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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 KELSON CLUTE
ALL RIGHTS RESERVED

913.1

GINN ANU 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 envu-onment 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
. * the matters discussed are fundamental to any system of cul-
S^ tivatuig 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
S^ public which, though no longer in school, takes an interest

^ 101 the fcultivation of plants in lawn, garden, and orchard.
>i\ Agronomy, as outlined in the following pages, is regarded
^^fi^as 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,

442842

vi AGRONOMY

and partly because city children are not brought much into
contact with farm animals. Animal husbandry may well be
tauglit as a separate course, and, if given in the semester fol-
lowing that m 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 framing plants, and the chief end of
the course will be missed if this book is used merely as a

PREFACE 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 mterest
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

PREFACE 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 sliould also be supplied with the catalogues of
reliable seedsmen and growers of nursery stock. These may
usually be liad 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

X AGRONOMY

sucli 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 X. CLUTE
Joliet, Illinois

CONTENTS

PAGE

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. iEolian
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.

CHAITER 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. Grafting 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 ti-ees. Transplanting
herbaceous perennials. Mulching and heeling in. Treatment of
woodlands. Enemies of the forest. Practical exercises.

CHAPTER 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.

CHAl'TER 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

Seventv-five Shrubs Useful for Planting 285

Fifteen Woody Vines Desirable for Arbors and Porches . 288
Fifty Desirable Herbaceous Perennials 289

INDEX 291

AGRONOMY

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 defined 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 um. The diiTerence between a
metal and a nonmetal, however, is not easily defined. A
metal is supposed to have the following properties : it must

1

2 AGRONOMY

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 212° 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 IN CHEMISTRY 3

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 platmum. 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 ferrtim. 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^,
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^O. In this two atoms of

Table of the More Common Chemical Elements

Name

Aluminum . .
Antimony (^slibium)

Argon

Arsenic ....
Barium . . . .
Bismuth . . . .

Boron

Bromine . . . .
Calcium . . . .
Carbon . . . .
Chlorine . . . .
Cobalt . . . .
Copper (cuprum)
Fluorine ....
Gold (aurum) . .
Hydrogen

Iodine

Iron (ferrum) .

Symbol

Al

Sb

A

As

Ba

Bi

B

Br

Ca

C

CI

Co

Cu

F

Au

H

I

Fe

Lead (plumhum) .
Lithium
Magnesium
Manganese
Mercury (Jiydraiujjjruin)
Nickel ....
Nitrogen
Oxygen ....
Phosphorus . .
Platinum .
Potassium (kalium)
Silicon ....
Silver (aryetilum)
Sodium (^natrium)
Sulphur ....
Tin (niannum)
Tungsten (icol/ram)
Zinc

Symbol

Pb

Li

Mg

Mn

Hg

Ni

N

O

P

Pt

K

Si

Ag

Na

S

Sn

W

Zn

4 AGRONOMY

hydrogen are joined to one of oxygen. When symbols in
parentliesis are followed by a number written below the line,
as Ca(NOg).,, it signifies that the elements and quantities in
parenthesis are to be multiplied by the number so written.
Calcium phosphate (Cag(PO^).^ would also be correctly
written CagP^O^.

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^). 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, suffocatmg, and highly inflammable gas. Again, when
carbon is burned in the air, as in ordmary wood and coal fires,
one atom of carbon unites with two of oxygen and forms a
colorless, suffocating gas known as carbon dioxide (CO^). In
a similar way sulphur may be burned to form sulphur dioxide
(SO.,). Calcium carbide, from which acetylene gas is produced,
is another union of carbon and is represented by the formula
CaC^. 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 m CHEMISTRY 6

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 connnon
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 mangau^ie ; m the second are oxygen, hydrogen, nitrogen,
chlorine, caPBhf phosphorus, sulphur, and silicon. Several of
these are not regarded as essential to plant growth, as is also
true of litliium, zmc, 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 AGRONOMY

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 (NaCl) 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^j^ plant, but
less abundantly than calcium, except in tHWB^s, 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 (CaCOg), and when carbon diox-
ide is driven off by burning, quicklime (CaO), which is used
in plastering, is left. Gypsum is calcium sulphate (CaSO^).

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^ie red and yellow colors to certain soils. Iron
is essentiaHBltplants. 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 AGROJfOMY

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 nmths of the water, and
about one half of the rocks and soil. It combines with a great
number of other elements, forinuig oxides, and is necessary
for all ordinary combustion and for the respiration of animals
and plants. With hydrogen and carbon it forms tlie carbo-
hydrates, of which the greater part of the plant body consists.
Iron and other metals bum 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 gunpomler, guncot-
ton, and nitroglycerin owe their effectivenesiRJPlhe 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 m CHEMISTRY 9

Chlorine (CI) 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 m 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^). 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 uncombined. Next 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
(SiOj), 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 shaj^ 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 (KAlSi30g),carnallite (KClMgC'US HgO), common salt (XaCl),
Epsom salts (MgSO^), copperas (FeSO^), nitric acid (HXOg).

6. Burn a piece of limestone to drive off the COg, 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 orduiary 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 tlie 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 mamly 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 cars'^ed 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

irom 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 weathenng 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

if^K"\'f^

III

Wm

rfc 71 .; ."*?#

/

^^SSsrf^"

m

Pl

»

^^Hlj^j

g^*r;-^^jrj*

m

.jd^i

K«^

1

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 m 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, Juliet, Illinois
A iX)rtion of the rock has been 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, ai-e active in dissolving

OKIGIN 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. Ilollister 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 nons 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 hundi'ed feet thick may have been removed for every

II. L. Uollister 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 U. L. HoUister Laud 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, the}^ 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

Photosraph l>yTl. I,. ITollietcr Land Co.

Fig, 7. A mouutaiuuus regicjii 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

Tlie 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 m 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 wliicli 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

Photosraph liy II. L. Ilollisfer 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 metamorphie 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.

IL Sedimextary, or Aqueous.

A. Inorganic.

1. Argillaceous — shale (formed from clay).

2. Silicious.

a. Sandstone (formed from sand).

b. Conglomerate (formed from pebbles).

c. Breccias (formed from irregular fragments).

3. Chemical — bog iron, rock salt, gypsum.

B. Organic.

1. Calcareous — limestone (formed from animal remains).

2. Carbonaceous — soft coals (formed from 2)lant8).

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 theii' 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 sj^ecimens 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."

CHAPTER III

TYPES OF SOILS

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.

^Nii2Bi9^3HEHHBHB8HiHIHtB8BB

■"^

^^^^^^^^^HC^'

-•"1

■^^P"w-

f"

' '-^ S ''' ^k^^^'^l^^^M

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, arid alluvial.

25

26

AGRONOMY

Photograph from Aiiiencau stetl and 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 by a
combination of both. In limestone regions the soluble part
of the rock may be carried a\\ ay 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 origmal rock from which little has been car-
ried away by water, as in many soils derived from granite rocks.

Fig. 12. A movina; saiul dune

Pliotograph by A. li 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 rams 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

AGKONOMY

^olian soils. These have been transported by wind. Sand
dunes are famiUar 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.

Plioto-rapli by A. B. Kliigh

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.

CoUuvial 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
have been transported
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

Fig. 14. A ridge of glacial debris that has
been sorted by running water

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.
Humus, 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 tlie
soil. It is a black,
loose substance
usually abundant
on the forest floor
and is an indispen-
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,

Fig. 15.

Section of an abandoned quarry partly
filled with water

The dark deposit at the top of the exposure is peat,

tlie light material below is marl, beneath this is the

mautle rock which merges into the bed rock

TYPES OF SOILS 31

and a cubic foot of it weighs from seventy-five to eiglity
pounds. Cla}^ 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 drymg 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 AGKONOMY

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. Keds 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, llagerstown
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 tlu-ive 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

I

accomplished by flooding with water. In ushig 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 hmder 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 (^Andropo(/on^ 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 hidication of a sour soil.

A test for acid soils. To discover whether a given soil is
acid or not, make it into a thin mortar with water and test
with blue litmus paper, or inclose a piece of the paper in a ball

Fkj. 17. a pitcher plant (Sarraceniu), a char-
acteristic plant of acid soils

36 AGRONOMY

of the moist soil for a few minutes. If the paper turns red, 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

I

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 :

Subsoil

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,
formmg 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 Jloceulated, or bound together in small groups
called soil cnanbs. 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 AGRONOMY

twice its 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 wliich, 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 vajwr (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 solL 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 wat^r to the boiling point. The same heat
would raise the temperature of a layer of soil, lialf an inch
thick, nearly 90 degrees.

Variations in temperature. Tlie 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-
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

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

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
I and add 32 (C. X | + 32 = F.). To change Fahrenheit to

44

AGRONOMY

centigratle, subtract 32 and multiply by | (F. — 32 x | = C).
Below zero centigrade one multiplies by | and subtracts the
product from 32, if it is not more than 32. If more, the differ-
ence between this and 32 mdicates the degrees below zero
Fahrenheit. If the temperatures below zero Fahrenheit are to
be changed to centigrade, atld 32 and multiply by |. The
result will be degrees below zero centigrade. In all cases

Fig. 20. ^Meau 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 underetood 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,

CONDITIONS AFFECTING SOIL FERTILITY 45

snow, hail, or dew, and varies with the locahty and season,
being usually greatest near coasts where moisture-laden winds
blow inland, and least where the prevailing wmds 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, FOK FOUU YkARS
ILLUSTRATING VARIATIONS THAT MAY OCCUR

Month

January . . .

February . . .

March . . . .

April . . . ,

May . . . ,

June . . . .

July . . . .

August . . ,

September . ,

October . . .

November . ,

December . ,

^ Annual . .

1908

.77
2.66
4.33
3.32
6.95
1.30
3.79
3.80
1.32

.82
2.77
1.30

33.13

1909

1.12

3.38
1..56
6.60
3.46
•3.80
1.69
2.95
3.09
1.68
4.55
3.50

37.38

1910

2.52
2.45

.24
3.81
4.90

.81
1.46
3.17
2.75
1.68

.62
1.12

25.53

1911

1.58
1.62
1.39
4.45
3.65
4.65
2.46
4.54
12.27
4.18
2.87
1.91

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 yeare 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 rain.
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. HoUister Laud Co.

Fig. 21. Sagebrush on the Western plains

The rainfall is insufficient for cultivated crops, but when irrigated tlie 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 FERTILITY 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 m
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

48

AGRONOMY

swamps, or perhaps it may come to the surface, f ormmg springs.
In certain seasons, or in places wliere 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 liills 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.

Plioto^'raph by H. L. IloUister Land Co.

Fig. 23. A check gate in an irrigation ditch

This holds back the water and causes it to flow
through smaller channels into the fields

AGRONOMY

Photograph by Mark Bennitt

Fig. 24. A field of wheat in tlie dry-farming region

Fig. 25. "Irrigating a fig orcliard in California

'o^^'^o " "o

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.

1 \ ^ ^ 1

Total 1911 45.57

Total 1910 25.53

12 in.

A

1

v.4y

•s. 35.

W

11 In.

10 in.

9 in.

Sin.

Tin.

I
/

Gin.

;
1

5 in.

1

4 in.

^

V

'\

/

/

,

3 in.

//

/ ^.,

'\\

\

/

/

^,^

2 in.

/

^

N^

/' /

r

^

7

^

\\

^

^v^

1 in.

/^

A~

\ >

/

\

y

/

\

\

1911
_1910

/yan.

Feb.

Mar.

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.

Gin.

/

\

5 in.

/

\

4 in.

/

\

J

\^

Sin.

/

\,

/

\

^

\

/

N

2 in.

/

\

\

/

\

/

1 in.

/

\

/

\

/

s

/Uan.

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.

I

CO:^^DITIONS AFFECTING SOIL FERTILITY 63

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. When 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 nm 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.

64 AGKONOMY

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 bullis 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. ISIake 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 V
Are there any lands that open ditches would serve better? any land
where irrigation could be practiced to advantage ?

References

Fanners' 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

Fig. 28. Pteridgphytes. A colony of walking
ferns (Camptosorus)

minimum. Between these extremes all sorts of vegetable forms
occur. Herbs, shrubs, vines, and trees vie with one another for

55

66

AGRONOMY

---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 Thallophytes^ 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 BryophyteB, which include the mosses and liverworts.
They are somewhat more liighly organ-
ized than the thallophytes, but are like
them in lacking true leaves, flowers,
and fruits. The Pteridophyfes 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 Sj^er-
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

3- — cell w

Fig. 29. An epidermal hair

from the bi^acken showing

the cells

cell w, cell wall ; cyto, cyto-
plasm; uu, 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 m 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, niultiplying, 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 mmute 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 cdXledi 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
mto two equal parts and then the division extends outward

to the surrounduig 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

f

^^^^-

"^aP^^^^I

M

1

■

■1

-I ' „■* ^ ^

n

mm

i

^

|te-^SWI|LMfti<^^^?i

foH

IMIII

11

I^K

HnH

V^K^^HI

H

1

I

H

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 tliis way filled
drains three hvmdred 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

GO

AGRONOMY

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 lily like
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 cylmder has a series of small tubes, or ducts, running
lengthwise tlu-ough 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 of the
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 wrm-
kles are well shown in the roots of the skunk cabbage or
the ii'is.

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 liairs growing from

the epidermis

62

AGRONOMY

Root hairs. Roots do not absorb through all parts of theu*
surface, as is commonly supposed. The waterproof epidermis
prevents the passage of moisture tlirough 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 hairs 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 hau's with which to absorb. On
seedlings that have been
sprouted in moist air the
root hairs appear like a
fme 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. 3G. A single root hair projecting
from an epidermal cell. (Much enlarged)

THE OEGANIZATION OF THE PLAJ^T 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 parclmtient 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.

G4

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 ; m 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 corm 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 okganizatio:n^ 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 stems this soon gives place to the outer hark,
which serves the same purpose. The central cylinder is made

Fig. 39. Structure of steins
o, basswood, a dicotyledon ; h, coi"n, 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 fihrovasvidar 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; il, duets; to,

wood ; p, pith

Fig. 41. A monocotyledon
bundle. (Much enlarged)

ph, phloem ; d, ducts ;
10, 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
circle. The sunflower or any of our
forest trees illustrates this type. The
dicotyledons are further distinguished
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 ^vood and its tubes are ducts; the part out-
side the cambium is bast, or phloem, and its tubes are called

Fig. 42. Cross section
of young dicotyledon
stem showing the circle
of fibrovascular bundles

Fig. 43. Part of a cross section of year-
old basswood twig

6, 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

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

tion

Fig. 47. Twig of horse-
chestnut, more than
twenty years old, show-
ing the circular scars
•which mark the posi-
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 pomts 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

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. 50. Accessory buds

of the butternut

(Juglans)

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,
Jiotver 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 {^sculus)

Fig. 53. A leaf of geranium

lam, lamina, or blade ; pet, petiole ;
stip, 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 OEGANIZATION OF THE PLANT

71

from the soil. The points upon the stem where leaves originate
are called nodes, and the spaces between are intemodes. 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 ear like

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 hranched ; the right, palmately hranched

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 jomed together and are more or

JL

Fig. 58. Ej)idermal cells and stoinata from the leaf of the ainaryllis, 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 spongy parenehyma. The openings

--■int
-sto

Fig. 59. Section through
the leaf of the beech

ep, epidermis; pal, palisade
tissue ; sp, spongy paren-
chyma ; hit, intercellular
spaces ; sto, stoniata

Fig. 60. Section through the leaf
of the rubber plant

cri, cuticle; ep, epidermis; lo, water-
storage tissue ; pal, palisade tissue ; up,
spongy parenchyma ; int, intercellular
spaces; sto, stomata

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 AGRONOMY

leaf and the outer air, therefore, the epidermis contains great
multitudes of tiny openings called stomata (singular, stoma),
which connect with the mtercellular 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 diminish the
size of the opening. The stomata are exceedingly minute.

THE ORGANIZATION OF THE PLANT

75

but they make up iu 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 CgH^.^Og, but this
is soon turned to starch, a more stable form of plant food, with
the formula CgHj^O^. 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. Stai'ch grains in
the cells of a potato

76

AGRONOMY

\

•^.v

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 givmg off carbon dioxide, but, unlike
animals, they have the additional process of photosynthesis,
m which carbon dioxide is taken in and oxygen released.

The two processes
differ also in other
respects. Respiration
occurs in every living
cell, in roots as well as
in stems and leaves,
and goes on continu-
ally, while photosyn-
thesis goes on only
in the green cells in
sunliglit.

The grape sugar
formed in the leaves
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 agam. 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

m

Fig. 64. Cells of the carrot with crystals of
carotin, which give the root its orange color

THE ORGANIZATION OF THE PLANT 77

again turned to starch by tlie leucoplasts or ami/loplasts, small
bodies allied to the chloroplasts. The leucoplasts 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

n

Fig. G5. Cells from a dahlia root, showing crystals of iuuliii, 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

AGRONOMY

a bushel of leaves picked from a tree in autumn are noticeably
heavier than the ashes from a bushel of leaves picked from
the same tree in spring. The growth of the stem and the

Fig. 66. Cells from the rind of au 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
the same age as the leaves.

The flower. When the season for
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

Sep

Fig. 07. Typical flower of
the houseleek

pet, petals; sta, stamens; car,
carpels ; sep, sepals

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 withm it are the ovules, des-
tined to ripen mto 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 tuhe 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 st-em, 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. 69. 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
wind, birds, insects,

A plant in which the monocotyledon number and other affcncics. 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

Fig. 70. Trillium

THE ORGANIZATION OF THE PLANT

81

fr

Fig. 71. A group of wind-pollinated flowers

Those on the loft are staminate ; those on the right are of two kinds, the easily
recognized staminate and the small starlike jjistillate near the tijjs 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

82

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 tlie stamens and pistils are so arranged that
pollination may be effected by pollen
from their own stamens. This is called
self or close pollination. Usually, liow-
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 contams
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 cu-cle, 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, y^^*s^ -^ ^^ ^,,^»,^

and a pistil composed ,(^I^ /Fffi^v {^,^\

ottljree carpel.; the ^^ (^®.) 1^®^>

Illy has three sepals, ^-^^^-^ >^^^ "^w^

three petals, six Sta- Fig. 73. Plans of three typical flowers

mens and a three- '^'^^ ^^^^ * monocotyledon, the other two repre-
, , • , •! rf-11 senting four-parted and five-parted dicotyledons

parted pistu. 1 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, nuist 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 tuiy pistils,

Fig. 74. Fruits modified for wind distribution

A, ironwood; B, 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

eacli 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, buttonwood; B, cat-tail; C, trumpet creeper;
1), catalpa ; E, dandelion ; F, clematis ; <l, olean-
der; //, actiuomeris ; /.anemone; ./, milkweed

86

AGRONOMY

-h — tCS

Fig. 76. External view of
lima bean

mic, micropyle ; hll, hilum ;
tes, testa

catcli 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 Idliim, 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 unvaryhig is the occurrence of either one
or two cotyledons in each kmd 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 monocotyledotis, 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.

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

Life cycle of plants. The life cycle of some plants is com-
pleted ill a single season. They spring up, flower, produce
.^„„ their seeds, and disappear within the interval
■plu of a few weeks or months. On the other
"^^'^ hand, 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
caw,cauiicie;;)/M, (jjvided into three groups — annuals, biennials,

plumule; co^.eoty- . .

ledon ; en<7, eiuio- and perennials. An annual is a plant that

sperm, es, es a QQjj^plg^gg j^g J^fg cycle within /^f^'B^- ■ -coi

a year. This may occur during a single grow- ( \\4|-«.-catt
ing season, as in the radish, when it is called \^^^..end
a summer annual ; or the plant may spring up j-j^. go. Embryo
in autumn, live through the winter, and fruit of four-o'clock
in the spring, as in some varieties of wheat, ^J^J^^ ''^caiiSe •
thus becoming a tvinter annual. Several of end, endosperm
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

f differ from annuals in
end / \^M that they require two
cot ^M|r-y^ growing seasons to
^» / J complete the round of
^ I their existence. The
V "^^ first year they store up
N^^^^, J^ much food, which they
v/ use the second year in
Fig. 81. Grain of corn producing seeds. Car-

The fruit and seed of a monocotyledon, end, endo- rotS, salsify, and bects
sperm ; cot, cotyledon ; j^ln, plumule ; cau, caulicle .

are biennials. In re-
gions with a long growing season the line dividing an-
nuals from biennials breaks down more or less completely.

88

AGRONOMY

Fig. 82. The showy lady 's-slipper (Cj/pnpedtum specfaWte)
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, excludmg much of its moisture,
goes into a resting condition. It is likely that this season of
dormancy was originally m response to a change in the season,
for in northern regions it occurs at the beginnmg 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 ta 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 gi-ound, ripen theii" 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 m autumn. Possibly half the species of
crocus produce their flowers in autumn, and the witch-hazel is
a well-known slirub 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 withholdmg 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,
mterwoven through the vegetable kingdom, bhid 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
dqes 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.
Genera (singular, yenu*^ are groups of related species. Red

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 2k 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 Leguminosre, 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 Rosales.

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 AGRONOMY

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 alha^ "white "; rubra, "red "; and wMZ</are," 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 TnfoUum inearnatum. 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 m 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 microscoj)e. 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 flowerj)ot 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 imge 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 jiortion 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 jieach.

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 tlie dicotyledons in as
many diiferent 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 hyjwgynous or
epigynous flowers : apple, orange, banana, i)ear, 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
com. 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 hydi-ogen 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 m other plants.
It is as if each plant exercised a conscious selection. Such a
condition, however, is to be explamed on purely physical
grounds by what is known as selective absorption. When minute
quantities of any mmeral 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-lovhig 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 ffuttation, 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 sj)ot 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 ahke, 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. Certam 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 hi 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. Weigh 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

I'niversity of Illiuois

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 widenmg 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,

Photofjraph 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 lb. to the acre, or
dried blood at the rate of 700 lb. to the acre.

Plot 2. Potash as muriate of potash at the rate of 80 lb. to the acre, or
potassium sulphate at the rate of 200 lb. to the acre.

Plot 3. Phosi>horns as acid phosphate at the rate of 320 lb. to the acre,
or bone meal at the rate of 200 lb. 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 G. 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

FERTILIZEKS 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 ariimonia
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 ram 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

FERTILIZEKS 107

of nitrogen to plants. Practically all the nitrogen used by
plants comes from the humus m 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 livmg 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^OH), and at this
point a new group of bacteria, known as Nitrosococcris, turns

108

AGRONOMY

the ammonium hydroxide into nitrous acid and hydrogen by the
addition of an atom of oxygen (NH^OH + O = HNO^, + H^).
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. Certam 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 (Psew-
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 alga? 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 leorume

FEETILIZERS

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 mycorrJiizas, 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
{Sarcodes sanguinea)

A saprophytic heathwort

(alMed to the Indian pipe,

Monotropa uniflora) from

the Pacific Coast region

110 AGRONOMY

and wlien this is missing it cannot thrive. In some cases,
however, the form of bacteria associated with one species may
be gradually induced to form partnersliips 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, algai, 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 hi 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? BuUetins

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 algae 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 AGRONOMY

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 AGEONOMY

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 deiv 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

TEMPERATURE, LIGHT, AND MOISTURE 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 pomt. 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
weatlier 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, corms, 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 retainmg 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

Fig. 87. Epidermal hairs and scales. (Much enlarged)

^.mullein; Z?, geranium ; C, deutzia; Z), hollyhock; £, dame's violet;
F, shepherdia

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." Wmters 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. Mulching is simply adding to
the cover of dead leaves with which the ground is naturally
protected in winter. Any loose litter Ls 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 wami.

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

TEMPEKATURE, LIGHT, AND MOISTURE 121

is greater than the roots can supply, and the drooping of the
fohage 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 specunens 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^ges 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 aliade plants. F'erns and many of the plants that
bloom in early sprmg 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.

I'lioto^rapli 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 inclmed 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 during 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 m 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

Pig. 89. Yucca glauca, a xero-
phyte of the Western plains

126

AGRONOMY

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

TEMPEKATURE, LIGHT, AND MOISTURE 127

characterized by weak stems, thin epidermis, few roots, Httle
conducting tissue, and large air spaces withhi stems and leaves,
all of which are necessary to fit them to their envuonment.
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 m water. These are sometimes known as

A group of hydrophytes, showing the zonation that often occurs

In the water, spatter-dock {X^>phar) and algae ; on the muddy shore, a belt 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 bur 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 sheltei-ed 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, "'Les.sons 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 uito 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. ]\Iany 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,

CtlEKAXTS

KlUUtARB

ASPAKAGl'S

-Pf.tiennial-

OxiONS - 2 rows

-Parsnips-
— 4-ro'ws —

-Carrots-
— 3 rows —

-Salsify-
— 3 rows—

-Kohl Kaiu-

3 rows

Peas

-3 double rows-

-^ Beets-

-^ — 2 rows -

w

; — SriNAcii —

I 3 rows

I

-Onion Sets-
2 rows

-Radishes-
— 2 rows —

-Lettcce-
2 rows

131

-CORN-

-witb-

-TURNIPS or-

— Squash —

-Pole Beans-
3 rows

-TOMATOES-

— 4 rows —

-Bush Beans-
3 rows

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 com, cucumbers,
tomatoes, and pole beans, are planted in lulls, 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.

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a^

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Lawn /^

Fig. 96. Four plans for school gardens on vacant lots
188

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 germmation of most seeds, and for this
reason, as well as to prevent the drymg 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 seedlmgs. 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, fruitmg 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 freezmg. 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 tlu-ee 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 tlu-ough 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 hate 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

Fig. 98.

AhandyreceptiiLk im .^
and other small things

uud.-., labuLs,

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 witli 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
bemg good, it is customary to test them before planting. A

A B

Ttffi. 9d. A seed tester, consisting of two soup plates, some sand, and a
i? piece of cloth

I

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 clotlis 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 hi 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-
mg 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

140

AGRONOMY

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

GARDEN 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 m 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 m the "habit of allowing
cabbage and tomato plants to wilt before F^«- 102. A sheared

r .,1.1, , 1 . plant

resettmg, 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 desu-es
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 agaui 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. Thinnmg
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

GAEDEN 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

AGROKOMY

^S

ai/a.A eaet-

Fk;. 104. Proper niL'tlKul of writing labels

chance of confusing the two words in deciphering them. Labels
should be so placed as to stand at the beginning of tlie rows
with the writing facing away from the seeds or plants they refer

to. Unless this
rule is consist-
ently followed,
when several

kinds are planted m 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

145

Name

Beans, bush
Beans, pole
Beets . .
Carrot . .
Chard, Swiss
Corn . . .
Cress . .
Cucumber .
Kohl-rabi .
Lettuce .
Melons . .
Mustard
Okra . .
Onion seed
Parsley , .
Parsnip . .
Peas . . .
Potato . .
Radish . .
Salsify . .
Spinach . .
Squash . .
Turnip . .

I

How

PLANTED

drills

hills

drills

drills

drills

hills

drills

hills

drills

drills

hills

drills

drills

drills

drills

drills

drills

hills

drills

drills

drills

hills

drills

Amount

quart

quart

ounce

ounce

ounce

quart

ounce

ounce

ounce

ounce

ounce

ounce

ounce

ounce

ounce

ounce

quart

peck

ounce

ounce

ounce

ounce

ounce

Will seed

Distances apart
OF Rows

150 ft.
125 hills

50 hills
100 ft.

50 ft.
125 hills
100 ft.

60 hills
200 ft.
200 ft.

60 hills

80 ft.

50 ft.
125 ft.
100 ft.
250 ft.
150 ft.
100 hills
125 ft.

75 ft.
100 ft.

25 hills
150 ft.

18 in.

4 ft.

12 to 18 in.
12 to 18 in.
18 to 20 in.
2^ to 4 ft.

1 ft.

4 or 5 ft.
18 to 24 in.
12 in.

5 or 6 ft.
12 in.

4 ft.

1 ft. or less
18 in.
18 in.

18 in. or more
21 ft.
12 in.
15 in.
12 in.

4 to 9 ft.
12 in.

Vegetables usually Transplanted

Name

How
planted

Amount

Will make

Distances apakt
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

/-.

f

Tf:'''^''

1

!

i

■''I.

-i^-M.

,,:.:.

/ .-J 3

1

I

1 ,J

Fig. 100. 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.

GARDEN 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 jiart 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 plauj 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 («) 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. IMake 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 httle to change. The range of
temperature, the make-up of the air, the amount and time
of ramfall, and the amount of sunhght 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 rammmg 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 stii-ring 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 subsoiling 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 H. 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 Ijas 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 com 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 kmd, 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

I'll I i| n . ^ 1 \llui & Co , Philadelphia

Fig. 110. Cultivating witii a wheel hoe

This imijlement has several attachments and may also be used as a rake, scarifier,

or hght 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 ordmarily extends would
be turned over and very thoroughly pulverized. In addition,
the bun'ows 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 onr 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 smartweed 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 diy up and new forms of

156 AGRONOMY

vegetation overpower those which grew in the water, cUffs
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 gohig 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' 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,
clirysanthemums, 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,

Photojfraph by Lord & IJuriiham, Kew York

Tig. 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

wliich 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 m 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
cold, and on very cold
nights the glass should be
covered by mats, old car-
pets, or a layer of straw.
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 tlirough 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.

Fig. 112.

A hotbed showing
of construction

the details

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 liaH
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 desii'ed 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

FORCIKG 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 growmg 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 jilant from seeds,
such as melon.

5. Try forcing some wild plant at the beginning of winter. Etherize
another plant of the same kind and com[)are 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,

Photo^'raph from AiTierican Stetl anil Wire Co.

Fig. 113. Spraying a field of young grain witli iron sulpliate to
eradicate mustard and otlier weeds

it is a weed. In some localities the worst Aveeds 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. Graiiifiekl 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

AGRONOMY

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-tiuoted
maxim, " One year's seeds, seven years' weeds."

Photograph from American Steel and Wire Co.

Fig. 115. A grainfleld 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 tlirive 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

167

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.

Plioto^'rapli 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

AGRONOMY

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 Imiing
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

Fiioto^rapk 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.

l'liotoj;rai)h 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 (^Amaranthua hlitoides). 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 QAmaranthus hyhridus). 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 extermmated.

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 wliitened 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 tragus'). This plant is ui 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 anotlier 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 t'l

Fig. 120. A tangle of the common bindweed

?teel aud 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 origmate new buds and produce a dozen or more
plants where but one was originally.

Plantain (Plantago sp.). Tliree 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. lanccolata)^
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
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.

Photograph from American Steel and Wire Co.

Fig. 121. A common wild lettuce related
to the prickly lettuce

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
artemisicefoUd). 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
of hay fever.

Wild mustard (Bras-
sica arvends). 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 troin American Steel and Wire Co.

Fig. 122. Ragweed, a common weed regarded
as the cause of hay fever

174

AGRONOMY

Oxeye daisy (^Chrysanthemum leucanthemtwi). 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-
heckia hirta), also
common in fields
and meadows, is a
native species.

Canada thistle
(Cnious arvensiii).
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

Photograph from American Steel and Wire Co.

Fig. 123. A plant of wild mustard
This species is especially harmful in grainfields

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 kmds 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.

WEEDS 175

Quack grass (^Agropyrum 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

AGKONOMY

Foxtail (^Setaria glauca). 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 (I^an-
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 Ainericaii Steel and Wire Co. ButtCrCUD ( HdnUTl-

FiG. 125. Youns plant of the Canada thistle, -, • \ o i

°^ ^ - ' cuius acris). 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-
sella). 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
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.

t

S

1;^-:^

,;-' V"'- >-'^-i'

■-' - V:.-..^i

Fig. 126. Wild carrot on a neglected lawn

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

(JLepidium), chickweed (^Stellaria), knotgrass (^Polygonum),
burdock (^Arctiwn), evening primrose (Oenothera), sneezeweed
(Helenium'), bugloss (Eehium), bouncing Bet (Saponaria'),
toadflax (Linaria), smartweed (Polygonum), dog fennel (^An-
tJiemis), and Jimson weed (^Datura). These may be looked up
in any botanical manual. A large number of other plants,
such as yarrow (^Achillea) and sheep sorrel (^Oxalis), come

>

• " -^ , *• •

•

*

i

' ""^-:%

^^A

\^

^T^^*'

WW^,

Ml i'.*

Photograph from Aniencuu Stetl 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 {Hieracium 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 parvijlora, 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,

-

fr

^^ti

IP»|/^

- ••'^ 1

r Jm'^

fg

-.■iJWCT

^8

r

Fig. 129.

Photograph from AmericaD Steel and Wire Co.

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 (^A(/ro8temma githago^ owes its common name to the
fact that it is nearly always found in grainfields, where its
seeds have l^een carried with the grain.

PRACTICAL EXERCISES

1. Make a list of the weeds known to grow in your locality.

2. AVliat 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 with 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. AVeeds and how to kill them.
188. Weeds used as Medicines.

Bureau of Plant Industry

8.3. The Vitality of Buried Seeds.
89. Wild Medicinal Plants of the United States.
107. American Root 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 asez-
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 ls 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 stolo7i 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

I

Fig. 131. Base of a sunflower stem showin:
offsets for reproducing the plant

PROPAGATION

183

favorable season. The potato and artichoke are good examples.
RooUtocks 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
" 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

Fig. 133. A corm of gla-
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,

^/

'i

,v

Fig. 134. A species of sunflower {TIelianthus 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

PROPAGATION

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, cluysanthemums, 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
wliich has struck root

From Bergen and Caldwell's
" Practical Botany "

186

AGRONOMY

cuttings are merely stuck in moist soil in a shady place.
Several forms of softwood cuttings have distinctive names.
heaf 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. Root 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 ui 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

AGRONOMY

desired to multiply. Besides the simple cuttings of three or
more joints, there are dngle eye cuttinyB 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 cuttinga
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 ait)und 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. 139. 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 twme 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
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, Jlute, or annular budding a
piece of bark extending part way around the stock is removed

Fig. 140. Three stages in the operation of budding
In the figure on the right the work has been 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 wliip 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

PKOPAGATION

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
jomed. 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

AGRONOMY

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. Tliis 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
Even fruits have been grafted
when half grown. The grafting of soft-wooded plants is most
successful when carried on 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

than for hard-wooded plants.

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 Imseed
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 AGKONOMY

PRACTICAL EXERCISES

1. From pictures, from dried specimens, and from jjlants 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 tyi>es 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 exi)eriment 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 ojjeration 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

1.57. 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 surroundmgs 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, liow-
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

198

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 la^vn 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

1

-4

|f

< ' . i

Fig. 144. Hickory Creek at Joliet, Illinois

An illustration of the way Nature arranges her
trees and shrubs

DECORATIVE 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

AGRONOMY

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 plantmg, such things may be allowed,
but they are out of place on the home grounds. The kettles.

iB^^^^^^^^^I

■

Ml

m

^J|::|tjff

M i

v., ■■;''§

A'

Photograph by Waii;iier I'ark Conservatories, Sidney, Ohio

Fig. 140. 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 PLAls^TIKG 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 lieavy 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 slmibs and
herbaceous plants should be arranged in u-regular 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 maintamed.
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

DECORATIVE PLANTING

203

Fig. 149. Slirubs in the curves of
a drive

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
another 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 pubhc.

Shrubs for winter effects. The best-planted grounds are not
designed solely for their beauty in summer. A proper selection
of slu-ubbery 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
gum, and Lombardy poplar. Numerous shrubs produce at-
tractive fruits that persist far into the winter, supplymg 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. Slirubs and trees are among
tlie 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

n

Fig. 151. Method of planting a corner lot,
to prevent paths being made across it

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 witli
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-
thig, they too should be planted in the flower garden and not
in the border. Among the better-known perennials are the
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. Jordau

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 plantmg 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 PLAi^TING 207

should cany 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 vitte 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 m 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 remam 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 or
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.

DECOEATIVE 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 ov 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 CoiiBervatories, 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

AGRONOMY

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 tlie 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 t)y Wagner Park Consenatories, Sidney, Ohio

¥iQ. 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 PLAITTING 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-increasingr demand for
wood in various industries has greatly dimmished 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 remamder 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 ordmary 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 preventmg 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 of
^ 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 nuilch 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 similar 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 iilants 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, liealtliy, 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. IIoIliBter 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

21T

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 tlie
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 pruninjj;. The tree

lias been allowed to grow so liigli 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 branches
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 heeided 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 Ulacs, 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 11. L. Hollister 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 hlaekherry 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. 100. Fruit spurs on

the second-year wood of

cherry which may bear

several crops

PRUNING

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. IGl. Two-year-old twig of
the peach showing three pedi-
cels, or stalks, that produced
fruit and will not bear again

Photo^'raph by U. L. HoUister Land Co.

Fig. 162. Peaches growing on wood of the preceding year

PhotoL'raph by H. L. IIoHister 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

I'liulograpL by II. L. IloUiuter Laud Co.

Fig. 164. Rome 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. ]\Iany 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. IlolUster 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

PRUNING

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 II. L. Uollieter 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. Ilollistcr Land Co.

Fig. 167. Young apple orchard in the Northwest

The darker speoimens 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 puttuig 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 V Make suggestions for improvement.

2. If there are no trees in the school garden to be i)runed, 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 iu the neighborhood that have been pol-
larded, visit them for study.

5. Try the eifect 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 jilants 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, " Manual of Gardenhig."
Fernow, "The Care of Trees."

Farmer^ 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 gettmg their food ready-
made from other organisms. In nourishing themselves they
tear down the tissues of the specimen upon which they liave
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 mto
parasites and saprophytes. Parasites feed upon living thmgs,
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 witli 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.

.1

f

'^

\

i

>fF

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 shrivel 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
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. 171. Mildew of peaches
From Dugarar's " Fungous Diseases of Plants "

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

\.

X

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

AGllONOMY

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 Dusraar's " Fungous Diseases of Plants "

harbor some form of mildew. The damping-off fungus wliich
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 famil^^
Their spores germmate 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 hmited number of hosts. One
of the most remarkable features of their hfe 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. 170. 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 livmg 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

I'lG, 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 vv^hich 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 uSes 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 remams 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
strauied 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 boilmg

-mm

I'liotograph 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 boilbig. This
mixture does not keep and should be used as soon as made.
The wash may also be made by taking double tlie quantity
of lime, slaking it with boiling water, and adding tlie sulphur
while still hot ; or the heat developed by the lime in slakmg
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 tlie 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 sjiots, 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 api>ear to the unaided eye like small black si)ecks) and examine
with the microscof)e. 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 sjjraying, 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.

2.31. Spraying for Cucumber and Melon Wilt.

24.3. 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 Impoilance.

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 liave 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 larvcBy feed voraciously until they reach maturity, mcreas-
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 mjured
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
mjurious to crops. Some of the more harmful insects are
mentioned in this book. ]\Iany 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-
times 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 Avork 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 ruinmg 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 codliii 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 larva? 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 larvsB and the
mature insects. Usually the plants are soon

killed if they are not protected. Hand pick-
A potato beetle . •' . • i r» . ,

mg and spray mg with Paris green or other

poisons will keep the pest within bounds.

May beetles. The larvae of the iNIay 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.

mSECT 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, wmged 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 carrymg some of tliem 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 ^ .g,

have an exceedingly disagreeable odor and ^ squash bu"-
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.

Mealy bug. 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 tliis 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 ivhite 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

riiotograph byBateniaa Mauuiaetiirm^ 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 had 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 AGKONOMY

Remedies against sucking insects. Poisonous sprays have
no effect upon insects whicli 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

iiaigBmtmmmii^^

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

AGROXOMY

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 dragon fiy, 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 ladybng, 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
fiies which deposit their eggs in
the larvcB of other insects. Some
are equipped with long oviposi-
toi-s, by means of which they are
able to reach the larvse of boring species, deep in the trunks
of trees. When the eggs hatch, the young worms live upon

Fig. 186. One of the larger ich-
neumon flies. (About natural size)

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 liave 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 larvse 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, ladybug.s,
ichneumon flies, ant lions, and other insects that prey upon harmful
species.

References

Bailey, "Manual of Gardening."
Fernow, "Care of Trees."

Farmer^ 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 flowers
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 otherv\nse might be expended in

Photograph by U. L. UoUiBter Laud 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

258

PLANT BREEDING

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
brand led 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 geva-
iiiuin sport, show-
ing one truss of
flowei's growing out
of anotlier

260

AGRONOMY

breeding is found in the seeds, however. By 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
Avas 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
nature of things the plants of a region are
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 tlie parts of tlie flower turned
to leaves

Fig. 100. Colum-
bine flower with
parts turned to
leaves

PLANT BREEDING 261

the normal plants, it may take jjossession of the field and ex-
clude the others. Wlien a variation in a plant makes it very
different from the original, it is commonly known as a sport,
or mutation. 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
watchmg 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
feni, 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.

Fig,

Photograph by W. A. Terry

191. Two leaf sports from the comuion
Christmas fern (Polyntichum)

PLANT BREEDING 263

the resulting seeds thus havmg the characteristics of two dif-
ferent strains. The plants from such seeds are called crosses^
or hyhrids. 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
contam 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 AGRONOMY

pollinating agencies. In pollinating the flower the ii|)e 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. 1j>2. Lungitudinal section of all plants that bear both kinds
flower and another prepared for ^ . ., „

jjj tj or organs m the same nower

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 ISIendel, 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 thbd
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
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

Fig. 193. Diagram to illu.sti*ate Mendel's law

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,

Photosrapli 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 jjlant, 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
• number was 20 with only one plant show-
ing it. The average was 15, twelve heads
possessing this number. The same data
can be expressed by a graph, similar to
the one on page 52, in which the squares
may represent the number of parts in one
direction and the number of specimens
in the other. Express your work by both
methods.

2. Visit any considerable area of one
crop, wild or cultivated, and select the speci-
mens you would breed from if you desired
to get (rt) larger flowers, (/>) more vigorous
plants, (c) deeper color, (J) more abundant
fruit, or (e) broader leaves.

3. Visit any patch of flowers in full
bloom and search for variations in color,
size, and number of parts in the flower.

4. In a row of young seedlings select p,^_ ^q;^ Variation iu the
those that are (a) most vigorous, (b) weak- j-ay flowers of sunflower
est, (c) deepest in color, (r7) 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 cuWeaved maple, Camperdown elm, weeping
mulberry, single-leaved mountain ash, single-leaved locust, iiectarine,
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.

/o

II

12

ruj

13

tnj 1

Hi-

mj III

15

iw mi II

16

IW IW

17

MJ II

18

IW

19

II

20

1

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 exj)eriment. 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^ Bulletin

334. Plant Breeding on the Farm.

Bureau of Plant Industry

16.5. The Application of the Principles of Heredity to Plant Breeding.
1()7. 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 man.y 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 unchangmg 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 with 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 ORIGm 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 contmue 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 bum 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 n-umber
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, smce 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 accunuilated, 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 Danvinian 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 Darwmian theory. While the
mam 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 certam 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 Draha vema. 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 ?

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 £is 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 attractmg
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 heet 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 \\\e field ov sugar
heet 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
mornmg-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 jNIediterranean
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. IVIany 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 m 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

OUR 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 ivonderherry, 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 encumber 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 Indian com^
all the grasses cultivated for food are natives of the Old
World. The list includes wheat, oats, harley, 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 bemg 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 hlooming, 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 nudiflora) : 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 arbuiifolia) : 3-8 feet ; pinkish ; early summer.

Cinquefoil, shrubby {Potentilla fruticosa) : 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 {liibes 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 (Comus stolonifera) : 4-8 feet ; white ; early summer ;
stems dark red, very showy in winter ; spreads by stolons.

Eldei, common (Sambucus Canadensis): 6-12 feet; 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 ai-e 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.

Goldenhell (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 (Crataegus 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 siunmer.

Leadwort (Amorpha fruticosa) : 4-6 feet ; pui-plish ; summer.

APPENDIX 287

Leatherwood {Dirca palustris) : 3-6 feet ; yellow ; early spring ; excel-
lent for wet places ; flowers appearing with the leaves ; bark exceedingly
tough.

Lilac, common (Syringa 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 spirteas ; bark shed in long strings ; medicinal.

Olive, Russian {Elceagnus angustifolius) : 8-15 feet; cream color; early
summer ; leaves silvery white from the numerous scales ; fruit silvery.

Osier, European {Cornus sanguinea) : 4-8 feet ; white ; early summer ;
stems deep red ; a form with white-edged leaves is common.

Pea bush {Desmodium penduUflonim) : 4-5 feet ; rose-purple ; autumn.

Pea tree, Siberian (Caragana arborescens) : 10-15 feet ; yellow ; spring.

Pearl bush {Exochorda grandifiora) : 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 leniago) : 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 plicatum) : 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 {Spiraea sp.) : 6-8 feet ; white ; early summer ; the various species
of spiraea are among our most decorative plants.

Spiraea, blue {Caryopteris maslacanlhus) : 2-4 feet ; bright blue ; late sum-
mer ; has the appearance of a spii'sea, 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 ; sevei'al cut-leaved varieties occur.

288 AGRONOMY

Sumac, fragrant {Rhus aromatica) : 3-6 feet ; yellow ; spring ; flowers in
catkins appearing before tlie leaves ; f rnits red, edible.

Sumac, varnish {Rhus copalUna) : 3-6 feet ; greenish ; summer ; leaves
brilliant red in autumn ; good slii-ub 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 ; flowei-s very fragrant ; several other species are cultivated.

Tamarisk {Tamarix sp.) : 10-15 feet; pinkish; summer; flowers and
leaves small ; branches wandlike.

Weigela { Weigela rosea) : 4-6 feet ; rose color ; summer.

Willow, goat {Salix caprea) : 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 tlie leaves are falling ; seeds propelled for long distances ; plant
much used in medicine.

fiftep:n 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; flowei*s 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 Halliana) : twiner ; flowei-s 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 {Lycium 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 labernamoniana) : 2-3 feet ; blue ; early summer.

Aster, New England {Aster Novan-Angliai) : 3-6 feet ; purple or pink ;
autumn.

Baby's breath {Gypsophila paniculata) : 2-3 feet ; white; spring.

Baptisia {Bapiisla australis) : 2-3 feet ; blue ; early summer.

Beardtongue {Pentstemon sp.) : 2-3 feet ; wliite to red ; summer.

Bellflower, Chinese {Platycodon grandifioi-um) : 2-3 feet ; blue ©r white ;
sunnner.

Black-eyed Susan {Rudbeckia triloba, E. hirta, and R. speciosa) : 1-3 feet ;
yellow and black ; summer and autunni.

Blanket flower {Gaillardia aristata) : 1-2 feet ; red and yellow ; summer
and autunm.

Bleeding heart {Dicentra spectabilis) : 2-3 feet ; pink ; early spring.

Bluebells {Meriensia 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 {Aquilegia sp.) : 2-3 feet ; white to yellow and blue ; spring.

Coneflower, purple {£"cAmacea 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) : 0-7 feet ; yellow ; late summer.

Goldenrod {Solidago rigida and others) : 3 feet ; yellow ; late sunnner.

Harebell {Campanula Carpathica) : 6-9 inches ; deep blue ; summer.

Hollyhock {AlUma 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 fonnosum) : 1-3 feet ; deep blue ; summer.

Lilies {Lilium sp.) : 2-4 feet ; white to yellow and red ; sunnner.

Lilies, day {Ileinerocallis 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 J feet ; white or blue ; summer.

Marsh mallow {Hibiscus moscheutos) : 4-6 feet ; white and pink ; late summer.

290 AGRONOMY

Mullein {Verbascum pannosum and V. nigruin): 3-6 feet; yellow; early
suniiiier.

Obedient plant {Physostegia Virginica) : 2-3 feet ; pinkish ; summer.

Oxeye {lleliopsis Icevis) : 2-3 feet ; copper-yellow ; summer.

Pea, perennial {Lalhyrus latifoliuH) : 3-0 feet ; pink or white ; summer.

Peony (Pteonia officinalis) : 2-4 feet ; white to red ; late spring.

Pheasant's eye {Adonis vemalis) : 6-9 inches ; yellow ; early spring.

Phlox, perennial {Phlox sp.) : 2-3 feet ; white to red and purple ; summer
and autunin.

Pink moss {Phlox subulata) : 6 inches ; pink ; spring.

Poppy, mallow {Callirhoe involucrata) : 6-9 inches ; rose-pink ; summer.

Poppy, perennial {Papaver orientale) : 2-3 feet ; red ; early summer.

Primrose, evening {Oenothera sp.) : 1-3 feet; yellow or white ; summer.

Pyrethrum {Pyrethrum hybridum) : 1-3 feet ; white to pink ; spring.

5t.-John's-wort {Hypericum ascyron) : 2-3 feet ; yellow ; early summer.

Senna, wild {Cassia Marylandica) : 3-0 feet ; yellow ; summer.

Sneezeweed {Helenium autumnale) : 3-0 feet ; yellow ; summer.

Sunflower {Helianthus sp.) : 0-10 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 ; sunnner.

Sweet William, wild {Phlox divaricata) : 1-2 feet ; blue ; late spring.

Yarrow {Achillea pLarmica) : 1-2 feet ; wiiite ; early summer.

Yucca {Yucca Jilamentosa) : 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
Atoin, 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, flbrovascular, 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, 119 ;
effect of, on plants, 117 ; protection
from, 118

Cold frames, 120; use of, 161

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
pjudosperm, 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, 16^; methods of, 157, 162
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 ; s<jlana-
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 ; f ormsof , 192 ; root, 194 ;
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

Huimis, 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 f i-om, 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 ;
cankerworm, 249; codlin moth,
249 ; corn-ear worm, 248 ; cucum-
ber beetle, 250 ; curculio, 249; cur-
rant worm, 248 ; cixtworm, 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, 199
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

AGRONOMY

Ovules, 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 ; cellvilar
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,

Practical exercises, 10, 24, 36, 53, 92,
100, 112, 128, 147, 156, 163, 180,
196, 214, 228r 243, 257, 269, 276,
283

Precipitation, 44

Pricking out, 141

Propagation, artificial, 183 ; by cut-
tings, 184 ; forms designed for,
182 ; natural methods of, 181

Pi'opagation, 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 ; deptli
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

Subsoil ing, 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,' 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

AGRONOMY

Vacuoles, 67

Variation, how induced, 261 ; 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,
1 72 ; buttercup, 1 76 ; 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, 169
quack gra&s, 175; ragweed, 173
sorrel, 177; spotted spurge, 170
spreading amaranth, 109; tumV)le-
weed, 170 ; wild carrot, 170 ; 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

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