sugar (glucose) in 
 
 water in a test tube. Add some Fehling's solution and 
 boil. What change in color do you notice? 
 
 2. Try the effect of Fehling's solution on each of the other 
 
 food substances as follows: Put a small amount of starch 
 into a test tube; into a second tube some white of egg; 
 into a third tube some fat or oil; into a fourth tube some 
 mineral matter (salt) ; and into a fifth tube some water. 
 Add a little water to each tube, then pour in a small 
 amount of Fehling's solution and boil as in 1 above. Do 
 any of the colors produced resemble at all the color of 
 the Fehling's solution when it was boiled with grape sugar? 
 
 3. From the preceding experiments state how you can deter- 
 
 mine whether or not a substance contains grape sugar. 
 
 4. (Optional.) Test as many foods as you can (e.g. onions, 
 grapes, pears, granulated sugar, honey, molasses, parsnip, raw 
 meat, milk, egg) in the following manner : Put a small amount 
 of a given food into a test tube, add a little water, and a 
 
 ^rom Peabody's "Laboratory Exercises." Henry Holt & Co., 
 New York, 
 c 
 
18 PLANT BIOLOGY 
 
 small spoonful of Fehling's solution, and boil. Before making 
 each test make sure that the test tube is clean. Prepare in 
 your note-book a table like the following, and fill in under 
 each head the names of the foods you have proved to contain 
 or to be without grape sugar. 
 
 GRAPE SUGAR PRESENT 
 
 GRAPE SUGAR ABSENT 
 
 
 
 25. To test foods for proteins (albuminous or nitrogenous 
 substances). Laboratory Study No. 10. 
 
 Materials : White of egg, corn starch, grape sugar, mutton tallow 
 or other fat, salt, water ; piece of meat, milk ; concentrated nitric 
 acid, ammonia ; test tubes; gas or alcohol lamp. 
 
 1. Pour a little concentrated nitric acid on a piece of hard 
 
 boiled egg in a test tube. 
 
 a. What change in color of the egg do you observe ? 
 
 b. (Optional.) Wash the egg with water, add a little concen- 
 
 trated ammonia, and note result. 
 
 2. Try the effect of nitric acid on each of the other food sub- 
 
 stances as follows: Put a small amount of starch 
 into a test tube; into a second tube some grape 
 sugar; into a third some mutton tallow or other 
 fat ; into a fourth some mineral matter (salt) ; 
 and into a fifth tube some water. Add a little con- 
 centrated nitric acid to each of these foods. Is 
 any color produced like that resulting from adding 
 nitric acid to protein? (In case a liquid is to be 
 tested with nitric acid, the mixture should be boiled 
 before deciding whether protein is present or absent.) 
 
 3. From the preceding experiments state how you can deter- 
 
 mine whether or not a food contains protein. 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 19 
 
 4. (Optional.) Prepare in your note-book a table like the follow- 
 ing, and place in the proper columns the names of the 
 foods tested in class. 
 
 PROTEIN PRESENT 
 
 PROTEIN ABSENT 
 
 
 
 26. To test foods for fats. Laboratory Study No. 11. 
 Suggested as home work. 
 
 Materials : Butter or olive oil, corn starch, grape sugar, piece of 
 boiled white of egg, salt, water ; various foods in the home kitchen, 
 including nuts. 
 
 1. Put on a piece of paper a piece of butter half the size of 
 
 a pea (or a drop of olive oil). Put the paper in a 
 warm place (e.g. in a hot oven or over a heated radi- 
 ator) for a few moments, then hold the paper between 
 yourself and the light. How is the paper affected by 
 the fat? 
 
 2. Try the effect of each of the other food substances (starch, 
 
 grape sugar, piece of boiled egg, i.e. protein, salt, i.e. 
 mineral matter, water) on paper, by adding an equal 
 quantity (half the size of a pea) of each to separate 
 pieces of paper. Put the pieces of paper in a warm 
 place as in 1 above. Hold each piece between yourself 
 and the light. Do any of these food substances affect 
 the paper as did the fat ? 
 
 3. From the preceding experiments state how you can de- 
 
 termine whether or not a food contains fat. 
 
 4. (Optional.) Prepare in your note-book a table like the follow- 
 
 ing, and place in the proper columns the names of the foods 
 tested at home or in class. 
 
20 PLANT BIOLOGY 
 
 FAT PRESENT 
 
 FAT ABSENT 
 
 
 
 NOTE. In case a food which is being tested may possibly contain 
 a small amount of fat, the food should be pulverized, shaken in a 
 test tube with ether or benzine (to dissolve out the fat) , and allowed 
 to stand for 24 hours. The clear liquid should then be poured upon 
 paper, and the ether or benzine allowed to evaporate. 
 
 Caution. Never handle ether or benzine near a flame or hot stove, 
 since the vapor of these substances is very inflammable. 
 
 27. To test foods for mineral matter. Laboratory Study 
 No. 12. Demonstration. 
 
 Materials: Salt, corn starch, grape sugar, piece of boiled egg, 
 butter or fat, water. 
 
 1. Place a piece of salt half the size of a pea on an old cook- 
 
 ing spoon and heat over as hot a flame as possible. 
 Does the salt burn and disappear? 
 
 2. In the same manner try the effect of heat on the other 
 
 food substances (starch, grape sugar, white of egg, fat, 
 water). Do any of these substances burn or disappear? 
 
 3. From the preceding experiments state how you can deter- 
 
 mine whether or not a food contains mineral matter. 
 
 4. (Optional home work.) Test at home in the same manner as 
 
 described in 1 above a match stick and a leaf. Do these 
 plant materials contain mineral matters ? How do you know ? 
 
 28. To test foods for water. Laboratory Study No. 13. 
 Home work. 
 
 1. Warm a little water on a spoon and place over it a dry, 
 cool, tumbler. What do you see on the inside of the 
 glass? How, then, can you tell whether or not water 
 is found in a given food ? 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 21 
 
 2. (Optional.) Test as many foods as you can by warming in turn 
 
 a small quantity of each in a spoon (without letting the food 
 burn), and holding over the spoon a dry, cool tumbler. 
 What do you learn as to the presence of water in foods ? 
 
 3. (Optional Demonstration.) To determine the amount of water 
 
 in potatoes: 
 
 a. Remove a thin layer of peel from a potato, weigh the potato, 
 and lay it aside in a warm dry place (protected from mice). 
 Weigh each day, and fill out in your note-book for each 
 day the first, third, and fifth columns in a table like the 
 following : 
 
 
 WEIGHT OF POTATO 
 
 Loss OF ORIGINAL WT. 
 
 PER CENT OF Loss 
 
 Without 
 Peel 
 
 With 
 Peel 
 
 Without 
 Peel 
 
 With 
 Peel 
 
 Without 
 Peel 
 
 With 
 
 Peel 
 
 j 
 
 First day 
 Second day 
 Third day 
 Fourth day 
 etc. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 b. Secure a second potato about the same size as the first, weigh 
 
 it each day, and place it beside the potato that was peeled. 
 Record results and percentages for each day in second, 
 fourth, and sixth columns of preceding table. 
 
 c. Which of the two potatoes decreases in weight the more 
 
 rapidly ? Almost all the loss of weight is due to the evapo- 
 ration of water; what do you infer, therefore, as to one 
 use of the peel ? 
 
 d. Continue to weigh the potato without the peel at intervals 
 
 until there is no further loss. What percentage of potato 
 is water? When potatoes are bought at $3 per barrel, 
 how much of this sum is paid for water ? 
 
22 PLANT BIOLOGY 
 
 IV. MANUFACTURE OF THE FOOD SUBSTANCES BY PLANTS 
 
 29. Is starch present in the green leaves of a plant that 
 has been exposed to sunlight? Laboratory Study No. 14. 
 
 Take several leaves from a vigorous plant (e.g. geranium, 
 hydrangea) which has been exposed to bright sunlight for 
 a number of hours. Boil them a few moments in a large test 
 tube or flask of water ; pour off the water, add alcohol, and 
 boil carefully over a piece of wire gauze or asbestos until all 
 the green coloring matter has been removed. Rinse the leaves 
 in water, add iodine solution, and spread the leaves on saucers, 
 or in Petri dishes. 
 
 1. Describe in your own words how the experiment was 
 
 performed. 
 
 2. Is starch present in the leaves ? How do you know ? 
 
 3. Why was it necessary to remove the green coloring 
 
 matter from the leaves before testing for starch? (If 
 you are in doubt, add some iodine to green leaves.) 
 
 4. (Optional.) How may grass stains be removed from clothing ? 
 
 30. Is starch present in the green leaves of a plant that 
 has been deprived of sunlight? 1 Laboratory Study No. 15. 
 
 Put a vigorous plant (e.g. fuchsia, squash, sunflower, or 
 bean seedling) in darkness for 48 hours or more. Remove 
 several leaves, and treat them as described in 29 above. 
 
 1. State briefly how the preparation of this experiment dif- 
 
 fers from that in the previous experiment. 
 
 2. Give your observation and conclusion. 
 
 3. State, therefore, whether sunlight is or is not necessary 
 
 for the manufacture of starch in green leaves. 
 
 31. Is starch present in colorless portions of green leaves? 
 
 Laboratory Study No. 16. 
 
 1 A most suggestive series of experiments on the formation of 
 starch in green leaves is found in the Botanical Gazette for September, 
 1909, pp. 224-228, by Sophia Eckerson, of Smith College. 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 23 
 
 Secure a plant having some portions that are colorless (e.g. 
 striped grass). Expose the plant to sunlight for two or three 
 hours, then remove several leaves and test them in the same 
 manner as described in 29 above. 
 
 1. State briefly how the preparation of this experiment 
 
 differs from that of the two preceding experiments. 
 
 2. What is your observation and conclusion as to the pres- 
 
 ence of the starch in the green and colorless portions ? 
 
 3. State, therefore, whether green material is or is not neces- 
 
 sary for the manufacture of starch. 
 
 This green material in leaves is called chlorophyll (from 
 Greek chloros = green + phullon = leaf). 
 
 32. Is carbon dioxid necessary for starch manufacture in 
 leaves? Laboratory Study No. 17. 
 
 Secure two vigorous potted plants, two bell-jars large 
 enough to go over the plant and pot, and two trays or other 
 receptacles having a greater di- 
 ameter than that of the bell-jar. 
 Place the plants in darkness for 24 
 hours at least, so that the leaves 
 may be free from starch (see 30 
 above). Now test the leaves of 
 both plants to make sure they 
 are free from starch. Into one 
 tray pour a quantity of lime water 
 and into the other tap water. 
 Put the plants on supports of 
 some kind so that the pots will 
 not touch the liquid, and cover 
 with the bell-jars. (See Fig. 3.) 
 Be sure that the edges of the bell- 
 jars are covered with the liquid, 
 so that no air can enter the jars. Place both preparations 
 where the plants can get no sunlight for 24 hours in order 
 to give time for the absorption of carbon dioxid in the jar 
 with the lime water. Place both preparations in strong 
 sunlight for several hours. 
 
 FIG. 3. Apparatus for demon- 
 strating the relation of carbon 
 dioxid to starch manufacture. 
 
24 PLANT BIOLOGY 
 
 / 
 
 1. Describe the preparation of the experiment. 
 
 2. Examine the lime water inside the bell-jar. What proof 
 
 have you that carbon dioxid has been absorbed ? 
 
 3. Remove a leaf from each of the plants and test for starch. 
 
 Tell what was done and state your observations. 
 Which leaf, therefore, contains starch? 
 
 4. What is your conclusion as to the necessity of carbon 
 
 dioxid for starch manufacture? 
 
 5. What chemical elements that are present in starch might 
 
 be furnished by the carbon dioxid (CO 2 ) ? 
 
 6. The other raw material needed by plants for the manu- 
 
 facture of starch is water (H 2 O) . What third chemical 
 element found in starch must be furnished by water? 
 
 7. Now name the two raw materials used by plants in the 
 
 manufacture of starch and state the chemical elements 
 which each can furnish. 
 
 33. Manufacture of carbohydrates. The substance first 
 made by the combination of carbon, hydrogen, and oxygen 
 in the leaves is not starch, but a simple carbohydrate which 
 is then made into grape sugar. When the plant manufactures 
 more sugar than it needs for immediate use, the surplus is 
 changed to starch, and this is what we have found stored in 
 the leaves. 
 
 34. Manufacture of proteins. We have already learned 
 that proteins contain carbon, hydrogen, oxygen, nitrogen, 
 and usually sulphur and phosphorus (see 21). The plant, 
 therefore, must somehow obtain these elements in order to 
 manufacture proteins. It has been proved that plants 
 manufacture sugar, and this probably supplies the necessary 
 carbon, hydrogen, and oxygen. The nitrogen that is needed 
 is furnished by compounds containing nitrogen such as salt- 
 peter (potassium nitrate, KNO 3 ), and the sulphur and phos- 
 phorus are secured from mineral compounds known as sul- 
 phates and phosphates. These compounds are derived from 
 soil water. From these compounds, namely, sugar and the 
 
COMPOSITION OF LIFELESS AND LIVING THINGS 25 
 
 mineral matters containing nitrogen, sulphur, and phos- 
 phorus obtained from the soil, the living plant manufactures 
 protein. 
 
 35. Do green plants give off a gas in sunlight? Labora- 
 tory Study No. 18. 
 
 Into a glass cylinder containing water fresh from the faucet 
 put a small amount of water plant (Elodea, Spirogyra, or 
 Milfoil), holding it to the bottom of the tall jar by means of 
 a weight if necessary. Stand the cylinder in direct sunlight. 
 
 1. Describe the preparation of the experiment. 
 
 2. What do you observe coming off from the plant ? (These 
 
 bubbles of gas have been proved to be composed of 
 oxygen.) 
 
 36. Do green plants give off a gas when deprived of sun- 
 light? Laboratory Study No. 19. 
 
 Place the glass cylinder prepared as directed above in 
 darkness for several hours (or, still better, a second cylinder 
 should be used for comparison). 
 
 1. In what respects do Experiments 18 and 19 differ? 
 
 2. Do you see any bubbles as long as the cylinder is kept 
 
 in the dark? 
 
 3. Under what condition, therefore, does a green plant give 
 
 off oxygen? 
 
 37. The oxygen supply for animals. We have seen that 
 starch is made of carbon dioxid (C0 2 ) and water (H 2 0). By 
 repeated experiments biologists have proved that in the pro- 
 cess of manufacturing carbohydrates more oxygen is present 
 in the CO2 and H^O than is needed. This is the oxygen we 
 have seen given off by the green water plant in sunlight. 
 Every green plant gives off oxygen into the air when manu- 
 facturing carbohydrates. Hence, in this process the carbon 
 dioxid is constantly being taken from the air and a fresh 
 supply of oxygen set free. 
 
CHAPTER III 
 
 THE STRUCTURE OF PLANTS 
 
 38. The parts of a plant. Laboratory Study No. 20. 
 
 Materials: A well-developed bean plant or other seedling or a 
 weed, for each two pupils ; one or more plants with flowers and if 
 possible with fruits for demonstration. 
 
 Nearly all the plants with which we are most familiar 
 consist of at least three kinds of 
 parts, namely, roots, stems, and leaves 
 (Fig. 4). 
 
 1 . Name and describe as to color and 
 
 form the parts of the plant that 
 grew beneath the ground. 
 
 2. How does the stem differ from the 
 
 root as to color and direction of 
 growth? What parts of the 
 plant above ground are attached 
 to the stem? 
 
 3. How does the main part of the leaf 
 
 differ in form from the root or 
 the stem? 
 
 4. Make a drawing, natural size, of the 
 
 plant you are studying, labeling 
 ground level, roots, stem, leaf. 
 
 5. On the plants used for demonstra- 
 
 tion, what parts besides those 
 named above do you find ? How 
 do the colors of these parts differ 
 from the color of the rest of the 
 plant? 
 26 
 
 FIG. 4. Roots, stems, 
 leaves, flowers, and fruits 
 of a buttercup plant. 
 
THE STRUCTURE OF PLANTS 27 
 
 39. Organs and functions. From our laboratory study 
 we have learned that a common plant consists of roots, stems, 
 and leaves, and that at certain seasons of the year flowers 
 and fruits are present. To each of these various parts is 
 given the name organ. Roots are useful to a plant, for one 
 thing, because they hold it in the ground, while stems support 
 the leaves, flowers, and fruits. In fact every organ of a 
 plant has some work to do, and this work is called its func- 
 tion. Hence, we may define an organ as a part of a plant that 
 has a certain function or functions to perform. 
 
 40. Microscopic structure of plants. When one exam- 
 ines by the aid of a compound microscope a small portion 
 of any of the organs of common plants, one finds that each 
 organ is composed of many smaller portions too minute to be 
 seen with the unaided eye. These tiny divisions are called 
 cells. We shall now attempt to become familiar by the use 
 of the compound microscope with the appearance of several 
 kinds of plant cells. 
 
 41. Study of plant cells. Laboratory Study No. 21. 
 
 Materials: (1) Slides prepared as follows : Cut a layer of an onion 
 bulb into small squares, and strip off from the inner surface of each 
 square a very thin layer. Place it on a glass slide and add a drop 
 of water. (If it is desirable to keep the slides for several hours, 
 put glycerin diluted with water over the onion cells.) Cover each 
 thin membrane with a cover glass. 1 (2) Prepared or freshly cut 
 thin sections of roots, stems, and leaves. 
 
 1. By the aid of the low power of the compound microscope, 
 examine the slide prepared as directed in (1) under 
 materials. Note that the thin membrane is com- 
 posed of a large number of tiny spaces each in- 
 
 1 The authors are indebted to Miss Elsie M. Kupfer, Head of 
 Department of Biology of Wadleigh High School, New York City, 
 for suggesting this admirable material for cell study. 
 
28 PLANT BIOLOGY 
 
 closed by lines more or less dark in color called 
 cell-walls. (These parts are usually seen more clearly 
 if the light is largely excluded by closing the dia- 
 phragm in the stage.) 
 
 a. Describe the general appearance of the membrane, 
 stating of what it is composed. 
 
 6. State whether or not the cells in the various parts of 
 the membrane differ in size and shape. 
 
 2. The cell-wall incloses a semifluid substance which makes 
 
 up the cell-body. Describe the appearance of the 
 cell-body. 
 
 3. Within the cell-body, often near the center of the cell, 
 
 is usually a tiny object called the nucleus. Describe 
 the location, shape, and color of the nucleus. 
 
 4. Make a drawing of three or four adjacent cells, several 
 
 times as large as they appear under the microscope. 
 Label cell-wall, cell-body, cell-nucleus. 
 
 5. (Demonstration.) Secure some growing sprays of Elodea 
 
 (a common water plant) . Pull off one of the youngest 
 leaves near the tip end, put it on a 
 slide with a drop of water, and cover 
 with a cover glass. Let the prepara- 
 tion stand in a warm place for a time. 
 Examine with the high power the cells of 
 
 which this leaf is composed. 
 Within each cell note some green bodies 
 called chlorophyll bodies (from Greek, 
 meaning leaf green). These are the 
 bodies which aid in starch manufac- 
 ture in green leaves. (See 31.) 
 FlG - 5 - 1 ~^ lodea a. Describe the form, color, and use of 
 
 chlorophyll bodies. 
 
 6. Carefully watch the chlorophyll bodies in several 
 cells and describe any movements you see. These 
 movements show that the substance of the cell is 
 in motion, and is carrying the chlorophyll bodies 
 along with it. 
 
 c. Make a drawing at least 2 inches long of one of the 
 cells with its chlorophyll bodies. Label cell-wall, 
 
THE STRUCTURE OF PLANTS 
 
 29 
 
 protoplasm 
 of cell-body 
 
 cell-nucleus 
 
 cell- 
 wall 
 
 chlorophyll bodies, and show by arrows the direction 
 of their movements. 
 
 6. (Demonstration.) Examine with the low power of the 
 microscope the sections of root, stem, and leaf, or 
 study Figures 11, 12, 15, 22. Write a paragraph on 
 the microscopic structure of root, stem, and leaf. 
 
 (Optional.) Make a drawing of four or five cells from 
 each of the organs studied. 
 
 42. Cells and protoplasm. Under the microscope cells 
 at first appear to be only plane surfaces surrounded by lines. 
 In reality, however, each cell has 
 not only length and breadth, but 
 also thickness, and each cell is 
 covered on all sides by a cell-wall 
 which is composed of a lifeless 
 substance known as cellulose. 
 This wall is often so transparent 
 that we can look through it and 
 see the cell-body and nucleus 
 within (Fig. 6). 
 
 The discovery of these minute 
 bodies of which organs are com- 
 posed was not made until about 
 the middle of the last century 
 (1848). With the rather imper- 
 fect microscopes then in use the 
 two discoverers, Schleiden and 
 Schwann, could see the cell-walls 
 only, and they did not know, as 
 we now know, that the most im- 
 portant part of the cell is not the lifeless wall of cellulose, 
 but the living substance which is found inside the cell -wall, 
 making up a large part of the cell-body and cell-nucleus. 
 
 FIG. 6. Plant cell. The spaces 
 in the cell-body are filled with 
 cell-sap. 
 
30 PLANT BIOLOGY 
 
 To this substance is given the name protoplasm. We know 
 now that the living substance or protoplasm is the essential 
 part, while the wall may be missing, so that in such a 
 case there is no resemblance to a cell or box. Biologists 
 now understand a cell to be a bit of protoplasm (cell-body) con- 
 taining a nucleus (which is a denser portion of the protoplasm). 
 
 Protoplasm, when examined with the highest powers of the 
 microscope, appears as a colorless, semifluid substance, in 
 which are often seen solid particles or granules, which are 
 probably little masses of food. The nucleus, as already 
 stated, is commonly found near the center of the cell, and is 
 composed of protoplasm denser than the protoplasm of the 
 body of the cell. The appearance and composition of the 
 protoplasm may be well represented by raw white of egg ; but 
 in making this comparison one should bear in mind that the 
 white of an egg is not living substance. 
 
 Within the cell, too, and occupying some of the space out- 
 side the nucleus, especially in plant cells, is cell-sap, which is a 
 lifeless fluid composed of water in which are dissolved the food 
 substances (such as sugar and mineral matters) used by cells 
 in their growth and repair, and in the various kinds of work 
 which they carry on (Fig. 6). 
 
 43. Assimilation, growth, and cell division. To make 
 protoplasm the plant must have proteins, water, and addi- 
 tional compounds containing iron, calcium, and several other 
 chemical elements. But only protoplasm has the power to 
 combine these compounds in such a way as to form living 
 matter. Bearing in mind the facts we learned in studying 
 food manufacture (33 and 34), we see that the plant begins 
 with simple substances, water and carbon dioxid, and manu- 
 factures a more complex substance, sugar. It uses this and 
 other substances to make a still more complex substance, 
 
THE STRUCTURE OF PLANTS 
 
 31 
 
 protein, and finally ends by making the most complex of all, 
 protoplasm. But, except in rare cases, all plants must have 
 compounds to start with ; they cannot make any of these 
 nutrients or protoplasm from chemical elements. 
 
 And thus we learn that food materials are gradually 
 changed by protoplasm into living substance like itself. To 
 this process is 
 given the name 
 assimilation 
 (Latin, ad = to 
 = similis =like) . 
 As a result 
 of the process 
 of assimilation 
 the amount of 
 protoplasm of 
 course increases 
 
 B C 
 
 FIG. 7. Cell division. 
 
 ool A > cel1 before division; B, cell with divided nucleus; C, single 
 cell that has divided into two cells. 
 
 grows. Were 
 
 this process to continue indefinitely, cells would become 
 large in size. This, however, does not occur; for when 
 a cell reaches its normal size, the nucleus divides, and the 
 halves separate from each other to form two nuclei. The 
 cell-body now divides into two parts, and cell-walls are 
 formed between the two cells (Fig. 7). Thus are produced 
 two cells, each having its own nucleus, and these in turn as- 
 similate, grow, and divide. In this way the number of cells 
 increases with the growth of the plant. 
 
CHAPTER IV 
 
 OSMOSIS AND DIGESTION 
 
 Materials : Four thistle tubes, four wide-mouthed bottles ; honey, 
 molasses, or a thick solution of grape sugar; starch (arrowroot if 
 possible), diastase ; white of egg, peptone ; iodine, Fehling's solution, 
 nitric acid. Procure the intestines of calf or beef, wash them thor- 
 oughly inside and out, and inflate them by the aid of a glass tube. 
 Tie at intervals of two or three feet, and allow this animal mem- 
 brane to dry. Cut off pieces about two inches long, and slit open 
 each of the pieces thus obtained. Membrane 
 prepared in this way may be kept in closed 
 bottles for years. If desired, the pieces of 
 membrane may 'be used at once without dry- 
 ing. Sausage coverings that have been pre- 
 served in salt may be thoroughly washed, 
 dried, and used. 
 
 Thistle tube No. 1. Hold one of the thistle 
 tubes upright, closing the smaller end by press- 
 ing on it with the thumb. Into the larger 
 end pour the honey, molasses, or grape sugar 
 solution, which has been sufficiently warmed to 
 pour easily. Half fill the tube and nearly fill 
 the bulb. Moisten one of the pieces of intestine 
 and tie it tightly over the bulb of the thistle 
 tube so that none of the liquid can escape. 
 Wash off any of the liquid from the outside of 
 the membrane, then dry it with a blotter, and 
 hold the thistle tube bulb down for several minutes to make sure 
 that the grape sugar solution does not leak out. Now stand the 
 
 32 
 
 FIG. 8. Apparatus 
 for thistle tube 
 No. 1 in osmosis 
 experiment. 
 
OSMOSIS AND DIGESTION 33 
 
 tube, membrane down, in one of the wide-mouthed bottles and fill 
 it with water up to the neck. Add grape sugar solution to the thistle 
 tube until the level of the water in the bottle and that of the 
 liquid in the thistle tube is the same. Connect a long piece of 
 glass tubing to the upper end of the inverted thistle tube, and 
 support this tube in a vertical position, so that the membrane does 
 not touch the bottom of the bottle (Fig. 8). 
 
 Thistle tube No. 2. Set up a control experiment exactly like 
 No. 1, except that water should be put into the thistle tube as well 
 as in the bottle. 
 
 44. Will water pass through a membrane ? Laboratory 
 Study No. 22. 
 
 1. Give in your own words a description of the way thistle 
 
 tube No. 1 was prepared, making a diagram of the 
 apparatus, and labeling level of water in bottle 
 and of grape sugar solution in thistle tube at the 
 beginning of the experiment. 
 
 2. At the end of a few hours compare the level of the liquid 
 
 in thistle tube No. 1 with the level in thistle tube 
 No. 2. 
 
 a. How many inches has the grape sugar risen in No. 1 ? 
 
 b. Is there a similar rise in the water in thistle tube 
 
 No. 2? 
 
 c. What must have passed into thistle tube No. 1 to 
 
 cause the liquid to rise? 
 
 d. Through what must this liquid have passed to get 
 
 into the thistle tube? 
 
 3. Do you conclude, therefore, that water will or will not 
 
 pass through a membrane ? 
 
 45. Will grape sugar pass through a membrane? Labor- 
 atory Study No. 23. 
 
 1. At the end of a few hours test the liquid in bottle No. 1 
 by putting a glass tube to the bottom of the bottle, 
 pressing the thumb over the top of the tube, and 
 removing the sample of liquid thus obtained to a 
 clean test tube; add Fehling's solution and boil. 
 
PLANT BIOLOGY 
 
 a. Describe what was done. 
 
 b. Is grape sugar present now? How do you know? 
 
 c. What must have happened to produce this result? 
 
 2. We have now proved that two different liquids have 
 
 passed through the membrane. 
 
 a. Name these two liquids. 
 
 6. Which of these two liquids has passed through the mem- 
 brane in the greater quantity ? How do you know ? 
 
 c. Which of these two liquids is the thicker or denser? 
 
 d. By a great many experiments it has been proved that, 
 
 when any two liquids of different density are sep- 
 arated by a plant or animal membrane, results sim- 
 ilar to those noted above follow. To this inter- 
 change of liquids is given the name osmosis. In this 
 process of osmosis, is the greater flow of liquid from 
 the less dense to the more dense, or from the more 
 dense to the less dense? 
 
 e. Why did not the water rise in thistle tube No. 2 ? 
 
 3. Do you conclude, therefore, that grape sugar will or will 
 
 not pass through a membrane? 
 
 46. Osmosis in living cells. Laboratory Study No. 24. 
 Peel a potato and then cut several cross sections about 
 
 inch in thickness. 
 
 FIG. 9. Cells from a 
 potato, showing cell- 
 walls, cell-sap, and 
 starch grains of differ- 
 ent sizes. 
 
 Allow these sections to stand in the 
 air until they bend readily. Half fill 
 one tumbler with water and a second 
 tumbler with a strong solution of 
 sugar or salt. Place some of the 
 sections in each of the two tumblers 
 and leave them for several hours. 
 
 1. Describe the preparation of this 
 
 experiment. 
 
 2. Remove a section of potato from 
 
 each of the liquids and bend 
 them. Compare the change that 
 has taken place in the rigidity or 
 stiffness of the sections placed 
 
 in the strong solution and those in the tap water. 
 
OSMOSIS AND DIGESTION 35 
 
 4. Potato sections, like those of all parts of living plants, 
 are composed of a large number of living cells, each one 
 inclosed by a cell membrane (Fig. 9). 
 Call to mind what you learned in 45, and state why the 
 cells become even more flabby in one solution and more 
 rigid in the other. 
 
 47. Will starch pass through a membrane? Laboratory 
 Study No. 25. 
 
 Thistle tube No. 3. Put into a third thistle tube a mixture of 
 starch and water, cover the bulb with a membrane, and invert in a 
 bottle of water, as already directed for the first thistle tube. See 
 that the level of the liquid is the same in all of the experiments. 
 
 1. In what respects does the preparation of thistle tube 
 
 No 3 resemble that of No. 1? How do the two 
 experiments differ? 
 
 2. At the end of a few hours test the liquid in bottle No. 3 
 
 by removing a sample to a test tube (as already 
 directed in 45), and adding iodine solution. 
 
 a. Is starch present? How do you know? 
 
 6. What is your conclusion as to the possibility of starch 
 passing through a membrane? 
 
 3. What have these experiments in osmosis taught you as 
 
 to one difference between starch and grape sugar? 
 
 48. Definitions and applications. The experiments we 
 have been performing have most important relations to the 
 study of all living plants and animals. We may give the 
 following as a definition of the process we are considering : 
 Osmosis is the interchange of liquids of different density that are 
 separated by a plant or an animal membrane, and in this pro- 
 cess the greater flow is always from the less dense to the more 
 dense. 
 
 We shall constantly refer to this principle of osmosis, and 
 we shall find that it explains in large measure the absorption 
 of soil water by roots, the transfer of sap from one part of a 
 
36 PLANT BIOLOGY 
 
 plant to another, as well as the processes by which the blood 
 of animals obtains and gives off food to various cells of the 
 body. 
 
 By the preceding experiments we have proved that there are 
 two classes of food substances. One kind (including water and 
 grape sugar) will readily pass through a membrane by osmosis ; 
 the other kind (represented by starch) will not. In our study 
 of cells we learned that the protoplasm or living substance is 
 inclosed by a cell-wall which separates one cell from another. 
 Now if cells are to make use of the food materials manufac- 
 tured in other parts of the plant, each food substance must be 
 in such a form that it can pass through these cell-membranes. 
 It is evident that water and grape sugar can .do this. We 
 find, however, large quantities of starch stored in cells 
 (Fig. 9). Hence, to be available for use in other cells, some 
 change must be made in this food substance before it 
 can be transferred from cell to cell. We shall now show by 
 experiment what this change is. 
 
 49. How starch is made ready to pass through a membrane. 
 
 - Laboratory Study No. 26. 
 
 Into each of two test tubes put a small amount of starch 
 (arrowroot- starch if it can be obtained), add some water, 
 shake, and boil. To the starch mixture in one test tube add 
 some diastase, equal in amount to one-half the size of a pea. 
 (Diastase is a chemical substance produced or secreted by 
 the protoplasm of plant cells.) Put the two test tubes side 
 by side in a warm place for 5 minutes if arrowroot starch, 
 24 hours if corn starch is used, then test a small amount of 
 the mixture in each test tube by adding a few drops of iodine. 
 
 1. Describe in your own words what has been done. 
 
 2. In which test tube do you find starch present ? 
 
 3. Now test with Fehling's solution a small quantity of 
 
 each mixture. In which tube do you find grape sugar ? 
 
OSMOSIS AND DIGESTION 37 
 
 4. What do you conclude, therefore, as to the effect of dias- 
 
 tase on starch? 
 
 5. Why is this change necessary if starch is to be used by 
 
 plants ? 
 
 50. To prove that starch is made soluble in growing plants. 
 
 Laboratory Study No. 27. 
 
 1. Pound two or three corn grains into a powder and put 
 
 some of this corn meal into a test tube, add water, and 
 boil. To one-half of the mixture add iodine, and to the 
 other half, Fehling's solution, and boil. Give a careful 
 description of the experiment and state your observa- 
 tions and conclusions. 
 
 2. Secure some germinating corn grains, cut them into small 
 
 pieces, and test some of them with Fehling's solution as 
 in 1 above. Describe the experiment, stating your ob- 
 servations and conclusions. 
 
 3. The change in starch that you have described is known 
 
 as digestion. What reason have you for believing that 
 digestion of starch takes place when corn grains ger- 
 minate ? 
 
 51. Definition of digestion. We may define digestion as 
 the chemical change whereby insoluble food substances are made 
 ready to pass through membranes and become ready for the use 
 of protoplasm. Let us now by experiment determine whether 
 or not protein needs digestion. 
 
 52. Will protein pass through a membrane? Laboratory 
 Study No. 28. 
 
 Thistle tube No. 4- Secure some white of egg, cut it with scis- 
 sors and mix it with water. (White of egg, we found, contains a 
 large amount of protein.) Prepare the fourth thistle tube in the 
 same way as directed for thistle tube No. 1 , only using white of egg 
 and water instead of grape sugar. See that the level of the liquid 
 is the same as in thistle tube No. 2. 
 
38 PLANT BIOLOGY 
 
 1. In what respects does the preparation of thistle tube 
 
 No. 4 resemble that of thistle tube No. 1 ? How do the 
 two experiments differ ? 
 
 2. Allow the experiment to stand for several hours, and then 
 
 remove with a glass tube a sample of the liquid in 
 bottle No. 4, and test it by adding nitric acid and boil- 
 ing. Is protein present ? How do you know ? 
 
 3. Do you conclude, therefore, that protein will or will not 
 
 pass through a membrane ? 
 
 53. Digestive ferments. We have stated that proto- 
 plasm secretes a substance called diastase, and have shown 
 that this diastase will change insoluble starch to soluble grape 
 sugar, which will pass from one cell to another by the process 
 of osmosis. Diastase is a substance known as a digestive 
 ferment. Now protoplasm produces other digestive ferments, 
 some of which will change insoluble protein to a soluble sub- 
 stance known as peptone. The latter will readily pass by the 
 process of osmosis through a membrane. 
 
 Fats, also, like starch and protein, are insoluble and can- 
 not, therefore, pass by osmosis through cell walls. To make 
 these food substances available for use they must also be 
 changed by the plant cells into such forms that they may be 
 readily transferred from one part of the plant to another. 
 These changes are caused by other chemical ferments pro- 
 duced by protoplasm. 
 
CHAPTER V 
 ADAPTATIONS OF THE NUTRITIVE ORGANS OF PLANTS 
 
 54. The nutritive organs of plants. From our study of 
 food manufacture (29-34) we learned that the plant foods are 
 produced in green leaves. Before this process of food manu- 
 facture can go on, however, the cells in the leaf must be sup- 
 plied with raw materials from the air and from the soil. 
 Since the roots, stems, and leaves are all concerned in food 
 making, these organs are known as the nutritive organs of 
 plants. Each of these organs has several functions ; we shall 
 now learn what some of these functions are, and how the 
 nutritive organs are adapted for the work they do. 
 
 I. THE STRUCTURE AND ADAPTATIONS OF ROOTS 
 
 55. The structure of roots. Laboratory Study No. 29. 
 A. Gross structure of roots. 
 
 Select the largest roots of a well-developed seedling or the 
 roots of common weeds. By means of your thumb and finger 
 nail gently scrape off the outer layers from a piece of one of 
 these roots. When no more of the material can be easily 
 removed by this method, pick to pieces the central part of 
 the root which is left. The outer layer you have removed is 
 largely composed of the cells of the cortex, and the central 
 part that has been exposed is called the central cylinder. 
 
 1. Tell what you have done. 
 
 2. Which is composed of the tougher and harder material, 
 
 the cortex or the central cylinder ? 
 39 
 
40 PLANT BIOLOGY 
 
 3. Make a diagram greatly enlarged of a piece of root 
 prepared as directed above. Label cortex, central 
 cylinder, fibers of central cylinder. 
 
 B. Root-hairs. 
 
 Note to the Teacher. Root-hairs may be grown for study as 
 follows : Cover the bottom of as many Petri dishes as are needed 
 with a layer of blue blotting paper. Soak the paper with water and 
 lay several grains of soaked barley, oats, or corn upon the bottom 
 of each dish. Put ttte covered dishes in a warm place for several 
 days. When the root- hairs have developed, wipe the moisture from 
 the inside of the covers, quickly replacing the latter. If Petri dishes 
 are not available, two clean glasses of any convenient size may be 
 used instead. Cover one of the plates with layers of wet blotting 
 paper, put the soaked grains in position, and cover with the second 
 glass, fastening the two together with threads or strings. Stand 
 one end of the preparation thus made in a jar with enough water to 
 reach the lower edge of the blotting paper. 
 
 Examine first with the naked eye and then with a hand 
 magnifier the roots of sprouted grains, developed as described 
 above. Notice tiny outgrowths from the sides of the roots; 
 these outgrowths are called root-hairs. 
 
 1. Look at the very tip of the root and state whether 
 
 root hairs are there present or absent. 
 
 2. State whether the root-hairs are longest near the tip 
 
 or in the direction of the grain. 
 
 3. Make a drawing much enlarged to show the shape of 
 
 one of the roots including the root-tip and the 
 various lengths of root-hairs. Label root-tip, root- 
 hairs. 
 
 C. Microscopical structure of the tip of a root. (Optional.) 
 
 Examine with the aid of the low power of the compound micro- 
 scope a root- tip mounted on a slide in drop of water and covered 
 with a cover glass. Make a sketch very much enlarged to 
 show 
 
THE NUTRITIVE ORGANS OF PLANTS 41 
 
 1. The outline of the root including the tip. 
 
 2. A loose mass of cells covering the lower end of the root which 
 
 make up the root<-cap. 
 
 3. Label root- tip, cells of the root- cap. 
 
 56. The functions of roots. Laboratory Study No. 30. 
 
 A. Roots as organs for holding the plant to the soil. 
 
 Secure a vigorously growing plant in a pot (e.g. a rubber 
 plant) or better try the following experiment on a 
 good sized weed in a field. Attach to the stem just 
 above ground level a spring balance. Pull on the 
 balance until the plant shows signs of letting go its 
 hold on the soil, then note the reading in pounds on 
 the scale. 
 
 1. In your own words describe what was done. 
 
 2. How much force in pounds was exerted on the 
 
 plant? 
 
 3. What important function of roots is shown by this 
 
 experiment ? 
 
 B. Roots as organs for absorbing soil-water. 
 
 (Before proceeding further with the root study, the osmo- 
 sis experiments, 44-53, should be performed if they 
 have not already been done.) 
 
 Study the diagram of a root-hair in the text-book (Fig. 12) 
 and if possible examine with the low power of the 
 microscope some of the younger (shorter) root- 
 hairs. Each root-hair is an elongated part of an 
 outer cell of the root. 
 
 1. Draw in your note-book a diagram of a root-hair, 
 
 labeling cell-wall, thin layer of protoplasm, cell- 
 sap, and nucleus. 
 
 2. What separates the soil-water from the cell-con- 
 
 tents? 
 
 3. Recall the characteristics of cellular structure as 
 
 given in 42. Now state which is the more dense, the 
 soil-water or the cell-contents. 
 
42 PLANT BIOL9GY 
 
 4. In which direction, therefore, will there be the greater 
 
 movement of liquid in the process of osmosis ? 
 
 5. How, then, is a root-hair adapted by structure for 
 
 absorbing soil-water? 
 
 C. Roots as organs for transmitting soil-water. 
 
 Place some seedlings or weeds in red ink so that only the 
 lower ends of the roots are in the liquid. Cut some 
 cross sections of these roots above the point where 
 they were in contact with the ink. Examine the 
 cross section of the root prepared in this way. 
 
 1. Describe the experiment as it was performed. 
 
 2. Through what part of the root (cortex or central 
 
 cylinder) has most of the liquid passed? How do 
 you know? 
 
 3. Make a sketch about an inch in diameter of the cross 
 
 section of the root, to show the colored and colorless 
 portions. Label : part of the root through which 
 liquid traveled, unstained portion of root, cortex, 
 central cylinder. 
 
 D. Roots as organs for the storage of food. 
 
 Cut some slices about an inch thick from parsnips or other 
 fleshy roots, and divide each slice vertically in 
 halves. Put the pieces in water and boil for a few 
 moments to partially cook them. Pour iodine 
 solution over some of the pieces; to others add 
 strong nitric acid ; boil still other pieces in a test 
 tube with Fehling's solution. 
 
 1. Describe the preparation of each of the experiments, 
 
 and state in each case your observations. 
 
 2. What do you conclude as to the presence or absence of 
 
 each of three of the food substances in various parts 
 of the fleshy root you are studying ? 
 
 3. What function of roots do these experiments demon- 
 
 strate ? 
 
 57. Adaptations of roots for holding to the soil. One 
 
 of the most obvious functions of roots is that of holding plants 
 firmly in the ground. If the soil is carefully removed from 
 
THE NUTRITIVE ORGANS OF PLANTS 
 
 43 
 
 the roots of a weed or a tree, these roots will be found to 
 extend outward in all directions to a distance even greater 
 than do the branches above ground. When one remembers 
 the tremendous force exerted upon trees by high winds, the 
 necessity for this extensive root anchorage will be evident. 
 In our dissection of the root even of a young plant we found 
 
 FIG. 10. Roots of a tree, showing method of transplanting a large tree. 
 (Courtesy of Isaac Hicks and Sons, Westbury, Long Island.) 
 
 that the central cylinder was composed of tough fibers which 
 are made up of elongated wood-cells (similar to those shown 
 in Fig. 15). As a plant grows older, these central cylinders 
 become so thick and tough that they will resist an enormous 
 strain without breaking. 
 
 58. Adaptations of roots for absorbing and transmitting 
 soil-water. A second function of roots we found to be that 
 of absorbing soil-water and transmitting it to the stem. The 
 
PLANT BIOLOGY 
 
 whole outer surface of young roots is covered with a single 
 layer of thin-walled cells which form the epidermis. Many of 
 these cells develop tubular outgrowths known as root-hairs 
 
 . 
 
 *& : /Ulx/Mx 
 
 ?*m 
 
 
 FIG. 11. Cross section of root, FIG. 12. Diagram of a lengthwise 
 
 showing root-hairs and epidermis section of two root-hairs with 
 
 cells on the outer surface, cells of adjacent cells of the epidermis, 
 
 cortex within, and woody central and with two cells of the cortex, 
 cylinder with its ducts. (Bailey.) 
 
 (see 56, B). By studying Fig. 12 it will be evident that each 
 root-hair consists of a cell-wall lined by a thin layer of 
 protoplasm. The interior of the cell is largely filled with 
 
 cell-sap. On the outside 
 of each root-hair is soil- 
 water. All the conditions 
 necessary for osmosis are 
 
 FIG. 13. Portion of a root-hair with ad- 
 hering particles of soil. (Strasburger.) 
 
 which separates the soil-water from the denser cell-sap/ 
 From the law of osmosis, we should expect a flow of liquids 
 in both directions, the greater flow being into the cell-sap 
 from the soil-water. It has been found, however, that the 
 
 therefore present. The 
 
 ce ll-wall IS the membrane 
 
THE NUTRITIVE ORGANS OF PLANTS 
 
 45 
 
 protoplasm permits the inward flow 
 of the soil-water, but practically 
 prevents the outward flow of the 
 cell-sap. Thus we see that proto- 
 plasm has a selective action. Since 
 the growing parts of roots have 
 countless root-hairs, these cells of 
 the epidermis together act like a 
 great sponge which absorbs the large 
 quantities of water and mineral mat- 
 ters which are needed by all plants. 
 This liquid passes from one cell to 
 another until it reaches the central 
 cylinder. A study of the micro- FIG. 14. Ducts that convey 
 
 scopical structure of the central cyl- ^he root 
 
 inder makes evident the fact that The walls of these ducts 
 
 , r /. ,-, , , are strengthened by spiral 
 
 this part of the root consists not fibers or rings. 
 only of tough wood cells as explained 
 
 in the preceding section, but also of tubular cells called ducts. 
 (See Fig. 14.) Through these ducts the sap is conveyed up- 
 ward to the stem. 
 
 II. THE STRUCTURE AND ADAPTATIONS OF STEMS 
 
 59. The structure of a woody stem. - Laboratory Study 
 No. 31. 
 
 A. The structure of a young stem. 
 
 Secure pieces of a young stem of a horse-chestnut, maple, 
 lilac, or other woody stem that shows the three 
 layers of bark. Split some pieces lengthwise in 
 halves. 
 
 1. Peel off the outer covering, the bark, from a piece of 
 the stem till the wood is exposed. The bark of 
 
46 PLANT BIOLOGY 
 
 a young stem usually consists of three more or 
 less distinct layers. 
 
 a. With a knife gently scrape off an outer or brown 
 
 bark, and expose a dark green layer known as the 
 green bark. Scrape this until you come to a 
 more or less tough layer known as the fibrous 
 bark or bast (which may be slightly green). 
 Describe each of these barks as to position and 
 color. 
 
 b. Pick into threads the fibrous bark ; in what direc- 
 
 tion of the stem do the fibers run? By break- 
 ing strips of each layer determine which of the 
 three barks is toughest. 
 
 2. Feel of the wood from which the bark has just been 
 
 removed. Describe the substance which covers 
 the wood, after scraping off a little with your 
 thumb nail. This is the cambium or growing 
 layer, which produces the new wood and bark. 
 When the bark is torn off, the cells of this layer 
 are broken and the slimy protoplasm oozes out. 
 
 3. By means of a penknife or pin dig into the wood and 
 
 also into the pith at the center of the stem. 
 Compare the wood and the pith as to relative 
 position and hardness. 
 
 4. By the aid of compasses make a diagram, at least three 
 
 inches in diameter, of the cross section of a 
 woody stem to show the relative thickness of 
 the various layers. (These layers might well be 
 represented by different colors.) Label brown 
 bark, green bark, fibrous bark or bast, cambium 
 layer, wood, pith. 
 
 B. The structure of an older stem. (Optional.) 
 
 Cut some cross sections of stems several years old. (Ad- 
 mirable material can be obtained by sawing into pieces 
 about two inches long white oak sticks three to four 
 inches in diameter.) Each piece should then be split 
 into halves and each surface planed and sandpapered. 
 These pieces are valuable as permanent preparations. 
 
THE NUTRITIVE ORGANS OF PLANTS 47 
 
 1. Which of the three regions (bark, wood, and pith) found in 
 
 the young stem can you readily distinguish ? Which 
 of the three becomes very much thicker and harder as 
 the stem grows older ? Which is very small in quan- 
 tity when compared with the young stem ? 
 
 2. The curved layers of wood in the cross section are known as 
 
 annual rings, so called because usually only one ring is 
 formed each year by the cambium layer. How many 
 years of growth are shown in the piece of wood you 
 are studying ? 
 
 3. The lines in the cross section extending like the spokes of a 
 
 wheel are the pith rays or medullary rays. Describe 
 the appearance of these rays. The shining, lighter 
 colored surfaces (to which the beauty of "quartered 
 oak" furniture is due), that appear in the longitudinal 
 sections of oak wood, are the pith rays. Find pith 
 rays in the middle surfaces of some of the oak pieces 
 you are studying, and describe them. 
 
 4. Make a Jarge diagram of the cross section of the piece of 
 
 wood you are studying. Label bark, wood, annual 
 rings, medullary or pith rays. 
 
 60. The structure of the corn stem. Laboratory Study 
 No. 32. (Optional.) 
 
 Cut pieces about two inches in length from full-grown corn stalks, and 
 split each piece in halves. (If necessary these pieces may be preserved 
 from year to year in 4 per cent formalin or in 70 per cent alcohol.) 
 
 Examine the cross and longitudinal sections of corn stem. Find 
 the rind (the outer layer), the woody bundles or fibers (thread-like 
 structures), and the pith (material between the bundles). 
 
 1. Thrust your pencil point into the pith; is this material hard or 
 
 soft? 
 
 2. Pull out one of the woody fibers ; is it tough or tender ? 
 
 3. Push your pencil point into the rind ; is it hard or soft ? 
 
 4. Make a drawing (X 2) showing both cross and longitudinal 
 
 surfaces. Label rind, woody bundles, pith. 
 
48 PLANT BIOLOGY 
 
 61. Experiments to show the upward path of sap through 
 stems. Laboratory Study No. 33. 
 
 A. Stand some live twigs (e.g. maple or horse-chestnut) in 
 
 red ink for a day or two ; cut off pieces above the 
 level of the ink, and split some of these pieces in 
 half lengthwise. 
 
 1. Describe the preparation of the experiment. 
 
 2. Through what part of the stem does the red ink rise ? 
 
 3. What do you conclude, therefore, as to the part of a 
 
 woody stem through which sap rises? 
 
 B. (Optional.) Stand in red ink some pieces of fresh corn stalk 
 
 (or if this cannot be obtained, some Tradescantia or 
 any lily stem). Cut some cross and longitudinal sec- 
 tions above the level of the ink. 
 
 1. Write an account of the experiment, stating your observations. 
 
 2. In the stem you are studying, is sap carried upward by the 
 
 rind (epidermis in the lily), or by the pith, or by the 
 woody fibers ? How do you know ? 
 
 62. Stems as organs for support and leaf exposure. 
 
 When we studied the manufacture of carbohydrates by plants, 
 we proved that green leaves must be exposed to sunlight in 
 order to carry on this important function. When the leaves 
 receive the proper amount of exposure, the food can be 
 manufactured rapidly. Hence, we should expect to find that 
 leaves are arranged in such a way as to secure the best 
 amount of sunlight. Where plants are more or less crowded, 
 as in forests or thickets, the main stems, such as the trunks of 
 trees, usually grow tall, thus lifting the leaves to the light. 
 The amount of light exposure of trees and of most other plants 
 is largely increased by branches and their subdividing twigs, 
 ^to which the leaves are attached. 
 
 In order that the trunk and its branches may be able to 
 support the leaves and withstand the force of storms, thick- 
 
THE NUTRITIVE OEGANS OF PLANTS 
 
 49 
 
 walled wood-cells are developed. Each wood-cell, when 
 separated out from the rest, and examined with the high 
 power of the compound microscope, is seen to be shaped 
 somewhat like a tiny toothpick, and the thin ends of these 
 cells fit together closely by overlapping. (See Fig. 15.) 
 
 sieve tube duct duc^ 
 
 FIG. 15. Woody bundle of sunflower stem. 
 
 pith 
 
 Stems like the corn stalk and bamboo have most of their sup- 
 porting material on the outside, and these stems are in the form of 
 cylinders which are either hollow (as in grasses) or filled with pith 
 through which pass the woody bundles (as in the corn stalk). It 
 has been proved that when a given amount of material is arranged 
 in the form of a hollow tube, it will withstand a much greater strain 
 without breaking than when this material is in the form of a solid 
 rod. This mechanical principle is made use of in the construction 
 of the frame of a bicycle and of the pillars that support buildings. 
 
 63. Stems as organs for the transmission of sap. Leaves 
 not only require an abundance of sunlight, but they must 
 
50 
 
 PLANT BIOLOGY 
 
 also be supplied with water and other materials from the 
 soil. Our experiment with red ink (see 61) showed that the 
 soil-water is carried upward through the woody portions of 
 stems. A microscopical examination of thin sections of 
 a stem (see Fig. 15) shows the presence of tubular cells 
 known as ducts, similar to those found in 
 the central cylinder of roots with which 
 they are connected. These are the 
 parts of the wood through which the 
 soil-water passes most readily up to the 
 leaves. 
 
 After the raw materials have been 
 changed into the plant foods by green 
 leaves, these plant foods, by the process 
 of digestion, are changed into such a 
 form that they can pass from the leaves 
 into the fibrous bark in which are tubular 
 cells known as sieve-tubes. (See Figs. 15 
 and 16.) Through these the liquid food 
 FIG. 16. Sieve tube, passes down the stem to be stored away 
 
 the leaf, stem, and 
 root. A, longitu- 
 dinal section show- 
 ing edge view of 
 
 middle) ; B, sur- 
 face view of sieve 
 plate. 
 
 In young stems the pith rays or medul- 
 j ( 59 B 3) th fi jj e xtend- 
 
 ing from the bark toward the center of 
 the stem, are supposed to serve as chan- 
 
 ' 
 
 nels for the passage of food across the 
 stem and also for the storage of food. 
 
 In the type of stem represented in the corn, lilies, and palm 
 trees, the woody material through which sap passes is not ar- 
 ranged in the form of annual rings, but the woody bundles are 
 scattered through the pith. Each bundle consists of ducts that 
 carry the soil-water up through the stem out into the leaves, of 
 sieve-tubes that convey downward from the leaves the manufac- 
 
THE NUTRITIVE ORGANS OF PLANTS 
 
 51 
 
 tured food substances, and of wood cells that help to strengthen the 
 bundle. 
 
 64. Changes in stems during their growth. In our dis- 
 cussion thus far, we have considered the adaptations of stems 
 for exposing leaves to the light and for transmitting food 
 materials to and from the leaves. But the stem has other 
 important functions which we are now to consider. In a 
 young twig, before the brown bark thickens and shuts out 
 the light, the green bark, on account of the presence of chlo- 
 rophyll, is enabled to carry on the manufacture of carbohy- 
 drates. In a very young, stem the surface is covered by thin 
 epidermis which helps to prevent 
 the undue escape of moisture. In 
 this layer are tiny openings that 
 allow the inward and outward 
 passage of gases that occur in 
 breathing and food manufacture. 
 Later this epidermis is replaced 
 by the outer or brown bark, which 
 serves as a means of protection 
 against unfavorable weather con- 
 ditions and insects. In this brown 
 bark the tiny openings referred 
 to above are developed into large 
 openings known as lenticels which 
 carry on the same functions. Ii> an old tree the outer bark 
 becomes very thick and corky and the green layer dis- 
 appears entirely. 
 
 The growth of the tree in thickness, as already stated, is 
 due to the activity of a layer of cells between the wood and the 
 fibrous bark. This is the cambium layer (Fig. 15). In early 
 spring the cambium cells by rapid growth and division form 
 on their innermost surface a new layer of wood (which appears 
 
 FIG. 17. Cross section of a 
 tree trunk showing bark, 
 wood (with its annual rings 
 and medullary rays), and pith 
 at center. (Courtesy of 
 New York Botanical Garden.) 
 
PLANT BIOLOGY 
 
 FIG. 18. Cross section of 
 young bamboo, showing hard 
 outer rind, woody bundles, 
 scattered through the pith. 
 The center of the stem is 
 hollow. (Courtesy of New 
 York Botanical Garden.) 
 
 as a ring in cross section), and 
 on their outer surface more fibrous 
 bark. As the season advances, 
 the activity of these' cells becomes 
 less and less, and finally growth 
 ceases during the winter. 1 
 
 Stems of plants like the corn, bam- 
 boo, and palm have no true cambium 
 layer, and therefore even in the case 
 of plants of this type that live on 
 from year to year no annual rings are 
 formed. In the growth of these stems, 
 new bundles develop in the pith be- 
 tween those already formed. 
 
 III. THE STRUCTURE AND ADAPTATIONS OF LEAVES 
 
 65. Leaf arrangement. 2 Along the sides of twigs leaves are 
 arranged in such a way as to secure as much light as possible with- 
 out being shaded by the leaves above them. Thus in plants like 
 the horse-chestnut, maple, and lilac, the leaves are arranged so that 
 at a given level on the twig two leaves are opposite each other, 
 while the next pair are at right angles to the first pair. This is 
 known as an opposite arrangement. The beech, elm, and rose, on 
 the other hand, have an alternate arrangement, only one leaf being 
 found at a given level on the twig. 
 
 66. External structure of a horse-chestnut twig. Laboratory 
 Study No. 34. (Optional.) (Maple, beech, or other woody twig 
 may be used with slight verbal changes.) 
 
 1 Sometimes trees form more than one ring during a season. 
 
 2 Before assigning this sect'ion for study, the teacher should dem- 
 onstrate from leafy twigs (e.g. maple, horse-chestnut, lilac, elm, 
 apple) the characteristic differences between the opposite and 
 alternate arrangement of leaves. 
 
THE NUTRITIVE ORGANS OF PLANTS 
 
 53 
 
 A. Leaf scars. (The horseshoe-shaped scars with the raised dots 
 
 like horseshoe nails indicate the places where the stalks 
 of the leaves were attached.) 
 
 1. Do the leaf scars occur in pairs, or is there only one scar 
 
 at a given level? How, therefore, were the leaves ar- 
 ranged on the 
 stem? 
 
 2. Count the num- 
 
 ber of dots on 
 several differ- 
 ent leaf scars ; 
 these dots are 
 the ends of 
 the wood 
 bundles that 
 carried sap to 
 the various 
 leaflets. Look 
 at the picture 
 ofhorse-chest- 
 nut leaves. 
 (See Fig. 20, 
 K.) How 
 many main 
 veins do you 
 find in one 
 compound 
 leaf? Com- 
 pare this 
 
 number with the number of dots on the leaf scars ; what 
 do you conclude ? 
 
 B. Buds. (At the end of most twigs is a single terminal bud; 
 
 the buds along the side of the twig are lateral buds. 
 Each bud is covered with bud-scales.) 
 
 1. State the position of each kind of bud on the twig. Where 
 are the lateral buds found with reference to the leaf scars ? 
 
 FIG. 19. Spray of young apple tree, showing 
 alternate arrangement. At the base of each 
 leaf stalk is a pair of small stipules. (Bailey.) 
 
FIG. 20. Forms of leaves. (Courtesy of Furman and Miller, Botanical Aid, 
 Western Publishing Co., Chicago, 111.) 
 
 Simple 
 
 A, lilac ; C, white oak ; G, oak ; 
 
 7, sweet gum ; 
 
 B, chestnut ; D, celandine ; H, geranium ; J, buttercup ; 
 
 
 Compound leaves 
 
 
 E, locust ; 
 
 L, cinquefoil ; 
 
 F, wild tamarind 
 
 K, horse-chestnut ; 
 
 M , wild strawberry ; 
 
 (twice compound). 
 
 
 54 
 
 
THE NUTRITIVE ORGANS OF PLANTS 55 
 
 2. Look carefully at the scales of the terminal bud to see if they 
 
 have any definite arrangement. State whether or not this 
 arrangement corresponds to that of the leaf scars. 
 
 3. (Demonstration.) Examine a terminal bud from which one 
 
 or two scales have been removed. Bud-scales are modified 
 leaves. How do these scales differ from ordinary leaves ? 
 What is the use of the scales to the bud ? How are they 
 adapted for this use ? 
 
 C. Bud-scale scars. (These are also called annual scars because 
 
 they are formed at the beginning of the growing season of 
 each year when the terminal bud opens and its scales fall 
 off. To prove this, remove one or two outside scales from 
 a terminal bud, and note the scar thus formed.) 
 1. How many groups of bud-scale scars or annual scars do you 
 
 find on the twig you are studying ? 
 
 2. Since one set is formed each spring, how many years of 
 growth are shown on the twig ? 
 
 D. Breathing pores or lenticels. Look for small elevations on the 
 
 bark. These locate the lenticels. Describe the lenticels. 
 
 E. Make a careful outline drawing of the twig, showing its form, 
 
 the position and shape of the leaf scars with their woody 
 bundles, the terminal and lateral buds, bud-scales, bud- 
 scale scars, and lenticels. Label each of the structures 
 shown in your drawing. 
 
 67. The structure of leaves. Laboratory Study No. 35. 
 A. Parts of a leaf. 
 
 1. Examine a simple leaf, e.g. maple, geranium, or lilac, 
 and note that it is made up of the following 
 parts : a leaf-stalk, which attaches the main part 
 of the leaf to the stem of the plant, and the 
 blade, the flat, expanded portion. 
 
 a. How does the blade differ in form from the leaf- 
 
 stalk? 
 
 b. Hold the leaf to the light. How many main veins 
 
 do you find? Where are they smallest? By 
 what are the main veins connected ? 
 
56 PLANT BIOLOGY 
 
 c. Make a drawing, natural size, by tracing the out- 
 line of the leaf-stalk and blade. Draw carefully 
 the principal veins and a few of their branches, 
 being careful to show their relative size and their 
 connections. Label leaf -stalk, blade, main veins, 
 network of veins. 
 
 2. (Optional.) Examine a compound leaf, e.g. rose, clover, 
 locust, pea, horse-chestnut. Notice that the blade is 
 divided into three or more parts known as leaflets, 
 which are attached either to the end of the leaf- 
 stalk or on either side of the mid-vein of the com- 
 pound leaf. 
 
 a. In what respect, therefore, does the blade of a com- 
 pound leaf differ from the blade of a simple leaf? 
 
 6. Compare the arrangement of the leaflets in a leaf like 
 the rose, locust, or pea with that in the Virginia 
 creeper or horse-chestnut. Which leaves have the 
 leaflets arranged like the bones in the palm of the 
 hand (palmately compound), and which have the 
 leaflets arranged along the side of the mid-vein as in 
 a feather (pinnately compound, from Latin, pinna 
 feather) ? 
 
 c. At the base of the leaf-stalk of the rose, clover, or pea leaf, 
 notice two leaf-like objects (small in the case of the 
 rose). These are known as stipules. Stipules are also 
 found as a part of many simple leaves. How do 
 stipules differ from the other parts of leaves ? (See 
 Fig. 19.) 
 
 B* Gross structure of leaves. Secure thick leaves such as 
 sedum, tulip, hyacinth, or onion. 
 
 1. Peel off from the upper and lower surface a thin 
 membrane known as the epidermis. Hold the 
 epidermis between yourself and the light. Tell 
 what you have done and state two characteristics 
 of epidermis. 
 
THE NUTRITIVE ORGANS OF PLANTS 57 
 
 2. Examine the material left after removing the epi- 
 
 dermis, scraping it with a knife. This inner 
 region of the leaf is known as mesophyll (Greek, 
 meso = middle + phullon = leaf). Describe the 
 mesophyll, stating how it differs from the epi- 
 dermis. 
 
 3. Look carefully for veins in the mesophyll. Describe 
 
 their appearance. 
 
 4. (Optional.) Make a diagram at least half an inch in thick- 
 
 ness of a small portion of the cross section of the leaf 
 you are studying, labeling upper epidermis, mesophyll, 
 veins, and lower epidermis. 
 
 C. Microscopical structure of leaves. Demonstration. 
 
 1. Strip off a piece of epidermis from one of the thick 
 leaves named in B above ; lay it on a glass slide, 
 add a drop of water, and cover with a cover glass. 
 Examine with the low power of the compound 
 microscope, comparing the specimen with Fig. 
 21. Notice the shape of the cells of which the 
 
 guard-cells sur- 
 rounding a, 
 stoma 
 
 / cells of epider- 
 mis 
 
 FIG. 21. Lower epidermis of a leaf. (Strasburger.) 
 
 epidermis (shown by the faint outlines of their 
 walls) is composed. Find little oval bodies scat- 
 tered among the cells of the epidermis, each hav- 
 
58 
 
 PLANT BIOLOGY 
 
 ing an opening in the middle. This opening is 
 called a stoma, plural stomata (Greek, stoma = 
 mouth). Each stoma is surrounded by two 
 guard-cells. 
 
 Make a diagram, greatly enlarged, of a stoma with its 
 guard-cells, together with the cells of the epi- 
 dermis that immediately surround it. Label 
 cells of the epidermis, guard-cells, stoma. 
 
 upper epidermis 
 
 chlorophyll bodies v ~ 
 
 air space 
 
 mesophyll cells con- 
 taining chloro- 
 phyll bodies 
 
 lower epidermis 
 
 stoma with a guard-cell on either side 
 FIG. 22. Cross section of a leaf. (Strasburger.) 
 
 2. Study Fig. 22 and make out the shape and location of 
 each of the following parts of which it is com- 
 posed : upper epidermis, mesophyll cells, chloro- 
 phyll bodies, air spaces between the cells, lower 
 epidermis, stoma. In your note -book make a 
 drawing considerably enlarged showing a small 
 portion of the cross section, and label each part. 
 
 68. Experiment to demonstrate the path of sap through 
 leaves. Laboratory Study No. 36. 
 
 Place in red ink the lower end of a leafy branch of any 
 vigorous plant, e.g. geranium or bean seedling, and allow 
 
THE NUTRITIVE ORGANS OF PLANTS 
 
 59 
 
 it to stand in sunlight or a warm place until the red color 
 appears in the leaves. 
 
 1. Give an account of the experiment, stating your observa- 
 
 tions. 
 
 2. What do you conclude as to the part of the leaf through 
 
 which soil -water is distributed to different parts of the 
 blade? 
 
 3. What cells of the root did you find specially adapted for 
 
 absorbing water from the soil ? Through what regions 
 of the root and stem is sap carried up to the leaves? 
 
 69. Is water vapor given off by the leaves of a green plant? 
 Laboratory Study No. 37. Demonstration. 
 
 1. Wrap sheet rubber or thin oilcloth about a pot containing 
 a vigorous plant which has been thoroughly watered. 
 Tie the rubber or oilcloth tightly about the stem to 
 prevent the escape of 
 water from the soil. If 
 rubber tissue cannot be 
 obtained, melted paraffin 
 may be poured over the 
 soil, and the pot painted 
 with hot paraffin. Cover 
 the plant thus prepared 
 with a large bell jar with 
 the inner surface dry, and 
 stand it in the sun for a 
 few hours. 
 
 a. Describe the preparation of 
 
 the experiment, stating 
 the reason for using the 
 rubber or paraffin. 
 
 b. State your observations and 
 
 conclusion. 
 
 c. Why is the bell jar necessary? 
 
 d. What becomes of the water 
 
 Vapor given off by the FIG. 23. Apparatus to show the 
 leaves of trees? excretion of water from a plant. 
 
60 PLANT BIOLOGY 
 
 2. (Optional.) Put the plant prepared as above on one of the 
 scale pans of a balance and with it a stoppered graduate 
 or a stoppered bottle. On the other pan put weights 
 enough to equalize the balance. At the end of 24 
 hours put enough water into the graduate or bottle to 
 cause the weights on the two pans to be equal. 
 
 a. Describe the preparation of the experiment. 
 
 b. What volume of water was necessary to equalize the weights 
 
 (i.e. how much water was given off from the plant in 
 24 hours) ? 
 
 c. In a similar way add water each 24 hours for a week or 
 
 until the plant shows signs of wilting. What is the total 
 amount of water given off during the experiment ? 
 
 d. Bearing in mind the relative amount of leaf surface of this 
 
 plant and on the trees of a forest of even a few acres, 
 what would you infer as to the quantity of water given 
 off by the trees of a forest during a summer season ? 
 
 70. Leaves as organs for food manufacture. While 
 studying the manufacture by plants of carbohydrates (sugar 
 and starch) we showed that the raw materials necessary for 
 this process are water and carbon dioxid. We have proved 
 that water enters the root-hairs by osmosis and travels in a 
 system of ducts through the woody portion of roots and stems 
 out to the leaves. Here the ducts of the stems connect with a 
 network of veins containing similar ducts by means of which 
 the soil-water is supplied to the cells that are to manufacture 
 the food. The carbon dioxid that is needed is secured from 
 the air. This gas passes through the openings (stomata) 
 in the epidermis, and enters the air spaces in the mesophyll, 
 and finally reaches the cells containing the chlorophyll 
 bodies. 
 
 The sunlight acting upon the chlorophyll bodies enables 
 them to combine the elements found in the water and carbon 
 dioxid to form carbohydrates. These, as we have seen, are 
 
THE NUTRITIVE ORGANS OF PLANTS 61 
 
 probably used in the manufacture of proteins. In the leaves, 
 as elsewhere in the plant, the various foods are digested and 
 thus are prepared to be carried by the tubular cells (sieve 
 tubes) in the veins and down through similar tubular cells in 
 the fibrous bark. (Fig. 16.) 
 
 71. Excretion of the by-products of food manufacture. 
 We showed in 35 that during the process of carbohydrate 
 manufacture oxygen is set free, and this gas is given off 
 through the stomata into the air. Water, too, is a by-prod- 
 uct of food manufacture and assimilation. In the manu- 
 facture of proteins mineral matters are necessary, and these 
 are carried up the stem dissolved in the soil-water. Since, 
 however, the soil-water is such a dilute solution, great quan- 
 tities of this liquid must be supplied ; hence, much more water 
 is taken in than is needed for food manufacture or making of 
 protoplasm. This excess of water is given off in large quan- 
 tity by the leaves of green plants (see 69). 
 
 The amount of water thus excreted by leaves is regulated 
 more or less by the action of the guard-cells that surround each 
 stoma. When the plant is well supplied with water, the stoma 
 remains wide open. If, on the other hand, the leaves lack a 
 sufficiency of water, these guard-cells close in upon the stoma, 
 and so prevent undue loss of moisture. In plants having 
 leaves in a horizontal position, the stomata are mostly located 
 on the lower surface, the upper surface, which is more exposed 
 to the sunlight, being covered with a continuous layer of 
 epidermal cells. Were the epidermis altogether absent from 
 leaves, the mesophyll cells would soon lose so much water 
 that they would die. 
 
 72. Storage of foods in plants. The foods that are 
 manufactured in the chlorophyll-bearing cells may be carr 
 ried, as we have seen, to other parts of the plant, there to be 
 
62 
 
 PLANT BIOLOGY 
 
 stored until needed. Whenever large amounts of starch, 
 sugar, protein, or fat are thus stored, the organs containing 
 these substances frequently become enlarged (e.g. carrot (Fig. 
 81), potato (Figs. 49, 60), and onion) and the walls of the cells 
 in these organs usually remain thin and soft, permitting the 
 inward and outward passage of food. (See Fig. 9.) 
 
 73. Summary of functions of the parts of the nutritive 
 organs of green plants. 
 
 NAME OP PART 
 
 WHERE PART is FOUND 
 
 PRINCIPAL FUNCTION OR FUNCTIONS 
 OF PARTS 
 
 Epidermis 
 
 Covering of root 
 
 Absorbs soil-water, largely 
 
 
 
 through root-hairs 
 
 Epidermis 
 
 Covering of stem 
 
 Protects inner layers, pre- 
 
 
 and leaves 
 
 vents undue escape of 
 
 
 
 moisture 
 
 Lenticels 
 
 Brown bark of 
 
 Permit entrance of and C0 2 
 
 
 stem 
 
 and escape of and C0 2 
 
 Stoinata 
 
 Epidermis of 
 
 Permit entrance of and C0 2 
 
 
 leaves 
 
 and escape of O and CO 2 
 
 Guard-cells 
 
 Surround stomata 
 
 Regulate escape of H 2 
 
 Air spaces 
 
 Between meso- 
 
 Serve as reservoirs of and 
 
 
 phyll cells 
 
 C0 2 and water vapor 
 
 Chlorophyll- 
 
 Mesophyll of 
 
 Manufacture carbohydrates 
 
 bearing cells 
 
 leaves, green 
 
 
 
 bark of stem 
 
 
 Ducts 
 
 Central cylinder of 
 
 Transport soil-water upward 
 
 
 root, woody part 
 
 through the plant 
 
 
 of stem, veins of 
 
 
 
 leaves 
 
 
 Sieve tubes 
 
 Fibrous bark of 
 
 Transport digested foods 
 
 
 stem, veins of 
 
 downward through plants 
 
 
 leaves 
 
 . " 
 
THE NUTRITIVE ORGANS OF PLANTS 
 
 63 
 
 NAME OF PART 
 
 WHERE PART is FOUND 
 
 PRINCIPAL FUNCTION OR FUNCTIONS 
 OP PARTS 
 
 Wood cells 
 
 Central cylinder of 
 root, woody part 
 of stem, veins of 
 leaves 
 
 Resist forces tending to break 
 roots, stems, or leaves 
 
 Cambium layer 
 
 Between bark and 
 wood of stem 
 
 Provides for growth of wood 
 and fibrous bark or bast 
 
 Pith 
 
 Interior of stem 
 
 Stores food 
 
 Pith-rays 
 
 Woody layer of 
 stem 
 
 Transfer food across stem, 
 and store food 
 
CHAPTER VI 
 
 RESPIRATION AND THE PRODUCTION OF ENERGY IN 
 PLANTS 
 
 I. THE STORAGE AND LIBERATION OF ENERGY 
 
 74. Examples of energy in plants. By energy we mean 
 the capacity to do work. In the preceding chapters we 
 have considered to some extent the structure of various parts 
 of plants and some of the functions which they are fitted to 
 perform. Now to carry on most of these functions requires 
 the expenditure of energy on the part of the plant. Thus, 
 for example, roots in growing expend considerable energy, 
 pushing their way through the soil. Stems in like manner 
 exert energy in lifting to the light and air their weight of 
 branches and leaves. We know, too, that soil-water is 
 carried up through plants to considerable heights (several 
 hundred feet in very large trees), that substances obtained 
 from the soil and air are digested and transported from one 
 part of a plant to another. Still another form of energy 
 exhibited to a certain degree by plants is heat, as the follow- 
 ing experiment will show. 
 
 75. To prove that heat energy is developed in growing seed- 
 lings. Laboratory Study No. 38. 
 
 Secure two wide-mouthed bottles of the same size (light- 
 ning fruit jars will answer) and put some wet blotting paper 
 in the bottom of each. Fill one of the jars half full of sprout- 
 ing peas. Fill the other jar half full of peas that have been 
 killed by being soaked in a 5 per cent solution of formalin for 
 
 64 
 
THE PRODUCTION OF ENERGY IN PLANTS 65 
 
 twenty-four hours. Rinse the seeds with boiled water to 
 remove the preserving fluid. Get two thermometers that 
 have approximately the same temperature reading in the air 
 of the laboratory. 1 Push the lower end of the thermometer 
 down among the sprouting seeds so that the mercury will be 
 covered by the seeds. Do the same with the second ther- 
 mometer in the jar of dead seeds. Set the jars side by side 
 in a warm place for twenty-four hours or more. 
 
 1. Describe the preparation of this experiment. In what 
 
 respects are the conditions the same in both jars? In 
 what one respect do the two jars differ? 
 
 2. Take the temperature readings of the thermometer in each 
 
 of the two jars and record results. What difference 
 do you notice in the temperature of the seeds in the two 
 jars? 
 
 3. What is your conclusion from the experiment as to the 
 
 development of heat energy in seedlings? 
 
 76. Energy and its transformations. We see from the 
 preceding discussion and experiment that plants exhibit 
 considerable energy or ability to do work. Animals and 
 man, however, show far more striking proofs of the output of 
 energy in their muscular movements, for example, in running, 
 swimming, and flying. Various machines, also, enable us to 
 make use of different forms of energy, and, as we shall now 
 see, one kind of energy may be readily transformed into 
 another by means of these machines. Suppose we consider 
 the work that goes on in an electric power plant. The coal 
 that is shoveled into the fire-box beneath the boilers by the 
 process of oxidation liberates heat, which is one of the forms 
 of energy. The heat changes the water into steam, which 
 expands and so exerts its power to run the engine, and thus 
 heat energy is transformed into the energy of motion. When 
 the engine is connected with a dynamo, this energy of mo- 
 
 1 If a difference in the reading of the two thermometers is evident, 
 this difference should be computed in the later readings on the ther- 
 mometers. 
 
66 PLANT BIOLOGY 
 
 tion is changed into electrical energy, and this in turn may be 
 converted into light or heat energy in our houses or into energy 
 of motion, as, for instance, in the running of a trolley car. 
 
 77. Source of the energy developed in living things. 
 In all these marvelous transformations of energy that we have 
 just enumerated no new energy is created and none is de- 
 stroyed. Whence, then, comes this abundant supply of 
 energy? We shall find the probable answer to this question 
 in considering again the processes carried on in the leaves of 
 plants. From the sun comes the radiant energy that is abso- 
 lutely essential for the activity of the chlorophyll bodies, by 
 which carbohydrates are formed. In the formation of these 
 compounds, the sun's radiant energy is used and apparently 
 disappears. 1 In reality, however, it has only been stored in 
 the chemical compounds formed thereby, since, as we have 
 said above, energy cannot be destroyed. 
 
 78. Oxidation as a means of liberating energy. Let us 
 now refer once more to the processes that take place in an 
 electric power plant. We have just said that the energy de- 
 rived from the rays of the sun is stored up in the wood, coal, 
 and other fuel. In order to set free from these compounds 
 the energy they contain, the wood or coal must be burned, or 
 in other words combined with oxygen. Every one knows that 
 when we wish to secure a large amount of heat from our fuel 
 we open wide the drafts in order to secure a plentiful supply 
 of oxygen. We demonstrated in our studies in oxidation 
 that whenever a substance is burned, heat energy is liberated 
 
 1 The authors are indebted to Mr. Paul B. Mann of the Morris 
 High School Department of Biology for the following demonstration 
 of the effectiveness of the radiant energy of the sun. Place a 
 radiometer (usually found in the physics equipment of schools) in 
 direct sunlight, and then remove it from the sun's rays. Try also 
 the effect of an electric light by bringing the radiometer near the 
 light bulb, and then slowly removing it to a distance. 
 
THE PRODUCTION OF ENERGY IN PLANTS 67 
 
 and usually light is seen. The energy set free by the oxida- 
 tion of fuel may be transformed at one time into light, at 
 another time into motion, or again into heat. 
 
 It is probably true that the liberation of energy in living 
 plants is somehow due to the action of oxygen. The pro- 
 cess, however, is doubtless extremely complicated, and just 
 what takes place no one knows. Certainly oxygen in some 
 form is essential for the life of every plant and animal. That 
 this is true of plants, the following experiment will show. 
 
 79. To prove that seeds need air in order to grow. 
 
 Laboratory Study No. 39. Demonstration or Home Work. 
 
 Secure two wide-mouthed bottles and place in the bottom 
 of each a wet sponge or some wet blotting paper, and pour 
 enough water in each bottle just to cover the sponge or paper. 
 Fill both bottles with pea seeds that have been soaked in 
 water for twenty-four hours. Insert a tightly fitting cork 
 into the mouth of one of the bottles to exclude the air. Leave 
 the other bottle open to the air, and add enough water from 
 day to day to make up for the loss by evaporation. Put 
 both bottles in a warm place. 
 
 1. Describe this experiment, showing in what respects the 
 
 conditions are the same for both groups of seeds. 
 
 2. In what one respect do the two groups of seeds differ? 
 
 3. At the end of several days examine both bottles of seeds, 
 
 and state your observation concerning the amount of 
 growth in each bottle. 
 
 4. State clearly your conclusion as to the necessity of air for 
 
 growth of pea seedlings. 
 
 80. Relation of oxygen and carbon dioxid to oxidation. 
 We have now demonstrated that seedlings will not grow 
 without air. Biologists have proved conclusively that oxygen 
 is the element in the air that is essential for the work of all 
 plants, and that without it they die. Hence, we may con- 
 clude, as in the case of the furnace, that the necessary energy 
 
68 PLANT BIOLOGY 
 
 of a plant is in some way set free by oxygen acting upon 
 plant compounds. When oxidation of compounds containing 
 carbon takes place, we find that carbon dioxid is produced 
 (11). Now if processes like oxidation are carried on in plants, 
 we should expect to find that C02 is formed. The following 
 experiment proves clearly that such is the case. 
 
 81. To prove that carbon dioxid is formed during the 
 growth of young seedlings. Laboratory Study No. 40. 
 
 In the bottom of two large jars, (fruit jars will answer) 
 place some wet blotting paper. Fill one of the jars half full of 
 germinating peas, and place a small wide-mouthed bottle 
 full of lime water on top of the seeds. Screw the top of the 
 jar on tightly. In the other jar place a bottle of lime water 
 and cover as in the previous jar. At the end of twenty-four 
 hours or more examine the lime water in both jars. 
 
 1. Describe the preparation of the experiment. 
 
 2. Compare the condition of the lime water in both jars. 
 
 What has caused the change in the lime water in both 
 jars? 
 
 3. Air, as we proved, contains a little carbon dioxid. Bearing 
 
 this fact in mind, account for the difference in the ap- 
 pearance of the lime water in the two jars. 
 
 4. What gas, therefore, do you find to be given off during 
 
 the growth of young seedlings ? 
 
 II. RESPIRATION 
 
 82. Respiration in plants. It should be clear from our 
 study thus far that all plants require oxygen, and that this 
 oxygen brings about in plants a process resembling oxidation 
 at least in the releasing of heat and other forms of energy 
 and in the producing of carbon dioxid. These various pro- 
 cesses take place in each living plant cell. Hence, every 
 cell uses oxygen and must necessarily form carbon dioxid. 
 This process which goes on in every living cell is respiration. 
 
THE PRODUCTION OF ENERGY IN PLANTS 
 
 69 
 
 In green plants during the night, when carbon dioxid is not 
 being used for starch manufacture, this gas is given off to the 
 surrounding air, which probably is not true to any great 
 extent during the daytime. The taking in of oxygen and the 
 giving off of carbon dioxid by plants corresponds to breath- 
 ing in animals. This exchange of gases is carried on 
 through the thin wails of roots, through the lenticels of 
 stems, and through the stomata of leaves. The process of 
 breathing must not be confused with that of carbohydrate 
 manufacture, and the following outline will show the funda- 
 mental difference between the two. 
 
 
 CARBOHYDRATE MANU- 
 FACTURE 
 
 RESPIRATION (INCLUDING 
 OXIDATION) 
 
 Where carried on 
 
 In cells containing 
 
 In all living cells 
 
 
 chlorophyll 
 
 
 When carried on 
 
 In sunlight 
 
 Throughout life of 
 
 
 
 cell 
 
 Substances taken from 
 
 C0 2 
 
 
 
 air 
 
 
 
 Substance formed in 
 
 Carbohydrates 
 
 C0 2 
 
 plant 
 
 
 
 Waste substance ex- 
 
 
 
 CO 2 
 
 creted to air 
 
 
 
 Advantage to plant 
 
 Manufacture of food 
 
 Release of energy 
 
CHAPTER VII 
 
 REPRODUCTION IN PLANTS 
 
 I. THE STRUCTURE AND FUNCTIONS OF FLOWERS 
 
 83. Necessity of plant reproduction. Every one knows 
 that plants like peas, beans, and corn live but one year. 
 Shrubs and trees, while they often live for many years, finally 
 die. This is true of all plants. It is evident, therefore, that 
 unless there were some means of producing new plants to 
 take the place of those now living, all forms of plant life 
 would soon cease to exist. The process by which new plants 
 are formed is known as reproduction. In the higher plants 
 this process is carried on by flowers, the function of which is 
 to produce seeds which will develop into new plants. We are 
 now to study the various parts of flowers and to consider the 
 work of each part in this process of reproduction. 
 
 84. Study of tulip flower (spring study). Laboratory 
 Study No. 41. 
 
 Material: While the trillium is a more satisfactory flower for 
 beginning the study of the process of reproduction, the danger 
 that the wild flowers will become exterminated seems to make the 
 study of the tulip advisable, especially in large city high schools. 
 The two flowers, however, are usually in season at the same time, 
 and if possible at least a few of the trilliums should be secured for 
 demonstration. If this is impossible, the distinction between calyx 
 and corolla should be taught from the apple blossom or other com- 
 mon flower. 
 
 70 
 
REPRODUCTION IN PLANTS 71 
 
 A. Floral envelopes. Most flowers have parts shaped more 
 
 or less like leaves which have either green or 
 bright colors. These parts are arranged in one 
 or more circles and make up the floral envelopes. 
 
 1. How many parts are there in the floral envelopes of a 
 
 tulip? State the color or colors of these parts 
 in the flower you are studying. 
 
 2. When there are two circles to the floral envelopes, an 
 
 outer composed of green parts and an inner made 
 up of brightly colored parts (as in the trillium or 
 the apple blossom), distinct names are given to 
 the various parts. The outer circle is called the 
 calyx and its parts are known as sepals; the 
 inner circle is called the corolla and each of its 
 parts is called a petal. 
 
 a. State the number and color of the sepals in the 
 
 calyx of the trillium. 
 
 b. How many petals do you find in the corolla? 
 
 Describe their color. 
 
 3. Draw a side view of a tulip before it has fully opened. 
 
 Label flower-stalk and floral envelopes. 
 
 B. Essential organs. In the central part of the flower are 
 
 the organs without which the work of the flower 
 cannot be performed. For this reason they are 
 called the essential organs. 
 
 1. The organs arranged in a circle just within the floral 
 
 envelopes are known as stamens. State the 
 situation and the number of stamens in the tulip. 
 What is the number of stamens in the trillium or 
 apple blossom ? 
 
 2. Each stamen consists of a stalk called the filament 
 
 and an enlarged part known as the anther. 
 Name and describe each of the parts of a stamen. 
 
 3. Make a drawing twice its natural size of one of the 
 
 stamens. Label filament, anther. 
 
 4. Find a flower the stamens of which have a powdery 
 
 substance known as pollen. Which part of the 
 stamen produces the pollen? 
 
 5. The organ at the center of the flower is called the 
 
 pistil. It consists of three divisions at the top 
 
72 PLANT BIOLOGY 
 
 which together are known as the stigma, and 
 the remainder of the pistil known as the ovary. 
 Describe the pistil of the tulip (and of the tril- 
 lium) as to position, shape, and color of its parts. 
 
 6. Make a drawing twice its natural size of the pistil. 
 
 Label stigma, ovary. 
 
 7. Cut thin cross sections of a well-developed ovary, 
 
 lay them on a dark-colored background, and 
 study one or more of them with a magnifier to 
 make out the following parts : wall of the ovary, 
 small objects within the ovary known as ovules. 
 (These ovules develop into seeds.) Describe 
 what you have done and tell what you have seen. 
 
 8. Make a drawing at least an inch in diameter of a cross 
 
 section of the ovary, labeling ovary wall and 
 ovules. 
 
 9. (Optional.) Make a drawing (corresponding in size to that 
 
 called for in 6 above) of a lengthwise section of the 
 ovary to show wall of ovary, ovules. Label. 
 
 85. Study of the gladiolus flower (autumn study). Lab- 
 oratory Study No. 42. 
 
 Note to the teacher. Be careful to remove each flower 
 close to the central stalk, so that the ovary may not be in- 
 jured. 
 
 A. Parts of the flower. 
 
 1. Remove the two leaves at the base of the flower, since 
 
 these leaf -like organs do not belong to the flower. 
 The outer brightly colored parts of the flower are 
 called the floral envelopes. These colored parts 
 unite to form a greenish tube below. 
 
 a. Count and record the number of divisions of which 
 the floral envelopes are composed. 
 
 6. State whether or not these divisions are all of the 
 same size. 
 
 2. The slender stalks with purple tips, inside, the floral 
 
 envelopes, are called stamens. How many sta- 
 mens do you find? 
 
REPRODUCTION IN PLANTS 73 
 
 3. The single white stalk with three divisions at the top 
 
 is the upper part of the pistil. The dark green 
 body below the tubular part of the floral en- 
 velopes is the lower part of the pistil. 
 Is the top of the pistil in the flower you are studying 
 lower or higher than the stamens ? 
 
 4. Make a drawing, natural size, of the side view of the 
 
 flower, and label the following parts : the divided 
 portion of the floral envelopes, the tubular por- 
 tion of the floral envelopes, the stamens, the 
 pistil. 
 
 B. Essential organs. The stamens and pistils are called 
 the essential organs of flowers because without 
 them the work of the flower cannot be performed. 
 
 1. Carefully slit open the tubular part of the floral 
 
 envelopes down to the lower part of the pistil. 
 
 Then remove the floral envelopes, leaving the 
 
 entire pistil uninjured. 
 a. State what you have done. 
 6. To what are the stamens attached ? 
 c. The enlarged part at the top of the stamen is 
 
 called the anther, the stalk-like part is called the 
 
 filament. Name and describe the parts of a 
 
 stamen. 
 
 2. Make a drawing, natural size, of a portion of the floral 
 
 envelope to which a stamen is attached. Label 
 division of floral envelopes, anther, filament. 
 
 3. Find a flower the stamens of which have a powdery 
 
 substance known as pollen. Which part of the 
 stamen produces the pollen? 
 
 4. The pistil consists of an enlarged portion at the base 
 
 called the ovary, a stalk-like portion called the 
 style, and a spreading portion at the top, each 
 part of which is called a stigma. Name and 
 describe each part of the pistil. 
 
 5. Make a drawing, natural size, of the pistil and label 
 
 ovary, style, stigmas. 
 
 6. Cut thin cross sections of a well-developed ovary, lay 
 
 them on a dark-colored background, and study 
 one or more of them with a magnifier to make 
 
74 
 
 PLANT BIOLOGY 
 
 7. 
 
 out the following parts: wall of ovary, small 
 objects within the ovary known as ovules. 
 These ovules develop into seeds. Describe what 
 you have done and tell what you have seen. 
 Make a drawing at least an inch in diameter of a 
 cross section of the ovary, labeling ovary wall, 
 ovules. 
 
 8. (Optional.) Make a drawing (corresponding in size to that 
 called for in 7 above) of a lengthwise section of the 
 ovary to show wall of ovary, ovules. - Label. 
 
 86. Pollination. We have learned in our study of flowers 
 that pollen is produced in the anther of the stamen, and ovules 
 
 in the ovary of the pistil. 
 Before an ovule can develop 
 into a seed, however, certain 
 portions of a pollen grain 
 and of an ovule must be 
 combined. Pollen must, 
 therefore, be transferred 
 from the anthers to the 
 
 pistils, and to this process is 
 
 stigma - 
 
 stamen 
 
 petal 
 
 ovary 
 
 given the name pol- 
 
 FIG. 24. Structure of a plum blossom. 
 (Bailey.) 
 
 lination. We shall now learn by experiment some 
 adaptations of the pistil for receiving and holding ^ 
 the pollen. 
 
 87. Experiment to show pollina- 
 tion. Laboratory Study No. 43. 
 
 Rub a small brush or the end of 
 a toothpick over a stamen (e.g. 
 tulip, Easter lily, or gladiolus) which 
 has an abundance of pollen, and FIG. 25. -A pollen adhering 
 
 .1 i i ,i 11 ,1 to stigma : B, pollen of plum 
 
 then brush this pollen over the sur- escaping from the anther of 
 
 face Of the Stigma. a stamen. (Bailey.) 
 
REPRODUCTION IN PLANTS 
 
 75 
 
 1. Describe what you have done. 
 
 2. Examine the surface of the stigma with a magnifier and 
 
 state what causes the pollen to stick to the stigma. 
 
 88. Microscopical Demonstration of Pollen Grains and their 
 Development. Laboratory Study No. 44. (Optional.) Prepare 
 some sugar solution by adding to ten teaspoonfuls of water one 
 teaspoonful of molasses or grape sugar and heat to boiling point. 
 Put some of this sugar solution in a clean Syracuse watch 
 glass. When the solution has cooled^'mix with it some pollen 
 from the flower of a tulip, a trillium, a sweet pea, or nasturtium. 
 Several of these glasses might well be prepared with slightly dif- 
 ferent strengths of sugar solution and piled one above the other to 
 keep out mold spores, x Leave the glasses until the pollen grains 
 have germinated. Study the preparation with the low power of 
 the compound microscope. 
 
 1. Find some pollen grains that have not begun to grow tubes. 
 Describe the form of one of the pollen grains. 
 
 FIG. 26. Different kinds of pollen grains, highly magnified, two of them 
 forming pollen tubes. (Duggar.) 
 
76 
 
 PLANT BIOLOGY 
 
 2. Find several grains that have formed tubes. What is the 
 
 color and shape of the tubes ? 
 
 3. Make a drawing at least a half inch in diameter of a pollen 
 
 grain before it has sprouted and a drawing of another grain 
 that has sprouted. Label pollen grain, pollen tube. 
 
 89. Pollination, germination of pollen grains, and fertili- 
 zation. We have now learned that pollen by the process of 
 pollination is carried to the stigma of the pistil and adheres 
 to the stigma by a sticky substance which is easily seen on 
 the stigma of the Easter lily and often by hairs, also, as is the 
 case in the tulip and gladiolus. It has been proved that this 
 sticky substance contains sugar which together with other 
 materials furnishes food for the growth of pollen tubes (see 
 88). As each tube forms, it makes its way down through 
 the stigma and style (if present), and finally reaches an ovule 
 in the ovary. The tip of the tube now penetrates an opening 
 called the micropyle (Greek, mi cro = small -\-pula = gate way) 
 
 in the ovule. Part of 
 the living substance of 
 the pollen grain now 
 unites with a part of 
 the living substance of 
 the ovule. This union 
 is known as fertilization. 
 After fertilization has 
 taken place the ovule 
 develops into a seed. 
 
 90. The cellular na- 
 ture of pollen and ovules. 
 
 (If flowers are studied 
 
 FIG. 27. Pollen grain of lily and the de- f i o n f 11Trm U ;~ ~ 110 - 
 velopment of the pollen tube, highly mag- 
 nified. (After strasburger.) gested that this Section 
 
 v sperin 
 , nuclei 
 
REPRODUCTION IN PLANTS 77 
 
 be omitted until after the cellular structure of plants has been 
 considered.) When the pollen grains are first formed in the 
 anther, each consists of a single cell. Later the nucleus of 
 this cell divides and forms two nuclei, one of which is the 
 generative nucleus. The generative nucleus then divides 
 and forms two sperm nuclei. The ovule is more complex 
 in its structure, being composed of many cells of different 
 kinds. But here, as is the case with the pollen grain, there is 
 one important cell that is essential in the process of reproduc- 
 tion, and this is known as the egg-cell (Figs. 27 and 29, A). 
 
 91. The formation of an embryo. When the pollen 
 grain germinates and forms the tube, the sperm nucleus is 
 carried by the tube down through the stigma and style into 
 the cavity of the ovary, and finally through the micropyle of 
 the ovule, until one of the sperm nuclei comes to lie beside 
 the nucleus of the egg-cell. The two nuclei now unite in the 
 process of fertilization to form a fertilized egg-cell. The 
 nucleus of this cell then divides and later the cell-body, thus 
 forming two distinct cells. Each of these divides to form two 
 cells, and the four cells thus produced give rise to eight, then 
 sixteen, thirty-two, and so on, until a many-celled structure 
 is developed which is a miniature plant called the embryo. 
 This embryo, together with other parts of the ovule, consti- 
 tutes the seed. Some of the cells of the embryo will later 
 form the roots, others the stem, and still others the leaves 
 of the plant (Fig. 29, A-E). 
 
 Hence, the new plant formed by this method of reproduc- 
 tion is clearly descended from two different parents, one 
 parent flower furnishing in its pistil the egg-cell and the 
 other in its stamen the fertilizing pollen. We may, therefore, 
 give the following as a general definition of the process we 
 are studying: Fertilization is the union of the nucleus of 
 
78 PLANT BIOLOGY 
 
 ^toowwi o/nu/l/16 qtWWunfiXlnq < 
 
 (MxL sKaoLoC Vrtkuvr 
 
 -VVUlA^toui^ 
 
 FIG. 28. Diagram of a 
 longitudinal section of a 
 pistil showing germination 
 of pollen grains. 
 
 a sperm cell with the 
 nucleus of an egg-cell. 
 Only one pollen grain or 
 sperm cell can be used in 
 fertilizing each egg-cell, 
 Usually, however, far larger 
 numbers of pollen grains be- 
 come attached to the stigma 
 than can be used by the 
 ovules in the ovary. All the 
 
 pollen grains that germinate 
 
 produce pollen tubes which FlG . 2 9. ^Fertilization of an ovule and 
 may be Said to begin a tne early stages in the development of 
 race down the Stigma and n embryo. -(Diagrammatic.) 
 
 style. The tubes that first enter ovules are the ones that 
 carry on the process of fertilization. Those that are beaten 
 in the race are of no further use and therefore die. 
 
 
EEPEODUCTION IN PLANTS 79 
 
 92. Self-pollination and cross-pollination. Pollination, 
 we have said, is the transfer of pollen from the anther to the 
 stigma. When the pollen is carried from the anther of a 
 flower to the stigma of the pistil of the same flower, the pro- 
 cess is known as self-pollination. In many of the flowers 
 that are self-pollinated, the anthers are above the stig- 
 mas, and when the pollen is ripe, the anthers burst open and 
 allow the pollen grains to fall upon the stigma or stigmas. 
 
 If pollen is carried from the anther of a flower to the stigma 
 of the pistil of a flower of the same kind but on another plant, 
 this transfer is called cross-pollination. Cross-pollination is 
 often accomplished by the help of the wind, as in the flowers 
 of the corn, of grasses, and of many trees. In these cases the 
 pollen is dry and light, and the pistils are usually hairy or 
 feathery to catch and hold the pollen grains. 
 
 Most bright-colored and sweet-scented flowers (like the 
 pansy and the clover) are visited by bees or other hairy in- 
 sects which carry pollen on their mouth parts, bodies, and 
 legs from one flower to another, thus insuring cross-pollina- 
 tion. We shall now study the pansy as a type of insect polli- 
 nated flowers. 
 
 93. Adaptations of the pansy for cross pollination. 
 
 Laboratory Study No. 45. 
 
 A. Floral envelopes. When there are two circles to the floral 
 envelopes, an outer composed of green parts 
 and an inner made up of brightly colored parts 
 as in the pansy, distinct names are given to the 
 various parts. The outer circle is called the 
 calyx, and its parts are known as sepals; the 
 inner circle is called the corolla, and each of its 
 parts is called a petal. 
 
 1. State the number and color of the sepals. 
 
 2. How many petals are there? Describe the color or 
 
 colors of each. 
 
80 PLANT BIOLOGY 
 
 3. Locate the pairs of petals that are nearly alike in size 
 
 and shape. 
 State the position of the odd petal. 
 
 4. On which of these petals do you find the most strik- 
 
 ing spots or lines of color ? 
 
 5. Make a drawing of the pansy in its natural position, 
 
 front view, and natural size. Label top petals, 
 side petals, lower petal, hairs on side petals, 
 color spots. 
 
 6. Remove the two upper petals, and the two side 
 
 petals. Now observe the tapering projection 
 on the lower or odd petal extending upward and 
 backward between the sepals. This is called 
 the spur. 
 
 a. Tell what you have done and seen. 
 
 6. Carefully remove the lower petal with the spur 
 attached, and make a drawing of it, natural 
 size. Label the spur and color spot. 
 
 7. Slit open the spur. Is the spur hollow or solid ? 
 
 8. The spur contains a sweet liquid called nectar which 
 
 attracts the bees and other insects. If you find 
 any nectar, describe it and tell how you found 
 it. Describe the taste of the nectar. 
 
 9. In what two ways, therefore, may pansies attract 
 
 bees? 
 
 10. On which petal would a bee be most likely to alight 
 
 in visiting a pansy? What is there on this 
 petal to guide the bee toward the supply of 
 nectar? 
 
 11. (Optional.) What structures on the side petals might make 
 
 it difficult for the bee to insert its mouth parts in 
 this region ? 
 B. Stamens. 
 
 1. Observe the stamens arranged around the pistil. 
 
 Carefully separate them with a needle or pin. 
 State the number and situation of the stamens: 
 
 2. Carefully bend two or more stamens away from the 
 
 pistil, and with the help of a magnifier look 
 
REPRODUCTION IN PLANTS 
 
 81 
 
 C. Pistil. 
 
 on their inner surface. Tell what you have 
 done, and state whether the openings in the 
 yellow anthers from which the pollen is dis- 
 charged are found on the inner surface (next 
 the pistil) or on the outer surface of the anther. 
 
 1. Examine the pistil after the stamens have been re- 
 
 moved. Carefully describe the three parts 
 (ovary, style, and stigma) of which it is com- 
 posed. 
 
 2. Observe a tiny cavity on the tip of the stigma. The 
 
 inside of this cavity is the real stigma or stig- 
 matic surface. Describe the shape and state 
 the situation of the stigmatic surface. 
 
 D. Cross-pollination of the pansy by bumblebees. 
 
 1. Hold a pansy in its natural position. 
 
 a. State the situation of the stamens with reference 
 
 to the odd petal (i.e. are they above or below 
 this petal?). 
 
 b. On what, therefore, will pollen probably fall if it 
 
 is shaken out of the anthers ? 
 
 2. To determine whether or not what you have just 
 
 stated is true, thrust a slender tooth-pick under 
 
 the stigma and then under 
 
 the stamens and into the 
 
 spur. Shake the flower 
 
 gently and then withdraw 
 
 the tooth-pick and examine 
 
 the surface with a hand 
 
 magnifier. Tell what you 
 
 have done and state whether 
 
 or not pollen is found on 
 
 the tooth-pick. 
 
 3. Examine a bumblebee. On what 
 
 part of the insect (i.e. 
 
 mouth-parts, head, or body) 
 
 would the pollen be most pm. 30. Head of a 
 
 likely to fall when the bee bee. 
 
82 
 
 PLANT BIOLOGY 
 
 FIG. 31. Hind 
 leg of a worker 
 bee. 
 
 thrusts its mouth-parts into the 
 spur as you have just done with 
 the tooth-pick? How are all 
 these parts adapted to hold 
 pollen? (Compare with Figs. 
 30, 31.) 
 
 4. Still holding the pansy in its natural 
 
 position, notice and state the posi- 
 tion of the stigma with reference 
 to the odd petal. 
 
 5. Now push a tooth-pick which has pollen 
 
 on it, a second time into the spur. 
 State whether or not the tooth- 
 pick hits the stigmatic cup before 
 you get it under the stigma. 
 
 6. Why, therefore, will a bee that has just 
 
 been to one pansy flower be almost 
 certain to deposit pollen on the stigmatic cup 
 of the next pansy it visits ? 
 
 7. (Optional home work.) Write a paragraph on "The Visit 
 of a Bee to a Pansy Blossom/' giving a complete 
 account of what the bee does and how it does it. 
 
 94. The advantages of cross-pollination in the pansy. Charles 
 Darwin, the great English biologist, proved by a long series of experi- 
 ments that seeds produced as the result of cross-pollination develop 
 into far more healthy plants than do the seeds which are formed 
 after self-pollination. Among the plants with which he experi- 
 mented was the pansy (Viola tricolor). He planted in each of five 
 pots seeds that had been produced by cross-pollination, and an equal 
 number of seeds that were the result of self-pollination. The results 
 of the experiments are given in his own words as follows: "The 
 average height of the fourteen crossed plants is here 5.58 inches, 
 and that of the fourteen self-fertilized 2.37; or as 100 to 42. In 
 four of the five pots, a crossed plant flowered before any one of the 
 self-fertilized ; as likewise occurred with the pair raised during the 
 previous year. These plants without being disturbed were now 
 
EEPEODUCTION IN PLANTS 83 
 
 turned out of their pots and planted in the open ground, so as to 
 form five separate clumps. Early in the following summer (1869) 
 they flowered profusely, and being visited by humble-bees set 
 many capsules which were carefully collected from all the plants 
 on both sides. The crossed plants produced 167 capsules, and the 
 self-fertilized only 17 ; or as 100 to 10. So that the crossed plants 
 were more than twice the height of the self-fertilized, generally 
 flowered first, and produced ten times as many naturally fertilized 
 capsules. 
 
 "By the early part of the summer of 1870 the crossed plants in 
 all the five clumps had grown and spread so much more than the 
 self-fertilized, that any comparison between them was superfluous. 
 The crossed plants were covered with a sheet of bloom, whilst only 
 a single self-fertilized plant, which was much finer than any of its 
 brethren, flowered. The crossed and self-fertilized plants had now 
 grown all matted together on the respective sides of the superficial 
 partitions still separating them ; and in the clump which included 
 the finest self-fertilized plant, I estimated that the surface covered 
 by the crossed plants was about nine times as large as that covered 
 by the self-fertilized plants. . . . 
 
 "The ensuing winter was very severe, and in the following spring 
 (1871) the plants were again examined. All the self-fertilized 
 were now dead, with the exception of a single branch on one plant, 
 which bore on its summit a minute rosette of leaves about as large 
 as a pea. On the other hand, all the crossed plants without excep- 
 tion were growing vigorously. So that the self-fertilized plants, 
 besides their inferiority in other respects, were more tender. 
 
 "Another experiment was now tried for the sake of ascertaining 
 how far the superiority of the crossed plants, or to speak more cor- 
 rectly, the inferiority of the self-fertilized plants, would be trans- 
 mitted to their offspring. The one crossed and one self-fertilized 
 plant, which were first raised, had been turned out of their pot and 
 planted in the open ground. Both produced an abundance of very 
 fine capsules, from which fact we may safely conclude that they had 
 been cross-fertilized by insects. Seeds from both, after germinating 
 on sand, were planted in pairs on the opposite sides of three pots. 
 
84 PLANT BIOLOGY 
 
 The naturally crossed seedlings derived from the crossed plants 
 flowered in all three pots before the naturally crossed seedlings 
 derived from the self -fertilized plants. 
 
 "The average height of the six tallest plants derived from the 
 crossed plants is 12.56 inches; and that of the six tallest plants 
 derived from the self-fertilized plants is 10.31 inches ; or as 100 to 
 82. We here see a considerable difference in height between the 
 two sets, though very far from equalling that in the previous trials 
 between the offspring from crossed and self-fertilized flowers. This 
 difference must be attributed to the latter set of plants having in- 
 herited a weak constitution from their parents, the offspring of self- 
 fertilized flowers ; notwithstanding that the parents themselves had 
 been freely intercrossed with other plants by the aid of insects." 
 (" Cross and Self Fertilization in the Vegetable Kingdom.") 
 
 Darwin, therefore, proved conclusively by these careful 
 experiments (1) that pansy blossoms which were cross-polli- 
 nated produced ten times as many seeds as those that were 
 self -pollinated ; (2) that the plants developed from these 
 seeds, produced as a result of cross-pollination, were far more 
 vigorous and prolific ; and (3) that the descendants of the 
 plants produced by self-pollination, even when their flowers 
 were cross-pollinated, were not able to develop seeds capable 
 of as vigorous growth as the descendants of plants produced 
 continuously by cross-pollination. 
 
 95. Prevention of self-pollination. We have found that 
 the pansy is well adapted to bring about cross-pollination, 
 and since, as Darwin proved, cross-pollination results in seeds 
 being formed. which produce much more vigorous and fruit- 
 ful plants, we should expect that the pansy would have de- 
 veloped some means of preventing self-pollination ; and this, 
 as we shall see, proves to be the case. 
 
 The anthers of the pansy, as we saw, are joined about the 
 pistil so as to form a band, and the openings for the escape of 
 
EEPRODUCTION IN PLANTS 85 
 
 pollen are on their inner surfaces, next to the style and ovary. 
 When the pollen is shaken out of the anthers, it first collects 
 in the space between the anthers and the pistil. In the natu- 
 ral position of the pansy blossom it should be remembered 
 that the pistil is directed downward, and the end of the stigma 
 rests on the lower petal, with the stigmatic cup opening out- 
 ward and away from the anthers. Between the two anthers, 
 on the under side of the pistil, and at the end nearest the 
 stigma, there is a V-shaped notch from which the pollen may 
 readily escape when the flower is shaken by the wind or 
 insects. Since the notch is immediately over the groove in the 
 lower petal, the pollen falls into this groove and cannot un- 
 aided get into the stigmatic cup, since, as before stated, this 
 cup opens away from the direction in which the pollen must 
 fall. That the pansy pretty effectually prevents self-polli- 
 nation the following results of some of Darwin's experiments 
 along this line show. Two vigorous pansy plants were 
 selected for the experiment. One was covered with a net so 
 that the bumblebees could not get at the flowers, and the 
 other was left uncovered. In the uncovered one 105 fine 
 capsules were formed, while on the covered one only 18 were 
 formed, and in these only a few good seeds developed ; 
 and Darwin states that even the few seeds formed were prob- 
 ably due to the agency of tiny insects that the net could not 
 exclude. 
 
 In many other flowers in which both pistil and stamens are 
 present we find other devices for preventing self-pollination. 
 Some of these are as follows: In apple and pear blossoms 
 the stamens usually ripen at different times from the stigmas 
 in the same blossom, so that self-pollination in such cases is 
 impossible. Likewise, when stamens and pistils are in differ- 
 ent flowers, as in the pumpkin, corn, and willow, cross-polli- 
 nation is obviously necessary, if seeds are to be formed. 
 
86 PLANT BIOLOGY 
 
 Moreover, in case cross- and self-pollination take place in a 
 given flower, it has been proved that the pollen from another 
 flower will usually grow down the pistil more rapidly than the 
 pollen produced in the same flower, and so in such cases fer- 
 tilization is more likely to result from cross-pollination than 
 from self-pollination. 
 
 96. Cross-pollination by insects. From our study of the 
 pansy we learned that insects are attracted by bright colors 
 and sweet odors. By many observations biologists have 
 
 FIG. 32. A, staminate squash blossom ; B, pistillate squash blossom. 
 (Bailey.) 
 
 learned that most flowers with these characteristics are vis- 
 ited by insects, and that these animals carry pollen from 
 blossom to blossom, thus insuring cross-pollination. Any 
 one familiar with apple, pear, or other fruit trees has seen 
 that at time of blossoming these trees are alive with buzzing 
 bees, and fruit growers know that were it not for these insect 
 visitors their fruit crops would prove a failure. Some 
 plants (the squash, for example) have two kinds of flowers, 
 one kind containing stamens, the other pistils. It is evident, 
 therefore, from what we have already learned that pollina- 
 
REPRODUCTION IN PLANTS 
 
 87 
 
 tion, fertilization, and the development of fruit and seeds 
 could not take place in plants like these if there were not 
 some means of transferring pollen from the staminate 
 flowers to pistillate flowers. One has only to watch squash 
 
 blossoms on a sunny day 
 to know that bees visit 
 them in great numbers and 
 that their hairy bodies are 
 dusted with yellow pollen 
 as they fly from flower to 
 flower. 
 
 FIG. 33. Corn stall: with " tassels " (stam- 
 inate flowers) at the top. (Duggar.) 
 
 FIG. 34. Developing ear 
 of corn (pistillate flowers) . 
 (Bailey.) 
 
 97. Cross-pollination by wind. There are many plants, 
 however, which have flowers without conspicuous color or 
 odor; among these are the grasses, the corn, and many 
 common trees like the oaks, birches, and pines. At the top 
 of the corn stalk in midsummer develop the " tassels," 
 and when these are shaken, they scatter great quantities of 
 
88 PLANT BIOLOGY 
 
 light, dry pollen. On another part of the plant the ears of 
 corn develop. Each ear consists in part of clusters of pistillate 
 flowers, and the threads of silk represent the styles of the 
 pistils. Farmers know that a single corn plant, growing in a 
 place apart from other corn plants, will not form vigorous 
 ears. To secure a good crop, pollen must be carried from the 
 tassels of one plant to the silk of another, and this is accom- 
 plished in a garden or a corn field by the wind. Much more 
 pollen must be produced, however, by wind- than by insect- 
 pollinated flowers, since in the former case a great deal more 
 is wasted. Many wind-pollinated flowers, such as grasses, 
 have feathery styles to catch and hold the pollen brought by 
 the wind. 
 
 98. Summary and definitions. 
 
 Floral envelopes of a flower = calyx + corolla. 
 
 Calyx: 'composed of sepals (often green in color); 
 
 principal use, to inclose and help protect the 
 
 essential organs from cold, rain, or biting 
 
 insects. 
 Corolla: composed of petals (usually bright colored); 
 
 principal use to attract insects and so secure 
 
 cross-pollination. 
 
 Essential organs of a flower = stamens + pistils. 
 
 Stamens: usually composed of filament and anther; 
 use, to produce pollen grains, each containing 
 a sperm-cell. 
 
 Pistil: usually composed of ovary, style, and stigma 
 (or stigmas) ; use, to produce ovules, each con- 
 taining an egg-cell, and to insure pollination, 
 germination of pollen grains, and fertilization. 
 
REPRODUCTION IN PLANTS 89 
 
 II. THE STRUCTURE AND FUNCTIONS OF FRUITS 
 
 99. Relation of fruits to reproduction. We have already 
 learned that the use or function of flowers is to insure the 
 production of seeds. As is generally known, seeds are found 
 in fruits. We are now to study several types of fruits. 
 
 100. Study of the bean or pea fruit. Laboratory Study 
 
 No. 46. 
 
 A . Outside of the fruit. 
 
 Study if possible young pods, well-developed pods, and 
 pods that have dried; or charts may be used 
 to show the developing pods. 
 
 1. Name and describe the structure which attached the 
 
 pod to the plant. 
 
 2. The main part of the fruit or pod is the pistil, which 
 
 in the bean or pea flowers consisted of ovary, 
 style, and stigma. Which of these parts are 
 found in the fruit you are studying? (Fig. 35.) 
 
 3. Bean and pea blossoms have calyx, corolla, stamens, 
 
 and pistil. What parts of the flower are present 
 in the fruit? What parts have disappeared? 
 
 4. Make a drawing, natural size, of the fruit you are 
 
 studying in the position in which it hung on the 
 plant. Label fruit-stalk, calyx (if present), and 
 the parts of the pistil that you find. 
 
 B. Inside of the fruit. 
 
 Split the pod lengthwise into halves. 
 
 1. Carefully move one of the seeds in the pod ; is it free 
 
 from the pod, or is it attached ? 
 
 2. (Optional.) The region of an ovary to which seeds are 
 
 attached is called the placenta (as was also the case 
 in the ovary of flowers). Locate the placenta in the 
 fruit you are studying. 
 
 3. (Optional.) State whether or not you find any undeveloped 
 
 seeds. Undeveloped seeds probably never were fer- 
 tilized. 
 
90 
 
 PLANT BIOLOGY 
 
 4. Draw, natural, size in the position in which the pod 
 hung on the plant the opened fruit. Label wall 
 of ovary, developing seeds (undeveloped seeds, 
 if present), seed -stalk. 
 
 MftMMM 
 
 covtUMd- ououj 
 
 FIG. 35. Development of the pea fruit from the pea flower. (Drawn 
 from Jung Chart.) 
 
 101. Study of the cucumber, Tokay grape, cranberry, or 
 tomato fruit. Laboratory Study No. 47. 
 
 A. Outside of the fruit. 
 
 1. All of the fruits named above are developed ovaries. 
 
 Describe the shape and color of the fruit you are 
 studying. 
 
 2. Make a drawing, natural size (or an inch in diameter 
 
 in case the grape or cranberry is used). Label 
 fruit-stalk (if present), ovary. 
 
 B. Inside of the fruit. 
 
 Cut a cross section of one of the fruits you are studying. 
 1. Carefully move one of the seeds within the fruit ; is 
 it attached or is it free ? 
 
REPRODUCTION IN PLANTS 91 
 
 2. Make a drawing, natural size (or an inch in diameter 
 
 in case the grape or cranberry is used), of one 
 half of the fruit, and show method of seed 
 attachment. 
 
 3. (Optional.) Pinch a seed of one of the fruits between your 
 
 thumb and forefinger. Is it hard or soft ? Is it dry or 
 slippery? Of what advantage are these character- 
 istics? 
 
 102. Seed dispersal. It is evident that stronger plants 
 will be developed from seeds if the latter are carried some 
 distance from the mother plant, for then they will not be 
 shaded by the mother plant, and the young plants will have 
 more light, air, food, and moisture, if they are not crowded 
 together. We shall now study some of the devices by which 
 plants secure the dispersal of their seeds. 
 
 103. Seed dispersal by wind. Laboratory Study No. 48. 
 Study one or more of the following fruits : 
 
 A. Winged fruits. 
 
 1. The maple fruit. 
 
 a. Find the fruit stalk, the two cells of the ovary each 
 containing a single seed, the wing attached to 
 each cell of the ovary. 
 
 Hold between yourself and the light a maple fruit 
 in the position in which it hung on the tree, and 
 draw it (X 2). Label fruit-stalk, cell of ovary, 
 containing one seed, wing, veins of wing. 
 
 6. Hold one of the fruits some distance above the desk 
 and let it fall. Describe the movements of the 
 fruit in falling. 
 
 c. Of what use are the wings if the wind were blowing 
 
 while the fruit is falling, or after the fruit has 
 fallen to the ground ? 
 
 d. Is the maple fruit a dry or a fleshy fruit? 
 
 2. The linden fruit. 
 
 a. Notice the wing-like attachment on the fruit-stalk. 
 Do the linden fruits occur singly or in clusters? 
 
92 
 
 PLANT BIOLOGY 
 
 Is the fruit hard or soft ? Draw in the position 
 on which it hung on the tree ( X 2) the fruit that 
 is given you. Label main fruit-stalk, wing- 
 like attachment, single fruit stalk, fruit. 
 b. c. d. Answer questions given under 1 (above). 
 3. The elm fruit or ailanthus fruit. 
 
 a. Notice the fruit stalk, the single-celled ovary, the 
 
 wing about the ovary. 
 
 Draw ( X 2) one of the above-named fruits. Label 
 fruit-stalk, ovary, wing. 
 
 b. c. d. Answer questions given under 1 above. 
 
 B. Tufted fruits (or seeds) . 
 
 1. The clematis, dandelion, thistle, or aster fruit. 
 
 a. Find the tiny seed-like ovary, containing a single 
 
 seed, and the tuft of hair. Draw ( X 2) one of 
 the fruits. Label ovary, tufts of hair. 
 
 b. c. d. Answer questions under A, above. 
 
 2. The milkweed fruit and seed. 
 
 a. (Optional.) Study Fig. 36. Describe the way the pod 
 
 opens when it is ripe. Are the seeds many or few ? 
 Draw one of the fruits (pods) to show the method of 
 
 opening. Label fruit-stalk, 
 ovary, seeds, style. 
 
 b. Examine one of the seeds 
 
 that has been detached 
 from the pod. Draw 
 (X2) one of the seeds 
 with its tuft of hair. 
 Label seed, tuft of hair. 
 
 c. Drop one of the tufted 
 
 seeds out of an open win- 
 dow when a breeze is 
 blowing or fan a seed 
 in the laboratory. State 
 your observation. What 
 
 FIG. 36. Milkweed pod is One US6 of the tuft of 
 
 opening. hair ? 
 
REPRODUCTION IN PLANTS 93 
 
 104. Seed dispersal by animals. Laboratory Study No. 
 49. Study one or more of the following fruits : 
 
 A. Burs and stickers. 
 
 1. Cocklebur. 
 
 a. Hold one of the fruits between yourself and the 
 light. Do the hooks all curve toward one end 
 of the fruit or in several directions ? 
 Notice the two larger projections at one end of the 
 fruit. These are the styles. Draw ( X 2) the 
 outside of one of the cockleburs, showing 
 the direction of the hooks. Label ovary, 
 hooks, two styles (large prongs at one end of 
 fruit). 
 
 6. Rub one of the cockleburs on a rough surface of 
 your clothing and try to remove it. By what 
 means does it cling to the cloth? How is a 
 cow or other hairy animal adapted to disperse 
 this fruit? 
 
 2. Burdock. 
 
 a. Each burdock consists of a large number of indi- 
 
 vidual fruits. Hold the burdock to the light. 
 In what directions do the hooks extend ? Why 
 is this an advantage in securing the distribu- 
 tion of fruits? 
 
 b. Answer questions under 1 b above. 
 
 3. Bidens (also called pitchforks or beggar's ticks). 
 
 a. Hold the fruit to the light or examine it with a 
 
 hand magnifier. In what direction do the 
 little barbs on the two prongs of the ovary 
 extend ? Why is this an advantage ? 
 Draw ( X 2) one of the bidens fruits. Label 
 ovary, prongs, barbs. 
 
 b. Answer questions in 1 b above. 
 
 B. Fleshy fruits. Suggested as home work. 
 
 1. In what ways are the seeds of apples, cherries, and 
 of many other fleshy fruits protected while they 
 are ripening? 
 
94 
 
 PLANT BIOLOGY 
 
 2. Many fleshy fruits are dispersed by birds and other 
 
 animals which are seeking food. How are these 
 animals rewarded for doing this work? 
 
 3. How are the seeds of ripe peaches and cherries, for 
 
 example, protected from injury? 
 
 105. Fruits and their classification. If one were asked 
 to give examples of fruits, one would doubtless give such 
 forms as apples, cherries, and peaches: But it is doubtful 
 if he would think of including among fruits, pea pods, pump- 
 kins, chestnuts, and corn. To 
 the botanist, however, these are 
 
 FIG. 37. Lengthwise sec- 
 tion of apple fruit, showing 
 seeds attached to a central 
 placenta. (Bailey.) 
 
 FIG. 38. Cross section of apple 
 fruit, showing seeds and their cov- 
 erings which constitute the core. 
 
 considered to be just as truly fruits as the forms commonly 
 thought of as fruits. Let us see why such diverse plant 
 products as those just named are all included under the head- 
 ing of fruits. Technically, a fruit is a ripened ovary and its 
 contents with any other part of the plant that is closely incorpo- 
 rated with it; and since the forms named above are all ripened 
 ovaries containing one or more seeds, it is evident that, 
 strictly speaking, they must be classed with the fruits as 
 much as apples and cherries. 
 
 Sometimes the flower contains a number of pistils which 
 form a pulpy mass, such as the raspberries and blackberries 
 
REPRODUCTION IN PLANTS 
 
 95 
 
 (see Fig. 40) ; hence each of these so-called berries is composed 
 of a number of separate fruits. Sometimes the end of the 
 stem which bears the pistils becomes pulpy and juicy and the 
 dry pistils are embedded in 
 its outer surface, as is the 
 case with strawberries (see 
 Fig. 42). In other fruits 
 the ovary may form a hard 
 woody wall, as in the nuts 
 like the chestnut (Fig. 39) 
 and acorn, or the wall may 
 be like a tough paper, as in 
 the pods of peas and locusts 
 (Fig. 43). In still other 
 forms the whole ovary may 
 become fleshy, as in the true 
 berries, such as the cran- 
 berry, grape, and tomato. 
 Or we may find a combina- 
 tion of a tough wall and a fleshy interior, as in the pumpkin, 
 squash, and cucumber. In cherries, plums, and peaches the 
 ovary forms two kinds of material, the inner very hard and 
 
 stone-like and the outer pulpy. 
 In fruits like the corn grain 
 and the wheat kernel the ovary 
 wall is so closely united with 
 the coats of the single seed that 
 these grains are commonly con- 
 sidered as seeds. 
 
 The facts just stated with 
 regard to different kinds of fruits suggest a simple form of 
 classification, based largely on the characteristics of the ovary 
 walls. Thus, for instance, all those fruits, such as bean pods, 
 
 FIG. 39. Chestnut fruits inside the 
 chestnut bur. (Bailey.) 
 
 FIG. 40. Raspberry fruits. 
 
 
PLANT BIOLOGY 
 
 grains, and nuts, in which the walls are 
 dry at maturity, are called dry fruits. 
 Those in which the walls are pulpy 
 throughout, as in the tomato, are termed 
 fleshy fruits; and those 
 which are partly fleshy 
 and partly stone-like , as 
 
 FIG, 41 . - Flower of the - th ch d h 
 
 strawberry. (Bailey.) J 
 
 are called stone jruits. 
 Another scheme for classifying fruits is 
 
 based upon the fact that some fruits break 
 
 open when ripe and scatter their seeds, 
 while others remain 
 closed. Examples of 
 fruits of the first kind 
 are the bean, milkweed, and pansy, and 
 of those that remain closed are cherries, 
 apples, and grains. Whether or not a fruit 
 breaks open at maturity depends upon 
 the character of the ovary wall, and this 
 in turn determines, as we shall now see, 
 the method by which its seeds are dis- 
 persed. 
 
 FIG. 42. Straw- 
 berry. (Bailey.) 
 
 FIG. 43. Pea pod. 
 (Bailey.) 
 
 106. Home work on fruits. Laboratory 
 Study No. 50. (Optional.) 
 Classify the fruits with which you are familiar in a table like 
 the following : 
 
 NAME 
 OF FRUIT 
 
 DRY 
 FROIT 
 
 FLESHY 
 FRUIT 
 
 STONE 
 FRUIT 
 
 OPEN 
 
 WHEN 
 
 RIPE 
 
 CLOSED 
 
 WHEN 
 
 RIPE 
 
 SEEDS 
 DIS- 
 PERSED 
 BY WIND 
 
 SEEDS 
 Dis- 
 PERSEDBY 
 ANIMALS 
 
 Cherry 
 
 
 
 X 
 
 
 X 
 
 
 X 
 
CHAPTER VIII 
 PLANT PROPAGATION 
 
 I. SEEDS AND THEIR DEVELOPMENT INTO PLANTS 
 
 107. Study of the bean seed and the development of the 
 bean seedling. Laboratory Study No. 51. 
 
 Materials: Dry bean seeds and seeds that have been soaked for 
 24 hours. Sprouted bean seeds and seedlings grown as follows: 
 To secure early stages, put seeds that have been soaking for 24 hours 
 between layers of wet blotting paper, or bury them in moist sawdust, 
 and allow them to stand in a warm place for two or three days. 
 For older stages of bean seedlings plant soaked seeds in boxes con- 
 taining moist sawdust, sand, or earth. If some of these boxes are 
 put in a warm place and others in a cool place all stages may be 
 obtained in two to four weeks. 
 
 1. What difference do you notice in the size of the dry and 
 
 soaked seed? How do you account for this dif- 
 ference ? 
 
 (Optional.) Half fill a bottle with dry bean seeds, and add 
 water enough to fill the bottle. Allow the seeds to 
 soak for 24 hours. How much do beans increase in size 
 when soaked ? 
 
 2. On one edge of a soaked seed find a scar called the hilum, 
 
 which marks the place where the bean was attached 
 to a small stem which connected it to the pod. 
 Locate the hilum, and state what caused this scar. 
 
 3. Make a sketch about two inches long of the seed, show- 
 
 ing the edge on which the scar is found. Label 
 scar or hilum. 
 H 97 
 
PLANT BIOLOGY 
 
 4. Pinch a soaked seed, and notice the opening near the 
 
 hilum through which water is forced from the 
 seed. This opening is called the micropyle (Greek, 
 micro = tiny -f- pula = gateway). 
 
 a. Describe the position and appearance of the micro- 
 
 pyle. What is the derivation of the word ? 
 
 b. Sketch the micropyle in your drawing in 3 above. 
 
 5. Carefully remove the seed-coat from a soaked bean. 
 
 All the structures within this seed-coat together 
 form a little bean plant, called a bean embryo. 
 Break off one of the two halves and make out the 
 following parts of the bean embryo: 1) the two 
 thickened halves of the bean called the seed leaves 
 or cotyledons; 2) a little sprout, the first stem or 
 hypocotyl (Greek, hypo = beneath + cotyl = cotyle- 
 don) ; and 3) the two tiny folded leaves forming 
 the first bud or plumule, lying between the cotyle- 
 dons. 
 
 a. State what you have done to show the parts of the 
 
 embryo. 
 
 b. Name and describe each of these parts. 
 
 c. Place the cotyledon you have removed close to its 
 
 point of attachment to 
 the hypocotyl, and 
 make a drawing about 
 two inches long, show- 
 ing all the parts named 
 above, labeling each 
 part. 
 
 6. Examine a bean seed that 
 has just begun to 
 sprout. 
 
 a. Name the part of the 
 
 bean embryo that first 
 breaks through the 
 seed -coats. 
 
 b. Make a drawing about 
 
 two inches long, to 
 
 FIG. 44. Germination of castor show the Sprouted 
 
 bean. (Osterhout.) Seed. Label. 
 
PLANT PROPAGATION 
 
 7. Look at a pot of young seedlings that are just pushing 
 
 their way above the surface of the soil or sawdust. 
 
 a. Which part of the embryo first appears above ground ? 
 
 b. What is the shape of this part ? 
 
 8. Study a whole seedling at this stage (see 7 above), 
 
 from which one cotyledon has been removed. 
 
 a. Describe the changes that have taken place in each 
 
 part of the embryo since the seed began to sprout. 
 
 b. Describe the position and appearance of the main root 
 
 and its branches that appear in this stage. 
 
 c. Make a drawing, natural size, of a seedling at this 
 
 stage and show by a horizontal line the ground level. 
 Label each part. 
 
 9. Study a well-developed seedling, comparing it with the 
 stages already drawn, and answer the following 
 questions : ' 
 
 a. What changes in the size of the cotyledons do you 
 
 notice as the seedling grows older? Most of the 
 food for the early development of the seedling is 
 furnished by the cotyledons; suggest, therefore, 
 the cause of the change in size of the cotyledons, 
 which you have noticed. 
 
 b. What parts of the developing embryo have changed in 
 
 color during germination ; how have they changed ? 
 
 B c 
 
 FIG. 45. Stages in the development of the squash seedling. (Bailey.) 
 
100 
 
 PLANT BIOLOGY 
 
 c. What parts of the oldest seedling have developed from 
 
 the plumule? 
 
 10. Draw the oldest stage of the bean seedling, and label 
 main or primary root, root-branches or secondary 
 roots, ground level, cotyledons (or scar left by coty- 
 ledons), hypocotyl, stem above cotyledons (epicotyl), 
 leaves, terminal bud. 
 
 108. Study of the corn seedling and its development from 
 the corn grain. Laboratory Study No. 52. (Optional.) 
 
 Materials: Dry and soaked corn grains; seedlings of various 
 sizes grown as described above for the bean seedling. Corn grains 
 should be planted with the pointed end down. 
 
 The structure of the corn grain and the development of the com 
 embryo can be understood much more easily if the study of the 
 corn seedling is made first, and later that of the corn grain. 
 
 A. Seedling just breaking ground. 
 
 1. Examine a pot of seedlings that are just pushing their 
 
 way through the soil or sawdust, and study a 
 seedling of this stage that is 
 given you. All the parts of 
 the seedling above the corn 
 grain have developed from 
 the first bud or plumule. 
 
 a. What is the shape of the part that 
 
 first breaks through the soil? 
 
 b. Look for the sheath leaf sur- 
 
 rounding the unfolding 
 leaves, and trace it down to 
 the ridge around the stem 
 from which it springs. How 
 does this sheath or first leaf 
 of the plumule differ from 
 the unfolding leaves? What 
 is its probable use? 
 
 2. Observe the scar on the grain, showing where it was 
 
 fastened to the cob, and notice the shape of the 
 
 FIG. 46. Wheat Seedling. 
 
PLANT PROPAGATION 101 
 
 grain at its opposite end. Does the plumule 
 develop from the blunt end or the pointed end ? 
 3. Make a sketch of the seedling (X 2) and label grain of 
 corn, scar where grain was attached to the cob, 
 stem of plumule, sheath leaf, unfolding leaf, main 
 root, rootlets, soil line. 
 
 B. Corn grain just sprouting. 
 
 1. Examine a corn grain that has just sprouted. Recall 
 
 to mind the end of the grain from which the main 
 root grew. (If you are not sure, look at your 
 drawing, or better yet the seedling.) 
 
 a. What part of the little corn plant breaks through the 
 
 covering first? 
 
 b. What other part of the embryo shows signs of growth? 
 
 2. Remove the thin covering from the grain, and observe 
 
 an oval body embedded in the corn grain. This is 
 the little corn plant or embryo. How does the 
 embryo differ in color from the rest of the grain? 
 
 3. The oval-shaped body from which the root and plumule 
 
 seem to spring in the grain of corn is called the 
 cotyledon. The remainder of the grain is endo- 
 sperm, which is the food material for the develop- 
 ment of the embryo. Make a sketch of the seed- 
 ling at this stage (X2) and label single cotyledon, 
 plumule, endosperm or food material, main root. 
 
 C. Corn grain. 
 
 1. Very carefully scrape away a little of the surface of the 
 
 cotyledon of a dry or soaked grain till the other 
 parts of the little plant or embryo come into view. 
 Make out the plumule and main root. 
 Sketch the corn grain and label cotyledon, plumule, 
 tiny root, food material around the plant (endo- 
 sperm). 
 
 2. Cut a corn grain in such a way as to divide the embryo 
 
 and endosperm lengthwise in half. Put one half in 
 iodine. Where in the corn grain is starch pres- 
 ent? Where is it absent? 
 
10 f 2 ' P'LANT BIOLOGY 
 
 D. Corn seedling well advanced. 
 
 1. What changes have taken place during the development 
 
 of the seedling in the roots? in the plumule? 
 
 2. How does the veining of the leaves in the corn plant 
 
 differ from that in the leaves of the bean plant ? 
 
 3. Where do you find aerial or air roots on the corn seedling? 
 
 (Roots growing above ground are aerial roots.) 
 
 4. Pinch the grain between your fingers. What changes 
 
 do you notice in the amount of food material? How 
 can you account for these changes ? 
 
 5. Make a sketch of the seedling and label corn grain, coty- 
 
 ledon, stem, leaves, aerial roots, soil roots. 
 
 109. Suggestions for growing seedlings at home. (Optional.) 
 
 A. Window box. Secure a wooden box at least six inches in 
 depth, and of a convenient size to place in front of a south window, 
 if you have such a window at home. Nearly fill the box with rich 
 earth which has been finely pulverized or sifted. If possible, mix 
 in thoroughly some well-rotted manure and a tablespoonful of pre- 
 pared fertilizer. Soak your seeds for twenty-four hours, and plant 
 them at a depth equal to four times the thickness of the seeds. 
 Cover the seeds with dirt, press it down firmly, and sprinkle with 
 water till the earth is thoroughly moistened to a depth of at least 
 four inches. See that your garden is kept as nearly as possible at a 
 temperature of 70 degrees. Add enough water day by day to keep 
 the ground moist. 
 
 B. Tumbler garden. Secure several pieces of blotting paper 
 or other porous paper, and cut it about as wide as the tumbler is 
 high. Wet the paper and roll it into a hollow cylinder that fits 
 inside the tumbler. Between the blotting paper and the glass 
 place the soaked seeds with their hilums in several different posi- 
 tions. Fill the interior of the tumbler with wet sawdust, cotton, or 
 crumpled paper. Cover the tumbler loosely and keep the contents 
 moist, and at a temperature of about 70 degrees. 
 
 C. Glass-plate garden. 1 Secure two pieces of glass about 5X7 
 
 1 The authors are indebted to Dr. Cyrus A. King, Head of Depart- 
 ment of Biology of Erasmus Hall High School, Brooklyn, N. Y., for 
 this method of germinating seeds. 
 
PLANT PROPAGATION 
 
 103 
 
 inches (picture negatives cleaned in hot water are admirable for 
 this purpose). Upon one of the glasses put a layer of wet cotton 
 wadding about half an inch thick. Arrange the seeds (which have 
 been soaked for 24 hours) with their hilums in several different 
 positions, and place on top of them the second plate of glass. Tie 
 strings about the two glasses, and stand the "garden" in about an 
 inch of water. The water will rise between the glasses and keep the 
 developing seedlings moist. After the seeds have begun to sprout, 
 turn the " garden" so that it rests on another edge, and note the 
 effect on direction of growth of the hypocotyl. 
 
 Observations to be made on the development of each seed 
 
 1. What part of the seedling first appears above ground ? (Make 
 
 drawings.) 
 
 2. Does this part come up straight or in the form of an arch ? 
 
 3. What kind of veining is found in the leaves ? 
 
 4. How many cotyledons are present, and what is their use ? 
 
 5. In what direction does the main root tend to grow ? the sec- 
 
 ondary roots ? 
 
 110. Comparison of seeds and seedlings. Study No. 53. 
 (Optional.) 
 
 Soak and plant at home as directed under Materials (107), 
 several kinds of seeds. Study the seeds and seedlings, and fill out 
 in your note-book a table like the following : 
 
 
 BEAN 
 
 PEA 
 
 SQUASH 
 
 CORN, ETC. 
 
 Number of cotyledons - . 
 
 
 
 
 
 
 
 
 
 Position of stored food . 
 
 
 
 
 
 
 
 
 
 Kinds of food present . . . 
 
 
 
 
 
 
 
 
 
104 
 
 PLANT BIOLOGY 
 
 Function of cotyledons . . 
 
 
 
 
 
 (Storage of food) .... 
 
 
 
 
 
 f T*Yliafi p p^ 
 
 
 
 
 
 
 
 
 
 
 Method of breaking ground . 
 
 
 
 
 
 (By arched hypocotyl) . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Veining of foliage leaves . . 
 (Npttpd^l 
 
 
 
 
 
 fp QrQ iipi\ 
 
 
 
 
 
 
 
 
 
 
 111. Nutrients stored in corn grains for the use of the seedling. 
 Laboratory Study No. 54. (Optional.) 
 
 Grind with a mortar and pestle some corn grains till a fine meal 
 is prepared. Test for each of the food substances and fill out in 
 your note-book a table like the folbwing : 
 
 NAME OF NUTRIENT 
 
 CHEMICAL USED 
 
 RESULT 
 
 CONCLUSION 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Fat 1 
 
 
 
 
 
 
 
 
 112. Of what importance is the endosperm in the develop- 
 ment of corn seedlings ? Laboratory Study No. 55. Home 
 work or demonstration. 
 
 Soak twenty-four or more corn grains over night. Care- 
 fully remove from half of them all the endosperm (food 
 
 1 To test for fat, put some of the cornmeal into a test tube, add 
 some ether, shake frequently, and let the tube stand for a time. At 
 the end of twenty-four hours pour'off the clear liquid upon pieces of 
 glazed paper. After the ether has evaporated, hold the paper to 
 the light. Be careful not to hold the ether near a flame. 
 
PLANT PROPAGATION 
 
 105 
 
 materials) from around the embryo corn plant. Plant the 
 corn grains and the corn embryos in rich soil, covering both 
 with the same depth of earth, and marking the location of the 
 two sets. Put them in a warm place. 
 
 1. Describe the preparation of the experiment. 
 
 2. At the end of two weeks state the number of each group of 
 
 seedlings that have pushed through the soil. 
 
 3. What difference in the size of the two sets of seedlings do 
 
 you notice at the end of two weeks? at the end of 
 three weeks? 
 
 4. What has this experiment taught you ? 
 
 II. OTHER METHODS OF PLANT PROPAGATION 
 
 113. Grafting. The method often adopted by fruit growers 
 to produce new and better varieties is that known as grafting. 
 This method of plant propa- 
 gation may be carried on in 
 the following manner. A 
 young shoot, known as the 
 scion (Fig. 47, A, b), is cut 
 
 FIG. 47. Methods of grafting. 
 
 in an oblique direction from a tree, the fruit of which is desired, 
 and a similar oblique cut is made across the twig of another tree, 
 called the stock (Fig. 47, A , a) , of a related kind. The two freshly cut 
 surfaces are then closely applied to each other, and the scion and 
 
106 PLANT BIOLOGY 
 
 stock are bound together by grafting wax (Fig. 47, B, c), which is put 
 around the outer bark to hold the two pieces in place and to pre- 
 vent evaporation. In this way the cambium layers of the two 
 plants are brought into close contact and soon unite. The ducts of 
 the stock likewise join those of the scion, and so sap is transmitted 
 to the grafted twig, which grows and develops its fruit as though it 
 were still a part of the plant from which it was taken. There are 
 many different ways of cutting and binding the twigs together, 
 and even buds may be used as scions (Fig. 47, C, 6). But the prin- 
 ciple is the same in every case. 
 
 Grafting is of necessity employed in producing new plants of 
 seedless grapes or oranges. It is also frequently adopted to com- 
 bine the desirable characteristics of two different plants. For 
 example, when the vineyards of France were being destroyed by 
 an insect that attacked the roots, the fruit-growers overcame the 
 difficulty by grafting the wine-producing scions upon the more vigor- 
 ous and resistant nutritive stock of grapevines introduced from 
 America. 
 
 114. Slips, runners, and layers. Another method of producing 
 new plants is that of cutting twigs of plants that are desired, and 
 
 FIG. 48, Strawberry plant with runner. (Bailey.) 
 
 placing the lower end of the stems in moist sand. Roots soon 
 develop on these so-called slips, and the new plants thus formed can 
 then be transplanted into good rich soil. Any one who has seen a 
 vigorous strawberry plant knows that it sends out a lot of slender 
 stems which grow so rapidly that they are known as runners. When 
 a portion of one of these runners lies upon the surface of moist soil, 
 
PLANT PROPAGATION 
 
 107 
 
 roots are formed as in the case of slips, and when they are firmly 
 established, the connection with the parent plant may be severed, 
 and thus a new strawberry plant secured. Still another method 
 of propagating plants is known as layering, which may be accom- 
 plished in raspberry or blackberry plants by burying the tips of 
 branches in the soil, thus inducing the production of roots. The 
 new plant can then be severed from the parent. 
 
 116. Tubers. New potato plants are commonly secured, not 
 by planting potato seeds, but by cutting into pieces a potato which 
 
 
 FIG. 49. Potato plant and tubers grown from dark colored potato in 
 center. (U. S. Dept. Agriculture.) 
 
 is a fleshy underground stem or tuber, each piece having one or more 
 "eyes," and putting these into the ground. In each eye is a bud, 
 and when this sprouts it develops stems and leaves above ground, 
 the new plant thus formed getting a considerable amount of 
 nutrition from the food stored in the tuber during the preceding 
 season. 
 
108 PLANT BIOLOGY 
 
 116. Bulbs. Still another method of propagating plants is 
 by means of bulbs, which, in the onion, for example, consist of a short, 
 thickened underground stem, to which are attached many layers 
 of thickened parts of leaves known as bulb-scales. Frequently, as 
 in the tulip and hyacinth, after the food stored in the bulb has been 
 used in the early spring to develop stem, leaves, and flowers, the 
 nutritive organs store away food for another season by producing 
 new bulbs close to the old one. 
 
 117. Home bulb culture. (Optional.) 
 
 Few plants are easier to cultivate or give greater satisfaction, 
 especially in winter, than those that grow from bulbs. Secure a few 
 tulip, hyacinth, or narcissus bulbs and bury them in pots of rich 
 earth. Water them well and put them in a dark, cool place for four 
 to six weeks, until the roots appear through the opening at the bot- 
 tom of the pot. Then put them in a warm, sunny place, keep them 
 well watered, and the flowers will appear in a few weeks. 
 
 III. CONDITIONS THAT ARE ESSENTIAL FOR THE GROWTH 
 
 OF PLANTS 
 
 118. The five essential conditions for plant growth are the 
 following : (1) moisture, (2) favorable temperature, (3) air, 
 (4) light, (5) food. We have already shown the necessity of 
 air for the germination of seeds (79) and for the liberation of 
 energy (76). The use of the food stored in the corn grain 
 for the corn embryo was also demonstrated in 112. We have 
 also proved that green plants do not manufacture carbohy- 
 drates in the absence of sunlight (30). We can likewise show 
 experimentally the relation of moisture and temperature to 
 the germination of seeds and to the growth of plants. 
 
 119. Relation of moisture to germination and growth. Labo- 
 ratory Study No. 56. (Optional.) Suggested as home work. 
 
 Secure three tumblers of same size (tin covered jelly-tumblers are 
 very satisfactory). In the bottom of each put a piece of 
 
PLANT PROPAGATION 109 
 
 sponge about half the size of the fist (a wad of cotton or paper 
 will answer). Label the first tumbler No. 1, and place upon 
 the sponge 10 pea seeds that have been soaked for 24 hours. 
 In the second tumbler (labeled No. 2) put 10 soaked peas, and 
 add enough water to come nearly to the top of the sponge. 
 Put 10 soaked pea seeds into the other tumbler (No. 3), and 
 add sufficient water to cover all the peas. To prevent the 
 evaporation of the water, cover the three tumblers, and place 
 them side by side in a moderately warm temperature (65- 
 70 F.), and label each " Please do not disturb." 
 
 1. Which one of the five conditions (enumerated in 118 above) is 
 
 different for the three groups of seeds ? 
 
 2. Name all of these conditions which are practically the same for 
 
 the seeds in all three of the tumblers. 
 
 3. At the end of a few days compare the seeds in the three tum- 
 
 blers. What percentage of the seeds in each of the three tum- 
 blers has germinated ? 
 
 4. State clearly your conclusion as to the relation of water to the 
 
 germination of pea seeds. 
 
 5. Allow the three tumblers to stand side by side in a warm, light 
 
 place for several weeks. Describe the changes that take place 
 in each tumbler, and state your conclusion as to the relation 
 of moisture to the growth of pea plants. 
 
 120. Relation of temperature to germination and growth. Labo- 
 ratory Study No. 57. (Optional.) Suggested as home work. 
 
 Prepare three tumblers with sponges (cotton or paper) as in 119 
 above, putting in water enough to come nearly to the top of 
 the sponge in each dish. In each tumbler place 10 soaked 
 peas, and put on the covers. Label No. 1, No. 2, and No. 3. 
 Set tumbler No. 1 in the refrigerator or in some place where 
 it will not freeze. Keep Tumbler No. 2 at the temperature 
 of the living room. Place No. 3 where the temperature is 
 over 100. Make sure that all tumblers have about the 
 same amount of light by covering each with black paper or a 
 cloth. By the aid of a thermometer find and record the tern- 
 
110 PLANT BIOLOGY 
 
 perature of each place where you put a tumbler. Each day 
 look at the tumblers, and if necessary add enough water to 
 keep the level the same in all three. 
 
 1. Which one of the five conditions named in 118 is different for 
 
 the three groups of seeds ? 
 
 2. Name all the conditions which are practically the same for the 
 
 seeds in all three of the tumblers. 
 
 3. At the end of a few days compare the seeds in the three tumblers. 
 
 What percentage of the seeds in each of the three tumblers 
 has germinated ? 
 
 4. State clearly your conclusion as to the relation of temperature to 
 
 the germination of pea seeds. 
 
 5. Allow the three tumblers to stand in the three different tem- 
 
 peratures for several weeks. Describe the changes that take 
 place in each tumbler, and state your conclusion as to the 
 relation of temperature to the growth of pea plants. 
 
 121. The soil. " From the soil all things come; and 
 into it all things at last return ; and yet it is always new, and 
 fresh, and clean, and always ready for new generations. This 
 soft, thin crust of the earth so infinitesimally thin that it 
 cannot be shown in proper scale on any globe or chart sup- 
 ports all the countless myriads of men, and animals, and 
 plants, and has supported them for countless cycles, and will 
 yet support for other countless cycles. In view of this 
 achievement, it is not strange that we do not yet know the 
 soil and understand it ; and we are in a mood to be patient 
 with our shortcomings." l 
 
 Even a casual examination of the soil in any region shows that 
 it has a complex structure. Usually it is composed of some coarse 
 particles known as gravel, finer grains called sand, and still more 
 minute ingredients, the mud or clay. The relative proportions of 
 these constituents determine whether the soil is a gravelly soil, a 
 sandy soil, or a clayey soil. The soil particles to which we have 
 
 1 Bailey's " Cyclopedia of American Agriculture," Vol. I, " Farms," 
 p. 323. 
 
PLANT PROPAGATION 111 
 
 referred supply the mineral ingredients needed by plants in the form 
 of soil-water. But soil, to be fertile, must contain a considerable 
 quantity of vegetable mold, the so-called humus, a dark brown or 
 black substance produced by the decay of vegetable matter. This 
 is the reason that florists mix with the dirt in their flower-pots a 
 handful of material obtained from the floor of the forest (see 
 frontispiece), where leaves have fallen and decomposed year after 
 year. 
 
 122. Moisture. If the student has tried the experiment in 
 119, he will have been convinced that the amount of moisture 
 supplied to seeds or plants has a great deal to do with their develop- 
 ment. Soils in very dry or arid regions are deficient in water, 
 and this must be supplied by irrigation. In semiarid regions proper 
 methods of tillage, as we shall see, will do much to keep the soil 
 in a proper condition for plant growth, so far as moisture is con- 
 cerned. Very moist or "heavy" soils, on the other hand, are 
 unfavorable for the growth of most plants, and so the excess of water 
 must be removed by drainage. 
 
 Reviewing some of the facts already learned, we see that a large 
 supply of water must be secured by plants from the soil, because 
 
 "1. A living plant contains a large proportion of water gen- 
 erally more than 75 per cent of its weight. 
 
 "2. Large quantities of water must pass through the plant in 
 order that the food solution in the soil may be carried to the leaves, 
 and the substances that it contains may be converted into organic 
 matter. This water loss takes place by transpiration from the 
 leaves and growing shoots. 
 
 "Careful and extended experiments in this country and Europe 
 have shown that 300 to 500 tons of water are taken from the soil 
 by the various crops for each ton of dry substance produced." 1 
 
 123. Relation of the soil to air. When the interstitial spaces 
 between the particles of soil are not filled with water, or when they 
 are only partly filled, they contain air. The air which circulates in 
 
 1 Bailey's " Cyclopedia of American Agriculture," Vol. I, " Farms," 
 p. 353. 
 
112 PLANT BIOLOGY 
 
 the soil differs in composition from the air above the surface. As a 
 rule, the soil air contains less oxygen and more carbonic acid (CC>2), 
 ammonia, and vapor of water. The increased amount of carbonic 
 acid and ammonia have their origin in the organic matter or humus. 
 A soil is not in the best condition for the production of crops unless 
 there is within its depths a free circulation of air. This is true 
 because oxygen in the soil is as essential for the life of the plant as 
 it is for the animal. . . . 
 
 "When the soil is full of water to within a few inches of the sur- 
 face, there can be no circulation of air among its particles. Ade- 
 quate ventilation can be provided for such a soil only by drainage. 
 Drainage ventilates the soil by lowering the ground water three or 
 four feet, and thus makes it possible for the roots of plants to pene- 
 trate soil more deeply. In time these roots die and decay and 
 afford passageways throughout the soil for the ready movement 
 of the air." 1 
 
 124. Relation of soil to heat. The influence of the tempera- 
 ture of the soil on crop production is a factor of considerable 
 importance. The life processes of a plant are practically suspended 
 below a certain minimum temperature, which is about 40 degrees 
 Fahrenheit for most cultivated crops. Above this temperature 
 all the vital activities, as germination and growth, increase until 
 the optimum is reached. Above this point these life processes de- 
 crease in activity until the point is reached when they cease. The 
 soil is a great factory that has its production vastly increased as 
 the temperature rises. . . . The minimum temperature at which 
 corn germinates and also the minimum for its growth is 48 or 
 49 F. Its optimum is about 93 F. . . . 
 
 "The sources of the heat of the soil are the internal heat of the 
 earth, the sun, and decaying vegetable matter. It is difficult to 
 estimate to just what extent the internal heat of the earth, which 
 itself is very great, affects the temperature near the surface of the 
 earth. However, the amount of heat from this source is insignificant, 
 is a constant factor, and is entirely beyond the control of man. 
 
 1 Bailey's "Cyclopedia of Agriculture," Vol. IX, "Farms," p. 357. 
 
PLANT PROPAGATION 113 
 
 Decaying organic matter furnishes some heat to the soil. For 
 example, manure heats the soil to a limited extent when it is spread 
 on the surface and plowed in. ... The sun is by far the most 
 important source of heat for the soil. When its rays are nearly 
 vertical there is tropical heat ; when its rays are withheld, the land 
 is locked in snow and ice. The heat received at the surface passes 
 downward by conduction." l 
 
 125. Cultivation of the soil. A moment's thought will 
 convince us that since all the food of man is ultimately de- 
 rived from plants, any measures that tend to improve crops 
 and reduce the cost of crop 
 production are of vital in- 
 terest to all of us. In the 
 past, before much was 
 known in regard to scien- 
 tific principles, farmers 
 put their seeds in the 
 ground, cultivated them 
 
 relatively little, and trusted Nature to do the rest. In 
 recent times, however, man has learned a great deal in 
 regard to soils, crops, and methods of cultivation, so that 
 the modern farmer is often able to double the yield of a 
 given area. The investigations of the National and State 
 Departments of Agriculture have done much to make farm- 
 ing a science, and the future will doubtless see far greater 
 improvements. 
 
 For the cultivation of plants the first requisite is a suitable 
 preparation of the soil. This involves, in the first place, 
 plowing, which turns under any weeds or other plants that 
 may have grown there before and which prepares for the work 
 of the harrow, an implement which pulverizes the soil so that 
 
 1 Bailey's "Cyclopedia of American Agriculture," Vol. I, "Farms," 
 pp. 355, 356. 
 
114 PLANT BIOLOGY 
 
 ready penetration of the roots of the growing plant is possible. 
 In small garden plots this work is done by the use of spades, 
 hoes, and rakes. It is often found necessary to add well- 
 rotted manures to increase the humus of the soil and chemi- 
 cally prepared fertilizers, which furnish available mineral 
 
 food for the crops. We 
 have already called at- 
 tention to the necessity 
 of proper drainage of 
 the soil before crops are 
 planted (122). Scien- 
 tific investigation has 
 demonstrated, too, that 
 frequent and thorough 
 
 stirring of the soil is most important not only to prevent 
 the growth of weeds, but also, and this is even more 
 essential, to conserve the soil moisture, and insure proper 
 aeration of the roots. It has been found that it is possible 
 to produce large crops on semiarid land if the top-surface of 
 the ground is kept in a thoroughly pulverized condition. 
 This is the so-called method of " dry farming." 
 
 IV. THE STRUGGLE FOR EXISTENCE AND ITS EFFECTS 
 
 126. Variation among plants. We have all heard the common 
 expression "as nearly alike as two peas." In reality, however, 
 if our powers of observation were sharp enough, we should probably 
 find that no two peas are exactly alike in shape, color, size, and 
 weight. The plants grown side by side from any two peas would 
 also vary in height, in number and position of leaves, and in the 
 number and vigor of flowers and seeds. In other words, as every 
 human being has certain distinguishing characteristics, so, too, we 
 should bear in mind that every individual plant, however small, 
 shows certain differences or variations from every other individual 
 of its class. 
 
PLANT PROPAGATION 
 
 115 
 
 127. The numbers of seeds produced by plants. A second fact 
 which is evident to all is that plants produce an enormous number 
 of seeds. Suppose we consider the case of a vigorous pea-vine. In 
 the course of a season it should produce at least 20 pods, each con- 
 taining at least 5 seeds. Hence, at the end of a single season, one 
 pea seed would, if conditions were favorable, have multiplied itself 
 100 times. If each one of these seeds were to be planted where it 
 
 FIG. 52. Variations in the corn ears produced in a single field. (Courtesy 
 of Dr. E. M. East, Bussey Institution, Harvard University.) 
 
 had plenty of moisture, light, food, air, and favorable temperature, 
 it likewise should give rise to 100 seeds, and so at the end of the 
 second season we ought to have 100 X 100, or 10,000 pea seeds, all 
 propagated from a single pea seed. Simple multiplication shows us 
 that at the end of five years a moderately prolific plant like the 
 garden pea would have given rise, had all conditions been favor- 
 able to 10,000,000,000 new seeds. Bergen has made a patient 
 count of the number of seeds produced by an average morning 
 glory plant, and finds it to be rather more than 3000 ; hence, 
 at the end of the fifth year, if such a rate of reproduction were 
 
116 
 
 PLANT BIOLOGY 
 
 to be continued, there would be 243,000,000,000,000,000 morning 
 glory seeds. 1 
 
 It is evident, however, that no pea vine or morning glory plant, 
 if left to itself, would be able to produce anything like the number 
 of seeds we have named, for otherwise at the end of a short term of 
 years there would not be room on the whole surface of the globe for 
 any other kinds of plants than these. As a matter of fact, the num- 
 ber of individuals of a given kind of organism does not vary much 
 from year to year. In the first place, many seeds are eaten by birds 
 and other animals. Again, many other seeds are not carried to a 
 place where they find all the conditions that are essential for germi- 
 nation (118). Still other seeds, even if planted in good soil 
 and in favorable surroundings, fail to germinate. Because of the 
 great losses of seeds in one or the other of these three ways, we can 
 get some idea of the reason why plants must produce a great abun- 
 dance of seeds if their kind is to be perpetuated. 
 
 128. The struggle for existence among plants. But even if 
 seeds finally germinate and get a foothold on the soil, a great many 
 
 FIG. 53. The struggle for existence and the survival of the fittest among 
 
 turnips. 
 
 of the plants thus started will never reach maturity and ripen their 
 seeds. In the first place, each plant is struggling to lift up its leaves 
 
 . l See Bergen's "Essentials of Botany" (1910), p. 202. 
 
PLANT PROPAGATION 
 
 117 
 
 to the light and air, and those that are most vigorous usually get 
 above and shade the others. Again, the supply of water and mineral 
 food in the soil of a given area is limited ; hence, plants that cannot 
 get what they need are dwarfed and finally starved to death. In 
 
 FIG. 54. Charles Darwin. 
 
 the third place, injurious insects destroy an enormous amount of 
 vegetation, the loss of cultivated crops alone from this cause being 
 estimated at $700,000,000 annually. Frosts, dry seasons, heavy 
 rains, and fungous diseases are other important factors in the life 
 of many plants. And so if we were able to see what is actually 
 going on in each square foot of the earth's surface, whether of forest, 
 
118 
 
 PLANT BIOLOGY 
 
 field, or meadow, we should doubtless witness a life and death 
 struggle for existence (1) between individual plants, of the same 
 kind, (2) between individual plants of different kinds, and (3) be- 
 tween plants and animals. 
 
 Charles Darwin in his great book on the "Origin of Species," 
 published in 1859, a book which has doubtless influenced human 
 thought more than any other book of modern times, closes his 
 chapter on the "Struggle for Existence" with the following words: 
 "When we reflect on this struggle we may console ourselves with the 
 full belief that the war of nature is not incessant, that no fear is 
 
 felt, that death is gen- 
 erally prompt, and that 
 the vigorous, the 
 healthy, and the happy 
 survive and multiply." 1 
 
 129. The survival of 
 the fittest. We have 
 seen in our study thus 
 far (1) that no two in- 
 dividual plants even of 
 the same kind are ex- 
 actly alike, (2) that 
 enormous numbers of 
 seeds are produced by 
 plants, and (3) that 
 there is inevitable com- 
 petition or struggle for 
 existence. The ques- 
 tion, then, that con- 
 fronts us is this : Which 
 of the many competi- 
 tors will survive in the 
 struggle, reach maturity, and finally reproduce themselves ? Obvi- 
 ously those individual plants that vary from the rest in such a 
 
 A. 
 
 FIG. 55. Dandelion plant. (Bailey.) 
 
 Darwin's " Origin of Species," p. 72. 
 
PLANT PROPAGATION 119 
 
 way that they can best adapt themselves to their surroundings. 
 Let us see, for instance, why certain weeds like the dandelion are 
 so common a nuisance on our lawns. In the first place these 
 weeds have fleshy roots that reach deep down into the soil, thus 
 helping the plant to get and keep a stock of moisture and food. 
 In the second place the reserve supply of nutrition stored in 
 these roots enables the plants to put forth leaves and flowers in 
 early spring, and so to get a good start ahead of their com- 
 petitors. Again, their short stems and tough leaves can be 
 trampled upon without killing the plant. Insects and fungous 
 diseases, for some reason, do not seem to attack them. And 
 finally dandelions produce a large number of tiny seed-like 
 fruits, each one of which is provided with a delicate tuft of hair 
 which a puff of wind will carry for a considerable distance, thus 
 insuring a wide dispersal of its seeds. In nature, then, plants like 
 the dandelion, pigweed, and thistle have survived in the struggle 
 for existence, because they are best fitted to their surroundings. 
 
 V. THE IMPROVEMENT OF PLANTS BY MAN 
 
 130. Artificial selection of favorable variations. In the pre- 
 ceding pages attention was frequently called to the fact that plants 
 show a tendency to vary more or less from each other. Now it 
 has been found that in a state of cultivation this tendency becomes 
 even more pronounced. A watchful farmer will often find that in 
 his cornfield one group of individuals ripens sooner than the rest, 
 and so if he wishes to sell earlier corn, he selects and plants next year 
 corn grains derived from plants that have varied in this direction. 
 Again, he may notice that the ears on certain stalks are larger and 
 ripen more kernels (see Fig. 52) ; these the crop-raiser who uses his 
 brains would select for seed in order to increase his yield per acre. 
 Variations in many other directions might be chosen by the success- 
 ful farmer which would add immensely to the value of his crops. 
 It is estimated that if every farmer were to select his seed carefully, 
 the corn production in the United States, which at present is about 
 $1,000,000,000, in a short time would be increased 10 per cent, which 
 would add $100,000,000 to our annual income. 
 
120 
 
 PLANT BIOLOGY 
 
 131. Artificial crossing of related species. Not only can man 
 secure new varieties of plants by watching for favorable variations 
 and perpetuating them from year to year, but he can actually be 
 instrumental in producing new kinds of plants. This process is 
 known as plant breeding. It depends fundamentally on the prin- 
 ciples we learned in treating of cross-pollination in flowers. Let 
 us illustrate plant breeding by the following account of the work 
 which has been done for the U. S. Department of Agriculture by 
 Dr. H. J. Webber of Cornell University. 1 
 
 In the winter of 1894-1895 a heavy frost destroyed practically 
 every orange tree in the northern and central part of the State 
 
 of Florida. The loss was over 
 $75,000,000. The problem that 
 confronted the orange growers 
 of the State was that of start- 
 ing their groves anew and if 
 possible of preventing a repeti- 
 tion of such an experience by 
 planting a more hardy kind of 
 orange tree. Dr. Webber, in 
 casting about for such orange 
 trees, finally chose a type called 
 the trifoliate orange (Fig. 56) 
 often used for an ornamental 
 shrub, and one that would not 
 be killed by winters as far north 
 as Philadelphia. The fruit of 
 this tree, however, is small, bitter, 
 and worthless for eating pur- 
 His task, therefore, was 
 
 FIG. 56. Spray from trifoliate 
 orange, showing leaves and fruit. 
 
 to* combine the characteristics of 
 
 a juicy, sweet-flavored fruit of the ordinary Florida orange tree 
 with the hardy, cold-resistant character of the trifoliate type. He 
 proceeded in this fashion: 
 
 1 See Year-books of U. S. Department of Agriculture, 1904, 1905, 
 1906. 
 
PLANT PROPAGATION 
 
 121 
 
 From the flower-buds of one type of orange trees he removed all 
 the stamens before blossoming time, and then covered the pistils 
 with paper bags to prevent the visit of insects bringing pollen. A 
 second set of buds on trees of the other type were likewise covered 
 with paper bags to prevent possible mixing of pollen by insect visi- 
 tors. When the stamens of one kind of orange blossoms and the 
 
 TRtfOUfSTE 
 
 FIG. 57. Fruits of two parent plants (orange and trifoliate) at left. Six 
 types of hybrid fruits (Rusk, Willits, 783, 771, 772, 767) developed 
 by cross-pollination from the parent plants, all being good fruits except 
 767, which proved to be worthless. Compare seeds and pulp in various 
 sections. 
 
 pistils of the other kind had matured, the bags were carefully 
 removed, and the pollen of one variety was dusted over the pistil 
 of the other (see 87). The paper bag was then replaced over 
 the artificially pollinated pistil, and the latter left to ripen. Fruits 
 
122 
 
 PLANT BIOLOGY 
 
 formed by the cross-pollination of two different kinds of plants are 
 known as hybrid fruits. The orange hybrid fruits thus developed 
 were sent to Washington, where the seeds were removed and planted 
 in greenhouses. When the young hybrid trees were about a foot 
 high, they were sent to Florida and grown in a garden of the Depart- 
 ment of Agriculture. 
 
 After a great many experiments in crossing the two kinds of 
 oranges, and after rejecting hundreds of plants that proved to be 
 worthless, Dr. Webber has succeeded in producing a type of tree that 
 will withstand the winters of regions from three hundred to four 
 hundred miles north of the present orange-growing section of Flor- 
 ida, and which will also produce a valuable, juicy fruit. These 
 new fruits, which have been named citranges, make a delightful 
 citrangeade and may be used in making pies, cakes, marmalades, 
 and the like. In a similar way Dr. Webber has produced new 
 varieties of tangerines, pineapples, cotton plants, and grass for hay. 
 
 The work of Luther Burbank 1 in California has likewise resulted 
 in astonishing colors and sizes of pinks and poppy blossoms, in 
 plums and peaches of great size, and in entirely new plants like the 
 " pomato," produced by crossing the potato with the tomato. 
 
 132. Some of the valuable crops of New York State. 2 - 
 New York ranks first of all the States of the Union in the 
 production of the following crops : 
 
 NAME OF CROP 
 
 ANNUAL VALUE 
 OF N. Y. CROP 
 
 FRACTIONAL 
 PART OF 
 U. S. CROP 
 
 Hay . 
 
 
 $69,027,200 
 20,996,900 
 25,756,430 
 
 i 
 
 i 
 * 
 
 Potatoes 
 Other Veg 
 
 
 stables ... . 
 
 
 1 See "New Creations in Plant Life," by W. S. Harwood. 
 
 2 The authors are indebted to Professors of Cornell University, 
 for the use of the figures recently compiled. 
 
PLANT PROPAGATION 
 
 123 
 
 (Since dairy products are directly dependent on agricultural 
 conditions, they are also included in this tabulation.) 
 
 Dairy Products 
 
 $55 474 155 
 
 i 
 
 Milk 
 
 36,284 833 
 
 
 i 
 
 
 
 5 
 
 In spite, however, of its preeminence among the States in the 
 production of the crops just named, experts tell us that the average 
 yield per acre throughout the State is probably less than half what 
 
 FIG. 58. Map of New York State, showing the crops grown in various 
 areas. (Courtesy of Prof. E. O. Fippin, of Cornell University.) 
 
 it should be or might be if more intelligence were used by the aver- 
 age farmer. The following quotation from an investigation made 
 among 1303 of the farmers in the vicinity of Cornell University, 
 near the center of the State of New York, shows in a striking way 
 
124 PLANT BIOLOGY 
 
 the commercial advantage of even a high school education. "Of 
 the owners, those who went only to district school made an average 
 labor income of $318. The average labor income of high school 
 men was $622. Of the more than high school men (i.e. college, 
 normal, or agriculture courses) it was $847. The differences are 
 emphatic. The labor income of the high school farmers is $304 
 greater than that of the district school men. This would be 5 per 
 cent interest on $6080. In other words the high school education 
 of a farmer is equivalent, on the average, to $6000 worth of 5 per 
 cent bonds." 1 
 
 133. Summary of some of the methods employed for 
 increasing crop production. The farmers of the future, 
 
 A 
 
 FIG. 59. A, pile of corn resulting from cross-pollination ; B, pile of corn 
 resulting from self-pollination. (Bailey.) 
 
 therefore, to be successful must have special training. They 
 must be able to carry on selection and breeding experiments, 
 or at least know how to take advantage of these experiments 
 in the choice of their seeds ; they should know the princi- 
 ples involved in thorough cultivation and in the application 
 of manures and fertilizers ; they should determine by experi- 
 ment the type of crop best adapted to the soil of their farms, 
 and should by proper rotation of crops (that is, by sowing 
 clover or other nitrogen-fixing plants, 150, one year and corn 
 the next) increase the fertility of their soil. If a farmer is a 
 fruit grower, he should know how to prune properly, and he 
 
 1 An Agricultural Survey of the Townships of Ithaca, Dryden, 
 Danby, and Lansing, published by Cornell University, 1911. 
 
PLANT PROPAGATION 125 
 
 should practice grafting to develop better types of fruits. If 
 he has soil adapted for woodland, he should plant forest 
 trees, and put into effect the principles of forestry. In fact, 
 there are countless ways in which the farmer of the future 
 can increase the yield of his acres if he but mixes brains with 
 the labor of his hands. ; 
 
CHAPTER IX 
 
 PLANTS IN THEIR RELATION TO HUMAN WELFARE 
 
 134. Introduction. Thus far in our study of plant biology 
 we have considered the principal functions carried on by 
 
 FIG. 60. Sweet potato plant. 
 
 plants and have observed some of the adaptations of struc- 
 ture for performing these functions. We have proved, for 
 example, that plants must feed, digest, breathe, and carry 
 
 126 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 127 
 
 on oxidation in order to live and grow, and must reproduce 
 their kind in order to perpetuate the species. We turn now 
 to a discussion of some of the uses of plants to man, and some 
 of the ways in which they are injurious. 
 
 I. SOME OF THE USES OF PLANTS TO MAN 
 
 135. Uses of plants for food. By repeated experiments 
 we have proved that various parts of plants contain generous 
 stores of starch, 
 sugar, protein, 
 and mineral mat- 
 ters. In our study 
 of human biology 
 we shall find that 
 the foods which 
 are essential for 
 our bodies are 
 composed of these 
 same substances. 
 It is for this 
 reason that man 
 and other animals 
 are so largely 
 dependent upon 
 plants for food. 
 As examples we 
 may mention 
 roots like pars- 
 
 FIG. 61. Coffee tree. Notice coffee berries along 
 sides of branches. (Courtesy of New York 
 Botanical Garden.) 
 
 nips, beets, 
 and sweet pota- 
 toes; stems, like 
 common potatoes, asparagus, and sugar cane ; leaves, such 
 as cabbage and lettuce; flowers, for example, cauliflower; 
 
128 
 
 PLANT BIOLOGY 
 
 fruits, like apples and peaches; and seeds and grains, like 
 beans, wheat, and corn. 
 
 136. Suggestions for further study of plants used as food. 
 
 Study No. 58. (Optional.) Visit a vegetable market, make a list 
 of the various plant products sold for food, and arrange them in 
 a table as follows : 
 
 NAME OF FOOD 
 
 PART OF PLANT EATEN 
 
 Root 
 
 Stem 
 
 Leaf 
 
 Flower 
 
 Fruit 
 
 Seed 
 
 String beans 
 
 
 
 
 
 X 
 
 X 
 
 Select one or more of the following topics for special study: wheat, 
 corn, potatoes, oats, rice. Consult Bailey's " Cyclopedia of Ameri- 
 can Agriculture," Vol. II, " Crops," any encyclopedia, or the publi- 
 cations of the U.S. 
 Department of 
 Agriculture. De- 
 termine (1 ) the parts 
 of the United States 
 (or of the world) 
 in which the . crop 
 is raised in large 
 quantity, (2) the 
 amount and value 
 of a year's crop, (3) 
 methods of harvest- 
 ing and preparing 
 the crop for the 
 FIG. 62. Tea plant. (Bailey.) market. 
 
 137. Uses of plants for flavoring extracts, beverages, and 
 medicines. We saw in a previous section that many parts 
 of plants are available for use as food by man. Because, 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 129 
 
 also, of the presence of various flavoring compounds in plants, 
 the following products are valuable. . For instance, vanilla 
 extract is made from the vanilla bean, pepper from pepper 
 berries, horse-radish from the root of the horse-radish plant, 
 and ginger from an underground stem. 
 
 We are dependent, too, upon plants for many beverages. 
 The coffee berry supplies us with coffee, tea leaves with tea, 
 and from the pods 
 and seeds of the cocoa 
 tree we obtain cocoa 
 and chocolate. 
 Grapes are used to 
 make wines, from 
 apples cider is pre- 
 pared, and from 
 grains of various 
 kinds other alcoholic 
 liquors are produced. 
 
 Quinine, the well- 
 known remedy for 
 malaria, was formerly 
 obtained from the 
 bark of a tree known 
 as cinchona, which 
 grows in Peru. This 
 medicine is now ob- 
 tained almost exclu- 
 sively from trees cul- 
 tivated in India and other Eastern countries. The camphor 
 tree furnishes camphor gum ; from the juice of poppy fruits 
 opium and morphine are obtained ; whole plants like pep- 
 permint supply us with valuable medicines. In fact, enormous 
 numbers of drugs are prepared from various parts of plants. 
 
 FIG. 63. Chocolate tree. (Courtesy of New 
 York Botanical Garden.) 
 
130 
 
 PLANT BIOLOGY 
 
 138. Suggestions for further study of parts of plants used as 
 drugs. Study No. 59. (Optional.) 
 
 Visit a drug store or consult an encyclopedia, e.g. Bailey's " Cyclo- 
 pedia of American Agriculture," Vol. II, " Crops," and make a list 
 of common drugs obtained from plants. Fill out in your note-book 
 a table like the following: 
 
 NAME OF DRUG 
 
 PART OF PLANT FROM WHICH IT is OBTAINED 
 
 Root 
 
 Stem 
 
 Leaf 
 
 Flower 
 
 Fruit 
 
 Seed 
 
 Catnip . . 
 
 
 X 
 
 X 
 
 
 
 
 139. Uses of plants for clothing. (Quoted from Bailey's 
 " Cyclopedia of American Agriculture," Vol. II, " Crops.") 
 " Fiber-producing plants are second only to food plants in 
 agricultural importance. In continental United States, 
 however, cotton, hemp, and flax are the only fiber plants 
 cultivated commercially; and aside from cotton and hemp, 
 most of the raw fibers used in our industries are imported." 
 
 " The cotton of commerce is the hair or fiber on seeds of plants 
 belonging to the Mallow family. . . . The plants are mostly 
 shrubby, more or less branching, and two to ten feet high. . . . 
 The fruit consists of three- to five-celled ' bolls/ which open at 
 maturity through the middle of the cells, each cell liberating seven 
 to ten seeds covered with long fibers. The fiber is a tubular hair- 
 like cell, Y^Vg- to -fifoy of an inch in diameter, somewhat flattened 
 and spirally twisted. It is this latter characteristic which gives 
 the cotton its spinning qualities. . . . 
 
 " Picking or gathering cotton in the fields is a heavy item of 
 expense. It must be picked by hand, as no mechanical appliance for 
 harvesting has yet been invented which gives satisfactory results 
 in practical working. The amount of cotton that one person can 
 pick in one day varies from one hundred to five hundred pounds, 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 131 
 
 FIG. -64. Cotton picking. 
 
 depending on the skill of the picker. One man can very easily 
 care for the cultivation of twenty acres of cotton, but it requires 
 two to four pickers to harvest such a crop rapidly enough to pre- 
 
132 PLANT BIOLOGY 
 
 vent loss. This extra labor in harvest time is usually supplied by 
 the wives and children of the laborers. The harvest season extends 
 over a period of about four months, beginning August 15 to Sep- 
 tember 10, according to locality. 
 
 " Cotton is probably a native of the tropical and semi-tropical 
 regions of both hemispheres. The earliest records of the Asiatics 
 and Egyptians speak of it ; Columbus found it growing abundantly 
 in the West Indies, while other early explorers found it growing 
 in Mexico and South America. . . . There is no region in the world 
 which has such a favorable combination of suitable land, intelli- 
 gent and plentiful labor, cheap capital and adequate transportation 
 facilities for the cultivation of cotton as the cotton belt of the 
 United States. It has been the chief source of supply of the cotton 
 mills of the world, for in this section has been raised several times 
 the quantity of cotton produced in all other countries of the globe. 
 There are various other countries which seem to possess the soil 
 and climatic requirements for its growth, but for various economic 
 reasons the industry has not been greatly developed in them ; 
 however, a considerable quantity is produced in the following coun- 
 tries in the order named: India, Egypt, China, Italy, Turkey, 
 Brazil, West Indies, Mexico, South America, Australia, and the 
 South Sea Islands." 
 
 140. Further study of fiber-producing plants. Study No. 60. 
 (Optional.) Select one or more of the following fiber-producing 
 plants for further study: flax, hemp, jute, raffia, hat-straw. Consult 
 Bailey's " Cyclopedia of American Agriculture," Vol. II, " Crops," 
 or any encyclopedia. Determine (1) the parts of the United States 
 (or of the world) in which the crop is raised in large quantity, (2) 
 the amount and value of a year's crop, (3) methods of harvesting 
 and preparing the crop for market. ' * 
 
 II. THE USES OF FORESTS AND FOREST CONSERVATION 
 
 141. Uses of forests for fuel, lumber, and other commercial 
 purposes. In the earlier days of our country's history all 
 the fuel for heating, for running locomotives and other en- 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 133 
 
 gines was supplied from the forests. About one hundred and 
 fifty years ago, coal was discovered in Pennsylvania, and one 
 would suppose that since that time our forests would have 
 been drawn upon less heavily for fuel. But it is estimated 
 that the United States burns annually at the present time 
 one hundred million cords of wood. While we are consider- 
 ing the uses of plants as fuel, we should remember that our 
 
 FIG. 65. A view showing how the forests of the Coal Period probably 
 looked. (Tarr and McMurry.) 
 
 enormous coal beds were without doubt formed from great 
 tree ferns and other plants which lived in bygone ages. Pe- 
 troleum, too, from which our kerosene oil is produced, is 
 believed to be a product of plant decomposition. 
 
 One has but to call to mind the enormous use of trees for 
 framing and finishing houses, for furniture, for railroad ties, 
 telephone and telegraph poles, for shipbuilding, and for 
 boxes, barrels, and paper manufacture, to realize how seem- 
 
134 
 
 PLANT BIOLOGY 
 
 ingly indispensable are forests. When the early settlers 
 reached this country, they found a virgin forest covering the 
 whole land. Their first work was to clear 1 and in order to get 
 open spaces for cultivation and as a means of protection 
 from attacks of the Indians. They cut down the trees ruth- 
 lessly and the timber and wood which was not needed was left 
 to decay or become the prey of forest fires. This forest de- 
 
 FIG. 66. Rock containing a fossil fern which grew in the swamps of the 
 Coal Period. (Tarr and McMurry.) 
 
 struction has continued even to our own day. But at last 
 men are beginning to see that unless this slaughter of our 
 trees is stopped, our timber supply will soon be gone. In fact, 
 government experts tell us that if the tree areas that yet re- 
 main are not managed according to a different system, twenty 
 years hence we shall reach the end of the timber supply in the 
 United States. 
 
 142. Further study of forest products. Study No. 61. (Op- 
 tional.) Select one or more of the following forest products for fur- 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 135 
 
 FIG. 67. Wrong methods of lumbering. (Warren.) 
 
 FIG. 68. Right method of lumbering. Notice carefully piled logs, wood 
 and brush, and uninjured young trees. 
 
136 PLANT BIOLOGY 
 
 ther study : maple sugar, rubber, tar, turpentine, wood pulp, alcohol, 
 charcoal. Consult Bailey's " Cyclopedia of American Agriculture," 
 Vol. II, " Crops," or any encyclopedia. Determine (1) the parts 
 of the United States (or of the world) in which the product is 
 obtained in large quantity, (2) the amount and value of a year's 
 crop, (3) methods of preparing the product for market. 
 
 143. Uses of forests in regulating rainfall and flow of 
 streams. We turn now from a consideration of our forests 
 as a source of lumber and manufactured products to a dis- 
 cussion of their effect on the fall of rain and the flow of 
 streams. It is probably true, in the first place, that the 
 destruction of large tracts of forest lands means a lessened 
 rainfall, at least so far as local showers are concerned. We 
 saw in our study of the functions of the nutritive organs of a 
 plant that great quantities of water are absorbed by the roots, 
 carried up through the woody bundles of the stem, and given 
 off through the stomata of leaves. It has been estimated 
 that a single oak tree of average size gives off in a single 
 season over one hundred and twenty-five tons of water. If 
 we were to multiply this amount by the number of trees in a 
 forest, we would get some idea of the enormous amount of 
 water lifted into the air by this agency. 
 
 Not only do trees help to produce rain ; they also conserve 
 the rain when it falls by holding it in the soil, and preventing 
 disastrous floods. Let us see how this is brought about. 
 When the raindrops, fall upon the tree tops, the water drips 
 from leaf to leaf, and finally reaches the ground. Here it 
 trickles down through the floor of the forest, which is formed 
 of thick layers of decaying leaves, interlacing roots, and earth 
 particles (see frontispiece). All these form a porous sponge 
 which absorbs and holds back the water. Suppose, now, the 
 trees are removed from the hillsides. When the rains come, 
 there is no means of absorbing the water ; instead, it flows 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 137 
 
 rapidly over the surface, swelling the streams into torrents, 
 which bring destruction and death as they flood the valleys 
 and fields along their course. As the water flows over the 
 surface of the land from which the trees have been cut, it 
 carries along the richest part of the soil, thus causing loss of 
 fertility in the uplands. The material thus carried away 
 fills up the river beds and harbor mouths, and in many cases 
 a heavy expense is entailed in its removal. 
 
 144. Dangers to forests. We have already called atten- 
 tion to the threatened destruction of our American forests 
 by careless lum- 
 bering. (See 141.) 
 This means not 
 only the whole- 
 sale cutting of 
 large areas of 
 trees, but the lack 
 of forethought 
 which lumber- 
 men show in 
 leaving dead tree 
 trunks and 
 branches to become the prey of destructive forest fires, 
 which, when once started, devastate wide areas. The annual 
 loss of property from this cause is conservatively estimated 
 at more than one hundred million dollars. 
 
 This forest debris of dead tree trunks and branches also 
 furnishes breeding places for insects, which, when hatched, 
 prey upon healthy trees. Another source of danger, espe- 
 cially to young forest growth, comes from permitting large 
 flocks of grazing animals like cattle and sheep to feed upon 
 and trample down the small trees. If we are to preserve the 
 
 FIG. 
 
 . Excessive erosion of land caused by de- 
 struction of forests. (Bailey.) 
 
138 
 
 PLANT BIOLOGY 
 
 remnants of our once vast forest resources, a public sentiment 
 must be thoroughly aroused which will compel the passage 
 and enforcement of conservation laws. 
 
 145. Necessity for reforesting and for forest protection. 
 
 Surely, enough has been said to show the necessity for forest 
 
 protection. For- 
 tunately, laws 
 are now being 
 passed that will 
 enable the Na- 
 tional and some 
 of the State gov- 
 ernments to ac- 
 quire large tracts 
 of land for forest 
 reservations. In 
 many States 
 these forest areas 
 will protect the 
 sources of large 
 streams. There 
 is great need of 
 trained experts 
 who will go 
 through the for- 
 ests, mark the 
 trees which are 
 mature enough 
 
 to be cut, and decide which way they should fall to do 
 the least damage to the younger growth. Again, large areas 
 now devastated should be replanted with young forest trees, 
 and this is also being done to a considerable extent. In many 
 
 FIG. 70. Planting young trees on hillsides. 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 139 
 
 foreign countries, notably in Germany, the forests are so 
 used that year after year they supply the requisite timber, 
 and still continue to do their much needed work in conserv- 
 ing the rainfall. Such must be the policy in our country 
 if we wish to escape most disastrous penalties that always 
 result from forest destruction. 
 
 Another method of forest protection is that afforded by 
 cutting trees in such a way as to form long, treeless strips of 
 land known as fire lanes. Systems of telegraphic communi- 
 cation from one part of the forest reserves to another and fire 
 wardens are necessary factors in efficient protection of forests. 
 
 III. FUNGI AND THEIR RELATION TO HUMAN WELFARE 
 
 146. Fungi. Thus far we have confined our attention to 
 plants which are easily visible to the naked eye and which 
 consist of roots, stems, and leaves. While we ordinarily 
 think of these as the common plants, in reality the most 
 common plant organisms are those which have neither roots, 
 stems, nor leaves, and which in many cases are microscopic 
 in size. The smallest and most numerous of these are known 
 as bacteria, which are found all about us, in the soil, in the air 
 we breathe, on the food we eat, and in the water we drink. 
 Bacteria belong to a great group of plants called fungi. 
 All fungi are characterized by the absence of chlorophyll, 
 hence plants of this group cannot manufacture their carbo- 
 hydrate food out of materials from the soil and air, but are 
 dependent on foods made by green plants. More familiar 
 to us, perhaps, than bacteria are the fungi known as mush- 
 rooms and toadstools, and the molds and mildews. Still 
 other fungi are the yeasts, the rusts, and the smuts. Because 
 of the enormous economic importance of many of these forms, 
 we shall consider more or less in detail the structure, func- 
 tions, and life-history of several of them. 
 
140 PLANT BIOLOGY 
 
 A. Bacteria 1 
 
 147. Microscopical appearance and size of bacteria. 
 
 Every one is familiar with the fact that if a bouquet of flowers 
 is left for some time in a vase of water, the stems decay and 
 disagreeable odors are given off. This is a common example 
 of the action of bacteria, for all decay is due to the work of 
 these organisms. When we come to examine the flower-stems 
 or the putrid water, we find a slimy scum. If we put a drop 
 of this scum on a slide, coyer with a cover-glass, and examine 
 with the highest powers of the microscope, usually we would 
 see many different forms of living things. Some of them 
 would probably appear relatively large, and these, as we shall 
 see later (Chapter IV, ' ' Animal Biology ") , are single-celled ani- 
 mals. A closer examination will disclose countless numbers 
 of very minute, colorless organisms ; these are the bacteria. 
 A careful study of many kinds of bacteria shows that they have 
 several characteristic shapes (see Fig. 71) by means of which 
 they can be roughly classified. Some are rod-shaped (like a 
 firecracker), some are spherical, or egg-shaped, and still others 
 are spiral-shaped. Each bacterium is a tiny bit of translucent 
 protoplasm, inclosed in a cell wall of cellulose. Thus far no 
 nucleus has been discovered in any kind of bacteria. Be- 
 cause of their cellulose walls, and because of their likeness 
 to certain low forms of green plants, biologists now regard 
 these organisms as plants rather than animals. 
 
 Some of the rod-shaped bacteria have one or more long, 
 hairlike projections from the ends, called cil'i-a, which give 
 the germs still further resemblance to firecrackers. These 
 cilia lash about rapidly, and thus drive the cells through the 
 
 1 Because of the importance of bacteria in relation to sanitation, 
 it may be found advisable to consider this whole topic in connection 
 with human biology. Sections 148-154 will therefore be repeated 
 in the book on human biology. 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 141 
 
 water. The spiral bacteria roll 
 over and over, and advance in a 
 spiral path like a corkscrew. Other 
 forms have rapid movements, but 
 it is not known how they are ac- 
 complished. 
 
 It is very difficult to get any 
 clear notion of the extreme minute- 
 ness of bacteria. It means but 
 little to say that the rod-shaped 
 forms are -5^517 of an inch in length. 
 The imagination may be somewhat 
 assisted if we remember that fifteen 
 hundred of them arranged in a 
 procession end to end would 
 scarcely equal the diameter of a 
 pin head. 
 
 148. Reproduction of bacteria. 
 When conditions are favorable, 
 the production of new cells goes 
 on with marvelous rapidity. The 
 process is something as follows : 
 The tiny cells take in through the 
 cell wall some of the food materials 
 that are about them, change this 
 food into protoplasm, and thus 
 increase somewhat in size. The 
 limit is soon reached, however, and 
 the bacterium begins to divide 
 crosswise into halves. The mother 
 cell thus forms two daughter cells 
 by making a cross partition (cell wall of cellulose) between the 
 two parts. (See Fig. 71, C.) If the daughter cells cling to- 
 
 FIG. 71. Various forms 
 bacteria. 
 
 A, a colony of spherical bac- 
 teria (coccus, plur. cocco) ; 
 B, rod-shaped bacteria (ba- 
 cillus, plur. bacilli) ; C, rod- 
 shaped bacteria dividing ; 
 D, rod-shaped bacteria, each 
 containing a spore ; E, spiral 
 bacteria (spirillum, plur. 
 spirilla) each with cilia. 
 
142 PLANT BIOLOGY 
 
 gether, a chain or a mass is formed. Oftentimes they separate 
 entirely from each other. In either case the whole mass of 
 bacteria is called a colony. 
 
 It usually takes about an hour for the division to take place. 
 Suppose, then, we start at ten o'clock some morning with a 
 single healthy bacterium. If conditions are favorable, there 
 would be two cells at eleven o'clock, and by twelve o'clock 
 each of these two daughter cells would form two granddaugh- 
 ter cells ; the colony would then number four individuals. 
 Should this process continue for twenty-four hours, or until 
 ten o'clock on the day after the single bacterium began its 
 race, the colony would number 16,777,216 bacteria. " It 
 has been calculated by an eminent biologist," says Dr. 
 Prudden, 1 " that if the proper conditions could be maintained, 
 a rodlike bacterium, which would measure about a thou- 
 sandth of an inch in length, multiplying in this way, would in 
 less than five days make a mass which would completely fill 
 as much space as is occupied by all the oceans on the earth's 
 surface, supposing them to have an average depth of one mile." 
 
 149. Necessary conditions for the growth of bacteria. 
 
 Such startling possibilities as those suggested in the preceding 
 section fortunately can never become realities, for the 
 favorable conditions to which we have referred soon cease to 
 exist. Bacteria, like all other living organisms, require food, 
 oxygen, moisture, and a certain degree of warmth. Let any 
 one of these conditions be withheld, and the cells either die 
 or cease to be active. Sometimes, when food or moisture 
 begins to fail, the protoplasm within each cell rolls itself 
 into a ball and covers itself with a much thickened wall. 
 This protects it until it again meets with conditions favorable 
 for growth. The process we have been describing is known as 
 
 1 " The Story of the Bacteria," by Dr. T. Mitchell Prudden. G. P. 
 Putnam's Sons, New York. 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 143 
 
 spore formation; the tiny protoplasmic sphere is called a spore, 
 
 and its dense covering a spore wall. (Fig. 71, D.) In this 
 
 condition bacteria may be blown 
 
 hither and yon as a part of the dust. 
 
 They may be heated even above the 
 
 temperature of boiling water without 
 
 being killed. When at length they 
 
 settle down on a moist surface that 
 
 will supply them with food, the spores 
 
 burst their thick envelope, assume 
 
 once more their rod-shaped or spiral 
 
 form, and go on feeding, assimilating, 
 
 and reproducing their kind. 
 
 150. Relation of bacteria to soil 
 fertility. Having discussed somewhat 
 the structure and functions of bacteria, 
 we are now to consider the great im- 
 portance of these microscopic organ- 
 isms to human welfare. In the first 
 place, were it not for their never end- 
 ing activity, all life upon the earth 
 would soon cease to exist. Let us see 
 why this is so. When animals or plants 
 die, their bodies fall upon the ground, 
 and were these lifeless masses not taken 
 
 FIG. 72. Roots of horse 
 
 care of, the whole surface of the earth bean, showing numerous 
 would long since have been covered 
 with a vast number of unburied or- 
 ganisms. All this dead material, however, as we have seen, 
 is food for the countless bacteria; they cause it to decay, 
 and thus decompose it into simpler chemical compounds 
 that can soak into the earth and then be used in the nu- 
 
144 PLANT BIOLOGY 
 
 trition of the higher plants. And since plants are con- 
 stantly taking from the soil the food materials which they 
 need, this soil would tend to become less and less fertile 
 were it not for the work of the bacteria that caused de- 
 composition. This is the reason why rotting manure adds 
 to the fertility of soil. 
 
 Again it has been proved that certain kinds of bacteria 
 directly increase the amount of nitrogen compounds that are 
 
 so essential for plant 
 growth. It has long 
 been known that corn 
 and other crops will grow 
 better in soil that has 
 just borne a crop of peas, 
 beans, clover, or other 
 members of the pea 
 family. Within recent 
 years an explanation of 
 this fact has been found. 
 When the roots of those 
 
 FIG. 73.- Bacteria from root-tubercles.- Pd-bearing plants are 
 
 (Duggar.) examined, small swellings 
 
 are seen. These contain 
 
 multitudes of bacteria that are able to take the free nitrogen 
 from the air, where it exists in such abundance, and store it 
 away in the form of nitrates which are very important mineral 
 matters needed by all crops. Since those bacteria can be put 
 into soils that do not have them, it may be possible in the 
 near future to restore much of the fertility which has been lost. 
 
 161. Relation of bacteria to the flavors of food. Again, 
 many of the flavors of food are due to the action of bacteria. 
 Meats, for instance, when freshly killed,. are tough and taste- 
 less. If allowed to stand, however, by the decomposing 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 145 
 
 action of bacteria these meats become tender and acquire 
 their distinctive flavors. A similar action takes place when 
 butter or cheese ripens, and the dairy industry has been per- 
 fected to such a degree that bacteria of certain kinds have 
 been proved to give rise to definite flavors, and these bacteria 
 can be produced in pure cultures for the dairymen. 
 
 152. Bacteria in the industries. Without the help of 
 bacteria the preparation of linen, jute, and hemp would be 
 impossible. All these valuable products are plant fibers 
 which are connected with woody materials so closely that they 
 cannot be separated without first subjecting the stems of 
 flax, hemp, and jute to a process of decay in large tanks of 
 water. Moisture and warmth induce the rapid growth of 
 germs, and this process loosens the tough fibers so they can 
 be separated from the useless parts of the plant. 
 
 The change of alcohol into vinegar is caused by bacteria. 
 Likewise in the preparation of indigo other forms of bacteria 
 are all important. 
 
 153. Bacteria as the foes of man. Unfortunately, how- 
 ever, there are certain germs that find favorable conditions 
 for growth only in living animal tissue. Thus the bacterium 
 of consumption grows in the lungs, the germ of diphtheria in 
 the throat, and the bacteria that cause typhoid fever in the 
 intestines. These disease-producing germs are called by Dr. 
 Prudden " man's invisible foes." Yet wonderful progress is 
 being made in the fight against them. We have learned how 
 to check the ravages of cholera, typhoid, and diphtheria, and 
 even consumption is found to be a preventable disease. 
 Further discussion of bacteria will be found in several of the 
 subsequent chapters. 1 
 
 1 For laboratory work on bacteria, see Chapter II, " Human Bi- 
 ology." Also consult Peabody's " Laboratory Exercises in Anatomy 
 and Physiology" (1902), pp. 100-107. 
 L 
 
146 
 
 PLANT BIOLOGY 
 
 B. Yeast (Optional) 
 
 154. Microscopical appearance and size of yeast. A small 
 piece of a cake of compressed yeast, mixed in a spoonful of water, 
 forms a milky fluid that is much like so-called bakers' or brewers' 
 yeast. If we examine with the microscope a bit of this mixture 
 in the same way in which the bacteria were studied, we find that it 
 consists of innumerable bodies of minute size. These are yeast 
 cells. Each cell is more or less egg-shaped, and is composed of color- 
 less protoplasm inclosed within a wall 
 of cellulose. By the use of special 
 stains, a nucleus becomes visible. 
 (The spherical dots seen in fresh yeast 
 cells are known as vacuoles and are 
 filled with a colorless. liquid.) Yeast, 
 like bacteria, is regarded as one of the 
 lowest forms of plant life. 
 
 155. Reproduction of yeast. Most 
 of the cells that we are looking at 
 are not separate individuals, but are 
 FIG. 74. Yeast cells, showing strung together in little chains. This 
 
 Sf.tT5Sit:JS fact leads us to a disc of the 
 
 shown. Clear spaces are vac- method of reproduction of yeast. When 
 uoles. there is a sufficient supply of food, 
 
 moisture, and oxygen, and when the temperature is favorable, 
 these living plant cells begin to feed and to grow. They soon reach 
 their full size, and then the cell wall is pushed out at the side by the 
 growing protoplasm. In this way a bud is formed. This continues 
 to grow and soon becomes a daughter cell, closed off from the mother 
 cell by a wall of cellulose. Meanwhile, one or more buds may be 
 forming on the outside of the daughter cells. If all these cells 
 cling together, a colony is formed which consists of a mother cell 
 (largest in size), one or more daughter cells, and several tiny grand- 
 daughter cells. The individual cells are easily separated from one 
 another. This method of reproduction is known as budding (Fig. 74) . 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 147 
 
 156. Changes caused by yeast. A yeast mixture may be easily 
 prepared for experimentation by pouring into a jar a cup of water, 
 adding a spoonful of molasses, and a spoonful of the milky fluid 
 made as described in 154. 
 
 If the jar with its contents is set aside in a warm place (70 to 
 90 F.) for a short time, it begins to "work," and bubbles of 
 gas rise to the surface. At the end of several hours, we notice 
 that the sweetness of the molasses is disappearing, that the mixture 
 begins to smell sour, and that a sharp, biting taste is becoming evi- 
 dent. All these changes are caused by the growth of living yeast 
 cells. 
 
 Now, what is the gas that is formed in this process, and what 
 causes the changes in taste and odor? To answer these questions 
 we must carry our experiments still further. When the mixture 
 is " working " well, the bottle should be tightly closed with a rubber 
 stopper, through which extends one arm of an inverted U-shaped 
 tube. The other end of this tube should run over to the bottom 
 of a test tube half-filled with limewater. The gas that has been 
 rising through the yeast mixture now passes through the U-tube, 
 and as it comes in contact with the limewater, the latter changes to 
 a milky-white color. This proves that the gas formed during the 
 growth of yeast is carbon dioxid. 
 
 After " working " a day or two, the yeast mixture will have a 
 strong taste and odor. A part of it should then be poured into a 
 glass Florence flask (commonly used in the chemical laboratory 
 for boiling liquids), and the mouth should be closed by a rubber 
 stopper. The short arm of a long delivery tube should be passed 
 through this stopper. When the flask is heated gently, some of the 
 liquid is changed to a vapor. If the delivery tube is cooled by cov- 
 ering it with cloths wet in cold water, the vapor condenses into a 
 liquid, which comes from the end of the tube in drops. This opera- 
 tion we have been describing is known as dis-til-la'tion. In distilling 
 a liquid, we first convert it into a vapor, and then condense this vapor 
 into a liquid. After collecting a few spoonfuls, the liquid should be 
 slowly distilled a second time. Then we obtain a colorless fluid 
 that has the distinct smell and taste of alcohol. It burns, too, with 
 
148 PLANT BIOLOGY 
 
 a pale blue flame. And so we learn that yeast, as it grows in the 
 molasses mixture, changes the sweet substances into carbon dioxid and 
 alcohol, a process that is known as alcoholic fer-men-ta f tion. 
 
 157. Uses of yeast. When bread is made, water (or milk), 
 butter, salt, sugar, and yeast are added to flour. After the mixture 
 has been stirred together, a sticky mass of dough is formed, which 
 in a warm place begins to rise. This is due to the fact that the yeast 
 cells change the sugar into alcohol and carbon dioxid. Bubbles of 
 gas are thus imprisoned in the sticky dough. While expanding and 
 seeking to escape, they make the solid mass porous. After the bread 
 has risen sufficiently, it is kneaded in order to break up the large 
 bubbles and in order to distribute the gas throughout the dough. 
 When the bread is baked, the alcohol and carbon dioxid' pass off 
 into the air, leaving the bread light and digestible. These minute 
 organisms are also of great commercial importance in the manufac- 
 ture of alcohol and of all kinds of liquors. It is known that 
 yeast cells are found commonly in the air. As different kinds of 
 fruits ripen, they are usually more or less covered with yeast or 
 its spores. When, therefore, grapes are gathered and their juice is 
 pressed out, the sweet liquid is soon alive with the busy cells, and 
 fermentation begins at once. In this way wines are produced. 
 Cider is produced by the fermentation of apple juice. 
 
 In the manufacture of beer and of other malt liquors, barley is 
 commonly used. The grain is soaked and allowed to sprout for 
 a short time, until the starch is changed to grape sugar. The barley 
 kernels are then killed by heat to prevent further changes, and the 
 grain is then known as malt. When this is put into water, the sugar 
 is extracted. Yeast is then added, and the mass ferments. The 
 beer thus formed contains 2 to 5 per cent of alcohol. 
 
 Distilled liquors, or spirits, are obtained from wines and other 
 fermented liquors by the process of distillation, the principles of 
 which have already been explained. Brandy is made by distilling 
 wine, whisky is obtained from fermented corn and rye, and rum is 
 manufactured from molasses. All of these liquors contain a large 
 percentage of alcohol (40 to 50 per cent). 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 149 
 
 158. Suggestions for laboratory work on yeast. No. 62. 
 Students should examine the appearance of yeast cells under the 
 low and high powers of the compound microscope. If time permits, 
 the demonstration of carbon dioxid production and of distillation 
 of alcohol might well be made. (See Peabody's " Laboratory Exer- 
 cises," pp. 94-99, Henry Holt & Co., New York City.) 
 
 C. Bread Mold (Optional) 
 
 169. Structure of bread mold. If pieces of bread or cake be 
 moistened, and placed in a dish, and covered with a bell- jar in the 
 
 FIG. 75. Bread mold, showing nutritive hyphae (A) ; reproductive hyphae 
 CB) ; and spore cases (C). (Osterhout.) 
 
 dark, in a few days grayish patches will appear in places on the 
 surface of the bread. This growth is due to the activity of one 
 of the fungi, known as a mold, and will probably be the kind 
 called bread mold. No care is required to produce the plant in 
 quantities ; on the contrary, as common experience shows, some 
 pains must be taken by the housekeeper to prevent it from spoil- 
 ing food. 
 
 When the bread mold is examined with a hand lens, it is seen to 
 
150 PLANT BIOLOGY 
 
 consist of a mass of fine interlacing threads called the mycelium. 
 (See Fig. 75.) Single threads are known as hyphce. 
 
 160. Reproduction and life history of bread mold. Some of 
 the hyphse in their growth assume an upright position, and each of 
 these at the upper end develops a little globular white mass or spore 
 case. (See Fig. 75.) An examination with the high power of the 
 microscope shows that the spore cases are filled with tiny cells 
 known as spores. When the spores are ripe, the spore cases appear 
 brown or black, they break open, and the spores are scattered. 
 If these spores fall on food of some kind, such as bread, they begin 
 to germinate, and each one produces another mass of threads with 
 spore cases on erect hyphaB. In other words, the mold produces 
 spores and the spores reproduce the mold. The spores of molds 
 are in the air nearly everywhere, hence we see why molds appear 
 so quickly on foods of various kinds, provided they are moist and in 
 a warm place. 
 
 161. Nutrition in the fungi. Molds, like other fungi, as we 
 have already said, cannot manufacture their own food out of the 
 materials obtained from the soil and air, but are dependent on foods 
 made by green plants. Certain of the threads called the nutritive 
 hyphce form ferments which digest the food compounds found in 
 bread or other substances on which the mold is growing, and then the 
 digested food is absorbed, used in growth, and in the production of 
 energy. Other threads develop the spore cases and so are called re- 
 productive hyphce. Hence, it is evident that fungi, like all plants, carry 
 on both nutritive and reproductive functions, but on account of the 
 lack of chlorophyll are, like animals, dependent on the green plants 
 for their supply of food. 
 
 162. Suggestions for laboratory work on bread mold. No. 
 
 63. Sow bread mold as suggested in 159 in sufficient quantity 
 to supply each two pupils with a piece of the moldy bread. Pupils 
 should examine a specimen with a hand magnifier, describe the 
 appearance of the mycelium and hyphae bearing spores, and 
 should then make a drawing to show these points. Some of the 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 151 
 
 spore cases should be placed on a slide in water and covered with a 
 cover glass. If the glass cover is tapped with a pencil, some of the 
 spore cases will be ruptured. The preparation should then be ex- 
 amined with the high power of the compound microscope, and the 
 ruptured spore cases drawn, together with a few of the escaping 
 spores. 
 
 D. Other Fungi (Optional) 
 
 163. Mushrooms. Mushrooms are forms of fungi which are 
 often called " toadstools," especially if they are supposed to 
 
 FIG. 76. An edible mushroom. 
 
 be poisonous. All fungi of this kind should, however, be called 
 mushrooms, since their structure and life history are similar. The 
 conspicuous part of the plant, the umbrella shaped structure so 
 familiar to all, is really the reproductive organ of the plant, the part 
 that bears the spores (Fig. 76). The nutritive organs are a mass of 
 threads (as in the mold) which lie beneath the surface, where they 
 absorb the foods from some decaying material in the soil to give 
 rise to the reproductive body. 
 
152 
 
 PLANT BIOLOGY 
 
 As indicated above, many mushrooms are poisonous, but a few 
 kinds are known to be edible. 1 Mushrooms are not especially nu- 
 tritious ; that is, they cannot take the place of the cereals and other 
 staple foods, but they serve to add to the variety of materials which 
 are more valuable for their flavoring qualities than for the quantity 
 of nutriment they contain. Commercially the cultivated mush- 
 room is of considerable importance, especially in Europe. Paris 
 is said to be the center for the sale of this product. In the year 
 
 1901 it was estimated that 10,000,000 
 pounds of cultivated mushrooms 
 passed through the markets of Paris. 
 In this country the mushroom is of 
 CDmmercial importance only in the 
 regions of the larger cities. 
 
 164. Rusts and smuts. The 
 fungi known as rusts receive their 
 name from the rusty appearance in 
 an early stage of their growth which 
 they cause on the stems and leaves 
 of plants which they attack. The 
 cereals, wheat, oats, barley, and rye, 
 are the crops which this fungus in- 
 jures most. In the case of wheat, 
 half of the crop or even more may 
 be destroyed. 
 
 The very suggestive name of smut 
 is given to another fungus which 
 
 affects all the cereals named above, and corn as well. In the case 
 of corn, this plant often affects the ears as well. The name is 
 probably given on account of the appearance of the mass of black 
 spores. If one touches these spores, especially those of corn smut, 
 with the finger, and then rubs the finger on some white paper or 
 
 1 So many deaths are caused by using poisonous instead of edible 
 mushrooms that it is never safe to eat wild forms until they have 
 been identified by an expert. 
 
 FIG. 77. Corn smut on an ear 
 of corn. 
 
PLANTS IN THEIR RELATION TO HUMAN WELFARE 153 
 
 cloth, a sooty mark is left. The damage done by smuts is very 
 considerable. In case of the corn crop alone it has been estimated 
 that a yearl}'- loss of 20 per cent of the crop, or $20,000,000, is caused 
 thereby, and in the other cereal crops the loss is even greater. It 
 should be mentioned in closing this discussion that the rusts and 
 smuts are only two of a large number of fungous diseases that affect 
 plants. 
 
CHAPTER X 
 
 PLANT CLASSIFICATION 
 
 I. COMMON METHODS OF CLASSIFICATION 
 
 165. Herbs, shrubs, and trees. One way of classifying 
 the common plants with which we are most familiar is that 
 of calling them either herbs, shrubs, or trees. This classifica- 
 
 FIG. 78. Base of one of the giant trees of California. (Tarr and McMurry.) 
 
 tion is based upon the general similarity in size, form, and 
 texture of the plants which are assigned to each group. Thus 
 when we think of a tree we have in mind a plant which, when 
 
 154 
 
PLANT CLASSIFICATION 
 
 155 
 
 1 
 
156 
 
 PLANT BIOLOGY 
 
 mature, is of large size, with a single woody trunk and branches. 
 This trunk may extend up nearly to the top of the tree, as in 
 the case of the pines and spruces, or some distance above the 
 ground the trunk may divide into branches, as is true in the 
 elms and maples. 
 
 A shrub, on the other hand, is usually of smaller size even 
 when fully grown than is a tree ; it commonly does not have a 
 single trunk, but several woody stems which often start from 
 the ground level, as in the lilac, rose, 
 and witch hazel. Both shrubs and 
 trees are alike in that their stems and 
 branches do not die down to the ground 
 at the end of the season. 
 
 An herb, as the term is used in plant 
 biology, is a plant of relatively small 
 size, with comparatively little woody 
 material in its stem, which dies down to 
 the ground level at the close of the 
 season. Such are beans, corn, and 
 morning glories. The roots or under- 
 ground stems of some herbs for ex- 
 ample, dahlias, carrots, and parsnips 
 
 remain alive ready for growth the next year. These facts 
 suggest another method of classifying plants, namely, as : 
 
 FIG. 80. An herb. 
 
 166. Annuals, biennials, and perennials. When a plant 
 attains its maturity in one season's growth and then dies, as 
 do beans, corn, and morning glories, such a plant is called an 
 annual. Many plants which have fleshy roots, like the beet, 
 carrot, and parsnip, do not produce flowers and seeds until the 
 second year. During the first season after the seed is planted 
 the food manufactured in the leaves passes down the plant 
 and is stored beneath the ground. At the end of the season 
 
PLANT CLASSIFICATION 
 
 157 
 
 the stems and leaves above ground die ; but if this root re- 
 mains in the ground or is planted the next season, stems, 
 leaves, and flowers develop rapidly, and finally seeds are 
 
 FIG. 81. Carrot. A, young seedling; B, enlarging root early in season; 
 C, section of enlarged root late in season. 
 
 formed, the food stored up the preceding season being drawn 
 upon for the development of these parts. Plants which have 
 a life history like this and which live for two years only are 
 
158 
 
 PLANT BIOLOGY 
 
 called biennials (Latin, bi = two -\-annus = year). Perennials 
 are plants that live year after year. Hollyhocks and dahlias, 
 for instance, store food in fleshy roots year after year, while 
 the parts above ground die, as in the case of beets and carrots. 
 Other perennials, like trees and shrubs, lose only their leaves 
 at the end of each season. 
 
 167. Deciduous and evergreen trees and shrubs. Trees 
 and shrubs may be classified as evergreen or deciduous. Since 
 the leaves of pines, spruces, and hemlocks remain green and 
 attached to the stem during the winter, these plants are known 
 as evergreens. Certain shrubs (rhododendrons, arbutus, and 
 wintergreen, for example) also keep their green leaves 
 throughout the winter, and so in a sense they may be regarded 
 as evergreens. Maples, elms, and horse-chestnuts, on the 
 other hand, shed their leaves in autumn; they are therefore 
 said to be deciduous (Latin, de = hom-\-cadere=to fall). 
 
 168. Field work on plant classification. Optional. No. 64. 
 
 If possible, teachers should accompany their pupils on a field trip, 
 point out and name the plants best adapted for a study in classifi- 
 cation, using perhaps an outline like the following: 
 
 NAME OF 
 PLANT 
 
 HERB 
 
 SHRUB 
 
 TREE 
 
 SIMPLE 
 LEAVES 
 
 COM- 
 POUND 
 LEAVES 
 
 OPPO- 
 SITE 
 LEAVES 
 
 ALTER- 
 NATE 
 LEAVES 
 
 DECID- 
 UOUS 
 
 EVER- 
 GREEN 
 
 Rose . 
 
 
 X 
 
 
 
 X 
 
 
 X 
 
 X 
 
 
 II. SCIENTIFIC METHOD OF CLASSIFICATION 
 
 169. Scientific classification of plants. The various 
 methods of grouping plants that we have thus far considered 
 do not indicate real relationships among plants, for these 
 schemes call attention only to certain superficial resemblances 
 
PLANT CLASSIFICATION 159 
 
 and differences in form, or size, or habit. True scientific 
 classification seeks to bring together into a given group all the 
 plants that are closely related to each other; that is, those 
 which are probably descended from common ancestors. In 
 the first place, all plants are divided into two great groups 
 known as seed-producing plants, and spore-producing plants. 
 The first is the group to which most of our attention has thus 
 far been given, and it embraces the herbs, shrubs, and trees, 
 with which we are most familiar. We should bear in mind, 
 however, that many plants, like the palm and rubber plant, 
 which do not produce flowers in our climate, develop flowers, 
 fruits, and seeds when they are growing in their natural 
 home. Other plants with inconspicuous flowers for ex- 
 ample, grasses, elms, and pines also belong to this great 
 group of seed-producing plants. 
 
 Sub-kingdom I, Seed-producing Plants (Optional) 
 
 170. Gymnosperms and angiosperms. Seed-producing plants 
 are still further subdivided into two groups. The first group includes 
 all plants like the pines, hemlocks, and spruces, in which the seeds are 
 not produced in ovaries, but at the base of scale-like leaves which are 
 usually grouped together to form cones; hence the name cone-bear- 
 ing plants, which will apply to the common forms. The whole group 
 is known as gymnosperms (from Greek meaning naked seeds). 
 
 Plants like beans, cucumbers, and pansies, on the other hand, 
 develop their seeds in ovaries, and these and all other plants of this 
 type constitute the second of the two sub-divisions, which is known 
 as the angiosperms (from Greek meaning having a vessel for seeds). 
 
 171. Monocotyledons and dicotyledons. Again, the seed-pro- 
 ducing plants may be classified according to the number of coty- 
 ledons found in the seed. The corn, gladiolus, and lilies, for example, 
 have seeds with one cotyledon, and hence these are known as mono-' 
 cotyledons (Greek, mono = one 4- cotyledon). Beans, peas, and 
 maples, on the other hand, have two cotyledons and are therefore 
 
160 
 
 PLANT BIOLOGY 
 
 called dicotyledons (Greek, di = two + cotyledons). There are 
 other striking characteristics which distinguish these two groups of 
 angiosperms, which have already been brought out in our laboratory 
 work, as the following table will show: 
 
 
 MONOCOTYLEDONS 
 (Corn, tulip, gladiolus) 
 
 DICOTYLEDONS 
 (Bean, horse-chestnut, 
 pansy) 
 
 Number of cotyledons 
 
 one 
 
 two 
 
 Veining of leaves 
 
 parallel 
 
 netted 
 
 Stem structure 
 
 woody bundles scat- 
 
 bark, wood in dis- 
 
 
 tered through pith 
 
 tinct annual rings, 
 
 
 
 pith in center 
 
 Number of stamens 
 
 based on plan of 
 
 based on plan of five 
 
 and other parts of 
 
 three or some 
 
 or some number 
 
 flower 
 
 multiple of three 
 
 other than three 
 
 172. Plant families. Continuing our classification of the angio- 
 sperm group still further, we find that the dicotyledons are sub- 
 divided into over one hundred and sixty so-called plant families, 
 some of which are the violet family, the buttercup family, the rose 
 family, and the pulse family. This grouping into families is based 
 largely upon flower structure, and so it sometimes happens that 
 an herb and a tree belong to the same family. For example, the 
 pea, bean, and the locust tree all belong to the pulse family, since 
 they have flowers closely resembling each other. 
 
 173. Plant genus. Again, each of the 160 or more families 
 is made up of a varying number of more closely related plant groups, 
 each of which is known as a genus. The rose family, for example, 
 has fourteen genera, some of which are the pear genus, the rose genus, 
 and the cherry genus. 
 
 174. Plant species. Once more, each genus consists of a vary- 
 ing number of species, the members of which resemble each other 
 
PLANT CLASSIFICATION 
 
 161 
 
 very closely. The pear genus consists of the pear species, the apple 
 species, and the crab apple species. Species, again, may be still 
 further subdivided into varieties, in which the plants are more closely 
 related (e.g. Baldwin and Greening varieties among apples) . And 
 finally a species (or variety) is made up of individual plants, that 
 resemble each other in all essential respects. 
 
 Sub-kingdom II, Spore-producing Plants (Optional) 
 
 A. Ferns 
 
 176. The fern plant. 
 We turn now from a dis- 
 cussion of seed-bearing 
 plants to a consideration 
 of those plants which 
 never produce flowers or 
 seeds. As a representa- 
 tive of the highest group 
 of plants without seeds, 
 we will study the ferns. 
 The majority of ferns 
 grow in damp, shady 
 places, and among the 
 common kinds we may 
 name the brake, the 
 maiden-hair, and the rock 
 fern. In any one of these 
 ferns the parts above 
 ground which are true 
 leaves are known as 
 fronds. The main axis 
 of each frond runs 
 throughout the leaf, and 
 to each side are attached 
 the leaflets, which may or 
 
 FIG. 82. Fern plant (Aspidium), showing 
 roots, rhizome, and frond : A, 'section of 
 fruit dot (sorus) , showing spore cases, some 
 of which are ejecting their spores ; B, por- 
 tion of a leaflet, showing unripe fruit dots ; 
 C, portion of a leaflet, showing ripe fruit 
 dots. (Strasburger.) 
 
162 
 
 PLANT BIOLOGY 
 
 may not be still further subdivided. Hence, a fern leaf is usually 
 compound, and is strikingly graceful in its appearance. 
 
 Beneath the ground the fronds grow from a horizontal stem called 
 the rhizome, which is more or less enlarged for food storage, depend- 
 ing on the kind of fern. To this rhi- 
 zome are attached the roots by which 
 the plant is supplied with soil-water. 
 The fern plant, therefore, like seed- 
 bearing plants, has all three kinds of 
 nutritive organs (roots, stem, and leaves), 
 and carries on carbohydrate manufacture 
 in the green fronds, storing away the 
 food in the rhizome, since the leaves die 
 to the ground each year. The follow- 
 ing spring the tiny leaves push up 
 through the ground from the under- 
 ground stem, unrolling and spreading 
 
 their leaflets from the base to the tip. 
 FIG. 83. Development of 
 fern plant. 
 
 A, a germinating fern spore ; 
 B, a later stage in germina- 
 tion ; C, a full-grown pro- 
 thallus, showing rhizoids, 
 antheridia (or spermaries, 
 
 :varie a B? g ."i?oncf amined with a microscope, M found to 
 
 antheridia (or spermary) ; consist of several smaller objects known 
 
 E, a sperm cell; F, a section as spore-cases. (B,C, Fig. 82.) When 
 
 of archegonia (or ovary) ., ., 
 
 containing an egg-cell ; G, these tm y s P ore cases are n P e > the y P en 
 
 young fern plant develop- often with considerable force, and eject a 
 
 ing from a fertilized egg- powder) each part icle of which is called 
 
 a spore. (Fig. 82, A.) Each spore con- 
 sists of a single cell. 
 
 176. Fern spores. On the under 
 surface of some of the leaflets of the 
 ferns named above are little dots which 
 are often brown. These are known as 
 fruit-dots (son). Each fruit dot, if ex- 
 
 cell in an ovary, still at- 
 tached to the heart-shaped 
 prothallus. (Parker.) 
 
 177. Fern prothallus. When the spores fall to the ground and 
 conditions are favorable, they start to germinate, and each finally 
 produces a small green, heart-shaped plant known as a prothallus 
 (Fig. 83, C). The prothallus, though tiny, consists of a great 
 
PLANT CLASSIFICATION 163 
 
 number of cells, some of which form tiny outgrowths from the under 
 surface like root-hairs (called rhizoids), which anchor the prothallus 
 to the soil and aid in securing food materials. 
 
 On the under surface likewise of each prothallus, in the region 
 of the rhizoids, are minute organs, circular in appearance, known as 
 antheridia (spermaries), in which are produced a large number of 
 sperm-cells (Fig. 83, D, E). At a little distance from the antheridia, 
 near the notch in the prothallus, are found other somewhat elon- 
 gated bodies called archegonia (ovaries). In each of these there is 
 developed a special cell known as the egg-cell (Fig. 83, F). 
 
 178. Fertilization of the egg-cells. When the sperm-cells are 
 ripe, the antheridia or spermaries are ruptured, and the sperm- 
 cells make their way by a curious twisting motion toward the open- 
 ings on the archegonia. A single sperm-cell moves down the tube 
 of each archegonium, and penetrates the egg-cell, and the two nuclei 
 unite in the process of fertilization. (See 91.) From the fertilized 
 egg-cell develops a fern plant composed of many cells of various 
 kinds, which are all derived from the fertilized egg-cell. 
 
 179. Alternation of generations. Thus we see that in the life- 
 history of the fern plant we have two distinct generations. The 
 first is the ordinary fern plant, which is familiar to all, and which is 
 known as the asexual generation or spore generation, because the spores 
 formed on the fronds produce the next generation (prothallus) 
 without fertilization or the union of two kinds of cells. The second 
 generation, the prothallus, is the sexual generation, because, as we 
 have seen, it can only produce a fern plant from the fertilized egg- 
 cell. In plants like the fern, in which an individual (fern) produces 
 another plant (prothallus) unlike itself, and this in turn gives rise 
 to a plant like the original (fern), we have so-called alternation of 
 generations. 
 
 180. Suggestions for the study of the fern. No. 65. If 
 this topic is suggested for study, pupils should be encouraged to 
 collect their own material, noting the surroundings or habitat of each 
 kind of fern. They should describe the location, form, and color 
 of each of the nutritive organs, and of the fruit dots, and draw the 
 
164 PLANT BIOLOGY 
 
 entire fern. Each student should study a prothallus with a hand 
 magnifier, making an enlarged drawing of the same to show its 
 form and the position and shape of the rhizoids, antheridia, and arche- 
 gonia. A demonstration of the steps in the life history may well 
 be shown from charts. 
 
 B. Mosses 
 
 181. The moss plant. A second group of flowerless plants 
 includes the mosses. In general, mosses are smaller plants than the 
 ferns, but like them are usually found in damp, shady places. If 
 one examines a moss plant when it is " in fruit," a slender stem will 
 be seen projecting from the leafy part below. At the upper end 
 of this slender stem, a covered cup-like structure is evident (Fig. 
 84, A,k). This cup, or capsule as it is called, is filled with tiny dust- 
 like particles, which when examined with a compound microscope 
 prove to be cells. They are called spores. The spores are repro- 
 ductive bodies similar to those produced in the spore cases of ferns. 
 
 182. The moss protonema. When these bodies are ripe, the 
 capsule opens and discharges some of the spores, which fall to the 
 ground and soon begin to grow, forming at first an elongated cell 
 (Fig. 84, H) which later divides, giving rise to two cells. This 
 process continues until a slender, green, thread-like mass is formed, 
 with many branches. This thread-like mass is called the protonema 
 (Fig. 84, G). Some of the branches produce buds which finally 
 grow into the leafy structure which we know as the moss plant 
 (Fig. 84, B, A). 
 
 183. The sexual generation of the moss. - At the top of some 
 moss plants at certain seasons of the year, in the midst of the rosette 
 of green moss leaves, may be found tiny flask-shaped organs, the 
 archegonia (ovaries) (Fig. 84, F). At the base of each of these 
 organs is produced an egg-cell. Sometimes in the same moss plant, 
 and sometimes in another, are to be found club-shaped organs called 
 antheridia (spermaries) (Fig. 84, E). In the antheridia are pro- 
 duced sperm-cells (Fig. 84, D). At the proper time the sperm- 
 cells make their way into the archegonia, and when a sperm-cell 
 
PLANT CLASSIFICATION 
 
 165 
 
 reaches an egg-cell they fuse, the two nuclei unite, and a fertilized 
 egg-cell is formed. This fertilized egg, by the process of growth and 
 
 FIG. 84. Development of a moss plant. 
 
 A, moss plant with spore case (k) having a lid (c) ; z, rhizoids ; B, young 
 moss plant ; C, enlarged view of spore ca'se, with lid (c) detached ; D, 
 single sperm-cell ; E, sperm ary with escaping sperms ; F, ovary with 
 dividing egg-cell (o) ; G, branching protonema ; H, spore germinating to 
 form protonema. 
 
 cell division (Fig. 84; F, o), finally forms the slender stalk with the 
 capsule and spores at the end of it like that referred to in 181 
 (Fig. 84, A, C). 
 
166 PLANT BIOLOGY 
 
 184. Alternation of generations in the moss. The protonema 
 and the leafy shoots with their antheridia and archegonia are known 
 as the sexual generation because it is this plant that produces eggs 
 and sperm- cells which must unite before the egg can develop into 
 the spore-bearing plant. The slender stalk with the capsule at the 
 end which is produced by the fertilized egg-cell is called the asexual 
 generation, since the spore-bearing plant can reproduce without the 
 union of two kinds of cells. The spore-bearing plant is dependent 
 on the leafy plant for all its food. In the fern, on the other hand, it 
 is evident that the spore-bearing plant and the plant producing 
 eggs and sperms are entirely independent plants. In both of these 
 groups of seedless plants, however, there is an alternation of genera- 
 tions. 
 
 186. Suggestions for the study of mosses. No. 66. The teacher 
 should secure plenty of material for the demonstration both of 
 the plants with spore cases and if possible the plants with arche- 
 gonia and antheridia. On account of its size the pigeon wheat 
 moss is desirable. The material may be collected and dried, since 
 both generations are not likely to be obtained at the same time of 
 year. If spore cases are on hand, the work might then be done when 
 the sexual plants can be secured in a fresh condition. The pupil 
 should describe and draw the leafy moss plant. The location of 
 archegonia and antheridia should be stated. Then the spore-bear- 
 ing plant should be described, together with the relation to the sexual 
 plant which produced it, and the spore case opened to show the spores. 
 The two plants should then be drawn and labeled. 
 
 C. Algce 
 
 186. Spirogyra. Any one who has ever been in parts of the 
 country where ponds or very slowly moving bodies of water abound 
 must have noticed either at the bottom or on the surface of the water 
 a green, slimy mass. It is so frequently found on the surface that it 
 is called " pond scum." If one examines a small portion of this mass 
 even with the naked eye, one will see that it consists of a great num- 
 ber of interlacing threads. When looked at with the compound 
 
PLANT CLASSIFICATION 
 
 167 
 
 microscope each of these threads is seen to be a series of cells joined 
 end to end. All the cells are practically the same in shape and 
 structure, however, so that a study of one will make clear the struc- 
 ture of all. 
 
 Inclosing each cell there is a thin cell wall. The first structures 
 one is likely to notice within the cell are the chlorophyll bodies. 
 In the pond scum known as Spirogyra the chlorophyll is arranged 
 in spiral bands, and it is this which has given the plant its name 
 (Fig. 85, B) . In other forms the chlorophyll is differently arranged, 
 
 chlorophyll band 
 
 nucleus 
 
 chlorophyll band 
 
 FIG. 85. Spirogyra. (Strasburger.) 
 A, two conjugating threads of Spirogyra ; B, single cell of Spirogyra. 
 
 sometimes in star-shaped masses, one in each half of the cell, and 
 sometimes diffused throughout the cell. If a little iodine is added 
 to the specimen when it is being examined under the microscope, 
 a nucleus may be distinguished near the center of each cell (Fig. 85, 
 B). In the cell-body and nucleus the protoplasm appears as a 
 clear and almost transparent mass. 
 
168 PLANT BIOLOGY 
 
 The thread or filament continues to increase in length by the 
 growth and division of certain individual cells that compose it. 
 At the close of the season most of the filaments perish, but some of 
 them undergo peculiar changes. The bands of chlorophyll lose their 
 definiteness, the protoplasm becomes massed, tiny outgrowths from 
 the sides of the cells occur, and ,these continue to extend till they 
 meet similar outgrowths from a neighboring filament (Fig. 85, A). 
 These outgrowths unite, and thus a tube from one cell to the other 
 is formed. The contents of one cell pass through to another, and 
 the two masses fuse. A thick wall forms about the united mass and 
 the old cell walls decay and fall away, leaving these thick-walled 
 zygospores on the bottom of the pond. In the spring the protoplasm 
 within each of these zygospores begins to grow, breaks through the 
 thick wall, and proceeds to form a new filament by cell division. 
 The formation of the zygospores is known as conjugation; it is a 
 kind of sexual reproduction, though the two cells taking part in the 
 process are the same in appearance. 
 
 If one observes pond scum on a sunny day, bubbles will be seen 
 escaping from the mass. A test of this gas proves it to be oxygen, 
 and as we should expect, it occurs in connection with the process of 
 carbohydrate manufacture the same as in other green plants. In 
 fact it has been proved that these simple plants manufacture foods, 
 digest, assimilate, respire, and reproduce as do the higher plants 
 we have studied. The differences, then, between a simple plant 
 like Spirogyra and a bean plant or an oak tree are mainly those of 
 structure and adaptations for the performance of functions which 
 are largely common to both. Indeed, it is evident that every cell 
 of the Spirogyra is in contact with the water, from which all the sub- 
 stances needed are obtained by absorption. Hence, any special 
 adaptations for securing food materials or of giving off wastes, such 
 as are found in higher plants, are unnecessary. 
 
 187. Suggestions for the study of Spirogyra. No. 67. It is 
 desirable that pupils should see the " pond scum " in its habitat, 
 even if they do not collect material for work. The escape of bubbles 
 may be noticed at this time or in the laboratory. The mass should be 
 described as to color and " feel/' and the fine threads noted by 
 
PLANT CLASSIFICATION 169 
 
 floating the mass in a saucer of water. A filament should then be 
 studied under the microscope, and the parts of a single cell described, 
 and several cells should be drawn. If fresh zygospore material can 
 be obtained, this should also be studied, and the parts described 
 above noted and drawn ; otherwise charts or pictures may be used. 
 
 188. Pleurococcus and other algae. Another and still simpler 
 form of plant life is known as Pleurococcus. It may be readily 
 obtained from the trunks on the north side of 
 
 large trees. It appears as a very thin green layer 
 closely adhering to the bark. If a little of this 
 material is scraped off and placed under the 
 
 compound microscope, it will be found that it is , 
 
 , ,. . , FIG. 86. Pleuro- 
 
 made up of a large number of tiny circular green coccus. (Sedg- 
 
 cells which adhere to each other more or less, wick and Wil- 
 since in the process of reproduction one cell son ' ) 
 divides to form two, each of which is considered to be an individual 
 plant. Thus the whole mass is made up of a large number of 
 one-celled plants. 
 
 The Spirogyra and Pleurococcus are only two of a large number 
 of simple plants known as algae. They differ widely in form, but 
 none of them develop roots, stems, or leaves. Among the most 
 common algae are the marine forms known as sea weeds, of which 
 there are many kinds. 
 
 189. Suggestions for the study of Pleurococcus. No. 68. As 
 indicated above, material for the study of Pleurococcus may be 
 easily obtained by removing pieces of bark from trees having a con- 
 siderable quantity of this plant on their surface. If collected in a 
 dry season, the bark should be placed under a bell-jar with sufficient 
 water to make the air moist, and allowed to stand for several days. 
 The place in which the Pleurococcus is found should be described, 
 and also the appearance of a mass of the plants. Single cells should 
 then be studied under the high power of the compound microscope, 
 and the cell and its contents described and drawn. 
 
 D. Fungi. (See Chapter IX, 147-166.) 
 
170 PLANT BIOLOGY 
 
 III. SUMMARY OF A CLASSIFICATION OF THE PLANT 
 KINGDOM 
 
 Division I Spore-producing plants. 
 Sub-division 1 Fungi (including bacteria, yeast, molds, 
 
 mushrooms, rusts, smuts). 
 Sub-division 2 Algce (including Spirogyra, Pleurococcus, and 
 
 sea weeds). 
 
 Sub-division 3 Mosses and their relatives. 
 Sub-division 4 Ferns and their relatives. 
 
 Division II Seed-producing plants. 
 
 Sub-division 1 Gymnosperms (including pines, spruces, hem- 
 locks). 
 Sub-division 2 Angiosperms, composed of : 
 
 Class I Monocotyledons (e.g. corn, lilies, gladiolus). 
 
 Class II Dicotyledons composed of 160 or more families, 
 
 one of which is 
 
 Rose family composed of 14 genera, one of which is the 
 Pear genus composed of 3 species, one of which is the 
 Apple species, of which there are many varieties, e.g. 
 Baldwin, Greening, etc. 
 
APPENDIX I 
 
 LABORATORY EQUIPMENT 
 
 The laboratory. It is very desirable that a definite room or 
 rooms be set apart for work in biology, since at least a minimum 
 equipment is essential, and this cannot be transferred from room 
 to room without considerable loss of efficiency. While it is desirable 
 to have tables or at least flat-topped desks of good size, satisfactory 
 
 FRONT ELEYATTDM. 
 
 END ELEVATION- 
 
 o 
 
 TOP. 
 FIG. 87. Plans for a laboratory table. 
 
 laboratory work can be done in an ordinary class room if it is well 
 lighted. The laboratory should be supplied with a demonstration 
 table and gas connection if possible, with sink and running water, 
 and a broad shelf should be placed in front of the windows for sup- 
 porting growing plants and aquaria, and for use in demonstrations 
 with the compound microscope. Ample closet room should be pro- 
 vided in which to store apparatus and supplies, so that they may be 
 kept free from dust. 
 
 171 
 
172 PLANT BIOLOGY 
 
 In case it is possible to equip a room with laboratory tables the 
 following type is suggested. In the first place the laboratory tables 
 should be firmly fixed to the floor, and arranged so that the light 
 comes from the left side, and if possible also from the back of the 
 room. The desk tops should be 30 inches from the floor and 20 
 inches wide, and should be made of maple or other hard wood. The 
 length of each table will of course depend upon the dimensions of 
 the room, but if possible no more than three pupils should be pro- 
 vided for at a single table. Each student should have at least 
 30 inches of the table space. (Fig. 87.) 
 
 " The finish of the laboratory table tops is a matter of importance, 
 since it must be such as to protect the wood from damage, and keep 
 it clean and smooth. Many prefer a black finish, to obtain which the 
 following method gives good results. 
 
 " Make up solutions : 
 
 (1) Copper sulphate (CuS0 4 ) . . . 625 grams 
 Potassium chlorate (KC10 ) . . . 625 grams 
 Water to make 5 liters 
 
 (2) Anilin oil 300 grams 
 
 Hydrochloric acid (HC1) . . , . 450 grams 
 
 Water to make 2500 liters 
 
 " Apply solution (1), followed immediately by (2) several times, 
 until the wood becomes a dark green, allowing the applications to 
 dry each time. The darker the tone reached, the better. The 
 wood must then be washed thoroughly with soap and hot water 
 applied with a brush. This is necessary in order to remove the super- 
 fluous salts. The table is finished with oil and will then be dead 
 black." 1 
 
 The advantages of the dull black finish are these: (1) there is 
 little reflection of light from this kind of surface into the eyes of the 
 pupils; (2) the black surface furnishes an admirable background 
 for many objects of study ; and (3) the tops are not injured by water, 
 acids, or other chemicals. 
 
 Experience has shown that unless the laboratory must be used 
 
 1 From Lloyd and Bigelow's "The Teaching of Biology." 
 
APPENDIX I 173 
 
 as an assembly room for a division at the beginning and close of 
 school, drawers and shelves beneath the desk are of little real use, 
 and often become mere receptacles for laboratory de*bris, unless 
 they are provided with locks. It is usually far safer and more satis- 
 factory to collect drawings, magnifiers, pencils, etc., at the close 
 of the period, and to distribute materials as they are needed during 
 the next period. If this work is properly systematized and the 
 assistance of pupils is made use of, very little of the laboratory 
 time is lost in this way. 
 
 Seats fixed to the floor, likewise, are of great advantage. The 
 authors have found that the best seat for this purpose is the Chandler 
 chair, which is furnished by the American Seating Company, 
 19 West 18th St., New York City. It has a strong iron base, which 
 can be screwed to the floor, and the chair seat turns on ball-bear- 
 ings through an arc of 180 degrees. The price of the chair is $2. 
 
 Apparatus and chemicals. The following lists of apparatus 
 and chemicals are suggested as a minimum equipment for a class 
 of 24. Most of the items can be purchased from any one of the fol- 
 lowing dealers : 
 
 Bausch and Lomb Optical Co., Rochester, New York. 
 Kny-Scheerer Co., 404 West 27th St., New York City. 
 O. T. Louis, 59 Fifth Avenue, New York City. 
 
 QUANTITY APPARATUS AND GLASSWARE ESTIMATED PRICE 
 
 1 Compound microscope, with |- and -inch objec- 
 tives, double nose-piece, 1 inch eye-piece, and 
 
 revolving disk-diaphragm $30.00 
 
 24 Magnifiers, doublets, 1^-inch focus 16.20 
 
 1 Harvard trip-scale balance 6.00 
 
 12 Evaporating dishes, 3 inches diameter ...... 1.50 
 
 1 2-quart agate double boiler 1.50 
 
 2 Alcohol lamps or \ .50 
 
 2 Bunsen burners (if gas is available) .40 
 
 3 ft. Rubber tubing (heavy) to fit Bunsen burners . . .60 
 144 Slides, plain, 1X3 inches .80 
 
174 PLANT BIOLOGY 
 
 1 oz . Cover glasses (round) $ .70 
 
 12 Sloyd knives 2.25 
 
 24 Forceps (heavy) 5.00 
 
 12 Dissecting scissors 2.25 
 
 50 Handles (adjustable) for dissecting needles ... 2.00 
 
 100 Needles for handles 25 
 
 144 6-inch test tubes -. 1.50 
 
 12 8-inch test tubes, hard glass 1.50 
 
 2 Chemical thermometers (Fahrenheit and Centigrade 
 
 scale on same) 2.00 
 
 1 Lactometer .50 
 
 1 Radiometer 1.10 
 
 2 Iron ring-stands (3 rings) 1.10 
 
 2 Pieces wire gauze (4X4 inches) .08 
 
 2 Pieces asbestos (4X4 inches) .07 
 
 6 Glass stirring rods .10 
 
 25 ft. Glass tubing, 5 mm. outside .30 
 
 10 ft. Rubber tubing to fit glass tubing .70 
 
 12 Thistle tubes (medium size) 1.00 
 
 12 Beakers, 150 to 250 cc 1.50 
 
 3 Bell jars 2 feet high and 10 inches in diameter . . 14.40 
 3 Bell jars about 8 inches high and 10 inches in diam- 
 eter 5.00 
 
 1 Bell jar, open top, 8 inches high and 8 inches in 
 
 diameter 2.00 
 
 1 piece Sheet rubber 2 feet square (should be kept in 
 
 lightning fruit jar when not in use) 1.50 
 
 24 Lightning fruit jars (1 quart) 3.00 
 
 6 Flasks, 250 cc 1.00 
 
 36 Petri dishes, 4 inches in diameter 6.00 
 
 1 Cylindrical graduate, 1000 cc 1.35 
 
 1 Cylindrical graduate, 100 cc .40 
 
 6 Tall glass cylinders (1000 cc.) 1.75 
 
 1 Box slide labels 10 
 
 1 Box labels, 2x3 inches 18 
 
 1 Steam sterilizer, copper bottom, 18 inches high . . 6.00 
 
APPENDIX I 175 
 
 50 8-ounce wide-mouthed bottles $2.20 
 
 50 4-ounce wide-mouthed bottles . 1.60 
 
 24 200 cc. narrow-mouthed bottles with ground glass 
 
 stoppers 2.60 
 
 100 Vials with corks, 3 inches high, 1 inch in diameter . 2.75 
 
 100 Corks to fit 8-ounce wide-mouthed bottles . . . 1.00 
 100 Corks to fit 4-ounce wide-mouthed bottles . . .-.,. .75 
 
 100 Corks to fit 6-inch test tubes V .40. 
 
 10 Rubber stoppers with 2 holes to fit 250-cc. flasks . . .45 
 
 10 Rubber stoppers with 1 hole to fit 6-inch test tubes . .30 
 2 Insect spreading boards ^1.00 
 
 QUANTITY CHARTS AND PREPARATIONS ESTIMATED PRICE 
 
 11 Jung plant charts (pansy, horse-chestnut, tulip, 
 
 linden, potato, carrot, pea,' Spirogyra, mold, fern, 
 
 moss) $13.20 
 
 1 Teachers' Botanical Aid, 28 charts, containing 300 
 drawings (Western Publishing House, Chicago, 
 
 111.) 12.50 
 
 11 Jung animal charts (fish (external), fish (internal), 
 frog, Amoeba, Paramecium, crayfish, bee, but- 
 terfly, cricket, finch, duck) 13.20 
 
 4 Leuckhart animal charts (grasshopper, bee, butter- 
 fly, metamorphosis of frog) 8.00 
 
 1 Model of heart and lungs (dissectible), natural 
 
 size 12.75 
 
 1 Model of digestive system on panel, natural size . 15.75 
 
 1 Model of circulatory system on panel, natural size . 11.75 
 
 1 Articulated human skeleton, clutch standard . . . 35.00 
 
 1 Life history of butterfly 6.00 
 
 1 Life history of honey bee 5.00 
 
 1 Life history of frog 5.00 
 
 1 Life history of fish 5.00 
 
 1 Half skeleton of fish (glass case) 3.00 
 
 1 Half skeleton of frog (glass case) 4.00 
 
176 PLANT BIOLOGY 
 
 8 Microscopical slides of plant tissue (cross section 
 and longitudinal section of young root, cross 
 section and longitudinal section of stem one year 
 old, cross section of hydrangea leaf, epidermis 
 of leaf, separate wood cells, ducts, conjugating 
 
 Spirogyra) $3.50 
 
 5 Microscopical slides of animals (Amoeba, Para- 
 mecium, frog's blood, human blood, mouth parts 
 
 of bee) 3.00 
 
 QUANTITY LIST OF CHEMICALS ESTIMATED PRICE 
 
 2 Ib. Hydrochloric acid $1.00 
 
 1 Ib. Nitric acid .28 
 
 1 Ib. Ammonia .26 
 
 1 oz. Iodine 30 
 
 5 oz. Potassium iodide ........... .90 
 
 lib. Ether 40 
 
 1 Ib. Caustic soda .30 
 
 1 Small tube red litmus paper .08 
 
 1 Small tube blue litmus paper .08 
 
 1 gal. 95 per cent alcohol 3.50 
 
 10 Ib. 40 per cent formalin 1.70 
 
 8oz. Glycerin -. .25 
 
 1 oz. Pepsin .30 
 
 1 Ib. Peptone 2.00 
 
 1 oz. Taka diastase . ' . . 1.70 
 
 lib. Salt .05 
 
 1 oz. Phosphate of lime .12 
 
 1 Ib. Grape sugar . .12 
 
 Ib. Cooking soda .10 
 
 1 Ib. Copper sulphate .35 
 
 1 Ib. Rochelle salt 30 
 
 1 jar Beef extract .75 
 
 1 Ib. Agar .90 
 
 Ib. Powdered sulphur 07 
 
 1 Ib. Potassium chlorate .20 
 
APPENDIX I 177 
 
 lb. Manganese dioxid $.35 
 
 1 lb. Granulated zinc .25 
 
 1 lb. Absorbent cotton .35 
 
 6 Small candles 10 
 
 1 lb. Marble pieces , . .10 
 
 51b. Plaster of Paris 10 
 
 5 oz. Potassium cyanide .10 
 
 1 oz. Ferric chloride .05 
 
 1 lb. Corn starch .10 
 
 ^ lb. Arrow root starch .15 
 
 1 oz. White egg albumen .12 
 
 1 oz. Powdered carmine .40 
 
 1 oz. Gluten .15 
 
APPENDIX II 
 
 ORDER OF TOPICS 
 
 The following order of topics, with time assignment for each, has 
 been found by the authors to be satisfactory : 
 
 I. Course begun in September and completed in June. 
 
 1. ^"he general structure of plants (organs of a plant) 2 lessons 
 
 2. Reproduction in plants. 
 
 a. Structure and adaptations of flowers ... 15 lessons 
 
 b. Structure and adaptations of fruits, including 
 
 fruit and seed dispersal 5 lessons 
 
 3. Plant propagation. 
 
 a. Seeds and their development into plants . . 6 lessons 
 6s Conditions essential for the growth of plants . 2 lessons 
 
 4. Cellular structure of plants, including fertilization 
 
 of flowers 5 lessons 
 
 5. Composition of living and lifeless things. 
 
 a. Elements, compounds, oxidation, with defini- 
 
 tions 10 lessons 
 
 b. Composition of food substances, with tests for 
 
 each 8 lessons 
 
 c. Manufacture of food substances by plants . . 5 lessons 
 
 6. Osmosis and digestion 5 lessons 
 
 7. Adaptations of the nutritive organs of plants. 
 
 a. Structure and adaptations of roots .... 5 lessons 
 
 b. Structure and adaptations of stems .... 3 lessons 
 
 c. Structure and adaptations of leaves .... 4 lessons 
 
 8. Respiration and the production of energy in plants 4 lessons 
 
 9. Plants in their relation to human welfare. 
 
 178 
 
APPENDIX II 179 
 
 a. Some uses of plants to man 3 lessons 
 
 b. Forests and forest conservation 3 lessons 
 
 10. Single-celled animals 5 lessons 
 
 11. Fish (and frog, if this form is taught) .... 14 lessons 
 
 12. The general structure of the human body ... 3 lessons 
 
 13. Microorganisms and their relation to human wel- 
 
 fare 10 lessons 
 
 14. Nutrients and their uses 7 lessons 
 
 15. Stimulants, narcotics, and poisons 10 lessons 
 
 16. Digestion of the nutrients 7 lessons 
 
 17. Circulation of the nutrients . . . . . . . 6 lessons 
 
 18. Respiration and the production of heat and power 
 
 in man 7 lessons 
 
 19. Additional topics in hygiene 9 lessons 
 
 20. Birds 5 lessons 
 
 21. Insects 15 lessons 
 
 II. Course begun in February and completed in January. 
 
 1. Composition of living and lifeless things. 
 
 a. Elements, compounds, oxidation, with defini- 
 
 tions 10 lessons 
 
 b. Composition of food substances, with test for 
 
 each 8 lessons 
 
 c. Manufacture of food substances by plants . 5 lessons 
 
 2. General structure of plants, including cellular 
 
 structure 5 lessons 
 
 3. Osmosis and digestion 5 lessons 
 
 4. Adaptations of the nutritive organs of plants. 
 
 a. Structure and adaptations of roots .... 5 lessons 
 
 6. Structure and adaptations of stems ... 3 lessons 
 
 c. Structure and adaptations of leaves ... 4 lessons 
 
 5. Respiration and the production of energy in plants 4 lessons 
 
 6. Reproduction in plants. 
 
 a. Structure and adaptations of flowers ... 15 lessons 
 
 b. Structure and adaptations of fruits, including 
 
 fruit and seed dispersal 5 lessons 
 
180 PLANT BIOLOGY 
 
 7. Plant propagation. 
 
 a. Seeds and their development into plants . . 6 lessons 
 
 6. Conditions essential for the growth of plants . 2 lessons 
 
 8. Plants in their relation to human welfare. 
 
 a. Some uses of plants to man 3 lessons 
 
 6. Forests and forest conservation 3 lessons 
 
 9. Insects 15 lessons 
 
 10. Birds 5 lessons 
 
 11. Fish (and frog, if this form is taught) .... 14 lessons 
 
 12. Single-celled animals 5 lessons 
 
 13. The general structure of the human body . . 3 lessons 
 
 14. Microorganisms and their relation to human wel- 
 
 fare 10 lessons 
 
 15. Nutrients and their uses 7 lessons 
 
 16. Stimulants, narcotics, and poisons 10 lessons 
 
 17. Digestion of the nutrients 7 lessons 
 
 18. Circulation of the nutrients 6 lessons 
 
 19. Respiration and the production of heat and 
 
 power in man 7 lessons 
 
 20. Additional topics in hygiene . 9 lessons 
 
APPENDIX III 
 
 BIOLOGY NOTE-BOOKS 
 
 Method of Recording Laboratory Observations. In preparing 
 note-book records of laboratory observations or experiments, 
 home work, or field trips, the teacher should insist, so far as possible, 
 that pupils give in clear, concise English a complete account of the 
 work that has been done. Students should be careful to state the 
 purpose of the experiment, and describe the preparation of the ex- 
 periment. He should indicate whether the work was done by him- 
 self or by some one else. The results observed should be sharply 
 distinguished from the conclusions derived from observation. 
 Pupils might well use as paragraph titles the section titles printed 
 in heavy face type (e.g. Carbon, Oxygen, etc.). On pp. 182-183 are 
 two accounts of the same experiments that were photographed from 
 the note-books of two different pupils. The method of writing up 
 an experiment shown in Fig. 88 is suggested for accounts that are 
 written in the laboratory ; that in Fig. 89, for accounts written at 
 home. 
 
 Drawings. In making drawings pupils should be supplied with 
 sharp-pointed pencils that are relatively hard. Clear outline draw- 
 ings should be insisted upon, and shading should as a rule not be 
 encouraged (Figs. 90, 91). The general title of the sheet of drawings 
 should be placed at the top of the sheet. When there are several 
 drawings on the same sheet, the general title should be placed at the 
 top, and the special title of each should be written just below the 
 individual drawing. In labeling, the dotted leaders may run in any 
 direction (see pp. 184-187), but they should not cross each other. 
 The labels, however, should all be written parallel to the top margin 
 
 181 
 
182 PLANT BIOLOGY 
 
 -. if, if ft ^a^a^4-U<^iA) -XV. 
 
 I 
 
 trt 
 
 ''s^i^^/i^ OH*SI*^ cAa*cs* 
 
 ^^X^^^^^**^^x^t^^<X^ . 
 
 1 ^<>2^^L^Z/~o^^^ 
 
 3 
 
 Jr- 
 
 FIG. 88. Specimen page from a note-book. 
 
APPENDIX III 183 
 
 /^^ xtfL^xvO^ 
 
 
 
 * 
 >Cttxo^-^x<vrTxV cA s^^r%4jCtAsJ-J'~iaJL>*A-A*^ 
 
 d^4scJd ^-^ - 
 
 ^^s^*A^.^ J(Ju^^ru<J^^in^L^-J xvxxx^/ 
 
 (^~dn-^JzJhs}~^^ 
 
 ^L^UL^ ^rLs 
 
 jZsaAJ^^ ^LJ-ui/ 
 
 D J 
 
 CA. ^*-<riXX>^lxCl/ 
 
 sCi^L^^ 
 FIG. 89. Specimen page from a note-book. 
 
184 
 
 PLANT BIOLOGY 
 
 FIG. 90. Drawing of an advanced stage of the corn seedling. 
 
APPENDIX III 185 
 
 of the sheet. If the drawings are made on separate sheets of paper 
 about the size of a page in the note-book, the sheets may be col- 
 lected, criticized, and rated, and then, if the left-hand margin of about 
 an inch is folded, the drawings can be fastened in the note-book by 
 pasting this narrow flap. 
 
 The following directions for guiding pupils in the preparation of 
 their note-books have been found by the authors to be of great assist- 
 ance. 
 
 1. In the upper right-hand corner of the outside front cover of 
 
 your note-book write your name, division (i.e. grade and 
 section), and the classroom in which you meet at 9 A.M. 
 thus: 
 
 JOHN S. JONES, 1-8 (or IA) 
 Room 416 
 
 Across the middle of the front cover write BIOLOGY NOTE- 
 BOOK. 
 
 2. Cover your note-book with manila paper, and on the front 
 
 cover put the information called for in 1 above. Be 
 sure to keep your note-book covered. 
 
 3. Write your name, division, and classroom in the upper right- 
 
 hand corner of the first page of your note-book. Leave 
 the rest of this page blank for the teacher's ratings and 
 comments. 
 
 4. Number each page of your note-book. 
 
 5. On each of the pages draw a vertical line about an inch from 
 
 the left margin. Always leave this marginal space for 
 the teacher's comments. 
 
 6. Begin each new subject on a new page, writing its title on the 
 
 first line. The first composition or notes should commence 
 on page 5, the preceding pages being reserved for index. 
 
 7. Write your compositions or notes in ink on both sides of the 
 
 page. 
 
 8. Indent about an inch the first word of each paragraph. 
 
 All other lines should begin at the left margin line. It is 
 
186 PLANT BIOLOGY 
 
 suggested that the paragraph titles used in the labora- 
 tory studies be employed and that they be underlined (e.g. 
 Parts of a Leaf). 
 
 9. Make sure that your statements in each paragraph or in 
 your notes are sufficiently full and clear to be readily 
 intelligible to one who knows nothing of the subject. 
 
 10. In your compositions or notes be careful to make clear what 
 
 you yourself did, what you saw, what you heard, and what 
 you read. Accounts of experiments may often be written 
 in four paragraphs as follows: object of experiment; 
 preparation of experiment ; result of experiment ; con- 
 clusion from experiment. 
 
 11. If, on account of absence, it is necessary that work be copied, 
 
 inclose such account in quotation marks, and write at 
 the end of such quotation the name of the pupil from 
 whom the account was copied. 
 
 12. Every correction indicated by the teacher should be made by 
 
 the student as soon as the note-book is returned. 
 
 13. Every student who wishes to do so can produce a first class 
 
 note-book, neat in appearance, and at least relatively 
 free from mistakes in spelling, punctuation, and grammar. 
 
 MARKS USED IN THE CORRECTION OF BIOLOGY PAPERS 
 
 cp = mistake in use or in omission of capital letter. 
 
 cl = meaning not clear. 
 
 gr = mistake in grammar. 
 
 n = composition is lacking in neatness. 
 
 II = error in paragraphing. 
 
 p = mistake in punctuation. 
 
 r = repetition of word or idea. 
 
 sp = error in spelling. 
 
 w = word improperly used. 
 
 ? = doubt as to the truth of the statement. 
 
 ( ) = words in parenthesis are to be crossed out. 
 
 A = some omission. 
 
APPENDIX III 
 
 187 
 
 FIG. 91. Drawing of side view of frog. 
 
APPENDIX IV 
 
 REVIEW TOPICS IN PLANT BIOLOGY 
 
 You should be prepared to give a good oral recitation on each of the 
 following topics. If you are not sure of any of the facts called for, 
 write down the topic or topics, and ask your teacher at the beginning of 
 the next recitation how to obtain the information. 
 
 A. COMPOSITION OF LIFELESS AND LIVING THINGS. 
 
 1. Chemical element: definition ; examples with symbols of each ; 
 
 characteristics of each (i.e. whether it is solid, liquid, or gas ; 
 color, odor, and taste ; ability of each to burn or to cause 
 burning). 
 
 2. Oxidation: definition; chemical element necessary; com- 
 
 pound formed by the oxidation of elements ; evidences of 
 oxidation. 
 
 3. Chemical compound: definition; examples; test for two of 
 
 them, with characteristics of each (as in 1 above). 
 
 4. Food substances : kinds ; chemical composition of each ; test 
 
 for each ; examples of foods containing each in abundance. 
 
 5. Manufacture of food substances by plants : s proofs of the neces- 
 
 sity of sunlight, chlorophyll, and carbon dioxide for carbo- 
 hydrate manufacture ; proofs of the excretion of oxygen in 
 carbohydrate manufacture ; manufacture of proteins. 
 
 B. GENERAL STRUCTURE OF PLANTS. 
 
 1. Parts of a plant ; organs and functions. 
 
 2. Structure of plant cells; protoplasm; assimilation, growth, 
 
 and cell division. 
 
 188 
 
APPENDIX IV 189 
 
 C. OSMOSIS AND DIGESTION. 
 
 1. Proofs that water and grape sugar will pass through a mem- 
 
 brane ; definition and law of osmosis. 
 
 2. Proofs that starch and protein will not pass through a mem- 
 
 brane; digestion of starch; definition of digestion; diges- 
 tive ferments. 
 
 D. ADAPTATIONS OF THE NUTRITIVE ORGANS OF PLANTS. 
 
 1. Roots: gross structure; structure of a root-hair ; functions of 
 
 roots ; adaptations of roots. 
 
 2. Stems : gross structure of a woody stem ; functions of stems ; 
 
 adaptations of stems ; changes in stems during growth. 
 
 3. Leaves: gross and microscopical structure; functions of 
 
 leaves ; adaptations of leaves. 
 
 E. RESPIRATION AND THE PRODUCTION OF ENERGY IN PLANTS. 
 
 1. Energy: examples in plants; proof that heat energy is de- 
 
 veloped in growing seedlings ; transformations of energy; 
 source of energy ; oxidation as a means of liberating energy. 
 
 2. Respiration : definition ; proof of the necessity of air for plants 
 
 and of the production of carbon dioxide by plants. 
 
 F. REPRODUCTION IN SEED-PRODUCING PLANTS. 
 
 1. Floral envelopes: names of the parts of each floral envelope; 
 
 position and general description of the floral envelopes 
 in the flowers studied; functions of each of the floral 
 envelopes. 
 
 2. Essential organs: name, number, position, and parts of each 
 
 of the essential organs; general description and func- 
 tions of the parts of each of the essential organs. 
 
 3. Pollination. 
 
 a. Self-pollination : definition ; devices to prevent it in flowers 
 
 studied. 
 6. Cross-pollination : definition ; devices to make it possible 
 
 in flowers studied ; agencies which secure cross-pollina- 
 
190 PLANT BIOLOGY 
 
 tion; comparative vigor of plants from seeds resulting 
 from cross-pollinated and from self-pollinated flowers. 
 
 4. Fertilization. 
 
 a. Cellular nature of pollen and ovules ; germination of pollen 
 
 grains. 
 
 b. Structure of ovule. 
 
 c. Process of fertilization ; production of the embryo. 
 
 5. Fruits. 
 
 a. Structure of each of fruits studied; definition of a fruit; 
 
 classification of fruits. 
 
 b. Necessity for seed-dispersal; agencies by which seed-dis- 
 
 persal is brought about ; adaptations of fruits and seeds 
 to secure dispersal by each of these agencies. 
 
 c. Adaptations for protecting seeds of unripe edible fruits; 
 
 adaptations for protecting seeds of ripe edible fruits. 
 
 G. PLANT PROPAGATION. 
 
 1. Bean seed and its development into a seedling: markings on 
 
 seed ; their cause or function ; seed covering ; position 
 and kinds of stored food; description of parts of em- 
 bryo ; parts of the plant which develop from the parts 
 of the embryo ; breaking of seedling through the soil. 
 
 2. (Optional.) Corn grain and its development into a seedling: 
 
 description of the parts of the embryo; position and 
 kinds of stored food ; breaking of seedling through the 
 soil ; various parts of the plant which develop from each 
 of the parts of the embryo. 
 
 3. Definitions: seed, seedling, germination, seed coats, micro- 
 
 pyle, hilum, embryo, cotyledon, plumule, hypocotyl, 
 endosperm, primary and secondary roots. 
 
 4. Experiments to show 
 
 a. Function of endosperm of corn grain. 
 6. (Optional.) Relation of water and temperature to germi- 
 nation. 
 
 5. (Optional.) Other methods of plant propagation: grafting; 
 
 slips, runners, and layers ; tubers ; bulbs. 
 
APPENDIX IV 191 
 
 6. Conditions essential for the growth of plants : five essential con- 
 
 ditions ; conditions of soil favorable for growth ; meth- 
 ods of soil improvement. 
 
 7. (Optional.) Struggle for existence and its effects: Variation 
 
 among plants; numbers of seeds produced by plants; 
 struggle for existence among plants; survival of the 
 fittest. 
 
 8. (Optional.) Improvement of plants by man: artificial selec- 
 
 tion of favorable variations ; artificial crossing of related 
 species ; some of the valuable crops of New York State ; 
 some of the methods of increasing crop production. 
 
 H. PLANTS IN THEIR RELATION TO HUMAN WELFARE. 
 
 1. Some uses of plants to man. 
 a. Uses of plants for food. 
 
 6. Uses of plants for flavoring extracts, beverages, and medi- 
 cines. 
 c. Uses of plants for clothing. 
 
 2. Forests and forest conservation. 1 
 
 a. Definitions. 
 
 (1) A forest means a growth of trees sufficiently dense to 
 
 form a fairly unbroken canopy of trees. A forest 
 has a population of animals and plants peculiar 
 to itself, a soil of its own making, and a climate 
 different from that of the open country. 
 
 (2) "Forestry is the preservation of forests by wise use." - 
 
 ROOSEVELT. 
 
 b. Value of forests. 
 
 (1) ^Esthetic value beauty of form and color of forest 
 
 trees. 
 
 (2) Value in affecting drainage. 
 
 (a) By retaining water in the soil through the agency 
 of the roots. 
 
 1 The authors are indebted to Miss Kate B. Hixon, of the Morris 
 High School, New York, N.Y., for the review topics on Forests and 
 Forest Conservation. 
 
192 PLANT BIOLOGY 
 
 (b) By preventing too rapid evaporation from the soil, 
 
 through the help of the foliage. 
 
 (c) By retarding the melting of snow, thus preventing 
 
 freshets. 
 
 (3) Value in affecting climate. 
 
 (a) By bringing moisture into the air, which falls as 
 
 rain. 
 (6) By setting oxygen free into the air in the process 
 
 of starch making, 
 (c) By acting as a windbreak. 
 
 (4) Economic value. 
 
 (a) As a source of lumber and fuel. 
 
 (6) As a source of food (nuts, maple sugar, etc.). 
 
 (c) As a source of industrial raw materials (paper, 
 
 tanning materials, wood alcohol, tar, pitch, 
 
 turpentine, rosin, fibers). 
 
 c. Dangers to forests. 
 
 (1) Fires. (4) Careless lumbering. 
 
 (2) Insects. (5) Fungi that cause disease. 
 
 (3) Grazing of cattle. 
 
 d. Results of deforestation. 
 
 (1) Main cause of freshets, which cause destruction of 
 
 property and loss of life ; they also fill up navi- 
 gable streams with soil and debris. 
 
 (2) Drouth, with the consequent lessening of water power. 
 
 (3) Timber famine, especially in hard woods. 
 
 e. Methods used by the Government Bureau of Forestry to 
 
 preserve forests. 
 
 (1) Allow only the cutting of dead or mature trees. 
 
 (2) Insist that each tree cut be replaced by another of the 
 
 same kind. 
 
 (3) Prevent the spread of fires. 
 
 (4) Destroy insects that are injurious to trees. 
 
 (5) Restrict cattle grazing to certain seasons. 
 3. Fungi and their relation to human welfare. 
 
 a. Bacteria; microscopical appearance and size; reproduc- 
 
APPENDIX IV 193 
 
 tion ; necessary conditions for growth ; relation 
 (1) to soil fertility, (2) to flavors of food, (3) to 
 the industries, (4) to diseases. 
 
 b. (Optional.) Yeast : microscopical appearance and size ; 
 
 reproduction; changes caused by yeast; uses 
 of yeast. 
 
 c. (Optional.) Bread mold; structure; reproduction and 
 
 life history ; nutrition in the fungi. 
 
 d. (Optional.) Other fungi: mushrooms, rusts, and smuts; 
 
 economic importance. 
 
 I. PLANT CLASSIFICATION. 
 
 1. Common methods of classification. 
 
 a. Herbs, shrubs, and trees : define each ; give examples. 
 
 6. Annuals, biennials, and perennials; define each; give 
 
 examples, 
 c. Deciduous and evergreen trees and shrubs: define each; 
 
 give examples. 
 
 2. (Optional.) Scientific method of classification. 
 
 a. Seed-producing plants. 
 
 (1) Gymnospefms and angiosperms. 
 
 (2) Monocotyledons and dicotyledons. 
 
 (3) Plant family, genus, species, variety. 
 
 b. Spore-producing plants. 
 
 (1) Ferns: fern plant; spores; prothallus; fertilization 
 
 of the egg-cells ; alternation of generations. 
 
 (2) Mosses : moss plant ; protonema ; sexual generation ; 
 
 alternation of generations. 
 
 (3) Algae : Spirogyra, its structure, methods of reproduc- 
 
 tion and functions; Pleurococcus and other 
 algae. 
 
 (4) Fungi (see H, 3, above). 
 
 Note. The following outlines were prepared by Miss Martha 
 F. Goddard, late of the Morris High School, New York, N.Y. 
 They furnish an admirable review of the most important nutritive 
 o 
 
194 PLANT BIOLOGY 
 
 and reproductive functions of plants. Pupils might either copy 
 the whole outline into their note-books, supplying the words repre- 
 sented by the figures, or make a list of the words, numbering them 
 to correspond to the figures below. 
 
 NUTRITION IN GREEN PLANTS THAT PRODUCE SEEDS 
 
 Soil-water, in which are dissolved compounds that contain nitro- 
 gen and other mineral matters needed by the plant, is absorbed by 
 (1) which are (2) found (3) of roots. The process by which this soil- 
 water enters is called (4). In the root-hair the membrane is the (5). 
 More liquid enters the root-hair than passes out, because (6). The 
 substances admitted in the soil-water are regulated by the action of 
 the (7) in the cell, through which the liquid must pass. The cell- 
 sap passes from one cell of the root to the next, until it reaches 
 thick-walled tubular cells called (8), which form part of the (9) of 
 the root, stem, and leaf. The liquid passes up through these un- 
 til it reaches spaces between the thin-walled leaf-cells, and finally 
 the sap gets into these cells. 
 
 A gas called (10) is taken in through epidermis cells of the leaf, and 
 through openings called (11) between certain cells of the epidermis 
 that are known as (12). In the soft cells of the inside of the leaf 
 are tiny masses of protoplasm which contain a green coloring matter 
 called (13). These green masses of protoplasm are called (14). 
 They can manufacture starch out of the (15) and the (16) in the 
 presence of (17). The elements in C0 2 and H 2 0, however, are not 
 in quite the right proportions, so (18) is given off as a waste product. 
 The soil- water is such a weak solution of mineral matter that not all 
 the water can be used by the plant, so this water that is not needed 
 is given off by a process called (19). The amount of water thus given 
 off is regulated by the action of the (20) that surround each (21). 
 
 During the night the starch is changed to (22) by a process known 
 as (23). This liquid food then passes down through the (24) of 
 the veins and bast or fibrous bark to places that serve for storage 
 or to growing regions where it is used to make a substance for cell- 
 wall building known as (25). Some of the sugar is made by the pro- 
 
APPENDIX IF 195 
 
 toplasm of the plant to unite with the nitrogen of the nitrates and 
 with the sulphur and phosphorus of other mineral matters derived 
 from the soil, and a compound is formed called (26) which the grow- 
 ing regions use to make into more (27). This last change is called 
 assimilation. 
 
 Some of the proteids may also be stored for future use. Food 
 may be stored in the (28), the (29), the (30), the (31), or in any thin- 
 walled cells. 
 
 OPTIONAL. THE LIFE-HISTORY OF A SEED-PLANT 
 
 See note, p. 193. 
 
 The mother-plant produces flowers which attract insects by their 
 (1) or by their (2). These animals carry (3) on their hairy bodies 
 from the (4) of one flower to the (5) of another. Here nourished 
 by a (6) it sends out a tube which grows down through (a) the (7), 
 (6) the (8), and (c) the (9), and here enters a tiny opening called the 
 (10) in the (11). There a nucleus of the pollen grain (called a sperm 
 nucleus) unites with a nucleus of the egg-cell in the ovule during the 
 process of (12) to form one cell (called a fertilized egg-cell) which 
 now develops into a tiny plant known as the (13) of the seed. This 
 little plant has (a) a minute stem called the (14), (6) one, two, or 
 more seed-leaves known as (15), and (c) usually a tiny bud called the 
 (16). 
 
 The mother-plant feeds this embryo until it has grown thus far, 
 and also stores up food for further growth. This may be put in the 
 cotyledons as in the (17) seed, or it may be packed around the 
 embryo, when it is called (18), as in the (19). To protect the embryo 
 until time for germination, the seed has one or more outer coverings 
 known as (20) . That the seed may be carried away from the mother- 
 plant, and so have better opportunities for development, the 
 mother-plant provides the fruit or the seeds (a) with (21) or (22) so 
 they may be carried by the wind, or (6) with (23) so they may cling to 
 the wool of animals, or (c) with (24) so they may tempt animals to 
 eat them ; in the last case (as in the peach or cherry) the contents 
 of the seed are protected by (25). 
 
196 PLANT BIOLOGY 
 
 When the seed has favorable surroundings, namely (26), (27), 
 and (28), it germinates. If it has one cotyledon, the plant is 
 called (29), the woody bundles in its stem will be (30), and the 
 veining of the leaves will probably be (31). If two cotyledons are 
 present in the seed, the plant is called (32), the woody bundles in 
 its stem will be arranged (33), and the veining of the leaves will 
 be (34). 
 
 The principal food materials stored in seeds are three in number, 
 namely, (a) (35), which is tested by (36) ; (6) (37), tested by (38) ; 
 and (c) (39), tested by (40). Sometimes a fourth nutrient (41) is 
 stored in other parts of the plant ; its presence may be detected 
 by (42). 
 
APPENDIX V 
 
 LIST OF SUGGESTED BOOKS OF REFERENCE IN BIOLOGY 
 
 GENERAL BIOLOGY 
 
 1. Cyclopedia of American Agriculture. Edited by L. H. Bailey. 
 
 4 vols. The Macmillan Co., N. Y. City. $20 net. 
 Vol. I, Farms; Vol. II, Crops; Vol. Ill, Animals; Vol. IV, 
 The Farm and the Community. We do not hesitate to say 
 that Vols. II and III of this series are the most valuable 
 books of reference known to us for teachers or students in plant 
 and animal biology. Experts on the many subjects treated 
 have epitomized in a readable form a vast amount of informa- 
 tion which could only be found by patient search through 
 many volumes. If schools cannot purchase these books, 
 teachers might well urge that they be put on the shelves of 
 the public library, for all four volumes will be found of great 
 value as books of general reference, especially in rural com- 
 munities. 
 
 2. Nature Study and Life, by Dr. C. F. Hodge. Ginn and Co. 
 
 $1.20. Contains many suggestions for the teaching of both 
 plant and animal biology. 
 
 3. General Biology, by Sedgwick and Wilson. Henry Holt and 
 
 Co. $1.75. While mainly devoted to a consideration of 
 the earthworm and the fern (both optional topics), this 
 book will give teachers a clear idea of the biology of a plant 
 and of an animal, and of the composition and character- 
 istics of protoplasm. It also contains an admirable account 
 of yeast, bacteria, Amoeba and Paramecium. 
 197 
 
198 PLANT BIOLOGY 
 
 4. Teaching of Biology, by Lloyd and Bigelow. Longmans, 
 
 Green and Co. $1.50. Deals largely with methods of 
 teaching nature study, botany, zoology, and human physi- 
 ology. 
 
 PLANT BIOLOGY 
 
 5. Practical Botany, by Bergen and Caldwell. Ginn and Co. 
 
 $1.30. 
 
 6. College Botany, by G. F. Atkinson. Henry Holt and Co. 
 
 $1.50. 
 
 7. Readers in Botany, by Jane C. Newell. Ginn and Co. 
 
 2 vols. $.60 each. 
 
 8. How to know the Wild Flowers, by Mrs. William Starr Dana. 
 
 - The Macmillan Co. $1 .50. 
 
 9. How to know the Fruits, by Maude G. Peterson. The 
 
 Macmillan Co. $1.50. 
 
 10. Tree Book, by Julia E. Rogers. Doubleday, Page and Co. 
 
 $4. 
 
 11. New Creations in Plant Life, by W. S. Harwood. The Mac- 
 
 millan Co. $1.75. 
 
 12. Bacteria, Yeasts, and Moulds in the Home, by H. W. Conn. 
 
 Ginn and Co. $1. 
 
 13. Farmers' Bulletins, which can be obtained free by applying to 
 
 the U. S. Dept. of Agriculture, Washington, D.C. The 
 various Bulletins contain many important facts relating 
 to both animals and plants. 
 
 ANIMAL BIOLOGY 
 
 14. Animal Life, by Jordan and Kellogg. Appleton. $1.20. 
 
 15. General Zoology, by Linville and Kelly. Ginn and Co. 
 
 $1.50. 
 
 16. American Natural History (vertebrates only), by W. T. 
 
 Hornaday. $3.50. 
 
 17. Insect Book, by L. 0. Howard. Doubleday, Page and Co. 
 
 $3. 
 
APPENDIX V 199 
 
 18. Manual of Insects, by Comstock. Comstock Publishing Co., 
 
 Ithaca, N.Y. $3.75. 
 
 19. Economic Entomology, by J. B. Smith. Lippincott. $2.50. 
 
 20. Birds of North-Eastern United States, by Frank Chapman. 
 
 Appleton. $3. 
 
 21. Bird Life (with colored plates), by Frank Chapman. Apple- 
 
 ton. $2. 
 
 22. Relation of Birds to Man, by Weed and Dearborn. Lippincott. 
 
 $2.50. 
 
 23. Food and Game Fishes, by Jordan and Everman. Doubleday, 
 
 Page and Co. $4. 
 
 24. Farmers' Bulletins (see 13 above). 
 
 25. Story of the Fishes, by J. N. Baskett. Appleton. $.65. 
 
 HUMAN BIOLOGY 
 
 26. The Human Mechanism, by Hough and Sedgwick. Ginn and 
 
 Co. $2.50. 
 
 27. General Physiology, by W. H. Howell. W. B. Saunders. 
 
 $4. 
 
 28. Studies in Physiology, by James E. Peabody. The Mac- 
 
 millan Co. $1.10. 
 
 29. Laboratory Exercises in Anatomy and Physiology, by James E. 
 
 Peabody. Henry Holt and Co. $.60. 
 
 30. Infection and Immunity, by George M. Sternberg. Put- 
 
 nams. $1.75. 
 
 31. Pathogenic Micro-organisms, by W. H. Park. Lea Brothers 
 
 and Co. $3.75. 
 
 32. Walter Reed and Yellow Fever, by H. A. Kelly. McClure, 
 
 Phillips and Co. $1.50. 
 
 33. The Malaria Mosquito, by B. E. Dahlgren. American 
 
 Museum of Natural History. $.15. 
 
INDEX 
 
 Aerial roots, 102. 
 
 Ailanthus fruit, 92. 
 
 Air, need of, for growth, 67. 
 
 relation of, to soil, 111. 
 Air roots, 102. 
 Air spaces, 60, 62, Fig. 22. 
 Alcohol, formed by yeast, 147. 
 Algae, 166-169. 
 Alternate arrangement, 52. 
 Alternation of generations, in fern, 
 163. 
 
 in moss, 166. 
 Angiosperms, 159, 170. 
 Annual, an, 156. 
 Annual rings, 47, 51, Fig. 17. 
 Annual scars, 55. 
 Anther, 71, 73, 81, 88, Fig. 25. 
 Antheridia, of fern, 162, Fig. 83, D. 
 
 of moss, 164. 
 
 Apparatus, price-list of, 173-175. 
 Apple, fruit, Figs. 37, 38. 
 
 leaves, Fig. 19. 
 Archegonia of fern, 163, Fig. 83, F. 
 
 of moss, 164, Fig. 84. 
 Artificial crossing of related species, 
 
 120. 
 
 Artificial selection, 119. 
 Asexual generation, of fern, 163. 
 
 of moss, 166. 
 Asparagus, 127. 
 Assimilation, 31. 
 
 Bacillus form of bacteria, Fig. 71, 
 
 B, C, D. 
 
 Bacteria, 140-145, Fig. 71. 
 Bamboo, 49, Fig. 18. 
 Bark, 45. 
 Bast, 46. 
 Bean fruit, 89. 
 Bean seed, 97-100. 
 Bee, Figs. 30, 31 
 
 Beggar's ticks, 93. 
 
 Benzine as used in testing for fat, 20. 
 
 Beverages, 128-130. 
 
 Bidens, 93. 
 
 Biennial, 158. 
 
 Biology, definition of, 4. 
 
 Blade of leaf, 55. 
 
 Body, cell-, 28, 29. 
 
 Books, list suggested for reference, 
 
 197-199. 
 
 Botany, definition of, 4. 
 Bread-making, 148. 
 Bread mold, 149-151. 
 Breathing in plants and animals, 69. 
 Budding of yeast, 146, Fig. 74. 
 Buds, 53. 
 
 of yeast, 146. 
 Bud-scales, 53. 
 Bud-scale scars, 55. 
 Bulbs, 108. 
 Bumblebees, 81. 
 Burbank, Luther, 122. 
 Burdock, 93. 
 Burs, 93. 
 
 Cabbage, 127. 
 
 Calyx, 71, 79, 88. 
 
 Cambium, 46, 51, 63. 
 
 Camphor, 129. ' 
 
 Capsule of moss, 164. 
 
 Carbohydrates, meaning of, 13, 14. 
 
 composition, 13, 14. 
 
 manufacture of, 24, 60, 69. 
 Carbon, 6. 
 Carbon dioxid, 7, 8. 
 
 in air, 11. 
 
 necessary for starch manufacture, 
 23. 
 
 formed in growing plants, 68. 
 
 formed by yeast, 147. 
 Castor bean seedling, Fig. 44. 
 
 201 
 
202 
 
 INDEX 
 
 Cauliflower, 127. 
 
 Cell-body, 28, 29. 
 
 Cell division, 30. 
 
 Cell-nucleus, 28, 29. 
 
 Cell-sap, 30. 
 
 Cells of plants, 27, 29, Figs. 6, 7. 
 
 definition, 30. 
 
 osmosis in, 34. 
 Cellulose, 29. 
 Cell-wall, 28, 29. 
 Central cylinder of roots, 39. 
 Charts, price-list of, 175-176. 
 Chemicals, price-list of, 176-177. 
 Cherries, 96. 
 Chestnut, fruits, Fig. 39. 
 
 leaf, Fig. 20, B. 
 Chlorophyll, 23, 28, 51, 60, 62, Fig. 
 
 22. 
 
 Chlorophyll bands, 167, Fig. 85. 
 Chocolate, 129, Fig. 63. 
 Cider, 148. 
 Cilia, 140, Fig. 71. 
 Cinchona, 129. 
 Citranges, 122. 
 
 Classification of plants, 154-170. 
 Clay, 110. 
 Coal, 133. 
 
 Coal period, forests of, Fig. 65. 
 Coccus form of bacteria, Fig. 71, A. 
 Cocklebur, 93. 
 Cocoa, 129, Fig. 63. 
 Coffee, 129, Fig. 61. 
 Colony of bacteria, 142, Fig. 71, A. 
 Compound, definition of, 12. 
 Compound leaf, 56. 
 Conditions essential for plant growth, 
 
 108-114. 
 
 Conjugation in spirogyra, 168. 
 Conservation of forests, 138. 
 Consumption, due to bacteria, 145. 
 Corn, cross-pollination, 85. 
 Corn grain, 95, 128. 
 Corn grains, 101. 
 
 nutrients stored in, 104. 
 
 use of endosperm of, 104. 
 Corn production in U. S., 119. 
 Corn seedling, 100. 
 Corn stalk, 47, 49, 50. 
 Corn "tassels," 87, Fig. 33. 
 
 Corn ears, 88. 
 
 silk, 88. 
 
 Corolla, 71, 79, 88. 
 Cortex of roots, 39. 
 Cotton, 130-132. 
 Cotyledon, 98, 101. 
 Crops, valuable, of N. Y. State, 122, 
 
 Fig. 58. 
 Crossing, artificial, of related species, 
 
 120. 
 Cross-pollination, 79. 
 
 by bumblebees, 81. 
 
 in pansy, 82-84. 
 
 by insects, 86. 
 
 by wind, 87. 
 Cucumber fruit, 90. 
 Cultivation of soil, 113. 
 
 Dairy products of N. Y. State, 123. 
 Dandelion plant, Fig. 55. 
 Dangers to forests, 137. 
 Darwin, Charles, 82, 118, Fig. 54. 
 Deciduous trees and shrubs, 158. 
 Decomposition, result of action of 
 
 bacteria, 140. 
 Diastase, 36. 
 Dicotyledons, 160, 170. 
 Digestion, definition of, 37. 
 
 of starch, 37. 
 Digestive ferments, 38. 
 Diphtheria, due to bacteria, 145. 
 Directions for note-books, 185-186. 
 Disease-producing bacteria, 145. 
 Dispersal of seeds, 91. 
 Distillation, 147. 
 Distilled liquors, 148. 
 Division of cell, 30. 
 Drainage, 111, 114. 
 Drawings, in laboratory, 181, Figs. 
 
 90, 91. 
 Drugs, 130. 
 Dry fruits, 96. 
 Ducts, 45, 50, 62, Fig. 14. 
 
 Egg-cell, 77. 
 
 Element, definition of, 12. 
 
 Elm fruit, 92. 
 
 Elodea, 25, 28. Fig. 5. 
 
 Embryo, 77, 98, Fig. 29. 
 
INDEX 
 
 203 
 
 Endosperm, 101. 
 
 use of, 104. 
 Energy, definition, 64. 
 
 transformations of, 65. 
 
 liberation of, 66, 67. 
 
 source of, 66. 
 Epidermis, of root, 44, 62. 
 
 of stem, 51, 62. 
 
 of leaf, 56, 61, 62, Figs. 21, 22. 
 Equipment of laboratory, 171-177. 
 Erosion, as result of destruction of 
 
 forests, 137. 
 
 Essential organs, 71, 73. 
 Evergreen trees and shrubs, 158. 
 Excretion of water, 61. 
 Existence, struggle for, 114-119, Fig. 
 53. 
 
 Family, plant, 160, 170. 
 Fat, composition of, 14, 15. 
 
 test for, 19. 
 
 Fehling's solution, preparation of, 17. 
 Fermentation, 148. 
 Ferments, digestive, 38. 
 Ferns, 161-164, Figs. 82, 83. 
 Fertilization, 76, 77, 88. 
 
 of egg-cell in fern, 163. 
 Fertilized egg-cell, 77. 
 Fertilizers, 114. 
 
 Fiber-producing plants, 130-132. 
 Fibers, 47. 
 Fibrous bark, 46. 
 Filament, 71, 73, 88, Fig. 25. 
 Fippin, E. O., 123. 
 Fire, lanes, 139. 
 
 wardens, 139. 
 Flavoring extracts, 128. 
 Flavors of food, 145. 
 Flax, 130. 
 
 Fleshy fruits, 93, 96. 
 Floods, prevention of, 136. 
 Floral envelopes, 71, 72, 79, 88. 
 Flowers, 70-88. 
 
 tulip, 70-72. 
 
 gladiolus, 72-74. 
 
 pansy 79-82. 
 Food substances, list of 13. 
 
 manufacture by plants, 22, 60. 
 
 transfer of, 50. 
 
 Food substances, storage of, 61. 
 
 in corn grains, 104. . 
 Forest conservation, 138. 
 Forest fires, 134, 137, 139. 
 Forests, dangers to, 137. 
 Fronds of ferns, 161. 
 Frosts, loss of crops due to, 117. 
 Fruit, definition of, 94. 
 
 hybrid, 122. 
 
 stalk, 91, 92. 
 Fruits, 89-96. 
 Fuel, 133. 
 
 Functions of organs, 27. 
 Fungi, relation to human welfare, 
 
 139-153. 
 
 Fungous diseases, loss of crops due 
 to, 117. 
 
 Garden, tumbler, 102. 
 
 glass-plate, 102. 
 Generations, alternation of, in fern, 
 
 163. 
 
 Generative nucleus, 77. 
 Genus, plant, 160, 170. 
 Germination of pollen grains, 76. 
 Gladiolus, 72-74. 
 Glass-plate garden, 102. 
 Goddard, Miss Martha F., 193. 
 Grafting, 105-106. 
 Grapes, 129. 
 Grape sugar, composition of, 14, 15. 
 
 test for, 16. 
 
 osmosis of, 33. 
 Gravel, 110. 
 Grazing animals, a danger to young 
 
 trees, 137. 
 
 Growth of crystals, 2 (footnote). 
 Growth of living things, 2, 30. 
 Growth of plants, five essential con- 
 ditions for, 108. 
 Guard-cells of stoma, 58, 61, 62, Fig. 
 
 21. 
 Gymnosperms, 159, 170. 
 
 Harrow, 114, Fig. 51. 
 
 Hay crop of N. Y. State, 122. 
 
 Heat, energy, 64. 
 
 relation of, to soil, 112. 
 Hemp, 130, 145. 
 
204 
 
 INDEX 
 
 Herb, 156, Fig. 80. 
 
 High school education, value of, 124. 
 
 Hilum, 97. 
 
 Hixon, Miss Kate B., 191 (footnote). 
 
 Horse-chestnut, stem, 45, 52. 
 
 leaves, Fig. 20, K. 
 Human welfare, relation of plants to, 
 
 126-153. 
 Humus, 111. 
 Hybrid fruits, 122. 
 Hydrogen, 9. 
 Hyphse of molds, 150. 
 Hypocotyl, 98. 
 
 Improvement of plants by man, 119- 
 
 125, Figs. 57, 59. 
 Indigo, preparation of, 145. 
 Insects, a danger to forests, 137. 
 
 loss of crops due to, 117. 
 Iodine solution, preparation, 15. 
 Irrigation, 111. 
 
 Jute, 145. 
 
 Kerosene, 133. 
 
 King, Dr. C. A., 102 (footnote). 
 
 Kupfer, Miss Elsie M. (footnote), 27. 
 
 Laboratory equipment, 171-177. 
 
 table, 171. 
 Lateral buds, 53. 
 Layer, 106. 
 Leaflets, 56. 
 Leaf scars, 53. 
 Leaf-stalk, 55. 
 Leaves, arrangement of, 52. 
 
 Structure of, 55. 
 Lenticels, 51, 55, 62. 
 Lettuce, 127. 
 
 Life-history of a seed-plant, 195. 
 Lifeless things, characteristics of, 1. 
 Lilac leaf, Fig. 20, A. 
 Lime water, preparation of, 5. 
 Linden fruit, 91. 
 Linen, preparation of, 145. 
 Living things, characteristics of, 1. 
 Lumber, 133. 
 
 Lumbering, wrong method of, Fig. 67. 
 right method of, Fig. 68. 
 
 Malt, 148. 
 
 Mann, Paul B., 66 (footnote). 
 
 Maple, fruit, 91. 
 
 sugar, 136. 
 Medicines, 129-130. 
 Medullary rays, 47, 50, Fig. 17. 
 Mesophyll, 57, 60. 
 Micropyle, 76, 98, Fig. 29. 
 Milkweed fruit and seeds, 92, Fig. 36. 
 Mineral matter, test for, 20. 
 Mixture, definition of, 12. 
 Moisture, relation to germination and 
 
 growth, 108-109. 
 Mold, bread, 149-151, Fig. 75. 
 
 vegetable, 111. 
 
 Monocotyledons, 159, 160, 170. 
 Mosses, 164-166, Fig. 84. 
 
 moss plant, 164. 
 
 protonema, 164. 
 Mushrooms, 151, Fig. 76. 
 
 Nectar, 80. 
 
 Nitric acid, test for protein, 18. 
 
 Nitrogen, 11. 
 
 Note-books in biology, 181-187. 
 
 Nucleus, 28, 29. 
 
 Nutrition, in fungi, 150. 
 
 in green plants that produce seeds, 
 
 194. 
 Nutritive hyphse, 150. 
 
 organs of plants, 39. 
 
 Oak, wood, 46. 
 
 leaves, Fig. 20, C, G. 
 
 tree, amount of evaporation from 
 
 136. 
 
 Opium, 129. 
 
 Opposite arrangement, 52. 
 Orange crop, 120-122. 
 Order of topics, 178-180. 
 Organs, of a plant, 27. 
 
 nutritive, 39. 
 Osmosis, 32-38. 
 
 water, 33. 
 
 of grape sugar, 33. 
 
 in living cells, 34. 
 
 of starch, 35. 
 
 definition and applications, 35. 
 
 protein, 37. 
 
INDEX 
 
 205 
 
 Osmosis, in root-hairs, 44. 
 Ovary, 72, 73, 81, 88. 
 Ovules, 72, 74. 
 Oxidation, definition of, 13. 
 
 liberation of energy by, 66. 
 
 relation of oxygen and carbon 
 
 dioxid to, 67. 
 Oxygen, 6. 
 
 given off by green plants in sun- 
 light, 25. 
 
 supply of, for animals, 25. 
 
 necessity of, for growth, 67. 
 
 Palmately compound, 56. 
 Pansy, 79-82. 
 
 Darwin's experiments with, 82-84. 
 Parsnips, 127, 156. 
 Peaches, 96, 128. 
 Pea, flower, Fig. 35. 
 
 fruit, 89, Figs. 35, 43. 
 Peppermint, 129. 
 Perennials, 158. 
 Petals, 71, 79, 88. 
 Pinnately compound, 56. 
 Pistil, 71, 73, 81, 88, Figs. 24, 28. 
 Pistillate flowers, 87, Figs. 32, B, 34. 
 Pith, 46, 47, 63. 
 Pith rays, 47, 63. 
 Placenta, 89. 
 Plant, family, 160, 170. 
 
 genus, 160, 170. 
 
 species, 161, 170. 
 
 variety, 161, 170. 
 Plants, parts of, 26-31. 
 
 organs and functions, 27. 
 
 microscopic structure, 27. 
 
 cells, 27. 
 
 nutritive organs, 39. 
 Pleurococcus, 169, Fig. 86. 
 Plow, 113, Fig. 50. 
 Plumule, 98. 
 Pollen, 71, 73, Fig. 26. 
 Pollen tubes, 75, Figs. 26, 27. 
 Pollination, 74, 76, 88. 
 Pond scum, 166. 
 Poppy, 129. 
 
 Potato crop of N. Y. State, 122. 
 Potatoes, 107, 127, Fig. 49. 
 Preparations for laboratory, 175. 
 
 Prevention of self-pollination, 84-85. 
 Primary root, 100. 
 Protection of forests, 138-139. 
 Protein, use of term, 13 (footnote). 
 
 composition of, 14, 15. 
 
 test for, 18. 
 
 manufacture of, 24, 61. 
 
 osmosis, 37. 
 
 Prothallus of fern, 162, Fig. 83. 
 Protonema of moss, 164. 
 Protoplasm, 30. 
 Prudden, Dr. T. M., 142. 
 Pumpkin, cross-pollination, 85. 
 
 Quartered oak, 47. 
 Quinine, 129. 
 
 Radiometer, 66 (footnote). 
 Rainfall, regulation of, 136. 
 Raspberry fruits, Fig. 40. 
 Reference books, list of, suggested, 
 
 197-199. 
 Reforesting, 138. 
 Repair of living things, 2. 
 Reproduction, of living things, 3. 
 
 in plants, 70-96. 
 
 Reproductive hyphse of molds, 150. 
 Respiration, definition, 68, 69. 
 Review topics in plant biology, 188- 
 
 196. 
 
 Rhizoids of ferns, 163, Fig. 83, Y7. 
 Rhizome of fern, 162, Fig. 82. 
 Rind, 47. 
 Root-hairs, 40, Figs. 11, 12, 13. 
 
 osmosis in, 44. 
 Roots, structure of, 39-41. 
 
 functions of, 41-43. 
 
 primary, 100. 
 
 secondary, 100. 
 
 aerial, 102. 
 Root-tip, 40. 
 Root-tubercles, 144, Fig. 72. 
 
 bacteria in, Fig. 73. 
 Rotation of crops, 124. 
 Runner, 106. 
 Rusts, 152. 
 
 Sand, 110. 
 Sap, of cell, 30. 
 
206 
 
 INDEX 
 
 Sap, path through roots, 42, 43. 
 
 path through stem, 48, 49. 
 
 path through leaves, 59. 
 Schleiden and Schwann, 29. 
 Science and its subdivisions, 3. 
 Scion, 105. 
 Sea weeds, 169. 
 Secondary root, 100. 
 Seed-coat, 98. 
 Seed-dispersal, 91-94. 
 Seed-leaves, 98. 
 
 Seedlings, comparison of, 103-104. 
 Seed-producing plants, 159161. 
 Seeds, 72, 74, 77, 97-105. 
 
 numbers, produced by plants, 115. 
 Selection, artificial, 119. 
 Self-pollination, 79. 
 
 prevention of, 84-86. 
 Sepals, 71, 79, 88. 
 Sexual generation, in fern, 163. 
 
 in moss, 164, 166. 
 Sheath leaf, 100. 
 Shrub, 156, Fig. 79. 
 Sieve tubes, 50, 62, Fig. 16. 
 Slip, 106. 
 
 Smuts, 152-153, Fig. 77. 
 Soil, 110-114. 
 
 moisture of 111. 
 
 air in, 111. 
 
 heat, relation of soil to, 112. 
 
 cultivation of, 113. 
 Soil water, absorption of, 41. 
 
 transmission of, 42, 48, 58. 
 Sorus of fern, 162, Fig. 82. 
 Source of energy, 66. 
 Species, plant, 161, 170. 
 Spermaries of fern, 163. 
 Sperm-cells of fern, 163. 
 Sperm nucleus, 77, Figs. 27, 28, 29. 
 Spirillum form of bacteria, Fig. 71, D, 
 Spirogyra, 167, Fig. 85. 
 Spore-cases, of mold, 150. 
 
 of ferns, 162, Figs. 82, 83. 
 Spore formation in bacteria, 143, 
 
 Fig. 71, D. 
 
 Spore-producing plants, 161-170. 
 Spores, of mold, 150. 
 
 of ferns, 162, Figs. 82, 83. 
 Spur, 80. 
 
 Squash, cross-pollination, 86, Fig. 32. 
 Squash, seedling, Fig. 45. 
 Stamens, 71, 72, 80, 88, Fig. 24. 
 Staminate flowers, 87, Figs. 32, A, 33. 
 Starch, composition of, 13, 15. 
 
 test for, 15. 
 
 manufacture in sunlight, 22. 
 
 manufacture by different kinds of 
 leaves, 22 (footnote). 
 
 manufacture by chlorophyll, 23. 
 
 digestion of, 36, 37. 
 Stems, structure, 45-48. 
 
 functions of, 4851. 
 
 changes during growth, 51. 
 Stickers, 93. 
 
 Stigma, 72, 73, 81, 88, Fig. 25. 
 Stipules, 56. 
 Stock, 105. 
 
 Stoma, 58, 60, 61, 62, Figs. 21, 22. 
 Stone fruits, 96. 
 Storage of foods, 61. 
 Story of bacteria, 142 (footnote). 
 Strawberry, flower, Fig. 41. 
 
 fruit, Fig. 42. 
 
 plant, Fig. 48. 
 Struggle for existence among plants, 
 
 114-119, Fig. 53. 
 Style, 73, 81, 88. 
 Sugar cane, 127. 
 Sun, as source of energy, 66. 
 Sunlight, necessary for starch manu- 
 facture, 22. 
 Survival of the fittest, 118-119, Figs. 
 
 53, 55. 
 Sweet potato, 127, Fig. 60. 
 
 Tea, 129, Fig. 62. 
 Temperature, of soil, 112. 
 
 relation of, to germination and 
 
 growth, 109. 
 Terminal bud, 53. 
 Toadstools, 151. 
 Tokay grape fruit, 90. 
 Tomato fruit, 90. 
 Topics, order of, 178-180. 
 Transfer of food materials, 50, 62. 
 Transformations of energy, 65. 
 Tree, 154, Figs. 78, 79. 
 Tubers, 107. 
 
INDEX 
 
 207 
 
 Tufted fruits or seeds, 92. 
 
 Tulip, flower, 70-72. 
 
 Tumbler garden, 102. 
 
 Typhoid fever due to bacteria, 145. 
 
 Uses of plants, 127-132. 
 of forests, 132-137. 
 
 Variation among plants, 114, Fig. 52. 
 
 Variety, plant, 161, 170. 
 
 Vegetable crop of N. Y. State, 122. 
 
 Vegetable mold, 111. 
 
 Veins of leaf, 55. 
 
 Vinegar, preparation of, 145. 
 
 Wall, of cell, 28, 29. 
 
 of ovary, 72, 73. 
 
 Water, composition and preparation, 
 10. 
 
 test for, 20. 
 
 Water, osmosis of, 33. 
 
 given off from leaves, 59. 
 Webber, Dr. H. J., 120-122. 
 Wheat, 128. 
 
 seedling, Fig. 46. 
 Window box, 102. 
 Wine, 129, 148. 
 Winged fruits, 91. 
 Wood, 46. 
 
 Wood-cells, 43, 49, 63. 
 Woody bundles, 47, 50, Fig. 15. 
 
 Yeast, 146-149, Fig. 74. 
 reproduction of, 146. 
 buds, 146. 
 
 changes caused by, 147. 
 148. 
 
 Zoology, definition, 4. 
 Zygospores of spirogyra, 168 
 
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