ALBERT R. MANN
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AGRICULTURE AND HoME ECONOMICS

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SAMUEL W. JOHNSON, M, A,

HOW CROPS GROW.

‘A TREATISE ON THE

CHEMICAL COMPOSITION, STRUCTURE
AND LIFE OF THE PLANT,

FOR STUDENTS OF AGRICULTURE.

WITH

NUMEROUS ILLUSTRATIONS AND TABLES OF ANALYSES.

BY

SAMUEL w> JOHNSON, M. A.,

PROFESSOR OF THEORETICAL AND AGRICULTURAL CHEMISTRY IN THE SHEF-
FIELD SCIENTIFIC SCHOOL OF YALE UNIVERSITY; DIRECTOR OF
THE CONNECTICUT AGRICULTURAL EXPERIMENT STATION;
MEMBER OF THE NATIONAL ACADEMY OF SCIENCES.

NEW YORK:
ORANGE JUDD COMPANY,
751 BROADWAY.

ae

Entered, according to Act of Congress, in the year 1890, by the
ORANGE JUDD COMPANY, |
In the Office of the Librarian of Congress, at Washington.

PREFACE.

——:0:——

BO 8. og :

‘The original edition of this work, first published i in
1868, was the regult.of studies undertaken in preparing
instruction in Agricultural Chemistry which the Author
has now been giving for three and thirty years. To-
gether with the companion volume, ‘‘ How Crops Feed,”
it was intended to present concisely but fully the then
present state of Science regarding the Nutrition of the
higher Plants and the relations of the Atmosphere,
Water, and the Soil, to Agricultural Vegetation. Since
its first appearance, our knowledge of the subject treated
of in the present volume has largely participated in the
remarkable advances which have marked all branches of
Science during the last twenty years and it has been the
writers’ endeavor in this revised edition to post the book
to date as fully as possible without greatly enlarging its
bulk or changing its essential character. In attempting
to reach this result he has been doubly embarassed, first,
by the great and rapidly increasing amount of. recent
publications in which the materials for revision must be
sought, and, second, by the fact that official duties have
allowed very insufficient time for a careful and compre-
hensive study of the literature. In conclusion, it is
hoped that while the limits of the book make necessary
the omission of a multitude of interesting details, little
‘has been overlooked that is of real importance to a fair
presentation of the subjects discussed.

III

TABLE OF CONTENTS.

INTRODUCTION... 0.00 ccceccenccne seus cece cccenectscesegenseeteneeseans re |
DIVISION I._CHEMICAL COMPOSITION OF THE PLANT.
CHAP. L—THE VOLATILE PART OF PLANTS.........++.- siale diasiesa asieieisions 12

1. Distinctions and Definitions.. ...........
2. Elements of the Volatile Part of Plants.
8. Chemical Affinity ..............0 scence eee eee e eter ee eeee es 29
4. Vegetable Organic Compounds or Proximate Elements 36
Ds WALTER asccce cies sain siemgre gaa ieienVeninins dareleice Veateniontieaen 37
2. Carbhy rates .... 1... cece cece crete cece eee e eee ee cone 39
2 yeceianle AGIOS s sesiixesisesasiersiccins airing THESES esse &
5. Albuminoids and Fermenis saee BT
6. Amides .........e cece eens ---.114
7. Alkaloids...............5 ++.120
8. Phosphorized Substances.. woe e122
CuHapP. II.—THE ASH OF PLANTS............ +6126
§ 1. Ingredients of the Ash. 126
Non-metallic Elements............ - 127

Carbon and its Compounds.
Sulphur and its Compounds..
Phosphorus and its fornpounds..
Chlorine and its Compounds.
Silicon and its Compounds.
Metallic Elements........-.. .----.----
Potassium and its Compounds.
Sodium and its Compounds..
_ Calcium and its Compounds...
Magnesium and its ‘compounds. .
Iron and its Compounds .......
Manganese and i

Carbonates ..

Sulphates.. 146
Phosphates .. RAO SRSATE: 147
Chlorides . eaeer 149
Nitrates ............c.2006 149

§2. Quantity, Distribution, an
Table of Proportions of Ash in Vegetable Matter
§ 3. Special gonipaetiten of the Ash of Agricultural Pla: ts 161

1. Constant Ingredients................ .-161
2, Uniform composition of normal
given plants......... --161
Table of Ash-analyses. ..164
3. Composition of Different p a 171
4, Like Silty of nat of similar plants.. “ie
5. Variability of ash of same species.................

6. Whatis arma composition of the ash of a plant? i
7. To what extent is each ash-ingredient essential
or aceidental................-- G2k58 Melee Roeser 180
Water-culture............... :
Essential ash-ingredients..

Is Sodium Essential to Agricultural Plants ? 186
Tron indispensable........ 2... sees cece eeee eee -192
. Manganese unessential...... -193
Is Chlorine indispensable ?.. 194
Silica is not essential............... -197

Ash-ingredients taken up in excess.
Disposition of superfluous matters.
State of Parte Was We in plant. .
4. Functions of the As. 21
CuapP. IIL.—§ 1: eats Relations among the Ingredients of

VI TABLE OF CONTENTS.

DIVISION I1.—THE STRUCTURE OF THE PLANT ND OFFICES
OF ITS ORGANS.

CHAP. I.—GENERALITIES..
Organism, Organi
Caap. I.—PRIMARY ELEMEN

g 254

CaP. III.—VEGETATIVE ORGAN! 256
. The Root......... 256
Offices of Root............- 260
Apparent Search for Food.. 263
Contact of Roots a Soil.. - 266
Absorption by Root......--....seeeees + +269

Soil Roots, Water Roots, Air Roots. . . 273

§2. The Stem.......-... sees ceseeeee seer cenees +e 282
Buds iio ceresieeneaais + 283
Layers, Tillering. . » 286
ROOt-StocKs ......-2 ees e eee ee eens - 287
PUDETS siscssa sai cucumiedinaw ydeek ee a2 288
Structure of the Stem... .... . .289
Endogenous Plants. ........... +++ -290
Exogenous Plants............--. +. -296
Sieve-cells........eseeesseeneee eee 2+ 803

§3. Leaves . + 306
‘Leaf Pores - 309

Exhalation of Water Vapor. ....... ..311
Offices of Foliage. ........-...e. sere oe B14
CHAP. IV.—REPRODUCTIVE ORGANS......-. -ee-eee eee ee BID
§ 1. The FlowWe?.... 0... cece cece eee cence eenes +42 B16
Fertilization. +2. B1Y
Hybridizing..........--....-- ae 00 BIE
Species. arieties...........- . 326
cee

§ 3. vitality of seeds and their influence on the Plants
PYOOUCO cvtecde as cairn sqdeamsinniceraesrcdrs cates teas 335
Terrien Be Vitality............. + 885
Use of old and unripe seeds. . - 338
Density of seeds......... ....... 339
Absolute weight of seeds. 340
Signs of Excellence..... 345

Ancestry. Race-vigo
DIVISION IIIl.—_LIFE OF THE PLANT.

CHAP. 1.—GERMINATION......6ccceeeeeeeeceenceeeces
1. Introductory................0.065
.2. Phenomena of poker pace ag
;3. Conditions of Germination...
Proper Depth of Sowing............
§ 4 Chentleal Pp yaiology of Germination
Chemistry of Mal
CHAP. ee 1. Food of the Plant weet independent of the Seed. “368
The Juices of the Plant. Their Nature and Movements369
SUAS OE BIS isso cic tieiscnigs necked tenia amare elu eae Va ides 370
Composition of Sap........... seen OTE
BUNS OF SAD? - 4. eccsncasuact awnis OF eeicansncveiess MchAveevd-sncwmotemsy 378
Motion of Nutrient Matters............ cc cce ce ec acne ee 379
§3. Causes of Motion of the Juices..............0 0c cece 385
Porosity of Tissues.............. om 385
TM DI DITION osiereis sersseieriains va wae » 386
Liquid Diffusion................. 390
Osmose or Membrane Diffusion. 393
Root Action................ 0.00. . 399
Selective Power of Plant. - 401
§ 4. Mechanical effects of Osmose........ ..........00.00 00. 406

APPENDIX.
TABLE.—Composition of Agricultural Products............02...00cc00e 409

HOW CROPS GROW.

INTRODUCTION.

The object of agriculture is the production of certain
plants and certain animals which are employed to feed,
clothe and otherwise serve the human race. The first
aim, in all cases, is the production of plants.

Nature has made the most extensive provision for the
spontaneous growth of an immense variety of vegetation ;
but in those climates where civilization most certainly
attains its fullest development, man is obliged to employ
art to provide himself with the kinds and quantities of
vegetable produce which his necessities or luxuries de-
mand. In this defect, or, rather, neglect of nature, ag-
riculture has its origin.

The aré¢ of agriculture consists in certain practices and
operations which have gradually grown out of an obser-
vation and imitation of the best efforts of nature, or have
been hit upon accidentally, or, finally, have been deduced
from theory.

The science of agriculture is the rational theory and
systematic exposition of the successful art.

Strictly considered, the art and science of agriculture
are of equal age, and have grown together from the ear-

2 HOW CROPS GROW.

liest times. Those who first cultivated the soil by dig-
ging, planting, manuring and irrigating, had their suffi-
cient reason for every step. In all cases, thought goes
before work, and the intelligent workman always has a
theory upon which his practice is planned. No farm
was ever conducted without physiology, chemistry, and
physics, any nore than an aqueduct or a railway was ever
built without mathematics and mechanics. Every suc-
cessful farmer is, to some extent, a scientific man. Let
him throw away the knowledge of facts and the knowl-
edge of principles which constitute his science, and he
has lost the elements of his success. The farmer without
his reasons, his theory, his science, can have no plan;
and these wanting, agriculture would be as complete a
failure with him as it would be with a man of mere
science, destitute of manual, financial and executive skill.

Other qualifications being equal, the more advanced
and complete the theory of which the farmer is the mas-
ter, the more successful must be his farming. The more
he knows, the more he can do. The more deeply, com-
prehensively, and clearly he can think, the more econ-
omically and advantageously can he work.

That there is any opposition or conflict between science
and art, between theory and practice, is a delusive error.
They are, as they ever have been and ever must be, in the
fullest harmony. . If they appear to jar or stand in con-
tradiction, it is because we have something false or incom-
plete in what we call our science or our art; or else we do
not perceive correctly, but are misled by the narrowness
and aberrations of our vision. It is often said of a ma-
chine, that it was good in theory, but failed in practice.
This is as untrue as untrue can be. If a machine has
failed in practice, it is because it was imperfect in theory.
It should be said of such a failure—the machine was
good, judged by the best theory known to its inventor,
but its incapacity to work demonstrates that the theory
had a flaw.

INTRODUCTION, 8

But, although art and science are thus inseparable, it
must not be forgotten that their growth is not altogether
parallel. There are facts in art for which science can, as
yet, furnish no adequate explanation. Art, though no
older than science, grew at first more rapidly in vigor
and in stature. Agriculture was practiced hundreds and
thousands of years ago, with a success that does not com-
pare unfavorably with ours. Nearly all the essential
points of modern cultivation were regarded by the Ro-
mans before the Christian era. The annals of the Chi-
nese show that their wonderful skill and knowledge were
in use at a vastly earlier date.

So much of science as can be attained through man’s
unaided senses, reached considerable perfection early in
the world’s history. But that part of science which re-
lates to things invisible to the unassisted eye, could not
be developed until the telescope and the microscope had
been invented, until the increasing experience of man and
his improved art had created and made cheap the other
inventions by whose aid the mind can penetrate the veil
of nature. Art, guided at first by a very crude and im-
perfectly-developed science, has, within a comparatively
recent period, multiplied those instruments and means of
research whereby science has expanded to her present
proportions.

The progress of agriculture is the joint work of theory
and practice. In many departments great advances have
been made during the last hundred years; especially is
this true in all that relates to implements and machines,
and to the improvement of domestic animals. It is,
however, in just these departments that. an improved
theory has had sway. More recent is the development of
agriculture in its chemical and physiological aspects. In
these directions the present century, or we might almost
say the last fifty years, has seen more accomplished than
all previous time.

4 HOW CROPS GROW.

The first book in the English language on the subjects
which occupy a good part of the following pages, was
written by a Scotch nobleman, the Earl of Dundonald,
and was published at London in 1795. It is entitled:
‘© A Treatise showing the Intimate Connection that sub-
sists between Agriculture and Chemistry.” The learned
Earl, in his Introduction, remarked that ‘‘the slow pro-
gress which agriculture has hitherto made as a science is
to be ascribed to a want of education on the part of the
cultivators of the soil, and the want of knowledge in such
authors as have written on agriculture of the intimate
connection that subsists between the science and that of
chemistry. Indeed, there is no operation or process, not
merely mechanical, that does not depend on chemistry,
which is defined to be a knowledge of the properties of
bodies, and of the effects resulting from their different
combinations.” Earl Dundonald could not fail to see that
chemistry was ere long to open a splendid future for the
ancient art that always had been and always is to be the
prime support of the nations. But when he wrote, how
feeble was the light that chemistry could throw upon the
fundamental questions of agricultural science! The
chemical nature of atmospheric air was then a discovery
of barely twenty years’ standing. The composition of
water had been known but twelve years. The only ac-
count of the composition of plants that Earl Dundonald
could give was the following: ‘‘ Vegetables consist of
mucilaginous matter, resinous matter, matter analogous
to that of animals, and some proportion of oil. * *
Besides these, vegetables contain earthy matters, formerly
held in solution in the newly-taken-in juices of the
growing vegetable.” He further explains by mentioning .
on subsequent pages that starch belongs to the mucil-
aginous matters, and that, on analysis by fire, vegetables
yield soluble alkaline salts and insoluble phosphate of
lime. But these salts, he held, were formed in the pro-

INTRODUCTION. 5

cess of burning, their lime excepted, and the fact of their
being taken from the soil and constituting the indispen-
sable food of plants, his Lordship was unacquainted with.
The gist of agricultural chemistry with him was, that
plants are ‘‘composed of gases with a small proportion of
calcareous matter ;” for ‘‘although this discovery may
appear to be of small moment to the practical farmer, yet
it is well deserving of his attention and notice, as it
throws great light on the nature and food of vegetables.”
The fact being then known that plants absorb carbonic
acid from the air, and employ its carbon in their growth,
the theory was held that fertilizers operate by promoting
the conversion of the organic matter of the soil or of
composts into gases, or into soluble humus, which were
considered to be the food of plants.

The first accurate analysis of a vegetable substance was®
not accomplished until fifteen years after the publication
of Dundonald’s Treatise, and another like period passed
before the means of rapidly multiplying good analyses
had been worked out by Liebig. So late as 1838, the Gét-
tingen Academy offered a prize for a satisfactory solution
of the then vexed question whether the ingredients of
ashes are essential to vegetable growth. It is, in fact,
during the last fifty years that agricultural chemistry has
come to rest on sure foundations. Our knowledge of the
structure and physiology of plants is of like recent devel-
opment. What immense practical benefit the farmer has
gathered from this advance of science! Chemistry has
ascertained what vegetation absolutely demands for its
growth, and points out a multitude of sources whence
the. requisite materials for crops can be derived. Cato
and CQolumella knew indeed that ashes, bones, bird-
dung and green manuring, as well as drainage and aera-
tion of the soil, were good for crops; but that carbonic
acid, potash, phosphate of lime, and compounds of nitro-
gen are the chief pabulum of vegetation, they did not

6 HOW CROPS GROW.

know. They did not know that the atmosphere dissolves
the rocks, and converts inert stone into nutritive soil.
‘These grand principles, understood in many of their de-
tails, are an inestimable boon to agriculture, and intelli-
gent farmers have not been slow to apply them in prac-
tice. The vast trade in phosphatic and Peruvian guano,
and in nitrate of soda; the great manufactures of oil of
vitriol, of superphosphate of lime, of fish fertilizers; and
the mining of fossil bones and of potash salts, are indus-
tries largely or entirely based upon and controlled by
chemistry in the service of agriculture.

Every day is now the witness of new advances. The
means.of investigation, which, in the hands of the scien-
tific experimenter, have created within the writer’s mem-
ory such arts as photography and electro-metallurgy, and
shave produced the steam-engine, the telegraph, the tele-
phoue and the electric light, are working and shall ever-
more continue to work progress in the art of agriculture.
This improvement will not consist so much in any re-
markable discoveries that shall enable us to “grow two
blades of grass where but one grew before ;” but in the
gradual disclosure of the reasons of that which we have
long known, or believed we knew; in the clear separa-
tion of the true from the seemingly true, and in the ex-
change of a wearying uncertainty for settled and positive
knowledge. ,

It is the boast of some who affect to glory in the suf-.
ficiency of practice and decry theory, that the former is
based upon experience, which is the only safe guide. But
this is a one-sided view of the matter. Theory is also
based upon experience, if it be worth the name. The
fancies of an ignorant and undisciplined mind are not
theory as that term is properly understood. Theory, in
the strict scientific sense, is always a deduction from
facts, and the best deduction of which the stock of facts
in our possession admits. It is therefore also the inter-

INTRODUCTION. q

pretation of facts. Itis the expression of the ideas which
facts awaken when submitted to a fertile imagination and
well-balanced judgment. A scientific theory is intended
for the nearest possible approach ‘to the truth. Theory
is confessedly imperfect, because our knowledge of facts
is incomplete, our mental insight weak, and our judg-
ment fallible. But the scientific theory which is framed
by the contributions of a multitude of earnest thinkers
and workers, among whom are likely to be the most gifted
intellects and most skillful hands, is, in these days, to a
great extent worthy of the Divine truth in nature, of
which it is the completest human conception and ex-
pression.

Science employs, in effecting its progress, essentially
the same methods that are used by merely practical men.
Its success is commonly more rapid and brilliant, because
its instruments of observation are finer and more skill-
fully handled ; because it experiments more industriously
and variedly, thus commanding a wider and more fruit-
ful experience ; because it. usually brings a more culti-
vated imagination and a more disciplined judgment to
bear upon its work. The devotion of a life to discovery
or invention is sure to yield greater results than a desul-
tory application made in the intervals of other absorbing
pursuits. It is then for the interest of the farmer to
avail himself of the labors of the man of science, when
the latter is willing to inform himself in the details of
practice, so as rightly to compreliend the questions which
press for a solution.

Agricultural science, in its widest scope, comprehends
a vast range of subjects. It includes something from
near ly every department of human learning. The natu-
ral sciences of geology, meteorology, mechanics, physics,
chemistry, botany, z0dlogy and physiology, are most in-
timately related to it. It is not less concerned with so-
cial and political economy. In this treatise it will not be

8 HOW CROPS GROW.

attempted to touch, much less cover, all this ground, but
some account will be given of certain subjects whose un-
derstanding will be of the most direct service to the agri-
culturist. The Theory of Agriculture, as founded on
chemical, physical and physiological science, in so far as
it relates to the Chemical Composition, the Structure and
the Life of the Plant, is the topic of this volume.

Some preliminary propositions and definitions may. be
serviceable ‘to the reader.

Science deals with Matter and Force.

Matter is that which has weight and bulk.

Force is the cause of changes in matter—it is appre-
ciable only by its effects upon matter.

Force resides in and is inseparable from matter.

Force manifests itself in motion and change.

All matter is perpetually animated by force—is there-
fore never at rest. What we call rest in matter is simply
motion too fine for our perceptions.

The different: kinds of matter known to. science have
been resolved into some seventy chemical elements or sim-
ple substances.

The elements of chemistry are forms of matter which
have thus far resisted all attempts at their simplification
or decomposition.

In ordinary life we commonly encounter but twelve
kinds of matter in their elementary state, viz.:

Oxygen, Carbon, Mercury, Tin,
Nitrogen, Tron, Copper, Silver,
Sulphur, Zinc, Lead, Gold.

The numberless other substances with which we are
familiar, are mostly compounds of the above, or of twelve
other elements, viz.:

Hydrogen, Silicon, Calcium, Manganese,
Phosphorus, Potassium, Magnesium, Chromium,
Chlorine, Sodium, Aluminum, Nickel.

INTRODUCTION. 9

So far as human agency goes, these chemical elements
are indestructible as to quantity, and not convertible
one into another.

We distinguish various natural manifestations of force
which, acting on or through matter, produce all material —
phenomena. In the subjoined scheme the recognized
forces are to some extent classified and defined, in a man-
rier that may prove useful to the reader.

: LIGHT ;
Act at sensi- Repulsive HEAT } Radiant
ble and in- J Attractive
sensible nd ELECTRICITY } Inductive
distances Repulsive MAGNETISM
GRAVITATION Cosmical }+Physical
COHESION
Act onl Ao aa awey yin eal
nsensible active } ;
stances SOLUTION Molecular
OSMOSE J
AFFINITY Atomic Chemical

VITALITY : Organic Biological

Within human experience the different kinds of force
are mostly convertible each into the others, and must
therefore be regarded as fundamentally one and the same.
Force, like matter, is indestructible. ‘Force acting on
a body may either increase its Kinetic Energy, or be
stored up in it as Potential Energy. Kinetic (or ac-
tual) energy is the energy of a moving body. Potential
(or possible) energy is the energy which a body may be
able to exert because of its state or position. A falling
stone or running clock gives out actual energy. The |
stone while being raised, or the clock while winding, ac-
quires and stores potential energy. In a similar manner
kinetic solar energy, reaching the earth as light, heat and
chemical force, not only sets in operation the visible ac-
tivities of plants, but accumulates in them a store of po-
tential energy which, when they serve as food or fuel, re-
appears as kinetic energy in the forms of animal heat,
muscular and nervous activity, or as fire and light.

The sciences that more immediately relate to agricult-
ure are Physies, Chemistry and Biology.

10 : HOW CROPS GROW.

Physics, or “natural philosophy,” is the science
which considers the general properties of matter and such
phenomena as are not accompanied by essential chunge
in its obvious qualities. All the forces in the preceding
scheme, save the last two, manifest themselves through
matter without destroying or masking the matter itself.
Iron may be hot, luminous, or magnetic, may fall to the
ground, be melted, welded, and crystallized ; but it re-
mains iron, and is at once recognized as such. The forces
whose play does not disturb the evident characters of sub-
stances are physical.

Chemistry is the science which studies the proper-
ties peculiar to the various kinds of matter, and those
phenomena which are accompanied by a fundamental
change in the matter acted un. Iron rusts, wood burns,
and both lose all the’external characters that serve for
their identification. They are, in fact, converted into
other substances. Chemical attraction, affinity, or chem-
ism, as it is variously termed, unites two or more ele-
ments into compounds, unites compounds together into
more complex compounds ; and, under the influence of
heat, light, and other agencies, is annulled or overcome,
so that compounds resolve themselves into simpler com-
binations or into theirelements. Chemistry is the science
of composition and decomposition ; it considers the laws
and results of affinity.

Biology, or physiology, unfolds the laws of the
propagation, development, sustenance, and death of liv-
ing organisms, both plants and animals.

When we assert that the object of agriculture is to de-
velop from the soil the greatest possible amount of cer-
tain kinds of: vegetable and animal produce at the least
cost, we suggest the topics which are most important for
the agriculturist to understand.

The farmer deals with the plant, with the soil, with
manures. These stand in close relation to each other,

INTRODUCTION. 11

and -to the atmosphere which constantly surrounds and
acts upon them. How the plant grows,—the conditions
under which it flourishes or suffers detriment,—the ma-
terials of which it is made,—the mode of its construction
and organization,—how it feeds upon the soil and air,—
how it sezves as food to animals,—how the air, soil,
plant, and animal stand related to each other in a per-
petual round of the most beautiful and wonderful trans-
formations,—these are some of the grand questions that
come before us; and they are not less interesting to the
philosopher or man of culture, than important to the
farmer who depends upon their practical solution for his
comfort ; or to the statesman, who regards them in their
bearings upon the weightiest of political considerations.

DIVISION 1.
CHEMICAL COMPOSITION OF THE PLANT.

CHAPTER 1.
THE VOLATILE PART OF PLANTS.
§ 1.

DISTINCTIONS AND DEFINITIONS.

ORGANIC AND InorGANIC Matter. —All matter may
be divided into two gr eat classes— Organic and Inorganic.

Organic matter is the product of growth, or of vital
organization, whether vegetable or animal. It is mostly
combustible, i. e., it may be easily set on fire, and burns
away into invisible gases. Organic matter either itself
constitutes the organs of life and growth, and has a pecu-
liarly organized structure, inimitable by art,—is made up
of cells, tubes or fibres (wood and flesh); or else is a
mere result or product of the vital processes, and desti-
tute of this structure (sugar and fat).

All matter which is not a part or product of a living
organism is txorganic or mineral matter (rocks, soils,
water, and air). Most of the naturally-occurring forms
of inorganic matter which directly concern agricultural
chemistry are incombustible, and destitute of anything
like organic structure.

By the processes of combustion and decay, organic
matter is disorganized or converted into inorganic matter,
‘while, on the contrary, by vegetable growth inorganic
matter is organized, and becomes organic.

13

14 HOW CROPS GROW.

Organic matters are in general characterized by com-
plexity of constitution, and are exceedingly numerous
and various; while inorganic bodies are of simpler com-
position, and comparatively few in number.

VoLATILE AND Frxep Matrer.—All plants and ani-
mals, taken as a whole, and all of their organs, consist of
a volatile and fixed part, which may be separated by
burning ; the former—usually by far the larger share—
passing into and mingling with the air as invisible gases ;
the latter—forming, in general, but from one to five per
cent. of the whole—remaining as ashes.

EXPERIMENT 1.—A splinter of wood heated in the flame of a lamp
takes fire, burns, and yields volatile matter, which consumes with flame,
and ashes, which are the only visible residue of the combustion.

Many organic bodies, products of life, but not essential
vital organs, as sugar, citric acid, etc., are completely
volatile when in a state of purity, and leave no ash.

Ust oF THE TERMS ORGANIC AND InoRGANIC.—It is
usual among agricultural writers to confine the term or-
ganic to the volatile or destructible portion of vegetable
and animal bodies, and to designate their ash-ingredients
as inorganic matier. This is not an entirely accurate
distinction. _ What is found in the ashes of a tree or of a
seed, in so far as it was an essential part of the organism,
was as truly organic as the volatile portion, and, by sub-
mitting organic bodies to fire, they may-be entirely con-
verted into inorganic matter, the volatile as well as the
fixed parts.

ULTIMATE ELEMENTS THAT CONSTITUTE THE PLANT, —
Chemistry has demonstrated that the volatile and de-
structible part of organic bodies is chiefly made up of four
substances, viz.: carbon, oxygen, hydrogen, and nitrogen,
and contains two other elements in lesser quantity, viz.:
sulphur and phosphorus. In the ash we may find phos-
phorus, sulphur, silicon, chlorine, potassium, sodium, cal-

THE VOLATILE PART OF PLANTS. 15

cium, magnesium, iron, and manganese, as well as oxy-
gen, carbon, and nitrogen.*

Thesé fourteen bodies are elements, which means, in
chemical language, that they cannot be resolved into
other substances. All the varieties of vegetable and ani-
mal matter are compounds,—are composed of and may be
resolved into these elements.

The above-named elements being essential to the or-
ganism of every plant and animal, it is of the highest im-
portance to make a minute study of their properties.

§ 2.

ELEMENTS OF THE VOLATILE PART OF PLANTS.

For the sake of convenience we shall first consider the
elements which constitute the combustible part of plants,
viz.:

Carbon, Nitrogen, Sulphur,
Oxygen, Hydrogen, Phosphorus,

The elements which belong exclusively to the ash will
‘be noticed in a subsequent chapter.

' Carbon, in the free state, is a solid. We are familiar
with it in several forms, as lamp-black, charcoal, black-
lead, and diamond. Notwithstanding the substances
just named present great diversities of appearance and
physical characters, they are identical in a certain chem-
ical sense, as by buroing they all yield the same product,
viz.: carbonic acid gas, also called carbon dioxide.

That carbon constitutes a large part of plants is evi-
dent from the fact that it remains in a tolerably pure
state after the incomplete burning of wood, as is illus-
trated in the preparation of charcoal. ~.—

1 * Hately, or to a slight extent, lithium, rubidium, iodine, bromine,
fluorine, barium, copper, zine, titanium, and boron. 3

16 HOW CROPS GROW.

EXP. 2.—If a splinter of dry pine wood be set on fire and the burning
end be gradually passed into the mouth of a narrow tube (see figure 1),
whereby the supply of air is cut off, or if it be thrust into
sand, the burning is incomplete, and a stick of charcoal re-
mains.

_Carbonization and Charring are terms used to
express the blackening of organic bodies by heat,
and are due to the separation of carbon in the free
or uncombined state.

The presence of carbon in animal matters also is
shown by subjecting them to incomplete com-
bustion.

EXP. 3.—Hold a knife-blade in the flame of a tallow candle ;
the full access of air is thus prevented,—a portion of carbon
escapes combustion, and is deposited on the blade in the form
of lamp-black. ‘

Oil of turpentine and petroleum (kerosene) contain so
much carbon that a portion ordinarily escapes in the free
state as smoke, when they are set on fire.

When bones are strongly heated in closely-covered iron
pots, until they cease yielding any vapors, there remains
in the vessels a mixture of impure carbon with the earthy
matter (phosphate of lime) of the bones, which is largely
used in the arts, chiefly for refining sugar, but also in the
manufacture of fertilizers under the name of animal char-
coal, or bone-black.

Lignite, bituminous coal, anthracite, coke—the porous,
hard, and lustrous mass left when bituminous coal is
heated with a limited access of air, and the metallic ap-
pearing gas-carbon that is found lining the iron cylinders
in which illuminating coal-gas is prepared, all consist
largely or chiefly of carbon. They usually contain more
or less incombustible matters, as well as a little oxygen,
hydrogen, nitrogen, and sulphur.

The different forms of carbon possess a greater or less
degree of porosity and hardness, according to their origin
and the temperature at which they are prepared.

Carbon, in most of its forms, is extremely indestructi-

THE VOLATILE PART OF PLANTS. 1?

ble under ordinary circumstances. Hence stakes and
fence posts, if charred before setting in the ground, last
much longer than when this treatment is neglected.

The porous varieties of carbon, especially wood char-
coal and bone-black, have a remarkable power of absorb-
ing gases and. coloring matters, which is taken advantage
of in the refining of sugar. They also destroy noizome
odors, and are used for purposes of disinfection.

Carbon is the characteristic ingredient of all organic
compounds. There is no single substance that is the ex-
clusive result of vital organization, no ingredient of the
animal or vegetable produced by their growth, that does

not contain this element.
Sgonyeen — Casio is a solid, and is recognized by our

ses of sight and feeling. Oxygen, on the other hand,
is an air or gas, invisible, odorless, tasteless, and not dis-
tinguishable in any way from ordinary air by the unas-
sisted senses.

It exists in the free (ancombined) state in the atmos-
phere we breathe, but there is no means of obtaining it
pure except from some of its compounds. Many metals
unite readily with oxygen, forming compounds (oxides)
which by heat separate again into their ingredients, and
thus furnish the means of procuring pure oxygen. Iron
and copper, when strongly heated and exposed to the air,
acquire oxygen, but from the oxides of these metals
(forge cinder, copper scale) it is not possible to separate
pure oxygen. If, however, the meta] mercury (quicksil-
ver) be kept for a long time near the temperature at
which it boils, it is slowly converted into a red powder
(red precipitate, red oxide of mercury, or mercuric ox-
ide), which on being more strongly heated is decomposed,
yielding metallic mercury and gaseous oxygen in a pure
state.

The substance usually employed as the most convenient

source of oxygen gas is the white salt called potassium
2

18 HOW CROPS GROW.

chlorate. Exposed to heat, this body melts, and present-
ly evolves oxygen in great abundance.

EXP. 4.—The following figure illustrates the apparatus employed for
preparing and collecting this gas.

A tube of difficultly fusible glass, 8 inches long and 4 inch wide, con-
tains the red oxide of mercury or potassium chlorate.* To its mouth is
connected, air-tight, by a cork, a narrow tube, the free extremity of
which passes under the shelf of a tub nearly filled with water. ” The
shelf has, beneath, afunnel-shaped cavity opening above by a narrow
orifice, over which a bottle filled with water is inverted. Heat being

applied to the wide tube, the common air it contains is first expelled,
and presently, oxygen bubbles rapidly into the bottle and displaces
the water. When the bottle is full, it may be corked and set aside, and.
its place supplied by another. Fillfour pint bottles with the gas, and
set them aside with their mouths in tumblers of water. From one
ounce of potassium chlorate about a gallon of oxygen gas may be thus
obtained, which is not quite pure at first, but becomes nearly so on
standing over water for some hours. When the escape of gas becomes
slow and cannot be quickened by increased heat, remove the delivery-
tube from the water, to prevent the latter receding and breaking the
apparatus.

As this gas makes no peculiar impressions on the senses,

*The potassium chlorate is best mixed with about one-quarter its
weight of powdered black oxide of manganese, as this facilitates the
preparation, and renders the heat of a common alcohol lamp sufficient.

THE VOLATILE PART OF PLANTS, ‘19

we employ its behavior toward other bodies for its recog-
nition.

EXP. 5.—Place a burning splinter of wood in a vessel of oxygen (lifted
for that purpose, mouth upward, from the water). The flame is at once
greatly increased in brilliancy. Now remove the splinter from the
bottle, blow out the flame, and thrust the still glowing point into the

oxygen. It is instantly relighted. The experiment may be repeated
many times. This is the usual test for oxygen gas.

Combustion.—W hen the chemical union of two bodies
takes place with such energy as to produce visible phe-
nomena of fire or flame, the process is called combustion.
Bodies that burn are combustibles, and the gas in which
a substance burns is called a supporter of combustion.

Oxygen is the grand supporter of combustion, and
nearly all cases of burning met with in ordinary exp€ri-
ence are instances of chemical union between the oxygen
of the atmosphere and some other body or bodies.

The rapidity or intensity of combustion depends upon
the quantities of oxygen and of the combustible that
unite within 4 given time. Forcing a stream of air into
a fire increases the supply of oxygen and excites a more
vigorous combustion, whether it be done by a bellows or
result from ordinary draught.

Oxygen exists in our atmosphere to the extent of about
one-fifth of the bulk of the latter. When a burning body
is brought into unmixed oxygen, its combustion is, of
course, more rapid than in ordinary air, four-fifths of
which is a gas, presently to be noticed, that is compara-
tively indifferent in its chemical affinities toward most
bodies.

‘In the air a piece of burning charcoal soon goes out ;
but if plunged into oxygen, it burns with great rapidity
and brilliancy.

Exp. 6.—Attach a slender bit of charcoal to one end of a sharpened
wire that is passed through a wide cork or card; heat the charcoal to

redness in the flame of a lamp, and then insert it into a bottle of oxy-
gen, Fig.3. When the combustion has declined, a suitable test applied

20 HOW CROPS GROW.

to the air of the bottle will demonstrate that another invisible gas has
taken the place of the oxygen. Such atest is lime-water.*
On pouring some of this into the bottle and agitating
vigorously, the previously clear liquid becomes milky,
and, on standing, a white deposit, or precipitate, as the
chemisf terms it, gathers at the. bottom of. the vessel.
Carbon, by-thus uniting to oxygen, yields carbonic acid
gas, which in its turn combines with lime, producing
carbonate of lime. These substances will be further
noticed in a subsequent chapter.

Metallic iron is incomustible in the at-
mosphere under ordinary circumstances, but
if heated to redness and brought into pure
oxygen gas, it burns as readily as wood burns in the air.

Exp. 7.—Provide a thin knitting-needle, heat one end red hot, and
sharpen it by means of a file. Thrust the point thus
mage into a splinter of wood (a bit of the stick of a
match, } inchglong); pass the other end of the needle
through a wid@ flat cork for a support; set the wood on
fire, and immérse the needle in a bottle of oxygen, Fig.
4. After the wood consumes, the iron itself takes fire
and burns with vivid scintillations. It is converted into
two distinct oxides of iron, of which one,—ferric oxide,—
will be found as a yellowish-red coating on the sides of
the bottle; the other,—magnetic oxide,—will fuse to
plack, brittle globules, which falling, often melt quite =
into the glass. : Fig. 4.

The only essential difference between these and ordi-
nary cases of combustion is the intensity with which the
process goes on, due to the more rapid access of oxygen
to the combustible.

Many bodies unite slowly with oxygen,—oxidize, as it
is termed,—without these phenomena of light and intense
heat which accompany combustion. Thusiron rusés, lead
tarnishes, wood decays. All these processes are cases of
oxidation, and cannot go on in the absence of oxygen.

Since the action of oxygen on wood and other organic
matters at common temperatures appears to be analogous
P Pat Tie eter put a B siceeagt) unslaked lime, as large as a
the whole for a few minutes in a well-stoppered battle’ On acanaing,

the excess of lime will settle, and the perfectly clear liquid above it is
ready for use.

THE VOLATILE PART OF PLANTS. a1

in a chemical sense to actual burning, Liebig has pro-
posed the term eremacausis (slow burning), to designate
the chemical process of oxidation which takes place in
decay, and which is concerned in many transformations,
as in the making of vinegar and the formation of salt-
peter.* i

Oxygen is necessary to organic life. The act of breath-
ing introduces it into the lungs and blood of animals,
where it aids the important office of respiration. Ani-
mals, and plants as well, speedily perish if deprived of
free oxygen, which has therefore been called vital air.

Oxygen has a nearly universal tendency to combine
with other substances, and form with them new com-
pounds. With carbon, as we have seen, it forms carbonic
acid gas or carbon dioxide. With iron it ungfes in vari-
ous proportions, giving origin to several distinct oxides.
In decay, putrefaction, fermentation, and respiration,
numberless new products are formed, the results of its
chemical affinities.

Oxygen is estimated to be the most abundant body in
nature. In the free state, but mixed with other gases, it
constitutes one-fifth of the bulk of the atmosphere. In
chemical union with other bodies, it forms eight-ninths
of the weight of all the water of the globe, and one-third
of its solid crust,—its soils and rocks,—as well as of all
the plants and animals which exist upon it. In fact,
there are but few compound substances occurring in or-
dinary experience into which oxygen does not enter as a
necessary ingredient.

Nitrogen.—This body is the other chief constituent of
the atmosphere, of which it makes up about four-fifths
the bulk, and in which its office would appear to be

* Recent investigation has demonstrated that the oxidations which
Liebig classed under the term eremdcausis, are for the most part strict-
ly dependent on the vital processes of extremely minute organisms,
which are in general characterized by the terms microbes or micro-
demes, and are more specifically designated bacteria, 1. e., ‘rod-shaped
animalecules or plantlets.” .

22 HOW CROPS GROW.

mainly that of diluting and tempering the affinities of
oxygen. Indirectly, however, it serves other most im-
portant uses, as will presently be seen.

For the preparation of nitrogen we have only to remove
the oxygen from a portion of atmospheric air. This may
be accomplished more or less perfectly by a variety of
methods. We have just learned that the process of burn-
ing is a chemical union of oxygen with the combustible.
If, now, we can find a body which is very combustible
and one which at the same time yields by union with ox-
ygen a product that may be readily removed from the air
in which it is formed, the preparation of nitrogen from
ordinary air becomes easy. Such a body is phosphorus,
a substance to be noticed in some detail presently.

Exp. 8.—The bottom of a dinner-plate is covered half an inch deep

with water; a bit of chalk hollowed out into a little cup is floated on
the water by means of a large flat cork or a piece of wood; into this
cup a morsel of dry phosphorus as large as a pepper- 3
corn is placed, which is then set on fire and covered by
a capacious glass bottle or bell-jar. The phosphorus
burns at first with a vivid light, which is presently ob-
secured by a cloud of snow-like phosphoric acid. The
combustion goes on, however, until nearly all the oxy-
gen is removed from the included air. The air is at
first expanded by the heat of the flame, and a portion
of it escapes from the vessel; afterward it diminishes
in volume as its oxygen is removed, so that it is need- Fig. 5.
ful to pour water on the plate to prevent the external 4
air from passing into the vessel. After some time the white fume will
entirely fall, and be absorbed by the water, leaving the inclosed nitro-
gen quite clear.
’ Exp. 9.—Another instructive method of preparing nitrogen is the fol-
lowing: A handful of green vitriol (protosulphate of iron or ferrous
sulphate) is dissolved in half a pint of water, the solution is put into
a quart bottle, a gill of ammonia-water or fresh potash-lye is added,
the bottle stoppered, and the mixture vigorously agitated for some
minutes; the stopper is then lifted, to allow fresh air to enter, and the
whole is again agitated as before. This is repeated occasionally for half
an hour or more, until no further absorption takes place, when nearly
pure nitrogen remains in the bottle.

Free nitrogen, under ordinary circumstances, mani-
fests no active properties, but is best characterized by its
chemical indifference to most other bodies. That it is

THE VOLATILE PART OF PLANTS. 28

incapable of supporting combustion is proved by the first
method we have instanced for its preparation.

Exp. 10.—A burning splinter is immersed in the bottle containing the
nitrogen prepared by the second method, Exp. 9; the flame immediate-
ly goes out.

Nitrogen cannot maintain respiration, so that animals
perish if confined in it. Vegetation also dies in an at-
mosphere of this gas. For this reason it was formerly
called Azote (against life). In general it is difficult to
effect direct union of nitrogen with other bodies, but at
a high temperature, in presence of alkalies, it unites with
carbon, forming cyanides.

The atmosphere is the great store and source of nitro-
gen in nature. In the mineral kingdom, especially in
soils, it occurs in small relative proportion, but in large
aggregate quantity as an ingredient of saltpeter and other
nitrates, and of ammonia. It is a constant constituent
of all plants, and in the animal it is a never-absent com-
ponent of the working tissues, the muscles, tendons and
nerves, and is hence an indispensable ingredient of food.

Hydrogen.— Water, which is so abundant in nature,
and so essential to organic existence, is a compound of
two elements, viz.: oxygen, that has already been consid-
ered, and hydrogen, which we now come to notice.

Hydrogen, like oxygen, is a gas, destitute, when pure,
of either odor, taste, or color. It does not occur nat-
urally in the free state, except in small quantity in the
emanations from boiling springs and volcanoes. Its most
simple preparation consists in abstracting oxygen from
water by means of agents which have no special affinity
for hydrogen, and therefore leave it uncombined.

Sodium, a metal familiar to the chemist, has such an
attraction for oxygen that it decomposes water with great
rapidity.

Exp. 11.—Hydrogen is therefore readily procured by inverting a bot-

tle full of water in a bowl, and inserting into it a bit of sodium as large
asapea. The sodium should first be wiped free from the naphtha in

24 HOW CROPS GROW.

which it is kept, and then be wrapped tightly in several folds of paper.
On bringing it, thus prepared, under the mouth of the bottle, it floats
upward, and when the water penetrates the paper, an abundant escape
of gas occurs.

Metallic iron, when at a red heat, rapidly decomposes
water, uniting with oxygen and setting hydrogen free,
as may be shown by passing steam from boiling water
through a gun-barrel filled with iron-turnings and heated
to bright redness. Certain acids which contain hydro-
gen are decomposed by iron, zinc, and some other metals,
their hydrogen being separated as gas, while the metal
takes the place of the hydrogen with formation of a salt.
Hydrochloric acid (formerly called muriatic acid) is a
compound of hydrogen with chlorine, and may accord-
ingly be termed hydrogen chloride. When this acid is
poured upon zinc the latter takes the chlorine, forming
zine chloride, and hydrogen escapes as gas. Chemists
represent such changes by the use of symbols (first letters
of the names of chemical elements), as follows :

Binns zn 6) 4 EB or
2(H Cl) + Zn = Zn Cl, + BH,

EXP. 12.—Into a bottle fitted with cork, funnel, and delivery tubes (Fig.
6) an ounce of iron tacks or zine
clippings is introduced, a gill 4
of water is poured upon them,
and lastly an ounce of hydro-
ehloric acid is added. A brisk
effervescence shorily com-
mences, owing to the escape
of nearly pure hydrogen gas,
which may be collected in a
bottle filled with water as di-
rected for oxygen. The first
portions that pass over are
mixed with air, and should be
rejected, as the mixture is dan-
gerously explosive.

One of the most strik-

ing properties of free hy- Fig. 6.
drogen is its levity. It is the lightest body in nature

THE VOLATILE PART OF PLANTS. 25

that has been weighed, being fourteen and a half times
3 lighter than common air. It is hence
<yused in filling balloons. Another propérty
_ igits combustibility ; itinflames on contact
with a lighted taper, and burns with a
flame that is intensely hot, though scarcely
luminous if the gas be pure. Finally, it
is itself incapable of supporting the com-
Fig. 7. bustion of a taper.

EXP. 13.—All these characters may be shown by the following single
experiment. A bottle full of hydrogen is lifted from the water over
which it has been collected, and a taper attached to a bent wire, Fig. 7,
is brought to its mouth. At first a slight explosion is heard from the
sudden burning of a mixture of the gas with air that forms at the mouth
of the vessel; then the gas is seen burning on its lower surface with a
pale flame. If now the taper be passed into the bottle it will be extin-
guished; on lowering it again, it will be relighted by the burning gas;
finally, if the bottle be suddenly turned mouth upwards, the light hy-
drogen rises‘in a sheet of flame.

_In the above experiment, the hydrogen burns only
where it is in contact with atmospheric oxygen; the pro-
duct of the combustion is an oxide of hydrogen, the uni-
versally diffused compound, water. The conditions of
the last experiment do not permit the collection or iden-
tification of this water; its production can, however,
‘readily be demonstrated. .
EXP. 14.—The arrangement shown in Fig. 8 may be employed to exhibit

LAA AAT (AI
Fig. &

the formation of water by the burning of hydrogen. Hydrogen gas is
generated from zine and dilute acid in the two-necked bottle. Thus

26 HOW CROPS GROW.

produced, it is mingled with spray, to remove which it is made to
stream through a tube loosely filled with cotton. After air has been
entirely displaced from the apparatus, the gas is ignited at the up-
eurved end of the narrow tube, and a clean bell-glass is supported over
the flame. Water collects at once, as dew, on the interior of the bell,
and shortly flows down in drops into a vessel] placed beneath.

In the mineral world we scarcely find hydrogen occur-
ring in much quantity, save as water. It is a constant
ingredient of plants and animals, and of nearly all the
numberless substances which are products of organic life.

Hydrogen forms with carbon a large number of com-
pounds, the most common of which are the volatile oils,
like oil of turpentine, oil of lemon, etc. The chief illu-
minating ingredient of coal gas (ethylene or olefiant gas),
the coal or rock oils (kerosene), together with benzine
and paraffine, are so-called hydro-carbons.

Sulphur is a well-known solid substance, occurring in
commerce either in sticks (brimstone, roll sulphur) or as
a fine powder (flowers of sulphur), having a pale yellow
color, and a peculiar odor and taste.

Uncombined sulphur is comparatively rare, the com-
mercial supplies being almost exclusively of volcanic ori-
gin ; but, in one or other form of-combination, this ele-
ment is universally diffused.

Sulphur is combustible. It burns in the air with a
pale blue flame, in oxygen gas with a beautiful purple-
blue flame, yielding in both cases a suffocating and fum-
ing gas of peculiar nauseous taste, which is called swJ-
phurous acid gas or sulphur dioxide,

EXP. 15.—Heat a bit of sulphur as large as a grain of wheat on a slip
of iron or glass, over the flame of a spirit lamp, for observing its fusion, :
combustion, and the development of sulphur dioxide. Further, scoop
out a little hollow in a piece of chalk, twist a wire round the latter to
serve for a handle, as in Fig. 3; heat the chaJk with a fragment of sul-
phur upon it until the latter ignites, and bring it into a bottle of oxygen

gas. The purple flame is shortly obscured by an opaque white fume of
sulphur dioxide.

Sulphur forms with oxygen another compound, the ¢ri-

oxide, which, in combination with water, constitutes com-
&

THE VOLATILE PART OF PLANTS. 2%

mon sulphuric acid, or oil of vitriol. This oxide is devel-
oped to aslight extent during the combustion of sulphur
in the air and the acid is prepared on a large scale for
commerce by a complicated process.

Sulphur unites with most of the metals, yielding com-
‘pounds known as sulphides, or formerly as sulphurets.
These exist in nature in large quuntities, especially the
sulphides of iron, copper, and lead, and many of them
are valuable ores. Sulphides may be formed artificially
by heating most of the metals with sulphur.

Exp. 16.—Heat the bowl of a tobacco-pipe to a low red heat in a stove
or furnace; have in readiness a thin iron wire or watch-spring made
into a spiral coil; throw into the pipe-bowl some lumps of sulphur, and
when these melt and boil, with formation of a red vapor or gas, intro-
duce the iron coil, previously heated to redness, into the sulphur vapor.
The-sulphur and iron unite; the iron, in fact, burns in the sulphur gas,
giving rise to a black iron sulphide, in the same manner as in Exp. 7 it
purned in oxygen gas and produced an iron oxide. The iron sulphide
melts to brittle, round globules, and remains in the pipe-bowL

With, hydrogen, the element we are now considering
unites to form a gas that possesses in a high degree the
odor of rotten eggs, and is, in fact, the chief cause of the
noisomeness of this kind of putridity. This gas, com-
monly called sulphuretted hydrogen, or hydrogen sulphide,
is dissolved in, and evolved abundantly from, the water
of sulphur springs.. It may be produced artificially by
acting on some metallic sulphides with dilute sulphuric
or hydrochloric acid.

EXP. 17.—Place a lump of the iron sulphide prepanedll in Exp. 16in acup
or wine-glass, add a little water, and lastly a little hydrochloric acid.
Bubbles of hydrogen sulphide will shortly escape.

In soils, sulphur occurs almost invariably in the form
of sulphates, compounds of sulphuric acid with metals, a
class of bodies to be hereafter noticed.

In plants, sulphur ig always present, though usually in
small proportion. The turnip, the onion, mustard, horse-
radish, and assafootida owe their peculiar flavors to vola-
tile oils of which sulphur is an ingredient.

’

28 HOW CROPS GROW.

Albumin, globulin, casein and similar principles, never
absent from plant or animal, possess also a small con-
tentofsulphur. In hair and horn it occurs to the amount
of three to five per cent.

When organic matters are burned with full access of
air, their sulphur is oxidized and remains in the ash as
sulphates, or escapes into the air as sulphur dioxide.

Phosphorus is an element which has such intense af-
finities for oxygen that it never occurs naturally in the
free state, and when prepared by art, is usually obliged to
be kept immersed in water to prevent its oxidizing, or
even taking fire. It is known to the chemist in the solid
state in two distinct forms. In the more commonly. oc-
curring form, it is colorless or yellow, translucent, wax-
like in appearance ; is intensely poisonous, inflames by
moderate friction, and is luminous in the dark ; hence its
name, derived from two Greek words signifying light-
bearer. The other form is brick-red, opaque, far less in-
flammable, and destitute of poisonous properties. Phos-
phorus is extensively employed for the manufacture of
friction matches. For this purpose yellow phosphorus is
chiefly used. When burned in air or in oxygen gas this ele-
ment forms a white substance—phosphorus pentoxide
(formerly termed anhydrous phosphoric acid)4“which dis-

Jsotves in water, at the same time uniting chemically with
.@ portion of the latter, and thus yielding a body of the
utmost agricultural importance, viz., phosphoric acid.

EXP. 18.—Burn a bit of phosphorus under a bottle, as in Exp. 8, omit-
ting the water on the plate. The snow-like cloud of phosphorus pen-
toxide gathers partly on the sides of the bottle, but mostly on the plate.
It attracts moisture when exposed to the air, and hisses from develop-
ment of heat when put into water. Dissolve a portion of it in hot
water, and observe that the solution is acid to the taste. Finally evapo-
rate the solution to dryness at a gentle heat. Instead of recovering
thus the white opaque phosphorus pentoxide, the residue is a trans-
parent mass of phosphoric acid, a compolund of phosphorus, oxygen
and hydrogen. d

In nature phosphorus is usually found in the form of

THE VOLATILE PART OF PLANTS. 29

phosphates, which are phosphoric acid whose hydrogen
has been partly or entirely replaced by metals.

In plants and animals, it exists for the most part as
phosphates of calcium (or lime), magnesium (or mag-
nesia), potassium (or potash), and sodium (or soda).

The bones of animals contain a considerable proportion
(10 per cent.) of phosphorus, mainly in the form of cal-
cium phosphate. It is from this that the phosphorus
employed for matches is largely procured.

Exp. 19.—Burn a piece of bone in a fire until it becomes white, or
nearly so. The bone loses about half its weight. What remains is
bone-earth or bone-ash, and of this 90 per cent. is calcium phosphate.

Phosphates are readily formed by bringing together
solutions of various metals with solution of phosphoric
acid.

EXP. 20.—Pour into each of two wine or test glasses a small quantity
of the solution of phosphoric acid obtained in Exp. 18. To one, add
some lime-water (see note p. 19) until a white cloud or precipitate is per-
ceived. This is acalcium phosphate. Into the other portion drop solu-
tion of alum. A translucent cloud of aluminium phosphate is immedi-
ately produced.

In soils and rocks, phosphorus exists in the state of
phosphates of calcium, aluminium, and iron.

The tissues and juices of animals and plants generally
contain small proportions of several highly complex “‘ or-
ganic compounds” in which phosphoric acid is associated
with the elements carbon, oxygen, hydrogen and nitrogen.
Such substances are chlorophyll, Jecithin and nuclein,
to be noticed hereafter.

We have thus briefly considered the more important
characters of those six bodies which constitute that part
of plants, and of animals also, which is volatile or de-
structible at high temperatures, viz.: carbon, hydrogen,
oxygen, nitrogen, sulphur, and phosphorus.

Out of these substances, which are often termed the
organic elements of vegetation, are chiefly compounded ail
the numberless products of life to be met with, either in
the vegetable or animal world.

30 HOW CROPS GROW.

ULTIMATE COMPOSITION OF VEGETABLE MATTER.

To convey an-idea of the relative proportions in which
these six elements exist in plants, a statement of the
ultimate or elementary percentage composition of several
kinds of vegetable matter is here subjoined.

Grain of Strawof Tubersof Grain 0 of Hay of Hea

Wueat. Wheat. £otato.

bey 4 44.0 46.5 ae
5.3 5.8 6.2 5.0
338.9 44.7 40.0 37.8
. 0.4 1.5 4.2 21

Ash, including sulphur =
Pd anne hone } 24 7.0 4.0 31 7.7
100.0 100.0 100.0 100.0 100.0
Sulphur......-..+-e- esse eee 0.12 0.14 0.08 0.21 0.18
Phosphorus......--.s+-+ +++ 0.30 0.80 0.34 0.34 0.20

Our attention may now be directed to the study of such
compounds of these elements as constitute the basis of.
plants in general; since a knowledge of them will pre-
pare us to consider the remaining elements with a greater
degree of interest.

Previous to this, however, we must, first of all, gain a
clear idea of that force—chemical affinity—in virtue of
whose action these elements are held in their combina-
tions and, in order to understand the language of chem-
ical science, must know something of the views that now
prevail as to the constitution of matter.

§ 3.
CHEMICAL AFFINITY.—THE ATOMIC-MOLECULAR THEORY.

Chemical Attraction or Affinity is that force or
kind of energy which unites or combines two or more sub-
stances of unlike character, to a new body different from
tis ingredients.

Chemical Combination differs essentially from mere
mixture. Thus we may put together in a vessel the two
gases, oxygen and hydrogen, and they will remain uncom-
bined for an indefinite time, occupying their original vol-

THE VOLATILE PART OF PLANTS. 31

ume ; but if a flame be brought into the mixture they in-
stantly unite with a loud explosion, and, in place of the
light and bulky gases, we find a few drops of water, which
is a liquid at ordinary temperatures, and in winter
weather becomes solid, which does not sustain combus-
tion like oxygen, nor itself burn as does hydrogen ; but
is a substance having its own peculiar properties, differ-
ing from those of all other bodies with which we are ac-
quainted.

In the atmosphere we have oxygen and nitrogen in a
state of mere mixture, each of these gases exhibiting its
own characteristic properties. When brought into chem-
ical combination, they are capable of yielding a series of
no less than five distinct compounds, one of which is the
so-called laughing-gas, while the others form suffocating
and corrosive vapors that are totally irrespirable.

Chemical Decomposition. —Water, thus composed
or put. together by the exercise of affinity, is easily de-
composed. or taken to pieces, so to speak, by forces that
oppose affinity—e. g., heat and electricity—or by the
greater affinity of some other body—e. g., sodium—as al-
ready illustrated in the preparation of hydrogen, Exp. 11.

Definite Proportions. —A further distinction be-
tween chemical union and mere mixture is, that, while
two or more bodies may, in general, be mixed in all. pro-
portions, bodies combine chemically” in comparatively
few proportions which are fixed and invariable. Oxygen
and hydrogen, e. g., are found united in nature, princi-
pally in the form of water ; and water, if pure, is always
composed of one-ninth hydrogen and eight-ninths oxy-
gen by weight, or, since oxygen is, bulk for bulk, sixteen
times heavier than hydrogen, of one volume or measure
of oxygen to two volumes of hydrogen.

Atoms.—It is now believed that matter of all kinds
consists of indivisible and unchangeable particles called

, »atoms, which are united to each other by chemical at-

32 HOW CROPS GROW.

traction, and cannot ordinarily exist in the free state.
On this view each particular kind of matter or chemical
substance owes its individuality either to the special kinds
or to the numbers of the atoms it consists of. Atoms
may be defined as the smallest quantities of matter which
can exist in chemical combination and the smallest of
which we have any knowledge or conception.

Atomic Weight of Elements.—On the hypothesis
that chemical union takes place between atoms of the
elements, the simplest numbers expressing the propor-
tions by weight* in which the elements combine, are ap-
propriately termed atomic weights. These numbers are
only relative, and since hydrogen is the element which
unites in the smallest proportion by weight, it is assumed
as the standard unit. From the results of a great
number of the most exact experiments, chemists have
generally agreed upon the atomic weights given in the
subjoined table for the elements already mentioned or
described.

Symbols.—For convenience in representing chemical
changes, the first letter (or letters) of the Latin name
of the element is employed instead of the name itself, and
is termed its symbol.

TABLE OF ATOMIC WEIGHTS AND SYMBOLS OF ELEMENTS.t

Element. Atomic Weight. Symbol.
Hydrogen 1 H

Carbon 12 Cc

Oxygen 16 Oo

Nitrogen 14 N

Sulphur 32 Ss
Phosphorus 31 P

Chlorine 35.5 cl

Mercury 200 Hg (Hydrargyrum)
Potassium 39 K (Kalium)
Sodium 23 Na (Natrium)
Caleium 40 Ca

Iron 56 Fe (Ferrum)

* Unless otherwise stated, parts or proportions by weight are always
to be understood.

+ Now, chemists receive as the true atomic weights double the num-
bers that were formerly employed, those of hydrogen, chlorine and a
few others excepted. The atomic weights here given are mostly whole
numbers. The actual atomic weights, as experimentally determined,
differ from the above by small fractions, which may be neglected.

THE VOLATILE PART OF PLANTS, 33

Multiple Proportions.—When two or more bodies
unite in several proportions, their quantities, when not
expressed by the atomic weights, are twice, thrice, four,
or more times, these weights; they are multiples of the
atomic weights by some simple number. Thus, carbon
and oxygen form two commonly occurring compounds,
viz., carbon monoxide, consisting of one atom of each in-
gredient, and carbon dioxide, which contains to one atom,
or 12 parts by weight, of carbon, two atoms, or 32 parts
by weight, of oxygen.

Molecules* contain and consist of chemically-united
atoms, and are the smallest particles of matter that can
have an individual or physical existence. While the
atoms compose and give character to the molecules, the
molecules alone are sensibly known to us, and they give
character to matter as we find it in masses, either solid,
liquid or gaseous. In solids the moleculés more or less
firmly cohere together; in liquids they have but little
cohesion, and in gases they are far apart and tend to sepa-
rate from each other. The so-called ‘‘ elements” are, in
fact, mostly compounds whose molecules consist of two
or more like atoms, while all other chemical substances
are compounds whose molecules are made up of two or
more unlike atoms.

Molecular Weights of Compounds.—The mole-
cular weight of a compound is the sum of the weights of
the atoms that compose it. For example, water being
composed of 1 atom, or 16 parts by weight, of oxygen,
and 2 atoms, or 2 patts by weight, of hydrogen, has the
molecular weight of 18.+

The following scheme illustrates the molecular compo-
sition of a somewhat complex compound, one of the car-

* Latin diminutive, signifying a little mass.

t We must refer to recent treatises on chemistry for fuller informa-
tion as to atoms and molecules and the methods of finding the atomic
and molecular weights.

3

34 4 HOW CROPS GROW.

bonates of ammonium, which consists of four elements,
ten atoms, and has a molecular weight of-seventy-nine.
Ammonia gas results from the union of an atom of
nitrogen with three atoms of hydrogen. One molecule
of ammonia gas unites with a molecule of carbon dioxide
gas and a molecule of water to produce a molecule of

ammonium carbonate.
Atoms. Atomic Molecular
weights. weights.

re aw" imal = (Messen, 1 a 1a | =
; mol. —({ Nitrogen = or
Carbonate. __} Carbon di- __{ Carbon, oa = at ae —79
Ymol. | Oxide 1 mol.~ { Oxygen, 2 = 82.6 F—
: Water, —_fHydrogen, 2 = at =18
1 mol.— {| Oxygen, Le Sse fr

Notation and Formulas of Compounds.—For the
purpose of expressing easily and concisely the composi-
tion of compounds, and the chemical changes they
undergo, chemists have agreed to make the symbol of an
element signify one atom of that element.

Thus H implies not only the light, combustible gas
hydrogen, but also one part of it by weight as compared
with other elements, and S suggests, in addition to the
idea of the body sutphur, the idea of 32 parts of it by
weight. Through this association of the atomic weight
with the symbol, the composition of compounds is
expressed in the simplest manner by writing the symbols
of their elements one after the other. Thus, carbon
monoxide is represented by CO, mercuric oxide by HgO,
and iron monosulphide by FeS. The symbol CO con-
veys to the chemist not only the fact of the existence
of carbon monoxide, but also instructs him that its mole-
cule contains an atom each of carbon and of oxygen, and
from his knowledge of the atomic weights he gathers the
proportions by weight of the carbon and oxygen in it.

When a compound contains more than one atom of an
element, this is shown by appending a small figure to the
symbol of the latter. For example: water consists of
two atoms of hydrogen united to one of oxygen, and its

THE VOLATILE PART OF PLANTS. 35

symbol is H,O. In like manner the symbol of carbon
dioxide is CO,.

When it is wished to indicate that more than one mole-
cule of a compound exists in combination or is concerned
in a chemical change, this is done by prefixing a large
figure to the symbol of the compound. For instance,
two molecules of water are expressed by 2 H,0.

The symbol of a compound is usually termed a formula
and if correct is a molecular formula and shows the com-
position of one molecule of the substance. Subjoined is
a table of the molecular formulas of some of the com-
pounds that have been already described or employed.

FORMULAS OF COMPOUNDS.

Name. Formula, Molecular Weight.
Water HO 18
Hydrogen Sulphide HS 34
Iron Monosulphide FeS 88
Mereuric Oxide pee 216
Carbon Dioxide 44
Calcium Chloride Cael, 111°
Sulphur Dioxide SO, 64
Sulphur Trioxide 80
Phosphorus Pentoxide P05 142

Empirical and Rational Formulas.—It is obvious
that many different formulas can be made for a body of
complex character. Thus, the carbonate of ammonium,
whose composition has already been stated (p. 33), and

which contains

latom of Nitrogen,
latom of Carbon,

3 atoms of Oxygen, and
6 atoms of Hydrogen,

may be most compactly expressed by the symbol
NCO,H,.

Such a formula merely informs us what elements and
how many atoms of each element enter into the compo-
sition of the substance. It is an empirical formula,
being the simplest expression of the facts obtained by
analysis of the substance.

Rational formulas, on the other hand, are intended to
convey some notion as to the constitution, formation, or

36 HOW CROPS GROW.

modes of decomposition of the body. For example, the
real arrangement of the atoms in ammonium carbonate
is believed to be expressed by the rational (or structural)
formula
o=c¢ Bh

in which the carbon is directly united to oxygen, to
which latter one hydrogen and the nitrogen are also
linked, the remaining hydrogens being combined to the
nitrogen.

Valence.—The connecting lines or dashes in the fore-
going formula show the valence of the several atoms, i. e.,
their ‘‘atom-fixing power.” The single dash from H
indicates that hydrogen is univalent or las a valence of
one. The two dashes connected with O express the
bivalence of oxygen or that the atom of this element can
combine with two hydrogens or other univalent atoms.
The nitrogen is united on one hand with 4 hydrogen
atoms, and also, on the other hand, satisfies half the val-
ence of oxygen ; it is accordingly guinguwivalent, i. e., has
five units of valence. Carbon is quadrivalent, being
joined to oxygen by four units of valence.

Equations of Formulas serve to explain the results
of chémical reactions and changes. Thus, the breaking
up by heat of potassium chlorate into potassium chloride
and oxygen is expressed by the following statement:

Potassium Chlorate. ‘ Potassium Chloride. Oxygen.
2 KCl10; = 2Kcl + 30,

The sign of equality, =, shows that what is written
before it supplies and is resolved into what follows it.
The sign + indicates and distinguishes separate com-
pounds.

The employment of this kind of short-hand for exhib-
iting chemical changes will find frequent illustration as
we proceed with our subject.

Modes of Stating Composition of Chemical

THE VOLATILE PART OF PLANTS. 37

Compounds.—These are two: 1, atomic or molecular
statements, and 2, centesimal statements, or proportions
in one hundred parts (per cent, p. ¢., or %). These
modes of expressing composition are very useful for com-
paring together different compounds of the same ele-
ments, and, while usually the atomic statement answers
for substances which are comparatively simple in their
composition, the statement per cent is more useful for
complex bodies. The composition of the two compounds
of carbon with oxygen is given below according to both

methods. ;
Atomic. Per cent. Atomic. Per cent.

Carbon (C), 12 42.86 (C) 12 27.27
Oxygen (0), 16 67.14 (O,) 32 92.73

Carbon Monoxide (CO), 28 100.00 Carbon Dioxide (CO,),44 100.00

The conversion of one mode of statement into the other is a case of
simple rule of three, which is illustrated in the following calculation
of the centesimal composition of water from its molecular formula.

Water, H,O, has the molecular weight 18, i. e., it consists of two
atoms of hydrogen, or two parts, and one atom of oxygen, or sixteen
parts by weight.

The arithmetical proportions subjoined serve for the calculation, viz. :

H,O Water H Hydrogen

18 5 100 ae ee oS cent sought (=11.11)
H,O Water (0) ygen
18 100 :206160=«SSséper peut sought (=88.89)

By multiplying together the second and third terms of these propor-
tions, and dividing by the first, we obtain the required per cent, viz., of
hydrogen, 11.11; and of oxygen, 88.89.

The reader must bear well in mind that chemical affin-
ity manifests itself with very different degrees of inten-
sity between different bodies, and is variously modified,
excited, or annulled, by other natural agencies and forces,
especially by heat, light and electricity.

g 4,

VEGETABLE ORGANIC COMPOUNDS, OR PROXIMATE
PRINCIPLES.

We are now prepared to enter upon the study of the
organic compounds, which constitute the vegetable struc-

38- HOW CROPS GROW.

ture, and which are produced from the elements carbon,
oxygen, hydrogen, nitrogen, sulphur, and phosphorus, by
chemical agency. The number of distinct substances
found in plants is practically unlimited. There are
already well known to chemists hundreds of oils, acids,
bitter principles, resins, coloring matters, etc. Almost
every plant contains some organic body peculiar to itself,
and usually the same plant in its different parts reveals
to the senses of taste and smell the presence of several
individual ‘substances. In tea and coffee occurs an
intensely bitter ‘‘ active principle,” caffeine. From
tobacco an oily liquid of eminently narcotic and poison-
ous properties, nicotine, can be extracted. In the orange
are found no less than three o7/s ; one in the leaves, one
in the flowers, and a third in the rind of the fruit.

Notwithstanding the great number of bodies thus
occurring in the vegetable kingdom, it is a few which
form the bulk of all plants, and especially of those which
have an agricultural importance as sources of food to
man and animals. These substances, into which any
plant may be resolved by simple, partly mechanical means,
are conveniently termed proximate princivles, and we
shall notice them in some detail under eight principal
* classes, viz.:

1. Water.

2. The CARBHYDRATES.

3. The VEGETABLE ACIDS.

4. The Fats and OILs.

5. The ALBUMINOIDS or PROTEIN Bopius and Frr-
MENTS.

6. The AMIDES.

7%. The ALKALOIDS.

8. PHOSPHORIZED SUBSTANCES.

1. Water, H,0, as already stated, is the most abund-
ant ingredient of plants. It is itself a compound of
oxygen and hydrogen, having the following centesimal
composition :

THE VOLATILE PART OF PLANTS. 39

ORV ROD. es isieeicice st 36 Bae Meseadearen 88.89
Hydrogen...... ccc eeee cece cece ees 11.11
100.00

It exists in all parts of plants, is the immediate cause
of the succulence of their tender portions, and is essen-
tial to the life of the vegetable organs.

In the following table are given the percentages of water in some of
the more common agricultural products in the fresh stute, but the pro-
portions are not quite constant, even in the same part of different
specimens of any given plant.

WATER IN FRESH PLANTS. (PER CENT.)

Average. Range.

Meadow grass «TL 60 to 78
Red clover. . 1.80 68 “ 86
Maize, as used 82 Tl “ 93

_ Cabbage....... 85 80 94
Potato tubers.. 15 + 77 * 82
Sugar beets.... 81 7 * 90
Carrots......... 86 79 * 90
PUTO PS is siessats peeisie wis). Sieisieea va on oie winlad nisin 91 86 « 93

Tn living plants, water is usually perceptible to the
eye or feel, as sap. But it is not only fresh plants that
contain water. When grass is made into hay, the water
is by no means all dried out, but a considerable propor-
tion remains in the pores, which is not recognizable by
the senses. So, too, seasoned wood, flour, and starch,
when seemingly dry, contain a quantity of invisible
water, which canbe removed by heat.

EXP. 21._Into a wide glass tube, like that shown in Fig. 2, place a
spoonful of saw dust, or starch, or a little hay. Warm over a lamp,
but very slowly and cautiously, so as not to burn or blacken the sub-
stance. Water will be expelled from the organic matter, and will col-
lect on the cold part of the tube.

It is thus obvious that vegetable substances may con-

‘tain water in at least two different conditions. Red

‘

clover, for example, when growing or
freshly cut, contains about 80 per cent of |
water. When ‘the clover is dried, as for
making hay, the greater share of this wa-
ter escapes, so that the air-dry plant con-
tains but about 15 percent. On subject-
ing the air-dry clover to a temperature
of 212° for some hours, the water is completely expelled,
and the substance becomes really dry, i. e., water-free.

40 HOW CROPS GROW.

To drive off all water from vegetable matters, the chemist usually
employs a water-oven, Fig. 9, consisting of a vessel of tin or copper
plate, with double walls, between which is a space that may be half
filled with water. The substance to be dried is placed in the interior
chamber, the door is closed, and the water is brought to boil by the
heat of a lamp orstove. The precise quantity of water belonging to,
or contained in, a substance, is ascertained by first weighing the sub-
stance, then drying it until its weight is constant. The loss is water.

In the subjoined table are given the average quantities, per cent, of
water existing in various vegetable products when air-dry.

WATER IN AIR-DRY PLANTS. PER CENT.
Meadow grass (hay)......... iba aa meunrdarntes seumeiee 15
Red clover Days o: vesvasessasaae i ot cnetecema cee asparsen 17

PINE: W00 Qoewiea-eez semrrecingasins Lads aaieiecpaisindieis o eisaleene 20

Wheat (rye, oat) ke: i
Maize kernel..... a ler disie ia aie aia vS wed uate aan b\eia anes 12

That portion of the water which the fresh plant loses
by mere exposure to the air is chiefly the water of its
juices or sap, and, on crushing the fresh plant, is mani-
fest to the sight and feel asa liquid. Itis, properly speak-
ing, the free water of vegetation. The water which
remains in the air-dry plant is imperceptible to the senses
while in the plant,—can only be discovered on expelling
it by heat or otherwise,—and may be designated as the
hygroscopic or combined water of vegetation.

The amount of water contained in either fresh or air-
dry vegetable matter is somewhat fluctuating, according
to the temperature and the dryness of the atmosphere.

2. The Carbhydrates. This group falls into three
subdivisions, viz. :

a. THE AMYLOSES, comprising Cellulose, Starch, Inu-
lin, Glycogen, the Dextrins and Gums, having the
formula (C,H1905)n.

6. THe Giucosss, which include Dextrose, Levulose,
Galactose and similar sugars, having the composition
CoH1.0¢.

ce. THE SvcrosEs, viz.: Cane Sugar or Saccharose,
Maltose, Lactose and other sugars, whose formula in
most cases is Cy,H..0;.

THE VOLATILE PART OF PLANTS. 41

On account of their abundance and uses the Carbhy-
drates rank as the most important class of vegetable sub-
stances. Their name refers to the fact that they consist

.of Carbon, Hydrogen and Oxygen, the last two elements
being always present in the same proportions that are
found in water.

These bodies, especially cellulose and starch, form by
far the larger share—perhaps seven-eighths—of all the dry
matter of vegetation, and most of them are distributed
throughout all parts of plants.

a. The Amyloses.

Cellulose (C,H,,.0;)n.—Every agricultural plant is
an aggregate of microscopic cells, i. e., is made up of
minute sacks or closed tubes, adhering to each other.

Fig. 10 represents an extremely thin slice from the stem of a cabbage,

magnified 230 diameters. The united walls of two cells are seen in sec-
tion at a, while at b an empty space is noticed.

The outer coating, or wall, of the vegetable cell con-
sists chiefly or entirely of cellulose. This substance is
accordingly the skeleton or framework of the plant, and
the material that gives toughness and solidity to its parts.
Next to water it is the most abundant body in the vege-
table world.:

42 HOW CROPS GROW.

Nearly all plants and all their parts contain cellulose,
but it is relatively most abundant in
rq stems and leaves. In seeds it forms a
! large portion of the husk, shell, or other
outer coating, but in the interior of the
seed it exists in small proportion.

The fibers of cotton (Fig. 11, a), hemp,
-and flax (Fig. 11, 6), and white cloth and
unsized paper made from these materials,
are nearly pure cellulose.

The fibers of cotton, hemp, and flax are simply
long and thick-walled cells, the appearance of
which, when highly magnified, is shown in Fig. 11,
where « represents the thinner, more soft, and col-

lapsed cotton fiber, and 6 the thicker and more dur-
able fiber of linen.

Wood, or woody fiber, consists of long
and slender cells of various forms and di-
mensions (see p. 293), which are delicate
‘when young (in the sap wood), but as
they become older fill up interiorly by the deposition of re-
peated. layers of cellulose, which is more or less inter-
grown with other substances.* The hard shells of nuts
and stone fruits contain a basis of cellulose, which is im-
pregnated with other matters. ~

When quite pure, cellulose is a white, often silky or
spongy, and translucent body, its appearance varying

* Wood was formerly supposed to consist of cellulose and so-called
“lignin.” On this view, according to F. Schulze, lignin impregnates
(not simply incrusts) the cell-wall, is soluble in hot alkaline solutions,
and 2 readily oxidized by nitric acid. Schulze ascribes to it the com-
position

Carbonscciscce svaecencctaeaeesancs 55.3
Hydrogen : sete 058
ORY BOM 6 aaiiwiseerepeareweciapaic carton 38.9

100.0

This is, however, simply the inferred composition of what is left after
the cellulose, etc., have been removed. “Lignin” cannot be separated
in the pure state, and has never been analyzed. What is thus desig-
nated is a mixture of several distinct substances. Fremy’s lignose, lig-
none, lignin, and lignireose, as well as J. Erdman’s glycolignose and
lignose, are not established as chemically distinct substances.

THE VOLATILE PART OF PLANTS. 43

somewhat according to the source whence it is obtained.
In.the air-dry state, at common temperatures, it usually
contains about 10 % of hygroscopic water. It has, in
common with animal membranes, the character of swell-
ing up when immersed in water, from imbibing this
liquid; on drying again, it shrinks in bulk. It is tough
and elastic.

Cellulose, as it naturally occurs, for the most part dif-
fers remarkably from the other bodies of this group, in
the fact of its slight solubility in dilute acids and alkalies.
It is likewise insoluble in water, alcohol, ether, the oils,
and in most ordinary solvents. It is hence prepared in
a state of purity by acting upon vegetable tissues con-
taining it, with successive solvents, until all other mat-
ters are removed.

The “skeletonized”’ leaves, fruit vessels, etc., which compose those
beautiful objects called phantom bouquets, are commonly made by dis-
solving away the softer portions of fresh succulent plants by a hot solu-
tion of caustic soda, and afterwards whitening the skeleton of fibers
that remains by means of chloride of lime (bleaching powder). They
are almost pure cellulose.

Skeletons may also be prepared by steeping vegetable matters in a
mixture of potassium chlorate and dilute nitric acid for a number of
days. .

EXP. 22.—To 500 cubic centimeters* (or one pint) of nitric acid of dens-
ity 1.1, add 30 grams (or one ounce) of pulverized potassium chlorate,
and dissolve the latter by agitation. Suspend in this mixture a num-
ber of leaves, etc.,t and let them remain undisturbed, at a temperature
not above 65° F., until they are perfectly whitened, which may require
from 10 to 20 days. The skeletons should be floated out from the
solution on slips of paper, washed copiously in clear water, and dried
under pressure between folds of unsized paper.

The fibers of the whiter and softer kinds of wood are now much em-
ployed in the fabrication of paper. For this purpose the wood is rasped

* On subsequent pases we shall make frequent use of some of the
French decimal weights and measures, for the reasons that they are
much more convenient than the English ones, and are now almost ex-
clusively employed in all scientific treatises and investigations. For
small weights, the gram, abbreviated gm. (equal to 154 grains, nearly),
is the customary unit. The unit of measure by volume is the cubic cen-
timeter, abbreviated c. c. (30 c. c. equal one fluid ounce nearly). Gram
weights and glass measures graduated into cubic centimeters are fur-
nished by all dealers in chemical apparatus.

+ Full-grown but not old leaves of the elm, maple, and maize, heads of
unripe grain, slices of the stem and joints of maize, ete., may be em-
ployed to furnish skeletons that will prove valuable in the study of the
structure of these organs.

44 HOW CROPS GROW.

to a coarse powder by machinery, then heated with a weak soda lye,
and finally bleached with chloride of lime.

Though cellulose is insoluble in, or but slightly affected
by, weak or dilute acids and alkalies, it is altered and dis-
solved by these agents, when they are concentrated or
hot. The result of the action of strong acids and alka-
lies is various, according to their kind and the degree of
strength in which they are employed.

Cellulose Nitrates.—Strong nitric acid transforms
cellulose into various cellulose nitrates according to its
concentration. In these bodies portions of the hydrogen
and oxygen of cellulose are replaced by the atomic group
(radicle), NOs. Cellulose hexanitrate, CiegHis (NOz)6Ox0,
is employed as an explosive under the name gun cotton.
The collodion employed in photography is a solution
in ether of the penta- and tetranitrates, Ci2H15(NOz)sO10
and C,,Hie(NO3),0i10. Sodium hydroxide changes these
cellulose nitrates into cellulose and sodium nitrate.

Hot nitric acid of ordinary strength destroys cellulose
by oxidizing it with final formation of carbon dioxide
gas and oxalic acid.

Cellulose Sulphates.—When cold sulphuric acid
acts on cellulose the latter may either remain apparently
unaltered or swell up to a pasty mass, or finally dissolve
to a clear liquid, according to the strength of the acid,
the time of its action, and the quality (density) of the
cellulose. In excess of strong oil of vitriol, cellulose
(cotton) gradually dissolves with formation of various
cellulose sulphates, in which OH groups of the cellulose
are replaced by SO, of sulphuric acid. These sulphates
are soluble in water and alcohol, and when boiled with
water easily decompose, reproducing sulphuric acid, but
not cellulose. Instead of the latter, dextrin and dextrose
(grape sugar) appears.

Soluble Cellulose, or Amyloid.—In a cooled mix-
ture of oil of vitriol, with about 4 its volume of water,

THE VOLATILE PART OF PLANTS. 45

cellulose dissolves. On adding much water to the solu-
tion there separates a white substance which has the same
composition as cellulose, but is readily converted into
dextrin by cold dilute acid. This form of cellulose as-
sumes a fine blue color when put in contact with iodine-
tincture and sulphuric acid.

EXP. 23.—Fill a large test-tube first with water to the depth of two or
three inches. Then add gradually three times that bulk of oil of vitriol,
and mix thoroughly. When well cooled pour a part of the liquid on a
slip of unsized paper in a saucer. After some time the paper is seen to
swell up and partly dissolve. Now flow it with solution of iodine,*
when these dissolved portions will assume a fine and intense blue color.
This deportment is characteristic of cellulose, and may be employed
for its recognition under the microscope. If the experiment be re-
peated, using a larger proportion of acid, and allowing the action to
continue for a considerably longer time, the substance producing the
blue color is itself destroyed, and addition of iodine has no effect.t Un-
altered cellulose gives with iodine a yellow color.

Paper superficially converted into amyloid constitutes vegetable
parchment, which is tough and translucent, much resembling bladder,
and very useful for various purposes, among others as a substitute for
sausage ‘‘skins.”

Exp. 24.—Into the remainder of the cold acid of Exp. 23 dip a strip of
unsized paper, and let it remain for about 15 seconds; then remove, and
rinse it copiously in water. Lastly, soak some minutes in water, to
which a little ammonia is added, and wash again with pure water.
These washings are for the purpose of removing the acid. The success
of this process for obtaining vegetable parchment depends upon the
proper strength of the acid, and the time of immersion. If need be,
repeat, varying these conditions slightly, until the result is obtaingd.

The denser and more impure forms of cellulose, as they
occur in wood and straw, are slowly acted upon by chem-
ical agents, and are not easily digestible by most animals ;
but the cellulose of young and succulent stems, leaves,
and fruits is digestible to a large extent, especially by
animals which naturally feed on herbage, and therefore
cellulose is ranked among the nutritive ingredients of
cattle-food.

Chemical composition of cellulose.—This body is a com-

* Dissolve a fragment of iodine as large as a wheat kernel in 20 ¢. c. of
alcohol, and add 100 c. c. of water to the solution.

+ According to Grouven,.cellulose prepared from rye straw (and im-
pure ?) requires several hours’ action of sulphuric acid before it will
strike a blue color with iodine (2ter Salzmiinder Bericht, p. 467).

46 HOW CROPS GROW.

pound of the three elements, carbon, oxygen, and hydro-
gen. Analyses of it, as prepared from a. multitude of
sources, demonstrate that its composition is expressed by
the formula (C. Hio O;)n, The value of in this form-
ula is not certainly known, but is at least two, and the
formula C,H» Oi. is very commonly adopted. In 100
parts it contains

100.00

Modes of estimating cellulose.—In statements of the composition of
plants, the terms fiber, woody fiber, and crude cellulose are often met
with. These are applied to more or less impure cellulose, which is ob-
ta*ned as a residue after removing other matters, as far as possible, by
ahernate treatment with dilute acids and alkalies. The methods are

~eonfessedly imperfect, because cellulose itself is dissolved to some ex-
tent, and a portion of other matters often remains unattacked.

The method of Henneberg, usually adopted (Vs. St., V1, 497), is as follows:
3 grams of the finely divided substance are boiled for half an hour with
200 cubic centimeters of dilute sulphuric acid (containing 1} per cent of
oil of vitriol), and, after the substance has settled, the acid liquid is
poured off. The residue is boiled again for half an hour with 200 c. ¢. of
dilute potash lye (containing 1} per cent of dry caustic potash), and, after
removing the alkaline liquid, it is boiled twice with water as before.
What remains is brought upon a filter, and washed with water, then
with alcohol, and, lastly, with ether, as long as these solvents take
up anything. This crude cellulose contains ash and nitrogen, for which
corrections must be made. The nitrogen is assumed to belong to some
allesuminoid, and from its quantity the amount of the latter is calcu-
lated; (see p. 118).

Even with these corrections, the quantity of cellulose is not obtained
with entire accuracy, as is usually indicated by its appearance and its
composition. While the crude cellulose thus prepared from the pea is
perfectly white, that from wheat bran is brown, and that from rape-
cake is almost black in color, from impurities that cannot be removed
by this method.

Grouven gives the following analyses of two samples of crude cellu-
lose obtained by a method essentially the same as we have described.
(2ter Salemiinder Bericht, p. 456.)

Rye-straw fiber. Flax fiber.

100.00
On deducting water.and ash, and making proper correction for the

THE VOLATILE PART OF PLANTS. 47

nitrogen, the above samples, together with one of wheat-straw fiber,
analyzed by Henneberg, exhibit the following composition, compared
with pure cellulose.

Rye-straw fiber. Flax fiber. Wheat-straw fiber. Pure cellulose.

41.0 45.4 44.4
6.4 6.3 6.2
52.6 48.3 49.4
100.0 100.0 100.0

Fr. Schulze has proposed (1857) another method for estimating cellu-
lose, which, though troublesome, is in most cases more, correct than the
one already described. Kihn, Aronstein, and H. Schulze (Henneberg’s
Journal fiir Landwirthschaft, 1866, pp. 289 to 297) have applied this
method in the following manner: One part of the dry pulverized sub-
stance (2 to 4 grams), which has been previously extracted with water,
alcohol, and ether, is placed in a glass-stoppered bottle, with 0.8 part
of potassium chlorate and 12 parts of nitric acid of specific gravity 1.10,
and digested at a temperature not exceeding 65° F. for 14 days. At the
expiration of this time, the contents of the bottle are mixed with some
water, brought upon a filter, and washed, firstly, with cold and after-
wards with hot water. When all the acid and soluble matters have
been washed out, the contents of the filter are emptied into a beaker,
and heated to 165° F. for about 45 minutes with weak ammonia (1 part
commercial ammonia to 50 parts of water); the substance is then
brought upon a weighed filter, and washed, first, with dilute ammonia,
as long as this passes off colored, then with cold and hot water, then
with alcohol, and, finally, with ether. The substance remaining con-
tains a small quantity of ash and nitrogen, for which corrections must
be made. The fiber is, however, purer than that procured by the other
method, and the writers named obtained a somewhat larger quantity,
by } to 14 per cent. The results appear to vary but about one per cent
from the truth. Theobservations of Kénig(Vs. St.16),and of Hoffmeis-
ter (Vs. St. 33, 155), show much larger differences in favor of Fr. Schulze’s
method.

Hugo Miller (Die Pflanzenfaser, p. 27) has described a method of ob-
taining cellulose from those materials which are employed in paper-
making, which is based on the prolonged use of weak aqueous solu-
tion of bromine.

Trials made on hay and Indian-corn fodder with this method by Dr.
Osborne, at the author’s suggestion, gave results widely at variance
with those obtained by Henneberg’s method.

The average proportions of cellulose found in various

vegetable matters, in the usual or air-dry state, are as fol-

lows:
AMOUNT OF CELLULOSE IN PLANTS,

Per cent. Per cent.

Potato tuber .. Red clover lant in flower.... 10
Wheat kernel. BY ers hiencaseesivincs 34
Wheat meal. . Timothy Wiis ilar eaenwlcen Iniehaine a 23
Maize kernel . Maize cobs..... a aiee Sear Se 38
paler i Oat StTaW....... cece ceee ee ee veces 40

es Wheat“ ..... saeieh etude velco ieiece 48
Buckwheat kernel YS: sesayerett, ccnsineisveinssisicinsnny 54

48 HOW CROPS GROW.

Starch (C,H100;)n is of very general occurrence in
plants. The cells of the seeds of wheat, corn, and all
other grains, and the tubers of the potato, contain this
familiar body in great abundance. It occurs also in the.
wood of all forest trees, especially in autumn and winter.
It accumulates in extraordinary quantity in the pith of
some plants, as in the Sago-palm (Sagus Rumphii), of
the Maiay Islands, a single tree of which may yield 800
pounds. The onion, and various plants of the lily tribe,
are said to be entirely destitute of starch.

The preparation of starch from the potato is very sim-
ple. The potato tuber contains about 70 per cent. water,
24 per cent starch, and 1 per cent of cellulose, while the
remaining 5 per cent consist mostly of matters which
are easily soluble in water. By grating, the potatoes are
reduced to a pulp; the cells are thus broken and the
starch-grains set at liberty. The pulp is agitated on a
fine sieve, in a stream of water. The washings run off
milky from suspended starch, while the cell-tissue is re-
tained by the sieve. The milky liquid is allowed to rest
in vats until the starch is deposited. The water is then
poured off, and the starch is collected and dried.

Wheat-starch may be obtained by allowing wheaten
flour mixed with water to ferment for several weeks. In
this process the gluten, etc., are converted into soluble
matters, which are removed by washing, from the unal-
tered starch.

Starch is now most largely manufactured from maize.
A dilute solution of caustic soda is used to dissolve the
albuminoids (see p. 87). The starch and bran remaining
are separated by diffusing both in water, when the bran
rapidly settles, and the water, being run off at the proper
time, deposits nearly pure starch, the corn-starch of com-
merce.

Starch is prepared by similar methods from rice, horse-
chestnuts, and various other plants..

THE VOLATILE PART OF PLANTS. 49

Arrow-root is starch obtained by grating and washing
the root-sprouts of Marania Indica, and M. arundinacea,
plants native to the East and West Indies.

EXP. 25.—Reduce a clean potato to pulp by means of a tin grater. Tie
up the pulp in a piece of not too fine muslin, and squeeze it repeatedly
in a quart or more of water. The starch grains thus pass the meshes of
the cloth, while the cellulose is retained. Let the liquid stand until
the starch settles, pour off the water, and dry the residue.

Starch, as usually seen, is either a white powder which
consists of minute, rounded grains, and hence has a
slightly harsh feel, or occurs in 5 or 6-sided columnar
masses which readily crush to a powder. Columnar
starch acquires that shape by rapid drying of the wet
substance. When observed under a powerful magnifier,
the starch-grains often present characteristic forms and
dimensions.

In potato-starch they are egg or kidney-shaped, and
are distinctly marked with curved lines or ridges, which

surround a point or eye; a, Fig. 12. Wheat-starch con-
sists of grains shaped like a thick burning-glass, or spec-
tacle-lens, having a cavity in the centre, b. Oat-starch
is made up of compound grains, which are easily crushed
into smaller granules, c. In maize and rice the grains
are usually so densely packed in the cells as to present an
angular (six-sided) outline, as in d. The starch of the
bean and pea has the appearance of ¢. The minute
4

50 HOW CROPS GROW.

starch-grains of the parsnip are represented at /, and
those of the beet at g. .

The grains of potato-starch are among the largest, be-
ing often 35 of an inch in diameter; wheat-starch
grains are about yyy of an inch; those of rice, syyq of
an inch, while those of the beet-root are still smaller.

The starch-grains have an organized structure, plainly
seen in those from the potato, which are marked with
curved lines or ridges surrounding a point or eye; a, Fig.
12. When a starch-grain is heated cautiously, it swells
and exfoliates into a series of more or less distinct layers.

Starch, when air-dry, contains a considerable amount of
water, which may range from 12 to 23 per cent. Most of
this water escapes readily when starch is dried at 212°,
but a temperature of 230° F. is needful to expel it com-
pletely. Starch, thus dried, has the same composition
in 100 parts as cellulose, viz.:

Hydrogen...
Oxygen.

Starch-grains are unacted upon by cold water, unless
broken (see Exp. 26), and quickly settle from suspension
in it, having a specific gravity of 1.5.

Lodine-Test for Starch.—The chemist is usually able to
recognize starch with the greatest ease and certainty by
its peculiar deportment towards iodine, which, when dis-
solved in water or alcohol and brought in contact with
starch-grains, most commonly gives them a beautiful
blue or violet color. This test may be used even in
microscopic observations with the utmost facility. Some
kinds of starch-grains are, however, colored red, some
yellow, and a few brown, probably because of the pres-
ence of other substances.

Exp. 26.—Shake together in a test-tube 20c.c. of water and starch
- of the bulk of a kernel of maize. Add solution of iodine drop by drop,
agitating until a faint purplish color appears. Pour off half the liquid

THE VOLATILE PART OF PLANTS. 51

into another -test-tube, and add at once to it one-fourth its bulk of
iodine solution. The latter portion becomes intensely blue by trans-
mitted, or almost black by reflected, light. On standing, observe that
in the first case, where starch preponderates, it settles to the bottom,
leaving a colorless liquid, which shows the insolubility of starch in
cold water ; the starch itself has a purple or red tint. In the case
iodine was used in excess, the deposited starch is blue-black.

By the prolonged action of dry heat, hot water, acids,
or alkalies, starch is converted first into amidulin, then
into dextrin, and finally into the sugars maltose and dex-
trose, as will be presently noticed.

Similar transformations are accomplished by the action
of living yeast, and of the so-called diastase of germinat-
ing seeds.

The saliva of man and plant-eating animals likewise
disintegrates the starch-grains and mostly dissolves the
starch by converting it into maltose (sugar). It is much
more promptly converted into sugar by the liquids of the
large intestine. It is thus digested when eaten by ani-
mals. Starch is, in fact, one of the most important
ingredients of the food of man and domestic animals.

The starch-grains are not homogeneous. After pro-
longed action of saliva, hot water, or of dilute acids on
starch-grains, an undissolved residue remains which De-
Saussure (1819) regarded as nearly related to cellulose.
This residue is not changed by boiling water, but, under
prolonged action of dilute acids, it finally dissolves.
With iodine, after treatment with strong sulphuric acid,

sit gives the blue color characteristic of cellulose. There-
fore it is commonly termed starch-cellulose.

Starch-cellulose amounts to 0.5 to 6 per cent of the
starch-grains, varying with the kind of starch and the
nature and duration of the solvent action. Whether it
be originally present or a result of the treatment by
acids, etc., is undecided.

The chemical composition of starch-cellulose is identi-

__cal with that of the entire starch-grain, viz.: (CeH,0;)n.

The starch-grains also contain a small proportion of

amidulin, or soluble starch, presently to be noticed.

52 HOW CROPS GROW.

Gelatinous Starch. When starch is heated to near boiling with 12 to
15 times its weight of water, the grains swell and burst, or exfoliate,
the water is absorbed, and the whole forms ajelly. This is the starch-
paste used by the laundress for stiffening muslin. The starch is but
very slightly dissolved by this treatment. On freezing gelatinous
starch, the water belonging to it is separated as ice and on melting
remains for the most part distinct.

EXP. 27.—Place a bit of starch as large as a grain of wheat in 30¢. c.
of cold water and heat to boiling. The starch is converted into thin,
translucent paste. That a portion is dissolved is shown by filtering
through paper and adding to one-half of the filtrate a few drops of
iodine solution, when a perfectly clear blue liquid is obtained. The
delicacy of the reaction is shown by adding to 30¢. ¢. of water a little
solution of iodine, and noting that a few drops of the solution of starch
suffice to make the large mass of liquid perceptibly blue.

When starch-paste is dried, it forms a hard, horn-like mass.

Tapioca and Sago are starch, which, from being heated while still
moist, is partially converted into starch-paste, and, on drying, acquires
amore or less translucent aspect. Tapioca is obtained from the roots
of various kinds of Manihot, cultivated in the West Indies and South
America. Cassava is a preparation of the same sti.rch, roasted. Sago
is made in the islands of the East Indian Archipelago, from the pith of
palms (Sagus). Itis granulated by forcing the paste through metallic
sieves. Both tapioca and sago are now imitated from maize starch..

Next to water and cellulose, starch is the most abund-
ant ingredient of agricultural plants.

In the subjoined table are given the proportions of starch in certain
vegetable products, as determined by Dr. Dragendorff. The quantities
are, however, somewhat variable. Since the figures below mostly
refer to air-dry substances, the proportions of hygroscopic water found
in the plants by Dragendorff are also given, the quantity of which,
being changeable, must be taken into account in making any strict
comparisons.

AMOUNT OF STARCH IN PLANTS.

Water. Starch.
Per cent. Per cent.
Wheat 13.2 59.5
Wheat flour 15.8 68.7
Ry Gasusiase non deaeadinte siontan 11.0 59.7
Oats 11.9 46.6
Barley 11.5 57.5
Timothy-seed........... 12.6 45.0
Rice (hulled)...... areas 13.3 61.7
POA Seas siciatrdcssaieinais eles esiaasieiniors 5.0 4 81.3
Beans (white). 16.7 33.0
Clover-seed . 10.8 10.8
Flaxseed.... 7.6 23.4
Mustard-seed. 8.5 9.9 2
Colza-seed .... s 5.8 8.6
Teltow turnips*. ...dry substance 9.8
Potatoes........21-ssceeceees dry substance 62.5

* A sweet and mealy turnip, grown on light soils, for table use.

THE VOLATILE PART OF PLANTS. 53

Starch is quantitatively estimated by various methods.

1. In case of potatoes or cereal grains, it may be determined roughly
by direct mechanical separation. For this purpose 5 to 20 grams of the
substance are reduced to fine division by grating (potatoes) or by sof-
tening in warm water, and crushing in a mortar (grains). The pulp
thus obtained is washed either upon a fine hair-sieve or in a bag of
muslin, until the water runs off clear. The starch is allowed to settle,
is dried, and weighed. The value of this method depends upon the care
employed in the operations. The amount of starch falls out too low,
because it is impossible to break open all the minute cells of the sub-
stance analyzed.

2. In many cases starch may be estimated with great precision by
conversion into sugar. For this purpose Sachsse heats 3 grams of air-
dry substance, contained in a flask with reflux condenser, in a boiling
water bath for 3 hours, with 200 c. c. of water and 20c.c. of a 25 per cent
hydrochloric acid. After cooling, the acid is nearly neutralized with
sodium hydroxide, and the dextrose into which the starch bas been con-
verted is determined by Allihn’s method, described on p.65. Winton,
Report Ct. Ag. Exp. St., 1887, p. 132. ;

3. For Dragendorff’s method, see Henneberg’s Journal, fiir Land-
wirthschaft, 1862, p. 206.

Amidulin, or Soluble Starch.—A substance soluble
in cold water appears to exist in small quantity in the in-
terior of ordinary starch-grains. It is not extracted by
cold water from the unbroken starch, as shown by Exp.
26. On pulverizing starch-grains under cold water by
rubbing,in a mortar with sharp sand, the water, made
clear by standing or filtration, gives with iodine the char-
acteristic blue coloration. Exp. 27 shows that when
starch is gelatin‘zed by hot water, as in making starch
paste, a small quantity of starch goes into actual solu-
tion.

Ordinary insoluble starch: may be largely converted
into soluble starch by moderate heating, either for a long
time to the temperature of boiling water or for a short
space to 375° F, Maschke obtained a perfectly clear solu-
tion of potato-starch by heating it with 30 times its bulk
of water in a sealed glass tube kept immersed for 8 days
in boiling water. Zulkowski reached the same result by
heating potato-starch (1 part) with commercial glycerine
(16 parts). In this case the starch at first swells and
the mixture acquires a pasty consistence, but, when the

54 HOW CROPS GROW.

temperature rises to 375° F., the starch dissolves to a
nearly clear thin liquid.

Amidulin also appears to be the first product of the
action of diastase (the ferment of sprouting seeds) on
starch and doubtless exists in malt. :

Soluble starch is colored blue by iodine and is thrown
down from its solution in water, or glycerine, by addition
of strong alcohol. It redissolves in water or weak alco-
hol. Its concentrated aqueous solutions gelatinize on
keeping and the jelly is no longer soluble in water.
Dilute solutions when evaporated leave a transparent
residue that is insoluble in water.

On boiling together diluted sulphuric acid and starch
the latter shortly dissolves, and if as soon as solution has
taken place, the acid be neutralized with carbonate of
lime and removed by filtration, soluble starch remains
dissolved. (Schulze’s Amidulin.)

Amylodextrin. Nageli has described as Amylodextrin I and Amylo-
dextrin II, two substances that result from the action of moderately
strong acids on potato-starch at common temperatures. The starch
when soaked for many weeks in 12% hydrochloric acid remains nearly
unchanged in appearance, but the interior parts of the grains grad-
ually dissolve out, being changed into amylodextrin II, which closely
resembles and is probably identical with amidulin.

The starch-grains that remain unchanged in outward appearance, if
tested with iodine solution from time to time, are at first colored blue,
but after some days they take on a violet tinge and after prolonged
action of the acid are made red and finally yellow by iodine. The grains,
which are now but empty shells, may be freed from acid by washing
with cold water, and then, if heated to boiling with pure water, they
readily dissolve to a clear solution (amylodextrin I), from which Nageli,
by freezing and by evaporation, obtained crystalline disks. These
bodies, when dry, have the same composition as cellulose, starch, and
amidulin.

Dextrin (C,H,.0;) was formerly thought to occur
dissolved in the sap of all plants. According to Von
Bibra’s investigations, the substance existing in bread-
grains, which earlier experimenters believed to be dex-
trin, is for the most part gum. Busse, who examined
various young cereal plants and seeds, and potato tubers,
for dextrin, found it only in old potatoes and young

THE VOLATILE PART OF PLANTS. 55

wheat plants, and there in very small quantity. Accord-
ing to Meissl, the soy bean contains 10 per-cent of dex-
trin. :

Dextrin is easily prepared artificially by the trans-
- formation of starch, or, rather, of amidulin derived from
starch, and its interest to us is chiefly due to this fact.
When starch is exposed some hours to the heat of an
oven, or for 30 minutes to the temperature of 415° F.,
the grains swell, burst open, and are gradually converted
into a light-brown substance, which dissolves readily in
water, forming a clear, gummy solution. This is dex-
trin, and thus prepared it is largely used in the arts,
especially in calico-printing, as a cheap substitute for
gum arabic. In the baking of bread it is formed from
the starch of the flour, and often constitutes ten per cent
of the loaf. The glazing on the crust of bread, or upon
biscuits that have been steamed, is chiefly due to a coat-
ing of dextrin. Dextrin is thus an important ingredient
of those kinds of food which are prepared from the
starchy grains by cooking.

Commercial dextrin appears either in translucent
brown masses or as a yellowish-white powder. On ad-
dition of cold water, the dextrin readily dissolves, leaving
behind a portion of unaltered starch. When the solu-
tion is mixed with strong alcohol, the dextrin separates
in white flocks. With iodine, solution of commercial
dextrin gives a fine purplish-red color.

There are doubtless several distinct dextrins scarcely dis-
tinguishable except by the different degrees to which they
affect polarized light or by various chemical deportment
(reducing effect on alkaline copper solutions). They are
characterized as erythrodextrins, which give with iodine
a red color, and achroodextrins, which give no color with
jodine. Investigators do not agree as to the precise num-
’ ber of dextrins that result from the transformation of
starch.

iH

56 HOW CROPS GROW.

Exp. 28.—Cautiously heat a spoonful of powdered starch in a porce:
lain dish, with constant stirring so that it may not burn, for the space
of five minutes; it acquires a yellow, and later, a brown color. Now
add thrice its bulk of water, and heat nearly to boiling. Observe that
a slimy solution is formed. Pour it.upon a filter; the liquid that runs
through contains dextrin. To a portion add twice its bulk of alcohol;
dextrin is precipitated. To another portion, add solution of iodine;
this shows the presence of dissolved but unaltered starch. To a
third portion of the filtrate add one drop of strong sulphuric acid and
boila few minutes. Test with iodine, which, as soon as all starch is
transformed, will give a red instead of a blue color.

Not only heat but likewise acids and ferments produce
dextrins from starch and, according to some authors,
from cellulose. In the sprouting of seeds, dextrin is
abundantly formed from starch and hence is an ingre-
dient of malt liquors.

The agencies that convert starch into the dextrins easily
transform the dextrins into sugars (maltose or dextrose),
as will be presently noticed.

The chemical composition of dry dextrin is identical
with that of dry cellulose, starch, and amidulin.

Inulin, Cz>He2Og6, closely resembles starch in many.
points, and appears to replace that body in the roots of
the American artichcke,* elecampane, dahlia, dandelion,
chicory, and other plants of the same natural family
(composite). It may be obtained in the form of minute
white grains, which dissolve easily in hot water, and sep-
arate again as the water cools. According to Bouchardat,
the juice of the dahlia tuber, expressed in winter, becomes
a semi-solid white mass after reposing some hours, from
the separation of 8 per cent of inulin.

Inulin, when pure, gives no coloration with iodine. -It
may be recognized in plants, where it occurs as a solu-
tion, usually of the consistence of a thin oil, by soaking
a slice of the plant in strong alcohol. Inulin is insolu-
ble in this liquid, and under its influence shortly separ-

* Helianthus tuberosus, commonly known as Jcrusalem artichoke, and
cultivated in Europe under the name fopinambour, is a native of the
Northern Mississippi States.

THE VOLATILE PART OF PLANTS. 5?
ates as a solid in the form of spherical granules, which
may be identified with the aid of the microscope, and
have an evident crystalline structure.

When long heated with water it is slowly but complete-
ly converted into a kind of sugar (levulose); hot dilute
acids accomplish the same transformation in a short
time. It is digested by animals, and doubtless has the
same value for food as starch.

In chemical composition, inulin, dried at 212°, differs
from cellulose and starch by containing for six times
C.H100;, the elements of an additional molecule of water ;
CggHoe0'35 = 6 C.H1,.0; + H,O Kilian.

¢ Levulin (C,H. 0;)n coexists with inulin in the mature
or frozen tubers of the artichoke, dahlia, etc., and, accord-
ing to Muentz, isfound in unriperye-grain. Itisahighly
soluble, tasteless, gum-like substance resembling dextrin,
but without effect on polarized light. It appears to be
formed from inulin when the latter is long heated with
water at the boiling point, or when the tubers contain-
ing inulin sprout. Dilute acids readily transform it into
Jevulose, as they convert dextrin into dextrose.

Guiyrcogen (0,H1.0;)n exists in the blood and mus-
cles of animals in small quantity, and abundantly in the
liver, especially soon after hearty eating. It is obtained
by boiling minced fresh livers with water, or weak potash
solution, and adding alcohol to the filtered liquid. It is
a white powder which, with water, makes an opalescent
solution. It is colored wine-red by iodine. Boiling di-
lute sulphuric acid converts it into dextrose. With saliva,
it is said to yield dextrin, maltose and dextrose. Accord-
ing to late observations, glycogen occurs in the vegetable
kingdom, having been identified in various fungi and in
plants of the flax and the potato families.

The Gums and Pectin Bodies.—A number of
bodies exist in the vegetable kingdom, which, from the
similarity of their properties, have received the common

58 HOW CROPS GROW.

designation of gums. The best known are Gum Arabic,
the gums of the Peach, Cherry and Plum, Gum Traga-
canth and Bassora Gum, Agar-Agar and the Mucilages
of various roots, viz., of mallow and comfrey; and of
certain seeds, as those of flax and quince. .

Gum Arabic exudes from the stems of various species
of acacia that grow in the tropical countries of the Hast,
especially in Arabia and Egypt. It occurs in tear-like,
transparent, and, in its purest form, colorless masses.
These dissolve easily in their own weight of water, form-
ing a viscid liquid, or mucilage, which is employed for
causing adhesion between surfaces of paper, and for
thickening colors in calico-printing.

Gum Arabic is, however, commonly a mixture of at
least two very similar gums, which are distinguished by
their opposite effect on polarized light and by the differ-
ent products which they yield when boiled with dilute
acids.

Cherry Gum.—The gum which frequently forms
glassy masses on the bark of cherry, plum, apricot, peach
and almond trees, is a mixture in variable proportions of
two gums, one of which is apparently the same as occurs
in gum arabic, and is fully dissolved in cold water, while
the other remains undissolved, but
swollen to a pasty mass or jelly.

Gum Tragacanth, which comes
to us from Persia and Siberia, has
much similarity in its properties
to the insoluble part of cherry
gum, as it dissolves but slightly in
water and swells up to a paste or
jelly.

The so-called Vegetable mucilages
much resemble the insoluble part
of cherry gum and are found in Fig. 18.
the seeds of flax, quince, lemon, and in various parts of
many plants.

ae)
“an

THE VOLATILE PART OF PLANTS. 59

Flux-seed muctiage is procured by soaking unbroken flaxseed in cold
water, with frequent agitation, heating the liquid to boiling, strain-
ing, an@ evaporating, until addition of alcohol separates tenacious
threads from it. Itis then precipitated by alcohol containing a little
hydrochloric acid, and washed by the same mixture. On drying, it
forms a horny, colorless, and friable mass. Fig. 13 represents a highly
magnified section of the ripe flaxseed. The external cells, a, contain
the dry mucilage. When soaked in water, the mucilage swells, bursts
the cells, and exudes.

The Pectin Bodies.—The flesh of beets, turnips, and
similar roots, and of most unripe fruits, as apples,
peaches, plums, and berries of various kinds, contain one
or several bodies which are totally insoluble in water, but
which, under the action of weak acids or alkaline solu-
tions, become soluble and yield substances having gummy
or gelatinous characters, that have been described under
the names pectin, pectic acid, pectosic acid, metapectic
acid, etc. Their true composition is, for the most part,
not positively established. They are, however, closely
related to the gums. The insoluble substance thus trans-
formed into gum-like bodies, Fremy termed pectose.

The gums, as they occur naturally, are mostly mix-
tures. By boiling with dilute sulphuric or hydrochloric
acid they are transformed into sugars.

In the present state of knowledge it appears probable
that the common gums, for the most part, consist of a
few chemically distinct bodies, some of which have been
distinguished more or less explicitly by such names as
Arabin, Metarabin, Pararabin, Galactin, Paragalactin,
etc. :

Arabin, or Arabic Acid, is obtained from some va-
rieties of Gum Arabic* by mixing their aqueous solution
with acetic acid and alcohol. It-is best prepared from
sugar-beet pulp, out of which the juice has been ex-
pressed, by heating with milk of lime; the pulp is
thereby broken down, and to a large extent dissolves,

* Those sorts of commercial Gum Arabic which deviate the plane of
polarization of light to the left contain arabin in largest proportion.

60 HOW CROPS GROW.

The liquid, after separating excess of lime and adding
acetic acid, is mixed with alcohol, whereupon arabin is
precipitated. Arabin, thus prepared, is a milk-white
mass which, while still moist, readily dissolves in water
to a mucilage. It strongly reddens blue litmus and ex-
pels carbonic acid from carbonates. When dried at 212°
arabin becomes transparent and has the composition
C12H2,.0,;. Dried at 230° it becomes (by Joss of a mole-
cule of water) Oy,H20010, or 2 CsH1003.

Arabin forms compounds with various metals. Those
with an alkali, lime, or magnesia as base are soluble in
water. Gum arabic, when burned, leaves 3 to 4 per cent
of ash, chiefly carbonates of potassium, calcium and mag-
nesium. Arabic acid, obtained by Fremy from beets by
the foregoing method, but not in a state of purity, was
described by him as ‘‘metapectic acid.” To Scheibler
we owe the proof of its identity with the arabin of gum
arabic.

Metarabin.—When arabin is dried and kept at 212°
for some time, it becomes a transparent mass which is no
longer freely soluble in water, but in contact therewith
swells up to a gelatinous mass. This is designated
metarabin by Scheibler. It is dissolved by alkalies, and
thus converted into arabates, from which arabin may be
again obtained.

The body named pararabin by Reichardt, obtained
from beet and carrot pulp by treatment with dilute hy-
drochloric acid, is related to or the same as metarabin.
Fremy’s “pectin,” obtained by similar treatment from
beets, is probably impure metarabin.

EXP. 34.—Reduce several white turnips or beets to pulp by grating.
Inclose the pulp in a piece of muslin, and wash by squeezing in water
until all soluble matters are removed, or until the water comes off
nearly tasteless. Bring the washed pulp into a glass vessel, with
enough dilute hydrochloric acid (1 part by bulk of commercial muriatic
acid to 15 parts of water) to saturate the mass, and let it stand 48 hours.

Squeeze the acid liquid, filter it, and add alcohol, when “ pectin” will
separate.

THE VOLATILE PART OF PLANTS. 61

It may be that metarabin is identical with the ‘‘pec-
tose” of the sugar beet, since both yield arabin under the
influence of alkalies. It is evident that the composition
‘found for dried arabin properly belongs to metarabin, and
1 is probable that arabin consists of metarabin OHO
plus one or several molecules of water, and that metara-
bin is an anhydride of arabin.

Arabin and metarabin, when heated with dilute sul-
phuric acid, are converted into a crystallizable sugar
called arabinose, O;H1.0;. The gums that exude from
the stems of cherry, plum and peach trees appear to con-
sist chiefly of a mixture of freely soluble arabates with
insoluble metarabin. Gum Tragacanth is perhaps mostly
metarabin. All these gums yield, by the eeaoe of hot’
dilute acids, the sugar arabinose.

Galactin, C,Hi,05, discovered by Mintz in the seeds
of alfalfa arid found in other legumes, has the appearance,
solubility in water and general properties of arabin, and
is probably the right-polarizing ingredient of gum arabic.
Boiled with dilute acids it is converted into the sugar
galactose, C,H120¢.

Paragalactin, O.Hi,0;.—In the seeds of the yellow
lupin exists up to 20 per cent of a body that is insoluble
in water, but dissolves by warming with alkali solutions,
and when heated with dilute acids yields galactose. <Ac-
cording to Steiger it probably has the composition C.H,,.0;.
Maxwell has shown it to exist in other leguminous seeds,
viz., the pea, horse-bean (Faba vulgaris) and vetch.

In the ‘‘ Chinese moss,” an article of food prepared in
China from sea-weeds, and in the similar gum agar or
‘vegetable gelatine” of Japan, exists asubstance which
is insoluble in cold water, but with that liquid swells up
to a bulky jelly, and yields galactose when heated with
dilute acids. This corresponds to metarabin.

Xylin, or Wood Gum.—The wood of many decidu-
ous trees, the vegetable ivory nut, the cob of Indian

62 2 HOW CROPS GROW.

corn and barley husks, contain 6 to 20 per cent of a sub-
stance insoluble in cold water, but readily taken up in
cold solution of caustic soda. On adding to the solution
an acid, and afterwards alcohol, a bulky white substance
separates, which may be obtained dry as a white powder
or a translucent gum-like mass. It dissolves very slightly
in boiling water, yielding an opalescent solution. The
composition of this substance was found by Thomsen to
be C,H,,03;.

Xylin differs from pararabin and pectose in not being
soluble in milk of lime. It is converted by boiling with
dilute sulphuric acid into a crystallizable sugar, xylose,
whose properties have been but little investigated.

Flax-seed Mucilage, C,H,,0;, resembles metarabin,
but by action of hot dilute acids is resolved into cellulose
anda gum, which latter is further transformed into dex-
trose. The yield of cellulose is about four per cent.

Quince-Seed Mucilage appears to be a compound of
cellulose and a body like arabin. On boiling with dilute
sulphuric acid it yields nearly one-third its weight of cel-
lulose, together with a soluble gum and a sugar, the last
being a result of the alteration of the gum. The sugar
is similar to arabinose.

The Soluble Gums in Bread-grains.—In the bread-
grains, freely soluble gums occur often in considerable
proportion.

TABLE OF THE PROPORTIONS (per cent.) OF GUM* IN VARIOUS AIR-DRY
GRAINS OR MILL PRODUCTS.

(According to Von Bibra, Die Getreidearten und das Brod.)

Wheat kernel ............. 0006 4.50, Barley flour.. ........seeceeeee
Wheat flour, superfine........ 6.25 | Barley bran..
Spelt flour (Triticum spelta).. 2.48| Oat meal.......
Neat DrVaN...... 0.00 cece eee eees 8.85} Rice flour.......
Spelt bran.... -». 12.52} Millet flour..
Rye kernel. 4.10} Maize meal.......
Rye flour... 7.25 | Buckwheat flour

Rye bran..... caer -. 10.40

* The “gum” inthe above table (which dates from 1859), includes per-
haps soluble starch and dextrin in some, if not all cases, and, accord-
ing to O’Sullivan, barley, wheat and rye contain two distinct left-pol-
arizing gums, which he terms a-amylan and b-amylan. These oceur in
paey to the extent of 2.3 per cent. By action of acids they yield
dextrose.

THE VOLATILE PART OF PLANTS. 63

The experiments of Grouven show that gum arabic is
digestible by domestic animals. There is little reason to
doubt that all the gums are digestible and serviceable as
ingredients of the food of animals.

b. The Glucoses, CsH120¢5 (or O;H100;), are a class of
sugars having similar or identical composition, but dif-
fering from each other in solubility, sweetness, melting
point, crystal-form and action on polarized light.

The glucoses, with one exception, contain in 100 parts :

CArDON oo. see ee cece cnn ee ee cneees 40.00

Hydrogen.. sees 6,67

OXY LED cree eves gibiien diac uid Soceniackss 53.33
100.00 *

Levulose, or Fruit Sugar (Fructose), C.H1.0.,
exists mixed with other sugars in sweet fruits, honey and
molasses. Inulin and levulin are converted into this
sugar by long boiling with dilute acids, or with water
alone. When pure, it forms. colorless crystals, which
melt at 203°, but is usually obtained as a syrup. lis
sweetness is equal to that of saccharose.

Dextrose or Grape Sugar, OeHi.0¢, naturally oc-
curs associated with levulose in the juices of plants and
in honey. Granules of dextrose separate from the juice
of the grapé on drying, as may be seen in old “‘ candied ”
raisins. Honey often granulates, or candies, on long
keeping, from the crystallization of its dextrose.

Dextrose is formed from starch and dextrin by the ac-
tion of hot dilute acids, in the same way that levulose is

produced from inulin. In the pure state it exists as
-minute, colorless crystals, and is, weight for weight, but
two-thirds as sweet as saccharose or cane-sugar. It fuses
at 295°,

Dextrose unites chemically to water. Hydrated glucose, CgHy,0,Hqo,
occurs in commerce in an impure state as a crystalline mass, which

becomes doughy at a slightly elevated temperature. This hydrate
loses its erystal-water at 212°.

Dissolved in water, dextrose yields.a syrup, which is

64 HOW CROPS GROW.

thin, and destitute of the ropiness of cane-sugar syrup.
It does not crystallize (granulate) so readily as cane-
sugar.

Exp. 30.—Mix 100 c. c. of water with 30 drops of strong sulphuric acid,
and heat to vigorous boiling in a glass flask. Stir 10 grams of starch
with a little water, and pour the mixture into the hot liquid, drop by
drop, so as not to interrupt the boiling. The starch dissolves, and passes
successively into amidulin, dextrin, and dextrose. Continue the ebul-
lition for several hours, replacing the evaporated water from time to
time. To remove the sulphuric acid, add to the liquid, which may be
still milky from impurities in the starch, powdered chalk, until the sour
taste disappears; filter from the calcium sulphate (gypsum) that is
formed, and evaporate the solution of dextrose* at a gentle heat to a
syrupy consistence. On long standing it may crystallize or granulate.

By this method is prepared the so-called grape-sugar, or starch-sugar
of commerce, ‘which is added to grape-juice for making a stronger
wine, andis also employed for preparing syrups and imitating molasses.
The syrups thus made from starch or corn are known in the trade as
glucose.t+ Imitation-molasses is a mixture of @extrose-syrup with some
dextrin to make it “ropy.”

Even cellulose is convertible into dextrose by the pro-
longed action of hot acids. If paper or cotton be first
dissolved in strong sulphuric acid, and the solution
diluted with water and boiled, the cellulose is readily
transformed into dextrose. Sawdust has thus been made ~
to yield an impure syrup, suitable for the production of
alcohol.

In the formation of dextrose from cellulose, starch, amidulin and
dextrin, the latter substances take.up the elements of water as repre-
sented by the equation

Starch, ete. Water. Glucose.
CgH O05 + H,O = CoH y.0,

In this process, 90 parts of starch, etc., yield 100 parts of dextrose.

Trommer’s Copper test.—A characteristic test for dextrose and levu-
lose is found in their deportment towards an alkaline solution of cop-
per, which readily yields up oxygen to these sugars, the copper being .
reduced to yellow cuprous hydroxide or red cuprous oxide. -

Exp. 31.—Prepare the copper test by dissolving together in 30 c. v. of
warm water a pinch of sulphate of copper and one of tartarie acid;
add to the liquid, solution of caustic potash until it acquires a slip-

* If the boiling has been kept up but an hour or so, the dextrose will
contain dextrin, as may be ascertained by mixing a small portion of
the still acid liquid with 5 times its bulk of strong alcohol, which will
precipitate dextrin, but not dextrose.

_ + Under the name glucose, the three sugars levulose, dextrose and
maltose were formerly confounded together, by chemists.

THE VOLATILE PART OF PLANTS. 65

peryfeel. Place in separate test tubes a few drops of solution of cane-
sugar, a similar amount of the dextrin solution, obtained in Exp. 28;
of solution of dextrose, from raisins, or from Exp. 30; and of molasses ;
add to each a little of the copper solution, and place them in a vessel
of hot water. Observe that the saccharose and dextrin suffer little or
no alteration for a long time, while the dextrose and molasses shortly
cause the separation of cuprous oxide. i.

Exp. 32.—Heat to boiling a little white cane-sugar with 30 ¢. c. of
water, and 3 drops of strong sulphuric acid, in a glass or porcelain dish,
for 15 minutes, supplying the waste of water as needful, and test the
liquid as in the last Exp. This treatment transforms saccharose into
dextrose and levulose.

The quantitative estimation of the sugars and of starch is commonly
based upon the reaction just described. For this purpose the alkaline
copper solution is made of a known strength by dissolving a given
weight of sulphate of copper, etc., in a given volume of water, and the
dextrose or levulose, or a mixture of both, being likewise made toa
known volume of solution, the latter is allowed to flow slowly from a
graduated tube into a measured portion of warm copper solution, until
the blue color is discharged. Saccharose is first converted into dex-
trose and levulose, by he&ting with an acid, and then examined in the
same manner. ‘

Starch is transformed into dextrose by heating with hydrochloric
acid or warming with saliva. The quantity of sugar stands in defjnite
relation to the amount of copper separated, when the experiment is
earried out under certain conditions. See Allihn, Jou. fiir Pr. Chemie,
XXII, p. 52, 1880.

Galactose, C,H..0,, is formed by treating right-
polarizing gum arabic, galactin, or milk-sugar with
dilute acids. It crystallizes, is sweet, melts at 289° and
with nitric acid yields mucic acid (distinction from ara-
binose, dextrose and levulose).

Mannose (Seminose?) C,H:,.0, is a fermentable sugar
prepared artificially by oxidation of mannite (see p. 74),
and, according to E. Fischer, is probably identical with
the Seminose found by Reiss as a product of the action
of acids on a body existing in the seeds of coffee and in
palm nuts. (Berichte. XXII, p. 365).

Arabinose, C;H,,.0;, obtained from arabin (of left-
polarizing gum arabic), and from cherry gum by action
of hot dilute acids, appears in rhombic crystals. It is
less sweet than cane sugar, and fuses at 320°.

ce. The Sucroses, C12Ho2011, are sugars which, boiled with
dilute acids, undergo chemical change by taking up the

5

66 HOW CROPS GROW.

elements of water and are thereby resolved into glucoses.
In this decomposition one molecule of sucrose usually
yields either two molecules of one glucose or amolecule each
of two glucoses, Cy2H 2011 + HO = O¢Hi20¢6 + CoHi20«.
Saccharose, or Cane Sugar, ©,,.H..01, so called
because first and chiefly prepared from the
sugar-cane, is the ordinary sugar of com-
merce. When pure, it is a white solid,
readily soluble in water, forming a color. Fig. 14,
less, ropy, and intensely sweet solution. It crystallizes
in rhombic prisms (Fig. 14), which are usually small, as
in granulated sugar, but in the form of rock-candy may
be found an inch or more in length. The crystallized
sugar obtained largely from the sugar-beet, in Europe,
and that furnished in the United States by the sugar-
maple and sorghum, when pure, are identical with cane-
sugar. a
Saccharose also exists in the vernal juices of the war-
nut, birch, and other trees. It occurs in the stems of
unripe maize, in the nectar of flowers, in fresh honey, in
parsnips, turnips, carrots, parsley, sweet potatoes, in the
stems and roots of grasses, in the seeds of the pea and
bean, and in a multitude of fruits.

EXP. 29.—Heat cautiously a spoonful of white sugar until it melts (at
356° F.) to a clear yellow liquid. On rapid cooling, it gives a transpar-
ent mass, known as barley sugar, which is employed in confectionery.
At a higher heat it turns brown, froths, emits pungent vapors, and be-
comes burnt sugar, or caramel, which is used for coloring soups, ale, etc.

The quantity per cent of saccharose in the juice of various plants is
given in the annexed table. It is, of course, variable, depending upon

the variety of plant in case of cane, beet, and sorghum, as well as upon
the stage of growth.

SACCHAROSE IN PLANTS.

Per cent.
Sugar-cane, AaVeTage..........es cece eens 18 Peligot.
x Sugar-beet, SE ssralanavaipiana ata setigh atari 10 a
SOLE WGI se ciiie ca pis siseasiniscssenombinrsinatisoteiscerneres 13 Collier.
Maize, just flowered................eeee 33 Liidersdorff.

Sugar-maple, sap, WPOrAER: 3 te
Redmaple, "§ 8 seaidenivens pa :

THE VOLATILE PART OF PLANTS. 67

The composition of saccharose is the same as that of
arabin, and it contains in 100 parts :

DAP DON cscscosumceanviers miei aiesseiete
Hydrogen.. iibiosa
OXY BOT eiciiedsiersialaieta'n sierdiaeyielaioreicie-via

100.00

Oane-sugar, by long boiling of its concentrated aqueous
solution, and under the influence of hot dilute acids (Exp.
32) and yeast, loses its property of ready crystallization,
and is converted into levulose and dextrose.

According to Dubrunfaut, a molecule of cane-sugar takes up the ele-
ments of a molecule (5.26 per cent.) of water, yielding a mixture of

equal parts of levulose and dextrose. This change is expressed in
chemical symbols as follows:

CHO + H,O = CyHy,0, --+ CeHi20,
Cane-sugar. Water. Levulose. Dextrose.

This alterability on heating its solutions occasions a
loss of one-third to one-half of the saccharose that is
really contained in cane-juice, when this is evaporated in
open-pans, and is one reason why solid sugar is obtained
from the sorghum in open-pan evaporation with such dif-
ficulty.

Molasses, sorghum syrup, and honey usually contain
all three of these sugars.

Honey-dew, that sometimes falls in viscid drops from
the leaves of the lime and other trees, is essentially a mix-
ture of the three sugars with some gum. The mannas of
Syria and Kurdistan are of similar composition.

Maltose, C;.H,.0.H.0, is formed in the sprouting
of seeds by the action of a ferment, called diastase, on
starch. It is also prepared by treating starch or glycogen
with saliva. In either case the starch (or glycogen) takes
up the elements of water, 2 C;Hi.0; + HO = 0,2H.0,1.
Maltose in crystallizing unites with another molecule of
water, which it loses at 212°. Maltose, thus dried,
attracts moisture with great avidity.

Boiled with dilute acids one molecule of maltose yields

68 HOW CROPS GROW.

two molecules of dextrose, C12H»201: + H.O = 2 CeHi20c.
Maltose is also produced when starch and dextrin are
heated with dilute acids, and thus appears to be an inter-
mediate stage of their transformation into dextrose.

Maltose is accordingly an ingredient of some commer-
cial “‘ grape-sugars” made from starch by boiling with
diluted sulphuric acid.

Lactose, or Milk Sugar, 0:,H..0,, + H,0, is the
sweet principle of the milk of animals. It is prepared
for commerce by evaporating whey (milk from which
casein and fat have been separated for making cheese).
In a state of purity it forms transparent, colorless crys-
tals, which crackle under the teeth, and are but slightly
sweet to the taste. When dissolved to saturation in
water, it forms a sweet but thin syrup. Heated to 290°
the crystals become water-free.

Lactose is said to occur with cane-sugar in the sapo-
dilla (fruit of Achras sapota) of tropical countries.
Treatment with dilute sulphuric acid converts it into
galactose and dextrose.

CyH001 + HO = CyHyO, + CoHi20,
Lactose. Water. Galactose. Dextrose.

Raffinose, C,sHs.0., + 5 H,O (?), first discovered
by Loiseau in beet-sugar molasses, was afterwards found
by Berthelot in eucalyptus manna, by Lippmann in beet-
root, and by Boehm & Ritthausen in cotton-seed. It
crystallizes in fine needles, and is but slightly sweet. It
begins to melt at 190° with loss of crystal-water, which
may be completely expelled at 212°. The anhydrous
sugar fuses at 236°. It is more soluble in water and has
higher dextrorotatory power than cane-sugar. Heated
with dilute acids it yields dextrose, levulose and galactose.

CigHy201g + 2 HO = 3 (CyHy 205).

The Sugars in Bread-Grains.—The older observers
assumed the presence of dextrose in the bread-graius.

THE VOLATILE PART OF PLANTS. 69

Thus, Vauquelin found, or thought he found, 8.5% of
this sugar in Odessa wheat. More recently, Peligot,
Mitscherlich, and Stein denied the presence of any sugar
‘in these grains. In his work on the Cereals and Bread,
(Die Getreidearten und das Brod, 1860, p. 163), Von
Bibra reinvestigated this question, and found in fresh-
ground wheat, etc., a sugar having some of the charac-
ters of saccharose, and others of dextrose and levulose.
Marcker and Kobus, in 1882, report maltose (which was
unknown to the earlier observers) in sound barley, and
maltose and dextrose in sprouted barley.

Von Bibra found in the flour of various grains the following quanti-
ties of sugar:

PROPORTIONS OF SUGAR IN AIR-DRY FLOUR, BRAN, AND MEAL.

Per cent.

Wheat flour. ......... 0 ccc cece cence e een eeeenenees 2.33
Spelt flour ..........eseeeeee Gree +» 141

eat DYAN....... 06s eee es Zyoin ++ 4,30
Spelt Dran......ccccsserecessvecseseesceses - 2.70
Rye flour.......... cece cece ee 3.46 é
Rye bran..... 1.86
Barley meal 3.04
Barley bran. 1.90
Oat meal. 2.19
Rice flour. 0.39
Millet flow 1.30
Maize meal... Rone beset + 371
Buckwheat meal......... cece cee ce eee ee een ecces 0.91

Glucosides.—There occur in the vegetable kingdom a
large number of bodies, usually bitter in taste, which
contain dextrose, or a similar sugar, chemically combined
with other substances, or that yield it on decomposition.
Salicin, from willow bark ; phloridzin, from the bark of
the apple-tree root ; jalapin, from jalap ; aeseulin, from
the horse-chestnut, and amygdalin, in seeds of almond,
peach, plum, apple, cherry, and in cherry-laurel leaves,
are of this kind. The sugar may be obtained from these
so-called glucosides by heating with dilute acids.

The seeds of mustard contain the glucoside myronic acid united to

potassium. This, when the crushed seeds are wet with water, breaks
up into dextrose, mustard-oil, and acid potassium sulphate, as follows:

Cy Hig K NS, O09 = CygHyO, + C,H;NCS + KHSO,
The cambial juice of the conifers contains coniferin, crystallizing in

40 HOW CROPS GROW.

brilliant needles, which yields dextrose and a resin by action of dilute
acid, and by oxidation produces vanillin, the flavoring principle of the
vanilla bean. :

Mutual Transformations of the Carbhydrates.—One of
the most remarkable facts in the history of this group of
bodies is the facility with which its members undergo
mutual conversion. Some of these changes have been
already noticed, but we may appropriately review them
here.

a. Transformations in the plant.—In germination, the
starch which is largely contained in seeds is converted
into amidulin, dextrin, maltose and dextrose. It thusac-
quires solubility, and passes into the embryo to feed the
young plant. Here these are again solidified as. cellulose,
starch, or other organic principle, yielding; in fact, the
chief part of the materials for the structure of the seed-
ling.

At spring-time, in cold climates, the starch stored up
over winter in the new wood of many trees, especially the
maple, appears to be converted into the sugar which is
found so abundantly in the sap, and this sugar, carried
upwards to the buds, nourishes the young leaves, and is
there transformed into cellulose, and into starch again.

_ The sugar-beet root, when healthy, yields a juice con-
taining 10 to 14 per cent. of saccharose, and is destitute
of starch. Schacht has observed that, in a certain dis-
eased state of the beet, its sugar is partially converted
into starch, grains of this substance making their appear-
ance. (Wilda’s Centralblatt, 1863, II, p. 217.)

In some years the sugar-beet yields a large amount of
arabin, in others but little.

The analysis of the cereal grains sometimes reveals the
presence of dextrin, at others of sugar or gum.

Thus, Stepf found no dextrin, but both gum and sugar in maize-meal
(Jour. fiir Prakt. Chem., 76, p. 92); while Fresenius, in a more recent
analysis (Vs. St., I, p. 180), obtained dextrin, but neither sugar nor gum.
The sample of maize examined by Stepf contained 3.05 p. c. gum and
3.71 p. c. sugar; that analyzed by Fresenius yielded 2.33 p. ¢. dextrin.

THE VOLATILE PART OF PLANTS. val

Mircker & Kobus made comparative analyses of well-cured and of
sprouted barley, with the following results per cent:

Grown.
Stare hii siicvssarcsmmsnacar ee warren te : 57,98
Soluble starch. stare 1.17
De@XtLIN. 650. caaje coins soos cee 7 0.00
Dextrose wwe 10; 4.92
Malton Gissasiscaeanaincs veawesig@asnes Le 7.92

The various gums are a result of the transformation of
cellulose, as Mohl first showed by microscopic study.

b. In the animal, the substances we have been describ-
ing also suffer transformation when employed as food.
During the process of digestion, cellulose, so far as it is
acted upon, starch, dextrin, and probably the gums, are
all converted into dextrose or other sugars, and from
these, in the liver especially, glycogen is formed.

c. Many of these changes may also be produced apart
from physiological agency, by the action of heat, acids,
and ferments, operating singly or jointly.

Cellulose and starch are converted, by boiling with a
‘dilute acid, into amidulin, dextrin, maltose and dextrose.
Cellulose and starch acted upon for some time by strong
nitric acid give compounds from which dextrin may be
separated. Cellulose nitrate sometimes yields gum (dex-
trin) by its spontaneous decomposition. A kind of gum
also appears in solutions of cane-sugar or in beet-juice,
when they ferment under certain conditions. Inulin and
the gums yield glucoses, but no dextrin, when boiled
with weak acids.

d. It will be noticed that while physical and chemical
agencies produce these metamorphoses mostly in one di-
rection, under the influence of life they go on in either
direction.

In the laboratory we can in general only reduce from a
higher, organized, or more complex constitution to a
lower and simpler one. In the vegetable, however, all
these changes, take place with the greatest facility.

The Chemical Composition of the Carbhydrates.—It .

72

HOW CROPS GROW.

has already appeared that the substances just-described
stand very closely related to each other in chemical com-

position.

pressed in formule.

CHEMICAL FORMULZ OF THE CARBHYDRATES.

In the following table their composition is ex-

Amyloses. Dried
Cellulose, Cy Hy Os
eee } Cy Hy O;*
Starch, Cy Hyp Os
Soluble starch,

Amidulin, Cg Hyp O; *
Amylodextrin,

Dextrin, Cg Hy O5 =
Inulin, 6 (Cg Hyp Os) + H, O = ~ Ogg He: O 1
Levulin, 2 (Cg Hy O5) + H, O = Crp He, O11
Glycogen, Cg Hip O5
Pectin, (2)
eet 2 (Cy Hyp 03) -+ Hy O Cus Hee O15
Galactin, Cs Hi O5
Paragalactin, Ce Hy O5
Flax-seed mucilage, Cg Hy O5
Quince-seed mucilage, Cy Hy O; + 2 (Cg Hyp O;)—H,O = Cyg Hog Ong

Glucoses. Crystallized ;
Levulose, Ce Hye Oo C5 Hye O5
Dextrose, Ce Hyg O, and Cy Hy Og Cs Hye O¢
Galactose, Co Hie O5 Cy Hye O¢
Mannose, Co Hyg Og C5 Hye O6
Arabinose, Cs Hi O5 Cs Hy O5

Sucroses.

Saccharose, Cyp Hop On. * Cie Hoe On
Maltose, Cio Hog Oro Cie Hee On
Lactose, Oye Hos Ors Cip Hey On
Raffinose, Cry Ayo Oor Cig Hos Ors

As above formulated, it is seen that all these bodies,
except arabinose, contain 6 atoms of carbon, or a num-
ber which is some simple multiple of 6, united to as much
hydrogen and oxygen as form in most cases 5, 6 or 11
molecules of water (H,O). Being thus composed of car-
bon and the elements of water they are termed Carbhy-
drates.

The mutual convertibility of the carbhydrates is the

* These soluble bodies when dried probably lose water which is
essential to their composition, as on drying they become insoluble.

‘,

THE VOLATILE PART OF PLANTS. "3

easier to understand since it takes place by the loss or
gain of several molecules of water.

The formule given are the simplest that accord with
the results of analysis. In case of many of the amyloses
it is probable that the above formule should be multi-
plied by 2, 4, or 6, or even more, in order to reach the
true molecular weight.

Isomerism.—Bodies which—like cellulose and dextrin, or like levu-
lose and dextrose—are identical in composition, and yet are character-
ized by different properties and modes of occurrence, are termed tsom-
eric; they are examples of isomerism. These words are of Greek deri-
vation, and signify of equal measure.

We must suppose that the particles of isomeric bodies which are com-
posed of the same kinds of matter, and in the same quantities, exist in
different states of arrangement. The mason can build, from a given
number of bricks and a certain amount of mortar, a simple wall, an
aqueduct, a bridge ora castle. The composition of these unlike struc-
tures may be the same, both in kind and quantity; but the structures
themselves differ immensely, from the fact of the diverse arrangement
of their materials. In the same manner we may suppose starch to dif-
fer from. dextrin by a difference in the relative positions of the atoms
of carbon, hydrogen, and oxygen in the molecules which compose
them.

By use of “structural formulz” it is sought to represent the different
arrangement of atoms in the molecules of isomeric bodies. In case
of substances so complex as the sugars, attempts of this kind have but
recently met with success. The following formule exhibit to the
chemist the probable differences of constitution between dextrose and
levulose.

Dextrose. Levulose.
H
H-b—0 H w_-t_o H
I Rie
H—C—0 H 0
—__ : C—H nto H
Ho H H OH
O H—C—O H H OH
pas OH H OH

To those familiar with advanced Organic Chemistry the foregoing
formuiz, to some extent, “account for” the chemical characters of
these sugars, and explain the different products which they yield
under decomposing influences.

APPENDIX TO THE CARBHYDRATES.
Nearly related to the Carbhydrates are the following substances :—

%4. HOW CROPS GROW.

Mannite, Cs5HyOy, is abundant in the so-called manna of the apoth-
ecary which exudes from the bark of several species of ash that
grow in the eastern hemisphere (raxinus ornus and rotundifolia). It
likewise exists in the sap of our fruit trees, in edible mushrooms, and
sometimes is formed in the fermentation of sugar (viscous fermenta-
tion). It appears in minute colorless crystals and has a sweetish taste.
It may be obtained from dextrose and levulose by the action of
nascent hydrogen as liberated from sodium amalgam and water,
CH 4,0, + Hy = CoHyyOy-

-Duicite, CyH,,0,, is a crystalline substance found in the common cow-
wheat (Melampyrum nemorosum) and in Madagascar manna. It is
obtained from milk-sugar by the action of sodium amalgam.

The isomeres manuite and dulcite, when acted on by nitric acid, are
converted into acids which are alsoisomeric. Mannite yields saccharic
acid, which is also formed by treating cane-sugar, dextrose, levulose,
dextrin and starch with nitric acid. _Dulcite yields, by the same treat-
ment, mucic acid, which is likewise obtained from arabin and other
gums. Milk-sugar yields both saccharic and mucic acid. Saccharic
acid is very soluble in water. Mucie acid is quite insoluble. Both
have the formula CgH,90,.

The Pectin-bodies. The juice of many ripe fruits, when mixed with
alcohol, yields a jelly-like precipitate which has long been known
under the name of pectin. When the firm flesh of acid winter-fruits is
subjected to heat, as in baking or stewing, it sooner or later softens,
becomes soluble in water and yields a gummy liquid from which by
adding alcohol the same or a similar gelatinous substance is separated.
Fremy supposes that in the pulp “ pectose”’ exists which is transformed
by acids and heat into pectin.

EXP. 33.—Express, and, if turbid, filter through muslin the juice of a
ripe apple, pear, or peach. Add to the clear liquid its own bulk of
alcohol. Pectin is precipitated as a stringy, gelatinous mass, which,
on drying, shrinks greatly in bulk, and forms, if pure, a white sub-
stance that may be easily reduced to powder, and is readily soluble in
cold water.

Pectosic and Pectic Actds. These bodies, according to Fremy, com-
pose the well-known fruit-jellies. They are both insoluble or nearly

.80 in cold water, and remain suspended in it as a gelatinous mass.
Pectosic acid is soluble in hot water, and is supposed to exist in those
fruit-jellies which liquefy on heating but gelatinize on cooling. Pec-
tie acid is stated to be insoluble in hot water. According to Fremy,
pectin is changed into pectosic and pectic acids and finally into meta-
pectic acid by the action of heat and during the ripening process.

EXP. 35.—Stew a handful of sound cranberries, covered with water,
just long enough to make them soft. Observe the speedy solution of
the firm pulp or ‘‘pectose.”’ Strain through muslin. The juice contains
soluble pectin, which may be precipitated from a small portion by
alcohol. Keep the remaining juice heated to near the boiling point in
a water bath (i. e., by immersing the vessel containing it in a larger
one of boiling water). After a time, which is variable according to
the condition of the fruit, and must be ascertained by trial, the juice
on cooling or standing solidifies to a jelly, that dissolves on warming,
and reappears again on cooling—Fremy’s pectosic acid. By further

THE VOLATILE PART OF PLANTS. v6)

heating, the juice may form a jelly which is permanent when hot—
pectic acid.

Other ripe fruits, as quinces, strawberries, peaches, grapes, apples,
etc.,may be employed for this experiment, but in any case the time
required for the juice to run through these changes cannot be pre-
dicted safely, and the student may easily fail in attempting to fol-
low them.

Scheibler having shown that Fremy’s metapectic acid of beets is
arabic acid, it is probable that Fremy’s pectin, pectic acid and pectosic
acid of fruits, are bodies similar to or identical with the gums already
described. The pectin bodies of fruits have not yet been certainly ob-
tained in a state of purity, since the analyses of preparations by vari-

_ ous chemists do not closely agree.

The Vegetable Acids.—Nearly every family of the
vegetable kingdom, so far as investigated, contains one
or more organic acids peculiar to itself. Those of more
general occurrence which alone concern us here are few
in number and must be noticed very concisely.

The vegetable acids rarely occur in plants in the free
state, but are for the most part united to metals or
to organic bases in the form of salts. The vegetable
acids consist of carboxyl, COOH, united generally to
a hydrocarbon group. They are monobasic, dibasic or
tribasic, according as they contain one, two or three
carboxyls.

The Monobasic Acids, to be mentioned here, fall into
two groups, viz.: Fatty acids and Oxyfatty acids.

Tuer Fatry Acips constitute a remarkable ‘‘homolo-
gous series,” the names and formule of a number of
which are here given:

Found in
Formic acid, H, COOH Pine needles, red ants, guano.
Acetic “« CH,COOH Vinegar and many vegetable juices.
Propionie “ C,H;COOH Yarrow-flowers.
Butyric “ C,H,COOH Butter,limburger cheese,parsnip seeds.
Valerie “ C,H,COOH Valerian root, old cheese.
Caproic “ C,;H,COOH Butter, cocoanut oil.
Oenanthylic’ C,H,,COOH (Artificial.) [fusel oil.
Caprylic “ C,H,COOH Butter, cocoanut oil, limburger cheese,
Pelargonic “ C,H,COOH Rose-geranium.
Caprice “ CG HyCOOH Butter, cocoanut oil.
Umbellic “ Cy H,COOH -Seeds of California laurel.
Lauric “ Cy, H.COOH Laurel oil, butter, bayberry tallow.

Tridecylic ‘“ Cy,H,;COOH (Artificial.)

%6

Myristic acid,C,,; HCOOH

HOW CROPS GROW.

Nutmeg oil.

Isocetic “* Cy Hy» COOH Seeds of Jatropha.

Palmitic * CH; COOH Butter, tallow, lard, palm oil.
Margaric “ CigHs COOH (Artificial.)

Stearic - “ C,H; COOH Tallow, lard.

Nondecylic “ C,gH;,COOH (Unknown.)

Arachic “ Cy Hy COOH Butter, peanut oil.

Medullic “ Coo Hy COOH Marrow of ox.

Behenic “ Cy Hy COOH Oil of Moringa oleifera.

—_ Cy» Hy COOH (Unknown.)

Lignoceric ‘“ C,;HyCOOH Beech-wood tar.

Hyenic « “* Coy Hy COOH Hyena-fat.

—_—— C.5H; COOH (Unknown.)

Cerotic “ Cy Hs COOH Beeswax, carnauba wax, wool-fat.

It is to be observed that these fatty acids make a nearly
complete series, the first of which contains one carbon
and two hydrogen atoms, and the last 27 carbon and 54
hydrogen atoms, and that each of the intermediate acids
differs from its neighbors by CH,. The first two acids
in this series are thin, intensely sour, odorous liquids
that mix with water in all proportions; the third to the
ninth inclusive are oily liquids whose consistency in-
creases and whose sourness and solubility in water dimin-
ish with their greater carbon content. The tenth and
other acids are at common temperatures nearly tasteless,
odorless, and fatty solids, which easily melt to oily liquids
whose acid properties are but feebly manifest. Of these
acids a few only require further notice.

Acetic Acid, C,H,0., or CH,COOH, formed in the
“acetic fermentation ” from cider, malt, wine and whis-
ky, alcohol being in each case its immediate source,
exists free in vinegar to the extent of about 5 per cent.
When pure, it is a strongly acid liquid, blistering the
tongue, boiling at 246°, and solidifying at about 60° toa
white crystalline mass. In plants, acetic acid is said to
exist in small proportion, mostly as acetate of potassium.

Butyric Acid, C,H,0., or CH;CH,CH,COOH, in the
free state, occurs in rancid butter, whose disagreeable
odor is largely due to its presence. In sweet butter it
exists only as a glyceride or fat of agreeable qualities.

THE VOLATILE PART OF PLANTS. 77

The other acids of this series are mostly found in veg-
etable and animal fats or fatty oils. (See p. 85.)

OxyFatry Acips.—The acids of this class differ from
the corresponding fatty acids by having an additional
atom of oxygen, or by the substitution of OH for H in
the latter. There are two acids of this class that may be
briefly noticed, viz.: oxyacetic, or glycollic acid, and oxy- |
propionic or lactic acid.

Glycollic Acid, C,H,0; or HOCH,COOH, exists in
the juices of plants (grape-vine), and like acetic acid may
be formed by oxidizing alcohol.

Lactic, ©;H,O;, or CH,CH (OH) COOH, is the acid
that is formed in the souring of milk, where it is produced
from the milk-sugar by a special organized ferment. It
is also formed in the “lactic fermentation” of cane-
sugar, starch and gum, and exists accordingly in sour-
kraut and ensilage.

The fatty and oxyfatty acids are monobasic, i.e., they
contain one carboxyl, COOH, and each acid forms one
salt only, with potassium, for instance, in which the hy-
drogen of the carboxyl is replaced by the metal. Thus,
potassium acetate is CH,COOK.

The oxyfatty acids are especially prone to form anhy-
drides by loss of the elements of water. Lactic acid
cannot be obtained free from admixed water when its
aqueous solutidhs are evaporated, without being partially
converted into an. anhydride. Gentle heat up to 2'70°
changes it, with loss of water, into so-called lactolactic
_ acid,* CgH1.0;, a solid, scarcely soluble in water, but that
slowly reproduces lactic acid by contact with water, and
dissolves in alkalies to form ordinary lactates. Lacto-
lactic acid, heated to 290°, loses water with formation
of lactide,+ C.H,0,, a solid nearly insoluble in water, but
also convertible into lactic acid by water, and into lactates
by alkalies.

# 2 (CsH,0,) = CgH,0; + H,O + CyH 905 = CyH,0, + H,0

78 HOW CROPS GROW.

Dibasic Acids.—The acids of this class requiring notice

are : .
cooH

Oxalic acid, C,H,0,, or
OOH
Malonte acid, CsH,0,, or CH, Coon
CH,—COOH
Succinic acid, C,H,0,, or
H,—COOH
; CH,—COOH
Matic acid (Oxysuccinic acid), C,H,0;, or re
'H(OH)—COOH

CH(OH) COOH
Tartaric acid (Dioxysuccinic CyH,O,, or
acid), H(OH) COOH

The salts formed by union of these acids with metallic
bases are either primary or secondary, according as the
metal enters into one or two of the carboxyls.

Oxalic acid, C,H,0,, exists largely in the common
sorrel, and is found in greater or, less
quantity in nearly all plants. The’ pure
acid presents itself in the form of color-
less, brilliant, transparent crystals, not
unlike Epsom salts in appearance (Fig. Fig. 15.
15), but having an intensely sour taste.

Primary potassium oxalate (formerly termed acid ox-
alate of potash), HOOC—COOK, occasions the sour taste
of the juice of sorrel, from which it may be obtained
in crystals by evaporating off the water. It may also be
prepared by dissolving oxalic acid in watgr, dividing the
solution into two equal parts, neutralizing * one of these
by adding solution of potash and then mixing the two
solutions and evaporating until crystals form.

Secondary potassium oxalate (neutral oxalate of potash),
KOOC—COOK, is the result of fully neutralizing oxali-
acid:with potash solution. It has no sour taste.

Primary calcium oxalate exists dissolved in the ce.
of plants so long as they are in active growth. Second-
ary calcium oxalate is extremely insoluble in water, and

yee
* As described in Exp. 38.

THE VOLATILE PART OF PLANTS. 19

very frequently occurs within the plant as microscopic
‘crystals. These are found in large quantity in the ma-
ture leaves and roots of the beet, in the root of garden
rhubarb, and especially in many lichens.

‘Secondary ammonium oxalate is employed as a test for
calcium.

Exp. 36.—Dissolve 5 grams of oxalic acid in 50 c. c. of hot water, add
solution of ammonia orsolid carbonate of ammonium until the odor of
the latter slightly prevails, and allow the liquid to cool slowly. Long,
needle-like crystals of ammonium oxalate separate on cooling, the
compound being sparingly soluble in cold water. Preserve for future
use.

EXP. 37.—-Add to any solution of lime, as lime-water (see note, p. 20),
or hard well-water, a few drops of solution of ammonium oxalate.
Secondary Calcium oxalate immediately appears as a white, powdery
precipitate, which, from its extreme insolubility, serves to indicate the
presence of the minutest quantities of lime. Add afew drops of hydro-
chlorie or nitric acid to the calcium oxalate; it disappears. Hence
ammonium oxalate is a test for lime only in solutions containing no free

mineralacid. (Acetic and oxalic acids, however, have little effect upon
the test.)

Malonic acid and Succinic acid occur in plants in
but small quantities. ‘The former has been found in
sugar-beets, the latter in lettuce and unripe grapes.

Malic acid, C,H,0,, is the chief sour principle of ap-
ples, currants, gooseberries, plums, cherries, strawberries,
and most common fruits. It exists in small quantity ina
multitude of plants. It is‘found abundantly in the gar-
den rhubarb, and primary potassium malate may be ob-
tained in crystals by simply evaporating the juice of the
leaf-stalks of this plant. Ht is likewise abundant as cal-
cium salt in the nearly ripe berries of the mountain ash,
and in barberries. Calcium malate also occurs in con-
siderable quantity in the leaves of tobacco, and is often
encountered in the manufacture of maple sugar, separat-
ing as a white or gray sandy powder during the evapora-
tion of the sap.

Pure malic acid is only seen in the chemical laboratory,
and presents white, crystalline masses of an intensely
sour taste. It is extremely soluble in water.

80 HOW CROPS GROW.

Tartaric acid, C,H,O., is abundant in the grape,
from the juice of which, during fermentation, it is de-
posited as argol. This, on purification,
yields the cream of tartar (bitartrate of
potash) of commerce. ‘Tartrates of po-
tassium and calcium exist in small quan-
tities in tamarinds, in the unripe berries Fig. 16.
of the mountain ash, in the berries of the sumach, in cu-
cumbers, potatoes, pineapples, and many other fruits.
‘The acid itself may be obtained in large glassy crystals
(see Fig. 16), which are very sour to the taste.

Of the Tribasic Acids known to occur in plants, but
one need be noticed here, viz., citric acid.

CH,COOH
(, Hy 0, or C(O) COOH
H,COOH

Citric acid exists in the free state in the juice of the
lemon, and in unripe tomatoes. It accompanies malic
acid in the currant, gooseberry, cherry, strawberry, and
raspberry. It is found in small quantity in tobacco
leaves, in the tubers of the artichoke (Helianthus), in the
bulbs of onions, in beet-roots, in coffee-berries, in seeds of
lupin, vetch, the pea and bean, and in the needles of the
fir tree, mostly as potassium or calcium salt. It also
exists in cows’ milk.

In the pure state, citric acid forms large transparent or
white crystals, very sour to the taste.

Relations of the Vegetable Acids to each other, and to the Amyloses.—
Oxalic, malic, tartaric and citric acids usually occur together in our
ordinary fruits, and some of them undergo mutual conversion in the
living plant.

According to Liebig, the unripe berries of the mountain ash contain
much tartaric acid, which, as the fruit ripens, is converted into malic
acid. Tartaric acid can be artificially transformed into malic acid, and
this into succinic acid.

When citric, malic and tartaric acids are boiled with nitric acid, or
heated with caustic potash, they all yield oxalic acid.

Cellulose, starch, dextrin, the sugars, yield oxalic acid when heated

THE VOLATILE PART OF PLANTS. 81

with potash or nitric acid. Commercial oxalic acid is thus made from
ey aia sugar and starch yield tartaric acid by the action of
nitric acid.

Definition of Acids, Bases, and Salts.—In the popular
sense, an acid is any body having a sour taste. It is, in
fact, true that all sour substances are acids, but all acids
are not sour, some being tasteless, others bitter, and some
sweet. A better characteristic of an acid is its capability
of forming salés by its interaction with bases. Thestrong-
est acids, i. e., those bodies whose acid characters are most
highly developed, if soluble, so as to have any effect on
the nerves of taste, are sour, viz., sulphuric acid, phos-
phoric acid, nitric acid, etc.

Bases are the opposite of acids. The strongest bases,
when soluble, are bitter and biting to the taste, and cor-
rode the:skin. Potash, soda, lime, and ammonia are ex-
amples. Magnesia, oxide of iron, and many other com-
pounds of metals with oxygen, are insoluble bases, and
hence destitute of taste. Potash, soda, and ammonia
are termed alkalies ; lime and magnesia, alkali-earths.

Salts are compounds that result from the mutual ac-
tion of acids and bases. Thus, in Exp. 20, the salt, cal-
cium phosphate, was produced by bringing together
phosphoric acid, and the base, lime. In Exp. 37, cal-
cium oxalate was made in a similar manner. Common
salt—in chemical language, sodium chloride—is formed
when caustic soda is mixed with hydrochloric acid, water
being, in this case, produced at the same time.

NaOH + HCL = = Nacl + H,0
Sodium hydroxide. Hydrochloric acid. Sodi chloride. Water.

In general, salts having a metallic base are formed by
substituting the metal for the hydrogen of the acid ; or if
an organic acid, for the hydrogen that is united to oxy-
gen, i.e., of carboxyl, COOH.

Ammonia, NH;, and many organic bases unite directly
to acids in forming salts.

6

82 HOW CROPS GROW.

NA, + HCl = NH,C}
Ammonia. Hydrochloric acid. Ammonium chloride.*

NH, + CH,COOH = CH,COONH,
Ammonia, Acetic acid. Ammonium Acetate.

Test for acids and alkalies.—Many vegetable colors are altered by sol-
uble acids or soluble bases (alkalies), in such a manner as to answer the
purpose of distinguishing these two classes of bodies. . A solution of
ecochineal may be employed. It has a ruby-red color when concen-
trated, but, on mixing with much pure water, becomes orange or yel-
lowish-orange. Acids do not affect this color, while alkalies turn it to
an intense carmine or violet-carmine, which is restored to orange by
acids.

EXP. 38.—Prepare tincturet of cochineal by pulverizing 3 grams of
cochineal, and shaking frequently with a mixture of 50c¢. c. of strong
alcohol and 200 c.v. of water. After a day or two, pour off the clear
liquid for use.

To acupof water add a few drops of strong sulphuric acid, and to an-
other similar quantity add as many drops of ammonia. To these liquids
add separately 5 drops of cochineal tincture, observing the coloration
in each case. Divide the dilute ammonia into two portions, and pour
into one of them the dilute acid, until the carmine color just passes into
orange. Should excess of acid have been incautiously used, add am-
monia, until the carmine reappears, and destroy it again by new por-
tions of acid, added dropwise. The acid and base thus neutralize each
other, and the solution contains sulphate of ammonia, but no free acid
or base. It will be found that the orange-cochineal indicates very mi-
nute quantities of ammonia, and the carmine-cochineal correspond-
ingly small quantities of acid.

In the formation of salts, the acids and bases more or
less neutralize each other’s properties, and their com-
pounds, when soluble, have a less sour or Jess acrid taste,
and act less vigorously on vegetable colors than the acids
or bases themselves. Some soluble salts have no taste
at all resembling either their base or acid, and have
no effect on vegetable colors. This is true of common
- salt, glauber salts or sulphate of sodium, and saltpeter or
nitrate of potassium. Others exhibit the properties of their
base, though in a reduced degree. Carbonate of am-
monium, for example, has much of the odor, taste, and

* Also termed ammonic chloride, ammonia hydrochlorate, ammonia
hydrochloride, and formerly muriate of ammonia.

+ Tinctures, in the language of the apothecary, are alcoholic solutions.
Tincture of litmus (procurable of the apothecary), or of dried red cab-
bage, may also be Sap loree Litmus is made red by soluble acids, and
blue by soluble bases. ith red cabbage, acids develop a purple, and
the bases a green color.

THE VOLATILE PART OF PLANTS. 83

effect on vegetable colors that belong to ammonia. Car-
bonate of sodium has the taste and other properties of caus-
tic soda in a greatly mitigated form. On the other hand,
sulphates of aluminum, iron, and copper, have slightly
acid characters.

5. Fats anp Ons (WAx).—We have only space here
to notice this important class of bodies in a very general
manner. In all plants and nearly all. parts of plants we
find some representatives of this group; but it is chiefly
in certain seeds that they occur most abundantly. Thus
the seeds of hemp, flax, colza, cotton, bayberry, peanut,
butternut, beech, hickory, almond, sunflower, etc., con-
tain 10 to 70 per cent of oil, which may be in great part
removed by pressure. In some plants, as the common
bayberry and the tallow-tree of Nicaragua, the fat is
. Solid at ordinary temperatures, and must be extracted by
aid of heat; while, in most cases, the fatty matter is
liquid. The cereal grains, especially oats and maize, con-
tain oil in appreciable quantity. The mode of occur-
rence of oil in plants is shown in Fig. 17, which repre-
sents a highly magnified section of the flax-seed. The
oil exists as minute, transparent globules in the cells, f.
irom these seeds the oil may be completely extracted by

ether, benzine, or sulphide of car-

“bon, which dissolve all fats with

readiness, but scarcely affect the
. other vegetable principles.

a Many plants yield small quanti-
“iit Tia i VND ties of wax, which often gives a
ee glossy coat to their leaves, or
5 forms a bloom upon their fruit.
. The lower leaves of the oat-plant
Bes at the time of blossom contain, in
a the dry state, 10 per cent of fat

Fig. 17. and wax (Arendt). Scarcely two
of these oils, fats, or kinds of wax, are exactly alike in

84 HOW CROPS GROW.

their properties. They differ more or less in taste, odor,
and consistency, as well as in their chemical composition.

The ‘‘oils” are the simplest in chemical composition,
and have the lowest melting points. The ‘‘ fats” have
larger content of carbon, and higher points of fusion.
The varieties of wax are most complex in composition,
and have the highest melting points and greatest content
of carbon. ‘These differences are mostly gradational. In
chemical constitution these bodies are alike.

EXP. 39.—Place a handful of fine and fresh corn or oatmeal, which has
been dried for an hour or so at a heat not exceeding 212°, in a bottle.
Pour on twice its bulk of ether, cork tightly, and agitate frequently for
half an hour. Drain off the liquid (filter, if need be)into a clean porce-
lain dish, and allow the ether to evaporate. A yellowish oil remains,
which, by gently warming for some time, loses the smell of ether and
becomes quite pure.

The fatty oils must not be confounded with the ethe-
real, essential, or volatile otls, which, however, do not occur
to much extent in agricultural plants. The former can
not evaporate except at a high temperature, and when
brought upon paper leave a permanent “‘ grease spot.”
The latter readily volatilize, leaving no trace of their
presence. The former, when pure, are without smell or
taste. The latter usually possess marked odors, which
adapt many of them to use as perfumes.

In the animal body, fat (in some insects, wax) is formed
or appropriated from the food, and accumulates in con-
siderable quantities. How to feed an animal so as to
cause the most rapid and economical fattening is one of
the most important questions of agricultural chemistry.

However greatly the various fats may differ in external
characters, ‘they are all mixtures of a few elementary fats.
The most abundant and commonly-occurring fats, espe-
cially those which are ingredients of the food of man and
domestic animals—e.g., tallow, olive oil, and butter—con-
sist mainly of three substances, which we may briefly
notice. These elementary fats are Stearin, Palmitin,

THE VOLATILE PART OF PLANTS. 85

‘and Olein,* and they consist of carbon, oxygen, and hy-
drogen, the first-named element being greatly prepon-
derant.

Stearin is represented by the formula O57Hi100,. It
is the most abundant ingredient of the common fats, and
exists in largest proportion in the harder kinds of tallow.

Exp. 40.—Heat mutton,or beef tallow in a bottle that may be tightly
corked, with ten times its bulk of concentrated ether, until a clear
solution is obtained. Let cool slowly, when stearin will crystallize out
in pearly scales.

Palmitin, O5:H».06., receives its name from the palm
oil, of Africa, in which it is a large ingredient. It forms
a good part of butter, and is one of the chief constituents
of beeswax, and of bayberry tallow.

Olein, C5;Hio,0, is the liquid ingredient of fats,
and occurs most abundantly in the oils. It is prepared
from olive oil by cooling down to the freezing point,
when the stearin and the palmitin solidify, leaving the
o'ein still in the liquid state.

Other elementary fats, viz., butyrin, laurin, myristin, etc., occur in
small quantity in butter, and in various vegetable oils. Flaxseed oil
contains linolein; castor oil, ricinolein, etc.

We have already given the formulae of the principal
fats, but for our purposes, a better idea of their composi-
tion may be gathered from a centesimal statement, viz. :

CENTESIMAL COMPOSITION OF THE ELEMENTARY FATS.
Stearin. Palmitin. Olein.

Carbon .. 75.9 T.4
Hydroge 12.2 11.8
Oxygen.... 11.9 10.8

100.0 100.0 100.0

Saponification.—The fats are characterized by forming
soaps when heated with strong potash or soda-lye. They
are by this means decomposed, and give rise to fatty

* Margarin, formerly thought to be a chemically-distinct fat, is a mix-
ture of stearin and palmitin. Oleomargarine is the commercial designa-

tion of an artificially-obtained mixture of fats, animal or vegetable,
that has nearly the consistence of dairy butter.

86 HOW CROPS GROW.

acids, which remain combined with the alkali-metal,
and to glycerin, a substance which acts as a base. The
fats are therefore termed glycerides.

EXP. 41.—Heat a bit of tallow with strong solution of caustic potash
until it completely disappears, and asoap, soluble in water, is obtained.
To one-half the hot solution of soap, add hydrochloric acid until the lat-
ter predominates. An oil will separate which gathers at the top of the
liquid, and, on cooling, solidifies to a cake. This is not, however, the
original fat. It has a different melting point, and a different chem-
ical composition. It is composed of the three fatty acids, corres-
ponding to the elementary fats from which it was produced.

When saponified by the action of potash, stearin yields
stearic acid, CisHs.0,; palmitin yields palmitic acid,
CigHs.0.; and olein gives oleic acid, C,sHs,0..* The
so-called stearin candles are a mixture of stearic and
palmitic acids. The glycerin, C;H,0;, that is simul-
taneously produced, remains dissolved in the liquid.
Glycerin is found in commerce in a nearly pure state, as
a colorless, syrupy liquid, having a pleasant, sweet taste.

The chemical act of saponification consists in the re-arrangement of
the elements of one molecule of fat and three molecules of water into
three molecules of fatty acid, and one molecule of glycerin.

* Palmitin. Water. Paimitie acid. Glycerin.

C51 H 9306 oo 3 (H,0) = 3 (Cyg E3202) -— C,H,Os

Saponification is likewise effected by the influence of strong acids
and by heating with water alone to a temperature of near 400° F.

Ordinary soap is nothing more than a mixture of stearate, palmitate,
and oleate of potasssium or of sodium, with or without glycerin. Com-
mon soft soap consists of the potassium compounds of the above-
named acids, mixed with glycerin and water. Hard soap is usually the
corresponding sodium-compound, free from glycerin. When soft soap
is boiled with common salt (chloride of sodium), hard soap and chlo-
ride of potassium are formed by transposition of the ingredients. On
cooling, hard-soap forms a solid cake upon the liquid, and the glycerin
remains dissolved in the latter.

Relations of Fats to Carbhydrates.—The oil or fat of
plants is in many cases a product of the transformation
of starch or other member of the cellulose group, for the
oily seeds, when immature, contain starch, which van-

* Oleic acid differs from stearic acid in containing two atoms less of
hydrogen. and is one of a series that bear this relation to the fatty acids
of corresponding content of carbon,

~

THE VOLATILE PART OF PLANTS. 8"

ishes as they ripen, and in the sugar-cane the quantity
of wax is said to be largest when the sugar is least abund-
ant, and vice versa. In germination the oil of the seed
is converted back again into starch, sugar, etc.

The Estimation of Fat (including wax) is made by warming the pul-
verized and dry substance repeatedly with renewed quantities of ether,
or sulphide of carbon, as long as the sulvent takes up anything. On
evaporating the solutions, the fat remains, and after drying thorough-
ly, may be weighed. The ether extract thus obtained is usually accom-

panied by asmall amount of other substances, especially chlorophyll
and lecithin, and is hence properly termed crude fat.

PROPORTIONS OF CRUDE FAT IN VARIOUS VEGETABLE PRODUCTS.

Per cent. Per cent.

Meadow grass..
Red clover (gre

Cotton seed..i0..i000.:
Flax Ce. arotgtalateratbigiateye

Oat StIAW.... cece ccc nee eee A ‘i nies
Colza SE pealsigrcraiersibipignc ates 45.

Wheat bran....

3.
3
Wheat straw............ eee a
Potato tuber..............e08 0.

6. THE ALBUMINOIDS OR PrRotEIDs.—The bodies of
this class essentially differ from those of the groups hith»
erto noticed, in the fact of their containing, in addition
to carbon, oxygen, and hydrogen, 15 to 18 per cent of
nitrogen, with a small quantity of sulphur, and, in some
cases, perhaps phosphorus.

These bodies, though found in some proportion in all
parts of plants, being everywhere necessary to growth,
are chiefly accumulated in the seeds, especially in those
of the cereal and leguminous grains.

The aléuminoids or proteids* that occur in plants are
so similar, in many characters, to those which constitute
a large portion of every animal organism, that we may
advantageously consider them in connection with the
latter.

*The nomenclature of these substances is unavoidably confused.
They are often termed ie eae or nitrogenized bodies, also albu-
minous bodies, and protein bodies. The term albuminoids has been
lattgrly restricted, by some authors, to the substances of which gela-
tine is a type. The word albuminates is applied to syntonin and
casein. =

~

88 HOW CROPS GROW.

Three familiar representatives of this class of bodies
are, albumin, or the white of egg; fibrin, or the clot of
blood, and casein, which yields the curd of milk.

General Characters. —Many of, these substances occur
in two very distinct modifications, one form being soluble
in water, or in highly-diluted acids or alkalies, or in salt-
solutions, the other insoluble in these liquids.

Some of the soluble proteids we find naturally dissolved
in the juices of living plants and animals. Some may be
obtained in the solid form by evaporating off at a very
gentle heat the water which is naturally associated with
them. They then appear as nearly colorless or yellow-
ish, amorphous solids, destitute of odor or taste, which
dissolve again in water, but are insoluble in alcohol.

Soluble compounds of proteids with magnesium or
iron occur in plants, or may be obtained from the blood
of animals, in the form of white or red crystals.

Solutions of most of thealbuminoids are readily coagu-
dated by heat and by concentrated mineral acids, the
albuminoids being thereby themselves chemically changed
and made insoluble. Some coagulate spontaneously.

The insoluble albuminotds, some of which also occur
naturally in plants and animals, are, when purified as
much as possible, white, flocky, lumpy or fibrous bodies,
quite odorless and tasteless.

The albuminoids, when subjected to heat, melt and
burn with a smoky flame and a peculiar odor—that of
burnt hair or horn—while a shining charcoal remains
which is difficult to consume.

Tests for the Albuminoids.—The chemist employs the behavior of
the albuminoids towards a number of reagents* as tests for their pres-
ence. Some of these are so delicate and characteristic as to allow the

* Reagents are substances commonly employed for the recognition
.of bodies, or, generally, to produce chemical changes. All chemical
phenomena result from the mutual action of at least two elements,
which thus act and react on each other. Hence the substance that
excites chemical changes is termed a reagent, and the phenomena or
results of its application are called reactions.

THE VOLATILE PART OF PLANTS. 89

distinction of this class of substances from all others, even in micro-
scopic observations. =

1. Solution of iodine colors them intensely yellow or bronze.

“2. Warm and strong hydrochloric acid colors these bodies blue,
violet, or brown, or, if applied in large excess, dissolves them toa
liquid of these colors.

3. In contact with nitric acid, especially when hot, they are stained a
deep ‘and vivid yellow, Silk and wool, which consist largely of pro-
teids, are commonly dyed or printed yellow by means of nitric acid.

4. A solution of mereurve nitrate in excess of nitric acid,* tinges them
of a deep red color. This test enables us to detect albumin, for exam-
ple, even where it is dissolved in 20,000 parts of water.

5. With caustic soda and very dilute solution uf copper sulphate,
successively applied, the proteids give a violet color which is intensi-
fied by farming. (Biuret test.)

The Albumins are soluble in water; the solutions as
naturally occurring, unless very dilute, are coagulated by
“heat.

Egg Albumin.—The white of a hen’s egg on drying
yields about 12 per cent of albumin in a state of tol-
erable purity. The fresh white of eggs serves to illus-
trate the peculiarities of this substance, and to exhibit
the deportment of the albuminoids generally toward the
above-named reagents.

Exp. 42.—Beat or whip the white of an egg so as to destroy the deli-
cate transparent membrane in the cells of which the albumin is held,
and agitate a portion of it with water ; observe that it mostly dissolves
in the latter. The solution is turbid from presence of globulin.

EXP. 43.—Heat a part of the undiluted white of egg in a tube or cup.
At 165° F. it becomes opaque, white, and solid (coagulates), and is con-
verted into the insoluble modification. A higher heat is needful to
coagulate solutions of albumin, in proportion as they are diluted wit:
water. :

Exp. 44.—Add strong alcohol to a portion of the solution of albumin
of Exp. 42. It precipitates the albumin, which for a time remains solu-
ble in water, but later coagulates and becomes insoluble.

Exp. 45.—Observe that albumin is coagulated by strong acids applied
in small quantity, especially by nitric acid.

Exp. 46.—Put a little albumin, either soluble or coagulated, into each
of five test tubes. To one, add solution of iodine; to a second, strong
hydrochloric acid; to a third, nitric acid; to a fourth, nitrate of mer-
cury, and to the last a few drops of solution of copper sulphate, and
then a little caustic soda or potash solution. Observe the characteristic
colorations that appear immediately, or after a time, as described
above. Inthe last four cases the reaction is hastened by a gentle heat.

* This solution, known as Millon’s reagent, is prepared by aupeline
mercury in its own weight of nitric acid of Le gr. 1.4, heating towar
ons piese of the process, and finally adding to the liquid twice its bulk
of water. .

90 HOW CROPS GROW.

Serum Albumin occurs dissolved in the blood, in milk,
and in nearly all the liquids of the healthy animal body ex-
cept the urine. Its characters are slightly different from
those of egg-albumin. The albumin of the blood-may
be separated by heating blood-serum (the clear yellow
liquid that floats above the clot). The albumin of milk
coagulates when milk-serum (whey) is heated to near
boiling.

On boiling entire milk, albumin éoagulates, and, mixed
* with fat and casein, is. deposited as a tough coating on
the sides of the vessel.

Animal albumin remains, when its solutions are evap-
orated at a temperature below 140° F., as a yellowish trans-
lucent and friable solid, which easily dissolves in water.

Vegetable Albumin.—In the juices of all plants is
found in small quantity a substance which agrees in
many respects with animal albumin, and has been termed
vegetable albumin. The clear iuice of the potato tuber
(which may be procured by grating potatoes, squeezing
the pulp in a cloth, and letting the liquor thus obtained
stand in a cool place until the st@rch has deposited) con-
tains such a body in solution, as may be shown by heat-
ing to near the boiling point, when a coagulum separates,
which, after boiling successively with alcohol and ether
to remove fat and coloring matters, in its chemical reac-
tions and composition closely approaches the coagulated
albumin of eggs.

The juice of succulent vegetables, as cabbage, yields
a similar substance in larger quantity, though less pure,
by the same treatment.

Water which has been agitated for some time in con-
tact with flour of wheat, rye, oats, or barley, is found
by the same method to have extracted an albuminoid from
these grains.

The coagulum, thus prepared from any of these sources, exhibits the
reactions characteristic of the albuminoids, when put in contact with
nitrate of mercury, nitric or hydrochloric acid.

THE VOLATILE PART OF PLANTS. 91

EXP. 47.—Prepare impure vegetable albumin from potatoes, cabbage,
or flour, as above described, and apply the nitrate of mercury test.

As already intimated, albumin is chemically changed
or decomposed in the process of coagulation. Coagu-
lated albumin is not readily dissolved by dilute acids or
by dilute aqueous solutions of alkali.

The so-called vegetable albumin is mostly known only
after coagulation by heat, and has been but imperfectly
studied. According to Ritthausen, the coagulum ob-
tained by heating the juice of potato tubers or the aque-
ous extracts of peas and horse-beans (Vicia faba) is solu-
ble in dilute potash and in acetic acid; it is therefore
not albumin. Sidney Martin reports a genuine albumin
in the juice of the papaw, but its composition has not
been determined.

Fibrin.—Animal Fibrin is insoluble in water, alco-
hol and salt-solutions ; it swells up in dilute acids, dis-
solves in alkalies, and is coagulated by heat.

The blood of the higher animals, when in the body or
when fresh drawn, is perfectly fluid. Shortly after it is
taken from the veins it partially solidifios—it coagulates
or becomes clotted. It hereby separates into two por-
tions, a clear, pale-yellow liquid—the seram—and the
clot. As already stated, the serum contains albumin.
On persistently squeezing and washing the clot with
water, the coloring matter of the blood is removed, and
a white stringy mass remains, which consists chiefly of

‘fibrin, being a decomposition-product of another albu-
minoid, fibrinogen.

In very dilute hydrochloric acid, fibrin swells up, but
does not dissolve. When freshly prepared, it absorbs
. oxygen from the air and gives off carbon dioxide. Heat-

ing to 176° to 212° coagulates and shrinks it, and ren-
ders it less elastic and incapable of absorbing oxygen.

Exp. 48.—Observe the separation of blood into serum and clot; coag-
ulate the albumin of the former by heat, and test it with warm hydro-
chloric acid. Tie up the clot in a piece of muslin, and squeeze and

92 HOW CROPS GROW.

wash in water until coloring matter ceases to run off. Warm it with
nitric acid as a test. *

” Flesh-Fibrin.—If a piece of lean beef or other dead
animal muscle be repeatedly squeezed and washed in
water, the coloring matters are gradually removed and a
white residue is obtained which resembles blood-fibrin in
its external characters, and as it represents the fibers of
the original muscle, and was supposed to be a simple
albuminoid, it was formerly designated flesh-fibrin. It
is, however, a mixture consisting largely of myosin (see
p. 97). It mostly dissolves in very dilute hydrochloric
acid to a clear liquid, from which addition of much com-
mon salt, or of a little alkali, throws down syntonin.
The term flesh-fibrin is therefore no longer properly em-
ployed to designate a distinct chemical substance.

Vegetable fibrin.—When wheat-flour or rye-flour is
mixed with a little water to a thick dough, and this is
washed and kneaded for some time in water, the starch
and albumin are mostly removed, and a yellowish tena-
cious mass remains, which bears the name gluten. When
wheat is slowly chewed, the saliva carries off the starch
and other matters, and the gluten mixed with bran is
left behind—well-known to country lads as ‘‘ wheat-
gum.”

EXP. 49.—Wet.a handful of good, fresh, wheat-flour slowly with a lit-
tle water to a sticky dough, and squeeze this under a fine stream of
water until the latter runs off clear. Heat a portion of this gluten with
Millon’s reagent.

Gluten is a mixture of several albuminoids, and con-
tains also some starch and fat. When boiled with alco-
hol it is partially dissolved.* The portion insoluble in

* The dissolved portion Ritthausen found to consist of two distinct
albuminoid or rather glutinoid bodies, viz.:

Gliadin, or vegetable glue, is very soluble in water and alcohol. It
strongly resembles animal glue and chiefly gives to wheat dough its
tenacious qualities.

Mucedin resembles gliadin, but is less soluble in strong alcohol, and
is insoluble in water. When moist, it is yellowish-white in color, has

a silky luster, and slimy consistence. It exists also in gluten made
from rye grain. (Ritthausén, Jour. fiir Prakt. Chem., 38,141, and 99, 463.)

THE VOLATILE PART OF PLANTS. 93

strong alcohol Liebig first designated as vegetable fibrin.
Ritthausen found this to be a mixture of two bodies,
which he distinguished as gluten-casein and gluten-fibrin.
The latter is extracted from gluten by hot weak alcohol
and separates on partially removing the alcohol by evap-
oration.

The albuminoids of crude gluten dissolve in very dilute potash-solu-
tion @ to 1 parts potash to 1,000 parts of water), and the liquid, after
standing some days at rest, may be poured off from any residue of
starch, On adding acetic acid in slight excess, the purified albuminoids
are separated in thesolid state. By extracting successively with weak,
with strong, and with absolute alcohol, the gluten-casein of Ritthausen
remains undissolved.

On evaporating the alcoholic solution to one-half, there separates, on
‘cooling, a brownish-yellow mass. This, when treated with absolute
alcohol, leaves gluten-fibrin nearly pure.

Vegetable fibrin is readily soluble in hot dilute alcohol,
but slightly so in cold dilute, and not at all in absolute al-
cohol. On prolonged heating with alcohol, it becomes in-
soluble in that liquid. It does not dissolve in water. It
has no fibrous structure like animal fibrin, but forms,
when dry, a tough, horn-like mass. In composition it
approaches washed muscle, but differs considerably from
blood-fibrin.

Wheat contains or yields* but a small proportion of
fibrin and less appears to exist in hard than in the soft
wheats. Rye contains less than wheat. Barley, from
which no gluten can be got, yields to alcohol a small pro-
portion of fibrin.

Maize-fibrin, Zein.—The meal of Indian corn, unlike
that of wheat and rye, when made into a dough, forms
no gluten, but it yields to warm, weak alcohol some
% per cent of fibrin quite similar to that from wheat,
though of somewhat different composition.

* Weyl and Bischof believe that gluten does not pre-exist in wheat
and rye, just as fibrin does not exist in living blood, but is a result of
chemical change during the wetting and kneading of the flour to a
dough. According to them a strong solution of common salt extracts
from wheat flour vegetable globulin (see is 97), and the residue, when
kneaded with water, forms no gluten. If, however, the salt solution of

lobulin, in contact with the flour, is largely diluted with water, the

lour will yield gluten by kneading.

94 HOW CROPS GROW.

Casein.—Animal Casein is the peculiar albuminoid of
milk, in which it exists dissolved to the amount usually
of 3 to 6 per cent. By saturating milk with magnesium
sulphate the casein separates as an opaque white precipi-
tate. Thus obtained it is freely soluble in water. Casein
is also precipitated from milk by adding a little acetic or
other acid, but is then nearly insoluble in water, has
a decided acid reaction, and reddens blue litmus. The
spontaneous curdling of milk, after standing at or-
dinary temperatures for some time, appears to be directly
due to the lactic acid which develops from milk-sugar as
the milk sours. When milk is swallowed by a mamma-
lian animal.it curdles directly, and in the making of cheese
the casein of milk is coagulated by the use of rennet, which
is an infusion of the membrane lining the calf’s stomach.
Coagulated casein, though insoluble in water, dissolves
in very dilute acids, and also in very dilute alkalies.

The coherent cheese curd which is separated from milk
by rennet is doubtless a decomposition-product of casein,
and carries with it a considerable portion of the phosphates
and other salts of the milk. These salts are not found in
the casein precipitated by acids, being kept in solution
by the latter, but casein appears to contain.a small amount
of phosphorus (equivalent to 0.9 per cent phosphoric
oxide) in organic combination. Skim-milk cheese, when
new, consists mainly of coagulated caséin with a little
fat. Cheese made from entire milk contains most of the
fat of the milk.

EXP, 50.—Observe the coagulation of casein when milk is treated
with a few drops of dilute hydrochloric acid. Test the-curd with
nitrate of mercury.

EXxP. 51.—Boil milk with a little magnesium sulphate (Epsom salts)
until it curdles.

Vegetable Casein.—Several distinct substances have
been described as vegetable caseins. Our knowledge with
regard to them is in many important respects very defi-
cient. Even their elementary composition is a matter of
uncertainty.

THE VOLATILE PART OF PLANTS, 95

Gluten-Casein.—That part of the gluten of wheat
which is insoluble inecold alcohol is digested in a highly
dilute solution of potash, and the clear liquid is made
faintly acid by acetic acid. The curdy white precipitate
thus obtained, after washing with water, alcohol and
ether, and dried, is the gluten-casein of Ritthausen. It
is insoluble in water, and in solutions of common salt,
easily soluble in weak alkalies and coagulated by acids.
Ritthausen obtained this body from wheat, rye, barley,
and buckwheat.

Legumin is the name that has been applied to the chief
albuminoid of oats, peas, beans, lupins, vetches, and other
legumes. It is extracted from the pulverized seeds by
dilute alkalies, and is thrown down from these solutions
by acids. From some leguminous seeds it may be partially
extracted by pure water, probably because of the presence
of alkali-phosphates which serve to dissolve it. It is
generally mixed with conglutin, from which it may be
separated by soaking in weak brine (a 5 per cent solution
~ of common salt). Thus obtained, it is insoluble in pure
water and in brine, but soluble in dilute alkalies, and has
a decided acid reaction. Legumin, as existing in the
horse-bean ( Vicia faba), is soluble in brine, but after solu-
tion in alkali and precipitation with acids, is insoluble
in salt solution. The casein, animal or vegetable, that
is thrown down from salt-solution by acids is evidently a
chemical compound of the original proteid with the acid
(acid-proteid). .

Exp. 52.—Prepare a solution of vegetable casein from crushed peas,
almonds, or pea-nuts, by soaking them for some hours in warm water,
to which afew drops of dilute ammonia-water or potash-lye has been

added, and allowing the liquid to settle clear. Precipitate the casein
by addition of an acid to the solution. .

The Chinese are said to prepare a vegetable cheese by
boiling peas to a pap, straining the liquor, adding gypsum
until coagulation occurs, and treating the curd thus ob-
tained in the same manner as practiced with milk-cheese,

96 HOW CROPS GROW.

viz.: salting, pressing, and keeping until the odor and
taste of cheese are develuped. It ig cheaply sold in: the
streets of Canton under the name of Tao-foo. Vegetable
casein appears to occur in small quantity in the potato,
and many plants; and may be exhibited by adding a few
drops of acetic acid to turnip juice, for instance, which
has been freed from albumin by boiling and filtering.

The Globulins are insoluble in water, but dissolve in
neutral salt-solutions. Some dissolve only in salt-solu-
tions of moderate strength and are thrown down from
these solutions by more salt. Others are soluble in sat-
urated salt-solutions. They are coagulated by heat.
Some animal globulins may first be noticed.

Vitellin is obtained from the yolk of eggs; fat and
pigment are first removed by ether, and the white residue
is dissolved in a solution of common salt (1 of salt to 10
of water). Addition of water to the filtered solution
separates the vitellin as a white, flocky mass.

_ Paraglobulin exists in blood serum, and may be
thrown down by saturating the serum with magnesium
sulphate. It may be obtained in transparent microscopic
disks that are probably crystalline. Its solutions in brine

coagulate by heat, like albumin.

Fibrinogen. —When blood fresh from the veins of the
horse is mixed directly with a saturated aqueous solution
of magnesium sulphate, fibrinogen dissolves, and the
liquid, after filtering from the red corpuscles, upon mix-
ing with a saturated brine of common salt, deposits this
body in white flocks, which unite to a tough, elastic
mass. Its solutions in brine coagulate at a lower tem-
perature than those of paraglobulin.

Fresh-drawn blood, after standing a short time, coag-
ulates of itself to a more or less firm clot. Under the
microscope this process is seen to consist in the rapid
formation of an intricate net-work of delicate threads or
fibrils. These are fibrin, and come from the coagulation

THE VOLATILE PART OF PLANTS. 9”

of fibrinogen. Coagulation here appears to be induced
by a ferment whose effect is suspended by strong saline
solutions, but is renewed when these are mixed with
much water. This ferment occasions decomposition of
the fibrinogen, fibrin being one of the products. The
fibrin-ferment is supplied from ruptured white blood-
corpuscles. The chemical composition of fibrinogen and
fibrin, as determined by analysis, is quite the same.

Myosin.—Lean beef or other dead muscle-tissue, after
mincing and washing with water to remove coloring mat-
ters, is soaked in 10 per cent salt-solution. Myosin dis-
solves and is precipitated from the filtered brine by diluting
with water. It dissolves also in dilute hydrochloric acid
and in dilute potash solution. Strong hydrochloric acid
converts it into syntonin. Myosin does not exist in liv-
ing muscle, but is formed after death, during rigor mor-
tis, from the juices of the muscles by a process of coag-
ulation. Its formation is accompanied by the develop-
ment of lactic and carbonic acids. Myosin is the chief
ingredient of what was formerly known as muscle-fibrin.

Vegetable Globulins occur abundantly in seeds where
they are chief ingredients of the so-called aleurone or
protein-granules. From these protein-granules, or from
the pulverized seeds, the globulins are extracted by salt-
solutions and by weak alkalies. The globulin which
water alone extracts from many seeds is dissolved by help
of the salts, which are there present. Such saline ex-
tracts are coagulated by heat and thus globulins have
figured, no doubt, as ‘‘ vegetable albumin.” Some glob-
ulins are only known in the amorphous or granular state ;
others occur as crystals.

Conglutin exists abundantly, according to Ritthausen,
in the seeds of peach, almond, lupin, radish, pea-nut,
hickory-nut, and hazel-nut, where it is usually associated
‘with legumin. It may be separated by weak brine, in
which it is invariably soluble, while legumin, after sepa-

vd

98 HOW CROPS GROW.

ration from alkali-solutions, is undissolved by brine. The
conglutin obtained from lupins and pea-nuts differs some-
what from that found in the hazel-nut, and in almond
and peach seeds. -Conglutin cannot be crystallized from
salt-solutions, as readily happens with vegetable vitellin.

Vegetable Vitellin.—Applying this designation to al-
buminoids which are insoluble in water, but dissolve in
saturated salt-solutions, and are thence precipitated by
water, we find vitellin more or less abundantly in seeds
of squash, hemp, sunflower, lupin, bean, pea, Brazil-nut,
castor-bean, and various other plants. It may be extracted
from squash seeds by common-salt-solution (of 10 per
cent) or dilute alkali. Diluting the brine with water or
neutralizing the alkali with acids precipitates the vitellin,
which, after washing with water, alcohol and ether, may
be obtained in crystals (microscopic octahedrons) by dis- -
‘solving in warm brine and slowly cooling. From seeds
of hemp and castor-bean Ritthausen obtained crystals
identical in appearance and composition with those of
squash seeds, but soluble in water, probably because of
the presence of alkali salts,

Vegetable Myosin.—Weyl and Bischof consider that
cereal and leguminous seeds.contain or yield myosin anal-
ogous to muscle-myosin, which differs from vitellin (and
conglutin) in being precipitated from its solution in weak
brine by saturating the same with salt. They find that

“wheat-flour contains but little if any proteid besides
myosin, and that when this is removed from the flour by
salt-solution or by very weak soda-lye or by hydrochloric
acid of 0.1%, the residue is incapable of yielding gluten.

-Gluten is therefore 2 decomposition-product of myosin.
These resuits are confirmed by the recent work of Mar-
tin (Jour. of Physiology, 1887). Zoeller found that the
pulp of potatoes, after starch and soluble matters had
been removed by copious washings with water, yielded to -
10% salt-solution an albuminoid which separated when the

THE VOLATILE PART OF PLANTS. 99

brine was saturated by addition of salt in excess. He also
precipitated myosin from the juice of the tubers by sat-
urating it with salt.

The myosins are precipitated by conversion into alkali-
proteids, when their brine-solutions are deprived of salt
by dialysis or when these solutions are kept for some
hours at 100° F. (Sidney Martin.)

Vegetable Paraglobulin is recently stated to exist in
papaw-juice, and in the seeds of lequirity, Abrus preca-
torius. It is distinguished from myosin by requiring a
higher temperature for coagulation from salt-solutions
and in not suffering conversion into an insoluble alkali-
proteid by dialysis or long heating to 100° F. (Martin.)

Acid-Proteids are bodies formed from proteids by the
prolonged action of acids. They are insoluble in water,
alcohol and brines, but easily soluble in dilute acids or
alkalies, and are precipitated by neutralizing these solu-
tions. The solutions of acid-proteids in acids are not co-
agulable by heat. The albumins and globulins are grad-
ually converted into acid-proteids by cold, highly dilute
acids, and more rapidly by stronger acids and gentle heat.
Syntonin is the acid-proteid resulting from solution ¥f.-
muscle-flesh, or myosin, in weak hydrochloric acid, and is
thrown down when the solution is neutralized by an
alkali, as a white gelatinous substance. Acid-proteids
may exist in seeds such as the oat, lupin, pea, bean, etc.,
which contain so much free acid, or acid salt, that the
water extract is strongly acid to test-papers.

Alkali-Proteids, or Albuminates.—The action of
dilute alkali-solutions on most proteids converts them
into bodies which, like acid-proteids, are insoluble in
water and salt-solutions, but soluble in dilute acids and
alkalies, and are thrown down from these solutions by
neutralization. Dilute acids do not convert them into
acid-proteids. Alkali-proteids are said to exist gener-
ally in the young cells of the animal, and may also occur

100 HOW CROPS GROW.

in plants in the alkaline juices of the cambium. The
*‘vegetable caseins,” viz., legumin and gluten-casein, as
they occur in the alkaline juices or extracts of plants,
are probably bodies of this class, and when precipitated by
acids unite to the latter, forming compounds with an
acid reaction. Casein-of milk has been by some consid-
ered to be an alkali-proteid, but is probably distinct.

Proteoses and Peptones.—These terms designate
bodies that result from the chemical alteration of albu-
minoids, under the influence of ‘‘ferments” which exist
in plants, but which have been most fully studied as they
occur in the digestive apparatus of animals.

The albuminoids, as found in plants, are mostly insol-
uble in the vegetable juices, and those-which are soluble
(probably because of the presence of salts, acids or alka-
lies) are mostly incapable of freely penetrating the cell-
membranes which inclose them, and cannot circulate in the
vegetable juices, and likewise, when they become the food
of animals, cannot leave the alimentary canal so as to be-
come incorporated with the blood until they have been
chemically changed. During the processes of animal
digestion the albuminoids of whatever kind undergo solu-
tion and: conversion into bodies which are freely soluble
in water, and rapidly penetrate the moist membranes of
the intestines, and thus enter into the circulation. These
bodies have been prepared for purposes of study by a
partly artificial digestion, carried on in glass vessels with
help of the digestive ferments obtained from the stomach
(pepsin) or pancreas (trypsin) of animals.*

It appears from Kiihne and Chittenden’s investigations
that a series of soluble and diffusible products are formed
from each albuminoid with progressive diminution of
carbon and increase of oxygen, and, in some cases, of
nitrogen. The first-formed products are termed pro-

* Reference may be had to Chittenden’s Studies in Physiological
Chemistry, Connecticut Acad., Vols. II and ITI, 1887 and 1889.

THE VOLATILE PART OF PLANTS. 101

teoses (albumoses, caseoses, globulosés, etc.) ; those last
produced they designate peptones, but investigators are
not as yet agreed as to the precise application of these
terms. What have been formerly called peptones are
now considered to be largely proteoses.

The composition of some of these bodies may be seen
from the following analyses by Chittenden and Painter :

Cc. H. N. Ss. oO.
Casein wigs cons ements 53.30 7.07 15.91 0.82 22.03
Protocaseose ..........-52.50 715 15.73 0.96 23.86
Deuterocaseose........ 61.59 6.98 15.73 0.75 25.03
Casein-Peptone........49.94 6.51 16.30 0.68 26.57

Of the several products which have been analyzed and
classed as proteoses and peptones, it is not certain that
any one is a strictly homogeneous substance. It is more
than probable that some of them are mixtures. The
proper use of these names is provisional, to characterize
certain evidently distinct stages of albuminoid metamor-
phosis, whoseeexact nature can only be cleared up by
further investigation.

The peptones may be defined as the final products of
the action of the peptic ferment. They are soluble in
water and freely diffusible through animal membranes.
The albumoses (or proteoses) are intermediate between
the albuminoids and the peptones, being mostly soluble
in water but not freely diffusible.

The proteoses much resemble the albuminoids from
which they are derived, not only in composition, but iu
many of their properties. The peptones have less re-
semblance, but appear capable of partially reverting to
proteoses, as some of the latter are said to yield coagula-
ble albuminoids when kept-in the moist state.

Weak acids and alkalies also convert the albuminoids
into proteoses and peptones, and probably the acid-pro-
teids, perhaps also the alkali-proteids, already mentioned,
contain proteases in admixture. Since pepsin-digestion
requires the aid of a free acid and trypsin-digestion suc-

102 HOW CROPS GROW.

céeds best in presence of a free alkali, the conditions
under which the-proteoses of digestion are formed are in
part identical with those that give rise to the acid-pro-
teids and alkali-proteids.

Peptones. have been found in small proportions in the
water-extract of various plants, e. g., seedlings, lupins,
barley-malt, young grass, alfalfa, etc. (Vs. St., XXIV,
363, 371, 440, and XXXII, 389.)

Vines has found a proteose in considerable quantity in
the seeds of Jupin, peony, and wheatand in the Brazil-
nut and castor-bean, and considers bodies of this class to
‘be of general occurrence in the protein-granules of plants.

The proteose (hemialbumose*) from lupins has, exclu-
sive of 0.81 p. c. of ash, the following composition per
cent according to Vines :"

Cc. H. N. Ss. 0.
52.58 7.24 14.87 1.52 — 23.79

Sidney Martin reports the existence Df a proteose
(hemialbumose) in the juice of the papaw or melon
tree (Carica papaya) where it is associated with the fer-
ment papain, which is very similar to that of the pan-
creatic secretion of animals.

Ferments are substances which produce or excite
chemical changes in a manner as yet mostly unexplained,
the ferments themselves not appreciably contributing of
their own substance to. the products of the processes
which they set in operation.

The ferments that figure in agricultural chemistry are
closely related to and apparently derived from the albu-
minoids, but in no case has their chemical composition
been positively established. They are distinguished and
characterized almost solely by the sources whence they
are derived; and the effects which they produce. The

*Kiihne first distinguished the products of pepsin or trypsin diges-
tion into hemialbumose and aitialbumose, the former being converted
by trypsin into amido-acids (see p. 114), the latter remaining unaltered
by the digestive ferments. Kiihne & Chittendon have more recently
snow e. ‘“hemialbumose” to be a mixture mainly of proto and dentero-
albumose.

THE VOLATILE PART OF PLANTS. 103

substances which the chemist can prepare, and to which
he gives special designations, are doubtless mixtures, and
in most cases contain but a small proportion of the real
ferment, which, in a state of entire purity, is unknown.

Leaven, or Yeast, which has been employed in mak-
ing bread, wine and beer for many centuries, contains, or
mainly consists of, a microscopic plant of very simple
structure (pp. 244-5), which, when placed in a solution of
cane-sugar, is able in the first place to cause the ‘‘ inver-
sion” of that substance into the two sugars, dextrose and
levulose, and, secondly, to transform both the latter into
alcohol and carbon dioxide. The ‘‘inverting” effect of
yeast upon cane-sugar has been traced to a substance
which can be separated from the yeast and obtained as a
dry, white powder. The alcoholic fermentation requires.
the living yeast plant for its accomplishment. Ferments
are accordingly divided into the two classes, wnorganized
and organized. We shall here notice briefly a few unor-
ganized ferments or enzymes, as they are also termed,
that have been somewhat carefully studied.

Invertin is obtained from dry, pulverized yeast by
heating it to 212° to coagulate albumin and then ex-
tracting with warm water. The invertin dissolves, and,
by addition of alcohol, is’ precipitated. Barth thus ob-
tained a substance containing 6 per cent of nitrogen
which was able, in the course of 48 hours, to transform
(invert) 760 times its weight of cane-sugar. Invertin
has no effect on starch or dextrin.

Diastase is the name applied to a substance that may be
obtained as a whitish powder from sprouted barley (malt)
by extracting with dilute alcohol and precipitation with
strong alcohol, which is capable of transforming 2,000
times its weight of starch, first into dextrin and finally
into maltose and dextrose. The purest diastase prepared
by Lintner contained 10.4 per cent. nitrogen and gave
reactions for albuminoids, but it had properties besides

104 HOW CROPS GROW.

its action on starch that strikingly distinguished it from
the ordinary proteids.

Pepsin is that ferment of the so-called gastric juice of
the animal stomach which enables this organ to dissolve
and ‘* peptonize” the albuminoids of the food. It may
be extracted from the inner coating of the stomach by
glycerine or very dilute hydrochloric acid, and is precip-
itable from these solutions by strong alcohol. Pepsin
requires the presence of a free acid to dissolve the albu-
minoids ; in neutral or alkaline solution it has no “ di-
gestive power.”

Trypsin is a ferment formed in the pancreas and exist-
ing in the pancreatic juice which, in mammalian animals,
during the digestion of food, is poured into the upper
intestine, where it continues and completes the solution
of albuminoids begun by the gastric juice. Trypsin acts
in neutral but most effectively in alkaline solutions ; its
operation is arrested by free acids. The results of its
action differ in some respects from those of pepsin.

Papain.—The milky juice of the Brazilian plant Car-
ica papaya, or melon-tree, contains this ferment, which,
like trypsin, is freely soluble in water, rapidly dissolves
albuminoids, best in neutral or alkaline solutions, convert-
ing them into proteoses and peptones. Papain itself, as
obtained by Wurtz & Bouchut, has the properties and
composition that characterize the proteoses,

Ferments appear to perform very important functions
in the vegetable as well as in the animal organism, and
have to be referred to frequently as-occasioning the con-
version of insoluble into soluble substances, and of com-
plex into simpler bodies.

Composition of the Albuminoids.—There are va-
rious reasons why the exact. composition of some of the
bodies just described is still asubject of uncertainty. They
are, in the first place, naturally mixed or associated with
other matters from which it is very difficult to separate

THE VOLATILE PART OF PLANTS. 105

them fully, Again, if we succeed in removing foreign
substances, it must usually be done by the aid of acids,
alkahes, salt-solutions, alcohol and ether, and there is
reason to believe that in many cases these reagents essen-
tially modify the properties and composition of the pro- ,
teids. These bodies, in fact, as a class, are extremely
susceptible to change and alter in respect to appearance, -
solubility, and other qualities that serve to distinguish
them, without any corresponding change in chemical
composition being discoverable by our methods of anal-
ysis. On the other hand, the substances that have been
prepared by different experimenters from the same
sources, and by substantially the same methods, often
show decided differences of composition.

Finally, the methods of analysis used in determin-
ing their composition are liable to considerable error,
and, if applied to the pure substances, are scarcely
delicate enough to indicate their differences with entire
accuracy.

In the accompanying table (p. 106) are given the most
recent and trustworthy analyses of the various vegetable
albuminoids, and of the corresponding substances of ani-
mal origin.

Referring to the analyses of Albumins we observe that
the egg-albumin differs from serum-albumin in contain-
ing about one per cent more of oxygen and one less of
carbon, while hydrogen, nitrogen and sulphur are prac-
tically the same. These two albumins have been very
thoroughly studied, their difference of composition is
well established, and they have positive differences in
their properties, so that there can be little doubt that
they are specifically distinct substances. Of the Vegeta-
ble Albumins none offer any reasonable guarantee of
purity. The composition of barley-albumin is near that
of the animal albumins, but it contains one-third less
sulphur. So far, then, as present data indicate, the veg-

106 HOW CROPS GROW.

COMPOSITION OF ALBUMINOIDS.

: a siel. .
sis] S/S] 8 :
5/3/38 /$| 8
oe] Ss & i) Analysts.

52.2/6.9]15.8:1.9]23.2| Chittenden & Polton.
ped ee 16.0 Le Pel Hammarsten.
+. |53.1/7.2 17.6:1.6 20. ‘
B2,8{4.2.16,8 13/230] } Bitthausen.

Ses = i pare er anti 1.1!22.5] Hammarsten.
uten-fibrin, wheat. ots 1.0/20.6 . 4
maize 0 0:7/21:7 } Ritthausen.

CASEINS.

MIL GAS O1 F001 s<scnangnanee 53.3/7.1 15.910.8 22.0; Chittenden & Painter.

Gluten-casein, wheat.. --/52,917.0,17.1 1.0/22.0) Ritthausen.

oT is ee b se epee eee ae ae 1.1)23.3| Chittenden & Smith.
uten-casein, buck wheat*. |50. 7.4'1.5)24.1 r

Legumin, lupins...........6. 51.4/7.0:17.5,0.6|23.5 | Ritthausen.

GLOBULINS.

Paraglobulin............eeee. -7/7.015.8 1.1/23.4)

Fibrinogen, blood.. '96.9:16.7 1.3'22.2 | Hammarsten.

Myosin, beef..... 8/7 1116.8 1.3/21.9 Chittenden & Cummins.

Cong latin, inp: ae . 7118.6 Ae ra

azel-nu 27. -6|0.6/22. :
Vitellin, squash........ ‘37.5 ;18.1|0.6/22.5| (Ritthausen.
«hemp (erystals).. -0|7.0;18.7/0.8)22.5 Fe
“ Brazil-nut.........4. -4/7.1;18.1]0.5/21.9|/° Weyl.
GLIADIN, wheat.............. -7|7,1/18.0/0.9/21.3) Ritthausen.
MUCEDIN, wheat............- 54.1'6.9 16.6 0.9121.5' Ritthausen.

See pp. 101 and 102 for analyses of Proteoses and Peptone.

etable albumins are not identical with those derived from
the animal.

As respects the Fibrins we have already seen that there
is no similarity in properties between that of blood and
those obtained from gluten. The analyses of the two
gluten-fibrins show either that these substances are quite
distinct or that they have not yet been obtayped in the
pure state.

The Vegetable Caseins, as analyzed by Ritthausen, are

*The analysis of milk casein should include 0.9 phosphorus. The
buckwheat casein contained 0.9 phosphorus, which is not included in
the analysis. Whether phosphorus is an ingredient of casein, or an
“impurity,” is not perhaps positively established.

THE VOLATILE PART OF PLANTS. 107

observed to contain more ‘nitrogen by 1.2 to 1.6 per cent

than exists in animal casein. Furthermore, they differ

from each other so widely in carbon content (2.7 per cent)

-as to make it highly probable that their true composition

was not in all cases correctly determined.

This conclusion is justified by the results of Chittenden

& Smith, who have recently analyzed five different prep-

arations of gluten-casein, made from wheat by Ritthau-

sen’s method. The average of their accordant analyses

is given above.* Since nitrogen was determined by two

methods (those of Dumas and Kjeldahl) these analyses
would appear to establish the composition of gluten-

casein, which accordingly closely agrees with that found

by Ritthausen for ‘‘albumin” from barley, and with

that of paraglobulin, and has the same nitrogen content

as the casein of milk.
The Animal Globulins agree in composition with each

* other as well as with animal fibrin which is formed from

globulin (fibrinogen). The Vegetable Globulins are strik-
ingly different in composition, containing 1.5 to 2 per
cent more nitrogen and mostly but half as much sul-
phur. The hazel-nut conglutin and the hemp-seed vitel-
lin have the same composition.

It is evident that the vegetable albuminoids, on the
whole, are distinct from those of the animal, but their
true composition and relations to each other, to a great
extent, remain to be established.

Some Mutual Relations of the Albuminoids.—It was
formerly supposed that these bodies are identical in com-
position, the differences among the analytical results
being due to foreign matters, and that they differ from
each oth® in the same way that cellulose and starch
differ, viz.: on account of different arrangement of the
atoms. Afterwards, Mulder advanced the notion that
the albuminoids are compounds of various proportions

*Kindly communicated by the authors.

a

108 HOW CROPS GROW. é
of hypothetical-sulphur and phosphorus radicles with
a common ingredient, which he termed protein (from
the Greek signifying ‘‘to take the first place,” because
of the great physiological importance of such a body):
Hence the designations protein-bodies and proteids.
The transformations which these substances are capable
of undergoing sufficiently show that they are closely
related, without, however, satisfactorily indicating in
what manner.

In the animal organism, the albuminoids of. the food,
of whatever name, are dissolved in the juices of the
digestive organs, and pass into the blood, where they
form blood albumin and globulin. As the blood nour-

‘ishes the muscles, they are modified into the fiesh-albu-

minoids; on entering the mammary system they are
converted into casein, while in the appropriate part of
the eirculation they are formed into the albumin of the
egg, or embryo.

In the living plant, similar changes of place and of
character occur among these substances.

The Albuminoids in Animal Nutrition.—We step
aside for a moment from our proper plan to direct atten-
tion to the beautiful adaptation of this group of organic
substances to the nutrition of animals. Those bodies
which we have just noticed as the animal albumincids,
together with others of similar composition, constitute
a large share of the healthy animal organism, and: espec-
ially characterize its actual working machinery, being
essential ingredients of the muscles and cartilages, as
well as of the nerves and brain. They likewise exist
largely in the nutritive fluids of the animal—in blood
and milk. So far as we know, the animal bBay has not
the power to produce a particle of albumin, or fibrin, or
casein except by the transformation of similar bodies pre-
sented to it fromexternal sources. They are hence indis-
pensable ingredients of the food of animals, and were

THE VOLATILE PART OF PLANTS. 109

therefore designated by Liebig as the plastic elements of
nutrition. They have also been termed the blood-build-
ing or muscle-forming elements. It is, in all cases, the
plant which originally constructs these substances, and
places them at the disposal of the animal.

The albuminoids are mostly capable of existing in the
liquid or soluble state, and thus admit of distribution
throughout the entire animal body, as in blood, etc. They
likewise readily assume the solid condition, thus becom-
ing more permanent parts of the living organism, as well
as capable of indefinite preservation for food in the seeds
and other edible parts of plants.

Complexity of Constitution.—The albuminoids are
highly complex in their chemical constitution. This fact
is shown as well by the multiplicity of substances which
may be produced from them by destructive and decom-
posing processes as by the ease with which they are
broken up into other and simpler compounds. Kept in
the dissolved or moist state, exposed to warm air, they
speedily decompose or putrefy, yielding a large variety of
products. Heated with acids, alkalies, and oxidizing
agents, they mostly give origin to the same or to anal-
ogous products, among which no less than twenty differ-
ent compounds have been distinguished.

The numbers of atoms that are associated in the mole-
cules of the proteids are very great, though not in most
cases even approximately known. The Haemoglobin of
blood, which forms red crystals that admit of preparing
in a state of great purity, contains in 100 parts—

c H N co) 8 Fe

542 72 16.1 21.6 0.5 0.4
The iron (Fe) is a constant and essential ingredient, and
if one atom only of this. metal exist in the haemoglobin
molecule, its empirical formula must be something like
CosoH ooo N igs FeS20199, and its molecular weight over 14,-
000. Haemoglobin readily breaks up into a proteid and a

110 HOW CROPS GROW.

much simpler red crystalline substance, Haemaeetin, yield-

ing about 96 per cent of the former and 4 per cent of
the latter. Haematin has approximately the formula

Cz2H;,N,FeO;, so that the proteid, though simpler than

haemoglobin, must have an extremely complicated mole-

cule, and it is, accordingly, difficult to decide whether a

few thousandths of the acids, bases or salts which may

be associated with these bodies, as they exist in plants or

pass through the hands of the chemist, are accidental or

essential to their constitution.

Occurrence in Plants.—Aleurone.—It is only in the
old and virtually dead parts of a living plant that albu-
minoids are ever wanting. In the young and growing
organs they are abundant, and exist dissolved in the sap
or juices. They are especially abundant in seeds, and
here they are often deposited in an organized form, chiefly

Fig. 18. Fig. 19.

in grains similar to those of starch, and mostly insoluble
in water. ;

These grains of albuminoid matter are, not, in many
cases at least, pure albuminoids. Hartig, who first de-
scribed them minutely, has distinguished them by the
name aleurone, aterm which we may conveniently em-
ploy. By the word aleurone is not meant simply an

THE VOLATILE PART OF PLANTS. 111

albuminoid, or mixture of albuminoids, but the organ-
ized granules found in the plant, of which the albumin-
oids are chief or characteristic ingredients.

In Fig. 18 is represented a magnified slice through the
outer cells (bran) of a husked oat kernel. The cavities
of these outer cells, a, c, are chiefly occupied with very
fine grains of aleurone. In one cell, b, are seen the
much larger starch grains. In the interior of the oat
kernel], and other cereal seeds, the cells are chiefly occu-
pied with starch, but throughout grains of aleurone are
more or less intermingled.

Fig. 19 exhibits a section of the exterior part of a
flax-seed. The outer cells, a, contain vegetable muci-
lage ; the interior cells, e, are mostly filled with minute
grains of aleurone, among which droplets of oil, f, are
distributed.

In Fig. 20 are
shown some of the
forms assumed by in-
dividual albuminoid- ¢ b e
grains ; a is aleurone Fig. 20.
from the seed of the vetch, d from the castor-bean, ¢
from flax-seed, d from the fruit of the bayberry (Myrica
cerifera) and e from mace (an appendage to the nutmeg,
or fruit of the Myristica moschata).

Crystalloid aleurone.—It has been already remarked

ei AW
MOON EN
SR

Fig. 21.

that crystallized albuminoids exist in plants. This was
first observed by Hartig (Hntwickelungsgeschichte des

112 HOW CROPS GROW.

Pflanzenkeims, p. 104). In form they sometimes imitate
crystals quite perfectly, Fig. 21, a; in other cases, 3,
they are rounded masses, having some crystalline planes
or facets. They are soft, yield easily to pressure, swell
up to double their bulk when soaked in weak acids or
alkalies, and their angles have not the constancy peculiar
to ordinary crystals. Therefore the term crystalloids, i.e.,
having the likeness of crystals, has been applied to them.

As Cohn first noticed (Jour. fur Prakt. Chem., 80, p.
129), crystalloid aleurone may be observed in the outer
portious of the potato tuber, in which it invariably pre-
sents a cubical form. It is best found by examining the
cells that adhere to the rind of a potato that has been
boiled. In Fig. 21, @ represents a cell from a boiled
potato, in the center of which is seen the cube of aleurone.
It. is surrounded by the exfoliated remnants of starch-
grains. In the same figure, 6 exhibits the contents of a
cell from the seed of the bur reed (Sparganium ramo-
sum), .a plant that is common along the borders of ponds.
Tn the center is a comparatively. large mass of aleurone,
having trystalloid facets.

As already stated, the proteids in the crystalloid aleu-
rones of hemp, castor-bean and squash have the chemical
characters of globulin. The aleurone of the Brazil-nut
(Bertholletia) and that of the yellow lupin contain, ac-
cording to Hartig and Kubel, 9.4% of nitrogen which
corresponds to some 50 or 60% of proteids.

Weyl obtained from the Brazil-nut a very pure amor-
phous vitellin with 18.1% of nitrogen. ‘The vitellin of
Brazil-nut, castor-bean, and of hemp and squash seeds has
been recrystalized from salt solutions by Schmiedeberg,
Drechsel, Griibler and Ritthausen. According to Vines,
seeds of lupin and peony yield a myosin to salt-solution,
and sunflower seeds, after treatment with ether to remove
oil, yield a globulin with the properties of myosin, but if
alcohol is used, the proteid has the character of vitellin.

THE VOLATILE PART OF PLANTS. 113

Vines, who has examined the aleurone of many plants,
finds it in all cases more or less soluble in water. ‘The
globulin doubtless goes into solution by help of the salts
present. Vines also states that a body soluble in water,
having the properties of a proteose (hemialbumose), is
universally present in aleurone.

Estimation of the Albuminoids.—The quantitative sep-
aration of these bodies, as they occur in plants, is mostly
impossible in the present state of science. In many cases
their collective quantity in an organic substance may be
calculated with approximate accuracy from its content of
nitrogen.

In calculating the nutritive value of a cattle-food the

. albuminoids are currently reckoned as equal to its nitro-
gen multiplied by 6.25. This factor is the quotient ob-
tained by dividing 100 by 16, which, some 25 years ago,
when cattle-feeding science began to assume its present
form, there was good reason to assume was the average
per cent of nitrogen in the albuminoids. As Ritthausen
has insisted, this factor is too small, since the albuminoids
of the cereals and of most leguminous seeds, as well as of
the various oil-cakes, contain nearer 17 than 16 per cent
of nitrogen, if our analyses rightly represent their com-
position, and the factor 6 (= 100 + 16.66) would be
more nearly correct.

This mode of calculation only applies with strictness
where all the nitrogen exists in albuminoid form. This
appears to be substantially true in most seeds, but in case
of young grass and roots there is usually a considerable
proportion of non-albuminoid nitrogen, for which due
allowance must be made. (See Amides.) *

*Ammonia, NH; and Nitric acid, NHO;. These bodies are mineral, not
organic substances, and are not, on the whole, considerable ingredients
of plants. They are however the principal sources of the nitrogen of
vegetation, and, serving as plant-food, enter plants through their roots,
chiefly from the soil, and exist within them in small quantity, and for
a time, pending the conversion of their nitrogen into that of the

amides and albuminoids, to whose production they are probably
essential. In seeds and fruits, and in mature plants, growing in soils

114 HOW CROPS GROW.

AVERAGE QUANTITY OF ALBUMINOIDS IN VARIOUS VEGETABLE
PRODUCTS.—ALBUMINOIDS = N x 6.25.
American, Jenkins. German, Wolff.

Maize fodder, green...........-.+-
Beet tops, BO lane wis ae atasas tra feta
Carrot tops, is iereda eee
Meadow grass, in bloom..........
Red clover, Bb ede aa tie
White clover, Fe die a'cin heap
Turnips, fresh...........-....000ee
Oarrots, ( isiswiqiscesmseininicea'ee nares
Potatoes, |! cadescccwswnese aden 2,
Corn eobs, ardryseiwscacss ss cane
Straw, Gey spiaatcsnaleiese:aiaiace: aot
Pea straw, SE. <racccsvelsraja Bio ape Guat
Bean straw, ov. s sees eee e ees
Meadow hay,in bloom.......... oe
Ked-clover hay, sigs iasaane
White-clover hay, “ ........ sees
Buckwheat kernel, air-dry......
ity be

PP O19

DBODARSCSHPNHATW HORN AABDAEOHO

To

SESARSSRESTSS awerra

Barley

Maize aa es

Rye “ “

Oat “ “

‘Wheat fas - '
Pea . “

Bean a ROL Oa crineteRinatals

THE AMIDES, AMIDOACIDS, IMIDES, AND AMINES.
—Ammonia and the ammonium salts, so important as
food to plants, and as ingredients of the atmosphere, of
soils, and of manures, occur in so small proportions in
living vegetation as to scarcely require notice in this
work occupied with the composition of Plants. They
are, however, important in connection with the amides
now to be briefly described. Ammonia, an invisible gas
of pungent odor which dissolves abundantly in water to
form the agua ammonia of spirits of hartshorn of the
apothecary, is a compound of one atom of nitrogen with
three atoms of hydrogen. It unites to acids, forming
the ammonium salts :
of moderate fertility, both ammonia and nitric acid, or strictly speak-
ing, ammonia-salts and nitrates, commonly occur in very small pro-
portions. In roots, stems, and foliage of plants situated in soils rich
in these substances, they may be present in notable quantity. The
dry leaves and stems of tobacco and beets sometimes contain several
per cent of nitrates. When these substances are presented to plants in
abundance, especially in weather, they may accumulate in the
roots and lower parts of the plant more rapidly than they can be assim-
ilated. On the other hand, when their supply in the soil is relatively
small they are so completely and rapidly assimilated as to be scarcely
detectable. Their possible presence should be taken into account when

it is undertaken to calculate the albuminoids of the plant from the
amount of nitrogen found in its analysis.

THE VOLATILE PART OF PILANTS. 115

CH, COOH' + NH, = CH, COONH,
Acetic acid. Ammonia. Ammonium acetate.

Amides.—This term is often used as a general desig-
nation for all the bodies of this section which result from
the substitution of the hydrogen of ammonia by any
atom or group of atoms. Ip a narrower sense amides
are those ammonia-derivatives containing ‘‘acid-radi-
cals” which are indicated in their systematic names.

Acetamide, CH,;CONH,. Many ammonium salts,
when somewhat strongly heated, suffer decomposition
into amides and water.

CH,COONH, = CH,CONH, + HO

Ammonium acetate, Acetamide. Water.

The above equation shows that acetamide is ammonia,
NH;, or HNH,, one of whose hydrogens has been re-
placed by the group of atoms, CH;,CO, the acetic acid
radical, so called, Acetamide is a white crystalline body.
The simple amides, like acetamide, are as yet not known
to exist in plants. They readily unite with water to
produce ammonium salts.

Carbamide, or Urea CO(NH,).. This substance—
the amide of carbonic acid CO(OH),—naturally occurs
in considerable proportion in the urine of man and mam-
malian avimals. It is a white, crystalline body, with a
cooling, slightly salty taste, which readily takes up the
elements of water and passes into ammonium carbonate.
Urea has not been found in plants, but derivatives of it
in which acid radicals replace a part of its hydrogen are
‘of common occurrence. (Guanin, allantoin.)

Amidoacids are acids containing the NH, group as a
part of the acid radical.

Amidoacetic Acid, C,H;NO,, or CH.(NH,)COOH,
is derived from acetic acid, CH,COOH, by the replace-
ment of H in CH; by NH,. The amidoacids have not a
sour, but usually a sweetish taste, and, like the amides,
act both as weak acids and weak bases. Amidoacetic

116 HOW CROPS GROW.

acid, also called glycocoll, has not as yet been found in
plants, but exists in the scallop and probably in other
shell-fish, and a compound of it, benzoylglycocoll or hip-
puric acid, is a nearly constant ingredient of the urine of
the horse and other domestic herbivorous animals.

Betain, or trimethylglycocoll, C;H1;N Ox, a crystalliza-
ble substance found in beet-juice, stands in close chem-
ical relations to amidoacetic acid.

Amidovaleric acid, C;H1:,:NO., occurs in ox-pancreas
and in young lupin plants. Amidocaproic acid, or
Leucin, C,H,,NO,, first observed in animals, has lately
been discovered in various plants. The same is true
of Tyrosin, or oxyphenyl-amidopropionic acid,
C,H,,NO;, and of phenyl-amidopropionic acid,
C,H NOg.

The above amidoacids are readily obtained as products
of decomposition of animal and vegetable albuminoids by
the action of hot acids. Amidoacetic acid was thus first
obtained from gelatin. Leucin and Tyrosin are com-
monly ‘prepared by boiling horn shavings with dilute sul-
phuric acid ; they are also formed from vegetable albu-
minoids by sitar treatment and are final results of the
digestion of proto- and deutero- -proteoses (hemialbumose)
under the action of trypsin and papain.

Asparagin and Glutamin.—These bodies, which are
found only in plants, are amides of amidoacids, being de-
rived from dibasic acids. Asparagin, the amide of

aumidosuccinic acid,
CH(NH,)COOH

H,CONH,
has been found in very many plants, especially in those
just sprouted, as in asparagus, peas, beans, etc. Aspara-
gin forms white, rhombic crystals, and is very soluble in
water.

Glutamin, the amide of amidoglutaric acid,

cx,00H 3 SON

THE VOLATILE PART OF PLANTS. 117

has been found, together with asparagin, in beet-juice
and in squash seedlings. ‘

The amides, when heated with water alone, and more
easily in presence of strong acids and alkalies, are con-
verted into ammonia and the acids from which they are
derived. Thus, asparagin yields ammonia and amido-
succinic acid at the boiling heat under the influence of
hydrochloric acid, or of potassium hydroxide, and gluta-
min is broken up by the last-named reagent at common
temperatures, and by water alone at the boiling point,
with formation of atnmonia and amidoglutaric acid.

The amidoacids are not decomposed by hot water or
acids with separation of ammonia. Amidosuccinic and
amidoglutaric acids result from albuminoids by boiling
with dilute sulphuric acid, and by the action of bromine.
The latter acid as yet has been obtained from vegetable
albuminoids only, and is prepared most abundantly from
gluten, and especially from mucedin.

Imides, closely related to the amides, are a series of
very interesting substances, into whose chemical consti-
tution we cannot enter here further than to say that they
contain several NH * groups, i. e., ammonia, NHg, in
which two hydrogens. are replaced by hydro-carbon, or
oxycarbon groups or carbon atoms.

These bodies are Uric acid; C;H,N,0,, Adenin, C;sH;N,,
Guanin, C;H;N;0, Allantoin, C,HeN,O3, Xanthin,
Hypoxanthin, C;H,N,O, Theobromin, C,H,0.02, Caffein,
CsHioN,O., and Vernin, CisHooN,Os. Of these the
first, so far as now known, occurs exclusively in the ani-
mal. Adenin, Guanin, Allantoin, Xanthin, and Hypo-
xanthin, are common to animals and plants; the last
three are exclusively vegetable.

Caffein exists in coffee and tea combined with tannic
acid. In the pure state it forms white, silky, fibrous
crystals, and has a bitter taste. In coffee it is found to

* Or its hydro-carbon derivatives,

118 HOW CROPS GROW.

the extent of one-half per cent ; in tea it occurs in much
larger quantity, sometimes as high as 6 per cent.

Theobromin resembles caffein in its characters. It
is found in the cacao-bean, from which chocolate is man-
ufactured, ‘

Vernin, discovered recently in various plants, young
clover, vetches, squash-seedlings, etc., yields guanin by
the action of hydrochloric acid. All these bodies stand
in close chemical relations to each other, being complex
imide derivatives of dioxymalonic (mesoxalic) acid.

The amides and amidoacids, like ammonia, are able to
combine directly with acids, are accordingly bases, but
they are weak bases, because the basic quality of their
ammonia is largely neutralized by the acid radicals already
present in them. On the other hand, amides and ami-
doacids often act as weak acids, for a portion of the hydro-
gen of the NH, group is easily displaced by metals.

The amides thus in fact possess in a degree the quali-
ties of both the acid and of the base (ammonia) from
which they are derived. They also are commonly ‘‘neu-
tral” in the sense of having no sharp acid or alkaline
taste or corrosive character.

In vegetation amides appear as intermediate stages be-
tween ammonium salts and albuminoids. They are, on
the one hand, formed in growing plants from ammo-
nium salts by a constructive process, and from them or
by their aid, probably, the albuminoids are built up. On
the other hand, in animal nutrition they are stages
through which the elements of the albuminoids pass in
their reversion to purely mineral matters. In germinat-
ing seeds and developing buds they probably combine
both these offices, being first formed in the germ from
the albuminoids of the seed, entering the young plant or
shoot, and in it being reconstructed into albuminoids.
Their free solubility in water and ability to penetrate
moist membranes adapt them for this movement, They

THE VOLATILE PART OF PLANTS. 119

temporarily accumulate in seedlings and buds, but disap-
pear again as growth takes place, being converted into
albuminoids, in which transformation they require the
conjunction of carbhydrates. Their ability to unite with
acid as well as bases further qualifies them to take part
in these physiological processes.

The imides are also at once weak bases and weak acids.
Uric acid and allantoin, relatively rich in oxygen, have
the acid qualities best developed. Guanin and caffein,
with less oxygen and more hydrogen, are commonly
classed among the organic bases, as in them the basic
characters are most evident.

Amines.—When the hydrogen of ammonia is replaced
by hydrocarbon groups (radicals) such as Methyl, CHa,
Ethyl, C,H;, Phenyl, C.H;, etc., compound ammonias or
amines result which often resemble ammonia in physical
and chemical characters, and some of them appear to be
stronger bases than ammonia, being able to displace the
latter from its combinations.

Trimethylamine, N(CHs)s, may be regarded as ammo-
nia whose hydrogens are all substituted by the methyl
group, CHg, and is a very volatile liquid having a rank,
fishy odor, which may be obtained from herring pickle, and
exhales from some plants, as from the foliage of Chenopo-
dium vulvaria, and the flowers of Crataegus oxycantha.
It is produced from detain (trimethylamidoacetic acid),
by heating with potash solution, just as ammonia is
formed from many amides under similar treatment.

Cholin, C;HisNO,., and Neurin, C;H,;NO, are organic
bases related to trimethylamine, which were first ob-
tained from the animal. Cholin is an ingredient of the
bile, and is found also in the brain and yolk of eggs,
where it exists asacomponent of lecithin. It has latterly
been discovered in the hop, lupin and pumpkin plants,
and in cotton seed; by oxidation it yields betain. Neu-
rin is readily formed from cholin by the action of alka-

120 HOW CROPS GROW.

lies and in the process of putrefaction. It is a violent
poison, and is perhaps one of the ingredients which, in
the seeds of the vetch and of cotton, prove injurious, or
even fatal, when these seeds are too largely eaten by ani-
mals. Cholin and Neurin are syrupy, highly alkaline
liquids.

7%. ALKALOIDS is the general designation that has
been applied to the organic bases found in many plants,
which are characterized in general by their poisonous
and medicinal qualities. Caffein and Theobromin, already
noticed, were formerly ranked as alkaloids. We may
mention the following :

Nicotin, CioHi4No, is the narcotic and intensely poi-
sonous principle in tobacco, where it exists in combina-
tion with malic and citric acids. In the pure state it is
a colorless, oily liquid, having the odor of tobacco in an
extreme degree. It is inflammable and-volatile, and so
deadly that a single drop will kill’a large dog. French
tobacco contains % or 8 per cent; Virginia, 6 or 7 per
cent; and Maryland and Havana, about 2 per cent of
nicotin. Nicotin contains 17.3 per cent of nitrogen,
but no oxygen.

Lupinidin, C,H,;N, Lupanin, C,;H.;N.0, and Lu-
pinin, Ori HyN.02, are bases existing in the seeds of the
lupin. The first two are liquids; the last is a crystal-
line solid. They are poisonous and are believed to occa-
sion the sickness which usually follows the use of lupin-
seeds in cattle food. ,

Sinapin, CigH2sNOs, occurs in white mustard. When
boiled with an alkali it is decomposed, pans neurin
as one product.

Vicin, CosHs:N11021, and Convicin, O1.H1,N,0;, are
crystalline bases that occur in the seeds of the vetch, with
regard to whose nature and properties little is known.

Avenin, COsgHe,NO;s, according to Sanson, is a sub-
stance of alkaloidal character, existing in oats. It is said

THE VOLATILE PART OF PLANTS. 121

to be more abundant in dark than in light-colored oats,
and, when present to the extent of more than nine-tenths
of one per cent, to act as a decided nerve-excitant on ani-
mals fed mainly on oats. Avenin is described as a gran-
ular, brown, non-crystallizable substance, but neither
Osborne (at the Connecticut Experiment Station) nor
Wrampelmeyer (Vs. St., XXXVI, p. 299) have been able
to find any evidence of the presence of such a body in oats.

Morphin, Cy,;HigNO;, occurs, together with several
other alkaloids, in opium, the dried milky juice of the
seed-vessels of the poppy cultivated in India. Its use in
allaying pain and obtaining sleep and its abuse in the
‘‘opium habit” are well known.

Piperin, C1;Hi,NOs, the active principle of white and
black pepper, is a white crystalline body isomeric with
morphin.

Quinin, CooH.4N.02, is the most important of several
bases used as anti-malarial remedies obtained from the
bark of various species of cinchona growing in the forests
of tropical South America, and cultivated in India.

Strychnin, CoiHo2N,02, and Brucin, CosH2gN.0H, is
the intensely poisonous alkaloid of nux vomica (dog
button).

Atropin, C1;H2,NO;, is the chief poisonous principle
of the “ Nightshade” or belladonna, and of stramonium
or ‘‘ Jamestown weed.”

Veratrin, CssHyyNQv, is the chief toxic ingredient of
the common White Hellebore, so much used as an
insecticide.

Solanin, CaHs:NOis (?), is a poisonous crystalline
alkaloid found in many species of Solanum, especially in
the black nightshade (Solanum nigrum). Itoccurs in the
sprouted tubers and green fruit of the potato (Solanum
tuberosum) and in the stems and leaves of the tomato
(Solanum lycopersicum).

The alkaloids, so far as investigated, appear to be more

122 HOW CROPS GROW.

or less complex derivatives of the bases Pyridin, O;H;N,
and Quinolin, CyH,;,N, which are colorless, volatile
liquids with sharp, unpleasant odor, produced from albn-

-Minoids at high temperatures, and existing in smoke,
bone-oil and tar. The alkaloids bear to these bases simi-
lar relations to those sbeISing, between the amines and
ammonia.

8. PHOSPHORIZED Sapa class of bodies
are important because of their obvious relations to the
nutrition of the brain and nerve tissues of the animal,
which have long been known to contain. phosphorus as
an essential ingredient. All our knowledge goes to show
that phosphorus invariably exists in both plants and ani-
mals as phosphoric acid or some derivative of this acid,
or, in other words, that their phosphorus is always
united to oxygen as in the phosphates, and is not directly
combined to carbon, hydrogen, or nitrogen.

Nuclein.—This term is currently employed to desig-
nate various imperfectly-studied bodies that resemble the
albuminoids in many respects, but contain several per
cent of phosphorus. They are easily decomposable,
boiling water being able to remove from them phosphoric
acid, and under the action of dilute acids they mostly
yield phosphoric acid, alouminoids and hypoxanthin,
C;H,N,0, or similar imide bases. They are very difficult
of digestion by the gastric juice. The nucleins are found
in the protoplasm and especially in the cell-nuclei (see
p. 245), of both plants and animals, and have been ob-
tained from yeast, eggs, milk, etc., by a process based on
their indigestibility by pepsin. Chemists are far from
agreed as to the nature or composition of the nucleins.

Lecithin, O,,Hs)NPO,.—This name applies to a num-
ber of substances that have been obtained from the brain
and nerve tissue of animals, eggs and milk, as well as
from yeast, and the seeds of maize, peas, and wheat.
The lecithins are described as white, wax-like substances,

THE VOLATILE PART OF PLANTS. 123

imperfectly crystallizable, similar to protagon in their
deportment toward water, and readily decomposed into
cholin, glycerophosphoric acid, and one or more fatty
acids. ‘Three lecithins appear to have been identified,
yielding respectively, on decomposition, stearic, palmitic,
and oleic acids.

The formula C,,H,)NPO, is that of distearic lecithin,
which is composed of glyceryl, C;H;, united to two
stearic acid radicals, and also to phosphoric acid, which
again is joined to cholin, as represented by the formula—

oo Gt
os Nope CogHaNcHt 0H

Lecithin is believed to be a constant and essential in-
gredient of plants and animals.

Protagon, C,¢oHsosN;POss, discovered by Liebreich in
the brain of animals, has been further studied by Gam-
gee & Blankenhorn. It is a white substance that swells
up with water to a gelatinous mass and finally forms an
opake solution. From solution in ether or alcohol it can
be easily obtained in needle-shaped crystals, whose com-
position is given below. Alkalies decompose protagon
into glycero-phosphoric acid, stearic and other fatty
acids, and cholin or neurin. Protagon was formerly
confounded with lecithin and thought to exist in plants,
but its presence in the latter has not been established.

Protagon. Lecithin.
CAaTDON ......-cc cee e cee cece rene 66.39 65.43

Hydrogen .. 11.16
Nitrogen.. 1.73
Phosphorus .. 3.84
OXYGEN... ec ece eee e cece ence eens 19.46 17.84

100.00 100.00

Knop was the first to show that the crude fat which is
extracted from plants by ether contains an admixture of
some substance of which phosphorus is an ingredient.
In the oil obtained from the sugar-pea he found 1.25 per
cent. of phosphorus. Tépler afterwards examined the

124 HOW CROPS GROW.

oils of a large number of seeds for phosphorus with the
subjoined results :

Source of Per cent. of | Source of Per cent. of
Sat. hace i Fat, phosphorus.
Lupin.. csstg uae
POCA a ciaists esieroscione
Horse-bean - 0.

WVoetehiicsssasdinacsacmarcessa.es 0.50

Winter lentil............... 0.39°
Horse-chestnut . ia

It is probable that the phosphorus in these oils existed
in the seeds as lecithin, or as glycerophosphoric acid,
which is produced in the decomposition of lecithin. Max-
well (Constitution of the Legumes), reckoning from the
phosphoric acid found in the ether-extract, estimates the
“pea kernel to contain 0.368 per cent, the horse-bean
(faba vulgaris) 0.600 per cent, and the vetch 0.532 per
cent of lecithin. Lecithin is thus calculated to make up
19.63 per cent of the crude fat of the pea, 31.54 per
cent of the crude fat of the horse-bean, and 35.24 per
cent of that of the vetch.

Chlorophyl, i. e., leaf-green, is the name applied to
the substance which occasions the green color in vegeta-
tion. Itis found in all those parts of most annual plants
and of the annually renewed parts of perennial plants
which are exposed to light.- The green parts of plants
usually contain chlorophyl only near their surface, and
in quantity not greater than one or two per cent of the
fresh vegetable substance.

Chlorophyl, being soluble in ether, accompanies fat or
wax when these are removed from green vegetable mat-
ters by this solvent. It is soluble in alcohol and hydro-
chloric and sulphuric acids, imparting to these liquids an
intense green color, but it suffers alteration and decom-
position so readily that it is doubtful if the composition

of chlorophy]l, as it exists in the living leaf, is accurately “

known, especially since it is there mixed with other sub-

THE VOLATILE PART OF PLANTS. 125

stances, separation from which is difficult or imprac-
ticable.

Chlorophyllan, obtained by Hoppe-Seyler from grass,
separates from its solution in hot alcohol in characteristic
acicular crystals which are brown to transmitted light,
and in reflected light are blackish green, with a velvety,
somewhat metallic lustre. This substance has the con-
sistence of beeswax, adheres firmly to glass, and at about
230° melts to a brilliant black liquid. The crystallized
chlorophyllan has a composition as follows :

CHLOROPHYLLAN.

Carbon..

Hydrogen. .

Nitrogen ..

Phosphorus. . .

Magnesium ....... eee eeee cece teen een anes

OK ON aia is5, 51055 c1015.05) lad aipnbakesdros culeatoemertniss 9.52
100.00

Chlorophyllan is chemically distinct from chlorophyl,
as proved by its optical properties, but in what the dif-
ference consists is not understood. Boiling alkali decom-
poses it with formation of chlorophyllanic acid that
may be obtained in blue-black crystals, and at the same
time glycerophosphoric acid and cholin, the decomposi-
tion-products of lecithin, are produced. Tschirch found
that chlorophyllan, by treatment with zinc oxide, yields
a substance whose optical properties lead to the belief
that it is identical with the chlorophyl that occurs in the
living plant. It was obtained as a dark-green powder,
but its exact chemical composition is not known.

The special interest of chlorophyl lies in the fact that
it is to all appearance directly concerned in those con-
structive processes by which the plant composes starch
and other carbhydrates out of the mineral substances
which form its food.

Xanthophy!] is the yellow coloring matter of leaves
and of many flowers. It occurs, together with chlorophyl,
in green leaves, and after disappearance of chlorophy]
remains as the principal pigment of autumn foliage.

126 HOW CROPS GROW.

CHAPTER II.

THE ASH OF PLANTS.

§ 1.
THE INGREDIENTS OF THE ASH.

As has been stated, the volatile or destructible part of
plants, i. e., the part which is converted into gases or
vapors under the ordinary conditions of burning, con-
sists chiefly of Carbon, Hydrogen, Oxygen and Nitro-
gen, together with small quantities of Sulphur and Phos-
phorus. These elements, and such of their compounds
as are of general occurrence in agricultural plants, viz.,
the Organic Proximate Principles, have been already
described in detail.

The non-volatile part or ash of plants also contains,
‘or may contain, Carbon, Oxygen, Sulphur, and Phos-
phorus. It is, however, in general, chiefly made up of
eight other elements, whose common compounds are
permanent at the ordinary heat of burning.

In the subjoined table, the names‘of the 12 elements
of the ash of plants are given, and they are grouped
under two heads, the non-metals and the metals, by- rea-
son of an important distinction in their chemical nature.

ELEMENTS OF THE ASH OF PLANTS.

Non-Metals. % Metals,
Oxygen. Potassium.
Carbon. Sodium.
Sulphur. Calcium.

- Phosphorus. Magnesium.
Silicon. Iron.
Chlorine. Manganese.

If to the above be added :

Hydrogen and Nitrogen

THE ASH OF PLANTS. 127

the list includes all the elementary substances that belong
to agricultural vegetation,

Hydrogen is never an ingredient of the perfectly
burned and dry ash of any plant.

Nitrogen may remain in the ash under certain con-
ditions in the form of a Cyanide (compound of Carbon
and Nitrogen), as will be noticed hereafter.

Besides the above, certain other elements are found, either occasion-
ally in common plants, or in some particular kind of vegetation ; these
are Iodine, Bromine, Fluorine, Titanium, Boron, Arsenic, Lithium,
Rubidium, Barium, Aluminum, Zine, Copper. These elements, how-
ever, so far as known, have no special importance in agricultural
chemistry, and mostly require no further notice.

We way now complete our study of the Composition
of the Plant by attending to a description of those ele-
ments that are peculiar to the ash, and of those com-
pounds which may occur in it.

It will be convenient also to describe in this section
some substances, which, although not ingredients of the
ash, may exist in the plant, or are otherwise important
to be considered.

The Non-metallic Elements, which we shall first
notice, though differing more or less widely among them-
selves, have one point of resemblance, viz., they and their
compounds with each other have acid properties, i. e.,
they either are acids in the ordinary sense of being sour
to the taste, or enact the part of acids by uniting to met-
als or metallic oxides to form salts. We may, therefore,
.. designate them as the acid elements. They are Oxygen,
St ylphur, Phosphorus, Carbon, Silicon, and Chlarine.

With the exception of BSilicon,! and the densef forms of
Carbon, these elements by themselves are readily volatile.
Their compounds with each other, which may occur in
vegetation, are also volatile, ‘with two “exceptions, viz.,
Silicic and Phosphoric acids.

In order that they may vesist the high temperature at
which ashes are formed, they must be combined with the
metallic elements or their oxides as salts.

128 HOW CROPS GROW.

Oxygen, Symbol O, atomic weight 16, is an ingredient
of the ash, since it unites with nearly all the other ele-
ments of vegetation, either during the life of the plant,
or in the act of combustion. It unites with Carbon,
Sulphur, Phosphorus, and Silicon, forming acid bodies ;
while with the metals it produces oxides, which have the
characters of bases. Chlorine alone of the elements of
the plant does not unite with oxygen, either in the living
plant, or during its combustion.

CARBON AND ITS COMPOUNDS.

Carbon, Sym. C, at. wt. 12, has been noticed already.
with sufficient fullness (p. 14). It is often contained as
charcoal in the ashes of the plant, owing to its being en-
veloped in a coating of fused saline matory wee shield
it from the action of oxygen.

Carbon Dioxide, commonly termed Carbonic acid,
Sym. CO, molecular weight 44, is the colorless gas
which causes the sparkling or effervescence of beer and
soda water, and the frothing of yeast.

Tt is formed by the oxidation of carbon, when vegeta-
ble matter is burned (Exp. 6). It is, therefore, found
in the ash of plants, combined with those bases which in
the living organism existed in union with organic acids ;:
the latter being destroyed by burning.

It also occurs in combination with calcium in the tissues
of many plants. Its compounds with bases are carbon-
ates, to be noticed presently. When a carbonate, as mar-
ble or limestone, is drenched with a strong acid, like
vinegar or muriatic acid, the carbon dioxide is set free
with effervescence. :

Carbonic Acid, H,0O;, or CO(OH)., mo. wt. 62.
This, the carbonic acid of modern chemistry, is not known
asa distinct substance, since, when set free from carbon-
ates by the action of a stronger acid, it falls into carbon
dioxide and water :

THE ASH OF PLANTS. 129

CaCO, + 2 HCl = CaCl, + H,CO, and H,CO, = H,0 + CO,
Carbon dioxide is also termed anhydrous carbonic acid,
or again, carbonic anhydride.

CYANOGEN, Sym. C.N,.—This important compound of Carbon and Ni-
trogen is a gas which has an odor like that of peach-pits, and which
burns on contact with a lighted taper with a fine purple flame. In its
union with oxygen by combustion, carbon dioxide is formed, and nitro-
gen set free: .
CN, +40 =2C0,+ Ny

Cyanogen may be prepared by heating an intimate mixture of two
parts by weight of ferrocyanide of potassium (yellow prussiate of
potash) and three parts of corrosive sublimate. The operation may
be conducted in a test-tube or small flask, to the mouth of which is
fitted a cork penetrated by a narrow glass tube. On applying heat, the
gas issues, and miay be set on fire to observe its beautiful fame.

Cyanogen, combined with iron, forms the Prussian blue of com-
merce, and its name, signifying the blue-producer, was given to it from
that circumstance. |

Cyanogen unites with the metallic elements, giving rise to a series
of bodies which are termed Cyanides. Some of these often occur in
small quantity in the ashes of plants, being produced in the act of
burning by the unfon of nitrogen with carbon andametal. For this
result, the temperature must be very high, carbon must be in excess,
the metal is usually potassium or calcium, the nitrogen may be either
free nitrogen of the atmosphere or that originally existing in the
organic matter.

With hydrogen, cyanogen forms the deadly poison hydrocyanie or
prussic acid, HCy, which is produced from amygdalin, one of the ingre-
*dients of bitter almonds, peach, and cherry seeds, when these are
erushed in contact with water. ;

When a cyanide is brought in contact with steam at high tempera-
tures, itis decomposed, allits nitrogen being converted into ammonia.

Cyanogen is a normal ingredient of one common plant. The oil of
mustard is allylsulphocyanate, C;H;CNS.

ia, J AND ITS COMPOUNDS.

Sulphur, Sym. 5, at. wt. 32.—The properties of this
element have been already described (p. 25). Some of
its compounds have also been briefly alluded to, but re-

quire more detailed notice.

HYDROGEN SULPHIDE, Sym. H.S, mo. wt. 34. This substance, familiarly
f known as sulphuretted hydrogen, occurs dissolved in the water of nu-
merous so-called sulphur springs, as those of Avon and Sharon, N. Y.,
from which it escapes as a fetid gas. It is not unfrequently emitted
from volcanoes and fumaroles. Itis likewise produced in the decay of
organic bodies which contain sulphur, especially eggs, the intolerable
odor of which, when rotten, is largely due to this gas. It is evolved
from manure heaps, from salt marshes, and even from the soil of moist
meadows.

9

130 HOW CROPS GROW.

The ashes of plants sometimes yield this gas when they are moistened
with water. In such cases, a sulphide of potassium or calcium has been
formed in small quantity during the incineration.

Hydrogen Sulphide is set free in the gaseous form by the action of an
acid on various sulphides, as those of iron (Exp. 17), antimony, etc., as
well as by the action of water on the sulphides of the alkali and alkali-
earth metals. It may be also generated by passing hydrogen gas into
melted sulphur.

Sulphuretted hydrogen has aslight acid taste. Itis highly poisonous
and destructive, both to animals and plants.

SULPHUR DIOXIDE, commonly called SULPHUROUS ACID, Sym. SO,, mo.
wt. 64. When sulphur is burned in the air, or in-oxygen gas, it forms
copious white suffocating fumes, which consist of one atom of sulphur,
united to two atoms of oxygen; SO, (Exp. 15).

Sulphur dioxide is characterized by its power of discharging, for a
time at least, most of the red and blue vegetable colors. It has, how-
ever, no action on many yellow colors. Straw and wool are bleached
by it in the arts.

Sulphur dioxide is emitted from voleanoes, and from fissures in the
soil of voleanic regions. It is produced when bodies containing sul-
phur are burned with imperfect access of air, and is thrown into the .
atmosphere in large quantities from fires which are fed by mineral
coal, as well as from the numerous roasting heaps of certain metallic

* ores (sulphides) which are wrought in mining regions.

Sulphur dioxide may unite with bases, yielding salts known as sul-
phites, some of which, viz., calcium sulphite and sodium sulphite, are
employed to check or "prevent fermentation, an effect also produced by
the acid itself.

Sulphur-Trioxide, Sym. 80s, mo. wt. 80, is known.
to the chemist as a white, silky solid, which attracts

moisture with great avidity, and, when thrown into
water, hisses like a hot iron, forming sulphuric acid.
Sulphur trioxide was formerly termed sulphuric acid or
anhydrous sulphuric acid, and now it is common in
statements of analysis to follow this usage.

Sulphuric Acid, Sym. H,S8O,, mo. w#. 98, is a sub-
stance of the highest importance, its manufacture being
the basis of the chemical arts. In its concentrated form
it ig known as ot! of vitriol, and is a colorless, heavy
liquid, of an oily consistency, and sharp, sour taste.

It is manufactured on the large scale by mingling sul-
phur dioxide gas, nitric acid gas, and steam, in large
lead-lined chambers, the floors of which are covered with
water. The sulphur dioxide takes up oxygen from the

THE ASH OF PLANTS. 131

nitric acid, and the sulphuric acid thus formed dissolves
in the water, and is afterwards boiled down to the proper
strength in glass vessels.

The chief agricultural application of sulphuric acid is
in the preparation of ‘‘ superphosphate of lime,” which
is consumed as a fertilizer in immense quantities. This
is made by mixing together sulphuric acid, somewhat
diluted with water, with bone-dust, bone-ash, or some
mineral phosphate. Commercial oil of vitriol is a mix-
ture of sulphuric acid with more or less water. The
strongest oil of vitriol commonly made, or ‘‘66° acid,”
contains 93.5% of H,SO, The so-called ‘60° acid”
contains 77.6% H,SO, or 83% of 66° acid. Chamber
acid or ‘51° acid” contains 63.6% H,SO,, or 67% of
66° acid.

Sulphuric acid occurs in the free state, though ex-
tremely dilute, in certain natural waters, as in the Oak
Orchard Acid Spring of Orleans, N. Y., where it is pro-
duced by the oxidation of sulphide of iron.

Sulphuric acid is very corrosive and destructive to most
vegetable and animal matters.

EXP. 53.—Stir a little oil of vitriol with a pine stick. The wood is im-
mediately browned or blackened, and a portion of it dissolves in the
acid, communicating a dark color to the latter. The commercial acid
is often brown from contact with straws and chips.

Strong sulphuric acid produces great heat when mixed with water,
as is done for making superphosphate.

EXP. 54.—Place in a thin glass vessel, as a beaker glass, 30. c. of water;
into this pour in a fine stream 120 grams of oil of vitriol, stirring all the
while with a narrow test-tube, containing a teaspoonful of water. Ifthe
acid be of full strength, so much heat is thus generated as to boil the
water in the stirring tube.

In mixing oil of vitriol and water, the acid should always be slowly
poured into the water, with stirring, as above directed. When water
is added to the acid, it floats upon the latter, or mixes with it but super-

ficially, and the liquids may be thrown about by. the sudden formation
of steam at the points of contact, when subsequently stirred.

Sulphuric acid forms with the bases an important class
of salts—the sulphates, to be presently noticed—some of
which exist in the ash, as well as in the sap of plants.

132 HOW CROPS GROW.

When organic matters containing sulphur—as hair,
albumin, etc.—are burned with full access of air, this
element remains in the ash as sulphates, or is partially
dissipated as sulphur dioxide.

FHOSPHORUS AND ITS COMPOUNDS.

Phosphorus, Sym. P, at. wt. 31, has been sufficiently
described (p. 248 Of its numerous compounds but two
require additional notice.

Phosphorus Pentoxide, Sym. P.0;, mo. wt. 142,
does not occur as such in nature. When phosphorus is
burned in dry air or oxygen, anhydrous phosphoric acid
is the snow-like product (Exp. 18). The term ‘‘ phos-
phoric acid,” as now encountered in fertilizer analyses,
has reference to ‘‘anhydrous phosphoric acid,” as phos-
phorus pentoxide was formerly designated. Phosphorus
pentoxide has no sensible acid properties until it has
united to water, which it combines with so energetically
as to produce a hissing noise from the heat developed.
On boiling it with water for some time, it completely dis-
sulves, and the solution contains—

Phosphoric Acid, Sym. H,PQ,, 98.—The chief in-
terest which this compound has for the agriculturist lies
in the fact that the combinations which are formed be-
tween it and various bases—phosphates—are among the
most important ingredients of plants and their ashes. .

When organic bodies containing phosphorus, as le-
cithin (p. 122), and, perhaps, some of the albuminoids,
are decomposed by heat or decay; the phosphorus appears
in the ashes or residue, in the condition of phosphoric
acid or phosphates.

The formation of several phosphates has been shown in
Exp. 20. Further account of them will be given under
the metals.

CHLORINE AND ITS COMPOUNDS.
Chlorine, Sym. Cl., at. wt. 35.5. —This element exists

THE ASH OF PLANTS. 133

in the free state as a greenish-yellow, suffocating gas,
which has a peculiar odor, and the property of bleaching
vegetable colors. It is endowed with the most vigorous
affinities for many other elements, and hence is never met
with, naturally, in the free state.

Exp. 55.—Chlorine may be prepared by heating a mixture of hydro-
chloric acid and black-oxide of manganese or red-lead. The gas being
nearly five times as heavy as common air, may be collected in glass
bottles by passing the tube which delivers it to the bottom of the re-
ceiving vessel. Care must be taken not to inhale it, as it energetically
attacks the interior of the breathing passages, producing the disagree-
able symptoms of a cold.

Chlorine dissolves in water, forming a yellow solution.

In some form of combination chlorine is distributed
over the whole earth, and is never absent from the plant.

The compounds of chlorine are termed chlorides, and
may be prepared, in most cases, by simply putting their
elements in contact, at ordinary or slightly elevated tem-
peratures. :

HYDROCHLORIC ACID, Sym. HCl, mo. wt. 36.5.—When Chlorine and
Hydrogen gases are mingled together, they slowly combine if exposed
to diffused light ; butif placed in the sunshine, they unite explosively,
and hydrogen chloride or hydrochloric acid isformed. This compound
isagas that dissolves with great avidity in water, forming a liquid
which has a sharp, sour taste, and possesses all the characters of an
acid. ~

The muriatic acid of the apothecary is water holding in solution
several hundred times its bulk of hydrochloric acid gas, and is pre-
pared from common salt, whence its ancient name, spirits of salt.

Hydrochloric acid is the usual source of chlorine gas. The latter is
evolved from a heated mixture of this acid with black oxide of manga-
nese. In this reaction hydrogen of the hydrochloric acid unites
with oxygen of the oxide of manganese, producing water, while
chloride of manganese and free chlorine are separated.

4 HCl + MnO, = MnCl, + 2H,O+2 C1.

When chlorine, dissolved in water, is exposed to the sunlight, there
ensues a change the reverse of that just noticed. Water is decom-
posed, its oxygen is set free, and hydrochloric acid is formed.

H,O + 2 Cl= 2 HCl1+ 0.

The two reactions just noticed are instructive examples of the differ-
ent play of affinities between several elements under unlike circum-
stances.

This aeid is a ready means of converting various metals or metallic
oxides into chlorides, and its solution in water is a valuable solvent
and reagent for the purpose of the chemist.

134 HOW CROPS GROW. =

IODINE, Sym. I, at. wt. 127.—This interesting body is a blac# solid at
ordinary temperatures, having an odor resembling that of chlorine.
Gently heated, it is converted into a violet vapor. It occurs in sea-
weeds, and is obtained from their ashes. It gives with starch a blue or

* purple compound, and is hence employed as a test for that substance
(p 49). It is analogous to chlorine in its chemical relations. It is not
known to occur in sensible quantity in agricultural plants, although it
may well exist in the grasses of salt-bogs, and in the produce of soils
which are manured with sea-weed.

BROMINE and FLUORINE may also exist in very small quantity in
plants, but these elements require no further notice in this treatise.

SILICON AND ITS COMPOUNDS.

Silicon, Sym. Si, at. wit. 28.—This element, in the
free state, is only known to the chemist. It may be pre-
pared in three modifications: one, a brown, powdery
substance ; another, resembling plumbago, and a third,
that occurs in crystals, having the form and nearly the
hardness of the diamond.

Silicon Dioxide, Sym. SiO,, mo. wt. 60.—This com-
poutnd, known also as Silica, is widely diffused in nature,
and occurs to an enormous extent in rocks and soils, both
in the free state and in combination with other bodies.

Free silica exists in nearly all soils, and in many rocks,
especially in sandstones and granites, in the form known
to mineralogists as guartz. The glassy, white, or trans-
parent, often yellowish or red, fragments of common sand,
which are hard enough to scratch glass, are almost inva-
riably this mineral. In the purest state, it is rock-crys-
tal. Jasper, flint, and agate are somewhat less pure
silica.

Silicates.—Silica is extremely insoluble in pure water
and in most acids. It has, therefore, none of the sensi-
ble qualities of acids, but is nevertheless capable of union
with bases. It is slowly dissolved by strong, and espe-
cially by hot, solutions of potash and soda, forming sol-

uble silicates of the alkali metals.

EXP. 56.—Formation of potassium silicate. Heat apiece of quartz or
flint, as large as a chestnut, as hot as possible in the fire, and quench
suddenly in cold water. Reduce it to fine powder in a porcelain mor-
tar, and boil it in a porcelain dish with twice its weight of caustic pot-

THE ASH OF PLANTS. 135

ash, and Bight or ten times as much water, for two hours, taking care
to supply the water as it evaporates. Pour off the whole into a tall
narrow bottle, and leave at rest until the undissolved silica has settled.
The clear liquid is a basic potassium silicate, i.v., a silicate which con.
tains w# number of molecules of base for each molecule of silica. It
has, in fact, the taste and feel of potash solution. The so-called water-
glass, now employed in the arts, is a similar sodium silicate.

When silica is strongly heated with potash or soda, or
with lime, magnesia, or oxide of iron, it readily melts to-
gether and unites with these bodies, though nearly infus-
ible by itself, and silicates are the result. The silicates
thus formed with potash and soda are soluble in water,
like the product of Exp. 56, when the alkali exceeds a
certain proportion—when highly basic ; but, with silica
in excess (acid silicates), they dissolve with difficulty.
A mixed silicate of sodium, calcium, and aluminum, with
a large proportion of silica, is nearly or altogether insol-
uble, not only in water, but in most acids—constitutes,
in fact, ordinary glass.

A multitude of silicates exist in nature as rocks and
minerals. Ordinary clay, common slate, soapstone, mica,
or mineral isinglass, feldspar, hornblende, garnet, and
other compounds of frequent and abundant occurrence,
are silicates. The natural silicates may be roughly dis-
tinguished as belonging to two classes, viz., the acid sil-
icates (containing a preponderance of silica) and basic
silicates (with large proportion of base). The former are
but slowly dissolved or decomposed by acids, while the
latter are readily attacked, even by carbon dioxide acid.
Many native silicates are anhydrous, or destitute of
water; others are hydrous, i. e., they contain water as a
large and essential ingredient.

The Silicic Acids. —Various silicic acids—compounds
of silica with water—are known to the chemist, or are
represented by the silicates found in nature. The silicic
acids themselves have little stability and are readily re-
solved into water and silica.

‘Soluble Silica, Si(OH),?—This body is known only in

136 HOW CROPS GROW.

solution. It is formed when the solution of art alkali-
silicate is decomposed by means of a large excess of some
strong acid, like the hydrochloric or sulphuric.

EXP. 57.—Dilute half the solution of potassium silicate obtained in
Exp. 56 with ten times its volume of water, and add diluted hydrochloric
acid gradually until the liquid tastes sour. In this Exp. the hydrochlo-
ric acid decomposes and destroys the potassium silicate, uniting itself
to the base with production of chloride of potassium, which dis-
solves in the water present. The silica thus liberated unites chemi-
cally with water, and remains also in solution.

By appropriate methods Doveri and Graham have
obtained solutions of silica in pure water. Graham pre-
pared a liquid that gave, when evaporated and heated,
14 per cent of anhydrous silica. This solution was clear,
colorless, and not viscid. It reddened litmus-paper like
an acid. Though not sour to the taste, it produced a
peculiar feeling on the tongue. Evaporated to dryness at
alow temperature, it left a transparent, glassy mass,
which had the composition H,SiO,. This dry residue
was insoluble in water. These solutions of silica in pure
water are incapable of existing for a long time without
suffering a remarkable change. Even when protected
as much as possible from all external agencies, they
sooner or later, usually in a few days or weeks, Jose their
fluidity and transparency, and coagulate to a stiff jelly,
from the separation of a nearly insoluble hydrate of silica,
which we shall designate as gelatinous silica.

The addition of y5$55 of an alkali or earthy carbon-
ate, or of a few bubbles of carbon dioxide gas to the strong
solutions, occasions their immediate gelatinization. A
minute quantity of potash or ‘soda, or excess of hydro-
‘ chloric acid, prevents their coagulation.

Gelatinous Silica.—This substance, which results
from the coagulation of the soluble silica just described,
usually appears also when the strong solution of a silicate
has strong hydrochloric acid added to it, or when a sili-
cate is decomposed by direct treatment with a concen-
trated acid,

THE ASH OF PLANTS. 137

It is‘’a white, opaline, or transparent jelly, which, on
drying in the air, becomes a fine, white powder, or forms
transparent grains. This powder, if dried at ordinary
temperatures, has a composition nearly corresponding to
the formula H,Si,0,, or to a compound of 3 SiO, with
2H,O. At the temperature of 212° F., it loses half its
water. Ata red heat it becomes anhydrous.

Gelatinous silica is distinctly, though very slightly,
soluble in water. Fuchs and Bresser have found by ex-
periment that 100,000 parts of water dissolve 13 to 14
parts of gelatinous silica.

The hydrates of silica which have been subjected to a
heat of 212°, or more, appear to be totally insoluble in
pure water.

These hydrates of silica are readily soluble in solutions
of the alkalies and alkali carbonates, and readily unite
with moist, slaked lime, forming silicates.

EXP. 58.—Gelatinous Silica.—Pour a small portion of the solution of
silicate potassium of Exp. 56 into strong hydrochloric acid. Gelatinous
silica separates and falls to the bottom, or the whole liquid becomes a
transparent jelly.

EXP. 59.—Conversion of soluble into insoluble hydrated silica.—Evapo-
rate the solution of silica of Exp. 57, which contains free hydrochloric
acid, in a porcelain dish. As it becomes concentrated, it is very likely
to gelatinize, as happened in Exp. 58, on account of the removal of the
solvent. Evaporate to perfect dryness, finally on a water-bath (i. e., on
a vessel of boiling water which is covered by the dish containing the
solution). Add to the residue water, which dissolves away the chlo-
ride of potassium, and leaves insoluble hydrated silica, 3 SiO, H,O, as
a gritty powder.

In the ash of plantg, silica is usually found in com-
bination with alkali-metals or calcium, owing to the
high temperature to which it has been subjected.

In the plant, however, it exists chiefly, if not entirely,
in the free state.

TITANIUM, an element which has many analogies with silicon, though
rarely occurring in large quantities, is yet often present in the form
of Titanic acid, TiO,, in rocks and soils, and, according to Salm-Horst-
mar, may exist in the ashes of barley and oats.

ARSENIC, in minute quantity, was found by Davy in turnips which
had been manured with a fertilizer (superphosphate), in whose prep-
aration arsenical oil of vitriol was employed.

138 HOW CROPS GROW.

. 3 =

‘When arsenic, in the form of Paris green or London purple,isapplied ~

to land the arsenic soon becomes converted into highly insoluble iron
compounds and is not taken up by plants in appreciable quantity.

The Metallic Elements which remain to be noticed,
viz.: Potassium, Sodium, Calcium, Magnesium, Iron,
Manganese, Aluminium, Zinc, and Copper, are basic in
their character, i. e., they: unite with the acid bodies
that have just been described, to produce salts. Hach
one is, in this sense, the base of a series of saline com-
pounds.

ALKALI-METALS.—The elements Potassium and Sodium
are termed alkali-metals. Their oxides dissolve in and
chemically unite to water, forming hydroxides that are
called alkalies. The metals themselves do not occur in
nature, and can only be prepared by tedious chemical
processes. They are silvery-white bodies, and are lighter
than water. Exposed to the air, they quickly tarnish
from the absorption of oxygen and moisture, and are
rapidly converted into the corresponding alkalies.
Thrown upon water, they mostly inflame and burn with
great violence, decomposing the liquid. Exp. 11.

Of the alkali-metals, Potassium is invariably found in
all plants. Sodium is especially abundant in marine and
strand vegetation ; it is generally found in agricultural
plants, but is sometimes present in them in but small
quantity.

POTASSIUM AND ITS COMPOUNDS.

Potassium, Sym. K ;* at. 2. 39.—When heated in
the air, this metal burns with a-beautiful violet light,
and forms potassium oxide.

Potassium Oxide, or Potash, K,O, 94, is the so-
called ‘‘actual potash” that figures in the analyses of
plants and valuation of fertilizers. Itis, however, scarcely
known as a substance, because it energetically unites
with water and forms hydroxide.

* From the Latin name Kalium.

THE ASH OF PLANTS. 139

Potassium Hydroxide, KOH, 56, is the caustic
potash of the apothecary and chemist. It may be pro-
cured in white, opaque masses or sticks, which rapidly
absorb moisture and carbonic acid from the air, and
readily dissolve in water, forming potash-lye. It strongly
corrodes many vegetable and most animal matters, and
dissolves fats, forming potash-soaps. Both the oxide
and hydroxide of potassium unite to acids forming salts.

SODIUM AND ITS COMPOUNDS.

Sodium, Na,* 23.—Burns with a brilliant, orange-
yellow flame, yielding sodium oxide.

Sodium Oxide, or Soda, Na,0, 62, is practically lit-
tle known, though constantly referfed to as the base of
the sodium salts. It unites to water, producing the hy-
droxide.

Sodium Hydroxide, or Caustic Soda, NaOH, 40.—
This body is like caustic potash in appearance and gen- -
eral characters. It forms soaps with the various fats.
While the potash-soaps are usually soft, those made with
soda are commonly hard.

ALKALI-EARTH Metats.—The two metallic elements
next to be noticed, viz., Calcium and Magnesium, give,
with oxygen, the alkali-earths, lime and magnesia. The
metals are only procurable by difficult chemical pro-
cesses, and from their gminent oxidability are not found
in nature. They are but a little heavier than water.
‘Their oxides are but slightly soluble in water.

CALCIUM AND ITS COMPOUNDS.

Calcium, Ca, 40, is a brilliant ductile metal having a
light yellow color. In moist air it rapidly tarnishes and
acquires a coating of lime.

Calcium Oxide, or Lime, CaO, 56, is the result

* From the Latin name Natrium.

140 HOW CROPS GROW.

of the oxidation of calcium. It is prepared for use
in the arts by subjecting limestone or oyster-shells to an
intense heat, and usually retains the form and much of
the hardness of the material from which itis made. It
has the bitter taste and corroding properties of the alka-
lies, though in a less degree. It is often called guick-
lime, to distinguish it from its compound with water.
It may occur in the ashes of plants when they have been
maintained at a high heat after the volatile matter has
been burned away.

Calcium Hydroxide, Ca (OH),, 74.—Quick-lime,
when exposed to the air, gradually absorbs water and
falls to a fine powder. It is then said to be air-slacked.
When water is poured upon quick-lime it penetrates the
pores of the latter, and shortly the falling to powder of
the lime and the development of much heat give evi-
dence of chemical union between the lime and the water.
This chemical combination is further proved by the in-
crease of weight of the lime, 56 Ibs. of quick-lime becom-
ing 74 lbs. by water-slacking. On heating slacked lime
to redness, water is expelled, and calcium oxide remains.

When lime is agitated for some time with much water,
and the mixture is allowed to settle, the clear liquid is
found to contain a small amount of lime in solution (one
part of lime to 700 parts of water). This liquid is called
lime-water, and has already been noticed as a test for
carbonic acid. Lime-water has the alkaline taste in a
marked degree.

MAGNESIUM AND ITS COMPOUNDS.

Magnesium, Mg, 24.—Metallic magnesium has a sil-
ver-white color. When heated in the air it burns with
extreme brilliancy (magnesium light), and is converted
into magnesia.

Magnesium Oxide, or Magnesia, MgO, 40, is found
in the drug-stores in the shape of a bulky white powder,

THE ASH OF PLANTS. 141

under the name of calcined magnesia. It is prepared by
subjecting either magnesium hydroxide, carbonate, or
nitrate, to a strong heat. It occurs in the ashes of
plants.

Magnesium Hydroxide, Mg(OH),, is produced
slowly and without heat, when magnesia is mixed with
water. It occurs rarely as a transparent, glassy mineral
(Brucite) at Texas, Pa., Hoboken, N. J., and a few
other places. It readily absorbs carbon dioxide and passes
into carbonate of magnesium. Magnesium hydroxide is
so slightly soluble in water as to be tasteless. It requires
55,000 times its weight of water for solution (Fresenius).

Heavy Metas.—The two metals remaining to notice
are Iron and Manganese. These again considerably re-
semble each other, though they differ exceedingly from
the metals of the alkalies and alkali-earths. They are
about eight times heavier than water. Each of these
metals forms two basic oxides, which are commonly
insoluble in pure water. .

IRON AND ITS COMPOUNDS.

Tron, Fe,* 56.—The properties of metallic iron are so
well known that we need not occupy any space in reca-
pitulating them.

Ferrous Oxide, or Protoxide of Iron, FeO, 72.—
When sulphuric acid in a diluted state is put in contact
with metallic iron, hydrogen gas shortly begins to escape
in bubbles from the liquid, and the iron dissolves, unit-
ing with the acid to form ferrous sulphate, the salt
known commonly as copperas or green-vitriol.

H,S0,, + Fe = FeSO, + H,.

If, now, lime-water or potash-lye be added to the solu-
tion of iron thus obtained, a white or greenish white pre-
cipitate separates, which is ferrous hydroxide, Fe(OH)?.

*From the Latin name Ferrum.

142 HOW CROPS GROW.

This precipitate rapidly absorbs oxygen from the air, be-
coming bleck and finally brown. The anhydrous pro-
toxide of iron is black. Carbonate of protoxide of iron
is of frequent occurrence as a mineral (spathic iron), and
exists dissolved in many mineral waters, especially in
the so-called chalybeates. The ferrous salts are mostly
white or green.

Ferric Oxide, or Peroxide of Iron, Fe,03, 160.—
When ferrous hydroxide is exposed to the air, it acquires
a brown color from union with more oxygen, and becomes
ferric hydroxide Fe(OH),. The yellow or brown rust
which forms on surfaces of metallic iron when exposed to
moist air is the same body. Ferric oxide is found in
the ashes of all agricultural plants, the other oxides of
iron passing into this when exposed to air at high tem-
peratures. It is fonnd in immense beds in the earth,
and is an important ore (specular iron, hematite). It
dissolves in acids, forming the ferric salts, which have
a yellow color.

MAGNETIC OXIDE OF IRON, Fe,0,, or FeO.Fe,0;, is a combination
of the two oxides above mentioned. It is black, and is strongly at-
tracted by the magnet. It constitutes, in fact, the native magnet, or
loadstone, and is a valuable ore of iron.

MANGANESE AND ITS COMPOUNDS.

Manganese, Mn, 55.—Metallic manganese is difficult
to procure in the free state, and much resembles iron,
Its oxides are analogous to those of iron just noticed,

Manganous Oxide, or Protoxide of Manganese,
MnO, 71, has an olive-green color. It is the base of all
the usually occurring salts of manganese. Its hydrox-
ide, prepared by decomposing manganous sulphate by
lime-water, is a white substance, which, on exposure to
the air, shortly becomes brown and finally black from
absorption of oxygen. The manganous salts are mostly
pale rose-red in color.

MANGANIC OXIDE, Mn,0;, occurs native as the mineral braunite, or;

THE ASH OF PLANTS. 143

combined with water, as manganite. It is a substance having a red or
black-brown color. It dissolves in cold acids, forming salts of an in-
tensely red color. These are, however, easily decomposed by heat, or
by organic bodies, into oxygen and manganous salts. %

RED OXIDE OF MANGANESE, Mn,0,, or MnO.Mn,0;.—This oxide re-
mains when manganese or any of its other oxides are subjected toa
high temperature with access of air. The metal and the protoxide
gain oxygen by this treatment, the higher oxides lose oxygen uhtil
this compound oxide is formed, which, as its symbol shows, corres-
ponds to the magnetic oxide of iron. It is found in the ashes of plants.

BLACK OXIDE OF MANGANESE, MnO,.—This body is found extensively
in nature. Itis employed in the preparation of oxygen and chlorine
(bleaching powder), and is an article of commerce.

Some other metals occur as oxides or salts in ashes, though not in
such quantity or in such plants as to possess any agricultural signifi-
cance in this respect.

ALUMINA, <AJ1,0;, the oxide of the metal Aluminium, is found in
eonsiderable quantity (20 to 50 per cent) in the ashes of the ground pine
(Lycopodium). Itis united with an organic acid (tartaric, according to
Berzelius ; malic, according to Ritthausen) in the plant itself. It is
often found in small quantity in the ashes of agricultural plants, but
whether an ingredient of the plant or due to particles of adhering elay
is not in all cases clear.

ZINC has been found in a variety of yellow violet that grows about
the zine mines of Aix-la-Chapelle.

CorpPrER is frequently present in minute quantity in the ash of plants,
especially of such as grow in the vicinity of manufacturing establish-
ments, where dilute solutions containing copper are thrown to waste.

The Salts or Compounds of Metals with Non-
metals found in the ashes of plants or in the unburned
plant remain to be considered.

Of the elements, acids and oxides, that have been
noticed as constituting the ash of plants, it must be re-
marked that with the exception of silica, magnesia, oxide
of iron, and oxide of manganese, they all exist in the
ash in the form of salts (compounds of acids and bases).
In the living agricultural plant it is probable that, of
them all, only silica occurs in the uncombined state.

We shall notice in the first place the salts which may
occur in the ash of plants, and shall consider them under
the following heads, viz. : Carbonates, Sulphates, Phos-
phates, and Chlorides. As to the Silicates, it ig unnec-
essary to add anything here to what has been already
mentioned.

144 HOW CROPS GROW.

THE CARBONATES which occur in the ashes of plants
are those of Potassium, Sodium, and Calcium. The
Carbonates of Magnesium, Iron, and Manganese are de-
composed by the heat at which ashes are prepared.

Potassium Carbonate, or Carbonate of Potash,
K,COs, 114.—The pearl-ash of commerce is a tolerably
pure form of this salt. When wood is burned, the potash
which it contains is found in the ash, chiefly as carbon-
ate. If wood-ashes are repeatedly washed or leached with
water, all the salts soluble in this liquid are removed ; by
boiling this solution down to dryness, which is done i in
large iron pots, crude potash is obtained, as a dark or.
brown mass. This, when somewhat purified, yields
pearl-ash. Potassium carbonate, when pure, is white, and
has a bitter, biting taste—the so-called alkaline taste. It
has such attraction for water, that, when exposed to the
air, it absorbs moisture and becomes a liquid.

{f hydrochloric acid be poured upon this carbonate a
brisk effervescence immediately takes place, owing to the
escape of carbon dioxide gas, and potassinm chloride and
water are formed, which remain behind.

K,CO, + 2 HC1= 2 KCl + H,0 + CO,.

Potassium Bicarbonate, KHCO;.—A solution of
potassium carbonate, when exposed to carbon dioxide, ab-
sorbs the latter, and the potassium bicarbonate is pro-
duced, socalled because to a given amount of potassium
it contains twice as much carbonic acid as the carhonate.
Potash-saleratus consists essentially of this salt. It
probably exists in the juices of various plants.

Sodium Carbonate, or Carbonate of Soda,
Na,COs, 106.—This substance, so important in the arts,
was formerly made from the ashes of certain marine
plants (Salsola and Salicornia), in a manner similar to
that now employed in wooded countries for the prepara-
tion of potash. It is at present almost wholly obtained

THE ASH OF PLANTS. 145

from common salt by somewhat complicated processes.
It occurs in commerce in an impure state under the name
of Soda-ash. United to water, it forms sal-soda, which
usually exists in transparent crystals or crystallized
masses. These contain 63 per cent of water, which
partly escapes when the salt is exposed to the air, leay-
ing a white, opaque powder.

Sodium carbonate has a nauseous alkaline taste, not
nearly so decided, however, as that of the carbonate of
potassium. It is often present in the ashes of plants.

Sodium Bicarbonate, NaHCO;.—The supercarbon-
ate of soda of the apothecary is this salt in a nearly pure
state. The cooking-soda of commerce is a mixture of
this with some simple carbonate. It is prepared in the
same way as potassium bicarbonate. The bicarbonates,
both of potassium and sodium, give off half their carbonic
acid at a moderate heat, and lose all of this ingredient
by contact with excess of any acid. Their use in baking
depends upon these facts. They neutralize any acid
(lactic or acetic) that’ is formed during the “rising ” of
the dough, and assist to make the bread “ light” by in-
flating it with carbon dioxide.

Calcium Carbonate, or Carbonate of Lime,
CaC0Os;, 112.—This compound is the white powder formed
by the contact of carbon dioxide with lime-water. When
slacked lime is exposed to the air, the water it contains
is gradually displaced by carbon dioxide, and carbonate of
lime is the result. Air-slacked lime always contains
much carbonate. This salt is distinguished from lime
by its being destitute of any alkaline taste.

In nature carbonate of lime exists to an immense ex-
tent as coral, chalk, marble, and limestone. These
rocks, when strongly heated, especially in a current of
air, part with carbon dioxide, and quick-lime remains
behind.

Calcium carbonate occurs largely in the ashes of most

10

146 HOW CROPS GROW.

plants, particularly of trees. In the manufacture of
potash it remains undissolved, and constitutes a chief
part of the residual leached ashes.

The calcium carbonate found in the ashes of plants is
supposed to come mainly from the decomposition by heat
of organic calcium salts (oxalate, tartrate, malate, etc.),
which exist in the juices of the vegetable, or are abun-
dantly deposited in its tissues in the solid form. Car-
bonate of lime itself is, however, not an unusual compo-
nent of vegetation, being found in the form of minute,
rhombic crystals, in the cells of a multitude of plants.

Tue SULPHATES which we shall notice at length are
those of Potassium, Sodium, and Calcium. Sulphate of
Magnesium is well known as Epsom salts, and Sulphate
of Iron_is copperas or green vitriol.

Potassium Sulphate, or Sulphate of Potash,
K,80,, 174.—This salt may be procured by dissolving
potash or carbonate of potash in diluted sulphuric acid.
On evaporating its solution, it is obtained in the form of
hard, brilliant crystals, or as a white powder. It has a
bitter taste. Ordinary potash, or pearl-ash, contains
several per cent of this salt.

Sodium Sulphate, or Sulphate of Soda, Na,S0,,
142.— Glauber’s salt is the common name of this famil-
iar substance. It has a bitter taste, and is much em-
ployed as a purgative for cattle and horses. It exists,
either crystallized and transparent, containing 10 mole-
cules, or nearly 56 per cent of water, or anhydrous.
The crystals rapidly lose their water when exposed to the
air, and yield the anhydrous salt as a white powder. '

Calcium Sulphate, or Sulphate of Lime, CaSO,,
136.—The burned Plaster of Paris of commerce is this
salt in a more or less pure state. It is readily formed by
pouring diluted sulphuric acid on lime or marble. It is |
found in the ash of most plants, especially in that of
clover, the bean, and other legumes.

THE ASH OF PLANTS. 147

In nature, sulphate of lime is usually combined with
two molecules of water, and thus constitutes Gypsum,
CaSO,.2 H,O, which is a rock of frequent and exten-
sive occurrence. In the cells of many plants, as for
instance the bean, gypsum may be discovered by the
microscope in the shape of minute crystals. It requires
400 times its weight of water to dissolve it, and being
almost universally distributed in the soil, is rarely absent,
from the water of wells and springs.

Land plaster is ground gypsum, that from Nova
Scotia being white, that from Onondaga and other local-
ities in New York State gray in color.

THE PHospHatTes which require special description
are those of Potassium, Sodium, and Calcium.

Numerous phosphates of each of these bases exist, or
may be prepared artificially. But three classes of phos-
phates have any immediate interest to the agriculturist.
As has been stated (p 132), phosphoric acid, prepared by
boiling phosphorus pentoxide with water, is represented -
by the symbol H,PO,. The phosphates may be regarded
as phosphoric acid in which one, two, or all the atoms
of hydrogen are substituted by one or several metals.

Potassium Phosphates or Phosphates of Potash.
—There are three of these phosphates formed by replac-
ing one, two, or three hydrogen atoms of phosphoric
acid by potassium, viz.: KH,PO,, primary or mono-
potassic phosphate; K,HPO,, secondary or dipotassic
phosphate, and K;PQ,, tertiary or tripotassic phos-
phate.* Of these salts, the secondary and tertiary phos-
phates exist largely (to the extent of 40 to 50 per cert)
in the ash of the kernels of wheat, rye, maize, and other
bread grains. The potassium phosphates do not occur
in commerce ; they closely resemble the corresponding
sodium-salts in their external characters.

*The primary phosphates are often designated acid or super-phos-
baad the secondary neutral phosphates, and the tertiary basic phos-
phates.

148 HOW CROPS GROW.

Sodium Phosphates, or Phosphates of Soda.—
Of these the disodic phosphate, NagHPO,, alone needs
notice. It is found in the drug-stores in the form of
glassy crystals, which contain 12 molecules (56 per cent)
of water. ‘The crystals become opaque if exposed to the
air, from the loss of water. This salt has a cooling, sa-
line taste, and is very soluble in water.

Calcium Phosphates, or Phosphates of Lime.
—Since one atom of calcium replaces two of hydrogen,
the formule of the calcium phosphates are written as
follows : monocalcic. or primary phosphate CaH,P.0,;
dicalcie or secondary phosphate, CaHPO, ; tricalete or
tertiary phosphate, CagP,0,.* Both the secondary and
tertiary phosphates probably occur in plants. The sec-
ondary is a white crystalline powder, nearly insoluble
in water, but easily soluble in acids. In nature it is
found as a urinary concretion in the sturgeon of the Cas-
pian Sea. It is also an ingredient of guanos, and proba-
bly of animal excrements in general.

The tricalcic phosphate, or, as it is sometimes termed,
bone-phosphate, is achief ingredient of the bones of ani-
mals, and constitutes 90 to 95 per cent of the ash or
earth of bones. It may be formed by adding a solution
of lime to one of sodium phosphate, and appears as a
white precipitate. It is insoluble in pure water, but dis-
solves in acids and in solutions of many salts. In the
mineral kingdom tricalcic phosphate is the chief ingre-
dient of apatite and phosphorite. These minerals are
employed in the preparation of the commercial super-
phosphates now consumed to an enormous extent as a
fertilizer. Plain superphosphate is essentially a mixture
of sulphate of lime with the three phosphates above no-
ticed and with free phosphoric acid.

The Phosphates of Magnesium, Iron, Alumin-
ium and Manganese, are bodies insoluble in water,

*These formulz correspond to 2 molecules of phosphoric acid,
=H,P,O,, with 2 and 4 H-atoms replaced by Ca.

e

THE ASH OF PLANTS. 149

that oceur in very small proportion in the ashes of plants
and in soils, but are important ingredients of some
fertilizers.

THE CHLoRIpEs are all characterized by their ready
solubility in water. The Chlorides of Calcium and Mag-
nesium are deliguescent, i. e., they liquefy by absorbing
moisture from the air. The Chlorides of Potassium and
Sodium alone need to be described.

Potassium Chloride, or Muriate of Potash,
KCl, 74.5.—This body-may be produced either by expos-
ing metallic potassium to chlorine gas, in which case the
two elements unite together directly ; or by dissolving
caustic potash in hydrochloric acid. In the latter case
water is also formed, as is expressed by the equation-
KHO + HCl = KCl + H?0.

Potassium chloride closely resembles common salt in
appearance, solubility in water, taste, etc. It is now an
important article of commerce and largely consumed as
a fertilizer. It is also often present in the ash and in
the juices of plants, especially of sea-weeds, and is like-
wise found in most fertile soils.

Chloride of Sodium, NaCl, 58.5.—This substance is’
common or culinary salt. It was formerly termed murt-
ate of soda. It is scarcely necessary to speak of its oc-
currence in immense quantities in the water of the ocean,
in saline springs, and in the solid form as rock-salt, in
the earth. Its properties are so familiar as to require no
description. It is rarely absent from the ash of plants.

Besides the salts and compounds just described, there
occur in the living plant other substances, most of which
have been indeed already alluded to, but may be noticed
again connectedly in this place.

These compounds, being destructible by heat, do not
appear in the analysis of the ash of a plant. |

Nirrates.—Mitrie acid (the compound by which ni-
trogen is chiefly furnished to plants for the elaboration

150 HOW CROPS GROW.

of the albuminoid principles) is not unfrequently pres-
ent as a nitrate in the tissues of the plant. It usually
occurs there ‘as potassium nitrate (niter, saltpeter),
KNO,. ,

The properties of this salt scarcely need description.
It is a white, crystalline body, readily soluble in water,
and has a cooling, saline taste. When heated with car-
bonaceous matters, it yields oxygen to them, and a defla-
gration, or rapid and explosive combustion, results.
Touch-paper is paper soaked in solution of niter and
dried. The leaves of the sugar-beet, sunflower, tobacco,
and some other plants, frequently contain this salt, and,
when burned, the nitric acid is decomposed, oftén with
slight deflagration, or glowing like touch-paper, and the
alkali remains in the ash as carbonate. The characters
of nitric acid and the nitrates are noticed at length in
“How Crops Feed.” See also p

OXALATES, CITRATES, MALATES, TARTRATES, and salts
of other less common organic acids, are generally to be
found in the tissues of living plants. On burning, the:
metals with which they were in combination—potassium
and calcium, in most cases—remain-as carbonates.

Ammonium Salts exist in minute amount in some
plants. What particular salts thus occur is uncertain,
and special notice of them is unnecessary in this chapter.

Since it is possible for each of the acids above described
to unite with each of the bases in one or several propor-
tions, and since we have as many oxides and chlorides as
there are metals, and even more, the question at once
arises—which of the 60 or more compounds that may thus
be formed outside the plant do actually exist within it?
In answer, we must remark that while most or all of them
may exist in the plant but few have been proved to exist
as such in the vegetable organism. As to the state in
which iron and manganese occur, we know little or noth-
ing, and we cannot always assert positively that ina given

THE ASH OF PLANTS. 151

plant potassium exists as phosphate, or sulphate, or car-

bonate. We judge, indeed, from the predominance of

potassium and phosphoric acid in the ash of wheat, that

potassium phosphate is a large constituent of this grain,

but of this we are scarcely certain, though in the absence

of evidence to the contrary we are warranted in assuming
these two ingredients to be united. On the other hand,.
calcium carbonate and calcium sulphate have been discov-

ered by the microscope in the cells of various plants, in
crystals whose characters are unmistakable.

For most purposes it is unnecessary to know more than
that certain elements are present, without paying atten-
tion to their mode of combination. And yet there is
choice in the manner of representing the composition of
a plant as regards its ash-ingredients. ;

We do not indeed so commonly speak of the calcium
or the silicon in the plantas of lime and silica, because
these rarely-seen elements are much less familiar than
their oxides.

Again, we do not speak of the sulphates or chlorides,
when we desire to make statements which may be com-
pared together, because, as has just been remarked, we
eannot always, nor often, say what sulphates or what
chlorides are present.

In the paragraphs that follow, which are devoted to a
more particular statement of the mode of occurrence, rel-
ative abundance, special functions, and indispensability
of the fixed ingredients of plants, will be indicated the
customary methods of defining them.

§ 2.

QUANTITY, DISTRIBUTION, AND VARIATIONS OF THE ASH-
INGREDIENTS.

The Ash of plants consists of the various acids, oxides,
and salts, that have been noticed in § 1, which are fixed
or non-volatile at a heat near redness.

152 HOW CROPS GROW.

Ash-ingredients are always present in-each cell of every
plant.

- The ash-ingredients exist partly in the cell-wall, in-
crusted or imbedded in the cellulose, and partly in the
plasma or contents of the cell (see p 249).

One portion of the ash-ingredients is soluble in water,
and occurs in the juice or sap. This is true, in general,
of the salts of the alkali-metals, and of the sulphates and
chlorides of magnesium and calcium. Another portion
is insoluble, and exists in_the tissues of the plant in the
solid form. Silica, the calcium phosphates and the mag-
nesium compounds, are mostly insoluble.

The ash-ingredients may be separated from the volatile
matter by burning or by any process of oxidation. In
burning, portions of sulphur, chlorine, alkalies, and phos-
phorus may be lost, under certain circumstances, by vola-
tilization. The ash remains as a skeleton of the plant,
and often actually retains and exhibits the microscopic
form of the tissues.

The Proportion of Ash is not Invariable, even in
the same kind of plant, and in the same part of the plant.
Different kinds of plants often manifest very marked dif-
ferences in the quantity of ash they contain. The fol-
lowing table exhibits the amount of ash in 100 parts (of
dry matter) of « number of plants and trees, and in their
several parts. In most cases is given an average proportion
as deduced from a large number of the most trustworthy
examinations. In some instances are cited the extreme
proportions hitherto put on record.

PROPORTIONS OF ASH IN VARIOUS VEGETABLE MATTERS.*
ENTIRE PLANTS, ROOTS EXCEPTED.

Average. Average.
Re Clover ........ccccecceevecees 6.7 | Turnips, 10.7—19.7....6e.ceeseeeee 15.5

WAGE: #8 snare theta Saains 7.2 | Carrot, 15.0—21.3........eseeeee 17.1

Timothy....... . T1 | He

Potatoes ...........05- ... 5.1 | Hemp.

Sugar beet, 16.3—18.6............17.5

Field beet, 14.0—21.8......-.-.-5++ ABQ ROA ED cos eie: svayecermsaiaseseeueserervinvaeds ajaraceceie 4.5

* These figures are copied unchanged from the old edition, and may
differ from later averages, but are approximately correct...

THE ASH OF PLANTS. 153

ROOTS AND TUBERS.

Potatoes, 2.6—8.0...........ce eee 4.1 | Turnip, 6.0—20.9.......cceseeerees ere
Sugar beet, 2.9—6.0. 4.4 | Carrot, is Ba ae ara pla oe
Field beet, 2.8—11.3............66 7.7 | Artichoke...
STRAW AND STEMS.
Wheat, 3.86.9. 0.0... cc cccc cece ee B.4| Peas, 6.5—9.4.......ccccrcecescons ve)
‘Rye, 4.9—5.6.... 5.3| Beans, 5.1—7.2.. . 61
Oats, 5.0—5.4.. até seeveee 58] Flax .....ee 7
Barley iccsincencs mavens tieesertsion an G8 || MAIZOs serdeisiars scents ereieiers piece aig Bareiniets oD
GRAINS AND SEED.
Wheat, 1.53.1. ....ccccccccee ee nn 2.0 ° hee aoe Rian OL
Rye, 1.6—2.7.... seseeesee 2.0 Peas, 2.4—2.9.. one
Oats, 2.56—4.0. - 33 Beans, 2.74.3

BOCs
PANNE

Barley, 1.8—2. . 23, Flax, ....
Maize, 1.3—2.1.., - 15, Sorghum...
WooD. ’
Red Pine......ccccessnececsnscene 0.3
bt Pine 3
: 27 3
. 13 3
BARK.
Birchivecscsnwsccwicionns Weiter TeEw AN, a Bits vanesvcsiemecncerarreseoes
Red Pine... Walnut..
White Pine...........cc cece cannes Cauto tree.

From the above table we ne —

1. That different plants yield different quantities of
ash. It is abundant in succulent foliage, like that of the
beet (18 per cent), and small in seeds, wood, and bark.

2. That different parts of the same plant yield unlike
proportions of ash. Thus the wheat kernel contains 2
per cent, while the straw yields 5.4 per cent. The ash
in sugar-beet tops is 17.5; in the roots, 4.4 per cent.
In the ripe oat, Arendt found (Das Wachsthum der
Haferpflanze, p. 84),

In the three lower joints of the stem... 4.6 per cent of ash.

In the two middle joints of the stem.... 5.3 ee

In the one upper joint of the stem....... 6.4 ae ee
In the three lower leaves.......... - 101 fe ae
In the two upper leaves....... - 10.5 ee se
DE GH OHC AT fciainscmcsanniaowatenvmanaakeneaanae 2.6 es ae

3. We further find that, in general, the upper and
outer parts of the plant contain the most ash-ingredi-
ents. In the oat, as we see from the above figures of
Arendt, the ash increases from: the lower portions to the
upper, until we reach the ear. If, however, the ear be

154 HOW CROPS GROW.

dissected, we shall find that its outer parts are richest in
ash. Norton found

In the husked kernels of brown oats.... 2.1 per cent oF pals
In the husk of brown oats............0005 8.2 af
In the chaff of brown oats............... 19.1 me ce

Norton also found that the top of the oat-leaf gave
16.22 per cent of ash, while the bottom yielded but 13.66
per cent. (Am. Jour. Science, Vol. II, 1847.)

From the table it is seen that wood.(0.3 to 2.7 per
cent) and seeds (1.5 to 3.7 per cent)—lower or inner
parts of the plant—are poorest in ash. The stems of
herbaceous plants (3.7 to 7.9 per cent) are next richer,
while the leaves of herbaceous plants, which have such
an extent of surface, are the richest of all (6 to 8 per
cent).

4. Investigation has demonstrated further that the
same plant in different stages of growth varies in the pro-
portions of ash in dry matter, yielded both by the entire
plant and by the several organs or parts.

The following results, obtained by Norton, on the oat,
illustrate this variation. _Norton examined the various
parts of the oat-plant at intervals of one week through-
out its entire period of growth. He found

Leaves. Stem. Knots. Chaff. Grain unhusked.

JUNE 4... 0... cee ee 10.8 10.4

June 1l...... cece ee 10.7 9.8

JUNE 18... . cee ee eee 9.0 9.3

TUNE 25... cee ee eee 10.9 9.1

July 2.2... ce eee 11.3 7.8 49
JULY Qscc0aeeer eres 12.2 78 4.3
July 16 79 6.0 3.3
July 23 7.9 10.0 9.1 3.6
July 30.... V4 9.6 12.2 4.2
Aug. 6... 7.6 10.4 13.7 4.3
Aug. 13... oe 6.6 10.4 18.6 4.0
AUg. 20.......0 0005 211 6.6 11.7 21.0 3.6
AUG Bi iclirsccniedea ee 22.1 U7 11.2 22.4 3.5
Sept. 3...........5 20.9 8.3 10.7 27.4 3.6

Here, in case of the leaves and chaff, we observe a con-
stant increase of ash, while in the stem there is a con-

THE ASH OF PLANTS. 155

stant decrease, except at the time of ripening, when these
relations are reversed. The knots of the stem preserved
a pretty uniform ash-content. The unhusked grain at
first suffered a diminution, then an increase, and lastly a
decrease again.

Arendt found in the oat-plant fluctuations, not in all
respects accordant with those observed by Norton.
Arendt obtained the following proportions of ash :

3lower 2middle Upper Lower Upper Entire
joints of jointsof jotntof leaves. leaves. Ears. plant.
‘ stem. stem. stem.

June 18...... 4.4 9.7 UT 8.0
June 30...... 2.5 2.9 3.5 9.4 7.0 3.8 5.2
July 10 3.5 4.7 5.2 10.2 6.9 3.6 5.4
July 21......4.4 5.0 5.5 10.1 9.7 2.8 5.2
July 31......6.4 5.3 6.4 10.1 10.5 2.6 51

Here we see that the ash increased in the stem and in
each of its several parts after the first examination. The
lower leaves exhibited an increase of fixed matters after
the first period, while in the upper leaves the ash dimin-
ished toward the third period, and thereafter increased.
In the ears, and in the entire plant, the ash decreased
quite regularly as the plant grew older. Pierre found
that the proportion of ash of the colza (Brassica olera-
cea) diminished in all parts of the plant (which was
examined at five periods), except in the leaves, in which
it increased. (Jahresbericht tiber Agriculturchemie, III,
p. 122.) The sugar-beet (Bretschneider) and potato
(Wolff) exhibit a decrease of the per cent of ash, both in
tops and roots.

In the turnip; examined at four periods, Anderson
(Trans. High. and Ag. Soc.,1859-61, p. 371) found the
following per cent of ash in dry matter :

July. Aug.11. Sept... Oct.5.

LOAVES «0.0. ce scene se een sens 7.8 20.6 18.8 16.2
BUIDS....scee cece cece er ceeees 17.7 8.7 10.2 20.9

In this case, the ash of the leaves increased during
about half the period of growth from 7.8 to 20.6, and

156 HOW CROPS GROW.

thence diminished to 16.2. The ash of the bulbs fluc-
tuated in the reverse manner, falling from 17.7 to 8.7,
then rising again to 20.9.

In general, the proportion of ash of the entire plant
diminishes regularly as the plant grows old.

5. The influence of the soil and season in causing the
proportion of ash of the same kind of plant to vary, is
shown in the following results, obtained by Wunder
Versuchs-Stationen, TV, p. 266) on turnip bulbs, raised
during two successive years, in different soils.

In sandy soil. In loamy soil.

r ‘ r : ‘
lst year. 2d year. 1st year. 2d year.
Per cent of ash..........13.9 11.3 9.1 10.9

6. As might be anticipated, different varieties of the
same plant, grown on the same soil, take up different
quantities of non-volatile matters.

In five varieties of potatoes, cultivated in the same soil
and under the same conditions, Herapath (Qu. Jour.
Chem., Soc. Il, p. 20) found the percentages of ash in
dry matter of the tuber as follows :

VARIETY OF POTATO.

White Prince’s Axbridge Forty-
Apple. Beauty. Kidney. Magpie. fold.
Ash per cent... 4.8 3.6 4.3 3.4 ~ 3.9

7. It has been observed further that different individ-
uals of the same variety of plant, growing side by side,
on the same soil (in the same field, at least), contain dif-
ferent proportions of ash-ingredients, according as they
are, on the one hand, healthy, vigorous plants, or, on the
other, weak and stunted. Pierre (Jahresbericht uber
Agriculturchemie, III, p. 125) found in entire’ colza
plants of various degrees of vigor the following percent-
ages of ash in dry matter :

In extremely feeble plants, 1856............ 8.0 per cent of: ash.
In very feeble plants, 1857..............0008 9.0

In feeble plants, 1857............ee cece ee eeee 11.4 LG ie

In strong plants, 1857.......... secure neeaee 11.0 ee a

In extremely strong plants, 1857........... 14.3 a as

THE ASH OF PLANTS. 157

Pierre attributes the larger per cent of ash in the
strong plants to the relatively greater quantity of leaves
developed on them.

Similar results were obtained by Arendt in case of oats.
Wunder ( Versuchs-St., IV, p. 115) found that the leaves
of small turnip-plants yielded somewhat more ash per
cent than large plants. The former gave 19.7, the lat-
ter 16.8 per cent.

8. The reader is prepared from several of the foregoing
statements to understand partially the cause of the vari-
ations in the proportion of ash-in different specimens of
the same kind of plant. |

The fact that different parts of the plant are unlike in
their composition, the upper and outer portions being, in
general, the richer in ash-ingredients, may explain in
some degree why different observers have obtained differ-
ent analytical results.

It is well known that very many circumstances influ-
ence thé relative development of the organs of a plant.
In a dry season, plants remain stunted, are rougher on
the surface, having more and harsher hairs and prickles,
if these belong to them at all, and develop fruit earlier
than otherwise. In moist weather, and under the influ-
ence of rich manures, plants are more succulent, and the
stems and foliage, or vegetative parts, grow at the ex-
pense of the reproductive organs. Again, different vari-
eties of the same plant, which are often quite unlike in
their style of development, are of necessity classed to-
gether in our table, and under the same head are also
brought together plants gathered at different stages of
growth.

In order that the wheat plant, for example, should
always have the same percentage of ash, it would be nec-
essary that it should always attain the same relative de-
velopment in each individual part. It must, then,
always grow under the same conditions of temperature,

158 HOW CROPS GROW.

light, moisture, and soil. This is, however, as good as
impossible, and if we admit the wheat plant to vary in
form within certain limits without losing its proper char-
acteristics, we must admit corresponding variations in
composition.

The difference between the Tuscan wheat, which is
. cultivated exclusively for its straw, of which the Leghorn.
hats are made, and the “ pedigree wheat” of Mr. Hallett
(Journal Roy. Ag. Soc. Eng., Vol. 22, p. 374), is in
some respects as great as between two entirely different
plants. The hat wheat has a short, loose, bearded ear,
containing not more than a dozen small kernels, while
the pedigree wheat has shown beardless ears of 8% inches
in length, closely packed with large kernels to the num-
ber of 120!

Now, the hat wheat, if cultivated and propagated in
the same careful manner as has been done with the pedi-
gree wheat, would, no doubt, in time become as prolific
of grain as the latter, while the pedigree wheat might
perhaps with greater ease be made more valuable for its
straw than its grain.

We easily see then, that, as circumstances are perpet-
ually making new varieties, so analysis continually finds
diversities of composition.

9. Of all the parts of plants, the seeds are the least lia-
ble to vary in composition. Two varieties or two indi-
viduals may differ enormously in their relative propor-
tions of foliage, stem, chaff, and seed; but the seeds
themselves nearly agree. ‘Thus, in the analysis of 67
specimens of the wheat kernel, collated by the author,
the extreme percentages of ash were 1.35 and 3.13. In
60 specimens out of the 67, the range of variation fell
between 1.4 and 2.3 per cent. In 42 the range was from
1.7 to 2.1 per cent, while the average of the whole was
2.1 per cent.

In the stems or straw of the grains, the variation is

THE ASH OF PLANTS, 159

much more considerable. Wheat-straw ranges from 3.8
to 6.9; pea-straw, from 6.5 to 9.4 per cent. In fleshy
roots, the variations are great; thus turnips range from
6 to 21 per cent. The extremest variations in ash-con-
tent are, however, found, in general, in the succulent
foliage. Turnip tops range from 10.7 to 19.7; potato
tops vary from 11 to near 20, and tobacco from 19 to 27
per cent.

Wolff (Die Naturgesetzlichen Grundlagen des Acker-
baus, 3 Aufl., p. 117) has deduced from a large number
of analyses the following eho for three important
classes of agricultural plants, viz.

Grain. Straw.

Cereal Crops 46cs2ccsccsieosececees 2 per cent. 5.25 per cent,

Leguminous Crops......ss..es0s Bu 5 Se

Oil-plants............seeeeeee neers 4. st 45
More general averages are as follows (Wolff, Joc. cit.) :
Annual and biennial plants. Perennial plants.

3 per cent.
1 “6 “a
“6

1% «

We may conclude this section by stating three propo-
sitions which are proved in part by the facts that have
been already presented, and which are a summing up of
the most important points in our knowledge of this sub-
ject.
1. Ash-ingredients are indispensable to the life and
growth of all plants. In mold, yeast, and other plants
of the simplest kind, as well as in those of the higher or-
ders, analysis never fails to recognize a proportion of
fixed matters. We must hence conclude that these are
necessary to the primary acts of vegetation, that atmos-
pheric food cannot be assimilated, that vegetable matter
cannot be organized, except with the codperation of those
substances which are invariably found in the ashes of the
-plant. This proposition is demonstrated in the most
conclusive manner by numerous synthetic experiments.

160 HOW CROPS GROW.

It is, of course, impossible to attempt producing a plant
at all without some ash-ingredients, for the latter are
present in all seeds, and during germination are trans-
ferred to the seedling. By causing seeds to sprout in a
totally insoluble medium, we can observe what happens
when the limited supply of fixed matters in the seeds them-
selves is exhausted. Wiegmann & Polstorf (Preisschrift
aber die unorganischen Bestandthetle der Pflanzen) plant-
ed 30 seeds of cress in fine platinum wire contained in a
platinum vessel. The contents of the vessel were moist-
ened with distilled water, and the whole was placed under
a glass shade, which served to shield from dust. Through
an aperture in the shade, connection was made with a gas-
ometer, by which the atmosphere in the interior could be
renewed with an artificial mixture, consisting, in 100, of
21 parts oxygen, 78 parts nitrogen, and 1 part carbonic
acid. In two days 28 of the seeds germinated ; afterwards
they developed leaves, and grew slowly with a healthy ap-
pearance during 26 days, reaching a height of two or
three inches. From this time on, they refused to grow,
began to turn yellow, and died down. The plants were
collected and burned ; the ash from them weighed. pre-
cisely as much as that obtained by burning 28 seeds like
those originally sown. This experiment demonstrates
most conclusively that a plant cannot grow in the absence
of those substances found in its ash. The development
of the cresses ceased so soon as the fixed matters of the
seed had served their utmost in assisting the organization
of new cells. We know from otherexperiments that, had
the ashes of cress been applied to the plants in the above
experiment, just as they exhibited signs of unhealthiness,
they would have recovered, and developed to a much great-
er extent. ;

II. The proportion of ash-ingredients in the plant is
variable within a narrow range, but cannot fall below or
exceed certain limits. The evidence of this proposition

THE ASH OF PLANTS. 161

is to be gathered both from the table of ash-percentages
and from experiments like that of Wiegmann & Polstorf,
above described.

III. We have reason to believe that each part or organ
(euch cell) of the plant contains a certain, nearly invaria-
ble, amount of fixed matters, which is indispensable to the
vegetative functions. Each part or organ may contain,
besides, a variable and unessential or accidental quantity
of thesame. What portion of the ash of any plant is es-
sential and what accidental is a question not yet brought
to asatisfactory decision. By assuming the truth of this
proposition, we account for those variations in the
amount of ash which cannot be attributed to the causes
already noticed. The evidences of this statement must
be reserved for the subsequent section.

§ 3.

SPECIAL COMPOSITION OF THE ASH OF AGRICULTURAL
PLANTS.

The result of the extended inquiries which have been
made into the subject of this section may be convenient-
ly presented and discussed under a series of propositions,
viz.:

1. Among the substances which have been described
(§ 1) as the ingredients of the ash, the following are in-
variably present in all agricultural plants, and in nearly
all parts of them, viz.:

poushy ae. ee cl.
Bases fea! Cal Acids (tee aca BO;
Magnesia, “Mgo. Silicic acid, SiO,
Oxide of iron, Fe,0,. Carbonic acid, oy

2. Different normal specimens of the same kind of
plant have a nearly constant composition. The use of
the word early in the above statement implies what has
been already intimated, viz., that some variation is noticed
in the relative proportions as well as in the total quantity

11

162 HOW CROPS GROW.

of ash-ingredients occurring in plants.. This point will
shortly be discussed in full. By taking the average of
many trustworthy ash-analyses we arrive ata result which
does not differ very widely from the majority of the in-
dividual analyses. This is especially true of the seeds of
plants, which attain nearly the-same development under
all ordinary circumstances. It is less true of foliage and
roots, whose dimensions and character vary to a great
extent. In the following tables (p. 164-170) is stated the
composition of the ashes of a number of agricultural
products which have been repeatedly subjected to analy-
sis. In most cases, instead of quoting all the individual
analyses, a series of averages is given. Of these, the first
is the mean of all the analyses on record or obtainable by
the writer,* while the subsequent ones represent either
the results obtained in the examination of a number of
samples by one analyst, or are the means of several single
analyses. In this way, it is believed, the real variations
of composition are pretty truly exhibited, independently
of the errors of analysis.

The lowest and highest percentages are likewise given.
These are doubtless in many cases exaggerated by errors of
analysis, or by impurity of the material analyzed. Chlo-
rine and sulphuric acid are for the most part too low, be-
cause they are liable to be dissipated in combustion, while
silica is often too high, from the fact of sand and soil ad-
hering to the plant.

In two cases, single and doubtless incorrect analyses by
Bichon, which give exceptionally large quantities of soda,
are cited separately. ,

A number of analyses that came to notice after making
out the averages are given as additional.

* At the time of preparing the first edition of this book, in 1868. More
recent analyses are comparatively few in number, excepting those of
wheat (grain and straw) by Lawes & Gilbert, and do not differ essen-
tially from those gle The numerous very incorrect ash-analyses
peprobed by Dr. E. Emmons and Dr. J. H. Salisbury, in the Natural

istory of New York, and in the Trans. of the New York State Agricul-
tural Society, are not included. :

THE ASH OF PLANTS. 163

The following table includes both the kernel and straw
of Wheat, Rye, Barley, Oats, Maize, Rice, Buckwheat,
Beans, and Peas; the tubers of Potatoes; the roots and
tops of Sugar-Beets, Field-Beets, Carrots, Turnips, and
various parts of the Cotton Plant.

For the average composition of other plants and vege-
table products, the reader is referred to a table in the ap-
pendix, p. 409, compiled by Prof. Wolff, of the Royal
Agricultural Academy of Wiirtemberg. That table in-
cludes also the averages obtained by Prof. Wolff for most
of the substances, cotton excepted, whose composition is
represented in the pages immediately following.

In both tables the carbonic acid, CO?, which occurs in
most ashes, is excluded, from the fact that its quantity
varies according to the temperature at which the ash is
prepared.

The following is a statement of the various Names and
Symbols that are or have been currently applied to the
Ash-Ingredients in Ohemical Literature. The changes
that have been made from time to time, both in symbols
and in names, are the results of progress in knowledge or
of attempts to improve nomenclature :

OLier Newer
Sy ubols. Symbols. Synonyms.

KO K,O0 Potash, Potassa, Potassium Oxide, Potassic Oxide.
«Nad . Na,O Soda, Sodium Oxide, Sodic Oxide.

MLO MgO Magnesia, Magnesium Oxide, Magnesic Oxide.

cao CaO Lime, Calcium Oxide, Calcie Oxide.

Fe,0, Fe,0; Iron Oxide, Peroxide of Iron, Sesquioxide of Iron,

_. Ferrie Oxide.

PO; P.O; Phosphoric Acid, Anhydrous Phosphoric Acid,
Phosphoric Anhydide, Phosphorus Pentox-
ide, Phosphoric Oxide.

SO, SO, Sulphurie Acid, Anhydrous Sulphuric Acid, sul-
phurie Anhydride, Sulphur Trioxide, Sul-
phuric Oxide.

Sid, SiO, Silicie acid, Anhydrous Silicic Acid, Silicice An-
hydride, Silicon Dioxide, Silicic Oxide, Silica
Silex.

CO, co, Carbonie Acid, Anhydrous Carbonic Acid, Car-

boniec Anhydride, Carbon Djoxide, Carbonic
Dioxide.

HOW CROPS GROW.

164

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THE ASH OF PLANTS.

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HOW CROPS GROW.

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[-penurqu09]—OLa ‘SLOOG0Ud GNV SLNVId TVUALINOTapV GAOS JO HSY AHL JO NOILISOdWOD

167

THE ASH OF PLANTS.

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HOW CROPS GROW.

168

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[-panuzqu09]—DLE ‘SLOAGOUd GNV SLINVId TVYALINOLSV DWOS dO HSV GTHL 40 NOMLISOdNWOD

169

THE ASH OF PLANTS.

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CROPS GROW.

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HOY.

170

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[panwu09]—DLE ‘SLOOGOUd ANV SENVId TVHALINOIM9V AWOS JO HSV FHL AO NOILISOdWOO

THE ASH OF PLANTS. 171

The composition of the ash of a number of ordinary
crops is concisely exhibited in the subjoined general state-

ment.
Magq- rime. Phosphor- sizica, Sulphur ontorine.

Alkalies. nesia. te Aci ic Acid.

CEREALS—

Grain*.... 30 12 3 46 2 2.5 1

Straw... 13—27 3 7 5 50—70 2.5 2
LEGUMES—

Kernel... 44 7 5 35 1 4 2

Straw... 27—41 7 25-39 8 5 2—6 6—7
RooT CRoPs—

Roots.... 60 3—9 6—12 8—18 i—4 5—12 3-9

Tops.... 37 3-16 10—35 3-8 3 6—13 5-17
GRASSES—

In flower.. 33 4 8 8 °35 4 5

3. Different parts of any plant usually exhibit decided
differences in the composition of their ash. This fact is
made evident by a comparison of the figures of the table
above, and is more fully illustrated by the following anal-
yses of the parts of the mature oat-plant, by Arendt, 1 to
6 (Die Haferpflanze, p. 107), and Norton, 7 to 9 (Am.
Jour. Sct., 2 Ser, 3, 318).

2 3 4 5 6 7 8 9
spe me fiddle Upper Lower Upper Ears. Chaff. Husk. eerie

‘tem. lem. Stem. Leaves. Leaves.

Potash.........5. 81.2 683 65.9 36.9 24.8 13.0 #
a 04 #415 10 09 04 O12 } 10.06 12.4 31-7
g . 21 3.6 3.9 3.8 3.9 8.9 2.3 8.6
3.6 5.3 86 16.7 17.2 7.3 \ 4.9 43 6.3
Oxide of Iron.... 1.0 0.0 0.2 2.7 0.5 trace f °"* 0.3 0.8
Phosphoric acid. 2.7 1.4 2.7 17° 4«615 36. 0.6 49.1
Sulphuric acid.. 0.0 1.3 11 3.2 7.5 49° 5.3 4.3 0.0
Silica ..........6. 4.1 93 204 340° 41.8 26.0 680 74.1 1.8
Chlorine........++ 8.6 11.7 4 16 24 3.8 3.1 14 0.2

The results of Arendt and Norton are not in all respects strictly com-
parable, having been obtained by different methods, but serve well to

establish the fact in question.

We see from the above figures that the ash of the lower
stem consists chiefly of potash (81%). This alkali is pre-
dominant throughout the stem, but in the upper parts,
‘where the stem is not covered by the leaf sheaths, silica
and lime occur in large quantity. Inthe ash of the leaves,
silica, potash, and lime are the principal ingredients. To
the chaff, ff and husk, silica constitutes three-fourths of the
ash, W while i ‘in ‘the; 2 or ain, ‘phosphoric acid appears as the char-

pane ae 7

*Exclusive of husk.

172 - HOW CROPS GROW.

acteristic ingredient, existing there in connection with a
large amount of potash (32%) and considerable magne-
sid. Chlorine acquires its maximum (11. 1%) in the mid-
dle stem, but in the kernel is present in small quantity,
while sulphuric acid is totally wanting in the lower stem,
and most abundant in the upper leaves.

Again, the unequal distribution of the ingredients of
the ash is exhibited in the leaves of the sugar-beet, which
have been investigated by Bretschneider ( Hoff. Jahresbe-
richt, 4, 89). This experimenter divided the leaves of 6
sugar-beets into 5 series or circles, proceeding from the

outer and older leaves inward. He examined each series
separately with the following results:

I Il. IW Iv. Vv.
Potash....-...ccseceeeeee 18.7 25.9 32.8 37.4 50.3
SOG <,c:cccisisinniee ocjetsorssedes 15.2 14.4 15.8 15.0 111
Chloride of Sodium.... 5.8 6.4 5.8 6.0 6.5
AMO} cdicresiaspraannassigsteteis A 19.2 182 15.8 47

Magnesia........0-.seeee . 22.3 13.0 8.9 6.7
Oxide of Iron.........6.. - 0.5 0.6 0.6 0.5
Phosphoric acid. or 4.8 5.8 84 12.7
Sulphuric acid... ‘2 5.6 5.6 6.2 5.9
SiG ais sciosiesiceencenmaied . 0.8 2.7 2.1 1.5

From these data we perceive that in the ash of the leaves
of the sugar-beet, potash and phosphoric acid regularly
and rapidly increase in relation to the other ingredients
from without inward, while lime and magnesia as rapidly
diminish in the same direction. The per cent of the other
ingredients, viz.,.soda, chlorine, oxide of iron, sulphuric
acid, and silica, remains nearly invariable throughout.

Another illustration is furnished by the following anal-
yes of the ashes of the various parts of the horse-chestnut
tree made by Wolff (Ackerbau, 2. Auf., 134):

Bark. Wood. Leaf-stems. Leaves. Flower-stems. Calyz.

Potash ......-0..eeeeees 12.1 25.7 46.2 27.9 63.6 61.7
TAM osie5:c:5 veeeerieane -76.8 42.9 21.7 29.3 9.3 12.3
Magnesia............55 1.7 65.0 3.0 2.6 1.3 5.9
Sulphuric acid....... trace trace 3.8 9.1 3.5 trace
Phosphoric acid....... 6.0 19.2 14.8 22.4 17.1 16.6
SiLCA a ccaseraeicias vee ee 11 2.6 1.0 4.9 0.7 1.7

ChIOrine........ eee eee 28 61 12.2 5.1 4.7 2.4

THE ASH OF PLANTS. 173

Ripe Fruit.

a ne
Stamens. Petals. Green Fruit. Kernel. Green Brown
Shell. Shell.

Potash,.......-.005 60.7 61.2 68.7 61.7 75.9 546
Lim Geasansosnsccanes 13.8 13.6 9.8 11.5 86 16.4
Magnesia.........64 3.1 “3.8 2.4 0.6 11 2.4
Sulphuric acid....trace trace 3.7 1.7 1.0 3.6
Phosphoric acid...19.5 17.0 20.8 22.8 53 18.6
Silica.........cacees 0.7 1.5 0.9 0.2 0.6 0.8
Chlorine........... 2.8 38 4.8 2.0 7.6 5.2

4, Similar kinds of plants, and especially the same parts
-of similar plants, exhibit a close general agreement in the
composition of their ashes; while plants which are un-
like in their botanical characters are also unlike in the
proportions of their fixed ingredients.

The three plants, wheat, rye, and maize, belong, botan-
ically speaking, to the same natural order, graminee, and
the ripe kernels yield ashes almost identical in composi-
tion. Barley and the oat are also graminaceous plants,
and their seéds should give ashes of similar composition.
That such is not the case is chiefly due to the fact, that,
unlike the wheat, rye, and maize-kernel, the grains of
barley and oats are closely invested with a husk, which
forms a part of the kernel as ordinarily seen. This husk
yields an ash which is rich in silica, and we can only prop-
erly corhpare barley and.oats with wheat and rye, when
the former are hulled, or the ash of the hulls is taken out
of the account. There are variéties of both oats and bar-
ley, whose husks separate from the kernel—the so-called
naked or skinless oats and rked or skinless barley—and
the ashes of these grains agree quite nearly in composi-
tion with those of wheat, rye, and maize, as may be seen
‘from the table on page 174.

By reference to the table (p. 166), it will be observed
that the pea and bean kernel, together with the allied
vetch and lentil (p. 171), also nearly agree in ash-com-
position.

So, too, the ashes of the root-crops, turnips, carrots,

174 HOW CROPS GROW.

and beets, exhibit a general similarity of composition, as
may be seen in the table (p. 168-9).

Wheat. Rye. Maize. Skinless Skinles

seas Average Average oats. barleys.
G Analysis Analysis
sevelly-ine twenty-one seven by Fr. y Fr.
ses, Analyses. Analyses. Scnulze. Schulze.
Potashivisicnicncssesenvees 31.3 28.8 27.7 33.4 35.9
SOD as sideiscvwsises vanievews 3.2 4.3 4.0 — 1.0
Magnesia........+.--6- 12.3 11.6 15.0 11.8 13.7
Lime..........5- seen BZ 3.9 1.9 3.6 2.9
Oxide of Iron.. - 0.7. 0.8 1.0 0.8 0.7
Phosphoric acid -46.1 45.6 47.1 46.9 45.0 -
Sulphuric acid........ 1.2 1.9 1.7 — ee
Silica......... cc... cee 1.9 2.6 2.1 2.4 0.7
Chlorine........-...... 0.2 0.7 _ 01 — —

The seeds of the oil-bearing plants likewise constitute
a group whose members agree in this respect (p. 170).

5. The ash of the same species of plant is more or less
variable in composition, according to circumstances.

The conditions that have already been noticed as in-
fluencing the proportion of ash are in general the same
that affect its quality. Of these we may specially notice :

a. The stage of growth of the plant.

&. The vigor of its development.

c. The variety of the plant or the relative development
of its parts, and

d. The soil or the supplies of food.

a. The stage of growth. The facts that the different
parts of a plant yield ashes of different composition, and
that the different stages of growth are marked by the
development of new organs or the unequal expansion of
those already formed, are sufficient to sustain the point
now in question, and render it needless to cite analytical
evidence. In a subsequent chapter, wherein we shall at-
tempt to trace some of the various steps in the progress-
ive development of the plant, numerous illustrations will
be adduced (p. 241).

6. Vigor of development. Arendt (Die Haferpflanze,
p- 18) selected from an oat-field a number of plants in
blossom, and divided them into three parcels: 1, com-

THE ASH OF PLANTS. 175

posed of very vigorous plants ; 2, of medium ; and, 3, of
very weak plants. He analyzed the ashes of each parcel,

with results as below : °
2 3
Silica .............. 39.9 42.0
Sulphuric acid... 4.1 5.6
Phosphoric acid.... Aes 8.5 8.8
Chlorine ............ vee 6. 5.8 4.7
Oxide of Iron.... aie 0.5 1.0
LUMO ssscus ge deke soniamane sede \e 5.4 5.1
Magnesia, Potash and Soda.45.3 34.3 * 30.4

Here we notice that the ash of the weak plants con-
tains 15 per cent less of alkalies, and 15 per cent more of
silica, than that of the vigorous ones, while the propor-
tion of the other ingredients is not greatly different.

Zoeller (Liebig’s Erndhrung der Vegetabilien, p. 340)
examined the ash of two specimens of clover which grew
on the same soil and under similar circumstances, save
that one, from being shaded by a tree, was less fully de-
veloped than the other.

Six weeks after the sowing of the seed, the clover was
cut, and gave the following results on partial analysis :

Shaded clover. Unshaded clover.

c. Bhe variety of the plant or the relative development
of its parts must obviously influence the composition of
the ash taken as a whole, since the parts themselves are
unlike in composition.

Herapath (Qu. Jour. Chem. Soc., II, p. 20) analyzed
the ashes of the tubers of five varieties of potatoes, raised
on the same soil and under precisely similar circum-
stances. His results are as follows:

White Prince's Axbridge

Apple. Beauty. Kidney. Magpie. Forty-fold.
Potash.......+.0-- ee eee! 69.7 65.2 70.6 70.0 62.1
Chloride of Sodium..—— — —= —_— 2.5
Lime......sssceeeeeee es 3.0 18 5.0 5.0 3.3
Magnesia........+ere 6.5 5.5 5.0 2.1 3.5
Phosphoric acid...... 17.2 20.8 14.9 14.4 20.7
Sulphuric acid........ 3.6 6.0 4.3 7.5 79

Silica = _ 0.2 —_— ——

176 HOW CROPS GROW.

d. The soil, or the supplies of food, manures included,
have the greatest influence in varying the proportions of
the ash-ingredients of the plant. It is to a considerable
degree the character of the soil which determines the
vigor of the plant and the relative development of its
parts. This condition, then, to a certain extent, in- °
cludes those already noticed.

It is well known that oats have a great range of weight
per bushel, being nearly twice as heavy, when grown on
rich Jand, as when gathered from a sandy, inferior soil.

* According to the agricultural statistics of Scotland, for ’
the year 1857 (Trans. Highland and Ag. Soc., 1857-9,
p. 213), the bushel of oats produced in some districts
weighed 44 pounds per bushel, while in other districts it
was as low as 35 pounds, and in one instance but 24
pounds per bushel. Light oats have a thick and bulky
husk, and an ash-analysis gives a result quite unlike that
of good oats.. Herapath (Jour. Roy. Ag. Society, XI,
p. 107) has published analyses of light oats from sandy
soil, the yield being six bushels per acre, and of heavy
oats from the same soil, after ‘‘warping,”* where the
produce was 64 bushels per acre. Some of his results,
per cent, are as follows:

Light oats. Heavy oats.
POtashiscs sii scvesaiarscenre 9.8 13.1
SOda.... ccc ee eee ee ee ee 46 7.2
Lime.....-.--- peer eee ee 6.8 4.2
Phosphoric acid...... 9.7 17.6
SUL CAs 00 sa ci8 casewaiedigis 56.5 45.6

Wolff (Jour. fiir Prakt. Chem., 52, p, 103) has anal-
ysed the ashes of several plants, eulttvated | in a poor soil,
with the addition of various mineral fertilizers. The in-
fluence of the added substances on the composition of the
plant is very striking. The following figures comprise
his results on the ash of buckwheat straw, which grew

*Thickly covering with sediment from muddy tide-water.

i

THE ASH OF PLANTS. 177

on the unmanured soil, and on the same, after applica-
tion of the substances specified below : °

1 2 3 4 5 6
Unma- Chloride Nitrate Carbonate Su’phate Carbonate
nured, 0, 0, Y 0,
sodium. potash. potash. magnesia. lime.

Potash...sccaccccecsenrcermdl.? 21.6 39.6 40.5 28.2 23.9
Chloride of potassium.... 7.4 26.9 0.8 3.1 6.9 9.7
Chloride of sodium....... 4.6 3.0 3.2 3.8 3.4 1.7

+15.7 14.0 12.8 11.6 14.1 18.6

Magnesia ........csceeeeeee 1.7 19 ~ 33 1.4 4.7 4.2
Sulphuric acid...........+ 4.7 2.8 2.7 4.3 1 3.5
Phosphoric acid.......... 10.3 9.5 6.5 8.9 10.9 10.0
Carbonic acid............. 20.4 16.1 27.1 22.2 20.0 23.2
Silica........ Gisnnae Andee 3.6 4.2 4.2 4.2 4.8 5.2

100.0 100.0 100.0 100.0 100.0 100.0

It is seen from these figures that all the applications
employed in this experiment exerted a manifest influ-
ence, and, in general, the substance added, or at least one
of its ingredients, is found in the plant in increased
quantity.

In 2, chlorine, but not sodium ; in 3 and 4, potash ;
in 5, sulphuric acid and magnesia, and in 6, lime, are
present in larger proportion than in the ash from the
unmanured soil.

6. What is the normal composition of the ash of a
plant ? It is evident from the foregoing facts and con-
siderations that to pronounce upon the normal composi-
tion of the ash of a plant, or, in other words, to ascer-
tain what ash-ingredients and what proportions of them
are proper to any species of plant or to any of its parts,
is a matter of much difficulty and uncertainty.

The best that can be done is to adopt the average of a
great number of trustworthy analyses as the approximate
expression of ash-composition. From such data, how-
ever, we are still unable to decide what are the abso-
lutely essential, and what are really accidental, ingredi-
ents, or what amount of any given ingredient is essential,
and to what extent it is accidental. Wolff, who appears
to have first suggested that a part of the ash of plants

12

178 HOW CROPS GROW.

may be accidental, endeavored to approach a solution of
this, question by comparing together the ashes of sam-
ples of the same plant, cultivated under the same circum-
stances in all respects, save that they were supplied with
unequal quantities of readily-available ash-ingredients.
The analyses of the ashes of buckwheat-stems, just
quoted, belong to this investigation. Wolff showed that,
by assuming the presence in each specimen of buckwheat-
straw of a certain excess of certuin ingredients, and de-
ducting the same from the total ash, the residuary ingre-
dients closely approximated in their proportions to those
observed in the crop which grew in an unmanured soil.

The analyses just quoted (p. 163) are here “‘ corrected ”
in this manner, by the subtraction of a certain per cent
of those ingredients which in each case were furnished
to the plant by the fertilizer applied to it. The num-
bers of the analyses correspond with those on the previ-
ous page.

1 2 3 4 5 6

20p.c. 20p.c¢. 25p.c. 85p.c. 166 p.¢.
Chloride Carbonate Carbonate git a Carbonates

After detuction of of of 0 of caic’mand
Of aiaacs beasts & Nothing. Polas- potas- potas- magne- magne-

sium. s1um. sium. sium.

Potash .....-cceseeeseee 31.7 O70 32.5 33.5 30.6 28.0
Chloride of potassium. 7.4 9.1 1.0 3.9 T.4 11.3
Chloride of sodium... 4.6 3.8 4.0 4.7 3.7 19
LAME coe sisieses eeeecon 15.7 17.3 16.0 14.6 15.3 14.6
Magnesia....... - L7 2.4 4.1 L7 2.3 29
Sulphuric acid........ 4.7 3.5 3.4 5.4 2.1 4,1
Phosphoric acid......10.3 11.7 8.1 11.2 11.8 11.7
Carbonic acid.........20.4 20.1 25.9 19.8 21.6 19.3
Silica.......... pete eee 3.6 5.2 5.2 5.3 5.2 6.1
100.0 100.0 100.0 100.0 100.0 100.0

The correspondence in the above analyses thus “‘ cor-
rected,” already tolerably close, might, as Wolff remarks
(loc. cit.), be made much more exact by a further correc-
tion, in which the quantities of the two most variable in-
gredients, viz., chlorine and sulphuric acid, should be
reduced to uniformity, and the analyses then he recalcu-
lated to per cent.

THE ASH OF PLANTS. 179

In the first place, however, we are not warranted
in assuming that the ‘“‘excess” of potassium chloride,
potassium carbonate, etc., deducted in the above analyses
respectively, was aii accidental and unnecessary to the
plant, for, under the influence of an increased amount of
a nutritive ingredient, the plant may not only mechani-
cally contain more, but may chemically employ more in
the vegetative processes. It is well proved. that vegeta-
tion, grown under the influence of large supplies of nitro-
genous manures, contains an increased proportion of
truly assimilated nitrogen as albuminoids, amido-acids,
etc. The same may be equally true of the various ash-
ingredients.

Again, in the second place, we cannot say that in any
instance the minimum quantity of any ingredient neces-
sary to the vegetative acts is present, and no more.

It must be remarked that these great variations are
only seen when we compare together plants produced on
poor soils, i. e., on those which are relatively deficient in
some one or several ingredients. If a fertile soil had
been employed to support the buckwheat plants in these
trials, we should doubtless have had a very different
result.

In 1859, Metzdorf ( Wilda’s Centralblatt, 1862, II, p.
367) analysed the ashes of eight samples of the red-
onion potato, grown on the same field in Silesia, but dif-
ferently manured.

Without copying the analyses, we may state some of
the most striking results. The extreme range of varia-
tion in potash was 54 per cent. The ash containing the
highest percentage of potash was not, however, obtained
from potatoes that had been manured with 50 pounds of
this substance, but from a parcel to which had been ap-
plied a poudrette containing less than three pounds of
potash for the quantity used.

The unmanured potatoes were relatively the richest in

180 HOW CROPS GROW.

lime, phosphoric acid, and sulphuric acid, although sev-
eral parcels were copiously treated with manures contain-
ing considerable quantities of these substances. These
facts are of great interest in reference to the theory of
the action of manures.

%. To what extent is each ash-ingredient essential,
and how far may it be accidental? Before chemical
analysis had arrived at much perfection, it was believed
that the ashes of the plant were either unessential to
growth, or else were the products of growth—were gener-
ated by the plant.

Since the substances found in ashes are tiniversally dis-
tributed over the earth’s surface, and are invariably pres-
ent in all soils, it is not possible, by analysis of the ash
of plants growing under natural conditions, to decide
whether any or several of their ingredients are indispen-
sable to vegetative life: For this purpose it is necessary
to institute experimental inquiries, and these have been
prosecuted with great painstaking, and with highly val-
uable results.

Experiments in Artificial Soils. —The Prince Salm-
Horstmar, of Germany, was one of the first and most
laborious students of this question. His plan of experi-
’ ment was the following: The seeds of a plant were sown
in a goil-like medium (sugar-charcoal, pulverized quartz,
purified sand) which was as thoroughly as possible freed
from the substance whose special influence on growth
was the subject of study. All other substances presum-
ably necessary, and all the usual external conditions of
growth (light, warmth, moisture, etc.), were supplied.

The results of 195 trials thus made with oats, wheat,
barley, and colza, subjected to the influénce of a great
variety of artificial mixtures, have been described, the
most important of which will shortly be given.

Experiments in Solutions.—Water-Culture.—
Sachs, W. Knop, Stohmann, Nobbe, Siegert, and others

THE ASH OF PLANTS. 181

have likewise studied this subject. Their method was
like that of Prince Salm-Horstmur, except that the plants
were made to germinate and grow independently of any
soil; and, throughout the experiment, had their roots im-
mersed in water, containing in solution or suspension. the
substances whose action was to be observed.

Water-Culture has recently contributed so much to our
knowledge of the conditions of vegetable growth, that
some account of the mode of conducting it may be prop-
erly given in this place. Cause a num-
ber of seeds of the plant it is desired to
experiment upon to germinate in moist
blotting-paper, and, when the roots have
become an inch or two in length, select
the strongest seedlings, and support
them so that the roots shall be immersed
in water, while the seeds themselves
shall be just above the surface of the
liquid.

For this purpose, in case of a single
maize plant, for example, provide a
quart cylinder or bottle with a wide
mouth, to which a cork is fitted, as in
Fig. 22. Cut a vertical notch in the
cork to its center, and fix therein the
stem of the seedling by packing with
cotton. Thecork thus serves as a sup-
port of the plant. Fill the jar with pure
water to such a height that when the
cork is brought to its place, the seed, S,
shall be a little above the liquid. If
the endosperm or cotyledons dip into the water, they
will speedily mould and rot ; they require, however, to be
kept in a moist atmosphere. Thus arranged, suitable
warmth, ventilation, and illumination alone are requi-
site to continue the growth until the nutriment of the seed

182 HOW CROPS GROW,

is nearly exhausted. As regards illumination, this should
be as full as possible, for the foliage ; but the roots should
be protected from it, by enclosing the vessel in a shield of
black paper, as, otherwise, minute parasitic alge would
in time develop upon the roots, and disturb their functions.
For the first days of growth, pure distilled water may ad-
vantageously surround the roots, but, when the first green
leaf appears, they should be placed in the solution whose
nutritive power is to be tested. The temperature should
- be properly proportioned to the light, in imitation of what
is observed in the skillful management of conservatory or
house-plants.

The experimenter should first learn how to produce
large and well-developed plants by aid of an appropriate
liquid, before attempting the investigation of other prob-
lems. For this purpose, a solution or mixture must be
prepared, containing in proper proportions all that the
plant requires, save what it can derive from the atmos-
phere. The experience of Nobbe and Siegert, Knop,
Wolff, and others,* supplies valuable information on this
point. Wolff has obtained striking results with a variety
of plants in using a solution made essentially as follows:

Place 20 grams of the fine powder of well-burned bones
with a half pint of water ina large glass flask, heat to boil-
ing, and add nitric acid cautiously in quantity just suffi-
cient to dissolve the bone-ash. In order to remove any
injurious excess of nitric acid, pour into the boiling liq-
uid asolution of pure potassium carbonate until a slight
permanent turbidity is produced; then add 11 grams of
potassium nitrate, 7 grams of crystallized magnesium sul-

phate, and 3 grams of potassium chloride, with water ©

enough to make the solution up to the bulk of one liter.
Wolff’s solution, thus prepared, contains in 1000 parts
as follows, eaolisi¥e of iron:

* See es pecially Tol lensHenneberg’ 3 Jour. fir Landwirthschaft, 1882, p.
537) for fu tt and concise instructions.

THE ASH OF PLANTS. 183 ~~

PHOSPhoric ACIA......sacrcecceccrceceeevscnseevene 8.2
TEN IG ivsaiasaii:siecae ois eysieieierwin apoiwisiane see aia vrayavdale ndeimetabisid. ayes 10.5
POCASH i5.cihisisinisisis esilvisisivicinsisleamsineiswyctlenemeaieecerse dase 9.1
MAQnesid....sccscccccccccccsscessccecresssneeeerans 1.4
Sulphuric acid......ccsccccceeceereevescceueseeeees 2.2
CHIOTIN Os iteecistivins stisiepcaimsianieibisie cisiteucseavomawestea sive 0.9
Nitric Acid ciecicseaccisgniciivacasneseienesevs scien tastatel 29.7
SO]UG, Matters ii,0i:sieinis:oia aiesdiassia aso nik sstisie rnrecriaveteneyeincorae bine aie 62
WAGCE sins crete se maameeei indiana wie oid a Risicreisune paousianeiniedeeren nie 938
1000

For use, dilute 15 or 20 c. c. of the above solution with
water to the bulk of a liter and add one or two drops of
strong solution of ferric chloride.

The solution should be changed at first every week, and,
as the plants acquire greater size, their roots should be
transferred to a larger vessel filled with solution of the
same strength, and the latter changed every 5 or 3 days.

It is important that the water which escapes from the
jar by evaporation and by transpiration throug! the plant
should be daily or oftener replaced, by filling it with pure
water up to the originallevel. The solution, whose prep-
aration has been described, may be turbid from the sepa-
ration of a little calcium sulphate before the last dilution,
as well as from the precipitation of phosphate of iron on
adding ferric chloride. The former deposit may be dis-
solved, though this is not needful; the latter will not dis-
solve, and should be occasionally put into suspension by
stirring the liquid. When the plant is half grown, fur-
ther addition of iron is unnecessary.

In this manner, and with this solution, Wolff produced
a maize plant five and three quarters feet high, and equal
in every respect, as regards size, to plants from similar
seed, cultivated in the field. The ears were not, however,
fully developed when the experiment was interrupted by
the plant becoming unhealthy.

With the oat his success was better. Four plants were
brought to maturity, having 46 stems and 1535 well-de-
veloped seeds. (Vs. St., VITI, pp.190-215.)

184 HOW CROPS GROW.

In similar experiments, Nobbe obtained buckwheat
plants, six to seven feet high, bearing three hundred
plump and perfect seeds, and barley stools with twenty
grain-bearing stalks. (Vs. St., VII, p. 72.)

In water-culture the composition of the solution is suf-
fering continual alteration, from the fact that the plant
makes, to a certain extent, a selection of the matters pre-
sented to it, and does not necessarily absorb them in the
proportions in which they originally existed. In this
way, disturbances arise which impede or become fatal- to
growth. In the early experiments of Sachs and Knop,
in 1860, they frequently observed that their solutions
suddenly acquired the odor of hydrogen sulphide, and
black iron sulphide formed upon the roots, in consequence
of which they were shortly destroyed. This reduction of
a sulphate to a sulphide takes place only in an alkaline
liquid, and Stohmann was the first to notice that an acid —
liquid might be made alkaline by the action of living
roots. The plant, in fact, has the power to decompose
salts, and by appropriating the acids more abundantly
than the bases, the latter accumulate in the solution in
the free state, or as carbonates with alkaline properties.

‘To prevent the reduction of sulphates, the solution
must be kept slightly acid, if needful, by addition of a
very little. free nitric acid, and, if the roots blacken, they
must be washed with a dilute acid, and, after rinsing with
water, must be transferred to a fresh solution.

On the other hand, Kihn has shown that when am-
monium chloride is employed to supply maize with nitro-
gen, this salt is decomposed, its ammonia assimilated, and
its chlorine, which the plant cannot use, accumulates in
the solution in the form of hydrochloric acid to such an
extent as to prove fatal to the plant (Henneberg’s Journal,
1864, pp. 116 and 135). Such disturbances are avoided by
employing large volumes of solution, and by frequently
renewing them.

THE ASH OF PLANTS. 185

The concentration of the solution is by no means a
matter of indifference. While certain aquatic plants, as
sea-weeds, are naturally adapted to strong saline solutions,
agricultural land-plants rarely succeed well in water cul-
ture, when the liquid contains more than 17455 of solid
matters, and will thrive in considerably weaker solutions.

Simple well-water is often rich enough in plant-food to
nourish vegetation perfectly, provided it be renewed suffi-
ciently often. Sachs’s earliest experiments were made
with well-water.

Birner and Lucanus, in 1864 (Vs. S¢., VIII, 154), raised
oat-plants in well-water, which in respect to entire weight
were more than half as heavy as plants that grew simul-
taneously in gardén soil, and, as regards seed-production,
fully equalled the latter. The well-water employed: con-
tained but syy, of dissolved matters, or in 100,000 parts:

POGASM saiexiewsersicenyasisre;naisie snare wisa'eieaivin eins 2.10
BiMe!) wis ssoctis serdivans/orgirnremeaisnigine seaniewors, 15.10
MAQNESIA...... eee ees e cree ence rece cree senee 1,50
Phosphoric Acid.......cceeeeecseeceer aces 0.16
Sulphuric acid........cceeceeceee cece eens 7.50
NGGUIC- ROT sai esnssiecs vais sine s eatineenie crema aialere 6.00
Silica, Chlorine, Oxide of iron........ traces
SOL Matters ciinesseguncininnaeaacituab es acaiaewes iiss 32.36
WERCER iisdecacorerececticisiasnisrdieduiacnieseinieininis aie i nie ievioie Warslatoatae nes 99,967.64
100,000

On the other hand, too great dilution is fatal to growth.
Nobbe (Vs. St., VIII, 337) found that in asolution con-
taining but yoy, of solid matters, which was continually
renewed, barley made no progress beyond germination,
and a buckwheat plant, which at first grew rapidly, was
soon arrested in its development, and yielded but a few
ripe seeds, and but 1.746 grm. of total dry matter.

While water-culture does not provide all the normal
conditions for the growth of land plants—the soil having
important functions that cannot be enacted by any liquid
medium—it isa method of producing highly-developed
plants, under circumstances which admit of accurate con-

186 HOW CROPS GROW.

trol and great variety of alteration, and is, therefore, of
the utmost value in vegetable physiology. It has taught
important facts which no other means of study could re-
veal, and promises to enrich our knowledge in a still
more eminent degree.

Potassium, Calcium, and Magnesium as soluble
Salts, Phosphorus as Phosphates and Sulphur as
Sulphates, are absolutely necessary for the life of
Agricultural Plants, as is demonstrated by all the ex-
periments hitherto made for studying their influence.

It is impossible to recount here in detail the evidence
to this effect that is furnished by the investigations of
Salm-Horstmar, Sachs, Knop, Nobbe, Birner and Luca-
nus, and others (Vs. S¢., VIII, p. 128-161).

Some.of the experimental proof of this statement is
strikingly exhibited by the-figures on Plate I, copied
from Nobbe, showing results of the water-culture of
buckwheat in normal nutritive solutions and in solutions
variously deficient.

Is Sodium Essential for Agricultural Plants?
This question has occasioned much discussion. A glance
at the table of ash-analyses (pp. 164-170) will show that
the range of variation is very great as regards this alkali-
metal. The older analysts often reported a considerable
proportion of sodium oxide, even 20% or more, in the ash
of seeds and grains. In most of the analyses, however,
sodium oxide is given in much smaller quantity. The
average in the ashes of the grains is less than 3 per cent,
and in not a few of the analyses it is entirely wanting.

In the older analyses of other classes of agricultural
plants, especially in root crops, similarly great variations
occur. Some uncertainty exists as to these older data, for
the reason that the estimation of sodium by the processes
customarily employed is liable to great inaccuracy, espe-
cially with the inexperienced analyst. On the one hand,
it is not or was not easy to detect, much less to estimate,

THE ASH OF PLANTS. 187

minute traces of sodium when mixed with much potassi-
um; while, on the other hand, sodium, if present to the
extent of a per cent or more, is very liable to be estimated
too high. It has therefore been doubted if these high
percentages in thé ash of yrains are correct.

Again, the processes formerly employed for preparing
the ash of plants for analysis were suchas, by too elevated
and prolonged heating, might easily occasion a partial
or total expulsion of sodium from a material which prop-
erly should contain it, and we may hence be in doubt
whether the older analyses, in which sodium is not men-
tioned, are to be altogether depended upon.

The later analyses, especially those by Bibra, Zoeller,
Arendt, Bretschneider, Ritthausen, and others, who have
employed well-selected and carefully-cleaned materials for
their investigations, and who have been aware of all the
. Various sources of error incident to such analyses, must
therefore be appealed to in this discussion. From these
recent analyses we are led to precisely the same conclu-
sions as were warranted by the older investigations. Here
follows a statement of the range of percentages of sodium
oxide in the ash of several field crops, according to the
newest analyses:

SODIUM OXIDE (SODA) IN LATER a ALYSES.

Ash of Wheat kernel, Eene Bibra, to{5% Bibra.
28% Lawes & Gilbert, 148%
“ «> Potato tuber, none, { meron. “4% Wolff.
= Me =
“ « Barley kernel, { 94 Zoeller, * 0% (Veltman,
nN Ritth « a9, Ritthan
_Ritthausen B itthausen.
“ © Sugar beet, { 7% Bretschneider, “ 16.6% Bretschneider.
« « Turnip root, 7.7% Anderson, “17.1% Anderson.

Although, as just indicated, sodium in some instances
has been found wanting in the wheat kernel and in po-
tato tubers, it is not certain that it was absent from other
parts of the same plants, nor has it been proved that
sodium is wanting in any entire plant which has grown
on a natural soil.’

188 HOW CROPS GROW.

Weinhold found: in the ash of the stem and leaves of
the common live-for-ever (Sedum telephium) no trace of .
sodium detectable by ordinary means ; while in the ash
of the roots of the same plant there occurred 1.8 per
cent of its oxide (Vs. S¢., IV, p. 190).

It is possible then that, in the above instances, so-
dium really existed in the plants, though not in those
parts which were subjected to analysis. It should be
added that in ordinary analyses, where sodium is stated
to be absent, it is simply implied that it is present, if at
all, in too small a quantity to admit of determining by
the usual method, while in reality a minute amount may
be present in all such cases.*

The final result of all the analytical investigations
hitherto made, with regard to cultivated agricultural
plants, then, is that sodium is an extremely variable in-
gredient of the ash of plants, and though generally pres-
ent in some proportion, and often in large proportion,
has been observed to be absent in weighable quantity in
the seeds of grains and in the tubers of potatoes.

Salm-Horstmar, Stohmann, Knop, and Nobbe & Sie-
gert have contributed experimental evidence bearing on
this question.

The investigations of Salm-Horstmar were made with
great nicety, and especial attention was bestowed on the
influence of very minute quantities of the various sub-
stances employed. He gives as the result of numerous
experiments, that, for wheat, oats, and barley, in the
early vegetative stages of growth, Sodium, while advan-
tageous, is not essential, but that for the perfection of
fruit an appreciable though minute quantity of this ele-
ment is indispensable. (Versuche und Resultate uber
die Nahrung der Pflanzen, pp. 12, 27, 29, 36.)
soditin mile maybe aoresteds demonatrare Cite Slemekt to be so Unie

versally distributed that it is next to impossible to find or to prepare
anything that is free from it. 7

THE ASH OF PLANTS. 189

Stohmann’s single experiment led to the similar con-
clusion, that maize may dispense with sodium in the
earlier stages. of its growth, but requires it for a full
development. (Henneberg’s Jour. fiir Landwirthschaft,
1862, p. 25.)

Knop, on the other hand, succeeded in bringing the
maize plant to full perfection of parts, if not of size, in a
solution which was intended and asserted to contain no
sodium. (Vs. S¢., III, p. 301.) Nobbe & Siegert came
to the same results in similar trials with buckwheat.
Vs. St., IV, p. 339.)

Later trials by Nobbe, Schréder and Erdmann, and by
others, confirm the conclusion that sodium may be nearly
or altogether dispensed with by plants.

The buckwheat represented in Plate I vegetated for 3
months in solutions as free as possible from sodium, with
the exception of VI, in which sodium was substituted
for potassium.

The experiments of Knop, Nobbe, Siegert and others,
while they prove that much sodium is not needful to
maize and buckwheat, do not, however, satisfactorily
demonstrate that a little sodium is not necessary, because
the solutions in which the roots of the plants were im-
mersed stood for months in glass vessels, and could
scarcely fail to dissolve some sodium from the glass.
Again, slight impurity of the substances which were em-
ployed in making the solution could scarcely be avoided
without extraordinary precautions, and, finally, the seeds
of these plants might originally have contained enough
sodium to supply this substance to the plants in appre-
ciable quantity.

To sum up, it appears from all the facts before us :

1. That sodium is never fotally absent from plants,
and that,

2. If indispensable, but a minute amount of it is
requisite.

190 HOW CROPS GROW.

3. That the foliage and succulent portions of the plant
may include a considerable amount of sodium that is not
necessary to the plant ; that is, in other words, accidental.

Can Sodium replace Potassium ?—The close simi-
larity of potassium and sodium, and the variable quanti-
ties in which the latter especially is met with in plants,
have led to the assumption that one of these alkali-metals
can take the place of the other.

Salm-Horstmar.and Knop & Schreber first demon-
strated that sodium cannot entirely take the place of
potassium—that, in other words, potassium is indispen-
sable to plant life. Plate I, VI, shows the development
of buckwheat during 3 months, in Nobbe, Schréder &
Erdmann’s water-cultures, when, in a normal nutritive
solution, potassium is substituted by sodium, as com-
pletely as is practicable.

Cameron concluded, from a series of experiments which
it is unnecessary to describe, that, under natural condi-
tions, sodium may partially replace potassium. A partial
replacement of this kind would appear to be indicated
by many facts. Thus, Herapath has made two analyses
of asparagus, one of the wild, the other of the culti-
vated plant, both gathered in flower. The former was
rich in sodium, the latter almost destitute of this sub-
stance, but contained correspondingly more potassium.
Two analyses of the ash of the beet, one by Wolff (1), the
other m Way @), exhibit similar differences :

Asparagus. peed Beet.

Wild. ~ Cultivated. 2.
Potassium oxide....... 18.8 50.5 wi: 0 25.1
Sodium oxide.... trace 7.3 34.1
Calcium oxide... 21.3 5.8 2.2
Magnesium oxid . 40 21
CHOLINE woe sceccevecs coe 16.5 8.3 4.9 34.8
Sulphur trioxide...... 9.2 4.5 3.5 3.6
Phosphorus pentoxide 12.8 12.4 12.9 1.9
SiCA cise soe ccsisissws se 1.0 3.7 3.7 L7

These results go to show—it being assumed that only a
very minute amount of sodium, if any, is absolutely nec-

THE ASH OF PLANTS. 191

essary to plant-life—that the sodium which appears to
replace potassium is accidental, and that the replaced
potassium is accidental also, or in excess above what is
really needed by the plant, and leaves us to infer that the.
quantity of these bodies absorbed depends to some ex-
tent on the composition of the soil, and is to the same
degree independent of the wants of vegetation.

Alkalies in Strand and Marine Plants.—The
above conclusions apply also to plants which most com-
monly grow near or in salt water. Asparagus, the beet
and carrot, though native to saline shores, are easily ca-
pable of inland cultivation, and indeed grow wild in com-
parative absence of sodium compounds.

The common saltworts, Salsola, and the samphire,
Salicornia, are, plants which, unlike those just men-
tioned, seldom stray inland.’ Gébel, who has analyzed
these plants as occurring on the Caspian steppes, found
in the.soluble part of the ash of the Salsola brachiata.
4.8 per cent of potassium oxide, and’ 30.3 per cent of
sodium oxide, and in the Salicornia herbacea 2.6 per
cent of potassium oxide and 36.4 per cent of sodium
oxide, the sodium oxide constituting in the first instance
no less than ~, and in the latter s, of the entire
weight, not of the ash, but of the air-dry plant. Potas-
sium is never absent from these forms of vegetation.
(Agricultur- Chemie, 3te Auf., p. 66.)

According to Cadet (Liebig’s Erndhrung der Veg.;
‘p. 100), the seeds of the Salsola kali, sown in common
garden soil, gave a plant which contained both sodium
and potassium ; from the seeds of this, sown also in
garden soil, grew plants in which only potassium-salts
with traces of sodium could be found. These strand-
plants are occasionally found at a distance from: salt-
shores, and their growth as strand-plants appears to be
due to their capacity for flourishing in spite of salt, and
not from their requiring it. (Hoffmann, Vs. St., XIU,
p. 295.)

192 HOW CROPS GROW.

Another class of plants—the sea-weeds (alge@)—de-
‘rive their natriment exclusively from the sea-water in
which they are immersed. Though the quantity of po-
tassium in sea-water is but »y-that of the sodium, it is
yet a fact, as shown by the analyses of Forchhammer
(Jour. fur Prakt. Chem.,' 36, p. 391) and Anderson
(Frans. High. and Ag. Soc., 1855-7, p. 349) that the
ash of sea-weeds is, in general, as rich, or even richer, in
potassium than in sodium. In 14 analyses, by Forch-
hammer, the average amount of sodium in the dry weed
was 3.1 per cent; that of potassium 2.5 per cent. In
Anderson’s results the percentage of potassium is inva-
riably higher than that of sodium.*

Analogy with land-plants would lead to the inference
that the sodium of the sea-weeds is in a great degree ac-
cidental. In fact, Fucus vesiculosis and Zygogonium sal-
inum have been observed to flourish in fresh water.
(Vs. Sé., XIII, p. 295.)

Iron is Essential to Plants.—It is abundantly
proved that a minute quantity of ferric oxide, Fe,Os, is
essential to growth, though the agricultural plant may
be perfect if provided with so little as to be discoverable
in its ash only by sensitive tests. According to Salm-
Horstmar, ferrous oxide, FeO, is indispensable to the
colza plant. (Versuche, etc., p. 35.) Knop asserts that
maize, which refuses to grow in entire absence of iron,
flourishes when ferric phosphate, which is exceedingly
insoluble, is simply suspended in the solution that bathes
its roots for the first four weeks only of the growth of
the plant. (Vs. St., V, p. 101.)

We find that the quantity of ferric oxide given in the
analyses of the ashes of agricultural plants is small, being
usually less than one per cent.

Here, too, considerable variations are observed. In

*Doubtless due to the fact that the material used by Anderson was
freed by washing from adhering common salt.

THE ASH OF PLANTS. 193

the analyses of the seeds of cereals, ferric oxide ranges.
from an unweighable trace to 2 and even 3%. In root
crops it has been found as high'as 5%. Kekule found
in the ash of gluten from wheat 7.1% of ferric oxide.
(Jahresbericht der Chem., 1851, p. 715.) Schulz-Fleethi
found 17.5% in the ash of the albumin from the juice of
the potato tuber. The proportion of ash is, however, so
small that in case of potato-albumin the ferric oxide
amounts to but 0.12 per cent of the dry substance. (Der
Rationelle Ackerbau, p. 82.)

In the ash of wood, and especially in that of bark, ferric
oxide often exists to the extent of 5 to 10%. The largest
percentages have been found in aquatic plants. In the
ash of the duckweed (Lemna trisulea) Liebig found
%.4%. Gorup-Besanez found in the ash of the leaves of,
the Trapa natans 29.6%, and in the ash of the fruit-
euvelope of the same plant 68.6%. (Ann.-Oh. Ph., 118,
p. 223.) ¢

Probably much of the iron of agricultural and land
plants is accidental. In case.of the Zrapa natans, we
cannot suppose all the iron to be essential, because the

larger share of it exists in the tissues as a brown powdery
~ oxide which may be extracted by acids, and has the ap-
pearance of having accumulated there mechanically.

Doubtless a portion of the iron encountered in anal-
yses -of agricultural vegetation has neyer once existed
within the vegetable tissues, but comes from the soil,
which adheres with great tenacity to all parts of plants.

Manganese is Unessential to Agricultural Plants.
Manganese is commonly much less abundant than iron,
and is often, if not usually, as good as wanting in agri-
cultural plants. It generally accompanies iron where
the latter occurs in considerable quantity. Thus, in the
ash of Trapa, the oxide Mn,O, was found to the extent
of 75-14. 7%. Sometimes it is found in much larger
quantity than oxide of iron; e. g.. C. Fresenius found

13

194 HOW CROPS GROW.

11.2% of oxide of manganese in ash of leaves of the red
beech (Fagus sylvatica) that contained but 1% of oxide
of iron. In the ash of oak leaves (Quercus robur) Neu-
bauer found, of the former 6.6, of the latter but 1.2%.

In ash of the wood of the larch (Larix Huropea), Bot-
tinger found 13.5% Mn,0, and 4.2% Fe,O;, and in ash
of wood of Pinus sylvestris 18.2% Mn,0,, and 3.5%
Fe,0;.. In ash of the seed of colza, Nitzsch found 16.1%
Mn;0,, and 5.5 Fe,Oz. In case of land plants, these
high percentages are accidental, and specimens of most
of the plants just named have been analyzed, which were
free from all but traces of oxide of manganese.

Salm-Horstmar concluded from his experiments that
oxide of manganese is indispensable to vegetation.
Sachs, Knop, and most other experimenters in water-
culture, make no mention of this substance in the mix-
tures, which in their hands have served for the more or
less perfect development of a variety of agricultural
plants. Birner & Lucanus have demonstrated that man-
ganese is not needful to the oat-plant, and cannot take
the place of iron. (Vs. St., VIII, p. 43.)

Is Chlorine Indispensable to Crops ?—What has
been written of the occurrence of sodium in plants ap-
pears to apply in most respects equally well to chlorine.
Tn nature, sodium is generally associated with chlorine
as common salt. It is most probably in this form that
the two substatices usually enter the plant, and in the
majority of cases, when one of them is present in large
quantity, the other exists in corresponding quantity.
Less commonly, the chlorine of plants is in combination
with potassium exclusively.

Chlorine is doubtless never absent from the perfect
agricultural plant, as produced under natural conditions,
though its quantity is liable to great variation, and is
often very small—so small as to be overlooked, except by
the careful analyst. In many analyses of grain, chlorine

THE ASH OF PLANTS, 195
ig not mentioned. Its absence, in many cases, is due,
without doubt, to the fact that chlorine is readily dissi-
pated from the ash of substances rich in phosphates or
silica, on prolonged exposure to a high temperature. In
some of the later analyses, in which the vegetable sub-
stance, instead of being at once burned to ashes, at a
high red heat, is first charred at a heat of low redness,
and then leached with water, which dissolves the chlo-
rides, and separates them from the unburned carbon and
other matters, chlorine is invariably mentioned. In the
tables of analyses, the averages of chlorine are undeni-
ably too low. This is especially true of the grains.

The average of chlorine in the 26 analyses of wheat by
Way and Ogston, p. 150, is but 0.08%, it not being found
at all in the ash of 21 samples. In Zoeller’s later anal=
yses chlorine is found in every instance, and averages
0.7%. In Lawes and Gilbert’s numerous analyses of
wheat-grain ash chlorine ranges from 0 to 1.14%, the
average being 0.1%. In wheat-straw ash they found
from 1.08 to 2.06%. The ash was in all cases prepared
by burning at a low red heat.

Like sodium, chlorine is particularly abundant in the
stems and leaves of those kinds of vegetation which grow
in soils or other media containing much common salt. It
accompanies sodium in strand and marine plants, and, in
general, the content of chlorine of any plant may be large-
ly increased or diminished by supplying it to or withhold-
ing it from the roots.

As to the indispensableness of chlorine, we have some-
what conflicting data. Salm-Horstmar believed that a
trace of it is needful to the wheat plant, though many of
his experiments in reference to this element were unsatis-
factory to himself. Nobbe and Siegert, who have made
an elaborate investigation. on the nutritive relations of
chlorine to buckwheat; were led to conclude that while
the stems and foliage of this plant are able to attain a

196 HOW CROPS GROW.

considerable development in the absence of chlorine (the
minute amount in the seed itself excepted), presence of
‘chlorine is essential to the perfection of the fruit.

Leydhecker came to the same conclusions as Nobbe
and Siegert regarding the indispensableness of chlorine
to the perfection of buckwheat. (Vs. Sé., VIIL, p. 177.)
' On the other hand, Knop excludes chlorine from the
list of necessary ingredients of maize, buckwheat, cress,
and Psamma arenaria, having obtained a maize plant 3
feet high, bearing 4 ripe seeds, harvested 23 “ chlorine-
‘free seeds” from 5 buckwheat-plants, and raised 40 to 50
ripe seeds from more than one cress-plant, all grown
without chlorine. (Vs. St., XIII, p. 219.)

Wagner also obtained, in absence of chlorine, maize-
plants 40 inches high, of 20 grams dry-weight. One of
these ripened 5 small seeds, of which two were proved
capable of germination ; but noneof these plants produced
any pollen and they were fertilized with pollen from
garden-plants. (Vs. St., XIII, pp. 218-222.)

From a series of experiments in water-culture, Birner
an@d Lucanus (Vs. S#., VIII, p. 160) conclude that chlo-
rine is not indispensable to the oat-plant, and has no spe-
cific effect on the production of its fruit. Chloride of
potassium increased the weight of the crop, chloride of
sodium gave a larger development'of foliage and stem,
chloride of magnesium was positively deleterious, under
the conditions of thetr trials.

Lucanus (Vs. St., VII, pp. 363-71) raised clover by
water-culture without chlorine, the crop (dry) weigh-
ing in the most successful experiments 240 times as much
as the seed. Addition of chlorine gave no better result.

Nobbe (Vs. S¢., VIII, p. 187) has produced normally
developed vetch and pea plants, but only in solutions
containing chlorine. Beyer (Vs. St., XI, p. 262) found
exclusion of chlorine in water-culture to prevent forma-
tion of seed in case of peas; the plants, after a month’s

THE ASH OF PLANTS. 197

healthy growth, produced new shoots only at the expense
of the older leaves. In similar trials oats gave a small
crop of ripe seeds when chlorine was not supplied.
When, however, the seeds thus obtained nearly free from
chlorine were vegetated in a solution destitute of this
element they failed to produce seed again, though their
growth and reproduction were normal when chlorine
was furnished them in the nutritive solution.

In Plate I, X shows the extent to which, in Nobbe’s
cultures, buckwheat developed when vegetating for 3
months in a solution destitute of chlorine, but otherwise
fully adapted to nourish plants.

In view of all the evidence, then, it would appear
probable that chlorine is needful for the cereals, and
that when the seed and nutritive media (soil or solution
and air) are entirely destitute of this element fruit cannot
be perfected. It is probable that in the cases where
fruit was produced in supposed absence of chlorine this
substance in some way gained access to the plants.

Until further more decisive results are reached, we
are warranted in adopting, with regard-to chlorine as
related to agricultural plants, the following conclu-
sions, Viz.:

1. Chlorine is never totally absent.

2. If indispensable, but a minute amount is requisite
for a very considerable vegetative development.

3. Some plants, as vetches and peas, require a not in-
considerable amount of chlorine for full development,
especially of seed.

4. The foliage and succulent parts may include a
large quantity of chlorine that is not indispensable to
the life of the plant.

Silica is not indispensable to Plants.—The numer-
ous analyses we now possess indicate that this substance
is always present in the ash of all parts of agricultural
plants, when they grow in natural soils.

198 HOW CROPS GROW.

In the ash of the wood of trees, it usually ranges from
1-3%, but is often found to the extent of 10-20%, or
even 30%, especially in the pine. In leaves, it is usually
more abundant than in stems. The ash of turnip leaves
contains 38-10% ; of tobacco leaves, 5-18% ; of the oat,
11-58%. (Arendt, Norton.) In ash of lettuce, 20% ; of
beech leaves, 26%; in those of oak, 31% have been
observed. (Wicke, Hennederg’s Jour., 1862, p. 156.)

The bark or cuticle of many plants contains an extra-
ordinary amount of silica. The cauto tree of South
America .(Hirtella silicea) is most remarkable in this
respect. Its bark is very firm and harsh, and is difficult
to cut, having the texture of soft sandstone. It yields
34% of ash, and of this 96% is silica. (Wicke, loc. cit.,
p. 143.)

' Another plant, remarkable for its content of silica, is
the bamboo. The ash of the rind contains 70%, and in
the joints of the stem are often found concretions of

hydrated silica, the so-called Tabashir.

' The ash of the common scouring rush (Equisetum hye-
male) has been found to contain 97.5% of silica. The
straw of the cereal grains, and the stems and leaves of
grasses, both belonging to the botanical family Grami-
nace, are specially characterized by a large content of
silica, ranging from 40-70% of the ash. The sedge and
rush families likewise contain much of this substance.

The position of silica in the plant would thus appear
to be, in general, at the surface. Although it is present
in other parts of the plant, yet the cuticle is usually rich-
est, especially where the content of silica is large. Davy,
in 1799, drew attention to the deposition of silica in the
cuticle of the grasses and cereals, and-advanced the idea
that it serves these plants an office of support similar to
that enacted'in animals by the bones.

In case of the pine (Pinus sylvestris), Wittstein has
obtained results which indicate that the age of wood or

THE ASH OF PLANTS. 199

bark greatly influences the content of cilica. He found
in ash of the—

Wood of a tree, 220 years old, * %
Ti 170 “

“ce “a 135 +“ a ;
And in
Bark eg 220 a 30.3
“ “ 170 “ 14.4
6 fe 135 ee 11.9

In the ash of the straw of the oat, Arendt found the
percentage of silica to increase as the plant approached
maturity. So the leaves of forest trees, which in autumn
are rich in silica, are nearly destitute of this substance
in spring time.

Silica accumulates then, in general, in the older and
less active parts of the plant, whether these be external
or internal, and is relatively deficient in the younger and
really growing portions. This rule is not without excep-
tions. Thus, the chaff of wheat, rye and oats is richer
in silica than any other part of these plants, and Béttin-
ger found the seeds of the pine richer in silica than the
wood.

In numerous instances, silica is deposited in or upon
the cell-wall in such abundance that when the organic
matters are destroyed by burning, or removed by sol-
vents, the form of the eell is preserved. in a silicious
skeleton. This has long been known.in case of the
Equisetums and Deutzias. Here the peculiar rough-
nesses of the stems or leaves are fully incrusted or inter-
penetrated by silica, and the ashes of the cuticle present
the same appearance under the microscope as the cuticle
itself.

The hairs of nettles, hemp, hops, and other rough-
leaved plants, are highly silicious.

According to Wicke, the beech owes the smooth and
undecayed surface which its trunk presents, to the silica
of the bark. The best textile materials, which are bast-

200 HOW CROPS GROW.

fibers of various plants, viz., common hemp, Manila
hemp (Musa textilis), aloe-hemp (Agave Americana),
common flax, and New Zealand flax (Phormium tenax)
are incrusted. with silica. In jute (Corchorus textilis)
some cells are partially incrusted. The cotton fiber is
free from silica. Wicke (Joc. cit.) suggests that the du-
rability of textile fibers is to a degree dependent on their
~ content of silica.

Sachs, in 1862, was the first to publish evidence that.
silica is not a necessary ingredient of maize. He ob-
tained in his early essays in water-culture a maize plant
of considerable development, whose ashes contained but
0.7% of silica. Shortly afterwards, Knop produced a
maize plant with 140 ripe seeds, and a dry-weight of 50
grammes (nearly 2 oz. av.) so free from silica that a
mere trace of this substance could be found in the root,
but half a milligramme in the stem, and 22 milligrammes
in the 15 leaves and sheaths. It was altogether absent
from the seeds. The ash of the leaves of this plant thus
contained but 0.54 per cent of silica, and the stem but
0.07 per cent. Way & Ogston had found in the ash of
field-grown maize, leaf and stem together, 27.98 per
cent of silica.

In the numerous experiments that have been made
more recently upon the growth of plants in aqueous solu-
tions, by Sachs, Knop, Nobbe & Siegert, Stohmann,
Rautenberg & Kiihn, Birner & Lucanus, Leydhecker,
Wolff, and Hampe, silica, in nearly all cases, has been
excluded, so far as it is possible to do so, in the use of
glass vessels. This has been done without prejudice to
the development of the plants. Nobbe & Siegert and
Wolff especially have succeeded in producing buckwheat,
maize, and the oat, in -full perfection of size and parts,
with this exclusion of silica.

Wolff (Vs. St., VIII, p. 200) obtained in the ash of
maize thus cultivated, 2 to 3% of silica, while the same

THE ASH OF PLANTS. 201

two varieties from the field contained in their ash 114 to
13%. The proportion of ash was essentially the same in
both cases, viz., about 6%. Wolfi’s results with the oat
plant were entirely similar.

Birner & Lucanus (Vs. S¢., VIII, p. 141) found that
the supply of soluble silicates to the oat made its ash very
rich in silica (40%) but diminished the growth of straw,
without affecting that of the seed, as compared with
plants nearly destitute of silica.

It is thus made certain that plants ordinarily rich in
silica may attain a high development in absence of this
substance. We shall see later, however (p. ), that
silica is probably not altogether useless to plants when
they grow under ordinary conditions.

Jodin reports having bred maize by water-culture, with
the utmost practicable exclusion of silica, for four gener-
ations—whereby this substance was reduced to the merest
traces—without interference with the normal develop-
ment of the plant. (Ann. Agron., IX, p. 385.)

The Ash-Ingredients, which are Indispensable
to Crops, may be taken up in Larger Quantity than
is Essential.—More than eighty years ago, Saussure de-
scribed a simple experiment which is Conclusive on this
point. He gathered a number of peppermint plants, and
in some determined the amount of dry-matter, which
was 40.3 per cent. The roots of others were then im-
mersed in pure water, and the plants were allowed to veg-
etate 24 months in a place exposed to air and light, but
sheltered from rain.

At the termination of the experiment, the plants,
which originally weighed 100, had increased to 216 parts,
and the dry matter of these plants, which at first was
40.3, had become 62 parts. The plants could have
acquired from the glass vessels and pure water no con-
siderable quantity of mineral matters. It is plain, then,
that the ash-ingredients which were contained in two

202 HOW CROPS GROW.

a
parts of the peppermint were sufficient-for the produc-
' tion and existence of three parts. We may assume,
therefore, that at least one-third of the ash of the origi-
nal plants was in excess, and accidental.

The fact of excessive absorption of essential ash-ingre-
dients is also demonstrated by the precise experiments of
Wolff on buckwheat, already described (see p. 164),
where the point in question is incidentally alluded to,
and the difficulties of deciding how much excess may
occur, are brought to notice. (See also pp. 192 and 194
n regard to potassium and iron.)

As further striking instances of the influence of the
nourishing medium on the quantity of ash-ingredients in
the plant, the following are adduced, which may serve to
put in still stronger light the fact that a plant does not
always require what it contains.

Nobbe & Siegert have made a comparative study of
the composition of buckwheat, grown on the one hand in
garden soil, and on the other in an aqueous solution of
saline matters. (The solution contained magnesium
sulphate, calcium chloride, phosphate and nitrate of
potassium, with phosphate of iron, which together con-
stituted 0.316% of the liquid.) The ash-percentage was
much higher in the water-plants than in the garden-
plants, as shown by the subjoined figures. (Vs. S¢., V,
p. 182.) ;

Per cent of ashin
Stems and leaves. Roots. Seeds. Entire plant.

Water-plant............ 18.6 15.3 2.6 16.7
Garden-plant........... 8.7 6.8 2.4 71
We have seen that well-developed plants contain a
larger proportion of ash than feeble ones, when they
grow side by side in the same medium. In disregard of
this general ruleg the water-plant in the present instance
has an ash-percentage double that of the land-plant,
although the former was a dwarf compared with the lat-
ter, yielding but 4 as much dry matter. The seeds, how-
ever, are scarcely different in composition.

THE ASH OF PLANTS. ; 203

Similar results were obtained by Councler with the
leaves of Acer negundo (Vs. St., XXIX, p. 242), 1,000
parts of the perfectly dry leaves contained :

Water-plant. Soil-plant.

Silica, Si Og isi ssscissg sac 8.51 23.72
Sulphurie oxide, SOx,,...... 38.97 9.69
Phosphoric oxide, P,0,,...26.00 4.56
Iron oxide, Fe,Og,.......... 1.94 1.22
Magnesium oxide, MgO,... 7.56 6.25
Calcium oxide, CaQ,....... 81.77 36.17
Sodium oxide, Na,O,....... 1.23 0.88
Potassium oxide, K,0,......96.92- 45.05

212.90 127.54

Leaves of the water-plant are much richer in ash-ingre-
dients, especially in sulphate and phosphate of potassium.
Those of the soil-plant contain more silica and lime.

Disposition by the Plant of Excessive or Super-
fluous Ash-ingredients.—The ash-ingredients taken
up by a plant in excess beyond its actual wants may be
disposed of in three ways. The soluble matters—those
soluble by themselves, and also incapable of forming in-
soluble combinations with other ingredients of the plant
—viz., the alkali chlorides, sulphates, carbonates, and
phosphates, the chlorides of calcium and magnesium,
may —

1. Remain dissolved in, and diffused throughout, the
juices of the plant ; or,

2. May exude upon the surface as an efflorescence, and
be washed off by rains.

Exudation to the surface has been repeatedly observed
in case of cucumbers and other kitchen vegetables, grow-
ing in the garden, as well as with buckwheat and barley
in water-culture. (Vs. St., VI, p.°37.)

Saussure found in the white incrustations upon cucum-
ber leaves, besides an organic body insoluble in water and
alcohol, calcium chloride with a trace of magnesium
chloride. The organic substance so enveloped the cal-
cium chloride as to prevent deliquescence of the latter.
(Recherches sur la Veg., p. 265.)

204 HOW CROPS GROW.

Saussure proved that foliage readily yields up saline
matters to water. He placed hazel leaves eight success-
ive times in renewed portions of pure water, leaving them
therein 15 minutes each time, and found that by this
treatment they lost ~; of their ash-ingredients. The
portion thus dissolved was chiefly alkaline salts ; but con-
sisted in part of earthy phosphates, silica, and oxide of |
iron. (Recherches, p. 287.)

Ritthausen has shown that clover which lies exposed to
rain after being cut may lose by washing more than one-
half of its ash-ingredients.

Mulder (Chemie der Ackerkrume, II, p. 305) attributes
to loss by rain a considerable share of the variations in
percentage and composition of the fixed ingredients of
plants. We must not, however, forget that all the exper-
iments which indicate great loss in this way: have been
made on the cut plant, and their results may not hold
good to the same extent for uninjured vegetation.

3. The insoluble matters, or those which become so in
the plant, viz., the calcium sulphate, the oxalates, phos-
phates, and carbonates of calcium and magnesium, the
oxides of iron and manganese, and silica, may be depos-
ited as crystals or concretions in the cells, or may incrust
the cell-walls, and thus be set aside from the sphere of
vital action.

In the denser and comparatively juiceless tissues, as in
bark, old' wood, and ripe seeds, we find little variation in
the amount of soluble matters. These are present in
large and variable quantity only in the succulent organs.

In bark (cuticle), wood, and seed envelopes (husks,
shells, chaff) we often find silica, the oxides of iron
and manganese, and calcium carbonate—all insoluble
substances—accumulated in considerable amount. In
bran, phosphate of magnesium exists in comparatively
large quantity. In the dense teak wood, concretions of
calcium phosphate have been noticed. Of a certain

THE ASH OF PLANTS. 205

species of cactus (Cactus senilis) 80% of the dry
matter consists of crystals of calcium oxalate and phos-
phate.

That the quantity of matters thus segregated is in some

_ degree proportionate to the excess of them in the nourish-
ing medium in which the plant grows has been observed
by Nobbe & Siegert, who remark that the two portions
of buckwheat, cultivated by them in solutions and in gar-
den-soil respectively (p. 203), both contained crystals
and globular: crystalline masses, consisting probably of
calcium and magnesium oxalates, and phosphates, depos-
ited in the rind and pith ; but that these were by far most
abundant in the water-plants whose ash-percentage was
twice as great as that of the garden-plants.

These insoluble substances may be either entirely unes-
sential, or, having once served the wants of the plant, may
be rejected as no longer useful, and by assuming the in-
soluble form, are removed from the sphere of vital action,
and become in reality dead matter. They are, in fact,
excreted, though not, in general,
formally expelled beyond the limits
of the plant. They are, to some
extent, thrown off into the bark
or into the older wood or pith,
or else are encysted in the living
cells.

The occurrence of crystallized salts
thus segregated in the cellsof plants
is illustrated by the following cuts.
Fig. 23 represents a crystallized con-
cretion of calcium oxalate, having a basis or skeleton of
cellulose, from a leaf of the walnut. -(Payen, Chamie In-
dustrielle, Pl, XXI.) Fig. 24showsa mass of crystals of the
same salt, from the leaf stem of rhubarb. Fig. 25 illus-
trates similar crystals from the beet root. Inthe root of
the young bean, Sachs found a ring of cells, containing

Fig. 23.

206 HOW CROPS GROW.

crystals of sulphate of lime. (Sttzungsberichte der Wien.
Akad., 37, p. 106.) Bailey ob-
served in certain parts of the in-
ner bark of the locust a series of
cells, each of which contained a
crystal. In the onion-bulb, and
many other plants, crystals are
abundant. (Gray’s Botanical
Text-Book, 6th ed., Vol. II, p. 52.)

Instances are not wanting in which there is an obvious
excretion of mineral matters, or at least a throwing of
them off to the surface. Silica, as we have seen, is often
found in the cuticle, but is usually imbedded in the cell-
wall. In certain plants, other substances accumulate in
considerable quantity without the cuticle. - A striking ex-
ample is furnished by Saxifraga crustata, a low European
plant, which is found in lime soils.
The leaves of this saxifrage are en-
tirely coated with a scaly incrusta
‘tion of calcium and magnesium [| (*
carbonates. At the edges of the /<%'
leaf this incrustation acquires a{ é
considerable thickness, as is illus-| 2
trated by figure 26, a. In an anal-|3
ysis made by Unger, to whom these | ;
facts are due, the fresh (undried) { }
leaves yielded to a dilute acid/4
4.14% of calcium carbonate, and!
0.82% of magnesium carbonate.

Unger learned by microscopic ° ) a9)
investigation that this excretion Fig. 26.
of carbonates proceeds mostly from a series of granular
expansions at the margin of the leaf, which are directly
connected with the sap-ducts of the plant. (Sitzungsbe-
richte.der Wien. Akad., 43, p. 519.)

In figure 26, a represents the appearance of a leaf, magnified 44 diam-

Fig. 24. Fig. 25,

THE ASH OF PLANTS. 207

eters. Around the borders are seen the scales of carbonates; some of
these have been detached, leaving round pits on the surface of the leaf:
c, d@ exhibit the scales themselves, e in profile: b shows a leaf, freed
from itsincrustation by an acid, and from its cuticle by potash-solution,
so as to exhibit the veins (ducts) and glands, whose course the carbon-
ates chiefly take, in their passage through the plant.

Further as to the state of ash-ingredients.—It is
by no means true that the ash-ingredients always exist in
plants in the forms under which they are otherwise famil-
iar to us. P

Arendt and Hellriegel have studied the proportions of ©
soluble and insoluble matters, the former in the ripe oat
plant, and the latter in clover at various stages of growth.

Arendt extracted from the leaves and stems of the oat
plant, after thorough grinding, the whole of the soluble
matters by repeated washings in water.* He found that
all the sulphuric acid and all the chlorine were soluble.
Nearly all the phosphoric acid was removed by water.
The larger share of the calcium, magnesium, sodium and
potassium compounds was soluble, though portions of each
escaped solution. Iron was found in both the soluble and
insoluble state. In the leaves, iron was found among the
insoluble matters after all phosphoric acid had been re-
moved. Finally, silica was mostly insoluble, though in
all cases a small quantity occurred in the soJuble condi-
tion, viz., 3-8 partsin 10,000 of the dry plant. (Wach-
sthum der Haferpflanze, pp. 168, 183-4. See, also, table
on p. 171).

Weiss and Wiesner discovered by microchemical in-
vestigation that iron exists as insoluble ferrous and ferric ~
compounds both in the cell-membrane and in the cell-
contents. (Sidzungsberichte der Wiener Akad., 40, 278.) -

Hellriegel found that in young clover a larger propor-
tion of the various bases was soluble than in the mature
plant. Asarule, the leaves gave most soluble matters,
the leaf stalks less, and the stems least. He obtained,

*To extract the soluble parts of the grain in this way was impossible.

208 HOW CROPS GROW.

among others, the following results (Vs. St., IV,
p. 59): i

Of 100 parts of the following fixed ingredients of clover,
were dissolved in the sap, and not dissolved—

In young leaves. In full-grown leaves.

dissolved..... ...75.2 37.3
Potash...... { undissolved. seh 248 62.7
‘ ssolved.......+. i ;
Lime........ { undissolved. " 5 m6
‘ issolved.........43. E
Magnesia... andeolyod 4 21.7
Phosphoric { dissolved.... 9 19.9
oxide, P.O, | undissolved......79.1 80.1
Silica dissolved........ 8 16.1
sas undissolved......73.2 83.9

These researches demonstrate that potassium and sodi-
um—bodies, all of whose commonly-occurring compounds,
silicates excepted, are readily soluble in water—enter into
insoluble combinations in the plant; while phosphoric
acid, which forms insoluble salts with calcium, magnesi-
um, and iron, is freely soluble in connection with these
bases in the sap.

It should be added that sulphates may be absent from
the plant or some parts of it, although they are found in
the ashes. Thus, Arendt discovered no sulphates in the
lower joints of the stem of oats after blossom, though in
the upper leaves, at the same period, sulphuric oxide
(SO;) formed nearly 7% of the sum of the fixed ingre-
dients. (Wachsthum der Haferpf., p. 157.) Ulbricht
found that sulphates were totally absent from the lower
leaves and stems of red clover, at a time when they were
present in the upper leaves and blossom. ( Vs. S¢., IV., p.
30 Tabdelle.) Both Arendt and Ulbricht observed that sul-
phur existed in all parts of the plants they experimented
upon; in the parts just specified, it was, however, no
longer combined tooxygen, but had, doubtless, become
* an integral part of some albuminoid or other complex or-
ganic body. Thus the oat stem, at the period above cited,
contained a quantity of sulphur, which, had it been con-
verted into sulphuric oxide, would have amounted to 14%

7

THE ASH OF PLANTS. 209

of the fixed ingredients. In the clover leaf, at a time
when it was totally destitute of sulphates, there existed
an amount of sulphur which, in the form of sulphuric
oxide, would have made 13.7% of the fixed ingredients,
or one per cent of the dry leaf itself. *

Other ash-ingredients.—Salm-Horstmar has describ-
ed some experiments, from which he infers that a minute
amount of Lithium and Fluorine (the latter as fluoride
of potassium) are indispensable to the fruiting of barley.
(Jour. fur prakt. Chem., 84. p.140.) The same observer,
some years ago, was led to conclude that atrace of Titan-
tum isa necessary ingredient of plants. The later re-
sults of water-culture would appear to demonstrate that
these conclusions are erroneous.

The rare alkali-metal, Rubidium, has been found inthe
sugar-beet, in tobacco, coffee, tea, andthe grape. It doubt-
less occurs, perhaps together with the similar Caesiwm in
many other plants, though always in very minute quan-
tity. Birner and Lucanus found that these bodies, in the
absence of potassium, acted as poisons to the vat. (Vs.
St., VIII, p. 147.)

According to Nobbe, Schroeder and Erdmann, Lith-
tum is very injurious to buckwheat, even in presence of
potassium. When lithium was substituted for two-
thirds of the potassium of a normal nutritive solution,
buckwheat vegetated indeed for 3 months, the stem
reaching a length of 18 inches, but the plant was small
and unhealthy, the leaves were pale and the older ones
dropped away, as shown by VIII, plate I: (Vs. St,
XIII, p. 356).

* Arendt was the first to estimate sulphuric oxide (SO) in vegetable
matters with accuracy, and to discriminate it from the sulphur of or-
ganic: compounds. This chemist separated the sulphates of the oat-
epee by extracting the pulverized material with acidulated water. He

ikewise estimated the total sulphur by. a special method, and by sub-
tracting the sulphur of the sulphuric oxide from the total he obtained as
a difference that portion of sulphur which belonged to the albuminoids,
etc. In his analysis of clover, U/bricht followed asimilar plan. (Vs. St.,
III, Bp 147.) As has already been stated, el of the older analyses are
wholly untrustworthy as regards sulphur and sulphuric oxide.

14

210 HOW CROPS GROW.

The investigations of A. Braun and of Risse (Sachs,
Exp. Physiologie, 153) show that Zinc is a usual ingredi-
ent of plants growing about zinc-mines, where the soil
contains carbonate or silicate of this metal. Certain
marked varieties of plants are peculiar to, and appear to
have been produced by, such soils, viz., a violet (Viola
tricolor, var. calaminaris), and a shepherd’s purse
(Thiaspi alpestre, var. calaminaris). In the ash of the
leaves of the latter plant, Risse found 13% of oxide of
zinc ; in other plants he found from 0.3 to 3.3%. These
plants, however, grow equally well in absence of zinc,
which may slightly modify their appearance, but is unes-
sential to their nutrition.

Boron as boric acid has recently been found in many
wines of California and Europe.

Copper is often or commonly found in the ashes of
plants; and other elements, viz., Arsenic, Barium and
Lead, have been discovered therein, but as-yet we are not
warranted in assuming that any of these substances are
of importance to agricultural vegetation. The soluble
compounds of copper, arsenic and lead are in fact very
injurious to plant life, unless very highly diluted.

Jodine, an invariable and probably a necessary constit-
uent of many alge, is not known to exist to any consid-
erable extent or to be essential in any cultivated plants.

§ 4.

FUNCTIONS OF THE ASH-INGREDIENTS.

Although much has been written, little is certainly
known, with reference to the subject of this section.

Sulphates.—The albuminoids, which contain sulphur
as an essential ingredient, obviously cannot be produced

_ | in absence of sulphates, which, so far as we know, are the

rie

exclusive source of sulphur to plants. The sulphurized

THE ASH OF PLANTS. 211

oils of the onion, mustard, horse-radish, turnip, etc., like-
wise require sulphates for their organization.
Phosphates.—The phosphorized substances (prota-
gon, lecithin, chlorophyl) require to their elaboration that
phosphates be at the disposal of the plant. Knophasshown
that hypophosphites cannot take the place of phosphates.
‘Lhe albuminoids which are probably formed in the foliage
must pass thence through the cells and ducts of the stem
into growing parts of the plant, and into the seed, where
they accumulate in large quantity. But the albuminoids
penetrate membranes with great difficulty and slowness
when in the pure state. Thedi-and tri-potassic phosphates
dissolve or form water-soluble compounds with many
albuminoids, and, according to Schumacher (Phystk der
Pflanze, p. 128), considerably increase the diffusive rate
of these bodies, and thus facilitate their translocation in
the plant.
Potassium.—The organic acids, viz., oxalic, malic,
tartaric, citric, ete., require potassium to form the salts
sof this metal, which exist abundantly in plants, e. g.,
potassium oxalate in sorrel, potassium bitartrate in the
grape, potassium malate in garden rhubarb; and without
potassium it is in most cases probably impossible for the
acids to accumulate or to beformed. Mercadante culti-
vated sorrel (Ozxalis acetosella and Rumex acetosa), in ab-
‘sence of potassium-salts; sodium, calcium, and magnesium
being supplied.. The plants failed to fructify, and their
juices contained but one-eighth as much free acid (or acid
salts?) as exists in the sap of the same kind of plants veg-
etating under normal conditions. The acids—oxalic, with
a little tartaric—were united to calcium (Berichte, 1875,
IT, p. 1200). The organic acids may result from the de-
composition of carbhydrates (starch or sugar), or they
may be preliminary stages in the production of the carb-
hydrates. In either case their formation is an index to
the constructive processes by which the plant originates

212 HOW CROPS GROW.

new vegetable substance and increases in dry weight.
Mercadante’s observations are therefore in accord with the
results of the investigations next to be considered.

In 1869, Nobbe, Schréder, and Erdmann employed the
method of water-culture to make an elaborate study of
the influence of potassium on the vegetative processes,
and found that, all other needful conditions of growth
being supplied, in absence of potassium buckwheat
plants vegetated for three months without any increase in
weight—that is to say, without producing new vegetable
matter, Examination of these miniature plants demon-
strated that (in absence of potassium) the first evident
stage in the production of vegetable substance, viz., the
appearance of starch in the chlorophyl granules of the
leaf, could not be attained. The experimenters therefore
drew the conclusion that potassium is an essential factor
in the assimilation of carbon and the formation of starch.
They found that the plants were able to produce starch
when potassium was supplied either as chloride, nitrate,
phosphate or sulphate. The ¢ransfer of the starch from,
the leaves to the fruit, or its conversion into a soluble
form, appeared to require the presence of chlorine; ac-
cordingly, potassium chloride gave the best developed
plants, especially at the period of fructification. This
conclusion was greatly strengthened by the observation,
repeatedly made, that the miniature plants which had
vegetated for three or four weeks without increase of
weight, or growth other than that which the seedling can
make at the expense of the seed, began at once, on suit-
able addition of potassium chloride to the nutritive solu-
-tion, to form starch, discoverable in all the chlorophyl
granules, and thenceforward developed new stems and
leaves and grew in quite the normal manner. In Plate
I the appearance of some of the plants produced in these
trials is shown. Ia represents the average plant raised
in the normal solution containing abundance of potas-

Sie Skee ee

PLATE I.

EXPLANATION. (See p. 212.)

Water-cultures of Japanese Buckwheat, supplied with the ingre-
dients of a Normal Solution, viz.: Sulphates, Nitrates, Phosphates and
Chlorides of Potassium, Magnesium, Calcium and Iron, except as stated
below.

Iand Ia. Solution normal. Potassium as Chloride.

IL. Solution without Potassium.

IIs. Without Potassium for 4 weeks, thereafter Potassium Chloride.

III. Potassium as Nitrate. Chlorine as in Normal.

TV. Potassium as Sulphate. Chlorine one-fourth of Normal.

V. Potassium as Phosphate. Chlorine one-fifth of Normal.

VI. Sodium but not Potassium.

VIL. Lithium.

IX. Without Calcium.

X. Without Chlorine.

XI. Without Nitrogen.

The meter-scale (392 inches) serves to measure the dimensions of the
plants.

THE ASH OF PLANTS. 213

sium chloride. II was deprived of potassium save that
contained -in the seed. In IV and V, respectively, the
chlorine of the solution was reduced to one-fourth and
one-fifth the amounts contained in the normal solution
and replaced by sulphuric acid in IV and by phosphoric
acid in V. In case of II,, the plant vegetated without
potassium for four weeks with a result similar to II, and
then for two months was supplied with potassium chlo-
ride. For numerous interesting details reference must
be made to the original paper (Vs. St., XIII, pp.
321-424),

Liipke, from water-cultures with the flowering bean
Phaseolus multiflorus, and common bean P. vulgaris,
has recently arrived at different conclusions. He finds
that these plants are able, under the utmost possible ex-
clusion of potassium, to assimilate carbon and produce
starch, in fact to grow and to carry on all the vegetative
functions that belong to the fully-nourished plant,
though on a diminished scale. In order to limit the
supply of potassium to the utmost, the cotyledons of some
of the plants were cut away when the plumule began to
appear above them. In this way 90% of the potassium
of the seed was removed* and while the plants were
thereby reduced in dimensions, their power to vegetate
in a healthy manner was not suppressed. After 65 days
of vegetation one of these plants yielded a crop of dry-
substance 4.8 times as much as was contained in the
newly sprouted seedling after excision of the cotyledons.

Some results of these cultures are shown in Plate IT.
The stem of the unmutilated flowering bean in normal
solution I, a, reached a final length of 80 inches, that de-
prived of potassium grew to 40 inches.

Nobbe’s conclusion that potassium is specifically essen-
tial or concerned in starch-production is accordingly erro-

*Liipke found that one seed of P. multiflorus contained 23 milligrams
Ee aes ere oxide; the seedling, after cutting off the cotyledons, con-
tains 2.3mm.

214 HOW CROPS GROW.

neous. As Liipke remarks, potassium is rather like nitro-
gen, phosphorus, sulphur, etc., one of the elements of
which probably a cercain quantity is indispensable to the
formation of every vegetable cell. Nobbe’s results per-
haps indicate that buckwheat requires relatively more
potassium than the bean for its processes of growth.
(Land. Jahrbiicher, 1388, pp. 887-913.)

Calcium.—Béhm (Jahresbericht wher Ag. Chemie,
1875-6, Bd. I, p. 255) and Von Raumer ( Vs. St., XXIX,
251) have furnished evidence that calcium (lime) is di-
rectly necessary to the formation of cell-tissue, that is to
say, of cellulose.

This evidence rests upon observations made with seed-
lings of the flowering bean (scarlet-runner), Phaseolus
multifiorus. When aseed sprouts, the young plant at first
is nourished exclusively by the nutritive matters contained
in the seed. When its roots enter the soil it begins to de-
rive water, nitrogen, and ash-ingredients from the earth.
When its leaves unfold in the light it begins to gather
carbon from the air and to increase in weight. If its
roots are placed in pure water it can acquire no ash-in-
gredients ; if its leaves are kept in darkness it can gain
nothing from the air. Thus circumstanced, it may live
and vegetate for a time, but constantly loses in total dry
weight, and its apparent growth is only the formation of
new parts at the expense of the old. For some days the
young stem shoots upward without green color, but per-
fectly formed, and then (in case of the flowering bean)
suddenly, at a little space below the terminal bud, a dis-
coloration appears, the stem wilts, withers, and dies
away. The growth of stem that thus occurs is accom-
panied by and depends upon the solution of starch in the
seed-lobes and its transfer to the points of growth where
it is made over into cellulose—the frame-work of the
stem. In absence of any external source of ash-ingredi-
ents the young stem dies long before the starch of the

THE ASH OF PLANTS. 215

cotyledons is consumed. But if the roots be placed in
a nutritive solution snited to water-culture, the stem
grows on without injury until the cotyledons are com-
pletely emptied of starch, and afterwards continues to de-
velop at the expense of the lower leaves. °

The arrest of growth in the stem evidently is due to
the absence of some one or more ash-ingredients, and
Béhm found in fact that, by withholding lime-salts from |
the roots, this characteristic malady was invariably pro-
duced. Hence he concludes that calcium compounds are
immediately concerned in the conversion of starch into
cellulose.

Magnesium.—Von Raumer,in the paper just referred
to (Vs. St., XXIX, pp. 263 and 273), gives his observa-
tions on the relations of the magnesium salts to the veg-
etative processes. He states that, all other conditions
being favorable, the exclusion of magnesium from a nu-
tritive solution in which the scarlet-runner vegetates is
followed by cessation of chlorophyl-production and. of
that enlargement of the new-formed cells wherein the
act of Powth largely consists. Accordingly, in absence
of magnesium-supply, the plants, which at first grew nor-
tally, after reaching a height of forty inéhes, began to
show signs of disturbed nutrition. The uppermost in-
ternodes (joints) of the stems almost ceased to lengthen
aud became exceptionally thick and hard, their leaves
failed to open, and both joints and leaves were white in
color with but the faintest tint of green. Soon new up-
ward growth ceased altogether, the terminal bud and
unfolded leaves dried away, and, while the lower, first-
formed and green leaves remained fresh for weeks and
the lower stem threw out new shoots, healthy growth
was at a stand-still, and the plants gradually withered
and perished. The normal growth of the bean plants
for a month or more in nutritive solutions containing no
magnesium is accounted for by the supply of this: ele-

if

216 HOW CROPS GROW.

ment existing in the seed,* which evidently was enough
for the necessities of growth until the stem was forty
inches high. From that point on the plants almost
ceased to grow, and gradually died from want of food
and in&bility to assimilate.

We have already seen that, according to Hoppe- Seyler,
magnesium is a constant and presumably an essential in-
gredient of chlorophyllan, a crystallized derivative of
chlorophyl. This makes evident that magnesium is di-
rectly concerned in and needful to the formation of the
chlorophyl granules which, so far as observation as yet
has gone, are the seat of those operations which first
construct organic substance from inorganic matter.

Magnesium and calcium occur in the aleurone of seeds
and, according to Gribler, form soluble, crystallizable
compounds with certain albuminoids, go that these ele-
ments, like potassium, may be concerned in the transport
of protein-bodies.

Silica.—Humphrey Davy was the first to suggest that:
the function of silica might be, in case of the grasses,
sedges, and equisetums, to give rigidity to the™slender
stems of these plants, and enable them to sustain the
often heavy Weight of the fruit.

The results of the many experiments in water-culture
by Sachs, Knop, Wolff, and others (see p. 200), in which
the supply of silica has been reduced to an extremely
small amount, without detriment to the development of
plants, commonly rich in this substance, prove in the
most conclusive manner, however, that silica does not
essentially contribute to the stiffness of the stem.

Wolff distinctly informs us that the maize and oat
plants produced by him, in solutions nearly free from
silica, were as firm in stalk, and as little inclined to
lodge or ‘‘lay,” as those which grew in the field.

*Common beans contain about one-fourth of one per cent of mag-
nesia.

THE ASH OF PLANTS. 217

The “lodging” of cereal crops is demonstrated to re-
sult from too close a stand and too little light, which
occasion a slender and delicate growth, and is not per-
ceptibly influenced by presence or absence of silica. .
Silica, however, if not necessary to the life of the cereals,
appears to have an important office in their perfect de-
velopment under ordinary circumstances. Kreuzhage
and Wolff have carefully studied the relations of silica to
the oat plant, using the method of water-culture. Ina
series of nine trials in 1880, where, other things being
equal, much silica, little silica, and no silica were sup-
plied, the numbers of seeds produced were 1,423, 1,039,
and 715 respectively, the corresponding weights being
46, 34, and 23 grams. The total crops weighed 196,
172, and 168 grams respectively, so that while the yield
of seed was doubled in presence of abundant silica, the
total crop (dry) was increased in weight but one-sixth.
The supply of silica was accompanied with an absolutely
diminished root-formation as well as by a relatively in-
creased seed-production. Similar trials in 1881 and 1882
gave like results (Vs. St., XXX, p. 161). Wolff con-
cludes that silica ensures the timely and uniform ripen-
ing of the crop as well as favors the maximum develop-
ment of seed. ‘

The natural supply of silica appears to be always suf-
ficient. Application of this substance in fertilizers has
never proved remunerative. In those water-cultures
where large seed-production has been obtained in ab-
sence of silica, it is probable that lime-salts, phosphates,
or other ash-ingredients, which are commonly taken up
more abundantly than in field culture, have brought’
about the same result that silica usually effects. This
action of the ash-ingredients is apparently due to a clog-
ging of the cell-tissnes and consequent check of the pro-
cesses of growth and would seem to be caused either by
the otherwise unessential silica or by an excess of the

218 : HOW CROPS GROW.

ingredients essential to growth. The hard, dense coat of
the seed of the common weed ‘‘stone-crop” (Lithosper-
mum) usually contains some 13 to 20 per cent of silica
and twice that amount of calcium carbonate. Héhnel
produced these seeds in water-culture from well-grown
plants deprived of silica and found them quite normally
developed. The seed-coat was permeated with calcium
carbonate, which appears to have fully replaced silica
without detriment to the plant (Haberlandt, Unter-
suchungen, II, p. 160).

Chlorine.—As has been mentioned, both Nobbe and
Leydhecker found that buckwheat grew quite well up to
the time of blossom without chlorides. From that
period on, in absence of chlorides, remarkable anomalies
appeared in the development of the plant. In the ordi-
nary course of growth, starch, which is organized in the
mature leaves, does not remain in them to much extent,
but is transferred to the newer organs, and especially to
the fruit, where it often accumulates in large quantities.
In absence of chlorides in the experiments of Nobbe and
Leydhecker, the terminal leaves becam. thick and fleshy,
from extraordinary development. of cell-tissue, at the
same time they curled together and finally fell off, upon
slight disturbance. ‘The stem became knotty, transpira-
tion of water was suppressed, the blossoms withered

/ without fructification, and the plant prematurely died.

The fleshy leaves were full of starch-grains, and it ap-
peared that in absence of chlorine the transfer of starch
from the foliage to the flower and fruit was rendered im-
possible; in other words, chlorine (in combination with
potassium or calcium) was concluded to be necessary to

_—was, in fact, the agent of—this transfer.

Knop believes, however, that these phenomena are due
to some other cause, and that chlorine is not essential to
the perfection of the fruit of buckwheat (see p. 196).
Knop (Chem. Centralblatt, 1869, p. 189) obtained some

THE ASH OF PLANTS. 219

‘ripe, well-developed buckwheat seeds in chlorine-free
water-cultures, while in the same solutions, with addition
of chlorides, other buckwheat plants remained sterile,
the flowers withering without setting seed. Knop states
that in other trials maize and bean plants grew better
without than with chlorides, In either case starch did
not accumulate in the stem or leaves of maize, while all
the organs of the bean were overloaded with starch both
in presence and absence of chlorides.

The experiments of Nobbe and Leydhecker are very
circumstantially described and have been confirmed by
the later work of Nobbe, Schréder, and Erdmann (Vs.
St., XIII, pp. 392-6). See p. 196.

Iron.—We are in possession of some interesting facts,
which throw light upon the function of this metal in the
plant. In case of the deficiency of iron, foliage loses its
natural green color, and becomes pale or white even in
‘the full sunshine. In absence of iron a plant may un-
fold its buds at the expense of already organized matters,
as a potato-sprout lengthens in a dark cellar, or in the
manner of fungi and white vegetable parasites ; but the
leaves thus developed are incapable of assimilating carbon,
and actual growth or increase of total weight is impossi-
ble. Salm-Horstmar showed (1849) that plants which
grow in soils or media destitute of iron are very pale in
color, and that addition of iron-salts very speedily gives
them a healthy green. Sachs found that maize-seed-
lings, vegetating in solutions free from iron, had their
first three or four leaves green ; several following were
white at the base, the tips being green, and afterward
perfectly white leaves unfolded. On adding a few drops’
of sulphate or chloride of iron to the nourishing medium,
“the foliage was plainly altered within twenty-four hours,
and in three to four days the plant acquired a deep, lively
green. Being afterwards transferred to a solution desti-
tute of iron, perfectly white leaves were again developed,

220 HOW CROPS GROW.

and these were brought to a normal color by addition of
iron.

E. Gris was the first to trace the reason of these effects,
and first found (in 1843) that watering the roots of
plants with solutions of iron, or applying such solutidns
externally to the leaves, shortly developed a green color
where it was previously wanting. By microscopic stud-
ies he found that, in the absence of iron, the protoplasm
of the leaf-cells remains a colorless or yellow mass, desti-
tute of visible organization. Under the influence of iron,
grains of chlorophyl begin at once to appear, and pass
through the various stages of normal.development. We
know that the power of the leaf to decompose carbon
dioxide and assimilate carbon resides in the cells that
contain chlorophyl, or, we may say, in the chlorophyl-
grains themselves. We understand at once, then, that
in the absence of iron, which is essential to the forma-
tion of chlorophyl, there can be no proper growth, no
increase at the expense of the external penne food
of vegetation.

Risse, under Sachs’s direction (Hzp. Physiologie, p.
143), demonstrated that manganese cannot take the place
of iron in the office just described.

CHAPTER III.
§ 1.

QUANTITATIVE RELATIONS AMONG THE INGREDIENTS
OF PLANTS.

Various attempts have been made to exhibit definite
numerical relations between certain different ingredients
of plants.

Equivalent Replacement of Bases.—In 1840, Lie-
big, in his Chemistry applied to Agriculture, suggested

» QUANTITATIVE RELATIONS. 221

that the various bases or basic metals might displace
each other in equivalent quantities, i. e., in the ratio of
their molecular or atomic weights, and that, were such
the case, the discrepancies to be observed among analyses
should disappear, if the latter were interpreted on this
view. Liebig instanced two analyses of the ashes of fir-
wood and two of pine-wood made by Berthier and Saus-
sure, as illustrations of the correctness of this theory.
In the fir of Mont Breven, carbonate of magnesium was
present ; in that of Mont La Salle, it was absent. In
the former existed but half as much carbonate of potas-
sium as in the latter. In both, however, the same total
percentage of carbonates was found, and the amount of
oxygen in the bases was the same in both instances.

Since the unlike but equivalent quantities of potash,
lime, and magnesia contain the same quantity of oxy-
gen, these oxides, in the case in question, really replaced
each other in equivalent proportions. The same was
true for the ash of pine-wood, from Allevard and from
Norway. On applying this principle to other cases it
has, however, signally failed. The fact that the plant
can contain accidental or unessential ingredients ren-°
ders it obvious that, however truly such a law as that of
Liebig may in any case apply to those substances which
are really concerned in the vital actions, it will be impos-
sible to read the law in the results of analyses.

Relation of Phosphates to Albuminoids.—Liebig
likewise considered that a definite relation exists be-
tween the phosphoric acid and the albuminoids of the
ripe grains. That this relation is not constant is evi-
dent from the following statement of data bearing on
the question. In the table, the amount of nitrogen (N),
representing the albuminoids (see p. 113), found in vari-
ous analyses of rye and whéat grain, is compared with
that of phosphoric acid (P,0;), the latter being taken as
unity. The ratios of P,O; to N were found to range as
follows :

222 HOW CROPS GROW.

P.O; N.

aa.
In 7 Samples ok Bye ennel by Fehling & Faiszt............ 1: 1.97—3.06
“u sé ' Mayer...... cad aicsareevaia SR oiseareeeis 1: 2.04—2.38
5 7 ea se Bi DBs. casio ob ssseassiweiiieesaisisn 1: 1.68—2.81
“6 ae ee se Siegert.........c2.cceeeeesenes 1: 2.35—2.96
“28 ae ec es the extreme range was from.... 1: 1.68—3.06
2 ef se Waeat: ‘kernel by Fehling & Faiszt........... 1: 2.71—2.86
ae bf sa ee Mayers vi ccdeeamtoxeanieans $
ti 2 “cc “ “ce Zoeller
«30 ag ce as Bibra. ...
oe 6 “ “ “ Siegert
“BL ae ee fa the extreme range was from.... 1: 1.83—3.55

Siegert, who collected these data (Vs. S¢., III, p. 147),
and who experimented on the influence of phosphatic and
nitrogenous fertilizers upon the composition of wheat and
rye, gives as the general result of his special inquiries that
Phosphoric acid and Nitrogen stand in no constant rela-
tion to each other. Nitrogenous manures increase the per
cent of nitrogen and diminish that of phosphoric acid.

Other Relations.—All attempts to trace simple and
constant relations between other ingredients of plants,
viz., between starch and alkalies, cellulose and silica, etc.,
have proved fruitless.

It is much rather demonstrated that the proportion of
the constituents is constantly changing from day to day as
the relative mass of the individual organs themselves un-
dergoes perpetual variation.

In adopting the above conclusionsit is not asserted that
such genetic relations between phosphates and albumin-
oids, or between starch and alkalies, as Liebig first sug-
gested and as various observers have labored to show, do
not exist, but simply that they do not appear from the
analyses of plants.

§2.
THE COMPOSITION OF THE PLANT IN SUCCESSIVE STAGES
OF GROWTH.

We have hitherto regarded the composition of the plant
mostly in a relative sense, and have instituted no compar-

COMPOSITION IN SUCCESSIVE STAGES. 223

isons between the absolute quantities of its ingredients at
different stages of growth. We have obtained a series of
isolated views of the chemistry of the entire plant, or of
‘its parts at some certain period of its life, or when placed
under certain conditions, and have thus sought to ascer-
tain the peculiarities of these periods, and to estimate the
influence of these conditions. It now remains to attempt
in some degree the combination of these sketches into a
panoramic picture—to give an idea of the composition
of the plant at the successive steps of tts development.
We shall thus gain some insight into the rate and manner
of its growth, and acquire data that have an important
bearing on the requisites for its perfect nutrition. For
this purpose we need to study not only the relative
(percentage) composition of the plant and of its parts at
various stages of its existence, but we must also inform
ourselves as to the total quantities of each ingredient at
these periods.

We shall select from the data at hand those which
illustrate the composition of the oat-plant. Not only the
ash-ingredients, but also the organic constituents, will be
noticed so far as our information and space permit.

The Composition and Growth of the Oat-Plant
may be studied as a type of an important class of agricul-
tural plants, viz.: the annual cereals—plants which com-
plete their existence in one summer, and which yield a
large quantity of nutritious seeds—the most valuable re-
sult of culture. The oat-plant was first studied in its
various parts and at different times of development by
Prof. John Pitkin Norton, of Yale College. ° His labori-
ous research published in 1846 (Trans. Highland and Ag.
Soc., 1845-7, also Am. Jour. of Sct. and Arts, Vol. 3, 1847)
was the first step in advance of the single and disconnected
analyses which had previously been the only data of the
agricultural physiologist. For several reasons, however,
the work of Norton was imperfect. The analytic meth-

224 HOW CROPS GROW.

ods employed by him, though the best in use at that day,
and handled by him with great skill, were not adapted to
furnish results trustworthy in all particulars. Fourteen
years later, Arendt* at Moeckern, and Bretschneidert at
Saarau, in Germany, at the same time, but independently
of each other, resumed the subject, and to their labors
the subjoined figures and conclusions are due.

Here follows a statement of the Periods at which the

plants wete taken for analysis :

[still closed.

ist Period June 18, Arendt—Three lower leaves unfolded, two upper
«19, Bretschneider—Four to five leaves developed.
2a Period June 30, (12 days), Arendt—Shortly before full heading.
“29, (10 days), Bretschneider—The plauts were headed.
3a Period July 10, (10 days), Arendt—Immediately after bloom.
. a PS we ayes peat nine eae loom.
“4 uly 1 days), Aren: eginning to ripen.
4th Period i » : 28, eo days) Bretschneider— fr “6
‘ uly ays), Aren: ully 1
5th Period \ ‘Aug. 6, (9 days), Bretschneider—I*

F uully ripe.

It will be seen that the periods, though differing some-
what as to time, correspond almost perfectly in regard to
the development of the plants. It must be mentioned
that Arendt carefully selected luxuriant plants of , equal
size, so as to analyze a uniform material (see p. 171),
and took no account of the yield ofa given surface of soil.
Bretschneider, on the other hand, examined the entire
produce of a square rod. The former procedure is best
adapted to study the composition of the well-nourished
individual plant; the latter gives a truer view of the crop.

The unlike character of the material as just indicated
is but one of the various causes which might render the
two series of observations discrepant. Thus, differences
in soil, weather and seeding, would necessarily influence
the relative as wellas the absolute development of the two
crops. The results are, notwithstanding, strikingly ac-
cordant in many particulars. In all cases the roots were
not and could not be included in the investigation, as it
is impossible to free them from adhering soil.

* Das Wachsthum der Haferpflanze, Leipzig, 1859. :
tWachsthumsverhidltnisse der Haferpflanze, Jour. fiir Prakt. Chem., 76,

COMPOSITION IN SUCCESSIVE STAGES. 225

The Total Weight of Crop per English acre, at the
end of each period, was as follows:

TABLE I.—Bretschneider. :
1st Period, 6,358 lbs. avoirdupois.

2a “ 10,603 « “
8a “ 16,623 « “
4th “ 14,981 “ es
6th ae 10,622 “

The Total Weights of Water and Dry Matter for
all but the 2d Period—the material of which was acci-

dentally lost—were: g
TABLE II.—Bretschneider..
Dry Matter, Water,

Ibs. av. per acre. lbs. av. per acre.
1st Period, 1,284 5,074
2d & 3d “ : i
4th aes 5,427 9,554
5th ae 6,886 3,736

1.—From Table I it is seen: That the weight of the
live crop is greatest at or before the time of blossom.*
After this period the total weight diminishes as it had
previously increased.

2.—From Table I] it becomes manifest: That the organ-
ic tissue (dry matter) continually increases in quantity up
to the maturity of the plant; and

3.—The loss after the 3d Period falls exclusively upon
the water of vegetation. At the time of blossom the
plant has its greatest absolute quantity of water, while
its least absolute quantity of this ingredient is found when
it is fully ripe.

By taking the difference between the weights of any
two Periods, we obtain:

The Increase or Loss of Dry Matter and Water

during each Period. .
TABLE III.—Bretschneider.
Dry Matter, Water,
Ibs per acre. Ibs per acre.
ist Period, (58 days), 1,284 Gain. 5,074 Gain.
2d & 3d‘ 0 days), 3,099 7,166
4th oe 20 a be 1,044“ 2,686 Loss.
5th “(9 days), 1,459 “ 5,818 *

*In Arendt’s Experiment, at the time of “heading out,” 3d Period.
15

226 HOW CROPS GROW.

On dividing the above quantities by the number of days
of the respective periods, there results:
The Average Daily Gain or Loss per Acre during

each Period.
TABLE IV.—Bretschneider.

Dry Matter. Water.
1st Period, 221lbs.Gain. 87 lbs. Gain.
2a & 3d “* 163 ae 377“ es
4th - ‘bl ae 134 “ Loss.
5th “ae 162 66 oe 646 “cs “as

4.—Table III, and especially ‘Table IV, show that the
gain of organic matter in Bretschneider’s oat-crop went
on most rapidly at or before the time of blossom (accord-
ing to Arendt at the time of heading out). This was, then,
the period of most active growth. Afterward the rate of
growth diminished by more than one-half, and at a later
period increased again, though not to the maximum.

Absolute Quantities of Carbon, Hydrogen, Oxy-
gen, Nitrogen (Organic Matter), and Ash in the dry
oat-crop at the conclusion of the several periods (dds.

per acre) :
TABLE V.—Bretschneider.

Carbon. Hydrogen. Oxygen. Nitrogen. Ash.*

1st Period, 593 80 455 46 110
2d & 3d 2,137 286 1,575 122 263.
4th a 2,600 343 2,043 150 291
5th ue 3,229: 405 2,713 167 372

Amounts of Carbon, Hydrogen, Oxygen, Nitro-
gen, and Ash-ingredients assimilated by the oat-crop
during the several periods. Water of vegetation is not
included (ibs. per acre) :

. TABLE VI.—Bretschneider.
Carbon. Hydrogen. Oxygen. Nitrogen. Ash-ingredients.
1st Period, 593 80 455 46
24. & 3a « 1,544 206 1,575 76 153
4th ce 453 57 468 28 28
5th ee 629 62 670 17 81

*In Bretschneider’s analyses, “ash” signifies the residue left after
earefully burning the plant. In Arendt’s investigation the sulphur
and chlorine were determined in the unburned plant.

COMPOSITION IN SUCCESSIVE STAGES. 22%

Relative Quantities of Carbon, Hydrogen, Oxy-
gen, Nitrogen (Organic Matter) and Ash in the dry
oat-crop, at the end of the several periods (per cent) :

TABLE VII.—Bretschneider. °
Carbon. Hydrogen. Oxygen. Nitrogen. (Organic Matter.) Ash.

ist Period, 46.22 6,23 35.39 3.59 91.43 8.57
2d & 3d “ 48.76 6.53 35.96 2.79 94.04 5.96
4th a6 47.91 6.33 37.65 2.78 94.67 5.33
5th ee 46.89 5.88 39.40 2.43 94,60 5.40

Relative Quantities of Carbon, Hydrogen, Oxy-
gen, and Nitrogen, in dry substance, after deducting

the somewhat variable arhount of ash (per cent) :
TABLE VIII.—Bretschneider.

Carbon. Hydrogen. Oxygen. Nitrogen.
1st Period, 50.55 6.81 38,71 3.93
2d & 3a “* 51.85 6.95 38.24 2.86
4th ie 50.55 6.96 39.83 2.93
5th a 49.59 6.21 41.64 2.56

5. The Tables V, VI, VII, and VIII, demonstrate that
while the absolute quantities of the elements of the dry
oat-plant continually increase to the time of ripening,
they do not increase in the same proportion. In other
words, the plant requires, so to speak, a change of diet
as it advances in growth. ‘They further show that nitro-
gen and ash are relatively more abundant in the young
than in the mature plant; in other words, the rate of
assimilation of Nitrogen and fixed ingredients falls be-
hind that of Carbon, Hydrogen, and Oxygen. Still oth-
erwise expressed, the plant as it approaches maturity
organizes relatively more carbhydrates and less albu-
minoids.

The relations just indicated appear more plainly when
we compare the Quantities of Nitrogen, Hydrogen, and
Oxygen, assimilated during each period, calculated upon
the amount of Carbon assimilated in the.same time and
assumed at 100.

TABLE IX.—Bretschneider.

Carbon. Nitrogen. Hydrogen. Oxygen.
1st Period, 100 7.8 13.4 73.6
2d & 3d “ 100 4.9 13.3 72.5
4th - & 100 6.1 12.3 100.8

228 HOW CROPS GROW.

From Table IX we see that the ratio of Hydrogen to
Carbon regularly diminishes as the plant matures; that
of Nitrogen falls greatly from the infancy of the plant to
the period of full bloom, then strikingly increases during
the first stages of ripening, but falls off at last to mini-
mum. The ratio of Oxygen to Carbon is the same during
the 1st, 2d, and 3d Periods, but increases remarkably
from the time of full blossom until the plant is ripe.

As already stated, the largest absolute assimilation of
all ingredients—most rapid growth—takes’ place at the
time of heading out, or blossom. At this period all the
volatile elements are assimilated at a nearly equal rate,
and at a rate similar to that at which the fixed matters
(ash) are absorbed. In the first period Nitrogen and
Ash; in the 4th Period, Nitrogen and Oxygen; in the
5th Period, Oxygen and Ash are assimilated in largest
proportion.

This is made evident by calculating for each period the
relative average daily increase of each ingredient, the
amount of the ingredients in the ripe plant being assumed
at 100, as a point of comparison. The figures resulting
from such a calculation are given in

TABLE X.—Bretschneider.
Carbon. Hydrogen. O,rygen. Nitrogen. Ash.

1st Period, 0.31 0.33 0.28 0.47 0.50
2d and3d 2.51 2.68 2.17 2.39 2.13
4th a 0.89 0.88 1.07 1.06 0.47
5th se 1.49 1.16 1.89 0.75 1.70

The increased assimilation of the 5th over the 4th
Period is, in all probability, only apparent. The results
of analysis, as before mentioned, refer only to those parts
of the plant that are above ground. The activity of the
foliage in gathering food from the atmosphere is doubt-
less greatly diminished before the plant ripens, as evi-,
denced by the leaves turning yellow and losing water of
vegetation. The increase of weight in the plant above
ground probably proceeds from matters previously stored

COMPOSITION IN SUCCESSIVE STAGES. 229

in the roots, which now are transferred to the fruit and
foliage, and maintain the growth of these parts after
their power of assimilating inorganic food (CO,, H.0,
NH,, NO) is lost.

The following statement exhibits the absolute average
daily increase of Carbon, Hydrogen, Oxygen, Nitrogen, and
Ash, Quring the several periods (/bs. per acre) :

TABLE XI.—Bretschneider.
Carbon. Hydrogen. Oxygen. Nitrogen. Ash.
14

Ist Period, 10.0 7.8 0.8 1.9
2dand3d “ 81.0 10.8 83.0 4.0 8.0
4th. es 22.6 2.9 23.4 1.4 1.4
bth Be 70.0 6.9 74.4 1.9 9.0

Turning now to Arendt’s results, which are carried
more into detail than those of Bretschneider, we will
notice:

A.—The Relative (percentage) Composition of the
Entire Plant and of its Parts* during the several
periods of vegetation. :

1. Fiber + is found in greatest proportion—40 per cent
—in the lower joints of the stem, and from the time
when the grain “heads out,” to the period of bloom.
Relatively considered, there occur great variations in the
same part of the plant at different stages of growth.
Thus, in the ear, which contains the least fiber, the
quantity of this substance regularly diminishes, not
absolutely, but only relatively, as the plant becomes
older, sinking from 2% per cent at heading to 12 per
cent at maturity. In the leaves, which, as regards
fiber, stand intermediate between the stem and ear, this

* Arendt selected large and well-developed Plank, divided them into
six parts, and analyzed each part separately. His divisions of the
plants were: 1, the three lowest joints of the stem; 2, the two middle
oints; 3, the upper joint; 4, the three lowest leaves; 5, the two upper
eaves; 6, the ear. The stems were cut just above the nodes, the leaves
included the sheaths, the ears were stripped from the stem. Arerfdt
rejected all plants which were not perfect when gathered. When
nearly ripe, the cereals, as is well known, often lose one or more of

their lower leaves. For the numerous analyses on which these conclu-
sions are based we must refer to the original.

tl. e., Crude cellulose; see p. 45.

230 HOW CROPS GROW.

substance ranges from 22 to 38 per cent. Previous to
blossom, the upper leaves, afterwards the lower leaves,
are the richest in fiber. In the lower leaves the maxi-
mum (33 per cent) is found in the fourth ; in the upper
leaves (38 per cent), in the second period.

The apparent diminution in amount of fiber is due in
all cases to increased production of other ingredients.

2. Fat and Wax are least abundant in the stem. Their
proportion increases, in general, in the upper parts of the
stem as well as during the latter stages of its growth. The
range is from 0.2 to 3 per cent. In the ear the propor-
tion increases from 2 to 3.7% per cent. In the leaves the
quantity is much larger and is mostly wax with little fat.
The smallest proportion is 4.8 per cent, which is found in
the upper leaves when the plant is ripe. The largest :
proportion, 10 per cent, exists in the lower leaves, at the
time of blossom. The relative quantities found in the
leaves undergo considerable variation from one stage of
growth to another.

3. Non-nitrogenous matters, other than fiber, viz., starch,
sugars, gums, etc.,* undergo great and irregular variation.
In the stem the largest percentage (57 per cent) is found
in the young lower joints; the smallest (43 per cent) in
ripe upper straw. Only in the ear occurs a regular in-
crease, viz., from 54 to 63 per cent.

4, The albuminoids,+ in Arendt’s investigation, exhibit
a somewhat different relation to the vegetable substance
from what was observed by Bretschneider, as seen from
the subjoined comparison of the percentages found at
the different periods :

PERIODS.

i. Il. Ill. Iv. Vv.
Arendt ...5.cceecsee 20.98 11.65 10.86 13.67 14.30
Bretschneider ..... 22.73 17.67 17.61 15.39

* What remains after deducting fat and_ wax, albuminoids, fiber and
ash, from the dry substance, is here included.
t Calculated by multiplying the percentage of nitrogen by 6.33.

These differences may be variously accounted for. They

COMPOSITION IN SUCCESSIVE STAGES. 231

are due, in part, to the fact that Arendt analyzed only
large and perfect plants. Bretschneider, on the other
hand, examined all the plants of a given plot, large and
small, perfect and injured. The differences illustrate
what has been already insisted on, viz., that the develop-
ment of the plant is greatly modified by the circum-
stances of its growth, not only in reference to its exter-
nal figure, but also as regards its chemical composition.

The relative distribution of nitrogen in the parts of the
plant at the end of the several periods is exhibited by the
following table, simple inspection of which shows the
fluctuations (relative) in the content of this element. The
percentages are arranged for each period separately, pro-
ceeding from the highest to the lowest :

PERIODS.

Upper leaves. Lower Teaves. ‘Upper leaves. Ears. Eats.
wes t leaves. Upper! leaves. Lower leaves Upper t leaves. Wiper t eaves.
Lower eee Ears. Bass. Lowerle leaves. Upper, Stem.

2.06
simi A cai Upper: ¢ stem. Upper stem. Lower leaves.
1.43
Upper stem. Miadles stem. Miaaie iit ae geen,
0.87 0.98 20

1:
Lower stem. | Lower stem. | Lower stem. Lows Easnie
0.80 0.88 0.83 0.79

5. Ash.—The agreement of the percentages of ash in
the entire plant, in corresponding periods of the growth
of the oat, in the independent examinations of Bret-
schneider and- Arendt, is remarkably close, as appears
from the figures below :

PERIODS.
I. II. Tit. © 3% Vv.
Bretschneider......... 8.57 5.96 5.33 5.40
Arendt.............0008 8.03 5.24 5.44 5.20 5.17

As regards the several parts of the plant, it was found
by Arendt that, of the stem, the upper portion was richest
in ash throughout the whole period of growth. Of the
leaves, on the contrary, the lower contained most fixed
matters. In the ear there occurred a continual decrease

232 HOW CROPS GROW.

from its first appearance to its maturity, while in the
stem and leaves there was, in general, a progressive
increase towards the time of ripening, The greatest
percentage (10.5 per cent) was found in the ripe leaves;
the smallest (0.78 per cent) in the ripe lower straw.

Far more interesting and instructive than the relative
proportions are

B.—The Absolute Quantities of the Ingredients
found in the Plant at the conclusion of the sev-
eral periods of growth.—These absolute quantities,
as found by Arendt, in a given number of carefully-
selected and vigorous plants, do not accord with those
obtained by Bretschneider from a given area of ground,
nor could it be expected that they should, because it is
next to impossible to cause the same amount of vegeta-
tion to develop on a number of distinct plots.

Though the results of Bretschneider more nearly rep-
resent the crop as obtained in farming, those of Arendt
give a truer idea of the plant when situated in the best
possible conditions, and attaining a uniformly high
development. We shall not attempt to compare the two
sets of observations, since, strictly speaking, in most
points they do not admit of comparison.

From a knowledge of the absolute quantities of the
substances contained in the plant at the ends of the several
periods, we may at once estimate the rate of growth, i. e.,
the rapidity with which the constituents of the plant are
either taken up or organized.

The accompanving table, which gives in alternate col-
umns the total weights of 1,000 plants at the end of the
several periods, and (by subtracting the first from the
second, the second from the third, etc.) the gain from
matters absorbed or produced during each period, will
serve to justify the deductions that follow, which are
taken from the treatise of. Arendt, and which apply, of
course, only to the plants examined by this investigator.

233

COMPOSITION IN SUCCESSIVE STAGES,

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234 HOW CROPS GROW.

1. The plant increases in total weight (dry matter)

through all its growth, but to unequal degrees in differ-
‘ ,ent periods. The greatest growth occurs at the time of
heading out; the slowest, within ten days of maturity.

We may add that the increase of the oat after blossom
takes place mostly in the seed, the other organs gaining
but little. The lower leaves almost cease to grow after
the 2d Period.

2. Fiber is produced most largely at the time of head-
ing out (2d Period). When the plant has finished blos-
soming (end of 3d Petiod), the formation of fiber
entirely ceases." Afterward there appears to occur a
slight diminution of this substance, more probably due
to unavoidable loss of lower leaves than to a resorption
or metamorphosis in the plant.

3. Fat is formed most largely at the time of blossom.
It ceases to be produced some weeks before ripening.

4. Albuminoids are very irregular in their formation.
The greatest amount is organized during the 4th Period
(after blossoming). ‘The gain in albuminoids within
this period is two-fifths of the total amount found in the
ripe plant, and also is nearly two-fifths of the entire gain
of organic substance in the same period. The absolute
amount organized in the 1st Period is not much less
than in the 4th, but in the 2d, 3d and ‘5th Periods the
quantities are considerably smaller.

Bretschneider gives the data for comparing the pro-
duction of albuminoids in the oat crop examined by him
with Arendt’s results. Taking the quantity found at
the conclusion of the 1st Period as 100, the amounts
gained during the subsequent periods are related as
follows:

PERIODS.
I. Tl, IW. (I.&Iil.) IV. (L,I &Iv.) v.
Arendt.......... 100 67) = 46 *(413) 120 | (233) 36
Bretschneider .100 ? 2 (165) 62 (227) 35

We perceive striking differences in the comparison. In

COMPOSITION IN SUCCESSIVE STAGES. 235

Bretschneider’s crop the increase of albuminoids goes on
most rapidly in the 2d and 3d Periods, and sinks rapidly
during the time when in Arendt’s plants it attained the
maximum. Curiously enough, the gain in the 2d, 3d
and 4th Periods, taken together, is in both cases as good
as identical (233 and 227), and the gain during the last
period is also equal. This coincidence is doubtless, how-
ever, merely accidental. Comparisons with other crops
of oats examined, though much less completely, by
Stockhardt (Chemischer Ackersmann, 1855) and Wolff
(Die Erschipfung des Bodens durch die Oultwr, 1856)
demonstrate that the rate of assimilation is not related
to any special times or periods of development, but
depends upon the stores of food accessible to the plant
and the favor of the weather, or other external conditions.

The following figures, which exhibit for each period
of both crops a comparison of the gain in albuminoids
with the increase of the other organic matters, further
strikingly demonstrate that, in the act of organization,
the nitrogenous principles have no close quantitative
relations to the non-nitrogenous bodies (carbhydrates
and fats).

The quantities of albuminoids gained during each
period being represented by 10, the amounts of carbhy-

drates, etc., are seen from the subjoined ratios :
PERIODS.

Ratioin
I. II & Ill. Iv. V. Ripe Plant.
Arendt.......... 10: 34 10: 114 10 : 28 10: 25 10 : 66

Bretschneider..10 : 30 10: 50 10:46 10: 120 10:51

5. The Ash-ingredients of the oat are absorbed through-
out its entire growth, but in regularly diminishing quan-
tity. The gain during the 1st Period being taken at 10,
that in the 2d Period is 9, in the 3d, 8, in the 4th, 54,
in the Sth, 2 nearly.

The ratios of gain in ash-ingredients to that in entire
dry substance, are as follows, ash-ingredients being
assumed as 1, in the successive periods :

236 HOW CROPS GROW.

1; 123, 1: 27, 1:16, 1:23, 1:19

Accordingly, the absorption .of ash-ingredients is' not
proportional to the growth of the plant, but is to some
degree accidental, and independent of the wants of
vegetation.

Recapitulation.—Assuming the quantity of each proxi-
mate element in the ripe plant as 100, it contained at
the end of the several periods the following amounts

(per cent):

Fiber. Fat. Carbhydrates* Albuminoids. Ash.

I. Period, 18 20 15 27 29
IL. ee 81 50 47 45 55
Ill. ee 100 85 70 57 79
IV. es 100 100 92 90 95
Vv. ee 100 100 100 100 100

Taking the total gain as 100, the gain during each
period was accordingly as follows (per cent):

Fiber. Fat. Carbhydrates* Albuminoids. Ash.

I. Period, 18 20 15 27 29
IL. ss 63 30 32 - 18 26
im, 19 35 23 42 24

, Iv. sf 0 15 22 33 16

Vv. ee 0 0 8 10 5

-100 100 100 100 100

6.—As regards the individual ingredients of the ash,
the plant contained at the end of each period the follow-
ing amounts,—the total quantity in the ripe plant being
taken at 100. Corresponding results from Bretschneider
enclosed in ( ) are given for comparison:

Sulphurie Phosphoric

Silica. Oxide. Oxide Lime. Magnesia. Potash.
Per cent. Percent. Percent. Per cent. Per cent. Per cent.
I. Period, 18 ( 22) 20 ( 42) 23 ( 23) 30 (31) 24 (31) 39 ( 42)

i * 41 52 42 58 42 70
Ill =“ 70350 malo) 73} 8) moh 8) eh 6) ase ®
Iv. i 93 ( 72) 90 ( 39) 91 ( 74) 99 (74) 8 (77 100 (100)
Vv. ce 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) 100 (95*)

The gain (or loss, indicated by the minus sign —) in
these ash-ingredients during each period is given below:

* Exclusive of Fiber.

COMPOSITION IN SUCCESSIVE STAGES. 237

Sulphuric Phosphoric re
Silica. Oxide. Oxide. Lime. Magnesia. Potash.

Per cent. Percent. Per cent. Per cent. Percent. Per cent.
I. Period, 18 ( 22) 20 (42) 28 ( 23) 30 (31) 24 (31) 39 (42)

Tr “* 23 32 19 28 18 31

i. “ 03) of at ase ms 6 82) oh 2) met)
Iv. 23 (15) 38 (—5*) 18 (10) 20 (—9*) 2 (4) 9 (11)
Vs otf “7 (28) 10 (56) 9 (27 1 (17) 16 (23) 0 (—5*)

100 (100) 100 (100) 100 (100) 100 (100) 100 (100) 100 (100)

These two independent investigations could hardly
give all the discordant results observed on comparing
the above figures, as the simple consequence of the
unlike mode of conducting them. We observe, for
example, that in the last period Arendt’s plants gathered
less silica than in any other—only 7 per cent of the
whole. On the other hand, Bretschneider’s crop gained
more silica in this than in any other single period, viz.:
28 per cent. Asimilar statement is true of phosphoric
oxide.t It is obvious that Bretschneider’s crop was tak-
ing up fixed matters much more vigorously in its last
stages of growth than were Arendt’s plants. As to
potash, we observe that its accumulation ceased in the
4th Period in both cases.

(¢.—Translocation of Substances in the Plant.
—tThe transfer of certain matters from one part of the
plant to another during its growth is revealed by the
analyses of Arendt, and since such changes are of inter-
est from a physiological point of view, we may recount
them here briefly.

It has been mentioned already that the growth of the
stem, leaves, and ear of the oat plant in its later stages
probably takes place to a great degree at the expense of
the roots. It is also probable that a transfer of carbhy-

*In these instances Bretschneider’s later etOpS appear to contain less
sulphuric oxide, limeand potash, than the earlier. Thisresult may be
due to the washing of the crop by rains, but is probably caused by
unequal development of the several plots.

+ Phosphoric oxide is the a te acid,” P.O;, of older and to a
great degree of current usage. See p. 1

238 HOW CROPS GROW.

drates, and certain that one of albuminoids, goes on from
the leaves through the stem into the ear.

Silica appears not to be subject to any change of posi-
‘tion after it has once been fixed by the plant. Chlorine
likewise reveals no noticeable mobility.

On the other hand, phosphoric oxide passes rapidly from
the leaves and stem towards or into the fruit in the ear-
lier as well as in the later stages of growth, as shown by
the following figures :

One thousand plants contained in the various periods
quantities (grams) of phosphoric oxide as follows :

1st 2a 3a 4th bth
Period. Period. Period. Period. Period.

3 lower joints of stem, 0.47 0.20 0.21 0.20 0.19
2middle “ 0.39 1.14 0.46 0.18
Upper joint oe 0.66 1.73 0.31 0.39
3 lower leaves “1.05 0.70 0.69 0.51 0.35
2 upper leaves “1,75 1.67 1.18 0.74 0.59
Ear, ~ 2.36 5.36 10.67 12.52

Observe that these absolute quantities diminish in the
stem and leaves after the 1st or 3d Period in all cases,
and increase very rapidly in the ear.

Arendt found that sulphuric oxide existed to a much
greater degree in the leaves than in the stem through-
out the entire growth of the oat plant, and that, after
blossoming, the lower stem no longer contained sulphur
in the form of sulphates at all, though its total in the
plant considerably increased. It is almost certain, then,
that sulphuric oxide originates, either partially or wholly,
by oxidation of sulphur or some sulphurized compound,
in the upper organs of the oat.

Magnesium is translated from the lower stem into the
upper organs, and in the fruit, especially, it constantly
increases in quantity.

There is no evidence. that Calcium moves upward in
the plant. On the contrary, Arendt’s analyses go to
show that in the ear, during the last period of growth, it

COMPOSITION IN SUCCESSIVE STAGES. 239

diminishes in quantity, being, perhaps, replaced by
magnesium,

As to potassium, ng transfer is fairly indicated, except
from the ears. These contained at blossoming (Period
TIT) a maximum of potassium. During their subsequent
growth the amount of this element diminished, being
probably displaced by magnesium.

The data furnished by Arendt’s analyses, while they
indicate a transfer of matters in the cases just named,
and in most of them with great certainty, do not and
cannot from their nature disprove the fact of other simi-
lar changes, and cannot fix the real limits of the move-
ments which they point out.

DIVISION II.

THE STRUCTURE OF THE PLANT AND
OFFICES OF ITS ORGANS.

CHAPTER I.
GENERALITIES.

We have given a brief description of those elements
and compounds which constitute the plant in a chemical
sense. They are the materials—the stones and timbers,
so to speak—out of which the vegetable edifice is built.
It is important, in the next place, to learn how these
building materials are put together, what positions they
occupy, what purposes they serve, and on what plan
the edifice is constructed.

It is impossible for the builder to do his work until he
has mastered the plans and specifications of the archi-
tect. So it is hardly possible for the farmer with cer-
tainty to contribute in any great, especially in any new,
degree, to the upbuilding of the plant, unless he is
acquainted with the mode of its structure and the ele-
ments that form it. It is the happy province of science
to add to the vague and general information which the
observation and experience of generations have taught,
a more definite and particular knowledge,—a knowledge

-acquired by study purposely and carefully directed to
special ends. °

An acquaintance with the parts and structure of the
plant is indispensable for understanding the mode by
which it derives its food from external sources, while the

16 241

242 , HOW CROPS GROW.

ingenious methods of propagation practiced in fruit- and
flower-culture are only intelligible by the help of this
knowledge.

ORGANISM OF THE PLant.—We have at the ontset
spoken of organic matter, of organs and organization.
It is in the world of life that these terms have their fit-
test application. The vegetable and animal consist of
numerous parts, differing greatly from each other, but
each essential to the whole. The root, stem, leaf, flower
and seed are each instruments or organs whose co-oper-
ation is needful to the perfection of the plant. The
plant (or animal) being thus an assemblage of organs, is
called an Organism; it is an Organized or Organic
Structure. The atmosphere, the waters, the rocks and
soils of the earth, do-not possess distinct co-operating
parts ; they are Inorganic matter.

In inorganic nature, chemical affinity rules over the
transformations of matter. A plant or animal that is
dead, under ordinary circumstances, soon loses its form
and characters ; it is gradually consumed, and, at the ex-
pense of atmospheric oxygen, is virtually burned up to
air and ashes.

In the organic world a something, which we call
Vitality, resists and overcomes or modifies the affinities
of oxygen, and insures the existence of a continuous and
perpetual succession of living forms.

An Organism or Organized Structure is characterized
and distinguished from inorganic matter by two par-
ticulars :

1. It builds up and increases its own mass by appro-
priating external matter. .It absorbs and assimilates
food. It grows by the enlargement of all its parts.

2. It reproduces itself It develops from a germ, and
in turn gives origin to new germs.

ULTIMATE AND CoMPLEX ORGANS.—In our account
of the Structure of the Plant we shall first consider the.

ELEMENTS OF ORGANIZED STRUCTURE. 243

elements of that structure—the Oells—which cannot be
divided or wounded without extinguishing their life,
and by whose expansion or multiplication all growth
takes place. Then will follow an account of the com-
plex parts of the plant—its Organs—which are built up
by the juxtaposition of numerous cells. Of these we
lave one class, viz., the Roots, Stems and Leaves, whose
office is to sustain and nourish the Individual Plant.
These may be distinguished as the Vegetative Organs.
The other class, comprising the Flower and Fruit, are
not essential to the existence of the individual, but their
function is to maintain the Race. They are the Repro-
ductive Organs.

CHAPTER II.

PRIMARY ELEMENTS.OF ORGANIZED STRUCTURE,

§ 1.

THE VEGETABLE CELL.

One of the most interesting discoveries that the micro-
scope has revealed, is that all organized matter originates
in the form of minute vesicles or cells. If we examine
by the microscope a seed or an egg, we find nothing but
a cell-structure—a mass of rounded or many-sided bags
lying closely together, and more or less filled with solid
or liquid matters. From these cells, then, comes the
frame or structure of the plant or of the animal. In the
process of maturing, the original vesicles are vastly mul-
tiplied and often greatly modified in shape and appear-
ance, to suit various purposes ; but still it is always easy,
especially in the plant, to find cells of the same essential
‘characters as those occurring in the seed..

244 HOW CROPS GROW.

Cellular Plants.—In the simpler forms or lower
orders * of vegetation, we find plants which, throughout
all the stages of their life, consist entirely of similar-
cells, and indeed many are known which are but a single
cell. The phenomenon of red snow, frequently observed
in Alpine and Arctic regions, is due to a microscopic
one-celled plant which propagates with great rapidity,
and gives its color to the surface of the snow. In the
chemist’s laboratory it is often observed that in the clear-
est solutions of salts, like the sulphates of sodium and
magnesium, a flocculent mold, sometimes red, some-
times green, most often white, is formed, which, under
the microscope, is seen to be a vegetation consisting of
single cells. Brewers’ yeast, Fig. 27, is nothing more
than a mass of one or few-celled plants.

In sea-weeds, mushrooms, the molds that grow on
damp walls, or upon. bread, cheese, etc., and in the
blights which infest many of the’ farmer’s crops, we have
examples of plants formed exclusively of cells.

Fig. 27. Fig. 28.

All the plants of higher orders we find likewise to
consist chiefly of globular or angular cells. All the
growing parts especially, as the tips of the roots, the
leaves, flowers and fruit, are, for the most part, aggrega-
tions of such minute vesicles.

If we examine the pulp of fruits, as that of a ripe

*Viz.: the Cryptogams, includin Molds and Mushrooms (Fungi),
Mosses, Ferns, Sea- Weeds (Alger) and Bacteria (Schizomycetes).

ELEMENTS OF ORGANIZED STRUCTURE. 245
apple or tomato, we are able, by means of a low magni-
fier, to distinguish the cells of which it almost entirely
consists. Fig. 28 represents a bit of the flesh of a ripe
pippin, magnified 50 diameters. The cells mostly cohere
together, but readily admit of separation.

Structure of the Cell.—By the aid of the micro-
scope it is possible to learn something with regard to the
internal structure of the cell itself. Fig. 29 exhibits the
appearance of a cell from the flesh of the Artichoke
(Helianthus), magnified 230 diameters; externally the
membrane, or wall of the cell, is seen in section. This
membrane is filled and distended by a
transparent liquid, the sap or free water
of vegetation. Within the cell is ob-
+ served a round body, 4, which is called
the nucleus, and upon this is seen a

Ae smaller nucleolus, c. Lining the inte-
rior of the cell-membrane and connected

with the nucleus, is a yellowish, turbid,
semi-fluid substance of mucilaginous
consistence, a, which is designated the protoplasm, or
formative layer. This, when more highly magnified, is
found to contain-a vast number of excessively minute
granules.

By the aid of chemistry the microscopist is able to dis-
sect these cells, which are hardly perceptible to the
unassisted eye, and ascertain to a good degree how they
are constituted. On moistening them with solution of
iodine, and afterward with sulphuric acid, the outer
membrane—the cell-wail—shortly becomes of a fine blue
color. It is accordingly cellulose, the only vegetable
substance yet known which is made blue by iodine after,
and only after, the action of sulphuric acid. At the
same time we observe that the interior, half-liquid, pro-
toplasm, coagulates and shrinks together,—separates,
therefore, from the cell-wall, and, including with it the

Fig. 29.

246 HOW CROPS GROW.

nucleus and the smaller granules, lies in the center of
the cell like a collapsed bladder. It also assumes a deep
yellow or brown color. If we moisten one of these cells
with nitric acid, the cell-wall is not affected, but the
liquid penetrates it, coagulates the inner membrane, and
colors it yellow. In the same way this membrane is
tinged violet-blue by hydrochloric acid. These reactions
leave no room to doubt that the slimy inner lining of the
cell or protoplasm contains abundance of albuminoids.
The protoplasm is not miscible with water and main-
tains itself distinct from the cell-sap. In young cells it
is constantly in motion, the granules suspended in it cir-
culating as in a liquid current.

If we examine the cells of any other plant we find
almost invariably the same structure as above described,
provided the cells are young, i. e., belong to growing
parts. In some cases isolated cells consist only of proto-
plasm and nucleus, being destitute of cell-walls during
a portion or the whole of their existence.

In studying many of the maturer parts of plants, viz.,
such as have ceased to enlarge, as the full-sized leaf, the
perfectly formed wood, etc., we find the cells do not cor-
respond to the description just given. In external shape,
thickness, and appearance of the cell-wall, and especially
in the character of the contents, there is indefinite va-
riety. But this is the result of change in the original
cells, which, so far as our observations extend, are always,
at first, formed closely on the pattern that has been de-
scribed.

Vegetable Tissue.—It does not, however, usually
happen that the individual cells of the higher orders of .
plants admit of being obtained separately. They are
attached together more or less firmly by their outer sur-
faces, so as to form a coherent mass of cells—-a tissue, as
itis termed. In the accompanying cut, Fig. 30, is shown |
a highly-magnified view of a portion of a very thin slice

s

ELEMENTS OF ORGANIZED STRUCTURE. 247

across a young cabbage-stalk. It exhibits the outline of
the irregular empty cells, the walls of which are, for the
most part, externally united and appear as one, a. At
the points indicated by 4, air-filled cavities between the
cells are seen, called intercellular spaces. A slice across
the potato-tuber (see Fig, 52, p. 300) has a similar ap-
pearance, except that the cells are filled with starch, and
it would be scarcely pos-
sible to dissect them apart;
but when a potato is boiled
the starch-grains swell,
and the cells, in conse-
quence, separate from each
other, a practical result of
which is to make the po-
tato mealy. A thin slice
of vegetable ivory (the seed
of Phytelephas macro-

Fig. 30. carpa) under the micro-
scope, dry or moistened with water, presents no evident
trace of cell-structure ; however, upon soaking in sul-
phuric acid, the mass softens and swells, and the indi-
vidual cells are revealed, their surfaces separating in
six-sided outlines.

Form of Cells.—In the soft, succulent parts of
plants, the cells lie loosely together, often with consider-
able intercellular spaces, and have mostly a rounded out-
line. In denser tissues, the cells are crowded together
in the least possible space, and hence often appear six-
sided when seen in cross-section, or twelve-sided if viewed.
entire. A piece of honey-comb is an excellent illustra-
tion of the appearance of many forms of vegetable cell-
tissue.

The pulp of an orange is the most evident example of
cell-tissue. The individual cells of the ripe orange may
be easily separated from each other. Being mature and

248 ? HOW CROPS GROW.

‘incapable of further growth, they possess neither proto-

plasm nor nucleus, but are filled with a sap or juice con-

taining citric acid, sugar and albuminoids.
In- the pith of the rush, star-shaped cells are found.

In common mold the cells are long and

fyfihread-like. In the so-called frog-spittle
/ (alge) they are cylindrical and attached

end to end. In the bark of many trees,
in the stems and leaves of grasses, they
are square or rectangular. :

} Cotton-fiber, flax, and hemp consist of
# long and slender celis, Fig. 3t. Wood is
/ mostly made up of elongated cells, tapered.

at the ends and adhering together by

their sides. See also Fig. 49, c, h, p. 292.

Each cotton-fiber is a single cell which forms an
external appendage to the seed-vessel of the cotton
‘plant. , When it has lost its sap and become air-dry,
\\, its sides collapse and it resembles a twisted strap.
\\) 4, in Fig. 31, exhibits a portion of a cotton-fiber
highly magnified. The flax-fiber, from the inner
\ park of the flax-stem, b, Fig. 31, is a tube of thicker

Fig. 31. walls and smaller bore than the cotton-fiber, and

. hence is more durable than cotton. Itis very flexi-

ble, and even when crushed or bent short retains much of its original
tenacity. Hemp-fiber closely resembles. flax-fiber in appearance.

Thickening af the Cell-Membrane.—The growth of the cell, which,
when young, has a very delicate outer 1,
membrane, often results in the thick-
ening of its walls by the interior dep-
osition of cellulose and woody mat-
ters. This thickening may take place
regularly and uniformly, or interrupt-
edly. The flax-fiber, b, Fig. 31, is an ex-
ample of nearly uniform thickening.
The irregular deposition of cellulose is
shown in Fig. 32, which exhibits a sec-
tion from the seeds (cotyledons) of the a .
common nasturtium (Tropeolum Fig. 32.
majus). The original membrane is coated interiorly_ with several dis-
tinct and successively-formed linings, which are not continuous, but
are irregularly devéloped. Seen in section, the thickening has a waved
outline, and, at points, the original cell-membrane is bare. Were these
cells viewed entire, we should see at these points, on the exterior of
the cell, dots or circles appearing like orifices, but being simply the

ELEMENTS OF ORGANIZED STRUCTURE. 249 -

unthickened portions of the cell-wall. The cells in fig. 32 exhibit each
a central nucleus surrounded by grains of aleurone.

Cell Contents.—Besides the protoplasm and nucleus,
the cell usually contains a variety of bodies, which have
een, indeed, noticed already as ingredients of the plant,
but which may be here recapitulated. Many cells are
altogether empty, and consist of nothing but the cell-
wall. Such are found in the bark or epidermis of most
plants, and often in the pith, and although they remain
connected with the actually living parts, they have no
longer any proper life in themselves.

All living or active cells are distended with liquid.
This consists of water, which holds in solution gum, dex-
trin, inulin, the sugars, albuminoids, organic acids, and
other vegetable principles, together with various salts,
both’ of organic and mineral acids, and constitutes the
sap of the plant. In oil-plants, droplets of oil occupy
certain cells, Fig. 17, p. 83; while in numerous kinds of
vegetation colored and milky juices are found in certain
spaces or channels between the cells.

The water of the cell comes from the soil, or in some -
cases from the air. The matters, which are dissolved in
the sap of the plant, together with the semi-solid proto-
plasm, undergo transformations resulting in the produc-
tion of various solid substances. By observing the sev-
eral parts of a plant at the successive stages of its devel-
opment, under the microscope, we are able to trace
within the cells the formation and growth of starch-
grains, of granular or crystalline bodies consisting chiefly
of albuminoids, and of the various matters which give
color to leaves and flowers.

The circumstances under which a cell develops deter-
mine the character of its contents. The outer cells of
the potato-tuber are incrusted with corky matter, the
inner ones are for the most part filled with starch.

In oats, wheat, and other cereals, we find, just within

250 HOW CROPS GROW.

the skin or epidermis of the grain, a few layers of cells
that contain scarcely anything but albuminoids, with a
little fat ; while the interior cells are chiefly filled with
starch. Fig. 18, p. 110.

Transformations in Cell Contents.—The same
cell may exhibit a great variety of aspect and contents at
different periods of growth. This is especially to be
observed in the seed while developing on the mother
plant. Hartig has traced these changes in numerous
plants under the microscope. According to this ob-
server, the cell-contents of the seed (cotyledons) of the
common nasturtium (Tropeolum majus) run through
the following metamorphoses. Up to a certain stage in
its development the interior of the cells are nearly devoid
of recognizable solid matters, other than the nucleus and
the adhering protoplasm. Shortly, as the growth of the
seed advances, green grains of chlorophyll make their
appearance upon the nucleus, completely covering it
from view. Ata later stage, these grains, which have
enlarged and multiplied, are seen to have mostly become
: detached from the nucleus, and lie near to and in contact
with the cell-wall. Again, in a short time the grains.
lose their green color and assume, both as regards appear-
ance and deportment with iodine, all the characters of
sfarch. Subsequently, as the seed hardens and becomes
firmer in its tissues, the microscope shows that the
starch-grains, which were situated near the cell-wall,
have vanished, while the cell-wall itself has thickened
inwardly—the starch having been converted into cellu-
lose or bodies of similar properties. Again, later, the nu-
cleus, about which, in the meantime, more starch-grains
have been formed,. undergoes a change and disappears ;
then the starch-grains, some of which have enlarged while
others have vanished, are found to be imbedded in a pasty
matter, which has the reactions of an alouminoid. From
this time on, the starch-grains are gradually converted

ELEMENTS OF ORGANIZED STRUCTURE. 251

from their surfaces inwardly into smaller grains of aleu-
rone, which, finally, when the seed is mature, completely
occupy the cells.

In the sprouting of the seed similar changes occur, but
in reversed order. The nucleus reappears, the aleurone
dissolves,and even the cellulose * stratified upon the inte-
rior of the cell (Fig. 32) wastes away and is converted into
soluble food (sugar ?) for the seedling plant.

Fig. 33.

The Dimensions of Vegetable Cells are very vari-
ous. Accreeping marine plant is known—the Caulerpa
prolifera (Fig. 33)—which consists of a single cell, though
it is often afoot in length, and is branched with what
have the appearance of leaves and roots. The pulp of

* Or more probably metarabin, paragalactin, xylin, or the like insol-
uble substances, which as yet have been but imperfectly distinguished -
from cellulose in the thickened cell-walls.

252 HOW CROPS GROW.

the orange consists of cells which are one-quarter of an
inch or more in diameter. The fiber of cotton is a single
cell, commonly from one to two inches long. In most
cases, however, the cells of plants are so small as to re-
quire a powerful microscope to distinguish them,—are,
in fact, no more than ydg5 to g¢z Of an inch in diame-
ter. The spores of Fungi are still smaller. The germs
of many bacteria are so minute as to be undiscoverable
by the highest powers of the microscope. :
Growth.—The growth of a plant is nothing more
than the aggregate result of the enlargement and multi-
plication of the cells which compose it. In most cases
the cells attain their full size in a short time. The con-
tinuous growth of plants depends, then, chiefly on the
coustant and rapid formation.of new cells.
Cell-multiplication.—The young and active cell

:
Fig 34, Fig. 35.

always contains a nucleus (Fig. 34, 6). Such a cell may
produce a new cell by division. In this process the nu.
cleus, from which all cell-growth appears to originate, is
observed to resolve itself into two parts, then the proto-
plasm, a, begins to contract or infold across the cell in a
line corresponding with the division of the nucleus, until
the opposite infolded edges meet,—like the skin of a sau-
sage where a string is tightly tied around it,—thus sepa-
rating the two nuclei and inclosing each within its new
cell, which is completed by a further external growth of
cellulose.

©

ELEMENTS OF ORGANIZED STRUCTURE. 2538

In one-celled plants, like yeast (Fig. 35), the new cells
thus formed, bud out from the side of the parent-cell,
and before they obtain full size become entirely detached
from it, or, as in higher plants, the new cells remain ad-
hering to the old, forming a tissue.

In free cell-formation nuclei are observed to develop in
the protoplasm of a parent cell, which enlarge, surround
themselves with their own protoplasm and cell-membrane,
and by the resorption or death of the parent cell become
independent.

The rapidity with which the vegetable cells may mul-
tiply and grow is illustrated by many familiar facts.
The most striking cases of quick growth are met with in
the mushroom family. Many will recollect having seen,
on the morning of a June day, huge puff-balls, some as
large as a peck measure, on the surface of a moist
meadow, where the day before nothing of the kind was
noticed. In such sudden growth it has been estimated
that the cells are produced at the rate of three or four
hundred millions per hour.

Permeability of Cells to Liquids.—Although the
highest magnifying power that can be brought to bear
upon the membranes of the vegetable cell fails to reveal
any apertures in them,—they being, so far as the best-
assisted vision is concerned, completely continuous and
imperforate,—they are nevertheless readily permeable to
liquids. ‘This fact may be shown by placing a delicate
slice from a potato tuber, immersed in water, under the
microscope, and then bringing a drop of solution of
iodine in contact with it. Instantly this reagent pene-
trates the walls of the unbroken cells without perceptibly
affecting their appearance, and, being absorbed by the
starch-grains, at once colors them intensely purplish-
blue. The particles of which the cell-walls and their
contents are composed must be separated from each
other by distances greater than the diameter of the par-

254 ‘HOW CROPS GROw.

ticles of water or of other liquid matters which thus per-
meate the cells.

§ 2.
THE VEGETABLE TISSUES.

As already stated, the cells of the higher kinds of
plants are united together more or less firmly, and thus
constitute what are known as VEGETABLE TissuEs. Of
these, a large number have been distinguished by vege-
table anatomists, the distinctions being based either on
peculiarities of form or-of function. For our purposes
it will be necessary to define but a few varieties, viz.:
Cellular Tissue, Wood-Tissue, Bast-Tissue and Vas-
cular Tissue.

Cellular Tissue, or Parenchyma, is the simplest of
all; being a mere aggregation of globular or polyhedral
cells whose walls are in close adhesion, and whose juices
commingle more or léss in virtue of. this connection.
Cellular tissue is the groundwork of all vegetable struc-
ture, being the only form of tissue in the simpler kinds
of plants, and that out of which all the other tissues are
developed.

Prosenchyma is a name applied to all tissues composed
of elongated cells, like those of wood and bast. Paren-
chyma and prosenchyma insensibly shade into each
other.

Wood-Tissue, in its simplest form, consists of
cells that are several or many times as long as they are
broad, and that taper at each end to a point. These
spindle-shaped cells cohere firmly together by their sides,
and ‘“‘break joints” by overlapping each other, in this
way forming the tough fibers of wood. Wood-cells are
often more or less thickened in their walls by depositions
of cellulose and other matters, according to their age

VEGETATIVE ORGANS OF PLANTS. 255

and position, and are sometimes dotted and perforated,
as will be explained hereafter—Fig. 53, p. 301.

Bast-Tissue is made up of long and slender cells,
similar to those of wood-tissue, but commonly more del-
icate and flexible. The name is derived from the occur-
rence of this tissue in the bast, or inner bark. Linen,
hemp, and most textile materials of vegetable origin,
cotton excepted, consist of bast-fibers. Bast-cells occupy
a place in rind, corresponding to that held by wood-
cells in the interior of the stem—Fig. 49, p. 293.

Vascular Tissue is the term applied to those un-
branched Tubes and Ducts which are found in all the
higner orders of plants, interpenetrating the cellular
tissue. There are several varieties of ducts, viz., dotied
ducts, ringed or annular ducts, and spiral ducts, of
which illustrations will be given when the minute struc-
ture of the stem comes under notice—Fig. 49, p. 293.

The formation of vascular tissue takes place by a sim-
ple alteration in cellular tissue. A longitudinal series of
adhering cells represents a tube, save that the bore is
obstructed with numerous transyerse partitions. By the
removal or perforation of these partitions a tube is devel-
oped. This removal or perforation actually takes place
in the living plant by a process of absorption.

CHAPTER IIL

THE VEGETATIVE ORGANS OF PLANTS.

§ 1.
THE ROOT.

The roots of plants, with few exceptions, from the
first moment of their development, grow downward. In
general, they require a moist medium. They will form
in water or in moist cotton, and in many cases originate
from branches, or even leaves, when these parts of the
plant are buried in the earth or immersed in water.. It
cannot be assumed that they seek to avoid the light,
because they may attain a full development without
being kept in darkness. The action of light upon them,
however, appears to be unfavorable to their functions.

The Growth of Roots: occurs mostly by lengthen-
ing, and very little or very slowly by increase of thick-
.ness. The lengthening is chiefly manifested toward the
outer extremities of the roots, as was neatly demonstrated
by Wigand, who divided the young root of a sprouted
pea into four equal parts by ink-marks. After three
days, the first two divisions next the seed had scarcely
lengthened at all, while the third was double, and the
fourth eight times its previous length. Ohlerts made
precisely similar observations on the roots of various
kinds of plants. The growth is confined to a space of
about one-sixth of an inch from the tip. (Linnea, 183%,
pp. 609-631.) This peculiarity adapts the roots to
extend ‘through the soil in all directions, and to occupy

256 -

VEGETATIVE ORGANS OF PLANTS. 257

its smallest pores, or rifts. It is likewise the reason that
a root, which has been cut off in transplanting or other-
wise, never afterwards extends in length.

Although the older parts of the roots of trees and of
the so-called root-crops acquire a considerable diameter,
the roots by which a plant feeds are usually thread-like
and often exceedingly slender.

Spongioles.—The tips of the rootlets have been
termed spongioles,: or spongelets, from the idea tNat
their texture adapts them especially to collect food for
the plant, and that the absorption of matters from the
soil goes on exclusively through them. In this sense,
spongioles do not exist. The real living apex of the
root is not, in fact, the outmost extremity, but is situ-
ated a little within that point.

Root-Cap.—The extreme end of the root usually con-
sists of cells that have become loosened and in part
detached from the proper cell-tis-
fy sue of the root, which, therefore,
‘\. shortly perish, and serve merely
jas an elastic cushion or cap to
protect the true termination or
living point of the root in its act
of penetrating the soil. Fig. 36
represents a magnified section of
part of a barley root, showing the
loose cells which slough off from
the tip. These cells are filled
with air instead of sap.

Q
S= 5. A striking illustration of the
aN 4, =
ie. root-cap is furnished by the air-
Big. 36. roots of the so-called Screw Pine

(Pandanus odoratissimus), exhibited in natural dimen-
sions, in Fig. 3%. These air-roots issue from the stem
above the ground, and, growing downwards, enter the
soil, and become roots in the ordinary sense.

17

258 HOW CROPS GROW.

When fresh, the diameter of the root is quite uni-
form, but the parts above the root-cap shrink on dry-
ing, while the root-cap itself retains
nearly its original dimensions, and
thus reveals its different structure.

Distinction between Root and
Stem.—Not all the subterranean
parts of the plant are roots in a
proper sense, although commonly
spoken of as such. The tubers of
the potato and artichoke, and the
fleshy horizontal parts of the sweet-
flag and pepper-root, are merely
underground stems, of which many
varieties exist.

These and all other stems are
easily distinguished from true roots
by the imbricated buds, of which
indications may usually be found on
their surfaces, e. g., the eyes of the
potato-tuber. The side or second-
ary roots are indeed marked in their
earliest stages by a protuberance on
the primary root, but these have noth-
ing in common with the structure of
true buds. The onion-bulb is itself ca
a fleshy bud, as will be noticed subse- Fig. 87,
quently. The true roots of the onion are the fibers
which issue from the base of the bulb. The roots of
many plants exhibit no buds upon their surface, and are
incapable of developing them under any conditions.
Roots of other plants, such as the plum, apple, and pop-
lar, may produce buds when cut off from the parent
plant during the growing season. The roots of the
former perish if deprived of connection with the stem
and leaves. The latter may strike out new stems and

VEGETATIVE ORGANS OF PLANTS. 259

leaves for themselves. Plants like the plum are, there-
fore, capable of propagation by root-cuttings, i. e., by
placing pieces of their roots in warm and moist earth.

Tap-roots.—All plants whose seeds divide into two
seed-leaves or Cotyledons, and whose stems increase
externally by addition of new rings of growth—the
Dicotyledonous plants, or Hxogens—have, at first, a single
descending axis, the fap-root, which penetrates vertically
into the ground. From this central tap-root lateral
roots branch out more or less regularly, and these lateral
-roots subdivide again and again. In many cases, espec-
ially at first, the lateral roots issue from the tap-root
with great order and regularity, as much as is seen in
the branches of the stem of a fir-tree or of a young grape-
vine. In older plants, this order is lost, because the
soil opposes mechanical hindrances to regular develop-
ment. In many cases the tap-root grows to a great
length, and forms the most striking feature of the radi-
cation of the plant. In others it enters the ground but
a little way, or is surpassed in extent by its side branches.
The tap-root is conspicuous in the Canada thistle, dock
(Rumex), and in seedling fruit trees. The upper por-
tion of the tap-root of the beet, turnip, carrot, and rad-
ish expands under cultivation, and becomes a fleshy,
nutritive mass, in which lies the value of these plants
for agriculture. The lateral roots of:other plants, as of
the dahlia and sweet potato, swell out at their extremi-
ties to tubers.

Crown Roots.—Monocotyledonous plants, or Endo-
gens, i. @., plants whose embryos have only one seed-
leaf, or Cotyledon, and whose stems do not increase by
external additions, such as the cereals, grasses, lilies,
palms, etc., have no single descending axis or tap-root,
but produce crown roots, i. e., a number of roots issue
at once from the base of the stem. This is strikingly
seen in the onion and hyacinth, as well as in maize.

260 HOW CROPS GROW.

Rootlets.—This term we apply to the slender roots,
but a few inches long, which are formed last in the
order of growth, and correspond to the larger roots as
twigs correspond to the branches of the stem.

THE OFFICES OF THE Roor are threefold:

1. To fix the plant in the earth and maintain it in an
erect position.

2. To absorb nutriment from the soil for the growth
of the entire plant, and,

3. In case of many plants, especially of those whose
terms of life extend through several or many years, to
serve as a store-house for the future use of the plant.

1. The Firmness with which a Plant is fixed in
the Ground depends upon the nature of its roots. It
is easy to lift an onion from the soil; a carrot requires
much more force, while a dock may resist the full
strength of a powerful man.. A small beech or seedling
apple tree, which has a tap-root, withstands the force of
a wind that would prostrate a maize-plant or a poplar,
which has only side roots. In the nursery it is the cus-
tom to cut off the tap-root of apple, peach, and other
trees, when very young, in order that they may be readily
and safely transplanted as occasion shall require. The
depth and character of the soil, however, to a certain
degree influence the extent of the roots and. the tenacity
of their hold. The roots of maize, which in a rich
and tenacious earth extend but two or three feet, have
been traced to a length of ten or even fifteen feet in
a light, sandy soil. The roots of clover, and especially
those of alfalfa, extend very deeply into the soil, and. the
latter acquire in some cases a length of 30 feet. The
roots of the ash have been known as much as 95 feet
long. (Jour. Roy. Ag. Soc., VI, p. 342.)

2. Root-absorption.—The Office of Absorbing
Plant Food from the Soil is one of the utmost impor-
tance, and one for which the root is most wisely adapted
by the following particulars, viz.:

VEGETATIVE ORGANS OF PLANTS. 261

a, The Delicacy of its Structure, especially that of the
newer portions, the cells of which are very soft and ab-
sorbent, as may be readily shown by immersing a young
seedling bean in solution of indigo, when the roois
shortly acquire a blue color from imbibing the liquid,
while the stem is for a considerable time unaltered.

It is a common but erroneous idea that absorption
from the soil can only take place through the ends of the
roots—through the so-called spongioles. On the con-
trary, the extreme tips of the rootlets cannot take up liq-
uids at all. (Ohlerts, Joc. cit., see p. 270.) All other
parts of the roots, which are still young and delicate in
surface-texture, are constantly active in the work of im-
bibing nutriment from the soil.

In most perennial plants, indeed, the larger branches
of the roots become after a time coated with a corky or
otherwise nearly impervious cuticle, and the function of
absorption is then transferred to the rootlets. This is
demonstrated by placing the old, brown-colored roots of
a plant in water, but keeping the delicate and unindu-
rated extremities above the liquid. Thus situated, the
plant withers nearly as soon as if its root-surface were all
exposed to the air.

6. Its Rapid Extension in Length, and the vast Sur-
face which it puts in contact with the soil, further adapts
the root to the work of collecting food. The length of
roots in a direct line from the point of their origin is
not, indeed, a criterion by which to judge of the effi-
ciency wherewith the plant to which they belong is nour-
ished ; for two plants may be equally flourishing—be
equally fed by their roots—when these organs, in one
case, reach but one foot, and in the other extend two feet
from the stem to which they are attached. In-one case,
the roots would be fewer and longer; in the other,
shorter and more numerous. Their aggregate length,
or, more correctly, the aggregate absorbing surface,
would be nearly the same in both.

262 HOW CROPS GROW.

The Medium in which Roots Grow has a great infiu-
ence on their extension. When they are situated in con-
centrated solutions, or in a very fertile soil, they are
short, and numerously branched. Where their food is
sparse, they are attenuated, and bear a comparatively
small number of rootlets. Ilustrations of the former
condition are often seen; moist bones and masses of
manure are not infrequently found, completely covered
and penetrated by a fleece of stout roots. On the other
hand, the roots which grow in poor, dry soils are very
long and slender.

Nobbe has described some experiments which com-
pletely establish the point under notice. (Vs. St., IV,
p. 212.) He allowed maize to grow in a poor clay soil,.
contained in glass cylinders, each vessel having in it a
quantity of a fertilizing mixture disposed in some pecu-
liar manner for the purpose of observing its influence on
the roots. When the plants had been nearly four months
in growth, the vessels were placed in water until the earth
was softened, so that by gentle agitation it could be com-
-pletely removed from the roots. The latter, on being
suspended in a glass vessel of water, assumed nearly the
position they had occupied in the soil, and_it was ob-
served that, where the fertilizer had been thoroughly
mixed with the soil, the roots uniformly occupied its
entire mass. Where the fertilizer had been placed in a
horizontal layer at the depth of about one inch, the roots
at that depth formed a mat of the finest fibers. Where
the fertilizer was situated in a horizontal layer at half the.
depth of the vessel, just there the root system was sphe-
roidally expanded. In the cylinders where the fertilizer
formed a vertical layer on the interior walls, the external
roots were developed in numberless ramifications, while
the interior roots were comparatively unbranched. In
pots, where the fertilizer was disposed as a central vertical
core, the inner roots were far more greatly developed

VEGETATIVE ORGANS OF PLANTS. 263

than the outer ones. Finally, in a vessel where the fer-
tilizer was placed in a horizontal layer at the bottom,
the roots extended through the soil, as attenuated and
slightly branched fibers, until they came in contact with
the lower stratum, where they greatly increased and ram-
ified. In all cases, the principal development of the
roots occurred in the immediate vicinity of the material
which could furnish them with nutriment.

It has often been observed that a plant whose aerial
branches are symmetrically disposed about its stem, has
the larger share of its roots on one side, and again we find
roots which are thick with rootlets on one side and
nearly devoid of them on the other.

Apparent Search for Food.—It would almost appear,
on superficial consideration, that roots are endowed with
a kind of intelligent instinct, for they seem to go in
search of nutriment.

The roots of a plant make their first issue independ-
ently of the nutritive matters that may exist in their
neighborhood. They are organized and put forth from
the plant itself, no matter how fertile or sterile the me-
dium that surrounds them. When they attain a certain
development, they are ready to exercise their office of
collecting food. If food be at hand, they absorb it, and,
together with the entire plant, are nourished by it—they
grow in consequence. The more abundant the food, the
better they are nourished, and the more they multiply.
The plant -sends out rootlets fn all directions; those
which come in contact with food, live, enlarge, and ram-
ify; those which find no nourishment, remain undevel-
oped or perish.

The Quantity of Roots actually belonging to any Plant
is usually far greater than can be estimated by roughly
lifting them from the soil. To extricate the roots of
wheat or clover, for example, from the earth, completely,
is a matter of extreme difficulty. Schubart was the first

264 HOW CROPS GROW.

to make satisfactory observations on the roots of several
important crops, growing in the field. He separated
them from the soil by the following expedient : An exca-
vation was made in the field to the depth of 6 feet, and :
a stream of water was directed against the vertical wall
of soil until it was washed away, so that the roots of the
plants growing in it were laid bare. The roots thus ex-
posed in a field of rye, in one of beans, and in a bed of
garden peas, presented the appearance of a mat or felt of
white fibers, to a depth of about 4 feet from the surface
of the ground. The roots of winter wheat he observed
as deep as 7 feet, in a light subsoil, forty-seven days after
sowing. ‘The depth of the roots of winter wheat, winter
rye, and winter colza, as well as of clover, was 3 to 4 feet.
The roots of clover, one year old, were 34 feet long, those
of two-year-old clover but four incheslonger. The quan-
tity of roots in per cent of the entire plant in the dry
state was found to be as follows. (Chem. Ackersmann,
I, p. 193.)

Winter WEAR examined last of April............. N%
- “ “ 66 MAY. eee cece ceee es 22%
“rye a fe SE BPP Vareisiersisreinssiniacesd 34“

Peas examined four weeks after sowing........... 44%

“ fs atthe time of blossom.............. aA

Hellriegel has likewise studied the radication of barley
and oats (Hoff, Jahresbericht, 1864, p. 106.) He raised
plants in large glass pots, and separated their roots from
the soil by careful washing with water. He observed
that directly from the base of the stem 20 to 30 roots
branch-off sideways and downward. ‘These roots, at
their point of issue, have a diameter of J, of an inch,
but a little lower the diameter diminishes to about 1}, of
an inch. Retaining this diameter, they pass downward,
dividing and branching to a certain depth. From these
main roots branch out innumerable side roots, which
branch again, and so on, filling every crevice and pore of
the soil.

VEGETATIVE ORGANS OF PLANTS. 265

To ascertain the total length of root, Hellriegel weighed

and ascertained the length of selected average portions.
Weighing then the entire root-system, he calculated the
entire length. He estimated the length of the roots of a
vigorous barley plant at 128 feet, that of an oat plant at
150 feet.* He found that a small bulk of good fine soil
sufficed for this development ; gy cubic foot (4-+-4-+ 23
in.) answered for a barley plant, », cubic foot for an
oat plant, in these experiments.
' Hellriegel observed also that the quality of the soil in-
fluenced the development. In rich, porous, garden-soil,
en y a barley plant produced 128 feet of
we \ roots, but in a coarse-grained, com-
pacter soil, a similar plant had but 80
feet of roots.

Root Hairs.—The real absorbent
surface of roots is, in most cases, not
to be appreciated without microscopic
aid. The roots of the onion and of
many other bulbs, i. e., the fibers which
issue from the base of the bulbs, are per-
fectly smooth and unbranched through-
out their entire length. Other agricul-
tural plants have roots which are not
only visibly branched, but whose finest
fibers are more or less thickly covered
with minute hairs, scarcely perceptible
to the unassisted eye. These root-hairs
consist always of tubular elongations of
the external root-cells, and through
them the actual root-surface exposed
to the soil becomes something almost

Fig. 38, incalculable. The accompanying fig-
ures illustrate the appearance of root-hairs.

Fig. 38 represents a young mustard seedling. A is

*Rhenish, 34= 35 English feet.

266 HOW CROPS GROW.

the plant, as carefully lifted from the sand in which it
grew, and B the same plant, freed from adhering soil
by agitating in water. The entire root, save the tip,
is thickly beset with hairs. In Fig. 39 a minute portion
of a barley-root is shown highly magnified. The hairs
are seen to be slender tubes that proceed from, and form
part of, the outer cells of the root.

‘The older roots lose their hairs, and suffer a thicken-
ing of the outermost layer of cells. These dense-walled
and nearly impervious cells cohere together and consti-
tute a rind, which is not found in the young and active
roots.

As to the development of the
root-hairs, they are more abund- /
ant in poor than in’ good soils,
and’ appear to be most numer-
ously produced from roots which
have otherwise a dense and un-
absorbent surface. The roots of.
those plants which are destitute
of hairs are commonly of consid-
erable thickness and remain
white and of delicate texture, :
preserving their absorbent power Big: 8D.
throughout the whole time that the plant feeds from the
soil, as is the case with the onion. :

The Silver Fir (Adies Picea) has no root-hairs, but its
rootlets are covered with a very delicate cuticle highly
favorable to absorption. The want of root-hairs is fur-
ther compensated by the great number of rootlets which
are formed, and which, perishing mostly before they be-
come superficially indurated, are continually replaced by
new ones during the growing season. . (Schacht, Der
Baum, p. 165.) ;

Contact of Roots with the Soil.—The root-hairs, as
they extend into the soil, are naturally brought into close

VEGETATIVE ORGANS OF PLANTS. 267

268 HOW CROPS- GROW.

contact with its particles, This contact is much more
intimate than has been usually supposed. If we care-
fully lift a young wheat-plant from dry earth, we notice
that each rootlet is coated with an envelope of soil. This.
adheres with considerable tenacity, so that gentle shak-
ing fails to displace it, and if it be mostly removed by

Fig. 42.

vigorous agitation or washing, the root-hairs are either
found to be broken, or in many places inseparably at-
tached to the particles of earth.

Fig. 40 exhibits the appearance of a young wheat-

VEGETATIVE ORGANS OF PLANTS. 269

plant as lifted from the soil and pretty strongly shaken.
S, the seed; 0, the blade; e, roots covered with hairs
and enveloped in soil. Only the growing tips of the
roots, w, which have not put forth hairs, come out clean
of soil. Fig. 41 represents tlie roots of a wheat-plant
one month older than those of the previous figure. In
this instance not only the root-tips are naked as before,
but the older parts of the primary roots, e, and of the
secondary roots, m, no longer retain the particles of soil ;
the hairs upon them being, in fact, dead and decom-
posed. The newer parts of the root alone are clothed
with active hairs, and to these the soil is firmly attached
as before. The next illustration, Fig. 42, exhibits the
j appearance of root-hairs with ad-
hering particles of earth, when mag-

nified 800 diameters: A, root-hairs
of wheat-seedling, like Fig. 40; B,
of oat-plant, both from loamy soil.
Here is plainly seen the intimate
attachment of the soil and rcot-
hairs. The latter, in forcing their
way against considerable pressure,
often expand around, and partially
envelop, the particles of earth.
(Sachs’s Exp. Phys. d. Pflanzen.)
Imbibition of water by the root.—
The force with which active roots
imbibe the water of the soil is
sufficient to force the liquid upward
into the stem and to exert a continu-
al pressure on all parts of the plant.
When the stem of a plant in vigor-
= ous growth is cut off near the root,
Fig. 48. and a pressure-gauge is attached to
it, as in Fig. 43, we have the means of observing and
measuring the force with which the roots absorb water.

270 HOW CROPS GROW.

The pressure-gauge contains a quantity of mercury in
the middle reservoir, 6, and the tube, c. It is attached
to the stem of the plant, p, by a stout india-rubber
pipe, g.* For accurate measurements, the space @ and
6 should be filled with water. Thus arranged, it is found
that water will enter a through the stem, and the mer-
cury will rise in the tube, e, until its pressure becomes
sufficient to balarce the absorptive power of the roots.
Stephen Hales, who first experimented in this manner
(1721) found in one instance that the pressure exerted
on a gauge, attached in spring-time to the stump of a
grape-vine, supported a column of mercury 324 inches
high, which is equal to a column of water of 364 feet.
Hofmeister obtained on other plants, rooted in pots, the
following results :
- Bean (Phaseolus multiflorus) 6 inches of mercury.

Nettle. sessed scaieicnesecaes 14 ee es

Vined; eupasanccoguanviesaiee a9 “

The seat of absorption Dutrochet demonstrated to be
the surface of the young and active roots. At least, he
found that absorption was exerted with as much force
when the gauge was applied to near the lower extremity
of a root as when attached in the vicinity of the stem.
In fact, when other conditions are alike, the column of
liquid sustained by the roots of a plant is greater the less
the length of stem that remains attached to them. The
stem thus resists the rise of liquid in the plant.

While the seat of absorptive power in the root lies
near the extremities, it appears from the experiments of
Ohlerts that the extremities themselves are incapable of
imbibing water. In trials with young pea, flax, lupine
and horseradish plants with unbranched roots, he found
that they withered speedily when the tips of the roots
were immersed for about one-fourth of an inch in water,

*For experimenting on small plants. a simple tube of glass may be
adjusted to the stump vertically by help of a rubber connector.

VEGETATIVE ORGANS OF PLANTS. 271

the remaining parts being in moist air. Ohlerts like-
wise proved that these plants flourish when only the
middle part of their roots is immersed in water. Keep-
ing the root-tips, the so-called spongioles, in the air, or
cutting them away altogether, was without apparent
effect on the freshness and vigor of the plants. The
absorbing surface would thus appear to be confined to
those portions of the root upon which the development
of root-hairs is noticed.

The absorbent force is manifested by the active root-
lets, and most vigorously when these are in the state of
most rapid development. For this reason we find, in
case of the vine, for example, that during the autumn,
when the plant is entering upon a period of repose from
growth, the absorbent power is trifling. Sometimes
water is absorbed at the roots so forcibly as not only to
distend the plant to the utmost, but to cause the sap of
the plant to exude in drops upon the foliage. This may
be noticed upon newly-sprouted maize, or other cereal
plants, where the water escapes from the leaves at their
extreme tips, especially when the germination has pro-
ceeded under the most favorable conditions for rapid
development.

The bleeding of the vine, when severed in the spring-
time, the abundant flow of sap from the sugar-maple
and the water-elm, are striking illustrations of this
imbibition of water from the soil by the roots. These
examples are, indeed, exceptional in degree, but not in
kind. Hofmeister has shown that the bleeding of a sev-
ered stump is a general fact, and occurs with all plants
when the roots are active, when the soil can supply them
abundantly with water, and when the tissues above the
absorbent parts are full of this liquid. When it is other-
wise, water may be absorbed from the gauge into the
stem and large roots, until the conditions of activity are
renewed. .

272 HOW CROPS GROW.

Of the external circumstances that affect this absorp-
tive power, heat and light would appear to be influential.
By observing a gauge attached to the stump of a plant
during a clear summer day, it will be usually noticed
that the mercury begins to rise in the morning as the
sun warms the soil, and continues to ascend for a num-
ber of hours, but falls again as the sun declines. Sachs
found in some of his experiments that, in case of potted
tobacco and squash plants, absorption was nearly or
entirely suppressed by cooling the roots to 41° F., but
was at once renewed by plunging the pots into warm
water.

The external supplies of water,—in case a plant is
stationed in the soil, the degree of moisture contained in
this medium,—obviously must influence any manifesta-
tion of the imbibing force. But full investigation shows
that this regular daily fluctuation is a habit of the plant
which is independent of small changes of temperature.
and even of considerable variation in the amount-of mois-
ture of the soil.

The rate of absorption,is subject to changes depend-
ent on causes not well understood. Sachs observed
that the amount of liquid which issued from potato
stalks cut off just above the ground underwent great
and continual variation from hour to hour (during rainy
weather) when the soil was saturated with water and
when the thermometer indicated a constant temperature.
Hofmeister states that the formation of new roots and
buds on the stump is accompanied by a sinking of the
water in the pressure-gauge.

Absorption of Nutriment from the Soti. —The food of
the plant, so far as it is derived from the soil, enters it
in a state of solution, and is absorbed with the water
which is taken up by the rootlets. ‘Ihe absorption of
the matters dissolved in water is in some degree inde-
pendent of the absorption of the water itself, the plant

fad

VEGETATIVE ORGANS OF PLANTS. 273

having apparently, to a certain extent, a selective power.
See p. 401.

8. The Root as a Magazine.—In Fleshy Tap-
Roots, like those of the carrot, beet, and turnip, the
absorption of nutriment from the soil takes place princi-
pally, if. not entirely, by means of the slender rootlets
which proceed abundantly from all their surface, and
especially from their lower extremities, while the older
fleshy part serves as a magazine in which large quantities
of carbhydrates, etc., are stored up during the first year’s
growth of these diennial plants, to supply the wants of
the flowers and seed which are developed the second year.
When one of these roots, put into the ground for a sec-
ond year, has produced seed, it is found to be quite
exhausted of the nutritive matters which it previously
contained in so large quantity.

Root Tubers, like those of the dahlia and sweet potato,
are fleshy enlargements of lateral or secondary roots
filled with reserve material, from which buds and new
steas may develop. Small tubers (Zudercles) are fre-
quently formed on the roots of the garden bean
(Phaseolus).

In cultivation, the farmer not only greatly increases
the size of these roots and the stores of organic nutritive
materials they contain, but, by removing them from the
ground in autumn, he employs to feed himself and his
cattle the substances that nature primarily designed to,
nourish the growth of flowers and seeds during another
summer.

Soil-Roots ; Water-Roots; Air-Roots.—We may
distinguish, according to the medium in which they are
formed and grow, three kinds of roots, viz.: soil-roots,
water-roots, and air-roots.

Most agricultural plants, and indeed by far the greater
number of all plants found in temperate climates, have
roots adapted especially to the soil, and which perish by

18

274 HOW CROPS GROW.

short exposure to dry air, or rot, if long immersed in
water. Many aquatic plants, on the other hand, speed-
ily die when their roots are removed from water, or from
earth saturated with water, and exposed to the atmos-
phere or stationed in earth of the usual dryness.

Air-roots are not common except among tropical plants
or under tropical conditions of heat and moisture, In-
dian corn, when thickly planted and of rank growth,
often throws out roots from the lower joints of the stem,
which extend through the air several inches before they
reach the soil. The same may be observed of many com-
mon plants, as the oat, grape, potato, and buckwheat,
when they long remain in hot, moist air. The Banyan-
tree of India sends out from its branches, vertically,
pendants several yards long which penetrate the earth
and there become soil-roots.

On the other hand, various tropical plants, especially

Orchids, emit roots which hang free in the air and never
reach the earth. In the humid farest ravines of Madeira
and Teneriffe, the Laurus Canariensis, a large tree,
sends out from its stem, during the autumn rains, a pro-
fusion of fleshy air-roots, which cover the trunk with
their interlacing branches and grow to ax inch in thick-
ness. The following summer they dry away and fall to
the ground, to be replaced by new ones in the ensuing
autumn. (Schacht, Der Baum, p. 172.)
.~- Aplant, known to botanists as the Zamia spiralis, not
only throws out air-roots, ec, Fig. 44, from the crown of
the main soil-root, but the side rootlets, 6, after extend-
ing some distance horizontally in the soil, send, from the
same point, roots downward and upward, the latter of
which, d, pass into and remain permanently in the air.
ais the stem of the plant. (Schacht, Anatomie der
Gewdchse, Bd. II, p. 151.)

The formation of air-roots may be very easily observed
by placing water to the depth of half an inch in a tall

VEGETATIVE ORGANS OF PLANTS. 275

vial, inserting a sprig of the common greenhouse-plant
Tradescantia zebrina, so that the cut end of the stem
shall stand in the water, and finally corking the vial air-
tight. The plant, which is very tenacious of life, and
usually grows well in spite of all neglect, is not checked
in its vegetative development by the treatment just de-
scribed, but immediately begins to adapt itself to its
new circumstances. In a few days, if the temperature
be 70° or thereabout, air-roots will be seen to issue from
the joints of the stem. These are fringed with a profu-
sion of delicate hairs, and rapidly extend to a length of
from one to two inches. The lower ones, if they chance

Fig. 44.
to penetrate the water, become discolored and decay ; the
others, however, remain for a tome time fresh, and of a
white color.
Some plants have roots which are equally able to exist
and perform their functions, whether in the soil or sub-

276 HOW CROPS GROW.

merged in water. Many forms of vegetation found in
our swamps and marshes are of this kind. Of agricul-
tural plants, rice is an example in point. Rice will grow
in a soil of ordinary character, in respect of moisture, as
the upland cotton-soils, or even the pine-barrens of the
Carolinas. It flourishes admirably i in the tide-swamps of '
the coast, where the land is laid under water for weeks
at a time during its growth, and it succeeds equally well
in fields which are flowed from the time of planting to
that of harvesting. (Russell, Morth America, its Agri-
culture and Climate, p. 176.) The willow and alder,
trees which grow on the margins of streams, send a part
of their roots into soil that is constantly saturated with
water, or into the water itself; while others Oconpy the
merely moist or even dry earth.

Plants that customarily confine their growth to the
soil occasionally throw out roots as if in search of water,
and sometimes choke up drain-pipes or even wells by the
profusion of water-roots which they emit. At Welbeck,
England, a drain was completely stopped by roots of
horse-radish plants at a depth of 7 feet. At Thornsby
Park, a drain 16 feet deep was stopped entirely by the
roots of gorse, growing at a distance of 6 feet from the
drain. (Jour. Roy. Ag. Soc., I, p. 364.) In New
Haven, Connecticut, certain wells are so obstructed by the
aquatic roots of the elm trees as to require cleaning out
every two or three years. This aquatic tendency has
been repeatedly observed in the poplar, cypress, laurel,
turnip, mangel-wurzel, and various grasses.

Henrici surmised that the roots which most cultivated
plants send down deep into the soil, even when the latter
is by no means porous or inviting, are designed especially
to bring up water from the subsoil for the use of the
plant. He devised the following experiment, which ap-
pears to prove the truth of this view. On the 13th of
‘May, 1862, a young raspberry plant, having but two

.

VEGETATIVE ORGANS OF PLANTS. Q1G

leaves, was transplanted into a large glass funnel filled
with garden soil, the throat of the funnel being closed
with a paper filter. The funnel was supported in the
mouth of a large glass jar, and its neck reached nearly to
the bottom of the latter, where it just dipped into a
quantity of water. The soil in the funnel was at first
kept moderately moist by occasional waterings. The
plant remained fresh and slowly grew, putting forth new
leaves. After the lapse of several weeks, four strong
roots penetrated the filter and extended down the empty
funnel-neck, through which they emerged, on the 21st
of June, and thenceforward spread rapidly in the water
of the jar. From this time on, the soil was not watered
any more, but care was taken to maintain the supply in
the jar. The plant continued to develop slowly; its
leaves, however, did not acquire a vivid green color, but
remained pale and yellowish ; they did not wither until
the usual time, late in autumn. The roots continued to
grow, and filled the water more and more. Near the
end of December the plant had seven or eight leaves, and
a height of eight inches. The water-roots were vigorous,
very Jong, and beset with numerous fibrils and buds. In
the funnel tube the roots made a perfect tissue of fibers.
In the dry earth of the funnel they were less extensively
developed, yet exhibited some juicy buds. The stem
and the young axillary leaf-buds were also full of sap.
The water-roots being cut away, the plant was put into
_garden soil and placed in a conservatory, where it grew
vigorously, and in May. bore two offshoots. (Henneberg’s
Jour. fur Landwirthschaft, 1863, p. 280.) This growth
towards water must be accounted for on the principles
asserted in the paragraph, Apparent Search for Food
(p. 263).
The seeds of many ordinary land plants—of plants,
indeed, that customarily grow in a dry soil, such as the
bean, squash, maize, etc.—will readily germinate in

278 HOW CROPS GROW.

moist cotton or sawdust, and if, when fairly sprouted,
the young plants have their roots suspended in water,
taking care that the seed and stem are kept above the
liquid, they will continue to grow, and with due supplies
of nutriment will run through all the customary stages
of development, produce abundant foliage, blossoms, and
perfect seeds, without a moment’s contact of their roots
with soil, (See Water Culture, p. 181.)

In plants thus growing with their roots in a liquid
medium, after they have formed several large leaves, be
carefully transplanted to the soil, they wilt and perish,
unless frequently watered ; whereas similar plants, started
in the soil, may be transplanted without suffering in the
slightest degree, though the soil be of the usual dryness,
and receive no water.

‘The water-bred seedlings, if abundantly watered as
often as the foliage wilts, recover themselves after a time,
and thenceforward continue to grow without the need of
watering.

It might appear that the first-formed water-roots are
incapable of feeding the plant from a dry soil, and hence
the-soil must be at first profusely watered ; after a time,
however, new roots are thrown out, which are adapted to
the altered situation of the plant, and then the growth
proceeds in the usual manner.

The reverse experiment would seem to confirm this
view. Ifa seedling that has grown for a short time only
in the soil, so that its roots are but twice or thrice
branched, have these immersed in water, the roots
already formed mostly or entirely perish in a short time.
They indeed absorb water, and the plant is sustained by
them, but immediately new roots grow from the crown
with great rapidity, and take the place of the original
roots, which becomie disorganized and useless. It is,
however, only the young and active rootlets, and those
covered with hairs, which thus refuse to live in water.

VEGETATIVE ORGANS OF PLANTS. 279

The older parts of the roots, whieh are destitute of fibrils
and which have nearly ceased to be active in the work of
absorption, are not affected by the change of circum-
stance. These facts, which are due to the researches of
Dr. Sachs (Vs. S¢., II, p. 13), would naturally lead to
the conclusion that the absorbeut surface of the root un-
dergoes some structural change, or produces new roots
with modified characters, in order to adapt itself to the
medium in which it is placed. It would appear that
when this adaptation proceeds rapidly the plant is not
permanently retarded in its growth by a gradual change
in the character of the medium which surrounds its
roots, as may happen in case of rice and marsh-plants,
when the saturated soil in which they may be situated at
one time is slowly dried. Sudden changes of medium
about the roots of plants slow to adapt themselves would
be fatal to their existence.

Nobbe has, however, carefully compared the roots of
buckwheat, as developed in the soil, with those emitted
in water, without being able to observe any structural
differences. The facts above detailed admit of partial, if
not complete, explanation, without recourse to the suppo-
sition that soil- and water-roots are essentially diverse in
nature. When a plant which is rooted in the soil is
taken up so that the fibrils are not broken or injured,
and set into water, it does not suffer any hindrance in
growth, as Sachs found by his later experiments. (2-
perimental Physiologie, p. 17%.) Ordinarily, the suspen-
sion of growth and decay of fibrils and rootlets is due,
doubtless, to the mechanical injury they suffer in remov-
ing from the soil. Again, when a plant that has been
reared in water is planted in earth, similar injury occurs
in packing the soil about the roots, and moreover the
fibrils cannot be brought into that close contact with the
soil which is necessary for them to supply the foliage
with water ; hence the plant wilts, and may easily perish

280 HOW CROPS GROW.

unless profusely watered or shielded from evaporation.

The air-roots of Orchids, which never reach the soil,
have a peculiar spongy texture and take up the water
which exists as vapor in the air, as shown by the experi-
ments of Unger, Chatin, and Sachs. Duchartre’s inves-
tigations led him to deny their absorptive power. | (Ele-
ments de Botanique, p. 216.) In his experiments made
on entire plants, the air-roots failed to make good the
loss by evaporation from the other parts of the plant.

It is evident from common observation that moisture
is the condition that chiefly determines root-develop-
ment. Not only do all seeds sprout and send forth roots
when provided with abundant moisture at suitable tem-
peratures, but generally -older roots and stems, and
fleshy leaves, or cuttings from these, will produce new
rootlets when properly circumstanced as regards moisture,
whether that moisture be supplied by aid of a covering
of damp soil, wet sand or paper, by stationing in humid
air, or by immersion in water itself.

Root-Excretions.—It was formerly supposed that
the roots of plants perform a function of excretion, the
reverse of absorption—that plants, like animals, reject
matters which are no longer of use in their organism,
and that the rejected matters are poisonous to the kind
of vegetation from which they originated. De Candolle,
an eminent French botanist, who first advanced this doc-
trine, founded it upon the observation that certain plants
exude drops of liquid from their roots when these are
placed in dry sand, and that odors exhale from the roots
of other plants. Numerous experiments have been in-
stituted at various times for the purpose of testing this
question. Noteworthy are those of Dr. Alfred Gyde
(Trans. Highland and Agr. Soc., 1845-47, pp. 273-92).
This experimenter planted a variety of agricultural plants,
viz., wheat, barley, oats, rye, beans, peas, vetches, cab-
bage, mustard, and turnips, in pots filled either with .

VEGETATIVE ORGANS OF PLANTS. 281

garden soil, sand, moss, or charcoal, and after they had
attained considerable growth, removed the earth, etc.,
from their roots by washing with water, using care not
to injure or wound them, and then immersed the roots
in vessels of pure water. The plants were allowed to re-
main in these circumstances, their roots being kept in
darkness, but their foliage exposed to light, from three
to seventeen days. In most cases they continued appa-
rently in a good state of health. At the expiration of
the time of experiment, the water which had been in
contact with the roots was evaporated, and was found to
leave a very minute amount of yellowish or brown mat-
ter, a portion of which was of organic and the remainder
of mineral origin. Dr. Gyde concluded that plants do
throw off organic and inorganic excretions similar in
composition to their sap; but that the quantity is ex-
ceedingly sinall, and is not injurious to the plants which
furnish them.

In the light of newer investigations touching the
structure of roots and their adaptation to the medium
which happens to invest them, we may well doubt
whether agricultural plants in the healthy state excrete
any solid or liquid matters whatever from their roots.
The familiar excretion of gum, resin, and sugar® from
the stems of trees appears to result from wounds or dis-
ease, and the matters which in the experiments of Gyde
and others were observed to be communicated by the
roots of plants to pure water probably came either from
the continual pushing off of the tips of the rootlets by
the interior growing point—a process always naturally
accompanying the growth of roots—or from the disor-
ganization of the absorbent root-hairs.

Under certain circumstances, small quantities of sol-
uble salts or free acids may indeed diffuse out of the

*From the wounded bark of the sugar-pine (Pinus Lambertiana) of
,California,

282 HOW CROPS GROW.

root-cells into the water of the soil. Thig is, however,
no physiological action, but a purely physical process.

Vitality of Roots.—It appears that in case of most
plants the roots cannot long continue their vitality if
their connection with the leaves be interrupted, unless,
indeed, they be kept at a winter temperature. Hence
weeds may be effectually destroyed by cutting down
their tops; although, in many cases, the process must
be several times repeated before the result is attained.

The roots of our root-crops, properly so-called, viz.,
beets, turnips, carrots, and parsnips, when harvested in
autumn, contain the elements of a second year’s growth
of stem, etc,, in the form of a bud at the crown of the
root. If the crown be cut away from the root, the latter
cannot vegetate, while the growth of the crown itself is
not thereby prevented.

As regards internal structure, the root closely resem-
bles the stem, and what is stated’ of the latter, on subse-
quent pages, applies in all essential points ‘to the former.

§ 2.
THE STEM.

Shortly after the protrusion of the rootlet from a ger-
minating seed, the Stem makes its appearance. It has,
in general, an upward direction, which in many plants
is permanent, while in others it shortly falls to the
ground and grows thereafter horizontally.

All plants of the higher orders have stems, though in
many instances they do not appear above ground, but
extend beneath the surface of the soil, and are usually
considered to be roots.

While the root, save in exceptional cases, does not
develop other organs, it is the special function of the
stem to bear the leaves, flowers, and seed of the plant,.

VEGETATIVE ORGANS OF PLANTS. 283

and even in certain tribes of vegetation, like the cacti,
which have no leaves, to perform the offices of these
organs. In general, the functions of the stem are sub-
ordinate to those of the organs which it bears—the leaves
and flowers. It is the support of these organs, and, it
would appear, only extends in length or thickness with
the purpose of sustaining them mechanically or provid-
ing them with nutriment.

Buds.—In the seed the stem exists in a rudimentary
state, associated with undeveloped leaves, forming a bud.
The stem always proceeds at first from a bud, during all
its growth is terminated by a bud at every growing point,
and only ceases to be thus tipped when it fully accom-
plishes its growth by the production of seed, or dies
from injury or disease.

In the leaf-bud we find a number of embryo leaves
and leaf-like scales, «in close contact and within each
other, but all at-
tached at the base }j
to a central conical |i
axis, Fig. 45. The (|\\
opening of the bud
consists in the
lengthening of this
axis, which is the
stem, and the con-
sequent separation
from each other as |
well as expansion of Fig. 45.
the leaves. If the
rudimentary leaves of a bud be represented by a nest of
flower-pots, the smaller placed within the larger, the
stem may be signified by a rope of India-rubber passed
through the holes in the bottom of the pots. The
growth of the stem may now be shown by stretching the
rope, whereby the pots are brought away from each

284 HOW CROPS GROW.

other, and the whole combination is made to assume the
character of a fully-developed stem, bearing its leaves at
regular intervals; with these important differences, that
the portions of stem nearest the root extend more rap-
idly than those above them, and the stem has within it
the material and the mechanism for the continual for-
mation of new buds, which unfold in successive order.

In Fig. 45, which represents the two terminal buds of
a lilac twig, is shown not only the external appearance
of the buds, which are covered with leaf-like scales,
imbricated like shingles on a roof; but, in the section,
are seen the edges of the undeveloped leaves attached to
the conical axis. All the leaves and the whole stem of
a twig of one summer’s growth thus exist in the bud, in
plan and in miniature. Subsequent growth is but the
development of the plan.

In the flower-bud the same structure is manifest, save
that the rudimentary flowers and fruit are enclosed
within the leaves, and may often-be seen plainly on cut-
ting the bud open.

Nodes; Internodes.—Nodes are those knots or parts -
of the stem where the leaves are attached. The portions
of the stem between the nodes are termed internodes.
It is from the nodes that roots most freely develop when
stems (layers or cuttings) are surrounded by moist air or
soil.

Culms.—The grasses and the common cereal grains
have single, unbranched stems, termed culms in botani-
cal language. The leaves of these plants clasp the stem
entirely at their base, and rest upon a well-defined, thick-
ened node. ;

Branching Stems.—Other agricultural plants besides
those just mentioned, and all the trees of temperate cli-
mates, have branching stems. As the principal or main
stem elongates, so that the leaves arranged upon it sepa-
rate from each other, we find one or more buds at the

VEGETATIVE ORGANS OF PLANTS, 285

point where the base of the leaf or of the leaf-stalk
unites with the stem. From these axillary buds, in case
their growth is not checked, side-stems or branches
issue, which again subdivide in the same manner into
branchlets.

In perennial plants, when young, or in their young
shoots, it is easy to trace the nodes and internodes, or
the points where the leaves are attached and the inter-
vening spaces, even for some time after the leaves, which
only endure for one year, are fallen away. The nodes
are manifest by the enlargement of the stem, or by the
scar, covered with corky matter, which marks the spot
where the leaf-stalk was attached. As the stem grows
older these indications of its early development are grad-
ually obliterated.

In a forest where the trees are thickly crowded, the
lower branches die away from want of light; the scars
resulting from their removal, or short stumps of the
limbs themselves, are covered with a new growth of
wood, so that the trunk finally appears as if it had always
been destitute of branches, to a great height.

‘When all the buds develop normally and in due pro-
portion, the plant, thus regularly built up, has a sym-
metrical appearance, as frequently happens with many
herbs, and also with some of the cone-bearing trees,
especially the balsam-fir.

Latent Buds.—Often, however, many of the buds
remain undeveloped, either permanently or for a time.
Many of the side-buds of most of our forest and fruit
trees fail entirely to grow, while others make no progress
until the summer succeeding their first appearance.
When the active buds are destroyed, either by frosts or
by pinching off, other buds that would else remain
latent are pushed into growth. In this way trees
whose young leaves are destroyed by spring frosts cover
themselves again, after a time, with foliage. In this way,

286 HOW. CROPS GROW.

too, the gardener molds a straggling, ill-shaped shrub or
plant into almost any form,he chooses; for, by removing
branches and buds where they have grown in undue pro-
portion, he not only checks excess, but also calls forth
development in the parts before suppressed. Close
pruning or breaking the young twigs causes abundant
development of flower-buds on fruit trees that otherwise
“yun to wood.”

Adventitious or irregular Buds are produced from
the stems as well as older roots of many plants, when
they are mechanically injured during the growing season.
The soft or red maple and the chestnut, when cut down,
habitually throw out buds and new stems from the
stump, and the basket-willow is annually polled, or pol-
larded, to induce the growth of slender shoots from an
old trunk.

Elongation of Stems.—While roots extend chiefly
at their extremities, we find the stem elongates equally,
or nearly so, in all its contiguous parts, as is manifest
from what has already been stated in illustration of its
development from the bud.

Besides the upright stem, there are a variety of pros-
trate and in part subterranean stems, which may be
briefly noticed.

Runners and Layers are stems that are sent out hor-
izontally just above the soil, and, coming in contact with
the earth, take root, forming new plants, which may
thenceforward grow independently. The gardener takes
advantage of these stems to propagate certain plants.
The strawberry furnishes the most familiar example of
runners, while many of the young shoots of the currant
fall to the ground and become layers. The runner is a
somewhat peculiar stem. It issues horizontally, and
usually bears but few or no leaves. The layer does not
differ from an ordinary stem, except by the circum-
stance, often accidental, of becoming prostrate. Many

VEGETATIVE ORGANS OF PLANTS. 287

plants which usually send out no layers are nevertheless
artificially Zayered by bending their stems or branches to
the ground, or by attaching to them a ball or pot of
earth. The striking out of roots from the layer is in
many cases facilitated by cutigng half through, twisting,
or otherwise wounding the stem at the point where it is
buried in the soil.

The ¢illering of wheat and other cereals, and of many
grasses, is the spreading of the plant by layers. The first
stems that appear from these plants ascend vertically,
but, subsequently, other stems issue, whose growth is,
for a time, nearly horizontal. ‘They thus come in con-
tact with the soil, and emit roots from their lower joints.
From these again grow new stems and new roots in rapid
succession, so that a stool produced from a single kernel
of winter wheat, having perfect freedom of growth, has
been known to carry 50 or 60 grain-bearing culms.
(Hallet, Jour. Roy. Soc. of Eng., 22, p. 372.)

Suckers.—When branches arise from the stem below
the surface of the soil, so that they are partly subter-
ranean and partly aerial, as in the Rose and Raspberry,
they are termed Suckers. These leafy shoots put out
roots from their buried nodes, and may be separated
artificially and used for propagating the plant.

Subterranean Stems.—Of these there are three
forms. They are usually taken to be roots, from the
fact of existing below the surface of the soil. This cir-
cumstance is, however, quite accidental. The pods of
the peanut (Arachis hypogwa) ripen beneath the
ground—the flower-stems lengthening and penetrating
- the earth as soon as the blossom falls; but these stems
are not by any means to be confounded with roots.

Root-stocks, or Rhizomes.—True roots are desti-
tute of leaves. This fact easily distinguishes them from
the rhizome, which is a stem that extends below the sur-
face of the ground. At the nodes of these root-stocks,

288 HOW CROPS GROW.

as they are appropriately named, scales or rudimentary
leaves are seen, and thence roots proper are emitted. In
the axils of the scales may be traced the buds from which
aerial and fruit-bearing stems proceed. Examples of
the root-stock are very cogmon. Among them we may
mention the blood-root and pepper-root as abundant in
the woods of the Northern and Middle States, various
mints, asparagus, and the quack-grass (Agropyrum*
repens) represented in Fig. 46, which infests so many
farms. ach node of the root-stock, being usually sup-
plied with roots, and having latent buds, is ready to
become an independent growth the moment it is detached

Fig. 46.

from its parent plant. In this way quack-grass becomes
especially troublesome, for the more the fields where it
has obtained a footing are tilled the more does it. com-
monly spread and multiply; only oft-repeated harrow-
ing in a season of prolonged dryness suffices for its
extirpation. q.

Corms are enlargements of the base of the stem, bear-
ing leaf-buds either at the summit or side, and may be
regarded as much-shortened rhizomes, with only a few
slightly-developed internodes. Externally they resemble
bulbs. The garden crocus furnishes an example.

Tubers of many plants are fleshy enlargements of the

*Formerly Triticum.

VEGETATIVE ORGANS OF PLANTS. 289

extremities of subterranean stems. Their eyes are the
points where the buds exist, usually three together,
and where minute scales—rudimentary leaves—may be
observed. The common potato and artichoke (Helian-
thus tuberosus) are instances of this kind of tubers.
Tubers serve excellently for propagation. ach eye, or
bud, may become a hew plant. From the quantity of
starch, etc., accumulated in them, they are of great
importance as food. The number of tubers produced by-
a potato-plant appears to be increased by planting orig-
inally at a considerable depth, or by “‘hilling up” earth
around the base of the aerial stems during the early
' stages of its growth. ,

Bulbs are greatly thickened stems, whose leaves—
usually having the form of fleshy scales or concentric coats
—are in close contact with each other, and arise from
nearly a common base, the internodes being undeveloped.
The bulb is, in fact, a permanent bud, usually in part
or entirely subterranean. From its apex, the proper
stem, the foliage, etc., proceed; while from its base
roots are sent out. The structural identity of the bulb
with a bud is shown by the fact that the onion, which
furnishes the commonest example of the bulb, often
bears bulblets at the top of its stem, in place of flowers.
In like manner, the axillary buds of the tiger-lily are
thickened and fleshy, and fall off as bulblets to the
ground, where they produce new plants.

STRUCTURE OF THE StEM.—The stem is so compli-
cated that to discuss it fully would occupy a volume.
For our immediate purposes it is, however, only neces-
sary to notice its structural composition very concisely.

The rudimentary stem, as found in the seed, or the
new-formed part of the maturer stem at the growing
points just below the terminal buds, consists of cellular
tissue, or is an aggregate of rounded and cohering cells,
which rapidly multiply during the vigorous growth of
the plant. 19

290 HOW CROPS GROW.

In some of the lower orders of vegetation, as in mush-
rooms and lichens, the stem, if any exist, always pre-
serves a purely cellular character; but in all flowering
plants the original cellular tissue of the stem, as well as
of the root, is shortly penetrated by vascular tissue,
consisting of ducts or tubes, which result from the
obliteration of the horizontal partitions of cell-tissue,
and by wood-cells, which are many times longer than
wide, and the walls of which are much thickened by
internal deposition.

These ducts and wood-cells, together with some other
forms of cells, are usually found in close connection, and
are arranged in bundles, which constitute the fibers of
the stem. They are always disposed lengthwise in the
stem and branches. They are found to some extent in
the softest herbaceous stems, while they constitute a
large share of the trunks of most shrubs and trees.
From the toughness which they possess, and the manner
in which they are woven through the original cellular
tissue, they give to the stem its solidity and strength.

Flowering plants may be divided into two great classes,
in consequence of important and obvious differences in
the structure of their stems and seeds. These are: 1,
Monocotyledons, or Endogens ; and 2, Dicotyledons, or Exo-
gens. As regards their stems, these two classes of plants
differ in the arrangement of the vascular or woody tissue.

Endogenous Plants are those whose stems enlarge by
the formation of new wood in the interior, and not by
the external growth of concentric layers. The embryos
in the seeds of endogenous plants consist of a single piece
—do not readily split into halves—or, in botanical lan-

guage, have but one cotyledon; hence are called monoco-
tyledonous. Indian corn, sugar-cane, sorghum, wheat,
oats, rye, barley, the onion, asparagus, and all the
grasses, belong to this tribe of plants.

If a stalk of maize, asparagus, or bamboo be cut

VEGETATIVE ORGANS OF PLANTS. 291

across, the fiber-like bundles of ducts and wood-cells are
seen disposed somewhat, uniformly throughout the sec-
tion, though less abundantly towards the center. On
splitting the fresh stalk lengthwise, these vascular bun-
dies may be torn out like strings. At the nodes, where
the stem is branched, or where leaf-stalks are attached,
the vascular bundles likewise divide and form a net-work,
In a ripe maize-stalk which is exposed to circumstances
favoring decay, the soft cell-tissue first suffers change
and often quite disappears, leaving the firmer vascular
bundles unaltered in form. A portion of the base of
such a stalk, cut. lengthwise, is represented in Fig. 47,
where the vascular bundles are seen arranged parallel to
each other in the internodes, and curiously interwoven
and branched at the nodes, both at those (a and b) from
which roots issued, or at that (c) which was clasped by
the base of a leaf.

The endogenous stem, as represented in the maize-
stalk, has no well-defined bark that admits of being

e
Fig. 47.

stripped off externally, and no separate central pith of
soft cell-tissue free from vascular bundles. It, like the
aerial portions of all flowering plants, is covered with a
skin, or epidermis, composed usually of one or several
layers of flattened cells, whose walls are thick, and far
less penetrable to fluid than the delicate texture of the
interior cell-tissue. The stem is denser and harder at
the circumference than towards the center. This is due
to the fact that the bundles are more numerous and
older towards the outside of the stem. .The newer bun-
dles, as they continually form at the base of the growing
terminal bud, pass to the inside of the stem, an’ after-

292 HOW CROPS GROW.

wards outwards and downwards, and hence the designa-
tion endogenous, which in plain English means inside-
grower,

In consequence of this inner growth, the stems of
most woody endogens, as the palms, after a time become
so indurated externally that all lateral expansion ceases,
and the stem increases only in height. In some cases,
the tree dies because its interior is so closely packed with

bundles that the descent of new ones, and the accom-
panying vital processes, become impossible. ;

In herbaceous endogens the soft stem admits the
in lefinite growth of new vascular tissue.

VEGETATIVE ORGANS OF PLANTS. 293

The stems of the grasses are hollow, except at the
nodes. Those of the rushes have a central pith free from
vascular tissue.

The Minute Structure of the Endogenous Stem
is exhibited in the accompanying cuts, which represent
highly magnified sections of a Vasculur Bundle or fiber
from the maize-stalk. As before remarked, the stem is
composed of a groundwork of delicate cell-tissue, in
which bundles of vascular-tissue are distributed. Fig.
48 represents a crags section of one of these bundles, ec,
g, 4, as well as of a portion of the surrounding cell-tis-

@ ce

d h
(i + am
—=

: Ly
.

A se HN 5

sue, a, a. The latter consists of quite large cells, which
have between them considerable inter-cellular spaces, 7.
The vascular bundle itself is composed externally of
, narrow, thick-walled’ cells, of which those nearest the
exterior of the stem, 4, are termed Jdast-cells, as they
correspond in character and position to the cells of the
bast or inner bark of our common trees; those nearest
the center of the stem, ¢, are wood-cells. In the maize
stem, bast-cells and wood-cells are quite alike, and are

Fig. 49.

294. HOW CROPS GROW.

distinguished only by their position. In other plants,
they are often unlike as regards length, thickness, and
pliability, though still, for the most part, similar in
form. Among the wood-cells we observe a number of
ducts, d, e, f, and between these and the bast-cells is a
delicate and transparent tissue, g, which is the camdium,
in which all the growth of the bundle goes on until it
is complete. On either hand is seeu a remarkably large
duct, 6, 6, while the residue of the bundle is composed
of long and rather thick-walled “—

Fig. 49 represents a section made vertically through
the bundle from ¢ tof. In this the letters refer to the
same parts as in the former cut: a, a is the cell-tissue,
enveloping the vascular bundle; the cells are observed
‘to be much longer than wide, but are separated from
each other at the ends as well as sides by an imperforate
membrane. The wood and bast-cells, ¢, h, are seen to
be long, narrow, thick-walled cells running obliquely to
‘a point at either end. The wood-cells of oak, hickory,
and the toughest woods, as well as the bast-cells of flax
and hemp, are quite similar in form and appearance.
The proper ducts of the stem are next in the order of
our section. Of these there are several varieties, as ring-
ducts, d; spiral ducts, e; dotted ducts, f. These are
continuous tubes produced by the absorption of the
transverse membranes that once divided them into such
cells as a, a, and they are thickened internally by ring-
like, spiral, or punctate depositions of cellulose (see Fig.
32, p. 248). Wood or bast-cells that consist mainly of
cellulose are pliant and elastic. It is the deposition of
other matters (so-called lignin) in their walls which ren-
ders them stiff and brittle.

At g, the cambial tissue is observed to consist of del-
icate cylindrical cells. Among these, partial absorption
of the separating membrane often occurs, so that they
communicate directly with each other through sieve-like

Ay

VEGETATIVE ORGANS OF PLANTS. 295

- partitions, and become continuous channels or ducts.
(Sieve-cells, p. 303.) The cambium is the seat of growth
by cell-formation. Accordingly, when a vascular bun-
dle has attained maturity, it no longer possesses a cam-
bium.

To complete our view of the vascular bundle, Fig. 50
represents a vertical section made at right angles to the
last, cutting two large ducts, 4, 6; a, a is cell-tissue;

b j
mi

Fig. 50.

Ly
H
c, ¢ are bast or wood-cells less thickened by interior
deposition than those of Fig. 49; d@ isaring and spiral
duct; 0, b are large dotted. ducts, which exhibit at g, g
the places where they were once crossed by the double
membrane composing the ends of two adhering cells, by
whose absorption and removal an uninterrupted tube
has been formed. In these large dotted ducts there
appears to be no direct communication with the sur-
rounding cells through their sides. The dots or pits

are simply very thin points in the cell-wall, through
which sap may soak or diffuse laterally, but not flow.

————
== =>

TALUOISES:

296 HOW CROPS GROW.

When the cells become mature and cease growth, the
pits often become pores by absorption of the membrane,
so that the ducts thus enter into direct communication
with each other.

Exogenous Plants are those whose stems contin-

ually enlarge in diameter by the formation of new tissue
uear the outside of the stem. They are outside-growers.
Their seeds are usually made up of two loosely-united
parts, or cotyledons, wherefore they are designated
dicotyledonous. All the forest trees of temperate cli-
mates, and, among agricultural plants, the bean, pea,
clover, potato, beet, turnip, flax, etc., are exogens.
_ In the exogenous stem the bundles of ducts and fibers
that appear in the cell-tissue are always formed just
within the rind. They occur at first separately, as in
the endogens, but, instead of being scattered throughout
the cell-tigsue, are disposed in a circle. As they grow,
they usually close up to aring or zone of wood, which
incloses unaltered cell-tissue—the pith.

As the stem enlarges, new rings of fibers may be.
formed, but always outside the older ones. In hard
stems of slow growth the rings are close together and
chiefly consist of very firm wood-cells. In the soft stems
of herbs the cellular tissue preponderates, and the ducts
and cells of the vascular zones are delicate. The harden-
ing of herbaceous stems which takes place as they become.
mature is due to the increase and induration of the
wood-cells and ducts. :

The circular disposition of the fibers in the exogenous
stem may be readily seen in a multitude of common
plants.

The potato tuber is a form of stem always accessible
for observation. If a potato be cut across near the stem-
end with a sharp knife, it is usually easy to identify upon
the section a ring of vascular-tissue, the general course
of which is parallel to the circumference of the tuber

VEGETATIVE ORGANS OF PLANTS. 297

except where it runs out to the surface in the eyes or
buds, and in the narrow stem at whose extremity it
grows. If aslice across a potato be soaked in solution
of iodine for a few minutes, the vascular ring becomes
strikingly apparent. In its active cambial cells, albu-
minoids are abundant, which assume a yellow tinge with
iodine. The starch of the cell-tissue, on the other hand,
becomes intensely blue, making the vascular tissue all
the more evident.

Since the structure of the root is quite similar to that
of the stem, a section of the common beet as well as one
‘of a branch from any tree of temperate latitudes may
serve to illustrate the concentric arrangement of the vas-
cular zones when they are multipled in number.

Pith is the cell-tissue of the center of the stem. In
young stems it is charged with juices; in older ones it
often becomes dead and sapless. In many cases, espec-
ially when growth is active, it becomes broken and nearly
obliterated, leaving a hollow stem, as in a rank pea-vine,
or clover-stalk, or in a hollow potato. In the potato

“tuber the pith-cells are occupied throughout with starch,
although, as the coloration by iodine makes evident, the
quantity of starch diminishes from the vascular zone
towards the center of the tuber.

The Rind, which, at first, consists of mere epidermis,
or short, thick-walled cells, overlying soft cellular tissue,
becomes penetrated with cells of unusual length and
tenacity, which, from their position in the plant, are
termed bast-cells. These, together with ducts of various
kinds, constitute the so-called bast, which grows‘chiefly
upon the interior of the rind, in successive annual layers,
in close proximity to the wood. With their abundant
development and with age, the rind becomes bark as it
occurs on shrubs and trees. The bast-cells give to the
bark its peculiar toughness, and cause it to come off the
stem in long and pliant strips.

298 HOW CROPS GROW.

All the vegetable textile materials employed in the man-
ufacture of cloth and, cordage, with the exception of cot-
ton, as flax, hemp, New Zealand flax, etc., are bast-fibers.
(See p. 248.)

In some plants the annual layers of bast are so sepa-
rated by cellular tissue that in old stems they may be
split from one another. Various kinds of matting are
made by weaving together strips of bast layers, especially
those of the Linden (Bass-wood or Bast-wood) tree. The
leather-wood or moose-wood bark, often employed for
tying flour-bags, has bast-fibers of extraordinary tenacity.
The bast of the grape-vine separates from the stem in
long shreds a year or two after its formation.

The epidermis of young stems is replaced, after a cer-
tain age, by the corky layer. ‘This differs much in dif-
ferent plants. In the Birch it is formed of alternate
layers of large- and small-celled tissue, and splits and
curls up. From the Plane-tree it is thrown off period-
ically in large plates by the expansion of the cellular tis-
sue underneath. Inthe Maple, Elm, and Oak, especially
in the Cork-Oak, it receives annual additions on its
inner side and does not separate: after a time it conse-
quently acquires considerable thickness, the growth of
the stem furrows it with deep rifts, and it gradually
decays or drops away exteriorly as the newer bark forms
within.

Pith Rays.—Those portions of the first-formed cell-
tissue which were interposed between the young and
originally ununited wood-fibers remain, and connect the
pith with the cellular tissue of the bark. They inter-
rupt the straight course of the bast-cells, producing the
netted appearance often seen in bast layers, as in the
Lace-bark. In hard stems they become flattened by
the pressure of the fibers, and are readily seen in most
kinds of wood when split lengthwise. They are espe-
cially conspicuous in the Oak and Maple, and form what

VEGETATIVE ORGANS OF PLANTS. 299
is commonly known as the stlver-grain. The botanist
terms them pith-rays, or medullary
\ rays.

Fig. 51 exhibits a section of
spruce wood, magnified 200 di-
ameters. The section is made
lengthwise of the wood-cells, four
of which are in part represented,
aud cuts across the pith-rays,
whose cell-structure and position
} in the wood are seen at m, n.
Branches have the same struct-
ure as the stems from which they
spring. Their tissues traverse
those of the stem to its center,
\| where they connect with the pith
and its sheath of spiral ducts.
Cambium of Hxogens.—The
Fig. 51. growing part of the exogenous
stem is between the fully formed wood and the ma-
ture bark. There is, in fact, no definite limit where
wood ceases and bark begins, for they are connected by
the cambial or formative zone, from which, on the one
hand, wood-fibers, and on the other, bast-fibers, rapidly
develop. In-the cambium, likewise, the pith-rays which
connect the inner and outer parts of the stem continue
their outward growth.
In spring-time the new cells that form in the cambial
region are very delicate and easily broken. For this
reason the rind or bark may be stripped from the wood
without difficulty. In autumn these cells become thick-
ened and indurated—become, in fact, full-grown bast and
wood-cells—so that to peel the bark off smoothly is im-
possible. :
Minute Structure of Exogenous Stems.—The ac-
companying figure (52) will serve to convey an idea of

h-

a

300 HOW CROPS GROW.

the minute structure of the elements of the exogenous
stem. It exhibits a section lengthwise, through a young
potato tuber magnified 200 diameters ; a, 6 is the rind;
e the vascular ring; f the pith. The outer cells of the
rind are converted into cork. They have become empty
of sap and are nearly impervious to air and moisture.
This corky-layer, a, constitutes the thin coat or skin that
may be so readily peeled off from a boiled potato. When-
ever a potato is superficially wounded, even in winter
time, the exposed part heals over by the formation of

Fig. 52.

cork-cells. The cell tissue of the rind consists at its
center, 3, of full-formed cells with delicate membranes
which contain “numerous and large starch grains. On
either hand, as the rind approaches the corky-layer or
the vascular ring, the cells are smaller, and contain
_ smaller starch grains ; at either side of these are noticed
cells containing no starch, but having nuclei, c, y. These
nucleated cells are capable of multiplication, and they
are situated where the growth of the tuber takes place.
The rind,* which makes a large part of the flesh of the
potato, increases in thickness by the formation of new
cells within and without. Without, where it joins the
corky skin, the latter likewise grows. Within, contigu-

*The word rind is here used in its botanical (not in the ordinary
sense, to denote that part of the tuber which corresponds to the rindo
the stém.

VEGETATIVE ORGANS OF PLANTS. 301

ous to the vascular zone, new ducts are formed. Ina
similar manner, the pith expands by
formation of new cells, where it joins
the vascular tissue. The latter consists,
in our figure, of ring, spiral, and dotted
ducts, like those already described as |
occurring in the maize-stalk. The deli-
cate cambial cells, c, are in the region of
most active growth. At this point new
cells rapidly develop, those to the right,
\¢ in the figure, remaining plain cells and
becoming loosely filled with starch ;
<y those to the left developing new ducts.

In the slender, overground potato-
stem, as in all the stems of most agri-
cultural plants, the same relatiun of
parts is to be observed, although “the
vascular and woody tissues often pre-
ponderate. Waod-cells are especially
abundant in those stems that need
strength for the fulfilment of their offices,
and in them, especially in those of our
trees, the structure isgecommonly more
complicated.

Pitted Wood-Cells of the Coni-
fers.—In the wood of cone-bearing trees
there are no proper ducts, such as have
been described. The large wood-cells which constitute
the concentric rings of the wood are constructed in a spe-
cial manner, being provided laterally with pits, or, accord-
ing to Schacht, with visible pores, through which the
fluid contents of one cell may easily diffuse (by osmose),
or even pass directly into those, of its neighbors.

Fig. 58, B represents a portion of an isolated wood-cell
of the Scotch Fir (Pinus sylvestris) magnified 200 diam-
eters. Upon it are seen nearly circular disks, 2, y, the

302 ‘HOW CROPS GROW.

structure of which, while the cell is young, is shown by
a section through them lengthwise. A exhibits such a
section through the thickened walls of two contiguous
and adhering cells. 2, in both A and B, shows a cavity
between the two primary cell-walls; y is the narrow
part of the channel, that | _ —
remains while the mem- ~
brane thickens around it.
This is seen at y, as a pit
in each cell-wall; or, as
Schacht believed, a pore
or opening from cell to
cell. In A it appears
closed ‘because the section
passes a little to one side
of the pore. (Schacht. )
In the next figure (54),
representing’ a transverse
section of the spring wood
of the same tree magnified
300 diameters, the struct-
ure and the gradual form-
ation of these gore-disks
ismadeevident. The sec-
tion, likewise, gives an in-
structive illustration of
the general character of the
simplest kirid of wood. R Iaolay a
are the young cells of the + £
rind; C is the cambinm, C2
where cell-multiplication Big:
goes on; Wis the wood, whose cells are more developed
the older they are, i. e., the more distant from the cam-
bium, as is seen from their figure and the thickness of
their walls. At @ is shown the disk in its earliest stage ;
6 and c exhibit it in a more advanced growth. At d the

\

VEGETATIVE ORGANS OF PLANTS. 303

disk has become a pore, the primary membrane has been
absorbed, and a free channel made between the two cells.
The dotted lines at d lead out laterally to two concentric
circles, which represent the disk-pore seen flatwise, as in
Fig. 53. At e the section passes through the new
annual ring into the autumn wood of the preceding year.

Sieve-cells, or Sieve-ducts.—The spiral, ring, and
dotted ducts and pitted wood-cells already noticed, ap-
pear only in the older parts of the vascular bundles, and,
although they may be occupied with sap at times when the
stem is surcharged with water, they are ordinarily filled
with air alone. The real transmission of the nutritive
juices of the growing plant, so far as it goes on through
actual tubes, is now admitted to proceed in an independ-
ent set of ducts, the so-called sieve-tubes, which are usu-
ally near to and originate from the cambium. These
are extremely delicate, elongated cells, whose transverse
or lateral walls are perforated, sieve-fashion (by absorp-
tion of the original membrane) so as to establish direct
communication from one to another, and this occurs
while they are yet charged with juices and at a time
when the other ducts are occupied with air alone. These
sieve-ducts are believed to be the channels through which
the organic matters that are formed in the foliage mostly
pass in their downward movement to nourish the stem
and root. Fig. 55 represents the sieve-cells in the over-
ground stem of the potato ; A, B, cross-section of parts
of vascular bundle; A, exterior part towards rind; B,
interior portion next to pith; a, a, cell-tissue inclosing
the smaller sieve-cells, A, B, which contain sap turbid
with minute granules ; 0, cambium cells; ¢, wood-cells
(which are absent in the potato tuber) ; d, ducts inter-
mingled with wood-cells. C represents a section length-
wise of the sieve-ducts ; and D, more highly magnified,
exhibits the finely perforated, transverse partitions,
through which the liquid contents more or less freely
pass.

804 * “HOW CROPS GROW.

Milk Ducts.—Besides the ducts already described,
there is, in many plants, a system of irregularly branched
channels containing a milky juice (latex) as in the

sweet potato, dande- A
lion, milk-weed, ete. sie 3K SON c
These milk-ducts@ o, Lay o(

occur in all parts of |” 3 Gas e
the plants, but most, \
abundantly in the
pith and inner, bark
of stems and in the
cellular tissue of,
roots. They often so
completely permeate
all the organs of the
plant that the slight-
est wound breaks
some of them and
causes a flow of latex.
The latter, like ani-d
mal milk, is a watery
fluid holding in sus-
pension minute gran-
ules or drops which
make it opaqueg’
The latex often con-
tains the organic
substances peculiar
to the plant, acquires
a sticky, viscid char-
acter, and hardens Fig. 55.
on exposure to the air. Opium, India-rubber, gutta-—
percha, and various resins are dried latex. Alkaloids
frequently occur, and ferments like papain (p. 104) are
probably not uncommon in this secretion.

Herbaceous Stems.—Annual stems of the exogenous

VEGETATIVE ORGANS OF PLANTS. 305

kind, whose growth is entirely arrested by winter, consist
usually of a singlé ring “of woody tissue with interior
pith and surrounding bark. Often, however, the zone
of wood is thin, and possesses but little solidity, while
the chief part of the stem is made up of cell-tissue, so
that the stem is herbaceous.

Woody Stems.—Perennial exogenous stems consist,
in temperate climates, of a series of rings or zones, cor-
responding in number with that of the years during
which their growth has been progressing. The stems of
our shrubs and trees, especially after the first few years of
growth; consist, for the most part, of woody tissue, the
proportion of cell-tissue being very small.

The annual cessation of growth which occurs at-the
approach of winter is marked by the formation of smaller
or finer wood-cells, as shown in Fig.-54, e, while the
vigorous renewal of activity in the cambium at spring-
time is exhibited by the growth of larger cells, and in
many kinds of wood in the production of ducts, which,
as in the oak, are visible to the eye at the interior of the
annual layers.

_ Sap-wood and Heart-wood.—The living processes
in perennial stems, while proceeding with most force in
the cambium, are not confined to that locality, but go on .
to a considerable depth in the wood. Except at the
cambial layer, however, these processes consist not in the
formation of new cells, nor the enlargement of those
once formed—not properly in growth—but in the trans-
mission of sap and the deposition of organized matter on
the interior of the wood-cells. In consequence of this
- deposition the inner or heart-wood of many of our forest
trees becomes much denser in texture and more durable
for industrial purposes. It then acquires a color differ-
ent from the outer or sap-wood (alburnum), becomes
brown in most cases, though it is yellow in the barberry
and red in the red cedar.
20 :

306 HOW CROPS GROW.

The final result of the filling up of the cell of the
heart-wood is to make this part of the stem almost or
quite impassable to sap, so that the interior wood may be
removed by decay without disturbing the vigor of the
tree. :

Passage of Sap through the Stem.—The stem,
besides supporting the foliage, flowers and fruit, has also
a most important office in admitting the passage upward
to these organs of the water and mineral matters which
enter the plant by the roots. Similarly, it allows the
downward transfer to the roots of substances gathered
by the foliage from the.atmosphere. To this and other
topics connected with the ascent and descent of the sap
we shall hereafter recur.

The stem constitutes the chief part by weight of many
plants, especially of forest trees, and serves the most im-
portant uses in agriculture, as well as in a thousand other
industries.

§ 3.
LEAVES.

These most important organs issue from the stem, are
, at first folded curiously together in the bud, and after-
wards expand so as to present a great amount of surface
to the air and light.

The leaf consists of a thin membrane of cell-tissue
directly connected with the cellular layer of the bark,
arranged upon a skeleton or net-work of fibers and ducts
continuous with those of the inner bark and wood.

In certain plants, as cactuses, there scarcely exist any
leaves, or, if any occur, they do not differ, except in
external form, from the stems. Many of these plants,
above ground, are in form all stem, while in structure
and function they are all leaf.

In the grasses, although the stem and leaf are distin-

ietOok, 4 Cet, "Cots +K.—Cot.
ec. a. a. b.
PLATE II.

EXPLANATION. (See p. 213.)
Water-cultures of Flowering Bean after vegetating 38 days.
a. In normal solution, seed with cotyledons.
b. In normal solution, seed witbout cotyledons.
c. In potassium-free solution, seed with cotyledons.
d. In potassium-free solution, seed without cotyledons.

VEGETATIVE ORGANS OF PLANTS. 307
guishable in shape, they are but little unlike in other
external characters.

In forest trees, we find the most obvious and striking
differences between the stem and leaves.

Color of Leaves.—A peculiarity most character-
istic of the leaves of the higher orders of plants, so long
as they are in vigorous discharge of their proper vegeta-
tive activities, is the possession of a green color, due to
the presence of Chilorophyl. (See p. 124.) This color
is also proper in most cases to the young bark of the
stem, a fact further indicating the connection between
these parts, or rather demonstrating their identity of
origin and function, for it is true, not only in the case
of the cactuses, but also in that of all other young
plants, that the green (young) stems perform, to some
extent, the same offices as the leaves, the latter being, in
fact, growths from and extensions of the bark.

The loss of green color that occurs in autumn, in the
foliage of our deciduous trees, or on the maturing of the
plant, as with the cereal grains, is related to the cessa-
tion of growth and death of the leaf, and results from
chemical changes in the chlorophyl-pigment.

Plants naturally destitute of chlorophyl, like Indian
pipe (Monotropa), Dodder (Cuscuta), Mushrooms,
Toadstools, and fungi generally, are parasites on living
or dead organisms, from which they derive their nour-
ishment. Such plants cannot construct organic sub-
stances out of inorganic matters, as do the plants having
chlorophyl.

When leaves, ordinarily green, are totally excluded
from light, or develop at a low temperature, they have a
pale yellow color; on exposure to light and warmth they
become green. In both cases the Chlorophyl-granules
are formed, but the chlorophyl-pigment appears only in
the latter. In absence of iron, leaves are white, contain
no chlorophyl] granules, and growth is arrested.

308 HOW CROPS GROW.

There are many leafy plants cultivated for ornamental purposes
with more or less brown, red, yellow, white, or variegated foliage,
which are by no means destitute of chlorophyl, as is shown by micro-
scopic examination, though this substance is associated with other
coloring matters which mask its green tint.

Structure of Leaves.—While in shape, size, modes
of arrangement upon and attachment to the stem, we
find among leaves no end of diversity, there is great sim-
plicity in the matter of their internal structure.

The whole surface of the Jeaf, on both sides, is cov-
ered with epidermis, a coating which, in many cases,
may be readily stripped off the leaf, and consists of thick-
walled cells, which are, for the most part, devoid of liq-
uid contents, except when very young. (#, #, Fig. 56.)

Fig. 56 represents the appearance of a bit of bean-leaf as seen ona
section from the upper to the lower surface, and highly magnified,

Below the upper epidermis, there often occur one or
more layers of oblong cells, whose sides are in close con-
tact, and which are arranged endwise, with reference to
the flat of the leaf. Below these, down to the lower epi-
dermis, for one-half to three-quarters of the thickness of
the leaf, the cells are commonly spherical or irregular in
figure and arrangement, and more loosely disposed, with
numerous and large interspaces.

The interspaces among the leaf-cells are occupied with
air, which is also, in most cases, the
only content of the epidermal cells.
The interior cells of the leaf are filled
with sap and contain the chlorophyl-
granules. Under the microscope, these
{ are commonly seen attached to the walls
of the cells, as in Fig. 56, or coating
“< grains of starch, or else floating free in

. the cell-sap.

(© ‘The structure of the veins or ribs of
the leaf is similar to that of the vascular
Fig. 56 bundles of the stem, of which they are
branches. At a, Fig. 56, is seen the cross section of a
vein in the bean-leaf.

VEGETATIVE ORGANS OF PLANTS. 309

The epidermis, while often smooth, is frequently beset
with hairs or glands, as seen’ in the figure. These are
variously shaped cells, sometimes empty, sometimes, as
in the nettle, filled with an irritating liquid.

Leaf-Pores.—The epidermis of the mature leaf is pro-
vided with a vast number of ‘‘ breathing pores,” or stomata,
by means of which the intercellular spaces in tlie interior
of the leaf are brought into direct communication with
the outer atmosphere. Hach of these stomata consists
usually of two curved guard-cells, which are disposed
toward each other like the
halves of an elliptical car-
riage-spring. (Figs. 52 and
53.) The opening between
them is an actual orifice in
the skin of the leaf. The
‘size of the orifice is, how-
ever, constantly changing,
as the atmosphere becomes
drier or more moist, and as
the sunlight acts more or
less intensely on its surface. In strong light they curve
outwards, and the aperture is enlarged ; in darkness they
straighten and shut together, like the springs of a heavily-
loaded carriage, and nearly or entirely close the entrance.
The effect of water usually is to .
close their orifices.

In Fig. 56 is represented a section
through the shorter diameter of a pore’}
on the under surface of a bean-leaf. +
The air-space within it is shaded black. _
Unlike the other epidermal cells, those
of the leaf-pores contain chlorophyll
granules.

Fig. 57 represents a portion of the epi-
dermis of the upper surface of a potato- of
leaf, and Fig. 58 a similar portion of the Fig. 58.
under surface of the same leaf, magnified
200 diameters. In both figures are seen the open stomata between the
semi-elliptical cells. The outlines of the other epidermal cells are

Fig. 57.

310 HOW CROPS GROW.

marked by irregular double lines. The round bodies in the guard-
cells of the pores are starch-grains, often present in these cells, when
not existing in any other partof the leaf.

The stomata are, with few exceptions, altogether want-
ing’ on the submerged leaves of aquatic plants. On
floating leaves they occur, but only on the upper surface.
Thus, as a rule, they are not found in contact with
liquid water. On the other hand, they are either absent
from, or comparatively few in number upon, the upper
surfaces of the foliage of land plants, which are exposed
to the heat of the sun, while they occur abundantly on
the lower sides of all green leaves. In number and size
they vary remarkably. Some leaves possess but 800 to
the square inch, while others have as many as 170,000 to
that amoynt of surface. About 100,000 may be counted
on an average-sized apple-leaf. In general, they are
largest and most numerous on plants which belong to
damp and shaded situations, and then exist on both sides
of the leaf..

The epidermis itself is most dense—consists of thick-
walled cells and several layers of them—in case of leaves
which belong to the vegetation of sandy soils in hot cli-
mates. Often it is impregnated with wax on its upper
surface, and is thereby made almost impenetrable to
moisture. On the other hand, in rapidly-growing plants
adapted to moist situations, the epidermis is thin and
delicate.

Exhalation of Water-Vapor.—A considerable loss
of water goes on from the leaves of growing plants when
they are freely exposed to the atmosphere. The water
thus lost exhales in the form of invisible vapor. The
quantity of water exhaled from any plant may be easily
ascertained, provided it is growing in a pot of glazed
earthen or other impervious materia]. A metal or glass
cover is cemented air-tight to the rim of the vessel, and
around the stem of the plant. The cover has an open-

VEGETATIVE ORGANS OF PLANTS. 311

ing with a cork, through which weighed quantities of
water are added from time to time, as required. The
amount of exhalation during any given interval of time
is learned with a close approach to accuracy by simply
noting the loss of weight which the plant and pot
together suffer. Hales, who first experimented in this
manner, found that a vigorous sunflower, three and a
half feet high, whose foliage had an aggregate surface of
39 square feet, gave off 30 ounces av. of water in a space
of 12 hours, during a very warm, dry day. The average
‘rate of perspiration” for 15 days, in July and August,
was 20 ouncesav. At night, with ‘any sensible, though
small’ dew, the perspiration was nothing.” Knop
observed a maize-plant to exhale, between May 22d and
September 4th, no less than 36 times its weight of water.
Heliriegel (at Dahme, Prussia) found that summer
wheat and rye, oats, beans, peas, buckwheat, red clover,
yellow lupine and summer colza, on the average exhaled
300 grams of water for 1 gram of dry matter produced
above ground, during the entire season of growth, when
stationed in a sandy soil. (Die Methode der Sandkultur,
p. 662.)

Exhalation is not a regular or uniform process, but
varies with a number of circumstances and conditions.
It depends largely upon the dryness and temperature of
the air. When the air is in the state most favorable to
evaporation, the loss from the plant is rapid and large,
. When the air is loaded with moisture, as during dewy-
nights or rainy weather, then exhalation is nearly or
totally checked.

The temperature of the soil, and even its chemical
composition, the condition of the leaf as to its texture,
age, and number of stomata, likewise affect the rate of
exhalation.

Exhalation is rather incidental than necessary to the
_ life of many plants, since it may be suppressed or reduced

312 HOW CROPS GROW.

to a minimum, as in a Wardian case or fernery, without
evident influence on growth; but plants of parentage
naturally accustomed to copious exhalation of water
flourish best where the conditions are. favorable.to this
process. Exhalation is not injurious, unless the loss
be greater than the supply. If water escapes froth the
leaves faster than it enters the roots, the succulent organs
soon wilt, and if this disturbance
goes on too far the plant dies.

Exhalation ordinarily proceeds to
a large extent from the surface of
the epidermal cells. Although the
cavities of these cells are chiefly oc- .
cupied with air, their thickened walls
transmit. outward the water which is
supplied to the interior of the leaf.
Otherwise the escape of vapor occurs
through the stomata. These pores
appear to have the funetion of facil-
itating exhalation, by their property
of opening when exposed to sunlight.
Thus evaporation from the leaves is
favored at the time when root-action
is most vigorous, and the plant is to
_ the greatest degree surcharged with
water. \

Access of Air to the Interior
of the Plant.—Not only does the Fig. 59
leaf allow the escape of vapor of water, but it admits of
the entrance and exit of gaseous bodies.

The particles of atmospheric air have easy access to
the interior of all leaves, however dense and close their
epidermis may be, however few or small their stomata.
All leaves are actively engaged in absorbing or exhaling
certain gaseous ingredients of the atmosphere during
the whole of their healthy existence.

REPRODUCTIVE ORGANS OF PLANTS. 313

The entire plant is, often, pervious to air through
the stomata of the leaves. These communicate with the
intercellular spaces of the leaf, which are, in general,
occupied exclusively with air, and these again connect
with the ducts which ramify throughout the veins of the
leaf and branch from the vascular bundles of the stem.
In the bark or epidermis of woody stems, as Hales long
ago discovered, pores or cracks exist, through which
the-air has communication with the longitudinal ducts.

These facts admit of demonstration by simplemeans. Sachs employs
for this purpose an apparatus consisting of a short, wide tube of glass,
B, Fig. 59, to which is adapted, below, by a tightly-fitting cork, a bent
glass tube. Thestem of a leaf is passed through a cork which is then
secured air-tight in the other opening of the wide tube, the leaf itself
being included in the latter, and the joints are made air-tight by smear-
ing with tallow. The whole is then placed in a glass jar containing
enough water to cover the projecting leaf-stem, and mercury is quickly
poured into the open end of the bent tube, so as nearly to fill the lat.
ter.’ The pressure of the column of this dense liquid immediately
forces air into the stomata of the leaf, and a corresponding quantity is
forced on through the intercellular spaces and through the vein ducts

into the ducts of the leaf-stem, whence it issues in fine bubbles at S, ‘

It is even easy in many cases to demonstrate the permeability of the
leaf to air by immersing it in water, and, taking the leaf-stem between
the lips, produce a current by blowing. In this case the air escapes
from the stomata.

The air-passages of the stem may be shown by a similar arrange-
ment, or in many instances, as, for example, with a stalk of maize, by
simply immersing one end in water and blowing into the other.

On the contrary, roots are destitute of any visible
external pores, and are not pervious to air or vapor in
the sense that leaves and young stems are.

The air passages in the plant correspond roughly to
the mouth, throat, and breathing cavities of the animal.
We have, as yet, merely noticed the direct communica-
tion of these passages with the external air by means of
microscopically visible openings. But the cells which
are not visibly porous readily allow the access and egress
of water and of gases by osmose. To the mode in which
this is effected we shall recur on subsequent pages.

The Offices of Foliage are to put the plant in com-
munication with the atmosphere and with the sun. On

314 HOW CROPS GROW.

the one hand it permits, and to a certain degree facili-
tates, the escape of the water which is continually
pumped into the plant by its roots, and on the other
hand it absorbs, from the air that freely penetrates it,
certain gases which furnish the principal materials for
the construction of vegetable matter. We have seen that
the plant consists of elements, some of which are volatile
at the heat of ordinary fires, while others are fixed at
this temperature. When a plant is burned, the former,
to the extent of 90 to 99 per cent of the plant, are con-
verted into gases, the latter remain as ashes.

The reorganization of vegetation from the products of
its combustion (or decay) is, in its simplest phase, the
gathering by a new plant of the ashes from the soil
through its roots, and of these gases from the air by its
leaves, and the compounding of these comparatively sim-
ple substances into the highly complex ingredients of the
vegetable organism. Of this work the leaves have by
far the larger share to perform; hence the extent of
their surface and their indispensability to the welfare of
the plant.

CHAPTER IV.
REPRODUCTIVE ORGANS OF PLANTS.
§ 1.

MODES OF REPRODUCTION.

Plants are reproduced in various ways. The simplest
cellular plants have no evident special organs of repro-
duction, but propagate themselves solely by a process of
division which begins in the protoplasm, as already de-
scribed in case of Yeast, p. 253. The lower so-called
flowerless plants (Cryptogams), including molds, blights,
mildews, mushrooms, toadstools (gt), mosses, lichens,

REPRODUCTIVE ORGANS OF PLANTS. 315

ete., reproduce themselves in part by spores, each of
which is'a single minute cell that is capable of develop-
ing into a plant like that from which it was thrown off.

In very many cases a portion or “cutting” of root,
stem or leaf, from herb or tree, placed in moist, warm
earth, will grow and develop into a new plant in all
respects similar to the original. The potato, grape,
banana, and sugar-cane plants are almost exclusively
propagated in this manner. In budding and grafting a
portion of stem, carrying a single bud or a number of
buds (scion), is planted, not in the soil, but in the cam-
bial layer of a living root or stem with which it unites
and thenceforward grows.

The higher orders of plants (Phanerogams) have spe-
cial reproductive organs, constituting or contained in
their flowers, whose office it is to produce seed, the essen-
tial part of which is the embryo, a ready-formed minia-
ture plant which may grow into the full likeness of its
parent.

: § 2.

THE FLOWER... -

In the higher plants the onward growth of the stem or
of its branches is not necessarily limited, until from the
terminal buds, instead of leaves, only flowers unfold.
When this happens, as is the case with most annual and
biennial plants, raised on the farm or in the garden, the
vegetative energy has usually attained its fullest develop-
ment, and the reproductive function begins to prepare
for the death of the individual by providing seeds which
shall perpetuate the species.

There is often at first no apparent difference between
the leaf-buds and flower-buds, but commonly, in the later
stages of their growth, the latter are to be readily dis-
tinguished from the former by their greater size, and by
peculiar shape or color.

316 HCW CROPS GROW.

The Flower is a short branch, bearing a collection of
organs, which, though usually having little resemblance
to foliage, may be considered as leaves, more or less mod-
ified in form, color, and office.

The flower commonly presents four different sets of
organs, viz., Calyx, Corolla, Stamens, and Pistils, and is
then said to be complete, as in case of the apple, potato,
and many common plants. Fig. 60 represents the com-
plete flower of the Fuchsia, or ladies’ ear-drop, now uni-
versally cultivated. In Fig. 61 the same is shown in
section.

The Calyx (cup) cz, is the outermost floral envelope.
Its color is red or white in the Fuchsia, though generally.
it is green. When it consists of several distinct leaves,
they are called
sepals. The calyx
is frequently small
and inconspicu-
ous. In some
cases it falls away
as the flower
opens. Inthe
Fuchsia it firmly
adheres at its base
to the seed-vessel,
Wand is divided into
‘four lobes.

The Corolla
(crown), ¢, or ea,
is one or several
eS series of leaves ,
ee OD which are situated BieeOh
within the calyx. It is usually of some other than a
green color (in the Fuchsia, purple, etc.), often has
marked peculiarities of form and great delicacy of struc-
ture, and thus chiefly gives beauty to the flower. When

REPRODUCTIVE ORGANS OF PLANTS. 317

-' the corolla is divided into separate leaves, these are
termed petals. -The Fuchsia has four petals, which are
attached to the calyx-tube.

The Stamens, s, in Figs. 60 and 61, are generally
slender, thread-like organs, terminated by an oblong
sack, the anther, which, when the flower attains its full
growth, discharges a fine yellow or brown dust, the so-
called pollen.

The anthers, as well as the grains of pollen, vary in form with nearly
every kind of plant. The yellow pollen of Pine and Spruce is not in-
frequently transported by the wind to a great distance, and when
brought down by rain in considerable quantities, has been mistaken
for sulphur.

The Pistil, », in Figs. 60 and 61, or pistils, occupy
the center of the perfect flower. They are exceedingly
various in form, but always have at their base the seed-
vessels, or ovaries, ov, in which are found the ovules‘ or
rudimentary seeds. The summit of the pistil is desti-
tute of the epidermis, which covers all other parts of ‘the
plant, and is termed the stigma, st.

As bas been remarked, the floral organs may be consid-
ered to be modified leaves ; or rather, all the appendages
of the stem—the leaves and the parts of the flower to-

-gether—are different developments of one fundamental
structure.

The justness of this idea is sustained by the transform-
ations which are often observed.

The Rose in its natural state has a corolla consisting
of five petals, but has a multitude of stamens and pistils.
In a rich soil, or as the effect of those agencies which are
united in “cultivation,” nearly all the stamens lose their
reproductive function and proper structure; and revert
to petals; the flower becoming “double.” The tulip,
poppy, and numerous garden-flowers, illustrate this in-
teresting metamorphosis, and in these flowers we may
often see the various stages intermediate between the
perfect petal and the unaltered stamen.

318 HOW CROPS GROW.

On the other hand, the reversion of all the floral =
organs into ordinary green leaves has been observed not
infrequently, in case of the rose, white clover, and other
plants.

While the complete flower consists of the four sets of
organs above described, only the stamens and pistils are
essential to the production of seed. The latter, accord-
ingly, constitute a perfect flower, even in the absence of
calyx and corolla.

‘The flower of buckwheat has no corolla, but a white or
pinkish calyx.

The grasses have flowers in which calyx and corolla are
represented by scale-like leaves, which, as the plants ma-
ture, become chaff.

In various plants the stamens and pistils are borne on
separate flowers. Such are called monecious plants, of
which the birch and oak, maize, melon, squash, cucum-
ber, and often the strawberry, are examples.

In case of maize, the staminate flowers are the “tas-
sels” at the summit of the stalk; the pistillate flowers
are the young ears, the pistils themselves being the
“¢ silk,” each fiber of which has an ovary at its base, that,
if fertilized, develops to a kernel.

Diecious planis are those which bear the staminate
(male, or sterile) flowers and the pistillate (female, or
fertile) flowers on different individuals; the willow, the
hop-vine, and hemp, are of this kind.

Nectaries are special organs—glands or tubes—secret-
ing a sugary juice or nectar, which serves as food to
insects. ‘The clovers and honeysuckles furnish familiar
examples.

Fertilization and Fructification.—The grand func-
tion of the flower is fructification. For this purpose
pollen must fall upon or be carried by wind, insects, or
other agencies, to the naked tip of the pistil. Thus sit-
uated, each pollen-grain sends out a slender microscopic

REPRODUCTIVE ORGANS OF PLANTS. 319

tube which penetrates the interior of the pistil until it
enters the seed-vessel and comes in contact with the ovule
or rudimentary seed. This contact being established,
the ovule is fertilized and begins to grow. Thencefor-
ward the corolla and stamens usually wither, while the
‘base of the pistil and the included ovules rapidly increase
in size until the seeds are ripe, when the seed-vessel falls
to the ground or else opens and releases its contents.

Fig. 62 exhibits the process of fertilization as observed
in a plant allied to buckwheat, viz., the Polygonum con-
volvulus. The cut represents a magnified section length-
wise through the short pistil; @ is the stigma or summit
of the pistil; 6 are grains of pollen ;
¢ are pollen tubes that have penetrated
into the seed-vessel which forms the
base of the pistil ; one has entered the
mouth of the rudimentary seed, g, and
reached the embryo sack, e, within
which it causes the development of a
germ; d represents the interior wall
of the seed-vessel; A, the base of the
seed and its attachment to the seed-
vessel.

Self-Fertilization occurs when
ovules are impregnated by pollen
from the same flower. In many plants
self-fertilization is favored by the posi-
tion of the organs concerned. In the
pendent flower of the Fuchsia as well
as in the upright one of the strawberry the stigma is just
below and surrounded by the anthers, so that when the
mature pollen is discharged it cannot fail to fall upon the
stigma. Some flowers, as those of the closed gentian
(Gentiana Andrewsii) and the small subterranean blos-
soms of sheep-sorrel (Ozalis acetosella), touch-me-not
(Impatiens), and of many violets, never open, and not

320 HOW CROPS GROW.

only are self-fertile but cannot well be otherwise. Some
plants which carry these closed and inconspicuous subter-
ranean flowers depend upon them for reproduction by
seed, their large and showy erial flowers being often bar-
ren, as in violets, or totally infertile (Voandzeia.) Flax
and turnips are self-fertilizing.

Cross-Fertilization results from the contact of the
pollen of one flower with the ovules of another. In many
plants remarkable arrangements exist that hinder or
totally prevent self-fertilization and favor or ensure cross-
fertilization.

In monecious plants, as hazel or squash, flowers of one
sort yield pollen, others, different, contain the ovules ;
so that two distiné and more or less distant blossoms of
the same plant are necessary for seed-production.

In the diwctous poplar and hops, the plant that pro-
duces pollen never carries ovules and that which bears the
latter is destitute of the former, so that two distinct
plunts must co-operate to form seeds.

It often happens that the pollen of a flower cannot fer-
tilize the ovules of the same flower. This may be either
because the stigma is behind the pollen in development,
as in case of various species of geranium, or becauge the
stigma has passed its receptive period before the pollen is
mature, as in Sweet Vernal Grass (Anthozanthum odo-
ratum). In both instances the ripened pollen may reach
stigmas that are ready in other flowers and fertilize their
ovuleg, insects being often the means of transportation.

In a large number of flowers, whose pollen and stigmas
are simultaneously prepared, the position of the organs
is such that self-fertilization is difficult or impossible.
The Iris, Crocus, Pansy, Milk-weed (Asclepias), and many
Orchids, are of this class. The offices of insects in search
of nectar, or attracted by odors, are here indispensable.
The common red clover cannot produce seed without
insect aid, and the bumblebee customarily performs this

REPRODUCTIVE ORGANS OF PLANTS. 321

service. The insect, in exploring a flower for nectar,
leaves upon its stigma pollen taken from the flower last
visited, and in emerging renews its burden of pollen to
bestow it in turn upon the stigma of a third flower. °

Cross-fertilization is doubtless often effected by insects
in case of flowers which are in all respects adapted for
self-fertilization, while flowers that casua] examination
would pronounce self-fertile are in fact of themselves
sterile. ‘The flowers of rye open singly, the long stamens
shortly mature and discharge their pollen, which falls on
the stigmas of flowers standing lower in the same head,
or on neighboring heads. According to Rimepare, the
individual rye-flower can fertilize neither itself nor the
different flowers of an ear, nor can the different ears of
one and the same plant pollinate one another with suc-
cess, although no mechanical hindrance exists. (Sachs,
Physiology of Plants, p. 790.) .

Results of Self-Fertilization and Cross-Fertili-
zation.—Sprengel, one of the early students of Plant-
Reproduction, wrote in 1793, ‘‘ Nature appears to be
unwilling that any flower shall be fertilized by its own
pollen.” Hxtensive observation indicates decidedly
that cross-fertilization is far more general than self-
fertilization, especially among the higher plants. Dar-
win has shown that, i many cases, the pollen of a flower
is incapable of fertilizing its own ovules, and that the
pollen from another flower of the same plant is scarcely
more potent. In these cases the pollen from a flower
borne by another plant of the same kind is potent, and
the more so the more unlike the two plants are.

_In Darwin’s trials on the reproduction of the Morning
Glory, Ipomea purpurea, carried out through ten gener-
ations, the average height of 73 self-fertilized plants was
66 inches, while that of the same number of crossed
plants was 85.8 inches, or in the ratio of 77% to 100.
The relative number of seeds produced by the self-fertil-

21

822 HOW CROPS GROW.

ized and cross-fertilized plants in the 1st, 3d, and 9th
generations were respectively as 64 to 100; 35 to 100,
and. 26 to 100.

In other cases, but, so far as observed, much less com-
monly, self-fertilization gives the best results both as
regards numbers and vigor of offspring. In Darwin’s ex-
periments.a variety of Mimulus luteus originated, of
which the self-fertilized progeny surpassed the cross-fer-
tilized, during several generations. In the seventh gen-
eration the ratio of superiority of: the self-fertilized, as
regards numbers of fruit, was as 187 to 100, and in respect
to size of plants as 126 to 100.

Continued self-fertilization, is thus limited by its ten-
dency, as statistically determined, to reduce both the
vegetative and reproductive vigor of the plant. On the
other hand, cross-fertilization is possible or practicable
only within very narrow bounds, and the-increased pro-
ductiveness that follows it soon reaches a limit, as is
shown by the history of vegetable hybrids.

That neither mode of fertilization is exclusively or speci-
ally adapted to the highest development of plants in gen-
eral, orof particular kinds of plants, is shown by the fact’
that in the course of Darwin’s researches on the Ipomea
purpurea, just referred to, in the sixth generation a self-
fertilized plant (variety) appeared, which was superior to
its crossed.collateral, and was able to transmit its vigor

. and fertility to its descendants.

- It is evident, therefore, that the causes which lead to
higher development co-operate most fully, sometimes in
the one, sometimes in the other, mode of impregnation
and do not necessarily belong to either. We must be-
lieve that excellence in offspring is the result of excel-
lence in. the parents, no matter what lines their heredity
may have followed, except as these lines have influenced
their individual excellence. That crossing commonly
gives better offspring than in-and-in breeding is due to

REPRODUCTIVE ORGANS OF PLANTS. 323

the fact that in the latter both parents are likely to pos-
sess by inheritance the same imperfections, which are
thus intensified in the progeny, while in cross-breeding
the parents more usually have different imperfections
which. often, more or less, compensate each other in the
immediate descendants.

Hybridizing.—As the sexual union of quite different
kinds of animals sometimes results in the birth of a
hybrid, so, among plants, the ovules of one kind (spe-
cies, or even genus) may be fertilized by the pollen of
another different kind, and the seed thus developed, in
its growth, produces a hybrid plant. As in the animal,
so in the vegetable kingdom, the range within which
hybridization is possible appears to be very narrow. It
is only between rather closely allied plants that fecunda-
tion can take place, and the more close the resemblance
the more ready and fruitful the result. Wheat, rye,
and barley, in ordinary cultivation, show no tendency to
“mix ;” the pollen of one of these similar plants rarely
fertilizing * the ovules of the others. But external sim-
ilarity is no certain mark of capacity for hybridization.
The apple and pear have never yet been crossed, while
the almond and nectarine readily form hybrids. (Sachs.)

Hybrids are usually less productive of seeds than the
parent plants, and sometimes are entirely sterile, but, on
the other hand, they are often more vigorous in their
vegetative development—produce larger and more numer-
ous leaves, flowers, roots, and shoots, and are longer-

*In the first edition was written, “being incapable of fertilizing.”
The experiments of Mr. Carman have lately shown that wheat and
rye may be made to produce fertile hybrids. A beardless wheat was
‘fertilized by rye-pollen and produced nine seeds, eight of which were
fully fertile, one nearly sterile. The last yielded 20 heads, which bore
only a few grains. The plants from the nine fertile seeds were polli-
nated again with rye and produced but afew fertile seeds. A few
plants, seven-eighths rye, were finally produced, which were, however,
totally sterile. Of the three-fourths cross, fertile progeny has been
raised for several years, and the characters of jhis genus-hybrid ap-

ear to be nearly fixed, though occasionally a sterile head appears.—

ral New Yorker, 1883, p. 644.

324 HOW CROPS GROW.

lived than their. progenitors. For this reason hybrids
are much valued in fruit- and flower-culture. :

Some genera of plants have great capacity for produc-
ing hybrids. The Vine and the Willow are striking
examples. The cultivated Vine of Europe and Western
Asia is Vitis vinifera. In the United States some
twelve distinct species are found, of which three, Vitts
riparia, Vitis estivalis, and Vitis labrusca, are native to
New England. Nearly all these kinds of grape cross
with such readiness that scores of new hybrids have been
brought into cultivation. ‘‘The kinds now known as
Clinton, Taylor, Elvira, Franklin, are hybrids. of V.
riparia and V. labrusea. York-Madeira, Eumelan,
Alvey, Morton’s Virginia, Cynthiana, are crosses of V.
labrusca and V. @stivalis. Delaware is a hybrid of V.
labrusca, V. vinifera, and V. e@stivalis. Herbemont,
Rulander, and Cunningham are hybrids of V. estivalis,
V. cinerea, and V. vinifera. The vine known in France
as ‘Gaston-Bazille” is a hybrid of V. labrusca, V. esti-
valis, V. rupestris, and. V. riparia.’”* The foregoing
are ‘‘spontaneous wild hybrids.” The ‘‘ Rogers Seed-
lings,” including Salem, Wilder, Barry, Agawam, Mas-
sasoit, etc., are examples of artificial hybrids of V. vin-
tfera and V. labrusca.
" Hybridization between plants is effected, if at all, by
removing from the flower of one kind the stamens
before they shed their pollen, and dusting the summit
of the properly-matured pistil with pollen from another
kind. Commonly, when two plants hybridize, the pollen
of either will fertilize the ovules of the other. In some
cases, however, two plants yield hybrids by only one
order of connection.

The mixing of different Varieties, as commonly hap-
pens among maize, melons, etc., is not hybridization,

*Millardet in Sachs’s Lectures on the Physiology of Plants, 1887, p. 785.

REPRODUCTIVE ORGANS OF PLANTS. 325

in the long-established sense of this word, but’ rather
“‘eross-breeding.” The two processes are, however, fun-
damentally the same, and their results are sufficiently
distinguished by the terms Species-hybrid, or Genus-
hybrid, and Variety-hybrid. We are thus led to brief
notice of the meaning of the terms Species and Vari-
ety, and of the distinctions employed in Botanical
Classification.

Species.—Until recently naturalists generally held
the view that in “the beginnimg” certain kinds of plants
and animals were separately created, with the power to
reproduce their own kind, but incapable of fertile hybrid-
ization, so that only such original kinds could be per-
petuated: Such supposed original kinds were called
Species. At present, on the contrary, most biologists
regard all existing kinds of plants and animals as prob-
ably the results of a very slow and gradual development
or evolution from one vastly remote ancestor of the sim-
plest type. On this view a Plant-Species comprises a
number of individuals, ‘‘among which we are unable to .
distinguish greater differences than experience shows us
we should find among a number of plants raised from
the seed of the same parent.”

On the former view, plants yielding fertile hybrids or
crosses must be Varieties of the same species. On the
latter view different Species may hybridize. They are
not originally different, and by Evolution or Reversion
may pass into each other. On either view, the distinc-
tion of plants into species is practically the same, being
largely a matter of expert judgment or agreement among
authorities, and not capable of exact decision by refer-
ence to fixed rules or known natural laws. The charac-
ters that are taken to be common to all the individuals
of a species are termed specific characters. The differ-
ences used to divide plants into species are called specific
differences.

326 HOW CROPS GROW.

Naturalists, acting under the older view, attempted to_
draw specific characters more finely than is now thought
practicable. Many plants formerly described as separate
species are now wnited together into a single species,
the various forms at first supposed to be specifically or
originally distinct having been shown to be of common
origin, either by producing them from each other or by
observing that they were connected through a series of
intermediate forms, insensibly grading into each other.

Varieties.—The individuals of any ‘‘species” differ.
In fact, no two individuals are quite alike. Cirenm-
stances of climate, soil, and situation increase these dif-
ferences, and varieties originate when such differences
are inherited and in the progeny assume a comparative
permanence. But as external conditions cause variation
away from any particular representative of a species, so
they may cause variation back again to the original type.

Varieties most commonly originate in propagation by
seed, especially in case of the trees or plants commonly
cultivated for their fruit, Seedling grapes, apples, or
potatoes are very likely to differ from their parents.
Seed which has been imperfectly ripened or long kept is
said to be prone to yield new varieties.

Less frequently variations arise in propagation by
cuttings, buds, grafts, or tubers. Pinks and Pelargo-
niums in the florist’s hands are prolific of these ‘‘ sports.”

The causes that produce varieties are probably numer-
ous, but in many cases their nature and their mode of
action is obscure or unknown. Scarcity or abundance
of nutriment, we can easily comprehend, may, on the one
hand, dwarf a plant, or, on the other, lead to the pro-
duction of a giant individual; but how, in some cases,
the peculiarities thus impressed upon individuals become
fixed, and are transmitted to subsequent generations,
while in others they disappear, is difficult to explain.

Varieties may often be perpetuated for a long time by

REPRODUCTIVE ORGANS OF PLANTS. B24

the seed. This is true of our cereal and leguminous
- -plants, which commonly reproduce their kind with strik-
ing regularity. Varieties of some plants cannot, with
certainty, be reproduced unaltered by the seed, but are
continued. in the possession of their peculiarities by cut-
tings, layers, and grafts. The fact that the seeds ‘of a
potato, a grape, an apple, or pear cannot be depended
upon to reproduce the variety, may perhaps be more
commonly due to unavoidable contact of pollen from
other varieties (variety-hybridization) than to inability
of the mother plant to perpetuate its peculiarities.
That such inability often exists is, however, well estab-
lished, and is, in general, most obvious in case of varie-
ties that have, to the greatest degree, departed from the
original specific type and of course, in sterile hybrids.

The sports which originate in the processes of. propa-
gating from buds (grafts, tubers, cuttings) are perpet-
uated by the same processes.

Species and Varieties, as established in our botanical
literature, are exemplified by the Vine, whose species are
vinifera, riparia, labrusca, etc., and some of whose
North American Varieties, the results of hybridization,
have already been enumerated.

Genus (plural Genera).—Species which resemble
each other ‘in most important points of structure are
grouped together by botanists into a genws. Thus the
various species of oaks,—,white, red, black, scrub, live,
ete.,—taken together, form the Oak-genus Quercus,
which has a series of characters common {p all oaks
(generic characters), that distinguishes them from every
other kind of tree or plant.

Families, or Orders, in botanical language, are
groups of genera that agree in certain particulars. Thus
the several plants well-known as mallows, hollyhock,
okra, and cotton, are representatives of as many diffcrent
genera. They all agree in a number of points, especially

.. 828 HOW CROPS GROW.

as regards the structure of their fruit. They are accord-
‘ingly grouped together into a natural family or order,
which differs from all others.

Classes, Series, and Classification.—Classes are
groups of orders, and Series are groups of classes. In
botanical classification, as now universally employed—
classification after the Natural System—all plants are
separated into two series, as follows:

1. Flowering Plants (Phanerogams), which produce
flowers and seeds with embryos, and

2. Flowerless Plants (Cryptogams), that have no
proper flowers nor seeds, and are reproduced, in part,
by spores which are in most cases single cells. This
series includes Ferns, Horse-tails, Mosses, Liverworts,
Lichens, Sea-weeds, Mushrooms, and Molds.

It was believed, until recently, that there exists a sharp and abso-
lute distinction between flowering and flowerless plants, but our
‘larger knowledge now recognizes that here, as among genera, species, |
and varieties, kinds merge or shade into each other.

The use of Classification is to give precision to our
notions and distinctions, and to facilitate the using and
acquisition of knowledge. Series, classes, orders, genera,
species, and varieties are as valuable to the naturalist as
pigeon-holes are to the accountant, or shelves and draw-
ers to the merchant. :

Botanical Nomenclature.—The Latin or Greek
names which botanists employ are essential for the dis-
crimination of plants, being equally received in all coun-
~ tries, and pelonging to all languages where science has a
home. They are made necessary, not only by the confu-
sion of tongues, but by confusions in each vernacular.

Botanical usage requires for each plant two names,
one to specify the genus, another to indicate the species.
Thus all oaks are designated by the Latin word Quercus,
while the red oak is Quercus rubra, the white oak is
Quercus alba; the live oak is Quercus virens, etc.

REPRODUCTIVE ORGANS OF PLANTS. 329

The designation of certain important families of plants
is derived from a peculiarity in the form or arrangement
of the flower. Thus the pulse family, comprising the
bean, pea, and vetch, as well as alfalfa and clover, are
called Papilionaceous plants, from the resemblance of
their flowers to a butterfly (Latin, papilio). Again, the
mustard family, including the radish, turnip, cabbage,
water-cress, etc., are termed Cruciferous plants, because
their flowers have four petals arranged like the four arms
of a cross (Latin, cruz).

The flowers of a large natural order of plants are
arranged side by side, often in great numbers, on the
expanded extremity of the flower stem. Examples are
the thistle, dandelion, sunflower, artichoke, China-aster,
etc., which, from bearing such compound heads, are
called Composite plants.

The Coniferous (cone-bearing) plants comprise the
pines, spruces, Jarches, hemlocks, etc., whose flowers are
arranged in conical receptacles.

The flowers of the carrot, parsnip, and caraway are
stationed at the extremities of stalks which radiate from
a central stem like the arms of an umbrella ; hence they
are called Umbelliferous plants (from umbel, Latin for
little screen).

§ 2.

THE FRUIT.

THE Frvuir comprises the seed-vessel and the seeds, to-
gether with their various appendages.

Fruits are either dehiscent when the seed-vessel opens
and sheds the seed or are indehiscent when it remains
closed. .

The seed-vessel, consisting of the base of the pistil in
its matured state, exhibits a great variety of forms and
characters, which serve, chiefly, to define the different

830 HOW CROPS GROW..

kinds of Fruits. Of these we shall only adduce such as
are of common occurrence and belong to the farm.

The Nut has a hard, leathery or bony indehiscent
shell, that usually contains a single seed. Examples are
the acorn, chestnut, beech-nut, and hazel-nut. The cup
of the acorn and the bur or shuck of the others is a sort
of fleshy calyx. 5

The Stone-fruit, or Drupe, is a nut enveloped by a
fleshy or leathery coating, like the peach, cherry, and
plum, also the butternut and hickory-nut. Raspberries
aud blackberries are clusters of small drupes.

Pome is a term applied to fruits like the apple and
pear, the core of which is the true seed-vessel, originally
belonging to the pistil, while the often edible flesh is the
enormously enlarged and thickened calyx, whose with-
ered tips are always to be found at the end opposite the
stem.

The Berry is a many-seeded fruit of which the entire
seed-vessel becomes thick and soft, as the grape, currant,
tomato, and huckleberry.

Gourd fruits have externally a hard rind, but are
fleshy in the interior. The melon, squash, and cucum-
ber are of this kind. -

The Akene is a fruit containing a single seed which
does not separate from its dry envelop. The so-called
seeds of the composite plants—for example, the sunflower,
thistle, and dandelion—are akenes. On removing the
outer husk or seed-vessel we find within the true seed.
Many akenes are furnished with a pappus, a downy or
hairy appendage, the remains of the calyx, as seen in the
thistle, which enables the seed to float and be carried
about in the wind. The fruit or grain of buckwheat is
akene-like. _

The Grains are-properly fruits. Wheat, rye, and
maize consist of the seed and the seed-vessel closely
united. When these grains are ground, the bran that

REPRODUCTIVE ORGANS OF PLANTS. 331

comes off is the seed-vessel together with the outer coat-
ings of the seed. Barley-grain, in addition to the seed-
vessel, has the petals of the flower or inner chaff, and
oats have, besides these, the calyx or outer chaff adher-
ing to the seed.

Pod is the name properly applied to any dry seed-ves-
sel which opens and scatters its seeds when ripe. Sev-
eral kinds have received Special designations ; of these
we need only notice one.

The Legume is a pod, like that of the bean, which
splits into two halves, along whose inner edges seeds are
borne. The pulse family, or papilionaceous plants, are
also termed leguminous, from the form of their fruit.

Tue SEED, or ripened ovule, is borne on a stalk which
connects it with the seed-vessel. Through this stalk it
is supplied with nutriment. while growing. When ma-
tured and detached, a scar commonly indicates the point
of former connection.

The seed has usually two distinct coats or integuments.
The outer one is often hard, and is generally smooth.
In the case of cotton-seed it is covered with the valuable
cotton fiber. The second coat is commonly thin and
delicate.

The Kernel lies within the integuments. In many
cases it consists exclusively of the embryo, or rudimen-
tary plant. In others it contains, besides the embryo,
what has received the name of endosperm.

The Endosperm forms the chief bulk of all the
grains. If-we cut a seed of maize in two lengthwise, we
observe, extending from the point where it was attached
to the cob, the soft ‘ chit,” 6, Fig. 63, which is the em-
bryo, to be presently noticed. The remainder of the
kernel, a, is endosperm; the latter, therefore, yields in
great part the flour or meal which is so important a part
of the food of man and animals.

The endosperm is intended for the support of the

332 HOW CROPS GROW.

young plant as it develops from the embryo, before it is
capable of depending on the soil and atmosphere for sus-
tenance. It is not, however, an indispensable part of the
seed, and may be entirely removed from it, without
thereby preventing the growth of a new plant.

The Embryo, or Germ, is the essential and most
important portion of the seed. It is, in fact, a ready-
formed plant in miniature, and has its root, stem, leaves,
and a bud, although these organs are often as undevel-
oped in form as they are in size.

As above mentioned, the chit of the seeds of maize and
the other grains is the embryo. Its form is with diffi-
culty distinguishable in the dry seeds, but when they
have been soaked for several days in water, it is readily
removed from the accompanying endosperm, and plainly
exhibits its three parts, viz., the Radicle, the Plumule,
and the Cotyledon.

In Fig. 63 is represented the embryo of maize. In A
and B it is seen in section imbedded in the endosperm.
C exhibits the detached embryo. The Radicle, r, is the
stem of the seed-plant, its lower extremity is the point
from which downward growth proceeds, and from which
the first true roots are produced. The Plumule, c, is
the central bud, out of which the stem, with new leaves,
flowers, etc., is developed. The Cotyledon, b, is in
structure a ready-formed leaf, which clasps the plumule
in the embryo, as the

stem in the mature \
maize-plant. The coty- V S
ledon of maize does not, \.
however, perform the B
functions of a leaf; on

~ the contrary, it remains in the soil during the act of
sprouting, and its contents, like those of the endosperm,
are absorbed by the seedling. The first leaves which ap-

Fig. 63,

REPRODUCTIVE ORGANS OF PLANTS. 333

pear above-ground, in the case of maize and the other
grains (buckwheat excepted), are those which in the
embryo were wrapped together in the plumule, where
they can be plainly distinguished by the aid of a mag-
nifier.

Tt will be noticed that the true grains (which have
sheathing leaves and. hollow jointed stems) are monocot-
yledonous (one-cotyledoned) in the seed. As has been
mentioned, this is characteristic of plants with endoge-
nous or inside-growing stems (p. 290).

The seeds of the Hzogens (outside-growers—p. 296) are
dicotyledonous, i. ¢., have two cotyledons. Those of
buckwheat, flax, and tobacco contain an endosperm.
The seeds of nearly all other exogenous agricultural
plants are destitute of an endosperm, and, exclusive of
the coats, consist entirely of embryo. Such are the seeds
of the Leguminose, viz., the bean, pea, and clover ; of
the Crucifere, viz., turnip, radish, and cabbage ; of ordi-
nary fruits, the apple, pear, cherry, plum, and peach; of
the Gourd family, viz., the pumpkin, melon and cucum-
ber; and finally of many hard-wooded trees, viz., the
oak, maple, elm, birch, and beech.

We may best observe the structure of the two-cotyle-
doned embryo in the ordinary garden- or kidney-bean.
After a bean has been soaked in warm water for several
hours, the coats may be easily removed, and the two
fleshy cotyledons, c, c, in Fig. 64, are found separated
from each other save at the point where the radicle, a, is

seen projecting like a blunt spur. On

j carefully breaking away one of the coty-

; ledons, we get a side view of the radicle,
a

\ iF ie a, and plumule, 4, the former of which
was partially and the latter entirely im-

bedded between the cotyledons. The
plumule plainly exhibits two delicate
ee on er the unaided eye may note: the veins.

334 HOW CROPS GROW.

These leaves are folded together along their mid-ribs, and
may be opened and spread out with help of a needle.

When the kidney-bean (Phaseolus) germinates, the
cotyledons are carried up into the air, where they become
green and constitute the first pair of leaves of the new
plant. The second pair are the tiny leaves of the plum-
ule just described, between which is the bud, whence all
the subsequent aerial organs develop in succession.

In the horse-bean (Vicia faba), as in the pea, the cot-
yledons never assume the office of leayes, but remain in
the soil and gradually yield a large share of their con-
tents to the growing plant, shriveling and shrinking
greatly in’ bulk, and finally falling away and passing into

decay.
§ 3.

VITALITY OF SEEDS AND THEIR INFLUENCE ON THE
PLANTS THEY PRODUCE.

Duration of Vitality.—In the mature seed the em-
bryo lies dormant. The duration of its vitality is very
various. The seeds of the willow, it is asserted, will not
grow after having once become dry, but must be sown”
when fresh; they lose their germinative power in two
weeks after ripening.

On the other hand, single seeds of various plants, as of
sorrel (Ozxalis stricta), shepherd’s purse (Thlaspi arv-
ense), and especially of trees like the oak, beech, and
cherry, remain with moist embryos many months or sev-
eral years before sprouting. (Nobbe & Haenlein, Vs.
St., XX, p. 79.)

Among the seeds of various plants, clover for example,
which, under favorable circumstances, mostly germinate
within one or two weeks, may often be found a number
which remain unchanged, sound and dry within, for
months or years, though constantly wet externally. The

REPRODUCTIVE ORGANS OF PLANTS. ~~ 335

outer coat of these seeds is exceptionally thick, dense,
and resistant to moisture. If this coat be broken by the
scratch of a needle the seed will shortly germinate. Ina
collection of such seeds, kept in water, individuals sprout
from time to time. In case of common sorrel (Rumexz
acetosella), Nobbe & Haenlein found that 10 per cent of
the seeds germinated between the 400th and 500th day
of keeping in the sprouting apparatus.

The appearance of strange plants in earth newly
thrown out of excavations may be due to the presence of
such resistant seed, which, scratched by the friction of
the soil in digging, are brought to germination after a
long period of rest. Lyell states that seeds of the yellow
Nelumbo (water lily) have sprouted after being in the
ground for a century, and R. Brown is authentically
said to have germinated seeds of a Nelumbo taken by
him from Hans Sloane’s herbarium, where they had been
kept dry for at least 150 years.

The seeds of wheat usually, for the most part, lose their
power of growth after having been kept from three to
seven years. Count Sternberg and others are said to
have succeeded in germinating wheat taken from an
Egyptian mummy, but only after soaking it in oil.
Sternberg relates that this ancient wheat manifested no
vitality when placed in the soil under ordinary circum-
stances, nor even when submitted to the action of acids
or other substances which gardeners sometimes employ
with a view-to promote sprouting.

Girardin claims to have sprouted beans that were over
a century old. Itis said that Grimstone with great pains
raised peas from a seed taken from a sealed vase found in
the sarcophagus of an Egyptian mummy, presented to
the British Museum by Sir G. Wilkinson, and estimated
to be near 3,000 years old.

Vilmorin, from his own trials, doubts altogether the
authenticity of the “‘mummy wheat,” and it is probable

836 HOW CROPS GROW.

that those who have raised mummy wheat or mummy
peas were deceived either by an admixture of fresh seed
with the ancient, or by planting in ordinary soil, which
commonly contains a variety of recent seeds that. come
to light under favorable conditions.

Dietrich (Hoff. Jahr., 1862-3, p. 77) experimented
with seeds of wheat, rye, and a species of Bromus, which
were 185 years old. Nearly every means reputed to favor
germination was employed, but without success. After
proper exposure to moisture, the place of the germ was
usually found to be occupied by a slimy, putrefying liq-
uid. Commonly, among the freshest seeds, when put to
the sprouting trial, some will mold or putrefy.

The fact appears to be that the circumstances under
which the seed is kept greatly influence the duration of
its vitality. Ifseeds, when first gathered, be thoroughly
dried, and then sealed up in air-tight vessels, there is no
evident reason why their vitality should not endure for
long periods. Moisture and the microbes that flourish
where it is present, not to mention insects, are the agen-
cies that usually put a speedy limit to the duration of
the germinative power of seeds.

In agriculture it is a general rule that the newer the -
seed the better the results of its use. Experiments have
proved that the older the seed the more numerous the
failures to germinate, and the weaker the plants it pro-
duces.

Londet made trials in 1856-7 with seed-wheat of the
years 1856, 55, ’54, and 753. The following table exhib-
its the results :

Per cent os seeds aa of leaves four days aa

sproute ter coming up. hundred seeds.
Seed of 1853
se 1854.. 0.4 to 0.8 inches. 269
(EE BBB seinen V2 365
(6 1856... eee 74 160«% 404

The résults of similar experiments made by Haberlandt
on various grains are contained in the following table:

REPRODUCTIVE ORGANS OF PLANTS. 337

Per cent of seeds that germinated in 1861 from the years:
1850 1851 1854 1855 1857 1858 1859 1860

Wheat...........+ 0 0 8 4 73 60 84 96
RYE .- csc eeeeneeees 0 0 0 0 0 0 48 100
Barley.........6.. 0 0 24 0 48 33 92 89
OAatSiiceasmcacseens 60 0 56 48 12 32 80 96
Maize......... 08 0 nottried 76 56 not tried 77 100 97

Results of the Use of Long-kept Seeds.—The
fact that old seeds yield weak plants is taken advantage
of by the florist in producing new varieties. It is said
that while the one-year-old seeds of Ten-weeks Stocks
yield single flowers, those which have been kept four
years give mostly double flowers.

In case of melons, the experience of gardeners goes
to show that seeds which have been kept several, even
seven years, though less certain to come up, yield plants
that give the greatest returns of fruit; while plantings
of new seeds run excessively to vines.

Unripe Seeds.—Experiments by Lucanus prove that
seeds gathered while still unripe,—when the kernel is
soft and milky, or, in case of cereals, even before starch
has formed, and when the juice of the kernel is like
water in appearance,—are nevertheless capable of germi-
nation, especially if they be allowed to dry in connection
with the stem (after-ripening). Such immature seeds,
however, have less vigorous germinative power than
those which are allowed to mature perfectly ; when sown,
many of them fail to come up, and those which do, yield
comparatively weak plants at first and in poor soil give a
poorer harvest than well-ripened seed. In rich soil,
however, the plants which do appear from unripe seed,
may, in time, become as vigorous as any. (Lucanus, Vs.
St., IV, p. 253.)

According to Siegert, the sowing of unripe peas tends
to produce earlier varieties. Liebig says: ‘‘The gar-
dener is aware that the flat and shining seeds in the pod
of the Stock Gillyflower will give tall plants with single
flowers, while the shriveled seeds will furnish low plants
with double flowers throughout. 22

338 HOW CROPS GROW.

Cohn found that seeds not fully ripe germinate some-
what sooner than those which are more mature, and he
believes that seeds in a medium stage of ripeness germi-
nate most readily.

Quick- and Slow-Sprouting Seeds.—When a con-
siderable number of agricultural or garden seeds, fresh
and of uniform appearance, are placed under favorable
circumstances for germinating, it is usually observed
that sprouting begins within two to ten days, and con-
tinues for one or several weeks before all or nearly all
the living embryos have manifestly commenced to grow.
Nobbe (in 1886 and 1887) found in extensive trials with
12 varieties of stocks, Matthiola annua, that the quick-
sprouting seeds, which germinated in three to four days,
yielded earlier and larger plants, which blossomed ‘with
greater regularity and certainty, and produced a pre-
ponderance (82 per cent) of sterile double flowers, while
the slow-sprouting seeds, that were ten to twelve days in
germinating, gave smaller plants that came later to
bloom, and yielded 73 per cent of fertile single flowers.

Should continued trials. prove these results to be of
constant occurrence, it is evident that by breeding exclu-
sively from the quick-sprouting seeds, the double-flower-
ing varieties should soon become extinct, from failure to
produce seed. On the other hand, exclusive use of the
slow-sprouting seeds would extinguish the tendency to
variation and double-blooming, which gives this plant
its value to the florist.

Dwarfed or Light Seeds.—Miiller, as well as Hell-
riegel, found in case of the cereals that light or small
grain sprouts quicker but yields weaker plants, and is
not so sure of germinating as heavy grain.

Liebig asserts (Natural Laws of Husbandry, Am.
Lid., 1863, p. 24) that ‘‘poor and sickly seeds will pro-
duce stunted plants, which will again yield seeds bearing
in a great measure the same character.” This is true
“in the long run,” i. e., small or light seeds, the result

REPRODUCTIVE ORGANS OF PLANTS. 339

of unfavorable conditions, will, under the continuance
of those conditions, produce stunted-plants (varieties),
whose seeds will be small and light. (Compare Tuscan
and pedigree wheat, p. 158.)
Schubart, whose observations on the roots of agricul-
--tural plants are detailed in a former chapter (p. 263),
says, as the result of much investigation, ‘‘the vigorous
development of plants depends far less upon the size and
weight of the seed than upon the depth to which it is
covered with earth, and upon the stores of nourishment
which it finds in its first period of life.” Reference is
here had to the immediate produce under ordinary agri-
cultural conditions.

Value of Seed as Related to its Density.—From
a seties of experiments made at the Royal Agricultural
College at Cirencester, in 1863-6, Church concludes that
the value of seed-wheat stands in a certain connection
with its specific gravity (Practice with Science, pp. 107,
342, 345, London, 1867). He found :—

1. That seed-wheat of the greatest density produces
the densest seed.

2. The seed-wheat of the greatest density yields the
greatest amount of dressed corn.

3. The seed-wheat of medium density generally gives
the largest number of ears, but the ears are poorer than
those of the densest seed.

4, The seed-wheat of medium density generally pro-
duces the largest number of fruiting plants.

5. The seed-wheats which sink in water, but float i in a
liquid having the specific gravity 1.247, are of very low
value, yielding, on an average, but 34.4 lbs. of dressed
grain for every 100 yielded by the densest. seed.

6. The densest wheat-seeds are the most translucent
or horny, and contain about one-fourth more proteids
(or 3 per cent more) than the opake or starchy grains
from the same kind of wheat, or even from the same
individual plant, or even from the same ear.

340 HOW CROPS GROW.

% The weight of wheat per bushel depends upon
many circumstances, and bears no constant relation to
the density of the seed.

The densest grains are not, according to Church,
always the largest. The seeds he experimented with
ranged from sp. gr. 1.354 to 1.401.

Marek has shown that specific gravity is no universal
test of the quality of seed, for while, in case of wheat,
flax, and colza, the large seeds are generally the denser,
the reverse is true of horse-beans (Vicia faba) and peas
(Vs. St., XIX, 40).

The Absolute Weight of Seeds from different
varieties of the same species is known to vary greatly,
as is well exemplified by comparing the kernels of com-
mon field maize with those of ‘“‘pop corn.” Similar dif-
ferences are also observable in different single seeds from
the same plant, or even from the same pod orear. ‘hus,
Harz obtained what were, to all appearance, normally
developed seeds that varied in weight as follows :

FROM SINGLE PLANTS. Milligrams.
Wheat, Triticum vulgare, - from 15 ta 37
Wheat, Triticum polonicum, & 21 to 55
Barley, Hordeum distichon, AG 31 to 41
Oats, Avena sativa, “ I9 to 30
Maize, Zea Mays cinquantino, * — $69"to 201
Pea, Pisum sativum, “148 to 502

FROM SINGLE FRUIT (PODS).
from 309 to 473
“ 33 to 66
“486 to 639
Differences often no less marked are found among the
seeds in any considerable sample, gathered from a large
number of plants and representing a crop. Nobbe, with
great painstaking, has ascertained the average, maxi-
mum and minimum weights, of 180 kinds of seeds, such
as are found in commerce or are used in Agriculture;
Horticulture, and Forestry. The following table gives
some of his results :

REPRODUCTIVE ORGANS OF PLANTS. 341

Absolute Weight of Commercial Seeds.

Number of Weight of one Seed in
Samples Milligrams.
Examined. Average. Maximum. Minimum

84 28. 54.1 4.7

66 41.0 48.9 27.7

119 23.3 47.9 13.0

95 37.6 45.8 15.2

22 282.7 382.9 114.5

32 22.0 42.4 14.2

2.2 3.0 14

35 1.2 1.7 0.8

43 185.8 564.6 46.1

Kidney Bean, Phaseolus,... 5 - 585.6 926.3: 367.3
Horse Bean, Vicid,...-.....+ 7 676.0 * 2061.0 256.4
. “3 0.6 0.7 0.5

5 2.5 2.7 2.4

4 6.9 9.0 2.4

5 V1 9.7 5.7

18 11 1.7 0.8

3 3.1 3.8 2.3

5 173.0 322.0 106.7

3 32.9 35.5 28.2

6 25.4 27.0 21.0
73 0.41 0.59 0.34

28: 0.15 0.21 0.10

355 1.60 2.08 1.14

53 0.61 0.69 0.47
. . ola annua,. 4 1.50 1.60 1.39
Oak, Quercus pedunculata,. 15 2013.4 4213.5 761.6

It is noteworthy, that in case of Oats, Rye, Wheat,
Maize, Beet, Spinage, and Squash, the heaviest seeds
weigh ¢hrice as much as the lightest. With Turnip,
Carrot, Kidney-bean, Letttice, and Blue grass, some
seeds are double the weight of others. The horse-bean
gives some seeds eight times as heavy as others. The
differences brought out in the Table in many cases are
due to the représentation of different varieties; the
larger seeds, to some extent, belonging to larger plants ;
but the great range of weight, noted with regard to the
seed of the Oak, applies to 15 crops of sound acorns from
one and the same tree, gathered in 15 successive years.

In many varieties of Indian Corn, the kernels at the
base of the ear are larger, and those at the tip are
smaller, than those of the middle portion. Other varie-
ties are characterized. by great. uniformity in the size of
the kernels, having been “bred up” to this quality by
careful. seed-selection.

It is well-known that the middle part of the ears of

3842 HOW CROPS GROW.

wheat and barley produce the heaviest kernels. Nobbe
numbered and weighed the spikelets from an ear of six-
rowed barley and from one of winter wheat. Either ear
contained 27 spikelets, each with three kernels. The
kernels of the smallest barley-spikelet, No. 2, from the
base of the ear, weighed 1.5 milligrams; those of the
largest, No. 10, weighed 103.5 mg. No. 27 weighed
32.5 mg. The corresponding numbers in wheat weighed
0.5, 34.5 and 10.8 mg.

Tn case of barley, each of the first five spikelets, count-
ing from the base, weighed less than 70 milligrams.
The 6th to the 22d, inclusive, weighed 75 mg. or more.
The 7th to the 16th weighed 90 mg. or more. The17th
to the 21st, 80 mg. or more. Thence, to the tip, the
weight rapidly declined to about 30 milligrams.

The wheat kernels exhibited quite similar variation of
weight.

Dividing the 27 spikelets into three groups of nine
each, we have the following comparison of weights of
seeds, to which is added the total lengths of the rootlets
that were formed after germination had gone on for five
days :

BARLEY. WHEAT.
Weight. Length of Root. Weight. IRngth of Root.
Spikelets, 1 to 9 426mg. 670 mm. 153 mg. 223 mm.
a 10 to 18 828 “ 3281 “* 282 “ 1094
ey 18 to 27 512 “ 1364 ‘ 191 * 454

The seeds of the middle portion of the ears of barley and
wheat are thus seen to be very considerably heavier than
those of either the base or tip, and also show greater ger-
minative vigor, as measured by the comparative growth
of the roots in a given short time.

The greater weight and germinative energy of the
seeds from the middle of the ears, stand in relation to
the fact that these seeds are the oldest—the flowers from
which they develop being the first to open and fructify.
In case of a head of summer rye, Nobbe found that the

“

REPRODUCTIVE ORGANS OF PLANTS. 343

33 spikelets, each with two buds, required a week for
blossoming ; the first of the 66 flowers to open were
mostly those of the thirties and forties, and the last
those of the tens, fifties, and sixties, counting from the
base upward. These middle seeds had accordingly an
earlier start, and better chance for full development,
than those at the base and tip of the ear.

Oat kernels usually grow in pairs, the upper one of
each pair being in general lighter and smaller than the
lower one. Nobbe counted out 200 upper kernels, 200
lower kernels, and 200 average kernels, without selection.
These were weighed, and, after soaking in water for 24
hours, were placed in a sprouting apparatus at a tem-
perature of about 70° F. The results were as follows :

100 seeds Number of seeds that sprouted.
weighed. On the Total in
Grams. 3d, 4th, 5th, 6th, 7th, 8th, 9th, 10th days. 10 days.
Upper Kernels, 1.53 2100 7% 16 3 2 1 199
Lower Kernels, 3.46 109 7% 9 3 2 198
Average Kernels,2.69 45 110 30 8 4 1 1 199

Here, as in case of wheat and barley, the light seeds
were. slower to germinate.

In general, it would appear that, other things being
equal, stronger and more perfect plants and larger
crops are produced from heavy than from small seeds.
Many comparisons are on record that have given such
results ; not only small trials in garden plats, but also
field experiments on a larger scale.

Lehmann sowed, on each of three plats of 92 square
feet, the same number (528) of peas, of the same kind
but of different weight, with results as here tabulated -

Weights of 100 No. of Yield (grams).
seed-peas. plants. Kernels. Pods. Straw. Total.
Small seed-peas, 160 gm. 423 998 280 2010 3288
Medium seed-peas, 221 “ 478 1495 357 2630 4482
Large seed-peas, 273“ 480 1814 437 3170 5421

Of the peas sown, there failed to germinate about 9

344 HOW CROPS GROW.

per cent, both of the large and medium sizes, and 20 per
cent of the small ones.

The total produce from the emall seeds was less abun-
dant in all respects than that of the medium, and this
less than that of the large seeds.

Calculated upon the same number of plants, the differ-
ences, though less in degree, are still very decided :

100 Plants Yielded Kernels. Pods. Straw. Total.

From small seeds, 236 66 415 WT
From medium seeds, 313 75 550 938
From large seeds, 378 91 660 1129

Lehmann, in another experiment, found that from the
same weight of seed a larger crop is given by large seed
than by small, although the number of plants may be
considerably less.

From the same weight (188 gm.) of seed-peas were
produced :

Number of Weight of Kernels
Seed-peas. Plants. per 92 sq. ft. Per 100 plants.
By small seed, 730 680 1590 234
By medium seed, 530 505 2294 440
By large seed, 384 360 2307 640

_ Driesdorff sowed separately, on the same land, winter
wheat, as winnowed, and the same divided by sifting into
three sizes. In April and May the vegetation from the
largest seed was evidently in advance, and .at harvest
the relative yield for 100 of unsifted seed was 121 from
the largest, 105 for the medium, and 95 for the smallest
seed.

Improved varieties are often the result of continued
breeding from the heaviest or largest seeds, accompanied
by high culture on rich soil, and thin planting, so that
the roots have abundant earth for unhindered develop-
ment.

Hallet, in 1857, selected two ears of Nursery Wheat,
‘the finest quality of red wheat grown in England,”’ con-
taining, together, 87 grains, and planted the kernels 12
inches apart every way. At harvest one prime grain

REPRODUCTIVE ORGANS OF PLANTS. 345

produced 10 ears, that contained in the aggregate 688
kernels. The finest 10 ears that could be selected from
the whole produce of the other 86 grains yielded but
598 kernels. The 79 kernels of the one best ear were
planted as before, and the produce of the finest seed, as
shown by the harvest, was used for the next year’s sow-
ing. The results of continuing this process of selection
are tabulated below :

Number of
Length, Containing, ears on

Year. inches. grains. finest stool.
1857. Origimal,........... oper sietaniaiwialnd vines 43 47
1858. Finest ear,.... 19 10
1859. “Finest @ar,........esseeeces esse sees 1% 91 22
1860. Kars imperfect from wet season,... 39
1861. Fimest Car,.......ccccee cece seen eens 83 123 52

In five years, accordingly, the length of the ears was
doubled, their contents nearly trebled, and the tillering
capacity of the plant increased five-fold. (Journal Royal
Ag. Soc., XXII, p. 374.)

Wollny has given account of 27 garden trials, with
large and small seeds of rye, buckwheat, beans, vetches,
peas, Inpins, soybeans, colza, mustard, maize, and red-
clover, on plats of four square meters (43 sq. ft.), during
the years 1873 to 1880, with the nearly invariable results :
1, that the quantity of crop increases with the size of
the seed ; 2, that the large seed produces principally
large seed, and the small seed small ; 3, that the relative
‘productiveness of the small seed is greater than that of
the large; and 4, that the vitality of ‘the plants from
small seed is usually less than that of the plants from
large seed.

The facts of experience fully justify the conclusion
that, in general, other things bemg equal, the heaviest
seed is the best.

Signs of Excellence.—So far as the common judg-
‘ment can determine by external signs, the best seed is that
-which, on the one-hand, is large, plump, and heavy, and.on

346 HOW CROPS GROW.

the other is fresh or bright to the eye, and free from
musty odor. The large, plump, and heavy seeds are
those which have attained the fullest development, and
can best support the embryo when it shall begin to
grow ; those fresh in color and odor are likely to be new,
and to have the most vigorous vitality.

Ancestry ; Race-Vigor; Constancy.—There are,
however, important qualities in seed that are involved in
their heredity and give no outward token of their pres-
ence. Race-vigor and Constancy are qualities of this
sort, and these wonderfully persist in some kinds of seed
and are lacking in others. All cultivated plants occur
in’ numerous varieties, and, as the years’ go on, older
varieties ‘run out” or are neglected and forgotten, their
place being taken by newer and often, or for a time, bet-
ter ones. It would appear that a long course of careful
cultivation under the most favorable and uniform condi-
tions, coupled with careful and intelligent selection of
seed from the best-developed plants, not only leads to
the formation of the best varieties, but tends to establish
their permanence, so that when soil, climate, and care
are unfavorable, the kind maintains its character and
makes a stout resistance to deteriorating influences.

In order to properly appreciate the value of seed, its
Pedigree must therefore be known. But seed of ances-
try, that has a long-established character for certain
qualities, in a given locality, may prove of little value
under widely different circumstances, or, if its products
be cultivated under new conditions, it may lose its char-
acteristics more or less, and develop into other varieties.
It is well known that various perennial plants of tropical
climates, like the castor bean, become annuals in north-
ern latitudes, and it may easily happen that the seed of
some prized variety which is of unquestioned pedigree, as
far as the remote lines of its descent can indicate, is of lit-
tle worth in soils or climates to which it is unaccustomed,

REPRODUCTIVE ORGANS OF PLANTS. B47

from not having the power to transmit the specially
valuable qualities of its progenitors. In high, northern
latitudes, the summer cereals ripen after a short period
of vapid growth, but seed of such grain, sown in the soil
of temperate regions, does not produce early varieties ; its
rate of growth, after a few years at most, is governed by
the climate to which it is exposed. In considering the
pedigree of seed, therefore, it is not merely the repute
or characters of the ancestry, but’ the probability that
the ancestral excellencies reside in and will be trans-
mitted by the seed, that constitutes the practical point.

DIVISION III.

LIFE OF THE PLANT.
" CHAPTER I.
GERMINATION.

§ 1.
INTRODUCTORY.

Having traced the composition of vegetation from its
ultimate elements to the proximate organic compounds,
and studied its structure in the simple cell as well as in
the most highly-developed plant, and, as far as needful,
explained the characters and functions of its various
organs, we approach the subject of VEGETABLE LIFE
and NUTRITION, and are ready to inquire how the plant
increases in bulk and weight and produces starch, sugar,
oil, albuminoids, etc., which constitute directly or in-
directly almost the entire food of animals.

The beginning of the agricultural plant is in the
flower, at the moment of fertilization by the action of a
pollen tube on the contents of the embryo-sack. Hach
embryo whose development is thus ensured is a plant in
miniature, or rather an organism that is capable, under
proper circumstances, of unfolding into a plant.

1 349

350 HOW CROPS GROW.

The first process of development, wherein the young
plant commences to manifest its separate life, and in
which it is shaped into its proper and peculiar form, is
called germination.

The GENERAL PRoczss and Conpitions of GERMIN-
ATION are familiar to all. In agriculture and ordinary
gardening we bury the ripe and sound seed a little way
in the soil, and in a few days, or weeks, it usually sprouts,
provided it finds a certain degree of warmth and moisture.

Let us attend somewhat in detail first to the phenom-
ena of germination and afterward to the requirements of
the awakening seed.

§ 2.

THE PHENOMENA OF GERMINATION.

The student will do well to watch with eare the various
stages of the act of germination, as exhibited in several
species of plants. For this purpose a dozen or more
seeds of each plant are sown, the smaller, one-half, the
larger, one inch deep, in a box of earth or sawdust, kept
duly warm and moist, and one or two of each kind are
uncovered and dissected at successive intervals of 12
hours until the process is complete. In this way it is
easy to trace all the visible changes which occur as the
embryo is quickened. The seeds of the kidney-bean,
pea, of maize, buckwheat, and barley, may be employed.

We thus observe that the seed first: absorbs a large
amount of moisture, in consequence of which it swells
and becomes more soft. We see the germ enlarging be-
neath the seed coats, shortly the integuments burst and
the radicle appears, afterward the plumule becomes
manifest.

In all agricultural plants the radicle buries itself in

GERMINATION. 351

the soil.. The plumule ascends into the atmosphere and
seeks exposure to the direct light of the sun.

The endosperm, if the seed have one, and in many
cases the cotyledons (so with the horse-bean, pea, maize,
and barley), remain in the place where the seed was
deposited. In other cases (kidney-bean, buckwheat,
squash, radish, etc.) the cotyledons ascend and become
the first pair of leaves.

The ascending plumule shortly unfolds new leaves,
and, if coming from the seed of a branched plant, lateral
buds make their appearance. The radicle divides and
subdivides in beginning the issue of true roots.

When the plantlet ceases to derive nourishment from
the mother-seed the process is finished.

§ 3.
THE CONDITIONS OF GERMINATION.

As to the Conditions of Germination we have to con-
sider in detail the following :— ,

a. Temperature.—Seeds sprout within certain more
or less narrow limits of warmth.

Sachs has approximately ascertained, for various agri-
cultural seeds, the limits of warmth at which germina-
tion is possible. The lowest temperatures range from
below 40° to 55°, the highest, from 102° to 116°. Below
the minimum temperature a seed preserves its vitality,
above the maximum it is kived. He finds, likewise, that
the point at which the most rapid germination occurs is
intermediate between these two extremes, and lies be-
tween 79° and 93°. Either elevation or reduction of
temperature from these degrees retards the act of
sprouting. ,

In the following table are given the special tempera-
tures for six common plants :

352 HOW CROPS GROW.

Lowest Highest Temperature of most
Temperature. Temperature. rapid Germination.
Wheat,* 40° F. 104° F. 84° F.
Barley, 4t 104 84
Pea, 44.5 102 84
Maize, 48 115 93
Scarlet-bean, 49 111 79
Squash, 54 115 93

For the agricultural plants cultivated in New England,
a range of temperature of from 55° to 90° is adapted for
healthy and speedy germination.

It will be noticed in the above Table that the seeds of
plants introduced into northern latitudes from tropical
regions, as the squash, bean, and maize, require and
endure higher temperatures than those native to temper-
ate latitudes, like wheat and barley. The extremes given
above are by no means so wide as would be found were
we to experiment with other plants: Some seeds will
germinate near 32°, the freezing point of water, as is
trae of wheat, rye, and water-cress, as well as of various
alpine plants that grow in soil wet with the constant
drip from melting ice. On the other hand, the cocoa-
nut is said to yield seedlings with greatest certainty when
the heat of the soil is 120°.

Sachs has observed that the temperature at which
germination takes place materially influences the relative
development of the parts, and thus the form, of the seed-
ling. Very low temperatures retard: the production of
new rootlets, buds, and leaves. The rootlets which are
rudimentary in the embryo become, however, very long.
On the other hand, very high temperatures cause the
rapid formation of new roots and leaves, even before
those existing in the germ are fully unfolded. The
medium and most: favorable temperatures bring the
parts of the embryo first into development, at the same
time the rudiments of new organs are formed which are
afterwards to unfold.

* Wheat, and probably barley, may, occAsionally, germinate at, or
very near, 32°.

GERMINATION. 353

b. Moisture.—A certain amount of moisture is indis-
pensable to all growth. In germination it is needful
that the seed should absorb water so that motion of the
contents of the germ-celfs can take place. Until the
seed is more or less imbued with moisture, no signs of
sprouting are manifested, and if a half-sprouted seed
be allowed to dry the process of growth is effectually
checked.

The degree of moisture different seeds will endure or
require is exceedingly various. The seeds of aquatic
plants naturally germinate when immersed in water.
The seeds of most agricultural plants, indeed, will
quicken under water, but they germinate most health-
fully when moist but not wet. Excess of water often
causes seeds to rot.

ce. Oxygen Gas.—Free Oxygen, as contained | in the
air, is likewise essential. Saussure demonstrated by ex-
periment that proper germination is impossible in its
absence, and cannot proceed in an atmosphere of other
gases. The chemical activity of oxygen appears to be
the means of exciting the growth of the embryo.

d. Light.—It has been erroneously taught that light
is prejudicial to germination, and -that therefore seed
must be covered. (Johnston’s Lectures on Ag. Chem. &
Geology, 24 Eng. Hd., pp 226 and 227.) Nature does
not bury seeds, but soatters them on the surface of the
ground of forest. and prairie, where they are, at the most,
half-covered and by no means removed from the light.
The warm and moist forests of tropical regions, which,
though shaded, are by no means dark, are covered with
sprouting seeds. The seeds of heaths, calceolarias, and
some other ornamental plants, germinate best when un-
covered, and the seeds of common agricultural plants
will sprout when placed on moist sand or sawdust, with
apparently no less certainty than when buried out of
sight.

23

354 HOW CROPS GROW.

Finally, R. Hoffmann (Jahresbericht uber Agricultur
Chem., 1864, p. 110) found, in special experiments with
24 kinds of agricultural seeds, that light exercises no
appreciable influence of any kind on germination.

The time required for Germination varies exceed-
ingly according to the kind of seed. It is said that the
fresh seeds of the willow begin to sprout within 12 hours
after falling to the ground. Those of clover, wheat, and
other grains, mostly germinate in three to ten days.
The fruits of the walnut, pine, and larch lie four to six
weeks before sprouting, while those of some species of
ash, beech, and maple are said not to germinate before
the expiration of one and a half or two years,

The starchy and thin-skinned seeds quicken most
readily. The oily sceds are in general more slow, while
such as are situated within thick and horny or other-
wise resistant envelopes require the longest periods to
excite growth.

The time necessary for germination depends naturally
upon the favorableness of other conditions. Cold and
drought delay the process, when they do not check it
altogether. Seeds that are buried deeply in the soil may
remain for years, preserving, but not manifesting, their
vitality, because they are either too dry, too cold, or
have not sufficient access to oxygen to set the germ in
action. :

Notice has already been made of the frequent presence
in clover-seed, for example, of a small proportion of
seeds that have a dense coat which prevents imbibition
of water and delays their germination for long periods.
See p. 335. ie

To speak with precision, we should distinguish the
time from planting the dry seed to the commencement
of germination, which is marked by the rootlet becom-
ing visible, and the period that elapses until the process
is complete ; i. e., until the stores of the mother-seed are

GERMINATION. 355

exhausted, and the young plant is wholly cast upon its
own resources.

At 41° F., in the experiments of Haberlandt, the root-
let issued after four days, in the case of rye, and in five
to seven days in that of the other grains and clover.
The sugar-beet, however, lay at this temperature 22 days
before beginning to sprout.

At 51°, the time was shortened about one-half in case

of the seeds just mentioned. Maize required 11, kidney-
beans 8, and tobacco 31 days at this temperature.

At 65° the cereals, clover, peas, and flax began to
sprout in one to two days; maize, beans, and sugar-beet
in three days, and tobacco in six days.

The time of completion varies with the temperature
much more than that of beginning. It is, for example,
according to Sachs,

at 41—55° for wheat and barley 40—45 days. *
at 95—100° “ « "49-12

At agiven temperature small seeds complete germina-
tion much sooner than large ones. Thus at 55-60° the
process is finished

with beans in 30—40 days.
“maize in 30-35‘
“ wheatin 20-2 «
~ “ eloverin 8—10 “

These differences are simply due to the fact that the
smaller seeds have smaller stores of nutriment for the
young plant, and are therefore more quickly exhausted.

Proper Depth of Sowing.—The soil is usually the
medium of moisture, warmth, etc., to the seed, and it
affects germination only as it influences the supply of
these agencies ; it is not otherwise essential to the pro-
cess. The burying of seeds, when sown in the field or
garden, serves to Gover them away from birds and keep
them from drying up. In the forest, at spring-time, we
may see innumerable seeds sprouting upon the surface,
or but half covered with decayed leaves,

356 HOW CROPS GROW.

While it is the nearly universal result of experience in
temperate regions that agricultural seeds germinate most
surely when sown at a depth not exceeding one or two
inches, there are circumstances under which a widely
different practice is admissible or even essential. In the
light and porous soil of the gardens of New Haven, peas
may be sown six to eight inches deep without detriment,
and are thereby better secured from the ravages of the
domestic pigeon.

The Moqui Indians, dwelling upon the table lands of
the higher Colorado, deposit the seeds of maize 12 or 14
inches below the surface. Thus sown, the plant thrives,
while, if treated according to the plan usual in the
United States arid Europe, it might never appear above
ground. The reasons for such a procedure are the fol-
lowing: The country is without rain and almost with-
out dew? In summer the sandy soil is continucusly
parched by the sun, at a temperature often exceeding
100° in the shade. It is only at the depth of a foot or
more that the seed finds the moisture needful for its
growth—moisture furnished by the melting of the winter
snows. *

R. Hoffmann, experimenting in a light, loamy sand,
upon 24 kinds of agricultural and market-garden seeds,
found that all perished when buried 12 inches. When
planted 10 inches deep, peas, vetches, beans, and maize,
alone came up; at 8 inches there appeared, besides the
above, wheat, millet, oats, barley, and colza; at 6 inches,
those already mentioned, together with winter colza,
buckwheat, and sugar-beets ; at 4 inches of depth the
wbove and mustard, red and white clover, flax, horse-
radish, hemp, and turnips; finally, at 3 inches, lucern
also appeared. Hoffmann states that the deep-planted
seeds generally sprouted most quickly, and all early dif-

* For these interesting facts, the writer is indebted to Prof. J. S.
Newberry. -

GERMINATION. 357

ferences in development disappeared before the plants
blossomed.

On the other hand, Grouven, in trials with sugar-beet
seed—made, most probably, in a-well-manured and rather
heavy soil—found that sowing at a depth of three-eighths
to one and a fourth inches gave the earliest and strongest
plants ; seeds deposited at a depth of two and a half
inches required five days longer to come up than those
planted at three-eighths of aninch. It was further shown
that seeds sown shallow, in a fine wet clay, required four
to five days’ longer to come up than those placed at the
same depth in the ordinary soil.

Not only the character of the soil, which influences the
supply of air and warmth, but the kind of weather
which determines both temperature and degree of moist-
ure, have their effect upon the time of germination, and
since these conditions are so variable, the ruleg of prac-:
tice are laid down, and must be received, with a certain
latitude.

§ 4.

THE CHEMICAL PHYSIOLOGY OF GERMINATION.

THE NvTRITION OF THE SEEDLING.—The young
plant grows at first exclusively at the expense of the
seed. It may be aptly compared to the suckling animal,
which, when new-born, is incapable of providing its
own nourishment, but depends upon the milk of its
mother.

The Nutrition of the Seedling falls into three pro-'
cesses, which, though distinct in character, proceed sim-
ultaneously. ‘These are: 1, Solution of the Nutritive
Matters of the Cotyledons or Endosperm ; 2, Transfer ;
and 3, Assimilation of the same.

‘1. The Act of Solution has no difficulty in case of

Ps
358 HOW CROPS GROW.

dextrin, gum, the sugars, and soluble proteids. The
water which the seed imbibes, to the extent of one-fourth
to five-fourths of its weight, at once dissolves them.

It is otherwise with the fats or oils, with starch and
with proteids, which, as such, are nearly or altogether
insoluble in water. In the act of germination provision
is made for transforming these bodies into the soluble
ones above mentioned. So far as these changes have
been traced, they are as follows :

Solution of Fats.—Sachs was the first to show that
squash-seeds, which, when ripe, contain -no starch,
sugar, or dextrin, but are very rich in oil (50%) and
albuminoids (40%), suffer by germination such chemical
change that the oil rapidly diminishes in quantity (nine-
tenths disappear), while, at the same time, starch, and
in some cases sugar, is formed. (Vs. St., III, p. 1.)

Solution of Starch.—The starch that is thus organized
from the fat of the oily seeds, or that which exists
ready-formed in the farinaceous (floury) seeds, undergoes
further changes, which have been previously alluded to
(p. 50), whereby it is converted into substances that are
soluble in water, viz., dextrin and dextrose.

Solution of Albuminoids.—Finally, the insoluble al-
buminovids are gradually transformed into soluble modi-
fications.

Chemistry of Malt.—The preparation and proper-
ties of malt may serve to give an insight into the nature
of the chemical metamorphoses that have just been
indicated.

The preparation is in this wise. Barley or wheat
(sometimes rye) is soaked in water until the kernels are
soft to the fingers; then it is drained and thrown up in
heaps. The masses of soaked grain shortly dry, become
heated, and in a few days the embryos send forth their
radicles. The heaps are shoveled over, and spread out
so as to avoid too great a rise of temperature, and when

‘. GERMINATION. 359

the sprouts are about half an inch in length, the germin-
ation is checked by drying. ‘The dry mass, after remov-
ing the sprouts (radicles), is malt, such as is used in the:
manufacture of beer.

Malt thus consists of starchy seeds, whose germination
has been checked while in its early stages. ‘The only
product of the beginning growth—the sprouts—being
removed, it exhibits in the residual seed the first results
of the process of solution.

The following figures, derived from the researches of
Stein, in Dresden ( Wilda’s Centralblatt, 1860, 2, pp. 8-
23), exhibit the composition of 100 parts of Barley, and
of the 92 parts of Malt, and the two and a half of Sprouts
which 100 parts of Barley yield.*

o : 100 pts. of } __ § 92 pts. of of
Composition of Barley. } = { Malt. \ SI { gatos, } op
2.11 0.29
47.43
2.09 0.08
9.02 0.37
1.96. 0.40
6.95
( ein 0.47,
water and destitute of nitrogen) 0.90 3.68
Cellulose). ........ceee cece eres 19.86 18.76 0.89
100. 92. 2.5

It is seen from the above statement that starch, fat,
and insoluble albuminoids have diminished in the malt-
ing process; while soluble albuminoids, dextrin, and
other soluble non-nitrogenous matters have somewhat
increased in quantity. With exception of 3% of soluble
‘extractive matters,” { the differences in composition
between barley and malt are not striking.

*The analyses refer to the materials in the dry state. Ordinarily
they contain from 10 to 16 percent of water. It must not be omitted to
mention that the proportions of malt and sprouts, as well as their
composition, vary somewhat according to circumstances ; and further-
mores the best analyses which it is possible to make are but approxi-
mate.

+t Later investigators deny the existence of dextrin in -barle
find, instead, ani@ulin and amylan. See p. 62, note. ne

¢ The term Bre Tee eaters un bach applied to soluble substances,
whose precise nature is not understood. ey constitute a mix
which the chemist is not able to analyze. y se

360 HOW CROPS GROW.

The properties of the two are, however, remarkably
different. If malt be pulverized and stirred in warm
water (155° F.) for an hour or two, the whole of the
starch disappears, while sugar and dextrin take its place.
The former is recognized by the sweet taste of the wort,
as the solution is called. On heating the wort to boiling,
a little albuminoid is coagulated, and may be separ-
ated by filtering. This comes in part from the trans-
formation of the insoluble albuminoids of the barley.
On adding to the filtered liquid its own bulk of alcohol,
dextrin becomes evident, being precipitated as a white
powder.

Furthermore, if we mix two to three parts of starch
with one of malt, we find that the whole undergoes the
same change. An additional quantity of starch remains
unaltered.

The process of germination thus develops in the seed
an agency by which the conversion of starch into soluble
cdrbhydrates is accomplished with great rapidity.

Diastase.—Payen & Persoz attributed this action to
the nitrogenous ferment which they termed Diastase,
and which is found in the germinating seed in the vicin-
ity of the embryo, but not in the radicles. They assert
that one part of diastase is capable of transforming 2,000
parts of starch, first into dextrin and finally into sugar,
and that malt yields one five-hundredth of its weight of
this substance. See p. 103.

A short time previous to the investigations of Payen
& Persoz (1833), Saussure found that Mucedin,* the
soluble nitrogenous body which may be extracted from
gluten (p. 92, note), transforms starch in the manner
above described, and it is now known that various albu-
minoids may produce the same effect, although the rap-

* Saussure designated this body mucin, but this term being established
as the name of the characteristic ingredient of animal mucus, Ritthau-
sen has replaced it by mucedin.

4

GERMINATION. 361

idity of the action and the amount of effect are usually
far less than that exhibited by the so-called diastase.

It must not be forgotten, however, that in all cases in
which the conversion of starch into dextrin and sugar is
accomplished -artificially, an elevated temperature is re-
quired, whereas, in the natural process, as shown in the
germinating seed, the change goes on at ordinary or even
low temperatures. :

It is generally taught that oxygen, acting on the albu-
minoids in presence of water, and within a certain range
of temperature, induces the decomposition which confers
on them the power in question.

The necessity for oxygen in the act of germination has
been thus accounted for, as needful to the solution of
the starch, etc., of the cotyledons.

This may be true at first, but, as we shall presently see,
the chief action of oxygen is probably of another kind.

How diastase or other similar substances accomplish
the change in question is not certainly known,

Soluble Starch.—The conversion of starch into
sugar and dextrin is thus in a sense explained. This is

3 not, however, the only change
1 > J
> / (©) «1 which starch is suscepti-
J 7 ble. In the bean (Phaseol-
4 4 e v,
6 s \ Ya
Uf

us multifiorus) Sachs (Sitz-
ungsberichte der Wiener
| a Akad., XXXVI, 5%) in-
RG forms us that the starch of
C7 the cotyledons is dissolved,
7

© |
as starch, without conver-
; Fig. 65. sion into dextrin or sugar,
as these substances do not appear in the cotyledons during
any period of germination, except in small quantity near
the joining of the seedling. Compare p. 52, Amidulin.

passes into the seedling, and
reappears (in part, at least)

362 HOW CROPS GROW.

The same authority gives the following account of the
microscopic changes observed in the starch-grains them-
selves, as they undergo solution. The starch-grains of
the bean have a narrow interior cavity (as seen in Fig.
- 65, 1). This at first becomes filled with a liquid.
Next, the cavity appears enlarged (2), its borders assume
a corroded appearance (3, 4), and frequently channels
are seen extending to the surface (4, 5, 6). Finally, the
cavity becomes so large, and the channels so extended,
that the starch-grain falls to pieces (7, 8). Solution:
continues on the fragments uatil they have completely
disappeared.

Soluble Albuminoids.—The insoluble proteids of
the seed are gradually transferred to the young plant,
probably by ferment-actions similar to those referred
to under the heading ‘‘ Proteoses and Peptones,” p. 100.

The production of small quantities of acetic and lactic
acids (the acids of vinegar and of sour milk) has been
observed in germination. ‘These acids perhaps assist in
the solution of the albuminoids.

Gaseous Products of Germination.—Before leav-
ing this part of our subject, it is proper to notice some
other results of germination which have been thought to
belong to the process of solution. On referring to the
table of the composition of malt, we find that 100 parts
of dry barley yield 92 parts of malt and 24 of sprouts,
leaving 54 parts unaccounted for. In the malting pro-
cess, 14 parts of the grain are dissolved in the water in
which it is soaked. The remaining 4 parts escape into
the atmosphere in the gaseous form.

Of the elements that assume the gaseous donation;
carbon does so to the greatest extent. It unites with
atmospheric oxygen (partly with the oxygen of the
seed, according to Oudemans), producing carbonic acid
gas (CO,). Hydrogen is likewise separated, partly in
union with oxygen, as water (H,0), but to some degree

GERMINATION. 363

in the frec state. Free nitrogen appears in considerable
amount (Schulz, Jour. fir Prakt. Chem., 87, p. 163),
while very minute quantities of Hydrogen and of Nitro-
gen combine to gaseous ammonia (NH,).

Heat developed in Germination.—These chemical
changes, like all processes of oxidation, are accompanied
with the production of heat. The elevation of temper- |
ature may be imperceptible in the germination of a sin-
gle seed, but the heaps of sprouting grain seen in the
malt-house, warm so rapidly and to such an extent that
much care is requisite to regulate the process ; otherwise
the malt is damaged by over-heating.

2, The Transfer of the Nutriment of the Seed-
ling from the cotyledons or endosperm where it has un-
dergone solution, takes place through the medium of the
water which the seed absorbs so largely at first. This
water fills the cells of the seed, and, dissolving their con-
tents, carries them into the young plant as rapidly as
they are required. The path of their transfer lies through
the point where the embryo is attached to the cotyle-
dons ; thence they are distributed at first chiefly down-
wards into the extending radicles, after a little while
both downwards and upwards toward the extremities of
the seedling.

Sachs has observed that the carbhydrates (sugar and
dextrin) occupy the cellular tissue of the rind and pith,
which are penetrated by nurwerons air-passages ; while
at first the albuminoids chiefly diffuse themselves through
the intermediate cambial tissue, which is destitute of
air-passages, and are present in largest relative quantity
at the extreme ends of the rootlets and of the plumule.

In another chapter we shall notice at length the phe-
nomena and physical laws which govern the diffusion of
liquids into each other and through membranes similar
to those which constitute the walls of the cells of plants,
and there shall be able to gather some idea of the causes

364 HOW CROPS GROW.

which set up and maintain the transfer of the materials
of the seed into the infant plant.

- 8. Assimilation is the conversion of the transferred
nutriment into the substance of the plant itself. This
process involves two stages, the first being a chemical,
the second, a structural transformation.

The chemical changes in the embryo are, in part,
simply the reverse of those which occur in the cotyle-
dons; viz., the soluble and structureless proximate prin-
ciples are metamorphosed into the insoluble and organ-
ized ones of the same or similar chemical composition.
Thus, dextrin may pass into cellulose, and the soluble
albuminoids may revert in part to the insoluble condi-
tion in which they existed in the ripe seed.

But many other and more intricate ehanges proceed in
the act of assimilation. With regard to a few of these
we have some imperfect knowledge.

Dr. Sachs informs us that when the embryo begins to
grow, its expansion at first consists in the enlargement
of the ready-formed cells. As a part elongates, the
starch which it contains (or which is formed in the early
stages of this extension) disappears, and sugar is found
in its stead, dissolved in the juices of the cells. When
the organ has attained its full size, sugar can no longer
be detected ; while the walls of the cells are found to
have grown both in circumference and thickness, thus
indicating the accumulati@n of cellulose.

Oxygen Gas needful to Assimilation.—Traube
has mdde some experiments, which prove conclusively
that the process of. assimilation requires free oxygen to
surround and to be absorbed by the growing parts of the
germ. This observer found that newly-sprouted pea~
seedlings continued to develop in a normal manner when
the cotyledons, radicles, and lower part of the stem
were withdrawn from the influence of oxygen by coat-
ing with varnish or oil. On the other hand, when the

GERMINATION. 365

tip of the plumule, for the length of about an inch, was
coated with oil thickened with chalk, or when by any.
means this part of the plant was withdrawn from contact
with free oxygen, the seedling ceased to grow, withered,
and shortly perished. Traube observed the elongation
of the stem by the following expedient.

A young pea-plant was fastened by the cotyledons to a
rod, and the stem and rod were both graduated by deli-
cate cross-lines, laid on at equal intervals, by means of a
brush ‘dipped in a mixture of oil and indigo. The
growth of the stem was now manifest by the widening of
the spaces between the lines; and, by comparison with
those on the rod, Traube remarked that no growth took
place at a distance of more than ten to twelve lines from
the base of the terminal bud.

Here, then, is a coincidence which appears to demon-
strate that free oxygen must have aceess to a growing
part. The fact is further shown by varnishing one side
of the stem of a young pea. The varnished side ceases
to extend, the uncoated portion continues enlarging,
which results in a cugvature of the stem.

Traube further indicates in what manner the elabora-
tion of cellulose from sugar may require the co-operation
of oxygen and evolution of carbon dioxide, as expressed.
by the subjoined equation.

Glucose. Oxygen. Carbon dioxide. Water. Cellulose.
2(CyHyO) + 240 = 12 (CO) + 14(H,0) + CHO.

When the act of germination is finished, which occurs
as soon as the cotyledons and endosperm are exhausted
of all their soluble matters, the plant begins a fully inde-
pendent life. Previously, however, to being thus thrown
upon its own resources, it has developed all the organs
needful to collect its food from without ; -it has unfolded
its perfect leaves into the atmosphere, and ‘pervaded a
portion of soil with its rootlets.

366 HOW CROPS GROW.

During the latter stages of germination it gathers its
nutriment both from the parent seed and from the exter-
nal sources which afterward serve exclusively for its
support.

Being fully provided with the apparatus of nutrition,
its development suffers no check from the exhaustion of
the mother seed, unless it has germinated in a sterile
soil, or under other conditions adverse to vegetative life.

CHAPTER ILI.

§ 1. -
THE FOOD OF THE PLANT WHEN INDEPENDENT OF THE
SEED.

This subject will be sketched in this place in but the
briefest outlines. To present it fully would necessitate
entering into a detailed consideration of the Atmosphere
and of the Soil, whose relations to the Plant, those of the
soil especially, are very numerous and complicated. A
separate volume is therefore required. for the adequate
treatment of these topics.

The Roots of a plant, which are in intimate contact
with the soil, absorb thence the water that fills the active
cells ; they also imbibe such salts as the water of the soil
holds in solution ; they likewise act directly on the soil,
and dissolve substances, which are thus first made of
avail to them. The compounds that the plant must
derive from the soil are those which are found in its ash,
since these are not volatile, and cannot, therefore, exist
in the atmosphere. The root, however, commonly takes

FOOD AFTER GERMIN'ATION. 367

up some other elements of its nutrition to which it has
immediate access. Leaving out of view, for the present,
those matters which, though found in the plant, appear
to be unessential to its growth, viz., silica and sodium
salts, the roots absorb the following substances, viz. :

Sulphates Potassium,

Phosphates Calcium,

Nitrates and or | Magnesium and
Chlorides Iron.

These salts enter the plant by the absorbent surfaces
of the younger rootlets, aad pass upwards, through the
stem, to the leaves and to the new-forming buds.

The Leaves, which are unfolded to the air, gather
from it Carbon dioxide Gas. This compound suffers
decomposition in the plant; its Carbon remains there,
its Oxygen or an equivalent quantity, very nearly, is
thrown off into the air again.

The decomposition of carbon dioxide takes place only
by day and under the influence of the sun’s light.

From the carbon thus acquired and the elements of
water with the co-operation of the ash-ingredients, the
plant organizes the Carbhydrates. Probably some of the
glucoses are the first products of this synthesis. Starch,
in the form of granules, is the first product that is
recognizable by help of the microscope.

The formation of carbhydrates appears to proceed in
the chlorophyl-cells of the leaf, where starch-granules
first make their appearance.

The Albuminoids require for their production the
presence of a compound of Witrogen. The salts of
Nitric Acid (nitrates) are commonly the chief; and may
be the only, supply of this element.

The other proximate principles, the fats, the alkaloids,
and the acids, are built up from the same food-elements.
In most cases the steps in the construction of organic
matters are unknown to us, or subjects of uncertain con-
jecture.

368 HOW CROPS GROW.

The carbhydrates, albuminoids, etc., that are organ-
ized in the foliage, are not only transformed into the
solid tissues of the leaf, but descend and diffuse to every
active organ of the plant. -

The plant has, within certain limits, a power of select-
ting its food. The sea-weed, as has been remarked,
contains more potash than soda, although the latter is
30 times more abundant than the former in the water of
the ocean. Vegetation cannot, however, entirely shut
out either excess of nutritive matters or bodies that are
of no use or even poisonous to it.

The functions of the Atmosphere are essentially the
same towards plants, whether growing under the con-
ditions of water-culture or under tlrose of agriculture.

The Soil, on the other hand, has offices which are pe-
culiar to itself. We have seen that the roots of a plant
have the power to decompose salts, e. g., potassium
nitrate and ammonium chloride (p. 184), in order to
appropriate’ one of their ingredients, the other being
rejected. In water-culture, the experimenter must have
a care to remove the substance which would thus accu-
mulate to the detriment of the plant. In agriculture,
the soil, by virtue of its chemical and physical qualities,
commonly renders such rejected matters comparatively
insoluble, and therefore innocuous.

The Atmosphere is nearly invariable in its composi-
tion at all times and over all parts of the earth’s surface.
Its power of directly feeding crops has, therefore, a nat-
ural limit, which cannot be increased by art.

The Soil, on the other hand, is very variable in com-
position and quality, and may be enriched and improved,
or deteriorated and exhausted.

From the Atmosphere the crop can derive no appreci-
able quantity of those elements that are found in its
Ash. .

In the Soil, however, from the waste of both plants

MOTION OF THE JUICES. 369

and animals, may accumulate large supplies of all the
elements of the Volatile part of Plants. Carbon, cer-
tainly in the form of carbon dioxide, probably or possi-
bly in the condition of Humus (Vegetable Mold, Swamp
Muck), may thus be put as food, at the disposition
of the plant. Nitrogen is chiefly furnished to crops by
the soil. Nitrates are formed in the latter from various
sources, and ammonia-salts, together with certain proxi-
mate animal principles, viz., urea, guanin, tyrosin, uric
acid and hippuric acid, likewise serve to supply nitrogen
to vegetation and are often ingredients of the best ma-
nures. It is, too, from the soil that the crop gathers all
the Water it requires, which not only serves as the fluid
medium of its chemical and structural metamorphoses,
but likewise must be regarded as the material from which
it mostly appropriates the Hydroger and Oxygen of its
solid components.

§ 2.

THE JUICES OF THE PLANT, THEIR NATURE AND
MOVEMENTS.

Very erroneous notions have been entertained with
regard to the nature and motion of sap. It was formerly
taught that there are two regular and opposite currents
of sap circulating in the plant. It was stated that the
“crude sap” is taken up from the soil by the roots,
- ascends through the vessels (ducts) of the wood, to the
leaves, there is concentrated by evaporation, ‘‘elabor-
ated” by the processes that go on in the foliage, and
thence descends through the vessels of the inner bark,
nourishing these tissues in its way down. The facts
from which this theory of the sap naturally arose admit
of a very different interpretation ; while numerous con-

24

370 HOW CROPS GROW.

siderations demonstrate the essential falsity of the theory
itself. ;

Flow of Sap in the Plant—not Constant or
Necessary.—We speak of the Flow of Sap as if a rapid
current were incessantly streaming through the plant,
as the blood circulates in the arteries and veins of an ani-
mal. This is an erroneous conception.

A maple in early March, without foliage, with its
whole stem enveloped in a nearly impervious bark, its
buds wrapped up in horny scales, and its roots sur-
rounded by cold or frozen soil, cannot be supposed to have
its sap in motion. Its juices must be nearly or abso-
Iutely at rest, and when sap runs copiously from an ori-
fice made in. the trunk, it is simply because the tissues
are charged with water under pressure, which escapes at
any outlet that may be opened for it. The sap is at rest
until motion is caused by a perforation of the bark and
new wood. So, too, when a plant in early leaf is situa-
ted in an atmosphere charged with moisture, as happens
on a rainy day, there is little motion of its sap, although,
if wounded, motion may be established, and water may
stream more or less from all parts of the plant towards
the cut.

Sap does move in the plant when evaporation of water
goes on from the surface of the foliage. This always
happens whenever the air is not saturated with vapor.
When a wet cloth hung out, dries rapidly by giving up
its moisture to the air, then the leaves of plants lose
their water more or less readily, according to the nature
of the foliage.

Mr. Lawes found that in the moist climate of England
common plants (Wheat, Barley, Beans. Peas, and Clover)
exhaled, during five months of growth, more than 200
times their (dry) weight of water. Hellriegel, in the
drier climate of Dahme, Prussia, observed exhalation to
average 300 times the dry weight: of various common

MOTION OF THE JUICES, 371

crops (p. 812). The water that thus evaporates from the
leaves is supplied by the soil, and, entering the roots,
more or less rapidly streams upwards through the stem as
long as a waste is to be supplied, but this flow ceases
when evaporation from the foliage is suppressed.

The upward motion of sap is therefore to a great de-
great independent of the vital processes, and compara-
tively unessential to the welfare of the plant.

Flow of Sap from the Plant; ‘‘ Bleeding.’’—It
is a familiar fact, that from a maple tree “ tapped” in
spring-time, or from a grape-vine wounded at the same
season, a copious flow of sap takes place, which continues
for a number of weeks. The escape of liquid from the
vine is commonly. termed “bleeding,” and while this
rapid issue of sap is thus strikingly exhibited in compar-
atively few cases, bleeding appears to be a universal phe-
nomenon, one that may occur, at least, to some degree,
under certain conditions with very many. plants.

The conditions under which sap flows are various,
according to the character of the plant. Our perennial
trees have their annual period of active growth in the
warm season, and their vegetative functions are. nearly
suppressed during cold weather. As spring approaches
the tree renews its growth, and the first evidence of
change within is furnished by its bleeding when an open-
ing is made through the bark into the young wood. A
maple, tapped for making sugar, loses nothing until the
spring warmth attains a certain intensity, and then sap
begins to flow from the waunds in its trunk. The flow
is not constant, but fluctuates with the thermometer,
being more copious when the weather is warm, and fall-
ing off or suffering check altogether as it is colder.

The stem of the living maple is always charged with
water, and never more so than in winter.* This water

* Experiments made in Tharand, Saxony, under direction of Stoeck-
hardt, show that the proportion of water, both in the bark and wood

372 HOW CROPS GROW.

is either pumped into the plant, so to speak; by the root-
power already noticed (p. 269), or itis generated in
the trunk itself. The water contained in the stem in
winter is undoubtedly that raised from the soil in the
autumn. That which first flows from an auger-hole, in
March, may be simply what was thus stored in the trunk ;
but, as the escape of sap goes on for 14 to 20 days at the
rate of several gallons per day from a single tree, new
quantities of water must be continually supplied. That
these are pumped in from the root is, at first thought,
difficult to understand, because, as we have seen (p. 272),
the root-power is suspended by a certain low tempera-
ture (unknown in case of the maple), and the flow of
sap often begins when the ground is covered with one or
two feet of snow, and when we cannot suppose the soil
to have a higher temperature than it had during the pre-
vious winter months. Nevertheless, it must be that the
deeper roots are warm enough to be active all the winter
through, and that they begin their action as soon as the
trunk acquires a temperature sufficiently high to admit
the movement of water init. That water may be pro-
duced. in the trunk itself to a slight extent is by no
means impossible, for chemical changes go on there in
spring-time with much rapidity, whereby the sugar of
the sap is formed. These changes have not been suffi-
ciently investigated, however, to prove or disprove the
generation of water, and we must, in any case, assume
that it is the root-power which chiefly maintains a-pres-
sure of liquid in the tree.

The issue of sap from the maple tree in the sugar-
season is closely connected with the changes of tempera-
ture that take place above ground. The sap begins to

of trees, varies considerably in different seasons of the year, ranging,
in case of the beech, from 35 to 49 per cent of the fresh-felled tree. The
eae proportion ‘of water in the wood-was found in the months of

cember and January; in the bark, in March to May. The minimum
of water in the wood occurred in May, June, and eee a ue bark,
much irregularity was observed. Chem. ‘Ackersmann, 1866, p.

MOTION OF THE JUICES. 373

flow from a cut wher the trunk itself is warmed to a cer-
tain point and, in general, the flow appears to be the
more rapid the warmer the trunk. During warm, clear
days, the radiant heat of the sun is absorbed by the dark,
rough surface of the tree most abundantly; then the
temperature of the latter rises most speedily and acquires
the greatest elevation—even surpasses that of the atmos-
phere by several degrees ; then, too, the yield of sap is
most copious. On clear nights, cooling of the tree takes
place with corresponding rapidity ; then the snow or
surface of the ground is frozen, and the flow of sap is
checked altogether. From trees that have a sunny ex-
posure, sap runs earlier and faster than from those hay-
ing a cold northern aspect. Sap starts sooner from the
spiles on the south side of a tree than from those lilacs
the north.

Duchartre (Comptes Rendus, IX, 754) passed a vine.
situated iu a grapery, out of doors, and back again,
through holes, so that a middle portion of the stem was
exposed to a steady winter temperature ranging from 18°
to 10° F., while the remainder of the vine, in the house,
was surrounded by an atmosphere of 70° F. Under
these circumstances the buds within developed vigor-
ously, but those without remained dormant and opened
not a day sooner than buds upon an adjacent vine whose
stem was all ont of doors, That sap passed through the
cold part of the stem was shown by the fact that the
interior shoots sometimes wilted, but again recovered
their turgor, which could only happen from the partial
suppression and renewal of a supply of water through the
stem. Payen examined the wood of the vine at the con-
clusion of the experiment, and found the starch which it
originally contained to. have been equally removed from
the warm and the exposed parts.

That the rate at which sap passed through the stem
was influenced by its temperature is a plain deduction

374 HOW CROPS GROW.

from the fact that the leaves within were found wilted
in the morning, while they recovered toward noon, al-
though the temperature of the air without remained
below freezing. The wilting was no doubt chiefly due
to the diminished power of the stem to transmit water ;
the return of the leaves to their normal condition was
probably the consequence of the warming of the stem by
the sun’s radiant heat.*

One mode in which changes of temperature in the
trunk influence the flow of sap is very obvious. The
wood-cells contain, not only water, but air. Both are
expanded by heat, and both contract by cold. Air,
especially, undergoes a decided change of bulk in this
way. Water expands nearly one-twentieth in being
warmed from 32° to 212°, and air increases in volume
more than one-third by the same change of temperature.
When, therefore, the trunk of a tree is warmed by the
sun’s heat, the air is expanded, exerts a pressure on the
sap, and forces it out of any wound made through the
bark and wood-cells. It only requires a rise of tempera-
ture to the extent of a few degrees to occasion from this
cause alone a considerable flow of sap from a large tree.
(Hartig. )

If we admit that water continuously enters the deep-
lying roots whose temperature and absorbent power must
remain, for the most part, invariable from day to day,
we should have a constant slow escape of sap from the
trunk were the temperature of the latter uniform and
sufficiently high. This really happens at times during’
every sugar-season. When the trunk is cooled down to
the freezing point, or near it, the contraction of air and
water in the tree makes a vacuum there, sap ceases to
flow, and air is sucked in through the spile ; as the trunk

* The temperature of the airis not always a sure indication of that
of the solid bodies which it surrounds. A thermometer will often rise -
by exposure of the bulb to the direct rays of the sun, 30 or 40° above its
indications when in the shade.

MOTION OF THE JUICES. 375

becomes heated again, the gaseous and liquid contents of
the ducts expand, the flow of sap is renewed, and pro-
ceeds with increased rapidity until the internal pressure
passes its maximum.

As the season advances and the soil becomes heated,
the rooit-power undoubtedly acts with increased vigor
and larger quantities of water are forced into the trunk,
but at a certain time the escape of sap from a wound
suddenly ceases. At this period a new phenomenon
supervenes, The buds which were formed the previous
summer begin to expand as the vessels are distended with
sap, and finally, when the temperature attains the proper
range, they unfold into leaves. At this point we have
a proper motion of sap tn the tree, whereas before there
was little motion at all in the sound trunk, and in the
tapped stem the motion was towards the orifice and
thence out of the tree.

’ The cessation of flow from a cut results from two cir-

cumstances: first, the vigorous cambial growth, where-

by incisions in the bark and wood rapidly heal up ; and,

second, the extensive evaporation that goes on from
foliage.

That evaporation of water from the leaves often pro-
ceeds more rapidly than it can be supplied by the roots
is shown by the facts that the delicate leaves of many
plants wilt when the soil about their roots becomes dry,
that water is often rapidly sucked into wounds on the
stems of trees which are covered with foliage, and that
the proportion of water in the wood of the trees of tem-
perate latitudes is least in the months of May, June, and
July.

Evergreens do not bleed in the spring-time. The oak
loses little or no sap, and among other trees great diver-
sity is noticed as to the amount of water that escapes at
a wound on the stem. In case of evergreens we have a
stem destitute of all proper vascular tissue, and admit-

376 HOW CROPS GROW.

ting a flow of liquid only through perforations of the
wood-cells, if these really exist (which Sachs denies).
Again, the leaves admit of continual evaporation, and
furnish an outlet to the water. The colored heart-wood
existing in many trees is impervious to water, as shown
by the experiments of Boucherie and Hartig. Sap can
only flow through the white, so-called sap-wood. In
early June, the new shoots of the vine do not bleed when
cut, nor does sap flow from the wounds made by break-
ing them off close to the older stem, although a gash in
the latter bleeds profusely. In the young branches,
there are no channels that permit the rapid efflux of
water.

Composition of Sap.—The sap in all cases consists
chiefly of water. This liquid, as it is absorbed, brings
in from the soil a small proportion of certain saline mat-
ters—the phosphates, sulphates, nitrates, ete., of potas-
sium, calcium, and magnesium. It finds in the plant
itself its organic ingredients. These may be derived
from matters stored in reserve during a-previous year, as
in the spring sap of trees; or may be newly formed, as
in summer growth.

The sugar of maple-sap, in spring, is undoubtedly pro-
duced by “the transformation of starch which is found
abundantly in the wood in winter. According to Hartig
(Jour.. fir Prakt. Ch., 5, p. 21%, 1835), all deciduous
trees contain starch in their wood and yield a sweet
spring sap, while evergreens contain little or no starch.
Hartig reports having been able to procure from the root-
wood of the horse-chestnut in one instance no less than
26 per cent of starch. This is deposited in the tissues
during summer and autumn, to be dissolved for the use
of the plant in developing new foliage. In evergreens
and annual plants the organic matters of the sap are
derived more directly from the foliage itself. The leaves
absorb carbon dioxide and unite its carbon to the ele-

MOTION OF THE JUICES. 377

ments of water, with the production of sugar and other
carbhydrates. In the leaves, also, probably nitrogen
from the nitrates and ammonia-salts gathered by the
roots, is united to carbon, hydrogen, and oxygen, in the
formation of albuminoids.

Besides sugar, malic acid and minute quantities of
proteids exist in maple sap. Towards the close of the
sugar-season the sap appears to contain other organic
substances which render the sugar impure, brown in
color, and of different flavor.

It is a matter of observation that maple-sugar is whiter,
purer, and “ grains” or crystallizes more readily in those
years when spring-rains or thaws are least frequent.
This fact would appear to indicate that the brown or-
ganic matters which water extracts from leaf-mold may
enter the roots of the trees, as is the belief of practical
men.

The spring-sap of many other deciduous trees of tem-
perate climates contains sugar, but while it is cane sugar
in the maple, in other trees it appears to consist mostly
or entirely of dextrose.

Sugar is the chief organic ingredient in the juice of.
the sugar cane, Indian corn, beet, carrot, turnip, and
parsnip.

The sap that flows from the vine and from many cul-
tivated herbaceous plants contains little or no sugar; in
that of the vine, gum or dextrin is found in its stead.

What has already been stated makes evident that we
cannot infer the quantity of sap im a plant from what
may run out of an incision, for the sap that thus issues
is for the most part water forced up from the goil. It is
equally plain that the sap, thus collected, has not the
normal composition of the juices of the plant; it must
be diluted, and must be the more diluted the longer and
the more rapidly it flows.

Ulbricht has made partial analyses of the sap obtained

378 HOW CROPS GROW.

from the stumps of potato, tobacco, and sun-flower
plants. He found that successive portions, collected
separately, exhibited a decreasing concentration. In
sunflower sap, gathered in five successive portions, the
liter contained the following quantities (grams) of solid
matter :

1. 2. 3. 4. B.
Volatile panicles . 1.45 0.60 0.30 0.25 0.21
Ash, .. evinu saad siae 1:68 1.56 1.18 0.70 0.60
TODAY csicwcieaeda cae se 3,03 2.16 1.48 0.95 0.81

The water which streams from a wound dissolves and
carries forward with it matters that, in the uninjured
plant, would probably suffer a much less rapid and ex-
tensive translocation. From the stump of a potato-stalk
’ would issue, by the mere mechanical effect of the flow of
water, substances generated in the leaves, whose proper
movement in the uninjured plant would be downwards
into the tubers.

Different Kinds of Sap.—It is necessary at this
point in our discussion to give prominence to the fact
-that there are different kinds of sap in the plant. As
we have seen (p: 289), the cross section of the plant pre-
sents two kinds of tissue, the cellular and vascular.
‘These carry different juices, as is shown by their chemi-
cal reactions. In the cell-tissues exist chiefly the non-
nitrogenous principles, sugar, starch, oil, ete. The
liquid in these cells, as Sachs has shown, commonly con-
tains also organic acids and acid-salts, and hence gives a
blue color to red litmus. In the vascular tissue albumin-
oids preponderate, and the sap of the ducts commonly
has an alkaline reaction towards test papers. These dif-
ferent kinds of sap are not, however, always strictly con-
fined to either tissue. In the root-tips and buds of
many plants (maize, squash, onion), the young (new-
formed) cell-tissue is alkaline from the preponderance of

MOTION OF THE JUICES. 379 |
albuminoids, while the spring sap flowing from the ducts
and wood of the maple is faintly acid.

In many plants is found a system of channels (milk-
ducts, p. 304), independent of the vascular bundles,
which contain an opaque, white, or yellow juice. This
liquid is seen to exude from the broken stem of the milk-
weed (Asclepias), of lettuce, or of celandine (Chelidon-
dum), and may be noticed to gather in drops upon a
fresh-cut slice of the sweet potato. The milky juice
often differs, not more strikingly in appearance than it
does in taste, from the transparent sap of the cell-tissue
and vascular bundles. The former is commonly acrid
and bitter, while the latter is sweet or simply insipid to
the tongue.

Motion of the Nutrient Matters of the Plant.—
The occasional rapid passage of a current of water up-
wards through the plant must not be confounded with
the normal, necessary, and often contrary motion of the
nutrient matters out of which new growth is organized,
but is an independent or highly subordinate process by
which the plant adapts itself to the constant changes
that are taking place in the soil and atmosphere as re-
gards their content of moisture.

A plunt supplied with enough moisture to keep its tis-
sues turgid is in a normal state, no matter whether the
water within it is nearly free from upward flow or ascends
rapidly to compensate the waste by evaporation. In.
both cases the motion of the matters dissolved in the sap
is nearly the same. In both cases the plant develops
nearly alike. In both cases the nutritive matters gath-
ered at the root-tips ascend, and those gathered by the
leaves descend, being distributed to every growing cell;
and these motions are comparatively independent of, and
but little influenced by, the motion of the water in which
they are dissolved.

The upward flow of sap in the plant is confined to the

380 HOW CROPS GROW,

vascular bundles, whether these are arranged symmetri-
cally and compactly, as in exogenous plants, or distrib-
uted singly through the stem, as in the endogens. This
is not only seen upon a bleeding stump, but is made evi-
dent by the oft-observed fact that colored liquids, when
absorbed into a plant or cutting, visibly follow the course
of the vessels, though they do not commonly penetrate
the spiral ducts, but ascend in the sieve-cells of the cam-
bium.*

The rapid supply of water to the foliage of a plant,
either from the roots or from a vessel in which the cut
stem is immersed, goes on when the cellular tissues of
the bark and pith are removed or interrupted, but is at
once checked by severing the vascular bundles.

The proper motion of the nutritive matters in the
plant—of the salts disssolved from the soil and of the
organic principles compounded from carbonic acid, water,
and nitric acid or ammonia in the leaves—is one of slow
diffusion, mostly through the walls of imperforate cells,
and goes on in all directions. New growth is the forma-
tion and expansion of new cells into which nutritive
substances are imbibed, but not poured through visible
passages. When closed cells are converted into ducts or
visibly communicate with each other by pores, their ex-
pansion has ceased. Henceforth they merely become
thickened by interior deposition. __

Movements of Nutrient Matters in the Bark or
Rind.—The ancient observation of what ordinarily ensues
when a ring of bark is removed from the stem of an exo-
genous tree, led to the erroneous assumption of a form-
al downward current of ‘elaborated ” sap in the bark.
When a cutting from one of our common trees is girdled
at its middle and then placed in circumstances favorable

* Asin ae experiment of Bt aatat a hyacinth in the juice of the
oke weed (Phytolacec), or in Hallier’s observations on cuttings dipped
in cherry-juice. (J's. St., IX, p. 1.)

MOTION OF THE JUICES. 381

for growth, asin moist, warm
air, with its lower extremity
in water, roots form chiefly
at the edge of the bark just
above the removed ring. ‘The
twisting, or half-breaking, as
well as ringing of a layer,
promotes the development of
roots. Latent buds are often
called forth on the stems of
fruit trees, and branches grow
more vigorously, by making
a transverse incision through
the bark just below the point
of their issue. Girdling a
y fruit-bearing branch of the
grape-vine near its junction
with the older wood has the

effect of greatly enlarging the
fruit. Itis well known that
a wide wound made on the
La stem of a tree heals up by the

i ly formation of new wood, and

‘i ity \t t/

Mm | commonly the growth is most
rapid and abundant above the
cut. From these facts it was
concluded that sap descends
in the bark, and, not being
able to pass below a wound,
leads to the organization of
new roots or wood just above
it.

The accompanying illustration,
Fig. 66, represents the base of a cut-
ting from an exogenous stem (pear
or currant), girdled at B and kept

, for some days immersed in water to
Fig. 66, the depth indicated by the line Z.

382 HOW CROPS GROW.

The first maifestation of growth is the formation of a protuberance at
the lower edge of the bark, which is known to gardeners as a callous,
Cc. This is an extension of the cellulartissue. From the callous shortly
appear rootlets, #, which originate from the vascular tissue. Rootlets
also break from the stem above the callous and also above the water,
if the air be moist. They appear, likewise, though in less number,
below the girdled place.

Nearly all the organic substances (carbhydrates, al-
buminoids, acids, etc.) that are formed in a plant are
produced in the leaves, and must necessarily find their
way down to nourish the stem and roots. The facts
just mentioned demonstrate, indeed, that they do go
down in the bark. We have, however, no proof that
there is a downward flow of sap. Such a flow is not
indicated by a single fact, for, as we have before seen,
the only current of water in the uninjured plant is the
upward one which results from root-action and evapora-
tion, and that is variable and mainly independent of the
distribution of nutritive matters. Closer investigation
has shown that the most abundant downward movement
of the nutrient matters generated in the leaves proceeds
in the thin-walled sieve-cells of the cambium, which, in
exogens, is young tissue common to the outer wood and the
inner bark—which, in fact, unites bark and wood. The
tissues of the leaves communicate directly with, and are
a continuation of, the cambium, and hence matters
formed by the leaves must move most rapidly in the
cambium. If they pass with greatest freedom through
the sieve-cells, the fact is simply demonstration that the
latter communicate most directly with those parts of the
leaf in which the matters they conduct are organized.

In endogenous plants and in some exogens (Piper me-
dium, Amaranthus sanguineus), the vascular bundles
containing sieve-cells pass into the pith and are not con-
-fined to the exterior of the stem. Girdling such plants '
does not give the result above described. With them,
roots are formed chiefly or entirely at the base of the
cutting (Hanstein), and not above the girdled place.

MOTION OF THE JUICES. 383

In all cases, without exception, the matters organized
in the leaves, though most readily and abundantly moy-
ing downwards in the vascular tissues, are not confined
to them exclusively. When a ring of bark is removed
from a tree, the new cell-tissues, as well as the vascular,
are interrupted. Notwithstanding, matters are trans-
mitted downwards, through the older wood. When but
a narrow ring of bark is removed from a cutting, roots
often appear below the incision, though in less number,
and the new growth at the edges of a wound on -the
trunk of a tree, though most copious above, is still de-
cided below—goes on, in fact, all around the gash.

Both the cell-tissue and the vascular thus admit of
the transport of the nutritive matters.downwards. In
the former, the carbhydrates—starch, sugar, inulin—the
fats, and acids, chiefly occur and move. In the large
ducts, air is contained, except when by vigorous rvot-
action the stem is surcharged with wacer. In the sieve-
ducts (cambium) are found the albuminoids, though not
unmixed with carbhydrates. Ifa tree have a deep gash
cut into its stem (but not reaching to the colored heart-
wood), growth is not suppressed on. either side of the
cut, but the nutritive matters of all kinds pass ont of a
vertical direction around the incision, to nourish the new
wood above and below. Girdling a tree is not fatal, if
done in the spring or early summer when growth is rapid,
provided that the young cells, which form externally,
are protected from dryness and other destructive influ-
ences. An artificial bark, i. e., a covering of cloth or
clay to keep the exposed wood moist and away from air,
saves the tree until the wound heals over.* In these
cases it is obvious that the substances which commonly
preponderate in the sieve-ducts must pass through the

*If the freshly exposed wood be rubbed or wiped with a cloth,
whereby the moist cambial layer (of cells containing nuclei and capa-
ble of multiplying) is removed, no growth canoccur. Ratzeburg.

.

384 HOW CROPS GROW,

cell-tissue in order to reach the point where they nourish
the growing organs.
Evidence that nutrient matters also pass upwards in
the bark is furnished, not only by tracing the course of
colored liquids in the stem, but also by the fact that
undeveloped buds perish in most cases when the stem is
girdled between them and active leaves. In the excep-
tions to this rule, the vascular bundles penetrate the
pith, and thereby demonstrate that they are the chan-
nels of this movement. A minority of these exceptions
again makes evident that the sieve-cells are the path of
transfer, for, as Hanstein has shown, in certain plants
(Solanaces, Asclepiades, etc.), sieve-cells penetrate the
pith unaccompanied by any other elements of the vascu-
. lar bundle, and girdled twigs of these plants grow above
as well as beneath the wound, although all leaves above
the girdled place be cut off, so that the nutriment of the
buds must come from below the incision.
The substances which are organized in the foliage of a
plant, as well as those which are imbibed by the roots,
move to any point where they can supply a want. Carb-
hydrates pass from the leaves, not only downwards, to
nourish new roots, but upwards, to feed the buds, flow-
ers, and fruit. In case of cereals, the power of the
leaves to gather and organize atmospheric food nearly or
altogether ceases as they approach maturity. The seed
grows at the expense of matters previously stored in the
foliage and stems (p. 237), to such an extent that it may
ripen quite perfectly although the plant be cut when the
kernel is in the milk, or even earlier, while the juice of
the seeds is still watery and before starch-grains have
begun to form.
. In biennial root-crops, the root is the focus of motion

for the matters organized by growth during the first
year ; but in the second year the stores of the root are
completely exhausted for the support of flowers and seed,

’

CAUSES OF THE MOTION OF JUICES. 385

so that the direction of the movement of these organized
matters is reversed. In both years the motion of water
is always the same, viz., from the soil upwards to the
leaves. *

The summing up of the whole matter is that the nutri-
ent substances in the plant. are not absolutely confined
to any path, and may move in any direction. The fact:
that they chiefly follow certain channels, and move in
this or that direction, is plainly dependent upon the
structure and arrangement of the tissues, on the sources
of nutriment, and on the seat of growth or other action.

§ 3.
THE CAUSES OF MOTION OF THE VEGETABLE JUICES.

Porosity of Vegetable Tissues.—Porosity is a
property: of all the vegetable tissues and implies that the
molecules or smallest particles of matter composing the tis-
sues are separated from each other by acertain space. In
a multitude of cases bodies are visibly porous. In many
more we can see no pores, even by the aid of the highest
magnifying powers of the microscope; nevertheless the
fact of porosity is a necessary inference from another
fact which may be observed,.viz., that of absorption. A
fiber of linen, to the unassisted eye, has no pores.
Under the microscope we find that it is a tubular cell,
the bore being much less than the thickness of the walls.
By immersing it in water it swells, becomes more trans-
parent, and increases in weight. If the water be colored
by solution of indigo or cochineal, the fiber is visibly

*The motion of water is always upwards, because the soil always
contains more water than the air. Ifa plant were so situated that its
roots should steadily lack water while its foliage had an excess of this
liquid, it cannot be doubted that then the “sap”? would pass down in
aregular flow. In this case, nevertheless, the nutrient matters would
take their normal course.

25

386 HOW CROPS GROW.

penetrated by the dye. It is therefore porous, not only
in the sense'of having an interior cavity which becomes
visible by a high magnifying power, but likewise in hav-
ing throughout its apparently imperforate substance in-
numerable channels in which liquids can freely pass.
In like manner, all the vegetable tissues are more or less
penetrable to water.

Imbibition of Liquids by Porous Bodies.—Not
onty do the tissues of the plant admit of the access of
water into their pores, but they forcibly drink in or
aosoro this liquid, when it is presented to them in excess,
until their pores are full.

When the molecules of a porous body have freedom
of motion, they separate from each other on imbibing a
liquid ; the body itself swells. Even powdered glass or
fine sand perceptibly increases in bulk by imbibing water.
Clay swells much more. Gelatinous silica, pectin, gum
tragacanth, and boiled starch hold a vastly greater amount
of water in their pores or among their molecules.

In case of vegetable and animal tissues, or membranes,
we find a greater or less degree of expansibility from the
same cause, but here the structural connection of the
molecules puts a limit to their separation, and the result
of saturating them with a liquid is‘a state of turgidity
and tension, which subsides to one of yielding flabbiness
when the liquid is partially removed.

The energy with which vegetable matters imbibe water
may be gathered from a well-known fact. In granite
quarries, long blocks of stone are split out by driving
plugs of dry wood into holes drilled along the desired
line of fracture and pouring water over the plugs. The
liquid penetrates the wood with immense force, and the
toughest rock is easily broken-apart,

The imbibing power of different tissnes and vegetable
matters is widely diverse. In general, the younger or-
gans or parts take up water most readily and freely.- The

CAUSES OF THE MOTION OF JUICES. 387

sap-wood of trees is far more absorbent than the heart-
wood and bark. The cuticle of the leaf is often com-
paratively impervious to water. Of the proximate ele-
ments we have cellulose and starch-grains able to retain,
even when air-dry, 10 to 15% of water. Wax and the
solid fats, as well as resins, on the contrary, do not
greatly attract water, and cannot easily be wetted with
it. They render cellulose, which has been impregnated
with them, unabsorbent.

Those vegetable substances which ordinarily manifest
the greatest absorbent power for water, are the gummy
carbhydrates and the albuminoids. In the living plant
the protoplasmic membrane exhibits great absorbent
power. Of mineral matters, gelatinous silica (Exp. 58,
p. 187) is remarkable on account of its attraction for
water.

Not only do different substances thus exhibit unlike
adhesion to water, but the same substance deports itself
variously towards different liquids.

One hundred parts of dry ox-bladder were found by
Liebig to absorb during 24 hours :—

268 parts of pure Water.

1330 “saturated Brine.
3B “Alcohol (84%).
17 as * Bone-oil.

A piece of dry leather will absorb either oil or water,
and apparently with equal avidity. If, however, oiled
leather be immersed in water, the oil is gradually and
perfectly displaced, as the farmer well knows from his
experience with greased boots. India-rubber, on the
other hand, is impenetrable to water, while oil of tur-
pentine is imbibed by it in large quantity, causing the
caoutchouc to swell up to a pasty mass many times its
original bulk.

The absorbent power is influenced by the size of the
pores. Other things being equal, the finer these are, the
greater the force with which a liquid is imbibed. This

388 HOW CROPS GROW.

is shown by what has been learned from the study of a
kind of pores whose effect admits of accurate measure-
ment. A tube of glass, with a narrow, uniform caliber,
is such a pore. Ina tube of 1 millimeter (about 35 of
an inch), in diameter, water rises 30 mm. In a tube of
vo millimeter, the liquid ascends 300 mm. (about 11
inches) ; and, in a tube of x35 mm., a column of 3,000
mm. is sustained. In porous bodies, like chalk, plaster
stucco, closely packed ashes or starch, Jamin found that
water was absorbed with force enough to overcome the
pressure of the atmosphere from three to six times; in
other words, to sustain a column of water in a wide
tube 100 to 200 ft. high. (Comptes Rendus, 50, p. 311.)
Absorbent power is influenced by temperature. Warm
water is absorbed by wood more quickly and abundantly
than cold. In cold water starch does not swell to any
striking or even perceptible degree, although consider-
able liquid is imbibed. In hot water, however, the. case
is remarkably altered. The starch-grains are forcibly
burst open, and a paste or jelly is formed that holds
many times its weight of water. (Exp. 27, p. 51.) On
. freezing, the particles of water are mostly withdrawn
from their adhesion to the starch. The ascent of liquids
in narrow tubes whose walls are unabsorbent, is, on the
contrary, diminished by a rise of temperature.
Adhesive Attraction.—The absorption of a liquid
into the cavities of a porous body, as well as its rise in a
narrow tube, are expressions of the general fact that
there is an attraction between the molecules of the liquid
and the solid. In its simplest manifestation this attrac-
tion exhibits itself as Adhesion, and this term we shall
employ to designate the kind of force under considera-
tion. Ifa.clean plate of glass be dipped in water, the
liquid touches, and sticks to, the glass. On withdraw-
ing the glass, a film of water comes away with it—the
adhesive force of water to glass being greater than the
cohesive force among the water molecules.

CAUSES OF THE MOTION OF JUICES. 389

Capillary Attraction.—If two squares of glass be
set up together upon a plate, so that they shall be
in contact at their vertical edges on one side, and one-
eighth of an inch apart on the other, it will be seen, on
pouring a little water upon the plate, that this liquid
rises in the space between them to a hight of several
inches where they are in very near proximity, and curves
downwards to their base where the interval is large.

Capillary attraction, which thus causes liquids to rise
in narrow channels or fine tubes, involves indeed the
adhesion of the liquid to the walls of the tube, but also
depends on a tension of the surface of the liquid, due to
the fact that the molecules at the surface only attract
and are only attracted by underlying molecules, so that
they exert a pressure on the mass of liquid beneath them.
Where the liquid adheres to the sides of a containing
tube or cavity, this pressure is diminished and there the
liquid rises. 3

Adhesion may be a Cause of Continual Move-
ment under certain circumstances. .When anew cotton
wick is dipped into oil, the motion of the oil may be fol-
lowed by the eye, as it slowly ascends, until the pores
are filled and motion ceases. Any cause which removes
oil from the pores at the apex of the wick will disturb
the equilibrium which had been established between the
solid and the liquid. A burning match held to the
wick, by its heat destroys the oil, molecule after mole-
cule, and this process becomes permanent when the wick
is lighted. As the pores at the base of the flame give up
oil to the latter, they fill themselves again from the
pores beneath, and the motion thus set up propagates
itself to the oil in the vessel below and continues as long.
as the flame burns or the oil holds out.

We get a further insight into the nature of this motion
when we consider what happens after the oil has all been
sucked up into the wick. Shortly thereafter the dimen-

390 HOW CROPS GROW.

sions of the flame are seen to diminish. It does not,
however, go out, but burns on for a time with continually
decreasing vigor. When the supply of liquid in the por-
ous body is insufficient to saturate the latter, there is
still the same tendency to equalization and equilibrium.
If, at last, when the flame expires, because the combus-
. tion of the oil falls below that rate which is needful to
generate heat sufficient to decompose it, the wick be
placed in contact at a single point, with another dry
wick of equal mass and porosity, the oil remaining in
the first will enter again into motion, will pass into the
-second wick, from pore to pore, until the oil has been
shared nearly equally between them.

In case of water contained in the cavities of a porous
body, evaporation from the surface of the latter becomes
remotely the cause of a continual upward motion of the
liquid.

The exhalation of water as vapor from the foliage of a
plant thus necessitates the entrance of water as liquid
at the roots, and maintains a flow of it in the sap-ducts,
or causes it to pass by absorption from cell to cell.

Liquid Diffusion.—The movements that proceed in
plants, when exhalation is out of the question, viz., such.
as are manifested in the stump of a vine cemented into a
gauge (Fig. 43, p. 248), are not to be accounted for by
capillarity or mere absorptive force under the conditions
as yet. noticed. To approach their elucidation we require
to attend to other considerations.

The particles of many different kinds of liquids attract
each other. Water and alcohol may be mixed together
in all proportions in virtue of their adhe-ive attraction.
If we fill a vial with water to the rim and carefully lower
it to the bottom of a tall jar of alcohol, we shall find
after some hours that alcohol has penetrated the vial,
and water has passed out into the jar, notwithstanding
the latter. liquid is considerably heavier than the former.

CAUSES OF THE MOTION OF JUICES. 391

If the water be colored by indigo or cherry juice, its
motion may be followed: by the eye, and after a certain
lapse of time the water and alcohol will be seen to have
become uniformly mixed throughout the two vessels.
This manifestation of adhesive attraction is termed Lig-
uid Diffusion.

What is true of two liquids likewise holds for two
solutions, i. e., for two solids made liquid by the action
of a solvent. A vial filled with colored brine, or syrup,
and placed in a vessel of water, will discharge its con-
tents into the latter, itself receiving water in return ;
and this motion of the liquids will not cease until the
whole is uniform in composition, i. e., until every mole-
cule of salt or sugar is equally attracted by all the mole-
cules of water.

When several or a large number of soluble substances
are placed together in water, the diffusion of each one
throughout the entire liquid will go on in the same way
until the mixture is homogeneous.

Liquid Diffusion may be a Cause of Continual
Movement whenever circumstances produce continual
disturbances in the composition of a solution or in that
of a mixture of liquids.

If into a mixture of two liquids we introduce a solid
body which is able to combine chemically with, and
solidify one of the liquids, the molecules of this liquid
will begin to move toward the solid body from all points,
and this motion will cease only when the solid is able to
combine with no more of the one liquid, or no more
remains for it to unite with. ‘Thus, when quicklime is
placed in a mixture of alcoho! and water, the water is in
time completely condensed in the lime, and the alcohol
is rendered anhydrous. :

Rate of Diffusion.—The rate of diffusion varies with
the nature of the liquids ; if solutions, with their degree
of concentration and with the temperature.

392 HOW CROPS GROW.

Colloids and Crystalloids.—There is a class of bodies
whose molecules are singularly inactive in many respects,
and have, when dissolved in water or other liquid, a
very low capacity for diffusive motion. These bodies
are termed Collo/ds,* and are characterized by swelling
up or uniting with water to bulky masses (hydrates) of
gelatinous consistence, by inability to crystallize, and by
feeble and poorly-defined chemical affinities. Starch,
dextrin, the gums, the albuminoids, pectin and pectic
acid, gelatin (glue), tannin, the hydroxides of iron and
aluminium and gelatinous silica, are colloids. Opposed.
to these, in the properties just specified, are those bodies
which erystallize, such as saccharose, glucose, oxalic,
citric, and tartaric acids, and the ordinary salts. —

Other bodies which have never been seen to crystallize
have the same high diffusive rate; hence the class is
termed by Graham Crystalloids. +

Colloidal bodies, when insoluble, are capable of imbib-
ing liquids, and admit of liquid diffusion through their
molecular interspaces. Insoluble crystalloids are, on
the other hand, impenetrable to liquids in this sense.
The colloids swell up more or less, often to a great bulk,
from absorbing a liquid; the volume of a.crystalloid
admits of no such change.

In his study of the rates of diffusion of various sub-
stances, dissolved in water to the extent of one per cent
of the liquid, Graham found the following

APPROXIMATE TIMES OF EQUAL DIFFUSION.
Hydrochloric acid, Crystalloid, 1.
7

Sodium Chloride, 24.
Cane Sugar, se Ts
Magnesium Sulphate, ss 7.
Albumin, : Colloid, 49.
Caramel, st 98.

* From two Greek words which signify glue-like. 5

+ We have already employed the word Crysta/loid to distinguish the
amorphous albuminoids from their modifications or combinations
which present the aspect of crystals (p. 107). This use of the word was
proposed by Nageli, in 1862. Graham had employed it, as opposed to
eolloid, in 1861.

CAUSES OF THE MOTION OF JUICES. 393

The table shows that the diffusive activity of hydro-
chloric acid through water is 98 times as great as that of
caramel (see p. 66, Exp. 29). In other words, a mole-
cule of the acid will travel 98 times as far in a given
time as the molecule of caramel.

Osmose,* or Membrane Diffusion.—When two
miscible liquids or solutions are separated by a porous
diaphragm, the phenomena of diffusion (which depend
upon the mutual attraction of the molecules of the dif-
ferent liquids, or dissolved substances) are complicated
with those of imbibition or capillarity, and of chemical
affinity. The adhesive or other force which the septum
is able to exert upon the liquid molecules supervenes
upon the mere diffusive tendency, and the movements
may suffer remarkable modifications.

If we should separate pure water and a solution of
common salt by a membrane upon whose substance. these
liquids could exert no action, the diffusion would pro-
ceed to the same result as were the membrane absent.
Molecules of water .would penetrate the membrane on
one side and molecules of salt on the other, until the
liquid should become alike on both. Should the water
move faster than the salt, the volume of the brine would
increase, and that of the water would correspondingly
diminish. Were the membrane fixed in its place, a
change of level of the liquids would occur. Graham has
observed that common salt actually diffuses into waiter,
through a thin membrane of ox-bladder deprived of its
outer muscular coating, at very nearly the same rate as
when no membrane is interposed.

Dutrochet was the first to study the phenomena of
membrane diffusion. He took a glass funnel with a long
and slender neck, tied a piece of bladder over the wide
opening, inverted it, poured in brine until the funnel
was filled to the neck, and immersed the bladder in a

* From a Gréek word meaning impulsion.

394 HOW CROPS GROW.

vessel of water. He saw the liquid rise in the narrow
tube and fall in the outer vessel. He designated the
passage of water into the funnel as endosmose, or inward
propulsion. At the same time he found the water sur-
rounding the funnel to acquire the taste of salt. The
outward transfer of salt was his exosmose. The more
general word, Osmose, expresses both phenomena; we
may, however, employ Dutrochet’s
terms to designate the direction of
~ osmose.

Osmometer.—When the apparatus
employed by Dutrochet is so con-
structed that the diameter of the nar-
row tube has a known relation to, is,
for example, exactly one-tenth that of
the membrane, and the narrow tube
itself is provided with a millimeter
scale, we have the Osmometer of Grah-
am, Fig 6%. The ascent or descent of
the liquid in the tube gives a measure
of the amount of osmose, provided the
hydrostatic pressure is counterpoised
by making the level of the liquid with-
in and without equal, for which pur-
. pose water is poured into or removed from the outer ves-

sel. Graham designates the increase of volume in the
osmometer as positive osmose, or simply osmose, and dis-
tinguishes the fall of liquid in the narrow tube as nega-
tive osmose.

In the figure, the external vessel is intended for the reception of
water. The funnel-shaped interior vessel is closed below with mem-
brane, and stands upon a shelf of perforated zinc for support. The
graduated tube fits the neck of the funnel by a ground joint.

Action of the Membrane.— When an attraction exists
the membrane itself and one or more of the substances
between which it is interposed, then the rate, amount,
and even direction, of diffusion may be greatly changed.

CAUSES OF THE MOTION OF JUICES. 395

Water is imbibed by the membrane of bladder much
more freely than alcohol; on the other hand, a film. of
collodion (cellulose nitrate left from the evaporation of
its solution in ether) is penetrated much more easily by
alcohol than by water. If, now, these liquids be sepa-
rated by bladder, the apparent flow will be towards the
alcohol; but if a membrane of collodion divide them,
the more rapid motion will be into the water.

When a vigorous chemical action is exerted upon the
membrane by the liquid or the dissolved matters, osmose
is greatly heightened. In experiments with a septum of
porous earthenware (porcelain biscuit), Graham found
that in case of neutral organic bodies, as sugar and alco-
hol, or neutral salts, like the alkali-chlorides and nitrates,
-very little osmose is exhibited, i. e., the diffusion is not
perceptibly greater than it would be in absence of the
porous diaphragm.

The acids,—oxalic, nitric, and hydrochloric,—mani-
fest a sensible but still moderate osmose. Sulphuric
and phosphoric acids, and salts having a decided alka-
line or acid reaction, viz., acid potassium oxalate, sodi-
um phosphate, and carbonates of potassium and sodium,
exhibit a still more vigorous osmose. For example, a
solution' of one part of potassium carbonate in 1,000
parts of water gains volume rapidly, and to one part of
the salt that passes into the water 500 parts of water
enter the solution.

Tn all cases where diffusion is greatly modified by a
membrane, the membrane itself is strongly attacked and
altered, or dissolved, by the liquids. When animal
membrane is used, it constantly undergoes decomposi-
tion and its osmotic action is exhaustible. In case
earthenware is employed as a diaphragm, portions of its
calcium and aluminium are always attacked and dis-
solved by the solutions upon which it exerts osmose.

Graham asserts that to induce osmose in bladder, the

396 HOW CROPS GROW.

chemical action on the membrane must be different on
the two sides, and apparently not in degree only, but
also in kind, viz., an alkaline action on the albuminoid
substance of the membrane on the one side, and an acid
action on the other. The water appears always to accu-
mulate on the alkaline or basic side of the membrane.
Hence, with an alkaline salt, like potassium carbonate,
in the osmometer, and water outside, the flow is inwards ;
but with an acid in the osmometer, there is negative
osmose, or the flow is outwards, the liquid then falling
in the tube.

Osmotic activity is most highly manifested in such
salts as easily admit of decomposition with the setting
free of a part of their acid, or alkali.

Hydration of the membrane.—It is remarkable
that the rapid osmose of potassium carbonate and other
alkali-salts is greatly interfered with by common salt, is,
-in fact, reduced to almost nothing by an equal quantity
of this substance. In this case it is probable that the
physical effect of the salt, in diminishing the power of
the membrane to imbibe water (p. 393), operates in a
sense inverse to, and neutralizes the chemical action of,
the carbonate. In fact, the osmose of the carbonate, as
well as of all other salts, acid or alkaline, may be due to
their effect in modifying the hydration,* or power of the
membrane, to imbibe the liquid, which is the vehicle of
their motion. Graham suggests this view as an explana-
tion of the osmotic influence of colloid membranes, and
it is not unlikely that in case of earthenware, the chem-
ical action may exert its effect indirectly, viz., by pro-
ducing bydrated silicates from the burned clay, which
are truly colloid and analogous to animal membranes in
respect of imbibition. Graham has shown a connection
between the hydrating effect of acids and alkalies on
colloid membranes and their osmotic rate.

*In case water is employed as the Hquid.

CAUSES OF THE MOTION OF JUICES. 397

“Tt is well ‘known that fibrin, albumin, and animal
membrane swell much more in very dilute acids and
alkalies than in pure water. On the other hand, when
the proportion of acid or alkali is carried beyond a point
peculiar to each substance, contraction of the colloid
takes place. The colloids just named acquire the power
of combining with an increased proportion of water
and of forming higher gelatinous hydrates in conse-
quence of contact with dilute acid or alkaline reagents.
Even parchment-paper is more elongated in an alkaline
solution than in pure water. When thus hydrated
and dilated, the colloids present an extreme osmotic
sensibility.”

An illustration of membrane-diffusion which is highly
instructive and easy to produce, is the following :

A cavity is scooped out in a carrot, as in Fig. 68, so

wow that the sides remain } inch or so thick,
and a quantity of dry, crushed sugar is
introduced ; after some time, the previ-
ously dry sugar will be converted into a
syrup by withdrawing water from the flesh
of the carrot. At the same time the latter
will visibly shrink from the loss of a por-
tion of its liquid contents. In this case
the small portions of juice moistening the
cavity form a strong solution with the sugar in contact
with them, into which water diffuses from the adjoining
cells. Doubtless, also, sugar penetrates the parenchyma
of the carrot.

In the same manner, sugar, when sprinkled over thin-
skinned fruits, shortly forms a syrup with the water
which it thus withdraws from them, and salt packed
with fresh meat runs to brine by the exosmose of the
juices of the flesh. In these cases the fruit and the
meat shrink as a result of the loss of water. :

Graham observed gum tragacanth, which is insoluble

Fig. 68.

398 HOW CROPS GROW. .

in water, to cause a rapid passage of water through a
membrane in the sime manner from its power of imbibi-
tion, although here there could be no exosmose or out-
ward movement.

The application of these facts and principles to explain-
ing the movements of the liquids of the plant is obvious.
The cells and the tissues composed of cells furnish pre-
cisely the conditions for the manifestation of motion by
the imbibition of liquids and by simple diffusion, as well
as by osmose. The disturbances needful to maintain
motion are to be found in the chemical changes that
accompany the processes of nutrition. The substances
that normally exist in the vegetable cells are numerous,
and they suffer remarkable transformations, both in
chemical constitution and in physical properties. The
rapidly-diffusible salts that are presented to the plant by
the soil, and the equally diffusible sugar and organic
acids that are generated in the leaf-cells, are, in part,
converted into the sluggish, soluble colloids, soluble
starch, dextrin, albumin, etc., or are deposited as solid
matters in the cells or upon their walls. Thus the dif-
fusible contents of the plant not only, but the mem-
branes which gccasion and direct osmose, are subject to
perpetual alterations in their nature. More than this,
the plant grows; new cells, new membranes, new pro-
portions of soluble and diffusible matters, are unceas-
ingly brought into existence. Jmbidition in the cell-
membranes and their’ solid, colloid contents, Diffusion
in the liquid contents of the individual cells, and Osmose
between the liquids and dissolved matters and the mem-
branes, or colloid contents of the cells, must unavoid-
ably take place.

That we cannot follow the details of these kinds of
action in the plant does not invalidate the fact of their
operation. ‘The plant is so complicated and presents
such a- number and variety of changes in its growth,

CAUSES OF THE MOTION OF JUICES, 3899

that we can never expect to understand all its mysteries.
From what has been briefly explained, we can compre-
hend some of the more striking or obvious movements
that proceed in the vegetable organism.

Absorption and Osmose in Germination.—The
absorption of water by the seed is the first step in Ger-
mination. The coats of the dry seed, when put into the
moist soil, dmbibe this liquid which follows the cell-walls,
from cell to cell, until these membranes are saturated
and swollen, At the same time these membranes occa-
sion or permit osmose into the cell-cavities, which, dry
before, become distended with liquid. The soluble con-
tents of the cells, or the soluble results of the transforma-
tion of their organized matters, diffuse from cell to cell
in their passage to the expanding embryo.

The quantity of water imbibed by the air-dry seed commonly
amounts to 50 and may exceed 100 per cent. R. Hoffmann has made
observations on this subject (Vs. St., VII, p. 50). The absorption was

usually complete in 48 or 72 hours, and was as follows in case of certain
agricultural plants :—

Per cent. Per cent.
Mustard .. doc. ceccasecenccessseee BO. OTS. aie a ernie secisie avarereid vinwininienr winrar
Millet ......cccceccaceverccscesees 25.0 |} Hemp............
MIZE... .. cece ese sceec tee neensees 44.0 | Kidney Bean...

Wheat...... Orr re eer 45.5 | Horse Bean.....
Buckwheat ..-...ccccceecee neeee 46.8
TBAT OY. i:0s0:0)e <aiaciorerein sre:njeieieie.cie a's anus 48.2
Turnip.... -51.0
RYE wees siaja addin siilaig eieio Derciace Sisleta. ye 57.7

Root-Action.—Absorption at the roots is unquestion-
ably an osmotic action exercised by the membrane that
bounds the young rootlets and root-hairs externally. In
principle it does not differ from the absorption of water
by the seed.. The mode in which it occasions the sur-
prising phenomena of bleeding or rapid flow of sap from
a wound on the trunk or larger roots is doubtless essen-
tially as Hofmeister first elucidated by experiment.

This flow proceeds in the ducts and wood-cells.
Between these and the soil intervenes loose cell-tissue

400 HOW CROPS GROW.

surrounded by a compacter epidermis. Osmose takes
place in the epidermis with such energy as not only to
distend to its utmost the cell-tissue, but to cause the
‘water of the cells to filter through their walls, and thus
gain access to the ducts. ‘The latter are formed in young
cambial tissue, and, when new, are very delicate in their
walls.

Fig. 69 represents a simple apparatus by Sachs for
imitating the supposed mechanism and process of Root-
action. In the Fig., gg represents a short, wide, open

glass tube; at a, the tube is tied over and se-

‘. curely closed by a piece of pig’s bladder ; it is then

filled with solution of sugar, and the other end,

6, is closed in similar manner by a piece of parch-
ment-paper (p. 59). Finally a cap of India-rub-

ber, A, into whose neck a narrow, bent glass

tube, 7, is fixed, is tied on over 6. (These join-

ings must be made very carefully and firmly.)

The space within r KX is left empty of liquid, and

, the combination is placed in a vessel of. water, as

in the figure. C represents a root-cell whose
exterior wall (cuticle),
a, is less penetrable
under pressure than its
interior, 6; 7 corres-
ponds to a duct of vas-
cular tissue, and the
isurrounding water
‘takes the place of that
Fig. 69. existing in the pores of

the soil. The water shortly penetrates the cell, C, dis-
tends the previously flabby membranes, under the accu-
mulating tension filters through 8 into r, and rises in
the tube; where in Sachs’s experiment it attained a
height of 4 or 5 inches in 24 to 48 hours, the tube, r,
being about 5 millimeters wide and the area of b, 700 sq.

CAUSES OF THE MOTION OF JUICES, 401

mm. When we consider the vast root-surface exposed
to the soil, in case of a vine, and that’ myriads of root-
lets and root-hairs unite their action in the compara-
tively narrow stem,’ we must admit that the apparatus
above figured gives us a very satisfactory glance into the
causes of bleeding.

Motion of Nutritive or Dissolved Matters; Se-
lective Power of the Plant.—The motion of the sub-
stances that enter the plant from the soil in a state of
solution, and of those organized within the plant is, to a
great degree, separate from and independent of that
which the water itself takes. At the same time that
water is passing upwards through the plant to make
good the waste by evaporation from the foliage, sugar or
other carbhydrate generated in the leaves is diffusing
against the water, and finding its way down to the very
root-tips. This diffusion takes place mostly in the cell-
tissue, and is undoubtedly greatly aided by osmose, i. e.,
by the action of the membranes themselves. The very
thickening of the cell-walls by the deposition of cellulose
would indicate an attraction for the material from which
cellulose is organized. The same transfer goes on sim-
ultaneously in all directions, not only into roots and
stem, but into the new buds, into flowers and fruit.
We have considered the tendency to equalization between
two masses of liquid separated from each other by pen-
étrable membranes. This tendency makes valid for the
organism of the plant the law that demand creates sup-
ply. In two contiguous cells, one of which contains
solution of sugar, and the other solution of potassium
nitrate, these substances must diffuse until they are
iningled equally, unless, indeed, the membranes or some
other substance present exerts an opposing and prepon-
derating attraction.

In the simplest phases of diffusion each substance is,
to a certain degree, independent of every other. Any

26

402 HOW CROPS GROW.

salt dissolved in the water of the soil mus¢ diffuse into
the root-cells of a plant, if it be absent from the sap of
this root-cell and the membrane permit its passage.
When the root-cell has acquired a certain proportion of
the salt, a proportion equal to that in the soil-water,
more cannot enter it. So soon as a molecule of the salt
has gone on into another cell or been removed from the
sap by any chemical transformation, then a molecule
may and must enter from without.

Silica is much more abundant in grasses and cereals
than in Ieguminous plants. In the former it exists to
the extent of about 25 parts in 1,000 of the air-dry foli-
age, while the leaves and stems of the latter contain but
3 parts. When these crops grow side by side, their
roots are equally bathed by the same soil-water. Silica
enters both alike, and, so far as regards itself, brings
the cell-contents to the same state of saturation that
exists'in the soil. The cereals are able to dispose of
silica by giving it a place in the cuticular cells; the
leguminous crops, on the other hand, cannot remove it
from their juices ; the latter remain saturated, and thus
further diffusion of silica from without becomes impos-
sible except as room is made by new growth. It is in
this way that we have a rational and adequate explana-
tion of the selective power of the plant, as manifested
in its deportment towards the medium that invests its
roots. The same principles govern the transfer of mat-
ters from cell to cell, or from organ to organ, within the
plant. Wherever there is unlike composition of two
miscible juices, diffusion is thereby set up, and proceeds
as long as the cause of disturbance lasts, provided im-
penetrable membranes do not intervene. The rapid
movereent of water goes on because there is great loss of
this liquid ; the slow motion of silica is a consequence
of the little use that arises for it in the plant.

Strong chemical affinities may be overcome by help of

CAUSES OF THE MOTION OF JUICES. 403

osmose. Graham long ago observed the decomposition
of alum (sulphate of aluminium and potassium) by mere
diffusion ; its potassium sulphate having a higher diffu-
sive rate than its aluminium sulphate. - In the same
manner acid potassium sulphate, put in contact with
water, separates into neutral potassium sulphate and
free sulphuric acid.*

We have seen (pp. 170-1) that the plant, when veg-
etating in solutions of salts, is able to decompose them.
It separates the components of potassium nitrate—appro-
priating the acid and leaving the base to accumulate in
the liquid. It resolves chloride of ammonium,—taking
up ammonia and rejecting the hydrochloric acid. The
action in these ‘cases we cannot definitely explain, but
our analogies leave no doubt as to the general nature of
the agencies that codperate to such results.

The albuminoids in their usual form are colloid
bodies, and very slow of diffusion through liquids.
They pass a collodion membrane somewhat (Schu-
macher), but can scarcely penetrate parchment-paper
(Graham). In the plant they are found chiefly in the
sieve-cells and adjoining parts of the cambium. Since
for their, production they must ordinarily require the
concourse of a carbhydrate and a nitrate, they are not
unlikely generated in the cambium itself, for here the
descending carbhydrates from the foliage come in con-
tact with the nitrates as they rise from the soil. On the
other hand, ‘the albuminoids become more diffusible in
some of their combinations. Schumacher asserts that

_carbonates and phosphates of the alkalies considerably
increase the osmose of albumin through collodion mem-
branes (Physik der Pflanzen, p. 128). It is probable that
those combinations or modifications of the albuminoids

*The decomposition of these salts is begun by the water in which
they are dissolved, and is carried on by osmose, because the latter
secures separation of the reacting substances.

404 HOW CROPS GROW.

which occur in the soluble crystalloids of aleurone
(p. 105) and haemoglobin (p. 97) are highly diffusible,
as certainly is the case with the peptones.

Gaseous bodies, especially the carbonic acid and oxy-
gen of the atmosphere, which have free access to the
intercellular cavities of the foliage, and which are for the
most part the only contents of the larger ducts, may be
distributed throughout the plant by osmose after having
been dissolved in the sap or otherwise absorbed by the
cell-contents. :

Influence of the Membranes.—The sharp separa-
tion of unlike juices and soluble matters in the plant
indicates the existence of a remarkable variety and range
of adhesive attractions. In orange-colored flowers we
see upon microscopic examination that this tint is pro-
duced by the united effect of yellow and red pigments
which are contained in the cells of the petals. One cell
is filled with yellow pigment, and the adjoining one with
red, but these two colors are never contained in the
same cell. In fruits we have coloring matters of great
tinctorial power and freely soluble in water, but they
never forsake the cells where they appear, never wander
into the contiguous parts of the plant. In the stems
and leaves of the dandelion, lettuce, and many other
plants, a white, milky, and bitter juice is contained, but
it is strictly confined to certain special channels and
never visibly passes beyond them. The loosely disposed
cells of the interior of leaves contain grains of chloro-
phyl, but this substance does not appear in the epidermal
cells, those of the stomata excepted. Sachs found that
solution of indigo quickly entered the roots of a seedling
bean, but required a considerable time to penetrate the
stem. Hallier, in his experiments on the absorption of
colored liquids by plants, noticed, in all cases when
leaves or green stems were immersed in solution of indigo,
or black-cherry juice, that these dyes readily passed into

CAUSES OF THE MOTION OF JUICES. 405

and colored the epidermis, the vascular and cambial tis-
sue, and the parenchyma of the leaf-veins, keeping
strictly to the cell-walls, but in no instance communi-
cated any color to the cells containing chloroplyl.
(Phytopathologie, Leipzig, 1868, p. 67.) We must infer
that the coloring matters either cannot penetrate the
cells that are occupied with chlorophyl, or else are chem-
ically transformed into colorless substances on entering
them.

Sachs has shown in numerous instances that the juices
of the sieve-cells and cambial tissue are alkaline, while
those of the adjoining cell-tissue are acid when examined
by test-paper. (Hap. Phys. der Pflanzen, p. 394.)

When young and active cells are moistened with solu-
tion of iodine, this substance penetrates the cellulose
without producing visible change, but when it acts upon
the protoplasm, the latter separates from the outer cell-
wall and collapses towards the center of the cavity, as if
its contents passed out, without a corresponding endos-
mose being possible (p. 224).

We may conclude from these facts that the membranes
of the cells are capable of effecting and maintaining the
separation of substances which have considerable attrac-
tions for each other, and obviously accomplish this result
by exerting their superior attractive or repulsive force.

The influence of the membrane must vary in character
with those alterations in its chemical and structural con-
stitntion which result from growth or any other cause.
It is thus,'in part, that the assimilation of external food

‘by the plant is directed, now more to one class of

proximate ingredients, as the carbhydrates, and now to
another, as the albuminoids, although the supplies of
food presented are uniform both in total and relative
quantity.

If a slice of red-beet be washed and put into water,
the pigment which gives it color does not readily dissolve

406 HOW CROPS GROV.

and diffuse out of the cells, but the water remains color-
less for several days. The pigment is, however, soluble.
in water, as is seen at once by crushing the beet, where-
by the cells ave forcibly broken open and their contents
displaced. The cell-membranes of the uninjured root
are thus apparently able to withstand the solvent power
of water npon the pigment and to restrain the latter
from diffusive motion. Upon subjecting the slice of
beet to cold until it is thoroughly frozen, and then plac-
ing it in warm water so that it quickly thaws, the latter
is immediately and deeply tinged with red. The sudden
thawing of the water within the pores of the cell-mem-
brane has in fact so altered them, that they can no
longer prevent the diffusive tendency of the pigment.
(Sachs. )

§ 4,

MECHANICAL EFFECTS OF OSMOSE ON THE PLANT.

The osmose of water from without into the cells of the
plant, whether occurring on the root-surface, in the
buds, or at any intermediate point where chemical
changes are going on, cannot fail to exercise a great me-
chanical influence on the phenomena of growth. Root-
action, for example, being, as we have seen, often suffi-
cient to overcome a considerable hydrostatic pressure,
might naturally be expected to accelerate the develop-
ment of buds and young foliage, especially since, as com-
mon observation shows, it operates in perennial plauts,
as the maple and grape-vine, most energetically at the
season when the issue of foliage takes place. Experi-
ment demonstrates this to be the fact.

If a twig be cut from a tree in winter and be placed in a
room having a summer temperature, the buds, before dor-

MECHANICAL EFFECT OF OSMOSE ON PLANTS. 407

mant, shortly exhibit signs of growth,
and if the cut end be immersed in wa-
ter, the buds will enlarge quite after
the normal manner, as long as the nu-
trient matters of the twig last, or until
the tissues at the cut begin to decay.
It is the summer temperature which
excites the chemical changes that re-
sult in growth. Water is needful to
occupy the expanding and new-form-
ing cells, and to be the vehicle for the
translocation of nutrient matters from
the wood to the buds. Water enters
the cut stem by imbibition or capillar-
ity, not merely enough to replace loss
by exhalation, but is also sucked in by
osmose acting in the growing cells.
Under the same conditions as to tem-
perature, the twigs which are connected
with active roots expand earlier and
more rapidly than cuttings. Artificial
pressure on the water which is pre-
sented to the latter acts with an effect
similar to that which the natural stress
caused by the root-power exerts. This
fact was demonstrated by Boehm
(Sttzungsberichte der Wiener Akad.,
1863), in an experiment which may be
made as illustrated by the cut, Fig. '70.
A twig with buds is secured by means
of a perforated cork into one end of a
short, wide glass tube, which is closed
below by another cork through which
passes a narrow syphon-tube, B. The
cut end of the twig is immersed in
water, IW, which is put under pressure
by pouring mercury into the upper

408 HOW CROPS GROW.

extremity of the syphon-tube. ” Horse-chestnut and grape
twigs cut in February and March and thus treated—the
pressure of mercury being equal to six to eight inches
above the level, M—after four to six wéeks, unfolded
their buds with normal vigor, while twigs similarly cir-
cumstanced but without pressure opened four to ‘eight
days later and with less appearance of strength.

Fr. Schulz (Karsien’s Bot. Unters., Berlin, II, 148)
found that cuttings of twigs in the leaf, from the horse-
chestnut, locust, willow and rose, subjected to hydro-
static pressure in the same way, remained longer turges-
cent and advanced much further in development of
leaves and flowers than twigs simply immersed in water.

The amount of water in the soil influences both the
absolute and relative quantity of this ingredient in the
plant. It is a common observation that rainy spring’
weather causes a rank growth of grass and straw, while
the yield of hay and grain is not correspondingly in-
creased. The root-action must operate with greater
-effect, other things being’ equal, in a nearly saturated
soil than in one which is less moist, and the young cells
of a plant situated in the former must be subjected to
greater internal stress than those of one growing in the
latter—must, as a consequence, attain greater dimen-
sions. It is not uncommon to find fleshy roots, espec-
ially radishes which have grown in hot-beds, split apart
lengthwise, and Hallier mentions the fact of a sound
root of petersilia splitting open after immersion in water
for two or three days. (Phytopathologie, p. 87.) This
mechanical effect is indeed commonly conjoined with
others resulting from abundant nutrition, but increased
bulk of a plant without corresponding increase of dry
matter is doubtless in great part the consequence of large
supplies of water to the roots and its vigorous osmose
into the expanding plant.

giving the Aver-

Ash, and Ash-ingredients in

+

APPENDIX.

1,000 parts of fresh or air-dry substances. According to Prof. E.

age quantities of Water, Nitr8gen,
von WOLFF, 1889.

COMPOSITION OF VARIOUS AGRICULTURAL PRODUCTS

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4Acg

HOW CROPS GROW.

410

[Continued]

COMPOSITION OF VARIOUS AGRICULTURAL PRODUCTS.—|

i

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INDEX.

Absorption ak the aes 260, 269, 272
Xr

Acces of interior of -
Sesde agg e see ke
Acetamide, .. «oe o 0 135
Acids, Definition of... « . 81
Acids, Testfor ..... . . 82

Acid elements, ......

Acid-proteids, ....... 99

Adhesion, . . rae

Agriculture, Art of. Caer ia

Agricultural products, Compo-
sition in 1,000 parts

abe passaces Saiente, Scope of. q

anes. inplant,. .. a
ayane Sarl SLAY oblast cote BBE
Albumin,. ........ .89
Albuminates, ...... . 99
Albuminoids, Characters and

composition, . . . 87, 104, 106
oids in animal nutrit-

ion, . . - + - 108

Albuminoids, ‘Diffusion of . °. °.403

Albuminoids in oat-plant, . . 234
Albuminoids, Mutual relations

of . ote se
Albuminoids, “Pro portion of, in

vegetable pro ited » . 2 114
Albumose, .... o = w» 5101
Alburnum,. .......
Aleurone, . 8
Alkali-earths, » 81
‘Alkali-earths, Metals of ©.”
Alkali-metals, . .... . .138
Alkalies,. ... Ciera

Alkali- ~proteids, " ae ee we
Alkaloids, . . « 6 « 0120
Allylsulphocyanate, . eR a ”

1

Alumina,. .. 2... «ee
uminium, « » 143

(0 (<a ee me ae

‘Amido-acids, ee oe eo w 2 114, 118
Amidoacetic acid, . . . . .« 115
fer docabrnle acid, . . . . -116
Amidovaleric acid, .. . 116

idulin,. . 1... 2 + « 52
Amines, . . - o %« 119
‘Ammonium Carbonate, . - . 33
Ammonium Salts in plant, 82, 113
Amylan,. .. se ee ww 62

411

Amyloid,. . a ae ae
Amylodextrin, os aac cot iat He

eee eee
re ie dh, Gah Ga ee ier
Ar

ADIN, sce cb es Se
Arabinose,,. . 2. 6 +» se 2 ©
Arrow root,. . . oo oe 6
Arsenic in plants," « « « 137,210
Ash-ingredients, . . . . 126, 161
‘Ash-ingredients, Excess of . . 201
Ash-ingredients, Excess of, how
disposed of,

_Ash-ingredients, Function of in

plant, . 210
Asteingrédients, State of, 2
Ast'of plants, .".".".".”. "13,126
saat ot plants, Analyses, Tables:

Ash of t plants, Composition of,

Ash cf ut plants, Composition of,
variations in

Asparagin, ..... - » 116
Assimilation, . «+ 364
Atmosphere, 0 Offices of...
Atomic weight, . e: “evidaaaay ve
BION «ahs ee kw a
Bark, aera

Barium in plants, bP Fassel te ee
mesa Definitionof. ...
Bast-cells, Bast-tissue, 293, 295, zn
Bean, Leaf, Section of ...

Beam, Seed, vv nw =”. 84
2: kt ewe eR ee
Betaln, he

Blood-fibrin, .
Bone-black, . . . . . + » » 15
Boron, Boricacid, . ... .
Buds, Structureof ..
Buds, Development under pres-
i a ne a ec Ne
ulbs, . . oe 2 oe ae
Buteelo wea,” teak e Re TE

412

Caesium, Action on oat, . . .209
Caffein,. . . «+ « - + - dT
Calcium, ws dine » » 139, 214

Calcium, carbonate, ee eo oe 0145
Caleium, hydroxide, ...
Caleium, oxide,......
Calcium, phosphate, ..
Calcium, sulphate, .
Callousj. « « « «© « « & « 2 OBZ
Calyx,6 6 «8 4% % & % %
Cambium,.....
Cane-sugar,. . . se eee
ey, attraction, eee se
et Oe
Carbhydrates, ...

Carbhydrates, Compasition’ - 72
Carbhyarates, Transformations #0
Corban: Properties of.” . «i Ae
Carbon in as. baa ew
Carbon dioxide, CH eee
Carbonates, .....
Carbonate of lime, . .. .
Carbonate of potash,. . ..
Carbonate of soda, .... ©
Carbonic acid, - 19, 128
Carbonic acid’as food of jant, 328
Carbonic acid in ash-analyses, 149
Carboxyl, .. 1... . « 015,77

Casein, ......... = &
Caseose, . . 2... «6 ss « 101
Cassava, .. - . OL
Causes of motion of juices, - 6385
Cell-contents, ..... . . 249
Cell-multiplication, . . . . .252
Cell, Structure of .-. . . . . 245
Cells, Forms of ..... . .27

Cellular plants,, . .....
Cellular tissue, . .....
Cellulose, . . i a
Cellulose, Composition er te a
Cellulose, Estimation ....
Cellulose nitrdtes,. . . .
Cullulose sulphates,. . .
Cellulose, Testfor. . .
Cellulose, Quantity of, in plants, 46
Chemical affinity, ....
Chemical affinity ovércome by
osmose,. . iy aa
Chemical combination, oa es 2
Chemical Beso Darton: - + 30

Chemistry, ..... 10
Chlorides, .. ae sib 133, 149
Chloride of ammonium, elepots
posed by plant, . . . 184
Chlorine, . . . 132
Chlorine essential to ' crops ? 9. 7.194
.Chlorine, function in plant, . 218
Chlorine in strand plants, . .191
Chlorophyl, . » 124, 307, 308
Chlorophy!. requires iron, . . 220
Chlorophyllan, .'- . . . . .125
Choline,. . . és « «119
Circulation of sap, oe eg 369
Citricacid, ....... . 80
Citrates, . . . » « « 80,149
Classes of plants, . so 6 « 2 829
Classification botanical, 329

HOW CROPS GROW.

Clover, washed byrain, . . » aa

Colloids, . . . + » + «© 6 es
cong tutes ee a tet. a ve ID OT
Combustion, . . . «+. + «18
Composite plants, . « 330
Concentration of plant-food, +185
Coneretions in plant, . .. . 205
Coniferous plants,. . . + » -330
Copper in plants,. . . . . . 210
Ork, os 3 i 0 ww ww ww 208
| Corm,. « « « « «© «© « « © « 288
ee he 8 Ae) ee
Cotyledon, ... » « 290, 333
Coniferous planks, oe ee 830
Cryp' Ae et « « 315, 329
Crystal Out | aleurone, o «. 211
Crystalloids,. . . . « « « - 392

Crystalsin plant, ... . - .206
Rot

- 129
“| 30

Cyanides, .....-.
Cyanogen,. .

Density of abode, ee ee RS

Dex Hae we ae ee eB
Dextrose, se eee 63
Diastas .

- 67, 103, 360
Diffusion of liquids, o 6 « « 390
Dicecious plants « - - 318
Drains stopped by’ roots, + » 276

Dey esther, E f ec ot ° sf, “on

plants,. .. ee a, ABT.
Ducts, . . . . - « « « «255, 294
Dulcite,

Dundonald’s treatise on * Apri-

eultural Chemistry, ... 4
Elements of Matter, .... . 8
Embryo,. . . ». « «© « « « . 333
Endogens, . ...- . 259, 290, 334
Endosmose, ...... . . 394
Endosperm, .. + « + « « 332
Enzymes, . . . « « « « » . 103
Epidermis, . o + » 6291
Epidermis of leaf,” eee + 6 808
Eremacausis,.. . . + - 20

age, . 6. -
Exogens, ....
Exosmose, .

é - 309

239, 293, 296, 334
o-. « 394
Exudation of ash-ingredients, Aes

Eyes of potato,. .. . . . . 289
Families,. . 1... «4 « + + 328
Fatty acids, .« . . 2... «1. %
Fats, - 83
Fats converted into starch, . » « 353
Fat in oat cro 230

Fat in Vegeta sble Products, << 7

Ferments, . ...... ~. 102
Ferric oxide,. . .... . . 142
Ferric pe arexine, os fee, i 142
Ferric Salts, . .... . 142
Ferrous oxide, ..... 141
Ferrous hydroxide, ... . . 141
Ferrous salts,. . ... . .- 142
Fertilization, ...... .319

Fibrin, . «6 16. «+ « « «91,96

INDEX. 413

Fibrinogen,. . . .. . . 91,96 Isomerism,. . i Val Ate AS
Flax fiber, Fig., + + « 41,248 | Juices of the Plant, ” 2 +e es 869
Flax seed mucilage, ws 58, 62 | Lactic Acid, . . ee ae a
Flesh Sbeiny > so + «© + « « 92} Lactose ete se 2 2 2.68)
Flower, oes we . . 817] Latent buds, .” Gr we ce ee BD
Flow of 8: sap, ce ee ee @ A8TL nals eel Se ce ee oe) Ber wr BOE
Fluorine in ye + + + + « 209) Layers, a oe ww « OE
Foliage, Offices of . + +s 2314 | Lead in plants," wer ay ee gah 10
Food of Plant, . . . . . . .366| Leaf pores, .. - . + . 809
Formative layer, . . . . . .245| Leaves, Structure Of os 306, 308
Formulas, Chemical, . . . 33,73 | Leaves, office in nutrition, . . 328
Fructification, . . .. . . #19] Lecithin,. ....... . 122
Fructose, ...... + «. 68 pees: sje eee @ 5 B82
Galactin, ee ee Se oe SL Locuneinny plants, os ep 3882
Galactose, . . - 65} Leucin, ......... AG
Gases, how distributed through- Levulin, ee eS 56
out the plant, a ae ce Levulose, . . . . 68
Gelatinous Silica,. . . . . . 136 seus, e : é - 41
Genus ; Genera one wo BB mi 8 + 139
Germ,. . . wee ee 6 88T igut uid Diffusion, Cae - 390
Germination, oa Oars * 349 Lithia, Lithium, in plants, | » 209
Germination, Conditions of .” .'361 Lupanin, Lupinin, Lupinidin, 120
Seen Chomical Physi- Magnesia, ...... - . .140
iggy Of . ews . « . 857 | Magnesium, . 140, 215
Girdl wide at det 8o OBB pene hydroxide, .” a we ws. edd.
Ginnbees Balt, Ge lee ass a ay a 148 hte cnet oxide, .... .140
Gliadin, . . SS ae cay once nate a fibrin, . 2... 1 1 1 2 8
Globulin, a ai sey Ga, Fp Se ke ee OG Malates.. fe sg das aes (a aR . 149
Glucoses,. .... .. . .89,63| Malicacid,...... - 79
Glucosides, ........ 69 alone acid, . eee ew ew
Glutamin, ....... . 16 t, Chemistry of oe + + 0858

Gluten, ... s ee B®

Gluten-Casein, © oe 6 eo + 693,95
Glycerin, ......... 86
Glycogen. . . : . . 56
Glycocoll, . . - + - 116
Glycollic acid, ee 0 AT
Gourd f pe » = . ol
+» B81

» 63

Grape Sugar,.. by ih.
Growiby | 2s

’ .

Growth ef Toots

Gum, Amount a in plants, | « » 62

Gum Arabic,., . 2... +. 6 « BT

Gum Tragacanth, ..... .57

ra Dp Sg 8M See

YpSUM, © 2 2 ee ee ts

. 110

Haemetin,. » « + » « « +
eee eter - + 109
+158, 344

Zy- - oe et

Halle’ ‘ee wheat,

ay ealpBidey a5 26, 129
Imbibition, ... o + + 2 386
Imide: eek a ae TT

Inorganic matier, . ee SG et
Internodes,. . ... . + - 284

Pe ce Soc. HS a os Se
Invertin, . os « « + 108
Iodine in plants,” « © « « 134, 210
Jodine, Solutionof. .....

Iron,
Iron, Function Of 6 a wa

alee, Se: ce. lone: BT
Ce Pala oe eee

Membrane-diifusion, " . oo

tion of Ea . « 404
Metals, Metallic elements, " + 138
Metapectic acid, . ... +. 59
Metarabin,........ .59

Milk ducts, ..... - . 304
Miik Sugar,. . . - 68
Molecules, Molecular ‘Weights, 32
Monecious plants, . . « 319
Motion caused by adhesion, - 389
Mucedin, . « » 92, 321
Multiple’ Proportions, ee

Muriate of potash, . ... . 149
apamatic acid,. . . «+ » » .133
Myos: » 2 « - 9, 98
Nectar, Nectarics,” 6-3. 6 8 = 4819
Neurin, . . 2. «2... + - «120
Nicotin, oe 6 © ow 6 6620
Niter, Nitrate of potassium,. . 149
Nitrates in plants, . . . .113,149
Nitric Acid in plant,. . . . .113

Nitrogen, Properties of . . . . 20

Nitrogen in ash, ... . 127
NODOS isan Go Ft ~ + 284
Non-metals, . . woe ua! 8 LET
Notation, Chemical .".°. °. *. 33
Nuclein,« . 1... «26 6 « 2 122
Nucleus, . .... «6... 300
Nut). 6.6 eee we ee ae et BOT

414 HOW CROPS GROW.

Nutrient matters in Bian, Mo- Pith rays, .

tionof. .. .'. . 401 | Plastic Elements of Nutrition, 109
Nutrition of seedling, - . . 657] Plumule, .....-+ sss.
Nutrition of plant, . .. . 366 | Pollarding,. . . . +. « « + .286
Oat plant omposition and Pollen, . . » - 318

e Polygonum convolvulus, Fertil-

Oats, Welght pet bushel, ” 2. 176 | sleigh of, Fig., . . . . .295
Oil in seeds, ete... . ... 83 | Pom » 331
Oil of wittol, pO eS oe aes 26, 130 Pardsit of Vegetable tissues, "385
Oils, Properties of . . . .-. 83| Potato leaf, Pores of, ae
Oleic acid, . ...... . .86{ Potato stem, Section of, Fi;
QOlein,. ....... =. . . 85] Potato tuber, Structure an dea
Orders, .. ab tee eat. “eo SOS tion of, Fig... .. . . .300
Organic matter, » 2 + « « » 12} Potash,. . . 1. «© - . 138,144
Organism, Organs,. . . . . .243| Potashlye,. ...... . 139
Osmose,. . . 393 | Potassium, . . » - 138, 211
Osmose, mechanical effects on Potassium carbonate, « a « 14d

plant, ..... =... . . 406] Potassium Chloride,. . . . . 149

Osmometer,. ..... .- . .894| Potassium hydroxide, a; 4 wy 18D
Ovaries,. ...... . . . 3818] Potassium oxide,. ... . . 138
Ovules, ...... .. . .318] Potassium phosphate, . .. .147

Oxalates,... . . . . . 78,149| Potassium silicate, . . , . . 134
Oxalicacid,. .... .. . .78{| Potassium sulphate, ... . .146
Oxides,. . 19,20 | Prosenchyma, . . .. . + . 255

Oxides of iron, described, . * 19, 141 | Protagon, . . . - «6.» 123
Oxides of manganese, described 142 Proteoses, . . « +» « + « « - 100
Oxyfatty acids, ++ + + « .77| Protoplasm, .. +245
Oxygen, Properties: of . . . . 16 | Protein bodies, or Proteids,. ‘i ee

if

Oxygen occurrence in ash, . .128 | Proximate Eemelpiss, v8
Geveens in Assimilation,. . . 364 | Quack grass,. . See BST
On eet in Germination, . . .353 Quantitative “relations amoung
Palmitic acid, .....-. 8 ingredients of plant,. . . 220
Palmitin,. .... ... . . «85 | Quartz, .. «+ 134
Papain,. . 2... + + « « +104 Quince seed mucilage, .° 2 2 + 62
Parenchyma,.. . » « « »265] Radicle, . . 2. 2 » oe
Papilionaceous plants, . . . 3830] Raffinose, .. %
Pappus, .. s+ «+ «ss « al Reproductive Organs, te

Pararabin,. . ...... . BF eevee se hase, ve .
Paraglobulin,. ... . « .96, 99 . cae
Paragalactin, ....... 61 Bock Cr stal, a o
Pecticacid,. . .... . . . 74 Root-action, imitated, F

Pectin bodies, . . . . .58,59, 74]! Root-action, Osmose in

Pectosic acid,... . . . . . . 74] Rootcap,. +257
Pectose,. . - . 58, 61,74 | Root distinguished. from stem, 258
Pedigree wheat, . . . » 158,344 | Root excretions,. . ... . .280
Pepsin, . . .... .. « .104/ Roothairs, .
Peptones, - « « 100 Bone. Seat of absorptive force
Permeability of cells, an cep ar OS. «0 «ee 2 270, 399
Petals,. . . 318 Root § stock, a, Pi febes cas oe ROR
Phanerogams, Phaenogams, 316, "329 Rootlets, . . oe 0 ee 6 260
Phloridzin, . . ae far erate 69 Roots, Growth of... es 6256
Phosphate of lime,” «+ + + «148 | Roots contact with soil, .-. . 266
Phosphate of soda,. . . . . .148 | Roots going down for water, . * 276
Phosphate of potash, . . . . 147 | Roots, Search of food by. . . 263
Phosphates,. . . + 28, 132, 147 | Roots, Quantity of . . . . . .263
Phosphates function in plants, 211 | Rubidium action on Oats, «+ » 209
Phosphates season to albu- Runners,, .... + + 286
minoids, . - - . » . 221 | Saccharose,
Phosphoric acid,. . . . . 27,132 | Saccharose, Amount of, in
Phosphorite, . «6 148 plants,. .. .
Phosphorized substances, - 122} Sago, . 2 2 6 - ee ee BL
Phosphorus, . . . .27| Salicin, . . 2 1 seuss 6 se 6D
Phosphorus pentoxide, ° -. » 27,132 | Salicornia, . . .....6-4.. . A9L
Physics, . . . . + + + + + +10] Sal-soda,.... . . .:0:. » . 145
Physiology, se ee ee es 10] Salsola, . . ee ee A19L
Piperin, . ~ « « # « 4 # « si@1,| Salts, Definition of woo ee BE
Pistils, . . ... .. . . . 318] Salts,in ashof plants, . . . .143

Pith, 2 6 0 6 6 0 2 eee e DOT Saltwort, eran eo oe ew wo AD

Sodium sulphate, . . 146
wae vartaniong of, in field

Tops, eww a ow OD
Sodium Chloride, " “a ew we oD
Soil. Offices of & 8 ee er 4 808
Solanin, 121

a 2 ee

tion
Soluble ‘silica, Me ee

- 135
Soluble starch, oe ee oe BB
Species,. . . oe 6 6 « 2 326
Spirits of salt, em es ae 18S
Spongioles, ...... . . 257
Spores, ..- + + 3 + + « O16
DOE 9 eB ch, WG ee BT
Stamens,. . + 318
Starch, amount in plants, | « + 51
Starch-cellulose, . ... . . 50
Starch estimation, ... . . 52
Starch in wood, . . « + 373, 376
Starch, Properties of)... 47
Starch, Testfor...... .49

Stearic acid, . ae ee www 86

INDEX. 415
séamphire, ..... . . . 191! Stearin, . . woo we 385)
BD Y ah Sd Rw ORAS 369 | Stem, Endogenous | aes . 290
Sap, Acid and alkaline . 378 | Stem, Exogenous ... . . .296
‘Sapascending,. ... 79, 384 | Stem, Structure of . . . . . 289
Sap descending, ... . . .882|Stems,......... . 282
Sap, Composition of. . . . .376|Stigma,......... .318
Sap of sunflower, . . . . . .878|Stomata,. ....... . .809
Sap, Spring flow ae + + + , «870|Stool,. 2. 2... 1 ew ee 6 287
Sap wood, . ‘ «+ . « .805 | Suckers, ...... . . . ‘287
Saponification, owl oe a a Sucroses, . » + . 39,65
Saxifraga crustata, ... -206 | Sugar, Estimation | of. ). «oe » OB
Seed, . . ast eer, Wee oe se . 832 | Sugar, in cereals,. . . . . . 69
Seed vessel,. ae » . + « 830) SugarinSap,...... . 877
Seed, Ancestry of . . . 346 | Sugar of mi . « » 68
Seeds, constancy of composition145 Sulphate of lime, ” oe eo w 146
Seeds, Density of . . . . . . 339 | Sulphate of potash,. ... . 146
Seeds, Weight of .. . 340 guiphate of soda, .... . 146
Seeds, Water imbibed by. . 399 Sulphates,. . . - « 26, 121, 146
Selective power of plant, . . .401 | Sulphates, Function of, .-s 210
Seminose,..... .. . . 65 | Sulphates reduced by plant, + 208
Sepals,. . .. .. . . . . 317 | Sulphides,. .---. . . . .26, 130
Sieve-cells, Cae » + . . 303 | Sulphide of potassium,. . . .130
Sieve-cells in pith; . » « . 843,345 | Sulphites, .. . 1... ws . 129
Silica, . < a se Sulphur, . . . ~ «2 . 25,129
Silica entrance into plant, . .402 | Sulphurinoat,. . . . . . . 208
Silica, Function of, in plant, . 216 | Sulphur dioxide,. . . . . 25, 130
Silica in ash, . . . « .197 | Sulphureted hydrogen, . .26, 115
Silica in textile materials, - . 200 | Sulphurets fe ee 8 a he RB
Silica unessential to plants,. .197 | Sulphuric ‘acid, + 2 6 « + 26,130
Silicates, .. .» . . . 1384] Sulphuric acidin oat, . . . .208
Silicate of Potassium, . . » 184 | Sulphuric oxide (SOs), «+ +. 209
Silicic acids,. . . . . . . . 135 | Sulphur trioxide (SO,), . . .25,130
Silicon, .. + « + « « 134 | Sulphurous acid, 2 + « 6 25,129
Silicon, Dioxide.” 7... 134 Symbols, Chemieal °.’. . - 3l
Silk of maize, .... . . .819| Tao-foo,. ......... 996
Silver-grain,. . .. . . . .299} Tapioca, ......... 51
Sinapin,. .... .. - . .120|Tap-roots,....... « 259
Soaps,. . ..... .. . . 93/ Tartaricacid,. ...... .80
Sodium, .. . be sas a ES ere Tartrates, ow ve ee 8 80.
Sodium’ carbonate, 7 Tassels of maize, woth ee Se ves ed!
Sodium essential to ag. ‘plants? 186 Theobromin, ee ae » « 118
Sodium hydroxide, ... 139 | Tillering, . ..... . + .287
gure in strand and marine Titanic acid,.. . ry » 137
«oe e ee se * 191 | Titanium, . as 137, 209

Sodium. oxide, ..°.. . . 139 | Translocation of substances in

plant,. « 1. 6 + 6 6 6 . 287
psin,. . . . + » » « . . 104
Tubers, ae « ¢ 273, 288
Tuscan hat-wheat, oo ee 2 18
osin, . . 116

timate Composition of Vege-

table Matters, . . .. .13,
Umbelliferous plants,. .. . ’330
Unripe seed, Plants from. .
Begg te ee tee 8
Valence, .. « .
Varieties, . . . 158, 326, "327
Vascular bundle of maize

stalk, ... «+ « « 291,293
Vascular-tissue,. .... - "255

Vegetable acids, . .....
Vegetable albumin, . .. . . 90
Vegetable casein,. . ... . 9

Vegetable cell, . ...--

Vegetable fibrin, ay ie gh ane
Vegetable globulins,. . . .
Vegetable mucilage, ... . 57
Vegetable myosins, » «+» «

416 HOW CROPS GROW.

Vegetable parchment,. . . . 44
Vegetable tissue, . . . a re

Vegetative organs, .... -
Vernin, .... oe e 2 sll8
Vicin,. .. ea Sar Yer, Fe AZO

Vitality of roots,. . .
Vitality of seeds,,. . ....
Vitellin, ii. 68 2%,
Water, Composition of. . . . 37
Water, Estimationof ... ».39
Water, Formationof .... %
Water in air-dry plants. . . . 39
Water in fresh plants,. . . . 38
Water in vegetation, Free. . . 39,
Water in vegetation, Hygro-

scopic, . 2 2 ee ee

Water-oven,....
Water-culture, ...
Water-glass,... «
ots, » 2 6

Water

Wood cells ‘of ‘conifers,
Woody stems, ...
Woody tissue,. ...

Zanthoph:

Zein, .
ine,

Vip os 38s

HOW CROPS FEED.

A TREATISE ON THE

ATMOSPHERE AND THE SOIL

AS RELATED TO THE

NUTRITION OF AGRICULTURAL PLANTS.

With Illustrations.

BY

SAMUEL W. JOHNSON, M.A.,

PRoFEessoR OF ANALYTICAL AND AGRICULTURAL CHEMISTRY IN THE SHEF-
FIELD SCIENTIFIC SCHOOL OF YALE COLLEGE; CHEMIST TO THE CoN-
NEctTicuT STATE AGRICULTURAL SociETY; MEMBER OF
THE NaTIONAL ACADEMY OF SCIENCES.

The work entitled ‘‘How Crops Grow’ has been received with very great
favor, not only in America, but in Europe, The Author, therefore, puts forth
this volume—the panion and ip it to the farmer—with the hope
that it also will be welcomed oF those who appreciate the scientific aspects
of Agriculture, and are persuaded that a true Theory is the surest guide to a
successful Practice. In this, as in the preceding volume, the Author's method
has been to bring forth all accessible facts, to present their evidence on the
topics under discussion, and dispassionately to record their verdict. If this
procedure be sometimes tedious, it is always safe, and there is no other mode
of treating a subject which can satisfy the earnest inquirer. It is, then, to all
Students of Agriculture, whether on the Farm or in the School, that this vol
ume is specially commended. : oe

CONTENTS.
DIVISION I.

The Atmosphere as Related to Vegetation.

CHAPTER I—ATMosPHERIC Arr as Foop or PLants.
CHAPTER I1.—T#e ATMOSPHERE a8 PHYSICALLY RELATED TO VEGETATION.

DIVISION IL.
The Svil as Related to Vegetable Production.

CHAPTER I.—IntRopvucroryY.

CHAPTER II.—Oricin aND FormaTION OF Sorts.

CHAPTER III.—Krinps oF Sos, THeIR DEFINITION AND CLASSIFICATION,

CHAPTER IV.—PuysicaL CHARACTERS OF THE SOIL.

CHAPTER V.—Tue Sor as a Source or Foop To Crops: INGREDIENTS
WHOSE ELEMENTS ARE OF ATMOSPHERIC ORIGIN.

CHAPTER VI.—Tue Sor as a Source or Foop To Crops INGREDIENTS
WHOSE ELEMENTS ARE DERIVED FROM ROcKs.

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