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 3 S B-
 
 AGRONOMY 
 
 A COURSE IN PRACTICAL GARDENING 
 FOR HIGH SCHOOLS 
 
 BY 
 
 WILLARD NELSON CLUTE 
 
 AUTHOR OF "LABORATORY BOTANY FOR HIGH SCHOOLS," "FLORA OF THE 
 
 UPPER SUSQUEHANNA," "OUR FERNS IN THEIR HAUNTS," 
 
 "FERN ALLIES OF NORTH AMERICA," ETC. 
 
 GINN AND COMPANY 
 
 BOSTON NEW YORK CHICAGO LONDON
 
 COPYRIGHT, 1913, BY WILLARD NELSON CLUTE 
 
 ALL RIGHTS RESERVED 
 
 913.1 
 
 Cbe 
 
 GIXX AND COMPANY PRO- 
 PRIETORS BOSTON U.S.A.
 
 PREFACE 
 
 This book has been prepared to meet the needs of high 
 schools in cities and towns where agriculture is taught, and 
 in which the problems that confront the teacher are in some 
 respects different from those that come up in rural communi- 
 ties. The environment of the city child makes it undesirable 
 to emphasize in his case the growing of stock, the production 
 and care of milk, the breeding of animals, and the cultivation 
 of field crops. There is, however, much information of a 
 practical nature regarding the cultivation of plants which he 
 finds necessary for the fullest enjoyment of his surroundings. 
 Though not engaged in growing crops for a livelihood, he is, 
 nevertheless, interested in the cultivation of vegetables and 
 flowers, the making of lawns and their care, the planting of 
 shrubbery, the trimming of trees, and similar matters. In the 
 present volume it has been the aim, therefore, to develop the 
 subject of agriculture from the urban viewpoint, though 
 y* the matters discussed are fundamental to any system of cul- 
 S^ tivating plants and are as applicable to rural communities as 
 elsewhere. Furthermore, it is expected that the book will 
 ^ also serve as a practical guide to that part of the general 
 
 X)ublic which, though no longer in school, takes an interest 
 n the cultivation of plants in lawn, garden, and orchard. 
 >i\ Agronomy, as outlined in the following pages, is regarded 
 a division of agriculture coordinate with animal husbandry. 
 The latter division, though often included in books of this 
 kind, is as distinct from agronomy as zoology is from botany, 
 and has been omitted from this book partly because the sub- 
 ject of agronomy is alone sufficient for one semester's work, 
 
 v 
 
 442842
 
 vi AGRONOMY 
 
 and partly because city children are not brought much into 
 contact with farm animals. Animal husbandry may well be 
 taught as a separate course, and, if given in the semester fol- 
 lowing that in which agronomy is given, will afford the pupil 
 a year's continuous work in agriculture. The practical nature 
 of the matter here presented has been proved by several sea- 
 sons' work with classes in a large city high school. No direc- 
 tions for work have been given that have not been tried out 
 with such classes. 
 
 Agronomy differs from the usual botanical course of the 
 high school in that it is largely the practice of an art rather 
 than the study of a science. It seeks to make the student 
 physically proficient as well as mentally alert. Although 
 usually given after a course in botany, it is by nature an 
 excellent introduction to the more technical study, since it 
 enables the student to bring to bear upon it a considerable 
 first-hand knowledge of plants and plant habits. In the high- 
 school curriculum botany may be considered as existing for 
 the sake of the drill it gives in observation and deduction, 
 as well as for the information it affords, and it is therefore 
 proper that it should be based largely upon experiment. In 
 agronomy, however, experiment has a much smaller place. 
 The fundamentals have so long been a matter of common 
 knowledge that they need not be made the subjects for ex- 
 periment, though the possibility of proving any phase of the 
 work by this means should not be overlooked. 
 
 The course in agronomy here presented is designed to 
 cover a half year of work in the laboratory and school garden 
 and to be given in the spring semester. It is essentially an 
 outdoor course in doing things, with the culture, propagation, 
 and amelioration of plants as the central theme. It presup- 
 poses a school garden in which the pupil can carry out the 
 work of cultivating and training plants, and the chief end of 
 the course will be missed if this book is used merely as a
 
 PKEFACE vii 
 
 convenient source of material for recitations. Few schools are 
 so situated as to make the possession of a school garden abso- 
 lutely impossible. If the school grounds are not large enough, 
 a vacant lot in the vicinity may be secured by rent or pur- 
 chase, or the home garden of one of the pupils may be used. 
 Some successfully managed school gardens are ten minutes' 
 walk from the school building. Wherever located the garden 
 ought to be securely fenced against the depredations of the 
 small boy and other irresponsible folk, and a certain degree 
 of permanency should be secured for the plantings, if possi- 
 ble, since at least part of the plants grown will be perennials, 
 which improve with the years if left undisturbed. Whenever 
 practicable, the school garden should be a part of the school 
 property. 
 
 Classes seldom need to be encouraged to take an interest 
 in gardening, but the teacher should see to it that the work 
 is properly planned in advance, that time is allowed for culti- 
 vating the crops, and that such experiments are carried on in 
 the experimental plots as will deepen the interest and value 
 of the work to the student. The food, fiber, and drug plants 
 little known in the region may be grown, the many varieties 
 of common vegetables may be tested, and attractive flowers 
 cultivated. Room should also be found for growing all sorts 
 of aberrant plants that may be discovered by the class, such 
 as those possessing double flowers, fasciated stems, color varia- 
 tions, and variations in the cutting of leaves. As a general 
 thing, the crops planted should be such as mature before 
 school closes for the summer or which do not mature until 
 autumn. In the first group are lettuce, spinach, cress, radishes, 
 onions, and turnips ; in the second are carrots, parsnips, and 
 salsify. The many forms of radishes now offered by seeds- 
 men are excellent subjects for showing the great variation 
 that may occur in a single plant part. A few experiments 
 may be carried on for a series of years, especially such as
 
 viii AGRONOMY 
 
 pertain to the training of special shrubs, trees, and vines, and 
 the propagation or breeding of plants. The greatest success 
 attends a class in which each pupil is allotted space for an 
 individual garden, though two pupils may work in partner- 
 ship with good results. 
 
 Every effort should be made to have the student secure 
 first-hand information. A single visit to an implement store, 
 for instance, will give him more information of real value 
 than hours of recitation about implements which he has never 
 seen or examined. For the same reason frequent field trips 
 to parks, market gardens, nurseries, greenhouses, public gar- 
 dens, and the like should be made. These trips should, if 
 possible, be taken in the hours allotted to agronomy in the 
 school day and should be counted as part of the regular 
 work. In many cases the period for this study may come 
 last in the day's program, thus allowing pupils to take as 
 much additional time for the work after school as they desire. 
 There is always a tendency on the part of the teacher to 
 assume more knowledge of familiar things than the student 
 possesses, and for this reason it is well to carry out all the 
 exercises suggested, though at first glance some may appear 
 too simple to be worth while. 
 
 To the end that the pupils be made conversant with the 
 literature of the subject, they should be encouraged to con- 
 sult the reference works named at the end of each chapter, as 
 well as more general works such as Bailey's " Cyclopedia of 
 American Horticulture " and " Cyclopedia of American Agri- 
 culture." Each student should also be encouraged to write 
 to the national government for such publications on plants 
 as may interest him. Upon application, the Superintendent 
 of Documents, Government Printing Office, Washington, D. C., 
 will send a list of publications to which a price is attached, 
 and the Editor and Chief of the Division of Publications, 
 Department of Agriculture, will send a monthly list of free
 
 PEEFACE ix 
 
 publications. In the case of the more expensive publications 
 the pupil's representative in Congress or his senator may se- 
 cure them free. The publications of his own state agricul- 
 tural experiment station will also be most useful, and those 
 of other states may often be obtained. All available pamphlets 
 of the kind should, of course, be in the school library. It is 
 often possible to secure enough duplicates of the more impor- 
 tant publications to allow one for each member of the class. 
 The pupils should also be supplied with the catalogues of 
 reliable seedsmen and growers of nursery stock. These may 
 usually be had upon request, and the writing of a letter for 
 this purpose may well be made a part of the class work. 
 
 At the time the work in agronomy is begun the weather 
 is not likely to be favorable for work in the open, but there 
 are, fortunately, many matters of theory and fact that may 
 be discussed in the classroom before the season for gardening 
 begins, and some of the experiments may also be performed. 
 The book has been arranged, as far as practicable, to follow 
 the progress of the seasons, but in the early weeks of the 
 course the theoretical may overshadow the practical, and mat- 
 ters may be discussed that will not be taken up in a practical 
 way until much later. By looking ahead and selecting those 
 exercises that may be performed as well at one time as at 
 another, the student will be enabled to approach the real 
 work of the course with considerable theoretical knowledge 
 that can be tested later by practice. 
 
 One cannot deal intelligently with plants without knowing 
 their names and relationships, and it is recommended that the 
 identification of plants by the use of a good manual of botany 
 be made part of the course. For this work the strictly tech- 
 nical manuals are better than the more popular volumes, since 
 they not only give the names but teach exactness, increase the 
 vocabulary, and familiarize the pupil with the use of scientific 
 keys. The small preliminary instruction needed for the use of
 
 such a manual may be given in the early part of the course, 
 thus preparing the student to name the flowers as fast as they 
 appear. 
 
 It is not easy to overestimate the value of all sorts of col- 
 lections for use in connection with agronomy. The accumula- 
 tion of striking objects with which to illustrate the course is, 
 however, not a matter of a single year, for the specimens must 
 be secured a few at a time as they are found. Soil maps, typ- 
 ical fungi, seed collections, samples of soils and fertilizers, 
 mineral specimens and pictures of unusual crops, specimen 
 plants, and unfamiliar farming operations all add to the attrac- 
 tiveness and interest of the course. If the school does not 
 possess a museum in which these may be kept, they should be 
 carefully preserved in the laboratory or classroom. 
 
 In most cases specific directions for performing an experi- 
 ment or for carrying on the other work of the course have 
 been omitted from this book, since the conditions in different 
 schools are likely to vary, and the teacher will naturally prefer 
 to work these out to fit his own local conditions. Indeed, in 
 many instances, the planning of the work may be left to the 
 student. No doubt mistakes will be made, but one may learn 
 much from his mistakes. If the pupils have not had an earlier 
 course in botany, or if it is desired to go deeper into the sub- 
 ject of the organization of the plant than is here presented, 
 the author's " Laboratory Botany for the High School " may 
 be found useful. 
 
 The sources of the illustrations in this volume are for the 
 most part indicated in connection with the illustrations them- 
 selves, but the author takes this opportunity to acknowledge 
 his indebtedness to the Bateman Manufacturing Company, 
 Greenloch, New Jersey ; Wagner's Park Conservatories, Sid- 
 ney, Ohio ; The Lord and Burnham Company, New York ; and 
 S. L. Allen, Philadelphia, for the loan of photographs and 
 other material. Several illustrations that originally appeared
 
 PREFACE xi 
 
 in Duggar's " Fungous Diseases of Plants " and Bergen and 
 Caldwell's " Practical Botany " have been secured through 
 the kindness of the authors of these books. Other drawings 
 in the book are the work of the author's pupils, and the data 
 for the tables of precipitation were supplied by Mr. F. M. 
 Muhlig, United States weather observer at Joliet. The author 
 is especially indebted to his friends, Mr. A. T. Weaver of the 
 American Steel and Wire Company and Mr. Mark Bennitt of 
 the H. L. Hollister Land Company, Chicago, for the use of 
 numerous excellent photographs, and to them, as well as to 
 the others mentioned, he extends his sincere thanks. 
 
 For a careful reading of the entire proof and for many help- 
 ful suggestions in connection therewith, the author is under 
 deep obligations to his colleague, Professor E. F. Downey of 
 the Flower Technical High School, Chicago; to Professor Grant 
 Smith, Chicago Teachers' College ; and to Professor John 
 H. Schaffner, head of the department of botany, Ohio State 
 University. To his failure to adopt in some instances the sug- 
 gestions made, must be attributed such errors as may be de- 
 tected. By far the larger number of drawings in the book are 
 the work of the author's wife, Ida Martin Clute, and to her 
 he is further indebted for invaluable assistance in preparing 
 the text and in correcting the proofs. 
 
 WILLARD N. CLUTE 
 JOLIET, ILLINOIS
 
 CONTENTS 
 
 CHAPTER I. A LESSON IN CHEMISTRY . . ...... 1 
 
 Chemical elements. Atoms and molecules. Chemical formulas. 
 Chemical compounds. Distribution of the elements. Elements found 
 in plants. Potassium. Sodium. Magnesium. Calcium. Aluminum. 
 Iron. Manganese. Oxygen. Hydrogen. Nitrogen. Chlorine. 
 Carbon. Phosphorus. Sulphur. Silicon. Practical exercises. 
 
 CHAPTER II. ORIGIN OF THE SOIL .......... 11 
 
 What the soil is. Depth of the soil. The subsoil. Origin of the soil 
 and subsoil. Weathering. Weathering by decomposition. Weather- 
 ing by disintegration. Work of glaciers. Modifications of the bed 
 rock. Table of rocks. Changes in mantle rock. Practical exercises. 
 
 CHAPTER III. TYPES OF SOILS ........... 25 
 
 Named for their origin. Sedentary soils. Lacustrine soils, 
 soils. Volcanic soils. Colluvial soils. Glacial soils. Alluvial soils. 
 Soil constituents. Sand and clay contrasted. Loam. Alkali soils. 
 Acid soils. A test for acid soils. Artificial soils. Practical exercises. 
 
 CHAPTER IV. CONDITIONS AFFECTING SOIL FERTILITY . 38 
 
 Structure. The air. Air in the soil. Temperature. Variations in 
 temperature. Other factors that modify temperatures. The Fahren- 
 heit and centigrade scales. Precipitation. Water in the soil. The 
 water table. Drainage. Irrigation. Dry farming. Physiologically 
 dry soils. Practical exercises. 
 
 CHAPTER V. THE ORGANIZATION OF THE PLANT .... 55 
 
 The great plant groups. The regions of the plant. Cellular structure 
 of the plant. Roots. Taproots. Structure of the root. Root hairs. 
 Osmosis. The stem. Structure of the stem. Buds. Leaves. Internal 
 structure of the leaf. Formation of plant food. Transpiration. 
 The flower. Pollination. The fruit. The seed. Life cycle of plants. 
 The rest period of plants. Genera, species, and varieties. Scientific 
 names. Practical exercises. 
 
 xiii
 
 xiv AGRONOMY 
 
 PAGE 
 
 CHAPTER VI. THE ELEMENTS NEEDED BY PLANTS ... 95 
 
 Source of the elements. Selective absorption. Use of water to the 
 plant. Root pressure. Carbon dioxide. Nitrogen. Calcium and 
 magnesium. Potassium and phosphorus. Sulphur and iron. Chlorine, 
 silicon, and others. Practical exercises. 
 
 CHAPTER VII. FERTILIZERS 101 
 
 The available mineral in the soil. Toxic substances in the soil. Ele- 
 ments that may be lacking. Sources of the needed elements. Manures. 
 Green manures. Nitrification. Bacteria and nitrification. Nitrogen 
 fixation. Mycorrhizas. Soil inoculation. Denitrifying bacteria. 
 - Harmful organisms in the soil. Limiting factors in plant growth. 
 Practical exercises. 
 
 CHAPTER VIII. THE PLANT IN RELATION TO TEMPERA- 
 TURE, LIGHT, AND MOISTURE 113 
 
 Growth temperature. Hardy and tender plants. Cardinal points. 
 Acclimatization. Frost. Locality and frost. How cold kills plants. 
 Other effects of cold. How plants avoid the effects of cold. Artifi- 
 cial protection from the cold. Treatment of frostbitten plants. 
 Effects of heat. Protection from heat. Need of light. Effects of 
 lack of light. Blanching. Protection from light. Effects of over- 
 watering. Time to water. Effects of lack of water. Water and 
 plant forms. Practical exercises. 
 
 CHAPTER IX. GARDEN MAKING 129 
 
 Location of the garden. Preparing the soil. The garden plan. How 
 to plant. When to plant. Autumn seed bed. Germination. Seed test- 
 ing. Double cropping. Transplanting. Inducing plants to fruit. 
 Thinning. Labels. Saving seed. Seed packets. Practical exercises. 
 
 CHAPTER X. TILLAGE 149 
 
 Need for tillage. Pulverizing the soil. Mulches. Work of earth- 
 worms and ants. Rotation of crops. Practical exercises. 
 
 CHAPTER XI. FORCING AND RETARDING PLANTS .... 157 
 
 Nature of the process. Retarding. Greenhouses and hothouses. Hot- 
 beds. Cold frames. Forcing single hills. Etherization. Forcing 
 plants in the window garden. Practical exercises. 
 
 CHAPTER XII. WEEDS 164 
 
 Definition of a weed. Harmfulness of weeds. Nature of weeds. 
 Eradicating weeds. Purslane. Spreading amaranth. Green ama- 
 ranth. Tumbleweed. Pigweed. Russian thistle. Spotted spurge.
 
 CONTENTS xv 
 
 PAGE 
 
 Dandelion. Plantain. Common bindweed. Black bindweed. Prickly 
 lettuce. Ragweed. Wild mustard. Oxeye daisy. Canada thistle. 
 Quack grass. Crab grass. Foxtail. Old witch grass. Buttercup. 
 Wild carrot. Sorrel. Other weeds. Practical exercises. 
 
 CHAPTER XIII. PROPAGATION 181 
 
 Natural methods. Typical forms for propagation. Artificial propaga- 
 tion. Cuttings. Hardwood cuttings. Layering. The sand box. Bud- 
 ding. Method of budding. Grafting. Different forms of grafting. 
 Inarching. Graf ting wax. Effect of stock on cion. Practical exercises. 
 
 CHAPTER XIV. DECORATIVE PLANTING 197 
 
 Purpose. Lawn making. Paths and lawn planting. Care of the 
 lawn. The border. Arrangement of the plants. Shrubs for winter 
 effects. Naming the shrubs and trees. Herbaceous plants. Arrange- 
 . ment of herbaceous perennials. Hedges. Bulbs. Carpet bedding. 
 Formal planting. Transplanting shrubs and trees. Transplanting 
 herbaceous perennials. Mulching and heeling in. Treatment of 
 woodlands. Enemies of the forest. Practical exercises. 
 
 CHAPTEIl XV. PRUNING .......... . . . . 215 
 
 Purpose of pruning. Time to prune. Pruning implements. Methods 
 of pruning. Making the cut. Specimens needing little pruning. 
 Pruning special crops. Thinning. Heading in. Root pruning. Gir- 
 dling. Cavities and broken limbs. Topiary work. Practical exercises. 
 
 CHAPTER XVI. PLANT DISEASES 230 
 
 Origin. Number of plant diseases. Rots. Wilts. Blights. Leaf spot. 
 Molds and mildews. Smuts. Rusts. Wound parasites. Other plant 
 diseases. Sprays and spraying. Bordeaux mixture. Lime-sulphur 
 wash. Ammoniacal copper carbonate. Potassium sulphide solution.' 
 Preventive measures. Practical exercises. 
 
 CHAPTER XVII. INSECT PESTS 245 
 
 How insects injure plants. Metamorphoses of insects. Forms of 
 insects that cause injury. Cutworms. Cabbage worm. Currant 
 worm. Tomato worm. Corn-ear worm. Tent caterpillar. Codlin 
 moth. Curculio. Cankerworms. Borers. Elm-leaf beetle. Cucumber 
 beetle. Blister beetles. Potato beetle. May beetles. Plant lice, or 
 aphids. Squash bug. Mealy bug. Scale insects. Preventing attacks 
 of insects. Poisons for chewing insects. Remedies against sucking 
 insects. Spray pumps. Other aids in fighting insects. Practical 
 exercises.
 
 xvi AGRONOMY 
 
 PAGE 
 
 CHAPTER XVIII. PLANT BREEDING 258 
 
 Need for breeding. Basis for breeding. Inducing variation. Hybrids 
 and hybridizing. Producing the cross. Mendel's law. Selection. 
 Roguing. Xenia. Parthenogenesis. Practical exercises. 
 
 CHAPTER XIX. THE ORIGIN OF SPECIES 272 
 
 Evolution. Struggle for existence. Natural selection. Results of 
 variation. Darwinian theory. Mutation theory. Practical exercises. 
 
 CHAPTER XX. OUR CULTIVATED PLANTS 277 
 
 Origin. Edible parts of plants. Root crops. Leaf crops. The 
 legumes. Solanaceous fruits. Gourd fruits. The grasses. Bush 
 fruits. Tree fruits New fruits. Practical exercises. 
 
 APPENDIX 
 
 SEVENTY-FIVE SHRUBS USEFUL FOR PLANTING 285 
 
 FIFTEEN WOODY VINES DESIRABLE FOR ARBORS AND PORCHES . 288 
 FIFTY DESIRABLE HERBACEOUS PERENNIALS 289 
 
 INDEX . . 291
 
 AGKONOMY 
 
 CHAPTER I 
 
 A LESSON IN CHEMISTRY 
 
 Chemical elements. The earth's crust, the animals and 
 plants upon it, and the multitude of substances with which 
 we are familiar are composed of a small number of simpler 
 forms of matter, known as chemical elements, combined in 
 various ways. A chemical element may be denned as a sub- 
 stance that has not been resolved into simpler substances, and 
 as thus defined there are only about eighty chemical elements 
 in the world. Gold may be taken as an illustration. Though 
 it be divided into particles too small to be visible in the 
 microscope, or heated until it becomes liquid, or subjected to 
 strong currents of electricity, it is still gold and nothing else. 
 A few chemical elements may be found " native," that is, 
 uncombined with others, but usually two or more unite to 
 form chemical compounds. By far the larger number are always 
 found thus combined. Oxygen may be cited as a familiar 
 example of an element that exists both free and combined. 
 As a free gas it forms about one fifth of the air we breathe ; 
 combined with other elements it makes up about half of the 
 water and rock of the earth's crust. Chemical elements are 
 often grouped as metals and nonmetals, the metals being 
 greatly in the majority. Usually the metals may be distin- 
 guished by names ending in urn. The difference between a 
 metal and a nonmetal, however, is not easily defined. A 
 metal is supposed to have the following properties: it must 
 
 1
 
 exist as a solid and have a metallic luster, must be capable 
 of conducting heat and electricity, must be opaque, hard, 
 malleable, ductile, and capable of forming compounds with 
 oxygen. Probably no single metal has all these properties, 
 but no substance would be accepted as a metal that did not 
 possess many of them. Iron, nickel, copper, and mercury are 
 among the more familiar metals. Carbon, sulphur, and phos- 
 phorus may be named as examples of the nonmetals. Theo- 
 retically, at least, each chemical element may exist as a solid, 
 a liquid, or a gas, but many have not yet been produced in all 
 three of these conditions. Increasing the temperature will 
 make many of the ordinary solids liquid, and the reverse of 
 this process, combined with pressure, serves to liquefy even 
 the lightest gases. Water, while not a chemical element, will 
 serve to illustrate this change of state. In its more familiar 
 form it is a liquid, but if heated to 21 2 F. it becomes a 
 gas, and if cooled below 32 F. it becomes a solid. 
 
 Atoms and molecules. An atom is the smallest part of a 
 chemical element that can enter into combination with other 
 parts. Atoms may therefore be said to be the units of which 
 more complex compounds are built. Not very much is known 
 regarding the size of atoms, but they are estimated to be 
 about one hundred-millionth of an inch in diameter and to 
 bear about the same relation to the size of a tennis ball that 
 the latter bears to the earth. Atoms usually do not long 
 exist as such, but combine with other atoms to form molecules, 
 which are the smallest enduring particles of a compound, just 
 as the atoms are the smallest part of a chemical element. All 
 the atoms of a single chemical element are exactly alike, 
 otherwise it would not be a chemical element. 
 
 Chemical formulas. Atoms have the same relation to chemi- 
 cal compounds that letters have to words, and the chemist is 
 therefore able to write a definite formula for the molecule of 
 every substance. Each element has its own chemical symbol,
 
 A LESSON IX CHEMISTRY 
 
 usually the initial of its name, as C for carbon and P for 
 phosphorus. When the initial is duplicated in the list of 
 symbols, one more distinguishing letter may be added, as 
 Ca for calcium and Pt for platinum. Occasionally an element 
 may be given the initial of an older name, as in the case of K 
 for potassium, where the initial stands for kalium. Iron has 
 the symbol Fe, derived from ferntm. The student familiar 
 with the names of the elements readily recognizes the kinds 
 of atoms that form a given compound when its formula is 
 read. When more than one atom of a kind enters into the 
 combination, the number is written below the line and im- 
 mediately following the symbol. Thus the formula CO 2 , 
 representing a molecule of carbon dioxide, is seen to consist of 
 one atom of carbon united with two atoms of oxygen. The 
 molecule of water is written H 2 O. In this two atoms of 
 
 TABLE OF THE MORE COMMON CHEMICAL ELEMENTS 
 
 X A M 1 . 
 
 SYMBOL 
 
 NAME 
 
 SYMBOL 
 
 Aluminum 
 
 Al 
 
 Lead (plumbum) 
 
 Pb 
 
 Antimony (stibium) 
 
 8b 
 
 Lithium 
 
 Li 
 
 Argon 
 
 A 
 
 Magnesium .... 
 
 Mg 
 
 Arsenic 
 
 As 
 
 Manganese 
 
 Mn 
 
 Barium 
 
 Ba 
 
 Mercury (Jiydrur<iyruin) 
 
 Hff 
 
 Bismuth .... 
 
 Bi 
 
 Nickel . ... 
 
 Ni 
 
 Boron 
 
 B 
 
 Nitrogen 
 
 N 
 
 Bromine 
 
 Br 
 
 Oxygen ... 
 
 o 
 
 Calcium 
 
 Ca 
 
 Phosphorus 
 
 P 
 
 Carbon 
 
 c 
 
 Platinum . ... 
 
 Pt 
 
 Chlorine . 
 
 Cl 
 
 Potassium (kalium) 
 
 K 
 
 Cobalt . . 
 
 Co 
 
 Silicon ... 
 
 Si 
 
 Copper (cuprum) 
 Fluorine . . . . 
 
 Cu 
 F 
 
 Silver (aryentum) 
 Sodium (natrittnt) 
 
 Ag 
 Xa 
 
 Gold (ciurutn) 
 
 Au 
 
 Sulphur 
 
 s 
 
 Hydrogen 
 
 H 
 
 Tin (fttannum) 
 
 Sn 
 
 Iodine 
 
 I 
 
 Tungsten (icolfram) 
 
 w 
 
 Iron (ferrum) 
 
 Fe 
 
 Zinc 
 
 Zn 
 
 
 

 
 4 AGRONOMY 
 
 hydrogen are joined to one of oxygen. When symbols in 
 parenthesis are followed by a number written below the line, 
 as Ca(NO g ) 2 , it signifies that the elements and quantities in 
 parenthesis are to be multiplied by the number so written. 
 Calcium phosphate (Ca g (PO 4 ) 2 ) would also be correctly 
 written CaP O . 
 
 m m m 
 
 Chemical compounds. When salt and sand, or charcoal and 
 sulphur, are stirred up together, the result is a mere mechan- 
 ical mixture. In a chemical compound an entirely new sub- 
 stance is formed, which may possess characteristics quite unlike 
 those of the combining elements. Under certain conditions 
 charcoal and sulphur may be made to form a chemical union 
 in which two atoms of sulphur join with one of carbon to pro- 
 duce carbon disulphide (CS 2 ). Sulphur, as everybody knows, 
 is a yellow solid and carbon a black solid, but the carbon 
 disulphide formed by their union is neither black, yellow, nor 
 a solid, but is a colorless liquid resembling water. Moreover, 
 while either pure carbon or sulphur may be eaten without 
 harm, when they are chemically combined they form a deadly 
 poisonous liquid, which, exposed to the air, soon turns to a 
 heavy, suffocating, and highly inflammable gas. Again, when 
 carbon is burned in the air, as in ordinary wood and coal fires, 
 one atom of carbon unites with two of oxygen and forms a 
 colorless, suffocating gas known as carbon dioxide (CO 2 ). In 
 a similar way sulphur may be burned to form sulphur dioxide 
 (SO 2 ). Calcium carbide, from which acetylene gas is produced, 
 is another union of carbon and is represented by the formula 
 CaC 2 . It is interesting to note that all the chemical elements 
 unite with others in definite and unvarying proportions. No 
 matter how much oxygen may be present when carbon is 
 burned, the molecule of carbon dioxide formed always consists 
 of two atoms of oxygen and one of carbon. Carbon, however, 
 may be made to form other combinations with oxygen. When 
 there is a lack of oxygen, carbon monoxide (CO) may be
 
 A LESSON IN CHEMISTRY 5 
 
 formed. Some elements, oxygen and carbon for instance, 
 readily combine with a great many others, while some, like 
 nitrogen and argon, are called inert, and only with difficulty 
 can be made to unite with others. In chemical reactions heat 
 is often evolved. A good illustration of this is seen in the 
 heat that results from the union of oxygen and carbon when 
 wood or coal is burned, or when water is added to quicklime 
 in the process of making mortar. 
 
 Distribution of the elements. The different elements are very 
 unequally distributed. Some, like radium, are found in very 
 minute quantities and always in combination with other ele- 
 ments, while others may form vast deposits which are nearly 
 pure. Only about forty of the elements are at all common, 
 while but five of these form 96 per cent of the planet on which 
 we live. These five in the order of their abundance are oxygen, 
 silicon, aluminum, iron, and calcium. Since the soil consists 
 of particles from many kinds of rocks, it contains a consider- 
 able number of chemical elements, but only sixteen that are 
 at all abundant, namely, oxygen, silicon, carbon, sulphur, 
 hydrogen, chlorine, phosphorus, fluorine, aluminum, calcium, 
 magnesium, potassium, sodium, iron, manganese, and barium. 
 
 Elements found in plants. Fifteen of the sixteen common 
 chemical elements in the soil are found in plants. Of these, 
 seven are metals and eight are nonmetals. In the first group 
 are potassium, sodium, magnesium, calcium, aluminum, iron, 
 and manganic ; in the second are oxygen, hydrogen, nitrogen, 
 chlorine, ctwHh? phosphorus, sulphur, and silicon. Several of 
 these are not regarded as essential to plant growth, as is also 
 true of lithium, zinc, copper, boron, and fluorine, which are 
 occasionally found in plants in certain regions. Some of the 
 characteristics of the fifteen elements usually found in plants 
 are given below. 
 
 Potassium (K) is a soft white metal, lighter than water. It 
 quickly oxidizes or unites with oxygen when exposed to the
 
 6 
 
 air, and must be kept in oil or other substances that do not 
 contain oxygen. It does not occur in the free state, but is 
 always combined with other elements, as carbonates, sulphates, 
 silicates, and chlorides. Potash is an oxide of potassium, and 
 feldspar and mica consist largely of this element. Potassium 
 is present in the ash of all plants, is found most abundantly 
 in the growing parts, and is essential to plant life. 
 
 Sodium (Na) is a soft, waxy, lustrous white metal much like 
 potassium in appearance and always occurs combined with 
 other elements. It oxidizes even in water and must be kept 
 in fluids lacking oxygen. Its various combinations are abun- 
 dant in the rocks. Sodium chloride (XaCl) is rock salt. What 
 we commonly call soda is an oxide or carbonate of sodium. 
 Chile saltpeter, or nitrate of soda, is largely used as a fertilizer. 
 Sodium, while usually found in plants, is known to be non- 
 essential, though it may take the place of potassium in neutral- 
 izing some of the acids formed in them. The chemical symbol is 
 taken from natrium, the name by which it was formerly known. 
 
 Magnesium (Mg) is a light, silvery white, moderately hard 
 metal which is malleable but not very tenacious. It is not 
 found native, but forms many compounds. It is permanent in 
 dry air, but tarnishes in the presence of moisture. Burned in 
 oxygen, it produces a blinding light and forms magnesium 
 oxide (MgO), or magnesia. Dolomite and asbestos contain 
 much magnesium, and Epsom salts is the sulphate of this 
 element. Magnesium is found in most parts of^jre plant, but 
 less abundantly than calcium, except in tll9rtiRs, where it 
 is usually more abundant. 
 
 Calcium (Ca) is a pale yellow, malleable, ductile, but some- 
 what brittle, metal. It is widely distributed, but never free. 
 It is the chief element in marbles, limestones, and dolomites. 
 Limestone is calcium carbonate (CaCO 3 ), and when carbon diox- 
 ide is driven off by burning, quicklime (CaO), which is used 
 in plastering, is left. Gypsum is calcium sulphate (CaSO 4 ).
 
 A LESSON IN CHEMISTRY 7 
 
 Plaster of Paris is derived from gypsum by burning. The rock 
 called apatite contains large amounts of calcium phosphate. 
 Calcium is one of the elements essential to plant life. It is 
 posed to neutralize the acids that would otherwise injure the 
 plant, as well as to play an important part in the production 
 of new tissues. Some plants, such as clover, beans, and peas, 
 are often called lime plants because they require so much of 
 this element for their proper development. 
 
 Aluminum (Al) is another of the white metals that is never 
 found native, though it is the principal constituent of every 
 clay bank and forms one twelfth of the earth's crust. It is 
 malleable and ductile and does not oxidize in the air. Clays 
 and feldspars are silicates of aluminum, and the ruby, emerald, 
 oriental amethyst, and sapphire are crystalline forms of the 
 same metal combined with oxygen. Corundum, or emery, is 
 an impure crystalline form. Though the metal itself is soft, 
 the crystalline forms are exceeded in hardness by the diamond 
 only. Alum is a combination of sulphur and potassium with 
 aluminum. Aluminum is usually found in plants, though it 
 forms no part of the plant food. 
 
 Iron (Fe) is too well known to need description. It is abun- 
 dant and widely distributed, occurring usually as carbonates 
 and oxides. It is an ingredient in practically all soils and 
 forms about one fifteenth of the earth's crust. Iron rust 
 and the ochers are oxides of iron, and it is these substances 
 which give^^e red and yellow colors to certain soils. Iron 
 is essentiaMBfcplants. Its presence is necessary for the 
 formation of chlorophyll, the green color of plants, though, 
 so far as known, it does not enter into the composition of 
 the color. 
 
 Manganese (Mn) is a hard, grayish-white metal that is fused 
 with difficulty, but readily oxidizes. While often found in 
 plants, it has been proved that it is not necessary to their 
 growth.
 
 8 
 
 Oxygen (0) at ordinary temperatures is a colorless, odor- 
 less gas. It is the most abundant of the elements, forming as 
 it does one fifth of the air, eight ninths of the water, and 
 about one half of the rocks and soil. It combines with a great 
 number of other elements, forming oxides, and is necessary 
 for all ordinary combustion and for the respiration of animals 
 and plants. With hydrogen and carbon it forms the carbo- 
 hydrates, of which the greater part of the plant body consists. 
 Iron and other metals burn in pure oxygen. 
 
 Hydrogen (H) is a colorless, tasteless, and odorless gas, and 
 is the lightest substance known. It does not occur free, but 
 is most abundant combined with oxygen in the form of water. 
 It burns with a blue flame and is a constituent of all acids. 
 Hydrogen and oxygen, if mixed at ordinary temperatures, 
 will remain a mere mixture, but if heated or ignited they 
 combine with a violent explosion and form water. 
 
 Nitrogen (N) is a heavy, inert, colorless, tasteless, odorless 
 gas that occurs free in the air, of which it forms about four 
 fifths. It is extremely inert, does not support combustion, nor 
 readily enter into combination with other elements. It is four- 
 teen times as heavy as hydrogen, and without it the air would 
 have little weight, birds could not fly, and the sails of ships 
 and windmills would be practically useless. Nitrogen also 
 serves to dilute the oxygen in the air; otherwise oxidation 
 in our bodies would proceed so rapidly as to be harmful. 
 Ammonia gas is largely nitrogen, and gunpoj^ler, guncot- 
 ton, and nitroglycerin owe their effectivenes^JRhe fact that 
 these are unstable compounds containing this element. Nitro- 
 gen does not exist in the mineral matter of the earth, though 
 the soil is the source of most of this element used by plants. 
 Here it- exists largely in the form of nitrates derived from the 
 decaying organic matter. Nitrogen is necessary to the formation 
 of proteins and is an essential constituent of the protoplasm of 
 all animals and plants.
 
 A LESSON IN CHEMISTRY 9 
 
 Chlorine (Cl) is a heavy, yellow-green, poisonous gas, with a 
 disagreeable, suffocating odor. It is never found free, but is 
 widely distributed in nature in compounds, the most familiar 
 of which is common salt (NaCl). Chlorine apparently takes 
 no part in the life processes of plants, but is common in the 
 compounds used by them. 
 
 Carbon (C) is a black solid, familiar to us in charcoal and 
 mineral coal. Graphite, or black lead, used in pencils, is 
 another form of this element. The diamond, the hardest sub- 
 stance known, is a crystalline form of carbon. Peat and muck 
 are impure forms. Carbon has never been liquefied, but it 
 may be turned to a gas at very high temperatures ; many of 
 its compounds are gases or liquids at ordinary temperatures. 
 When carbon unites with oxygen, heat and light result. In 
 slow combustion, such as that in our bodies, no light is pro- 
 duced, but the amount of heat that finally results is the 
 same as if the substances burned more rapidly. The carbon 
 so abundant in plants is not derived from the soil, but from 
 the small quantity of carbon dioxide in the air. Carbon is 
 believed to occur in more different compounds than any 
 other element. 
 
 Phosphorus (P) is a pale yellow, poisonous substance about 
 as soft as wax and has a disagreeable odor. It does not occur 
 native, but in such combinations as phosphates of lime and 
 aluminum it is present in large quantities in many rocks. 
 It burns with a yellow-white light when exposed to the air, 
 and must be kept under water in the laboratory. Phosphorus 
 is a necessary constituent of the nucleus of plant and animal 
 cells and is also found in considerable abundance in seeds. 
 
 Sulphur (S) is a yellow substance occurring native or com- 
 bined with various elements, as sulphates and sulphides. It 
 melts readily, and burns with a bluish flame and suffocating 
 odor, producing sulphur dioxide (SO 2 ). Sulphur is an essen- 
 tial element in all plant and animal bodies.
 
 10 AGRONOMY 
 
 Silicon (Si) when pure consists of lustrous brown or black 
 crystals, but it does not exist in nature uncombincd. Xext to 
 oxygen it is the most widely distributed of the elements and 
 forms one fourth of the earth's crust. In combination with 
 oxygen, silicon forms the clear and glasslike mineral quartz 
 (SiO 2 ), and is thus the principal element in sand. From 60 
 to 90 per cent of most soils is quartz. 
 
 PRACTICAL EXERCISES 
 
 1. Look over the list of chemical elements given on page 3 and 
 name those possessed by the class in the shape of jewelry, coins, etc. 
 
 2. Make a list of these and of the others that may be found in the 
 schoolroom. 
 
 3. Visit the chemistry department of the school, or the nearest drug 
 store, and list any other uncombined elements that you may find. 
 
 4. In the laboratory, by appropriate experiments, make carbon diox- 
 ide, sulphur dioxide, magnesium oxide, etc. 
 
 5. Pick out the chemical elements in the following combinations : 
 orthoclase(KAlSi 3 O 8 ),carnallite(KClMgCl 2 6H 2 O), common salt(XaCl), 
 Epsom salts (MgSO 4 ), copperas (FeSO 4 ), nitric acid (HXO 3 ). 
 
 6. Burn a piece of limestone to drive off the CO 2 , leaving quicklime 
 (CaO). Add water to a piece of quicklime to make calcium hydroxide 
 and note the heat developed by the chemical reaction. 
 
 7. Boil some water in a Florence flask and watch the space above the 
 boiling water. What is the color of the gas (steam)? 
 
 8. Watch the bubbles of gas rising from any water plant when in 
 sunlight. Catch some of it by sinking a short-stemmed glass funnel 
 into the water over the plants, with the stem just below the surface, 
 and inverting over it a test tube filled with water. The gas will rise 
 and displace the water in the tube and may be tested with a glowing 
 splinter. 
 
 References 
 
 Hopkins, " Soil Fertility and Permanent Agriculture." 
 Snyder. "Chemistry of Plant and Animal Life."
 
 CHAPTER II 
 
 ORIGIN OF THE SOIL 
 
 What the soil is. All ordinary plants are rooted in the soil, 
 which serves them as a source of food materials and affords a 
 convenient place of anchorage. The soil, however, is far from 
 being the simple collection of rock fragments that it is often 
 supposed to be. Fragments of rock are important, to be sure, 
 and in ordinary soils form from 60 to 95 per cent of their 
 weight ; but any good agricultural soil must contain, in addi- 
 tion, air, water, humus, bacteria, and similar organisms. So 
 important are all of these that none can be omitted without 
 impairing the fertility of the land. From the rock fragments 
 come all the minerals used by plants. These are steadily, 
 though very slowly, dissolved out by the soil water and carried 
 in solution into the plant. The humus, formed of decaying 
 plant and animal remains, is the principal source of the all- 
 important nitrogen ; but since the plants cannot use it as 
 humus, it must first be worked over into nitrates by the 
 bacteria. The higher plants are so dependent upon the good 
 offices of the bacteria in this respect that if the latter should 
 all disappear from the soil, crops would soon be unable to 
 grow in it. The air in the soil is required for the activities 
 of the bacteria, as well as for the respiration of the under- 
 ground parts of the plants. 
 
 Depth of the soil. The soil ranges from a few inches to many 
 feet in depth. In humid regions that is, in regions of abun- 
 dant rainfall the decaying humus gives it a darker color and 
 enables us to distinguish it from the underlying materials ; but 
 in arid regions, where the rainfall is scanty, the humus is 
 
 11
 
 12 AGRONOMY 
 
 destroyed almost as fast as made, and no such difference in 
 color may be seen except in the occasional low, wet lands. 
 The soil in arid lands, however, is often more fertile than that 
 of humid regions and can be cultivated to a greater depth. 
 This is mainly because the scanty rainfall has not washed out 
 and carried away the food materials in it. Such soils need 
 only to be irrigated to give abundant crops. 
 
 The subsoil. The soil is commonly regarded as extending 
 downward as far as traces of organic matter or humus are 
 found. In humid regions this is from a few inches to several 
 feet. Below this is the subsoil, lighter in color, more compact, 
 and consisting almost entirely of rock fragments. It is there- 
 fore little adapted to growing crops, though rich in the mate- 
 rials needed by plants. While not of itself able to produce 
 good crops, it forms a storehouse of food materials upon which 
 the plant can draw, and, slowly breaking down under the at- 
 tacks of wind and weather, gradually becomes part of the 
 soil itself. 
 
 Origin of the soil and subsoil. If one digs down far enough 
 anywhere on the earth, he comes at last to the solid rock. 
 This is called bed rock. Here and there it comes to the sur- 
 face, forming outcrops, such as may be seen in the cliffs of 
 broken country or where a rapid stream has carved out a 
 deep valley. Usually, however, it is buried under a thick 
 deposit of rock fragments, called mantle rock, which has been 
 derived from the bed rock in various ways. Sections of man- 
 tle rock may be seen in railway cuts, gravel pits, brickyards, 
 and the openings for quarries and mines. Since the bed rocks 
 range from soft and porous sandstones and limestones to 
 compact and flinty granites, the mantle rock may differ in 
 composition according to the locality, and the soil derived 
 from the mantle rock necessarily partakes of the same char- 
 acteristics. Soils derived directly from the underlying bed 
 rock are known as residual or sedentary soils ; those brought
 
 ORIGIN OF THE SOIL 13 
 
 Jrom a distance by running water or other means are called 
 drift or transported soils. 
 
 Weathering. The agencies that have served to break up the 
 bed rock into mantle rock and the mantle rock into soil are 
 grouped under the general title of weathering agencies. Two 
 phases of weathering may be distinguished, namely, weather- 
 ing by decomposition and weathering by disintegration. The 
 first is largely a chemical process in which some or all of 
 
 FIG. 1. An outcrop of limestone showing weathering 
 
 the minerals in the rock are resolved into their simpler com- 
 pounds, resulting in very fine particles ; the second is largely 
 a mechanical or grinding process and the resulting particles 
 are usually larger. 
 
 Weathering by decomposition. Air and water are the chief 
 elements that are effective in decomposition. The oxygen in 
 the air readily enters into combination with other elements in 
 the rocks and soon tears down the surface layers exposed to 
 it, forming new compounds. Results of this process are seen 
 in the rusting of iron and the dulling of nearly all surfaces 
 exposed to the air for any length of time. In the quarry we
 
 14 AGRONOMY 
 
 readily distinguish the newly quarried blocks from older ones, 
 by their fresh look. The carbon dioxide in the air unites with 
 water to form carbonic acid, and this also attacks various 
 elements in the rocks and tears them from their compounds. 
 
 Water breaks up the rocks by dissolving out the more 
 soluble compounds. Pure water wears the rock very slowly, 
 but when it contains, as it often does, carbon dioxide or 
 other acids derived from the humus or the roots of plants. 
 
 FIG. 2. Underground channel in limestone made by water, Joliet, Illinois 
 A portion of the rock has heen dissolved and carried away 
 
 it is a most powerful agent in weathering. Limestones, espe- 
 cially, are quickly dissolved by such means, and the occur- 
 rence of caves and underground channels in these rocks is 
 thus explained. Here and there water charged with dissolved 
 minerals may come to the surface and we then have min- 
 eral springs. Sandstones, though usually more enduring than 
 limestones, are often rapidly disintegrated by having the ma- 
 terials which bind the sand grains together dissolved. Rain 
 water usually contains small amounts of ammonia and nitric 
 acid, and these, like the carbonic acid, are active in dissolving
 
 OEIGIN OF THE SOIL 
 
 15 
 
 the rocks. The weathering effects of water are not confined 
 to a layer near the surface, as in decomposition by the air, 
 but extend downward as far as the water can penetrate. 
 
 Photograph by H. L. Hollister Land Co. 
 
 FIG. 3. A deep valley in Colorado, excavated mainly by running water 
 
 Not only does the water dissolve the rocks, but it carries 
 the dissolved materials away to be deposited elsewhere when 
 the water evaporates, thus building up in one place what it 
 tears down in another. In this way the stalactites and stalag- 
 mites found in limestone caves are formed, and our beds of 
 rock salt, gypsum, and bog irons are due to the same process.
 
 16 
 
 AGRONOMY 
 
 A cubic mile of ordinary river water has been estimated to 
 contain about a quarter of a million tons of rock constituents. 
 It is not difficult to understand, then, that in many soils formed 
 by the decomposition of limestone rock, a layer of limestone 
 nearly a hundred feet thick may have been removed for every 
 
 Photograph by II. L. Ilollister Land Co. 
 
 FIG. 4. Twin Falls, Idaho 
 
 Here the Snake River has worn a channel hundreds of feet deep in 
 hard igneous rock 
 
 foot of soil left. In contrast to this, water, under certain con- 
 ditions, instead of decreasing the bulk of the soil in weathering, 
 may actually increase it by entering in combination with some 
 of the elements in the rocks. Thus granitic rocks in turning 
 to arable soil may be increased in bulk more than 80 per cent. 
 Weathering by disintegration. By disintegration the rocks 
 are broken up into small pieces like the original rock and 
 suffer little, if any, chemical change. In this process heat,
 
 OKIGIN OF THE SOIL 
 
 17 
 
 cold, and gravity, and water influenced by these forces, are 
 the important agents. Variations in temperature have a 
 greater effect in weathering than is commonly supposed. 
 Under the rays of the noonday sun, exposed rocks rapidly 
 rise in temperature and expand; at night they as rapidly 
 cool and contract. This alternate heating and cooling is 
 
 Photograph by II. L. llollister Land Co. 
 
 FIG. 5. A crest in the Rocky Mountains showing rock fragments 
 split off by alternating heat and cold 
 
 frequently sufficient to cause the splitting off of large flakes 
 weighing many pounds, with reports like pistol shots. The 
 different minerals in the rocks have their own rate of expan- 
 sion and contraction, and if these varying movements under 
 changes of temperature do not cause the actual splitting off 
 of particles of rock, they leave minute openings between 
 them into which water may penetrate and begin its work of 
 dissolution. Changes of temperature have little effect upon
 
 18 AGRONOMY 
 
 rocks that are not exposed, but the great banks of irregular 
 fragments at the base of cliffs show how rapidly the work of 
 tearing down the solid rock goes on under favorable condi- 
 tions. When water is present in the rocks the lowering of 
 the temperature below the freezing point causes weathering to 
 progress still more rapidly, since the expansive force of water 
 in freezing is equal to the weight of a column of ice a mile 
 
 Photograph by E. Vickers 
 
 FIG. 6. A hard portion of a rocky ledge 
 The softer parts have been carried away by the stream 
 
 high, or about 150 tons to the square foot. Most rocks go to 
 pieces rapidly under alternate freezing and thawing. Even 
 polished granite soon deteriorates in severe climates through 
 the freezing of water that finds its way between the crystals 
 in the rock. The obelisk known as Cleopatra's Needle, which 
 resisted the atmosphere of Egypt for many centuries, began 
 to deteriorate at once when removed to the latitude of New 
 York, and had to be protected. When pieces of the rock 
 have been chipped off by the cold and carried to the base 
 of a cliff by gravity, running water may carry them for
 
 OEIGIN OF THE SOIL 19 
 
 long distances, dragging them over the bed rock, grinding 
 them against other pieces, and rapidly reducing them in size, 
 the finer particles being carried away by the current and 
 deposited elsewhere. Waterworn pebbles are easily recog- 
 nized by their rounded surfaces, and the fine sand and clay 
 
 Photozraph by II. L. Ilollister Land Co. 
 
 FIG. 7. A mountainous region showing the weathered crests and 
 snow-filled valleys 
 
 to be found in every shallow are but deposits of rock dust 
 ground from the pebbles by the streams. 
 
 It is not alone the particles of rock in the stream beds 
 that are carried away by running water. During every heavy 
 rain the torrents of muddy water running away from culti- 
 vated fields show how rapidly the most fertile parts are be- 
 ing removed. When the current slackens, this material is 
 dropped, the largest particles first, the smallest much later. 
 The latter often continue suspended in the water for days.
 
 20 AGRONOMY 
 
 The delta at the mouth of many large rivers is made up of 
 these finer particles, and consequently delta soils are among 
 the most fertile in the world. 
 
 Work of glaciers. Another most effective agent in grinding 
 up the bed rock, but one that is no longer active in our coun- 
 try, was the great ice sheet that ages ago spread from colder 
 regions southward over a large part of North America. One 
 or perhaps several of these extended their movements to cen- 
 tral Pennsylvania and the Ohio River valley, and westward 
 nearly to the Rocky Mountains. In the northern part of the 
 United States the ice sheet was a mile or more thick and 
 moved over the country with irresistible force, breaking off 
 great fragments of rock as it went, and now advancing with 
 a cold season, now retreating with a warm one, ground the 
 immense rocks to bowlders, the bowlders to pebbles, the peb- 
 bles to sand, and the sand to powder. The interior of Green- 
 land is still covered with such an ice sheet, and similar 
 accumulations of ice in the form of glaciers are found in 
 Switzerland, the Rocky Mountains, and other elevated parts 
 of the world, where the process of grinding up the bed rock 
 in this way may still be witnessed. Upon the final retreat of 
 the ice sheet the country over which it moved was left strewn 
 with vast deposits of rock fragments, and these, sometimes 
 intermingled, sometimes sorted out by running water into 
 beds of clay, sand, and gravel and thrown up into hills and 
 ridges, between which were many small lakes and marshes, 
 cover much of the country in the northeastern states. The 
 topography of a glaciated country is quickly recognized by 
 the geological student. 
 
 Modifications of the bed rock. It is believed that not only 
 has the mantle rock been derived from the bed rock by 
 processes already noted, but that much of the bed rock itself 
 was originally formed from harder rock that was first weath- 
 ered into small particles and later consolidated by various
 
 ORIGIN OF THE SOIL 21 
 
 forces. The rocks from which all the other rocks are sup- 
 posed to have been derived are called igneous rocks. They 
 are hard and compact, and include the granites, diorites, ba- 
 salts, and lavas. Usually they are found deep in the earth 
 and are buried under not only many feet of mantle rock but 
 of other bed rocks as well. Rocks derived from the igneous 
 
 Photograph by II. L. Hollister Land Co. 
 
 FIG. 8. Glacier-covered slope in the Rocky Mountains 
 Note the banks of rock fragments which have been carried down by the ice 
 
 rocks are called sedimentary, or aqueous, rocks because they are 
 regarded as having first been laid down in the bottom of shal- 
 low lakes or seas as beds of mud, sand, or gravel, and later 
 compacted into rock. Limestones, sandstones, and shales are 
 some of the better-known sedimentary rocks. Some of the 
 sedimentary rocks have been subjected to great heat and 
 pressure since their formation, thus altering their structure. 
 Such rocks are called metamorphic rocks. Slates, marbles,
 
 22 AGRONOMY 
 
 and quartzites are good illustrations of metamorphic rocks. 
 By consulting the following table the student should have 
 no difficulty in discovering to which group the rocks in 
 his own region belong. 
 
 TABLE OF ROCKS 
 I. IGNEOUS. 
 
 1. Granite. 
 
 2. Basalt. 
 
 3. Diorite. 
 
 4. Lava. 
 
 II. SEDIMENTARY, 01: A^rF.ors. 
 
 A. Inorganic. 
 
 1. Argillaceous shale (formed from clay). 
 
 2. Silicious. 
 
 a. Sandstone (formed from sand). 
 
 I. Conglomerate (formed from pebbles). 
 
 c. Breccias (formed from irregular fragments). 
 
 3. Chemical bog iron, rock salt, gypsum. 
 R. Organic. 
 
 1. Calcareous limestone (formed from animal remains). 
 
 2. Carbonaceous soft coals (formed from plants). 
 
 3. Silicious diatom earth, chert. 
 
 III. METAMORPHIC. 
 
 1. Slate (derived from shale). 
 
 2. Quartzite (derived from sandstone). 
 
 3. Marble (derived from limestone). 
 
 4. Anthracite (derived from soft coals). 
 
 Changes in mantle rock. The weathered fragments of the 
 bed rock have not lain undisturbed where they fell. The 
 work of weathering is unceasing. Little by little the parti- 
 cles have been reduced in size ; running water has sorted 
 them over time and again ; floods from the melting ice sheet 
 have spread them out; ants, earthworms, and other animals 
 have slowly turned them over, bringing deeper layers to the
 
 ORIGIN OF THE SOIL 23 
 
 surface; generation after generation of plants have grown 
 in the debris, and, dying, have left their remains to enrich 
 the deposit ; bacteria, the smallest of living things, have 
 here found a congenial home and have added their share to 
 
 FIG. 9. A glaciated valley in southern New York 
 Note the irregular surface 
 
 the cycle of changes ; thus have the ragged fragments of rock 
 that in the beginning were unable to support the growth of 
 plants been turned into the rich and fertile soil in which 
 are grown the luxuriant crops upon which the very life of 
 man depends.
 
 24 AGRONOMY 
 
 PRACTICAL EXERCISES 
 
 1. In the school garden measure the depth of the soil by making an 
 opening down to the subsoil. Compare this as to depth with any other 
 soil sections with which you are familiar. 
 
 2. Ascertain from wells, railway cuts, trenches for sewers, and the 
 like the average depth of the mantle rock in your vicinity. 
 
 3. If the mantle rock varies in depth in your locality, make a table 
 to show this. 
 
 4. Make a collection of specimens to illustrate the kinds of rock in 
 the table on page 22. 
 
 5. Make a list of the different kinds of bed rock in your vicinity. 
 
 6. Visit a gravel pit and collect as many different kinds of rock 
 fragments as possible. 
 
 7. Make a list of all the above-mentioned fragments that are unlike 
 the bed rock in your region. 
 
 8. Visit the best farm or garden in the vicinity and decide whether 
 the soil is a sedentary or a transported one. 
 
 9. Visit the nearest outcrop of rock and search for signs of weath- 
 ering. Make a list of all forms seen. Decide which is more effective 
 in that place. 
 
 10. Make a similar visit to a field on a hillside. 
 
 11. Account for differences in the color of the soil on hilltops and 
 in lowlands. In which are the crops best ? Why ? 
 
 References 
 
 Dryer, "Lessons in Physical Geography." 
 Gilbert and Brigham, "Physical Geography." 
 King, "The Soil." 
 Salisbury, "Physiography."
 
 Named for their origin. Soils, as we have seen, may be 
 divided into residual and drift soils, depending upon whether 
 they have originated from the underlying rocks or have been 
 transported from distant regions by water and other agencies. 
 
 FIG. 10. Vegetation invading a shallow lake 
 
 It is possible, also, to name the soils from the agencies most 
 active in forming them, and the principal groups thus natu- 
 rally break up into smaller divisions. The residual soils may be 
 divided into the true sedimentary and the lacustrine, while drift 
 soils include the aeolian, volcanic, colluvial, glacial, and alluvial. 
 
 25
 
 26 
 
 AGRONOMY 
 
 Photograph from Amer.cau stttl auil Wire Co. 
 
 FIG. 11. A small pond nearly filled with aquatic vegetation 
 
 Sedentary soils. Sedentary soils are formed from the under- 
 lying rock, either by decomposition, disintegration, or In ;i 
 combination of both. In limestone regions the soluble part 
 of the rock may be carried away by the water, leaving a soil
 
 TYPES OF SOILS 
 
 27 
 
 quite unlike one made from limestone fragments. Such soils 
 may actually need to have lime added to them to enable them 
 to produce good crops. Sandstone rocks are formed of grains 
 of sand cemented together by lime, clay, iron, or silica. When 
 the cementing material is dissolved out by water, a sandy soil 
 is left. Other residual soils may be formed from weathered 
 fragments of the original rock from which little has been car- 
 ried away by water, as in many soils derived from granite rocks. 
 
 FIG. 12. A moving sand dune 
 
 Photograph by A. B. Klugh 
 
 Lacustrine soils. These differ from true residual soils in 
 having been built up in lakes and ponds by an accumulation of 
 plant and animal remains, together with fine particles of rock 
 brought in by rains or blown in by wind. In our Northern states 
 many of what were once shallow lakes have been completely 
 filled in this way and now contain a rich black soil much valued 
 for growing certain crops, such as celery. Such soils, however, 
 often lack some of the minerals needed by plants, and these 
 have to be supplied before good crops can be produced.
 
 28 
 
 AGRONOMY 
 
 soils. These have been transported by wind. Sand 
 dunes are familiar examples. Less well known, though more 
 important, are the deposits of wind-blown materials known as 
 loess that cover large areas in China, Europe, and parts of the 
 Middle West. Loess is composed of particles much finer than 
 sand grains and makes very fertile soils. Parts of Iowa and 
 Kansas are covered with loess to the depth of hundreds of feet. 
 
 Photograph by A. B. Klugh 
 
 FIG. 13. A sand dune captured by vegetation 
 
 Volcanic soils. As the name indicates, these are formed of 
 the ashes and dust thrown out by volcanoes. They are rare 
 in the United States except in the Far West, but in other 
 countries are often encountered. After weathering, they form 
 very fertile soils. Much of the land cultivated in the Hawaiian 
 Islands is of this type. 
 
 Colluvial soils. These have been formed by gravity acting 
 upon the pieces of rock quarried from the cliffs by changes of 
 temperature and freezing water. Good illustrations are found
 
 TYPES OF SOILS 
 
 29 
 
 in the banks of talus at the base of cliffs almost anywhere. 
 The soil brought down by avalanches also belongs to this 
 class. Since the materials that compose it are coarse, rough, 
 and irregular, a colluvial soil is of little value for cultivation, 
 though it may support a luxuriant growth of lichens, mosses, 
 ferns, and small shrubs. The soil on hillsides may also be 
 regarded as partly colluvial. 
 
 Glacial soils. Glacial soils have been derived from many 
 kinds of bed rock by the glacial ice that once covered a great 
 part of the northeast- 
 ern states and various 
 other parts of the earth. 
 They consist of sand, 
 clay, and gravels either 
 separate or intermin- 
 gled. Such soils are 
 the rule in the states 
 north of the Ohio River 
 and east of the Great 
 Plains, but south and 
 west they gradually 
 thin out and disappear. 
 
 Alluvial soils. These 
 
 FlO. 14. A ridge of glacial debris that has 
 have been transported b een sor ted by running water 
 
 by streams that during 
 
 periods of flood pick up much material that is dropped as soon 
 as the current slackens. The soil in our ordinary bottom lands 
 has been formed in this way, and the soil in the delta region 
 along the lower Mississippi is of the same nature. Alluvial 
 soils are extremely fertile, since they consist in great measure 
 of the richest soil washed down from other fields. 
 
 Soil constituents. Ordinary arable land is a mixture of 
 various ingredients. When these are separated, we know 
 them as sand, clay, silt, humus, and the like. Peat is a black
 
 30 
 
 AGRONOMY 
 
 deposit formed by the decay of plants under water, and may 
 be seen in the process of formation along the shores of many 
 lakes and ponds. It also occurs in extensive deposits called 
 peat bogs, which mark the site of old lakes that have been 
 filled by such accumulations. When pure, peat contains 
 enough carbon to make it useful as fuel. Most of our coal 
 
 beds have been 
 formed from peat. 
 ffumus, sometimes 
 called vegetable 
 mold or leaf mold, 
 is, like peat, formed 
 from plant remains, 
 but in this case the 
 decay has taken 
 place in or on the 
 soil. It is a black, 
 loose substance 
 usually abundant 
 on the forest floor 
 and ig an indispen- 
 
 FIG. 15. 
 
 Section of an abandoned quarry partly 
 tilled with water 
 
 The dark deposit at the top of the exposure is peat, 
 
 the light material below is marl, heneath this is the 
 
 mantle rock which merges into the bed rock 
 
 sable element in all 
 fertile soils. Muck 
 is a black deposit, 
 midway between 
 humus and peat, that occurs in swamps and low grounds. The 
 words " peat " and " muck " are often used rather loosely to 
 designate the same substance. Marl is a deposit of lime and 
 clay, like a whitish mud, which forms at the bottom of ponds. 
 The lime is derived from the decay of the shells and bones 
 of water animals. Marl is valued for adding to soils deficient 
 in lime. Clay is a soft powder or rock flour usually resulting 
 from the weathering of feldspar rocks. Clay consists of parti- 
 cles less than one five thousandth of a millimeter in diameter,
 
 TYPES OF SOILS 31 
 
 and a cubic foot of it weighs from seventy-five to eighty 
 pounds. Clay is powdery when dry, sticky when wet, and is 
 easily molded. Silt consists of particles somewhat coarser than 
 clay. They range in diameter from five thousandths to five 
 hundredths of a millimeter. When moist, silt becomes a soft 
 mud, and in drying inclines to crumble. Sand consists of loose 
 hard grains from five hundredths of a millimeter to one milli- 
 meter in diameter, resulting from the weathering of sandstones 
 and quartzes. The grains may be angular or rounded, but are 
 always harsh and granular to the touch. A cubic foot of sand 
 weighs from one hundred to one hundred ten pounds. Wet 
 sand is held together by the moisture ; when dry, the grains 
 at once fall apart. Crravel is a mixture of many kinds of rock 
 fragments and differs from sand chiefly in the size of the parti- 
 cles composing it. The smaller fragments are called pebbles ; 
 the larger, bowlders. Glacial pebbles are angular in shape. 
 When pebbles are rounded it is an indication that they have 
 been worked over by water. Gravel is usually accompanied 
 by varying amounts of sand and clay, and often forms rich 
 soils. Peat, muck, marl, and humus are all of organic origin ; 
 clay, silt, sand, and gravel are inorganic. The nature of the 
 soil greatly influences the plants that grow on it. This is shown 
 from the fact that plants on the same kind of soil in different 
 parts of the world resemble one another. 
 
 Sand and clay contrasted. The best soil for ordinary crops 
 is a mixture of clay, sand, silt, and humus. Owing to the 
 contrasting characters of clay and sand, the soil is heavy or 
 light, cold or warm, moist or dry, worked with difficulty or 
 easily worked, according to whether one or the other predom- 
 inates. Neither forms a good soil by itself, but intermingled 
 in various proportions they give a wide range of soils from 
 which the farmer and gardener can select one suited to the 
 crop he proposes to grow. Clay consists of the finest of soil 
 particles. It would require 400,000 of the smallest, side by
 
 32
 
 TYPES OF SOILS 33 
 
 side, to measure an inch. Clay is slow to absorb water, and its 
 reluctance in this- respect causes it to gully badly in heavy 
 storms. It is equally slow to give up moisture once absorbed. 
 The particles of wet clay cling together with great tenacity, 
 and as they dry they form a compact mass traversed by 
 numerous cracks, due to the shrinking of the mass as the 
 water evaporates. The total surface of the particles of clay 
 to which the water clings is very great. When thoroughly wet 
 it is able to hold much water, often as much as 40 per cent. 
 In wet weather, therefore, it may contain too much water for 
 good crops, while in dry weather it may bake and become too 
 hard for the roots of plants to penetrate. Owing to its great 
 water content, it warms slowly, but it cools as slowly, and in 
 autumn the vegetation lasts longest on the clays. Because of 
 the smallness of the particles composing clay, the air spaces are 
 correspondingly small. In consequence the air cannot move 
 through it freely and it is always poorly aerated in spite of 
 the fact that it contains a greater amount of pore space than 
 sand. Clay is the source of considerable plant food, mostly 
 potash, and it also fixes other plant foods that may be in the 
 soil. The farmer calls clay a cold and heavy soil, but the 
 heaviness refers to the difficulty with which it is worked, and 
 not to its weight, for it is much lighter than sand. 
 
 Sand consists of hard separate grains. These have little 
 tendency to stick together, even when wet, though in certain 
 positions, as on seabeaches, they may form a firm, hard sur- 
 face when saturated with water. Sand does not bake nor 
 crack, and in drying returns to the loosely granular form. It 
 absorbs water readily and as readily gives it up. It often con- 
 tains less than 5 per cent of water. Plants, however, can get 
 more of the contained moisture from sand than from clay. 
 Sand does not gully as badly as clay because it so rapidly 
 absorbs water. It warms up quickly and cools much more 
 rapidly than clay. Owing to its large air spaces, air moves
 
 34 AGRONOM V 
 
 through it readily. Sand contains very little plant food be- 
 cause this is so easily washed out by the rains. It is called a 
 light soil because it is so easily worked, though, bulk for 
 bulk, it is heavier than any other. The roots of plants pene- 
 trate sand without difficulty, but the readiness with which it 
 parts with its moisture renders it unsuitable for most crops. 
 Like clay, sand is of a variety of colors. Reds and yellows, due 
 to compounds of iron, are most abundant. 
 
 Loam. A soil containing about equal parts of sand and 
 clay with some humus is called loam. If the sand is in excess, 
 it is called a sandy loam ; if the clay predominates, it is a 
 clay loam. Other constituents in the soil may modify it suf- 
 ficiently to entitle it to some other designation, as silt loam or 
 gravelly loam. Clay soils have from 80 to 100 per cent of clay ; 
 clay loams, from 60 to 80 per cent. Sandy soils have from 
 80 to 100 per cent of sand ; sandy loams, from 60 to 80 per 
 cent. The national Department of Agriculture is at present 
 analyzing and mapping the soils of the United States. As 
 fast as mapped, each type of soil is given a name to distin- 
 guish it. This is usually derived from some town located 
 upon the soil indicated, as Hammond silt loam, Hagerstown 
 loam, and Miami sand. 
 
 Alkali soils. In various parts of the West the soils contain 
 an excess of the salts of sodium, magnesium, calcium, and potas- 
 sium, in which the ordinary cultivated plants will not grow. 
 Such soils are known as alkali soils. They usually occur 
 in regions deficient in rainfall, and the deposits are due to the 
 fact that the water from the scanty rains soon evaporates, leav- 
 ing on the surface the salts it has dissolved out of the soil. 
 Among these salts may be such familiar substances as common 
 table salt, Glauber and Epsom salts, and sal soda. Many 
 wild plants are not very sensitive to these salts and may 
 even thrive in such soils, but before the crops of the farmer 
 will grow, the alkali must be removed. In many soils this is
 
 TYPES OF SOILS 
 
 35 
 
 accomplished by flooding with water. In using this means care 
 must be taken to see that proper underdrainage is provided 
 by means of tiles, if the natural drainage is not sufficient. 
 
 Acid soils. Some soils will not support a good growth of 
 cultivated crops because of various acids left in them by the 
 decaying vegetation, which hinder the growth of the bacteria 
 necessary to turn the humus into available plant food. Such 
 soils are called acid, or sour, soils. Though not adapted to ordi- 
 nary crops, sour soils may support a luxuriant vegetation, and 
 some wild plants have become so accustomed to acid soils that 
 they will thrive in no 
 other. Among plants 
 of this kind may be 
 mentioned huckleber- 
 ries, cranberries, trail- 
 ing arbutus, and many 
 other plants of the heath 
 family. Most of the 
 plants found in peat 
 bogs are lovers of acid 
 soils. On the other 
 hand, clover, beans, 
 peas, and other legumes are very intolerant of such soils and 
 cannot live in them. Lettuce, beets, spinach, and timothy are 
 other plants that will not grow in sour soils. The majority of 
 sour soils are found in low and poorly drained districts, but 
 the proper combination of conditions will turn any soil acid, 
 and many upland soils are of this kind. The bird's-foot violet, 
 sorrel, and beard grass (Andropoyori) are regarded as indica- 
 tors of acid soils in uplands. When mosses grow on the lawn 
 or in the fields it is also a pretty sure indication of a sour soil. 
 
 A test for acid soils. To discover whether a given soil is 
 acid or not, make it into a tnin mortar with water and test 
 with blue litmus paper, or inclose a piece of the paper in a ball 
 
 FI<J. 17. A pitcher plant (Sarracenia), a char- 
 acteristic plant of acid soils
 
 36 AGRONOMY 
 
 of the moist soil for a few minutes. If the paper turns reel, the 
 soil is acid. Litmus paper may be found in any chemical 
 laboratory or at the nearest drug store. Blue litmus paper has 
 the property of turning red in the presence of acids, and red 
 litmus paper will turn blue in alkaline mediums. Acid soils are 
 easily neutralized by the application of lime, marl, or gypsum. 
 Artificial soils. The florist and gardener often find it expe- 
 dient to make artificial soils for their plants. Seedings and cut- 
 tings need a light and porous soil consisting largely of sand ; 
 ferns need a considerable proportion of humus. The grower, 
 therefore, usually obtains peat, sand, leaf mold, and other in- 
 gredients and mixes his soil to suit the needs of the plants. A 
 good potting soil for all ordinary plants is made by building up 
 a mound consisting of a layer of sods from any good soil, a layer 
 of sand, and a layer of stable manure ; then another layer of sods, 
 sand, and manure, and so on. This is allowed to stand until 
 the sods have decayed, after which it is thoroughly mixed and 
 is ready for use. 
 
 PRACTICAL EXERCISES 
 
 1. On a soil map of your region locate such types of sedimentary 
 and drift soils as occur. 
 
 2. What is the name of the soil upon which the school garden is 
 located ? your own home ? 
 
 3. Visit deposits of sand, clay, peat, marl, and humus and collect 
 good samples of each for study. 
 
 4. Weigh a cubic foot of soil from the school garden and estimate 
 the number .of tons in an acre 7 in. deep. 
 
 5. Test the soil in the .school garden and in your own garden for 
 acidity. Make the same test of the soil in the nearest peat bog. 
 
 6. Make a list of the more conspicuous plants in a peat bog. Com- 
 pare with a similar list from a meadow or pasture. 
 
 7. Pour ammonia water through a tube filled with powdered clay and 
 examine that which filters through. What has become of the ammonia ? 
 
 8. Measure out equal amounts of sand and clay and place in sepa- 
 rate vessels. Add measured quantities of water to each until they are 
 saturated. Which absorbs water more rapidly? Which absorbs the
 
 TYPES OF SOILS 
 
 37 
 
 greater amount? What per cent of water did each absorb? What 
 filled the space before the water entered ? 
 
 9. Fill a two-quart jar about two thirds full of soil from the school 
 garden. Add water until the jar is full and let stand for a day. Then 
 shake thoroughly and let the mixture settle. How do the various mate- 
 rials arrange themselves in settling? Determine from the experiment 
 the kind of loam your soil is most like. Try the same experiment with 
 the subsoil. Is the result the same ? 
 
 10. Put about a pint each of soil and subsoil from the school garden 
 into air-tight receptacles and bring into the laboratory. Test for mois- 
 ture and organic content as follows : Procure two small pans and weigh 
 them. Place 100 g. of soil in one and a like amount of subsoil in the 
 other, weighing quickly to avoid loss by evaporation. Expose the soil 
 to the air of the room for three days and weigh pan and soil again. 
 The difference between this and the former weight will give the amount 
 of capillary water each specimen contained. Now get two crucibles and 
 place 10 or 15 g. of the dry soil and subsoil in them. Heat in an oven 
 for five hours and weigh again. The difference in weight gives the 
 amount of the hygroscopic moisture present. Next heat each sample 
 to red heat over a Bunsen burner for half an hour and weigh again. 
 The difference now represents roughly the amount of organic material 
 in the soil. Fill out the following table : 
 
 
 SOIL 
 
 SUHSOII, 
 
 AVeight of soil pan 
 
 
 
 Weight of pan and moist soil 
 
 
 
 Weight of pan and air-dry soil 
 
 
 
 Amount of capillary moisture 
 
 
 
 Weight of crucible 
 Weight of crucible and soil after baking . 
 Amount of hygroscopic water found .... 
 Weight of crucible after burning 
 Amount of organic matter present 
 
 
 
 
 
 
 11. Breathe upon a glass slide, throw some sand upon it, shake off all 
 loose grains, and examine those that remain with the microscope. The 
 pink or black particles are hornblende ; the thin, clear, or dusky flakes 
 are mica ; and the gray particles are feldspar or granite. Mix up some clay 
 in water and examine a drop of the turbid fluid in the same way. How 
 do the two mounts compare as to size and composition of the particles ? 
 
 442842
 
 CHAPTER IV 
 
 CONDITIONS AFFECTING SOIL FERTILITY 
 
 Structure. While humus, water, and air are necessary 
 constituents, mineral matter is the basis of all fertile soils, 
 forming from 60 to 90 per cent of their weight. The prevail- 
 ing mineral constituent is nearly always silica, with varying 
 amounts of alumina or clay and the oxides of iron, calcium, 
 magnesium, and others. Even in the poorest soils there are 
 enough of the elements needed by plants for at least a hundred 
 ordinary crops, and the subsoil contains immense additional sup- 
 plies ; but these are often so solidly bound in the rocks as to be 
 only slowly available to plants. The texture of the soil, then, 
 determines in great measure not only what crops can grow 
 upon it, but the rapidity with which weathering can make the 
 needed elements available. A block of stone will support only 
 a few mosses and lichens ; grind it to sand and many more 
 highly specialized plants will grow upon it ; reduce it to pow- 
 der and it will grow our cultivated crops. A gram of good 
 soil contains from two billions to twenty billions of soil par- 
 ticles. In a cubic foot of the finest clay the total exposed 
 surface of the particles is not far from 175,000 square feet. In 
 a sandy soil the area falls to about 10,000 square feet. The 
 particles in a cubic foot of light loam have a total surface area 
 of about one acre. Since water containing the dissolved food 
 materials is held on the surface of these particles, one easily 
 understands how a fine soil and a fertile soil are nearly 
 synonymous terms. In the soil the finest particles are not 
 separate, but are flocculated, or bound together in small groups 
 called soil crunibs. When for any reason the soil crumbs are 
 
 38
 
 CONDITIONS AFFECTING SOIL FERTILITY 39 
 
 broken down into their original particles, the soil is said to 
 be puddled. The roots of plants, and the water and air nec- 
 essary for their growth, have difficulty in penetrating pud- 
 dled soils, and the farmer is careful not to work his land 
 when doing so may induce this condition. Puddled clay is 
 so impervious to water that it is often placed in the bottom 
 of artificial ponds to prevent the water from leaking out. 
 
 
 FIG. 18. A stony field in southern New York, showing glacial debris 
 At the time the photograph was taken this field was planted with corn 
 
 The presence of lime and humus also has considerable 
 effect on the texture of the soil. Lime has the faculty of 
 flocculating clay soils, but in sandy soils small amounts 
 of lime serve to bind the particles together ; in addition, it 
 serves to correct acid soils and promotes the growth of the 
 soil bacteria. Humus makes heavy soils more open and pro- 
 motes the movement of air in them, thus making them 
 warmer. It also absorbs and holds for the plants nearly
 
 40 AGKONO.MY 
 
 twice it's weight of water and is the source of most of the 
 nitrogen used by them. 
 
 The air. We are living at the bottom of an ocean of air 
 from which all the animals and plants derive elements neces- 
 sary to existence. From it animals obtain the oxygen for res- 
 piration, while the plants, in addition to a similar use of oxygen, 
 make use of the carbon dioxide, forming from it nearly half 
 their dry weight. The air is made up of several gases, two 
 of which, oxygen and nitrogen, comprise more than 98 per cent 
 of its bulk. The proportions of the principal gases are given 
 in the following table : 
 
 Nitrogen 77.95 
 
 Oxygen 20.61 
 
 Water vapor (average) 1.40 
 
 Argon 1.00 
 
 Carbon dioxide 0.03 
 
 The air also contains small quantities of krypton and neon. 
 Water vapor, which varies in quantity with the locality, is 
 not strictly a part of the air. The air is possibly several hun- 
 dred miles deep and at sea level presses on every square inch 
 of surface with a weight of nearly 15 pounds, or more than 
 46,000 tons, to the acre. The pressure varies somewhat with 
 the weather, being greatest in calm, fine weather and least as 
 a storm approaches. Differences in pressure are measured by 
 the barometer, in which a column of mercury rises with high 
 pressure and lowers with a decrease of pressure. These varia- 
 tions in pressure exert a considerable influence over the air 
 and water in the soil. When the barometer is falling, the les- 
 sened pressure causes the air to flow out of caves, mines, and 
 other underground cavities, while the water in wells rises and 
 springs flow more copiously. In some localities the underly- 
 ing porous rocks absorb so much air when the pressure is high 
 that when it is relaxed the amount of air rising from wells 
 and other openings in the soil may be sufficient to cause a
 
 CONDITIONS AFFECTING SOIL FERTILITY 41 
 
 perceptible draft. Wells of this kind are called blowing wells 
 and form very good natural barometers. When a storm ap- 
 proaches, the draft is outward, and when fair weather returns, 
 the air flows back into the ground. The same phenomena aid 
 in the ventilation of the soil, but even without this there is 
 more or less exchange between the gases in the soil and those 
 outside by a process of diffusion, in which different gases tend 
 to mix until all parts of the mixture have equal amounts of 
 each. The ventilation of the soil is also promoted by the air 
 which flows in when the water, after a rain, sinks downward. 
 
 Air in the soil. About half the bulk of dry soil is pore 
 space filled with air. Clay, although apparently more com- 
 pact than sand, has a greater amount of pore space. The 
 spaces, however, are smaller and the air moves more freely 
 in sand. As has been previously stated, air is essential to a 
 fertile soil. It supplies the underground parts of plants with 
 the oxygen necessary for respiration, it makes the soil warmer, 
 promotes the growth of soil bacteria, and aids in weathering. 
 Ordinary plants cannot live in a saturated soil, and a few days' 
 flooding may destroy an entire crop. Certain aquatic plants 
 thrive in such soils, but these have become adapted to their 
 habitat and have other ways of obtaining their oxygen. 
 
 Temperature. All parts of the earth receive the same amount 
 of sunlight in the course of a year, but the shape of our planet 
 makes the distribution of temperature very uneven. The heat 
 is greatest where the sun's rays are vertical and least where 
 they fall obliquely, since in the latter case the same amount of 
 heat is distributed over a greater area. For this reason hill- 
 sides sloping toward the sun are warmer than level fields, 
 while northern slopes are colder. Few realize the enormous 
 heat received from the sun, although familiar with the fact 
 that a lens may bring together the few rays that fall upon it 
 and set fire to paper or wood. It is estimated that the energy 
 received from the sun is equal to one horse power per hour for
 
 42 
 
 AGRONOMY 
 
 every square yard of surface. A man of average size lying on 
 the earth will receive more heat in one hour than is needed to 
 raise a gallon of water to the boiling point. The same heat 
 would raise the temperature of a layer of soil, half an inch 
 thick, nearly 90 degrees. 
 
 Variations in temperature. The changes of the seasons and 
 the alternations of day and night cause the temperature of 
 middle latitudes to range from many degrees below zero to 
 more than a hundred above in the course of a year. These 
 changes affect the soil for some distance downward, though 
 
 in most parts of the United 
 States the difference between 
 the day and night tempera- 
 tures is not perceptible three 
 feet below the surface, and at 
 seventy-five feet below, sum- 
 mer's heat and winter's cold 
 are alike unknown. This ex- 
 
 J I 
 
 FIG. 19. Diagram to show the distri- 
 bution of the sun's rays 
 
 When the sun is near the horizon, the 
 
 same amount of heat is spread over a 
 
 greater area than when it is overhead 
 
 plains the fact that water 
 from deep wells is cool even 
 in summer. In the tropics 
 this point of unvarying tem- 
 perature, both for day and 
 night and for the seasons, is little more than a foot below the 
 surface. Much of the heat received by the soil is used in 
 evaporating the water in it. For this reason wet soils are 
 cold soils. The heat used in evaporating one pound of water 
 would warm 7500 pounds of soil one degree. Some of the 
 heat falling on the earth is also reflected back and serves to 
 increase the temperature of the air. 
 
 Other factors that modify temperatures. The temperature 
 of the soil is also affected by its color, slope, and composition. 
 Southern slopes are warmer than northern slopes because they 
 receive the more direct rays of the sun. Soils sheltered from
 
 CONDITIONS AFFECTING SOIL FERTILITY 43 
 
 the sun in any way are cold ; hence the saying, " There is 
 a difference of 100 miles of latitude between the north and 
 south sides of a tight board fence." The fence not only shuts 
 off the heat rays from one side of it, but it reflects back much 
 heat to the soil on the other. The best place for the early 
 vegetables is on the sunny side of such a fence. We see other 
 effects of the reflection of heat in our greenhouses and hot- 
 beds, where the air under the glass is warmed in large measure 
 by the heat reflected back from the soil. Dry soils are warmer 
 than wet ones, and well-aerated soils are warmer than those 
 in which the air does not circulate freely. Color also influences 
 the amount of heat absorbed by soils. Black soils absorb most, 
 red next, yellow next, and light soils least of all. In an experi- 
 ment with two samples of the same soil, one of which was 
 whitened with magnesia and the other blackened with lamp- 
 black, there was found to be a difference of more than 12 de- 
 grees in favor of the black specimen. A soil containing much 
 humus is warmer than one that lacks it. The decay of or- 
 ganic matter adds as much warmth to the soil as would be 
 given off if the matter were burned more rapidly in the air. 
 
 The Fahrenheit and centigrade scales. There are two scales 
 in common use by which temperature is measured. In both, 
 the freezing and boiling points of water are cardinal points. 
 The Fahrenheit scale is the one most used in the United States 
 at present. On this scale zero is placed 32 degrees below the 
 freezing point of water, and the boiling point 180 degrees 
 above it, making 212 degrees between zero and the boiling 
 point. A much better arrangement is found in the centigrade 
 scale, where the freezing point of water is called zero and 
 the distance between it and the boiling point is divided into 
 100 degrees. A degree in the centigrade scale is therefore 
 larger than a degree Fahrenheit. To change a given number, 
 of degrees centigrade to Fahrenheit one must multiply by 
 | and add 32 (C. x f + 32 = F.). To change Fahrenheit to
 
 44 
 
 AGRONOMY 
 
 centigrade, subtract 32 and multiply by | (F. 32 x | = C.). 
 Below zero centigrade one multiplies by | and subtracts tin- 
 product from 32, if it is not more than 32. If more, the differ- 
 ence between this and 32 indicates the degrees below zero 
 Fahrenheit. If the temperatures below zero Fahrenheit are to 
 be changed to centigrade, add 32 and multiply by jj. The 
 result will be degrees below zero centigrade. In all cases 
 
 FIG. 20. Mean annual rainfall in the United States 
 From Brigham's " Commercial Geography " 
 
 where temperatures are recorded without the scale indicated, 
 as in this book, it is understood to refer to the Fahrenheit 
 scale. The centigrade scale, however, has found favor with 
 scientific men, and it is probable that in the near future it 
 will supplant the other. 
 
 Precipitation. The most important function of the soil is to 
 afford water for plants. In many parts of the West thousands 
 of acres are barren and useless for want of this indispensable 
 factor. When it is applied to the soil in irrigation, the desert 
 at once becomes a garden. Precipitation may occur as rain,
 
 45 
 
 snow, hail, or dew, and varies with the locality and season, 
 being usually greatest near coasts where moisture-laden winds 
 blow inland, and least where the prevailing winds blow in the 
 opposite direction. On parts of the Gulf coast the annual rain- 
 fall is about 70 inches, on the northwest coast it may be from 
 105 to 112 inches. In the Mojave desert, surrounded by moun- 
 tains that intercept the moisture, it is less than 2 inches a year. 
 
 PRECIPITATION AT JoLIKT, ILLINOIS, FOR FOUR YEARS 
 ILLUSTRATING VARIATIONS THAT MAY OCCUR 
 
 MONTH 
 
 1908 
 
 1909 
 
 1910 
 
 1911 
 
 January 
 
 .77 
 
 1.12 
 
 2.52 
 
 1.58 
 
 February 
 
 2.66 
 
 3.38 
 
 2.45 
 
 1.62 
 
 March 
 
 4.33 
 
 1.56 
 
 .24 
 
 1.39 
 
 April 
 
 3.32 
 
 6.60 
 
 3.81 
 
 4.45 
 
 Mav 
 
 6.95 
 
 3.46 
 
 4.90 
 
 3.65 
 
 June 
 
 1.30 
 
 3.80 
 
 .81 
 
 4.65 
 
 July 
 
 3.79 
 
 1.69 
 
 1.46 
 
 2.46 
 
 August 
 
 3.80 
 
 2.95 
 
 3.17 
 
 4.54 
 
 September 
 
 1.32 
 
 3.09 
 
 2.75 
 
 12.27 
 
 October 
 
 .82 
 
 1.68 
 
 1.68 
 
 4.18 
 
 November 
 
 2.77 
 
 4.55 
 
 .62 
 
 2.87 
 
 December 
 
 1.30 
 
 3.50 
 
 1.12 
 
 1.91 
 
 
 
 
 
 
 1 Annual 
 
 33.13 
 
 37.38 
 
 25.53 
 
 45.57 
 
 
 
 
 
 
 The heaviest rainfall in the world is found in the Khasi hills, 
 north of the Bay of Bengal, where the precipitation may reach 
 600 inches a year. More than 40 inches have fallen in a single 
 day there. The rainfall of the United States seems generally 
 to increase as one goes eastward. Over much of the Rocky 
 Mountain region it is from 10 to 20 inches, on the western 
 edge of the Great Plains it is from 20 to 30 inches, in the north- 
 central states it is from 30 to 40 inches, and the eastern states 
 
 1 The average annual precipitation at this station for eighteen years is 34.58 
 inches.
 
 46 
 
 AGKONOMY 
 
 have from 40 to 50 inches. Over most of the Gulf states the 
 rainfall is from 50 to 60 inches. About 215,000,000,000,000 
 cubic feet of water fall annually in the United States. This 
 would cover 5,000,000,000 acres a foot deep, or keep ten 
 Mississippi rivers constantly flowing. In figuring precipita- 
 tion, 10 inches of snow are considered equal to 1 inch of ram. 
 Dew may form within the soil as well as upon it, but the 
 amount of moisture added in this way is negligible. Dry soils 
 
 Photograph by H. L. Hollister Laud Co. 
 
 FIG. 21. Sagebrush on the Western plains 
 
 The rainfall is insufficient for cultivated crops, but when irrigated the lan'd 
 yields abundant harvests 
 
 are also able to absorb moisture from damp air, the moisture 
 condensing upon the soil particles. Sands absorb least and 
 humus most. Quicklime slakes when exposed to the air, by 
 absorbing moisture in this way. So strong is this tendency 
 of quicklime to absorb moisture that the chemist uses it to 
 dry the air used in various experiments. A fine soil will also 
 absorb moisture from a coarser one. Clay may sometimes take 
 water from sand, though the latter may contain less moisture 
 than the clay.
 
 CONDITIONS AFFECTING SOIL FEETILITY 47 
 
 Water in the soil. A part of the water which falls in rain 
 immediately evaporates, a part sinks into the soil, and the rest 
 drains away into streams and ponds. This latter is known as 
 the run-off. The water that sinks into the soil is called the 
 percolating water. The run-off is greater in clay than in sand, 
 on slopes than on the level, and in cultivated soil than in 
 pasture or woodland. Clay gullies more easily than sand be- 
 cause the water cannot penetrate it so readily. Pastures and 
 woodlands protected by the close ground cover are scarcely 
 affected by a rain that may wash out the crops in cultivated 
 fields. The water that enters the soil exists there in three 
 forms, known as free, capillary, and hygroscopic water. Free 
 water responds to the pull of gravity and goes downward until 
 it reaches a point where the soil is saturated. Capillary water 
 is not affected by gravity, but moves from moist to dry regions 
 like a drop of water on blotting paper or the oil in a lamp 
 wick. Much dissolved plant food is brought up from the sub- 
 soil by the capillary water, and the alkali in certain soils is 
 due to the same cause. Hygroscopic water is not affected by 
 either gravity or dryness. It clings closely to the soil particles 
 and binds them into soil crumbs. It is present even in air-dry 
 soils and roadside dust, but is not available to plants. Plants 
 depend largely for their moisture on the capillary water in the 
 upper layers of soil, though some of the free water deeper in 
 the earth may return by capillarity. Water rises highest by 
 capillarity in fine-grained soils. Clays and silts can lift water 
 in this way from six to ten feet. In sandy soils water will 
 not rise more than two feet. 
 
 The water table. The free water sinks downward until it 
 reaches a point where all the spaces between the particles are 
 filled with water, or where, as we say, the soil is saturated. 
 This point is known as the water table, or permanent ground 
 water. It now spreads out laterally and slowly drains off by 
 seeping out of the soil at the edge of streams, lakes, and
 
 AGRONOMY 
 
 swamps, or perhaps it may come to the surface, forming springs. 
 In certain seasons, or in places where there is a stratum of 
 impervious subsoil, there may be saturated areas above the 
 water table that will cause tile drains to run. The real water 
 table, however, lies deeper. It varies with the rainfall, rising 
 in wet seasons and falling in dry ones. We dig our ordinary 
 
 Photograph by II. L. Hollister Land Co. 
 
 FIG. 22. One of the main laterals, or branches, of an irrigation canal 
 From this stream smaller channels lead to the separate fields 
 
 wells down into it, and in dry seasons they may dry up, owing 
 to the lowering of the water table. The fluctuating water 
 level may sometimes affect the character of mineral springs 
 flowing from it, giving them an excess first of one mineral 
 and then of another as the water comes in contact with differ- 
 ent rock strata. Above ground a water surface is level, but 
 in earth the water table curves upward under hills chiefly 
 because the soil retards the downward progress of the free
 
 CONDITIONS AFFECTING SOIL FERTILITY 49 
 
 water after a rain. Ponds and marshes are usually at the 
 level of the water table. 
 
 Drainage. In the eastern United States it is estimated that 
 there are a hundred million acres of swamp that could be 
 rendered useful by drainage. All soils have to be drained 
 before cultivated crops can be grown in them. The majority 
 are drained naturally. Sand is often too well drained. When 
 the saturated con- 
 dition of the soil 
 results from the 
 seepage of water 
 from higher levels, 
 tile drains may be 
 used to carry it 
 away, but when 
 the land lies very 
 little above the nat- 
 ural drainage, tile 
 drains would be 
 useless and open 
 ditches must take 
 their place. Lands 
 that are not per- 
 manently wet are 
 often benefited by 
 tile draining. The 
 
 removal of the surplus water deepens the area into which 
 the roots of plants can spread, warms the soil by admitting 
 the air, and promotes further weathering of the subsoil. 
 Draining wet lands may actually give the plants more water 
 by increasing the area from which the roots can absorb, 
 thus making them more drought-resistant. Drainage also 
 makes it possible to begin the work on wet lands earlier in 
 the spring. 
 
 Photograph by II . L. Ilollister Land Co. 
 
 FIG. 23. A check gate in an irrigation ditch 
 
 This holds hack the water and causes it to flow 
 through smaller channels into the fields
 
 50 
 
 AGRONOMY 
 
 Photograph by Mark Bennitt 
 
 FIG. 24. A field of wheat in the dry-fanning region 
 
 Photograph by H. L. HollUtcr Land Co. 
 
 FIG. 25. 'Irrigating a fig orchard in California 
 
 Irrigation. Ordinary crops can be produced with as little 
 as twenty inches of rainfall if it is properly distributed, but 
 when it does not come in the growing season, or is limited in
 
 CONDITIONS AFFECTING SOIL FERTILITY 51 
 
 amount, the lands must be irrigated if crops are to be grown. 
 Many otherwise sterile soils are very fertile when water is 
 applied. Irrigation, however, can be carried on only when the 
 
 13 in. 
 
 Trital 1911 45.57 
 Total 1910 25.53 
 
 Ay. 4 yfs. 35.40 
 
 12 in. 
 
 11 In. 
 
 10 in. 
 
 9 in. 
 
 Sin. 
 
 7 in. 
 
 Gin. 
 
 in. 
 
 4 in. 
 
 Apr. 
 
 May 
 
 June 
 
 July 
 
 Aug. 
 
 Sept. 
 
 Oct. 
 
 Nov. 
 
 Dec. 
 
 FIG. 26. Precipitation at Joliet, Illinois 
 
 The heavy line represents the average for the years 1908, 1909, 1910, and 1911. 
 See page 45 for the precipitation by months. (Data supplied by F. M. Muhlig, 
 United States Weather Observer) 
 
 land is properly located with reference to a permanent source of 
 water supply. Usually some near-by lake or stream is selected, 
 a dam built across it, and the water which falls in its basin 
 stored for the use of the crops. From the dam, canals are made 
 to run through the lands to be irrigated, and smaller ditches,
 
 52 
 
 AGRONOMY 
 
 into which the water may be turned as needed, traverse the 
 fields. Crops on irrigated land are usually certain, since the 
 farmer is relieved from any dependence on the natural rainfall. 
 Dry farming. Twenty inches of rainfall, properly distrib- 
 uted, is about the minimum amount that will produce ordinary 
 crops. In a few localities, where the rainfall is less, crops are 
 produced by a system of dry farming in which the scanty 
 moisture is stored up in the soil until there is sufficient for a 
 
 Tin. 
 
 Cin. 
 
 5 in. 
 
 4 in. 
 
 \ 
 
 Sin. 
 
 A 
 
 Z- 
 
 2 in. 
 
 \ 
 
 \/ 
 
 lin. 
 
 Feb. 
 
 Mar. 
 
 Apr, 
 
 May 
 
 June 
 
 July 
 
 Aug. 
 
 Sept. 
 
 Oct. 
 
 Nov. 
 
 Dec. 
 
 FIG. 27. Diagram showing precipitation at Joliet, Illinois, in 1909 
 Data supplied by F. M. Muhlig, United States Weather Observer 
 
 crop. This method consists in keeping the surface of the soil 
 constantly loose, partly for the purpose of absorbing all the 
 rain that falls, partly to prevent the evaporation of the water 
 already in the soil. A crop may thus be grown every other 
 year, or two crops in three years, the land remaining without 
 a crop, though carefully tilled, during the intervening time. 
 Crops have been grown by this method in regions where the 
 rainfall is but twelve inches. In some cases it is possible to 
 get a crop annually by cultivating the soil during that part 
 of the year when it is not occupied by plants. The selection 
 of drought-resistant plants may also facilitate dry farming.
 
 CONDITIONS AFFECTING SOIL FERTILITY 53 
 
 Physiologically dry soils. A physically dry soil is one in 
 which there is no moisture, but even in a soil containing much 
 water, if the plants are unable to absorb it, it is physiologically 
 dry to them. In winter, though the soil may be saturated, it 
 is physiologically dry because the moisture is locked up in the 
 form of ice. Strong salts or acids of any kind in the water 
 may also prevent absorption. It is probable that many plants 
 which grow in bogs find the soil physiologically dry to them, 
 though at the same time it may be soaked with water. 
 
 PRACTICAL EXERCISES 
 
 1. Take two bottles of equal size and fill with roily water made by 
 shaking up some clay with rain water or distilled water. Add to one 
 bottle one tenth its bulk of a solution of lime and water and stand both 
 bottles where they will not be disturbed. Examine at intervals to see 
 which settles first, and explain the result. 
 
 2. Weigh out three samples of clay of 200 g. each. To one add 
 10 g. of slaked lime, to another add 10 g. of sand, and to the third add 
 10 g. more of the clay. Add enough water to make plastic and form 
 into three balls. AVhen these are thoroughly dry, pile weights, little by 
 little, upon each until it is crushed. Explain the different effects of 
 sand and lime. 
 
 3. Take four straight-sided lamp chimneys and fill one each with 
 sand, clay, peat, and soil from the school garden. These materials 
 should all be dry and well pulverized. Tie a piece of cheesecloth over 
 the bottom end of each chimney and stand them in a rack, with the 
 bottoms dipping into a shallow pan of water. In which does the water 
 rise most rapidly? In which most slowly? Do you conclude that in 
 drying they would follow the same order ? Try it and see. 
 
 4. Visit the nearest barometer and barograph to learn how the 
 pressure of the air is measured and recorded. Examine both centigrade 
 and Fahrenheit thermometers. 
 
 5. . Fill a glass with water, lay a sheet of writing paper over it, and 
 holding the paper in place, quickly invert the glass. When the hand is 
 removed, why does the water not run out ? 
 
 6. Light a piece of paper, thrust it into a glass jar, and invert the 
 jar in a shallow dish of water. Explain the action that takes place in 
 the water.
 
 54 AGRONOMY 
 
 7. Select two thermometers graduated alike and place them so that 
 their bulbs only will be exposed to the sun. Cover one bulb with a 
 white cloth and the other with a black one. Which thermometer now 
 measures higher ? How much ? Explain. 
 
 8. Take the two thermometers and cover both bulbs with the same 
 kind of cloth. Wet one cloth and leave the other dry. What difference 
 do you now find in the way they register ? Explain. Does fanning them 
 have any effect upon the temperature registered ? 
 
 9. Change 40 C. to Fahrenheit ; 60; 85. 
 
 10. Change 68 F. to centigrade; 95; 41. 
 
 11. From the nearest weather observer find the average rainfall by 
 months for the past five years. Plot the curve for the year as in 
 Fig. 26, p. 51. The numbers at the left indicate the amount of rain- 
 fall in inches. What is. the average annual rainfall of your region ? 
 
 12. Plot the rainfall curve for the present year or for the preceding 
 one. Is the rainfall well distributed through the growing season? 
 
 13. Make a similar curve for the average temperature by months 
 for the past five years. 
 
 14. In a rainfall of half an inch how many cubic inches fall on an 
 acre of ground ? how many gallons ? how many barrels ? How many 
 gallons fall on the school garden ? on your own plot in it ? 
 
 15. What is the total amount of water that fell on the school gar- 
 den last month ? 
 
 16. If an acre of ground is half pore space, how many gallons of 
 water will be contained in the upper 7 in. when the soil is saturated ? 
 
 17. From wells in the vicinity ascertain how far below the surface 
 the water table lies. 
 
 18. Visit a marsh, hillside, or ledge of rocks, and decide what causes 
 the water table to come to the surface here. 
 
 19. Visit lands that have been tile drained. Are there any other 
 lands in the vicinity that would" be benefited by the same treatment ? 
 Are there any lands that open ditches would serve better? any land 
 where irrigation could be practiced to advantage ? 
 
 References 
 
 Farmers' Bulletins 
 
 46. Irrigation in Humid Climates. 
 138. Irrigation in Field and Garden. 
 187. Drainage of Farm Lands. 
 263. Practical Information in Irrigation. 
 371. Drainage of Irrigated Lands.
 
 CHAPTER V 
 
 THE ORGANIZATION OF THE PLANT 
 
 The great plant groups. The vegetation of the earth con- 
 sists of a bewildering variety of forms. At one extreme 
 are plants consist- 
 ing of a single cell 
 and therefore lack- 
 ing roots, stems, 
 leaves, flowers, or 
 fruits ; at the other 
 are the great trees, 
 like the giant red- 
 woods and euca- 
 lypti, which tower 
 to the height of 
 hundreds of feet 
 and spread millions 
 of leaves to the sun- 
 shine. Some spe- 
 cies are adapted to 
 live in ponds and 
 streams, and spend 
 their whole life im- 
 mersed in water ; 
 others inhabit des- 
 erts in which rain 
 rarely falls and 
 moisture is at the 
 minimum. Between these extremes all sorts of vegetable forms 
 occur. Herbs, shrubs, vines, and trees vie with one another for 
 
 55 
 
 FIG. 28. Pteridgphytes. A colony of walking 
 ferns (Camptosorus)
 
 56 
 
 ACKOXO.MV 
 
 -cyto 
 
 a roothold and access to the light and air, while mosses, ferns, 
 and fungi grow among and upon them. This great diversity 
 of form makes it necessary to place the plants in different 
 groups, according to their common characteristics, and bota- 
 nists generally make four great groups of this kind. First and 
 simplest in structure are the TkaUophytes, comprising the algae, 
 fungi, and bacteria. None of these have true leaves or stems, 
 or produce either flowers or fruits. Next above these come 
 the Bryophytef, which include the mosses and liverworts. 
 They are somewhat more highly organ- 
 ized than the thallophytes, but are like 
 them in lacking true leaves, flowers, 
 and fruits. The Pteridophytes consist of 
 the ferns and their allies. These plants 
 have stems and leaves, and some spe- 
 cies bear structures that are essentially 
 flowers, but none bear seeds. Last and 
 most highly specialized are the Sper- 
 matophytes, or true flowering plants, 
 which are distinguished from all the 
 others by the production of seeds. 
 
 Only two of these groups are of 
 much interest to the farmer and gar- 
 dener. The thallophytes have to be 
 taken into account because from their 
 ranks come not only the bacteria that 
 flavor cheese, butter, and other prod- 
 ucts, turn cider to vinegar, and render 
 soils fertile, but also the multitudes 
 of plant diseases and fungus pests that injure the cultivated 
 crops, destroy our foods, cause disease in the lower animals, 
 and even attack man himself. The cultivated plants, however, 
 are spermatophytes, and so are the weeds that struggle with 
 them for the possession of the soil. The word spermatophyte 
 
 Icell w 
 
 FIG. 29. An epidermal hair 
 
 from the bracken showing 
 
 the cells 
 
 cell w, cell wall ; cyto, cyto- 
 plasm; nit, nucleus; s, starch 
 grains
 
 THE ORGANIZATION OF THE PLANT 57 
 
 means " seed plant," and this name was given to the highest 
 group of plants in recognition of the way in which they are 
 reproduced. All the other groups are developed from tiny 
 one-celled structures called spores. These are individually 
 too small to be seen with the unaided eye, but in masses are 
 recognized as the black mold on bread, the smoke from puff- 
 balls, and the like. 
 
 The regions of the plant. A typical flowering plant is 
 often said to consist of root and shoot. The stem, however, 
 is the real axis of the plant and bears all the other organs. It 
 is present in the seed, and the first root grows from it ; in- 
 deed, roots normally grow from stems, not stems from roots, 
 as is popularly supposed. The root grows downward in the 
 soil, holding the plant in place and absorbing necessary mois- 
 ture and minerals. The shoot pushes up into the air from 
 which it takes other necessary food material. In the leaves 
 and other green parts of the plant these materials from both 
 the earth and air are ultimately combined to form plant food 
 by means of energy derived from sunlight. After a store of 
 plant food is secured, flowers appear, and seeds are formed 
 for the purpose of reproducing, multiplying, and distributing 
 the species. These two functions, growth and reproduction, 
 are common to all plants. During the early part of their 
 existence the growth processes are in the ascendant ; later, 
 reproductive functions prevail. 
 
 Cellular structure of the plant. All parts of the plant are 
 formed of minute boxlike structures called cells-, which are 
 usually much too small to be seen without the aid of the mi- 
 croscope. The ordinary undifferentiated cell consists of a semi- 
 fluid, nearly transparent substance called protoplasm surrounded 
 by a thin membrane known as the cell wall. Within the proto- 
 plasm are one or more spaces called vacuoles containing a 
 watery fluid, the cell sap. Somewhere in the protoplasm, also, 
 usually at one side of the cell, is a denser, darker part called
 
 58 
 
 AGRONOMY 
 
 the nucleus. The nucleus is the center of the cell's activities. 
 When a new cell is to be formed, the nucleus first divides 
 into two equal parts and then the division extends outward 
 
 to the surrounding cell 
 wall. Soon there are 
 two new cells in place 
 of the original one, 
 new walls having been 
 constructed between 
 them. These two cells 
 now grow to maturity 
 and are ready to re- 
 peat the process. All 
 
 growth is essentially like this. When growing alone, the cell 
 inclines to take a spherical shape, but in plant and animal tis- 
 sues, where it is crowded on all sides, it becomes more or less 
 
 FIG. 30. Cells with nuclei from the epidermis 
 of the onion bulb 
 
 Photograph by the United States Department of Agriculture 
 
 FIG. 31. The root system of the corn plant 
 
 angular. The cells in the woody parts of plants, in bark and 
 the like, are very different from the cell just described, but 
 all began as cells of this kind.
 
 THE ORGANIZATION OF THE PLANT 
 
 59 
 
 Roots. The root, or underground portion, of the plant is 
 the first to put forth from the germinating seed. No matter 
 in what position the seed may happen to be lying when growth 
 begins, the root, in response to gravity, tends to grow straight 
 downward, often curving considerably to do so. This is of 
 great advantage to the young plant, since it quickly brings 
 it into contact with the neces- 
 sary moisture and other food 
 materials, and also gives it a 
 hold in the soil. The root, how- 
 ever, is not pulled down by 
 gravity, but simply uses this 
 force as a guide. After reach- 
 ing the soil it may turn aside 
 for moisture or food materials, 
 or to avoid obstacles, such as 
 stones, in the soil. In its search 
 for moisture it often goes 
 long distances. Instances are 
 known where the roots of a 
 tree have in this way filled 
 drains three hundred feet away. 
 Soon after penetrating the soil 
 the first root begins to give 
 off branches, and these branch 
 and branch again, spreading 
 out laterally and thoroughly exploring the soil for food mate- 
 rials. These lateral roots are often very numerous. A single 
 corn plant may have enough roots to measure a quarter of a 
 mile or more when placed end to end. In humid regions 
 roots seldom descend more than four or five feet, but in arid 
 regions they may go much deeper. The main root of such 
 plants as mesquite, shepherdia, and alfalfa have been known 
 to go down fifty or sixty feet in search of moisture. 
 
 FIG. 32. Wild hyacinth (Camassia) 
 with multiple primary roots
 
 AGEONOMY 
 
 Taproots. In a large number of species the main root 
 continues to grow, becoming the main axis of the plant 
 underground. Such a root is called a taproot. Frequently 
 
 the taproot is used for the storage 
 of food and is often much enlarged 
 for this purpose. Good examples of 
 taproots may be seen in the carrot, 
 parsnip, and dandelion. All our root 
 crops are cultivated for the food 
 stored by the plant in the main or 
 lateral roots. In some plants the 
 first root fails to keep ahead of the 
 others, and no taproot is found in 
 mature specimens. The root system 
 of the corn illustrates this. The 
 onion, hyacinth, and other lilylike 
 plants exhibit good examples of 
 what are called multiple primary 
 roots, where several roots of equal 
 size arise together from the base of 
 the stem. Plants with taproots are 
 said to have an axial root system ; 
 without a taproot it is inaxial. 
 Structure of the root. The young roots of plants are alike 
 in all essential particulars. In the center is a somewhat fibrous 
 portion known as the central cylinder, and surrounding it is a 
 softer layer, the cortex. On the outside is a thin skin formed 
 of waterproof cells, which is known as the epidermis. The 
 central cylinder has a series of small tubes, or ducts, running 
 lengthwise through it, and it is along these ducts that the 
 water absorbed by the plant travels upward. Roots that 
 continue to live for some years, annually spreading into 
 wider territory and absorbing a greater amount of food mate- 
 rial, need a larger number of ducts for transporting these 
 
 FIG. 33. Taproot 
 parsnip 
 
 The sectional specimen shows 
 the central cylinder and cortex
 
 THE ORGANIZATION OF THE PLANT 
 
 61 
 
 substances. The new ducts are provided by a ring of growing 
 cells, called cambium cells, that originate just inside the cor- 
 tex and encircle the central cylinder. The cambium may also 
 add other fibrous and corky cells to the cortex, and in time 
 these form the bark seen in the roots of old trees. The activi- 
 ties of the cambium, therefore, result in increasing the diam- 
 eter of the root from year to year, but growth in length takes 
 place at the tip of the 
 root only, and never at 
 the base, as is generally 
 supposed. If growth in 
 length occurred at the 
 base of the root instead 
 of at the tip, the whole 
 root would have to be 
 pushed through the soil, 
 a task which the plant 
 would soon find impossi- 
 ble of accomplishment. 
 
 In the wild state the 
 seeds of plants are scat- 
 tered on the surface of 
 the soil and germinate 
 without getting very far 
 below it, but at maturity 
 we commonly find the 
 base of the stem, or even the whole stem, some distance 
 underground. In many cases this burial of the stem is due 
 to the contraction of the roots. These penetrate the soil, 
 and, after becoming established, contract and pull the plant 
 downward. The contraction is mainly in the central cylinder 
 and results in wrinkling the cortex. Such contraction wrin- 
 kles are well shown in the roots of the skunk cabbage or 
 the his. 
 
 FIG. 34. Enlarged cross section of a young 
 
 root showing epidermis, cortex, and central 
 
 cylinder 
 
 The large openings in the central cylinder are 
 
 the ducts. Note the root hairs growing from 
 
 the epidermis
 
 62 
 
 AGROXOMY 
 
 Root hairs. Roots do not absorb through all parts of their 
 surface, as is commonly supposed. The waterproof epidermis 
 prevents the passage of moisture through all the older parts, 
 and only a small portion near the tip, where there are special 
 
 structures, called root hairs, de- 
 signed for the purpose, is able to 
 perform this office for the plant. 
 At first glance a waterproof epi- 
 dermis might seem a disadvantage 
 to the plant, but its utility is seen 
 when we learn that it serves to 
 prevent moisture once absorbed 
 from passing out into the soil 
 again. The root hairs are tiny 
 tubes closed at the end, which 
 project from a zone of epidermal 
 cells just back of the root tip. As 
 the root adds to its length, new 
 root hams are developed on the side of the zone toward the 
 growing point, while on the other the old ones slowly shrivel 
 and disappear. The advancing root is thus always provided 
 with a zone of fresh root hairs with which to absorb. On 
 seedlings that have been 
 sprouted in moist air the 
 root hairs appear like a 
 fine white down. They are 
 very numerous and spread 
 out in all directions among 
 the soil particles, affording 
 a much larger surface for 
 absorption than would the epidermal cells alone. As the roots 
 push onward through the soil the development of fresh root 
 hairs constantly brings the plant into contact with new sources 
 of food materials. 
 
 FIG. 35. A bit of epidermis with 
 young root hairs. (Enlarged) 
 
 FIG. 36. A single root hair projecting 
 from an epidermal cell. (Much enlarged)
 
 THE ORGANIZATION OF THE PLANT 63 
 
 Osmosis. Root hairs absorb from the soil by a physical 
 process known as osmosis. In this, when two liquids of different 
 densities are separated by a membrane, such as a cell wall and 
 its lining of protoplasm, there is at once set up a tendency for 
 each liquid to pass through the membrane to the other until 
 both liquids are of equal density. In osmosis the current from 
 the less dense liquid into the denser is always the stronger. 
 One can illustrate the process very well by filling a small jar 
 with molasses and tying a piece of parchment paper or hog's 
 bladder over the open end to represent a cell, and immersing 
 this jar in a larger jar of clear water for a few hours. If care 
 has been taken to make a water-tight joint between the jar and 
 its parchment cover, sufficient clear water will pass through 
 the membrane into the molasses to distend the covering of the 
 jar to its utmost. In the plant the evaporation of water from 
 the leaves or its use in forming plant food renders the sap in 
 the cells more dense than the soil water, and this consequently 
 flows into the plant, carrying the dissolved minerals with it as 
 these processes continue. Once in the root, the water spreads 
 from cell to cell through the cortex until it finally reaches the 
 ducts in the central cylinder and is sent upward to the shoot. 
 The root hairs not only absorb the water that clings to the 
 soil particles with which they come in contact, but this absorp- 
 tion sets up a capillary movement which drains adjacent parti- 
 cles of their moisture. If there should happen to be a large 
 enough amount of any soluble substance in the soil, the cur- 
 rent of water would set outward from the plant and cause its 
 death. This is what happens when we put salt upon weeds 
 or grass, and explains why ordinary plants cannot live in 
 alkali soils. 
 
 The stem. For convenience the shoot may be divided into 
 stem and leaves. The flowers, which at first might appear to 
 belong to a third division, are really homologous with leaves 
 and frequently show the relationship by becoming leaflike.
 
 64 
 
 AGRONOMY 
 
 In the green rose all the petals of the flower revert to leaves. 
 Stems are of most varied forms : in forest trees, tall, strong, 
 
 and enduring for cen- 
 turies ; in the herbs, 
 low, weak, and lasting 
 but a single season. 
 In the crocus the stem 
 is reduced to a short, 
 thick, and solid mass ; 
 in the onion it is a 
 platelike disk at -the 
 
 bottom of the bulb ; in the dandelion and the first-year plants 
 of many other species it is a collarlike organ at the top of the 
 root ; and in Solomon's seal and iris it is a thick, elongated, 
 subterranean, rootlike structure. In every case its chief func- 
 tions are to properly expose the leaves to the light and to 
 
 FIG. 37. Conns of the gladiolus 
 
 The right-hand figure shows the leaf bases re- 
 moved. The corin is a form of stem 
 
 
 FIG. 38. The rootstock or rhizome of Solomon's seal 
 An underground stem. The dark spots are branch scars 
 
 transport foods and food materials. Short-stemmed plants 
 gain illumination by spreading out their few leaves close to 
 the earth in rosettes ; others may send up a tall column with 
 many branches, upon which multitudes of leaves are hung; 
 while between these extremes are many different forms.
 
 THE ORGANIZATION OF THE PLANT 
 
 65 
 
 Structure of the stem. The stem, like the root, has a central 
 cylinder and a cortex. When young it also has an epidermis, 
 but in perennial steins this soon gives place to the outer bark, 
 which serves the same purpose. The central cylinder is made 
 
 a b 
 
 FIG. 39. Structure of stems 
 
 a, basswood, a dicotyledon; b, corn, a monocotyledon 
 
 up of many thin-walled cells, called pith cells, through which 
 run strands of heavier fibers and two sets of tubes which form 
 the fibrovascular bundles. It is the woody tissue of these fibro- 
 vascular bundles, packed closely together, that gives the trunks 
 
 FIG. 40. A single dicotyle- 
 don bundle. (Much enlarged) 
 
 pa, parenchyma ; ph, phloem ; 
 
 c, cambium; d, ducts; w, 
 
 wood ; p, pith 
 
 p 
 
 FIG. 41. A monocotyledon 
 bundle. (Much enlarged) 
 
 ph, phloem; d, ducts; 
 ic, wood ; p, pith 
 
 of trees their great solidity and strength. Plants that live but 
 a single season and rise only a short distance above the earth 
 do not need to develop these bundles so extensively, though 
 some are always necessary.
 
 66 
 
 AGRONOMY 
 
 The way in which the bundles are arranged in stems 
 makes it possible to separate the flowering plants into two 
 very natural groups. In one, called 
 the monocotyledonous group, these bun- 
 dles are scattered throughout the cen- 
 tral pith. A cornstalk or an asparagus 
 stem is a good example of this. In 
 the other, known as the dicotyledonous 
 group, the bundles are arranged in a 
 FIG. 42. Cross section circle. The sunflower or any of our 
 of young dicotyledon forest trees illustrates this type. The 
 
 stem showing the circle dicot ledong are further distinguished 
 of nbrovascular bundles * 
 
 by the presence of a ring of cambium, 
 
 which cuts through each bundle in the circle and separates 
 the two sets of tubes. The part of the bundle inside the 
 cambium is the wood and its tubes are ducts; the part out- 
 side the cambium is bast, or phloem, and its tubes are called 
 
 FIG. 43. Part of a cross section of year- 
 old basswood twig 
 
 b, bark ; pa, parenchyma ; ph, phloem ; 
 
 c, cambium ; med, medullary rays ; 
 
 w, wood ; p, pith 
 
 FIG. 44. Section of oak wood 
 
 showing the annual rings and 
 
 medullary rays 
 
 sieve tubes. Water and food materials pass upward through the 
 ducts, but elaborated food is transported downward through 
 the sieve tubes. The wedges of pith that extend outward
 
 THE ORGANIZATION OF THE PLANT 
 
 67 
 
 FIG. 45. Lilac 
 buds 
 
 The sectioned spec- 
 imen shows the em- 
 bryo leaves and 
 stem 
 
 between the bundles are called medullary rays. These serve 
 to transport foods across the stem. The activities of the 
 cambium annually add new layers to both 
 the wood and bast. In consequence dicoty- 
 ledon stems yearly increase in diameter. In 
 the new wood new ducts are also formed, 
 and these circles of ducts serve to distinguish 
 the wood of one season from that of another. 
 Monocotyledons, on the 
 other hand, lack cambium 
 and commonly do not in- 
 crease in diameter after 
 the stem once starts upward. Externally 
 the two groups also present several notice- 
 able differences. The monocotyledons have 
 more conspicuous joints, seldom branch, 
 and, since they lack a cambium, have no 
 bark. Among the well-known monocoty- 
 ledons are sugar cane, rice, wheat, and all 
 the other grains and grasses, as well as such 
 plants as the lily, iris, and tulip. Our fruit 
 and forest trees and most of our garden 
 plants are dicotyledons. 
 
 Buds. All ordinary stems increase in 
 length at the tip. At this point the rudi- 
 mentary stem is crowded with undeveloped 
 leaves, forming what is known as a bud. In 
 woody plants, in addition to this terminal 
 bud, other growing points may develop 
 along the sides of the stem, late in the 
 growing season, from which new twigs or 
 flowers arise the following year. These 
 are called lateral buds. They always occur at the joints of the 
 stem and just above a leaf. Extra buds, called accessory buds, 
 
 FIG. 46. Naked buds 
 of viburnum
 
 FIG. 47. Twig of horse- 
 chestnut, more than 
 twenty years old, show- 
 ing the circular scars 
 which mark the posi- 
 tion of former bud scales. (Re- 
 duced about one half) 
 
 FIG. 48. The two types of bud ar- 
 rangement, opposite and alternate 
 68
 
 THE ORGANIZATION OF THE PLANT 
 
 69 
 
 FIG. 49. Accessory buds 
 of box elder (Acer) 
 
 are often found with the lateral buds. 
 These usually produce flowers. When 
 growing points originate elsewhere, as 
 on injured roots and stems, they are 
 called adventitious buds. As the end 
 of the growing season approaches, the 
 stem ceases to elongate, and the buds 
 prepare for winter 
 by developing va- 
 rious devices in- 
 tended to protect 
 them from the ef- 
 fects of the cold. 
 Bud scales, formed 
 
 from the outer layers of leaflike parts, 
 are usually developed, though some 
 
 buds pass the 
 winter with- 
 out them. In 
 many species 
 the buds are 
 further pro- 
 tected by coats 
 of hair within 
 the scales or 
 
 F i G . 50 . A ccessory buds 
 
 of the butternut 
 
 (Juglans) 
 
 by a kind of varnish on the outer 
 parts. Others are almost covered 
 by the bark of the twig during win- 
 ter. Buds which are not protected 
 by bud scales are called naked buds. 
 On the return of spring the bud 
 scales that are too hard to function 
 as leaves are cast off, the stem begins to lengthen again, and 
 the rest of the bud scales develop into leaves. The lateral 
 
 FIG. 51. Accessory buds of 
 
 the golden bell (Forsythia) 
 
 These are flower buds
 
 70 
 
 AGRONOMY 
 
 buds may also grow into twigs or flowers, but many of them 
 usually fail to develop. They may remain alive, however, but 
 continue in a resting condition, length- 
 ening just enough each year to avoid 
 being covered by the new wood and 
 bark. Such buds are called dormant 
 buds and are able to grow out to form 
 twigs if the other twigs are injured. 
 
 The horticulturist often classes buds as 
 leaf buds when they contain only leaves, 
 flower buds when they produce flowers 
 only, and mixed buds when they contain 
 both leaves and flowers. Flower buds 
 that are formed in autumn are usually larger and different 
 in shape from leaf buds, and by these characteristics they 
 may be distinguished even in winter and the crop anticipated. 
 
 -lam 
 
 FIG. 52. Flower bud of 
 the buckeye 
 
 FIG. 53. A leaf of geranium 
 
 lam, lamina, or blade ; pet, petiole ; 
 slip, stipules 
 
 FIG. 54. Morning-glory leaf show- 
 ing arrangement of the veins 
 
 Leaves. The leaf is essentially an expanded part of the 
 stem, whose chief function is to make food for the plant from 
 the gases in the air and the water and minerals brought up
 
 THE ORGANIZATION OF THE PLANT 
 
 71 
 
 from the soil. The points upon the stem where leaves originate 
 are called nodes, and the spaces between are internodes. Leaves 
 occur singly or in pairs at the nodes. When complete a leaf 
 consists of a flattened green portion, the blade ; a stemlike part, 
 the petiole ; and where the petiole joins the stem, two earlike 
 
 FIG. 55. Leaf show- 
 ing pinnate venation 
 
 The geranium leaf on 
 page 53 illustrates pal- 
 mate venation 
 
 A "'' B 
 
 FIG. 56. Two forms of parallel venation 
 
 A , lily of the valley, veined from base to apex ; 
 B, canna, veined from midrib to margin 
 
 or strap-shaped green parts called stipules. The stipules are 
 frequently absent, or they may take the form of spines or ten- 
 drils. Ramifying through the blade are strands of heavy tissue 
 called veins. These are really fibrovascular bundles which 
 serve to distribute food materials to the cells and aid in keep- 
 ing the blade expanded. Monocotyledons and dicotyledons
 
 72 
 
 AGRONOMY 
 
 may usually be distinguished by the difference in the veining 
 of the leaves. In the monocotyledons the main veins usually 
 run parallel from base to apex or from midrib to margin, and 
 all the lesser veins are parallel and joined to one another at 
 the tips. This is called parallel venation. In the dicotyle- 
 dons the venation is known as reticulated or netted. Here the 
 small veins form an irregular network and the main veins 
 either spread out through the leaf, like the fingers on the 
 
 FIG. 57. Two types of branched leaves 
 The left figure is pinnately branched ; the right, palmately branched 
 
 hand, in the form known as palmate venation, or they branch 
 out from the midrib, forming the pinnate venation to be seen 
 in the elm, dandelion, and others. There are also two types of 
 branched leaves, the palmately and the pinnately branched, 
 corresponding to the two types of venation in dicotyledons. 
 
 Internal structure of the leaf. Although the leaf blade is so 
 thin, it consists of several layers of cells which show consider- 
 able differentiation in structure. In a cross section there may 
 be distinguished an upper and lower layer of clear cells, form- 
 ing the epidermis, between which are the layers of green cells
 
 THE ORGANIZATION OF THE PLANT 
 
 73 
 
 that give color to the leaf. The cells in the layer nearest the 
 upper epidermis are closely joined together and are more or 
 
 FIG. 58. Epidermal cells and stoinata from the leaf of the amaryllis, a 
 monocotyledon. (Much enlarged) 
 
 less elongated at right angles to the surface of the leaf, form- 
 ing the palisade tissue. Below this layer the cells are more 
 loosely joined to form the sponyy parenchyma. The openings 
 
 int 
 ----sto 
 
 FIG. 59. Section through 
 the leaf of the beech 
 
 ep, epidermis; pal, palisade 
 tissue ; sp, spongy paren- 
 chyma ; int, intercellular 
 spaces ; slo, stoinata 
 
 FIG. 60. Section through the leaf 
 of the rubber plant 
 
 cw, cuticle; ep, epidermis; w, water- 
 storage tissue ; pal, palisade tissue ; up, 
 spongy parenchyma; int, intercellular 
 spaces ; sto, stoinata 
 
 between these cells are known as intercellular spaces. The 
 epidermal cells are nearly air and water proof, and to facilitate 
 the exchange of gases and water between the interior of the
 
 74 AGR<>N>MY 
 
 leaf and the outer air, therefore, the epidermis contains great 
 multitudes of tiny openings called atomata (singular, stoma), 
 which connect with the intercellular spaces. Each stoma 
 
 FIG. 61. Epidermal cells and stomata from the leaf of the begonia, a 
 dicotyledon. (Much enlarged) 
 
 is provided with a pair of guard cells roughly semicircular 
 in shape, which can, upon occasion, enlarge or dimmish the 
 size of the opening. The stomata are exceedingly minute,
 
 THE OBGANIZATION OF THE PLANT 
 
 75 
 
 but they make up in number what they lack in size. There 
 may be several million in the epidermis on the underside of a 
 single ordinary leaf. The stomata have been estimated to oc- 
 cupy nearly one twentieth of the area of the leaf. It is a curi- 
 ous fact that gases can enter the leaf through these minute 
 openings more rapidly than they can pass through a single 
 opening equal in area to all the stomata. 
 
 Formation of plant food. Food is formed only in the green 
 cells of the plant. This is because the energy necessary for 
 combining the food materials is derived from the sunlight by 
 
 the green coloring matter called 
 chlorophyll. In the cell this color 
 is found in small bodies known 
 as chloroplasts. The chloroplasts 
 really form the food, though they 
 are helpless without chlorophyll. 
 The first food product formed is 
 usually grape sugar, represented 
 by the formula C 6 H 12 O 6 , but this 
 is soon turned to starch, a more stable form of plant food, with 
 the formula C 6 H 1Q O 5 . Plants of the iris, lily, and amaryllis 
 families rarely form starch. In such 
 plants oil formed from the same three 
 chemical elements may be the first visi- 
 ble product of photosynthesis. Starch, 
 wood, and several other substances 
 contain the same proportion of carbon, 
 hydrogen, and oxygen, and the differ- 
 ence between them is accounted for by 
 assuming a different multiple of the 
 formula for each. The hydrogen and 
 oxygen in the combination are derived from the soil water, 
 and the carbon comes from the carbon dioxide in the air. The 
 latter goes into the leaf through the stomata, and, spreading 
 
 FIG. 62. Cells of a moss with 
 chloroplasts 
 
 FIG. 63. Starch grains in 
 the cells of a potato
 
 76 AGRONOMY 
 
 through the intercellular spaces, mixes with the moisture in 
 the cell walls and thus enters the cells. Here it is combined 
 into food and the excess oxygen given off. The whole process 
 is known as photosynthesis. It is popularly supposed that photo- 
 synthesis in plants is the equivalent of respiration in animals, 
 but this is an error. Plants also respire, exactly as animals do, 
 taking in oxygen and giving off carbon dioxide, but, unlike 
 animals, they have the additional process of photosynthesis, 
 in which carbon dioxide is taken in and oxygen released. 
 
 The two processes 
 differ also in other 
 W respects. Respiration 
 
 occurs in every living 
 cell, in roots as well as 
 in stems and leaves, 
 ^ ^ ^ and goes on continu- 
 
 .> ^% ally? while photosyn- 
 
 fs i^ggO^ thesis goes on only 
 
 in the green cells in 
 sunlight. 
 
 The grape sugar 
 FIG. 64. Cells of the carrot with crystals of ~ 1-0.11 
 
 , . , . ., . -.. formed in the leaves 
 
 carotin, which give the root its orange color 
 
 is, as we have noted, 
 
 almost immediately turned to starch. Later, especially at 
 night, this food is distributed through the plant, by way of the 
 sieve tubes, to be used in the formation of new tissues, or it is 
 stored in stems, roots, and other organs until needed. Starch, 
 however, cannot pass through the cell walls, and before it can 
 be moved it must be turned back to grape sugar again. This 
 is accomplished by means of vegetable ferments called enzymes, 
 and the process is called digestion. A green and starchy 
 banana or pear laid aside for a time will become sweet by the 
 same process. The underground parts of the plant are favor- 
 ite places for the storage of food. Here the grape sugar is
 
 THE ORGANIZATION OF THE PLANT 77 
 
 again turned to starch by the leueoplasts or amyloplasts, small 
 bodies allied to the chloroplasts. The leueoplasts and starch 
 grains may be easily seen in young shoots of the canna. 
 
 Transpiration. Another important service performed for 
 the plants by the leaves is the transpiration of water. The 
 transpiration stream, passing off through the stomata, not only 
 keeps the cell sap denser than the soil water, thus providing 
 for a continuous inflow of food materials in solution, but the 
 mere evaporation of so much moisture enables the plant to 
 
 
 FIG. 65. Cells from a dahlia root, showing crystals of iiiulin, a substance 
 
 allied to starch 
 
 keep cool in the midst of the downpour of heat on a summer 
 day. At the end of the growing season most of our broad- 
 leaved plants prepare for the approaching winter by casting 
 their leaves. By so doing they avoid transpiration in winter 
 when most of the moisture in the soil is locked up by the 
 frost. But even in milder climates the leaves are eventually 
 thrown off. In regions of summer drought they may all be 
 cast at once ; otherwise the individual leaves fall one by one, 
 and the tree always has a crown of verdure. One reason for 
 the casting of the leaves is that after a season of food making 
 a considerable amount of useless mineral matter has accumu- 
 lated in the leaf, which impairs its usefulness. The ashes from
 
 78 
 
 a bushel of leaves picked from a tree in autumn are noticeably 
 heavier than the ashes from a bushel of leaves picked fmm 
 the same tree in spring. The growth of the stem and the 
 
 FIG. 66. Cells from the rind of ail orange, showing the colored chromoplasts 
 
 production of new leaves which shade the older ones make 
 it desirable to cut off the latter after a time. The fall of the 
 leaf is caused by a layer of brittle cells which the plant con- 
 structs across the petiole. When the 
 parts are cast off, a smooth scar is 
 left, over which a thin cover of bark 
 is deposited. Great numbers of flow- 
 ers and embryo fruits are cut off 
 by the plants in the same way, and 
 many woody species also cut off some 
 of their twigs. The latter are usually 
 
 the young twigs of the season and of 
 
 FIG. 67. Typical flower of 
 
 the houseleek 
 pet, petals; sta, stamens; car, the same age as the leaves. 
 
 carpels; sep, sepals _ TT1 
 
 The flower. When the season lor 
 
 reproduction arrives the flowers appear. These may be re- 
 garded as transformed branches designed for reproduction. 
 The flower when complete has four sets of organs, called
 
 THE ORGANIZATION OF THE PLANT 
 
 79 
 
 FIG. 68. A typical mono- 
 cotyledon flower 
 
 respectively the sepals, petals, stamens, and carpels. On the 
 outside are the green and leaf like sepals ; next within are the 
 colored and more delicate petals; then come one or more 
 circles of threadlike organs with knobbed ends, the stamens; 
 
 and last, occupying the center of the 
 flower, are one or more bottle-shaped 
 or club-shaped carpels. Taken collec- 
 tively, the sepals form the calyx and 
 the petals the corolla. The carpels 
 when united form the pistil, though 
 often the carpels themselves are called 
 pistils. The base of the pistil is the 
 ovary and within it are the ovules, des- 
 tined to ripen into seeds. In order 
 that fertile seeds be produced, however, it is necessary that 
 the flower be pollinated, that is, that the tiny grains of pollen 
 formed in the knobs, or anthers, of the stamen fall upon the 
 stiyma at the apex of the pistil. In this position each grain 
 puts out a pollen tube which grows down through the sub- 
 stance of the pistil until it meets and enters an ovule, after 
 which fertilization, or the union of an 
 egg and sperm, is accomplished. Each 
 flower, therefore, must receive at least 
 as many pollen grains as it ripens 
 seeds, and it usually receives many 
 more, for some fail to reach the stigma 
 and are therefore wasted. The end of 
 the stem, from which the floral parts 
 rise, is called the receptacle. When the 
 other sets of organs in the flower ap- 
 pear to spring from the base of the ovary, the flower is said to 
 be hypogynous. Sometimes the receptacle grows up about the 
 ovary in such a way that the floral parts seem to grow from 
 the top of the ovary. In such cases the flower is epigynous. 
 
 FIG. 
 
 . A typical dicoty- 
 ledon flower
 
 80 
 
 AGRONOMY 
 
 Pollination. Stamens and carpels are the only organs in 
 the flower that are necessary to the production of seeds, and 
 for this reason are often distinguished as the essential organs. 
 A considerable number of plants, of which the willow and 
 cottonwood are examples, have only these two kinds of 
 
 organs, showing very 
 clearly that the others 
 are not necessary. In 
 some species the sta- 
 mens and pistils are 
 in separate flowers, as 
 in the pumpkin and 
 cucumber; in others 
 they may be on sep- 
 arate plants, as in the 
 willow. Even when 
 both sets are found in 
 the same flower, as in 
 the lily and most of 
 our common plants, 
 they are usually sepa- 
 rated from each other 
 by a distance too great 
 to be bridged with- 
 out the aid of the 
 FIG. 70. Trillium wind, birds, insects, 
 
 A plant in which the monocotyledon number an( ] other agencies. Of 
 (three) is especially prominent 
 
 these, the two most 
 
 important are undoubtedly wind and insects. Wind-pollinated 
 flowers are generally inconspicuous, lacking sepals and petals 
 and producing neither perfume, pollen, nor nectar, since the 
 wind will work without pay ; but flowers that depend upon 
 insects and birds for pollination must provide a reward in 
 the form of nectar or extra pollen, and must advertise it by
 
 THE ORGANIZATION OF THE PLANT 
 
 81 
 
 FIG. 71. A group of wind-pollinated flowers 
 
 Those on the left are staminate ; those on the right are of two kinds, the easily 
 recognized staminate and the small starlike pistillate near the tips of the branches 
 
 perfume and brightly colored petals or sepals. These latter 
 organs may also be of service to insect-pollinated flowers by 
 being so arranged that visitors cannot remove the nectar
 
 AGRONOMY 
 
 without being dusted with pollen and at the same time brush- 
 ing off upon the pistil the pollen brought from other flowers. 
 Many insect-pollinated flowers, in order to better direct the 
 attention of insects to the nectar, have various colored lines 
 and dots, called nectar guides, on the petals and sepals. In 
 addition, the petals and sepals may protect the nectar from 
 being dried up by the sun or diluted by rain and dew. In 
 some flowers the stamens and pistils are so arranged that 
 pollination may be effected by pollen 
 from their own stamens. This is called 
 self or dose pollination. Usually, how- 
 ever, the stigma and stamens ripen at 
 different times, or are so placed that 
 pollen from another flower is required 
 in order to produce seeds. When this 
 occurs the process is called cross polli- 
 nation. All the highly specialized flow- 
 ers are adapted for cross pollination, 
 and this arrangement has been found 
 to produce more vigorous and versatile 
 offspring. Wind-pollinated flowers have 
 to produce a great abundance of dry, 
 powdery pollen grains to insure that, 
 when these are intrusted to currents of 
 air, enough will find the waiting pistils to render their ovules 
 fertile. Insect-pollinated flowers, on the contrary, having 
 adopted a more certain method of transfer, do not have to 
 produce so much pollen. In some species the flower contains 
 only one or two anthers, and yet it finds this number sufficient 
 for its needs. 
 
 In adapting themselves to insects and other agencies for the 
 transfer of pollen, flowers have become more varied than any 
 other organ of the plant. Running through all their variations, 
 however, a general plan of the flower may be discerned. In 
 
 FIG. 72. Flower of the 
 nasturtium (Tropaeolum), 
 with two large nectar 
 guides and three " false " 
 nectar guides 
 
 False nectar guides are 
 
 supposed to discourage the 
 
 visits of small insects
 
 THE ORGANIZATION OF THE PLANT 83 
 
 the flowers of monocotyledons there are normally three parts 
 in each circle, or whorl, or if there are more than this, the num- 
 ber is some multiple of three. The iris has three sepals, three 
 petals, three stamens, 
 and a pistil composed 
 of three carpels; the 
 lily has three sepals, 
 three petals, six Sta- FIG. 73. Plans of three typical flowers 
 
 meilS and a three- The ^ rst a monocotyledon, the other two repre- 
 senting four-parted and five-parted dicotyledons 
 
 parted pistil. I he 
 
 flowers of dicotyledons are usually distinguished from those 
 of monocotyledons by having four or five parts in each circle, 
 though they often exhibit a much wider range of variation. 
 
 The fruit. The fruit results from the ripening of the pistil, 
 or carpels, often in conjunction with other parts of the flower. 
 Its development is one of the results of pollination. Flowers 
 that fail to secure pollination are usually cut off and fall from 
 the plant soon after blooming. There are many exceptions to 
 this rule, however. All seedless fruits, among which may be 
 mentioned navel oranges, seedless grapes, bananas, the currant 
 of commerce, pineapples, and seedless or coreless apples and 
 pears, must of course be produced without pollination. The 
 secondary effects of pollination and the resultant fertilization 
 are often far-reaching, and may extend not only to the ovary, 
 or carpel, but to the receptacle and other parts as well. Fruits 
 that develop as the result of incomplete pollination often lack 
 the flavor of the seeded forms, and by their incomplete develop- 
 ment indicate the fact that they have failed to receive sufficient 
 pollen. In a majority of fruits the pistil alone is represented, 
 as in peas, beans, plums, and tomatoes. In the apple, pear, and 
 similar fruits the core, only, represents the pistil, the fleshy 
 part being the receptacle that has grown up around it. 
 
 The fleshy part of the strawberry is also a receptacle, and 
 all the seedlike parts upon it are the remains of tiny pistils,
 
 FIG. 74. Fruits modified for wind distribution 
 
 A, ironwood ; J3, white ash; C, ailanthus; D, hop tree; E, box elder; 
 
 F, basswood ; G, pine ; H, locust ; /, silver bell ; J, sterculia ; K, black 
 
 ash ; L, Norway maple 
 
 84
 
 THE ORGANIZATION OF THE PLANT 
 
 85 
 
 each consisting of a single carpel. In the blackberry each 
 small pistil becomes fleshy and the receptacle serves merely 
 to hold them together. The raspberry is somewhat like the 
 blackberry, but when ripe the pistils separate from the recep- 
 tacle. A few fruits, such as the mulberry, pineapple, and 
 osage orange, are the 
 product of several 
 flowers and are called 
 compound fruits. In 
 the pineapple each 
 " eye " represents a 
 separate flower. 
 
 The object of the 
 plant in producing 
 flowers and fruits is, 
 of course, the contin- 
 uation of the species 
 by the formation of 
 seeds. Many plants 
 too tender to en- 
 dure great cold or 
 drought are able to 
 form seeds that can 
 do so, and thus the 
 life of the species is 
 carried over the un- 
 favorable season. In 
 addition, seeds may 
 multiply and distribute the plants as well. The fruit is de- 
 signed to protect the developing seeds and to aid in distribut- 
 ing them when mature. In some the fruit becomes sweet 
 and juicy, to attract birds and mammals ; in others it forms 
 winglike sails, by means of which the seeds are carried long 
 distances by the wind ; in still others it develops hooks that 
 
 FIG. 75. Seeds modified for wind distribution 
 
 A, buttomvood; B, cat-tail; C, trumpet creeper; 
 ]), ratalpa; E, dandelion; F, clematis; G, olean- 
 der ; //, actiuomeris ; /, anemone ; ./, milkweed
 
 86 
 
 AGRONOMY 
 
 FIG. 76. External view of 
 lima bean 
 
 mic, micropyle ; hil, hilum ; 
 tes, testa 
 
 catch into the clothing of man and the other animals ; while 
 not a few shoot their seeds for some distance or in other 
 
 ways provide for their dispersal. 
 
 The seed. The seed consists of an 
 outer covering, called the testa, within 
 which is a young plant, or embryo. The 
 testa is marked externally by a scar, 
 the hilum, where the seed was attached 
 to the parent plant. Near the hilum is 
 a tiny opening through the testa called 
 the micropyle. The embryo always 
 consists of a stemlike part, the cauli- 
 cle, to which are attached one or two seed leaves, or cotyledons. 
 In most cases a tuft of very rudi- 
 mentary leaves, a bud in fact, is found 
 at one end of the caulicle. This is 
 the plumule. The embryo is always 
 provided with a food store sufficient 
 to give it a start in life. In plants 
 like the bean this food supply may 
 be stored in the young plant or it 
 may be stored within the testa but 
 outside the embryo, as in the castor 
 bean, in which case it is known as the endosperm, or albumen. 
 So unvarying is the occurrence of either one 
 or two cotyledons in each kind of seed that this 
 fact is commonly seized upon to divide the 
 world of flowering plants into two groups. The 
 plants whose seeds contain only one cotyledon 
 are called monocotyledons, and those whose seeds 
 contain two are called dicotyledons. The differ- 
 ences between the groups, as we have seen, are 
 not confined to the cotyledons alone, but are manifested in 
 all the conspicuous parts of the plant. 
 
 -tes 
 
 FIG. 77. Embryo of lima bean 
 
 plu, plumule; can, caulicle; 
 cot, cotyledon; tes, testa 
 
 FIG. 78. Seed 
 of the castor 
 bean, showing 
 the projecting 
 caruncle
 
 THE ORGANIZATION OF THE PLANT 
 
 87 
 
 of four-o'clock 
 cot, cotyledon ; 
 caw, caulicle ; 
 end, endosperm 
 
 Life cycle of plants. The life cycle of some plants is com- 
 pleted in a single season. They spring up, flower, produce 
 v-- -can their seeds, and disappear within the interval 
 \-plu of a few weeks or months. On the other 
 \-cot l iail cl, some of the lofty trees that still inhabit 
 ^ the earth have been growing for many hun- 
 
 FIG. 79. Seed dreds or even thousands of years. As regards 
 of honey locust their length of life, however, plants may be 
 cau.caolicle ; phi, t |j v ided into three groups annuals, biennials, 
 
 plumule ;co,coty- 
 
 ledon ; end, endo- and perennials. An annual is a plant that 
 
 sperm; tes, testa completeg itg life cycle within 
 
 a year. This may occur during a single grow- 
 ing season, as in the radish, when it is called 
 a summer annual ; or the plant may spring up 
 in autumn, live through the winter, and fruit 
 in the spring, as in some varieties of wheat, 
 thus becoming a winter annual. Several of 
 the common summer annuals of our gardens may be treated as 
 winter annuals. Lettuce and spinach are sometimes grown in 
 this way. It is clear from the behavior of these plants that they 
 do not die from the cold but are killed by fruiting. Biennials 
 
 differ from annuals in 
 -- end -& 
 
 that they require two 
 growing seasons to 
 complete the round of 
 their existence. The 
 first year they store up 
 much food, which they 
 use the second year in 
 pioducing seeds. Car- 
 rots, salsify, and beets 
 are biennials. In re- 
 gions with a long growing season the line dividing an- 
 nuals from biennials breaks down more or less completely. 
 
 .cot. 
 
 I .plu 
 
 FIG. 81. Grain of corn 
 
 The fruit and seed of a monocotyledon, end, endo- 
 sperm ; cot, cotyledon ; pin, plumule ; cau, caulicle
 
 88 
 
 Fiu. 82. The showy lady's-slipper (Cypripedium spectabile) 
 A type of the highest monocotyledons 
 
 Perennials are plants that live more than two years. They 
 are not killed by fruiting, though this makes heavy drafts 
 upon their vitality. Like biennials, most perennials store up
 
 THE ORGANIZATION OF THE PLANT 89 
 
 more or less food in summer, which is expended in growth 
 during the following spring. The rhubarb and asparagus, 
 among garden vegetables, and the lily and iris, among decora- 
 tive plants, are good examples of this. Most of the asparagus 
 crop is produced from food made by the plant the preceding 
 year. There are two classes of perennials. In the herbaceous 
 perennials the stems die down to the ground in winter. Lilies, 
 peonies, asparagus, and rhubarb are examples of this class. 
 The woody perennials comprise our trees, shrubs, vines, and 
 other forms that put up stems, which continue to live for a 
 succession of years. Trees have a single trunk and usually 
 attain heights of more than twenty feet. Shrubs have several 
 stems and are less than twenty feet high. Bushes resemble 
 shrubs, though they are somewhat smaller, usually being no 
 taller than a man. Vines have stems too weak to stand alone 
 and consequently must be supported by stronger plants. They 
 may be root climbers like the poison ivy, twiners like the bitter- 
 sweet, true climbers like the grape and woodbine, or scramblers 
 like the climbing rose. 
 
 The rest period of plants. In perennial species, after a 
 season of growth, the vegetative processes gradually cease, 
 buds are formed, the leaves are thrown off, the wood cells 
 thicken, and the protoplasm, excluding much of its moisture, 
 goes into a resting condition. It is likely that this season of 
 dormancy was originally in response to a change in the season, 
 for in northern regions it occurs at the beginning of winter 
 and in the tropics at the beginning of the dry season. A 
 period of rest, however, seems natural to most plants. Many 
 seeds refuse to grow if planted as soon as ripe ; the spring 
 flowering plants will not respond to warmth when brought 
 into the house in early winter ; and potatoes, onions, parsnips, 
 and the like, stored in cellars, do not begin to sprout until 
 the approach of spring. The hyacinth, narcissus, crocus, and 
 tulip, after flowering in the open ground, ripen their foliage
 
 90 AGRONOMY 
 
 and remain dormant during the summer, but in autumn begin 
 to grow again, making more or less root growth all winter. 
 The white, or Madonna, lily rests for a time in summer and 
 makes new growth in autumn. Possibly half the species of 
 crocus produce their flowers in autumn, and the witch-hazel is 
 a well-known shrub with the same habit. Greenhouse plants, 
 coming as they do from a region in which the season of rest 
 is the dry season, are benefited by withholding water after 
 the season for growth is over. Calla lilies and other bulbous 
 plants are often allowed to become entirely dry after flowering. 
 Our own plants seem to be adjusted to a season of cold for 
 the rest period, though in many cases an exposure to dryness 
 is as effective. In cold climates hardiness is often a matter 
 of complete dormancy. 
 
 Genera, species, and varieties. Although each kind of plant 
 has adopted the form most suited to its position in life, and 
 in consequence has become different from all others, this has 
 not resulted in a multitude of disconnected forms. Strong 
 lines of resemblance run through the different groups, and, 
 interwoven through the vegetable kingdom, bind it into one 
 related whole. As a general thing, the more decided the re- 
 semblance between different forms, the closer the relationship. 
 There are certain types of leaf and flower on which nature 
 has rung a thousand changes, producing plant after plant 
 essentially alike though ever varied. The casual observer 
 do.es not fail to note these differences, and usually recognizes 
 groups like the violets, lilies, asters, grasses, and legumes at 
 sight, though he may fail when it comes to the lesser distinc- 
 tions that separate species from species. The botanist, how- 
 ever, finds it convenient to carefully delimit these smaller 
 divisions. To the unit of his classification he gives the name 
 of (species and defines it as a group of like individuals. All 
 the plants of white clover or of field corn form a species. 
 Crenera (singular, yenuz) are groups of related species. Ked
 
 THE ORGANIZATION OF THE PLANT 91 
 
 clover, white clover, yellow clover, and many other clover 
 species belong to the clover genus, and all have a common 
 resemblance in leaf, flower, and fruit. Going beyond the 
 clovers, however, one finds many other plants whose general 
 appearance suggests a relationship to them. Among these are 
 beans, peas, alfalfa, vetch, locust, cowpeas, and soy beans. 
 These differ enough to be put in different genera, but all are 
 included with the clovers in a larger group called & family, 
 which holds the same relation to genera as the genera them- 
 selves hold to species. The family to which the clovers and 
 their allies belong is the Leguminosse, or legume family. There 
 are more than two hundred of these families, each composed 
 of many genera and species. In a similar way families are 
 grouped in orders. The legumes are placed with the rose- 
 worts and various others in the order Resales. 
 
 The species themselves, though called groups of like indi- 
 viduals, constantly exhibit minor differences that may be 
 brought out by selection or by modifying the surroundings 
 of the plant. The radish is a species, but cultivation has made 
 many forms of it. Such forms the gardener calls varieties, but 
 the botanist calls them elementary species. The cultivated 
 cabbage has produced several striking elementary species or 
 varieties, among which are included kale, collards, cauliflower, 
 Brussels sprouts, and kohl-rabi. 
 
 Scientific names. Scientists have given each species of ani- 
 mal and plant a scientific name to facilitate handling it in 
 literature, correspondence, and conversation. These names 
 have usually been taken from the Latin or Greek and have 
 the merit of being the same the world over an obvious ad- 
 vantage when the common or popular name may change from 
 one locality to another and is rarely the same in the tongues 
 of different nations. In speaking to our neighbors we may 
 use the common name only, but in dealing with strangers it 
 may often be necessary to use the scientific name to avoid
 
 92 AGKONOMY 
 
 being misunderstood. Each species has a specific name con- 
 sisting of a single word, which is applied to it much as the 
 given names of people are applied to them. Such specific 
 names as alba, "white "; rubra, "red "; and vulgare," common," 
 are frequently used. The generic name, always written before 
 the specific, shows to what larger group a species belongs. 
 Thus the crimson clover is Trifolium incarnatum. The red 
 clover is also a species of Trifolium called Trifolium pratense. 
 Only one species in each genus can have the same specific 
 name, though this may be used again and again in other 
 genera. Alba is a common specific name for white-flowered 
 species in many genera. The generic name, however, can be 
 used for but one group of plants. There is but one genus 
 Trifolium in all the world. In naming lesser divisions of a 
 species it is customary to give them varietal names taken 
 from the Latin or Greek, though in many cases such plants 
 are named after prominent persons, gardeners, and the like. 
 
 PRACTICAL EXERCISES 
 
 1. Strip off a piece of epidermis from one of the scales of an onion 
 bulb, mount, and examine with the microscope. Find and label all parts 
 of the cell mentioned on page 57. In the cells of ditch moss or the hairs 
 from the flowers of gloxinia or tradescantia, note the circulation of the 
 protoplasm. 
 
 2. Make thin sections of a potato and examine in the same way, to 
 see starch grains. Apply a drop of dilute iodine solution to a piece of 
 laundry starch. Note the color. Test the mount of potato in the same 
 way. 
 
 3. Mount a leaf of the ditch moss (Elodea) or a leaf from any of 
 the broad-leaved true mosses and note the chloroplasts. 
 
 4. Mount thin sections of the carrot or orange peel and examine 
 the chromoplasts. Make a similar mount of the epidermis from the 
 underside of a nasturtium petal. 
 
 5. Soak seeds of radish or mustard for a short time and throw them 
 against the inside of a clean moist flowerpot to which they will stick. 
 Invert the flowerpot over a shallow dish of water for a few days and
 
 THE ORGANIZATION OF THE PLANT 93 
 
 an abundance of root hairs will be produced by the germinating seeds. 
 Examine with the microscope. 
 
 6. Make longitudinal and cross sections of parsnip or carrot to see 
 the regions of the root. Find, draw, and label the parts. 
 
 7. Make thin cross sections of any young root and examine with 
 the microscope for the cellular structure. 
 
 8. Perform the experiment with osmosis described on page 63. 
 
 9. Peel one end of a potato, set the peeled end in a dish of water, 
 make a hole an inch or more deep in the other end, and in this hole put 
 some dry sugar. Explain the moisture that appears in the hole. 
 
 10. Cut slices of potato a quarter of an inch thick and place some 
 in salt water and some in fresh water. Account for the difference in 
 rigidity in the two sets at the end of an hour. 
 
 11. Make cross sections of cornstalk or asparagus and compare with 
 similar sections of geranium, begonia, or any of our forest trees. Make 
 sketches to show the differences noted. 
 
 12. In a thin section of begonia or geranium stem locate the pith, 
 wood, ducts, bast, and cortex. 
 
 13. Get a thrifty young willow twig and girdle it by removing a 
 ring of bark an inch wide two or three inches from the lower end. 
 Stand this in water so that the girdled portion is covered. Where do 
 roots appear? What light does this throw on the passage of foods 
 and food materials through the stem ? 
 
 14. On twigs of lilac, cherry, peach, golden bell, cottonwood, or 
 horse-chestnut locate the flower and leaf buds. 
 
 15. Locate accessory buds in walnut, pipevine, red maple, box elder, 
 butternut, and peach. 
 
 16. Select leaves to illustrate parallel, palmate, and pinnate vena- 
 tion. Make sketches to show the different forms. 
 
 17. With the microscope examine the epidermis from the underside 
 of a leaf for the stomata. Draw. 
 
 18. In a thin cross section of a leaf locate the tissues described on 
 page 72. 
 
 19. Thrust the petiole of a geranium leaf through a small hole in a 
 piece of cardboard and place the latter so that the petiole of the leaf 
 will dip into a glass of water. Over the blade of the leaf invert a drink- 
 ing glass, which should rest upon the cardboard. Explain the presence 
 of the moisture that forms on the upper glass in a short time.
 
 94 AGRONOMY 
 
 20. Select a representative flower and locate the organs named on 
 page 79. 
 
 21. Distinguish the monocotyledons from the dicotyledons in as 
 many different kinds of flowers as you can find. 
 
 22. Locate the nectar guides and nectaries, if any, in barberry, 
 buttercup, toadflax, catalpa, horse-chestnut, nasturtium, and phlox. 
 
 23. Decide whether the following were produced by hypogynous or 
 epigynous flowers : apple, orange, banana, pear, cranberry, olive, and 
 tomato. 
 
 24. Make a collection of seeds to show as many methods of seed 
 dispersal as possible. Visit the nearest museum for other examples. 
 
 25. Find the two cotyledons in the bean and the single one in the 
 corn. Examine other seeds to discover whether they are monocotyledons 
 or dicotyledons. In which seeds do you find endosperm ? 
 
 References 
 
 Atkinson, " College Botany." 
 Bergen and Caldwell, "Practical Botany." 
 Bergen and Davis, "Principles of Botany." 
 Campbell, " University Text-Book of Botany." 
 Clute, " Laboratory Botany for the High School." 
 Coulter, Barnes, and Cowles, "Textbook of Botany." 
 Green, "Vegetable Physiology." 
 Stevens, " Plant Anatomy."
 
 CHAPTER VI 
 
 THE ELEMENTS NEEDED BY PLANTS 
 
 Source of the elements. The chemical elements indispensable 
 to plants are ten in number ; namely, oxygen, hydrogen, nitro- 
 gen, potassium, magnesium, calcium, iron, sulphur, phosphorus, 
 and carbon. Several others have been found in plants, but 
 these have been proved unnecessary by growing plants to 
 maturity in media in which these elements were lacking. Al- 
 though the ten elements indicated are all essential, most of 
 them are taken in very minute quantities. The small amount 
 of ashes left when wood is burned represents the mineral 
 matter taken up by the plant in forming it, and much of this 
 is likely to be silicon and other elements that are nonessen- 
 tial. Very little is known of the part played by some of the 
 essential minerals in the economy of the plant. Possibly their 
 presence acts simply as a stimulant for various plant processes. 
 The only element taken entirely from the air is carbon. Oxy- 
 gen is taken from the air for respiration, but that used in 
 making food is taken combined with hydrogen as soil water. 
 All the other elements are derived from the soil, in which they 
 exist as compounds and not as single elements. These com- 
 pounds are usually chlorides, carbonates, sulphates, phos- 
 phates, and nitrates. In most of these there is considerable 
 oxygen, the termination ate in the names of the compounds 
 indicating its presence. These materials are dissolved out of 
 the soil by the soil water and carried into the plant by osmosis. 
 
 Selective absorption. Analysis of the ash of plants has shown 
 that all the species of a given area do not contain the same 
 proportion of the different minerals, though growing under 
 
 95
 
 96 AGRONOMY 
 
 exactly the same conditions and absorbing the same soil water. 
 Clover when growing with barley may take up five or six times 
 as much lime as the barley does, while the latter takes up 
 eighteen times as much silica as the clover. Similar differences 
 in the absorption of food materials are found in other plants. 
 It is as if each plant exercised a conscious selection. Such a 
 condition, however, is to be explained on purely physical 
 grounds by what is known as selective absorption. When minute 
 quantities of any mineral are dissolved in the soil water, they 
 will pass into the plant by osmosis, but in every instance each 
 substance in the water acts with reference to similar substances 
 in the plant as if it were the only element concerned. It fol- 
 lows, therefore, that if the plant happens to be using a certain 
 substance, the depletion of the supply in the cells will induce 
 more of it to filter in ; but if the plant has no use for it, the 
 density of the solution for this particular substance on both 
 sides of the cell wall soon becomes equal and the osmotic 
 action with reference to it ceases. Plants cannot exclude 
 poisons and other harmful or useless substances when suffi- 
 ciently diluted by the soil water. 
 
 Use of water to the plant. In addition to carrying the dis- 
 solved minerals into the plant, water forms a very essential 
 part of the plant food, maintains the turgor of the cells and 
 thus keeps the plant in shape, is the medium in which all the 
 vital processes of the plant go on, aids in the transfer of food 
 within the plant, and, finally, by its evaporation, serves to cool 
 the plant and keep the cell sap denser than the soil water. 
 The amount of water transpired by growing plants is remark- 
 able. It is estimated that for every pound of dry matter pro- 
 duced by ordinary crops, from 250 to 400 pounds of water is 
 transpired, while mustard is said to require 900 pounds of 
 water for each pound of dry matter. A healthy apple tree has 
 been estimated to transpire 35,000 pounds of water during 
 the growing season. A moist spot may be drained through
 
 THE ELEMENTS NEEDED BY PLANTS 97 
 
 the simple expedient of planting such water-loving species as 
 willow and cottonwood in the vicinity. A great part of the 
 living plant is water. Turnips, melons, and the like contain 
 more than 90 per cent of water, and even in air-dry plants the 
 amount is seldom less than 10 per cent. The amount of water 
 may differ greatly in different parts of the same plant ; thus 
 the flesh of the watermelon, peach, plum, and the like contain 
 much more water than the seeds or the vegetative parts of 
 the specimen. 
 
 Root pressure. Most of the water given off by plants escapes 
 through the stomata as water vapor, but occasionally, as at the 
 close of a warm day in summer, the roots may continue to absorb 
 more than the leaves can evaporate in the cool air of evening. 
 This excess moisture may appear on the leaves as minute glob- 
 ules or even larger drops of water. Such excretion of water 
 is called guttation, and the force exerted by the roots in send- 
 ing it upward is root pressure. In some plants this force is very 
 great. In the birch it is sufficient to hold up a column of water 
 more than eighty feet high. It is root pressure that causes 
 grapes to " bleed " when trimmed in spring, and the same 
 force makes the sap run from wounds in trees. The drops of 
 water to be seen on the leaves of such plants as nasturtium in 
 the early morning are due to root pressure, and so is much of 
 what passes for dew on grassy areas. Often the roots of weeds 
 cut down by the hoe will continue to send up water for some 
 time and show, by a moist spot in the dry surface soil, where 
 each plant stood. 
 
 Carbon dioxide. The gas, carbon dioxide, though found in 
 the atmosphere in so small an amount as three parts in ten 
 thousand, is nevertheless the only source of the carbon in 
 plants. In a ton of dry wood at least a thousand pounds is 
 carbon, all of which has been derived from the air. The carbon 
 in our hard and soft coals, peat, and the like was stored up in 
 the same way and from the same source in other days. This
 
 98 AGRONOMY 
 
 element is the characteristic element of all animal and plant 
 life, as silicon is of the mineral kingdom, but the carbon 
 fixed in any form of organic life is only one stage in a constant 
 cycle of changes. Upon the death of the organism it is again 
 united with oxygen by the processes of decay and liberated 
 as carbon dioxide, only to be selected by new plants and formed 
 into starch and plant tissues again. Though forming so small 
 a proportion of the air, it is nevertheless estimated that there 
 are 3,400,000,000,000 tons of it in the atmosphere more 
 than 25 tons for each acre of soil. In plants and animals carbon 
 is most frequently found united with hydrogen and oxygen to 
 form carbohydrates, a carbohydrate being defined as a substance 
 consisting of these three elements, with the hydrogen and 
 oxygen in the proportions in which they form water. Starch, 
 sugar, wood, and cellulose are all carbohydrates. 
 
 Nitrogen. Four fifths of the air is nitrogen, but ordinary 
 plants cannot use it. Their supply is derived almost entirely 
 from the nitrogen in the humus of the soil. A few plants, to 
 be described later, are able to make use of atmospheric nitro- 
 gen, but the rest use nitrogen only in the form of nitrates ; 
 that is, nitrogen combined with other elements, such as calcium, 
 potassium, magnesium, sodium, and the like. One of the chief 
 uses of these latter elements to plants seems to lie in their 
 ability to combine with nitrogen in a form that the plants can 
 use. Nitrogen is one of the elements most frequently lacking 
 in soils, though there are not less than 35,000 tons in the air 
 over each acre worth about ten million dollars at present 
 prices if it were only available for plants. Nitrogen intensifies 
 the color of plants, increases the growth of leaves and stems, 
 and, when abundant, may hinder seed formation by favoring 
 growth processes. Some grain crops, when supplied with plenty 
 of nitrogen, grow so luxuriantly that the stems are unable to 
 support the weight of the plant. Nitrogen is also necessary for 
 the formation of protoplasm and all other proteins.
 
 THE "ELEMENTS NEEDED BY PLANTS 99 
 
 Calcium and magnesium. Calcium and magnesium, which 
 are much alike, are most familiar to us in limestone and dolo- 
 mite. In addition to being useful in forming compounds with 
 nitrogen that the plant can use, these elements form unions 
 with various acids in the plant which would otherwise be 
 harmful. Calcium is an important part of the chlorophyll and 
 nucleus, and promotes the hardiness of plants. On soils con- 
 taining much calcium or lime, plants endure drought and frost 
 much better than in soils in which it is lacking. Certain plants, 
 such as alfalfa, clover, peas, and beans, are often known as 
 lime plants because they cannot exist in soils deficient in this 
 element. Spinach, beets, lettuce, and many others cannot grow 
 without lime. On the other hand, many plants of sandy and 
 boggy soils are so sensitive to lime that they cannot endure 
 even small amounts in the soil water. Magnesium is important 
 in forming seeds, and its absence may not be noticed until 
 flowers and fruits fail to develop. While absolutely essential 
 to plant growth, magnesium in the absence of lime acts like 
 a poison. Calcium is usually more abundant than magnesium 
 in leaves and stems, but in seeds the ratio is usually reversed. 
 
 Potassium and phosphorus. Potassium is supposed to aid in 
 the production and transportation of the carbohydrates and 
 to reduce the acidity of cell sap. It increases the turgidity of 
 the cell and hastens the ripening of wood and fruit. It also 
 increases the plant's resistance to frost and is reputed to deepen 
 the color of flowers and fruits. Certain plants contain so much 
 potassium or potash that they are called potash plants. Phos- 
 phorus is associated with the production of proteins, and its lack 
 prevents the development of seeds. Fleshy roots may also con- 
 tain much potassium. When soils are deficient in this element 
 the addition of sodium is followed by renewed plant growth. 
 
 Sulphur and iron. Sulphur and iron, so frequently found 
 together in nature, are necessary constituents of protoplasm. 
 Iron is also essential to the formation of chlorophyll in plants.
 
 100 AGRONOMY 
 
 Chlorine, silicon, and others. Small amounts of chlorine, 
 silicon, sodium, manganese, aluminum, and other minerals are 
 usually found in the ash of plants. They are present in most 
 soils and, being dissolved in the soil water, flow into the plant 
 with it. Silicon is often abundant in the older, denser parts 
 of plants, and the flinty exterior of scouring rushes and grass 
 stems is due to it. The " shells " of diatoms and the stems of 
 certain scouring rushes contain so much silicon or silica that 
 the organic parts may be burned or dissolved out, leaving a 
 perfect skeleton of the mineral. Silica, however, does not 
 appear to be essential to the life of the plant. It was once 
 thought that it was necessary to give strength to the stems of 
 grasses and other plants, but this is shown to be a mistake 
 by the fact that silica is often many times more abundant 
 in the leaves of plants than in their stems. Some regard 
 chlorine as essential, since it is usually present in the plant. 
 
 PRACTICAL EXERCISES 
 
 1. Take two geranium leaves and place one in fresh water and the 
 other in a 10 per cent salt solution for half an hour. Explain the dif- 
 ference in the two. 
 
 2. AVeigh a good-sized potato and thoroughly dry it by heating in 
 an oven. Weigh again. What per cent of moisture did it contain ? Place 
 in a crucible and heat to redness to drive off the organic matter. What 
 per cent is ash ? 
 
 3. Thoroughly water a pot of young oat seedlings and turn a bell 
 jar over them. Account for the drops of water that soon appear on the 
 tips of the leaves. The same experiment may be performed with nas- 
 turtium or fuchsia plants if oats are not at hand. 
 
 4. Clover hay may yield three tons to the acre. How many inches 
 of rainfall would be needed to supply the necessary moisture if none 
 were wasted and the plants used 250 pounds of water in producing 
 each pound of dry matter? 
 
 References 
 
 Hopkins, " Soil Fertility and Permanent Agriculture." 
 Snyder, " Chemistry of Animals and Plants."
 
 CHAPTER VII 
 
 FERTILIZERS 
 
 The available mineral in the soil. The elements needed by 
 plants exist in the soil in very unequal proportions. Some are 
 so abundant as to be practically inexhaustible ; others occur in 
 such small quantities, or are so slowly weathered out of the 
 soil, that cropping for a few years may deplete the supply to 
 a point where more must be added before the land will again 
 be fully productive. It has been estimated that in the upper 
 seven inches of certain soils there is sufficient iron to produce 
 a hundred-bushel corn crop every year for two hundred thou- 
 sand years, and enough calcium, sulphur, and magnesium to 
 produce such crops for from two thousand to fifty thousand 
 years, but only enough nitrogen and phosphorus for from fifty 
 to seventy years. Other soils may differ as to the amounts of 
 each element they contain, but the proportions are likely to 
 be about as given here. It is thus seen that the soil is not an 
 indestructible asset, but that it may easily wear out by having 
 all its store of certain elements abstracted by growing crops. 
 Nor is it necessary that an element be entirely lacking in a 
 soil to render it unfertile. If the element be in a form that is 
 not available to plants, the effect is the same as if it were 
 entirely absent. 
 
 Toxic substances in the soil. Occasionally an analysis of 
 the soil may show that it contains sufficient food materials for 
 good crops, yet the plants that grow upon it do not flourish 
 because of certain substances excreted by the roots of the 
 plants themselves, which seem to be toxic or poisonous to 
 that particular crop. When crops of one kind are grown for 
 
 101
 
 102 AGRONOMY 
 
 several years in succession upon the same land, for instance, the 
 yield begins to decrease long before the available mineral food 
 has been used up. Thrifty crops of the same kind growing 
 elsewhere, if watered with extracts from such soils, give every 
 evidence of having been poisoned. When supplied with cer- 
 tain chemical elements, however, they regain their health. 
 Many wild plants exhibit similar peculiarities, and their 
 
 Photograph by the University of Illinois 
 
 FIG. 83. Wheat crop averaging 9.6 bushels to the acre 
 
 The soil has been limed and a crop of legumes plowed under. Compare with 
 the following figure 
 
 inability to grow in the same soil for any length of time is 
 attributed to an increase of the toxic elements. After growing 
 for a year or so in a given spot the old parts die, while the new 
 ones move out from the center in a constantly widening circle 
 known as a " fairy ring." Such rings are more common in 
 fungi, lichens, and ferns, but they also occur in flowering plants. 
 Most of these poisonous excretions appear to be harmful only 
 to the species that produced them, which explains one of the 
 benefits of a rotation of crops. By growing different crops on
 
 FERTILIZERS 103 
 
 the land the toxic substances excreted by one kind have time 
 to escape or become neutralized before the same crop is again 
 grown there. In some cases, however, the excretions from one 
 set of plants seem harmful to others. The butternut tree has 
 been found antagonistic to the shrubby cinquefoil that some- 
 times, infests the pastures in New England and elsewhere, 
 
 Photograph by the University of Illinois 
 
 FIG. 84. Wheat crop averaging 21.5 bushels to the acre 
 
 This wheat was grown on land adjoining that shown in preceding figure. In ad- 
 dition to lime and legumes the soil has had an application of phosphorus 
 
 while a similar antagonism seems to exist between grass and 
 certain fruit and shade trees. Additions of various substances 
 to the soil seem to neutralize these poisonous excretions of 
 plants and enable them to continue in vigorous growth. Some 
 contend that this is the only value to be derived from fertiliz- 
 ers. Whatever the reason for adding fertilizers, the fact re- 
 mains that good crops cannot long be produced without them. 
 Nor will an excess of one needed element compensate for the
 
 104 AGRONOMY 
 
 lack of another ; a sufficient amount of each must be present. 
 Often supplying a single lacking element in the soil will more 
 than double the returns from the crop. 
 
 Elements that may be lacking. Soils are seldom deficient in 
 sulphur, iron, or magnesium, and calcium is usually abundant 
 enough, though it may sometimes be lacking even in soils de- 
 rived from the weathering of limestone rocks, because it is 
 easily dissolved and carried off by the water. Phosphorus, nitro- 
 gen, and potash, however, belong to a different category. They 
 are seldom abundant in any soil and are so rapidly removed 
 by crops that the lack of one of them is usually the cause of 
 a decreased yield. Soils may be analyzed by the chemist and 
 the exact amount of each mineral constituent determined, but 
 there are various ways of making the plants themselves tell 
 what essential element is lacking. One of the best methods 
 of determining this is to make ten plots, side by side, in soil 
 as nearly uniform as possible, and add to each plot a different 
 fertilizer or combination of fertilizers containing the elements 
 likely to be lacking. The usual arrangement is as follows : 
 
 Plot 1. Nitrogen as nitrate of soda at the rate of 160 Ib. to the acre, or 
 dried blood at the rate of 700 Ib. to the acre. 
 
 Plot 2. Potash as muriate of potash at the rate of 80 Ib. to the acre, or 
 potassium sulphate at the rate of 200 Ib. to the acre. 
 
 Plot 3. Phosphorus as acid phosphate at the rate of 320 Ib. to the acre, 
 or bone meal at the rate of 200 Ib. to the acre. 
 
 Plot 4. Calcium as lime at the rate of 40 bu. to the acre. 
 
 Plot 5. Nothing. This plot serves as a check for comparison. 
 
 Plot 6. Nitrogen and potash in the proportions given above. 
 
 Plot 7. Nitrogen and phosphorus in the proportions given above. 
 
 Plot 8. Potash and phosphorus in the proportions given above. 
 
 Plot 9. Potash, phosphorus, and nitrogen in proportions as above. 
 
 Plot 10. Same as Plot 9 with the addition of lime. 
 
 The crops to be tested should be sown across all the plots, and 
 will soon show which element is deficient by a more thrifty 
 growth in the plot containing this element. It is desirable that
 
 FERTILIZERS 105 
 
 different crops be used in the test, since the lacking element 
 may not be the same for each. In any soil the need for cal- 
 cium may be easily discovered by treating part of a field with 
 lime and comparing the treated area with the part not treated. 
 The lime should be applied at the rate of twenty bushels or 
 more to the acre. When red clover and alfalfa grow well on a 
 given soil, this is a good indication that it contains sufficient 
 calcium. A growth of mosses indicates a lack of this element. 
 Sources of the needed elements. It is only in exceptional 
 cases that the cultivator concerns himself about any element 
 in the soil except potash, nitrogen, and phosphorus. These 
 three are seldom abundant, and the farmer always adds fer- 
 tilizers containing them when they can be cheaply obtained. 
 Stable manure is called a " complete " fertilizer because it con- 
 tains portions of all three. Before the advent of the white 
 man the Indian had discovered the value of fish as a ferti- 
 lizer. Near the coast it was the custom to place a fish in each 
 hill of corn. In many places fish is still used for fertilizer. 
 Several other available sources of the necessary elements exist. 
 Nitrogen is found in guano, fish guano, dried blood, slaughter- 
 house waste, bone meal, linseed and cottonseed meal, ammo- 
 nium sulphate (a product of gas works), potassium nitrate, and 
 sodium nitrate, or Chile saltpeter. The sodium nitrate is the 
 most soluble. Potash is found in wood ashes, muriate of pot- 
 ash, sulphate of potash, and kainit. Phosphorus occurs in bones 
 and bone meal, phosphate rock, and Thomas slag, which is a 
 by-product in the manufacture of steel. When necessary to 
 apply calcium it may be in the form of ground limestone, quick- 
 lime, marl, gypsum, shells, and bones. In applying fertilizers it 
 is well to remember that some are more soluble than others and, 
 applied in too great quantity, may easily make the soil water 
 so dense as to kill or greatly retard the plants it was designed 
 to help. Other fertilizers, becoming available more slowly, may 
 not show their effects upon the crops until the second season.
 
 106 AGRONOMY 
 
 Manures. The word manure comes from the Latin word manus 
 meaning " hand." The reason for the derivation is seen when 
 it is known that to manure originally meant to dig or culti- 
 vate by hand. Thus in Defoe's " Robinson Crusoe," written 
 in 1719, we find the expression, " The ground that I had 
 manured, or dug up, for them was not great." Digging about 
 the plant was early found to make it more thrifty, and the 
 old farmer's maxim that " tillage is manure " is true in a 
 more literal sense than he perhaps imagines. When it was 
 found that adding various matters to the soil had the same 
 effect upon the plants as cultivation, these substances soon 
 gained the name of " manures." 
 
 Green manures. Frequently the cultivator plows under a 
 growing crop for the purpose of adding humus and its con- 
 tained nitrogen to the soil. Such additions are known as 
 green manures. Barley, turnips, and similar crops, and even 
 weeds, may be used for this purpose, but clover, alfalfa, and 
 other legumes are usually relied upon. These latter bear 
 upon their roots numerous small nodules containing bacteria 
 which are capable of fixing atmospheric nitrogen in the soil, 
 and are therefore especially valuable for such purposes. 
 Legumes actually leave the soil in better condition than they 
 find it. 
 
 Nitrification. Undoubtedly the most important single ele- 
 ment of plant food is nitrogen. This element is not found 
 in combination in the rocks because it is too inert to readily 
 combine with other elements, and the large quantities in the 
 air are not available to ordinary plants, though some species 
 are believed to be able to absorb nitrogen from the ammonia 
 in the air through their leaves. Small amounts of both am- 
 monia and nitric acid may be added to the soil by being brought 
 down from the air in rain water or snow and converted into 
 plant food by the soil bacteria, but the amount thus added to 
 the soil is too insignificant to make it important as a source
 
 FERTILIZERS 107 
 
 of nitrogen to plants. Practically all the nitrogen used by 
 plants comes from the humus in the soil. Nor can the plant 
 use all the combinations of nitrogen derived from humus. 
 In the soil this element may exist as ammonia, nitrites, and 
 nitrates, but plants can use only the nitrates. 
 
 Bacteria and nitrification. The changing of nitrogenous 
 substances in the humus to forms that are available to plants 
 is accomplished by bacteria, of which there are some fifty 
 million in every cubic centimeter of rich soil. These bacteria 
 are the smallest of living things. They are most numerous 
 near the surface of the soil, but are found in lessened 
 numbers as far down as the lowest layers of the subsoil. 
 Like other plants, they need warmth, moisture, and oxygen 
 for growth, but, unlike them, must have organic food. They 
 are very intolerant of acids and will not live in sour soils. 
 In bogs and other water-soaked soils the absence of air pre- 
 vents the growth of bacteria, the soil becomes sour by the 
 accumulation of acids from the dead vegetation, and the 
 organic material, instead of being turned to nitrates, forms 
 peat. The addition of lime to such soils corrects the acidity, 
 but draining is necessary to promote the activities of the 
 bacteria. The fertility of the soil is then effected exactly as 
 it would be by the addition of more nitrogen. 
 
 Three sets of bacteria are concerned in the work of nitrifi- 
 cation. The first group simply turns the nitrogenous parts 
 of the humus to ammonia, a process which is often called 
 ammonification. In this process the animal and vegetable 
 matter in the soil serves as food for the bacteria which may 
 be said to digest it, excreting ferments, or enzymes, for the 
 purpose. Considerable carbon dioxide is also liberated in this 
 process, and this serves to further weather the soil particles. 
 The ammonia produced by the bacteria combines with soil 
 water to form ammonium hydroxide (NH 4 OH), and at this 
 point a new group of bacteria, known as Nitrosococcus, turns
 
 108 
 
 A(iKNOMV 
 
 the ammonium hydroxide into nitrous acid and hydrogen by the 
 addition of an atom of oxygen (NH 4 OH + O = HNO 2 + H 4 ). 
 The nitrous acid combining with various minerals in the soil 
 form nitrites, and a third set of bacteria, of the genus Nitro- 
 bacter, now adds another atom of oxygen to this compound, 
 forming the nitrates used by plants. Although nitrites and 
 nitrates differ principally in the possession of one more atom 
 of oxygen by the latter, plants seem able to use only the 
 nitrates. Nitrobacter, so far as known, is the only bacterium 
 that can turn nitrites into nitrates. 
 
 Nitrogen fixation. Certain plants known as legumes, of 
 which the bean, pea, clover, and alfalfa are examples, have the 
 power to fix atmospheric nitrogen, or, rather, they have set up 
 
 a partnership with bac- 
 teria which are able to 
 do so. In this partner- 
 ship the bacteria (Pseu- 
 domonas radicicola), in 
 return for the carbohy- 
 drates which they need, 
 give to the legumes the 
 nitrogen which they are 
 able to take from the 
 
 air. Such a partnership as this is called symbiosis, and the part- 
 ners are known as symbionts. Certain algae in the soil seem 
 also to have entered into symbiotic relations with bacteria for 
 the purpose of getting nitrogen. By carefully digging up 
 any legume and washing off the soil clinging to the roots the 
 nodules which the bacteria inhabit are easily seen. Another 
 bacterium, Azotobacter chroococcum, appears to be able to fix 
 atmospheric nitrogen by itself, oxidizing carbohydrates in the 
 soil in the process. The fact that lands allowed to lie without 
 cultivation, or fallow, for a time, increase in nitrogen content 
 is attributed to the presence of this and other bacteria. The 
 
 FIG. 85. Nodules on the roots of a legume
 
 FEETILIZEES 
 
 109 
 
 fixing of nitrogen, however, cannot go on without lime. Owing 
 to the power of their bacterial symbiont to fix nitrogen from 
 the air, legumes are able to thrive in soils too poor in nitrogen 
 to support other crops. In sandy regions, where the loose and 
 open soil permits the loss of nitrates almost as fast as formed, 
 legumes are usually abundant. 
 
 Mycorrhizas. In a considerable number of plants, among 
 which are various trees and shrubs, the older parts of the 
 roots are inhabited by fungi known 
 as mycorrhizas, which enter into sym- 
 biosis with them. Such associations 
 are common, or possibly the rule, 
 among woody plants, but are espe- 
 cially abundant in the heath family, 
 to which the rhododendron, cranberry, 
 and blueberry belong. The mycor- 
 rhizas extend out into the soil and 
 function like root hairs. They appear 
 to have the power to fix nitrogen 
 from the humus in the soil and ab- 
 sorb sugars derived from fallen leaves 
 by other soil bacteria. Certain flow- 
 ering plants, like the Indian pipe and 
 the pinesap, which lack chlorophyll, ab- 
 sorb all their food in this way. Mycor- 
 rhizas are also frequently associated 
 with plants that transpire slowly; 
 otherwise these plants would find 
 difficulty in getting sufficient food. 
 
 Soil inoculation. In many soils it is difficult to get a good 
 crop of legumes because the necessary bacteria for symbiosis 
 do not occur there. Experiments seem to show that each 
 species of legume, if it does not have its own special bacterial 
 species, has at least a special form with which it is associated, 
 
 FIG. 86. The snow plant 
 (Barcodes sanguined) 
 
 A saprophytic heathwort 
 
 (allied to the Indian pipe, 
 
 Monotropa uniflora) from 
 
 the Pacific Coast region
 
 110 AGRONOMY 
 
 and when this is missing it cannot thrive. In some cases, 
 however, the form of bacteria associated with one species may 
 be gradually induced to form partnerships with another. 
 When the necessary bacteria are lacking, the soil may be inocu- 
 lated by a few bushels of soil brought from another field in 
 which the desired crop grows well. This is scattered over 
 the field at the time of planting exactly as one would scatter 
 seeds. In a few instances the bacteria of two species seem to 
 be interchangeable. Fields in which red clover or alfalfa will 
 not grow because their bacterium is absent, may be made to 
 produce these crops by inoculating with soil brought from 
 the nearest patch of wild sweet clover. In the same way the 
 bacterial symbiont of cowpeas may be supplied from soils in 
 which the wild partridge pea occurs. Several attempts, more 
 or less successful, have been made by the national govern- 
 ment and by private parties to send out dormant cultures of 
 bacteria for use with certain crops. The seeds of the crop 
 desired are inoculated with the bacteria before sowing. In 
 the case of many cultivated species of legumes, and possibly 
 all wild ones, the bacteria with which they form associations 
 are transported into new soils by clinging to the seeds. 
 
 Denitrifying bacteria. Along with the bacteria in the soil 
 which turn nitrogenous substances to nitrates are found other 
 bacteria which reverse the process, and, by extracting the 
 oxygen from nitrates, set free the nitrogen. This process 
 goes on most rapidly in soils which are not properly aerated. 
 Stable manure, left in piles, loses much nitrogen in this way. 
 When plenty of oxygen is present the bacteria do not attack 
 the nitrates. 
 
 Harmful organisms in the soil. As we have seen, the living 
 elements of the soil are quite as important as its mineral 
 constituents. In addition to the nitrifying and denitrifying 
 bacteria and the nitrogen-fixing bacteria, there are many 
 yeasts, algse, fungi, germs of plant diseases, and hosts of
 
 FERTILIZERS 111 
 
 protozoa. The protozoa are one-celled animals that feed upon 
 the helpful bacteria, often to such an extent as to effect the 
 fertility of the soil. These may be killed or reduced in 
 numbers by burning or boiling the soil, or by treating it with 
 disinfectants. Such treatment does not appear to materially 
 harm the bacteria. The increase in fertility in soils burned 
 over is attributed to the fact that the burning killed the 
 protozoa. Florists usually bake the soil in which young 
 seeds are to be sown, or they may pour boiling water over it, 
 and in this way get rid of the harmful organisms in it. 
 
 Limiting factors in plant growth. The production of the 
 maximum crop is thus seen to depend on many things besides 
 a sufficient amount of the necessary chemical elements in the 
 soil. The temperature may be too high or too low, there 
 may be too little sunshine at some critical period of plant 
 growth, or the soil itself may contain too much or too little 
 moisture. Any unfavorable condition at once becomes the 
 limiting factor in plant growth, and changing this condition 
 frequently results in doubling or trebling the crop. In the 
 West water is often the limiting factor, but under irrigation 
 or in regions of sufficient rainfall the lack of some mineral 
 constituent of the soil is likely to prevent the maximum yield. 
 The presence of insects or plant diseases may also affect the 
 crop, and thus the limiting factor may even change from year 
 to year, with favorable or unfavorable seasons. By supplying 
 the soil with sufficient fertilizers and regulating by irriga- 
 tion, drainage, and cultivation the amount of moisture in it, 
 the farmer renders favorable such conditions as can be con- 
 trolled, which fortunately are among the most important. The 
 photographs on pages 102 and 103 illustrate very clearly the 
 change that may result from adding a single chemical element 
 to the soil. Here the application of a fertilizer containing 
 phosphorus had the effect of immediately adding nearly twelve 
 bushels an acre to the crop.
 
 112 AGRONOMY 
 
 PRACTICAL EXERCISES 
 
 1. Make an expedition to the fields and woods for evidences of 
 "fairy rings." 
 
 2. In the experiment garden make a test of the soil as directed on 
 page 104. 
 
 3. Make a collection of all of the commercial fertilizers. Label. 
 
 4. Make a list of all the legumes, cultivated or wild, that can be 
 found in the school garden. 
 
 5. Make a list of the wild legumes of the region. 
 
 6. Make up an extract of rich soil by soaking it in water. Put a 
 drop of the turbid water on a slide and examine with the high power of 
 the microscope for the bacteria. 
 
 7. Dig up clover or other legumes and look for the nodules on their 
 roots. 
 
 8. Crush a nodule and examine it under the microscope. 
 
 9. What is the limiting factor of plant growth in your region? 
 
 References 
 
 Hopkins, " Soil Fertility and Permanent Agriculture." 
 
 Roberts, "The Fertility of the Land." 
 
 Voorhees, "Fertilizers." 
 
 Warren, " Elements of Agriculture." 
 
 Farmers' Bulletins 
 
 16. Leguminous Plants. 
 
 31. Alfalfa or Lucerne. 
 
 44. Commercial Fertilizers. 
 
 77. The Liming of Soils. 
 
 89. Cowpeas. 
 123. Red Clover Seed. 
 144. Rotation of Crops. 
 192. Barnyard Manure. 
 237. Lime and Clover. 
 245. Renovation of Worn-out Soils. 
 278. Leguminous Crops for Green Manuring. 
 
 Bureau of Plant Industry 
 
 71. Soil Inoculation for Legumes. 
 173. Seasonal Nitrification as influenced by Crops and Tillage.
 
 CHAPTER VIII 
 
 THE PLANT IN RELATION TO TEMPERATURE, LIGHT, AND 
 MOISTURE 
 
 Growth temperature. The range of temperature that vege- 
 tation in the aggregate can endure is remarkable. Seeds in 
 the dormant condition have been exposed to the temperature 
 of liquid air, many degrees below zero, without impairing 
 their vitality ; and, on the other hand, some algse can exist in 
 hot springs where the temperature of the water reaches nearly 
 to the boiling point. No single species, however, can endure 
 anything like this range of temperature. Ordinary plants are 
 balanced midway between two rather close extremes of heat 
 and cold, growing Well so long as neither is too closely 
 approached, going into a dormant condition when brought 
 nearer, and dying when either extreme is reached. Differ- 
 ences in temperature are among the principal factors control- 
 ling the distribution of plants. Elevated country and mountain 
 ranges act as barriers to the spread of tropical plants, because 
 the upper regions are cold, and a stretch of warm lowland may 
 prevent the migration of alpine vegetation from one summit 
 to another; in fact, there is scarcely a species that is not 
 sharply limited in some part of its range by temperature. 
 
 A temperature of 122 above zero is fatal to most land 
 plants in the growing condition, and aquatics usually perish 
 at somewhat lower temperatures. Plants and plant parts gen- 
 erally can endure the greatest amounts of heat and cold when 
 they contain the least water. In seeds, developed by the plants 
 for carrying them over unfavorable seasons, the protoplasm 
 is brought to the resting and more resistant condition by the 
 
 113
 
 114 ACRONOMY 
 
 exclusion of most of the moisture. Some hardy arctic plants, 
 however, can be frozen and thawed several times a day during 
 the growing season without being injured. 
 
 The plants of a given region have their own peculiarities 
 in the matter of the temperature at which growth processes 
 begin. In the arctics certain seaweeds thrive in water that 
 seldom rises above 32, and are easily killed by temperatures 
 a few degrees higher. Most plants of the temperate zone will 
 begin to grow at about 41 above zero, and some, such as 
 oats, wheat, rye, and peas, can make some growth when the 
 temperature is just above the freezing point; but the best tem- 
 perature for germination is between 60 and 70, and many 
 species, even in the colder parts of the world, will not start 
 to grow until such temperatures are reached. Up to a certain 
 point heat seems to stimulate growth processes just as it does 
 chemical reactions. In the tropics the temperature at which 
 seeds germinate is usually ten or twelve degrees higher than 
 that required for more northern plants, the most desirable being 
 between 70 and 80. The seeds of many tropical species, 
 when planted in our hothouses, must be given a temperature 
 above 90 to get the best results. These facts explain why 
 some seeds are planted earlier than others. Peas and spinach 
 are cool-weather plants and may be planted as soon as the 
 ground can be worked in spring; indeed, unless the season 
 is fairly cool these crops do not do well. Corn and tomatoes, 
 on the other hand, which came originally from the tropics, 
 must wait until both the soil and air are thoroughly warmed. 
 
 Hardy and tender plants. As regards the sensitiveness of 
 the plants to cold, gardeners are accustomed to group them 
 as hardy, half-hardy, and tender species. Hardy plants are 
 those that endure the winter season unharmed. The perennial 
 plants of any region are necessarily hardy plants. Half-hardy 
 plants are those that need artificial protection during the 
 winter, though in mild seasons they may survive without this.
 
 TEMPERATURE, LIGHT, AND MOISTURE 115 
 
 Tender plants are those that die as soon as frost comes. 
 These are general terms, however, and indicate relative con- 
 ditions only, since a plant that is perfectly hardy in one 
 region may be only half hardy or even tender in a colder one. 
 On the other hand, the trees that are deciduous in cold regions 
 may become evergreen when removed to warm regions. Vio- 
 lets, which flower for only a few weeks in spring in the 
 Northern states, may bloom throughout the autumn, winter, 
 and spring near the Gulf. 
 
 Cardinal points. As has been indicated, there are three 
 important temperature points for every species of plant : the 
 minimum, or lowest point at which growth processes can pro- 
 ceed ; the maximum, or highest point at which growth is possi- 
 ble ; and the optimum, or most favorable temperature. These 
 points are called cardinal points, or the upper, middle, and lower 
 zeros. They are not the same for all plants, and in general are 
 higher for tropical plants than for those of temperate regions. 
 Each species may also have a different maximum, minimum, 
 and optimum for its vegetative and reproductive processes. In 
 such cases the cardinal points for growth are usually higher 
 than those for reproduction. The large number of species that 
 flower in early spring, often before the leaves have appeared, 
 are instances of this fact. 
 
 Acclimatization. Some plants of tropical regions can be 
 induced to grow much farther north than they occur in nature, 
 and the same is true with respect to northern plants in more 
 southern regions. The adaptation of plants to such conditions 
 is called acclimatization. Complete acclimatization is possible 
 only with plants that are able to make new adjustments of 
 their cardinal points, raising or lowering them to fit the new 
 conditions. Sometimes the vegetative point may be thus 
 changed, but not that for reproduction, in which case the 
 plant may produce plenty of stems and leaves, but no flowers 
 or fruits. Our most persistent and successful weeds are largely
 
 116 AGKONOMY 
 
 so because of the facility with which they are able to make 
 new adjustments of their cardinal points. 
 
 Frost. The air always contains some moisture, and the 
 warmer the air the more it can contain. When it contains all 
 that it will hold at a given temperature, it is said to be satu- 
 rated. If the temperature of moist air be lowered beyond the 
 saturation point, some of the moisture has to be dropped. If 
 this occurs in the air, the dropped moisture is called rain or 
 fog ; if deposited on the earth, it is dew or frost. The point 
 at which the water begins to condense out of the air is called 
 the dew point. Frost differs from dew only in that it is depos- 
 ited at temperatures below the freezing point of water. There 
 is always danger of frost when the weather report predicts 
 temperatures eight or ten degrees above freezing, since in any 
 given locality the temperature may fall a few degrees below 
 that predicted. A still clear night favors the formation of 
 frost by promoting the cooling of the earth and air by radia- 
 tion. When the sky is cloudy, the clouds, like a blanket, keep 
 in the heat. A fog at night, or much smoke or dust in the air, 
 protects in the same way. A windy night may also protect 
 from frost by moving the cold air about and keeping it from 
 settling down in any one place. 
 
 Locality and frost. Danger from frost is not confined to 
 northern latitudes. In any region where the temperature goes 
 below the freezing point there is danger from late spring and 
 early autumn frosts. The location, however, often has much 
 to do with immunity from frost. In the vicinity of large bodies 
 of water frosts are often long delayed in autumn because, as 
 the temperature lowers, the water gives off the heat absorbed 
 during the summer and thus keeps the surrounding air warm. 
 In rooms or cellars where the temperature might fall below 
 the freezing point, this may be prevented by exposing therein 
 tubs of water which will give off heat in the same way. Cold 
 air is heavier than warm air and tends to settle in the hollows
 
 117 
 
 and displace the warm air there. In consequence frost often 
 visits the bottom lands long before it touches the hilltops, 
 because the latter are nightly bathed in the warm air crowded 
 up from below. For this reason farmers usually plant the late 
 crops of buckwheat on the hillsides. In certain valleys there 
 is a zone part way up the slope, called the verdant zone or 
 thermal belt, in which late spring and early autumn frosts are 
 almost unknown. This zone is due to the movement of the 
 warm air out of the valley at night. Other inclosed valleys 
 drained by a stream may be nearly exempt from frost because 
 the cold air flows away over the stream. This distribution of 
 temperature has a curious effect upon the distribution of plants. 
 Northern plants are usually found farthest south in the val- 
 leys, and southern plants farthest north on the hillsides, exactly 
 the opposite of what at first glance one would assume to be 
 the natural occurrence. 
 
 How cold kills plants. Some tropical plants are so sensitive 
 to cold that they may be killed by exposure to temperatures 
 several degrees above the freezing point, but usually plants 
 are killed by the freezing of the protoplasm or the sap within 
 the cells. Freezing of the cell sap takes place at a tempera- 
 ture somewhat lower than 32, since water containing dissolved 
 substances requires a greater degree of cold to congeal it than 
 does pure water. Often it is not the mere cold that kills plants, 
 but rather the withdrawal of moisture from the cell by the 
 formation of ice crystals in the intercellular spaces. In such 
 cases the effects of cold are exactly the same as those of dry- 
 ing. Otherwise hardy plants are often killed in winter by the 
 heaving due to the alternate freezing and thawing of the soil 
 and the consequent breaking of the roots. 
 
 Other effects of cold. In plants that are not killed outright 
 by the cold, the lowered temperature may injure the less 
 resistant parts. Some plants, such as the catalpa, grape, rasp- 
 berry, and sumac, continue to grow until stopped by the cold,
 
 118 AGRONOMY 
 
 and the stems do not form strong buds at the tip. In these 
 the buds and stems are usually killed back several inches 
 annually. Flower buds that are formed in autumn are often 
 killed by the cold, especially by a cold interval in late spring 
 after they have started into growth. Flowers, of course, are 
 sensitive to cold and may fail to set fruit even if the temper- 
 ature does not fall to the freezing point. In severe winters 
 the trunks of trees are often split open by the cold. Another 
 effect of the cold is seen in the improvement in the flavor of 
 certain vegetables such as salsify and parsnips. 
 
 How plants avoid the effects of cold. Most perennial plants 
 have devised various ways of protecting their more delicate 
 parts from the cold. A large number have developed the 
 geophilous, or subterranean, habit, and at the approach of cold 
 weather the parts above ground die and the life of the plant 
 retreats to the underground parts. Examples are seen in the 
 species that produce bulbs, conns, tubers, rhizomes, and sim- 
 ilar structures. The same arrangement also protects from 
 drought. Bulbous plants are always plentiful in dry regions. 
 Plants above ground have other means of protection. The 
 trees protect the living cambium by a thick and nearly water- 
 proof bark, and their buds are protected by scales, hairs, and 
 varnish. Most of the broad-leaved trees drop their leaves to 
 avoid transpiration, but the pines and their allies with needle- 
 shaped leaves that do not transpire much are not obliged to do 
 so. The twigs and stems of many plants have a dense coating 
 of scales, epidermal hairs, or wax, as an additional protection. 
 How effective epidermis and bark are in retaining moisture 
 in the plant may be seen by comparing the behavior of a 
 peeled apple or potato with that of one in its natural state. 
 Herbs that retain their leaves adopt the rosette habit, and thus 
 their leaves, close to the earth, are protected all winter by the 
 dead vegetation and the snow. The majority of these devices, 
 it may be noted, are not so much protections from the cold
 
 TEMPERATURE, LIGHT, AND MOISTURE 119 
 
 as they are means of avoiding the injuries likely to be caused 
 by sudden changes of temperature. On the other hand, the 
 dark colors of bud scales readily absorb heat in sunshine and 
 
 F 
 
 FIG. 87. Epidermal hairs and scales. (Much enlarged) 
 
 A, mullein; B, geranium; C, deutzia; D, hollyhock ; E, dame's violet; 
 F, shepherd ia 
 
 may thus increase the temperature of the buds during the 
 cool days of early spring. 
 
 Artificial protection from the cold. Snow is of such great 
 value as a protection of plants in winter that it is frequently 
 called " the poor man's manure." Winters in which there is 
 little snow are very trying to plants because they are left un- 
 protected and are thus easily heaved by the frost. Man often 
 adds to the natural protection of plants by mulching, shading,
 
 120 AGRONOMY 
 
 windbreaks, and cold frames. Mn1<-hin<i is simply adding to 
 the cover of dead leaves with which the ground is naturally 
 protected in winter. Any loose litter is good for this purpose. 
 Straw, leaves, and stable manure are the materials most fre- 
 quently used. In addition to protecting plants from being 
 heaved by the cold, a mulch retards the thawing of the ground 
 in spring and thus holds back early plants that might other- 
 wise be injured by late frosts. Windbreaks are belts of trees, 
 usually evergreens, planted on the windy side of gardens and 
 fields to protect them from the high winds of winter and early 
 spring. In nature the forest acts as a natural cover for a vast 
 number of plants. Cold frames are frames of wood covered 
 with glass or thin cloth, which are sometimes placed over 
 plants. They are either sunk in the ground to the level of the 
 soil, or are banked up with manure. On very cold nights they 
 are covered with mats as an additional protection. Sprinkling 
 plants with cold water may protect them from frost when the 
 temperature does not go much below the freezing point. In 
 orchard practice the blooming trees are often protected from 
 late spring frosts by smudge fires, which give off great quan- 
 tities of smoke that act like clouds in keeping the earth warm. 
 
 Treatment of frostbitten plants. Plants that have been 
 frostbitten may often be saved by gradual thawing, especially 
 in cases where the injury is due to a withdrawal of moisture 
 from the cell. If possible, such plants should be removed at 
 once to a cool cellar, sprinkled with water, and kept out of 
 the direct rays of the sun for a few days. Out of doors the 
 plants may be sprinkled with water and protected from the 
 sunlight. Frostbitten plants and fruits should be handled as 
 little as possible until thawed. 
 
 Effects of heat. The first noticeable effect of great heat 
 upon the plant is the wilting due to increased evaporation. 
 As the temperature rises, the plant is called upon for more 
 and more moisture until a point is reached where the demand
 
 TEMPER ATUEE, LIGHT, AND MOISTURE 121 
 
 is greater than the roots can supply, and the drooping of the 
 foliage ensues. If this continues long enough, it may cause 
 the death of the plant, though in bright sunshine a great 
 many plants wilt during the hottest part of the day and 
 revive as the temperature falls. The watery parts of plants, 
 especially the fruit and young leaves, being less resistant to 
 heat than the rest of the plant, are often destroyed by exposure 
 to the hot sun. Evergreens and other plants are sometimes 
 winterkilled, not so much by the cold as by a sudden spell of 
 warm weather that calls upon stem and leaves for more mois- 
 ture than they can spare at a time when the roots are only 
 feebly absorbing. 
 
 Protection from heat. Since the direct rays of the sun are 
 more harmful than the heated air, tender specimens may be 
 protected in a measure by screens of thin cloth, paper, brush, 
 or lath. Newly transplanted specimens are often sheltered by 
 old newspapers or by a broad leaf, such as that of the burdock 
 or rhubarb. In all such shading it is well to provide for a 
 circulation of air under the cover. Plants in greenhouses and 
 the like are usually shaded by covering the underside of the 
 glass with whitewash. Evergreens and other plants that are 
 not perfectly hardy will often best endure the winter if planted 
 on the north side of buildings or in places where the direct 
 sunshine may be avoided. 
 
 The plants themselves have various devices which protect 
 them from the heat. The leaves of species exposed to the sun 
 are frequently covered with a dense coat of hairs or scales 
 which shade the tender cells. On a hot day the leaves of 
 corn roll up and thus expose a smaller surface for evaporation. 
 The prickly lettuce, the compass plant, and the eucalyptus 
 turn the e^lges of their leaves to the sun, and many tropical 
 species shed part or all of their leaves during the season of 
 greatest heat. The acacias and many other plants of the pea 
 family, with branched leaves, alter the position of their leaflets
 
 122 AGRONOMY 
 
 to avoid the heat, while in various other plants the chloro- 
 plasts are able to change their position in the cell. 
 
 Need of light. Light is necessary for the existence of every 
 independent plant, since the energy for food making is derived 
 from this source. The general effect of light upon plants, how- 
 ever, is to inhibit growth, and chlorophyll itself, the very sub- 
 stance by means of which the chloroplasts turn sunlight into 
 useful energy, is broken down in strong light. Bacteria soon 
 die when exposed to direct sunlight, and many of the higher 
 plants cannot live long under such" conditions. These latter 
 grow in forests, ravines, and other secluded places and are 
 known as shade plants. Ferns and many of the plants that 
 bloom in early spring are shade plants. Many of our forest 
 trees are essentially shade plants when young. Absence of 
 sufficient light, however, is quite as bad as too much. In in- 
 sufficient light the formation of wood cells entirely ceases. 
 As in the case of temperature, the plant is balanced between 
 two harmful extremes. 
 
 Effects of lack of light. Sun-loving plants grown in deep 
 shade are deficient in chlorophyll, and have small leaves and 
 weak stems which are greatly elongated, or " drawn." The 
 flowers are also paler and the fruit scanty and lacking in flavor. 
 Aromatic plants have their aromatic properties lessened when 
 grown in shade. Plants may receive too little light by being 
 planted so closely together that they shade one another, or 
 where a subsequent growth of weeds springs up and over- 
 shadows them. Fruit trees and flowering plants, generally, 
 may fail to form flower buds unless pruned sufficiently to let 
 the light into the mass of foliage. A large number of woody 
 plants have the faculty of self-pruning. This is regarded as 
 a response to insufficient light. The cottonwood is one of the 
 best-known trees with this habit. In winter the earth beneath 
 old trees is thickly strewn with twigs a foot or more long, cut 
 off by the tree as smoothly as the leaves are. -
 
 TEMPERATURE, LIGHT, AND MOISTURE 123 
 
 Blanching. Plant parts produced in darkness are paler and 
 tenderer than when grown in the light, and this fact gives 
 reason for the process known as blanching. Plants may be 
 blanched by heaping up the soil about them, or by covering 
 them with boards, tiles, or anything else that will exclude 
 light. Celery and sea kale are always blanched for the table 
 in this way, and asparagus often is. Endive is blanched by 
 tying the outer leaves 
 over the center a few 
 weeks before using, and 
 by the same method 
 the heads of cauliflower 
 are protected from the 
 light and kept white. 
 
 Protection from light. 
 Light and heat are so 
 closely allied that what 
 will protect from one 
 will usually protect 
 from the other. The 
 lath house, built of com- 
 mon lath or of wider 
 strips separated from 
 one another by suffi- 
 cient space to admit 
 some of the light, is 
 
 often used for growing shade plants, slow-growing seedlings, 
 and similar specimens. In addition to this protection from 
 light and the attendant heat, the lath house retains the 
 moisture in the air. Artificial shading by means of thin cloth 
 or lath screens is frequently employed in the cultivation of 
 tobacco, coffee, pineapples, and ginseng. In summer radishes 
 and lettuce come to much greater perfection when grown in 
 the shade. 
 
 Photograph by the University of Illinois 
 
 FIG. 88. Cauliflower plant 
 The leaves are tied above to blanch the center
 
 124 AGRONOMY 
 
 Effects of overwatering. Although plants need much mois- 
 ture, they may very easily have too much, which results in 
 various abnormal conditions. Tomatoes, cabbage, melons, 
 plums, and other fruits are liable to crack from this cause, 
 when heavy rains follow a drought. Anything that will cause 
 a reduction in the water supply may act as a remedy. In the 
 case of cabbage, pulling on the stem so as to break some of 
 the roots may prevent the heads from bursting. House plants 
 are frequently overwatered. Few plants can long keep up the 
 struggle if left standing in a jardiniere containing an inch or 
 more of water. 
 
 Time to water. Air in the soil is a necessity. A saturated 
 soil is as harmful as one that is too dry. About 50 or 60 per 
 cent of the moisture a soil can hold is about the amount de- 
 sirable. When watering plants it is better to give the ground 
 a good soaking at considerable intervals than to give it more 
 frequent applications of smaller amounts. Light watering 
 makes plants shallow rooted and more susceptible in times of 
 drought. A few plants, such as the geranium, petunia, and 
 tomato, possess glandular hairs which have the faculty of ab- 
 sorbing moisture from the air or from dew. This accounts for 
 their ability to thrive in places too dry for ordinary plants. 
 The so-called " Spanish moss " of the Southern states, which is 
 really a relative of the pineapple, absorbs all its moisture 
 through its leaves. 
 
 Effects of lack of water. Plants grown without an adequate 
 supply of water are inclined to be short and stunted, but the 
 lack of moisture favors the development of flower buds and 
 causes the wood to ripen. A large number of our spring 
 flowering plants form their flower buds daring the heat and 
 drought of summer, and florists allow their plants to become 
 pot-bound when flowers are desired, since this prevents the 
 absorption of much water and food materials. Removing part 
 of the root system may have the same* effect.
 
 TEMPERATURE, LIGHT, AND MOISTURE 125 
 
 Water and plant forms. Although the character of the soil 
 determines in great measure the kind of plants that will thrive 
 in it, and temperature may have much to do in determining 
 their distribution, water is of still greater importance, since it 
 affects both the form and structure of vegetation. The plants 
 of the world - may be separated into three ecological groups, 
 known as xerophytes, hydrophytes, and mesophytes, accord- 
 ing to the amount of water to which they are adjusted. The 
 xerophytes, or drought plants, can 
 thrive with a very limited sup- 
 ply of moisture. They inhabit 
 deserts and other dry locali- 
 ties and are characterized by 
 many adaptations for conserv- 
 ing moisture, such as condensed 
 stems, reduced leaf surface, 
 thick epidermis, an extensive 
 root system, and various tis- 
 sues for water storage. Many 
 xerophytes are leafless and the 
 stems perform the work of pho- 
 tosynthesis, others have leaves 
 for a part of the year but drop 
 them when seasons of drought occur. In the species which 
 retain their leaves, the latter are usually covered with hairs, 
 scales, or bloom. Xerophytes often have their stems under- 
 ground in the form of rootstocks, bulbs, and corms, and the 
 production of thorns and spines by woody species is common. 
 The cactus, yucca, and houseleek are xerophytes. All xero- 
 phytes do not live in deserts, however. A rocky ledge or a 
 sand dune, though located in a region of abundant rainfall, 
 may hold so little moisture that the plants that grow upon 
 them are exposed to desert conditions and may have all the 
 characteristics of drought plants. The lichens which grow upon 
 
 FIG. 89. Yucca glauca, a xero- 
 phyte of the Western plains
 
 126 
 
 AGMXXOMY 
 
 FIG. 90. Tree yuccas, xerophytic plants of the Mohave Desert 
 
 the trunks of trees, rocks, and in similar places are examples 
 of such plants. Hydrophytes are water plants and thrive only 
 in regions of abundant rainfall. The water lily, pickerel weed, 
 ditch moss, and pondweed are good illustrations. They are 
 
 FIG. 91. The American lotus (Nelumbo), a hydrophyte
 
 TEMPEEATUKE, LIGHT, AND MOISTURE 127 
 
 characterized by weak stems, thin epidermis, few roots, little 
 conducting tissue, and large air spaces within stems and leaves, 
 all of which are necessary to fit them to their environment. 
 The leaves under water are usually narrow or much branched, 
 though those exposed to the air may be as large as, or larger 
 than, in other plants. Along with the true hydrophytes are 
 often found other plants that are xerophytic in structure, 
 though growing in water. These are sometimes known as 
 
 Fio. 92. A group of hydrophytes, showing the zonation that often occurs 
 
 In the water, spatter-dock (yuphar) and algse ; on the muddy shore, a helt of cat- 
 tails ; in the background, cottonwoods and willows 
 
 xerophytic hydrophytes. They are, for the most part, plants 
 which absorb so slowly that they have been obliged to adopt 
 the structure of xerophytes in order to retain what mois- 
 ture they absorb. The scouring rush illustrates plants of this 
 type. The mesophytes occupy the middle ground between the 
 xerophytes and hydrophytes. They are the common plants 
 of our woods and fields, and though of far more economic 
 importance than either of the other classes, they are of much 
 less botanical interest.
 
 128 AGRONOMY 
 
 PRACTICAL EXERCISES 
 
 1. Visit the nearest hothouse and note the character of the tropical 
 perennials that require great heat for growth. 
 
 2. Ascertain from the nearest weather observer, or from farmers who 
 have kept records, the average date of the last killing frost in spring 
 and the earliest killing frost in autumn. How many days of growing 
 weather does this give you ? Find the date of the latest recorded spring 
 frost and the date of the earliest autumn frost. How many days from 
 frost to frost ? How does this compare with the average ? 
 
 3. Into a bright tin cup, nearly filled with water, drop pieces of ice 
 one by one, stirring the mixture with a thermometer. When moisture 
 begins to appear on the outside of the tin cup, the thermometer will 
 register the dew point. Where is the dew point higher, in the school- 
 room or in a sheltered place outside ? In which place does the air hold 
 the more moisture ? 
 
 4. Find a place where a board, paper, or other object has been lying 
 on the grass for a few days. Remove it and account for the appearance 
 of the grass underneath. 
 
 5. Examine potatoes or other plants that have grown in a cellar or 
 other dark place. Explain the appearance of the plants. 
 
 6. Make lath screens for use in the garden later, or draw plans to 
 scale for a lath house to be constructed in the garden for growing the 
 shade plants. 
 
 References 
 
 Dryer, "Lessons in Physical Geography." 
 Goff, "Principles of Plant Culture." 
 Salisbury, " Physiography." 
 
 Farmers' Bulletin 
 
 104. Notes on Frost. 
 
 Weather Bureau 
 
 311. Climate ; its Physical Basis and Controlling Factors.
 
 CHAPTER IX 
 
 GARDEN MAKING 
 
 Location of the garden. The ideal location for a garden is 
 in a well-drained spot, open to the south and east, and pro- 
 tected at least on the north by a belt of evergreen trees, a 
 high wall, or a tight board fence, but any place is suitable if 
 it receives the direct rays of the sun for at least half of the 
 
 FIG. 93. A class at work on a city lot, Joliet, Illinois 
 
 day. Land sloping toward the north should be avoided and 
 so should a locality where there is much smoke. In the 
 majority of cases, however, it is not possible to select a new 
 site for the garden, and one's efforts must be directed toward 
 bettering the one he already possesses. The nearer it can be 
 
 129
 
 130 AGRONOMY 
 
 made to approach ideal conditions the better. If the garden 
 is to contain fruit trees, these should be placed along the 
 north line or otherwise disposed so that they will not shade 
 the growing crops. 
 
 Preparing the soil. The best soil is a deep and moderately 
 light loam, but here, again, one must make the best of his 
 situation. Large stones should be removed, but small ones 
 may remain. Gravelly soils are early soils because during the 
 day the stones absorb much heat which they radiate at night. 
 If the soil is a stiff clay, it may be lightened by the addition 
 of sand, coal ashes, lime, stable manure, dead leaves, and other 
 litter. Sandy soils may be improved by digging into them 
 anything that will add humus, and any soil will be benefited 
 by the application of well-rotted manure. The soil should be 
 made mellow by plowing or deep spading, all lumps should 
 be broken up with the rake or hoe, and the surface finally 
 leveled with a rake. The care with which the seed bed is 
 made will be reflected in the crops. It is not economy to 
 plant until the soil has been properly prepared. 
 
 The garden plan. Before planting, a plan of the garden 
 drawn to scale should be made. In this plan all paths and 
 permanent crops and the area devoted to each vegetable 
 should be indicated. By this means one can discover in 
 advance exactly how many plants he will have room for, and 
 can plant any part of his space without encroaching upon 
 that reserved for other things. Permanent plants, such as 
 raspberries, currants, asparagus, and rhubarb, should be re- 
 stricted to the borders where they will not interfere with the 
 cultivation of the other crops year after year. Many paths 
 should be avoided, but those that are maintained should enable 
 one to reach all parts of the garden expeditiously and should 
 be wide enough to permit of being traversed with a wheel- 
 barrow. It is no longer the custom to plant the smaller 
 vegetables in narrow beds. They should be planted in rows,
 
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 RHVBABB 
 
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 131 
 
 10 ft.
 
 132 
 
 AGRONOMY 
 
 the longer the better, to permit of the ground being worked 
 more easily. Care must be taken, however, to so arrange the 
 planting with reference to the points of the compass that tall 
 growing plants are not placed where they will shade lower 
 ones. In general, it is well to place nearest the house the 
 salad plants and others that are gathered frequently, leaving 
 the field crops, like potatoes and cabbage, to occupy more 
 distant spots. 
 
 How to plant. A few plants, such as corn, cucumbers, 
 tomatoes, and pole beans, are planted in hills, but all that, can 
 
 FIG. 95. Gardening at the Flower Technical High School for Girls, Chicago 
 
 be grown in drills or rows are so planted to facilitate culti- 
 vation. Care should be taken to have the rows straight and 
 far enough apart to avoid crowding. The proper distances 
 may be learned by consulting the planting table on page 145. 
 To facilitate measurements in the garden, the handle of hoe or 
 rake should be laid off in six-inch sections. The marks can be 
 scratched in the wood with any sharp-pointed instrument and 
 inked, if desired. Straight rows may be secured by means of a 
 garden line, such as masons use, stretched between two stakes.
 
 Lawn 
 
 Lawn 
 
 Exp'ts 
 
 Experiments 
 
 U[ 
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 Lawn 
 
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 FIG. 96. Four plans for school gardens on vacant lots 
 
 133
 
 134 AGRONOMY 
 
 When not in use it should be kept with the seeds where it 
 will be ready when more planting is to be done. Seeds must 
 not be planted too deep. In general they should be planted 
 three or four times as deep as their diameters. Seeds whose 
 cotyledons do not rise above the soil may be planted deeper 
 than those whose cotyledons do, and large seeds may be planted 
 deeper than smaller ones. Very small seeds may be simply 
 scattered on the surface and pressed into the soil with a hoe 
 or a piece of board. When sown in light, well-drained soil, 
 the seeds may have the earth firmed over them to induce 
 capillarity, but in wet or heavy soils this should be omitted, 
 else it may be so compacted that delicate plants cannot push 
 through it and the air necessary for germination be excluded. 
 Darkness favors the germination of most seeds, and for this 
 reason, as well as to prevent the drying out or puddling of 
 the surface layer of soil, it is well to mulch newly planted 
 seeds with a light covering of loose straw or lawn clippings 
 through which the young plants easily push their way. Cover- 
 ing the planted seeds with paper or cloth serves the same pur- 
 pose, but in such cases the cover should be removed as soon 
 as the young plants appear. 
 
 When to plant. The seeds of the hardier plants may be 
 sown as soon as the ground can be worked in spring, or they 
 may even be sown in the autumn and allowed to rest in the 
 soil through the winter. This is the way all the wild species 
 are planted. Other seeds must not be planted until the soil is 
 thoroughly warmed. Several garden plants thrive only in the 
 cool moist days of early spring, and do not grow well if 
 planted later. This is especially true of spinach, cress, radishes, 
 lettuce, and the like. In hot dry weather these plants soon 
 " run to seed." Among the vegetables that are usually planted 
 early are beets, cabbage, cress, lettuce, onions, peas, radishes, 
 salsify, and spinach. These are either cool-season or long-sea- 
 son plants that are not injured by light frosts. Warm-season
 
 
 
 
 
 
 
 
 
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 135
 
 136 AGRONOMY 
 
 plants, such as corn, cucumbers, okra, peppers, and tomatoes, 
 must not be planted outdoors until all danger from frost 
 is past. 
 
 Autumn seed bed. The seeds of all hardy plants may be 
 sown in autumn and will lie in the earth unharmed until 
 spring. Some will even grow in autumn and go through the 
 cold season as seedlings. Autumn seed sowing has the ad- 
 vantage that it may be done at a time when other work is not 
 crowding, as in spring, and the stay in the soil over winter 
 will aid in softening the seed coats of many species. In 
 autumn, also, fruiting plants are everywhere and seeds are 
 abundant. It is much easier to carry home a dozen plants as 
 seeds than to transport the same number when they have 
 grown for a year or more. The autumn seed bed should be 
 made in a sheltered situation, and when cold weather has 
 come, it should be mulched with some good litter that is 
 free from weed seeds. 
 
 Germination. The promptness with which the young plants 
 appear above the soil depends upon the kind of seed planted, 
 the temperature of the soil, the amount of moisture present, 
 and various other things. In cold, wet soils seeds of most sorts 
 are slow to germinate, if they grow at all, though a few will 
 sprout at temperatures but slightly above freezing. Increas- 
 ing the temperature, however, hastens germination, and in 
 dry weather soaking the seeds before planting has the same 
 effect. Hardy plants usually do best at temperatures of from 
 50 to 70, tender plants from 60 to 80, and tropical plants 
 from 75 to 95. In favorable weather from three days to two 
 weeks may elapse between planting and the appearance of 
 the seedlings. Seeds of canna, lotus, honey locust, and some 
 others have testas so hard that they delay germination by ex- 
 cluding moisture and air, but they grow readily when a hole is 
 filed through the testa before planting. Boiling water is some- 
 times poured over such seeds to hasten germination. The
 
 GARDEN MAKING 
 
 137 
 
 seeds of nut trees and our stone fruits have testas so thick 
 that they may remain in the earth for a year or more before 
 growing. In such cases germination may be hastened by 
 cracking the shells or by stratifying the seeds. The latter 
 process consists in plac- 
 ing the seeds in layers 
 in boxes of moist sand 
 or moss and keeping 
 them moist during the 
 winter. The seeds may 
 be kept in a cool cel- 
 lar or buried a foot or 
 more deep in a well- 
 drained spot. Seeds 
 may fail to grow for 
 various reasons. They 
 may be too old, may 
 have been frozen before 
 being thoroughly dried, 
 their testas may exclude 
 oxygen or moisture, or 
 they may have been 
 immature when gath- 
 ered. The seeds of 
 many plants will not 
 grow the same season 
 they are produced, even 
 if surrounded by the 
 most favorable circum- 
 stances. The length of 
 time that good seeds retain their vitality depends somewhat 
 upon the species. A few seeds must be planted almost as soon 
 as ripe if they are to grow at all, while others will remain alive 
 for from two to twenty years. In general, starchy seeds retain 
 
 98. A handy receptacle for seeds, labels, 
 and other small things 
 
 This is easily made and can be carried into the 
 garden whenever planting is to be done
 
 138 
 
 AGRONOMY 
 
 their vitality longer than oily ones. There is no truth, how- 
 ever, in the idea that seeds thousands of years old, found in 
 the pyramids or dug out of Indian graves, will grow. Weed 
 seeds are especially persistent, but few of them can grow after 
 twenty years. In some seeds the age seems to affect the crop, 
 fresh seeds producing more vigorous plants with a tendency 
 to put forth leaves and stems only, while older ones are likely 
 to be more fruitful. Growers of melons prefer seeds several 
 years old for this reason. 
 
 Seed testing. When a crop is planted upon which much 
 depends, or when for any reason there is doubt about the seeds 
 being good, it is customary to test them before planting. A 
 
 A B 
 
 Fi<;. 99. A seed tester, consisting of two soup plates, some sand, and a 
 
 piece of cloth 
 
 serviceable seed tester may be made of a dinner plate, a sheet 
 of glass, and two pieces of rather thick cloth cut to fit the plate. 
 The cloths are dipped in water, the excess moisture wrung 
 out, and the seeds to be germinated placed between them. 
 The cloths are placed on the plate and covered with the glass 
 or another plate to keep in the moisture, and the apparatus 
 set away in a warm place. From time to time the seeds are 
 examined and those which have germinated removed. By this 
 means one may very quickly discover what proportion of a 
 given lot of seeds is viable. Wet sand may be used in place 
 of the cloth in the seed tester, if desired. 
 
 Double cropping. Different crops vary greatly in the time 
 taken to mature. Long-season crops, such as salsify and pars- 
 nips, are planted early in spring, occupy the ground until frost,
 
 GARDEN MAKING 
 
 139 
 
 and are often left in the soil over winter. On the other hand, 
 lettuce, radishes, and the like take but a few weeks to mature, 
 and if such crops are planted together in one part of the gar- 
 den, two and three separate crops may be grown on the same 
 soil in one season. Among the plants most useful for second 
 crops are beans, cress, celery, cabbages, kohl-rabi, lettuce, 
 mustard, radishes, spinach, 
 and turnips. Celery and 
 cabbages used as late crops 
 are started elsewhere and 
 transplanted ; the others are 
 grown from seeds planted 
 where they are to remain. 
 Another method of get- 
 ting two crops from the 
 same soil, often practiced 
 with long-season crops, is 
 to plant together two crops, 
 each of which has different 
 requirements as to light, 
 shade, etc. Pumpkins, tur- 
 nips, and squashes are often 
 planted with corn, and clover 
 with grain crops. Radishes 
 may be planted with salsify, 
 beets, and other slow-grow- 
 ing crops, and help to mark 
 
 the rows until the other plants have developed. Radishes 
 and lettuce may also be planted between the hills in melon 
 patches, where they will mature before the space is needed 
 by the chief crop. 
 
 Transplanting. Almost any plant can be transplanted, but 
 some endure such treatment better than others. Plants with 
 strong taproots are more difficult to transplant. In general, 
 
 FIG. 100. A garden plan which may be 
 
 used for a school garden or for the 
 
 home lot
 
 AGKONOMY 
 
 when directions on a seed packet say the seeds should be 
 sown where the plants are wanted, transplanting should not 
 be attempted. There are several advantages, however, to be 
 gained by transplanting. Earlier crops may be produced by 
 starting plants in the house before they can grow out of doors, 
 and transplanting them to the garden when the weather has 
 moderated. Plants that require a long season to come to 
 
 maturity may also be in- 
 duced to fruit earlier by 
 this means. By starting 
 plants in this way they 
 may be set in the place of 
 those that mature early 
 and a second crop thus 
 secured, or they may be 
 used to fill up gaps in 
 the plantings caused by 
 the depredations of in- 
 sects, plant diseases, or 
 the failure of the seeds 
 to grow. Warm-season 
 plants are usually long- 
 season plants also, and 
 several of these, such as 
 eggplants, peppers, and tomatoes, are always transplanted, 
 thus securing earlier and more abundant crops. Other plants 
 that are able to mature from seed planted in the open ground 
 are usually treated in this way, especially cabbage, cauliflower, 
 and celery. Beets, chard, lettuce, and onions are occasionally 
 transplanted. 
 
 Transplanting should be done on cool or cloudy days and 
 preferably in the late afternoon. Young plants may be trans- 
 planted as soon as they have developed their second or third 
 leaves. Moving very young plants in this way is called 
 
 FIG. 101. A transplanting trowel and a 
 
 dibber 
 A trowel of this kind is often used as a dibber
 
 GAKDEN MAKING 141 
 
 pricking out. The plants should be taken up with as many of 
 the roots as possible, and should not be allowed to become dry 
 by exposure to the sun and air. The holes in which they are 
 planted may be made with a pointed instrument of wood or 
 metal called a dibber. After the plants are placed in the holes 
 the dibber is again thrust into the ground an inch or more 
 from them and used to crowd the soil against them, thus mak- 
 ing it firm. If the weather is very dry, the plants should be 
 watered after setting, and protected from the wind and the 
 direct rays of the sun until again estab- 
 lished. Excessive transpiration may be 
 reduced or avoided by removing some of 
 the leaves or by cutting off part of each 
 leaf. The latter operation is called shearing. 
 Some growers are in the -habit of allowing 
 
 cabbage and tomato plants to wilt before FlG - 102 - A sheared 
 
 plant 
 resetting, with the idea that by so doing 
 
 the plants will develop new roots instead of endeavoring to 
 revive the old ones. These species are quite tenacious of life 
 and survive much abuse. Frequently cabbage plants for 
 transplanting are simply pulled up from the seed bed. 
 
 Inducing plants to fruit. It is natural that all mature peren- 
 nial plants should flower and fruit annually, but it is a well- 
 known fact that many do not do so. Fruiting is a very 
 exhausting process. Annuals are killed outright by it, while 
 in perennials a heavy crop of fruit may so depress the vitality 
 of the plant as to make it impossible for it to bear at all the 
 following season. When a plant sets more fruits than it should 
 bear, some of them should be removed. On the other hand, in 
 all plants in which great development of the vegetative parts 
 is desired, it is customary to remove all the flowering shoots 
 and fruits as soon as they appear. Thus we pick off the berries 
 of asparagus and pinch out the flower stalks of rhubarb. 
 Annuals may be made to take on a perennial character by
 
 142 AGRONOMY 
 
 removing the flower buds as fast as they form. If one desires 
 flowers and fruit, however, all efforts should be bent toward 
 aiding the plant to store up reserve food, since the more food 
 it has, the likelier it is to bloom. Fruiting is really a device 
 of the plant for self-preservation, and whatever threatens the 
 growth processes may serve to bring it about. A plant injured 
 by lightning or defoliated by insects is likely to spring into 
 bloom again even in autumn. Pinching back the tips, remov- 
 ing some of the roots, withholding water, or planting in sterile 
 soil will usually induce the plant to fruit. Certain varieties 
 of strawberries, pears, apples, plums, and other plants are often 
 infertile when pollinated with pollen from their own flowers. 
 Even when planted in groups they may produce abundant 
 bloom but set little fruit. The remedy here is to plant among 
 them other varieties with effective pollen. In a few other forms 
 the pistils and stamens are produced on separate individuals, 
 and no fruits can be produced, therefore, if the pollen-bearing 
 plant is absent. Still other plants are adapted to cross-pollination 
 by insects, and though the pollen-bearing plant or flower may 
 be present, they set no fruits if the necessary insect fails to 
 visit them. In growing melons, cucumbers, tomatoes, and 
 the like in the hothouse, in winter, pollination must be per- 
 formed by hand. Morning is the best time for this work. A 
 soft camel's-hair brush, to which the pollen adheres, may be 
 used for the transfer of the pollen, or a stick of sealing wax 
 which has been electrified by rubbing with a cloth may be 
 used to pick up the pollen grains and drop them upon the 
 stigmas of the flowers to be pollinated. 
 
 Thinning. When the young plants are well up, it will be 
 necessary to thin them, if planted very thickly. Thinning 
 should be done as early as the plants can be conveniently 
 handled, so that the specimens left may have room to develop 
 naturally. Plants that are not thinned become drawn and 
 spindling and do not produce good crops. The distance apart
 
 GABDEN MAKING 
 
 143 
 
 in the row depends somewhat upon the habit of the plant. 
 Plants with long narrow leaves, like salsify or onion, may stand 
 closer than those with broad, spreading 
 leaves, like turnip and parsnip. The main 
 consideration should be to see that one 
 plant does not unduly shade another. 
 
 Labels. All planted seeds should be prop- 
 erly labeled, partly as a matter of record and 
 partly to indicate their whereabouts until 
 the young plants are large enough to be 
 seen. Older plants should also be labeled, 
 especially if there are several varieties of 
 the same species cultivated, or if other 
 plants are grown that might be mistaken 
 for them. The best label for temporary 
 purposes is a wooden stake painted white. 
 Such labels can be purchased from seeds- 
 men at small cost. Those six inches long 
 and about three quarters of an inch wide 
 are about the right size, though smaller or 
 larger ones may be had. On a label of this 
 kind, words written with a pencil will be 
 legible for years, though splashed with dirt 
 by every passing storm. For more perma- 
 nent labels, however, it is desirable to use a 
 piece of galvanized-iron wire about fifteen 
 inches long with a coil at the upper end to 
 which a small label is attached. These small 
 labels, called tree labels, may be obtained at 
 slight expense. When more than one word 
 is to go on a label, the first word is written 
 near the top and lengthwise of it, and the second word is written 
 under the first and further from the top. This insures that, as 
 the label becomes less legible in course of time, there will be no 
 
 FIG. 103. Two forms 
 of labels 
 
 The one on the right is 
 the common garden or 
 pot label ; the other is 
 a more permanent form 
 for marking plants in 
 the borders
 
 144 
 
 AGRONOMY 
 
 FIG. 104. Proper method of writing labels 
 
 chance of confusing the two words in deciphering them. Labels 
 should be so placed as to stand at the beginning of the rows 
 with the writing facing away from the seeds or plants they refer 
 
 to. Unless this 
 
 / Le tfayaAeaet H^* rule is consist- 
 
 ently followed, 
 when several 
 
 kinds are planted in the same row, there is no way of discover- 
 ing on which side of the label the plants are that bear the name. 
 Saving seed. In many cases it is as well to save the seeds 
 of desirable crops as it is to buy new supplies of the seedsman 
 annually. For the purpose of seed production one should 
 select the best specimens and take care that inferior stock 
 does not become mixed with it, through cross-pollination. By 
 careful selection one may produce even better crops than the 
 original. It is not 
 desirable, however, 
 to save the seeds of 
 double flowers or 
 of plants that grow 
 near other varieties 
 of the same species, 
 because they are not 
 likely to come true 
 from seed the fol- 
 lowing year. The 
 different varieties of 
 corn readily mix in 
 this way, and so do plants that produce flowers of several dif- 
 ferent colors. Seeds should be spread out to dry in a shady 
 place, and when thoroughly dried should be stored in a tin 
 box in a cool, dry place. In warm climates seeds are usually 
 short-lived, and in all regions they require uniform conditions 
 as regards temperature and moisture. 
 
 FIG. 105. A seed-tight packet that may be made 
 by simply folding a sheet of paper. See page 146
 
 GARDEN MAKING 
 TABLE OF SEEDS AND DISTANCES FOR PLANTING 
 
 NAME 
 
 How 
 
 PLANTED 
 
 AMOUNT 
 
 WILL SEED 
 
 DISTANCES APAHT 
 OF Rows 
 
 Beans, bush . . . 
 Beans, pole 
 Beets 
 
 drills 
 hills 
 drills 
 
 quart 
 quart 
 ounce 
 
 150 ft. 
 125 hills 
 50 hills 
 
 18 in. 
 4ft. 
 12 to 18 in. 
 
 Carrot 
 
 drills 
 
 ounce 
 
 100 ft. 
 
 12 to 18 in. 
 
 Chard, Swiss . 
 Corn 
 
 drills 
 hills 
 
 ounce 
 quart 
 
 50 ft. 
 125 hills 
 
 18 to 20 in. 
 1\ to 4 ft. 
 
 Cress 
 
 drills 
 
 ounce 
 
 100 ft. 
 
 1 ft. 
 
 Cucumber .... 
 Kohl-rabi .... 
 Lettuce 
 
 hills 
 drills 
 drills 
 
 ounce 
 ounce 
 ounce 
 
 60 hills 
 200 ft. 
 200 ft. 
 
 4 or 5 ft. 
 18 to 24 in. 
 12 in. 
 
 Melons 
 
 hills 
 
 ounce 
 
 60 hills 
 
 5 or 6 ft. 
 
 Mustard .... 
 Okra 
 
 drills 
 drills 
 
 ounce 
 ounce 
 
 80 ft. 
 50 ft. 
 
 12 in. 
 4 ft. 
 
 Onion seed 
 Parsley 
 
 drills 
 drills 
 
 ounce 
 ounce 
 
 125 ft. 
 100 ft. 
 
 1 ft. or less 
 18 in. 
 
 Parsnip 
 
 drills 
 
 ounce 
 
 250 ft. 
 
 18 in. 
 
 Peas 
 
 drills 
 
 quart 
 
 150 ft. 
 
 18 in. or more 
 
 Potato 
 Radish 
 
 hills 
 drills 
 
 peck 
 ounce 
 
 100 hills 
 125 ft. 
 
 2i ft. 
 12 in. 
 
 Salsify 
 
 drills 
 
 ounce 
 
 75 ft. 
 
 15 in. 
 
 Spinach 
 
 drills 
 
 ounce 
 
 100 ft. 
 
 12 in. 
 
 Squash 
 
 hills 
 
 ounce 
 
 25 hills 
 
 4 to 9 ft. 
 
 Turnip 
 
 drills 
 
 ounce 
 
 150 ft. 
 
 12 in. 
 
 
 
 
 
 
 VEGETABLES USUALLY TRANSPLANTED 
 
 NAME 
 
 How 
 PLANTED 
 
 AMOUNT 
 
 WILL MAKE 
 
 DISTANCES APART 
 OF Rows 
 
 Cabbage . . . 
 
 hills 
 
 ounce 
 
 2000 plants 
 
 2 ft. or more 
 
 Cauliflower . . 
 
 hills 
 
 ounce 
 
 3000 plants 
 
 2 ft. or more 
 
 Celery .... 
 
 drills 
 
 ounce 
 
 5000 plants 
 
 2 ft. 
 
 Eggplant . 
 
 hills 
 
 ounce 
 
 2000 plants 
 
 2 ft. 
 
 Onion sets . 
 
 drills 
 
 quart 
 
 50 ft. 
 
 12 in. 
 
 Pepper .... 
 
 hills 
 
 ounce 
 
 2000 plants 
 
 2 ft. 
 
 Tomato .... 
 
 hills 
 
 ounce 
 
 2000 plants 
 
 3 to 4 ft.
 
 146 
 
 AGRONOMY 
 
 Seed packets. In handling seeds a convenient packet in 
 which they may be placed is desirable. The packet shown in 
 the illustration on page 144 may be made at any time without 
 paste or elaborate manipulation, and yet will hold the smallest 
 seeds securely. To make it, take a sheet of paper of the de- 
 sired size 5 inches by 7 inches is a convenient shape and 
 fold it once the long way of the paper with the two edges to- 
 gether. Next fold back these edges about a quarter of an inch 
 from the edge and repeat the process. Then turning the folded 
 side down with the fold farthest away, bend back the corners 
 
 FIG. 10G. Method of closing the ordinary seed packet 
 
 of the folded side until they meet the opposite edge and form 
 a right angle with it. Next bend the unfolded corners down 
 and tuck the tips under the first fold and the packet is done. 
 When the packet is to be filled either end may be quickly 
 opened. When it is desired to close an ordinary seed packet 
 such as the seedsmen use, fold one corner of the open end three 
 quarters of the way across, fold the opposite corner back upon 
 this, and tuck the tip under the first fold. The illustrations will 
 aid in making this matter clear. All packets of seeds should be 
 carefully labeled with the name of the seeds within and the date 
 at which they were collected. It is unwise to trust the mem- 
 ory for data of this kind which may materially affect the crop.
 
 GAKDEN MAKING 147 
 
 PRACTICAL EXERCISES 
 
 1. Carefully measure the school garden and make a plan of it, drawn 
 to a scale of ^ or | inch to the foot. Neatly label all sections. 
 
 2. How many acres .in the school garden ? If less than one, estimate 
 the fraction of an acre. What fraction of an acre is your own part of 
 the school garden? 
 
 3. Make a plan, drawn to scale, of an average lot in your town. 
 Allow space for house and lawns and indicate the place in the garden 
 which each vegetable is to occupy. 
 
 4. Write to the nearest seedsman for a seed catalogue, which may 
 be had free, and make a list of the vegetables named in your plan; with 
 an estimate of the quantity of seed needed for planting the garden. 
 
 5. Make out an order for these seeds, with the quantities and prices, 
 and file with your teacher. 
 
 6. Write to your representative in Congress for sufficient seeds to 
 plant your own garden. 
 
 7. Get a packet of any large seeds (radishes, beans, or corn will do) 
 and divide it into (a) full shapely seeds, (ft) irregular and small seeds, 
 and (c) broken seeds, weed seeds, and dirt. What percentage of the packet 
 is good seeds ? 
 
 8. Make a seed tester and test twenty large seeds and twenty small 
 ones for vitality. What per cent of each germinated ? Which do you 
 conclude would be best to plant ? 
 
 9. Plant your own part of the school garden and cultivate it after 
 every rain. 
 
 10. Try covering half a row of planted seeds with a light mulch. 
 How does this affect the germination of the seeds ? Compare with the 
 part of the row left uncovered. 
 
 11. Transplant lettuce, beets, cabbage, or other plants to your garden. 
 
 12. Select a row of young seedlings planted rather thickly, and thin 
 out half the row to the proper distances between plants and allow the 
 other to go untouched. What effect has crowding ? 
 
 13. Fertilize half a row of spinach, lettuce, or radishes with nitrate 
 of soda, making two" applications about a week or ten days apart. How 
 does the subsequent growth compare with the untreated plants ? 
 
 14. Plant the seeds of desirable trees and shrubs in the school garden 
 where they may grow into good specimens for use on Arbor Day. If 
 there are small specimens already growing for this purpose, transplant
 
 148 AGRONOMY 
 
 them to a new location in order that they may develop an abundance 
 of fibrous roots. 
 
 15. Properly label all seeds as soon as sown. Make seed packets 
 according to the directions given on page 146. 
 
 16. Make a collection of vegetable and flower seeds for the school 
 museum. Have the specimens uniform. Small bottles known as shell 
 vials are excellent containers. 
 
 References 
 
 Bailey, "Manual of Gardening." 
 French, "The Book of Vegetables." 
 Green, "Vegetable Gardening." 
 
 Farmers' Bulletins 
 
 33. Peach Growing for Market. 
 
 35. Potato Culture. 
 
 52. The Sugar Beet. 
 
 61. Asparagus Culture. 
 
 76. Tomato Growing. 
 
 94. The Vegetable Garden. 
 113. The Apple, and how to grow it. 
 121. Beans, Peas, and Other Legumes for Food. 
 148. Celery Culture. 
 154. The Fruit Garden. 
 156. The Home Vineyard. 
 161. Practical Suggestions for Fruit Growing. 
 218. The School Garden. 
 235. Home Vegetable Garden. 
 
 Bureau of Plant Industry 
 
 69. American Varieties of Lettuce. 
 109. American Varieties of Garden Beans. 
 184. The Production of Vegetable Seeds.
 
 CHAPTER X 
 
 TILLAGE 
 
 Need for tillage. There are certain factors in crop pro- 
 duction that man can do little to change. The range of 
 temperature, the make-up of the air, the amount and time 
 of rainfall, and the amount of sunlight are beyond his power 
 to vary ; but the soil, fully as important as any of these, may be 
 greatly modified by his efforts. By drainage he adds to its 
 depth and warmth, by the addition of manures he enhances 
 its fertility, and by proper cultivation he promotes the develop- 
 ment of the plants growing in it. Given warmth, moisture, and 
 fertility, tillage is still necessary for the highest development 
 of growing plants. Even wild species become more luxuriant 
 and give finer flowers and better flavored fruits when properly 
 cultivated. The chief difference between our food plants and 
 others of the same kind growing wild is due to the fact that the 
 soil about the food plants is tilled. Tillage renders the soil less 
 compact, enables the roots of plants to penetrate it more easily, 
 adds to its ability to absorb rainfall, prevents the escape of 
 moisture already in the soil, assists the air to penetrate more 
 deeply, thus adding to its warmth and promoting weathering, 
 distributes the bacteria, and discourages the weeds by prevent- 
 ing their becoming established. The great amount of pore space 
 which tillage adds to the soil may be realized by digging a hole 
 in any piece of ground and then endeavoring to put back into 
 the hole all the soil removed. Wherever trenches are dug for 
 pipes or tiling we see an amount of soil left over that, in spite 
 of soaking with water and ramming with heavy instruments, 
 cannot be returned to the trench from which it was dug. 
 
 149
 
 150 AGRONOMY 
 
 Pulverizing the soil. The soil is pulverized and made fit 
 for crops by plowing, harrowing, spading, and raking. In ex- 
 tensive field operations the plow is used to break up the soil, 
 while the harrow, like a gigantic rake, is used to break up the 
 large clods and level the surface ; in the smaller areas, such 
 as the home garden, the same results are attained by the use 
 of the spade and the rake. The object of plowing or spading 
 
 FIG. 107. Plowing 
 
 is not only to loosen the soil, but to turn it over, thus bring- 
 ing new food supplies to the surface and fresh soil into cul- 
 tivation, while the topsoil, together with such fertilizers as 
 have been applied, is turned under to become fitted for a 
 succeeding crop. In humid regions the soil is stirred to a depth 
 of six or seven inches, but in arid regions the stirring may 
 extend much deeper without harm to the soil. When the soil 
 is underlaid by a stiff and heavy subsoil, the latter is often 
 loosened by siibsoiling or trenching. In subsoiling the subsoil 
 plow follows the surface plow in the same furrow but at a 
 greater depth. Trenching is restricted to small areas and is
 
 TILLAGE 151 
 
 done with a spade. In this operation a layer of soil the width 
 and depth of the spade is removed, forming a trench, and the 
 soil in the bottom of this trench is loosened by spading. Then 
 the trench is filled by the soil from a new trench adjoining it, 
 and so the work continues until the last trench is reached, 
 when the first soil thrown out is used to fill it. The subsoil is 
 often loosened by the explosion of small charges of dynamite. 
 In the home garden the spading fork is to be preferred to the 
 
 Photograph by II. L. Ilollister Land Co. 
 
 FIG. 108. Plowing with a tractor 
 
 On the larger farms in the West a tractor is often used. With this it is possible 
 to plow a dozen or more furrows at once 
 
 spade, since it breaks up the soil more thoroughly and is more 
 easily thrust into stony soil. After plowing or spading, the 
 harrow and rake are used to further pulverize the soil. The 
 more thoroughly this work is done, the better will be the seed 
 bed. Care must be taken not to work the soil when it is either 
 too wet or too dry, otherwise the soil crumbs will be broken 
 up and the soil puddled. A puddled soil is almost imper- 
 meable to air, water, and the roots of plants. Where an old 
 road or path across a field has been plowed up, the effects of
 
 152 
 
 AGRONOMY 
 
 the puddling which it lias undergone is often apparent for 
 years in the inferior plants along its course. A heavy rain in 
 summer often puddles the surface layer of soil so completely 
 as to form a crust thick enough to prevent small seedlings 
 from forcing their way up to the surface. 
 
 Mulches. Quite as much water evaporates from a saturated 
 soil as from a free water surface. As fast as it is removed 
 from the surface, more rises by capillarity to take its place. 
 
 Photograph by S. L. Allen & Co., Philadelphia 
 
 FIG. 109. Cultivating corn with the horse cultivator 
 
 The underside of a board or other object lying on the ground 
 is constantly kept wet by the rise of water in this way. A 
 windy day dries up the soil by removing the water as fast as 
 it rises. This steady loss of moisture from the soil can be 
 checked by any sort of loose cover. The mulch of stable 
 manure or other litter often spread on the ground about 
 newly planted trees and shrubs is placed there for this pur- 
 pose, though such mulches are not desirable for growing
 
 TILLAGE 
 
 153 
 
 plants because they prevent the stirring of the soil. A layer 
 of dry, porous earth is fully as effective in breaking up the 
 capillary chain. One of the main objects in cultivating plants 
 is to maintain a mulch of this kind, which is commonly called 
 a dust mulch or summer mulch. The dust mulch is also a 
 great aid to the suppression of weeds, since it contains so 
 little moisture that their seeds cannot germinate. In dry 
 
 Photograph hy S. L. Alle 
 
 FIG. 110. Cultivating with a wheel hoe 
 
 . & Co., Philadelphia 
 
 This implement has several attachments and may also be used as a rake, scarifier, 
 
 or light plow 
 
 farming the dust mulch is used to retain the moisture, and so 
 effective is it for this purpose that we are often advised to 
 " water the garden with a hoe " ; that is, to keep the water 
 already in the soil from escaping by constant cultivation of the 
 surface. The soil should be loosened after every rain. When 
 plants in large plots are cultivated, the cultivator, drawn by
 
 154 AGRONOMY 
 
 a horse, is usually employed ; in market gardens and smaller 
 plots the wheel hoe, operated by hand, may be used ; while in 
 the home garden the rake and hoe are most frequently seen. 
 Of the latter there are many styles, ranging from the shuffle 
 hoes and scarifiers of the expert gardener to the common im- 
 plement found in every garden. Planting in long rows adds 
 much to the economy in any kind of cultivation and is abso- 
 lutely necessary when the wheel hoe or cultivator is used. 
 
 Anything that decreases the amount of pore space in the 
 soil makes it easier for the water to pass from one soil particle 
 to another, and thus promotes the loss of water through capil- 
 larity. Footprints in soft soil show for days, by their darker 
 color, where the moisture is evaporating most rapidly. In 
 planting seeds the escape of moisture is often promoted by 
 compacting the soil about them, the cultivator in this case 
 being willing to sacrifice some moisture in order that the 
 growing seeds may be properly supplied. Covering the soil 
 with a light mulch serves the same purpose. 
 
 Work of earthworms and ants. Individually, earthworms 
 and ants are insignificant creatures, seemingly too small to 
 have any effect upon the soil, but when their work in the 
 aggregate is considered, they are seen to be of great assistance 
 in keeping the soil in good condition. The earthworms burrow 
 into the earth, swallowing bits of soil and decaying vegetable 
 matter as they go, and later bring this up to the surface, 
 forming the well-known castings seen about the entrance to 
 their burrows. It is estimated that in this way earthworms 
 bring up from lower levels ten tons of soil per acre annually, 
 nearly an inch in five years. In the course of a century the 
 entire soil as far down as cultivation ordinarily extends would 
 be turned over and very thoroughly pulverized. In addition, 
 the burrows made by these animals aid in keeping the soil 
 porous and well aerated. In dry soils ants take the place of 
 earthworms and turn over the soil nearly as rapidly.
 
 TILLAGE 155 
 
 Rotation of crops. In some sections of our country there 
 are farms upon which no other crop than wheat has ever 
 been grown ; on others, cotton or corn have been grown con- 
 tinuously. When the same crop has been grown upon one 
 piece of land for a series of years, however, there is a possi- 
 bility that the soil may be depleted of some necessary element 
 and fail to give adequate returns. Other plants, needing 
 different proportions of the minerals, would be able to thrive 
 where the first crop would fail. Again, certain toxic sub- 
 stances excreted by one set of plants may accumulate in the 
 soil until they put an end to the healthy growth of these 
 plants long before the food materials are exhausted, though 
 these toxic substances are not harmful to other crops. It has 
 been found, also, that when the same crop is grown in the 
 same place for any length of time, the insect and fungous 
 pests that trouble it greatly increase and the weeds associated 
 with the crop multiply. In meadows, daisies often overspread 
 the grasses, and wild mustard thrives in grainfields. Ragweed 
 comes in with the wheat, and srnartweed and foxtail grass grow 
 with the corn. The advantages of a change or rotation of 
 crops are thus seen to be many, and everywhere that modern 
 methods obtain, some .kind of rotation is practiced. A still 
 further advantage of crop rotation is that it permits the cul- 
 tivation of deep and shallow-rooted crops alternately, and 
 thus the whole soil is laid under tribute. The usual rotation 
 consists of a grain crop such as oats or wheat, a cultivated 
 crop such as corn, a forage crop such as clover or alfalfa, 
 and, in addition, the field may be used as pasture for a year 
 or more. Somewhere in the rotation it is usually planned to 
 have a legume crop, which, when finally plowed under, en- 
 riches the soil by the addition of much nitrogen. Even in 
 small gardens the benefits to be derived from a rotation of 
 crops are worth securing. In nature there is also a more or 
 less well-defined rotation. Ponds dry up and new forms of
 
 156 AGRONOMY 
 
 vegetation overpower those which grew in the water, cliffs 
 weather to soil and a different flora comes in. In fields allowed 
 to lie fallow the plant covering changes little by little for 
 years, and in the waste places there is always more or less 
 succession of one group of plants by another. In parts of our 
 country there has also been a steady migration of trees into 
 the prairie region since the glacial period, and the movement 
 is still going on. 
 
 PRACTICAL EXERCISES 
 
 1. Visit the nearest hardware or implement store and examine the 
 machines used in tilling the soil. Make a list of the kinds seen and 
 the uses to which they are put. 
 
 2. After a rain mark off 3 sq. yd. in the open ground. Cover 1 sq. yd. 
 with a mulch of leaves or stable manure, pulverize the top layer of 
 soil in the second, and let the third go untouched. At the end of a 
 week examine as to moisture content in the upper layers. 
 
 3. In England it has been estimated that there are 53,767 earth- 
 worms to the acre. Find the average number of worms to the square 
 foot in the school garden by examining three different spots, and 
 estimate the number to the acre upon this basis. How does your own 
 locality compare with England in this respect? 
 
 4. Find out from the farmers near by what the common crop rota- 
 tions of the region are. Are there any fields in which rotation is not 
 practiced? If so, how do present crops compare with former crops? 
 
 5. Make a table of the crop rotations practiced in your county. 
 
 References 
 
 Hopkins, " Soil Fertility and Permanent Agriculture." 
 King, " The Soil." 
 
 Farmers 1 Bulletins 
 
 245. Renovating Worn-out Soils. 
 
 327. Conservation of Natural Resources. 
 
 342. Conservation of Soil Resources.
 
 CHAPTER XI 
 
 FORCING AND RETARDING PLANTS 
 
 Nature of the process. In nature each species of plant has 
 its own season of growth and bloom, determined largely by 
 conditions of temperature, moisture, and the like. Man, by 
 regulating these conditions, creates an artificial season, and 
 hastens, delays, or extends the flowering and fruiting period, 
 thus obtaining his vegetables and fruits " out of season " at 
 any time of the year. Hastening the development of a plant 
 is called forcing. This is accomplished by high temperatures, 
 increased moisture, and an abundance of plant food, and results 
 in great succulence and brittleness. Lilies, hyacinths, narcissi, 
 and other bulbous plants are among those that are most 
 easily brought into bloom in this way, either in our homes or 
 in commercial establishments. Owing to the amount of food 
 stored in their bulbs, they may even be forced without soil 
 in which to root, if they are kept supplied with water. On 
 some private estates melons, grapes, peaches, strawberries, 
 cucumbers, and tomatoes are produced in midwinter in houses 
 devoted to this purpose, while the growing of roses, carnations, 
 chrysanthemums, sweet peas, and the like for use in winter is 
 a regular business with the florist. In the vicinity of large 
 cities lettuce, radishes, onions, rhubarb, and asparagus are 
 often grown in this way for the early markets. The business 
 of forcing is carried on under glass in various kinds of houses 
 or shelters, but these all fall under the general heads of 
 greenhouses, cold frames, hotbeds, and hothouses. 
 
 Retarding. The operation of holding back the growth of 
 plants for the production of blossoms later is called retarding. 
 
 157
 
 158 
 
 AGRONOMY 
 
 This is the exact opposite of forcing. All the early spring flow- 
 ering plants may be treated in this way, being placed in cold 
 storage until required for blooming. Plants that have started 
 into growth may be retarded to a certain extent by keeping 
 the temperature lower than that required for vigorous growth. 
 Greenhouses and hothouses. Strictly speaking, a greenhouse 
 is a building used for keeping plants green through the winter, 
 
 Photograph by Lord & Burnham, New York 
 
 FIG. 111. A glass bouse in which a variety of vegetables and flowering plants 
 may be grown during the winter 
 
 and may or may not be heated, depending somewhat on the 
 location, while the hothouse is a heated building in which 
 plants may be grown, or warm-climate plants protected, dur- 
 ing the winter. Ordinarily, however, this distinction is not 
 maintained and the terms are used interchangeably. A con- 
 servatory partakes more of the character of the greenhouse, 
 being properly a place for conserving and showing plants
 
 FORCING AND RETARDING PLANTS 159 
 
 which are grown elsewhere. Plant houses have glass roofs 
 and sides to admit as much light as possible during the short 
 days of winter, and are heated largely by the sun's rays, at 
 least by day. The hotbed has been described as " a trap to 
 catch sunbeams," and the hothouse is merely a larger trap. 
 The heat rays coming from the sun pass through the glass 
 easily, but when reflected back from the soil the glass pre- 
 vents their escape. The interior therefore warms up rapidly 
 when the sun shines. On bright days the heat may be so 
 greatly increased as to injure or kill the plants if the house 
 is not ventilated. At night and on very cold days the warmth 
 is maintained by some sort of artificial heating system. The 
 first hothouses were kept warm by quantities of fermenting 
 manure placed in pits beneath the benches upon which the 
 plants were grown, and such means may still be depended 
 upon to keep the frost out of small houses during the winter. 
 In general, however, some sort of hot-water heating system 
 is used. 
 
 Hotbeds. Hotbeds are really small plant houses kept warm 
 by fermenting manure and the sun's heat, and are used for 
 growing plants before the weather will permit of their being 
 grown in the open. Early crops of lettuce, radishes, and other 
 vegetables are raised in this way, and long-season crops, such 
 as tomatoes, peppers, and eggplants, are started here and 
 carried along until transplanting time. To make a hotbed, a 
 pit should be dug 2 feet deep and about 1 foot wider than 
 the frame that is to be placed over it. This pit is to be filled 
 with manure to supply the heat, and should contain a good 
 share of straw or other material in order that the heat may 
 be long continued. The manure should be placed in a pile 
 and forked over at intervals for several days before using, to 
 insure that the fermenting material has been thoroughly mixed 
 through it. When the whole pile is steaming it should be 
 placed in the pit in layers about 6 inches deep, and each layer
 
 160 AGRONOMY 
 
 thoroughly tramped down. Over the pit of manure a layer of 
 good soil 6 inches deep should be spread, and in this the 
 plants are grown. The hotbed frame is made of boards, and 
 the roof, which is made of one or more hotbed sashes, should 
 slope toward the south. The front of the bed may be 6 inches 
 or 1 foot high and the back 12 to 20 inches. Hotbed sashes 
 are 3 by 6 feet in size, and the frame is made about 6 feet 
 wide and long enough to take one or more sashes. Old win- 
 dow sash may be used if hotbed sash are not at hand. When 
 the manure is first put into the pit and the sashes put on, 
 the heat often rises too high for plant growth. Seeds should 
 not be planted until the temperature at midday falls below 
 
 90. The frame is usually 
 banked up on the outside 
 with manure as an addi- 
 tional protection from the 
 sfll cold, and on very cold 
 
 nights the glass should be 
 covered by mats, old car- 
 
 Fio. 112. A hotbed showing the details ^ QT a j of straw, 
 
 of construction 
 
 Hotbeds are sometimes 
 
 made upon a level pile of manure placed on the surface of 
 the ground. In this case the manure should project beyond 
 the frame at least a foot on all sides. The heat in a hotbed 
 is not sufficient to carry it through the entire winter, and its 
 use is usually confined to the late winter and spring. In the 
 Northern states the hotbed is not begun much before the 
 middle of February, and in many cases the middle or end of 
 March is early enough. In managing the hotbed care should 
 be taken to give the plants air whenever the weather is favor- 
 able. This may be accomplished by lifting the lower end of 
 the sash and placing a block under it, or on fine days the sash 
 may be shoved part way off the frame. Plenty of air tends to 
 make the plants sturdier.
 
 FORCING AND RETARDING PLANTS 161 
 
 Cold frames. The cold frame differs from the hotbed in a 
 single feature: it lacks the pit of manure. It cannot therefore 
 be used for growing plants in very cold weather, though as 
 the air becomes warmer in spring it is often used to start 
 tomato, cabbage, and other plants for transplanting. Its great- 
 est usefulness is found in carrying half-hardy plants over the 
 winter and in prolonging the growing season of lettuce, 
 radishes, pansies, and the like in autumn. Cold frames are 
 banked up with manure to aid in keeping out the frost, and 
 in severe weather may be covered with mats. Both cold frames 
 and hotbeds do best if placed in sheltered situations, though 
 cold frames for carrying half-hardy or dormant plants through 
 the winter are often placed on the north side of a fence or 
 building. In the latter case the object is simply to protect 
 the plants, and no light is needed. Cold frames designed to 
 shelter plants for a few weeks in spring may be made with 
 oiled paper or cloth in place of the glazed sash. 
 
 Forcing single hills. Single plants of such species as rhu- 
 barb, asparagus, and sea kale may be made to grow much 
 earlier than they would naturally, by placing a box or half 
 barrel over each hill and piling manure around it. The top is 
 sometimes covered with a light of glass, thus making a mini- 
 ature cold frame of it. Single boxes of this kind are now being 
 offered for sale and serve a variety of purposes. In autumn 
 manure is often piled over hills intended for forcing, to keep 
 the ground from freezing deeply. Asparagus, rhubarb, and 
 onions are often forced in the house by setting the "roots" 
 upright and close together in a box and placing the box in a 
 warm room or cellar. If kept moist, the young shoots will 
 soon appear. These plants may also be grown under the 
 greenhouse benches in the same way. Light is not necessary 
 for forcing plants of this nature, since the food stored in the 
 roots or other underground parts is drawn upon for making 
 shoots. If it is desired to force the same roots again, they
 
 162 AGRONOMY 
 
 must be set out in spring in good soil and allowed one or 
 more years in which to recuperate. 
 
 Etherization. A large number of plants that form their 
 flower buds at the end of the growing season do not readily 
 resume growth when kept in sufficient warmth. These same 
 plants, however, if allowed to remain dormant and brought 
 into warmth at the end of winter, begin at once to grow. From 
 this it is seen that plants require a season of rest, and if we 
 are to induce such species to bloom in midwinter, something 
 to take the place of this rest must be devised. Freezing, as a 
 substitute for rest, has been found useful. If rhubarb plants 
 designed for indoor forcing are carried in before frost, they 
 fail to make proper growth, but if dug up in the field and 
 exposed to a few frosts, they grow at once when planted. 
 Heat appears to have the same effect as cold, and many spe- 
 cies may be as easily forced by plunging their branches into 
 hot water for a short time. Drought also affects plants like 
 cold, and some specimens behave in the same way if treated 
 with ether. In etherization the plants are placed in an air-tight 
 receptacle and exposed to the fumes of ether for twenty-four 
 hours or longer. When brought into warmth they are ready 
 to grow, the ether appearing to have the same effect upon 
 them as the long rest through the winter. Lilacs etherized in 
 August have been brought into full bloom a few weeks later. 
 In etherization about one third of an ounce of ether to each 
 cubic foot of space is the right amount. 
 
 Forcing plants in the window garden. The conditions in 
 most dwellings are not favorable to plant growth, especially in 
 winter. The dryness of the air, the lack of sunlight, the pres- 
 ence of coal gas and illuminating gas in the air, and the differ- 
 ence between the day and night temperatures all conspire to 
 kill or enfeeble vegetation. Only the hardiest plants can be 
 induced to grow and bloom under such circumstances. Plants 
 produced from bulbs, corms, and the like are an exception to
 
 FORCING AND RETARDING PLANTS 163 
 
 this, since the food necessary for their growth and even the 
 blossoms themselves are formed in the underground parts dur- 
 ing the preceding season. If given sufficient water they are 
 able to develop their flowers with very little light, since blos- 
 soming with them is largely a mere expansion of parts already 
 formed. They may be grown in soil or water, but in either 
 case they are usually set aside in some cool dark place, after 
 planting, to form roots before being placed in the light. The 
 most popular subjects for growing in this way are the paper- 
 white narcissus and the Chinese sacred lily, a closely related 
 species, but tulips, crocuses, hyacinths, and other bulbous plants 
 are also grown. After flowering, the plants are usually thrown 
 away, since they cannot be satisfactorily forced a second time. 
 
 PRACTICAL EXERCISES 
 
 1. At the proper time make a hotbed or cold frame in the school 
 garden and plant in it seeds of long-season plants that may be trans- 
 planted to the open ground later. Make a sowing of lettuce, beets, or 
 onions for transplanting. 
 
 2. Dig up spring flowering plants before they start into growth and 
 place in cold storage, to be brought out and flowered when those in the 
 fields have gone. 
 
 3. Try forcing sea kale, asparagus, or rhubarb. 
 
 4. Make a single forcing hill for growing some plant from seeds, 
 such as melon. 
 
 5. Try forcing some wild plant at the beginning of winter. Etherize 
 another plant of the same kind and compare results. 
 
 References 
 
 Bailey, "The Forcing Book." 
 Bailey, "Manual of Gardening."
 
 CHAPTER XII 
 
 WEEDS 
 
 Definition of a weed. A weed is properly defined as a plant 
 out of place. No matter how beautiful the flowers may be, or 
 how highly the species may be regarded for decorative planting, 
 if it competes with cultivated plants for possession of the soil, 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 113. Spraying a field of young grain with iron sulphate to 
 eradicate mustard and other weeds 
 
 it is a weed. In some localities the worst weeds with which 
 the farmer has to contend are ferns. Many species that in 
 foreign lands are cherished as beautiful flowering plants are 
 counted mere weeds at home. Indeed, some of the weeds that 
 now bother our cultivated crops, such as bouncing Bet and 
 
 164
 
 WEEDS 
 
 165 
 
 toadflax, were originally brought from Europe as desirable 
 additions to the flower garden, and only later took up a free 
 life in the fields. A few of our weeds are native, but most of 
 our noxious species have been derived from the Old World, 
 where centuries of struggle with crop and cultivator have 
 developed to the utmost their ability to resist all attempts to 
 dislodge them. Nor are weeds entirely confined to specimens 
 growing in cultivated areas. The plants that come up in walks 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 114. Grainfield showing the effect of spraying with iron sulphate 
 The portion on the left is unsprayed. Note the abundant young mustard plants 
 
 and drives, on railway embankments, and in similar places are 
 weeds. Other weeds, like the ditch moss and water hyacinth, 
 are confined to the water, but prove their weediness by chok- 
 ing up the streams and rivers, and in some cases actually 
 preventing navigation. 
 
 Harmfulness of weeds. Weeds are harmful in several ways. 
 They absorb water needed for the growth of cultivated crops, 
 prevent the formation of plant food by shading, harbor fungous 
 and insect enemies, render more difficult the task of keeping
 
 166 
 
 the soil loose and open, and in many, cases their seeds gathered 
 with the crop injure its value. Weeds should not be allowed 
 to grow even in the borders of cultivated grounds, since from 
 this point they may seed the soil for several years to come. 
 In this connection it is well to remember the oft-quoted 
 maxim, " One year's seeds, seven years' weeds." 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 115. A grainfield showing wild mustard in blossom. The portion on 
 the right has been sprayed with iron sulphate 
 
 Nature of weeds. Some of the qualities that conduce to 
 weediness in plants are abundant and easily distributed seeds, 
 the ability to grow rapidly, to endure injury and shading, and 
 to thrive upon little moisture and in sterile soils. Many secure 
 immunity from grazing animals by offensive odors, prickly 
 leaves and stems, and other disagreeable characteristics. Some 
 are winter annuals that grow in spring before more valuable 
 crops have started ; others are summer annuals that wait until
 
 WEEDS 
 
 the crops are well along, but grow so rapidly when they do 
 appear that they soon overtake and choke out their competi- 
 tors; while still others are perennials that spring again and 
 again from underground parts after being cut down by the 
 gardener. A few are mat plants or rosette plants that form 
 dense carpets over the soil, and some are vines that climb on 
 other plants, but the great majority simply grow erect and take 
 the ground by virtue of a more luxuriant growth. 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 116. Spraying a lawn with a baud sprayer to eradicate weeds 
 
 Eradicating weeds. One of the most effectual methods of 
 eradicating weeds is to prevent them from seeding. All annual 
 species are easily held in check in this way. When crops are 
 frequently cultivated the weeds are unable to get a start. A 
 favorite way of clearing a field of weeds is to plant it for one 
 or more seasons to some crop that must be hand cultivated. 
 All weeds may be killed by applications of salt, but since what 
 will kill weeds will also kill more valuable plants, this method 
 cannot be used except on walks, drives, and similar places. 
 Asparagus, however, can stand an application of salt strong 
 enough to kill the weeds that grow with it. Plants which
 
 168 
 
 A<;I;ONO.MY 
 
 depend upon peculiar soil conditions may be eradicated by 
 changing these conditions. Sedges which delight in moist soil 
 may be exterminated by draining, and mosses, sorrel, and various 
 other plants that like acid soils may be driven out by liming 
 the soil. Perennial plants must either be starved out by fre- 
 quently cutting off the leaves, or they may be dug up. A 
 large number of weeds are also killed by spraying with iron 
 sulphate, or " copperas," in the proportion of six pounds of iron 
 
 Photograph from Bergen and Caldwell's " Practical Botany" 
 
 FIG. 117. A tumbleweed (Cycloloma) blown into heaps by the wind 
 
 sulphate to four gallons of water. Grainfields may be practi- 
 cally freed from wild mustard in this way, the spray doing no 
 harm to the cultivated plants. All crops are not so resistant 
 and one must discover what the particular requirements of a 
 crop are before spraying. For destroying algse, the fine, fila- 
 mentous green growths that often appear in lily ponds and the 
 like, copper sulphate is often used. The water should be treated 
 with one part copper sulphate to three million parts of water. 
 Fish are very easily poisoned by this substance, and care must
 
 WEEDS 
 
 169 
 
 be taken not to have it too strong if used in ponds in which 
 there are desirable species. 
 
 Not all weeds are equally noxious ; moreover, what may be 
 a bad weed in one locality may be comparatively harmless in 
 another, perhaps because the crops are different, but there are 
 some species whose reputation for noxious qualities is world- 
 wide. Some of these are listed here. Other and more local 
 species may be studied in books devoted to the subject. 
 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 118. Dandelions gone to seed on a neglected lawn 
 
 Purslane (Portulaca oleracea). This is a fleshy little mat 
 plant with small yellowish flowers that open only in sunshine, 
 and is related to the portulaca, or rose moss, of our flower 
 gardens. It will grow in almost any soil, and stores so much 
 water in its thick leaves that, after it has begun to bloom, it 
 can ripen its seeds though severed from the soil. 
 
 Spreading amaranth (Amaranthus Uitoides). This species 
 resembles the purslane, but it is larger, less fleshy, and has 
 clusters of insignificant greenish flowers. Single specimens 
 may form mats more than a yard across.
 
 170 
 
 AGRONOMY 
 
 Green amaranth (Amamnthus kybridut). This is also known 
 as redroot and pigweed. It grows to the height of several feet, 
 with broad coarse leaves topped by a dense pyramid of green- 
 ish flowers. It is a most abundant and well-known weed, but 
 
 is easily exterminated. 
 
 Tumbleweed (Amaran- 
 thus albus). Before the 
 advent of the so-called 
 Russian thistle this was 
 the best-known tumble- 
 weed. It is a rather low 
 plant with branches dis- 
 posed in globular form. 
 When mature, the whole 
 plant separates from the 
 root and is blown about 
 the country, scattering 
 the minute seeds as it 
 goes. 
 
 Pigweed ( Chenopodium 
 album). This weed is 
 also known as lamb's 
 quarters. It is a pale 
 green plant with some- 
 what triangular leaves 
 that are whitened by a 
 mealy deposit, and is thus easily recognized. It is a close ally 
 of the beet and spinach and is often eaten as a pot herb. 
 
 Russian thistle (Salsola trains'). This plant is in no sense 
 a thistle, being more closely related to the pigweeds. It is 
 extremely prickly, and from this circumstance its name is 
 derived. It is another of the tumbleweeds and in conse- 
 quence spreads rapidly. It is well known in the Middle West, 
 where it was accidentally introduced during the latter part of 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 119. The common plantain
 
 WEEDS 
 
 171 
 
 the last century, and is now a familiar plant in waste grounds, 
 roadsides, railway embankments, and the like. 
 
 Spotted spurge (Euphorbia maculata). The spotted spurge 
 is another of the mat plants, and is readily distinguished by its 
 small, thin, hairy leaves with a red blotch in the center, and 
 by its much-branched slender stem, pressed close to the earth. 
 The juice is milky. It delights in dry open places and grows 
 readily in soils too sterile for the growth of other plants. 
 
 Photograph from American 
 
 FIG. 120. A tangle of the common bindweed 
 
 and Wire Co. 
 
 Dandelion (Taraxacum officinale). Its yellow flowers and 
 feathery heads of seeds make this most abundant rosette plant 
 too well known to require description. Its long and fleshy 
 taproot is often removed by digging, but if any is left in the 
 soil, it may originate new buds and produce a dozen or more 
 plants where but one was originally. 
 
 Plantain (Plantago sp.). Three species of plantain are 
 frequent as weeds in grassy areas. Of these, Plantago major
 
 172 
 
 AGRONOMY 
 
 and P. Rugelii are common dooryard weeds with broad and 
 rounded leaves and slender spikes of inconspicuous flowers. 
 The third species, the narrow-leaved plantain (P. lanccolatcf), 
 is easily distinguished by its rosette of long narrow leaves 
 
 veined lengthwise of the 
 blade. All the plantains 
 are easily dug up. 
 
 Common bindweed (Con- 
 volvulus sepiuni). The 
 large white or pink fun- 
 nel-shaped flowers, like 
 morning-glories, make the 
 bindweed conspicuous 
 and well known. It is 
 fond of rich soil and 
 forms tangled mats over 
 the vegetation in the 
 fields where it grows. It 
 has a creeping under- 
 ground rootstock that 
 makes it one of the hard- 
 est of weeds to eradicate. 
 Black bindweed (Poly- 
 gonum convolvulus). The 
 climbing stems of this 
 plant overrun other plants 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 121. A common wild lettuce related 
 to the prickly lettuce 
 
 in its vicinity, after the 
 manner of the common 
 bindweed, to which, how- 
 ever, it is not closely related. It is a much slenderer plant 
 with greenish flowers and seeds that suggest its relative the 
 buckwheat. Being annual instead of perennial, it is a much 
 less formidable species than the common bindweed, though 
 its vigorous growth makes it a harmful weed.
 
 WEEDS 
 
 173 
 
 Prickly lettuce (Lactuca scariola). Although the intro- 
 duction of this plant into America occurred but recently, it 
 has already spread so extensively as to become a common 
 weed. It may be known by its erect prickly stems and bluish- 
 green leaves, most of which are turned edgewise and point 
 north and south. It is frequently a winter annual and is re- 
 garded by botanists as being the parent of our garden lettuce. 
 
 Ragweed (Ambrosia 
 artemisicefolicf). Rag- 
 weed, a homely plant 
 with much-dissected 
 leaves, is found al- 
 most everywhere in 
 cultivated land. At 
 flowering time the in- 
 significant greenish- 
 yellow flowers shed 
 great quantities of yel- 
 low, dustlike pollen, 
 which collects upon the 
 shoes and clothing of 
 all who pass through it. 
 The pollen is regarded 
 with good reason as be- 
 ing one of the causes 
 
 FIG. 122. Ragweed, a common weed regarded 
 
 oi nay lever. as ^j ie cause O f i ia y fever 
 
 Wild mustard (Bras- 
 
 sica arvemis*). Several species of mustard are known under 
 the general name of wild mustard, but the species named above 
 is the most widespread and troublesome. The mustards may 
 be distinguished by their coarse hairy leaves, clusters of bright 
 yellow flowers, and long spikes of seed pods. They spring up 
 quickly, grow rapidly, and soon smother less strenuous plants. 
 The turnip is a closely related species of Brassica. 
 
 Photograph from American Steel and Wire Co.
 
 174 
 
 AGRONOMY 
 
 Oxeye daisy (Chrysanthemum leucanthemum). The large 
 white flowers of this species, universally known as daisies or 
 marguerites, are sufficient to identify it. It is a perennial, 
 spreading rapidly by means of its many small seeds, and be- 
 comes a bad weed in meadows and pastures, crowding out the 
 
 rightful tenants of 
 the soil. It is some- 
 times known as 
 whiteweed. The 
 yellow daisy (Rud- 
 beckia hirta), also 
 common in fields 
 and meadows, is a 
 native species. 
 
 Canada thistle 
 (Cnicus arvemis). 
 Many other spe- 
 cies of thistle are 
 confused with this 
 much-dreaded plant, 
 which, in spite of 
 the name it bears, 
 is an Old World 
 species, and not a 
 native of this con- 
 tinent. It may be 
 known by its very 
 prickly stems and leaves and its pale lavender blossoms of 
 small size. Owing to the fact that its rootstock is widely 
 creeping and deep in the earth, it is very difficult to eradicate 
 when once established. The plant has two kinds of blossoms, 
 those on some specimens being completely sterile. This has 
 given the impression in some sections that the plant does not 
 ripen good seeds in parts of its range. 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 123. A plant of wild mustard 
 This species is especially harmful in grainfields
 
 WEEDS 175 
 
 Quack grass (Ayropyrum repens). This is a perennial species 
 whose slender and wide-creeping rootstock sends up new stems 
 at frequent intervals that later bear slender close-set spikes of 
 greenish flowers. It is one of the hardest of weeds to root out, 
 but this may be accomplished by planting fields infested with 
 it to some hoed crop and cultivating frequently. Though so 
 generally useless, this species is closely related to the wheat. 
 
 Photograph from American Steel aud Wire Co. 
 
 FIG. 124. The oxeye daisy on the border of a field 
 
 Crab grass (Panicum sanguinale). This species, often called 
 finger grass, is a coarse annual that does not begin to grow 
 until the weather is quite warm and the cultivated crops well 
 started. At first the stems are erect, but later they lie upon 
 the soil with only the tips erect, and root wherever a joint 
 comes in contact with the earth. When pulling it up, every 
 root must be loosened or it will continue to thrive. The flow- 
 ering stems are topped by several slender spikes that radiate 
 from a common center.
 
 176 
 
 AGRONOMY 
 
 Foxtail (Setaria glaucof). This is another annual grass that 
 does not make its appearance until very late in spring. It has 
 a most extensive root system, and when it is pulled up often 
 brings more valuable plants with it. The fruiting part is a 
 bristly spike two or three inches long, from the appearance 
 
 of which the common 
 name is derived. 
 
 Old witch grass (Pan- 
 icum capillare). This is 
 an annual that thrives 
 in dry soils. It appears 
 in early summer, put- 
 ting up several coarse 
 hairy stems that bear 
 large panicles of many 
 purplish threadlike di- 
 visions. Late in the year 
 these panicles break 
 from the plant and are 
 blown about by the 
 wind. This species is 
 sometimes called tickle 
 grass in allusion to its 
 feathery panicle. 
 
 Photograph from American Steel and Wire Co. BllttCrCUO ( RttnUn- 
 
 FIG. 125. Young plant of the Canada thistle, 7 -NO i 
 
 culus acrts). several 
 one of our worst weeds 
 
 species of buttercup 
 
 may become weeds, but the one here given is best entitled to 
 the name. It takes entire possession of many damp meadows 
 and is so acrid that cattle will not touch it. Drying dispels 
 the acrid properties, and when cut with the hay it is harmless. 
 Wild carrot (Daucus carota). The wild carrot is also called 
 bird's nest and Queen Anne's lace, in allusion to its flower 
 clusters. It is a vile pest in many thin soils and its sturdy
 
 WEEDS 
 
 177 
 
 taproot makes it hard to conquer. The plant is supposed 
 to be identical with the cultivated carrot, but in the wild 
 state it is reputed to 
 be poisonous. 
 
 Sorrel (Rumex aceto- 
 selld). This plant, com- 
 monly known as sour 
 grass or horse sorrel, 
 is a perennial weed 
 with numerous creep- 
 ing subterranean stems 
 and thrives in sterile 
 soil. Early in summer 
 
 it turns its haunts a 
 
 FIG. 126. Wild carrot on a neglected lawn 
 rusty red by a multi- 
 tude of small flowers. It is supposed to be an indicator of 
 acid soils and may be controlled by the application of lime. 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 127. A field overrun by wild carrot 
 
 Other weeds. Among less noxious though ever-present weeds 
 may be mentioned shepherd' s-purse (Capsella), pepper-grass
 
 178 
 
 AGRONOMY 
 
 (Lepidiwm), chickweed (Stellaria), knotgrass (Polyyonum), 
 burdock (Arctiwny, evening primrose (Oenothera'), sneezeweed 
 (Helenium), bugloss (Echiwrn), bouncing Bet (Saponaria), 
 toadflax (JLinaricf), smartweed (Polyyonum), dog fennel (An- 
 themis), and Jimson weed (Datura). These may be looked up 
 in any botanical manual. A large number of other plants, 
 such as yarrow (AchillecC) and sheep sorrel (Oxalis'), come 
 
 Photograph from American Steel and Wire Co. 
 
 FIG 128. A plant of dog fennel, a common weed along roadsides and in 
 
 low grounds 
 
 under the designation of weeds, since they frequently grow 
 among cultivated crops, but they are seldom harmful enough 
 to be classed with the noxious species and are not difficult 
 to eradicate. 
 
 It should not be supposed that the plants we now recognize 
 as weeds are the only ones with which the cultivator is likely 
 to have to contend. New weeds are practically certain to ap- 
 pear from time to time, either derived from our native flora
 
 WEEDS 
 
 179 
 
 or as immigrants from other parts of the world. The orange 
 hawkweed (Hieradum aurantiacum), which within a generation 
 has spread over large areas in the Eastern states, is a case in 
 point, and the Russian thistle, which appeared somewhat 
 earlier, is another. The rapidity with which these weeds have 
 spread is accounted for by their methods of seed distribution. 
 Plants with wind-dis- 
 tributed seeds are 
 usually good travel- 
 ers, but those whose 
 seeds lack special 
 means of distribution 
 are often very slow 
 in conquering new 
 territory. The ox eye 
 daisy, which has 
 proved such a pest 
 in New England, is 
 still rare or absent 
 in the north -central 
 states, while the yel- 
 low daisy, originally 
 a Western plant, has 
 spread to the East in 
 comparatively recent 
 times. New weeds 
 
 are likely to be first found along traveled ways, especially if 
 their seeds are not modified in some way for distribution, and 
 a new line of traffic is usually responsible for their introduc- 
 tion. Galinsoga parviflora, a harmless Mexican plant, was 
 unknown in the Northern and Eastern states until the inhabit- 
 ants began railway traffic with Mexico. Now it is common in 
 many places as far north as Canada. The teasel is an Old 
 World plant that has long been known as a weed in America, 
 
 Photograph from American Steel and Wire Co. 
 
 FIG. 129. Yarrow, a nearly harmless weed of 
 wide distribution
 
 180 AGRONOMY 
 
 but it is still rare except in the vicinity of railroads. Other 
 weeds owe their appearance in new regions to their having 
 been brought in with the seeds of cultivated crops. The corn 
 cockle (Agrostemma giihago) owes its common name to the 
 fact that it is nearly always found in grainfields, where its 
 seeds have t>een carried with the grain. 
 
 PRACTICAL EXERCISES 
 
 1. Make a list of the weeds known to grow in your locality. 
 
 2. What qualities make them bad weeds ? 
 
 3. Make a list of the weeds that spring up in the school garden. 
 
 4. Underscore the weeds in the above lists that are perennials. 
 
 5. Make a collection of weed seeds labeled with both scientific and 
 common names. 
 
 6. Make a list of the ways in which these weed seeds are distributed, 
 with examples of each. 
 
 7. Estimate the number of seeds produced by one weed in a season. 
 If all these seeds should grow the following year and produce the same 
 number of seeds and continue to reproduce in this way, how many years 
 would it take to produce one plant for each acre of land in the world ? 
 
 8. Make a list of weeds that have come into your region witli the 
 seeds of cultivated crops. Make a similar list for those that have come 
 in along the railroads. 
 
 References 
 
 Long, "Common Weeds of the Farm and Garden." 
 Pammel, " Weeds of the Farm and Garden." 
 
 Farmers' Bulletins 
 
 28. Weeds and how to kill them. 
 188. Weeds used as Medicines. 
 
 Bureau of Plant Industry 
 
 83. The Vitality of Buried Seeds. 
 89. Wild Medicinal Plants of the United States. 
 107. American Boot Drugs.
 
 CHAPTER XIII 
 
 PROPAGATION 
 
 Natural methods. The one means by which all plants higher 
 in the scale of life than the ferns are multiplied is by seeds. 
 Many species, in addition to' 
 this, have devised various 
 ways of multiplying asex- 
 ually or vegetatively by 
 means of special parts of 
 the plant which take root 
 and soon become separate 
 individuals. This latter 
 method is often more cer, 
 tain than reproduction by 
 seeds, since the new plant 
 may remain attached to 
 the old one until estab- 
 lished ; and some species, 
 such as the potato and 
 horse-radish of our gar- 
 dens, and the sugar cane 
 and sweet potato, have 
 almost abandoned seeds in 
 favor of it. In most cases, 
 however, seed production 
 and vegetative multipli- 
 cation proceed side by 
 
 side, one being used for multiplying the plant in a particular 
 station and the other for spreading it into other regions. 
 
 181 
 
 FIG. 130. A lilac shrub that has pro- 
 duced numerous suckers
 
 182 
 
 AGRONOMY 
 
 Typical forms for propagation. The branches of almost any 
 plant may strike root under favorable circumstances, but in 
 plants that depend very much upon vegetative methods there 
 are usually well-defined parts developed for the work. Several 
 of these have received distinctive names, such as sucker, stolon, 
 offset, tuber, rootstock, bulblet, and cormel. A snicker is pro- 
 duced by an adventitious bud upon some underground part, 
 
 usually a root. Many 
 plants, among which 
 may be mentioned the 
 lilac, plum, locust, and 
 white poplar, sucker 
 freely. In such species 
 injury to the root or 
 cutting back the top 
 may induce suckering. 
 A stolon is a slender 
 branch that bends over 
 and roots at the tip, as 
 in the black raspberry, 
 currant, June berry, 
 and golden bell. The 
 offset is a short, thick, 
 horizontal branch, either 
 on the surface or un- 
 derground, which pro- 
 duces a plant at the tip. It differs from a stolon chiefly in 
 being shorter and thicker and designed solely for reproduction. 
 The century plant, house leek, and ostrich fern produce nu- 
 merous offsets. Runners differ from offsets mainly in being 
 slenderer and longer, and in producing new plants at each node, 
 as in the strawberry. Tubers are short, much thickened under- 
 ground branches that lie in the soil over a season of cold or 
 drought and produce new plants upon the return of a more 
 
 FIG. 131. Base of a sunflower stem showin 
 offsets for reproducing the plant
 
 PROPAGATION 
 
 183 
 
 favorable season. The potato and artichoke are good examples. 
 Rootstocks are also subterranean stems, but differ from tubers 
 
 FIG. 132. Onion bulbs 
 The sectioned specimens show the origin of bulblets 
 
 in being the main axes of the plants instead of branches, and 
 in living much longer. When the rootstock branches, how- 
 ever, these shoots act exactly like tubers in forming new 
 plants. The iris and Solomon's seal 
 are good illustrations of rootstocks. 
 Bulblets, or bulbils, are budlike struc- 
 tures, really small buds, produced in 
 the axils of bulb scales, as in many 
 lilies and the " potato " onion, or on 
 the aerial parts of plants, such as 
 
 may be seen in the tiger lily and the FIG. 133. A corm of gla- 
 " top " onion. Cormels are small con- 
 densed stems with one or more buds, 
 and are produced by corms, such as the gladiolus and crocus. 
 Artificial propagation. In multiplying his specimens the 
 gardener takes advantage of all the methods evolved by 
 
 diolus with several small 
 cormels attached
 
 184 
 
 AGRONOMY 
 
 plants, to which he adds various others which careful manip- 
 ulation and a knowledge of plant growth make possible. 
 Often injury to the plant will cause it to produce parts 
 designed for reproduction. Cuts near the base of bulbs or 
 corms will cause bulblets or cormels to develop. Even bulb 
 scales, when treated as softwood cuttings, may develop into 
 new plants. All vegetative multiplication depends upon a 
 division of the plant, which fact may be made use of in many 
 ways. Cormels and bulblets are removed from 
 the plant and treated like seeds. Rootstocks 
 are separated into bits, each of which contains 
 one or more buds and a few roots. Tubers, 
 like rootstocks, are cut into pieces, a single 
 specimen thus producing several new plants. 
 Runners, offsets, stolons, and suckers are sep- 
 arated from the parent plant and set where 
 wanted. Other species, such as the phlox, 
 
 FIG. 134. A species of sunflower (Helianthus laetiflorus) showing the 
 evolution of a tuber from an offset 
 
 golden glow, and chrysanthemum, which grow in clumps with- 
 out well-defined rootstocks or other means of propagation, 
 may be simply cut in pieces and each piece planted separately. 
 Chief among the artificial methods which man has devised 
 for multiplying plants may be named cuttings, layering, bud- 
 ding, and grafting. 
 
 Cuttings. Nearly all plants may be increased in number by 
 detached parts, which, placed in moist sand or even water, 
 soon strike root and become independent individuals. The 
 " slips " by which house plants are commonly propagated are
 
 PKOPAGATIOX 
 
 185 
 
 good examples. These cuttings are placed in two groups : 
 green or softwood cuttings, made mostly from herbaceous plants 
 and intended to be rooted at once ; and hardwood cuttings, 
 made from woody plants late in autumn. The latter are kept 
 in a dormant condition through the 
 winter and are rooted the following 
 spring. This latter form of cutting 
 is the one commonly employed in 
 multiplying the woody plants, but 
 many of these may also be propa- 
 gated by softwood cuttings, espe- 
 cially roses, currants, golden bell, 
 willow, and poplar. For this pur- 
 pose the cuttings should be taken 
 while the wood is young and ten- 
 der. In making any kind of cut- 
 ting it is desirable that the cuts be 
 made just below the nodes, since 
 the new roots usually spring from 
 these parts. Among the plants com- 
 monly grown from softwood cut- 
 tings are carnations, geraniums, 
 begonias, chrysanthemums, and 
 those specimens known as " foliage 
 plants." When set, about one third 
 of each cutting should project above 
 the soil. To prevent loss of mois- 
 ture while they are making roots, it 
 is customary to remove part or all 
 the leaves before setting and to protect them from the drying 
 effects of the air by sheltering with glass or thin cloth. Plenty 
 of warmth and moisture is necessary to make most cuttings 
 root rapidly, but they should not be kept so close as to pre- 
 vent ventilation. The hardier plants, however, will root if the 
 
 FIG. 135. A geranium cutting 
 which has struck root 
 
 From Bergen and Cakhvell's 
 " Practical Botany "
 
 186 
 
 AGRONOMY 
 
 cuttings are merely stuck in moist soil in a shady place. 
 Several forms of softwood cuttings have distinctive names. 
 Leaf cuttings are made from leaves or parts of leaves, which 
 are pegged down on moist sand and kept close. After a time 
 
 FIG. 136. A Jamaican fern (Faydenia) in which 
 the leaves form new plants at their tips 
 
 tiny plants will begin to form along the edge of the leaves. 
 Begonias, wax plants, and bryophyllums are multiplied in this 
 way, and among wild plants the sundews and many ferns have 
 the same faculty. Stem cuttings are the ordinary " slips " or 
 twigs taken with three, or more joints. Tuber cuttings are 
 pieces of tubers with one or more " eyes," or buds. Cuttings
 
 PROPAGATION 187 
 
 of this kind are the customary means of multiplying potatoes, 
 artichokes, and dahlias. Root cuttings may be used for getting 
 additional plants of quince, horse-radish, blackberry, sea kale, 
 phlox, butterfly weed, and the like. In such cases adventitious 
 buds are formed on the roots, although they do not normally 
 occur in this way. In the case of phlox and butterfly weed, 
 however, small roots left in the soil after the plant is dug are 
 almost certain to send up new plants, and in horse-radish and 
 sea kale the larger roots are depended upon for increasing 
 the number of plants. Dandelion roots can also originate buds 
 
 FIG. 137. Tubers of artichoke (Helianthus) and potato, which are usually 
 propagated by tuber cuttings 
 
 in this way, and a single piece of root left in digging may pro- 
 duce several new plants. Hoot cuttings, like tuber cuttings, 
 are entirely covered by the soil when planted. 
 
 Hardwood cuttings. Hardwood cuttings are made from ma- 
 ture wood not more than two years old and usually younger. 
 They are cut at least six inches long and are taken late in 
 autumn when the wood is dormant. They are not set until 
 the following spring and must be kept in a cool moist place 
 until used. In common practice they are tied in bundles of 
 about one hundred each and buried a foot or more deep and 
 upside down in a well-drained spot, or they may be kept in 
 moist sand in a cool cellar. During the winter a tissue called 
 the callus forms over the cut ends, and from this or near it the 
 new roots start. In plants that root rather easily the cuttings 
 are often set out in autumn. Nearly all our trees, shrubs, and 
 woody vines may be propagated by hardwood cuttings, though 
 the form of these depends somewhat upon the species it is
 
 188 
 
 AGROV.MY 
 
 desired to multiply. Besides the simple cuttings of three or 
 more joints, there are single eye cuttings consisting of a single 
 node with its buds. These are planted in the soil, usually in 
 the greenhouse, and treated as if they were seeds. Heel cut- 
 tings are made by removing a twig with part of the old wood 
 attached to it, the latter forming the " heel." Mallet cutt'tinjx 
 are sections of the main stem with the twig attached. In 
 
 some species, especially 
 those with very hard 
 wood, these latter root 
 more readily than the 
 simple stem cuttings. 
 In general, hardwood 
 cuttings should be set 
 so that not more than 
 one bud appears above 
 the soil. 
 
 Layering. Layering 
 is a modification of re- 
 production by cuttings 
 used with plants that do 
 not readily strike root 
 from separate pieces. In 
 this method the twig is 
 induced to strike root, 
 while still attached to 
 the parent plant, by being bent down and covered with moist 
 soil. Often the branch is cut part way through where it is 
 covered with soil, or it may be bent or twisted, or a layer of 
 bark may be removed to further influence the production of 
 roots. The black raspberry, hobblebush, and golden bell root 
 naturally at the tips, and other plants may be made to do so. 
 This is called tip layering and is really the forming of an arti- 
 ficial stolon. In vine layering the branch may be covered with 
 
 FIG. 138. Three forms of hardwood cuttings 
 
 On the left, the ordinary form ; in the middle, a 
 heel cutting; on the right, a mallet cutting
 
 PROPAGATION 189 
 
 soil at several points, and when these form roots, they are cut 
 up into separate plants. Grapes, honeysuckles, wistaria, and 
 many others may be propagated thus. Branches that rise 
 from the base of shrubs often form roots and may be removed 
 to form new plants. This process is often hastened by the 
 grower, who first cuts back the plant to make it throw up 
 numerous shoots and then heaps the soil up around them so 
 that they will root. This is known as mound layering. What 
 is essentially a form of layering may be often seen in green- 
 houses where various tropical species, such as the rubber plant, 
 are multiplied by tying a ball of wet moss about a branch near 
 the tip, first injuring the bark to make it root at that point. 
 The moss is kept wet and in due time is filled with roots, after 
 which the branch is cut off. This is called air layering or pot 
 layering. 
 
 The sand box. Although established plants thrive only in 
 rich soil, cuttings root better in clean, sharp sand. The willow, 
 wandering Jew, and nasturtium root readily in water. The 
 nurseryman roots his cuttings in beds of moist sand in the 
 greenhouse, but for home work a box of sand set in a shady 
 place and covered with glass or thin cloth is very useful. 
 Care should be taken to see that the sand is free from inju- 
 rious fungi and insects, and after being used for one lot of 
 cuttings should be sterilized by baking or pouring boiling 
 water through it before it is used for another. The cuttings 
 should be given a warm and even temperature and should 
 not be allowed to suffer for water or fresh air. 
 
 Budding. Budding does not increase the number of plants, 
 but it may be employed to increase the number of a certain 
 kind. It is really a form of transplanting whereby the bud of 
 a desirable species is made to grow upon one less desirable 
 and thus change the nature of the plant. It is used for mak- 
 ing worthless species productive, for multiplying forms that 
 will not come true from seeds, and for hastening the fruiting
 
 190 
 
 AGRONOMY 
 
 of others. All of our superior fruits and many of our nut 
 trees are budded or grafted upon other stock because their 
 characters are not fixed in the seed. Having one good plant, 
 however, we may make as many others as we choose by bud- 
 ding. In this process it makes no difference if the fruits pro- 
 duced by the stock are worthless. The bud will form a new 
 crown that will produce fruits like the plant from which it 
 was taken. In growing the stocks, therefore, 
 seeds from any source may be sown. The 
 plants are budded when one or two years 
 old, and thereafter have all the character- 
 istics of the superior strain. Usually only 
 closely related forms can be budded success- 
 fully. The plants most frequently treated in 
 this way are the stone fruits, nut trees, and 
 some of the citrous fruits. Budding is per- 
 formed in late June, July, August, and early 
 September. 
 
 Method of budding. In the common form 
 of budding a T-shaped cut is made in the 
 bark of the stock, the upper edges of the cut 
 are carefully turned back, and a new bud 
 with more or less bark attached is inserted, 
 after which the bark of the stock is pressed 
 into place and tied for a week or more until 
 the bud has grown fast. The cut in the stock 
 should go halfway around the twig or stem, and the cut at 
 right angles to it should be about an inch and a half long. 
 Both should extend inward as far as the new wood. The 
 bud should be selected from a vigorous and healthy plant, 
 and removed with an upward cut of a sharp knife, beginning 
 a quarter of an inch below the bud and ending the same dis- 
 tance above it. The cut should be made just deep enough to 
 remove a thin shaving of the new wood, which may afterwards 
 
 FIG. 130. A twig 
 
 with buds removed 
 
 for budding
 
 PKOPAGATION 
 
 191 
 
 be removed with the knife, or, if very thin, it may be inserted 
 with the bud. The leaf that occurs below each bud may be 
 severed where the blade joins the petiole, and the latter left 
 for a handle. The bud and the bark removed with it should 
 be inserted in the cleft in the stock and care taken to see that 
 the cambium of bud and stock are in contact. The bark of the 
 stock should be tied securely about the bud with two or three 
 turns of twine or waxed cotton, but the bud itself must not 
 be covered, and as 
 soon as it has been 
 incorporated with 
 the stock, which 
 should occur in 
 about ten days, the 
 
 wrappings must be .4 1^1 t* 
 
 removed. The bud 
 remains dormant 
 until spring, and 
 as soon as growth 
 begins, the part of 
 the stock above 
 the bud should be 
 removed and the 
 latter left to form 
 
 the new plant. In budding young plants the bud is inserted 
 about two inches above the soil ; in larger specimens it may be 
 inserted anywhere on the young growth. By selecting buds 
 of different varieties one may have several kinds of fruit on 
 the same tree. While budding, neither bud nor stock should 
 be allowed to become dry. It is also well to bud on the north 
 side of the stock, where the bud will not be exposed to the 
 sun. Several other forms of budding are in use, but the prin- 
 ciple is the same in all. In ring, flute, or annular budding a 
 piece of bark extending part way around the stock is removed 
 
 Flo. 140. Three stages in the operation of budding 
 In the figure on the right the work has heen completed
 
 192 AGRONOMY 
 
 and a similar piece of bark with a bud from another plant is 
 fitted in. This method is most frequently used in budding 
 thick-barked trees such as hickory and magnolia, the work 
 being performed in early spring. Prong budding is really a 
 form of grafting in which a short twig is treated as a bud. 
 
 Grafting. Grafting is in many respects like budding, since 
 it consists in transferring a part of one plant to another, but 
 in the present case a small twig, called a don, or graft, is used 
 instead of a bud. The cions are collected and stored in autumn, 
 exactly like hardwood cuttings, and the only practical differ- 
 ence between them is that the cutting is designed to draw 
 part of its nourishment from the soil through its own roots, 
 while the cion is intended to become a part of another plant 
 with no roots of its own. The essential thing in all grafting 
 is to see that the cambium of stock and cion meet, and that 
 the point where they join is protected by grafting wax until 
 the two have grown together. Grafting must be done in late 
 winter or early spring while both stock and cion are dormant. 
 As in budding, cion and stock must be from nearly allied 
 species. Sour apples or pears may grow on sweet-apple stock 
 and peaches on plum stock, but widely separated species can 
 seldom, if ever, be made to unite. A single tree may be made 
 to bear half a hundred different varieties of apples by graft- 
 ing, and each will come true to its nature. In species with 
 dioecious flowers grafting may be employed to make sterile 
 forms fertile. 
 
 Different forms of grafting. Two principal forms of grafting 
 may be distinguished : cleft grafting used in working over old 
 trees ; and whip grafting, the method commonly employed with 
 small or young stock. In cleft grafting, a branch about two 
 inches thick is sawed off, the stump is split with a chisel or 
 knife, and the base of the cion, cut to slender wedge shape, 
 is inserted in the cleft. Usually two cions are used, one on 
 each side of the cleft, and to insure that the cambiums of
 
 PROPAGATION 
 
 193 
 
 stock and cion shall meet, the cions are often made to diverge 
 
 slightly. The cleft is then covered thoroughly with grafting 
 wax, to keep out insects and decay 
 until the wound heals. Crown grafting 
 is like cleft grafting except that it is 
 used in renewing the top of shrubs 
 and vines that have been cut off at 
 the surface of the soil. Cleft grafting 
 is rarely used except in attempts to 
 give old trees a new lease of life. For 
 all ordinary work whip grafting is em- 
 ployed. Numerous forms of this are in 
 use, but they differ for the most part 
 only in the way cion and stock are 
 joined. In the form called saddle graft- 
 ing the top of the stock is cut in wedge 
 shape and the cion is cut with a deep 
 notch to match it. In splice grafting 
 a long tapering cut from one side of 
 
 the stock to the other fits a similar cut on the cion. Tongue 
 
 grafting is an improved form of splice 
 
 grafting, in which a longitudinal cut is 
 
 made about one third of the distance 
 
 from the tip of the cut in both cion and 
 
 stock. These are then wedged together, 
 
 forming a close union that is not readily 
 
 injured by the weather. In veneer graft- 
 ing a notch is made through the bark of 
 
 the stock, and the base of the cion, cut 
 
 to fit, is inserted. Bridge grafting is 
 
 sometimes employed to repair injuries 
 
 to the bark of large trees. The edges 
 
 of the wound are first straightened up and several twigs of 
 
 the same species are obtained, their ends cut wedge shape 
 
 FIG. 141. Cleft grafting 
 
 This method is used on 
 large specimens 
 
 \ 
 
 FIG. 142. Three forms of 
 whip grafting
 
 194 
 
 A.GBONOMY 
 
 and inserted into the bark above and below the wound. In 
 this way the sap is carried past the injury until the tree can 
 cover it with bark. In root grafting the cion is joined to a 
 piece of root. This is regarded as one of the best forms of 
 grafting, since the cion may also put out roots and help to 
 nourish the plant ; in fact, this hardly differs from growing 
 
 a plant from a hardwood cut- 
 ting. In all the forms of whip 
 grafting, stock and cion are 
 carefully bound together with 
 waxed cotton twine or graft- 
 ing wax until a perfect union 
 occurs. Root grafts, being un- 
 derground, do not need this 
 protection. 
 
 Although herbaceous plants 
 are rarely grafted, it can be 
 accomplished. Grafts between 
 the tomato and the potato, the 
 morning-glory and the sweet 
 potato, the artichoke and the 
 sunflower, are now and then 
 reported. In grafting herba- 
 ceous plants veneer grafting 
 is the best form to use, but 
 in this case the cut in the 
 stock should be made deeper 
 than for hard-wooded plants. Even fruits have been grafted 
 when half grown. The grafting of soft-wooded plants is most 
 successful when carried oh under glass, where the conditions 
 of temperature and moisture can be controlled. 
 
 Inarching. Inarching is a form of grafting in which cion and 
 stock are united while both are still joined to their own roots. 
 In this, one stem is bent over toward the other, the cambium 
 
 FIG. 143. Tongue grafting 
 Illustration of one of the best methods
 
 PROPAGATION 195 
 
 of each exposed, and the two stems bound together until a 
 union is formed. The top of the stock is now cut off and the 
 cion cut away from its roots. In the same way a small plant 
 in a pot may be inarched to the branches of a large tree. In 
 the forest one may often see examples of natural inarching 
 where two plants have come into contact. 
 
 Grafting wax. To make grafting wax, take four parts of 
 rosin, two parts of beeswax, and one part of tallow or linseed 
 oil, and melt all together. When thoroughly mixed pour into 
 cold water, and, when cool enough, work it like molasses candy 
 until it assumes a light straw color. Make into rolls and wrap 
 in waxed paper until wanted. If a harder wax is desired, the 
 amount of rosin or beeswax may be increased. The hands 
 should be greased with tallow before attempting to work the 
 wax. Waxed twine for tying buds and grafts may be prepared 
 by putting a ball of No. 18 knitting cotton in the kettle of 
 melted wax for a few minutes. 
 
 Effect of stock on cion. Usually the nature of the stock has 
 little effect on the cion, but cases are known in which apples 
 grafted on wild-crab stock have produced more acid fruits, 
 while late apples may ripen earlier as a result of grafting 
 them on stocks of earlier varieties. Certain species may be 
 dwarfed by grafting them on slow-growing stock, and the 
 time of fruiting may often be greatly modified by the kind of 
 stock and cion selected. Apples usually grow for ten or more 
 years before fruiting, but a young seedling grafted on old 
 stock may fruit in a year or two. On the other hand, a twig 
 from an old tree grafted upon a seedling may grow for years 
 before producing fruit. Many French grapes are grafted on 
 American stocks, which are more resistant to the dreaded 
 plant louse, Phylloxera, which infests the roots. Rarely the 
 union of graft and stock, may produce twigs with characters 
 that appear intermediate between the two. Such specimens 
 are known as graft hybrids.
 
 196 AGRONOMY 
 
 PRACTICAL EXERCISES 
 
 1. From pictures, from dried specimens, and from plants in the gar- 
 den, learn to recognize the various forms by which plants are propagated 
 vegetatively. 
 
 2. In the school garden examine all the crops grown, with a view 
 to propagating them. Which are most susceptible to treatment in this 
 way, the crop plants or the permanent species? Can you discover the 
 reason for the difference? 
 
 3. In the borders find plants to illustrate propagation by each of 
 the methods given in this book. Make a list of them. 
 
 4. Make softwood cuttings and root them in the hotbed or cold 
 frame. 
 
 5. In autumn make hardwood cuttings of all the types mentioned, 
 and store as required. In spring, if cuttings of this kind have been left 
 by a former class, try rooting them in the cold frame, in the hot bed, or 
 in the open. 
 
 6. Layer any vine that may be convenient in the school garden. 
 Try layering currant bushes for planting later at home. 
 
 7. If cions are at hand in time to graft, make several kinds of whip 
 grafts. If materials for practical grafting are not at hand, make grafts 
 of any twigs for practice. 
 
 8. Plant seeds of different trees in the experiment plots, for use of 
 the next class in budding and grafting. 
 
 9. Bud a convenient plum or peach tree. Each class should plant 
 seeds to produce young trees for this purpose for the next class. If your 
 budding operation is successful, take the plant home and set it out. 
 
 10. If a large peach or plum tree is available, set in it buds from 
 other trees bearing different kinds of the same fruit. One may have 
 specimens of all the kinds in the neighborhood by this method. 
 
 11. Make grafting wax and carry some home for use in your own 
 grounds. 
 
 References 
 
 Bailey, "Manual of Gardening." 
 Goff, " Principles of Plant Culture." 
 
 Farmers' Bulletins 
 
 157. The Propagation of Plants. 
 
 408. School Exercises in Plant Production.
 
 CHAPTER XIV 
 
 DECORATIVE PLANTING 
 
 Purpose. The purpose of decorative planting is to add to 
 the comfort and attractiveness of our surroundings by plant- 
 ing those plants that are conspicuous either for the beauty of 
 their flowers, the color and cutting of their foliage, or the 
 symmetry of their form, thus making homes of houses and 
 parks of wildernesses. Not all planting of this kind, how- 
 ever, can be called decorative. To be entitled to the name it 
 must proceed along definite lines, with a preconceived design 
 in mind ; for unless a definite plan is adhered to, the result is 
 likely to be lacking in harmony and coherence. In planting the 
 home grounds the aim should be to set off the house to the 
 best advantage, emphasizing the good points and concealing 
 the poor ones ; in short, to make a picture, with the house as 
 the central figure and the borders as the frame. 
 
 Lawn making. Few things add more to the beauty of the 
 home grounds than a broad expanse of well-kept lawn, but 
 this can be produced only by proper care in the making. If 
 the old lawn is unsatisfactory, it is best to spade or plow it up 
 in late fall or early spring and start a new one. The first 
 step in lawn making is to see that the land is properly drained. 
 If it is not, this should be taken care of by one or more lines 
 of tile drain. After digging, the soil should be very thor- 
 oughly worked over until it is well pulverized and carefully 
 leveled. If the soil is lacking in fertility, a quantity of well- 
 rotted manure should be worked into it, or other fertilizers 
 applied. Small lawns should be perfectly level unless the 
 residence is on sloping ground. In the latter case it is much 
 
 197
 
 IDS 
 
 AGRONOMY 
 
 better to have the lawn slope gently away from the house 
 than to cut it up by banks and terraces, since every divi- 
 sion, whether by path or terrace, tends to make it look 
 smaller than it really is. If terraces cannot be avoided, 
 
 they are best placed 
 near the house, where 
 they may become, in a 
 measure, a part of the 
 building, or else as 
 far away as possible 
 at the street line or 
 on the borders of the 
 property. On no ac- 
 count should the center 
 of the small lawn be 
 lower than the borders, 
 since a concave surface 
 tends to make distances 
 appear shorter and the 
 lawn, in consequence, 
 smaller. A slightly con- 
 vex surface, on the 
 other hand, gives a 
 more spacious look to 
 the property, and in 
 large lawns the center 
 is often raised slightly 
 to prevent it from look- 
 ing hollow at this point. 
 Since the grasses are 
 
 cool-weather plants and flag during the summer, it is best to 
 seed the lawn in late fall or early spring, so that the plants 
 may become established before the hot weather sets in. If 
 seeded later, care should be taken that the young plants do 
 
 FIG. 144. Hickory Creek at Joliet, Illinois 
 
 An illustration of the way Nature arranges her 
 trees and shrubs
 
 DECOKATIVE PLANTING 
 
 199 
 
 not suffer from drought. Bare spots in an old lawn can be 
 loosened with a rake and reseeded at any time. Occasionally 
 when a lawn is wanted quickly, or the soil on a sloping bank 
 is to be retained, the whole area may be sodded. For this 
 work sods from an old pasture are best, since they consist of 
 only the most resistant grasses and are fairly free from weeds. 
 Ground to be sodded should be prepared as carefully as for 
 seeding. After the sods are laid they should be thoroughly 
 
 FIG. 145. Forest and stream illustrating Nature's method of planting 
 
 watered and then beaten into place with the back of a spade 
 or rolled with a heavy roller. It is difficult to make grass 
 grow in deep shade, under evergreen trees and the like, and 
 some other ground cover is often used. Among the best 
 plants for this purpose are the periwinkle or myrtle, lily of 
 the valley, and moneywort. 
 
 Paths and lawn planting. In small lawns the paths should 
 be straight and direct, but in larger areas they may curve, 
 especially if the surface of the land is uneven. Every path or 
 drive crossing the lawn makes it look smaller and adds to the 
 care that must be bestowed upon it ; no unnecessary walk,
 
 200 
 
 AGKONOMY 
 
 therefore, should be permitted. Paths and drives are often 
 sunk a few inches below the surface of the lawn, which thus 
 conceals or renders them less conspicuous and contributes to 
 the appearance of spaciousness so desirable to maintain. For 
 the same reason the center of the lawn should be kept open 
 and free from flower beds, shrubs, and trees. In large grounds, 
 and in strictly formal planting, such things may be allowed, 
 but they are out of place on the home grounds. The kettles, 
 
 Photograph by Wagner 1'ark Conservatories, Sidney, Ohio 
 
 FIG. 146. A corner planted in the natural style 
 
 vases, sections of sewer pipe, paint buckets, and tubs filled 
 with flowers that are often seen on lawns are in bad taste and 
 should not be tolerated. Such objects, when used at all, should 
 be restricted to formal planting. Occasionally it is desired to 
 separate the lawn from adjoining fields without seeming to 
 do so. This can be accomplished by digging a ditch deep 
 enough to conceal a fence placed in the bottom. The side of 
 the ditch nearer the house may be slightly raised, thus hiding 
 the ditch and making the lawn appear to merge into the 
 fields beyond.
 
 DECORATIVE PLANTING 201 
 
 Care of the lawn. The care of a well-established lawn con- 
 sists in cutting, fertilizing, watering, and rolling it. It should 
 be cut frequently, and if this is done, the clippings may be 
 left to form a mulch for the grass roots and to prevent the 
 seeds of weeds from becoming established. Cutting the lawn 
 is most easily done in the morning, since at this time the cells 
 of the grass are distended with water and therefore more 
 brittle. The lawn should be watered only when in need of it, 
 and then it should be thoroughly soaked. An occasional heavy 
 watering is much to be preferred to the daily sprinkling that is 
 often given it. The latter causes the surface to bake, and 
 makes the grass more shallow-rooted and more easily burned 
 up in summer. Commercial fertilizers are best for the lawn ; 
 the winter dressing of stable manure so often applied is not 
 only unsightly and unsanitary, but it may introduce many 
 noxious weeds from seeds mixed with the manure. Late in 
 the season the grass may be allowed to grow longer and form 
 a cover for the roots during winter. In early spring the lawn 
 should be carefully raked and then rolled with a heavy roller, 
 to settle back into place any grass roots that may have been 
 lifted by the frost. 
 
 The border. The shrubs and flowering plants that so often 
 find a place on the lawn are better located on its borders. Here 
 they add a distinct note to the ornamentation of the grounds. 
 Shrubs and flower beds scattered over the lawn give it a spotty 
 appearance, out of all harmony with the rest of the picture. 
 Nor should flowering plants designed for cutting be allowed 
 anywhere on the lawn or in the borders. They are best re- 
 stricted to some part of the garden where the loss of their 
 blossoms will not be so much noticed. The flowering plants 
 in the borders should be allowed to finish their season of 
 bloom undisturbed. In planting the border it should be 
 remembered that Nature always works in curves, and if an 
 appearance of naturalness is to be produced, straight lines
 
 202 
 
 AGRONOMY 
 
 should be avoided. The line where lawn and border meet 
 should be a series of graceful curves, and the shrubs and 
 herbaceous plants should be arranged in irregular groups. 
 In this, one can have no better guide than Nature herself, 
 and a visit to the bushy margins of an old field or the edge 
 of a woodland will be of great assistance to the observant 
 student. In making the outline of the border a stout rope 
 or the garden hose may be used to get the desired curved 
 effect, and the line can then be marked out along this. 
 
 Arrangement of the plants. Trees, shrubs, vines, and her- 
 baceous plants may all find appropriate locations in the border. 
 
 FIG. 147. The wrong way to 
 plant shrubs on a lawn 
 
 Such an arrangement makes a 
 spotty appearance 
 
 FIG. 148. The correct way to 
 plant a lawn 
 
 Shrubs arranged on the borders; 
 center of the lawn kept open 
 
 The trees and shrubs are used to form the framework of the 
 plan, and the less rugged and assertive plants are grouped 
 about them. In arranging them care must be taken that the 
 taller specimens do not shut out the view from the windows 
 and veranda of the house. In large grounds, especially, vistas 
 to distant points in many directions should be maintained. 
 Grounds that have been planted for some time often have 
 these views obscured by an undue growth of shrubbery un- 
 less it is properly trimmed. On the other hand, undesirable 
 views or unsightly objects can be entirely concealed from
 
 DECOBATIVE PLANTING 
 
 203 
 
 view by screens of shrubbery planted for the purpose. A pro- 
 fusion of low-growing shrubs should be used to conceal the 
 foundations of the house, and vines may be trained over walls 
 
 and pillars, thus carrying the 
 green of the lawn upward 
 and making the house appear 
 more a part of the landscape. 
 Shrubs should rarely be planted 
 singly. Their beauty is greatly 
 enhanced if several are set to 
 form an irregular group, but 
 care must be taken to allow 
 for future growth, else they 
 will soon begin to crowd one 
 
 FIG. 149. Shrubs in the curves of anot her and fail of their best 
 
 development. Not only should 
 
 the line where lawn and border meet be irregular, but the sky 
 line should partake of the same character. This is brought 
 about by alternating groups of tall and shorter shrubs and 
 trees. It is desirable, also, to bring 
 some of the shrubs out toward 
 the margin of the lawn, forming 
 recesses or bays between them in 
 which herbaceous plants may be 
 grown. Shrubs may be planted on 
 the concave side of all curves in 
 paths and drives, thus seeming to 
 give a reason for the curve as well 
 as adding to the spacious appear- 
 ance of the grounds by preventing 
 
 all parts being seen at once. At the angles where paths 
 intersect, and where " short cuts " are likely to be made, it 
 is well to plant thorny shrubs like the barberry, locust, and 
 prickly ash. Such plantings are also frequently made in the 
 
 FIG. 150. A corner planting
 
 204 
 
 AGRONOMY 
 
 front of shrubbery where it borders the street, to prevent the 
 encroachment of the public. 
 
 Shrubs for winter effects. The best-planted grounds are not 
 designed solely for their beauty in summer. A proper selection 
 of shrubbery will not only look well in summer but will add 
 numerous pleasing tints to the winter landscape and brighten 
 the borders with the colors of a milder season. In this class 
 are the bright scarlets and purples of the dogwoods and some 
 willows and wild roses, the yellow and gray of willow and 
 beech, the green of euonymus and cat brier, and the white 
 
 of the birch and button- 
 wood. At the leafless 
 season, also, the form 
 of the plant is thrown 
 into strong relief, and 
 various species may be 
 planted for the pictur- 
 esque note they add to 
 the winter landscape. 
 Among common species 
 desirable for this pur- 
 pose are the hawthorns, 
 the river birch, black 
 
 FIG. 151. Method of planting a corner lot, 
 to prevent paths being made across it 
 
 gum, and Lombardy poplar. Numerous shrubs produce at- 
 tractive fruits that persist far into the winter, supplying food 
 for the winter birds and adding a touch of color to the thick- 
 ets. The winterberry, greenbrier, bittersweet, burning bush, 
 and the roses are good for this purpose. 
 
 Naming the shrubs and trees. Shrubs and trees are among 
 the most permanent of living things and often outlast the 
 works of man himself. It is desirable, therefore, that the 
 student become acquainted with those commonly planted, 
 either by identifying them by the use of a botanical manual, 
 which is much the better way, or by visiting named collections
 
 DECORATIVE PLANTING 
 
 205 
 
 in parks, botanical gardens, and private grounds. The more 
 permanent of the herbaceous perennials may also be identified. 
 Complete lists of these, with notes on the qualities that make 
 them desirable for planting, may be obtained from the nearest 
 nursery company. A large number of the more desirable are 
 natives of our own fields and woods, and the person inter- 
 ested in decorating his grounds will find many of them ready 
 to his hand in the nearest woodland or thicket. Few exotic 
 
 species surpass our 
 native elders, sumacs, 
 dogwoods, viburnums, 
 wild crabs, currants, 
 and gooseberries for 
 decorative planting. 
 Trees and shrubs with 
 variegated foliage are 
 usually less hardy than 
 those with green leaves 
 and are seldom satis- 
 factory in the home 
 grounds. 
 
 Herbaceous plants. 
 Herbaceous plants may 
 be considered in two 
 groups, the annuals and the perennials. The annuals are fre- 
 quently desirable for quickly covering bare spaces and for 
 giving an abundance of bloom, but they require to be planted 
 anew each year, and for most purposes perennials are more 
 desirable. Some of the most showy flowers, however, are an- 
 nuals. We could ill spare such species as morning-glory, 
 four-o'clock, nicotiana, nasturtium, sweet pea, petunia, aster, 
 cosmos, salvia, and verbena, but the best place for most of them 
 is in the flower garden where their beauty may be admired and 
 the flowers removed without injuring the appearance of the 
 
 FIG. 152. 
 
 An artificial pond planted with 
 lotus and water lilies
 
 206 
 
 AGRONOMY 
 
 surroundings. Many of the perennial species are desirable for 
 the flowers they produce, but when these are needed for cut- 
 ting, they too should be planted in the flower garden and not 
 the border. Among the better-known perennials are the 
 
 in 
 
 lilies, columbines, irises, phloxes, peonies, sunflowers, bell- 
 worts, bleeding hearts, and pinks. Left to themselves, the 
 herbaceous perennials soon form large clumps, which may 
 often be divided and used to make further plantings. 
 
 Photograph by O. L. Jordan 
 
 FIG. 153. An old planting in which the border has all the appearance of a 
 
 natural growth 
 
 Arrangement of herbaceous perennials. In planting the her- 
 baceous perennials the general rules for planting shrubbery 
 may be followed, especially those regarding mass planting and 
 the avoidance of straight lines. Since they are always planted 
 for the decorative effect of their flowers, they should be placed 
 in front of the shrubbery, which thus forms a natural back- 
 ground and renders the flowers more conspicuous. Tall plants 
 should be placed in the rear and successively smaller ones
 
 DECORATIVE PLANTING 207 
 
 should carry the belt of verdure down to meet the lawn. A 
 general group of perennials may consist of several sorts inter- 
 mixed, and if care is taken to choose species that bloom at 
 different seasons, a succession of flowers may be had from the 
 same spot during the summer. In mixed plantings, where two 
 kinds of flowers are to bloom at once, or where adjacent plant- 
 ings come into bloom at the same time, one must avoid the 
 planting together of inharmonious colors, such as magenta and 
 scarlet, or purple and blue. White flowers may be used to 
 separate warring colors and also to serve as a foil for all 
 others. Both purple and blue flowers add a sense of distance 
 to the view, and, if planted in bays in the shrubbery, appear 
 to increase the size of the garden. Yellow and red flowers 
 have the opposite effect. By planting them on jutting points 
 they add to the apparent depth of the bays. 
 
 Hedges. In some cases it is desirable to divide two plots of 
 ground, or to set off the home grounds from the street, by means 
 of a hedge. For repelling intruders or keeping stock within 
 bounds, the hedge is made of some thorny material, such as 
 Osage orange, honey locust, barberry, or buckthorn. About 
 dwellings it is more usual to plant privet, lilac, box, or some 
 of the evergreens like arbor vitse and hemlock. Hedge plants 
 are set thickly in straight lines and are trimmed into shape 
 annually during the summer season. The words " hedge " and 
 " edge " are obviously of similar derivation, and edgings are 
 naturally lines of small plants like small hedges set along the 
 borders of other plantings. Pansies, alyssum, lobelias, and 
 many other low-growing species are used for this purpose. 
 
 Bulbs. All plants propagated by thickened underground 
 parts are called bulbs by the florist and general gardener, 
 and, for the purposes of planting, no other distinction need be 
 made. The chief value that attaches to bulbs is found in the 
 fact that the flowers are usually showy, and, being formed in 
 the preceding summer, are practically certain to appear when
 
 208 AGRONOMY 
 
 the bulbs are properly planted, pushing upward almost as soon 
 as the snow is gone and blooming at a time when flowers of 
 any kind are rare. In addition to the spring flowering bulbs 
 there are a few that bloom in summer. Summer flowering 
 species are nearly always tender and have to be dug up and 
 kept from the cold during the winter. The gladiolus and 
 tuberose belong to this class. The spring flowering bulbs are 
 not only hardy but they have to be planted in autumn in time 
 to make root growth if they are to bloom the following spring. 
 During summer they may be dug up and stored in a cool dry 
 place, or they may be allowed to remain in the soil and annuals 
 planted over them. Many low-growing species may be natural- 
 ized on the lawn and will bloom before the grass is high enough 
 to require cutting. If not cut too closely in mowing, they will 
 continue to bloom from year to year. Taller species, such as 
 the daffodil and narcissus, are occasionally naturalized along 
 the margin of streams and the edges of woodlands, where they 
 thrive as well as our native species. In planting the spring 
 flowering bulbs, a well-drained spot, protected on the north and 
 west, should be selected. They may be planted in masses in- 
 formal groups, and as soon as the ground is frozen should be 
 covered with several inches of coarse straw, leaves, or other 
 litter. In spring the mulch should not be removed until the 
 growing plants require it ; otherwise they may be injured by 
 the cold. In the public parks and other large grounds bulbs 
 are frequently arranged in geometrical and other designs. 
 
 Carpet bedding. This is the term applied to a form of plant- 
 ing in which plants with bright-colored foliage are arranged 
 in formal designs and kept trimmed to an even surface, giving 
 an effect not unlike a carpet or rug. Ribbon bedding is much 
 like this, since it consists in setting plants in long, straight 
 rows. This kind of planting may be used along walks and in 
 other situations where straight lines prevail, but is not adapted 
 to plantings in the natural style.
 
 DECORATIVE PLANTING 
 
 209 
 
 Formal planting. The rules for planting given in this book 
 are for that style of gardening known as the English or natural 
 style. It is patterned closely after nature and is the one most 
 in use in the United States and Great Britain. A more formal 
 method, known as the Italian or geometrical style, once in great 
 vogue and still extensively used in parks and large estates, 
 consists in making all planting on geometrical lines. Here 
 clipped shrubs, plants in vases, sundials, pergolas, angular 
 beds, balustrades, terraces, arbors, fountains, statuary, weeping 
 trees, carpet bedding, and straight lines find an appropriate 
 
 Photograph from Wagner Park Conservatories, Sidney, Ohio 
 
 FIG. 154. A formal garden 
 Note how this planting harmonizes with the style of architecture 
 
 use, and when thus assembled have an attractiveness that is 
 beyond question. Such planting, however, is out of place in 
 the small lawn unless the entire area is treated in the 
 same style. 
 
 Transplanting shrubs and trees. As a rule, shrubs and 
 trees cannot be transplanted with safety when in full leaf. 
 They are usually moved in autumn after the leaves have fallen 
 or in spring before the buds have pushed forth, but if care is 
 taken to keep the plants from drying out, they may be moved 
 in spring until the leaves are nearly full grown. Nurserymen 
 commonly prolong the planting season by digging up their 
 stock in autumn and keeping it in cold storage until wanted.
 
 210 
 
 Specimens may thus be had in a dormant condition long after 
 the same kinds of plants in the field have produced their 
 leaves. In transplanting trees and shrubs die rules that govern 
 the transplanting of garden plants in general may be observed. 
 If many of the large roots have been severed in digging, the 
 top of the specimen must be cut back to balance the loss and 
 
 Photograph \>y Wagner Park Conservatories, Sidney, Ohio 
 
 Fi. 155. The natural style of planting applied to the home grounds 
 
 prevent too great transpiration. In doing this it is better to 
 remove weak branches and superfluous twigs rather than to 
 cut off the top or main branches and thus destroy the natural 
 shape of the specimen. In the case of shrubs, when it may 
 be desirable to retain as many branches as possible, the leaves 
 only may be removed. The removal of the leaves is also prac- 
 ticed in moving shrubs in early autumn before the leaves 
 have fallen. The roots should never be allowed to become
 
 DECORATIVE PLANTING 211 
 
 dry while transplanting, and, before the specimen is set, all 
 broken and bruised roots should be cut back to the sound 
 wood with a sharp clean cut. Specimens should be set slightly 
 deeper than they stood originally, and it is well to have the 
 same side toward the north. The hole in which the plant is 
 to be set should always be large enough to allow the roots to 
 spread out naturally. This hole is sometimes made by explod- 
 ing a small charge of dynamite, which loosens the subsoil and 
 makes it easy for the new roots to penetrate it. The best soil 
 should be used for filling about the roots and should be well 
 firmed about them. If the plant is set in poor soil, enough 
 good soil should be procured elsewhere to fill up the hole. 
 When the hole is half filled, the plant may be gently worked 
 up and down to settle the earth about the roots, or water 
 may be thrown into the hole for the same purpose. No air 
 spaces about the roots should be permitted. 
 
 Transplanting herbaceous perennials. As with the woody 
 plants, the best time to transplant herbaceous perennials is in 
 fall or spring, but owing to the fact that these plants are 
 smaller and more easily handled, they may be moved at any 
 time if a few simple rules are observed. In the case of wild 
 plants, many of which are among our most ornamental spe- 
 cies, the rule most frequently followed is, " Transplant when 
 you find them." By using care in the digging, keeping the 
 specimen moist, and protecting from the sun until established 
 in the new locality, one can move almost any specimen without 
 loss even when in bloom. 
 
 Mulching and heeling in. Newly set herbaceous plants are 
 benefited by a light mulch over their roots, which keeps the 
 moisture from evaporating and the soil from baking. Plants 
 set in autumn should be more heavily mulched as soon as the 
 ground is frozen, and this should not be removed until the 
 frost is out of the ground in spring. Such a mulch prevents 
 the heaving due to the alternate thawing and freezing of the
 
 212 AGRONOMY 
 
 ground, and is especially desirable in the case of plants in 
 exposed places. More plants are killed annually by having 
 their roots broken when heaved by the frost than by the cold 
 of winter itself. It often happens that more plants are dug 
 than can properly be planted at one time, and in such cases 
 the surplus is heeled in until they can be planted. In heeling 
 in, a trench is dug deep enough to receive the roots, and the 
 plants are placed within this in such a way that the tops rest 
 on the earth. Soil is then thrown on the roots in widening 
 the trench, and then another layer of plants with tops over- 
 lapping the first is put in, and so on. Plants are frequently 
 heeled in over winter. In such cases the roots should be 
 heavily mulched as soon as the ground is frozen, but if the 
 tops are mulched, it may form a retreat for mice that may 
 damage the bark or buds. Plants should always be heeled in 
 in a light, well-drained spot. 
 
 Treatment of woodlands. The ever-increasing demand for 
 wood in various industries has greatly diminished the immense 
 forests that once covered our country, and the remnant is fast 
 disappearing. All this greatly enhances the value of the tim- 
 ber still standing. In some regions trees are already treated 
 as farm crops, and everywhere there is being manifested a 
 desire to manage the woodlands so that the greatest amount 
 of timber may be obtained from the area they cover. Formerly 
 it was the custom to cut down the entire stand of trees in 
 lumbering and to clear the ground, but at present in all 
 forests where conservative methods are practiced, only the 
 marketable timber is removed and the remainder is left to 
 produce a new crop. The forests may thus be made to yield 
 perennial supplies. Properly cared for, most forests will con- 
 tinue to reproduce themselves. When this does not occur nat- 
 urally, it is usual to plant young trees of the desired variety. 
 In all broken country there are many areas too steep or too 
 infertile to produce ordinary crops, but on which excellent
 
 DECORATIVE PLANTING 213 
 
 timber can be grown. Many of these are being reforested by 
 planting with young trees. It is probable that in time all 
 such regions will be again covered with forest. At present a 
 wood lot managed as a growing crop of fence posts, railway 
 ties, and telegraph poles may be made to yield quite as much 
 as the same area planted to annual crops, and with no greater 
 amount of labor or capital spent upon it. The steadily advanc- 
 ing prices of all kinds of timber make it clear that in future 
 a much greater revenue may be derived from such wood lots 
 than from the ordinary crops. 
 
 Enemies of the forest. The three greatest dangers that 
 threaten the forest, aside from wasteful cutting, are fires, in- 
 sects, and plant diseases. To reduce these to a minimum, it 
 is desirable that all dead and dying trees and underbrush that 
 might furnish food for the fire or a lurking place for insects 
 and fungi be removed. Vigorous trees are least susceptible 
 to insect and fungous attacks, and only the best trees should 
 be left to grow. The misshapen specimens and others that 
 crowd the good trees for light and room should be removed. 
 In the forest, trees whose timber is of no value are as much 
 weeds as are mustard and pigweed in a field of grain. In 
 extensive forests, where injury from fires is most likely to 
 occur, the ground is divided into sections by fire lanes 
 broad, cleared strips wide enough to confine the forest fire, 
 once started, to a single section. The custom of allowing 
 cattle to graze in the forest is extremely harmful, since the 
 young trees are destroyed and the perpetuation of the forest 
 prevented. 
 
 Quite aside from their value as a source of timber and fuel, 
 forests are of great benefit in preventing floods by delaying 
 the run-off from rain and melting snow. In forested areas 
 much of this moisture sinks into the soil, to reappear later in 
 springs which keep the small streams from drying up in 
 summer,
 
 214 AGRONOMY 
 
 PRACTICAL EXERCISES 
 
 1. Make a planting plan for a city lot of average size on a scale <>f 
 or ^ in. to the foot, indicating on it the house, walks, and drives, and 
 the location and nature of the planting. 
 
 2. From a catalogue of decorative plants, to be had of any nursery- 
 man for the asking, select and list the species suggested for planting 
 your plan. 
 
 3. With such suggestions as seem desirable for improving the plant- 
 ing, make a similar plan of your home grounds or of the school grounds. 
 
 4. Visit parks, cemeteries, and private grounds for studies in good 
 and bad planting effects. 
 
 5. If there are Italian, or formal, and Japanese gardens within 
 reach, visit them and compare with the natural style of planting. 
 
 6. Make a planting plan, drawn to scale, of some small park in 
 the vicinity, or make a planting plan for turning some near-by vacant 
 space into a park. 
 
 7. Select desirable plants and plant a section of the school-garden 
 border. 
 
 8. On Arbor Day plant one or more trees or shrubs on the school 
 grounds, in the school garden, or in your home grounds. 
 
 9. At the beginning of winter mulch all plants in the school garden 
 that are likely to be harmed by the cold. Do the same for your own 
 grounds. 
 
 10. Make one or more trips to a public park or large private estate, 
 and list all the shrubs found in bloom. Make a s'imilar list of all the 
 perennials. 
 
 11. By the use of a good botanical manual name all the shrubs and 
 perennials as they bloom in the school garden and near-by fields during 
 the time devoted to this course. 
 
 12. Remove to the school-garden borders for observation all abnor- 
 mal plants encountered, such as four-leaved clovers, albinos, fasciated 
 stems, and the like. 
 
 References 
 
 Bailey, " Manual of Gardening." 
 Maynard, "Landscape Gardening." 
 Parsons, "Landscape Gardening Studies." 
 Waugh, "The Landscape Beautiful." 
 Waugh, " Landscape Gardening."
 
 CHAPTER XV 
 
 PRUNING 
 
 Purpose of pruning. The object of pruning is to repair inju- 
 ries, promote the proper growth of the specimens, and secure 
 more shapely, healthy, and fruitful plants. Many species grow 
 so luxuriantly that 
 they require an an- 
 nual trimming to 
 keep them within 
 bounds. Others, 
 again, may produce 
 a crown of foliage 
 so dense that suffi- 
 cient light and air 
 do not penetrate 
 it; in consequence 
 of this few flower 
 buds are formed, 
 and what fruit is 
 produced is pale in 
 color and poorly 
 flavored. Such a 
 specimen is ben- 
 efited by pruning. 
 Although woody 
 species are the ones usually pruned, a few herbaceous plants 
 commonly receive the same treatment, especially tomatoes, 
 tobacco, okra, and various garden flowers. Many woody 
 plants are self-pruning and annually cut off many of their 
 
 215 
 
 Photograph by II. L. Hollister Land Co. 
 
 FIG. 156. Apple blossoms 
 Showing the good results of proper pruning
 
 216 
 
 AGRONOMY 
 
 young twigs. The habit of cutting off the useless flowers after 
 blooming may also be regarded as a form of self-pruning, as is 
 the casting of the leaves in autumn. It is commonly supposed 
 that only flowers that fail to be pollinated are cut off by the 
 plant, but many young fruits are also severed from the branches, 
 otherwise the plant could not make sufficient food for all, and 
 even if it could, the load would be more 
 than it could bear. The advantages to 
 be derived from thinning the fruit on 
 trees heavily loaded is obvious. 
 
 Time to prune. An old rule for 
 pruning is, " Prune when the knife is 
 sharp," indicating that when a plant 
 needs pruning one time is as good as 
 another, but such a rule has many ex- 
 ceptions. The time for pruning any 
 plant depends somewhat upon the time 
 at which it produces its flowers. Plants 
 that form their flower buds in autumn 
 should not be pruned in winter, as this 
 would remove the embryo flowers and 
 fruits. Such plants should be pruned 
 in spring and summer, shortly after 
 they have fruited and before new flower 
 buds have been formed. On the other 
 hand, many plants produce their flowers 
 on the new wood, that is, on twigs produced from winter buds. 
 These may be pruned in winter, since new and vigorous wood 
 will usually be more floriferous than older twigs. In general, 
 winter pruning increases the amount of wood formed and sum- 
 mer pruning induces flowering. Summer pruning has the ad- 
 vantage over winter pruning in that one may then see how 
 the crown of foliage ,is displayed and may more readily 
 remove branches that shade others. Moreover, the cambium, 
 
 FIG. 157. A common form 
 of pruning shears
 
 PRUNING 
 
 217 
 
 active at this season, soon covers the wound with a protective 
 layer of bark. One should be careful not to overprune ; a little 
 pruning yearly is much better than more at longer intervals. 
 
 Pruning implements. A good sharp knife is a most efficient 
 pruning instrument, and the intelligent horticulturist seldom 
 needs anything else. Prun- 
 ing shears with stout blades 
 may take the place of the 
 knife, but when shrubbery 
 has been allowed to go for 
 some time, large branches 
 may require the use of 
 a saw. There are various 
 kinds of pruning shears 
 and saws on the market, 
 some forms of the latter 
 having teeth on both sides 
 of the blade. 
 
 Methods of pruning. 
 There are several rules 
 that may be observed in 
 pruning any shrub or tree. 
 It is always proper to re- 
 move branches that shade 
 others as well as those that 
 grow toward the interior 
 of the crown. These latter 
 are soon ciit off from the 
 light by the growth of the 
 outside branches, and, if not removed, would soon die anyway. 
 Branches that have grown too rapidly for the symmetry of 
 the plant may be cut back, but in all cases where part of a 
 twig is removed care must be taken to cut above a bud facing 
 outward, else the new growth is likely to grow toward the 
 
 FIG. 158. An apple tree 
 
 An example of improper pruning. The tree 
 
 has been allowed to grow so high that it is 
 
 difficult to gather the fruit
 
 218 AGRONOMY 
 
 center. In selecting the branches to remain, every endeavor 
 should be made to have no gaps in the crown of foliage. There 
 should be enough branches to fill it out on all sides. In shap- 
 ing young fruit trees and the like, the branches should not be 
 allowed to spring from a common point, and all forks should 
 be avoided. Looking down upon the specimen and imagining 
 a circle with the trunk of the plant in the center, endeavor to 
 train it in such a way that from three to five main brand ics 
 radiate out at equal distances and form the framework of a 
 well-balanced crown. In setting young fruit trees they are 
 sometimes pruned to mere whips and a new head developed 
 from the fresh twigs that will spring forth. Orchard trees are 
 usually headed low to facilitate gathering the fruit. 
 
 Making the cut. In removing branches all cuts should be 
 made close to the stem, and no stubs left to harbor insects and 
 the germs of disease. In removing very large limbs there is 
 always danger that they may fall by their own weight and 
 thus tear down the bark and wood of the main stem before the 
 cut is complete. This may be avoided by first making a cut 
 part way through the branch on the underside and a foot or 
 more from the trunk.* A cut from above meeting this or a 
 little beyond it will sever the limb, after which the stub may be 
 sawed off close to the trunk. If the branch removed is more 
 than an inch in diameter, the wound should be immediately 
 covered with a coat of paint or grafting wax to keep out injury 
 from the weather, bacteria, and insects. Scars left by the 
 removal of smaller branches may be disregarded, as the tree 
 will soon cover them with bark. 
 
 Specimens needing little pruning. The evergreen trees should 
 never be pruned. When properly grown the branches radiate 
 on all sides from the ground up, and the trees lose much of 
 their beauty when trimmed like other trees. An evergreen 
 tree, once deprived of its lower branches, rarely renews them. 
 Shade trees seldom require pruning except to remove dead
 
 PEUNING 
 
 219 
 
 branches and to repair damage by storm. Many shrubs also, 
 among which are lilacs, deutzias, spiraeas, and forsythias, do 
 well without much pruning. The plants most frequently 
 pruned are those grown for their fruit, and the object in 
 pruning is to force them to bear more and better crops by the 
 production of new wood upon which the fruits are borne. In 
 
 Photograph by II. L. Bollister Land Co. 
 
 FIG. 159. Cherry trees in bloom in an irrigated orchard 
 
 temperate regions flowers seldom appear on wood that is more 
 than two years old. In the tropics flowers often appear on the 
 large branches or even the trunks of trees. In the hands of the 
 skilled gardener all the flowering shrubs may be induced to 
 bear the maximum number of flowers by judicious pruning. 
 
 Pruning special crops. Some plants produce but one crop 
 of flowers and fruits on a Branch, no matter how long it may 
 remain on the plant after fruiting, and such branches are as
 
 220 
 
 AGRONOMY 
 
 well removed as not. Other species form certain short branches, 
 called fruit spurs, that bear many successive crops. It is neces- 
 sary, therefore, to know how each specimen fruits before it can 
 be pruned intelligently. The raspberry 
 and blackberry always fruit on canes 
 grown the previous year and do not 
 bear fruit on these canes a second time. 
 As soon, therefore, as the fruiting season 
 is over, the old canes should be removed 
 to make room for the new ones. When 
 the latter have reached a height of two 
 or three feet, the tips are also removed, 
 which causes side branches to form and 
 increases the wood upon which the fruit 
 is borne. In grapes the fruit is borne 
 upon the new wood, that is, upon wood 
 produced the same year as the fruit. In 
 training these plants it is customary to 
 allow one or more main stems to grow, 
 and these are trained upon posts, wires, 
 or trellises. From each joint of these 
 stems a branch arises which bears fruit. 
 After the crop is gathered these young 
 branches are cut back nearly to the 
 main stem, only mere stubs with two 
 or three buds being left. The following 
 season, when these buds begin to grow, 
 the best are selected to form the fruiting 
 branches for that year. Grapes should 
 be pruned when perfectly dormant. If 
 pruned later than February, they are likely to bleed and to be 
 harmed thereby. Apples, pears, and cherries form short fruit 
 spurs on the old wood. These bear fruit year after year, and 
 care should be taken not to injure them when pruning or 
 
 FIG. 160. Fruit spurs on 
 
 the second-year wood of 
 
 cherry which may bear 
 
 several crops
 
 PEUNING 
 
 221 
 
 when gathering the fruit. Short- 
 ening the new growth of these 
 trees induces the formation of 
 more fruit spurs. The peach fruits 
 on wood one year old ; that is, 
 branches produced one summer 
 should fruit the next. Since check- 
 ing the growth favors fruiting, cut- 
 ting back part of the new growth 
 late in summer influences the 
 formation of flower buds. The 
 peach is a luxuriant and rapid 
 grower, and, if allowed to go 
 unpruned, is likely to produce 
 more wood than fruit. Currants 
 produce fruit on both the old 
 and new wood, but wood more 
 than three years old is considered 
 unprofitable and may be removed. 
 The new growth tends to produce 
 more fruit buds if it is pinched 
 back to leave from two to six 
 buds on each twig. 
 
 Thinning. Thinning, or the re- 
 moval of some of the fruit when 
 the tree is overloaded, is a form 
 of pruning. Several advantages 
 are gained by thinning. If all the 
 fruit is left on the tree, the load 
 may be so great as to break the 
 branches, while the effort to pro- 
 duce so great a crop results in a 
 quantity of undersized, flavorless 
 specimens. It is much better to 
 
 FIG. 161. Two-year-old twig of 
 the peach showing three pedi- 
 cels, or stalks, that produced 
 fruit and will not bear again
 
 Photograph by H. L. Hollister Land Co. 
 
 FIG. 162. Peaches growing on wood of the preceding year 
 
 Photograph by H. L. Hollister Land Co. 
 
 FIG. 103. An overloaded branch of a plum tree 
 
 The fruit should be thinned by removing all small or imperfect specimens 
 
 222
 
 PRUNING 
 
 223 
 
 remove some of the fruit than to endeavor to save it all by 
 propping up the limbs. Overbearing may also weaken the 
 plant so much as to prevent all fruit bearing the following 
 season. In thinning, the effort should be made to have the 
 
 Photograph by II. L. Hollister Laud Co. 
 
 FIG. 164. Eome Beauty apples 
 Note that the fruit is produced from short spurs on the old wood 
 
 fruit uniformly scattered over the tree. The inferior and 
 poorly placed specimens are of course the ones to be removed. 
 Wormy and defective fruits may often be brought down by 
 gently shaking the tree occasionally.
 
 224 
 
 AGRONOMY 
 
 Heading in. Many species, especially when young, make 
 such luxuriant growth that some of it needs to be removed in 
 order that the rest may ripen into strong wood. Removal of 
 
 Photograph by H. L. Hollister Land Co. 
 
 FIG. 165. A heavily loaded branch of currants 
 
 the excess growth is called heading in. The peach, pear, crab, 
 and poplar are among those most frequently headed in, but 
 any rank-growing species may need it. When nearly all the
 
 PKUNIKG 
 
 225 
 
 crown is removed, by cutting off the main branches, this is 
 called pollarding. Poplars and willows are often pollarded, but 
 other trees may be ruined by this process. Heading in may 
 
 Photograph by H. L. Hollister Land Co. 
 
 FIG. 166. Young plum tree, heavily loaded with fruit, grown under irrigation 
 
 be rendered unnecessary by removing the tips of the tender 
 growth with the thumb and finger when it has reached the 
 desired length. This latter operation is called pinching or
 
 226 AGRONOMY 
 
 stopping. In annual plants pinching induces both branching 
 and flowering. Melon and cucumber vines are often stopped to 
 make them fruit earlier, and raspberries and blackberries are 
 regularly pinched to cause branching. Since the majority of 
 buds form twigs, the removal of the buds may take the place 
 of pruning. This is called disbudding. In annual plants dis- 
 budding is often used to throw the strength of the plant into 
 a few superior flowers or fruits. The florist regularly increases 
 the size of chrysanthemum flowers by removing all but the 
 terminal buds. Other forms of pinching that are self-explana- 
 tory are topping, detasseling, and suckering. 
 
 Root pruning. In rich soils trees sometimes fail to fruit be- 
 cause of too exuberant growth. In such cases fruiting may 
 be induced by anything that will check the vegetative func- 
 tions. This is often exemplified in trees that have been injured 
 by lightning, defoliated by insects, subjected to an extended 
 drought, or planted in sterile soil. Under any of these condi- 
 tions they are likely to begin fruiting. A geranium plant 
 blooms most freely when it has become pot-bound, that is, 
 when the soil in the pot is crowded with roots, and removing 
 part of the root system of a plant has the same effect. All 
 fruiting may be regarded as a life-saving process, in that it 
 provides the plant with a means for continuing the species, 
 and any injury is likely, therefore, to call it into action. One 
 of the most frequent methods in use is root pruning, in which 
 a trench is dug around the tree and some of the feeding roots 
 cut off, or a sharp spade may be driven into the soil at the 
 proper distance for this purpose. The roots usually extend as 
 far out as the branches ; therefore the distance from the tree 
 at which the roots should be severed depends upon its size. 
 Care should be taken not to remove too many roots at one 
 time, else the plant may be injured. The purpose is merely to 
 check the growth. In some cases it is best to remove part of 
 the roots one year and more the next.
 
 PRUNING 
 
 227 
 
 Girdling. Removing a zone of bark from a tree will kill it 
 because the plant food which passes down through the bark to 
 the roots can no longer reach them and they die of starvation. 
 Girdling a fruiting branch, however, may increase the size of 
 the fruit it bears by retaining in it all the plant food made by 
 the leaves. At the end of the season the branch, of course, 
 dies, since the removal of the bark kills the cambium and pre- 
 vents the formation of new ducts. In plants like the grape, 
 
 Photograph by II. L. Hollister Land Co. 
 
 FIG. 167. Young apple orchard in the Northwest 
 
 The darker specimens are peach trees which will yield several crops of fruit 
 hefore they have to he removed to make room for the apple trees 
 
 where the fruiting branch is removed at the end of the season 
 anyway, this method is occasionally employed. When a valu- 
 able tree is girdled, it may sometimes be saved by at once re- 
 ducing the top to lessen evaporation, and protecting the wound 
 until new bark can form over it. Bridge grafting may also be 
 resorted to in helping the tree to cover the wound. 
 
 Cavities and broken limbs. When decay has been allowed 
 to go unchecked until a cavity has been formed in the trunk
 
 228 AGRONOMY 
 
 of a tree, the life of the specimen may be prolonged by filling 
 the cavity with cement. Before putting in the cement all the 
 dead wood should be removed and the cavity sterilized with 
 any good disinfectant such as corrosive sublimate or copper 
 sulphate. It is also well to give the cavity a good coat of paint 
 or tar. If it is very large, concrete may be used as a filling 
 and cement used to finish off the work. The edges of the 
 cavity should be straightened up and painted, and under 
 normal conditions, if the cement has been made just even with 
 the wood, the bark should soon grow over the wound. When 
 a limb has been partly split off from a tree, or when the trunk 
 has been split by a storm, it may often be saved by bolting it 
 together by an iron bolt extending through both parts. Bind- 
 ing the two together with wire serves only to increase the in- 
 jury, since this soon stops the movement of sap and causes 
 death to the parts. 
 
 Topiary work. That form of ornamental gardening in which 
 trees and shrubs are sheared into grotesque forms, often sim- 
 ulating animals and the like, is called topiary work. For this 
 purpose evergreen species are usually employed. Hedges, ar- 
 bors, and arches are forms of topiary work. Other examples 
 may often be seen in old cemeteries and on large private 
 grounds. In the formal style of gardening the less grotesque 
 forms are allowable, but all are out of place on home grounds. 
 
 PRACTICAL EXERCISES 
 
 1. Visit parks, private grounds, and the trees along the streets for 
 examples of pruning. Do you find any trees that need pruning? any 
 that have been badly pruned ? Make suggestions for improvement. 
 
 2. If there are no trees in the school garden to be pruned, visit a 
 bushy field or neglected roadside and practice upon the shrubs and trees 
 found there. 
 
 3. Examine fruiting apple, peach, and plum trees, raspberry and cur- 
 rant bushes, and grapevines to discover where the fruit is borne. Later in 
 the season identify the flower buds on species that form them in autumn.
 
 PRUNING 229 
 
 4. If there are any trees in the neighborhood that have been pol- 
 larded, visit them for study. 
 
 5. Try the effect of girdling the branch of some tree that can be 
 spared. 
 
 6. Pinch back melons, cucumbers, cosmos, and various erect-growing 
 plants and compare the subsequent growth with that of others of the 
 same kind that have not been so treated. 
 
 7. Visit cemeteries, parks, and large private grounds for examples 
 of topiary work. 
 
 8. Remove all but the principal flower bud from a plant and com- 
 pare the size of the single flower thus produced with that of the flowers 
 on a similar plant that has not been disbudded. 
 
 9. If there are hedges on the school grounds, prune them ; if not, 
 select a desirable spot and plant one. 
 
 10. Select two tomato plants as nearly alike as possible. Remove 
 all suckers from one as soon as they appear and allow the other to grow 
 naturally. How does the fruit of the two plants compare in size ? in 
 number? in total weight? 
 
 11. Repair any cavities in the trees on the school grounds by the 
 method described in this book. 
 
 References 
 
 Bailey, "The Pruning Book." 
 Bailey, ft Manual of Gardening." 
 Fernow, "The Care of Trees." 
 
 Farmers' Bulletin 
 
 181. Pruning.
 
 CHAPTER XVI 
 
 PLANT DISEASES 
 
 Origin. Plants, like animals, are afflicted with diseases which 
 are caused for the most part by low forms of plant life belong- 
 ing to the great group known as the Thallophytes. Most of 
 these are bacteria or fungi plants without chlorophyll and 
 therefore reduced to the necessity of getting their food ready- 
 made from other organisms. In nourishing themselves they 
 tear down the tissues of the specimen upon which they have 
 fastened, and in due time, if unchecked, may cause its death. 
 Not all, however, thrive upon living things. There are vast 
 numbers that find sustenance in the bodies of dead animals 
 and plants and even in their cast-off parts. Of the latter 
 type are the bacteria of the soil that turn dead vegetation into 
 nitrates and the organisms of decay that resolve dead bodies 
 back into the elements from which they came, thus relieving 
 the soil of forms that would otherwise encumber it. We can 
 easily imagine the confusion that would exist if all the leaves 
 that have fallen in the forest had remained as they were when 
 they fell. The majority of the fungi and bacteria must be 
 classed as helpful species ; it is only when they attack the 
 things we value that they become enemies. As regards the* 
 manner in which they feed, plant pests may be divided into 
 parasites and saprophytes. Parasites feed upon living things, 
 and saprophytes upon dead ones. The organism preyed upon 
 is called the host. In general, parasites are much smaller than 
 saprophytes. The parasites are again divided into the external 
 parasites, which live upon the exterior of the plant and send 
 special organs into its tissues for food; and the internal 
 
 230
 
 PLANT DISEASES 
 
 231 
 
 parasites, which, safe within the tissues of their hosts, bid 
 defiance to most attempts to dislodge or kill them. All the 
 fungi spread by means of spores, minute one-celled bodies that 
 function like the seeds of flowering plants. They are often 
 
 FIG. 168. Live oak in Audubon Park, New Orleans, covered with Spanish 
 
 moss (Tillandsia) 
 This is often regarded as a parasite, but it is an independent plant 
 
 given off in inconceivable numbers. The common field mush- 
 room produces two thousand million spores. Others are capa- 
 ble of shedding a million spores a minute and keeping this up 
 for several days. The largest puffballs may produce twenty 
 million million spores. The spores are extremely small and
 
 232 
 
 AGRONOMY 
 
 light and may float in the air for long distances before coming 
 to rest, thus spreading the species very widely. Like other 
 plants, they need warmth and moisture to grow, and increase 
 most rapidly in warm, cloudy weather. The harmful bacteria 
 in the soil may be carried from one field to another in the dirt 
 
 FIG. 169. Bacterial wilt of melons 
 From Duggar's "Fungous Diseases of Plants" 
 
 that adheres to the feet of animals, on the implements used in 
 stirring the soil, and even by currents of water during rains. 
 
 Number of plant diseases. An immense number of organ- 
 isms produce disease in plants, and if these could all live on 
 the first species encountered, it is likely that few plants of 
 any kind would come to maturity. Fortunately most plant 
 diseases are restricted to a single species or a related group
 
 PLANT DISEASES 
 
 233 
 
 of species ; hence plants of one kind may be grown without 
 danger close beside other kinds that are diseased. These 
 organisms that cause disease are usually given the name of the 
 effect they produce. Among the more familiar are the rots, 
 smuts, rusts, mildews, blights, 
 and wilts. Often the causal 
 organisms are not closely re- 
 lated, but if they produce simi- 
 lar effects, they are likely to be 
 named accordingly, just as a 
 rise in temperature in man is 
 called a fever, no matter what 
 its cause. Some of the more 
 common plant diseases are men- 
 tioned here ; others may be 
 found described in the reports 
 of agricultural experiment sta- 
 tions and in manuals devoted 
 to the subject. 
 
 Rots. Many kinds of fruits 
 and vegetables are attacked by 
 rots which cause their tissues to 
 break down into a watery mass 
 and thus spoil the specimen. 
 Good examples are found in the 
 rot of apples and other fruits, 
 carrots, cabbage, and the like. The wet rot of potatoes is 
 another familiar form. Rots are caused both by bacteria 
 and other fungi. 
 
 Wilts. The wilts are readily recognized from the fact that 
 the leaves of the plant attacked begin at once to droop and 
 soon after the death of the individual ensues. In many cases 
 the wilting is caused by the fungus growing in the ducts of 
 the plant and thus shutting off its supply of moisture. 
 
 FIG. 170. Mildew of cherry 
 
 From Duggar's " Fungous Diseases 
 of Plants "
 
 234 
 
 AGRONOMY 
 
 Blights. Blights affect the leaves of plants, often caus- 
 ing them to slirivel as if touched by fire and soon resulting 
 
 in their death. The 
 potato blight may 
 spread through an 
 entire crop and effect 
 its ruin in two or 
 three days. 
 
 Leaf spot. The 
 leaves of plants are 
 frequently attacked 
 
 FIG. 171. Mildew of peaches 
 From Duggar's " Fungous Diseases of Plants " 
 
 by fungi that cause 
 discolored spots in 
 the tissues. Sometimes these are sufficiently numerous to 
 cause the death of the plant or render it unfit for food. 
 
 FIG. 172. Leaf spot on pear 
 From Duggar's " Fungous Diseases of Plants " 
 
 The brown spots that appear on bean pods and other fruits 
 are closely allied to the leaf-spot diseases.
 
 PLANT DISEASES 
 
 235 
 
 Molds and mildews. The molds and mildews may be either 
 parasites or saprophytes. As parasites they cover the leaves 
 of many species with a cottony or powdery growth which is 
 
 FIG. 173. Downy mildew on the grape 
 From Duggar's "Fungous Diseases of Plants" 
 
 the plant body, or they push into the interior of the plant, 
 whence later their spores are released. The plants are often 
 called downy mildews, to distinguish them from other species. 
 One form of mildew is nearly always present on the lilac, and
 
 '236 
 
 AGKONOMY 
 
 others are common on the grape, woodbine, and willow ; in 
 fact, there are few species of cultivated plants that do not 
 
 FIG. 174. The hollyhock rust 
 
 The small dots are the fruiting bodies containing multitudes of spores 
 From Duggar's "Fungous Diseases of Plants" 
 
 harbor some form of mildew. The damping-off fungus which 
 attacks young seedlings at the point where the stem leaves 
 the soil may be included in this group.
 
 PLANT DISEASES 
 
 237 
 
 Smuts. The smuts cause the black powdery masses that are 
 often to be seen upon corn, oats, and other grains. They are 
 particularly fond of mem- 
 bers of the grass family. 
 Their spores germinate in 
 spring soon after the seeds 
 of the plants which they 
 infect begin to grow. Get- 
 ting into the plant through 
 the stomata or through a 
 break in the tissues, they 
 grow with the growing 
 plant until seeds begin to 
 be formed. At this point 
 they fill up the young seed 
 with their own tissues and 
 soon produce a mass of 
 exceedingly minute black 
 spores that float away to 
 infect other plants, or that 
 cling to the seeds of the 
 plants upon which they 
 grow, and are transported 
 with them. The seeds of 
 oats are often treated with 
 formalin or hot water to 
 destroy the spores before 
 they are planted. 
 
 Rusts. The rusts cause 
 rusty brownish or blackish 
 patches on the leaves and 
 stems of many plants. Fields of wheat or corn, late in the 
 season, will furnish good examples, and others may be found 
 in asparagus beds. Often the wheat rust is so abundant as to 
 
 FIG. 175. Anthracnose of beans 
 
 From Duggar's " Fungous Diseases of 
 Plants"
 
 238 AGRONOMY 
 
 ruin the crop. There are numerous species of rust, each re- 
 stricted for the most part to a limited number of hosts. One 
 of the most remarkable features of their life history is the 
 fact that two different species of plants are usually required 
 to complete their round of existence. The wheat rust is found 
 in spring upon the barberry and not until later does it infect 
 the wheat plant. The corn rust grows first upon a species of 
 oxalis ; the apple rust upon coniferous trees. Late in the 
 season the rusts produce spores which last through the whiter 
 
 FIG. 176. Apples affected by apple scab 
 From Duggar's " Fungous Diseases of Plants " 
 
 and set up the infection upon the first host plant again. It 
 occasionally happens that the first of the two plants necessary 
 for a complete life cycle of a rust is absent from the locality. 
 In this event most species are able to omit this part of the 
 cycle and begin at once upon the second host. Many rusts 
 produce no less than four different kinds of spores. 
 
 Wound parasites. Many enemies of the woody plants are 
 fungi that gain entrance through wounds, as where a branch 
 has been torn off by the wind, or through a break in the bark 
 caused by insects or mammals. These parasites live upon the 
 old parts of the tree until well established, but ultimately 
 extend to the living parts and cause their death. Often their
 
 PLANT DISEASES 239 
 
 presence is not suspected until the spore-bearing parts appear, 
 and then it is too late to eradicate them. The oyster mush- 
 room and some of the shelf fungi are among the better known 
 of the wound parasites. The entrance of such parasites may 
 be prevented by promptly covering all wounds with paint 
 or grafting wax. 
 
 Other plant diseases. The list of plant diseases is a very 
 long one. It includes the black knot on plum, fire blight of 
 
 FIG. 177. Potatoes affected, by potato scab 
 From Duggar's "Fungous Diseases of Plants" 
 
 the apple and pear, peach yellows, plum pockets, potato scab, 
 cedar apples, witches'-brooms, peach-leaf curl, clubroot of 
 cabbage, anthracnoses, and a host of others. It is usually not 
 necessary to positively identify the organism causing the dis- 
 ease in order to remedy it, since what will control one disease 
 will be likely to control all the others like it. The main thing 
 is to discover the trouble before it has had time to spread, and 
 to take prompt measures for its suppression. In a majority 
 of cases the most efficient treatment is to spray with some
 
 240 AGRONOMY 
 
 good fungicide, meanwhile removing all affected plants if the 
 disease has progressed very far. 
 
 Sprays and spraying. The spray to be used for fungi de- 
 pends partly upon the time of the year in which it is applied, 
 and partly upon the kind of fungus to be exterminated. When 
 the plants are leafless and dormant, the lime and sulphur wash 
 is the one to be applied, while the Bordeaux mixture and the 
 ammoniacal copper carbonate solution may be used as the buds 
 begin to open and at intervals throughout the summer. As 
 yet there is no known remedy against some plant diseases. 
 Fire blight of the apple and pear, in which the branches die 
 from the tip inward as if touched by fire, is one of these. The 
 only way to save specimens attacked by it is to cut out the 
 blight a foot or more below the part affected as soon as it 
 appears. As a general thing, internal parasites are not injured 
 by sprays, though they may be kept from spreading by such 
 means. External parasites are usually killed outright. When 
 in doubt as to the proper spray to use, it is a good rule to 
 choose Bordeaux. Powdered sulphur sprinkled upon the leaves 
 is also of use, especially in combating mildew. 
 
 Bordeaux mixture. The spray mixture adapted to the great- 
 est variety of us"es is undoubtedly Bordeaux mixture, made 
 from lime and copper sulphate or "bluestone." A standard 
 mixture consists of 5 pounds of copper sulphate, 5 pounds 
 of lime, and 50 gallons of water. To make it, the lime and 
 copper sulphate are dissolved in a little water in separate 
 receptacles, and then further diluted with about half of the 
 50 gallons before mixing. If mixed without diluting, it makes 
 a thick curdled mass that does not readily mix with the water. 
 When properly mixed the liquid should be of a brilliant, sky- 
 blue color. Three or four pounds of soap are sometimes added. 
 The lime in this mixture is chiefly used to neutralize the 
 copper sulphate, and it should always be in excess of the 
 quantity needed for this. The solution may be tested by
 
 PLANT DISEASES 
 
 241 
 
 dipping into it any bright piece of steel. If it has a coating of 
 copper upon it when withdrawn, more lime should be added. 
 Another test is to put a few drops of potassium ferrocyanide 
 into a little of the solution. If it turns brick red, more lime 
 is needed. If the potassium ferrocyanide remains yellow, suffi- 
 cient lime is present. An excess of lime does no harm. The 
 mixture here described is often known as the 5-5-50 solution, 
 the numbers referring to the quantity of each ingredient 
 employed. Other 
 proportions may 
 be taken : the 
 4-4-50 and the 
 3-3-50 are pop- 
 ular. The mix- 
 ture should be 
 strained before 
 using. This spray 
 does not poison 
 insects, and if a 
 poison is desired 
 with it, arsenate 
 of lead in the pro- 
 portion of two 
 or three pounds 
 to fifty gallons may be added. Copper sulphate is often used 
 alone with water in the proportion of one pound to twenty 
 gallons. This can be used only before the buds open, never 
 on the leaves. 
 
 Lime-sulphur wash. For spraying all woody plants in 
 the dormant condition, the lime-sulphur wash is preferred. 
 It consists of fifteen pounds each of lime and sulphur and 
 fifty gallons of water. To make it, bring the water to the 
 boiling point and add the lime. Make a paste with the sul- 
 phur and a small quantity of hot water, add to the boiling 
 
 Photograph by Bateman Manufacturing Co. 
 
 FIG. 178. Spraying a young fruit tree by means of a 
 bucket pump sprayer
 
 242 
 
 AGRONOMY 
 
 mixture, and continue boiling for about half an hour. Five 
 or ten pounds of salt is often added while boiling. This 
 mixture does not keep and should be used as soon as made. 
 The wash may also be made by taking double the quantity 
 of lime, slaking it with boiling water, and adding the sulphur 
 while still hot; or the heat developed by the lime in .slaking 
 may be sufficient. This latter is called the unboiled wash. 
 
 FIG. 179. Potato field attacked by late blight, showing the difference 
 between sprayed and unsprayed rows 
 
 From Duggar's " Fungous Diseases of Plants " 
 
 Ammoniacal copper carbonate. This spray is made by add- 
 ing five ounces of copper carbonate and three pints of am- 
 monia to about fifty gallons of water. A paste is first made 
 with the copper carbonate and a little water, the ammonia is 
 added, and then the rest of the water. The mixture should 
 stand until it settles, and only the clear liquid on top should 
 be used. This spray is effective against rusts, leaf spots, and 
 blights.
 
 PLANT DISEASES 243 
 
 Potassium sulphide solution. The potassium sulphide solu- 
 tion is made by mixing one ounce of liver of sulphur with 
 three gallons of water. It is used as soon as made, and is an 
 excellent remedy for mildews. 
 
 Preventive measures. Since few plant diseases can be com- 
 pletely cured and many are only held in check with difficulty, 
 it is wise to take every precaution against the entry of dis- 
 ease. Some plants are more resistant than others of the same 
 species, and these should be grown. In some cases it seems 
 possible to breed up a resistant strain. Disease always attacks 
 the less thrifty individuals first. Plants should be kept in 
 good health by proper cultivation and thus rendered more 
 resistant. Diseased plants, when they occur, should be removed 
 and burned. If allowed to remain, they only spread the trouble 
 to other healthy individuals. Burning the plants kills the 
 spores that might otherwise set up new areas of infection. 
 
 PRACTICAL EXERCISES 
 
 1. List the plant diseases known to be in your locality. Underscore 
 the most destructive. 
 
 2. Tear apart decaying logs and examine the white threadlike 
 growths which form the plant body of the higher fungi. See if you 
 can trace the fruiting parts of puffballs, mushrooms, and shelf fungi 
 to such plant bodies. 
 
 3. Examine the "smoke" from a puffball with microscope. The 
 small objects seen are spores. Draw several. 
 
 4. Make a spore print by placing the cap or top of a mushroom, 
 with gills down, upon a piece of clean paper. Cover with a bell jar or 
 drinking glass for a day. The spores will be discharged in immense 
 quantities. Some species have white spores, and these will show best if 
 colored paper is used. 
 
 5. Make a collection of leaves and stems to show rusts, mildews, 
 leaf spots, and smuts. These should be preserved, with proper labels, for 
 the use of other classes. 
 
 6. Scrape off some spores from specimens affected with rust and 
 examine with the microscope. The summer spores are one celled, but 
 the winter spores are usually two or several celled.
 
 244 AGRONOMY 
 
 7. Remove some of the ascocarps of lilac mildew from a lilac leaf 
 (they appear to the unaided eye like small black specks) and examine 
 with the microscope. Compare with the fruiting parts of any other 
 mildew you can find. Crush the ascocarps to see ascospores and asci. 
 Make a collection of mildewed leaves. The fruiting bodies, or ascocarps, 
 are likely to be mature in late summer. 
 
 8. Make a collection of the fungi that grow on wood. 
 
 9. Visit museums for other kinds of fungi. 
 
 10. Make a collection of the different ingredients used in making 
 insect sprays. 
 
 11. Make up standard solutions of the various sprays and use in the 
 garden. If no plants there need spraying, spray those that are most 
 likely to need it. 
 
 12. Visit a hardware or implement store and study the various forms 
 of sprayers in stock. 
 
 References 
 
 Bailey, "Manual of Gardening." 
 
 Duggar, " Fungous Diseases of Plants." 
 
 Stevens and Hall, " Diseases of Economic Plants." 
 
 Farmers' Bulletins 
 
 75. The Grain Smuts. 
 
 146. Insecticides and Fungicides. 
 
 227. Lime-Sulphur-Salt Wash. 
 
 231. Spraying for Cucumber and Melon Wilt. 
 
 243. Fungicides. 
 
 259. Disease-Resistant Crops. 
 
 Bureau of Plant Industry 
 
 17. Some Diseases of the Cowpea. 
 
 76. Copper as an Insecticide. 
 
 171. Some Fungous Diseases of Economic Importance.
 
 CHAPTER XVII 
 
 INSECT PESTS 
 
 How insects injure plants. After the young plants have 
 broken through the soil with every indication of becoming 
 thrifty and fruitful specimens, or after older and well-estab- 
 lished plants have given indications of an abundant crop, a 
 multitude of fungous and insect pests have still to be reckoned 
 with by the gardener before a return for his labor is assured. 
 Nearly all the insects that prey upon cultivated plants are so 
 voracious and multiply in such numbers that the crop is some- 
 times destroyed in spite of every effort of the gardener to pre- 
 vent it. It is estimated that insects and plant diseases cause 
 more than a billion dollars' damage to crops each year. As 
 regards the way in which they injure crops, insects may be 
 divided into two groups those with mouth parts adapted to 
 chewing, and those with mouth parts adapted to sucking. The 
 chewing insects harm the plants by eating stems and foliage, 
 or by burrowing into fruits, stems, and other plant parts. The 
 sucking insects do not defoliate the plant, but by sucking the 
 juices from the tender tissues they are nearly or quite as harm- 
 ful. Chewing insects may be controlled by poisons, but such 
 substances have no effect upon sucking insects whose food 
 comes entirely from the interior of the leaf. These latter must 
 be fought with smothering sprays and gases. 
 
 Metamorphoses of insects. There are two general lines along 
 which insects develop from the egg to maturity. In grasshop- 
 pers, crickets, katydids, and the like, the newly hatched insect 
 has considerable resemblance to adult forms and gradually 
 acquires the characters of maturity as it grows in size. Such 
 
 245
 
 246 AGRONOMY 
 
 insects are said to have an incomplete metamorphosis. The 
 great majority of insects, however, have a complete metamor- 
 phosis. When hatched they show no sign of the kind of adult 
 insects they are designed to be. They begin life as wormlike 
 creatures called caterpillars or worms, though it should be 
 understood that they are not closely related to the true worms, 
 such as the earthworm. The young worms, or more properly 
 the larvce, feed voraciously until they reach maturity, increas- 
 ing rapidly in size and casting their skins from time to time 
 as these become too small. When full-grown they stop feed- 
 ing and either spin a cocoon about themselves or creep away 
 into some safe shelter under a loose piece of bark, along old 
 fences, or even in the soil, where they remain motionless 
 for several days, weeks, or months, during which time they 
 undergo great changes in form and structure. This stage is 
 called the pupa stage and is the one in which large numbers 
 pass the winter. At length there emerges from the dull and 
 motionless pupa a winged insect, often brightly colored, 
 which flies away to mate and deposit eggs upon the proper 
 food plant and thus start the life cycle anew. 
 
 Forms of insects that cause injury. Crops may be injured 
 by insects in either the larval or adult stage. An insect is 
 seldom equally harmful in both stages. Usually the greatest 
 damage is caused by the voracious larvse, the mature insects 
 often living on the nectar of flowers and frequently being 
 beneficial as agents for the transfer of the pollen. In some 
 cases the larvae are much less destructive than the mature 
 insects, possibly because they feed on plants that are not 
 valued by man, while others, like the potato bug and the 
 asparagus beetle, in both their larval and adult stages are 
 injurious to crops. Some of the more harmful insects are 
 mentioned in this book. Many others, less widely distributed, 
 though often as destructive in restricted localities, may be 
 found in any work on entomology. As with plant diseases,
 
 INSECT PESTS 247 
 
 it is usually not necessary to identify the exact species that 
 causes the damage. It is sufficient to know how they injure 
 the crops and to be able to adopt the methods that will most 
 readily exterminate them. 
 
 Cutworms. Cutworms are dull, earth-colored, or striped 
 worms that seek refuge in the soil during the day, coming out 
 at night to feed. They cause" immense losses to many culti- 
 vated crops, cutting off the young seedlings just as they appear 
 aboveground and often following along a row until all the 
 plants are taken. Some climbing species creep up the stems 
 of plants and cut off their tops or even ascend trees to feed on 
 the buds. In some grounds they occur in great numbers. Two 
 hundred or more have been taken out of a single row sixty 
 feet long. They are very hard to exterminate, owing to their 
 nocturnal habits and manner of hiding, but they may some- 
 tunes be killed by putting poisoned food about their haunts. 
 Clover, pigweed, or other tender vegetation sprayed with 
 poison makes attractive bait. Cabbage, tomato, and other plants 
 grown singly may be protected by a collar of stiff paper about 
 the stems at the surface of the ground. When evidences of 
 the work of cutworms is seen, the worms should be dug out 
 and killed. This is easy, since they do not go very far to hide 
 during the day. One method of keeping them in check is to 
 pick them by hand at night by the light of a lantern. The half- 
 grown cutworms spend the winter in the earth, and cultivating 
 the soil up to the time of frost tends to reduce their num- 
 bers. The mature insect is a dull-colored moth of nocturnal 
 habits and is seldom recognized. 
 
 Cabbage worm. The cabbage worm is a light green, smooth 
 worm that infests cabbage, cauliflower, turnip, and other plants 
 of the cress family. It feeds on the leaves, and when resting 
 extends along the veins, which it so closely resembles as to 
 be frequently overlooked. The worms may be easily poisoned. 
 This does not injure the cabbage for food, since the leaves are
 
 248 AGRONOMY 
 
 wrapped in such a way that the poison cannot penetrate to 
 the edible portion of the head. The small white butterfly, so 
 common in cabbage patches, is the mature form of this species. 
 
 Currant worm. Two broods of the currant worm occur 
 annually : the first appears before the fruit is ripe ; the second 
 about midsummer. The currant worm is a green- and black- 
 spotted larva and so voracious that a small colony will defo- 
 liate a currant or gooseberry bush in a very short time if not 
 checked. It is easily controlled by poisons, white hellebore 
 being one of the best for use in small gardens. 
 
 Tomato worm. The tomato worm is a very large, smooth 
 green worm with a hornlike projection at one end and oblique 
 white markings on its sides. On account of its large size it is 
 easily located by the gardener and falls an easy prey to para- 
 sitic insects. It passes the pupa stage in the earth and is often 
 dug up when the ground is spaded in spring. At this stage it 
 may be identified by a curved projection extending down one 
 side like a handle. At maturity it becomes one of the sphinx 
 or humming-bird moths often seen about long-tubed flowers 
 in the late afternoon. A related species does much damage 
 to crops of tobacco. 
 
 Corn-ear worm. The corn-ear worm is closely allied to the 
 cutworms and army worms, but is found on or within the re- 
 productive parts of the corn plant. It destroys the tassel by 
 eating it off, and later creeps down into the ear between the 
 husks and the cob, eating the kernels as it goes and ruining the 
 ear for food. There is no known preventive for it at present. 
 
 Tent caterpillar. The webworms, or tent caterpillars, are 
 readily recognized by the webs they spin on trees and bushes 
 and within which they feed. These webs may be removed and 
 the insects destroyed by burning them out with a torch made 
 of a piece of cloth wound about the end of a pole and saturated 
 with kerosene. A corncob soaked in oil and fastened to a pole 
 also makes a good torch.
 
 INSECT PESTS 249 
 
 Codlin moth. The larva of the codliu moth is a small white 
 worm that is often discovered feeding in the fruit of the apple. 
 The mature insect lays her eggs in the blossoms and the very 
 young fruit, and after the larva hatches out it enters the fruit, 
 usually at the blossom end. To prevent its depredations the 
 trees must be sprayed as soon as the petals fall and while the 
 calyx is still open. 
 
 Curculio. The curculio is a small white worm that inhabits 
 the fruit of the peach, plum, cherry, and similar species. The 
 eggs are inserted just beneath the skin of the young fruit, and 
 the worm hatches out and feeds upon the pulp. Poisons have 
 no effect upon the worm, but the trees may be sprayed with 
 poisons to protect them from the mature insect. Peaches, how- 
 ever, and stone fruits in general, are very sensitive to sprays, 
 and instead of using such methods the trees may be jarred 
 every morning for some days after flowering and the insects 
 caught, as they fall from the trees, and burned. 
 
 Cankerworms. The cankerworms are also called inchworms, 
 measuring worms, and spanworms. They eat the foliage of 
 many plants, and, when disturbed, drop to the ground on the 
 end of a long thread which they spin. The pupa stage is 
 passed in the soil. The female is wingless and climbs the 
 trees to lay her eggs. Her ascent may be stopped by a band 
 of cloth or cotton around the trunk. Beneath this she will 
 hide and may then be caught and killed. 
 
 Borers. Numerous species of borers infest the trunks of 
 trees and occasionally other parts as well. They make their 
 burrows in the wood and bark, weakening the stem, destroy- 
 ing the cambium, and causing the death of the tree. Their 
 presence is indicated by small mounds of fine wood dust 
 about the base of the trees, or by the gum that oozes out of 
 the wounds in some species. Borers should be cut out as soon 
 as discovered, or killed by pushing a stout wire into their 
 burrows until it crushes them. In some cases a few drops of
 
 250 AGRONOMY 
 
 carbon disulphide injected into their burrows with a small oil 
 can, and the opening afterwards plugged up, is effective. 
 
 Elm-leaf beetle. The elm-leaf beetle is a small beetle that 
 destroys the leaves on elm trees. It is very destructive, but 
 at present is practically confined to the New England States. 
 It may be controlled by sprays. 
 
 Cucumber beetle. The cucumber beetle is a small yellow- 
 and black-striped insect that is very destructive to cucumbers, 
 melons, and allied plants by eating the leaves of the seedlings. 
 The young plants are sometimes protected by frames covered 
 with screen, or they may be sprayed with poisons or dusted 
 with white hellebore. 
 
 Blister beetles. The blister beetles are long-necked, black 
 or gray insects that feed on the foliage and flowers of many 
 species. They very frequently injure the flowers of composite 
 plants, such as asters, by eating the ray flowers. Hand picking 
 and spraying with poisons are the only remedies. 
 
 Potato beetle. The potato beetle is more commonly known 
 as the potato bug. The mature insect is a nearly hemispheri- 
 cal creature with pale yellow and black stripes, 
 and the larvae are repulsive-looking red objects 
 with black markings. This insect is usually 
 most abundant on potato plants, the foliage 
 of which is eaten by both the larvae and the 
 mature insects. Usually the plants are soon 
 
 killed if they are not protected. Hand pick- 
 A potato beetle J 
 
 ing and spraying with Paris green or other 
 
 poisons will keep the pest within bounds. 
 
 May beetles. The larvae of the May beetle or June bug are 
 the whitish grubs common in grasslands and not infrequently 
 found in cultivated fields as well. They feed underground 
 and often do much damage by eating the roots of plants. The 
 mature insect is a brownish beetle familiar to all by its habit 
 of buzzing around the lights in spring.
 
 INSECT PESTS 251 
 
 Plant lice, or aphids. Plant lice are small, usually wing- 
 less insects, black, green, orange, or white in color, that are 
 found on the stems, the underside of the leaves, and even on 
 the roots of plants. They increase in number with incredible 
 rapidity, and when a colony gets crowded, winged individu- 
 als are produced that may spread the species to other plants. 
 They suck the juice from the tender parts and weaken or kill 
 the plants upon which they are allowed to thrive. One species 
 that frequents lettuce, peas, and other cultivated crops is known 
 as the green fly or green bug. Plant lice excrete a sweetish 
 fluid that is greatly relished by ants, and the latter may usu- 
 ally be found in attendance upon them. Ants also contribute 
 to the spread of the aphids by carrying some of them off to 
 new pastures when the colony on a given leaf becomes crowded. 
 The attendant ant of the corn-root louse actually carries the 
 aphids off to a safe place and cares for them 
 until the corn is up and then places them on 
 the roots of the young plants, where they 
 spend the rest of the summer. 
 
 Squash bug. The squash bugs are large 
 angular insects found on the underside of the 
 leaves of squash, pumpkin, and the like. They F 
 
 have an exceedingly disagreeable odor and ^ squash bug 
 are commonly known as " stinkbugs." The 
 egg masses are conspicuous as large, shining brown patches 
 and may be gathered by hand and burned. Kerosene emulsion 
 may be used as a spray for the mature insects. 
 
 Mealybug. House plants and the specimens of the florist 
 often become infested with mealy bugs. These are small 
 fuzzy insects, white in color, that suck the juices from plants 
 and are hard to exterminate because ordinary sprays do not 
 harm them. No absolutely certain remedy seems to be known. 
 
 Scale insects. In appearance scale insects are minute scale- 
 like objects clinging close to the bark of young trees of many
 
 252 
 
 AGRONOMY 
 
 FIG. 182. Scale insects on 
 a maple leaf 
 
 kinds, often covering every available spot. The scale is a 
 waxy substance secreted by the insect, and under this it lives, 
 sucking the juice from the tree and multiplying rapidly. If 
 not eradicated, it will ultimately cause the death of the plant. 
 Strong sprays that can be used when 
 the plant is dormant are most useful in 
 combating this pest. The lime-sulphur 
 spray used against fungous pests is also 
 effective against this one, although it 
 can be used in winter only. 
 
 Preventing attacks of insects. It is 
 more difficult to protect plants from 
 winged insects than from creeping ones, 
 since the former can go from one plant 
 to another through the air. Creeping 
 insects may be trapped or repelled in 
 numerous ways. The foliage of plants 
 likely to be attacked may be sprinkled with ashes or slaked 
 lime. Bands of sticky paper or tar may check the advances 
 of climbing species, and whitewashing the trunks of trees will 
 discourage many others. Small plants may be screened, but, 
 in general, poisons and sprays are most effective. Bands of 
 cotton fastened about the trunks of trees some distance from 
 the ground are favorite hiding places for many insects, which 
 may thus be easily caught and killed. 
 
 Poisons for chewing insects. For all kinds of chewing insects 
 one of the poisons adapted to the purpose should be used. Of 
 these the most useful for general purposes in the small garden 
 is white hellebore, which may be procured at any drug store. 
 This may be sprayed on the infested plants in the proportion 
 of 1 ounce to 3 gallons of water, or it may simply be dusted 
 on the foliage when wet with the dew. White hellebore is 
 not so poisonous as some of the other remedies used, but 
 its convenience serves to recommend it. Paris green, an
 
 INSECT PESTS 
 
 253 
 
 aceto-arsenite of copper, is a dry green powder extensively 
 used upon field crops. It is made up in various strengths 
 with water, 1 pound to 150 gallons being near the average. 
 When used on stone fruits it is made much weaker, while for 
 potatoes it is used stronger. In preparing it the poison is 
 formed into a paste with 3 or 4 pounds of lime and a little 
 water and is then diluted to the proper degree. The foliage 
 
 Photograph by Batemau Manufacturing Co. 
 
 FIG. 183. Spraying trees in winter to destroy scale insects 
 
 of many plants is injured by Paris green, and it is gradually 
 being replaced by arsenate of lead, which does not have this 
 defect. Arsenate of lead is a white pasty mixture that may 
 be purchased of dealers in seeds or drugs. It is used as a 
 spray in the proportion of 2 or 3 pounds to 50 gallons of 
 water. The poison sticks well and does not injure the foliage, 
 two qualities which make it desirable. Poisons should not be 
 left where children and farm animals may find them.
 
 254 AGRONOMY 
 
 Remedies against sucking insects. Poisonous sprays have 
 no effect upon insects which suck the juices out of plants. 
 These insects must be killed by suffocating them in various 
 ways. One of the best and cheapest insecticides for this pur- 
 pose is Persian insect powder, for sale by all druggists. It may 
 be applied by means of a small bellows, and is very efficient in 
 clearing insects out of small crevices where sprays have diffi- 
 culty in penetrating. The standard spray is kerosene emulsion, 
 made by adding 2 gallons of kerosene to 1 gallon of hot 
 soft water in which half a pound of soap has been dissolved. 
 This is then very thoroughly churned in order to make an 
 emulsion that will mix with water. When wanted for use, 
 it is diluted with from 10 to 30 gallons of soft water. The 
 strong solutions are used for scale insects ; the weaker ones 
 for plant lice. Whale-oil soap is often used for house plants 
 and greenhouse specimens. The spray is made by dissolving 
 2 pounds of whale-oil soap in 1 gallon of soft water. A strong 
 soapsuds, made from any kind of soap (naphtha soap pre- 
 ferred), is also useful. Tobacco water is made by pouring hot 
 water over a quantity of tobacco stems and allowing them to 
 steep for several hours. This liquid is then diluted and used 
 as a spray. In plant houses, cold frames, and the like, tobacco 
 smoke is often relied upon for killing aphids. Carbon disulphide, 
 which may be purchased of the druggist, is an ill-smelling 
 liquid that turns to gas as soon as exposed to the air. It is 
 heavier than air and may be used to exterminate ants and 
 other vermin that burrow underground. A little of the liquid 
 is poured into the entrance of the burrow, which is then 
 stopped up. Carbon disulphide is very inflammable and should 
 not be used where there are fires of any kind. In the larger 
 operations of the horticulturist hydrocyanic gas is sometimes 
 used. It is a deadly poison and must be handled with great 
 caution. In fumigating with this, a tentlike covering is placed 
 about the entire plant and filled with the gas.
 
 INSECT PESTS 255 
 
 Spray pumps. Many kinds of spray pumps designed to 
 throw liquid upon the plants in minute droplets are for sale 
 by dealers. Sprayers or atomizers quite effective enough for 
 small gardens may be had for as little as fifty cents. Some 
 pumps may be used with an ordinary bucket, and others are 
 carried like a knapsack. For large fields spray pumps drawn 
 by horses are used. In lieu of a spray pump the liquids may 
 be sprinkled on the plants by hand, using a bunch of twigs 
 or a whisk broom for the purpose. 
 
 Other aids in fighting insects. Although insects often mul- 
 tiply prodigiously and may suddenly become exceedingly 
 numerous in a locality, it is seldom that an unusual increase 
 
 FIG. 184. A good form of hand sprayer 
 
 is long maintained. The number of insects averages about 
 the same from year to year. This is doubtless due to the fact 
 that each species has its own natural enemies, and when it 
 becomes abundant, the species that prey upon it also become 
 more numerous and soon reduce it. One of the most powerful 
 of these enemies is the common toad. This animal lives entirely 
 upon insects and is not very particular as to the kind. In the 
 course of a single summer it destroys many thousands of 
 harmful ones. Small snakes also live upon insects and mice, 
 while the usefulness of birds as insect eaters is well known. 
 A large number of the latter, among which are the wood- 
 peckers, swallows, warblers, vireos, and wrens, are entirely 
 insectivorous, while others that eat some seeds make insects
 
 256 
 
 ACROXOMY 
 
 FIG. 185. Ladybng 
 
 Showing larvae and mature 
 insect 
 
 the bulk of their diet, seeming to prefer them to seeds. Even 
 those listed as true seed eaters do not feed to any great extent 
 upon the seeds of cultivated plants, and 
 usually feed their young upon insects. In- 
 sects also have their contagious diseases, 
 and may be exterminated by spreading 
 the infection among them. Last, but by 
 no means least, are the insects that prey 
 upon others. The dragonfly, often called 
 the mosquito hawk, feeds almost exclu- 
 sively upon mosquitoes ; the tiger beetle 
 attacks and 
 kills many 
 kinds of in- 
 sects ; the ant lion preys upon 
 ants ; ground beetles eat the eggs 
 of other species ; the spider cap- 
 tures flies, grasshoppers, crickets, 
 and the like ; and certain wasps 
 stock the larder for their young 
 with captured flies. The ladybird, 
 or ladybuy, lives almost entirely 
 upon aphids and scale insects, 
 both in the larval and the mature 
 state, and is one of the most effec- 
 tive aids we have in keeping these 
 pests in check. Most remarkable 
 of all, however, are the ichneumon 
 flies which deposit their eggs in 
 the larvae of other insects. Some 
 are equipped with long oviposi- 
 tors, by means of which they are 
 
 FIG. 186. One of the larger ich- 
 neumon flies. (About natural size) 
 
 able to reach the larvse of boring species, deep in the trunks 
 of trees. When the eggs hatch, the young worms live upon
 
 INSECT PESTS 257 
 
 the tissues of their host, instinctively avoiding the vital parts 
 until, having reached maturity, they eat their way out to the 
 air and spin their small cocoons upon the body of their host. 
 Soon the perfect insect emerges and flies away to look for new 
 victims, leaving the parasitized host to die. The tomato worm 
 is very frequently parasitized, and a search in any large tomato 
 patch late in summer will probably reveal many worms cov- 
 ered with the tiny white cocoons of the parasite. 
 
 PRACTICAL EXERCISES 
 
 1. Make a list of the insects injurious to plants in your locality, 
 showing what crops they injure. Underscore the chewing insects in 
 the list. 
 
 2. Place a cross before the names of insects in the preceding list 
 that have been found in the school garden. 
 
 3. Make a list of the five most destructive insects in your locality and 
 indicate whether it is the larvae or perfect insect that does the damage. 
 
 4. Make a collecting trip for insects, securing, if possible, eggs, 
 larvae, pupae, and perfect insects of the same species. This may be pos- 
 sible with the cabbage worm and a few others. Catch young crickets 
 or grasshoppers and compare with mature forms. 
 
 5. Search tomato vines for parasitized tomato worms. Similarly, 
 parasitized worms may be found on grapevines, the box elder, the apple, 
 and many others. 
 
 6. Collect and label samples of all of the poisons used for combat- 
 ing insects. 
 
 7. Examine collections of insects for the dragon flies, ladybugs, 
 ichneumon flies, ant lions, and other insects that prey upon harmful 
 species. 
 
 References 
 
 Bailey, "Manual of Gardening." 
 Fernow, "Care of Trees." 
 
 Farmers' Bulletins 
 
 99. Insects Injurious to Shade Trees. 
 127. Important Insecticides. 
 146. Insecticides and Fungicides. 
 155. How Insects affect the Health in Rural Districts. 
 196. Usefulness of the Common Toad.
 
 CHAPTER XVIII 
 
 PLANT BREEDING 
 
 Need for breeding. It is well known that fruits and flmvns 
 as they grow in the wild rarely attain the perfection of which 
 they are capable under more favorable circumstances. The 
 struggle for sufficient light and food materials, the constant 
 conflict with insects and disease, and the vicissitudes to which 
 the plants are exposed by the climate of the region all operate 
 to reduce that vitality which otherwise might be expended in 
 
 Photograph by U. L. Ilollieter Land Co. 
 
 FIG. 187. Four potatoes to the yard 
 These are the result of irrigation farming 
 
 brighter flowers and larger, better-flavored, and more abundant 
 fruits. All cultivation is in recognition of this fact ; reduced 
 to its simplest terms, it is the selection of the most likely 
 plants, the supplying them with abundant food, and the pro- 
 tecting of them from their enemies. Cultivation always results 
 in better and larger crops, but man has not been content to 
 rest here. Having been taught by this experience that plants 
 can be greatly modified by proper treatment, he is ever on the 
 watch to extend his operations further and produce still better 
 
 268
 
 PLANT BKEEDING 
 
 259 
 
 specimens. This work of improving plants by inducing them 
 to attain the highest development possible is called plant 
 breeding. 
 
 Basis for breeding. The work of plant breeding is made 
 possible by the fact that all plants tend to vary within certain 
 limits. There is probably no species that is absolutely fixed as 
 to type, though some vary more than others. Even in the 
 plants which present the least amount of variation, nobody 
 ever saw two plants or even two leaves that were exactly 
 alike. Usually the plants that vary most 
 come from families that contain great num- 
 bers of species ; in fact, the species them- 
 selves may be looked upon as illustrations 
 of greater variations from the original stock 
 which have been developed through ages of 
 natural selection. Every one is so familiar 
 with the slight variations that occur in all 
 plants that they seldom occasion remark. 
 In any large area devoted to a single species 
 we expect to find the tall and the short, the 
 branched and the unbranched, the smooth 
 and the hairy, the pale and the more deeply 
 colored, the vigorous and the sickly, the 
 drought-resistant and the less hardy. It is 
 only when variation is manifested in the plant parts with which 
 we are especially concerned, such as the size and color of the 
 flowers or the abundance, size, and flavor of the fruits, that 
 we notice it and endeavor to make these favorable variations 
 permanent. That they can be made permanent, or even in- 
 creased in value, is shown by the superior plants everywhere 
 seen in cultivation. Strongly marked variations are usually 
 apparent in the seedlings soon after they have started into 
 growth, but others may not appear until the species has 
 reached maturity. The point of departure for most plant 
 
 FIG. 188. A gera- 
 nium sport, show- 
 ing one truss of 
 flowers growing out 
 of another
 
 260 
 
 AGRONOMY 
 
 breeding is found in the seeds, however. Iy repeated sow- 
 ings of great numbers of seeds one will ultimately secure the 
 material necessary for a start and can then breed from it. 
 
 The common cut-leaved maple 
 was not found until a million 
 maple seeds had been sown. 
 and it is said that a bushel 
 of apple seeds were sown 
 before that desirable form, the 
 wealthy apple, was secured. 
 The weeping mulberry was an 
 accidental seedling that sprung 
 into being fully developed, and 
 the Lombardy poplar is re- 
 garded as a sport from the Eu- 
 ropean black poplar. In the 
 more permanent plants, such 
 as shrubs and trees, variations 
 occur which are often confined 
 to a single branch or a single cluster of flowers. These are 
 called bud variations. Good illustrations may 
 be found in the nectarine, which is regarded 
 as a bud variation of the peach, and in the 
 seedless navel orange, which has been derived 
 in the same way from the seeded orange. It 
 is probable that variations from the normal 
 are much more frequent in nature than we 
 suspect, and the fact that they seldom persist 
 is no proof that they do not occur. In the bine flower with 
 nature of things the plants of a region are P arts t u ed to 
 better adapted to that region than any other 
 set would be, and are thus able to hold the ground and crowd 
 out any different forms that might arise. If, as may occasion- 
 ally happen, the new form is better fitted to the locality than 
 
 FIG. 189. A nasturtium sport, show- 
 ing the parts of the flower turned 
 to leaves 
 
 FIG. 100. Colum-
 
 PLANT BREEDING 261 
 
 the normal plants, it may take possession of the field and ex- 
 clude the others. When a variation in a plant makes it very 
 different from the original, it is commonly known as a sport, 
 or imitation. Thus a red-flowered form may suddenly appear 
 among plants that normally bear white or yellow flowers, 
 double flowers may spring up in the midst of single-flowered 
 specimens, or well-flavored fruits may be discovered among 
 inferior kinds. The Lucretia dewberry was derived from the 
 wild dewberry in this way, and many of our bush fruits have 
 had a similar origin. The Concord grape is another interest- 
 ing example of a sport derived from a familiar wild plant. 
 
 Inducing variation. While one may occasionally find among 
 wild plants a desirable specimen that has arisen from seed or 
 bud variation, and transplant it to better quarters before the 
 common plants of the region have overwhelmed it, the task of 
 watching either wild or cultivated plants until such variations 
 occur is a tedious one. Fortunately for the plant breeder, it 
 has been found possible to hasten matters and to induce vari- 
 ation by manipulating the plants in various ways. Increasing 
 the food supply is one of the most efficient means of produc- 
 ing variation. It seems as if many qualities latent in the plant 
 are only brought out when food is abundant and all the other 
 conditions for growth are favorable. A change in location may 
 also cause plants to vary. When they have grown for any 
 length of time in one region, they become in a measure spe- 
 cially adapted to it and have little further need of change ; 
 removal to a different region calls for new adjustments, and 
 consequently favors variation. Farmers and gardeners often 
 send to other localities for a change of seed, and it is believed 
 that the practice of buying new seeds from the seedsmen each 
 year, instead of saving seeds from the previous crop, may 
 affect the character and variability of the new plants grown. 
 A difference in the amount of light received by the plant is 
 still another cause of variation. Pruning has a similar effect,
 
 262 
 
 AGRONOMY 
 
 partly through admitting more light to the plant, and partly 
 through checking growth processes. Injury to the plant may 
 also result in variation. It is a remarkable fact that when the 
 type has once been induced to " break," or vary, the tendency 
 for the resulting forms to continue to do so is strong. A 
 
 notable instance is 
 found in the plant 
 known as the Boston 
 fern, which is fre- 
 quently grown in the 
 window garden. A 
 few years ago a sport 
 with much-divided 
 leaves was put on 
 the market, but it 
 was soon eclipsed by 
 numerous much finer 
 forms that had been 
 developed from it. 
 When once a desira- 
 ble variation has been 
 secured, its value 
 need not be jeop- 
 ardized by further 
 breeding. It may 
 then be multiplied 
 
 vegetatively ; in fact, many improved plants will not come 
 true from seeds, and their number must be increased in this 
 way. Most of our fruits, flowers, and garden vegetables have 
 arisen through variations from less desirable types. 
 
 Hybrids and hybridizing. Another way in which new plants 
 may be obtained or variations started is by crossing, or hybridiz- 
 ing. In this process pollen from the flowers of one species, or 
 variety, is applied to the stigmas in the flowers of another, 
 
 Photograph by W. A. Terry 
 
 FIG. 191. Two leaf sports from the common 
 Christmas fern (Polystichum)
 
 PLANT BREEDING 263 
 
 the resulting seeds thus having the characteristics of two dif- 
 ferent strains. The plants from such seeds are called crosses, 
 or hybrid*. A few hybrids between different genera are known, 
 but usually only closely related species, or varieties, are likely 
 to cross, and the closer the relationship the more successful 
 the operation is likely to be. The apple will not hybridize 
 with the pine, nor the strawberry with the milkweed. The 
 reason species do not cross more readily is because the tendency 
 in nature is away from such crossing. If it were otherwise, we 
 would have an endless confusion of plant forms in which no 
 type would be recognizable. Among the more interesting forms 
 of commercial value that have been produced by hybridizing 
 are the plumcot, a hybrid between the plum and apricot; the 
 citrange, a hybrid between the trifoliate orange, or citron, and 
 the sweet orange ; and the tangelo, produced by crossing the 
 tangerine orange and the grapefruit (pomelo). Among plants 
 cultivated for their flowers, the canna, gladiolus, and orchid 
 have been extensively hybridized. 
 
 Producing the cross. In crossing plants the essential thing 
 is to protect from all foreign pollen the stigmas of the flowers 
 to be pollinated. This is accomplished by slipping a small 
 paper bag over the flowers just before they open, and tying 
 the open end of the bag about the twig which bears them. If 
 one is to be absolutely sure of his cross, the flowers that are 
 to supply the pollen should be similarly treated. If the flowers 
 contain both carpels and stamens, as is usually the case, there 
 is a chance that the flowers to be crossed may be pollinated 
 by their own stamens unless these are removed. It is custom- 
 ary, therefore, to cut away the corolla with a sharp pair of 
 scissors before the flower expands, and remove the stamens 
 with small forceps or the scissors. In plants like the pump- 
 kin, cucumber, and corn, which bear their stamens and carpels 
 in separate flowers, this treatment is not required, though the 
 flowers should be protected from the wind, insects, and other
 
 264 AGRoxo.MY 
 
 pollinating agencies. In pollinating the flower the ripe anther 
 is crushed to expose the pollen, which is then thickly applied 
 to the waiting stigmas. Fresh pollen is always best, but 
 
 in a few cases, especially in 
 orchids, it may remain alive 
 for months. After pollination 
 the flower is once more cov- 
 ered with the paper . bag 
 until the stigma is no longer 
 receptive and the ovary has 
 begun to increase in size. In 
 FIG. 102. Longitudinal section of all plants that bear both kinds 
 flower and another prepared for c -i a 
 
 f OrallS m the Same fl W6r 
 
 pollination 
 
 two crosses can be made, the 
 
 stamens of one plant supplying pollen for the other, and 
 vice versa. Sometimes a considerable difference exists in the 
 progeny of the two crosses, though usually there is practi- 
 cally none. 
 
 Mendel's law. About half a century ago an Austrian monk 
 named Gregory Mendel, while experimenting with different 
 strains of peas in the monastery garden, discovered the curious 
 law that governs the union of male and female elements by 
 which hybrids are produced. An account of his experiments 
 was published at the time, but the significance of the results 
 did not impress the botanists of his day, and it was not until 
 1900, when the law was again independently discovered, that 
 the importance of Mendel's work was recognized and the origi- 
 nal experimenter given proper credit. Briefly the law is this : 
 when two species, or forms, are crossed, the resulting hybrids 
 tend to resemble one parent to the exclusion of the other. 
 Thus if a red-flowered and a white-flowered form be crossed, 
 the next generation is likely to have all red or all white 
 flowers. If the flowers are red, we say the red color is dominant 
 and the white recessive; or if the flowers are white, the red is
 
 PLANT BREEDING 265 
 
 recessive and the white dominant. That the color said to be 
 recessive is merely latent and not lost is shown when the next 
 generation of plants is produced. Here the recessive color 
 appears again in approximately one quarter of the specimens ; 
 and if these recessive plants are now bred together for gener- 
 ations, they will bring no plants of the other color. Quite a 
 different state of affairs exists in the behavior of the remain- 
 ing three quarters of the specimens. If the recessive color 
 is white, then these 
 latter will be red, but 
 only about one third 
 of them, that is, one 
 quarter of the whole 
 number of plants, 
 will be capable of 
 producing only red 
 flowers in the next 
 generation, and so on 
 indefinitely. The re- 
 maining 50 per cent 
 of the original num- 
 ber will produce as 
 
 before, approximately 
 
 , FIG. 193. Diagram to illustrate Mendel's law 
 one quarter pure red, 
 
 one quarter pure white, and one half mixed, and this con- 
 dition will continue through many successive generations. In 
 explanation of this it is assumed that in the original white- 
 flowered species all the gametes, or sexual cells, of the plant 
 had the tendency to produce other white-flowered forms, and 
 the equivalent cells in the red-flowered plants had a tendency 
 to produce red flowers. When they are bred together, there- 
 fore, the resulting plants are bound to have a mixture of red 
 and white gametes, one of which becomes dominant in this 
 second generation. In the next generation, however, the male
 
 266 AGRONOMY 
 
 and female gametes have another chance to pair, and this 
 naturally results in some plants being produced from the 
 pairing of two white gametes, and others from two rejl ones, 
 while still others continue to be mixed as before. The example 
 cited is probably much simpler than is usually the case in 
 nature when a cross is made, since it is concerned with a 
 single character only. It is likely that a similar relationship 
 exists between each pair of contrasting characters in the plants 
 hybridized, one character being dominant and one recessive in 
 the first generation, but both appearing in the second in the 
 proportions indicated. Smooth leaves may be recessive to 
 downy ones, short stems may be dominant over long ones, 
 large flowers dominant over small ones or the reverse. Thus 
 the skillful cultivator is presented the opportunity of varying 
 his plants in many ways by combining the characters differ- 
 ently. It must not be assumed, however, that all plants be- 
 have in the manner outlined in the foregoing. There are some 
 crosses which are more or less perfect blends of the original 
 forms, and others in which the characters do not appear to 
 separate out according to Mendel's law in the succeeding gen- 
 eration. In others certain characters may blend, though the 
 species as a whole behaves according to the law. What these 
 characters are and how they function in crossing is still a sub- 
 ject for investigation. Crossing two forms in which some of 
 the characters are alike may also result in intensifying these 
 characters. 
 
 Selection. Variations of whatever kind merely offer oppor- 
 tunities for plant breeding; they give different plants, not 
 necessarily better ones. The new forms are possibly as fre- 
 quently below a desired standard as above it. Any permanent 
 improvement must be made by careful and wise selection. 
 The gardener practices a certain form of plant breeding, 
 though possibly unconsciously, when he selects seeds from his 
 best plants for producing the next year's crops. To achieve
 
 PLANT BREEDING 
 
 267 
 
 any noteworthy success, however, the plant breeder must have 
 an ideal type clearly in mind and breed toward it. No progress 
 will be made if the ideals are constantly changing and the 
 plants selected for one feature one year, and another feature 
 the 'next. By keeping the desired form constantly in view, 
 taking advantage of all favorable variation and always select- 
 ing the best, a steady advance may be made for a series of 
 years. Now and then a sport may develop which will suddenly 
 carry the work forward with a bound, but usually the small 
 variations must be depended upon. There is a point, however, 
 
 Photograph from Bergen and Caldwell's "Practical Botany" 
 
 FIG. 194. A prize ear of corn that sold for two hundred fifty dollars 
 
 beyond which each plant refuses to go. It would probably 
 be impossible to produce tomatoes as large as pumpkins, 
 though the size might be greatly increased by selection and, 
 in fact, has been. Nor is it likely that a blue-flowered form 
 could be developed from one with red flowers, though the color 
 in the blue flowers might be varied greatly by such means. 
 The average amount of sugar in sugar beets has been raised 
 from 8 per cent to 18 per cent within a very short time, 
 while single specimens have been found with much higher 
 sugar content. In plant breeding it is usual to pay more 
 attention to the average advance than to single cases, since
 
 268 AGRONOMY 
 
 widely aberrant forms are seldom stable. It is better to breed 
 from a plant, all of whose members show some advance along 
 the lines desired, than to breed from one which shows a 
 greater advance in a single member. In breeding for large 
 flowers, for instance, one should select plants in which all the 
 flowers are a little larger, rather than a small-flowered form 
 which may produce one or two superior blossoms. It is also 
 desirable to breed for one thing at a time, or, if more is 
 attempted, to choose characters which will not conflict in 
 developing. 
 
 Roguing. After a form has been developed to a point 
 where its superiority to the common form is apparent, it can- 
 not be depended upon to continue in this state without assist- 
 ance. Left to itself it will soon " run out," that is, it will return 
 to the general average of the type, and the improvement gained 
 by breeding be lost. When the plants have acquired the de- 
 sired form, further variation is undesirable and effort must 
 now be directed to fixing the type. All plants, therefore, that 
 are not close to the ideal form should be destroyed as soon as 
 detected, to prevent the good and bad plants from mixing by 
 pollination. This is called roguing. If one is endeavoring to 
 breed a certain strain of plants, he will sow as many seeds as 
 possible, preserve only the best for subsequent breeding, and 
 destroy the others. 
 
 Xenia. When a cross between two plants is made, any dif- 
 ferences due to the union will not appear until a new genera- 
 tion has been grown from the seeds resulting from the cross. 
 In certain cases, however, the seeds themselves, or even the 
 fruit, may show the effects of crossing. A good illustration 
 may be had in corn, which readily mixes when two sorts are 
 grown together. This effect is known as xenia. Ordinarily, 
 when a plant is fertilized, a single gamete from the pollen tube 
 unites with another in the ovule to form the cell from which 
 the embryo is produced. In cases of xenia another gamete
 
 PLANT BREEDING 269 
 
 from the pollen tube unites with the nucleus of the cell 
 in which the female, or egg, cell is located, and this, though 
 unable to form an embryo, may nevertheless grow and form 
 part or all of the endosperm, or albumen, which usually sur- 
 rounds the embryo in the seeds. In the corn, xenia affects 
 only the endosperm, though the fact that the second union 
 of cells has been made is proof that the embryo in such 
 seeds has also been produced from the sexual cells of two 
 different strains. 
 
 Parthenogenesis. While it is the rule that neither seeds nor 
 young plants result from flowers unless fertilization takes place, 
 there are not a few species that are able to produce new embryos 
 without this process. The production of young plants in this 
 way, from what are essentially unfertilized eggs, is called par- 
 thenogenesis. This phenomenon is not entirely confined to plant 
 life. The aphids, or plant lice, reproduce by parthenogenesis, 
 and there are sometimes as many as thirteen generations of 
 parthenogenetically produced females before a generation con- 
 taining males is produced. Parthenogenesis differs from ordi- 
 nary vegetative reproduction in plants in that it always results 
 from an egg cell, while in vegetative reproduction any part of 
 the plant may give rise to a new plant. 
 
 PRACTICAL EXERCISES 
 
 1. Find the amount of variation that is exhibited by a hundred 
 specimens of one kind selected at random, counting or measuring the 
 parts as necessary. The following list is suggestive : pods of catalpa 
 (variation in length and diameter) ; peas or beans (number in pod) ; 
 sepals (colored organs) in hepatica (variations in number ; in color) ; 
 petals of bloodroot (number) ; ray flowers of daisy, sunflower, or other 
 composite (number); lobes of the leaves in mulberry (number) ; leaves 
 in poplar or apple (width and breadth) ; leaflets in mountain ash, locust, 
 or rose (number) ; fruits in a cluster of currants or grapes (number). 
 In counting or measuring make a column of figures in numerical order, 
 and opposite each figure make a straight mark each time a count falls 
 upon it. Every fifth mark is; made across the preceding four, so that the
 
 270 AGRONOMY 
 
 marks may be counted by fives. In the illustration which represents 
 the variation in the ray flowers of 55 specimens of sunflower the lowest 
 number of rays found was 12, and five speci- . _ 
 
 mens possessed this number. The highest / \J 
 number was 20 with only one plant show- i i 
 
 ing it. The average was 15, twelve heads ' ' 
 
 possessing this number. The same data I O NJI 
 
 can be expressed by a graph, similar to 
 
 the one on page 52, in which the squares 13 //// / 
 may represent the number of parts in one 
 
 direction and the number of specimens / J- //// /// 
 in the other. Express your work by both N 1 1 1^1 
 
 methods. 15 IHJ IHJ II 
 
 2. Visit any considerable area of one / hji i NJI 
 crop, wild or cultivated, and select the speci- 
 
 mens you would breed from if you desired / 7 fiJJ II 
 to get () larger flowers, (i) more vigorous 
 
 plants, (c) deeper color, (<Z) more abundant / Q IrU 
 fruit, or (e) broader leaves. 
 
 3. Visit any patch of flowers in full / 7 // 
 bloom and search for variations in color, o/") / 
 size, and number of parts in the flower. i/ / 
 
 4. In a row of young seedlings select FlG 195 variation in the 
 those that are (a) most vigorous, (I) weak- ray nowers O f sunflower 
 est, (c) deepest in color, (d) palest, (e) with 
 
 broadest leaves, and (/) with narrowest leaves. Are the differences 
 great enough to be readily noticeable? Would they affect the crop? 
 
 5. Visit and examine any sport that may be growing in the neigh- 
 borhood, especially the cutrleaved maple, Camperdown elm, weeping 
 mulberry, single-leaved mountain ash, single-leaved locust, nectarine, 
 purple-leaved plum, purple-leaved barberry, golden elder, yellow rasp- 
 berry, and the like. Compare with normal plants. 
 
 6. In the school garden or other convenient place cross-pollinate 
 one or more flowers. Make a reciprocal cross in others. If two desirable 
 varieties are crossed, save the seeds for the next class to use. 
 
 7. Plant hemp seed and study the difference between the male 
 (staminate) and the female (pistillate) plants. Examine cucumber or 
 melon plants and distinguish pistillate and staminate blossoms. 
 
 8. If seeds of hybrid plants are to be obtained (perhaps left 
 by a previous class), grow the plants to observe the workings of 
 Mendel's law.
 
 PLANT BREEDING 271 
 
 9. Pick out two antagonistic strains in some garden plant, such as 
 tall and short, broad-leaved and narrow-leaved, large flowers and small, 
 and by selection breed up two different races. Leave the seeds for the 
 next class to use in continuing the experiment. Be sure to make a full 
 record of your work for future reference. 
 
 10. Examine ears of corn that have mixed for illustrations of xenia. 
 Cross-pollinate corn of two different colors and observe the effects. 
 
 References 
 
 Bailey, "Plant Breeding." 
 
 Davenport, "Domesticated Animals and Plants." 
 
 Davenport, "Principles of Breeding." 
 
 De Vries, "Plant Breeding." 
 
 Farmers 1 Bulletin 
 
 334. Plant Breeding on the Farm. 
 
 Bureau of Plant Industry 
 
 165. The Application of the Principles of Heredity to Plant Breeding. 
 167. New Methods of Plant Breeding.
 
 CHAPTER XIX 
 
 THE ORIGIN OF SPECIES 
 
 Evolution. Everything in nature is subject to change. No 
 sooner is a form produced or a structure completed than it 
 begins to be modified by many agencies. Ultimately it grows 
 old, slowly deteriorates, and finally disappears. Such changes 
 have always been in existence. We know from the fossil ani- 
 mals and plants found in the rocks that there has been a steady 
 succession of different forms in the world, beginning with the 
 strange and incongruous forms of past ages and ending with 
 the species of the present day. The fact that such forms are 
 embedded in the solid rock shows that the very rocks them- 
 selves have changed since animals and plants first inhabited 
 the earth, and also indicates how very profoundly our planet 
 has been modified since time began. When we realize that 
 the one unchanging feature of existence is change, it is easy 
 to appreciate the fact that the plants and animals of our day 
 are quite unlike those that first inhabited the earth. All have 
 changed Avith changing conditions ; indeed, within the memory 
 of living men some of our flowers and fruits have been greatly 
 modified in this way. Our present species, then, appear to be 
 the latest forms in a long line of descent the last links in a 
 chain that might be traced back to the dawn of creation. The 
 process by which our modern plants have come to be what 
 they are, the steps by which they have changed, little by little, 
 are included in the term " evolution." It is usual to assume that 
 evolution has always progressed from the simple to the com- 
 plex, and so it has in most cases ; but evolution may proceed 
 in any direction useful to the organism, and the best we can 
 say of it is that it works through change. 
 
 272
 
 THE ORIGIN OF SPECIES 273 
 
 Struggle for existence. Every plant is able to ripen many 
 more seeds than are needed to reproduce the original specimen. 
 In some annuals nearly a million seeds may be produced, and 
 the perennials often do as well and continue to do so for many 
 years in succession. But the earth is already so densely pop- 
 ulated that there is no chance for all the plants from these 
 seeds to come to maturity, even if they escape the multitude 
 of dangers that attend them on every side. Many of the seeds 
 fall in places where germination is impossible, on rocks, in 
 roads and streets, in streams and ponds, and others are eaten 
 by birds, insects, and other animals. Those that germinate are 
 subject to plant diseases and the attacks of insects, late frosts 
 may cut them down, the hot sun may burn them up, and 
 drought may cause their death. Many spring up in the shade 
 of other plants or in uncongenial soil and die for want of food, 
 while the crowd of other plants seeking the same advantages 
 with regard to light and food materials is so great that only 
 the exceptional individual is able to survive. Thus there is a 
 very real and constant struggle going on, a struggle of species 
 with species, of individual with individual, and all with the 
 untoward forces of nature. As applied to plants and animals 
 this is called the struggle for existence, and it results in the 
 survival of the fittest. Here we discover one reason for the 
 numerous seeds produced by plants. The greater the mimber 
 produced, the greater the chance that at least a few will 
 survive to replace the original form. 
 
 Natural selection. The plants that survive all the vicissi- 
 tudes of nature and finally come to maturity are, as we have 
 seen, those that in the long run are best fitted to survive. A 
 slightly larger amount of food in the seed may have given 
 them a start over weaker plants in the vicinity, a more rapidly 
 growing root may have brought them into contact with mois- 
 ture sooner, the ability to get along with less light may have 
 enabled them to survive, or any one of a hundred other things
 
 274 AGRONOMY 
 
 may have given them some advantage over their competitors 
 and helped them to hold their lead in the race. Those less 
 able to carry on the struggle ultimately and inevitably perish. 
 Thus there is in nature a constant and widespread selection 
 of the best, quite akin to that which man exercises, with this 
 difference, that in natural selection the plants are steadily 
 adapted to their habitats and the species and varieties kept up 
 to standard ; while in artificial selection, such as man prac- 
 tices, the aim has been to produce better strains for certain 
 purposes without regard to the ability of the plant to survive 
 in the struggle with other plants, since cultivation relieves the 
 plant of much of this struggle. This explains why our garden 
 plants are so easily overcome by weeds. They have been cul- 
 tivated so long, that they have lost the power to take care of 
 themselves. The weeds, on the other hand, have been de- 
 veloped into most efficient plants both by nature and by the 
 hand of the gardener. Only the most resistant could withstand 
 the two. 
 
 Results of variation. Without variation evolution would 
 be at a standstill and no possibility of improvement would 
 exist. The tendency of plants to constantly vary in different 
 directions has saved whole races from extinction, while the in- 
 ability to change with changing conditions has as certainly 
 caused the death of many others. Plants are never perfectly 
 adapted to their habitats, but variation enables them to fit 
 into the plant covering of the region with the least friction, 
 while nature constantly weeds out the unfit. Usually the 
 changes in plants are cumulative, and, given sufficient time, 
 two plants nearly alike at the beginning may ultimately come 
 to be very different if exposed to different conditions. It is 
 not difficult to see that all the plants which now inhabit the 
 earth may have been derived from a single primitive form 
 through long ages of variation. This explains the existence 
 of many plants of the same general type they have been
 
 THE ORIGIN OF SPECIES 275 
 
 derived from a common ancestor in the not far distant past. 
 In the case of plants that less closely resemble one another, it 
 is conceivable that the common ancestor has existed farther 
 back in the line of descent. 
 
 Darwinian theory. Ever since man began to think about 
 plants he has speculated more or less as to their origin. Al- 
 though the great mass of people have always believed that 
 plants have existed unchanged from the beginning, there have 
 been people in every age to point out evidences of change, 
 and it was early suggested that plants have descended from 
 earlier and different forms through modifications of structure. 
 For many centuries proofs of this idea accumulated, but the 
 whole subject did not receive adequate treatment until Charles 
 Darwin issued his " Origin of Species " in 1859. In this book 
 was gathered a great mass of facts in support of the conten- 
 tion that all plants and animals have arisen by the slow proc- 
 esses of variation and natural selection, and to this theory of 
 organic descent the name of the Darwinian theory has come 
 to be applied. 
 
 Mutation theory. As the study of nature has progressed, 
 many instances of evolution have been encountered that are 
 difficult to reconcile with the Darwinian theory. While the 
 main features of evolution have not been questioned, there 
 has seemed to be need of additional explanations to account 
 for the origin of certain forms which it is difficult to imagine 
 could be produced by gradual changes. These are supplied by 
 the mutation theory of Hugo De Vries. This new theory does 
 not take the place of the Darwinian theory but rather sup- 
 plements it. The new theory holds that new species do not 
 always arise from old ones by a succession of slight modifica- 
 tions, but that they may spring into being fully developed, 
 much as sports and bud variations appear among cultivated 
 plants. This theory is capable of experimental proof, and De 
 Vries has produced a number of distinct forms from a single
 
 276 AGRONOMY 
 
 sowing of seeds of certain species. Following this, it has been 
 shown that many of what the botanist calls species are made 
 up of numerous simpler forms grouped around a certain type. 
 These forms are known as elementary species and agree pretty 
 closely with what the gardener calls forms or varieties. Ele- 
 mentary species may be separated out of the botanical species 
 by breeding. More than two hundred such forms have been 
 produced in Europe from the species called Draba verna. It 
 is supposed that many plants are constantly throwing off such 
 forms, but owing to the crowd of plants better adapted to 
 the locality, these seldom have a chance to mature. New 
 forms are able to persist only when they are better adapted 
 to their habitat than their parents are. It therefore appears 
 that species have arisen by either of two methods by slow 
 modifications or by sudden sports, or mutations. Having arisen, 
 however, they at once fall under the influences that result in 
 further change, and so long as their development is in harmony 
 with their position in life, so long will they exist to carry on 
 the family line. 
 
 PRACTICAL EXERCISES 
 
 1. In spring visit a weed patch, a neglected garden, or other waste 
 ground, and note the number of seedlings springing up. See if you can 
 discover any that are leading in the race for light and air. What do 
 you think gave them this lead V 
 
 2. Measure off a square yard on the lawn or in a pasture and count 
 and name the different kinds of plants found growing in it. 
 
 3. Take any abundant plant and count the seeds produced by a 
 single specimen. If each seed produced a mature plant capable of ripen- 
 ing a similar number of seeds, how many years would it take to produce 
 one plant for each square foot of soil in the world ? Why does not your 
 particular plant become as abundant as this ? Give two reasons. 
 
 References 
 
 Darwin, "The Origin of Species." 
 De Vries, " The Mutation Theory." 
 Vernon, " Variation in Animals and Plants."
 
 CHAPTER XX 
 
 OUR CULTIVATED PLANTS 
 
 Origin. It is a matter of common knowledge that all the 
 plants at present cultivated in the world have been derived 
 from wild ancestors. In some cases the very species from 
 which they originated are still in existence, but more fre- 
 quently the plants have been so long in cultivation, or have 
 been so greatly changed by this process, that the species from 
 which they have been derived are not to be recognized, and 
 even the place of origin of some is unknown. The manner in 
 which the selection of these plants first began is easily imagined. 
 Owing to the tendency of plants to vary, there must always 
 have appeared, here and there in the wild, plants that bore 
 superior fruits and seeds. These even the wild man would 
 prefer and in time would come to protect both from the 
 encroachments of less desirable plants and from other wild 
 men who might wish to appropriate them. When it occurred 
 to some genius of that far-off time that the valued plant could 
 be better protected by removing it to the vicinity of his hut, 
 agriculture may be said to have begun. As more and more 
 plants came to be protected in this way, the best were naturally 
 selected, and so through hundreds or thousands of years our 
 grains have been bred from wild grasses, our potherbs from 
 thick-leaved species with edible qualities, our fruits from the 
 smaller, less juicy, and poorly flavored forms of wood and 
 glen, and our seed crops from those plants which, either by 
 reason of their size, abundance, or the ease with which they 
 are gathered, offered a promising field for the grower. The 
 work has undoubtedly been helped along by sports that have 
 
 277
 
 278 AGRONOMY 
 
 occurred from time to time, both in cultivation and in the 
 wild, and which have brought to the gardener much better 
 varieties than he could produce by years of selection. 
 
 Edible parts of plants. Instances are comparatively few in 
 which the entire plant is used for food. Young beets and tur- 
 nips are often used in this manner as potherbs, but usually 
 only a part of each plant is considered edible. Ripe fruits are 
 the only parts that seem to have been made to be eaten. The 
 juicy pulp that surrounds the seeds of some species is sup- 
 posed to have been developed for the purpose of attracting 
 animals and thus securing the distribution of the seeds ; but 
 when we eat the seeds themselves, as in the case of peas and 
 beans, or the roots, stems, and leaves of other species, we take 
 what the plant has laid by for itself. There is scarcely a plant 
 part, however, that man does not find edible in some species. 
 In practically every instance, no matter what part is used, it 
 will be found to be that in which the plant stores its reserve 
 food. In the carrot, parsnip, salsify, and radish it is the root 
 that is eaten ; indeed, the word " radish " is derived from a 
 Latin word meaning "root." Stems in general are too tough to 
 be palatable, but we must not overlook in this connection the 
 young stems of asparagus, the swollen stems of kohl-rabi, or 
 the underground stems of the potato and Jerusalem artichoke. 
 Lettuce, endive, chard, spinach, and cabbage are good examples 
 of plants that are eaten for their leaves, while several others 
 are valued for their leafstalks or petioles alone, among which 
 may be mentioned rhubarb, celery, and sea kale. The young 
 flower buds form the edible parts of the cauliflower and globe 
 artichoke. Peas and beans are true seeds, but the grain of 
 corn is a fruit, and so are melons, tomatoes, and peppers. The 
 greengrocer usually divides his wares into the two groups, 
 fruits and vegetables, and while there can be no question about 
 the vegetables, since even the fruits are vegetable in origin, 
 many of the .things he calls vegetables are certainly fruits also.
 
 OUR CULTIVATED PLANTS 279 
 
 Root crops. Most of our plants with edible roots are little 
 changed from the originals. This is quite natural, since the 
 only improvement desired has been the increased size of the 
 roots and a greater storage of food. The beet is a native of 
 the Mediterranean region and still grows wild there and as 
 far east as Persia. The carrot, turnip, parsnip, and radish are 
 found in southern and central Europe, and, all but the turnip, 
 having escaped from cultivation in this country, have shown 
 themselves able to maintain an existence in the wild state. 
 Salsify, or vegetable oyster, like the beet, still grows wild in the 
 Mediterranean region. From the garden beet the field -or sugar 
 beet has arisen, and from the turnip comes the rutabaga. The 
 potato, though in no sense a root, is usually classed with the 
 root crops. It is a native of western South America, where 
 its relatives still abound. It was cultivated by the natives of 
 the region before the discovery of America, but does not seem 
 to have been known to the North American Indians. The sweet 
 potato is a true root, the product of a plant belonging to the 
 morning-glory family. It is regarded as a native of South 
 America, but has long been in cultivation in China and is 
 thought by some to have had a separate origin in each country. 
 The Jerusalem artichoke is a species of sunflower, which grows 
 wild in the Northern states and Canada, and was occasionally 
 cultivated by the Indians before the advent of the whites. 
 
 Leaf crops. Chief of the plants grown for their leaves is the 
 cabbage, which is still found in the wild state in the south of 
 England, the Channel Islands, and on the shores of the North 
 Sea. The wild plant has thickish leaves, but it is quite unlike 
 the hard-headed specimens of our gardens. From this same 
 plant has come a long list of varieties that are valued in cul- 
 tivation, such as kale, cauliflower, Brussels sprouts, kohl-rabi, 
 and the like. Lettuce came originally from the Mediterranean 
 region, but is now widely distributed in both the Old World 
 and the New as a pernicious weed. It is not easy to realize
 
 280 AGRONOMY 
 
 that the weedy, prickly lettuce of waste places and neglected 
 gardens is the same species as the tender, smooth-leaved, solid- 
 headed plant so highly valued in cultivation. The lettuce 
 was once grown for its loose leaves, which were little changed 
 from the original, but nowadays it has been bred to make solid 
 heads like a cabbage. The spinach, which much resembles the 
 lettuce in form, has been known since earliest times. It is a 
 native of Persia. The onion is another species valued for its 
 edible leaves, though many think the bulbous part is a root. 
 It is, however, a true bulb made up of the thickened bases of 
 the leaves. The cultivated onion is a native of western Asia 
 and has been known for centuries. Many other species grow 
 wild in both Europe and America. The leek is a species of 
 onion and grows wild on both sides of the Atlantic. Celery 
 has long been in cultivation, but may still be found wild in 
 parts of Europe and western Asia. It belongs to the same 
 plant family as the parsley, parsnip, carrot, fennel, dill, corian- 
 der, and other species valued for their aromatic seeds. Aspara- 
 gus, though not a leaf crop, may be mentioned in this connec- 
 tion. It has been cultivated for many centuries, and is, of 
 course, a native of the Old World. In the wild state the 
 stems of asparagus are rather slender, but under proper cul- 
 tivation they reach a diameter of more than an inch. 
 
 The legumes. Some species of legumes seem to have been 
 among the first plants cultivated by man. The seeds of peas 
 and lentils have been found among materials referred to the 
 Bronze Age of Europe. The word " legume " comes from the 
 Latin legere, meaning " to gather," and seems originally to 
 have been applied to any species of plant gathered by hand. 
 The seeds of the plants now called legumes were usually prom- 
 inent in such gathered crops, and the name has since come to 
 be restricted to them. The lentil, little grown in America, has 
 long been cultivated in the warmer parts of the Old World, 
 especially in the Mediterranean region, and the pea has
 
 OUB CULTIVATED PLANTS 281 
 
 probably been derived from a wild species growing in the 
 same region. Beans, at least the common varieties, have come 
 from South America. The soy bean and cowpea are natives 
 of China. 
 
 Solanaceous fruits. Several edible fruits are produced by 
 the nightshade family (Solanaceae). This family contains 
 many poisonous species, though the fruits are usually edible. 
 In addition to the food plants, the family contains the tobacco 
 plant and the petunia. Of the species grown for their fruits 
 the tomato takes first place, although the latest of the group 
 to be used as food. Less than a hundred years ago it was re- 
 garded as poisonous and was grown only for ornament under 
 the name of love apple. The tomato is still found wild in its 
 native land, Peru, but is now grown almost the world over. 
 The fruit has been greatly increased in size by cultivation. 
 The red pepper, husk tomato, and eggplant are relatives of the 
 tomato. The first two are of American origin ; the last is said 
 to be a native of southwestern Asia. The ivonderberry, or 
 garden huckleberry, is a species of nightshade developed from 
 a common weed in the central and western states. It may be 
 mentioned in this connection that the potato is the enlarged 
 underground stem of another species of nightshade. 
 
 Gourd fruits. Some species of the gourd family are poison- 
 ous or unfit for food, but the group also contains a large num- 
 ber of edible species. They all have long and weak stems that 
 spread out over the ground or climb on other plants, trellises, 
 and the like. The cucumber is one of the oldest of this group 
 in cultivation, having been known in China for quite three 
 thousand years. The melons are natives of Africa. The water- 
 melon still grows wild in central Africa, and the muskmelon 
 extends eastward and northward to western Asia. The pump- 
 kin is a native of America, and was cultivated by the Indian 
 in his cornfields at the time of the discovery of the continent, 
 just as it is still cultivated.
 
 282 AGRONOMY 
 
 The grasses. With the exception of maize, or I//</i<i corn, 
 all the grasses cultivated for food are natives of the Old 
 World. The list includes wheat, oats, barley, rye, millet, sugar 
 cane, sorghum, and rice. The grains have been cultivated so 
 long that the origin of most of them is lost in antiquity. 
 Wheat has been cultivated at least five thousand years. Rice, 
 though cultivated in ancient times, still exists in the wild 
 state, but it is a question whether wild wheat can now be 
 found. Indian corn is a product of the warmer parts of the 
 New World and was cultivated by the Indians long before the 
 time of Columbus. It is not native to the Old World. Eng- 
 lishmen use the word " corn " for several kinds of grain, and 
 when references to corn are encountered in early English liter- 
 ature and in the Bible, it should be understood that the grain 
 we call corn is not the one meant. 
 
 Bush fruits. All the common bush fruits, raspberries, black- 
 berries, currants, gooseberries, and the like, grow wild in both 
 Europe and America. Some of the species in cultivation are 
 of Old World origin, others have originated on this side of 
 the world, and some are hybrids between them. They are 
 usually but little changed from their wild relatives, the most 
 noticeable difference being found, as would be expected, in 
 the larger fruits. 
 
 Tree fruits. Our tree fruits are all closely related and be- 
 long to groups allied to the rose family. They have been 
 cultivated from the earliest times and are much modified in 
 consequence. The apple, cherry, and peach are natives of 
 western or southern Asia, the pear comes from Europe, and 
 the different species of plums are found both in Europe and 
 America. The grape, while not a tree fruit, may be mentioned 
 here. Nearly all the common varieties cultivated in eastern 
 and southern North America have originated from native 
 species. The European grapes do not thrive in the eastern 
 states, but are extensively grown on the Pacific coast.
 
 OUR CULTIVATED PLANTS 283 
 
 New fruits. That there are many other plants in the wild 
 which might be made to take the place of plants now culti- 
 vated is beyond question. Those that have been developed 
 are without doubt those that first came to hand in a promis- 
 ing form, but many still remain that, with the same amount 
 of care in developing, would yield equally valuable results. 
 We neglect the common elderberry, the wild crab, the many 
 species of hawthorn, the papaw, the persimmon, wild rice, and 
 many others simply because we have other species as good. 
 The huckleberries and blueberries are just being brought under 
 cultivation, and the cranberry is essentially wild, though cared 
 for and even planted in bogs suited to its requirements. 
 Even in the wild state these are very desirable plants. Call- 
 ing to mind, however, the advances made by other fruits when 
 carefully cultivated and selected, it seems likely that these 
 and many others may yet be made to yield much finer fruits 
 than they now produce. 
 
 PRACTICAL EXERCISES 
 
 1. Make a list of the wild fruits, seeds, roots, and leaves that you 
 know are edible. 
 
 2. Make a list of the wild plants with which you are familiar that 
 are related to cultivated crops. 
 
 3. Make a list of wild species that you think would be valuable for 
 domestication. 
 
 4. What do you conclude to be the greatest obstacle to introducing 
 them into cultivation ? 
 
 References 
 
 Bailey, " Evolution of our Native Fruits." 
 
 Bailey, " Survival of the Unlike." 
 
 Davenport, " Domesticated Animals and Plants." 
 
 De Candolle, "Origin of Cultivated Plants." 
 
 De Vries, " Species and Varieties ; their Origin by Mutation." 
 
 Sargent, "Corn Plants." 
 
 Willis, "A Practical Flora."
 
 APPENDIX 
 
 SEVENTY-FIVE SHRUBS USEFUL FOR PLANTING 
 
 [With notes on their height, color, time of blooming, etc.] 
 
 Alder, white (Clethra alnifolia) : 4-10 feet ; white ; summer ; flowers very 
 fragrant. 
 
 Almond, flowering (Prunus Japonica) : 3-5 feet ; pinkish ; spring. 
 
 Ash, prickly (Zanthoxylum Americanum) : 6-8 feet ; yellowish ; spring. 
 
 Azalea (Azalea nudiftora) : 6-15 feet ; pink ; spring. 
 
 Barberry (Berberis vulgaris) : 4-7 feet ; yellow ; spring ; stems thorny ; 
 fruit scarlet, persisting into the winter ; used for jelly. 
 
 Barberry, Japanese (Berberis Thunbergii) : 2-4 feet ; yellowish ; spring ; 
 thorny stems ; fruit scarlet, in small clusters, persistent ; much used for 
 low hedges. 
 
 Barberry, purple (Berberis vulgaris var. purpurea) : 4-6 feet ; yellowish ; 
 spring ; leaves purple-tinged ; used for hedges. 
 
 Bladder nut (Staphylea trifolia) : 6-12 feet ; white ; spring ; pods large, 
 three-angled, inflated ; flowers in racemes. 
 
 Box (Buxus sempervirens) : 4-6 feet ; greenish ; spring ; leaves small, ever- 
 green ; much used for hedges. 
 
 Buckthorn (Rhamnus cathartica) : 8-12 feet ; whitish ; spring ; thorny and 
 much used for hedges ; fruit black. 
 
 Buffalo berry (Shepherdia argentea) : 6-8 feet ; yellowish ; late spring ; fruit 
 red, edible ; leaves silvery-scaly beneath. 
 
 Burning bush (Euonymus atropurpureus) : 8-12 feet ; purplish-red ; early 
 summer ; fruit pale pink, at length splitting and showing the scarlet aril 
 which surrounds the seed. 
 
 Button bush (Cephalanthus occidentalis) : 4-10 feet ; white ; summer ; flow- 
 ers in globular heads, fragrant ; good for planting in wet places. 
 
 Chokeberry (Pyrus arbutifolid) : 3-8 feet ; pinkish ; early summer. 
 
 Cinquefoil, shrubby (Potentillafruticosa) : 1-3 feet ; yellow ; early summer; 
 foliage grayish ; does well in dry situations. 
 
 Coralberry (Symphoricarpos vulgaris) : 2-4 feet ; pink ; summer ; fruit coral 
 red ; plant desirable for dry banks ; spreads by stolons. 
 
 Crab, wild (Pyrus coronaria) : 8-15 feet; pink; early summer; fruit fra- 
 grant, hard, and sour ; used for preserves. 
 
 Cranberry, high-bush (Viburnum opulus) : 6-12 feet; white; late spring; 
 fruit red, persistent ; regarded as the parent of the snowball tree. 
 
 285
 
 286 AGRONOMY 
 
 Currant, flowering (Ribes aureum) : 4-8 feet ; yellow ; early spring ; flower 
 very strongly spicy-scented ; fruit black. 
 
 Currant, wild (Kibes floridum) : 3-7 feet ; greenish ; early spring. 
 
 Daphne (Daphne mezereum) : 1-4 feet ; rose-purple or white ; early spring ; 
 flowers appear before the leaves. 
 
 Deutzia (Deutzia scabra) : 4-6 feet ; white ; late spring ; leaves sprinkled 
 with stellate hairs. 
 
 Deutzia, small (Deutzia gracilis) : 2-3 feet ; white ; spring ; much used for 
 low borders. 
 
 Dogwood, or red osier (Cornus slolonifera) : 4-8 feet ; white ; early summer ; 
 stems dark red, very showy in winter ; spreads by stolons. 
 
 Elder, common (Sambucus Canadensis) : 6-12feet; creamy white; early sum- 
 mer ; valued alike for its large panicles of flowers and for its purplish-black 
 fruit ; medicinal ; several variegated and cut-leaved forms are known. 
 
 Elder, red-berried (Sambucus pubens) : 6-10 feet ; greenish ; spring ; berries 
 bright red, ripening in early summer at the time the preceding species is 
 blooming ; several cut-leaved forms are cultivated. 
 
 Fringe tree (Chionanthus Virginica) : 7-10 feet ; white ; spring. 
 
 Golden bell (Forsythia suspensa) : 6-8 feet ; bright yellow ; early spring ; 
 flowers appear before the leaves and cluster thickly along the branches ; 
 one of our most decorative species ; branches drooping. 
 
 Golden bell (Forsythia viridissima) : 6-12 feet ; yellow; early spring ; more 
 erect than the preceding. 
 
 Gooseberry, early (Ribes gracilis) : 3-6 feet ; pale yellow ; early spring ; the 
 first shrub to put forth leaves in spring ; thorny ; much used for hedges. 
 
 Hardback (Spiraea tomentosa) : 1-3 feet ; pink ; summer. 
 
 Hawthorn (CratfKgus sp.) : 10-15 feet ; white ; spring. 
 
 Hazel (Corylus sp.) : 6-12 feet ; yellow and red ; early spring ; the flowers 
 are borne in catkins and are among the first to appear in spring ; the fruit 
 is the well-known filbert. 
 
 Honeysuckle, Tartarian (Lonicera Tatarica) : 6-10 feet ; pink ; late spring ; 
 red berries. 
 
 Hop tree (Ptelia trifolia) : 6-12 feet ; greenish ; early summer ; flowers 
 sweet scented ; fruits round, broad-winged. 
 
 Hydrangea (Hydrangea paniculata) : 4-8 feet ; white ; summer. 
 
 Jersey tea (Ceanothus Americanus) : 1-3 feet ; pale cream ; early summer ; 
 excellent for dry places ; the feathery flower clusters are borne in profusion ; 
 seeds are thrown long distances by the splitting of the pod ; the young 
 seed pods contain much vegetable soap. 
 
 June berry (Amelanchier sp.) : 6-20 feet ; white ; early spring ; fruit red 
 or blackish, sweet, and edible. 
 
 Kerria (Kerria Japonica) : 3-5 feet ; orange-yellow ; early summer ; twigs 
 bright green in winter. 
 
 Kerria, white (Rhodotypus kerrioides) : 3-6 feet ; white ; early summer. 
 
 Laurel, mountain (Kalmia latifolia) : 2-8 feet ; pinkish ; early summer. 
 
 Leadwort (Amorpha fruticosa) : 4-6 feet ; pui-plish ; summer.
 
 APPENDIX 287 
 
 Leatherwood (Direct paluslris) : 3~6 feet ; yellow ; early spring ; excel- 
 lent for wet places ; flowers appearing with the leaves ; bark exceedingly 
 tough. 
 
 Lilac, common (Syrinya vulgaris) : 8-15 feet ; purple or white ; early spring. 
 
 Lilac, Persian (Syringa Persica) : 8-15 feet; purple ; spring ; more spread- 
 ing than the preceding species. 
 
 Ninebark (Physocarpus opulifolius) : 6-12 feet ; white ; early summer ; 
 flowers like those of the spiraeas ; bark shed in long strings ; medicinal. 
 
 Olive, Russian (Elceagnus anyustifolius) : 8-15 feet; cream color; early 
 summer ; leaves silvery white from the numerous scales ; fruit silvery. 
 
 Osier, European (Cornus sanguined) : 4-8 feet ; white ; early summer ; 
 stems deep red ; a form with white-edged leaves is common. 
 
 Pea bush (Desmodium penduliflorum) : 4-5 feet ; rose-purple ; autumn. 
 
 Pea tree, Siberian (Caragana arborescens) : 10-15 feet ; yellow ; spring. 
 
 Pearl bush (Exochorda grandiflora) : 6-12 feet ; white ; spring. 
 
 Privet (Ligustrum sp.) : 4-12 feet ; white ; summer ; nearly evergreen ; 
 the various species are much used for hedges. 
 
 Quince, Japanese (Cydonia Japonica) : 6-10 feet ; bright red ; early spring ; 
 flowers appearing with the leaves ; shrub thorny. 
 
 Raspberry, flowering (Rubus odoratus) : 2~5 feet ; purple ; summer ; thorn- 
 less ; leaves large, lobed ; fruit insipid. 
 
 Rhododendron (Rhododendron sp.) : 6-12 feet ; white to pink ; summer. 
 
 Rose of Sharon (Hibiscus Syriacus) : 8-12 feet ; white to red ; late summer ; 
 very attractive, the flowers like hollyhocks. 
 
 Senna, bladder (Colutea arborescens) : 8~10 feet ; yellow ; early summer ; 
 pods inflated. 
 
 Sheepberry (Viburnum lentago) : 6-12 feet; white; summer; fruit black, 
 edible. 
 
 Silver bell (Halesia tetraphylla) : 8-15 feet ; white ; spring ; the bell-shaped 
 flowers are succeeded by curious four-angled and winged fruits. 
 
 Smoke tree (Rhus cotinus) : 8-15 feet ; greenish ; spring ; the smoke-like 
 masses regarded by many as flowers are really flower stalks. 
 
 Snowball, Japanese ( Viburnum plicctium) : 6-10 feet ; white ; early summer ; 
 the flower clusters consist of sterile flowers, and the whole plant resembles 
 the common snowball, or guelder-rose. 
 
 Snowberry (Symphoricarpos racemosus) : 2-5 feet ; pink ; summer ; fruit 
 white, persisting into the winter. 
 
 Spicebush (Benzoin odoriferum) : 6-10 feet ; yellow ; early spring ; flowers 
 appear with the leaves ; bark spicy. 
 
 Spiraea (Spircea sp.) : 6-8 feet ; white ; early summer ; the various species 
 of spiraea are among our most decorative plants. 
 
 Spiraea, blue (Caryopteris mastacanthus) : 2-4 feet ; bright blue ; late sum- 
 mer ; has the appearance of a spiraea, whence the common name. 
 
 Sumac, common (Rhus glabra and R. typhinia) : 5-15 feet ; greenish ; 
 early summer ; foliage turns brilliant crimson in autumn ; fruits acid, 
 edible ; several cut-leaved varieties occur.
 
 288 AGKONOMY 
 
 Sumac, fragrant (Rhus aromatica) : 3-6 feet ; yellow ; spring ; flowers in 
 catkins appearing before the leaves; fruits reel, edible. 
 
 Sumac, varnish (Khus copallina) : 3~6 feet; greenish; summer; leaves 
 brilliant red in autumn ; good shrub for dry places. 
 
 Sweet shrub (Calycanthus floridus) : 3-8 feet ; brownish-purple ; late 
 spring ; flowers very fragrant when wilted, and of an unusual color. 
 
 Syringa, mock orange (Philadelphus coronarius) -. 6-10 feet ; cream color ; 
 late spring ; flowers very fragrant ; several other species are cultivated. 
 
 Tamarisk ( Tamarix sp.) : 10-15 feet; pinkish; summer; flower.s and 
 leaves small ; branches wandlike. 
 
 Weigela ( Weigela rosea) : 4-6 feet ; rose color ; summer. 
 
 Willow, goat (Salix capred) : 6-10 feet ; yellowish ; spring ; has immense 
 catkins of flowers that appear in earliest spring. 
 
 Winterberry (Ilex verticillata) : 3-8 feet ; white ; summer ; a hardy decid- 
 uous holly with red berries that last through the winter ; excellent for wet 
 places. 
 
 Witch hazel (Hamamelis Virginiana) : 6-12 feet ; yellow ; late autumn ; 
 blooms as the leaves are falling ; seeds propelled for long distances ; plant 
 much used in medicine. 
 
 FIFTEEN WOODY VINES DESIRABLE FOR ARBORS AND 
 
 PORCHES 
 
 Bittersweet (Celastrus scandens) : twiner ; capsules orange-yellow, split- 
 ting at maturity and showing the scarlet arils. 
 
 Clematis, panicled (Clematis paniculata) : climbs by twining leafstalks; 
 flowers white, borne in great profusion. 
 
 Clematis, purple (Clematis lanuginosa) : climbs like the preceding ; flowers 
 large, purple, very showy. 
 
 Creeper, trumpet (Tecoma radicans) : half twiner; flowers large, tubular, 
 dull orange-red ; seeds winged. 
 
 Dutchman's pipe (Aristolochia macrophylla) : twiner ; flowers shaped like 
 a pipe ; leaves large, making a dense shade. 
 
 Grape, wild (Vitis sp.) : tendril climbers ; any of the wild grapes are desir- 
 able for covering arbors and trellises ; fruit makes excellent jelly and wine. 
 
 Honeysuckle, Hall's (Lonicera Haliiana) : twiner ; flowers white turning 
 yellow, very fragrant. 
 
 Honeysuckle, trumpet (Lonicera sempervirens) : twiner ; flowers long, 
 slender, trumpet shaped, scarlet. 
 
 Ivy, Boston (Ampelopsis tricuspidata) : tendril climber, holding fast by 
 small disks at the tips of the tendrils ; will cling to walls of any kind. 
 
 Matrimony vine (Lyciwn vulgare) : half twiner ; stem thorny ; flowers 
 purplish ; fruit red, inedible. 
 
 Rose, climbing (Rosa sp.) : climbing by means of recurved prickles ; several 
 species are useful for covering arbors, pillars, and porches.
 
 APPENDIX 289 
 
 Virgin's-bower (Clematis Virginiana) : climbing by twining leafstalks; 
 flowers numerous, white ; fruit with downy appendages. 
 
 Wistaria ( Wistaria Sinensis) : twiner ; flowers blue or white in large 
 clusters, very showy. 
 
 Woodbine, common (Ampelopsis quinquefolia) : tendril climber ; fruit bluish- 
 black, inedible. 
 
 Woodbine, Western (Ampelopsis Engelmanni) : like the common woodbine, 
 but tendrils tipped with disks that cling closely to supports of all kinds. 
 
 FIFTY DESIRABLE HERBACEOUS PERENNIALS 
 
 Aconite (Aconitum napellus) : 3-4 feet ; deep blue ; summer. 
 
 Amsonia (Amsonia laberncemontana) : 2-3 feet ; blue ; early summer. 
 
 Aster, New England (Aster Novce-Anglice) : 3~6 feet ; purple or pink ; 
 autumn. 
 
 Baby's breath (Gypsophila paniculata) : 2-3 feet ; white; spring. 
 
 Baptisia (Baptisia australis) : 2-3 feet ; blue ; early summer. 
 
 Beardtongue (Pentstemon sp.) : 2-3 feet ; white to red ; summer. 
 
 Bellflower, Chinese (Platycodon grandifloruiri) : 2-3 feet ; blue or white ; 
 summer. 
 
 Black-eyed Susan (Rudbeckia triloba, E. hirta, and R. speciosa) : 1-3 feet ; 
 yellow and black ; summer and autumn. 
 
 Blanket flower (Gaillardia aristata) : 1-2 feet ; red and yellow ; summer 
 and autumn. 
 
 Bleeding heart (Dicentra spectabilis) : 2-3 feet ; pink ; early spring. 
 
 Bluebells (Merlensia Virginica) : 2-3 feet ; sky blue ; spring. 
 
 Boltonia (Boltonia asteroides) : 4-5 feet ; white ; early autumn. 
 
 Butterfly weed (Asclepias tuberosa) : 1-2 feet ; orange-yellow ; summer. 
 
 Columbine (Aqullegia sp.) : 2-3 feet ; white to yellow and blue ; spring. 
 
 Coneflower, purple (Echinacea purpurea) : 2-3 feet ; purplish-red; summer. 
 
 Coreopsis (Coreopsis sp.) : 2-3 feet ; yellow ; summer. 
 
 Dame's violet (Hesperis matronalis) : 1-2 feet ; white to pink ; spring. 
 
 Golden glow (Rudbeckia laciniata) : 6-7 feet ; yellow ; late summer. 
 
 Goldenrod (Solidago rigida and others) : 3 feet ; yellow ; late summer. 
 
 Harebell (Campanula Carpalhica) : 6-9 inches ; deep blue ; summer. 
 
 Hollyhock (Althcea rosea) : 3-8 feet ; white to red and yellow ; summer. 
 
 Iris (Iris sp.) : 1-3 feet ; white to yellow and purple ; spring. 
 
 Jacob's ladder (Polemonium sp.) : 1-2 feet ; blue ; spring. 
 
 Larkspur (Delphinium fonnosuiri) : 1-3 feet ; deep blue ; summer. 
 
 Lilies (Lilium sp.) : 2-4 feet ; white to yellow and red ; summer. 
 
 Lilies, day (Hemerocallis sp.) : 2-4 feet ; orange, golden yellow, and dull 
 red ; late spring and summer. 
 
 Lily of the valley (Convallaria majalis) : 6-9 inches ; white ; early spring. 
 
 Lily, plantain (Funkia sp.) : 1-1^ feet ; white or blue ; summer. 
 
 Marsh mallow (Hibiscus moscheulos) : 4-6 feet ; white and pink ; late summer.
 
 290 AGRONOMY 
 
 Mullein (Verbascum pannosum and V. nigrum): 3-6 feet; yellow; early 
 Bommer. 
 
 Obedient plant (Physostegia Virginica) : 2-3 feet ; pinkish ; summer. 
 
 Oxeye (Ileliopsis Icevis) : 2-3 feet ; copper-yellow ; summer. 
 
 Pea, perennial (Luthyrus latifolius) : 3-6 feet ; pink or white ; summer. 
 
 Peony (Pceonia officinalis) : 2-4 feet ; white to red ; late spring. 
 
 Pheasant's eye (Adonis vernalis) : 6-9 inches ; yellow ; early spring. 
 
 Phlox, perennial (Phlox sp.) : 2~3 feet ; white to red and purple ; summer 
 and autumn. 
 
 Pink moss (Phlox subulata) : 6 inches ; pink ; spring. 
 
 Poppy, mallow (Callirliae involucrala) : 6-9 inches ; rose-pink ; summer. 
 
 Poppy, perennial (Papaver orientate) : 2-3 feet ; red ; early summer. 
 
 Primrose, evening (CEnothera sp.) : 1~3 feet ; yellow or white ; summer. 
 
 Pyrethrum (Pt/relhrum hybridu.ni) : 1-3 feet ; white to pink ; spring. 
 
 St.-John's-wort (Ilypericum ascyron) : 2-3 feet ; yellow ; early summer. 
 
 Senna, wild (Cassia Marylandica) : 3-6 feet ; yellow ; summer. 
 
 Sneezeweed (Helenium aulumnale) : 3-6 feet ; yellow ; summer. 
 
 Sunflower (Helianthus sp.) : 6-10 feet ; yellow ; late summer and autumn. 
 
 Sweet flag (Acorus calamus) : 2-3 feet ; green ; summer. 
 
 Sweet William (Dianthus barbatus) : 1-2 feet ; white to pink ; summer. 
 
 Sweet William, wild (Phlox divaricata) : 1-2 feet ; blue ; late spring. 
 
 Yarrow (Achillea ptarmica) : 1-2 feet ; white ; early summer. 
 
 Yucca (Yucca filamentosa) : 3-6 feet ; cream color ; summer.
 
 INDEX 
 
 Absorption, selective, 95 
 
 Acclimatization, 115 
 
 Acid soils, 35 ; effect of lime on, 36 ; 
 
 plants of, 35 ; test for, 35 
 Air, 40 ; as a weathering agent, 13 ; 
 
 composition of, 40 ; in soil, 41 ; 
 
 moisture in, 116 ; value of, in soil, 
 
 41 ; variations in pressure, 40 ; 
 
 weight of, 40 
 Albumen, 86 
 Alkali soils, 34 
 Aluminum, characteristics of, 7 ; in 
 
 plants, 100 
 Ammonification, 107 
 Amyloplasts, 77 
 Annuals, 87 ; value of, 205 
 Anthers, 79 
 Arid regions, 11 
 Artificial soils, 36 
 Atom, definition of, 2 ; size of, 2 
 
 Bacteria, and nitrification, 107 ; de- 
 nitrifying, 110 ; in symbiosis, 108 ; 
 need of lime, 109 ; requirements 
 for growth, 107 
 
 Bed rock, 12 ; modifications of, 20 ; 
 outcrops of, 12 
 
 Biennials, 87 
 
 Blanching, effects of, 123 
 
 " Bleeding " of plants, 97 
 
 Borders, arrangement of plants in, 
 202 ; character of, 201 
 
 Bowlders, 31 
 
 Bridge grafting, 193 
 
 Bud scales, 69 ; use of, 69 
 
 Bud variations, 260 
 
 Budding, methods of, 190 ; uses of, 
 189 
 
 Buds, accessory, 67, 69 ; adventitious, 
 69; dormant, 70; flower, 70; lat- 
 eral, 67; leaf, 70; mixed, 70; 
 naked, 69 ; protection of, 69 ; ter- 
 minal, 67 
 
 Bulbs, value of, 207 
 
 Bundles, fibrovascular, 65; arrange- 
 ment in dicotyledons, 66 ; arrange- 
 ment in monocotyledons, 66 
 
 Bushes, 89 
 
 Calcium, characteristics of, 6 ; test 
 for, in soils, 105 ; use of, by plants, 
 98 
 
 Calcium carbide, 4 
 
 Calyx, 79 
 
 Cambium, in roots, 61 ; in stems, 66, 67 
 
 Carbohydrates, 98 
 
 Carbon, characteristics of, 9 ; occur- 
 rence of, 97 
 
 Carbon dioxide, amount in air, 97 ; 
 formation of, 4 
 
 Carbon disulphide, 4 
 
 Carpels, 79 
 
 Carpet bedding, 208 
 
 Caruncle, 86 
 
 Cavities in trees, 228 
 
 Cell, 57 
 
 Cell sap, 57 
 
 Cell wall, 57 
 
 Centigrade scale, 43 ; rule for chang- 
 ing, to Fahrenheit, 43 
 
 Chemical compounds, 1, 4 
 
 Chemical elements, change of state 
 in, 2 ; distribution of, 5, 101 ; found 
 in plants, 5 ; in plant food, 75 ; lack- 
 ing in soils, 104 ; most abundant, 5 ; 
 native, 1 ; number needed by plants, 
 95 ; table of the more common, 3 
 
 Chemical formulas, 2 
 
 Chemical symbols, 2 
 
 Chlorine, characteristics of, 9 ; in 
 plants, 100 
 
 Chlorophyll, 75 
 
 Chloroplasts, 75 
 
 Chromoplasts, 78 
 
 Cion, effects of stock on, 195 
 
 Clay, amount of pore space in, 41 ; 
 characteristics of, 31 ; run-off of 
 water in, 47 
 
 291
 
 292 
 
 AGRONOMY 
 
 Cleavage planes, 78 
 
 Cold, artificial protection from, lilt ; 
 effect of, on plants, 117 ; protection 
 from, 118 
 
 Cold frames, 120 ; use of, 101 
 
 Contraction wrinkles, 61 
 
 Cool-season plants, 134 
 
 Corolla, 79 
 
 Cotyledons, 86 
 
 Crops, grain, 282; leaf, 279; root, 
 279 
 
 Cross pollination, 82 
 
 Crossing, 262 
 
 Cultivated plants, origin of, 277 
 
 Cuttings, green or softwood, 185 ; 
 growing in shade, 189 ; hardwood, 
 185; heel, 188; leaf, 186; mallet, 
 189 ; method of making, 185 ; prop- 
 agation by, 185; root, 187; single 
 eye, 188; stem, 186; tuber, 186; 
 use of, 184 
 
 Darwinian theory, 275 
 
 Decorative planting, purpose of, 197 
 
 Delta soils, 20 
 
 Dew, 116 
 
 Dew point, 116 
 
 Dibber, 141 
 
 Dicotyledon flower, plan of, 83 
 
 Digestion in plants, 76 
 
 Double cropping, 138 ; crops for, 139 
 
 Ducts, in stems, 66 ; in roots, 60 
 
 Earth, composition of, 1 
 Elementary species, 91, 276 
 Embryo, 86 
 Endosperm, 86 
 Enzymes, 76 
 Epidermal hairs, 118 
 Essential organs, 80 
 Evolution, nature of, 272 
 
 Fahrenheit scale, 43; rule for chang- 
 ing, to centigrade, 44 
 
 Fairy rings, 102 
 
 Families, plant, 91 
 
 Fertilization, 79 ; double, 268 
 
 Fertilizers, effect on soil, 103 ; how 
 to apply, 105 
 
 Flower, epigynous, 79 ; hypogynous, 
 79 ; parts of, 79 
 
 Flowers, characteristics of insect- 
 pollinated, 82 ; characteristics of 
 wind-pollinated, 82 ; insect-polli- 
 nated, 81 ; wind-pollinated, 80 
 
 Forcing plants, in the window gar- 
 den, 162-; methods of, 157, K^ 
 Forcing single hills, 161 
 Formal style of planting, 208 
 Frost, conditions favoring, 116 ; dif- 
 ference from dew, 116; effect of 
 locality on formation of, 116 ; pro- 
 tecting from, 116 
 
 Frostbitten plants, treatment of, 120 
 Fruit, a result of pollination, 83 ; 
 parts of the flower represented in, 
 83, 85 ; seedless, 83 
 Fruit spurs, 220 
 Fruiting, how induced, 141 
 Fruits, bush, 282 ; gourd, 281 ; modi- 
 fied for wind distribution, 84, 85 ; 
 new, 283 ; purpose of, 85 ; solana- 
 ceous, 281 ; tree, 282 
 
 Garden styles, 209 
 
 Garden, arrangement of crops in, 
 130 ; location of, 129 ; plan of, 
 130, 135, 139; planting, 132; pre- 
 paring the soil in, 130 ; time of 
 planting, 134 ; tools, 151, 154 
 
 Genera, 90 
 
 Geophilous habit, 118 
 
 Germination, 136 
 
 Girdling, 227 
 
 Glaciers, work of, 20 
 
 Gourd fruits, 281 
 
 Graft hybrids, 195 
 
 Grafting, bridge, 193 ; cleft, 192 ; 
 crown, 193 ; formsof , 192 ; root. 1 94 ; 
 saddle, 193 ; splice, 193 ; tongue, 
 193; value of, 192; veneer, 193; 
 whip, 192 
 
 Grafting wax, 195 
 
 Grain crops, 282 
 
 Gravel, 31 
 
 Guard cells, 74 
 
 Guttation, 97 
 
 Half-hardy plants, 114 
 
 Hardwood cuttings, 187 ; heel, 188 ; 
 
 mallet, 188 ; single eye, 188 
 Hardy plants, 114 ; sowing seeds of, 
 
 136 
 
 Heading in, 224 ; methods of, 226 
 Heat, amount received from sun, 41 ; 
 
 effect on plants, 120 ; protection 
 
 from, 121 
 
 Hedges, plants for, 207 
 Heeling in, 211 
 Hilum, 86
 
 INDEX 
 
 293 
 
 Hotbeds, 159 
 
 Humid regions, 11 
 
 Humus, 30; a source of nitrogen, 
 
 107 ; effect on soil, 39, 43 
 Hybridizing, 262 ; how accomplished, 
 
 263 
 Hybrids, 262 ; method of producing, 
 
 263 
 
 Hydrogen, characteristics of, 8 
 Hydrophytes, 126 ; xerophytic, 127 
 
 Inarching, 194 
 
 Insects, damage to plants from, 245 ; 
 forms that cause injury, 246 ; meta- 
 morphoses of, 245 ; methods of 
 combating, 255 ; poisons for, 252 ; 
 preventing attacks of, 252 ; smoth- 
 ering sprays for, 254 
 
 Insects, helpful : ant lion, 256 ; 
 dragon fly, 256 ; ichneumon fly, 
 256 ; ladybird, 256 ; ladybug, 256 ; 
 spiders, 256 ; tiger beetle, 256 
 
 Insects, injurious: blister beetles, 250; 
 borers, 249 ; cabbage worm, 247 ; 
 cankerwonn, 249; codlin moth, 
 249 ; corn-ear worm, 248 ; cucum- 
 ber beetle, 250 ; curculio, 249 ; cur- 
 rant worm, 248 ; cutworm, 247 ; 
 elm-leaf beetle, 250; May beetle, 
 250 ; mealy bug, 251 ; plant lice, 
 251; potato beetle, 250; scale in- 
 sect, 251 ; squash bug, 251 ; tent 
 caterpillar, 248 ; tomato worm, 247 
 
 Insects, poisons for : arsenate of lead, 
 253 ; Paris green, 252 ; white helle- 
 bore, 252 
 
 Insects, smothers for : carbon disul- 
 phide, 254 ; hydrocyanic gas, 254 ; 
 kerosene emulsion, 254 ; Persian 
 insect powder, 254 ; tobacco smoke, 
 254 ; tobacco water, 254 ; whale- 
 oil soap, 254 
 
 Intercellular spaces, 73 
 
 Iron, characteristics of, 7 ; in plants, 
 99 
 
 Labels, forms of, 143; method of 
 
 writing, 141 
 Lath houses, 123 
 Lawn, care of, 201 ; how to make, 
 
 198; paths in, 199; seeding, 198; 
 
 sodding, 19!) 
 Layering, air, 189 ; forms of, 188 ; 
 
 mound, 189 ; nature of, 188 ; pot, 
 
 189; tip, 188; vine, 188 
 
 Leaf crops, 279 
 
 Leaves, branching, 72 ; epidermis of, 
 
 72 ; fall of, 77 ; structure of, 71, 
 
 73 ; veining of, 72 
 
 Legumes, as food, 280 ; and bacteria, 
 
 108, 110 
 Leucoplasts, 77 
 Life cycle of plants, 87 
 Light, effect of lack of, 122 ; needed 
 
 by plants, 122 ; protection from, 
 
 123 
 
 Lime, effect on soil, 39 
 Lime plants, 7, 99 
 Loam, 34 
 
 Magnesium, characteristics of, 6 ; in 
 
 plants, 99 
 Manganese, characteristics of, 7 ; in 
 
 plants, 100 
 Mantle rock, 12 ; changes in, 22 ; 
 
 turned to soil, 23 
 Manure, derivation of the word, 106 ; 
 
 green, 106 
 Marl, 30 
 
 Medullary rays, 67 
 Mendel's law, 264 ; illustrations of, 
 
 265 
 
 Mesophytes, 127 
 Metals, and nonmetals, 1 ; properties 
 
 of, 2 
 
 Micropyle, 86 
 Molecules, 2 
 
 Monocotyledon flower, plan of, 83 
 Mulch, dust or summer, 152 
 Mulching, 120, 152, 211 
 Mutation theory, 275 
 Mutations, 261 
 Mycorrhizas, 109 ; plants associated 
 
 with, 109 
 
 Nectar guides, 82 
 
 Nitrates, 108 
 
 Nitrification, 106; bacteria concerned 
 in, 107 
 
 Nitrites, 108 
 
 Nitrogen, characteristics of, 8 ; fixa- 
 tion of, 108 ; source of, 105 ; use 
 of, by plants, 98 ; value of, 106 
 
 Nonmetals, examples of, 2 
 
 Nucleus, 58 
 
 Orders, 91 
 
 Osmosis, 63 ; in the plant, 63 
 
 Ovary, 79 
 
 Overwatering, effect of, 124
 
 294 
 
 A(}H()X()MY 
 
 ( )vules, 79 
 
 Oxygen, characteristics of, 8 
 
 Palisade tissue, 73 
 
 Parasites, 230 ; wound, 238 
 
 Parenchyma, 73 
 
 Parthenogenesis, 269 
 
 Peat, 29 
 
 Pebbles, 31 
 
 Perennials, 88 ; arrangement of, 206 ; 
 herbaceous, 89 ; use of herbaceous, 
 206 ; woody, 89 
 
 Petals, 79 
 
 Petiole, 71 
 
 Phloem, 66 
 
 Phosphorus, characteristics of, 9 ; 
 source of, 105 ; use of, to plant, 99 
 
 Photosynthesis, 75 ; contrasted with 
 respiration, 76 
 
 Pith cells, 65 
 
 Plan of the flower, 83 
 
 Plant breeding, advantages of, 258 ; 
 basis for, 259 ; results of, 267 
 
 Plant diseases, blights, 234 ; how 
 caused, 230 ; leaf spots, 234 ; meth- 
 ods of preventing, 243; mildews, 
 235 ; molds, 235 ; number of, 232 ; 
 rots, 233 ; rusts, 237 ; smuts, 237 ; 
 variety, 239 ; wilts, 233 
 
 Plant food, distribution of, 76 ; for- 
 mation of, 75 ; source of the ele- 
 ments in, 75, 97, 105 ; storage of, 
 76 
 
 Plant growth, limiting factors in, 111, 
 114 
 
 Plant hairs, 118 
 
 Plant houses, 158 ; how heated, 159 
 
 Plants, antagonisms of, 103 ; cellular 
 structure of, 57 ; 'edible parts of, 
 278 ; effects of cold on, 117 ; effects 
 of overwatering, 124 ; life cycle of, 
 87 ; regions of, 57 ; relationships of, 
 90 ; rest period of, 89 ; time to 
 water, 124 ; variations in, 259 
 
 Plowing, 150 
 
 Pollarding, 225 
 
 Pollen, 79 ; of wind-pollinated flow- 
 ers, 82 
 
 Pollination, 79 ; agencies for, 80 ; 
 organs necessary for, 80 ; second- 
 ary effects of, 83 
 
 Potash plants, 99 
 
 Potassium, characteristics of, 5 ; 
 sources of, 105 ; use of, to plants, 
 99 
 
 Practical exercises, 10, 24, 36, 53, 92, 
 100, 112, 128, 147, 156, 163, 180, 
 196, 214, 228r 243, 257, 21,'t, 276, 
 283 
 
 Precipitation, 44 
 
 Pricking out, 141 
 
 Propagation, artificial, 183; by cut- 
 tings, 184-, forms designed for, 
 182 ; natural methods of, 181 
 
 Propagation, forms for: bulblet, 183 ; 
 cormel, 183 ; offset, 182 ; rootstock, 
 182 ; runner, 182 ; stolon, 182 ; 
 sucker, 182 ; tuber, 182 
 
 Pruning, implements for, 217 ; 
 methods of, 217, 218; plants that 
 do not need, 218; purpose of, 215 ; 
 season for, 216, 220 ; special crops, 
 219 
 
 Rainfall, annual, in United States, 46 ; 
 distribution of, in United States, 
 44, 45 ; distribution of, in world, 45 
 
 Receptacle, 79 
 
 Respiration in plants, 76 
 
 Rest period of plants, 89 
 
 Retarding plants, 157 
 
 Ribbon bedding, 208 
 
 Rocks, aqueous, 21 ; igneous, 21 ; 
 metamorphic, 21 ; sedimentary, 21 ; 
 table of, 22 
 
 Roguing, 268 
 
 Root crops, 279 
 
 Root grafting, 194 
 
 Root hairs, absorption by, 63 ; ad- 
 vantage of, 62 ; structure of, 62 
 
 Root pressure, 97 
 
 Root pruning, 226 
 
 Root system, axial, 60; inaxial, 60; 
 of corn, 58, 59 
 
 Roots, central cylinder in, 60 ; cortex 
 of, 60 ; ducts in, 60 ; epidermis of, 
 60 ; extent of, 59 ; multiple primary, 
 60 ; structure of, 59, 60 
 
 Rose, green, 64 
 
 Rotation of crops, character of, 155 ; 
 reason for, 155 
 
 Run-off, 47 
 
 Sand, amount of pore space in, 41 ; 
 
 characteristics of, 31, 33; run-off 
 
 of water on, 47 
 Saprophytes, 230 
 Scientific names, 91 
 Seed packets, how to close, 146 ; how 
 
 to make, 146
 
 INDEX 
 
 295 
 
 Seed tester, 138 
 
 Seeds, advantages of, 85 ; conditions 
 needed for germination, 136; depth 
 to plant, 134 ; drying, 144 ; plant- 
 ing table for, 145 ; receptacle for, 
 137 ; saving, 144 ; structure, 86 ; 
 vitality of, 137 
 
 Selection, artificial, 266 ; natural, 
 273 
 
 Selective absorption, 95 
 
 Self-pollination, 82 
 
 Self-pruning, 122 
 
 Sepals, 79 
 
 Shade plants, 122 ; artificially pro- 
 tected, 123 
 
 Shearing plants, 141 
 
 Shrubs, 66 ; for winter effects, 204 ; 
 location of, on lawns, 202 ; naming, 
 204 
 
 Sieve tubes, 66 
 
 Silicon, characteristics of, 10 ; in 
 plants, 100 
 
 Silt, 31 
 
 Sodium, characteristics of, 6 ; in 
 plants, 100 
 
 Soil, absorption of water by, 46 ; 
 seolian, 28 ; alluvial, 29 ; amount 
 of chemical elements in, 38 ; bac- 
 teria in, 11, 107; capillarity in, 
 47 ; colluvial, 28.; constituents, 
 29; definition of, 11; depth of, 
 11 ; drift, 13 ; effects of ants on, 
 154 ; effects of earthworms on, 
 154 ; effects of lime on, 39 ; effects 
 of puddling, 151 ; flocculated, 38 ; 
 glacial, 29 ; harmful organisms in, 
 110 ; inorganic, 31 ; lacustrine, 27 ; 
 methodsof pulverizing, 150; names 
 of, 25 ; organic, 31 ; origin of, 12, 
 25; puddled, 39; puddled, and 
 plants, 39 ; residual, 12 ; sedentary, 
 26 ; structure of, 38 ; temperature 
 of, 42 ; toxic substances in, 101 ; 
 treatment for harmful organisms 
 in, 111 ; ventilation of, 41 ; vol- 
 canic, 28 ; water in, 47 ; weather- 
 ing of, 11 
 
 Soil crumbs, 38 
 
 Soil inoculation, 109 
 
 Soil maps, 34 
 
 Solanaceous fruits, 281 
 
 Species, 90 ; elementary, 91, 270 
 
 Spermatophytes, 56 
 
 Spores, 57 ; number of, 231 
 
 Sports, 255 
 
 Spray pumps, 255 
 
 Sprays : ammoniacal copper carbon- 
 ate, 242 ; Bordeaux mixture, 240 ; 
 copper sulphate, 168 ; iron sul- 
 phate, 168 ; kerosene emulsion, 
 254 ; lime-sulphur wash, 241 ; 
 potassium sulphide, 243 ; tobacco 
 water, 254 ; whale-oil soap, 254 
 
 Starch grains, 75 
 
 Stems, forms of, 64 ; how increased 
 in diameter, 67 ; internodes, 71 ; 
 nodes of, 71 ; structure of, 65 ; 
 use of, 64 
 
 Stigma, 79 
 
 Stipules, forms of, 71 
 
 Stock, effects on cion, 195 
 
 Stomata, 73, 74 ; number in leaves, 
 75 ; use of, 74 
 
 Struggle for existence, results of, 
 273 
 
 Subsoil, how distinguished, 12 
 
 Subsoiling, 150 
 
 Sugar, grape, 75 ; turned to starch, 76 
 
 Sulphur, characteristics of, 9 ; in 
 plants, 99 
 
 Summer annuals, 87 
 
 Sun, amount of heat from, 41 ; dis- 
 tribution of rays, 42 
 
 Sunlight, distribution of, 41 
 
 Survival of the fittest, 273 
 
 Symbiosis, 108 
 
 Taproots, 65 
 
 Temperature, 41 ; adjustment of 
 
 plants to, 113 ; distribution of, 41 ; 
 
 effects of color on, 43 ; maximum, 
 
 115; minimum, 115; of growth 
 
 processes, 114; optimum, 115; 
 
 variations in, 42 
 Tender plants, 115 
 Testa, 86 
 Thermal belt, 47 
 Thinning, 142, 221 
 Tillage, effects of, 1 149 ; purpose of, 
 
 149 
 
 Topiary work, 228 
 Toxic substances in soils, 101 
 Transpiration, how plants avoid, 77 ; 
 
 use of, 77 
 Transplanting, advantages of, 140 ; 
 
 implements for, 140 ; seedlings, 
 
 139 ; trees and shrubs, 209 ; when 
 
 performed, 140 
 Trees, 89 
 Trenching, 150
 
 296 
 
 A<;KON<>.MY 
 
 Vacuoles, 57 
 
 Variation, how induced, '2<>l ; results 
 of, 274 
 
 Venation, netted, 72 ; palmate, 72 ; 
 parallel, 72 ; pinnate, 72 ; reticu- 
 lated, 72 
 
 Verdant zone, 117 
 
 Vines, methods of climbing, 89 
 
 Warm-season plants, 134 
 
 Water, amount in plant parts, 97 ; 
 amount transpired by plants, 90 ; 
 as a weathering agent, 14, 18 ; 
 capillary, 47 ; hygroscopic, 47 ; 
 percolating, 47 ; plant form and, 
 125 ; use of, to plants, 96 
 
 Weathering, by decomposition, 13 ; 
 by disintegration, 16 
 
 Weathering agents, 13, 17 
 
 Weeds, distribution of, 179 ; harm- 
 fulness of, 165, 166 ; how to eradi- 
 cate, 167; less harmful, 178; origin 
 of, 164 ; sprays for, 108 
 
 Weeds, injurious: black bindweed, 
 172; buttercup, 176; Canada this- 
 tle, 174 ; common bindweed, 172 ; 
 crab grass. 175; dandelion, 171; 
 foxtail, 176; green amaranth, 170; 
 old witch grass, 176; oxeye daisy, 
 174 ; pigweed, 170 ; plantain, 171 ; 
 prickly lettuce, 173 ; purslane. Kilt ; 
 quack grass, 175; ragweed, 173; 
 sorrel, 177; spotted spurge, 170; 
 spreading amaranth, ]<!); tumble- 
 weed, 170 ; wild carrot, 176 ; wild 
 mustard, 173 
 
 Windbreaks, 120 
 
 Winter annuals, 87 
 
 Woodlands, enemies of, 213 ; value 
 of, 212 
 
 Xenia, 268 
 Xerophytes, 125 
 Xerophytic hydrophytes, 127 
 
 Zero, upper, middle, and lower, 115
 
 ANNOUNCEMENTS
 
 BOOKS IN BOTANY 
 
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