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THEORY OF HORTICULTURE.

THE THEORY

OF

HORTICULTURE:

oR,

AN ATTEMPT TO EXPLAIN
THE PRINCIPAL OPERATIONS OF GARDENING

UPON PHYSIOLOGICAL PRINCIPLES.

BY

JOHN LINDLEY, PH.D. F.R.S.,

VICE-SECRETARY OF THE HORTICULTURAL SOCIETY OF LONDON, AND PROFESSOR OF
BOTANY IN UNIVERSITY COLLEGE.

“Though I am very sensible that It is from long experience chiefly that we are to expect the most certain rules
of practice, yet {t is withal to be remembered that the likeliest method to enable us to make the most judicious
observations, and to put us upon the most probable meana of mnproving any art, is to get the best insight we can
into the nature and properties of those things which we are desirous to cultivate and improve." Hales's Vegetable
Statics, |, 876.

SECOND AMERICAN EDITION, WITH NOTES, src.

BY

A. J. DOWNING.

NEW YORK:

WILEY AND HALSTED,
851 BROADWAY
1859.

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420
L14«
1257

Entered according to the act of Congress, in the year 1852, by
JOHN WILEY,
In the Clerk’s Office of the District Court for the Southern District of New York,

R. CRAIGHEAD,
Printer, Stereotyper, and Electrotyper,
Carton Building,
$1, £3, and 85 Centre Street.

THE MEMORY

oP

THOMAS ANDREW KNIGHT.

PREFACE

TO THE

AMERICAN EDITION,

Wirsin the last ten years, the taste for Horticultural
pursuits has astonishingly increased in the United States.
There are, at the present moment, at least twelve societies
in different parts of the Union devoted to the improvement
of gardening, and to the dissemination of information on
this subject. Nor is it surprising that gardening should
be a favourite pursuit in this country, when we consider the
fertility of our soil, the ease and abundance in which all the
finer fruits of temperate climates may be produced, and the
comparative facility. with which individuals may become
landholders. But although a taste for Horticulture is
widely diffused, and its practice is frequently very successful,
yet few of our amateurs or professed cultivators understand
the rationalia of the operations they pursue; and hence
they are unable to improve or modify their methods so
as to ensure full success under varying circumstances, or
safely to apply the directions they may receive from books
or other sources. .

Vill PREFACE TO THE

The works on Horticulture which have hitherto been
published in this country, are nearly restricted to details
of practice, rarely attempting to convey any information
beyond short directions for the culture of particular crops,
or monthly memoranda for the management of different
departments of the garden. Several of these, moreover,
being chiefly compiled from similar foreign treatises, are by
no means adapted to our climate, and are consequently
of little value to the novice in the art of gardening. It
may, therefore, be presumed that a work like the present,
which explains, those universally applicable principles upon
which all correct horticultural operations necessarily depend,
will prove quite as useful to amateurs and cultivators
generally in this country, as in Great Britain, where it has
supplied a most important desideratum. It is the only
treatise of the kind extant, at least in the English language ;
and probably, no person living is so well qualified for
preparing such a work as Professor Lindley. It is at once
remarkably simple, and highly philosophical; free from
superfluous technicalities, and at the same time truly
scientific. Without entering into tedious subordinate
details, it offers a lucid explanation of the general nature
of vegetable actions, and of the important principles which
lie at the foundation of all the operations of Horticulture,
and which the intelligent gardener or amateur can readily
apply for himself to each particular case.

A knowledge of these leading principles, at once invests
with new and peculiar interest even the most mechanical,

AMERICAN EDITION, 1x

and apparently unmeaning and irksome details of the art.
With what increased satisfaction are the common processes
of manuring or transplanting carried on, to say nothing
of the more delicate operations of budding, grafting,
propagating by layers, &c., when we are acquainted with
the structure of the plants we are endeavoring to control,
and comprehend the why and the wherefore of every step
we pursue! With this knowledge of vital actions, new
modes of culture, and various improvements in the
operations of the art, are continually suggested to the
reflective mind; which derives additional pleasure from the
prosecution of scientific experiments, of which the ignorant
laborer, who turns over the soil and sows his seeds in
precisely the same manner under all circumstances, never
dreams.

Besides the higher gratification which Horticulture
affords, when its principles are understood, the increased
profit, derived from the superior quality and augmented
quantity of the products, and the greater certaintv of
success in culture, should, rot be forgotten. Were the
labours of the gardener always confined to the same en-
closure, the same soil, and the same climate, a formal routine
of practice would frequently produce all the desired results.
But as scarcely two soils are exactly alike, as the position
or exposure of a garden has a great influence on its
productiveness, and as his operations must be varied
according to varying circumstances to ensure success, how
important is it that the enterprising cultivator should

1*

x PREFACE.

understand those really simple general principles, founded
upon the very nature of things, upon which all his under-
takings are based. Among the simplest operations, it is
one thing to prune a tree properly, so as to keep it in
a healthy and productive state, with just the proper
proportion of fruit and leaf-buds; and quite another to cut
away a certain bulk of wood annually, merely because
pruning is generally thought a beneficial practice. Similar
comparisons might be drawn from many familiar cases
between the injurious results of empirical practice, as
contrasted with those which follow the application of correct
principles, and some knowledge of vegetable physiology.
The notes appended to this edition are rendered necessary
in some cases, by the difference between the climate of
England and of this country; or they relate to different
applications of principles: it is hoped that they will in some
degree increase the value of the work to the American

reader. A. J.D.

Newburgh, on the Hudson, March, 1852.

A few notes signed G. were contributed to the first American
edition by Professor Gray.

PREFACE

TO THE

ENGLISH EDITION.

Tus book is written in the hope of providing the intelligent
gardener, and the scientific amateur, correctly, with the rationalia
of the more important operations of Horticulture; in the full
persuasion that, if the physiological principles on which such
operations, of necessity, depend, were correctly appreciated by
the great mass of active-minded persons now engaged in
gardening in this country, the grounds of their practice would
be settled upon a more satisfactory foundation than can at
present be said to exist. It is, I confess, surprising to me, that
the real nature of the vital actions of plants, and of the external
forces by which they are regulated, should be so frequently misap-
prehended even among writers upon Horticulture; and that ideas
relating to such matters, so very incorrect as we frequently find
them to be, should obtain among intelligent men, in the present
state of what I may be permitted to call horticultural physiology.
There must be a great want of sound knowledge of this subject,
when we find an author, who has made himself distinguished in
the history of English gardening, giving it as his opinion, “that

xi PREFACE To THE

the weak-drawn state of forced Asparagus in London is occa-
sioned by the action of the dung immediately upon its rocts!”

It does not scem possible to account for this in any other way
than by referring it to the want of some short guide to the
horticultural application of vegetable physiology, unmixed with
other things ; and so arranged that the intimate connexion of one
branch of practice with another, and of the whole with a few
well ascertained facts upon which everything else depends, may
be distinctly perceived from a single point of view. The
admirable papers of Mr. Knight are scattered through the
Horticultural Transactions ; and the writings of other physiolo-
gists are dispersed through so many different works, that the
labor of finding them, when wanted, is greater than is willingly
undertaken even by those who have access to ample libraries.
With regard to general works on Horticulture, it is very far
from my wish to say one word in disparagement of the many
excellent publications upon this subject which have already
appeared in this country; on the contrary, the improved state
of gardening among us may be reasonably ascribed to the
influence of some of these valuable works: but it must be
admitted that the true principles of physiology are not, in such
books, so separated from the details of routine on the one hand, or
so applied to them on the other, as to be readily understood by
those who want either the skill or the inclination to distinguish
empirical directions from rules which are plainly founded upon
the very nature of things. I must also be permitted to observe
that, although results are correctly stated in such books, they
are not unfrequently referred to wrong causes.

In preparing the following pages for the press, my anxious
desire has been to strike out all unnecessary matter, even
although it may be required to complete the physiological

ENGLISH EDITION. xi

explanation of common facts; and to ‘introduce little beyond
that which every gardener ean verify for himself. Vegetable
anatomy is no doubt the foundation of all correct views of
physiological action; chemistry is of the first importance, when
the general functions of plants are considered in a large and
general way; and electricity probably exercises an important
influence over the vital actions of all living things. But these
are the refinements of science, belonging to the philosopher in
his laboratory, and not to the worker in gardens; they are
indispensable to the correct appreciation of physiological
phenomena, but not to the application of those phenomena to
the arts of life; electricity, in particular, appears to me, in the
present imperfect state of our knowledge of its relation to
vegetable functions, altogether incapable of forming a part of
any horticultural theory.

What the gardener wants is, not a treatise upon botany, nor’
a series of speculations upon the possible nature of the influence
on plants of all existing forces, nor an elaborate account of
chemical agencies inappreciable by his senses and obscurely
indieated by their visible results; but an intelligible explanation,
founded upon well ascertained facts, which he can judge of by his
own means of observation, of the general nature of vegetable
actions, and of the causes which, while they control the powers
of life in plants, are themselves capable of being regulated by
himself. The possession of such knowledge will necessarily
teach him how to improve his methods of cultivation, and lead
him to the discovery of new and better modes.

Tt is very true that ends of this kind are often brought
about by accident, without the smallest design on the part of
the gardener; and there are, doubtless, many men of unculti-
yated or idle minds, who think waiting upon Providence much

xiv PREFACE TO THE

better than any attempt to improve their condition by the
exertion of their reasoning faculties. For such persons, books
are not written.

I hope that what has now been said will not lead any one
to suppose that this sketch is offered to the reader as a
complete theory of Horticulture in all its varied branches;
such a work would be alike tedious to the author and the
reader, and, I fear, as unprofitable ; for, if a gardener, when once
made acquainted with the general principles of science, has not
the skill to apply them to each particular case, it is to be feared
that no disquisition, however elaborate, would enable him to do
so. So far has it been from my intention to enter into subor-
dinate details, that I have carefully avoided them, from a fear
of complicating the subject, and making that obscure which in
itself is sufficiently clear. All that 4 physiologist has really to
do with Horticulture is, to explain the general nature of the
vital actions of a plant, and the manner in which these are
commonly applied to the arts of cultivation; if he quits this
ground, he extends his limits so much that there is no longer a
horizon in view. No one, indeed, could advantageously inves-
tigate the minor points of cultivation in all their branches,
unless he were both a good physiologist and a practical gardener
of the greatest experience, 2 combination of qualifications which
no man has ever yet possessed, and to which J, most assuredly,
have not the shadow of pretension.

In conclusion, let me, in impressing upon the minds of gar-
deners the importance of attending to first principles, also caution
them against attempting to apply them, except in a limited
manner, and by way of safe experiment, until they fully under-
stand them. The difference between failure and success, in
practice, usually depends upon slight circumstances, very easily

ENGLISH EDITION. xv

overlooked, and not to be anticipated beforehand, even by the
most skilful ; their importance is often unsuspected till an experi-
ment has failed, and may not be discovered till after many
unsuccessful attempts, during which more mischief may be done
by extensive failures than the result is worth when attained.
No man understood this better than the late Mr. Knight, the
best horticultural physiologist that the world has seen, whose
experiments were conducted with a skill and knowledge which
few can hope to equal. So fully was he aware of the uncertain
issue of experimental investigations in Horticulture, that he
thought it necessary, in recommending a new mode of cultivating
the Pine-apple, and in objecting to methods at that time commonly
in use, to express himself in the following words :—*I beg to
be understood that I condemn the machinery only which our
gardeners employ, and that I admit most fully their skill in the
application of that machinery to be very superior to that which I
myself possess. Nor do I mean, in the slightest degree, to
censure them for not having invented better machinery, for it is
their duty to put in practice that which they have learned; and,
having to expend the capital of others, they ought to be cautious
in trying extensive experiments, of which the results must
necessarily be uncertain; and, I believe, a very able and experi-
enced gardener, after having been the inventor of the most
perfect machinery, might, in very many instances, have lost both
his character and his place before he had made himself
acquainted with it, and consequently become able to regulate
its powers.”

CONTENTS.

BOOK I.

Pass

Or THE PrinoraL CIRCUMSTANCES CONNECTED WITH VEGETABLE
Lire WHICH ILLUSTRATE THE OPERATIONS O¥ GARDENING .

CHAPTER I.
GERMINATION.

The Nature of a Seed.—Its Duration.—Power of Growth.—
Causes of Germination.—Temperature. Pee —Humidity.
—Chemical Changes : i ‘ ‘ ‘

CHAPTER ILI.
GROWTH BY THE ROOT.

Roots lengthen at their Points only.—Absorb at that Part
chiefly.—Increase in Diameter like Stems.—Their Origin.—
Are feeding Organs.— Without much Power of selecting their
Food.—Nature of the latter.—-May be poisoned.—Are con-
stantly in Action.—Sometimes poison the Soil in which they
grow.—Have no buds,—But may generate them .

CHAPTER III.
GROWTH BY THE STEM.

Origin of the Stem.—The Growing Point.—Production of
Wood, Bark, Pith, Medullary Rays.—Properties of Sap-wood,
Heart-wood, Liber, Rind, &c.—Nature and Office of Leaf-
buds —Embryo-buds.—Bulbs. Rigi uae of Sap, and its

Nat re ‘ a x ‘ Fi i

5

10

22

XVill CONTENTS.

CHAPTER IV.

Pace

ACTION OF LEAVES.

Their Nature, Structure, Veins, Epidermis, Stomates.—Effect of
Light.—Digestion or Decomposition of Carbonie Acid.—
Insensible Perspiration.—Formation of Secretions.—Fall of
the Leaf.—Formation of Buds by Leaves... ‘ *

CHAPTER V.
ACTION OF FLOWERS.

Structure of Flowers.—Names of their Parts—Tendency of the
Parts to alter and change into each other, and into Leaves.—
Double Flowers.—Analogy of Flowers to Branches.—Cause
of the Production of Flowers—Of Productiveness—Of
Sterility.—Uses of the Parts of a Flower.—Fertilisation—
Hybrids.—Crossbreds . : . . . :

CHAPTER VL
OF THE MATURATION OF THE FRUIT.

Changes it undergoes.—Superior and inferior Fruit.—Is fed by
Branches upon organisable Matter furnished by Leaves.—
Physiological Use of the Fruit.—Nature of Secretions.—The
Changes they undergo.—Effect of Heat.—Of Sunlight.—Of
Water.— Seeds.—Origin of their Food.—Cause of their Lon-
gevity.—Of their Destruction.—Difference in their Vigour .

CHAPTER VII.
OF TEMPERATURE.

Limits of Temperature endurable by Plants.—Effects of a too
high Temperature.—Of a too low Temperature.—Frost.—
Alternations of Temperature.—Day and Night.—Winter and
Summer.—Temperature of Earth and Atmosphere

87

69

19

CONTENTS. xix

BOOK IL.
Pace
Or THe PaystoLoeicAL PRINCIPLES UPON WHICH THE OPERATIONS
or HorticuLruRE ESSENTIALLY DEPEND : a : » 101
“ CHAPTER I.
Of Bottom Heat i oe Ge ce luz
CHAPTER. II.

Of the Moisture of the Soil.—Watering ei: ita - 4 . 218

CHAPTER IIL

Of Atmespherical Moisture and Temperature 7 6 6 1285
CHAPTER IV.

Of Ventilation Bo a kw ae RO
CHAPTER V.

Of Seed sowing . é F - i 7 . 159
7 CHAPTER VI.

Of Seed-saving . . . . 2 ne ae . 169
CHAPTER VII.

Of Seed-packing . . woe wo oa 7 6 + U9

CHAPTER VIII.
Of Propagation by Eyes and Knaurs . . . 3 . 184

CHAPTER IX.
Of Propagation by Leaves ‘i : ‘ 2 : : . 190

CHAPTER X.
Of Propagation by Cuttings. : . . ee « 199

CHAPTER XI.
Of Propagation by Layers and Suckers fe es » 207

xx CONTENTS.

CHAPTER XII.
Of Propagation by Budding and Grafting

CHAPTER XIII.

Of. Pruning
. CHAPTER XIV.

Of Training
CHAPTER XV.

rt Potting

CHAPTER XVI.
Of Transplanting

CHAPTER XVIL
Of the Preservation of Races by Seed

CHAPTER XVIIL

Of the Improvement of Races

CHAPTER XIX.

Of Resting

CHAPTER XX.
Of Scil and Manure : : F *
Inprx i ‘ é 5 ‘ . °

. 256

. 267

- 295

. 806

. 818

THE THEORY

OF

HORTICULTURE

INTRODUCTION.

'

1. HortTIcuLTURE is that branch of knowledge
which. relates to the cultivation, multiplication, and
amelioration of the Vegetable Kingdom. It divides
into two branches, which, although mutually. depen-
dent, are, in fact, essentially distinct: the art and the
science. Under the art of horticulture is compre-
hended whatever concerns the mere manner of exe-
cuting the operations connected with cultivation, mul-
tiplication, and amelioration; the science explains the
reasons upon which practice is founded. It is to the
consideration of the latter subject that the following
pages are dedicated.

2. It must have been remarked by all intelligent
observers, that in the majority of works upon hor-
ticultural subjects, the numerous directions given in
any particular ramification into which the art is sus-

1

2 INTRODUCTION.

ceptible of being divided, are held together by no
bond of union, and that there is no explanation of
their connexion with general principles, by which
alone the soundness of this or that rule of practice
may be tested; the reader is therefore usually oblig-
ed to take the excellence of one mode of cultivation
and the badness of another, upon the good faith of
gardening authors, without being put into possession
of any laws by which they may be judged of before-
hand. Horticulture is by these means rendered a
very complicated subject, so that none but practised
gardeners can hope to pursue it successfully; and,
like all empirical things, it is degraded into a code of
peremptory precepts.

3. It will nevertheless be found, if the subject is
carefully investigated, that in reality the explanations
of horticultural operations are simple, and free from
obscurity; provided they are not encumbered with
speculations, which, however interesting they may
be in theory, are only perplexing in practice, in the
present state of knowledge. When, for example,
chemical illustrations, unless of the simplest kind,
or minute anatomical questions, or references to the
agency of the electrical fluid, are discussed, the sub-
ject becomes embarrassed with considerations which
are too refined for the apprehension of the majority
of readers of gardening works, and which have little
obvious application to practical purposes. Instead,
therefore, of introducing points of obscure or doubt-
ful application, or such as are not absolutely requi-
site for the explanation of phenomena, all which ne-
cessarily tend to complicate the theory of horticul-

INTRODUCTION. 3

ture, it seems better strictly to confine our attention
to the action of the simplest vital forces; for the gene-
ral nature of these has been undoubtedly ascertained,
and is easily understood by every class of readers.
It is certain, for instance, that plants breathe, digest,
and perspire; but it may be a question whether the
exact nature of their respiration, digestion, and per-
spiration is beyond all further explanation: it is
therefore better to limit our consideration to the na-
ked fact, which is all that it imports the gardener to
know, without inquiring too curiously into those phe-
nomena. For it must always be remembered, that
the object of a work like the present is not to eluci-
date the laws of vegetable life in all their obscure
details, but to teach, to those acquainted with the art
of gardening, what the principles are upon which
their practice is founded.

4, In order to attain this end, it is necessary, in the
first place, to explain briefly, but distinctly, the na-
ture of those vital actions which have a direct refer-
ence to cultivation; omitting everything that tends
to embarrass the subject, or which is not susceptible
of a direct practical application; and in the next
place, to show how those facts bear upon the routine
of practice of the horticulturist, by making them ex-
plain the reason of the treatment which is employed
in various branches of the gardeners art.

5. The first part of this work will therefore em-
brace the principal laws and facts in vegetable phy-
siology, as deduced from the investigations of the
botanist ; and the second, the application of those

4 INTRODUCTION.

laws to practice, as explained by the experience of
the horticulturist.

§. If the laws comprehended in the first book are
correctly explained, and the facts connected with
them rightly interpreted, they must necessarily afford,
in all cases, the reasons why one kind of cultivation
is better than another; and all kinds of practice at
variance with those laws must be bad. Since, from
the very nature of things, this cannot be otherwise,
it follows that, by a careful consideration and due un-
derstanding of these laws, the intelligent cultivator
will acquire the most certain means of improving his
practice.

BOOK I.

OF THE PRINCIPAL CIRCUMSTANCES CONNECTED
WITH VEGETABLE LIFE WHICH ILLUSTRATE THE
OPERATIONS OF GARDENING.

7. A PLANT is a living body composed of an irrita-
ble, elastic, hygrometrical matter, called tissue. It is
fixed to the earth by roots, and it elevates into the
air a stem bearing leaves, flowers, and fruit. It has
no power of motion except when it is acted upon by
wind or other external forces; itis therefore peculiar-
ly susceptible of injury or benefit from the accidental
circumstances that may surround it; and, having no
free agency, it is above all other created beings suited
to acknowledge the power of man.

8. In order to turn this power to account, it is ne-
cessary to study the manner of life which is peculiar
to the vegetable kingdom, and to ascertain what the
laws are by which the numerous actions essential to
the existence of a plant are regulated. It is, more-
over, requisite that the causes which modify those ac-
tions, either by increasing or diminishing their force,
should be understood.

9. The vital actions of plants have so little resem-
blance to those of animals, that we are unable to ap-
preciate their nature, in even the smallest degree, by
a reference to our own sensations, or to any know-
ledge we may possess of animal functions. Nor,

6 VITAL ACTIONS.

when we have thoroughly studied the phenomena of
vegetation, are we able to discover any analogies, ex-
cept of a general and theoretical nature, bétween the
animal and vegetable kingdoms. It is therefore ne-
cessary that plants should be studied by themselves,
as an abstract branch of investigation, without at-
tempting to reason as to their habits from what we
know of other organic beings; and consequently we
are not, in this part of Natural History, to acknow-
ledge any theory which is not founded upon direct
experiment, and proved by the most satisfactory
course of inquiry.

10. In discussing this subject, it will be most con-
venient for my present purpose, if I divide the mat-
ter into the heads of, 1. Germination; 2. Growth by
the Root; 3. Growth by the Stem; 4. Action of the
Leaves; 5. Action of the Flowers; and, 6. Matura-
tion of the Fruit. By this means the life of a plant
will be traced through all its principal changes, and
it will be easy to introduce into one or other of these
heads every point of information that can be interest-
ing to the cultivator; who will be most likely to seek
it in connexion with those phenomena he is best
acquainted with by their effects.

GERMINATION. q

CHAPTER I.

GERMINATION.

The Nature of a Seed.—Its Duration —Power of
Growth.— Causes of Germination.—Temperature.—
Light.—Humidity.— Chemical Changes.

11. A SEED is a living body, separating from its
parent, and capable of growing into a new individual
of the same species. It is a reproductive fragment,
or vital point, containing within itself all the elements
of life, which, however, can only be called into ac-
tion by special circumstances.

12. But while it will with certainty become the
same species as that in which it originated, it does not
possess the power of reproducing any peculiarities
which may have existed in its parent. For instance,
the seed of a Green Gage plum will grow into a new
individual of the plum species, but it will not pro-
duce the peculiar variety called the Green Gage.
This latter property is confined to leaf:buds, and
seems to be owing to the seed not being specially or-
ganized after the exact plan of the branch on which
it grew, but. merely possessing the first elements of
such an organization, together with an invariable
tendency towards a particular kind of developement.

13. Under fitting circumstances a seed grows; that
is to say, the embryo which it contains swells, and

8 VITAL ACTIONS.

bursts through its integuments; it then lengthens,
first in a direction downwards, next in an upward
direction, thus forming a centre or axis round which
other parts are ultimately formed. No known power
can overcome this tendency, on the part of the em-
bryo, to elevate one portion in the air, and to bury the
other in the earth; but it is an inherent property with
which nature has endowed seeds, in order to ensure
the young parts, when first called into life, each find-
ing itself in the situation most suitable to its exist-
ence; that is to say, the root in the earth, the stem
in the air.

14. The conditions required to produce germina-
tion are, exposure to moisture, and a certain quantity
of heat; in addition, it is necessary that a communica-
tion with the atmosphere should be provided, if ger-
mination is to be maintained ina healthy state. A
seed, when fully ripe, contains a larger proportion of
carbon than any other part, and so long as it is thus
charged with carbon, it is unable to grow. The only
means it possesses of ndding itself of this principle,
essential to its preservation, but forming an impedi-
ment to its development as a new plant, is by con-
verting the carbon into carbonic acid; for which
purpose a supply of oxygen is necessary. It cannot
obtain oxygen in sufficient quantity from the air, for
it is cut off from free communication with the air by
various means, either natural, as being enclosed in a
thick layer of pulp, or in a hard shell or stone; or ar-
tificial, as being buried to a considerable depth below
the surface of the soil. It is from the water absorbed

GERMINATION, 9

in germination that the seed procures the requisite
supply of oxygen; fixing hydrogen, the other ele-
ment of water, in itstissue: and thus it is enabled to
form carbonic acid, which it parts with by its respira-
tory organs, until the proportion of fixed carbon is
lowered to the amount suited to its growth into a
plant.

15. But the formation and respiration of carbonic
acid takes place most freely, though not exclusively,
in darkness; if exposed to light, the seed again parts
with some of its oxygen, and again fixes its carbon
by the decomposition of its carbonic acid.

16. In addition to this, the absorption of water
causes all the parts to soften and expand; many of
the dry, but soluble, parts to become fluid; sap, or
vegetable blood, to be formed; and a sort of circula-
tion to be established, by means of which a commu-
nication is maintained between the more remote parts
of the embryo.

17. Heat seems to set the vital principle in action,
to expand the air contained in the numerous micro-
scopic cavities of the seed, and to produce a distension
of all the organic parts, which thus have their irrita-
bility excited, never again to be destroyed except with
death. What degree of heat seeds find most condu-
cive to their germination, probably varies in different
species. Chickweed (Alsine media) and Groundsel
(Senecia vulgaris) will germinate at a temperature
but little above 32° Fahr.

18. Germination being established by the absorp-
tion and deeomposition of water, and by the requisite

1*

10 VITAL ACTIONS.

elevation of temperature, all the parts enlarge, and
new parts are created, at the expense of a mucilagi-
nous saccharine secretion which the germinating seed
possesses the power of forming. With the assistance
of this substance, the root, technically called the radi-
cle, at first a mere point, or rather rounded cone,
extends and pierces the earth in search of food; the
young stem rises and unfolds its cotyledons, or rudi-
mentary leaves, which, if they are exposed to light,
decompose carbonic acid, fix the carbon, become
green, and, by processes hereafter to be explained,
when speaking of leaves, form the matter by which
all the pre-existing parts are solidified. And thus a
plant is born into the world; its first act having been
to deprive itself of a principle (carbon) which, in
superabundance, prevents its growth; but, in some
other proportion, is essential to its existence.

CHAPTER II.
GROWTH BY THE ROOT.

Roots lengthen at their Points only.— Absorb at that Part
chiefly. —Increase in Diameter hike Stems.— Their
Origin.—Are feeding Organs.— Without much Power
of selecting their Food.—Nature of the latter— May be

powoned.— Are constantly in Action.— Sometimes
poison the Soil in which they grow.—Have no buds.—
But may generate them.

19. THE root, being the organ through which food

GROWTH BY THE ROOT. 11

is conveyed from the earth into the plant, is the part
which is the soonest developed. Even in the embryo,
at the earliest commencement of germination, it is the
part immediately connected with the root that first
begins to move, by lengthening all its parts, and pro-
truding itself beyond the seed-coats into the earth.

20. But as soon as this primitive lengthening of the
root has taken place, and the upper part of the embryo,
namely the young stem, has begun to exist as a sepa-
rate organ, the root changes its property, ceases to grow
by a general distension of its tissue, and simply in-
creases in length by the addition of new matter to its -
point. A root is therefore extended much in the same
way as an icicle, by the constant superposition of
layer over layer to its youngest extremity; with this
difference, however, that an icicle is augmented by
the addition of matter from without, while the root
lengthens by the perpetual creation of new matter
from within.

21. For this reason, the extreme points of the roots
are exceedingly delicate, and are injured by very
trifling causes; they, moreover, as all newly formed
vegetable matter is extremely hygrometrical, have
the power of absorbing, with rapidity, any fluid or
gaseous matter that may be presented to them. On
this account they are usually called spongelets.

22. In the roots of ordinary Exogens,* when the

* [For an explanation of this term, see note under paragr. 50.] ©

12 VITAL ACTIONS.

tissue is very young, the spongelet (jig. 1. a) consists

of very lax tender cellular tissue, resting upon a blunt
cone of woody matter, composed principally of woody
tubes, and connected with the alburnum™* of the stem
(fig. 1. 6); it is, therefore, placed in the most favour-
able position possible for communicating to the gene-
ral system of circulation the fluids taken up by its
highly absorbent tissue.

23. It is the opinion of most vegetable physiolo-
gists, that the absorbing or feeding powers of roots
are conducted principally at these points; and that
the general surface of the root possesses little or no
power of the kind. And, indeed, it seems highly
probable that this is so, when we consider that the
bark of the root, through whose thickness all fluids
would have to pass before they reach the alburnum,
has at least two offices to perform, either of which
might be interfered with by a current fluid setting
through it. One of those offices is to convey in a
downward direction, or to store up, the matter which
has descended to the roots from the branches and

* [Or sap-wood. Vid. paragr. 49.]

GROWTH BY THE ROOT, 13

leaves; the other is to give off such superfluous mat-
ter as it is necessary for its health that the plant
should part with. a

24, But although there can be no doubt that the
spOngelets act as absorbents with more force than any
other part of the root, yet it is equally certain that
the whole surface of young roots also possesses an
absorbing property, only in a more limited degree.
It is not until their tissue is solidified that roots be-
come incapable of passing fluid through their sides ;
and when very young and soft, there is probably but
little difference between their action and that of the
spongelets themselves; for it is to be remembered
that the latter are not special organs, but are only the
very youngest part of the root.

25, The absorbent power of the spongioles must be
much greater than would have been supposed, if we
consider that it is almost entirely through their action
that the enormous waste of fluid, which takes place
in plants by perspiration, is made good; and hence
their importance to plants, and the danger of destroy-
ing them, become manifest.

26: The spongioles and youngest parts of roots are
found to be rich in nitrogen, a principle once sup-
posed to be unknown in the vegetable kingdom; and
it seems that a supply of this gas is indispensable to
their healthy condition.

27. Roots being furnished with the power of per-
petually adding new living matter to their points, are
thus enabled to pierce the solid earth in which they
grow, to insinuate themselves between the most

14 VITAL ACTIONS,

minute crevices, and to pass on from place to place
as fast as the food in contact with them is consumed.
So that plants, although not locomotive like animals,
do perpetually shift their mouths in search of fresh
pasturage, although their bodies remain stationary.

28. The only known exceptions to the rule that
roots do not lengthen by a general distension of their
tissue, occur in parts growing in air or water, which
are non-resisting media, or in certain endogenous
trees, whose roots lengthen to such a degree as to
hoist the trunk up into the air off the ground, with
which it at first was level.

29. It is not, however, merely in length that the
root increases; if such were the case, all roots would
be mere threads. They also augment in diameter,
simultaneously with the stem, and under the influence
of exactly the same causes. Neither is it by an em-
bryo alone that roots are formed. A plant, once in
a state of growth, has the power of producing roots
from various parts, especially from its stem, and from
older roots.

30. The immediate cause of the formation of roots
is involved in obscurity, and is one of the most im-
portant parts of vegetable physiology still to be in-
vestigated with reference to horticulture. We all
know how difficult it is to cause the cuttings of some
kinds of plants to produce young roots, and how ra-
pidly they are emitted by others ; it is to be supposed,
that the difficulty would be diminished in all such
cases, if we knew exactly under what circumstances
roots are formed. Nothing, however, sufficiently cer-

GROWTH BY THE ROOT. 15

tain and general to merit quotation has yet been as-
certained concerning this important subject, except
the following facts, viz. that roots are most readily,
if not exclusively, formed in darkness and moderate
moisture; that they are not, like branches, the de-
velopement of previously formed buds, but appear
fortuitously and irregularly from the woody rather
than the cellular part of a plant; and that their pro-
duction is in some way connected with the presence
of leaves or leaf-buds, because portions of a stem
having neither leaves nor leaf-buds produce roots un-
willingly, if at all; and that such roots perish if their
appearance be not speedily followed by the formation
of leaves. Thus, although the first appearance of the
root in the embryo plant, at the time of germination,
precedes the expansion of the seed-leaves, yet the
root will not live unless the seed-leaves are enabled
to act. ;

31. But although the immediate cause of the for-
mation of roots is unknown, the remote cause is appa-
rently the elaboration of organisable matter by the
leaves; for there can be no doubt that the develope-
ment of roots is much assisted by the descending sap.
When a ring of bark is removed from a branch,
if the wound is wrapped in damp moss, roots will
invariably push from the upper lip of the wound,
while the lower will produce none; a fact so well
known, that it has been one of the causes of an opi-
nion, that roots are bundles of wood liberated from
the central perpendicular system, and that the wood

16 VITAL ACTIONS.

itself is nothing but a mass of roots formed by the
leaves and buds.

32. The principal office of the root is to attract
food from the ground. For this purpose it is fur-
nished, as has been seen, with an extremely hygrome-
trical point, or spongelet, which is capable of absorb-
ing incessantly whatever matter of a suitable kind
may lie in its neighbourhood. Its force of absorption
is always proportioned to the quantity of food that a
plant requires: when the sap is consumed rapidly by
the leaves, as in the spring, the roots are in rapid
action also; and as the summer advances, and the
leaves require a smaller quantity of food, the roots
become more and more torpid.

33. The proportion borne by the root to the stem
is very variable. In such plants as succulent Euphor-
bias, and probably in all plants whose perspiring
powers are feeble, the roots are much smaller than
the stem; but, in others, the circle occupied by these
organs must be very much greater than that of the
branches. In young Oaks this is well known to be
the case, but the disproportion diminishes as such
plants advance in age.

34. There is no period of the year when the roots
become altogether inactive, except when they are
actually frozen. At all other times, during the win-
ter, they are perpetually attracting food from the
earth, and conveying it into the interior of the plant,
where it, at the season, is stored up till it is required
by the young shoots of the succeeding year. The

GROWTH BY THE ROOT. 17

whole tissue of a plant will therefore become dis-
tended with fluid food by the return of spring, and
the degree of distension will be in proportion to the
mildness and length of the previous winter. As the
new shoots of spring are vigorous or feeble in pro-
portion to the quantity of food that may be prepared
for them, it follows, that the longer the period of
rest from growth, the more vigorous the vegetation
of a plant will become when once renewed, if that
period is not excessively protracted.

35. Powerful as the absorbing action of roots is
found to be, those organs have little or no power of
selecting their food; but they appear, in most cases,
to take up whatever is presented to them in a suffi-
ciently attenuated form. Their feeding property
depends upon the mere hygrometrical force of their
tissue, set in action in a peculiar manner by the vital
principle; this force must be supposed to depend
upon the action of capillary tubes, of which every
part of a vegetable membrane must, of necessity, con-
sist, although they are, in all cases, invisible to the
eye, even aided by the most powerful microscopes.
Whatever matter is presented to such a set of tubes
will, we must suppose, be attracted through them,
provided its molecules are sufficiently minute; and,
as we have no reason to believe that there is, in gene-
ral, any difference in the size of the molecules of
either gaseous matter or fluids consisting principally
of water, it will follow that one form of such matters
will be absorbed by the roots of plants as readily as
another. For this reason, plants are peculiarly liable

18 VITAL ACTIONS.

to injury from the presence of deleterious matter
in the earth; and it is probable that, if in many
cases they reject it, it is because it does not acquire a
sufficient state of tenuity; as in the case of certain
coloured infusions.

36. But although this appears to be a general rule,
there are some exceptions of importance. If a Pea
and a grain of Wheat are placed side by side in earth
of the same kind, and made to grow under the same
circumstances, the Wheat plant will absorb silex in
solution from the earth, and the Pea will absorb
none; whence it would seem that the Pea is unable
to receive a solution of flint into its system, and that,
consequently, it possesses what amounts, practically,
to a power of selection. In like manner, Dr. Dau-
beny has proved the Pelargoniums, Barley, and the
Winged Tea (Tetragonolobus) will not receive stron-
tian; and it is mentioned in Saussure, that he could
not make Polygonum Persicaria absorb, by its roots,
a solution of acetate of lime, although it took up mu-
riate of soda (common salt) freely.

37. It is a curious fact, that the poisonous sub-
stances which are fatal to man are equally so to
plants, and in nearly the same way. So that, by pre-
senting opium or arsenic, or any metallic or alkaline
poison, to its roots, a tree may be destroyed as readily
as a human being.

38. The natural food of plants consists of carbon
in the state of carbonic acid, of nitrogen, certain
earths and salts, and water. The latter, if distilled,
has little power, by itself, of sustaining vegetable

GROWTH BY THE ROOT. 19

life:" but, as in nature it is universally mixed with
various other substances, it conveys to the roots the
organisable matters that are required; and it fur-
nishes, by its decomposition, a considerable supply
of the oxygen consumed in the formation of carbonic
acid, and all the hydrogen that is incorporated in the
tissue of plants.* It has been proved, experimen-
tally, that plants cannot long exist upon pure water ;
but if they are so circumstanced as to be able to
obtain and decompose carbonic acid, they will grow
in the absence of other matters, It is only, however,

* [The natural food of plants consists of water holding in solution
a quantity of carbonic acid and ammonia: the two former, viz. car-
bonic acid and water, are absolutely indispensable to the support of
vegetable life; the latter is equally essential to complete develope-
ment and for the formation of particular organs or products. In
assimilating their food, vegetables extract hydrogen from the water,
and carbon from the carbonic acid; the oxygen of both being
restored (either wholly or in part, according to the kind of product
which is formed,) to the atmosphere from which both were derived.
The statement in the text, that water “furnishes, by its decomposi-
tion, a considerable supply of the oxygen consumed in the formation
of carbonic acid,” is very ambiguous, if not altogether incorrect ;
since plants do not form, but decompose or consume carbonic acid ;
and they do not consume oxygen, except very partially, and in the
formation of some of their products; for, even in the formation of
those products which contain most oxygen (such as the vegetable
acids) from their universal food, a portion of oxygen is liberated.
Water is not only an essential portion of the food of plants, inas-
much as it furnishes all the hydrogen they consume; but also
the vehicle by which the other elements they require, nitrogen, and
a certain (but variable and more less essential) quantity of saline or
earthy matters, are conveyed into their system.—We shall have
occasion to return to the consideration of this subject in a note upon
Chap. XX. G.]}

20 VITAL ACTIONS.

when the peculiar principles, whether earthy or
saline, on which they naturally feed, are presented to
them, that they become perfectly healthy ; and espe-
cially when they have the means of obtaining nitro-
gen, which appears, from its great abundance in the
youngest parts, to be indispensable to plants upon
the first formation of their tissue.*

39. In addition to their feeding properties,t roots
are the organs by which plants rid themselves of the
secreted matter which is either superfluous or delete-
rious to them. If you place a plant of Succory
in water, it will be found that the roots will, by
degrees, render the water bitter, as if opium had been
mixed with it; a Spurge will render it acrid; anda
leguminous plant mucilaginous. And, if you poison
one half of the roots of any plant, the other half will
throw the poison off again from the system. Hence
it follows, that, if roots are so circumstanced that
they cannot constantly advance into fresh soil, they
will, by degrees, be surrounded by their own excre-
mentitious secretions.

40. It would also seem to follow that, under the

* Mr. Riggs states that those seeds of the same kind, which con-
tain the largest quantity of nitrogen, germinate the earliest. He
found nitrogen in young roots having the proportion of one to five
of carbon. Theodore de Saussure also ascertained that germinating
seeds absorb this gas.

+ According to Mr. Knight, the roots of trees retain the original
vigour of the variety, after the trunks have become debilitated; or,
to use his own words, the powers of life do not become expended
so soon in roots as in bearing branches. (Ses Hort. Trans. voh
ii p. 252.)

GROWTH OF THE STEM. 21

circumstances just named, they would be poisoned,
because they have little power of refusing to take up
whatever matter is presented to them in a fitting
state (85.) But it is by no means certain that the
excrementitious matter of all plants is poisonous
either to themselves or to others; and therefore the
consequences of roots growing in soil from which
they cannot advance are uncertain, and only to be
judged of by actual inquiry into the nature of the
secretions.* .

41. In general, roots have no buds, and are, there-
fore, incapable of multiplying the plant to which they
belong. But it constantly happens, in some species,
that they have the power of forming what are called

* There is some difference of opinion among physiologists,
whether excrementitious matter is thrown off from crops in so con-
siderable a quantity as to affect succeeding crops injuriously, or
whether the difficulty of growing successive erops upon the same
spot arises from the exhaustion of certain specific elements from the
soil needful to the growth and perfection of one crop, but not neces-
sary of another. It is more likely that the incapacity of soils to
bear the same crop for a long series of years suspends partly or both
these causes; but the fact that while wheat cannot be raised but
four or five times in succession from ordinary soils and that on the
other hand in certain deep alluvial soils of the west excellent crops
of this grain have been taken twenty or more years in succession
would go far to prove that the necessity of a change of crops arises
more from the exhaustion of the particular food required for that
crop than from the injurious accumulation of excrementitious matter.
However this may be, the practice of rotation of crops, the best
possible one for keeping the soil of either the farm or garden in
good condition, is based upon the fact that plants require change
of soil whether our object is to raise the largest product, or to do so
at the least outlay of manure.

22 VITAL ACTIONS.

adventitious buds; and, in such cases, they may be
employed for the purposes of propagation. There
is no rule by which the power of a plant to generate
such buds by its roots can be judged of; experiment
is therefore necessary, in all cases, to determine the
point.

CHAPTER II.

GROWTH BY THE STEM.

Origin of the Sem—The growing Point—Production,
of Wood, Bark, Pith, Medullary Rays.— Properties
of Sap-wood, Heart-wood, Inber, Rind, &c..—Nature
and Office of Leaf-buds.—Hmbryo-buds.—Bulbs.—
Conveyance of Sap, and its Nature.

42. As soon as the root is fully in action, which is
shortly after it has begun to lengthen, the vitality of
the living point that exists at the bottom of the seed-
leaves is excited, and a stem begins to be formed.
At first the stem is a mere point of living matter, often
invisible to the eye, but sometimes partially develop-
ed; in which latter case it is called the plumule. But,
as soon as nutritive matter is conveyed into it by the
nascent root, all its parts receive an impulse, which
forces them into a growth upwards; what matter
already exists is distended, enlarged, and solidified;
new matter is rapidly generated in all directions from
the vital centre, and, if it were not for the current
setting upwards from the root, it would possibly

GROWTH BY THE STEM. 23

grow into a spherical figure. Pressed upon, how-
ever, by the surrounding earth, impelled upwards by
the current of sap ascending from the root, and
attracted into the air by the necessity it feels of respi-
ration, the young stem assumes a cylindrical form, its
sides having a tendency to solidify, and its point
to grow longer. This point, or plumule, or first leaf:
bud, soon attracts to itself the food which the root
procures from the earth, and a part.of the nutritive
matter which is stored up in the seed-leaves. It feeds
especially upon the latter until the store is exhausted,
and by the time this happens it isclothed with leaves,
which are themselves able to feed it after the seed-
leaves have perished. In brief, the stem is a branch
produced by the first leaf-bud which the embryo
plant possesses.

43. When the stem is first called into existence, it
is merely a small portion of cellular tissue : an organic
substance, possessing neither strength nor tenacity,
and altogether unsuited to the purposes for which
the stem is destined. If such matter formed exclu-
sively its solid contents, the stem would have neither
toughness nor strength, but would be brittle like
a mushroom, or like those parts of plants of which
cellular tissue is the exclusive component; such, for
example, as the club-shaped spadix of an Arum, or
the soft prickles of a young Rose branch. Nature,
however, from the first moment that the rudiment of
a leaf appears upon the growing point of a stem, .
occupies herself with the formation of woody matter,
consisting of tough tubes of extreme fineness, which

94 VITAL ACTIONS.

take their rise in the leaves, and which, thence pass-
ing downwards through the cellular tissue, are incor-
porated with the latter, to which they give the
necessary degree of strength and flexibility. In trees
and shrubs, they combine intimately with each other,
and so form what is properly called the wood and
inner bark; in herbaceous and annual plants, they
constitute a lax fibrous matter. No woody matter
appears till the first leaf, or the seed-leaves, have
begun to act; it always arises from their bases; it
is abundant, on the contrary, in proportion to the
strength, number, and development of the leaves;
and in their absence is absent also.

44. When woody matter is first plunged into the
cellular tissue of the nascent stem, it forms a circle
a little within the circumference of the stem, whose
interior it thus separates into two parts; namely, the
bark or the superficial, and the pith or the central,
portion; or, in what are called Endogens, into a
superficial coating analogous to bark, and a central
confused mass of wood and pith intermingled. The
effect of this, in Exogens, is, to divide the interior of
a perennial stem into three parts, the pith, the wood,
and the bark.

45. As the cellular tissue of the stem is not sensi-
bly lengthened more in one direction than in ano-
ther, and as it is the only kind of organic matter that
in stems increases laterally, it is sometimes con-
venient to speak of it under the name of the horizon-
tal system ; and, for a similar reason, to designate the
woody tubes which are plunged among it, and which

3ROWTH BY THE STEM. 25

only increase by addition of new tubes having the
same direction as themselves, as the perpendicular
system.

46. Wood properly so called, and liber or inner
bark, consist, in Exogens, of the perpendicular sys-
tem, for the most part; while the pith and, external
rind or bark are chiefly formed of the horizontal sys-
tem. The two latter are connected by cellular tissue,
which, when it is pressed into thin plates by the
woody tubes that pass through it, acquires the name
of medullary rays. It is important, for the due expla-
nation of certain phenomena connected with cultiva-
tion, to understand this point correctly; and to
remember that, while the perpendicular system is
distributed through the wood and bark, the horizon-
tal system consists of pith, outer bark, and the medul-
lary processes which connect these two in Exogens,
and of irregular cellular tissue analogous to medul-
lary rays in Endogens. So that the stem of a plant
is not inaptly compared to a piece of linen, the hori-
zontal cellular system representing the woof, and the
woody system the warp.

47. Whenever the stem is wounded, the injury is
repaired by the cellular or horizontal system, which
forms granulations that eventually coalesce into
masses (fig. 2. A), within which the perpendicular
system or woody matter is subsequently developed.
Thus the restoration of the communication be-
tween the two sides of an annular excision is effect-
ed by granulations of the upper and lower lips, and
of the medullary rays, which finally run together

2

26 VITAL ACTIONS.

over the wood (fig. 2. B), and form a coating, below
which new liber and alburnum may be generated.
In cuttings, the ‘ callus,”
which forms at the end pla-
ced in the ground, is the
cellular horizontal system,
preparing for the reception
of the perpendicular sys-
tem, whichis to pass down-
wards in the form of roots.
Many plants will endure
extensive lacerations of
their surface, and close up
such wounds with great
facility. The well known
fact of large inscriptions
cut in trees below the bark
(which inscriptions were
effected by removing very
broad spaces of the bark and wood) being covered
over in time by new bark and wood, so as to be
no longer visible from the outside, sufficiently proves
this. In such cases, however, the reparation of the
injury takes place chiefly, if not exclusively, by the
annual addition of new matter to the lips only of the
wound, the effect of which is to reduce the circle
annually to a less diameter, till at last the centre is
closed up.

48. In the bark of trees and shrubs two distinct
parts are found: the one external and cellular; and
the other internal, resting upon the wood, and con-

GROWTH BY THE STEM. 2?

sisting of woody matter mixed with cellular. The
external is the rind or cortical integument, the inter-
nal is the liber. These two parts grow independently
of each other, by their inner faces; the rind belong-
ing exclusively to the horizontal system, the liber
composed of the perpendicular and horizontal systems
intermixed.

49. In all Exogenous plants whose stems acquire
an age beyond that of a very few years, the wood is
distinguishable into two parts, heart-wood, and sap-
wood or alburnum, The former is more or less cen-
tral, and coloured brown or some dark tint; the lat-
ter is external, pale yellow, and much softer. Heart-
wood was originally alburnum, and altered its nature
with age, in consequence of the solid matter with
which all its tubes and vessels were choked up; al-
burnum is the youngest wood, with all its communi-
cations free and open, no solid matter having had
time to accumulate within them. The reason why
solid matter collects in the tubes of wood, so as gra-
dually to choke them up, is this: the wood is the
channel through which all the fluid matter of a plant,
whether crude or digested, passes, in its way upwards
to the leaves, or in its horizontal direction from the
bark to the central parts of the stem. When sap
leaves the earth and passes into the stem, it ascends
by the woody matter of the finest fibres of the root ;
having left them, it flows into the new wood from
which those fibres emanated, and passes along this
until it reaches the leaves; on its return from them

28 VITAL ACTIONS.

it descends through the liber, in part passing off hori-
zontally towards the centre through the medullary
rays. Wherever it passes it deposits a portion of its
solid parts; and, consequently, that portion of the
wood, namely, the oldest or the heart-wood, through
which it has passed the most frequently, will have the
greatest quantity of matter accumulated within it,
independently of all other reasons for its hardening.
50. The stem of a plant consists, then, of the fol-
lowing parts, viz.: 1. Wood, the oldest of which is
heart-wood, and the newest alburnum; and this is the
substance through which sap ascends: 2. Bark, the
external coating, down the liber or inner face of which
sap descends: 8. Pith, a central portion of the hori-
zontal system: and, 4. fedullary Rays, serving to
connect the rind with the pith, to hold all the parts
together, and to maintain a communication between
the centre and the circumference of a stem. The
stems of all plants have these four parts more or less
evident. They are most visible in Huropean trees or
shrubs, in any of which they can be distinctly ob-
served ; they are least apparent in annual and herba-
ceous plants, because their lines of separation are not
defined, all the four parts adhering to each other so
firmly as to render it’ difficult to separate them; and
in Endogens they are all mixed together, in conse-
quence of the manner of growth of those plants not
requiring the same kind of arrangement of parts as is
indispensable in Exogens.* This will be sufficiently

* As this work excludes every thing botanical that does not

GROWTH BY THE STEM. 29

illustrated by the comparison of the stems of an Oak,
a Cabbage, and an Asparagus.

51. Tubers, the root-stock of the Iris and Ginger,
what are called the roots (cormi) of the Colchicum
and Crocus, are all so many different forms of
stem.

52. It is the property of a stem, during its growth,
to form upon its surface, at irregularly increasing or
diminishing distances, minute vital points of the same
nature as that’ in which the stem itself originated.
Each of those points becomes, or may become, a leaf:

directly bear upon horticultural purposes, I have not explained the
difference between Exogens and Endogens; wishing the reader to
refer for information upon all such points to works upon pure bo-
tany. Nevertheless, as these words are of frequent occurrence, I
may as well state that they denominate the two greatest classes in
the vegetable kingdom, to one or other of which almost all the
flowering plants of common occurrence are referable, and that they
derive their names from the peculiarity of their manner of growth.
Exocens (literally outside-growers) are plants whose woody matter is
augmented annually by external additions below the liber, and,
consequently, they are continually enclosing within their centre the
woody substances formed in previous years; to such plants, a lateral
communication between the centre and the circumference, by means
of medullary rays, seems necessary. Enpocens (literally inside-
growers) are plants whose woody matter is augmented annually by
internal additions to their centre; and, consequently, they are con-
tinually pushing to their circumference the woody substance formed
in previous years.

[All the trees or shrubs of the United States, except the few Palms
of our southern confines, are examples of Exogens: the Palms afford
the best example of Endogens, while the stem of an Asparagus ex
hibits a similar structure in an herb. A. G.]

30 VITAL ACTIONS.

bud, capable of forming other stems or branches like
that on which it appeared; and each is protected and
nourished by a leaf which springs from the bark im-
mediately below the bud. Such leaf-buds are the
parts that enable a stem, when reduced to the state
of a cutting, to produce a new individual like itself;
and, without them, no propagation by portions of the
stem could take place.

58. Leaf-buds are capable, under fitting circum-
stances, of growing when separated from their mother
branch, whether they are planted in the earth, or in-
serted below the bark of a kindred species. In the
former case, they emit roots into the soil; in the lat-
ter, they produce wood, which adheres to the wood
on which they may be placed. Under ordinary cir-
cumstances, leaf-buds will not form anywhere except
at the axils* of leaves; but occasionally they appear
from other parts, such as the root, the spaces of the
stem which lie between the leaves (the internodes),
and even from the leaves themselves. In all such
cases, they are termed adventitious, because of the un-
certainty of their appearance. A very remarkable
state of them is the embryo-bud, a name applied to the
knaurs, knurs, nodules, or hard concretions, found in
the bark of various trees, which seem to have, occa-
sionally, the power of propagating the individual,
notwithstanding their deformed and indurated
state.

* The azil is the acute angle formed by a leaf and stem, at the

origin of the former; all bodies growing within that angle are said
to be azillary.

GROWTH BY THE STEM. 31

54. Bulbs are buds of a particular kind, larger
than common, containing an unusual quantity of se-
creted matter, and separable, spontaneously, from the
part which bears them. They are magazines in which
certain plants store up the nutritive matter collected
from the leaves. The identity of a bulb and a bud,
in all essential circumstances, is obvious, if the bud of
any tree (fig. 4.) is compared with the bulbs of the
Tiger Lily (jig. 3.).

55. As leaf-buds are thus the parents of wood, one
of the means of propagating the individual to which
they belong, the origin of branches, and consequently
the source of the developement of leaves themselves,
they may be considered the most important organs of
vegetation, so far as any one organ can be called most
important where all are so mutually dependent the
one on the other, and so powerfully concur in main-
taining the system of vegetable life, that it is difficult

32 VITAL ACTIONS.

to abstract one part without impairing the efficiency
of the remainder.

56. The office of the stem is, to convey the crude
fluid obtained by the roots from the soil, and called
sap, into the leaves for elaboration, and then to re-
ceive it back again. Sap is, originally, water contain-
ing various gases, earths, and salts, in solution: but,
as soon as it enters the stem, it dissolves the vegeta-
ble mucilage it finds there, and becomes denser than
it was before; it is further changed by the decompo-
sition of a part of its water, acquires a saccharine
character, and, rising upwards through the alburnum,
takes up any soluble matter it passes through. Its
specific gravity keeps thus increasing till it reaches
the summit of the branches; and, by degrees, it is
all distributed among the leaves. In the leaves it is
altered, and then returned into the stem; not, how-
ever, into the alburnum, where it would meet the as-
cending current, but into the bark, through which it
falls, passing off horizontally through the medullary
rays into the interior of the stem, and fixing itself in
the interior of the bark, especially of the root. It
may be said, that, in trees, the alburnum and liber
have each two equally important offices to perform:
the alburnum giving strength and solidity to the stem,
and conveying sap upwards; the liber not only con-
veying sap downwards, but covering over the albur-
num, protecting it from the air, and enabling it to
form without interruption. It is, therefore, indispen-
sable to the healthy condition of plants, that ncither
the alburnum nor the liber should be injured. The

:

GROWTH BY THE STEM. 38

central wood is of little consequence, and may be de-
stroyed, as it constantly is in hollow trees; and the
rind is of comparatively small importance, for it is
continually perishing under the influence of the at-
mosphere: but the liber and alburnum are naturally
in a state of constant renovation, and cannot be per-
manently injured without injury to the plant.

57. But although, under ordinary circumstances,
the sap of Exogens rises through the alburnum and
descends through the liber, yet the simplicity of
structure in plants is such, that, together with the per-
meability of their tissue, it enables them, in cases of
emergency, to alter their functions, and to propel
their fluids by lateral instead of longitudinal commu-
nications. The trunk of a tree has been sawed
through beyond the pith in four opposite directions ;
namely, from north to south, from west to east, from
south to north, and from east to west, at intervals of
a foot, so as completely to cut off all longitudinal com-
munication between the upper and lower parts of
the stem, as effectually as if those two parts had been
dissevered ; and yet the propulsion of the sap from
the roots into the head of the tree went on as before:
which could only have been éffected by a lateral
transmission of this fluid through, or between, the
sides of the woody tissue. So when “ringing” is
practised, and the alburnum is partially destroyed,
the ascending fluid diverges into the stratum of wood
beneath the annulation; and, when it has passed by,
it again returns into its aecustomed channels; at the
same time, it is probable, although not proved, that

Q%

84 VITAL ACTIONS,

some portion of the descending sap forces its way
laterally below the wound, out of the bark into the
alburnum, using the latter as a means of communi-
cating with the bark below the ring.

Some curious experiments upon this subject were
contrived by Mr. N. Niven (Gardener's Magazine, vol.
xiv.) In one case, he di- 5
vested the stem of a tree
of a deep ring of bark, and
of the first twelve layers of
wood below it (fig. 5.); ne-
vertheless the tree continu-
ed to live and be healthy.
From the exposed surface
of the wood no sap made
itsappearance, except from
a cut which had been in-
advertently made with the
saw on one side, to the
depth of, perhaps, five or
six layers of wood beyond S&=
the twelve actually remov-
ed. From that cut a flow
of sap took place, and continued to run during the
whole of the season in which the operation was per-
formed. In this case, the sap must have ascended
exclusively by the alburnum.*

MTR

A HR

ART if

* [This is a possible case; but the American, familiar with the
practice of girdling trees, (which is nothing more than ringing with
the hatchet,) so common in the new settlements, well knows that it
destroys vitality as certainly os cutting down the tree at once. It

oF
GROWTH. BY THE STEM. 85

In another case, by making four deep and wide in-
cisions into the trunk of a tree (ig. 6.), and removing

Ait

ies

the centre, the upper part of the trunk was placed

may be assumed that the removal of any ring of bark, so broad that
the wound cannot be healed over in a single season, will cause the
death of the tree.—During the deep snows of winter, in the northern
States, young apple-orchards are often destroyed by field-mice, which
girdle the trees near the ground, and they perish in the course of the
ensuing season. The trees may however be preserved, by taking a
suitable circle or section of bark, in the spring, from the limb of
another apple-tree, and adapting it carefully to the wounded bark,
the edges of which are to be pared to an even line, and the whole
bound up and covered with grafting clay. It is not absolutely ne-
cessary that the bark introduced should encompass the whole trunk ;
as the union by a single portion will preserve the life of the tree,
and the remainder of the wound will gradually become covered with
new bark. A. J. D.J

36 VITAL ACTIONS.

upon four separate pillars of bark and alburnum ;
and the tree upon which the operation was performed
continued to live for two years, after which it was
not observed. In the latter instance, no doubt can
be entertained that the whole of the ascending sap
was directed into the four pillars of alburnum, which
were allowed to remain.

58. The cause of the flow of the sap appears to be
the attraction of it by the leaves, which continually
diminish its quantity; and the necessity that the sap
abstracted should be replaced by a further supply
sent upwards from the roots. The consequence of
this is, that sap always begins to flow at the ends of
the branches, a circumstance which has led to the
erroneous idea that it proceeds from above downwards
through the alburnum. The flow of the sap must
not, however, be confounded with the motion of the
sap, which takes place in the winter as well as in the
summer, and is a mere impletion of the system, caused
by the attraction of the roots, unaffected by the ex-
halation of the leaves.

ACTION OF LEAVES. 37

CHAPTER IV.
ACTION OF LEAVES

Their Nature, Structure, Veins, Epidermis, Stomates.—
Liffect of Inght.— Digestion or Decomposition of
Carbonic Acid.—Insensible Perspiration. —Forma-
tion of Secretions.—Fall of the Leaf—Formation of
Buds by Leaves.

59. A LEAF is an appendage of the stem ofa plant,
having one or more leaf-buds in its axil. In those
cases where no buds are visible in the axil, they are,
nevertheless, present, although latent, and may be
brought into developement by favourable circum-
stances. As this is a universal property of leaves, to
which there is no known exception, it follows that all
the modifications of leaves, such as scales, hooks,
tendrils, &c., and even the floral organs, hereafter to
be described, have the same property.

60. Considered with respect to its anatomical struc-
ture, a leaf is an expansion of the bark, consisting of
cellular substance, among which are distributed veins.
The former is an expansion of the rind; the latter
consist of woody matter arising from the neighbour-
hood of the pith, and from the liber. As the tissue
forming veins has a double origin, it is arranged in
two layers, united firmly during life, but separable
after death, as may be seen in leaves that have been

88 VITAL ACTIONS.

lying for some time in water. Of these layers, one is
superior and arises from the neighbourhood of the
pith, the other inferior and arises from the liber; the
former maintains a connexion between the wood and
leaf; the latter establishes a communication with the
bark. As sap, or ascending fluid, rises through the
wood, and principally the alburnum, afterwards de-
scending through the liber, it follows from what has
been stated, that a leaf is an organ of which the upper
system of veins is in communication with the as-
cending, and the lower system with the descending,
current of sap.

61. A leaf has moreover a skin, or epidermis,
drawn all overit. This epidermis is often separable,
and is composed of an infinite number of minute cavi-
ties, originally filled with fluid, but eventually dry
and filled with air. In plants growing naturally in
damp or shady places it is very thin; in others, in-
habiting hot, dry, exposed situations, it is very hard
and thick; and its texture varies between the two
extremes, according to the nature of the species. The
epidermis is pierced by numerous invisible pores,
called stomates, through which the plant breathes
and perspires. Such stomates are generally largest
and most abundant in plants which inhabit damp and
shady places, and which are able to procure at all
times an abundance of liquid food; they are fewest
and least active under the opposite conditions. It
will be obvious, that, in both these cases, the struc-
ture of a leaf is adapted to the peculiar circumstan-
ces under which the plant to which it belongs natu

ACTION OF LEAVES. 39

rally grows. Now, as this structure is capable of
being ascertained by actual inspection with a micro-
scope, it follows, as a necessary consequence, that the
natural habits of an unknown plant may be judged
of with considerable certainty by a microscopical ex-
amination of the structure of its epidermis. The rule
will evidently be, that plants with a thick epidermis,
and only a few small stomates, will be the inhabitants
of situations where the air is dry and the supply of
liquid food extremely small; while those with a thin
epidermis, and a great number of large stomates, will
belong to a climate damp and humid; and interme-
diate degrees of structure will indicate intermediate
degrees of atmospherical and terrestrial conditions.
It is, however, to be observed, that the relative size
of stomates is often a more important mark in inves-
tigations of this nature than their number ; those or-
gans being in many plants extremely numerous, but
small and apparently capable of action in a very lim-
ited degree; while in others, where they are much
less numerous, they aro large and obviously very ac-
tive organs. Thus the number of stomates in a
square inch of the epidermis of Crinum amabile is
estimated at 40,000, and in that of Mesembryanthe-
mum at 70,000, and of an Aloe at 45,000; the first
inhabiting the damp ditches of India, the last two
natives of the dry rocks of the Cape of Good Hope:
but the stomates of Crinum amabile are among the
largest that are known, and those of Mesembryanthe-
mum and Aloe are among the smallest; so that the
70,000 of the former are not equal to 10,000 of the

40 VITAL ACTIONS.

Crinum. Again, the Yucca aloifolia has four times
as many stomates as a species of Cotyledon in my
collection, but those of the latter are about the 73,
of an inch in their longer diameter, large and active,
while the stomates of the Yucca are not more than
z¥s0 Of an inch long in the aperture, and compara-
tively inert. The Yucca, therefore, with its nume-
rous stomates, has weaker powers of perspiration and
respiration than the Cotyledon.

62. A leaf, then, is an appendage of the stem of a
plant, consisting of an expansion of the cellular rind,
into which veins are introduced, and enclosed in a
skin through which respiration and perspiration take
place. It is in reality a natural contrivance for ex-
posing a large surface to the influence of external
agents, by whose assistance the crude sap contained
in the stem is altered and rendered suitable to the
particular wants of the species, and for returning into
the general circulation the fluids in their matured
condition. In a word, the leaf of a plant is its lungs
and stomach, traversed by a system of veins.

63. As the leaf is an extension of the rind of a
stem, its epidermis is also an extension of the skin of
the same part; and hence it is that in plants which
produce no true leaves, such as the Stapelia, the
office of the leaf is performed by the rind and epider-
mis of the bark.

64. The functions of respiration, perspiration, and
digestion, which are the particular offices of leaves,
are essential to the health of a plant; its healthiness
being in proportion to the degree in which these func-

ACTION OF LEAVES. 2 41
J

tions are duly performed. Consequently, whatever
tends to impede the free action of leaves, tends also
to diminish the healthiness of a plant.

65. These functions are performed by means of the
vital forces of vegetation, which we cannot estimate
or comprehend, assisted by the influence of an exter-
nal agent, the nature of whose action may be under-
stood from its effects. That agent is solar light.

66. It is the property of solar light, when striking
upon the leaf of a plant, to cause: 1. A decomposi-
tion of carbonic acid; 2. An extrication of nitrogen ;
and, 3. Insensible perspiration. By their vital forces
plants appear to decompose water, independently of
the action of light.

67. Carbonic acid is originally introduced into the
interior of a plant, either dissolved in the water it
imbibes by its roots, or by attraction from the atmo-
sphere, or by the combination of the oxygen obtained
by a decomposition of water or otherwise, with the
carbon in its interior. When a leaf is exposed to the
direct influence of the sun, it gives off oxygen, by
decomposing the carbonic acid; whereupon the car-
bon remains behind in the interior of the leaf in a
solid state. Although the nature of the air thus ex-
tricated can only be determined by a chemist, yet the
extrication itself can be easily seen by any one who
will plunge a leaf in water and expose it to the sun;
for bubbles of oxygen will be seen to form themselves
upon the surface of the leaf. But, if the same leaf
be observed in the total absence of solar light, there
will be little or no extrication of air, and what little

42 VITAL ACTIONS.

is given off will be found to be carbonic acid, which
plants exhale at all times in small quantities; oxygen,
however, which was before expelled, is inhaled.
Hence plants decompose carbonic acid during the
day, and form it again during the night, the oxygen
they inhale at that time entering again into combina-
tion with their carbon; and, during the healthy state
of a plant, the decomposition by day, and recomposi-
tion by night, of this gaseous matter, is perpetually
going on.* The quantity of carbonic acid decomposed

* [This absorption of oxygen and recomposition of carbonie acid
during the night, might perhaps be left out of the account in a gene-
ral view of the subject, except as an explanation of the manner in
which plants are injured or destroyed by the protracted absence of
light. According to the celebrated chemist from whom the following
remarks are cited, this process is not at all connected with the life
or growth of vegetables, but is entirely chemical.—“It is true that
the decomposition of carbonic acid is arrested by the absence of light.
But then, namely at night, « true chemical process commences, in
consequence of the action of the oxygen in the air upon the organic
substances composing the leaves, blossoms, and fruit. . . . The
substances composing the leaves of different plants being known, it
is a matter of the greatest ease and certainty to calculate which of
them, during life, should absorb most oxygen by chemical action,
when the influence of light is withdrawn. . . . . Whilst the
tasteless leaves of Agave Americana absorb only 0°3 of their volume
of oxygen, in the dark, during 24 hours, the leaves of the Pinus
Abies, which contain volatile and resinous oils, absorb 10 times;
those of Quereus Robur containing tannic acid 14 times; and the
balmy leaves of the Populus alba 21 times that quantity. This
chemical action is shown very plainly, also, in the leaves of the Co-
tyledon calycinum, the Cacalia ficoides, and others; for they are sour,
like sorrel, in the morning, tasteless at noon, and bitter in the even-
ing. The formation of acids is effected during the night by a true
brocess of oxidation: these are deprived of their acid properties

ACTION OF LEAVES. 43

is in proportion to the intensity of the light which
strikes a leaf, the smallest amount being in shady
places; and the healthiness of a plant is, ceteris pari-
bus, in proportion to the quantity of carbonic acid
decomposed; therefore, the healthiness of a plant

during the day and evening, and are changed, by the separation of
a part of their oxygen, into compounds containing oxygen and
hydrogen either in the same proportions as in water, or even with
an excess of hydrogen, which is the composition of all tasteless and
bitter substances. . . . . Most vegetable physiologists have
connected the emission of carbonic acid during the night with the
absorption of oxygen from the atmosphere; and have considered
these actions as a true process of respiration in plants, similar to that
of animals, and, like it, having for its result the separation of carbon
from some of their constituents. This opinion has a very weak and
unstable foundation. The carbonic acid, which has been absorbed
by the leaves and by the roots, together with water, ceases to be
decomposed on the departure of daylight. It is dissolved in the
juices which pervade all parts of the plant, and escapes every mo-
ment through the leaves, in quantity corresponding to the water
which evaporates. . . . . Plants during their life constantly
possess the power of absorbing by their roots, moisture, and, along
with it, air and carbonic acid. Is it, therefore, surprising that the
carbonic acid should be returned unchanged to the atmosphere,
along with water, when light (the cause of the fixation of its carbon)
is absent? Neither this emission of carbonic acid nor the absorption
of oxygen has any connexion with the process of assimilation; nor
have they the slightest relation to one another; the one is a purely
mechanical, the other a purely chemical process. A cotton wick,
enclosed in a lamp which contains a liquid saturated with carbonie
acid, acts exactly in the same manner as a living plant in the night.
Water and carbonic acid are sucked up by capillary attraction, and
both evaporate from the exterior part of the wick.” Liebig, Organie
Chemistry in its applications to Agriculture and Physiology, (London,
1840,) pp. 27—38, passim ; a work which comprises a masterly view
of the chemical phenomena of vegetation. G.]

44 VITAL ACTIONS.

should be in proportion to the quantity of light it
receives by day.

68. But, while this is true as a general axiom, it is
necessary to observe that some plants are naturally
inhabitants of shady situations, and are so organised
as to be fit for such places and for no others: plants
of this description will not endure full exposure to the
sun; not because an abundant decomposition of car-
bonic acid is otherwise than favourable to them, but
because their epidermis allows the escape of water
too freely by insensible perspiration. under the solar
stimulus,

69. The mere fact of plants absorbing fluids from
the earth, would render it probable that they have
some means of parting with a portion of it by their
surface; but that they do perspire is susceptible of
direct proof, and is by no means a mere matter of
inference.

70. We do not indeed see vapour flying off from
the surface of plants; neither do we from that of ani-
mals, except when the air is so cold as to condense
the vapour; yet we know that in both cases perspira-
tion is perpetually going on, and it would appear that
in plants it takes place more abundantly than in ani-
mals. Ifa plant covered with leaves is placed under
a glass vessel, and exposed to the sun, the sides of the
vessel are speedily covered with dew, produced by
the condensation of the insensible perspiration of the
plant. If the branch of a plant is placed in a bottle
of water, and the neck of the bottle is luted to the
branch, so that no evaporation can take place, never-

’

ACTION OF LEAVES. 45

theless the water will disappear; and this can only
happen from its having been abstracted by the branch
which lost it again by insensible perspiration. Hales,
an excellent observer, devised many experiments

mA

46 VITAL ACTIONS.

connected with this subject ;* among others the fol-
lowing, which he relates thus:—"“ August 13. In the
very dry year 1723, I dug down 24 feet deep to the
root of a thriving baking pear tree, and laying bare
a root half an inch in diameter (fig. 7) I cut off the
end of the root at 7, and put the remaining stump
(¢) into the glass tube dr, which was an inch in
diameter, and eight inches long, cementing it fast at
7; the lower part of the tube dz was eighteen inches
long and a quarter of an inch diameter in bore.

Then I turned the lower end of the tube (z) upper-
most, and filled it full of water, and then immediately
immersed the small end z into the cistern of mercury
at the bottom, taking away my finger which stopped
up the end of the tubez ..... The root imbibed
the water with so much vigour, that in six minutes’
time the mercury was raised up the tube d z as high
as 2, namely, eight inches. ... . The next morning
at eight o’clock the mercury was fallen to two inches
in height, and two inches at the end of the root 7 were
yet immersed in water. As the root imbibed the
water, innumerable air bubbles issued out at 2, which
occupied the upper part of the tube at r as the water
left it.” On another occasion he planted a sunflower
33 feet high in a garden pot, which he covered with
thin milled lead, cementing all the joints so that no
vapour could escape except through the sides of the
pot and through the plant itself; but providing an
aperture capable of being stopped, through which the

* See Vegetable Statics, London, 1727.

ACTION OF LEAVES. 47

earth in the pot could be watered. After fifteen days,
viz., from July 8 to August 8, he found, upon making
all necessary allowances for waste, that this sunflower
plart 84 feet high, with a surface of 5616 square
inches above the ground, had perspired as follows:—

Ounces
Avoirdupois.

In twelve hours of a very dry warm day . 380,

On anotherday:. . . .... . . 20,

Ina dry warm night withoutdew. . . 8,

Ina night with some smalldew ... 0;
and that when the dew was copious, or there was
rain during the night, the plant and pot were
increased in weight two or three ounces. Other per-
sons have instituted other experiments of a similar
nature, the result of all which is, that the insensible
perspiration of plants is very considerable,* Hales

* The amount of this force is strikingly illustrated by the fol-
lowing circumstances recorded by the late Mr. Braddick. “One
experiment I will mention, as it may serve to show the great power |
of the rising sap in the vine, while its buds are breaking. On the
20th of March, in the middle of a warm day, I selected a strong
seedling vine five years old, which grew in a well prepared soil,
against a south-west wall; I took off its head horizontally with
a clean cut, and immediately observed the sap rising rapidly
through all the pores of the wood, from the centre to the bark. J
wiped away the exuded moisture, and covered the wound with a
piece of bladder, which I securely fastened with cement, and a
strong binding of waxed twine. The bladder, although first drawn
very close to the top of the shoot, soon began to stretch, and to rise
like a ball over the wound; thus distended, and filled with the sap
of the vine, it felt as hard as a cricket ball; and seemed to all
appearance, as if it would burst. I caused cold water from a well

48 VITAL ACTIONS.

says his sunflower perspired seventeen times more
than a man. There is, however, this important
peculiarity in vegetable perspiration, that it takes
place only or principally in sunlight. The last expe-
riment shows that, while the sunflower was losing
from twenty to thirty ounces of water daily during
the day, it lost only three ounces during the night
without dew, and that there was no loss whatever if
a slight dew were present. Here it is probable that
the small amount which was lost at night was parted
with by the sides of the garden pot, and that the
plant itself lost nothing ; for it is in evidence that the
perspiration of plants is in proportion to the quantity
of sunlight that strikes them, and that in darkness
they perspire little or not at all.* It is no doubt
true, that in a dry atmosphere plants will lose their
water day and night ; but it is equally certain that
under such circumstances they will lose very much
more by day than by night. They will, however,
lose much more by day in a dry atmosphere in a
given time, than they will in an atmosphere abound-
ing in moisture.

to be thrown on the roots of the plant; but neither this nor any
other plan that I could devise, prevented the sap from flowing,
which it continued to do with so much force as to burst the bladder
in about forty-eight hours after the operation was performed; the
weather continuing the whole time warm and genial.—( Hort. Trans.,
v. 202.)

* M. De Candolle distinguishes between erhalaison or perspira-
tion, which is a vital action, deperdition or evaporation, which is
merely physical. But the latter is too small in amount to be worth
taking into account for practical purposes.

ACTION QF LEAVES. 49

71. Although perspiration thus appears to be prin-
cipally excited by the solar rays, and to be in a given
plant in proportion to their intensity, yet we are not
authorised in concluding that perspiration is not
increased or diminished by the medium in which a
plant grows. Immersed in water, perspiration is
necessarily arrested; in an ordinary atmosphere,
it will be in proportion to the quantity of elastic
vapour the atmosphere may contain; and it is proba-
ble, although there are no experiments upon the sub-
ject, that it is increased in proportion to the rare-
faction of the air.

72. Since a plant does not perspire at night, and
since its absorbing points, the roots, remain during
that period in contact with the same hamid medium
as during the day, they will attract fluid into the
system of the plant during the night, and, conse-
quently, the weight of the individual will be increased,
as Hales found to be the case. In like manner,
if plants in the shade are abundantly supplied with
moisture at the roots, they also will gain more than
they can lose; and, as this will be a constant action,
the result must necessarily be to render all their
parts soft and watery.

73. It is evident, from what has been stated, that
leaves must derive the food they digest from the
earth through the medium of the roots; and that
they, while alive, maintain a kind of perpetual suck-
ing action upon the stem, which is communicated to
the spongelets. - That this must be of a very powerful
nature is apparent from the fact, that the smallest

8

50 VITAL ACTIONS.

leaf at the extremity of the branch of a lofty tree
must assist in setting in action the absorbing power
of roots, at a distance equal, perhaps, to three thou-
sand times its own length. If this reciprocal action
is not.maintained without interruption, and if any-
thing occurs to check it during the period of vegeta-
tion, the plant will suffer in proportion to the amount
of interruption. For example, if the roots are placed
in a warmer medium than the branches, and are
thus induced to absorb fluid faster than the slower
action of the leaves can consume it, the superfluous
sap will burst through the stem and distend ils tissue
till the excitability is impaired or destroyed. Or if,
on the other hand, a branch is caused to grow in
a warm medium, while the roots remain in a very
cold medium, the former will consume the liquid sap
faster than the latter can supply it, and the con-
sequence will be, that the leaves will die, or the fruit
will fall off, or the flowers be unable to set their
fruit, from want of a constant and sufficient supply
of food. Not that it is necessary for the temperature
of the earth and air to be equal, for this does not
happen in nature; but it is requisite that they should
have some near relation to each other.

74. It is generally, however, believed, that leaves
absorb fluid from the air; and their stomates appear
well adapted for that purpose, by their position in
most abundance on the under side of leaves; and
the possibility of recovering drooping or sickly plants,
by syringing their epidermis copiously, seems to ren-

ACTION OF LEAVES. 51

der this fact almost certain.* It is, however, thought
by some, that leaves have no power of absorbing
water, even in an elastic state; and that the renova-
tion of plants by syringing is owing to a diminution
of perspiration.

75. It is to the action of leaves,—to the decompo-
sition of their carbonic acid, and of their water;
to the separation of the aqueous particles of the sap

* Mr. Knight entertained the opinion, that water is sometimes
absorbed by leaves to such an extent as to cause a descent of the
sap through the alburnum ; a derangement of function to which he
even ascribed the attacks of mildew fungi upon plants. The secon-
dary and immediate causes, he says, of this disease, and of its con-
geners, “have long appeared to me to be the want of a sufficient
supply of moisture from the soil, with excess of humidity in the air,
particularly if the plants be exposed to a temperature below that
to which they have been accustomed. If damp and cold weather
in July succeed that which has been warm and bright, without the
intervention of sufficient rain to moisten the ground to some depth,
the wheat crop is generally much injured by mildew. I suspect
that in such cases an injurious absorption of moisture, by the leaves
and stems of the wheat plants, takes place: and I have proved that
under similar circumstances much water will be absorbed by the
leaves of trees, and carried downwards through their alburnous
substance ; though it is certainly through this substance that the
sap rises, under other circumstances. If a branch be taken from a
tree when its leaves are mature, and one leaf be kept constantly
wet, that leaf will absorb moisture, and supply another leaf below
it upon the branch, even though all communication between them
through the bark be intersected; and, if a similar absorption takes
place in the straws of wheat, or the stems of other plants, and
a retrograde motion of the fluids be produced, I conceive that the
ascent of the true sap or organisable matter into the seed-vessels
must be retarded, and that it may become the food of the parasitical
plants, which then only may grow luxuriant and injurious,”—
(Hort. Trans., i. 86.)

52 VITAL ACTIONS.

from the solid parts that were dissolved in it; to the
deposition thus effected of various earthy and other
substances, either introduced into plants, as silex and
metallic salts, or formed there, as the vegetable alka-
loids; to the extrication of nitrogen; and, probably,
to other causes as yet unknown,—that the formation
of the peculiar secretions of plants, of whatever kind,
is owing: And this is brought about principally,
if not exclusively, by the agency of light. Their
green colour becomes intense, in proportion to their
exposure to light within certain limits, and feeble, in
proportion to their removal from it; till, in total and
continued darkness, they are entirely destitute of
green secretion, and become blanched or etiolated.
The same result attends all their other secretions ; tim-
ber, gum, sugar, acids, starch, oil, resins, odours, fla-
vours, andall the numberless narcotic, acrid, aromatic,
pungent, astringent, and other principles derived
from the vegetable kingdom, are equally influenced,
as to quantity and quality, by the amount of light to
which the plants producing them have been exposed.

76. It is, however, to be observed that, as has
already been stated (68), the capability of planis to
bear the action of direct light varies according to
their specific nature. One species is organised to suit
the atmosphere of a dense wood, into which diffuse
light only will penetrate; another is planted by nature
on the exposed face of a sunburnt rock, upon which
the rays of a shadeless sun are daily striking; in
these cases, the light which is necessary to the one
would be destructive of the other. The organic dif-

ACTION OF LEAVES. 58

ference of such species seems to consist chiefly in the
epidermis, which regulates the amount of perspi-
ration (61). It is therefore to be remarked, that it is
not the greatest quantity of light which can be
obtained that is most favourable to the healthiness of
plants, but the greatest quantity they will bear with-
out injury. If the former were true, the concentrated
light of a lens would be better than the strongest
ordinary light; but the effect of the concentrated
light of a lens is to burn the surface, and the ordi-
nary solar rays produce the same effect upon many
plants, probably by exhausting the tissue of its water
faster than it can be supplied from the roots.

77. In the course of time, a leaf becomes incapable
of performing its functions; its passages are choked
up by the deposit of sedimentary matter; there is no
longer a free communication between its parenchyma
and that of the rind, or between its veins and the
wood and liber. It changes colour, ceases to decom-
pose carbonic acid, absorbs oxygen instead, gets into
a morbid condition, and dies: it is then thrown off.
This phenomenon, which we call the fall of the leaf, is
going on the whole year round, except mid-winter,
in some plant or other. Those which lose the whole
of their leaves at the approach of winter, and are
called deciduous, begin, in fact, to cast their leaves
within a few weeks after the commencement of their
vernal growth; but the mass of their foliage is not
rejected till late in the season. Those, on the other
hand, which are named evergreens, part with their
leaves much more slowly; retain them in health

54 VITAL ACTIONS.

at the time when the leaves of other plants are perish-
ing; and do not cast them till a new spring has com-
menced, when other trees are leafing, or even later.
In the latter class, the functions of the leaves are
going on during all the winter, although languidly ;
they are constantly attracting sap from the earth
through the spongelets, and are, therefore, in a state
of slow but continual winter growth. It usually hap-
pens that the perspiratory organs of these plants are
less active than in deciduous species.

78. In general, a leaf is an organ of digestion and
respiration, and nothing more; some leaves have,
however, the power of forming leaf-buds, if placed in
or upon earth, under suitable circumstances. The
Bryophyllum calcinum forms buds at the indenta-
tions of its margin; Malaxis paludosa throws off
young buds from its margin; Tellima grandiflora
oceasionally,buds at the margins of its leaves: the
same thing happens to many Ferns; and several
other cases are known.

ACTION OF FLOWERS. 55

CHAPTER V.
ACTION OF FLOWERS.

Structure of Flowers.—Names of their Parts —Ten-
dency of the Parts to alter and change into each other,
and wnto Leaves.—Double Flowers—Analogy of
Flowers to Branches.—Cause of the Production of
Flowers.— Of Productiveness.— Of Sterility. — Uses of
the Parts of «@ Flower.—Fertihzation.—Hybrids.—
Crossbreeds.

79. A FLower is that part of a plant which is
formed for the purpose of reproducing the species
by means of seeds. It consists of floral envelopes
and sexes.

80. The floral envelopes are: 1. the calyx, which
is usually green, and always the most external; and,
2. the corolla, which is commonly thin, gaily coloured,
more fugitive than the calyx, and placed next within
it; each of these consists of leaves, called sepals in the
calyx, and petals in the corolla. Both calyx and
corolla are usually present; but in some cases only
one envelope is formed, as in the Marvel of Peru ; and
in other cases the flower has no envelopes, as in the.
Willow. Envelopes are, therefore, not a necessary
part of a flower.

81. In the middle of the flower stand the sexes,

56 VITAL ACTIONS.

called stamens and pistil, of which the pistil occupies
the centre, and the stamens surround it; except in
those cases where the sexes are produced in separate
flowers, when each sex is central in its own flower.
The stamens consist of a filament and an anther, in
the inside of the latter of which is secreted a powdery
substance called pollen. The pistil consists of ovary,
style, and stigma, in the inside of the first of which
are ovules or young seeds.

82. Although the floral envelopes may be, and often
are, absent, wholly or in
part, yet the sexes are al-
ways present. Consequent-
ly the latter are all that is
essential to a flower, and
no part can be a flower
from which they are ab-
sent.

83. Notwithstanding the
difference in form and of:
fice of the parts of a flow-
er, they have evidently a
strong tendency, in cul-
tivated plants, to change
into or assume the appear-
ance of each other, In the
Poppy, the Garden Ane-
mone, and many others,
the stamens change into
petals; in the Anemone, the Ranunculus, &c., the
pistil changes into petals; in the Primrose, Cowslip,

ACTION. OF FLOWERS. 57

&c., the calyx changes into petals; in the Houseleek,
the stamens become pistils; andso on. Hence the
origin of double flowers. In a double Barbadoes
Lily, described by me in the Transactions of the Hor-
ticultural Society, in which the parts were very much
confused, the young seeds were borne by the edges
of the stamen-like petals. (fig. 8.)

84. In their ordinary state the parts of a flower are
extremely unlike leaves, and each has its allotted
office, which is not the office of a leaf; they are also
incapable of forming leaf-buds in their axils. But,
although such is the case, there is found a strong and

general tendency on the parts of both the floral
envelopes and sexes to change to leaves, like the
leaves of the stem. In the white clover (Trifolium
repens, fig. 9), all the parts often become leaves; in
the Fraxinella (jig. 10), this has also been remarked ;*

* Proceedings of the Horticultural Society, vol. i. p. 37.

58 VITAL ACTIONS.

so has it in the Nasturtium, in Sieversia montana, and
many other instances. A
partial alteration into leaves
is of very frequent occur-
rencein the parts of a flower.
Tn the Rose, the sepals and
pistilare frequently changed
into leaves; in the Double
Cherry, the pistil is almost
always to be found in the
form of a leaf; and books
on structural botany abound
in the records of similar
cases. It sometimes happens that buds are not only
formed, but developed, at the axils of the parts of a
flower, as in a Celastrus scandens observed by Kunth,
(fig. 11.) In the Pear, it is
not uncommon to find two or
three small pears growing out
of an older one ( jig. 12), each
of which pears may be traced
to the axil of some one of the
parts of the flower; and rose-
buds are frequently seen growing out of Roses. A
very striking and uncommon case of this sort was
observed by the late Mr. Knight in the Potato (fig.
13), whose flowers produced young potatoes in the
axils of the sepals and petals.* Occasionally, the
centre of a flower lengthens and bears its parts upon
its sides, as in the Pear and Apple, whose fruit is

* Proceedings of the Horticultural Society, vol. '. p. 89. fig. 2.

ACTION OF FLOWERS, 59

often found in the state of ashort branch. Still more
rarely a flower lengthens, and produces from the axils

of its parts other flowers arranged over its sides, as in
the Double Pine-apple of the Indian Archipelago.
The following very striking illustrations of these facts
have, among many others, occurred in the present
season (1839). Fig. 14 represents a branch of a Pear,
in which one flower (a) is in a deformed state, but

60 VITAL ACTIONS.

14

still sufficiently recognisable, and another completely
changed into a branch; the calyx assuming the
appearance of leaves or leafy scales (ss), the petals

ACTION OF FLOWERS. 61

also partially transformed into leaves ( p p), while the
whole apparatus of stamens and pistils is converted
into an ordinary branch. ig. 15 shows the state of

plants of Potentilla nepalensis with their flowers
changing to branches: a is a flower in the ordinary

62 VITAL ACTIONS,

condition; at ditis partly changed in a slight degree;
at call the sepals, petals, and stamens are converted into
leaves, but the pistils are little changed; at d the
sepals, petals, and stamens are but little altered, but
the receptacle of the fruit is lengthening into a branch,
and is covered by the carpels partly converted into
leaves, and some of them near the apex producing
flowers from their axils; finally, at e, the whole of
the floral apparatus is changed into a rosette of leaves.
It therefore appears, that although the parts of a
flower are different both in appearance and office
from leaves, yet that they do all assume, under parti-
cular circumstances, the same appearance and office.
Hence it is inferred that they are really nothing more
than leaves in a modified state; and, consequently,
that a flower is a very short branch, and a flower-bud
analogous in many respects toa leaf-bud. A leaf-bud
is a collection of leaf-scales of the same or similar
form, arranged round a central very short branch,
having a growing point. A flower-bud is a collection
of leaf-scales of different forms, arranged round a
central very short branch, not having a growing point
under ordinary circumstances. In this latter respect
it resembles those buds of the Larch which form
leaves in starry clusters, without extending into a
branch. Many points in horticulture could not be
explained until the existence of this analogy was
made out.*

* [This doctrine has been taught at different times, by different
independent observers. Among other persons, I find that Mr. Knight
had come to the same conclusion, at a time when the views of

ACTION OF FLOWERS. 68

85. What it is that causes a plant to convert some
of its buds into flowers, by fashioning the leaves into
calyx, corolla, stamens, and pistils, while other buds
become branches clothed with ordinary leaves, is be-
yond the reach of explanation. There are, however,
some facts connected with it which require notice. It
is clear that plants begin to fructify at some determin-
ate period, varying in different species. In annuals
this occurs in a few weeks or months after germina-
tion; in biennials a longer period is required before
this condition is arrived at; and in shrubs and trees
a still greater age must be acquired. The American
Aloe will not flower before it is thirty years old, under

Wolffius and Goethe were quite unknown in England. He says:
“The buds of fruit trees which produce blossoms, and those which
afford leaves only, in the spring, do not at all differ from each other,
in their first stage of organisation, as buds. Each contain the rudi-
ment of leaves only, which are subsequently transformed into the
component parts of the blossom, and in some species of the fruit also.
I have repeatedly ascertained that a blossom of a Pear or Apple tree
contains parts which previously existed as the rudiments of five
leaves, the points of which subsequently form the five segments of
the calyx; and I have often succeeded in obtaining every gradation
of monstrosity of form, from five congregated leaves (that is, five
leaves united circularly upon an imperfect fruit-stalk) to the perfect
blossom of the Pear tree. The calyx of the Rose, in some varieties,
presents nearly the perfect leaves of. the plant, and the large and
long leaves of the Medlar appear to account for the length of the
segments, in the empalement of its blossom. The calyx of the blos-
som of the Plum and Peach tree is formed precisely as in the pre-
ceding cases, except that the leaves which are transmuted into the
calyx separate at the base of the fruit, and become deciduous, instead
of passing through and remaining a component part of it.” (Trans-
actions of the Horticultural Society, vol. ii. p. 364. May 6, 1817.)

64 VITAL ACTIONS.

the most favourable conditions; and under unfavour-
able circumstances, the age at which it fructifies is so
much increased as to have given rise to the vulgar
belief that it flowers only after a hundred years. This
very curious subject has been little investigated, and
we have no comparative statements of the ages at
which different species begin to bear; but the fact is
certain. It is often, however, in the power of man to
advance or retard these periods artificially. What-
ever produces excessive vigour in plants is favour-
able to the formation of leaf-buds, and unfavourable
to the production of flower-buds ; while, on the other
hand, such circumstances as tend to diminish luxu-
riance, and to check rapid vegetation, without affect-
ing the health of the individual, are more favourable
to the production of flower-buds than of leaf-buds.
Thus, a plant in a sterile soil and exposed situation
flowers sooner and more abundantly than one in a
rich and shaded place; young vigorous plants flower
later and less abundantly than old ones. In India
and China, fruit trees are made to bear by cutting
their roots, or exposing them periodically to dryness;
and in this country the same practice is observed, es-
pecially with the fig-tree. An apparent exception to
this law is found in the fact that a seedling fruit tree
may be made, by grafting upon any old stock, to bear
flowers at an earlier age than it otherwise would have
done ; for the effect of grafting it thus is certainly not
to render it less vigorous, but the contrary. But it
is probable that all these facts arise out of one com-
mon law, which is, that the period when a plant be-

ACTION OF FLOWERS. 65

gins to flower depends upon the presence in its sys-
tem of a sufficient quantity of secreted matter fit for
the maintenance of the flowers when produced. Un-
der ordinary circumstances, a considerable part of all
the nutritious secretions elaborated by the leaves are
expended in the production of new leaves; but, after
a time, a greater supply is formed than the. leaves re-
quire, and the gesidue collects in the system; as soon
as the residue has arrived at the necessary amount,
flowers may begin to form. If the sterile branch of a
tree is ringed,* it ceases to be sterile; and this can
only be accounted for upon the supposition that the
secreted matter of the branch, instead of being con-
veyed away into the trunk and roots, is stopped by
the annular incision, above which it is compelled to
accumulate. If a tree that is unproductive be trans-
planted, it begins to bear; in this case the operation
injures its roots; sap is therefore less abundantly sup-
plied in the succeeding season to the leaves; the
leaves are therefore less able to grow than they pre-
viously were, and they consequently do not consume
the nutritious matter lying in the branches, and which

* One of the effects of ringing has been observed to consist in the
formation of numerous barren shoots below the wound, while fertile
shoots appear above it. This is conformable to the theory of the
formation of flowers being determined by « superabundance of
nutritious matter in a given place. The bark below the annular
excision is cut off from a supply of the sap elaborated by the leaves
above it; and, at the same time, in consequence of the obstruction
of the wound to the ascent of the crude sap, an unusual supply of
the latter is forced towards the buds in the bark below the wound,
which buds, being chiefly fed with crude sap, push forth into
branches and leaves, but bear no flowers.

66 VITAL ACTIONS.

they would have expended, had they been able to
grow with their former vigour; hence the nutritious
matter accumulates, and flower-buds are formed. In
this country, if a fruit tree has its crop destroyed one
year, it bears the more abundantly the next;* owing,
no doubt, to the accumulation in its system of that
nutritious matter which would not have been present
there, had the crop which was destroyed, been allow-
ed to grow: and the reverse of this is well known to
be the fact ; an excessive crop one year being follow-
ed by a scanty crop the succeeding year. So, when
a young seedling fruit tree is made to bear prema-

* The “bearing year” of the apple orchards, all over this country,
is 2 well known popular illustration of this remark. This arises
simply from the tendency in the apple, when left to itself, to bear
such large crops one year, as to require the next year to recover
sufficient strength to bear again. This becomes a kind of fixed
constitutional habit in a given variety, and is continued by grafting,
so that whole orchards bear one year, and are unfruitful the next,
with great regularity. On the other hand, certain sorts, like the
Bellflower and Holland pippin, which bear but moderate crops, in
strong soils bear every year. A. J. D.

The habit itself may be corrected or changed, when the tree or
orchard is young, by picking off all the fruit that sets the first year
the tree bears a good crop, and thus forcing it to take its bearing
year the next season, In parts of the country where the “apple
year” is pretty uniformly the same in all the orchards, we have known
clever orchardists to increase their profits by thus inducing their
young orchards to take the barren year of the country around for their
fruitful one, and the habit once formed the tree will continue it, In
a garden where the cost of labor is not so much an object, apple trees
may have half their fruit regularly thinned-off when they are as
large as bullets, by which process the tree will not exhaust itself,
and will bear a moderate crop the next year. A. J. D,

ACTION OF FLOWERS. 67

turely by grafting it upon an old stock, the effect of
which will apparently not be to diminish its vigour,
it may be conceived that, in the first place, the seed-
ling will receive a considerable quantity of nutritious
matter from the old stock, where it has been already
collected, and that thus the supply will be greater
than the consumption, however large the latter may
be; and, secondly, that, at the time of union of itself
with the stock, there will be sufficient interruption of
continuity in the bark to oppose some obstacle to the
descent from the seedling of whatever matter it may
have received or formed. Hence, it is an axiom in
vegetable physiology, that the production of flower-
buds depends upon the presence of nutritious matter
in sufficient abundance for their support.

86. The use of the calyx and corolla is too uncer-
tain and unimportant to demand much notice. The
calyx is usually regarded as a protecting organ, and
the corolla as a part for the embellishment of the
sexes. They neither appear to be of much physiolo-
gical importance; more especially the corolla, or it
would not be absent in such large numbers of plants.

87. The use of the stamens is to effect the fertilisa-
tion of the young seed contained in the pistil. To
this end, the pollen of the anther must be applied to
the stigma; the result of which is, that an embryo,
the rudiment of a future plant, is generated in the
inside of the young seed, and, when mature, is capa-
ble of multiplying the species. It is, however, to be
observed that. the seed, when ripe, will not renew the
species from which it is derived, with all its indi-

68 VITAL ACTIONS.

vidual peculiarities ; the seed of a Green Gage Plum,
for instance, will not, with any certainty, produce a
plant having the sweet green fruit of that variety,
but it may produce a plum whose fruit is red and
acid. All that the seed will certainly do is to pro-
duce a new individual of the plum species; the pecu-
liarities of individuals are perpetuated by other
means, and especially by leaf-buds. (See Book II.)

88. If the pistil of one species be fertilised by the
pollen of another species, which may take place in the
same genus, or if two distinct varieties of the same
species be in like manner intermixed, the seed which
results from the operation will be intermediate be-
tween its parents, partaking of the qualities of both
father and mother. In the first case the progeny is
hybrid, or mule; in the second, it is simply crossbred.

89. In general, crossbreds are capable of producing
fertile seed, and thus of perpetuating one of the spe-
cies from which they sprang. Hybrids, on the con-
trary, are often sterile, and therefore incapable of
yielding seed.

90. Reasoning from a few facts, and from the ana-
logy of the higher orders in the animal kingdom, it
has been believed that all vegetable hybrids are
sterile; and, when sterility is not the consequence
of the intermixture of two species, it has been thought
that such species are not naturally distinct, however
different their appearance. But facts prove that
undoubted hybrids may be fertile; and when we
consider that plants are not analogous to the higher
orders of animals, but to the lowest, concerning

MATURATION OF THE FRUIT. 69

whose habits we know nothing whatever, it is obvious

that no analogical inferences can be safely estab
lished.

CHAPTER VI
OF THE MATURATION OF THE FRUIT.

Changes tt undergoes.—Superior and inferior Frutt.
—Is fed by Branches upon organisable Matter fur-
nished by Leaves.—Physiological Use of the Fruit.—
Nature of Secretions.—The Changes they undergo.—
Effect of Heat.—Of Sunlight.—Of Water.—Seeds.
Origin of their Food.— Cause of their Longevity.— Of
their Destruction.—Difference in their Vigour.

91. ArreR the fertilisation of the seed has taken
effect, the pistil by itself, or the pistil and surround-
ing parts, go on growing; alter their appearance, as
well as size ; acquire new qualities.of colour, texture,
flavour, &.; and become the fruit. There are two
kinds of fruit essentially very different; in some
instances, the pistil grows separately from the floral
envelopes, which drop off, and the fruit is formed by
an enlargement and alteration of the sides of the
pistil only; it is then called superior: in other
instances, the pistil and floral envelopes all grow
together, and the fruit consists of an enlargement and

70 VITAL ACTIONS.

alteration of the whole flower; it is then said to be
inferior. There is this essential difference between
the two,—that the superior fruit adheres to the branch
by the base of the pistil alone; while the attachment
of the inferior fruit is secured by the base, not only
of the pistil, but of all the floral envelopes surround-
ing it. A Peach is a superior fruit; an apple infe-
rior.

92. A flower being a kind of branch, as has been
already shown, and the fruit being an advanced stage
of a flower, it follows that a fruit is also a kind
of branch. It has originally the same kind of organic
connexion with the plant as other branches, and, like
them, requires to be supplied with food, in the absence
of which it perishes or languishes. Nevertheless, as
its leaves have in but a slight degree the power
of forming secretions, and consequently of producing
woody tissue in its interior, it will soon drop off its
parent, unless the supply of food to it be copious,
and its healthy condition permanently secured. Now,
as the supply of food to the plant is determined by
the attracting force of the leaves of which it consists,
and as a superior fruit consists of a smaller number
of leaves than an inferior fruit, it follows that the
attracting power of an inferior fruit is, ceteris paribus,
greater than that of a superior, and consequently the
former is less likely to drop off; and as the pistil of
a superior fruit, being unprotected, is more exposed
to external influences, such as that of frost, or a cold
dry atmosphere, than an inferior, it also follows that
the latter is less liable to suffer from such causes, as

MATURATION OF THE FRUIT. 71

compared with a superior fruit of similar constitu-
tional power.*

98. It is, however, to be remarked that these rules.
may be interfered with by special causes; as in the
case of the Fig, where the superior fruit is seated on,
an enlarged receptacle, which acts as if it were a
large surface of leaves adhering to the pistil.

94, It may be conceived that, as the fruit is an
altered state of a leaf, its physiological action will
resemble that of a leaf, in proportion as it retains its
organicsimilitude ; and this is found to happen, a fruit
decomposing carbonic acid, &., under the influence
of light, so long as it retains its original green folia-
ceous character. In the Pea, for example, whose pod
is green until it begins to die, the action is always
similar to that of a leaf: but in the Peach, whose tex-
ture becomes pulpy, and unlike that of a leaf, the
physiological action eventually ceases to be exactly
that of the latter organ.

95. But although a fruit has, like a leaf, the power
of forming secretions by elaborating the sap which is

* The following table shows which of our commonly cultivated
plants have superior or inferior fruits :—

Superior. Inferior.
Strawberry. Apple.
Raspberry. Pear.
Peach. Quince.
Plum, ce. Medlar.
Apricot. Currant,
Cherry. Gooseberry.
Grape. Melon.

Fig. Cucumber.

72 VITAL ACTIONS.

attracted into it, yet, because of its smallness, the
amount of this power is inconsiderable ; it contributes
little to the general secretions of the plant that bears
it, but expends its powers in the elaboration of matter
for its own use. That it does, however, form wood,
like ordinary leaves, is evident, if the flower-stalk of
a Cherry is compared with the stalk of the fruit of the
same tree; and this becomes still more apparent when
the elaborating forces of many separate fruits are, in
consequence of their compact arrangement, brought
to contribute to the lignification of a common stalk,
as in the Pinaster tree.

96. The great purpose for which the fruit is formea
seems to be the protection and nutrition of the seed,
the perfect maturation of which is essential to the per-
petuation of the races of plants. In most cases the
whole of the fluid or nutritious parts is consumed in
effecting this end; but in certain instances there is a
surplus, which, if sweet, and unmixed with delete-
rious secretions, becomes fit for food. In either case,
the fruit has, in common with leaves, the power of
attracting food from the surrounding parts; and we
see that this property causes the destruction of some
fruits by their neighbours which are more advanced
in growth, or accidentally more vigorous, and whose
attracting power is so great as to draw to themselves
all the food intended for the weaker fruits, which then
fall off. Of the food thus to be consumed in the ma-
turation of the fruit, a portion is derived from the
atmosphere, but the principal part has to be prepared
by the leaves, which obtain it from the earth through

MATURATION OF THE FRUIT. 73

the roots. It is, therefore, evident, that all causes, of
whatever nature, which interfere with the healthy
and regular action of leaves and roots, will also inter-
fere with the fruit. Or, if the leaves are placed in
such a manner with respect to the fruit, or at so great
a distance from it, that the fruit is unable to attract
food from them, it must either suffer or perish. This
explains why fruit formed upon naked branches will
not continue to grow; and why the presence of a leaf
immediately above a fruit, on the same branch, is so
beneficial to it. The size and excellence of fruit will
hence be in proportion to the abundance of organisa-
ble matter prepared and stored up in its vicinity.*

97. Although fruit has, in common with leaves,

* The accumulation of sap, and its consequent viscidity, may,
however, he attended with disadvantage to a plant, as really hap-
pens in the Potatoe, the most farinaceous varieties of which are
liable to a disease called the “curl.” Mr. Knight attributed this to
the inspissated state of the sap, which, he conceived, if not suffi-
ciently fluid, might stagnate in and close the fine vessels of the leaf
during its growth and extension, and thus occasion the irregular
contractions which constitute this disease. He therefore suffered
a quantity of Potatoes, the produce almost wholly of diseased
plants, to remain in the heap, where they had been preserved dur-
ing winter, till each tuber had emitted shoots of three or four inches
in length. These were then carefully detached, with their fibrous
roots, from the tubers, and were committed to the soil, when, having
little to subsist upon except water, not a single curled leaf was pro-
duced, though more than nine tenths of the plants which these
identical tubers subsequently produced were much diseased, The
same effect has been produced by other persons, by taking up
the tubers intended for seed before they were full grown, and con-
sequently, before the excessive inspissation of their secretions had
taken place.

: 4

74 VITAL ACTIONS.

the property of elaborating the sap, yet there is this
difference between them; that, while leaves return
back into the stem what matters they form, fruit
retains the principal part of what it forms for the use
of itself or of the seeds it contains. This difference is
probably to a considerable extent dependent upon
the imperfect condition of the bark of the fruit-stalk,
which has little power of carrying off from the fruit
the matter which is formed within it. In those cases,
however, in which the fruit has stomates, the aqueous
particles are given off through the surface of the
fruit, which then becomes hard or dry when ripe;
but in others, in which there are no stomates, or very
few, or very imperfect ones, the aqueous particles
cannot be given off to any considerable amount, and
the fruit becomes succulent.

98. The maturation of the fruit is dependent, then,
upon the action of the leaves and roots, and the secre-
tions that it forms are principally derived from the
former. Consequently, whatever contributes to the
healthy condition of the leaves and roots will have a
directly beneficial influence upon the fruit, and vice
versa. It is, however, certain, that the juices fur-
nished by the leaves undergo a further alteration by
the vital forces of the fruit itself, which alteration
varies according to species. Thus the fruit of the
Peach is sweet, but there is no perceptible sweetness
in its leaves; and the fruit of the Fig is sweet and
nutritious, while the leaves of that }lant are acrid
and deleterious.

99. Among the immediate causes of the peculiar

MATURATION OF THE FRUIT. 75

changes that occur in the secretions of fruits, are heat
and light; without which the peculiar qualities of
fruits are imperfectly formed, especially in species
that are natives of countries enjoying a high summer
temperature. It is found that among the effects of a
high temperature and an exposure to bright light, is
the production of sugar and of certain flavours; and
that under opposite circumstances, acidity prevails.*
As sugar is more rich in carbon than vegetable acids,
and has no free oxygen as they have, the sweetness
of pulpy fruits ripened under bright sunshine may
be understood to arise from the decomposition of
carbonic gas, and the expulsion of oxygen, being
greater under sunshine than in the shade. Another
cause may be, the greater facility with which vegeta-
ble acids enter into combination with gum and starch,
and so form sugar, at a high than at a low tempera-
ture.t

100. One of the most essential of the alterations

* [Fruits remain acid in cold summers: on the other hand, nearly
all the trees of tropical climates produce oils, caoutchoue, and other
substances which contain little or no oxygen. G.]

+ For Table of the Proportions of Carbon and Water in a few of
the commonest Vegetable Secretions, vide next page.

The gummy, mucilaginous, and gelatinous parts appear very sus-
ceptible of changing into sugar; thus M. Couverchel found that, if
Apple jelly is treated with a vegetable acid dissolved in water, a
sugar like that of Grape sugar is the result; that the gum of Peas
placed with oxalic acid in a temperature of 125°, is converted into
sugar; that the gum obtained from starch, mixed with the juice of
green Grapes, renders it saccharine; and, finally, that tartaric acid,
assisted by heat, produces the same effect; which is what causes
most fruits to become sweet when cooked. (De Candolle, Phys. Veg.,
p. 585.

76 VITAL ACTIONS.

which occur in fruits during ripening, is the decom-
position or dissipation of the water that they attract
from the stem. A diminished supply of water will,
under equal circumstances, produce an accelerated
maturation, because less time will be required to
decompose or dissipate this element; and, on the
other hand, an excessive supply of water will retard
or prevent ripening, in consequence of the longer
time required for the same purpose.

Table of the Proportions of Carbon and Water in a few of the
commonest Vegetable Secretions.

Water, Oxygen
Substance. Carbon. or its in
Elements. Excess.
Gum... . . (Berzelius) | 57-318 42°682
Starch ditto 43°481 56°518
Tannin. . . ditto 51°160 41477 3568
Sugar of Sugar-Cane ditto 44:2 55°79
Grape Sugar de Saussure) | 36°71 60-08 341
Lignine. . . é (Prout) | 50 50
Acid, Citrie . . | (Berzelius 41°309 84°234 24394
Malice . . . . (Prout) | 40°68 45°76 13°56
Oxalic. 2. (ditto 19-04 42°85 38-11
Tartaric . . . (ditto) | 32 36 32
i Ulmie . . . P. Boullay) | 56-7 43:3
I—— Gallic . . . (Berzelius) | 56.64 43°36
Acetic. . . (ditto) 46°23 53°17
Hydrogen |
in Excess.
Oil, Olive Th. de Saussure | 17-21 1071 12°08
oho. ae } 7440 | 18°87 4-45
isson)
of Anise (Zh, de Saussure) | 83°468 14887 6-465
i—— of Lavender . (ditto 75°50 14°59 9°55
of Roses - . (ditto 82-053 4°442 12631
of Turpentine (Gay Lussac)| 88°348 * 3 11°652
Hydrocyanic Acid ( Gay Lussae 44-39 3-90
& Thenard) ay (51°71
Nitrogen.)

MATURATION OF THE FRUIT. 77

101. Seeds are affected by all circumstances that
affect the fruit, which indeed, as has been already
stated, appears to be created for their nutrition and
preservation. In general, the fruit attracts organisa-
ble matter from the stem through the stalk, and the
seed from the fruit through its placenta*; and this
accounts, independently of other causes, for the
importance of the fruit to the seed.

102. When the seed is ripe it is dry, all its free
water being parted with; and its interior is occupied
by starch or fixed oil, or some other such substance,
together with earthy matters. It would seem that,
so long as these secretions remain undecomposed, so
long does the vitality of the seed continue unim-
paired; and hence the great age at which certain
kinds of seeds have been found to grow. But, as it
is difficult to prevent their decomposition, so is it
difficult to preserve seminal vitality for any consider-
able time; and the difference found in the duration
of the growing powers of seeds probably depends
principally upon chemical differences in their consti-
tuent parts. Oily seeds, which readily decompose,

* The placenta i is a soft part of the inter or of a fruit, upon which
the seed is formed. It is composed of thin-sided parenchyma, the
most absorbent of all the forms of tissue, and is in communication,
by its whole surface, with the parenchyma of the fruit.

+ Not to speak of the doubtful instances of seeds taken from the
Pyramids having germinated, Melons have been known to grow at
the age of 40 years, Kidney beans at 100, Sensitive-Plant at 60,
Rye at 40; and there are now growing, in the garden of the Horti-
cultural Society, Raspberry plants raised from seeds 1600 or 1700
years old. (See Introduction to Botany, ed. 3, p. 868.)

78 VITAL ACTIONS.

are among the most perishable; starchy seeds, which
are least subject to change, are the most tenacious of
life.

108. Warmth, moisture, and an excess of oxygen,
but especially warmth and moisture, while they are
the greatest causes of germination, are probably, on
that same account, the chief causes of death. Seeds
remain dormant so long as the proportion of carbon
peculiar to them is undiminished; water is decom-
posed by their vital force (14); and its oxygen, com-
bining with the carbon, forms carbonic acid, which
is given off. The effect of access of water is, there-
fore, to rob seeds of their carbon; and the effect
of destroying their carbon is to deprive them of the
principal means which they possess of preserving
their vitality.

104. Although a seed, if fully formed, is in all
cases capable of perpetuating its race, yet there is
a difference in the degree to which this capability
extends, All seeds will not equally produce vigor-
ous seedlings: but the healthiness of the new plant
will correspond with that of the seed from which it
sprang. For this reason, it is not sufficient to sow a
seed to obtain a given plant: but, in all cases where
any importance is attached to the result, the plumpest
and heaviest seeds should be selected, if the greatest
vigour is required in the seedling; and feeble or less
perfectly formed seeds, when it is desirable to check
natural luxuriance. It is apparently for this reason,
that old Melon seed is preferred to new; for the
latter would give birth to plants’too luxuriant for

OF TEMPERATURE. 79

the small space in which the Melon can be cultivated,
under the artificial circumstances required in this
country.

105. As both fruit and seeds are maintained at the
expense of the leaves, the destruction of the former,
when young, will enable the latter to store up against
a succeeding season, for the support of future flowers,
all that organisable matter which the fruits and seeds
destroyed would have otherwise consumed.*

CHAPTER VII.
OF TEMPERATURE.

Limits of Temperature endurable by Plants.—Effects of
a too high Temperature—of a too low Temperature,
—Frost.—Alternations of Temperature.—Day and
Night— Winter and Summer.—Temperature of
the Earth and Atmosphere.

106. THz extreme limits of temperature which

* When any young trees or plants show forth fruit they are
usua ly looked upon with great satisfaction, and allowed to mature
as large a number as possible, by those who know little of such
matters. It is almost invariably the case, however, that such an
over-crop on a young tree confirms that delicacy of constitution of
which it is the index, and gives it for ever after a sickly and dwarf-
ish habit. In all such instances the fruit should be plucked off
annually, till the tree or plant has attained vigor and size enough to
enable it to mature its fruit without exhaustion, A. J. D.

80 VITAL ACTIONS.

vegetables are capable of bearing, without destruction
of their vitality, have not been determined with pre-
cision; it is however known, that, on the one hand,
certain seeds may be boiled without being killed,
and that, on the other, they are capable of bearing
many degrees of freezing without suffering. In like
manner, some plants are found to endure the most
intense cold known upon the globe, while others
sustain, occasionally, a temperature as high as 140°,
as was observed by Dr. Coulter on the banks of the
Rio Colorado.* The number of plants, however,
capable of sustaining extremes of temperature, is
small, and the greater part of the species known to us
are proved to exist within the limits of 82° and 90°.
What amount of temperature a given species will
prefer, under different circumstances, seems redu-
cible to no general rule, but has to be deter-
mined experimentally in each case, or is judged of
by the known climate of which a plant may be a
native. It is probable that every species has a con-
stitution better suited to some particular amount of
temperature than to any other, although it can bear
a greater or less degree without sustaining injury.
107. Although many plants will live in a temper-
ature much below that of freezing, yet no plant is
able to grow unless the temperature is above 32°, for
physical reasons that require no explanation. When
temperature rises, the air contained in the minute
cells of plants expands, the fluids become thinner,

* The temperature borne by Oscillatorias in thermal springs is

much higher than this; but no such power is possessed by cultivu
ble plants.

OF TEMPERATURE. 81

the excitability of the tissue is aroused, and, at the
same time, insensible perspiration is commenced, the
effect of which is to bring into play the absorbing
powers of the roots, and thus to set the machinery of
vegetation in action. The degree of temperature
required to produce this effect is extremely variable
in different species of even the same climate, and is,
of course, much more variable between plants of dif-
ferent climates. For example, the common weeds
called Chick-weed, Groundsel, and Poa annua,
evidently grow readily at a temperature very near
that of 32°; while the Nettles, Mallows, and other
weeds around them, remain torpid. In like manner,
while our native trees are suited to bear the low tem-
perature of an English summer, and, in most cases,
suffer if they are removed into a country much
warmer, such plants as the Mango, the Coffee, &c.,
inhabitants of tropical countries, soon perish, even in
our warmest weather, if exposed to the open air.
108. When, in the case of a given plant, the tem-
perature is permanently maintained at a much higher
degree than the species requires, it is over-excited.
If the atmosphere is preserved in a proportional state
of humidity, the tissue grows faster than the vital
forces of the plants are capable of solidifying it, by
the decomposition of carbonic acid, and by other
means; its excitability is gradually expended, the
whole of its organisation becomes enfeebled, the vital
functions are deranged, and a state of general debi-
lity is brought on.* Such plants are soft and watery,

* According to Mr. Knight, the effect of an excessively high tem
4%

82 VITAL ACTIONS.

with thin leaves, long joints, slender stems, and with
no disposition to produce flowers, A slight lowering
of temperature affects them more than a much greater
lowering would have done under other circumstances ;
and a permanent abstraction of light readily destroys
them. Their inability to decompose carbonic acid,
and to assimilate their food in proportion to their
rate of growth, prevents their becoming so green as
is natural to them, and gives them a pallid hue; and,
if it is their property to secrete other colouring mat-
ter, that, like all their other secretions, is greatly
diminished. But if, with a preternatural elevation
of temperature, there is a proportionate abstraction of
moisture, the loss of fluid, by perspiration and evapo-
ration, goes on faster than the roots can make it
good, or the tissue transmit it; the secretions of the
species are elaborated faster than the parts to receive

perature is to cause, in unisexual plants, the production of male
flowers only, while a very low temperature produces the contrary
result. A Water Melon plant was grown in a house, the heat of
which was sometimes raised to 110° during the middle of warm and
bright days, and which generally varied, in such days, from 90°
to 105°, declining during the evening to about 80°, and to 70° in the
night; the air was kept damp by copious sprinkling with water, of
nearly the temperature of the external air, and little ventilation
was allowed. The plant, under these circumstances, grew with
great health and luxuriance, and afforded a most abundant blossom;
but all its flowers were male. “This result,” he says, “did not, in
any degree, surprise me; for I had many years previously suc-
ceeded, by long-continued very low temperature, in making Cucum-
ber plants produce female flowers only; and I entertain but little
doubt that the same fruit-stalks might be made, in this and the pre-
ceeding species, to support either male or female flowers in obedience
to external causes.” (Hort. Trans vol. iii. p. 460.)

OF TEMPERATURE. 83

them can be farmed; the old leaves “burn” and dry
up; and young leaves perish, in like manner, as fast
as they are formed.

109. Such being the result of preternaturally high
temperature in dryness and in moisture, it is easy to
conceive that, although such extremes cannot but be
prejudicial, yet that they may be approached for parti-
cular purposes with advantage. A high temperature
and dryness will be favourable to the formation of se-
cretions of whatever kind ; while a high temperature,
with moisture, will lead to the production of leaves
and branches only.*

110. An unnaturally low temperature is productive
of evils of another kind. A certain amount of heat
is necessary to each particular species, to enable it to
grow at all: the immediate effect of heat being to
rouse the vital forces, and to bring them into action.
If the amount of heat to which a plant is exposed be
sufficient to effect this purpose, the functions of the
plant are natural and healthy; the consequences of
exceeding it have been explained, those of diminish-
ing it are not less disadvantageous. If the tempera-
ture to which a growing plant is exposed is not low-
ered so much as to destroy it, but just reduced to that
point within which it will continue to live, the plant
is brought, by the absence of a sufficient exciting
cause, into a state not unlike that already described as
resulting from over-excitement. It absorbs food from

* According to Humboldt, this happens to the Wheat grown about
Xalapa in Mexico, which will not mount into ear, but produces an
abundance of grass, on which account it is cultivated as a fodder plant,

84 VITAL ACTIONS.

the earth and air, but it cannot assimilate it; its tissue
grows, but is not solidified by the incorporation of as-
similated matter; aqueous particles accumulate in the
interidr, a general yellowness ensues, partly from the
want of a sufficient power of decomposing carbonic
acid, and partly from inability to decompose the water
collected in the interior.* The consequence of this is
a want of the means of forming the usual secretions ;
flavour, sweetness, nutritive matter, are each dimi-
nished; and the power of flowering and fruiting is
lost, probably from the absence of a sufficient secre-
tion of organisable matter (85). If the unhealthiness
of the plant is not so great as to prevent the produc-
tion of flowers, still they may not expand, as often
happens to double roses in cold summerst+ in England;
or, if the flowers do unfold, the fertilising power of

* The cause of the formation of different colours in different plants is
too obscure a subject to suit the purpose of this work. It is, however,
as well to observe that the effect of decomposing carbonic acid and ex-
haling oxygen is the production of a green colour, the intensity of which
is, in general, in proportion to the decomposing cause, that is to say, to
light: but that, if from any circumstances water is not given off, but is
retained in the system and allowed to accumulate, the green colour is
altered and changes to yellow; as if the vegetable blue, which must
exist in combination with yellow in order to form green, were dis-
charged. Such, indeed, is Macquart’s explanation of the phenomenon a
and it appears most conformable to theory and fact. For a short ex-
planation of these and other opinions connected with vegetable colour-
ing, see Introduction to Botany, ed. 8, book ii, chap. xvi.

+ Want of a sufficiently high temperature, and too much water in the
soil, seem to be, either together or separately, the cause of the diffi-
culty experienced by gardeners in making the Double yellow Rose ex-
pand its flowers.

OF TEMPERATURE. 85

the pollen is impaired or destroyed, and no produc-
tion of seed takes place.

111. Should the temperature be so much lowered
as to result in freezing, a destruction of some plants
and injury to others take place, owing to physical
causes quite different from those whose operation has
been explained in the last paragraph. In what de-
gree frost acts upon the vegetable fabric depends upon
the specific nature of a plant; the least frost destroy-
ing some species, while others, under equal circum-
stances, endure any known amount of natural cold:
but, as general phenomena, it is in evidence, that,
when a plant is frozen, the following effects are pro-
duced :—1st, The fluids contained within the cells of
tissue are congealed, and consequently expanded;
2nd, Such expansion produces, to some extent, a la-
ceration of the sides of the cells, and impairs excita-
bility by the unnatural extension to which the sides
of the cells, if not lacerated, are subjected; 3rd, It
expels air from the aeriferous cavities; 4th, It also
introduces air, either expelled from the air passages,
or disengaged by the glacial decomposition of water,
into parts naturally intended to contain fluid; 5th,
The green colouring matter and other secretions are
decomposed; 6th, The vital fluid, or latex, is de-
stroyed, and the action of its vessels paralysed; 7th,
The interior of the tubes, in which fluid is conveyed,
is obstructed by a thickening of their sides. These
phenomena may be considered in part mechanical, in
part chemical, and in part vital. The two latter are
beyond control, and probably depend either upon the

86 VITAL ACTIONS.

quality of fluid and organic matter, which may resist
the action of cold in different degrees, according to
their various modifications, or else upon specific vi-
tality. Salt and water freeze at different tempera-
tures, according to the density of the mixtures, from
4° to 27°; oil of turpentine at 14°; oil of bergamot
at 23°; vinegar at 28°; milk at 80°.; water at 32°;
olive oil at 86°; oil of anise at 50°; and it is not to
be doubted that, in like manner, the fluid contents of
plants, which we know are infinitely modified, will
resist the action of cold in very different degrees.* It
is recognised indeed as a general law, that the diffi-
culty of freezing water is in proportion to its density.

112. The effect of congealing the aqueous particles
contained in plants is, in itself, sufficient to cause such
a derangement of function as may end in death, and
the other supposed causes may be left out of conside-
ration. It will thus follow that, omitting differences
arising out of the peculiar nature of different species,
plants will suffer from frost in proportion to the abun-
dance and fluidity of their secretions; those whose
tissue is driest, and whose secretions are most dense,
being the most capable of resisting frost. Hence young
shoots are destroyed by a degree of cold which does
not affect old shoots of the same species; and hence,
also, the diminished capability of ‘‘ unripe” shoots, or
of plants growing in wet situations, or of trees when

* See a paper on frost in the Transactions of the Horticultural So-
ciety, new series, vol. ii. p. 308. [A copious abstract of Dr. Lindley’s
highly interesting memoir upon this subject will be found in the Arne
rican Journal of Science and Arts, for March, 1840. G.]

ON TEMPERATURE. 87

they first begin to vegetate, of enduring extreme
cold.*

1138. The effect of cold is, as has been seen, to di-
minish excitability ; of heat, to stimulate it: but, if the
latter stimulus were constantly equal, it may be con-
ceived that the excitability would soon become im-
paired or expended. Nature has, however, provided
against this result, not only by the fluctuations of tem-
perature that occur at different periods of the day, but
more particularly by the periodical fall of temperature
at night and its rise during the day; an arrangement
intimately connected with all the vital actions of vege-
tation. In the day, when light is strongest, and its
evaporating and decomposing powers most energetic,
temperature rises and stimulates the vitality of plants,

* M. De Candolle gives the following as the laws of temperature
with respect to its influence upon vegetation :—

1, All other things being equal, the power of each plant, and
of each part of a plant, to resist extremes of temperature, is in the
inverse ratio of the quantity of water they contain.

2. The power of plants to resist extremes of temperature is direct-
ly in proportion to the viscidity of their finids.

8. The power of plants to resist cold is in the inverse ratio of the
rapidity with which their fluids circulate.

4, The liability to freeze, of the fluids contained in plants, is
greater in proportion to the size of the cells.

5. The power of plants to resist extremes of temperature is in
a direct proportion to the quantity of confined air which the
structure of their organs gives them the means of retaining inthe more
delicate parts.

6. The power of plants to resist extremes of temperature is in
direct proportion to the capability which the roots possess of ab-
sorbing sap less exposed to the external influence of the atmosphere
and the sun.

&8 VITAL ACTIONS.

so as to meet the demand thus made upon them; then,
as light diminishes, and with it the necessity for exces-
sive stimulus, temperature falls, and reaches its mini-
mum. at night, the time when there is the least demand
upon the vital furces of vegetation ; so that plants, like
animals, have their diurnal seasons of action and re-
pose. During the day, the system of a plant is ex-
hausted of fluid by the aqueous exhalations that take
place under the influence of sun-light; at night, when
little or no perspiration occurs, the waste of the day is
made good by the attraction of the roots, and by morn-
ing the system is again filled with liquid matter, ready
to meet the demand to be made upon it on the ensuing
day.* No plants will reniain in a healthy state unless
these conditions be observed.

114. The alternation of seasons seems to be intended
to produce the like effects in a more extended manner;

* The treatment of green-house plants by the majority of garden-
ers, is directly opposed to the natural laws here so correctly stated.
The gardener raises the temperature in a cold winter night very
frequently much higher than it is in the day, and the dry heat
stimulates the plants into an unnatural and sickly growth, when
they ought to be resting. The heating apparatus of a good green-
house should be so arranged as to afford a steady but rather low
temperature at night, increasing towards morning, so that with the
returning sunlight some ventilation can be allowed. In other words
the plant-house should be at its lowest safe temperature about mid-
night, and its highest at noon-day. But as usually managed, it is
warmest and dryest at midnight, so that the system of the plant is
doubly exhausted by the process of growth that takes place at that
time. A. J. D.

+ The incessant vegetation of arctic countries during their sum-
mer is an exception to this rule; but not such as to affect the general
truth of the foregoing propositions,

ON TEMPERATURE. 89

so that the summer season may be regarded as one
long day, and the winteras a night of similar duration. *
The long days, bright light, and elevated temperature
of summer push the powers of vegetation to their
limits ; towards the end of the season excitability be-
comes impaired, all the vessels and perishable parts are
worn out, leaves choke up and can neither breathe nor
digest, and the system of a plant, by the incessant ex-
halation of aqueous matter, becomes dried up, as it
were, and exhausted. Atthattime, temperature keeps
falling, and light diminishing, till at last, upon the
arrival of winter, neither the one nor the other is suffi-
cient to excite the vital actions, and a plant sinks into
comparative repose. Atthis time, however, its vital
actionsare not arrested; ifthey were, it would be dead
or absolutely torpid; they are only diminished in in-
tensity. The roots continue to absorb from the soil
food, which is slowly impelled into the system, whence
it finds no exit; it therefore gradually accumulates,
and in the course of time refills all those parts which
the previous summer’s expenditure had emptied. In
the meanwhile the excitability of the plant is recovered
by rest, and may be even conceived to accumulate with
the food that the absorbentsystem of the roots is storing
up. At length, when the temperature of the season
has reached the requisite amount, excitability is once
more aroused, an abundance of liquid food is ready to
maintain it, and growth recommences; rapidly or
slowly in proportion to the amount of excitement, to
the length of previous repose, and to the quantity of
food which had been accumulated. In hot climates,

90 VITAL ACTIONS.

where winter is unknown, the requisite periodicity of
* stimulus and rest is provided for by what are called
the dry and the rainy seasons; the former being equi-
valent to the winter, the latter to the summer, of north-
ern latitudes.

115. As plants have little power of generating heat,
like animals, except in particular cases, and very lo-
cally,* they are principally dependent upon the media
that surround them for the heat which they require.
Considering the great importance of heat in their
economy, it is, for the purposes of gardening, a most
necessary object to ascertain what proportion is usually
borne to each other, in different countries, by the tem-
peratures of the earth and atmosphere, the chief media
by which plants can be affected. Upon the tempera-
ture of the atmosphere there are numerous observa-
tions in many countries ; upon that of the earth, so few
as to afford no sufficient data for the solution of this
problem. It is usually considered that the tempera-
ture of springs affords sufficient evidence of the tempe-
rature of the earth; but, so far as vegetation is con-
cerned, this evidence is unsatisfactory. Springs, de-
riving their origin from considerable depths, have a
nearly uniform temperature all the year round: but
the temperature of the earth’s surface varies with the
seasons; is extremely different in summer and winter;
and is affected by the quality of the soil, in proportion
as that is more or less absorbent and retentive of heat.

* Aljlusion is here, of course, made to the extrication of heat dur-

ing the periods of flowering and germination, phenomena which
have no obvious connexion with cultivation.

OF TEMPERATURE. 91

What we want to know, as respects vegetation, is, not
the mean temperature of the earth at some distance
from its surface, but the temperature immediately be-
low the surface; i. e. of that part of the soil into which
the roots of plants penetrate, and whence they derive
their food. It is also requisite that this should be as-
certained monthly, so as to furnish the means of com-
paring the terrestrial temperature with the periodical
state of vegetation.* Such being the case the tempe-

* The following proportions between the mean temperature of
the earth, as indicated by springs, and that of the atmosphere,
have been collected from various sources :—

Mean

Authority. Temp. of | Temp. of

Earth. Atmo-

sphere.

Berlin. . . . . . . . | Wahlenberg| 49°28°| 46-40°
Carlstrom ...... ditto 47°30 | 42°03
Upsall s- a. eos ee ditto 43°70 | 42°08
Paris . . . . =... « |(Catacombs)|{ 53:00 | 51:00
Charleston . . . . . . | Volney 63-00 68-00
Philadelphia... .. ditto 58-00 | 53-42
Virginia. 2... . . | ditto 57-00 | 67-00
Massachusetts . . . . . | Dewey 47-21 | 44°73
Vermont. . . . . . . | Volney 44:00 | 56-00
Raith . . ... . . . | Ferguson 47°10 | 47:00
Gosport . . . . . . . | Watson 52°46 51-42
Kendal . . 2. ws. ditto 47-20 | 47-04
Keswick . 2. 2. ws. ditto 46:60 | 48:00
Leith ai ko we we ditto 47°30 48°36
South of England. . . . | Rees’ Cyclo. | 48°00 | 50°62
Torrid Zone. . . . . . | Volney 63°00 81°50

It must be obvious, from these returns, imperfect as they are,
that the results are of little value with respect to vegetation, and
that indications from springs, from their very nature, can be but
little employed in inquiries where it is necessary to determine
the fluctuating terrestrial temperature of the surface of the earth
in different months. For example, Mr. Ferguson found the

92 VITAL ACTIONS.

rature indicated by springs will be too high in winter
and too low in summer; a most material error.

116. From the observations of Mr. Ferguson, of
Raith, with thermometers buried at different depths
in the ground, it appears, that in the years 1816 and
1817, at that place, in 56° 10’ N. lat. and 50 feet
above the sea, the mean temperatures, indicated by
geothermometers buried respectively to the depths of
one foot and two feet, varied from 19° to 21° Fahr.
between summer and winter, the earth being colder
in winter and hotter in summer to that amount; and
the highest mean observed was 55:29, in July, 1817,
at a foot below the surface.* Other observations, of

temperature of a spring at Raith, 487°; but the mean tempe-
rature of the earth, one foot below the surface, was 48°58°, and
two feet, 44°55°.

* Observations made on the Temperature of the Earth, at one and
two feet below the Surface, in the Garden of Robert Ferguson, Esq,, of
Raith :-—

1816. 1817.

One Two One Two

Foot. | Feet. | Foot. | Feet.
January . . . 2 es ee ee 330°] 86°3°F 35.6°| 38-7
February. . . . 2. +. es. 337 | 36-0] 37:0 | 40-0
Marcel. 4% ae oe 35:0 | 3867 | 394 | 40-2
API goa 8B ae BR es 39°77 | 3884 45:0 | 42-4
May. sk oe ey He es 40°0 | 43°3 | 468 | 447
PUNTER Ge PR Re 516 | 500] 511 | 494
JULY fo ew HO 54:0 | 625 | 55:2 | 55-0
JANIPUSE: ao es a so BL 500 | 562°5 | 53-4] 53-9
September . . . . 1... 516 | 5137 53:0 | 527
October i. 4) dows By ao le 47:0 | 493 | 46-7 | 49-4
November ........ 40°83 | 43:8 | 41:0 | 447
December . ....... 35°77 | 40°0 | 35°9 | 40°8
Mean of Year. . . .... 43°8 | 441] 449 | 45-9

OF TEMPERATURE. 93

a similar kind, have been made in the garden of the
Horticultural Society, from which we learn that, in
the valley of the Thames, the maximum mean of ter-
restrial temperature, at one foot below the surface,
has been found to be 64:81° in July, which is the
hottest nionth of the year; but that the greatest differ-
ence between the mean temperature of the earth and
atmosphere is in the month of October, when it
amounted, in the two years during which the ob-
servations were made, to between 8 and 4 degrees;
and that, in general, the mean temperature of the
earth, a foot below the surface, is at least one degree,
and more commonly a degree and a half, above the
mean of the atmosphere. In these cases, if the ter-
restrial temperatures be compared with those of the
atmosphere, it will be found that in the spring, when
vegetation is first generally set in motion, the tempe-
rature of the earth not only rises monthly, but re-
tains a mean temperature higher than that of the
atmosphere by from one to two degrees; and that, in
the autumn, when woody and perennial plants re-
quire that their tissue should be solidified, and their
secretions condensed, in order to meet the approach
of inclement weather, the terrestrial temperature re-
mains higher in proportion than that of the atmo-
sphere, the earth parting with its heat very slowly.*

117. There appears to be no series of direct ob-
servations, upon the superficial temperature of the
earth, at the different periods of vegetation, in other

* Quarterly Averages of Temperature obtained from Thermometers
buried in the Earth in the Garden of the Horticultural Society ; re

94

VITAL ACTIONS.

countries; but some statements are to be found, here
and there, concerning the temperature occasionally
observed, from which it is to be inferred, that the
earth is heated, at least for short periods of time, very
much above the atmosphere ;* and it is probable that
this excessive elevation of temperature is necessary to

duced from the Register kept by Mr. Robert Thompson, by order of
the Garden Committee :—

October, Novem

1837. July, August, ete bel

er, December,

1838. January, February, March,
April, May, June, . .
July, August, Se stember,
October, November, December,
1839, January, February, March,

April, May, June,

Average monthly mean, from July, 1837,
to June, 1889, inclusive,

Earth. Mean of

Atmo-
sphere.

One
Foot.

Two
Feet.

60°44°
43°86
34.57
52°01
60°23
43°28
39°51
52°18

62°19°
46°13
37°21
52:23
62°15
45°83
40°21
53°05

61:49°
47°85
38°71
50°99
61°30
47°53
41°37
51-98

49°87 | 50°15 | 48°26

* Memoranda concerning the Temperature immediately below the
Surface of the Earth, occasionally remarked in different Countries :—

Egypt
Tropics
Oronoco

France

Chile
New Grenada
Cape of G. Hope

Bermuda

13838°—144°.

Often 126°—1349,

According to Edwards
and Colin.
Humboldt, Fragm. As.

Coarse white sand at|Humboldt.

140°, the atmosphere

being 84°5°.

118°—122°; once 127°,

the atmosphere being

91°6°.

113°—118° among dry

‘ass,

85° usual summer temp.
1 foot below surface.

159° under the soil of a
bulb garden.

142° thermometer bare-

ly covered.

Arago as quoted by Ed-
wards and Colin.

Boussingault.

Hay, in Loudon’s Gard.
Mag. vi. 487.
Herschel [MSS.).

Col. Emmett.

OF TEMPERATURE. 95

the healthy condition of many plants. From some
interesting observations communicated to me by Sir
John Herschel, it appears that the temperature of the
earth, at the Cape of Good Hope, is often excessive.
On the 5th of December, 1837, between one and two
o'clock in the day, he observed the heat, under the
soil of his bulb garden, to be 159°; at 8 P. M. it was
150°, and even in shaded places 119°: the tempera-
ture of the air in the shade, in the same garden, at the
same period, was 98° and 92°. At5-p. m. the soil of
the garden having been long shaded, was found to
have, at 4 inches in depth, a temperature of 102°.
‘On the 8d of December, a thermometer buried 4 inch
deep, in contact with a seedling fir of the year’s plant-
ing, quite healthy, and having its seed-leaves, marked
as follows:—at 11h. 25 m. a. M. 148°2°, at Oh. 48m.
Pp. M. 149°5°, at Lh. 34m. Pp. M. 149°8°, at 1h. 54m. p.
M. 150°8°, and at 2h. 46m. p. Mm. 148°.” Sir John
Herschel observes that such observations ‘go to show
that at the Cape of Good Hope, in the hot months,
the roots of bulbous and other plants which do not
seek their nourishment very deep, must frequently,
and, indeed, habitually, attain temperatures which
we can only imitate in our hothouses by actually sus-
pending over the soil plates of red-hot iron. For it
must be remarked, that heating the ground from be-

Lantao, China ‘Water of rice fields 113°;[Meyen.
adjacent sandy soil
much higher; for to-
wards midday the
black sides of the boat
were 142°50,

96 VITAL ACTIONS.

low would not distribute the temperature in the same
way.”

These observations seem to confirm the late Mr.
Harvey’s suspicions, that the real force of the sun’s
rays in tropical countries is still far from being ascer-
tained. When, therefore, we are informed by tra-
vellers that the temperature in the sun, at Gondar,
has been seen to be 113° (Bruce); at Benares, 110°,
118°, 118° (Harvey); or at Sierra Leone, 138° (Win-
terbottom); it must be supposed that, in reality, the
temperature would have been found much higher in
those places, had more efficient means of observation
been employed. Mr. Foggo, indeed, succeeded, by
means of a large thermometer, having the ball covered
with black wool, and fully exposed to the direct rays
of the sun, unsheltered from the wind, in obtaining,
at Edinburgh, on the 29th of July, at 3h. 10 P. w., an
indication of 150°, and at 2h. P.M. of 140°; while
another instrument, similarly prepared, and resting
in contact with herbage, was found to indicate only
119° and 110°; so that, as Mr. Foggo remarks, a differ-
ence of 30° was produced in these cases solely from
the manner in which the instruments were exposed.
(Edinburgh Philosophical Journal, No. xxvii.)

118. For horticultural purposes,-.a very extensive
series of observations requires to be made at a very
great number of different places, with a view to deter-
mine the connexion between the temperature of the
soil and the seasons of vegetation; for it does not
appear that any such have yet been recorded, except
in this country, where, from their fewness, they are

OF TEMPERATURE. 97

by no means so satisfactory as could be desired. In
making these, the nature of the soil in which the
thermometers are plunged, should, among other
circumstances, be very precisely described; for it
is obvious that the result will be essentially affected
by the peculiar conducting power of the earth.

119. But although we have no geothermomeirical
observations which have a direct relation to the con-
nexion between terrestrial temperature and vege-
tation, yet an approximation to the amount of heat in
the earth may perhaps be obtained indirectly. It
seems improbable that the surface of the earth should
be colder than the mean temperature of the air that
rests upon it; and it seems certain, from the evidence
afforded by this country (116), that, in fact, it is
at least a degree or two above it; therefore, in the
tropical parts of America, where Humboldt found
the mean temperature of the coldest month not to be
lower than 79°16° at Cumana, we shall be justified in
concluding that the temperature of the earth’s surface
never falls permanently below that amount; and as
the mean summer temperature* of the place was
found to be 82:04°, so it is probable that the earth
will have something above that degree of warmth, on
an average, in the sammer.t

* For the warmest month, this great observer gives 84°38° as
the mean; which corresponds remarkably with the temperature
x foot below the surface in New Grenada, where, according to
w correspondent of Mr. Hay, it is 85° during summer, “as « gen-
tleman, a planter there, wrote home for his information.” (See
Loudon’s Gard. Mag., vi. 437.)

+ [The mean temperature the State of New-York, for fourteen

98 VITAL ACTIONS.

*,* To collect together evidence as to the real
amount of temperature at the different seasons of
vegetation, in various parts of the globe, would be to
render a most important service to horticulture; for
it is hopeless to expect that the cultivation of plants
can be perfect, in the absence of one of the first data
that require to be ascertained. What, for instance,
are the terrestrial and atmospheric temperatures of
the melon fields of Persia, Bokhara, Spain, or Smyrna,
where that delicious fruit acquires its greatest ex-
cellence? In the meanwhile, the few facts recorded
in the following table will serve to show the prac-
tical importance of such information, it being borne
in mind that, as has been already shown (119,) the
mean temperature of the soil will probably be, on an-
average, a degree or two above the recorded means
of the warmest and coldest months. Thus, the tem-
perature of the earth at Calcutta, for instance, may
be computed to be not more than 88°, nor less than
72°; and if we compare places so similar in climate
as Marseilles, Vienna, and London, it will be found

years, (from 1826 to 1839 inclusive,) as deduced from observations
made under the direction of the Regents of the University, and
embodied in their Report for 1840, is 44:°31° Fahr. The lowest mean
for a single year of observations at many stations, is 44:11° (1836);
the highest, 49°99° for (1828.) The mean temperature of the
warmest and coldest months, for a series of years, have not been
embodied, but somewhat ample data have been collected. At
Albany, the mean temperature of the coldest month for 1839
(January) was 23°38°; of the warmest month (July), 72°38°. On
Long Island, near the city of New-York, the mean temperature of
the coldest month in the same year was 28°89, and of the warmest
(July) 70°69°. G.]

OF TEMPERATURE. 99

that the difference in the terrestrial temperature,
as indicated by that of the atmosphere in the warmest
month of summer, is quite sufficient to explain why
we have so little success in the cultivation of the vine
in the open air in England. ’

100

VITAL ACTIONS.

120. A ‘Table of Mean Temperatures of the
hottest and coldest months:

St. Petersburg
Moscow
Melville Is-
land. .
Copenhagen
Bdinbureh A
Geneva .
Vienna .
Paris .
London . .
Philadelphia
New-York .
Pekin.
Milan.
Bordeaux
Marseilles
Rome. .
Funchal .
Algiers
Cairo .
Vera Cruz .
Havana .
Cumana .
Canton
Macao
Canaries. .
Lohooghat,
(5300 feet
ubove the sea)
Fattehpur
Gurra-wurrah

Caleutta . {

Ava 5
Bareilly .
Chunar . ,
Cape of G’d
He
(Feldhausen)
Bahamas
Swan River.
Bermuda

. 46

Mean Temp. of
Latitude. | Longitude. }—— ——= Authorities.
wae Coldest
Month. Month.
59°56’ NJ 30°19! E. |65°66° 8°60° |Humboldt.
55 45 N.| 37 82 E. |70°52 608 ditto.
74 47 Nj110 48 W. |39°08 |-—35°52 |Hugh Murray
os a8 » . . (42°41 |}—32°19 |Ed. Phil. Journal.
55 41 Nj 12 85 E. |65°66 27°14 |Humboldt.
55 567 N.| 8 10 W. 59°36 38°30 ditto.
12 NJ 6 8 E. /66°56 84°16 ditto.
48 12 N.| 16 22 BE. (70°52 26°60 ditto.
48 50 N.| 2 20 EK. [65°30 8614 ditto.
51 30 NJ O 65 W. {64°40 37°76 ditto.
39 56 N.| 75 16 W. |77-00 82°72 ditto,
40 40 N.| 73 58 W. (80°70 25°34 ditto.
389 54 NJ116 27 E, |84:38 24°62 ditto.
45 28 N.) 9 11 E. |74°66 36°14 ditto.
44 50 N 0 84 W. |73°04 41-00 ditto.
43 17 N.| 5 22 E. /74°66 44°42 ditto.
41 53 N.| 12 27 E, /77-00 42°26 ditto,
32 87 Nj 16 56 W. |75°56 64:04 ditto,
386 48 NJ 38 1 EK, |82.76 60°08 ditto.
30 2 N.) 80 18 E. 85°82 66°12 ditto.
19 11 NJ 96 1 W. /81°86 71-06 ditto.
23 10 NJ} 82 13 W, |83°84 69.98 ditto.
10 27 N.} 65 15 W, |84.38 79°16 ditto. [endar.
23 10 Nj113 13 E, {84°50 57:00 |Anglo-Chin. Cal-
22 10 N.jJ113 32 E. |86°60 63°60%| ditto.
28 80 N.| 16 00 W. 78-90%] 63°70 |Brande’s Journal.
Transae, Med.
29 23 N79 56 E 69°34 | 43°57 Phy’s Soc’y.
Cele
25 66 N.| 80 45 E. /74-04 | 68°74 |Gleanings in Sci.
23 10 Nj 79 54 BE. |87-45 60°23 ditto.
22 40 Ni 88 25 E, [85°70 66°20 ditto.
oe ef... 186786 40:10 |Journ. As. Soc.
21 51 Nj 95 98 E |88-15 64:12 |Gleanings in Sci.
28 23 N.} 79 23 E. {91-91 66°50 ditto.
25 9 N.| 82 54 E, /90-00 58°00 Ed. Ph. Journ.
34 23 8.] 18 25 EL |74-27 57°43 |Herschel, MSS.
[MSS.
26 30 N.| 78 80 W. [83:52 69°07 |Hon. J. C. Lees,
32 00 S. 115 50 E. |78-00 54°84 |Milligan.
82 15 N.| 64 80 W. 76-75 57°90 |Col. Emmett.

BOOK IL

OF THE PHYSIOLOGICAL PRINCIPLES UPON WHICH
THE OPERATIONS OF HORTICULTURE ESSENTIALLY
DEPEND.

EVERY operation in horticulture depends for suc-
cess upon a correct appreciation of the nature of the
vital actions described in the last Book; for although
there have been many good gardeners entirely unac-
quainted with the science of vegetable physiology, and
although many points of practice have been arrived at
altogether accidentally yet it must be obvious that the
power of regulating and modifying knowledge so ob-
tained cannot possibly be possessed, unless the external
influences by which plants are affected are clearly un-
derstood. Indeed, the enormous difference that exists
between the skill of the present race of gardeners and
their predecessors can only be ascribed to the general
diffusion, that has taken place, of an acquaintance with
some of the simpler facts in vegetable physiology.

In attempting to apply the explanations of science
to the routine of horticultural practice, it appears de-
sirable, in order to avoid frequent repetition, that all
the subordinate details of the art should be omitted,
and that those general operations should alone be ad-
verted to which, under many different modifications,
and in various forms, constitute the foundation of
every gardener’s education.

102 APPLICATION OF PRINCIPLES.

CHAPTER I

OF BOTTOM HEAT.

THIS term is, in common practice, made use of ouly
in those cases where the temperature of the soil in
which plants grow is artificially raised considerably
above that which we are acquainted with in England ;
and there seems to be a general idea that such an artifi-
cial elevation of temperature is only necessary in a few
special instances, It has, however, been shown (116),
that the mean temperature of that part of the soil in
which plants grow is universally something higher than
that of the air by which they are surrounded, and con-
sequently it appears that nature, in all cases, employs
some degree of bottom heat as a stimulus and protec-
tion* to vegetation. At the same time, it must be ad-

* That the warmth of the soil acts as a protection to plants
may be easily understood. A plant is penetrated in all direc-
tions by innumerable microscopic air passages and chambers, so
that there is a free communication between its extremities. It
may therefore be conceived that if, as necessarily happens, the
air inside the plant is in motion, the effect of warming the air in
the roots will be to raise the internal temperature of the whole in-
dividual ; and the same is true of its fluids) Now, when the tem-
perature of the soil is raised to 150° at noonday by the force of the
solar rays, it will retain a considerable part of that warmth
during the night: but the temperature of the air may fall to such
a degree that the excitability of a plant would be too much and
suddenly impaired, if it acquired the coldness of the medium
surrounding it; this is prevented, we may suppose, by the

OF BOTTOM HEAT. 103

mitted that, in some cases, the amount is extremely
small; for Von Baer found Ranunculus nivalis and
Oxyria reniformis flowering in Nova Zembla, where
the soil was not warmed above 344°; and, in Jakutzsk,
Erdmann states that Summer Wheat, Rye, Cabbages,
Turnips, Radishes, and Potatoes are cultivated, al-
though the ground is not thawed above three feet in
depth.

That elevating the temperature of moist soil causes
an unusual degree of vigour in plants unaccustomed
in nature to such an elevation, is a fact which requires
no proof: it is attested by the condition of vegetation
round hot springs, and in places artificially heated by
subterraneous fires; and this has probably been the
cause of the employment of tan and hotbeds, by which
means botiom heat has been generally obtained for
rearing delicate species, and especially seeds. But if
this stimulus acts in the first instance beneficially in all
cases alike, it soon becomes a source. of mischief in
those species which are natives of climates where such
terrestrial heat is unknown, thelatter ‘drawing up,” as
the saying is, becoming weak and sickly, and speedily
presenting a diseased appearance (108).

On the other hand, it is equally well known that,
unless the temperature of the soil be raised permanent-
ly to at least 75°, the seeds of tropical trees will not
germinate ; or, if they do, they push forth feebly, and
warmth communicated to the general system from the soil,
through the roots; so that the lowering of the temperature of the
air, by radiation during the night, is unable to affect plants injuri-

ously, in consequence of the antagonist force exercised by the
heated soil.

104 APPLICATION OF PRINCIPLES.

from the first present the sickly appearance of plants
suffering from cold (110). Hence arises the impossi-
bility of making the seeds of tropical plants germinate
when sown in the open air in this country, where the
mean temperature of the earth seldom rises to 65°,
and that for only short periods of time. It is, there-
fore, obvious that all plants require some bottom heat ;
but the amount varies with their species, and the only
means or power of determining what the amount
should be, isafforded by the known degree of warmth
of the climate of which a plant may be a native.

When plants are cultivated in glass houses, there is
little difficulty in supplying them with the amount of
bottom heat which they may require; but this can
either not be effected at all, or only toa limited degree,
by a selection of soils and situations, when plants are
cultivated in the open air; and hence one of the many
difficulties of acclimatising in a cold country the spe-
cies of a warmer climate. It is true that plants will
exist within wide limits of temperature, and, conse-
quently, a few degrees of difference in the natural bot-
tom heat to which they are exposed may not affect
them so far as to destroy them; but it cannot be
doubted that the conditions most favourable to their
growth are those which embrace a temperature rather
above than below that to which they are accustomed
in their native haunts.

The Orange tree is found in perfection where the
temperature of the soil may be computed to rise to 80°
or 85°, and never to fall below 58°, as in the Bermu-
das, Malta, and Canton. How injudicious, then, is

OF BOTTOM HEAT. 105

our practice of exposing it during summer to the open
air, in tubs, where the soil scarcely rises in tempera-
ture above 66°, and preserving it during winter in
cold conservatories, the soil of which often sinks to
36°; under such circumstances the Orange exists in-
deed, but where are the perfume and juiciness of its
fruit, and where the healthy vigour of its noble foliage?
The Vine cannot be grown in the open air of this
country to any useful purpose, except when trained
to walls, in soils and situations unusually exposed to
the beams of the sun; it is only then that it can ob-
tain for its roots such a permanent warmth of 75°,
which it will have at Bordeaux, or 80° in Madeira.

It may hence be considered an axiom in horticul-
ture, that all plants require the soil, as well as the at-
mosphere, in which they grow, to correspond in
teniperature with that of the countries of which they
are natives. It has also been already shown, that the
mean temperature of the soil should be a degree ortwo
above that of the atmosphere (119).

This explains why it is that hardy trees, over whose
roots earth has been heaped or paving laid, are found
to suffer so much, or even to die; in such cases, the
earth in which the roots are growing is constantly
much colder than the atmosphere, instead of warmer.
We have here,* also, the cause of the common circum-

* Mr, Knight long since mentioned an important fact con-
nected with this subject:—“It is well known,” he said, “that
the bark of Oak trees is usually stripped off in the spring, and
that in the same season the bark of other trees may be easily
detached from their alburnum, or sap-wood, from which it is, at

5*

106 APPLICALION OF PRINCIPLES.

stance of Vines that are forced early not setting thei
fruit well, when their roots are in the external border
and unprotected by artificial means; and to the same
cause is often to be ascribed the shrivelling of grapes,
which, as we all know, most commonly happens to
Vines whose roots are in a cold and unsunned bor-
der.

Mr. Reid of Balcarras has, indeed, shown that one
of the causes of canker and immature fruit even in
orchards is the coldness of the soil. He found that, in
a cankered orchard, the roots of the trees had entered
the earth to the depthof 3 feet; and he also ascertained
that, during the summer months, the average heat of

that season, separated, by the intervention of a mixed cellular
and mucilaginous substance; this is apparently employed in the
organisation of a new layer of fibre, or inner bark, the annual
formation of which is essential to the growth of the tree. If, at
this period, a severe frosty night, or very cold winds, occur, the
bark of the trunk, or main stem, of the Oak tree becomes again
firmly attached to its alburnum, from which it cannot be sepa-
rated until the return of milder weather. Neither the health of
the tree, nor its foliage, nor its blossoms, appear to sustain any
material injury by this sudden suspension of its functions; but
the crop of acorns invariably fails. The Apple and Pear trees
appear to be affected to the same extent by similar degrees of
cold. Their blossoms, like those of the Oak, unfold perfectly
well, and present the most healthy and vigorous character; and
their pollen sheds freely. Their fruit, also, appears to set well;
but the whole, or nearly the whole, falls off just at the period
when its growth ought to commence. Some varieties of the
Apple and Pear are much more capable of bearing unfavourable
weather than others; and even the Oak trees present, in this
respect, some dissimilarity of constitution.” (Hort. Trans, vi
229.)

OF BOTTOM HEAT 107

the soil, at 6 inches below the surface, was 61°; at
9 inches, 57°; at 18 inches, 50°; and at 8 feet, 44°.
He took measures to confine the roots to the soil near
the surface, and the consequence was, the disappear-
ance of canker, and ripening of the fruit. (Jemoirs
of Caledonian Hort. Soc. vi. part 2; and Gardener's
Magazine, vii. 55.)*

If, on the other hand, we take cases of growth in
the artificial climate of hot-houses, we find that Bigno-
nia venusta, and many other tropical plants, will not

* This must be understood by our readers as applicable to the
climate of England. In that temperate and damp climate, the great
drawback to the cultivation is the coldness of the soil. In this
country, where there is five times more sunshine and heat than in
Great Britain, the drawback is of the opposite kind, viz the dry-
ness and want of moisture in the soil during a good part of the sum-
mer. Instead, therefore, of its being desirable to confine the roots
near the surface, we find it of the greatest advantage in almost any
species of culture, and especially for fruit-trees, to deepen the soil
by trenching or sub-soil ploughing, so that the roots can run
down twice the usual depth. This not only gives them « larger
area from which to obtain their food, but, by placing the food
deeper, it maintains that moisture and temperature which enable
the roots to go on supplying the demands of the leaves, and keeping
up growth, when trees in shallow soil cease growing, and
become parched and starved by the heats of midsummer. We
may add that canker, or a diseased state of the sap, usually arises in
this country, not from coldness of the soil, but from sudden alterna-
tions of temperature. The blights of the pear, apricot, and other
trees, the most fatal diseases in the United States, are forms of
canker induced by sudden thawing of the sap vessels after severe
frost. Exeept in New England and the extreme northern portions
of the country, a northern exposure is found preferable to a southern
one for orchards and fruit gardens, on account of the greater uni-
formity of temperature, and the much lessened tendency to disease
in the trees so situated. A. J. D

108 APPLICATION OF PRINCIPLES.

flower unless in a high bottom heat; and that Palm
trees, planted in the soil of conservatories which it is
impracticable to heat sufficiently, soon become un
healthy.

The reason why it is necessary to plants in a grow-
ing state, that the mean temperature of the earth
should be higher than that of the air, is sufficiently
obvious. Warmth acts as a stimulus to the vital
forces (17), and its operation is in proportion to its
amount, within certain limits, If, then, the branches
and leaves of a plant are stimulated by warmth to a
greater degree than the roots, they will consume the
sap of the stem faster than the roots can renew it;
and, therefore, nature takes care to provide against
this by giving to the roots a medium permanently
more stimulating, that is, warmer, than to the branches
and leaves.

Such being the fact, it is obvious that one of the
first of a gardener’s cares should be, to secure the
means of insuring a proper temperature to the soil in
which he grows his plants, and that this is requisite
for hardy as well as tender species; and I entertain
little doubt that the time is at hand when it will be
considered quite as necessary to furnish heat for the
soil as for the air; not, however, heat without mois
ture, for that would evidently produce much greater
evils than it was intended to cure, as has indeed been
found by inconsiderate experimenters. I quite agree
with Mr. Writgen in believing that it is the tempera-
ture and moisture of a soil, much more than its mine-
ralogical quality, that determine its influence upou

OF BOTTOM HEAT. 109

vegetation. (See Lrster Jahresbericht, dc., am Mittel
und Nieder-Rhein, p. 64.)

Mr. Fintelmann, the king of Prussia’s gardener at
Potsdam, is celebrated for his success in the difficult
art of forcing Cherries, and he has given an account
of his practice, (Gard. Mag., vol. iii. p. 64,) in which
it appears that the most peculiar feature is the strict
attention he pays to the temperature of the roots. He
first soaks the roots in water heated by the mixture of
equal parts of boiling and cold water; he afterwards
sprinkles the trees with luke-warm water, and he con-
tinues to employ it of the same temperature as long as
watering is required.

It seems, indeed, clear, that the success of the Dutch
in obtaining an abundance of fresh vegetables, such as
Lettuces, during the whole winter, is in part owing to
their being able to maintain a gentle bottom heat. No
doubt this is connected with the abundant light which
their forcing structures admit, and with other causes of
considerable importance; but none of those canses can
be suppossed likely, in the absence of the bottom heat,
to produce such a result as the Dutch gardeners
obtain.

If it is necessary that the temperature of the soz! in
which plants grow should be carefully regulated, and
adjusted to their natural habits, it is no less requisite
that the water in which aquatics are cultivated should
be also brought to a fitting heat. Mr. William Kent
succeeded well in making many tropical species flower,
by growing them in lead cisterns plunged in a tan-bed,
(Hort, Trans., iii. 34,) in a close heat. In like manner,

110 APPLICATION OE PRINCIPLES.

Mr. Christie Duff procured flowers in abundance from
Nymphea rubra,ceerulea, and odorata, by placing them
in a cistern in a pine stove upon the end flues, where
the fire enters and escapes; or by plunging them into
tan-beds in pine houses, varying in temperature from
80° to 100°. (Hort. Trans., vii. 286.) Very lately,
Mr. Sylvester, of Chorley, in Lancashire, obtained fine
flowers from Nelumbium luteum, by paying attention
to the temperature of water. When he kept the
latter at 85°, the plants grew vigorously, and were in
perfect health, but flowerless; but by lowering it to
70°-75°, which more nearly approaches the heat to
which the plant is naturally accustomed, the magnifi-
cent blossoms were produced and succeeded by seeds ;
the red Nelumbium, however, which inhabits countries
with a greater summer heat than the yellow, at the
same time suffered by this lowering of temperature,
none of its blossom buds having been able to unfold.
(Bot. Mag., xiii. nu. s. t. 8753.) The water of rice
fields, in which the red Nelumbium flourishes, was
seen by Meyen at 113°, at Lantao, in China, (117).
An opinion has, nevertheless, been entertained, that
bottom heat is useless; there is in the Horticultural
Transactions (vol. ili. 288,) a paper to show that it is
injurious; and the authority of Mr. Knight has been
referred to in support of the opinion, in consequence
of that great horticulturist having expressed a belief
that the “bark-bed is worse than useless.” (Hort.
Trans., iv. 73.) But Mr. Knight repeatedly disavowed
entertaining any such sentiments. In one place, he
stated that the temperature of the air of the stoves in

OF BOTTOM HEAT. 111

which his Pine-apple and other stove plants grew,
without bark or other hot-bed, usually varied from 70°
to 85°; and that the mould in his pots, being sur-
rounded by such air, acquired and retained, as it ne-
cessarily must, very near the same aggregate tempera-
ture, but subject to less extensive variation (Gard.
Mag., v. 365) : in another, he says the temperature of
the air was varied in his stove generally from about
70° to 85° of Fahrenheit; and he ascertained, by
keeping a thermometer immersed in the mould of the
pots, that the temperature of the soil varied very con-
siderably less than that of the air of the stove; the
mould being in the morning generally some degrees
warmer than the air of the house, and in the middle
of the day, and early part of the evening, some de-
grees cooler. (Hort. Trans., vii. 255.)

It is, therefore, clear that he considered a high tem-
perature necessary for the roots of his Pine-apple
plants; and we find, from one of his papers, (Hort.
Trans., iv. 544,) that he considered it better to obtain
the requisite temperature from the atmosphere than
from a bark-bed, the usual source of bottom heat, “ be-
cause its temperature is constantly subject to excess
and defect ;” and he even admitted that if the bark-
bed could be made to give a steady temperature of
about 10° below that of the day temperature of the air
in the stove, Pine plants would thrive better in a com-
post of that temperature than in a colder.

It is, therefore, plain that the dispute about bottom
heat was not as to the necessity of it, but as to the man-
ner of obtaining it, which, as it concerns the art of
gardening, I need not further notice.

112 APPLICATION OF PRINCIPLES.

We have, doubtless, much to learn, as to the pro-
per manner of applying bottom heat to plants, and as
to the amount they will bear under particular circum-
stances, It is, in particular probable that in hot-
houses plants will not bear the same quantity of bot-
tom heat as they receive in nature, because we can-
not give them the same amount of light and atmos-
pheric warmth; and it is necessary that we should
ascertain experimentally whether it is not a certain
proportion between the heat of the air and earth that
we must secure, rather than any absolute amount of
bottom heat.

It may also be, indeed it no doubt is, requisite
to apply a very high degree of heat to some kinds
of plants at particular seasons, although a very much
lower amount is suitable afterwards; a remark that
is chiefly applicable to the natives of what are called
extreme climates, that is to say, where a very high
summer temperature is followed by a very low winter
temperature. Such countries are Persia, and many
parts of the United States, where the summers are
excessively hot, and the winter’s cold intense. The
seeming impossibility of imitating such conditions
artificially will probably account for many of the dif-
ficulties we experience in bringing certain fruits, the
Newtown pippin, the cherry, the grape, the peach,
and the almond, to the perfection they acquire in
other countries.

This subject will be frequently recurred to here:
after.

OF THE MOISTURE OF THE SOIL, 113

CHAPTER IL

OF THE MOISTURE OF THE SOIL—WATERING.

Ir has already (38) been shown that water is one
of the most important elements in the food of
plants, partly from their having the power of decom-
posing it, and partly because it is the vehicle through
which the soluble matters found in the earth are con-
veyed into the general system of vegetation. Its
importance depends, however, essentially upon its
quantity.

We know, on the one hand, that plants will not
live in soil which, without being chemically dry, con-
tains so little moisture as to appear dry; and, on the
other hand, an excessive quantity of moisture, is
in many cases, equally prejudicial. The great points
to determine are, the amount which is most conge-
nial to a given species under given circumstances,
and the periods of growth when water should be
applied or withheld.

When a plant is at rest, that is to say, in the winter
of northern countries and the dry season of the
tropics, but a small supply of water is required by
the soil, because at that time the stems lose but little
by perspiration, and consequently the roots demand
but little food; nevertheless, some terrestrial mois-
ture is required by plants with perennial stems, even
in their season of rest, because 84) it is necessary
that their system should, at that time, be replenished

114 APPLICATION OF PRINCIPLES.

with food against the renewal of active vegetation :
hence, when trees are taken out of the earth in
autumn, and allowed to remain exposed to a dry air
all the winter, they either perish, or are greatly enfee-
bled. If, on the other hand, the soil in which they
stand is filled with moisture, their system is dis-
tended with aqueous matter at a time when it cannot
be decomposed or thrown off, and the plant either
becomes naturally susceptible of the influence of cold
in rigorous climates (112), or is driven prematurely
into growth, when its new parts perish from the unfa-
vourable state of the air in which they are developed.
The most suitable condition of the soil, at the period
of vegetable rest, seem to be that in which no more
aqueous matter is contained than the results from the
capillary attraction of the particles.

Nevertheless, there are exceptions to this, in the
case of aquatic and marsh plants, whose peculiar con-
stitution enables them to bear with impunity, during
winter, an immersion in water; and in that of many
kinds of bulbs, which, during their season of rest, are
exposed to excessive heat. The latter plants are,
however, constructed in a peculiar manner; their
roots are annual, and perish at the same time as the
leaves, when the absorbent organs are all lost, so that
the bulb cannot be supposed to require any supply
of moisture, inasmuch as it possesses no means of
taken it up, even if it existed in the soil. This will
be again adverted to in a future chapter.

It is when plants are in a state of growth that
an abundant supply of moisture is required in the

OF THE MOISTURE OF THE SOIL. 115

earth. As soon as young leaves sprout forth, perspi-
ration commences (70), and a powerful absortion
must take place by the roots; the younger the leaves
are, the more rapid their perspiratory action; their
whole epidermis must, at that time, be highly sensi-
ble to the stimulating power of light (66); but as
they grow older their cuticle hardens, the stomates
(61) become the only apertures through which
vapour can fly off, and by degrees even these aper-
tures are either choked up, or have a diminished irri-
tability. As a general rule, therefore, we are autho-
rised to conclude that the ground should be abun-
dantly supplied with moisture when plants first begin
to grow, and that the quantity should be diminished as
the organisation ofa plant becomes completed. There
are, however, some especial cases, which appear
to be exceptional, in consequence of the unnatural
state in which we require plants to be preserved for
our own peculiar purposes. One of the effects of an
excessive supply of moisture is, to keep all the newly
formed parts of a plant tender and succulent, and
therefore such a constant supply is desirable when
the leaves of plants are to be sent to table, as in the
case of Spinach, Lettuces, and other oleraceous
annuals. Another effect is, to render all parts natu-
rally disposed to be succulent, much more so than
they otherwise would be; thus we find market-gar-
gardeners deluging their Strawberry plants with
water while the fruit is swelling, in order to assist in
that, to them, important operation. While, however,
in this case, the size of the fruit is increased by a

116 APPLICATION OF PRINCIPLES.

copious supply of water to the earth, its flavour is, in
proportion, diminished; for, in consequence of the
rapidity with which the strawberry ripens, and, per-
haps, the obstruction of light by its leaves, the excess
of aqueous matter taken into the system cannot be
decomposed, and formed into those products which
give flavour to fruit; but it must necessarily remain
in an unaltered condition.

It is for the reason just given, that the quantity of
water in the soil should be diminished when succu-
lent fruit is ripening; we see this happen in nature,
all over the world, and there can be no doubt of its
being of great importance. Not only is the quality
of such fruit impaired by a wet soil, as has just been
shown, but because of its low perspiratory power, the
fruit will burst from excess of moisture, as occurs to
the plum and grape in wet seasons. The melon,
although an apparent exception to this rule, is not
really so; that fruit acquires its highest excellence in
countries where its roots arealways immersed in water,
as in the floating islands of Cashmere, the irrigated
fields of Persia, and the springy river-beds of India.
But it is to be remembered that the leaves of this
plant have an enormous perspiratory power, arising
partly from their large surface, and partly from the
thinness and consequent permeability of their tissue,
so that they require a greater supply of fluid than
most others, and, in the next place, the heat and
bright light of such countries are capable of decom-
posing and altering the fluids of the fruit with a
degree of rapidity and force to which we can here

OF THE MOISTURE OF THE SOIL. 117

nave no parallel. In this country the melon does not
succeed if the roots are immersed in water, as I ascer-
tained some years ago, in the garden of the Horticul-
tural Society, by repeated experiments. Melons
were planted in earth placed on a tank of water, into
which their roots quickly made their way; they
grew in a curvilinear iron hot-house, and were trained
near to the glass, and consequently were exposed to
all the light and heat that can be obtained in this
country. They grew vigorously and produced their
fruit, but it was not of such good quality as it would
have been had the supply of water to the roots been
less copious. Thus, in the tropics, the quantity of rain
that falls in a short time is enormous; and plants are
forced by it into a rapid and powerful vegetation,
which is acted upon by a light and temperature
bright and high in proportion, the result of which is
the most perfect organization of which the plants are
susceptible: but, if the same quantity of water were
given to the same plants at similar periods in this
country, a disorganisation of their tissue would be
the result, in consequence of the absence of solar
light in sufficient quantity.

The effect of continuing to make plants grow in
a soil more wet than suits them is well known to be
not only a production of leaves and ill-formed shoots,
instead of flowers and fruit, but, if the water is in
great excess, of a general yellowness of appearance,
owing, as some chemists think, to the destruction, by
the water, of a blue matter which, by its mixture
with yellow, forms the ordinary verdure of vegeta-

118 APPLICATION OF PRINCIPLES.

tion. If this condition is prolonged, the vegetable
tissue enters into a state of decomposition, and death
ensues. In some cases the joints of the stem sepa-
rate, in others the plant rots off at the ground, and
all such results are increased in proportion to the
weakness of light, and the lowness of temperature.
De Candolle considers that the collection of stagnant
water about the neck of plants prevents the free
access of the oxygen of the air to the roots; but
it seems to me that much more mischief is produced
by the coldness of the soil in which water is allowed
to accumulate. It seems also probable that the extri-
cation of carburetted hydrogen gas is one cause
of the injury sustained by plants whose roots are sur-
rounded by stagnant water; but upon this point we
want much more satisfactory evidence than we yet
possess.

It is because of the danger of allowing any accu-
mulation of water about the roots of plants that
drainage is so very important. In very bibulous
soils this contrivance is unnecessary; but in all
those which are tenacious, or which, from their low
situation, do not permit superfluous water to filter
away freely, such a precaution is indispensable. No
person has ever seen good fruit produced by trees
growing in lands imperfectly drained; and all expe-
rienced gardeners must be acquainted with cases
where wet unproductive borders have been rendered
fruitful by contrivances which are only valuable
because of their efficiency in regulating the humidity
of the soil. Mr. Hiver (Gard. Mag., v. 60,) speaks of

OF THE MOISTURE OF THE SOIL. 119

the utility of mixing stones in great quantities with
the soil, ‘‘as they prevent the accumulation of water
in very wet weather, and retain sufficient moisture
for the purposes of the plant in dry seasons;” and
when we hear of such precautions as are detailed
in the following good account of preparing a Vine
border, we only learn how important it is to provide
effectually for the removal of superfluous water from
around the roots, and how useless a waste of money
is that which is expended in forming deep rich beds
of earth.

“Tn preparing a Vine border,” says Mr. Griffin, of
Woodhall, a successful grower of grapes, “ one foot
in depth of the’mould from the surface is cleared out
from the whole space; a main drain is then sunk
parallel to the house, at the extremity of the border,
one foot lower than the bottom of the border; into
this, smaller drains are carried diagonally from the
house across the border. The drains are filled with
stone. The cross drains keep the whole bottom
quite dry; but if the subsoil be gravel, chalk, or
stone, they will not be necessary. The drainage
being complete, the whole bottom is covered with
brick, stone, or lime rubbish, about six inches thick,
and on this is laid the compost for the vines.” (Hort.
Trans. iv., 100.)

The practice of placing large quantities of pot-
sherds or broken tiles at the bottom of tubs or pots,
or other vessels in which plants are rooted, is only
another exemplification of the great necessity of
attending to the due humidity of the soil, and to the

120 APPLICATION OF PRINCIPLES.

prevention of stagnant water collecting about the
roots; and the injury committed by worms, upon the
roots of plants in pots, is chiefly produced by these
creatures reducing the earth to a plastic state, and
dragging it among the potsherds so as to stop up the
passage between them, and destroy the drainage.*

One of the means of guarding the earth against an
access on the one hand, and a loss on the other, of too
much water, is by paving the ground with tiles or
stones ; and the advantages of this method have been
much insisted upon. But it is certain that, in cold
summers at least, such a pavement prevents the soil
from acquiring the necessary amount of bottom heat;
and it is probable that, what with this effect, and the
obstruction of a free communication between the at-
mosphere and the roots of a plant, the practice is disad-
vantageous rather than the reverse.t

* [Glazed flower-pots are totally unfit for most plants, except
with the most careful attention to drainage, and even then they are
much inferior to common unglazed ones, The latter permit the
excess of water to escape through their porous sides, which is impos-
sible in the glazed pot; in which, if the aperture at the bottom
become stopped, the earth is sodden with water, the plant suffers
and soon perishes. A. J. D.]

{ Here, again, it is necessary for the American reader to make
allowances for the differences of climate. Covering the soil in
summer, is, in this country, one of the most valuable aids to good
cultivation ever put in practice. The best mode of doing this is,
indeed, not by paving, but by what is technically called mulching.
This consists in spreading over the surface of the ground, so far as
the roots of tree or plant extend beneath it, a layer of tan-bark,
saw-dust, barn-yard litter, straw, salt-hay, sea-weed, or the like, of
sufficient thickness to maintain, as nearly as possible, an uniform

OF WATERING. 121

More commonly recourse is had to the operation of
simple watering, for the purpose of maintaining the
earth at a due state of humidity, and to render plants
more vigorous than they otherwise would be; an in-
dispensable operation in hot-houses, but of less moment
in the open air. Itis, indeed, doubtful whether, in the
latter case, it is not often more productive of disadvan-
tage than of real service to plants. When plants are
watered naturally, the whole air is saturated with hu-
midity at the same time as the soil is penetrated by the
rain; and in this case the aqueous particles mingled
with the earth are very gradually introduced into the
circulating system: for the moisture of the air pre-
vents a rapid perspiration. Notso when plants in the
open air are artificially watered. This operation is
usually. performed in hot dry weather, and must neces-
sarily be very limited in its effects ; it can have little if
any influence upon the atmosphere: then, the parched
air robs the leaves rapidly of their moisture, so long as
the latter is abundant; the roots are suddenly and vio-
lently excited, and after a short time the exciting

state of temperature and moisture for the roots. From an experi-
ence of some years we do not hesitate to say that mulching the sur-
face of the ground over newly-planted trees is not only far better
than any after watering—but that—if the layer is thick enough to
keep the surface cool—it renders watering wholly unnecessary. In
the case of bearing fruit-trees, especially the more delicate kinds, as
dwarf pears, apricots, &c., mulching not only precludes the necessity
of stirring the soil, by preventing weeds from growing, but it con-
duces so much more to the health of the tree, and the size and excel-
lence of the fruit than any other practice in horticulture, that the
more intelligent growers in the United States now consider it
indispensable in this climate. A. J. D.

6

122 APPLICATION OF PRINCIPLES.

cause is suddenly withdrawn by the momentary supply
of water being cut off by evaporation, and by filtration
through the bibulous substances of which soil usually
consists. Then again, the rapid evaporation from the
soil in dry weather has the effect of lowering the tem-
perature of the earth, and this has been before shown
to be injurious (p. 113); such a lowering, from such a
cause, does not take place when plants are refreshed
by showers, because at that time the dampness of the
air prevents evaporation from the soil,just as it prevents
perspiration from the leaves. Moreover, in stiff soils,
the dashing of water upon the surface has after a little
while the effect of ‘‘puddling” the ground and render-
ing it impervious, so that the descent of water to the
roots is impeded, whether it is communicated artifi-
cially, or by the fall of rain.* It is, therefore, doubtful

* [No error is more common in this country than surface-
watering newly transplanted trees; and we do not hesitate to
affirm that full one half the failures, in our dry summers, arise
from this injudicious practice. By pouring water daily on the
top of the ground, under a powerful sun and strong wind, the sur-
face becomes so hard that access of the air to the roots is almost
precluded; and the water rarely penetrates more than a couple
of inches; while the operator imagines he is supplying the thirsty
roots with abundant moisture, he is doing them an injury by the
application of a very transient stimulus, which is followed by an
increased sensibility to the drought. In late spring planting, it is
always preferable to water abundantly in the hole, while planting
the tree, before filling in the upper layer of soil. This will in
most cases suffice, until the tree becomes sufficiently established
by the emission of new rootlets to support itself; and also serves
to ensure its growth by filling up all the small hollows around the
lesser fibres. In seasons of continued drought, when it becomes
absolutely necessary to water flagging trees, two or more inches

OF WATERING. 1238

whether artificial watering of plants in the open air is
advantageous, unless in particular cases; and most as-
suredly, if it is done at all, it ought to be much more
copious than is usual. It is chiefly in the case of an-
nual crops that watering artificially is really impor-
tant; and with them, if any means of occasionally de-
luging ground can be devised, by means of sluices or
otherwise, in the same way that we water meadows, it
may be expected to be advantageous.* Mildew, which
is so often produced by a dry air acting upon a delicate
surface of vegetable tissue, is completely prevented in
annuals by very abundant watering.t The ravages

of the surface soil should always be removed, the trees watered
copiously, and the earth replaced before the surface dries. This
will prevent evaporation and encrusting of the ground, and the
moisture will be retained for a much longer period. A. J. D.]

* “Tn the vicinity of Liegen (a town in Nassau), from three to
five perfect crops of grass are [annually] obtained from one meadow ;
and this is effected by covering the fields with river-water, which
is conducted over the meadow in spring by numerous small canals,
This is found to be of such advantage, that supposing a meadow not
60 treated to yield 1000 lbs, of hay, then from one thus watered
4-5000 lbs. are produced. In respect to the cultivation of meadows,
the country around Liegen is considered to be the best in all Ger-
many.” Liebig, Organ. Chem., p. 105.—G.

+ The mildew which attacks the young fruit of the foreign
grape, when reared in the open air, is one of the most troublesome
to the cultivator in this country. An effectual remedy is the flowers
of sulphur dusted-over the bunches with a dredging-box (or the
solution applied with a syringe), when the grapes are of the size of
small peas. But the most certain prevention of this, as well as most
diseases to which plants are subject, consists in keeping the vines in a
thrifty and vigorous condition. The first crop or two of a young
thrifty vine is almost invariably fine and free from mildew; but
every subsequent year (if the common mode of pruning is followed),

124 APPLICATION OF PRINCIPLES,

of the Botrytis effusa, which attacks Spinach; of
Acrosporium monilioides, which is found on the
Onion ; and the mildew of the Pea, caused by the ra-
vages of Erysiphe communis, may all be stopped, or
prevented, by abundant watering in dry weather. Mr.
Knight first applied this fact to the securing a late
crop of peas for the table, in the following manner :—

The ground is dug in the usual way, and the spaces
which will be occupied by the future rows are well
soaked with water. The mould upon each side is
then collected,so as to form ridges seven or eight inches
above the previous level of the ground, and these are
well watered ; after which,the seeds are sowed in single
rows along the tops of the ridges. The plants very
soon appear above the soil,and grow with much vigour,
owing to the great depth of the soil and abundant
moisture. Water is given rather profusely once in
every week or nine days, even if the weather proves
showery ; but, if the ground be thoroughly drenched
with water by the autumnal rains, no further trouble
is necessary. Under this mode of management, the
plants will remain perfectly green and luxuriant till

as the plant grows older, the proportion of fair fruit is smaller, until
at last nothing but shrivelled and mildewed bunches are seen. By
laying down Lalf of the long shoots of each vine annually, thus form-
ing new plartts, and never allowing the same to bear more than two
years, a full crop, free from rust or mildew, may be obtained an-
nually. Even the finer native sorts, as the Isabella, are sometimes
liable to mildew on old vines: when this occurs, they should be
headed back, to bring up asupply of young wood, and plentifully
manured, The young and thrifty shoots will then have sufficient
vigour to withstand the attacks of mildew, to which the enfeebled
fruit produced from the old wood is so liable. A. J. D.

OF ATMOSPHERICAL MOISTURE. 125

their blossoms and young seed-vessels are destroyed
by frost, and their produce will retain its proper
flavour, which is always taken away by mildew.
(Hort. Trans., ii. 87.)

CHAPTER III

OF ATMOSPHERICAL MOISTURE AND TEM-
PERATURE-*

THE constituent parts of the atmosphere that sur-
rounds us are either the same in different regions, or
the differences, if any, are not appreciable by chemi-
cal processes. It is far otherwise as regards temper-
ature and humidity, which are so intimately con-
nected that they cannot be considered apart from
each other.

From what has been already stated (Book I. Chap.
IV.), it is apparent that of the vital functions of
plants none are more important than those of perspi-
ration and evaporation; and that, while a certain
amount of loss of their fluid particles is necessary, a
great excess or diminution of the loss must be inju-
rious. Although the solar rays appear to be the

* This subject has already been fully treated by Professor Daniell,
in his excellent paper, “On Climate with regard to Horticulture,”
published in the Transactions of the Horticultural Society, vol. vi.
p. 1. It is impossible for any one to discuss the same topic without
profiting largely by this important treatise, which I have very much
followed in the present chapter.

126 APPLICATION OF PRINCIPLES.

immudiate cause of perspiration, which proceeds in
proportion to their intensity (71), yet this action is
’ necessarily modified by the state of the medium, that
is, of the atmesphere which surrounds them: in pro-
portion to its heat and dryness will their power be
augmented, and in yroportion to its cold and mois-
ture diminished. The physiological effect of an
excessive augmentation of perspiration is to dry
up the juices and to destroy the texture of the leaves;
on the other hand excessive obstruction of that func-
tion prevents the decomposition and assimilation
of the fluids, and the formation of new organised
matter, as well as of the secretions peculiar to a
species. A state of the atmosphere, therefore, which
is most favourable to the maintenance of the perspi-
ratory action in the most healthy state, is that which
it must be the business of a gardener to secure by all
the means in his power.

Among the hygrometers intended for measuring
the quantity of elastic vapour in the atmosphere, the
most convenient for use is that invented by Professor
Daniell. In this instrument, the amount of moisture
in a given atmosphere is indicated by what is called
the dew-point; that is to say, by the point of the
thermometric scale at which the cold is sufficient
to cause a deposition of dew; the amount being cal-
culated by the difference between the natural tempe-
rature and an artificial temperature created for the
purpose of determining the point at which the elastic
vapour of the air is precipitated by cold. ‘The
natural scale of the hygrometer,” says Mr. Daniell,

OF ATMOSPHERICAL MOISTURE. 127

“is included between the points of perfect dryness
and perfect moisture; the latter, of course, being that
state of the atmosphere at which the dew-point coin-
cides with the temperature of the air. The inter-
mediate degrees may be ascertained by dividing the
elasticity of vapour at the temperature of the dew-
point, by the elasticity of the temperature of the air:
the quotient will express the proportion of moisture
actually existing, to the quantity which would be
required for saturation; for, calling the term of satu-
ration 1-000, as the elasticity of vapour at the tempe-
rature of the air is to the elasticity of vapour at the
temperature of the dew-point, so is the term of satu-
ration to the actual degree of moisture.”

By means of this and similar contrivances,* we are
at all times able to ascertain exactly the quantity of
water that exists in an elastic state in the air.

In this country, the changes of moisture are said to
extend from 1:000, or saturation, to -889, or even
so low as ‘120, under a south wall, for a short space
of time; “a state of dryness which is certainly not
surpassed by an African harmattan,” but one which
produces less disastrous consequences, because it is
accompanied by a far lower temperature and a weaker
solar radiation. The mean degree of moisture of the
air near London has been found by Mr. Thompson to
be ‘897, on an average of ten years, while the mean

* Other hygrometers have been invented to answer the same
end; but, as Mr. Daniell’s is that most eligible in this country, I
have thought it more convenient to confine my observations
to it.

128 APPLICATION OF PRINCIPLES.

temperature is 50°62: * in other parts of the world
it is very different; and the amount of those differ:
ences, together with the means of imitating them arti-
ficially, constitutes one of the most delicate and diffi-
cult parts of the gardener’s art. All that relates
to this subject, however, to be treated usefully, must
be considered in a very special way, and in such
detail as can only be expected in a separate work
upon the subject. An idea of the difference between
the atmospherical moisture of London and that of
other parts of the world may, however, be collected
from the following table showing the amount of rain
that falls in a few different countries:

Inches per Annum.

London. . .. . 1. 24°01 Average of 10 years,
St. Petersburgh . . . . 16°

Algiers... : 27°

Fattehpur (East Tai) ‘ 85°94 Average of 4 years.
Madeira. . . src 31°

Sagar (East Indies) . . from 81:15 to 64°76

Bahamas . . Hos 54°99°

Calcutta . . . . . . from 59°83 to 81°
Ceylon... . 2... 84-3

Macao... . . . . from 488 to 1073

Equator. . . .... 96°

Coast of Malabar. . . . 123-50 Average of 14 years,
Grenada. . ae 126°

Leogane, St. Domingo : 150°

Bengal, 20 to 22 inches i in a single month.

Bombay, 32 inches in 12 days.

Tavoy, 203°5 inches in six months; as much as
85 in a day (July 31, 1831).+

* See the various meteorological journals published by the Horti
cultural Society, in their Transactions, from the year 1826 inclusive,
+ [The average fall of rain (and snow) in the State of New York,

OF ATMOSPHERICAL MOISTURE. 129

We possess, to a certain extent, the power of modi-
fying the moisture of the air even in the open air,
and have almost complete control over that of glazed
houses.

It is found by experience that the effect of wind is
to increase the dryness of the air, and, consequently,
the perspiration of vegetable surfaces. ‘ Evapora-
tion,” says Mr. Daniell, ‘ increases in a prodigiously
rapid ratio with the velocity of the wind; and any-
thing which retards the motion of the latter is very
efficacious in diminishing the amount of the former.
The same surface which, in a calm state of the air,
would exhale 100 parts of moisture, would yield 125
in a moderate breeze, and 150 in a high wind.”
Hence the great importance, in gardens, of walls, and
screens, which break the wind, and keep the air in
repose in their vicinity. The difference between the
effect of a given amount of cold upon the blossoms
of exposed fruit trees, and those of the same species
trained upon walls, is well known; and appears to be
owing to this circumstance, much more than to any
difference of temperature in the two situations.*
for 14 years (1826-1839 inclusive,) as deduced from observations
made under the direction of the Regents of the University, and col-
lected in their Report presented March, 1840, is 84°40 inches. The
highest average (from 54 stations) for any single year is 44°40 (A. D.
1827); the lowest (for 1839) 82°10 inches. ]

* This has been illustrated by Mr. Howard, in the results of
some interesting experiments made by him on the annual amount of
evaporation. During three years, in which the evaporating gauge
was placed forty-three feet from the ground, the annual average
result was 37°85 inches; during other three years, when the instru-
ment was lower and less exposed, the average was 33°37 inches; and

6*

130 APPLICATION OF PRINCIPLES.

It is to be remarked that the easterly winds are, in
this country, both the coldest and the driest. Mr.
Daniell tells us that the “ moisture of the air flowing
from any point between N, E. and 8. £. inclusive, is,
to that of the air from the other quarters of the com-
pass, in the proportion of 814 to ‘907, upon an ave-
rage of the whole year;” and Mr. Thompson has
found the hygrometer to indicate not uncommonly
from 20° to 30° of dryness, during the long pre-
valence of the north-easterly winds in spring. At
the same time, the air is very cold, the effect of which
is to cause the sap-vessels of the stem to contract, and
refuse to convey their fluid; so that the blossoms of
fruit trees in a north-east wind, while they are robbed
of their fluid contents by evaporation, can get no as-
sistance from the roots through the stem, and neces-
sarily perish. I find, however, from Mr. Thompson’s
observations, that the greatest dryness we experience
in this climate is, not when the wind is in the east,
but when it isin the south. For example: in nine
years, between 1826 and 1834, the four driest days
were, in the year 1834, in June, when it was 88° on
the Ist, 35° on the 2d, and 31° on the 21st; on the
1st of June, 1833, it was 30°, and always with a south
wind; and, during the whole of those nine years,
there was but one other day on which the dryness
was found as high as 80°, namely on the 10th of April,
1834, with a north-east wind. The duration of dry-

when the gauge was upon or near the ground the annual average
was only 20-28 inches, or little more than half the amount evapo
rated in a free and elevated exposure,

OF ATMOSPHERICAL MOISTURE. 181

ness, with a south wind, was, however, very short,
not exceeding one or at most two days, and was in-
variably accompanied with great heat and followed
by heavy rain; while the north-easters last for weeks,
without rain and with a comparatively low tempera-
ture. The following statement by Mr. Thompson
puts this in a clear light. There occurred between
1826 and 1834 inclusive,—

Wind North . . ‘1 days, above 20° of dryness,
N. East. 89 do. do.
East. un} 48 do. do.
S. East 27 do. do.
South . 85 do. do.
S. West . 80 do. do.
West ‘ 85 do. do.
N. West . 22 do. do.

These facts sufficiently explain the fatal effects of
certain winds upon vegetation, the small comparative
value “in this country of walls with north and east
aspects, and the general want of success that attends
late spring planting. Here, also, we in part discover
an explanation of the utility of shades interposed be-
tween the sun and plants newly committed to the
earth; they not only cut off the solar rays, but also
intercept currents of air, and thus diminish the
amount of perspiration by two opposite methods.

The following table, for which I am again indebted
to Mr. Thompson, will be found to show that the
average degree of dryness, in the middle of the day,
throughout the year, is, with a

1382 APPLICATION OF PRINCIPLES,

Degrees Amount
of Dryness. of Moisture,
North wind : é : 655° . 816
North-east 7 : : 7°30 . $ "94
East 7 . . 6:20 . : 825
Average, with wind from the ' 6°68 : : 811
three coldest points
South wind . : ; 4:23 . ‘ 877
South-west . : . 4°10 ‘ 859
West . P , ‘ 6:20 . . 733

Average, with wind from the

6:04 % ‘ 823
three warmest points }

Wind, for the Year 1831; calculated by Mr. Robert Thompson, from the Meteorological

A TABLE showing the Temperature, Dryness, and Moisture of the Air, with relation to the
Observations made in the Garden of the Horticultural Society of London.

OF ATMOSPHERICAL MOISTURE, 183

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134

TABLE.—(conrinvzp.)

APPLICATION OF PRINCIPLES,

North West.

Hygrom.

“HOON 12 AINISIOW
Jo dalgeq uBsoyy

‘UOON 10 ssautsiq.
Jo volseq usa

0-0 |1000

56 | 988
0-0 |1000
6-0! 749

Thermometer.

“BIpoW

“BUITUTT UBO}T

“CUIXB Way

50°3 | 28-0 | 39-1

47:0 | 42°5 | 44-7

54'5 | 38-0 | 46-2

West.

Hygrom,

‘COON 18 GIN BIO;
Jo aoigeq usayy

“WOON 18 ssousIG
JO sa1g0q Uva

6-2 | 788

Thermometer.

TIpOW

“RUITOLTY Uva}T

“BUNIXB]Y UBOT

1
8
5.
7

South West.

Hygrom.

“NOON 78 oInjIsIopy
jo valgeq uve

‘WOON 12 ssaudiqg
jo ea13aq wayyy

471 859 | 59-4 | 43-2| 51:3

Thermometer.

“SIPS

“BUNTY Teo

LSHPSSENS

RBS S8aResa5

“BUNTXBY Uva}

60-4 | 44-2 | 52:2

South.

Hygrom.

“UOON 7B OANISIOPL
jo oaidog uBeyy

“WOON 10 ssauAIg
jo aalgeq uveyy

4.2! 877

Thermometer.

“BPO

wUIUIY UTA TL

“BUIIXB Uva}

1831

September
October

November -

December -

' 59-1 | 43°7 | 514

Means

OF ATMOSPHERICAL TEMPERATURS. 135

As to temperature in the open air, unconnected
with atmospherical humidity, there seems to be no
means of regulating or modifying it to any consider-
able extent. In some respects, however, we have
even this powerful agent under our control; but, in
order to exercise such control, it is necessary to un
derstand correctly the theory of what is called radia-
tion, which cannot be better explained than in the
words of Mr. Daniell. ‘The power of emitting heat
in straight lines in every direction, independently of —
contact, may be regarded as a property common to
all matter; but differing in degree in different kinds
of matter. Coexisting with it, in the same degrees,
may be regarded the power of absorbing heat so
emitted from other bodies. Polished metals and the
fibres of vegetables may be considered as placed at
the two extremities of the scale upon which these pro-
perties in different substances may be measured. If
a body be so situated that it may receive just as
much radiant heat as itself projects, its temperature
remains the same; if the surrounding bodies emit
heat of greater intensity than the same body, its tem-
perature rises, till the quantity which it receives ex-
actly balances its expenditure, at which point it again
becomes stationary ; and if the power of radiation be
exerted under circumstances which prevent a return,
the temperature of the body declines. Thus, if a
thermometer be placed in the focus of a concave me-
tallic mirror, and turned towards any portion of the
sky, at any period of the day, it will fall many de-
grees below the temperature of another thermometer

136 APPLICATION OF PRINCIPLES.

placed near it, out of the mirror; the power of radia-
tion is exerted in both thermometers, but to the first
all return of radiant heat is cut off, while the other
receives as much from the surrounding bodies, as it-
self projects. This interchange amongst bodies takes
place in transparent media as well as in vacuo; but
in the former case, the effect is modified by the
equalising power of the medium.

“Any portion of the surface of the globe which is
fully turned towards the sun receives ‘more radiant
heat than it projects, and becomes heated; but when,
by the revolution of the axis, this portion is turned
from the source of heat, the radiation into space still
continues, and, being uncompensated, the temperature
declines. In consequence of the different degrees in
which different bodies possess this power of radiation,
two contiguous portions of the system of the earth
will become of different temperatures; and if on a
clear night we place a thermometer upon a grass-plat,
and another upon a gravel walk or the bare soil, we
shall find the temperature of the former many degrees
below that of the latter. The fibrous texture of the
grass is favourable to the emission of the heat, but
the dense surface of the gravel seems to retain and
fix it. But this unequal effect will only be perceived
when the atmosphere is unclouded, and a free passage
is open into space; for even a light mist will arrest
the radiant matter in its course, and return as much
to the radiating body as it emits. The intervention
of more substantial obstacles will of course equally
prevent the result, and the balance of temperature

OF ATMOSPHERICAL TEMPERATURE. 137

will not be disturbed in any substance which is not
placed in the clear aspect of the sky. A portion of
a grass-plat under the protection of a tree or hedge,
will generally be found, on a clear night, to be eight
or ten degrees warmer than surrounding unsheltered
paris; and it is well known to gardeners, that less
dew and frost are to be found in such situations, than
in those which are wholly exposed.” (Hort. Trans.,
vi. 8.)

These laws plainly direct us to the means we are
to employ to moderate . atmospherical temperature.
A screen, of whatever kind, interposed between the
sun and a plant, intercepts the radiant heat of the
sun, and returns it into space; and thus, in addition
to the diminution of perspiration by the removal ofa
part-of the stimulus that causes it, actually tends to
lower the temperature that surrounds the plant. In
like manner, the interposition of a screen, however
slight, between a plant and the sky, intercepts the
radiant heat of the earth; and, instead of allowing it
to pass off into space, returns it to the ground, the
temperature of which is maintained at a higher point
than it otherwise would be. Hence it is that plants
growing below the deep projecting eaves of houses, or
guarded by a mere coping of thatched hurdles, suffer
less in winter than if they were fully exposed to the
sky.

It is also obvious from what has been stated, that
plants growing upon grass will be exposed to a greater
degree of cold in winter than such as grow upon
gravel: but it does not therefore follow that hard

138 APPLICATION OF PRINCIPLES,

gravel is, with respect to vegetation, a better coating
for the surface of the ground than turf; it has its dis-
advantages as well as its advantages, and the former
probably outweigh the latter. In superior heating
power is its only advantage ; the objections to it are,
its dryness in summer, and its comparative imper-
meability to rain, so that it causes the force of per-
spiration to be inversely as the absorbing power of
the roots.

It is well known that blackened surfaces absorb
heat much more than those of any other colour; and
it has been expected that the effect of blackening gar-
den walls, on which fruit trees are trained, would be
to accelerate the maturation of the fruit; but notwith-
standing a few cases of apparent advantage, one of
which, of the Vine, is mentioned in the Horticultural
Transactions, vol. iii. p. 380, this has been, in general,
found either not to happen at all, or to so smal] an
extent as not to be worth the trouble. It is true, that
so long as the wall is so little covered by the
branches and leaves of a plant, the absorbent power
of the blackened surface is brought into play; but
this effect is lost as soon as the well becomes covered
with foliage. In the early spring, however, before
the leaves appear, the flowers are brought rather more
forward than would otherwise be the case; and in the
autumn the wood certainly becomes more completely
ripened, a result of infinite consequence in the north-
ern parts of the country.

It is rather to a judicious choice of soil and situa:
tion that the gardener must look for the means of

OF ATMOSPHERICAL TEMPERATURE. 189

softening the rigour of climate. Wet tenacious soils
are found the most difficult to heat or to drain, and
they will, therefore, be the most unfavourable to the
operations of the gardener; extremely light sandy
soils, on the other hand, part with their moisture so
rapidly, and absorb so much heat, that they are
equally unfavourable; and it is the light loamy soils,
which are intermediate between the two extremes,
that, as is well known, form the best soil for a gar-
den. Situation is, however, of much more conse-
quence than soil, for the latter may be changed or
improved, but a bad (that is, cold) situation is incur-
able. Cold air is heavier than warm air, and, conse-
quently, the stratum of the atmosphere next the soil
will be in general colder than those above it. When,
therefore, a garden is placed upon the level ground of
the bottom ofa valley, whatever cold air is formed upon
its surface remains there, and surrounds the herbage;
and, moreover, the cold air that is formed upon the
sides of low hills rolls down into the valley as quick-
ly as it is formed. Hence the fact which to many
seems surprising, that what are called sheltered places
are, in spring and autumn, the coldest. We all know
that the Dahlias, Potatoes, and Kidneybeans of the
sheltered gardens in the valley of the Thames, are
killed in the autumn by frosts whose effects are un-
felt on the low hills of Surrey and Middlesex.* Mr.

* [A contrary effect is experienced in the valleys of our large
rivers and lakes in the United States. On the banks of the Hudson
a margin of land from half a milc to a mile in width on each side ig
very effectually protected from the late spring and early autumnal

140 APPLICATION OF PRINCIPLES.

Daniell says he has seen a difference of 30°, on the
same night between two thermometers, placed, the
one in a valley, and the other on a gentle eminence,
in favour of the latter. Hence, he justly observes,
the advantages of placing a garden upon a gentle
slope must be apparent; ‘‘a running stream at its foot
would secure the further benefit of a contiguous sur-
face not liable to refrigeration, and would prevent any
injurious stagnation of the air.”

In addition to this, it has been said that, to obtain
the most favourable conditions of climate in this
country, a garden should have a south-eastern expo-
sure. This, however, has been recommended, I
think, without full consideration. It is true that in
such an exposure the early sunbeams will be re-
ceived; but, on the other hand, vegetation there
would be exposed to several unfavourable actions.
There would be little protection from easterly
winds, which, whether south-east or north-east, are
the coldest and driest that blow; in the next place
an exposure to the first sun of the morning, is very
prejudicial to garden productions that have been
frozen by the radiation of the night; it produces

frosts; while beyond that limit vegetation is blackened by them.
In autumn the warm vapour which rises on a cold night from so
large a surface probably protects the adjacent shores: and even
when moderate frosts actually occur, the morning fog, which lasts
an hour or two, by softening the sun’s rays and causing a gradual
thaw, often prevents any injurious result to vegetation. Some of
our large inland lakes, the surfaces of which are never frozen, have
a decided effect upon the local climate, rendering it much more mild
than it otherwise would be—A. J. D.]

OF ATMOSPHERICAL TEMPERATURE, 141

a sudden thaw, which, as gardeners well know,*
causes the death of plants which, if slowly thawed,
would sustain no inconvenience from the low temper-
ature to which they had been exposed.t It is proba-
ble, as I have elsewhere endeavoured to show, that
this singular effect may be accounted for as follows :—
“Jn such cases, it may be supposed that the air,
forced into parts not intended to contain it, is
expanded violently, and thus increases the disturb-

* See Hort. Trans., iii, 43.

+ [In the northern and eastern sections of the Union many beau-
tiful shrubs and plants, which are the ornaments of our gardens in
summer, but perish if exposed to the rigorous cold of winter, are
easily preserved upon this principle. The first impulse of the
novice in gardening is to place such half-hardy plants (as the more
delicate China Roses, Carnations, dc.) in some warm sheltered spot,
open to the genial rays of the sun in winter: a practice invariably
followed by their destruction. Our sun, even in mid-winter, often
shines with great brightness, and the thawing and distension of the
tissue of tender plants which therefore follows causes certain death,
If, on the contrary, the same species are placed in « cool shaded
aspect, or, what is preferable, if they are shielded from the sun by
a loose covering of straw, mats, or even boards, and thus kept from
thawing except in the most gradual manner, they will be found to
have sustained no injury whatever. We have seen a large num-
ber of the choicest Camellias preserved without any artificial heat
through a cold winter, when the mereury ranged below zero for seve-
ral weeks, simply by covering them with a common glazed frame,
well clothed with mats to, exclude the direct rays of the sun, or pre-
vent sudden variations of temperature. For the same reason, or-
chards of Peach trees in the middle States, on the cold north sides
of hills, are often more vigorous and of greater longevity than those
in a full southern aspect: the heat of our summers being sufficient to
ripen their fruit and wood in such situations, while they are thus
secured from the evils of great and sudden changes of temperature
in winter. A. J. DJ

142 APPLICATION OF PRINCIPLES.

ance already produced by its expulsion from the
proper air cavities; while, on the other hand, when
the thaw is gradual, the air may retreat by degrees
from its new situation without producing additional
derangement of the tissue. It is also possible that
leaves from which their natural air has been expelled
by the act of freezing, may, from that circumstance,
have their tissue too little protected from the evapo-
rating force of the solar rays, which, we know, pro-
duce a specific stimulus of a powerful kind upon those
organs.” (Hort. Trans., n. s., ii. 805.)

In our glazed houses, we have full control over the
state of the atmosphere, as regards both its moisture
and temperature, by means familiar to every gar-
dener; but the manner of applying those means, and
the causes that oppose their action, deserve to be the
subject of inquiry.

It will have been seen, from what has been already
stated upon that subject, that in general, in warm
countries, the air is occasionally at least, if not per-
manently, filled with vapour to a much greater extent
than in northern latitudes,* and, as in our glazed
houses we cultivate exclusively the natives of warm
countries, it is also obvious that, as a general rule, the
air of such houses requires, at certain periods, to be
damper than that of the external air. Those periods

* “Captain Sabine, in his meteorological researches between the
tropics, rarely found at the hottest period of the day so great a dif-
ference as 10° between the temperature of the air and the dew-
point: making the degree of saturation about -730, but most fre-
quently 5° or ‘850; and the mean saturation of the air could not
have exceeded ‘910.” (Daniell.)

OF. ATMOSPHERICAL TEMPERATURE. 143

are when vegetation is most active. Onthe other hand
countries nearer the equator are subject to seasons
of dryness, the continuance of which is often much
greater than anything we know of here in the open
air, and consequently artificial means must also be
adopted to bring about, in glazed houses, that state
of things at particular periods; namely, those of the
repose of plants. These facts afford abundant proof
of the necessity of regulating the moisture of the
atmosphere with due precision.

By throwing water upon the pavement of glass
houses, by means of open tanks of water, by reser.
voirs placed upon them, by syringing, and by other
contrivances,* the quantity of water in the air may
be easily increased, even up to the state of saturation.
But there are some circumstances, easily overlooked,
which interfere very seriously with this power, and
which, it may be conceived, may reduce it very much
below the expectations of the cultivator.

The most unsuspected of these is the destruction
of aqueous vapour, by the hot, dry, absorbent surface
of flues. The advantages derived from hot-water
pipes, or steam pipes, over brick flues, are so well
known, as not to require any evidence to prove the
fact. Gardeners explain the difference in the action
of the two, by saying that the dry heat produced by
hot-water pipes is sweeter than that given off by flues;
which is not a very intelligible expression. The fact

* A discharge of steam into a glazed house has occasionally been

employed; but the method requires much attention on the part of
\he operator, and seems inferior to other contrivances.

144 APPLICATION OF PRINCIPLES.

is, that the air of houses heated by flues is, under
equal circumstances, much drier than that where hot-
water pipes are employed ; because the soft-burnt clay
of the brick flues robs the air of its moisture, while
the unabsorbent surface of iron pipes abstracts
nothing.

Another source of dryness is the coldness of the
glass roof, especially in cold weather, when its tem-
perature is lowered by the external air, in conse-
quence of which the moisture of the artificial atmo-
sphere is precipitated upon the inside of the glass,
whence it runs down in the form of “drip.” Mr.
Daniell observes that the glass .of a hot-house, at
night, cannot exceed the mean of the external and
internal air; and, taking them at 80° and 40°, 20
degrees of dryness are kept up in the interior, or a
degree of saturation not exceeding °528. To this, in
a clear night, we may add at least 6° for the effects
of radiation, to which the glass is particularly
exposed, which will reduce the saturation to -424;
and this is a degree of drought which must be
very prejudicial. It will be allowed that this is not
an extreme case, and much more favourable than
must frequently occur during the winter season.
Some idea, he adds, may be formed of the prodi-
giously increased drain upon the functions of a plant,
arising from .an increase of dryness in the air, from
the following consideration:—If we suppose the
amount of its perspiration, in a given time, to be 57
grains, the temperature of the air being 75° and the
dew-point 70°, or the saturation of the air being ‘849,

OF ATMOSPHERICAL TEMPERATURE. 145

the amount would be increased to 120 grains in the
same time, if the dew-point were to remain station-
ary, and the temperature were to rise to 80°; or, in
other words, if the saturation of the air were to fall
to ‘726. (Hort. Trans. vi. 20.) It is well known that
the effect of maintaining a very high temperature in
hot-houses at night, during winter, is frequently
to cause the leaves to wither and turn brown, as if
scorched or burnt; and this is apparently owing to
the dryness of the air, in consequence of the above
causes.

It is evident that the mode of preventing this dry-
ing of the air by the cold surface of a glass roof will
be, either by raising the temperature of the glass,
which can only be effected by drawing a covering of
some kind over our houses at night, so as to intercept
radiation, or by double glass sashes; or else by
keeping the temperature of the air of the house as
low as possible, consistently with the safety of the
plants, and so diminishing the difference between the
temperature of the external and internal air.

A bad system of ventilation is another cause of the
loss of vapour in the atmosphere of glazed houses,
to which reference will be made in the succeeding
chapter.

It is, in all appearance, to the attention that, since
the appearance of Mr. Daniell’s paper, in 1824, upon
this subject, has been paid to the atmospherical mois-
ture of glazed houses, that the great superiority of
modern gardeners over those of the last generation is
mainly to be ascribed ; there are, however, traces of

7

146 APPLICATION OF PRINCIPLES.

the practice at a much earlier period, although, from
not understanding the theory of the practice, no
general improvement took place. In the year 1816,
an account was laid before the Horticultural Society
of a very successful mode of forcing grapes and nec-
tarines, as practised by Mr. French, an Essex farmer,
with very rude materials, and under unfavourable
circumstances. It is not a little remarkable, that,
although Mr. French himself correctly referred his
success to the skilful management of the atmospheri-
cal moisture of his forcing-houses, the subject was so
little understood at that time, that the author of the
account not only shrank from adopting the opinion,
but evidently, from the manner in which he speaks
of Mr. French’s explanation, had no idea of its just-
ness. The method itself is sufficiently remarkable to
deserve being extracted.

“ About the beginning of March, Mr. French com-
mences his forcing, by introducing a quantity of new
long dung, taken from under the cow-cribs in his
straw yard; being principally, if not entirely, cow
dung, which is laid upon the floor of his house,
extending entirely from end to end, and in width
about six or seven feet, leaving only a pathway
between it and the back wall of the house. The dung
being all new at the beginning, a profuse steam arises
with the first heat, which, in this stage of the process,
is found to be beneficial in destroying the ova of
insects, as well as transfusing a wholesome moisture
over the yet leafless branches; but which would
prove injurious, if permitted to rise in so great a

OF ATMOSPHERICAL TEMPERATURE. 147

quantity when the leaves have pushed forth. Ina
few days, the violence of the steam abates as the buds
open, and in the course of a fortnight the heat begins
to diminish ; it then becomes necessary to carry in a
small addition of fresh dung, laying it in the bottom,
and covering it over with the old dung fresh forked
up: this produces a renovated heat, and a moderate
exhalation of moist vapour. In this manner the
heat is kept up throughout the season, the fresh sup-
ply of dung being constantly laid at the bottom in
order to smother the steam, or rather to moderate the
quantity of exhalation ; for it must always be remem-
bered, that Mr. French attaches great virtue to the
supply of a reasonable portion of the vapour. The
quantity of new dung to be introduced at each turn-
ing must be regulated by the greater or smaller
degree of heat that is found in the house, as the sea-
son or other circumstances appear to require it. The
temperature kept up is pretty regular, being from 65
to 70 degrees.” (Hort. Trans., i. 245.)

In this case, which attracted much attention at the
time, it is evident that the success of the practice
arose principally out of two circumstances; firstly,
the moisture of the atmosphere was skilfully main-
tained in due proportion to the temperature; and,
secondly, a suitable amount of bottom heat was
secured. Thisis, as will be elsewhere remarked, the
principal cause of the advantages found to attend the
Dutch mode of forcing. The reporter upon Mr.
French’s practice speaks with surprise of the rudeness
of the roof of his forcing-houses, and of the nume-

148 APPLICATION OF PRINCIPLES.

rous openings into the air through the laps of the
glass and the joints of the sashes; but these were
points of no importance under the mode of manage-
ment adopted.

The impossibility of preserving any plants except
succulents, in a healthy state, for any long period, in
a sitting-room, is evidently owing to the impracticabi-
lity of maintaining the atmosphere of such a situation
in a state of sufficient dampness.*

An excess of dampness is indispensable to plants,
in a state of rapid growth, partly because it prevents
the action of perspiration becoming too violent, and
partly because under such circumstances a considera-
ble quantity of aqueous food is absorbed from the
atmosphere, in addition to that obtained by the
roots.

But it is essential to observe that, when not in
a state of rapid growth, a large amount of moisture in
the air will be prejudicial rather than advantageous to

* And the success of those who do, in spite of the adverse cireum-
stances, succeed in raising fine plants in sitting-rooms, will usually
be found to be owing to their taking great pains to keep the leaves
in a healthy condition by frequently syringing or washing them
with a sponge. One of the most successful parlor-plant amateurs
we ever knew, gave her plants “a bath,” as she called it, twice a
week. Removing them into a large closet and laying them on their
sides in a flat tub, she cleaned every pore of the upper and under
sides of the leaves by a very severe syringing with warm water.
The plants gained health, not only by the cleansing and the absorp-
tion of moisture, but by the motion of the stems and branches caused
by dashing water on them from the syringe, which in a good degree
compensated for the absence of wind-motion, s0 beneficial to the
growth of all trees and plants in the open air. A. J. D.

OF ATMOSPHERICAL TEMPERATURE. 149

a plant; if the temperature is at the same time high,
excitability will remain in a state of continued action,
and that rest which is necessary (113) will be with-
held, the result of which will be an eventual destruc-
tion of the vital energies. But, on the other hand, if
the temperature is kept low while the amount of
atmospherical moisture is considerable, the latter is
absorbed, without its being possible for the plant to
decompose it; the system then becomes, in the
younger and more absorbent parts, distended with
water, and decomposition takes place, followed by
the appearance of a crop of microscopical fungi; in
short, that appearance presents itself which is techni-
cally called * damping off.”

The skilful balancing of the temperature and mois-
ture of the air, in cultivating different kinds of plants,
and the just adaptation of them to the various seasons
of growth, constitute the most complicated and diffi-
cult part of a gardener’s art. There is some danger
in laying down any general rules with respect to this
subject, so much depends upon the peculiar habits of
species, of which the modifications are endless. It
may, however, I think, be safely stated, that the fol-
lowing rules deserve especial attention :—

1. Most moisture in the air is demanded by plants
when they first begin to grow, and least when their
periodical growth is completed.

2. The quantity of atmospheric moisture required
by plants is, ceteris paribus, in inverse proportion to
the distance from the equator of the countries which
they naturally inhabit.

150 APPLICATION OF PRINCIPLES.

3. Plants with annual stems require more than
those with ligneous stems.

4, The amount of moisture in the air most suitable
to plants at rest is in inverse proportion to the quan-
tity of aqueous matter they at that time contain.
(Hence the dryness of the air required by succulent
plants when at rest.)

CHAPTER IV.
OF VENTILATION,

By far the larger number of gardeners attach great
importance to preserving the power of ventilating
their houses abundantly, without perhaps sufficiently
considering the nature of the plants they have to ma-
nage; and, as has been justly enough said, by sup-
posing that plants require to be treated like man
himself, they consult their own feelings rather than
the principles of vegetable growth. There can be no
doubt, however, that the effect of excessive ventila-
tion is more frequently injurious than advantageous ;
and that many houses, particularly hot-houses, would
be more skilfully managed, if the power of ventilation
possessed by the gardener were much diminished.

Animals require a continual renovation of the air
that surrounds them, because they speedily render it
impure by the carbonic acid given off, and the oxygen

OF VENTILATION. 151

abstracted by animal respiration. But the reverse is
what happens to plants; they exhale oxygen during
the day, and inhale the carbonic acid of the atmo-
sphere, thus depriving the latter of that which would
render it unfit for the sustenance of the higher orders
of the animal kingdom; and, considering the manner
in which glass houses of all kinds are constructed,
the buoyancy of the air in all heated houses, would
enable it to escape in sufficient quantity to renew it-
self as quickly as can be necessary for the main-
tenance of the healthy action of the organs of vege-
table respiration: It, therefore, is improbable that
the ventilation of houses in which plants grow is
necessary to them, so far as respiration is concerned.
Indeed, Mr. Ward has proved that many plants will
grow better in confined air, than in that which is often
changed. By placing various kinds of plants in cases,
made, not indeed air-tight, for that is impossible with
such means as can be applied to the construction of a
glass house, but so as to exclude as much as possible
the. admission of the external air, supplying them
with a due quantity of water, and exposing them
fully to light, he has shown the possibility of culti-
vating. them without ventilation, with much more
success than usually attends ordinary glass-house
management.

In forcing-houses, in particular, it will be evident
from what is about to follow, that ventilation, under
ordinary circumstances, in the early spring, must be
productive of injury rather than benefit. Many gar-
deners now admit air very sparingly to their vineries

152 APPLICATION OF PRINCIPLES.

during the time that the leaves are tender, and the
fruit unformed. Some excellent stoves have no pro-
vision at all for ventilation; and we have the direct
testimony of Mr. Knight as to the disadvantage of the
practice in many cases to which it has been commonly
applied.

It may be objected, says this great horticulturist,
that plants do not thrive, and that the skins of grapes
are thick, and other fruits without flavour, in crowd-
ed forcing-houses: but in these it is probably light,
rather than a more rapid change of air, that is want-
ing; for, ina forcing-house which I have long de-
voted almost exclusively to experiments, I employ
very little fire heat, and never give air till my grapes
are nearly ripe, in the hottest and brightest weather,
further than is just necessary to prevent the leaves
being destroyed by excess of heat. Yet this mode of
treatment does not at all lessen the flavour of the
fruit, nor render the skins of the grapes thick; on
the contrary, their skins are always most remarkably
thin, and very similar to those of grapes which have
ripened in the open air. (Hort. Trans., ii. 225.)

While, however, the natural atmosphere cannot be
supposed to require changing in order to adapt it to
the respiration of plants, it is to be borne in mind that
the air of houses artificially heated may be rendered
impure by the means employed to produce heat.
Sulphurous acid gas escapes from brick flues, am-
moniacal vapour from fermenting manure, and there
may be many unsuspected sources of the introduction
of vaporous impurities; an inconceivably minute

OF VENTILATION. 158

quantity of which is enough to deteriorate the air, so
far as vegetation is concerned. Drs. Turner and
Christison found that 75455 of sulphurous acid gas
destroyed leaves in forty-eight hours; and similar
effects were obtained from hydro-chloric or muriatic
acid gas, chlorine, ammonia, and other agents, the
presence of which was perfectly undiscoverable by
the smell. We also know that the destructive pro-
perties of air poisoned by corrosive sublimate, per-
haps by its being dissolved in the vapour of a hot-
house, are not at all appreciable by the senses.

Ventilation is necessary, then, not to enable plants
to exercise their respiratory functions, provided the
atmosphere is unmixed with accidental impurities ;
but to carry off noxious vapours generated in the arti-
ficial atmosphere of a glazed house, and to produce
dryness, or cold, or both.

When the external air is admitted into a glazed
house containing a moist atmosphere, it, under ordi-
nary circumstances, is much colder than that with
which it mixes; the heated damp air rushes out at
the upper ventilators, and the drier cold air takes its
place; the latter rapidly abstracts from the plants
and the earth, or the vessels in which they grow, a
part of their moisture, and thus gives a sudden shock
to their constitution, which cannot fail to be injurious.
This abstraction of moisture is in proportion to the
rapidity of the motion of the air. But it is not mere-
ly dryness that is thus produced, or such a lowering
of temperature as the thermometer suspended in the
interior of the house may indicate; the rapid evapo-

7T*

154 APPLICATION OF PRINCIPLES,

ration that takes place upon the admission of dry air
produces a degree of cold upon the surface of leaves,
and of the porous earthen pots in which plants grow,
of which our instruments give no indication. To
counteract these mischievous effects, many contri-
vances have been proposed, in order to ensure the
introduction of fresh air warm and loaded with mois-
ture, such as compelling the fresh air to enter a house
after passing through pipes moderately heated, or
over hot-water pipes surrounded by a damp atmo-
sphere, and soon; the advantages of which, of course,
depend upon the objects to be attained.

If ventilation is merely employed for the purpose
of purifying the air, as is often the case in hot-houses
and in dung-pits, it should be effected by the intro-
duction of fresh air, damp and heated.

If itis only for the purpose of lowering the tempera-
ture, as in green-houses, or in the midst of summer, the
external air may be admitted without any precautions.

But it is very commonly required in the winter,
for the purpose of drying the air in houses kept at
that season at alow temperature; such, for instance,
as those built for the protection of Heaths, and many
other Cape and New Holland plants: in these cases
it should be brought into the house as near the tem-
perature of the house as possible, but on no account
loaded with moisture. One of the principal reasons
for drying the air of such houses, is to prevent the
growth of parasitical fungi, which, in the form of
mouldiness, constitute what gardeners technically call
“damp.” These productions flourish in damp air at

OF VENTILATION. 155

a low temperature, but will not exist either in dry
cold air or in hot damp air. If the air of cool green-
houses is allowed to become damp, the fungi imme-
diately spring up on the surface of any decayed
leaves, or other matter which may be present, when
they spread rapidly to the young and tender parts of
living plants; and when this happens, they consume
the juices, choke the respiratory organs, and speedily
destroy the object they attack.

Ventilation is also required in the winter in such
places as dung-pits or frames, especially those in
which salad, cucumbers, and similar plants are grown.
In those cases the object is to dry the. air, in order
that the plants may not absorb more aqueous par-
ticles than they can decompose and assimilate.
Although plants of this kind will bear a high degree
of atmospherical moisture in summer, when the days:
are long and the sun bright, and when, consequently,
(66, 67,) all their digestive energies are in full acti-
vity, yet they are by no means able to endure the
same amount in the short dark days of winter, when,
from the want of light, their powers of decomposition
or digestion are comparatively feeble. Hence, no
doubt, the advantage of growing winter cucumbers
in forcing-houses, instead of dung-frames.

One of the causes of success in the Dutch method
of winter forcing is, undoubtedly, their avoiding the
necessity of winter ventilation, by intercepting the
excessive vapour that rises from the soil, and which
would otherwise mix with the air. For this purpose
they interpose screens of oiled paper between the

156 APPLICATION OF PRINCIPLES.

earth and the air of their houses, and in their pits for
vegetables, they cover the surface of the ground with
the same oiled paper, by which means vapour is effec-
tually intercepted, and the air preserved from exces-
sive moisture.

In forcing-houses, ventilation is thought to be
required at the time when the fruit is ripening, for
the purpose of increasing the perspiration of the
plants, and, consequently, of assisting in the elabora-
tion of the secretions to which fruit owes its flavour;
but, even for this, its utility is perhaps overrated,
and it is quite certain that it may be easily carried to
excess; for if it is so powerful as to injure the leaves
by over-drying the air, an effect the reverse of what
was intended will be produced; that is to say, the
quality of the fruit will be deteriorated (64, 75).
Upon this subject Mr. Knight has made the following
observations :—‘' A less humid atmosphere is more
advantageous to fruits of all kinds, when the period
of their maturity approaches, than in the earlier
stages of their growth; and such an increase of ven-
tilation at this period, as will give the requisite
degree of dryness to the air within the house, is
highly beneficial, provided it be not increased to such
an extent as to reduce the temperature of the house
much below the degree in which the fruit had pre-
viously grown, and thus retard its progress to matu-
rity. The good effect of opening a peach-house, by
taking off the lights of its roof during the period of
the last swelling of the fruit, appears to have led
many gardeners to overrate greatly the beneficial

OF VENTILATION. 157

inflxence of a free current of air upon ripening fruits ;
for I have never found ventilation to give the proper
flavour or colour to a peach, unless that fruit was, at
the same time, exposed to the sun without the inter-
vention of glass; and the most excellent peaches
I have ever been able to raise were obtained under
circumstances where change of air was as much as
possible prevented, consistently with the admission
of light (without glass), to a single tree.” (Hort. Trans.,
ii, 227.)

It is not improbable that one of the advantages
of ventilation depends upon a cause but little
adverted to, but which certainly requires to be well
considered.

It was an opinion of Mr. Knight, that the motion
given to plants by wind is beneficial to them by ena-
bling their fluids to circulate more freely than they
otherwise would do; and in a paper printed in the
Philosophical Transactions for 1803, p. 277, he addu-
ces, in support of his opinion, many experiments and
observations; of which the following is sufficiently
striking :—

“The effect of motion on the circulation of the sap,
and the consequent formation of wood, I was best
able to ascertain by the following expedient. arly
in the spring of 1801, I selected a number of young
seedling Apple trees, whose stems were about an inch
in diameter, and whose height between the roots and
first branches was between six and seven feet. These
trees stood about eight feet from each other; and, of
course, a free passage for the wind to act on each tree

158 APPLICATION OF PRINCIPLES.

was afforded. By means of stakes and bandages of
hay, not so tightly bound as to impede the progress
of any fluid within the trees, I nearly deprived the
roots and lower parts of the stems of several trees of
all motion, to the height of three feet from the ground,
‘leaving the upper part of the stems and branches in
their natural state. In the succeeding summer, much
new wood accumulated in the parts which were kept
in motion by the wind; but the lower parts of the
stems and roots increased very little in size. Remov-
ing the bandages from one of these trees in the fol-
lowing winter, I fixed a stake in the ground, about
ten feet distant from the tree, on the east side of it;
and I attached the tree to the stake at the height of
six feet, by means of a slender pole, about twelve
feet long; thus leaving the tree at liberty to move
towards the north and south, or, more properly, in
the segment of a circle, of which the pole formed a
radius; but in no other direction. Thus circum-
stanced, the diameter of the tree from north to south
in that part of its stem which was most exercised by
the wind exceeded that in the opposite direction, in
the following autumn, in the proportion of thirteen to
eleven.”

Now, if the effect of motion is to increase the
quantity of wood in a plant, it is evident that ventila-
tion, which causes motion, must tend to produce a
healthy action in the plants exposed to it; and such a
state must also be favourable to the developement of
all those secretions upon which the organisation of
flowers, the setting of fruit, and the elaboration of

OF SEED-SOWING, 159

colour, odour, flavour, &c., so much depend. Some
suggestions by Mr. Knight, as to the manner in which
this result can be artificially produced, will be found
in the Hort. Trans., vol. iv. p.2and 8: but the sub-
ject has yet attracted little attention. (See also Hort.
Trans., new series, i. 34.)

CHAPTER V.
OF SEED-SOWING.

WHEN a seed is committed to the earth, it under-
goes certain chemical changes (14) before it can de-
velope new parts and grow. These changes are
brought about by heat and water, assisted by the ab-
sence of light. In many seeds the vital principle is
so strong, that to scatter them upon the soil, and to
cover them slightly with earth, are sufficient to ensure
their speedy germination; but in others the power
of growth will only manifest itself under very favour-.
able conditions; it is, therefore, necessary to consider
well upon what the circumstances most suitable to
germination depend.

Moisture is necessary, but not an unlimited quan-
tity. Ifseed is thrown into water and exposed to a
proper temperature, the act of germination will take
place; but, unless the plant is an aquatic, it will
speedily perish ; no doubt because its powers of respi-

160 APPLICATION OF PRINCIPLES.

ration are impeded, and itis unable to decompose the
water it absorbs, which collects in its cavities and be-
comes putrid. There must, therefore, be some
amount of water, which to the dormant as well as the
vegetating plant is naturally more suitable than any
other; and experience shows that quantity to be just
so much as the particles of earth can retain around
and among them by the mere force of attraction. To
this is to be ascribed the advantage derived from
those mixtures of peat, loam and sand, which gar-
deners prefer for their seedlings; the peat and sand
together keep asunder the particles of loam which
would otherwise adhere and prevent the percolation
of water ; the loam retains moisture with force enough
to prevent its passing off too quickly through the
wide interstices of sand and peat. If, during the de-
licate action of germination, the changes that the seed
undergoes take place without interruption, the young
plant makes its appearance in a healthy state; but,
if by irregular variations of heat, light and moisture,
the progress of germination is sometimes accelerated
and sometimes stopped, the fragile machinery upon
which vitality depends may become so much de-
ranged as to be no longer able to perform its actions,
and the seed will die. Itis for the purpose of secur-
ing uniformity in these respects, that we employ, in
delicate cases, the steady heat of a gentle hot-bed,
shaded; and, in all cases whatever, the assistance of
a coating of earth scattered over the seed.

Under what depth of earth seed should be buried
must always be judged of by the experience of a gar-

OF SEED-SOWING. 161

dener: but it should be obvious that minute seeds,
whose powers of growth must be feeble in proportion
to their size, will bear only a very slight covering;
while others, of a larger size and more vigour, will
be capable, when their vital powers are once put in
action, of upheaving considerable weights of soil.
As, however, the extent of this power is usually un-
certain the judicious gardener will take care to em-
ploy, for a covering, no more earth than is really
necessary to preserve around his seeds the requisite
degree of darkness and moisture.* Hence the com-
mon practices of sowing small seeds upon the surface
of the soil, and covering them with a coating of moss,
which may be removed when the young seedlings
are found to have established themselves. In other
cases very minute seeds are mixed with sand before
they are sown.

The latter practice is not, however, merely for the
sake of covering the seed with the smallest possible
quantity of soil, but has for its object the separation
of seeds to such a distance, that when they germinate
they may not choke upeach other. If seedlings, like
other plants, are placed so near together that they

* It may, perhaps, be as well to notice, in this place, an erroneous
opinion, not uncommonly entertained, that seeds must be “well”
buried in order that the young plants, when produced, may have
“ sufficient hold of the ground.” The fact is, that a seed, when it
begins to grow, plunges its roots downwards and throws its stem
upwards from a common point, which is the seed itself; and, con-
sequently, all the space that intervenes between the surface of the
soil and the seed is occupied by the base of the stem, and not by
roots.

162 APPLICATION OF PRINCIPLES.

either exhaust the soil of its organisable matter, or
overshadow each other so as to hinder the requisite
quantity of light, some will die in order that the
remainder may live; and this, in the case of rare
seeds, should, of course, be guarded against very
carefully.

With regard to the temperature to which a seed
should be subjected, in order to secure its germina-
tion, this, undoubtedly, varies with different species,
and depends upon their peculiar habits, and the tem-
perature of the climate of which they are native. So
far as general rules can be given upon such a subject,
it may be stated that the temperature of the earth
most favourable for germination is 50° to 55° for the
seeds of cold countries, 60° to 65° for those of “green-
house plants,” and 70° to 80° for those of the torrid
zone. No seed, however, has been known to refuse
to germinate in the last mentioned temperature, al-
though those to which such a heat is necessary will
not, in general, grow in a healthy manner in a lower
temperature. We have no exact experiments upon
this subject, except in a few cases recorded by Messrs
Edwards and Colin, by whom there is a very valu-
able set of observations upon the temperatures borne
by certain agricultural seeds (Annales des Sciences,
new series, vol. v. p. 5), the result of which may be
thus stated :—

At 446°, Wheat, Barley, and Rye could germinate.
95°, in water, for three days, four-fifths of the Wheat and Rye,
and all the Barley, were killed.
104°, in sand and earth, the same seeds sustained the tempera-
ture for a considerable time, without inconvenience.

OF SEED-SOWING. 163

At 118°, under the same circumstances most of them perished.
122°, ditto ditto, all perished.

But it was found that, for short periods of time, a
rnuch higher temperature could be borne.

At 143°6°, in vapour, Wheat, Barley, Kidneybeans, and Flax retain-
ed their vitality for a quarter of an hour; but in 27} mi-
nutes, the three last died at a temperature of 125°6°.

167°, in vapour, they all perished.

167°, in dry air, they sustained no injury.

It will be presently seen that some seeds will bear
a much higher temperature.

The foregoing observations apply to seeds in a per-
fect state of health; when they have become sickly
or feeble, from age or other causes, some precautions
become necessary, to which, under other circum-
stances, no attention requires to be paid.

When the vital energies of a seed are diminished,
it does not lose its power of absorbing water, but it is
less capable of decomposing it (14). The conse-
quence of this is, that the free water introduced into
the system collects in the cavities of the seed, and pro-
duces putrefaction; the sign of which is the rotting
of the seeds in the ground. The remedy for this is to
present water to the seed in such small quantities ata
time, and so gradually, that no more is absorbed than
the languid powers of the seed can assimilate; and to
increase the quantity only as the dormant powers of
vegetation are aroused. One of the best means of
doing this is, to sow seeds in warm soil tolerably dry ;
to trust for some time to the moisture that exists in
such earth, and in the atmosphere, for the supply re-

164 APPLICATION OF PRINCIPLES,

quired for germination ; and only to administer water
when the signs of germination have become visible ;
even then the supply should be extremely small. If
this is attended to, carbonic acid is very slowly form-
ed and liberated, the chemical quality of the contents
of the seed is thus insensibly altered, each act of respi-
ration may be said to invigorate it, and by degrees it
will be brought to a condition favourable to the assi-
milation of food in larger quantities. Mr. Knight
used to say that these effects were produced in no way
so well as by enclosing seeds between two pieces of
loamy turf, cut smooth, and applied to each other by
the underground sides; such a method is, however,
scarcely applicable to any except seeds of consider-
able size.*

Other expedients have occasionally been had re-
course to successfully. Where seeds are enclosed in
a very hard dry shell, it is usually necessary to file it
thin, so as to permit the embryo to burst through its
integuments when it has begun to swell. Under natu-
ral circumstances, indeed, no such operation is prac-
tised: but it is to beremembered that such seeds will
have fallen to the ground as soon as ripe, and before
their shell acquired the bony hardness that we find
after having become dry.

Sometimes it has been found useful to immerse

* The sowing of very small and delicate seeds in the open air
should be deferred until the season is so far advanced, that all pro-
bable danger from cold weather is past. Suspending a shingle or
board over the place where they are sown, by laying it upon bricks

placed edgewise, until the first leaves are perfectly formed, will be
found a great advantage in sowing all delivate seeds. A. J. D.

OF SEED-SOWING,. 165

seeds in tepid water until signs of germination mani-
fest themselves, and then to transfer them to earth:
but this process cannot be applied with advantage to
seeds in an unhealthy state; and it is only of use to
healthy seeds, by accelerating the time of growth, a
practice which may, in out-door crops, be sometimes
desirable when applied to seeds which, like the Beet,
the Carrot, or the Parsnep, will, in dry seasons, lie so
long in the ground without germinating, that they
become a prey to birds or other animals.

Of late years, the singular practice has been intro-
duced of boiling seeds, to promote germination. This
was, I believe, first recommended by Mr. Bowie, who
stated, in the Gardener's Magazine, vol. viii. p. 5, (1882,)
that ‘he found the seeds of nearly all leguminous
plants germinate more readily by having water heated
to 200°, or even to the boiling point of Fahrenheit’s
scale, poured over them, leaving them to steep and
the water to cool for twenty-four hours.” Subse-
quently, the practice has been adopted by other per-
sons with perfect success; and, some years ago, seed-
lings of Acacia lophantha were exhibited before the
Horticultural Society by the late Mr. Thomas Cary
Palmer, which had sprung from seeds boiled for as
much as five minutes. I am also acquainted with
other cases, one of the more remarkable of which was
the germination of the seeds of the Raspberry, picked
from a jar of jam, and which must therefore have
been exposed to the temperature of 230°, the boiling
point of syrup. It is difficult to understand in what
way so violent an action ean be beneficial to any

166 APPLICATION OF PRINCIPLES.

thing possessing vitality; the fact, however, is cer-
tain. As such instances of success are confined to
seeds with hard shells, it is possible that the heated
fluid may act in part mechanically by cracking the
shell, in part as a solvent of the matters enclosed in
the seed, and in part as a stimulant.

Mr. Lymburn, nurseryman at Kilmarnock, has
lately called attention to the effect produced upon
germinating seeds by alkaline substances. He states
that experiments made by Mr. Charles Maltuen, and
narrated in Brewster's Journal of Sctence, having
shown that the negative or alkaline pole of a galvanic
battery caused seeds to germinate in much less time
than the positive or acid pole, he was induced to
observe the effects on seeds of acetic, nitric, and sul-
phuric acids, and also of water rendered alkaline by
potash and ammonia. ‘In the alkaline, the seeds
vegetated in thirty hours, and were well developed in
forty; while in the acetic and sulphuric they took
seven days; and, even after a month, they had not
begun to grow in the acetic.” This experiment led
to others upon lime; ‘a very easily procured alkali,
and which he inferred to be more efficient than any
other from the well-known affinity of quick or newly
slacked lime for carbonic acid. Lime, as taken from
the quarry, consists of carbonate of lime, or lime
united to carbonic acid; but, in the act of burning,
the carbonic acid is driven off; and hence the great
affinity of newly slacked lime for carbonic acid. He
depended, therefore, upon this affinity, to extract the
carbon from the starch, assisted by moisture” (Gard.

OF. SEED-SOWING. 167

Mag., xiv. 74); and it is stated that the results were
exceedingly striking. Old Spruce Fir seed, which
would scarcely germinate at two years old, produced
a fine healthy crop when three years old, having been
first damped and then mixed with newly. slacked
lime; and, under the same treatment, an average
crop of healthy plants was obtained when the seed
was four years old. Unfortunately, the manner in
which the original experiments upon acids and alka-
lies were conducted is not explained, (it is to be
presumed that the water employed was only acidu-
lated with the acids spoken of,) and I am not aware
of the experiments having been repeated.—The last
method of promoting germination, to which it is
necessary to advert, is the mixing seeds with agents
that have the power of liberatingoxygen. It has been
shown (14) that a seed cannot germinate until the car-
bon with which it is loaded is to a considerable extent
removed; the removal of this principle is effected by
converting it into carbonic acid, for which purpose
a. large supply of oxygen is required. | Under ordi-
nary circumstances, the oxygen is furnished by the
decomposition of water by the vital forces of the
seed ; but, when those forces are languid, it has been
proposed to supply oxygen by some other means.
Humboldt employed a dilute solution of chlorine,
which has a powerful tendency to decompose water
and set oxygen at liberty, and, it is said, with great
success. Oxalic acid has also been used for the same
purpose.

Mr. Otto, of Berlin, states that he employs oxalic

168 APPLICATION OF PRINCIPLES.

acid to make old seeds germinate. The seeds are put
into a bottle filled with oxalic acid, and remain there
till the germination is observable, which generally
takes place in from twenty-four to forty-eight hours;
when the seeds are taken out, and sown in the usual
manner. Another way is to wet a woollen cloth
with oxalic acid, on which the seeds are put, and itis
then folded up and kept in a stove; by this method
small and hard seeds will germinate equally as well
as in the bottle. Also very small seeds are sown in
pots and placed in a hot-bed; and oxalic acid, much
diluted, is applied twice or thrice a day till they begin
to grow. Particular care must be taken to remove
the seeds out of the acid as soon as the least vegeta-
tion is observable. Mr. Otto found that by this means
seeds which were from twenty to forty years old
grew, while the same sort, sown in the usual manner,
did not grow at all (Gard. Mag., viii. 196): and it is
asserted by Dr. Hamilton (Jd, x. 368, 453,) and
others, that they have found decided advantages from
the employment of this substance. Theoretically
it would seem that the effects described ought to be
produced, but general experience does not confirm
them; and it may be conceived that the rapid abstrac-
tion of carbon, by the presence of an unnaturally
large quantity of oxygen, may produce effects as
injurious to the health of the seed as its too slow
destruction in consequence of the languor of the vital
principle.

The length of time that some seeds will lie in the
ground, under circumstances favourable to germi-

OF SEED-SAVING. 169

nation, without growing, is very remarkable, and
inexplicable upon any known principle, If the Haw-
thorn be sown immediately after the seeds are ripe, a
part will appear as plants the next spring; a larger
number the second year; and stragglers, sometimes
in considerable numbers, even in the third and fourth
seasons. Seeds of the genera Ribes, Berberis, and
Peeonia, have a similar habit. M. Savi is related by
De Candolle to have had, for more than ten years, a
crop of Tobacco from one original sowing; the young
plants having been destroyed yearly, without being
allowed to form their seed. This matter does not,
perhaps, concern the theory of horticulture, for
theory is incapable of explaining it; but it is a fact
that it is useful to know, because it may prevent still
living seeds from being thrown away, under the idea
that, as they did not grow the first year, they will
never grow at all.

CHAPTER VI.
OF SEED-SAVING.

THE maturation of the seed being a vital action
indispensable to the perpetuation of a species, is, in
wild plants, guarded from interruption by so many
wise precautions, that no artificial assistance is requir-
ed in the process; but in gardens, where plants. are
often enfeebled by domestication, or exposed to con-

170 APPLICATION OF PRINCIPLES.

ditions very different from those to which they are
subject’in their natural state, the seed often refuses to
ripen, or even to commence the formation of an
embryo. In such cases, the skill of gardeners must
aid the workings of nature, and art must effect that
which the failing powers of a plant are unable to bring
about of themselves.

Sterility is a common malady of cultivated plants ;
the finer varieties of fruit, and all double and highly
cultivated flowers, being more frequently barren than
fertile. This arises from several different causes.

The most common cause of sterility is an unnatural
developement of some organ in the vicinity of the
seed, which attracts to itself the organisable matter
that would otherwise be applicable to the support of
the seed. Of this the Pear, the Pine-apple, and the
Plantain are illustrative instances. The more deli-
cate varieties of Pear, such as the Gansel’s Bergamot
and the Chaumontelle, have rarely any seeds; of
Pine-apple, none, except the Enville now and then,
have seeds, and that variety, though a large one, is
of little value for its delicacy, and probably ap-
proaches nearly to the wild state of the plant; of
Plantains, few, except the wild and crabbed sorts, are
seedful. The remedy for this appears to be, in with-
holding ‘from such plants all the sources from which
their succulence can be encouraged. If, in conse-
quence of any predisposition to form succulent tissue
(on which the excellence of fruit much depends), the
organisable matter of the plant be once diverted trom
feeding the seed to those parts in which the succu-

OF SEED-SAVING. 171

lence exists, it will continue, by the action of endos-
mose, to be attracted thither more powerfully than to
any other part, and the effect of this will be the
starvation of the seed: but a scanty supply of food,
an unhealthy condition of the plant itself, or with-
holding the usual quantity of water, will all check
the tendency to luxuriance, and therefore will favour
the developement of the seed, whose feeble attracting
force is, in that case, not so likely to be overcome by
the accumulation of attracting power in the neigh-
bouring parts. Thus we see the Pine-apples are
more frequently seedful under the bad cultivation of
the Continent, than in the highly kept and skilfully
managed pineries of England. Abstraction of
branches, in the neighbourhood of fruit, has also been
occasicnally found favourable to the formation of
seed; evidently because the food that would have
been conveyed into the branches, having no outlet, is
forced into the fruit.

Another cause of sterility is the deficiency of pollen
(87) in the anthers of a given plant, as in vegetable
mules (88), which usually partake of the spermatic
debility so well known in similar cases in the animal
kingdom. It has often been found that sterility of
this kind is cured by the application, to the seedless
plant, of the vigorous pollen of another less debilitated
variety.

In some plants, such as Pelargoniums, when culti-
vated, the anthers shed their pollen before the stigma
is ready to receive its influence, and thus sterility re-
sults. All such cases are provided for, by employing

172 APPLICATION OF PRINCIPLES.

the pollen of another flower. (See Sweetin the Gar.
dener’s Magazine, vii. 206.)

An unfavourable state of the atmosphere obstructs
the action of pollen, and thus produces sterility.
Pollen will not produce its impregnating tubes in too
low a temperature, or when the air is charged with
moisture; neither, in the absence of wind or insects,
have some plants the power of conveying the pollen
to the stigma, their anthers having no special irrita-
bility, and only opening forthe discharge of the pollen,
not ejecting it with force. If we watch the Hazel, or
any of the Coniferous order, in which the enormous
quantity of pollen employed to secure the impregna-
tion of the seed renders it easy to see what happens,
it will be found that no pollen is scattered in damp
cold weather; but, in a sunny, warm, dry morning,
the atmosphere surrounding such plants is, in the im-
pregnating season, filled with grains of pollen dis-
charged by the anthers. In wet springs the crops of
fruit fail, because the anthers are not sufficiently
dried to shrivel and discharge their contents, which
remain locked up in the anther cells till the power of
impregnation is lost. In vineries and forcing-houses
generally, into which no air is admitted to disturb the
foliage, nor any artificial means employed for the
same end, and when the season is too early for the
presence of bees, flies, and other insects, the grapes
will not set: and in the frames of melons and cucum-
bers, from which insects are excluded, no seed is
formed unless the pollen is conveyed by hand, from
those flowers in which it is formed, to others in which

OF SEED-SAVING. 173

the young fruit alone is generated. In all cases of
this kind, the remedy for sterility is obvious enough
where plants exist in an artificial.condition ; but, when
they occur in the orchard or the flower- sails in the
open air, science suggests no assistance.

It sometimes happens that particular parts of plants,
distant from the fruit, are so constructed as to attract
to themselves the food intended for the fruit, and thus
to prevent the formation of seed. For example :—
The early varieties of Potato do not readily produce
seed, owing to the abstraction by their tubers of the
nutritive matter required for the support of the seed.
Mr. Knight found that by destroying the tubers in
part, as they formed, seeds were readily procured from
such varieties.*

But perhaps the most frequent cause of sterility
is the monstrous condition of the flowers of many cul-
tivated plants. It has been fully explained (84) that
the floral organs of plants are nothing more than
leaves, so modified as to be capable of performing
special acts, for particular purposes; but they are
not capable of performing those acts any longer than
they retain their modified condition; and therefore
the stamens cannot secrete pollen, when, by acciden-
tal circumstances, they are changed into leaves, as
happens in double flowers; then, there is nothing

* Vice versa, the produce of the potatoes may be much increased
by plucking off the blossoms, in which case the nutritive matter
which would have been expended upon them and the berries, or
fruit, serves to increase the size of the tubers, for which alone the
plant is cultivated. This fact, so perfectly consistent with theory,
has been completely confirmed by experiment.

174 APPLICATION OF PRINCIPLES.

to fertilise the stigma, and, of course, no seed is pro-
duced. Or the carpels themselves may be converted
into leaves, and have lost their seed-bearing property.
Double flowers in the latter case cannot possibly bear
seed; but in the condition first mentioned they may,
and often do. To bring this about, the cultivator
plants in the vicinity of his sterile flowers others of
the same species, in which a part at least of the
stamens are perfect, and they furnish a sufficiency of
pollen for the impregnation of the other flowers in
which there are no stamens.

In some cases, principally in those of Composite
flowers, the seed is formed and advanced towards
perfection, and then decays; this is owing to the
flower heads of such plants being composed, in a great
measure, of soft scales, absorbent and retentive of
moisture, to which, in their own country, they are
not exposed in the fruiting season, but by which they
are affected under the hands of the cultivator. When
the heads of such flowers are soaked with moisture,
which they cannot get rid of, the scales rot, and decay
spreads to all the other parts, and thus the production
of seed is prevented. The Chinese Chrysanthemum
is a familiar instance of this, Such plants seed rea-
dily if the flower heads are kept warm and dry; and
it is thus that the sterile Chrysanthemum has been
made seedful; that is to say, by growing it in a
dry warm winter border, protected from showers by
a roof of glass, or by using some such means of guard-
ing it; or by rearing it in a warm dry climate.

When seeds are freely produced, it is not altoge-

OF SEED-SAVING. 175

ther a subject of indifference in what way they are
saved, if it is desired that their progeny should be the
most perfect that can be obtained. Weak seeds
produce weak plants, and therefore recourse should
be had, in all delicate cases, to artificial means for
giving vigour to the seed. Jn general, the cultivator
trusts to his eye for separating the plumpest and most
completely formed seeds; or to floating them in
water, selecting only the heavy grains that, sink, and
rejecting all those which are buoyant enough to float.
But the energy of the vital principle in a seed may be,
undoubtedly, increased by abstracting neighbouring
fruits, by improving the general health of the parent
plant, by a full exposure of it to light, and by pro-
longing the period of maturation as much as is con-
sistent with the health of the fruit. It is a constant
rule that seedlings take after their parents, an unheal-
thy mother producing a diseased offspring, and a
vigorous parent yielding a healthy progeny in all
their minute gradations and modifications; and this is
so true, that, as florists very well know, semi-double
Ranunculi, Anemones, and similar flowers, will rarely
yield double varieties, while the seeds of the latter as
unfrequently give birth to semi-double degenerations.
Independently of these things, it is indispensable that
the seed of a plant, when saved, should be perfectly
ripe, if it is intended to be laid by for future sowing.
The effect of ripening is to load the seed with carbon
in the form of starch, or some such substance (102),
and to deprive it of water, conditions necessary for
its preservation: but, if a seed is gathered before

176 APPLICATION OF PRINCIPLES.

being ripe, these conditions are not secured; and, in
proportion to the deficiency ofcarbon and superabun-
dance of water, is the seed liable to perish.

The complete maturation of the seed is, however, a
disadvantage, when it has to be sown immediately
after being gathered; for the embryo is formed, and
capable of germinating, long before the period of
greatest maturity. There are two periods in the
latter part of the organisation of a seed which,
although separated by no limits, require to be distin-
guished. The first is that when the embryo is com-
pleted; and the second is when nature has, in ad-
dition, furnished it with the means of maintaining
its vitality for a long period. It is just as capable of
growing at the expiration of the first period as of the
second ; it will do so immediately if committed to the
ground, and we see it actually happening to Peas,
Beans, Corn, and other field crops, in wet summers ;
but, at the end of the second period, it cannot germi-
nate till it has relieved itself of all the carbon which,
during that period, was deposited in its tissue.

If seeds are to be preserved for a length of time, a
state of complete dryness is so necessary to them that
it has been recommended to increase it by artificial
means: not, however, by the application of heat, or
by any process like that of kiln-drying, for that would
destroy their vitality ; but by some of those chemical
processes which dry the atmosphere without raising
its temperature. It occurred to Mr. Livingstone, that
air made dry by means of sulphuric acid might be
advantageously employed for this purpose, and he

OF SEED-PACKING. 177

says that the success of his experiments was com-
plete. He placed the seeds to be dried in the pans
of Leslie’s ice machine, and carefully replaced the
receiver without exhausting the air; small seeds
were sufficiently dried in one or two days, and the
largest seeds in lessthan a week. (ort. Trans., iii.
184.)

Other contrivances might easily be adopted. Muri-
ate of lime, for instance, which has the property of
absorbing the moisture of the atmosphere, might, per-
haps, be employed with advantage in drying the air
in which seeds are placed after being gathered.

The reason why it is so important that seeds which
have to be long kept should be thoroughly dried, is,
partly because seeds have the power of decomposing
water, which causes the commencement of germina-
tion (14), and, if this happens while they are cut off
from the other means of existence, the process of
growth must be stopped, and their death will follow
and, in part, from the tendency of vegetable matter in
contact with water to putrefy, if the actions of life are
not in play.

CHAPTER VII.
OF SEED-PACKING.

Ir seldom happens that seeds are sown as soon as
they are ripe: it is sometimes desirable that they
g*

178 APPLICATION OF PRINCIPLES.

should be preserved. for long periods of time: the
power of conveying them for great distances, through
various climates, is oneof those upon which man most
depends for the improvement of the horticultural re-
sources of all countries; and for this purpose large
sums are annually expended, both by governments
and individuals. It is, therefore, an object of the first
importance to ascertain, what is not well understood,
as it would seem, namely, the causes by which the
destruction of the germinating power of seeds is
effected; for it is only by doing this that their pre-
servation can be secured.

Seeds are probably possessed of different powers of
life, some preserving their vital principle through
centuries of time, while others have but an epheme-
ral existence under any circumstances. The reasons
for this difference are unknown to us, and apparently
depend upon a first cause, over which we have,
therefore, no control; but the fact of great longevity
in some seeds is certain, and there seems no reason
why the conditions which enable them to preserve
their germinating power for long periods of time
should not be discovered and imitated.

Without admitting such doubtful cases as those of
seeds preserved in mummies having germinated, there
are many instances of seminal longevity about which
there can be no doubt. Books contain an abundance
of instances of plants having suddenly sprung up from
the soil obtained from deep excavations, where the
seeds must be supposed to have been buried for ages.
Professor Henslow says that in the fens of Cambridge-

OF SEED-PACKING. 179

shire, after the surface has been drained and the soil
ploughed, large crops of white and black mustard
invariably appear. Miller mentions a case of Plan-
tago Psyllium having sprung from the soil of an
ancient ditch which was emptied at Chelsea, although
the plant had never been seen there in the memory
of man. De Candolle says that M. Gerardin succeed-
ed in raising Kidneybeans from seed at least a hun-
dred years old, taken out of the herbarium of Tourne-
fort; and I have myself raised Raspberry plants from
seeds found in an ancient coffin, in a barrow in Dor-
setshire, which seeds, from the coins and other relics
met with near them, may be estimated to have been
sixteen or seventeen hundred years old.

In these cases, the only circumstances that we can
conceive to have operated must have been such a de-
gree of dryness as prevented the decomposition of the
seed on the one hand, and the excitement of its germi-
nating powers on the other, a moderately low tempe-
rature, and in some of them the exclusion of air; for
moisture, beat, and communication with the air, are
necessary to enable seeds to grow (14). The tendency
of moisture exposed to the air, and in contact with
inert vegetable matter, such as a torpid seed, is by de-
grees to produce decay, which rapidly spreads to the
neighbouring parts. But, if the vitality of a seed is
excited by a fitting temperature, the moisture with
which it is in contact is then decomposed, the oxygen
so obtained combines with the carbon of the seed, and
forms carbonic acid, which flies off, and by degrees re-
duces the amount of carbon lodged in the tissue of the

180 APPLICATION OF PRINCIPLES.

seed to that which is best suited for the growth of the
embryo (103) ; then, if the embryo is so situated that it
cannot obtain from the surrounding medium food upon
which to subsist, its germination stops, and, being de-
prived of its carbon, the safeguard of its vitality is re-
moved, and it perishes. If, however, the amount of
moisture in contact with a seed is very small, as in the
dry earth at the bottom of a tumulus for instance, the
temperature at the same time low, and the access of at-
mospheric air cut off, neither putrefaction nor germi-
nation is likely to occur. If seeds are exposed to a
high temperature in dryness, they will not perish un-
less the temperature rises beyond anything likely to
occur under natural circumstances. Edwards and
Colin found that even wheat, barley, and rye, inhabit-
ants of temperate countries, would bear when dry 104°
for a long time without injury, although they died in
three days in water at 95°; and a much higher pro-
longed temperature may be expected to produce no
ill effect upon seeds inhabiting hotter countries.
There is no apparent reason why the exposure of dry
seeds to the air should destroy vitality, unless the ex-
posure is very much prolonged; nor have we any
evidence to show that it does, so long as they remain
dry. The way in which the atmosphere would act
injuriously upon dormant seeds is, by its oxygen ab-
stracting their carbon; and it was formerly supposed
that the carbonic acid extricated by germinating seeds
was formed in this way. But the very valuable ob-
servations and experiments of Messrs. Edwards and
Colin (see Comptes rendus de l’ Académie des Sciences,

OF SEED-PACKING. 181

vil. 922,) show that carbonic acid is formed by the as-
sistance of the oxygen obtained by the decomposition
of water.

If we apply these considerations to the plans usually
employed for preserving artificially the vitality of
seeds, we shall find them offer a ready explanation of
the success that attends some methods of packing, and
the constant failure of others.

The great object of those who have devised means
of packing seeds for distant journeys has, in general,
been to exclude the air, and all other considerations
have been subordinate to this. Enclosure in bottles
hermetically sealed, in papers thickly coated with
wax, in tin boxes, andsimilar contrivances, have been
resorted to with this object in view: but no advan-
tage can be derived from excluding the air, and the
disadvantage is very great; for the effect of exclud-
ing the air is to include whatever free moisture seeds
may contain or be surrounded by; this moisture is
sufficient, in high temperatures, either to deprive the
seed of its carbon of preservation, or to induce decay
of the tissue, especially of the seed-coats, which have
no vitality themselves, and in either case the embryo
perishes.

Packing in charcoal has been recommended, it is
difficult to say why; and experience shows what
might have been anticipated, that it produces no other
effect than packing in earth or other dry non-con-
ducting material.

Clayed sugar has been employed, and, as it is said,
occasionally with advantage; but I have seen no in-

182 APPLICATION OF PRINCIPLES.

stance of success, and, on the contrary, its tendency
to absorb moisture from the air till it becomes capable
of fermenting, is in itself an objection to the employ-
ment of this substance.

The most common method of packing is to enclose
seeds in paper, to surround parcels of such papers
with envelopes of the same material, and to enclose
the whole in a deal box. It is in this manner that
seedsmen usually despatch their orders to India, and
other distant parts of the world. The evils of this
method have been pointed out by Dr. Falconer, in
the Proceedings of the Horticultural Society, vol. i. p.
49. “On one occasion,” he says, “I received from
England a large assortment of garden vegetable seeds,
from a London seedsman. They were packed in the
thick dark brown paper which is generally used by
grocers and seedsmen, and which, for the facility of
folding, is usually in a somewhat damp state. The
packages were nailed up in a large wooden box, with
numerous folds of this paper, and the box was then
hermetically sealed in a tin case; it then found its way
into the ship’s hold. The damp paper, which in the
temperature of England, say at 50°, would have mat-
tered little, became an important agent when the ship
got into the tropics; at about 80° the damp became a
hot vapour, and, when the seeds reached me, I found
them all in a semi-pulpy and mildewed state.”

Upon the whole, the only mode which is calculated
to meet all the circumstances to which seeds are ex-
posed during a voyage is to dry them as thoroughly
as possible, enclose them in coarse paper, and to pack

OF PROPAGATION BY EYES AND KNAURS. 183

the papers themselves very loosely in coarse canvass
bags, not enclosed in boxes, but freely exposed to the
air; and to insure their transmission in some dry
well-ventilated place. Thus, if the seeds are origi-
nally dried incompletely, they will become further
dried on their passage; if the seed paper is damp, as
it almost always is, the moisture will fly off through
the sides of the bags, and will not stagnate around the
seeds. It is true that, under such circumstances, the
seeds will be exposed to the fluctuations of tempera-
ture, and to the influence of the atmosphere; but nei-
ther the one nor the other of these is likely to be pro-
ductive of injury to the germinating principle. The
excellence of this method I can attest from my own
observation. Large quantities of seeds have been
annually transmitted from India for many years,
doubtless gathered with care, it is to be presumed
prepared with every attention to the preservation of
the vital principle, and certainly packed with all those
precautions which have been erroneously supposed
to be advantageous ; the hopelessness of raising plants
from such seeds has at length become so apparent,
that many persons have altogether abandoned the
attempt, and will not take the trouble to sow them
when they arrive. But the seeds sent from India by
Dr. Falconer, packed in the manner last described, ex-
posed to all the accidents which those first mentioned
can have encountered, have germinated so well, that
we can scarcely say that the failure has been greater
than if they had been collected in the south of Europe.

I have no doubt that the general badness of the

184 APPLICATION OF PRINCIPLES.

seeds from Brazil, from the Indian Archipelago, and
from other intertropical countries, is almost always
to be ascribed to the seeds having been originally in-
sufficiently dried, and then enclosed in tightly packed
boxes, whence the superfluous moisture had no means
of escape.

For seeds containing oily matter, which are pecu-
larly liable to destruction (by their oil becoming
rancid ?), ramming in dry earth has been found advan-
tageous; as in the case of the Mango.

CHAPTER VIII.
OF PROPAGATION BY EYES AND KNAURS.

THE power of propagating plants by any other
means than that of seeds depends entirely upon the
presence of leaf-buds (fiz. 16), or, as they are technical-

OF PROPAGATION BY EYES AND KNAURS. 185

ly called, “eyes” (52), which are in reality rudimentary
branches in close connexion with the stem. All stems
are furnished with such buds, which, although held
together by a common system, have a power of inde-
pendent existence under fitting circumstances; and,
when called into growth, uniformly produce new
parts, of exactly the same nature, with respect to each
other, as that from which they originally sprang.

Under ordinary circumstances, an eye remains fix-
ed upon the stem that generates it. There it grows,
sending woody matter downwards over thealburnum,
and a new branch upwards, clothed with leaves, and
perhaps flowers: but it occasionally happens that
eyes separate spontaneously from their mother stem,
and when they fall upon the ground they emit roots
and become new plants (p. 29. jig. 8). This happens
in several kinds of Lily, and in other genera.

Man has taken advantage of this property, and has
discovered that the eyes.of many plants, if separated
artificially from the stem and placed in earth, will,
under favourable circumstances, produce new plants,
just as such eyes would have done if they had spon-
taneously disarticulated ; hence the system of propa-
gation by eyes, an operation employed only to a
limited extent in actual practice, but which in theory
seems applicable to all plants whatever. The only
species very generally so increased are the Potato and
the Vine. Of the latter, the eye, with a small portion
of the stem adhering to it, is commonly taken as the
means of obtaining young plants; being placed in
earth, with a bottom heat of 75° or 80°, and kept in

186 APPLICATION OF PRINCIPLES.

a damp atmosphere, it speedily shoots upwards into
a branch, and at the same time establishes itself in
the soil by the developement of the requisite quantity
of roots. In order to insure success in this operation
upon the Vine, it is only necessary that the eye
should be dormant, and that a small piece of well-
ripened wood should, as has been already stated, be
separated with it; it will then grow in much the same
way and under the same circumstances as a seed.
There is no doubt that many plants could be thus
multiplied just as easily as the Vine, but it is equally
certain that a far larger number cannot be so increas-
ed. The reason of this is, probably, that such eyes
are not sufficiently excitable, and that consequently
they decay before their vital energies are roused;
and, in addition, that they do not contain within
themselves a sufficient quantity of organisable matter
upon which to exist until new roots are formed, capa-
ble of feeding the nascent branch.

Mr. Knight’s explanation of this, although in part
applicable to cuttings only, yet seems to deserve
being introduced in this place. ‘Every leaf-bud
is well known to be capable of extending itself intoa
branch, and of becoming the stem of a future tree;
but it does not contain, nor is it at all able to prepare
and assimilate, the organisable matter required for its
extension and development. This must be derived
from a different source, the alburnous substance of
the tree, which appears the reservoir, in all this tribe
of plants, in which such matter is deposited. I found
avery few grains of alburnum to be sufficient to sup-

OF PROPAGATION BY EYES AND KNAURS. 187

port a bud of the Vine, and to occasion the formation
of minute leaves and roots: but the early growth of
such plants was extremely slender and feeble, as if
they had sprung from small seeds; and the buds of
the same plant, wholly detached from the alburnum,
were incapable of retaining life. The quantity of
alburnum being increased, the growth of the buds
increased in the same proportion; and when cuttings
of a foot long, and composed chiefly of two-years old
wood, were employed, the first growth of the buds
was nearly as strong. as it would have been, if the
cuttings had not been detached from the tree. The
quantity of alburnum in every young and thriving
tree, exclusive of the Palm tribe, is proportionate to
the number of its buds; and if the number of these
were, in any instance, ascertained and compared with
the quantity of alburnous matter in the branches and
stem and roots, it would be found that nature has
always formed a reservoir sufficiently extensive to
supply every bud. But those of a cutting, under
the most favourable circumstances, must derive their
nutriment from a more limited and precarious source ;
and it is therefore expedient that the gardener should,
in the first instance, make the most ample provision
conveniently within his power for their maintenance,
and that he should subsequently attend very closely
to the economical expenditure of such provision.”
(Horticultural Transactions, ii. 115.)

In the Potato the requisite provision of organisa-
ble matter is always secured, in consequence of the
great difficulty of separating an eye of that plant,

188 APPLICATION OF PRINCIPLES,

without fragments of the amylaceous tuber adhering
to it.

The provision of alimentary matter may, however,
be, in some cases, disadvantageous, by promoting too
great a development of stems and leaves, of which the
Potato itself is an instance. Theoretically, the more
nutritive matter there is for the eyes, the greater crop
there will be, ceteris paribus, and so there probably is
of leaves and stems; and it would seem that whole
potatoes should be more advantageous to plant than
sets. But I have proved, by a series of numerous
experiments, that the weight of potatoes per acre
is greater, under equal circumstances, from sets than
from whole tubers, by upwards of from seven cwt. to
three tons per acre; and considerably more, on com-
parison of the clear produce, after deducting the
weight of sets employed in both cases. (Hort. Trans.
n. 8.1. 445, and it. 156.) In these instances, I sup-
posed the rankness of the vegetation from the whole
tubers to be the cause of the diminished crop, for the
stems were unable to support themselves, and were
blown about, laid, and broken by the wind.

While, however, in such plants as the Potato, all
the eyes were equally capable of forming new tubers,
it is found by experience that they do so with differ-
ent degrees of rapidity, according to the age of that
part of the stem or tuber which furnishes them. It
is stated by a writer in the Gardener's Magazine (vol.
i. p. 406), that it is well known in Lancashire to some
cultivators of the Potato, “that different eyes germi-
nate, and give their produce, or become ripe, at times

OF PROPAGATION BY EYES AND KNAURS. 189

varying very materially, say several weeks, from
each other; some being ripe or fit for use as early as
the middle of May, and others not till
June or July. This will be understood
by reference to the accompanying
sketch. The sets nearest the extremity
of the Potato (fig. 17, a) are soonest ripe,
and in Lancashire, are planted in warm
places in March or the beginning of
April, and are ready for the market
about the 12th or 15th of May. The
produce of the next sets (6) is ready in about a fort-
night after, and that from the root end (c and d) still
later. These roots and sets (from 0 to d) are usually
put together, and the extremity of the root end is
thrown aside for the pigs.” This fact, if correctly
stated, shows, not that the youngest eyes, or those
nearest the point of the Potato, are the ripest, which
is impossible, but that they ‘are more excitable, and
consequently grow more rapidly than those at the
middle or base.

Besides the cases of propagation by eyes now men-
tioned, there is another of which a notice is given by
Signor Manetti (Gardener's Magazine, vii. 663), as
practised in Italy upon the Olive. It appears that,
from old Otive trees, certain knots or excrescences,
called wovoli, are cut out of the bark, of which a por-
tion is left adhering to them, and being planted, grow
into young Olive trees. Of these I have no further
account; but it is evident that the uovoli are no other
than our knaurs, already spoken of (53) under the

190 APPLICATION OF PRINCIPLES.

name of embryo buds ; concretions found in the bark
of many, and probably of all, trees, and supposed to
have been adventitious buds developed in the bark,
and, by the pressuré of the surrounding parts, forced
into those tortuous woody masses in the shape of
which we find them. They, in general, present an
oblong or conical form, are sometimes collected into
clusters, and usually exhibit little or no appearance
* of a tendency to further growth. It is, however,
not uncommon to find them lengthening into branches
as is shown in a Poplar, for which I am indebted to
Sir Oswald Mosley; and although they have never
yet been used for the purposes of propagation, except
in the case of the Olive, there seems to be no reason
why they should not be so employed, if any neces-
sity were to arise for them. The real amount of
their powers of growth is unknown, and would be a
good subject of investigation.

CHAPTER IX.
OF PROPAGATION BY LEAVES.

In the beginning of the last century, Richard
Bradley, a Fellow of the Royal Society, published a
translation from the Dutch of Agricola, of a book
upon the propagation of plants by leaves; in which
it was asserted that, by the aid of a mastic invented
by the author, the leaves of any plant, dipped at the

OF PROPAGATION BY LEAVES. 191

stalk end into this preparation, would immediately
strike root; and the book was adorned with copper-
plates exhibiting both the process and its result,
in the form of fields stuck full of Orange leaves grow-
ing into trees.

Although this work was very absurd, yet it proba-
bly originated in the discovery that the leaves of
some plants will grow under special circumstances ;
a fact often supposed to be much more rare than
it really is. In Professor Morren’s French Transla-
tion of my Outlines of the First Principles of Horticul-
ture, Rochea falcata* is named as producing adventi-
tious buds (58) from the upper side of its leaves ; and
the Orange, the Aucuba, and the Fig, as other
instances of leaves which will multiply their species
(p. 152); the power of Bryophyllum to do the same
thing is familiar to every one. Hedwig found the
leaves of the Crown Imperial, put into a plant-press,
produce bulbs from their surface. There is a well-
known case of the same effect having been observed
in Ornithogalum thyrsoideum. M. Auguste de St.
Hilaire mentions an instance of leaf-buds generated
by fragments of the leaves of ‘ Theophrasta,” which
had been buried by M. Neumann, chief gardener
at the Garden of Plants at Paris, and:of young Dro-
seras -furnished by the leaves of Drosera intermedia.
Mr. Henry Cassini is said to have seen young plants
produced by the leaves of Cardamine pratensis ; Eng-
lish botanists know that offsets spring from the mar-
gins of the leaves of Malaxis paludosa; in our stoves

* See, also, De Candolle’s Physiologie Végétale, ii. 672.

192 APPLICATION OF PRINCIPLES.

we see Ferns of many kinds, especially Woodwardia
radicans, propagating themselves by offsets from the
leaves; Mr. Turpin tells us that floating fragments
of Watercress leaves, cut up by a species of Phryga-
nea for its nest, “produce presently from their base,
and below the common petiole, at first two or three
colourless roots, then in their centre a small conical
bud, green, in which are found, or rather from which
successively arise, all the aérial parts of a new Water-
cress plant, while the roots multiply and lengthen.”
(Comptes rendus, 1839, sem. 2, 488.) Mr. Flourens
also mentions a case of Purslane, whose leaves,
divided into three, produced as many new plants,
each having a root, stem, and leaves. In the Zrans-
actions of the Horticultural Society, is an account of
a Zamia each of whose scales produced a new plant,
when the central part of the stem was decayed.
Finally, the following case is named in the same
work (vol. v. p. 442,) by Mr. Knight :—

“Tn an early part of the summer, some leaves of
Mint (Mentha piperita), without any portion of the
substance of the stems upon which they had grown,
were planted in small pots, and subjected to artificial
heat, under glass. They emitted roots, and lived
more than twelve months, having assumed nearly the
character of the leaves of evergreen trees; aud upon
the mould being turned out of the pots, it was found
to be everywhere surrounded by just such an inter-
woven mass of roots as would have been emitted by
perfect plants of the same species. These roots pre-
sented the usual character of those organs, and con-

OF PROPAGATION BY LEAVES. 193

sisted of medulla, alburnum, bark, and epidermis;
and as the leaf itself, during the growth of these, in-
creased greatly in weight, the evidence that it gene-
rated the true sap which was expended in their for-
mation appears perfectly conclusive.”

‘In our gardens, we know of many other cases of
the same kind. Hoya is a common instance, and three
others are here. figured (jig. 18); viz., Gesnera (a),

194 APPLICATION OF PRINCIPLES.

Clianthus puniceus (5), Gloxinia speciosa (c). In these,
and all such cases, the first thing that happens is an
excessive development of the cellular tissue, which
forms a large convex “callus” at the base; from
which, after a time, roots proceed; and by which
eventually a leaf-bud, the commencement of a new
stem, is generated.

It is not surprising that leaves should possess this
quality, when we remember that every leaf does the
same thing naturally while attached to the plant that
bears it; that is to say, forms at its base a bud which
is constantly axillary to itself. Leaves, however,
have not been often employed as the means of pro-
pagating a species; and it is probable that most
leaves, when separated from their parent, are incapa-
ble of doing so, for reasons which we are not as yet
able to explain. The most common case of their em-
ployment is in the form of the scales of a bulb, which
will, with some certainty, produce new plants under
favourable circumstances. Those circumstances are,
a strong bottom heat, moderate moisture, and a rich
stimulating soil,

When plants are produced by leaves under ordinary
circumstances, the conditions most favourable to their
doing so are of the same nature. A moderate amount
of moisture prevents their dying from perspiration or
perishing from decay ; a good bottom heat stimulates
their vital forces, and causes them to exercise what-
ever power they possess; and, in addition, they are
covered by a slightly shaded bell glass, which main-
tains around them an atmosphere of uniform humi-

OF PROPAGATION BY CUTTINGS. 195

dity, and, at the same time, cuts off the approach of
those direct solar rays, which, acting as a stimulus to
perspiration, would have a tendency to exhaust the
leaves of their fluid before they could organize, at
their base, the new matter from which the leaf-bud is
evidently produced.

CHAPTER X.
OF PROPAGATION BY CUTTINGS.

THIs, which is the most common of all modes of
artificial propagation except grafting, depends upon
essentially the same principle as propagation by eyes;
that is to say, the pieces of a plant called cuttings
possess a power of growth in consequence of their
bearing leaf:buds or eyes upon their surface. In
striking by eyes, we have the great difficulty to en-
counter of keeping the eye active till it has organised
roots with which to feed itself; the earth furnishes
such a supply unwillingly or unsuitably, nature in-
tending that the bud should, in the first instance, be
supported by the soluble nutriment ready prepared
and lodged in its immediate vicinity, in the pith or
some other part of the stem. For this reason, cut-
tings, which consist of eyes and the part containing
their proper aliment, usually strike root more freely
than eyes by themselves,

This being so, it is plain that a cutting is only capa-
ble of multiplying a plant when it bears buds upon its

196 APPLICATION OF PRINCIPLES.

surface; and as the stem is the only part upon which
buds certainly exist, so the stem is the only part from
which cuttings should be prepared. And again, as the
internode, or that space of the stem which intervenes
between leaf and leaf, has no buds, their station being
confined to the axil of
the leaves, a cutting pre-
pared from an internode
only is as improper as
one from the root. It
is no doubt true, that
we constantly propagate
plants from pieces of
what are called roots, as
in the Potato, or the Scir-
pus tuberosus (fig. 19);
but such roots are, in
reality, the kind of stem called a tuber (51); and, in
like manner, other cases of similar propagation are
also successful, because the part called a root is, in
reality, an underground stem covered with the rudi-
ments of leaves, to each of which an eye belongs.
The Rose, the Lilac, and many other plants, have
subterranean stems, cuttings of which will there-
fore answer the purpose of propagation. It will
also occasionally happen, that, owing to unknown
causes, morsels of the true root will generate what
are called adventitious buds; and hence we do
occasionally see the root employed for propagation,
as in Cydonia japonica ;* but these are rare and ex-

* Also the Paper Mulberry, the Paulownia, &e A. J.D.

OF PROPAGATION BY CUTTINGS. 197

ceptional cases, and by no means affect the general
rule. Mr. Knight attempted to account for this, by
supposing that the powers which roots of various
forms, and cuttings, and other detached parts of
plants, possess of emitting foliage, “ are wholly, and
in all cases, dependent upon the presence of true sap
previously deposited within them.” (Hort. Trans., v.
242.) But this is a very obscure expression, and
does not seem to throw any light upon the subject.

When the vine grows in a very warm damp stove,
its stem emits roots into the air; the same thing hap-
pens to the Maize on the lower part of its stem; and
in these and all such cases, the roots are found to be
emitted from buds. Hence it has been inferred that
the roots of a plant are as much productions of buds
as branches are, and that the stem is nothing more than
a, collection of such roots held together under the form
of wood and bark. The present is not the place for
a renewal of this discussion, for the arguments in
favor of and opposed to which, the reader is referred
to my Introduction to Botany, 3d edit. p. 309, &. It
is sufficient here to remark that the question turns
upon whether the buds and leaves actually them-
selves produce roots, or merely furnish the organis-
able matter out of which roots are formed; and that,
therefore, for the purpose of horticulture, either the
one or the other is equally capable of explaining the
facts connected with cuttings.*

* The following curious fact, recorded by Mr. Livingstone, which
seems to have escaped observation, deserves to be mentioned here :—
“The Pterocarpus Marsupium, one of the most beautiful of the large

198 APPLICATION OF PRINCIPLES.

As far as physiology can explain the operation of
propagation by cuttings, it appears that roots are
formed by the action of leaves; that branches are de-
veloped from the buds; and that the buds are main-
tained by the suitable aliment stored up in the stem.
Every thing beyond this seems to be connected with
specific constitutional powers, of which science can
give no explanation.

In considering what conditions are most favourable
to the maintenance of a cutting in the state required,
in order to enable it to become a young plant, it will
be most convenient, in the first place, to examine the
rationale of some one method which is known to be
successful. For this purpose, the following detail, by

trees of the East Indies, and which grows in the greatest perfection
about Malacea, affording, by its elegant wide-expanding boughs,
and thick-spreading pinnated leaves, a shade equally delightful
with the far-famed Tamarind tree, is readily propagated by cuttings
of all sizes, if planted even after the pieces have been cut for many
months, notwithstanding they appear quite dry, and fit only for the
fire. I have witnessed some of three, four, five, six, and seven
inches in diameter, and ten or twelve feet long, come to be fine trees
ina few years. While watching the transformation of the log into
the tree, I have been able to trace the progress of the radicles from
the buds, which began to shoot from the upper part of the stump a
few days after it had been placed in the ground, and marked their
progress till they reached the earth. By elevating the bark, minute
fibres are seen to descend contemporaneously as the bud shoots into
a branch. In a few weeks these are seen to interlace each other.
In less than two years the living fibrous system is complete; in five
years no vestige of its log origin can be perceived; its diameter
and height are doubled, and the tree is in all respects as elegant
and beautiful as if it had been produced from seed.” (Hort. Trans.,
iv. 226.)

OF PROPAGATION BY CUTTINGS. 199

Mr. Knight, of his mode of striking the Mulberry, is
selected :—

‘A considerable number of cuttings were taken
from the most vigorous bearing branches of a Mul-
berry tree, in the middle of November, 1812, and
were immediately reduced to the length adapted to
small pots, in which I proposed them ultimately to be
planted, and which were between four and five inches
deep. Each cutting was composed of about two parts
of two-years-old wood, that is, wood of the preceding
year, and about one third of yearling wood, the pro-
duce of the preceding summer; and the bottom of
each was cut so much aslope, that its surface might
be nearly parallel with that of the bottom of the pot
in which it was to be placed.

“The cuttings were then inserted in the common
ground, under a south wall, and so deeply immersed
in it, that one bud only remained visible above its
surface ; and in this situation they remained till April.
At this period the buds were much swollen, and the
upper ends of the cuttings appeared similar to those
of branches which had been shortened in the preced-
ing autumn, and become capable of transmitting any
portion of the ascending fluid. The bark at the lower
ends had also begun to emit those processes which
usually precede the production ofroots. The cuttings
were now removed to the pots to which they had
been previously fitted, and placed in a moderate hot-
bed; and a single bud only of each cutting remained
visible above the mould, and that being partially co-
vered ; and in this situation they vegetated with so

200 APPLICATION OF PRINCIPLES

much vigour, and emitted roots so abundantly, that I
do not think one cutting in a hundred would fail,
with proper attention. Some of the pots were placed
round the edges of a melon bed, which affords a very
eligible situation where a few plants only are want-
ed.” (Horticultural Transactions, ii. 117.) In this
case success appears to have depended upon the fol-
lowing circumstances :—

1. The cuttings were prepared in November, at the’
end of the season of growth, when all the organisable
matter required for the cutting was formed, and
locked up in the proper places in itsinterior. It was
not necessary, therefore, to take any means of insur-
ing a further supply of aliment. But had it been
otherwise, that is to say, if the cuttings had been pre-
pared in the summer, in the midst of their growth, it
would have been indispensable to allow a leaf or two
to remain attached to the upper end of the cutting,
to assist in the formation of alimentary matter.

2. Although but one eye was allowed to grow, yet
the cuttings themselves were four or five inches long,
and they consisted, to the extent of two thirds, of
two-years-old wood. By this means the quantity
of food for the nascent branch was intended to be so
great as to insure it against suffering from an inade-
quate supply, until it had formed roots. ‘The im-
portance of this has already been shown by Mr.
Knight in a previous part of this Book.

3. The cuttings were taken off in November, and
not in the spring.* This gave them time to form

* [Taking off the cuttings in November is unquestionably the

OF PROPAGATION BY CUTTINGS. 201

granulations of cellular substance or the lower or
wounded end, before the powers of absorption by the
alburnum were aroused, and so to protect themselves
against a too copious supply cf aqueous matter before
the growing bud could dispose of it by its leaves
(64). This protection is afforded by the thinnest
stratum of new cellular tissue, which covers over the
ends of the wounded vessels, and acts as a vital filter
through which all the crude food must pass from the
soil. 7

4, The lower end of the cuttings was so divided as
to be parallel with the bottom of the pot; and it
appears from the context, although it is not expressly
so stated, that this end was to touch the bottom of
the pot.» The importance of this precaution is well
known; cuttings of the Lemon and Orange, which
are by no means willing to strike if it is neglected,
become young plants readily if it is attended to; and
in all difficult cases it is had recourse to. The object
of it seems to be to place the absorbent or root end
of the cutting in a situation where, while it is com-
pletely drained of water, it may, nevertheless, be in
better practice in so mild a climate as that of England; and is pre-
ferable, even in this country, with all very hardy shrubs, as the
Currant, &e. But in the case of those which are more tender in the
bark, as some of the varieties of the common Althea, the severe
frost of our winters often seriously injures or destroys the cuttings.
When of moderate size, they are also liable to be thrown out by the
heaving of the ground in spring: we therefore generally prefer
early spring planting, for cuttings, But they often succeed best
when they are taken off in November, kept in damp mould in the
cellar through the winter, and carefully planted in March or April.
a0 DB)

g*

202 APPLICATION OF PRINCIPLES.

the vicinity of a never-failing supply of aqueous
vapour. If it were surrounded by earth, water would
readily collect about it in a condensed state, and the
vessels being all open in consequence of being cut
through, would rise at once into the interior; but
the application of the root end immediately to the
earthen bottom of the pot, with which it is so cut as
to be nearly parallel, necessarily prevents any such
accumulation and introduction of water, unless over-
watering is allowed, and this all good gardeners
will take care to avoid. An ingenious plan of Mr.
Forsyth’s is intended to answer this purpose rather
more perfectly. He
puts a small sixty pot
(jig. 20, a d) into one
of larger size, having
first closed up the bot-
tom of the former with
clay (a); then having
filled the bottom of the
outer pot with crocks,
he fills up the sides
(ec c) with propagating
soil, in which his cuttings are so placed that their
root ends rest against the sides of the inner pot; the
Jatter is then filled with water, which passes very
slowly through the sides until it reaches the cuttings.
(See Gardener's Magazine, vol. xi. p. 564.) In many
cases, especially in striking such plants as Heaths,
gardeners employ a stratum of silver sand, placed
immediately over the earth in which such plants

OF PROPAGATION BY CUTTINGS. 203

love to grow. The cuttings are inserted into the
sand, but so near the earth that the roots, presen.
after their emission, find themselves in it, and conse-
quently in contact with a source of food. This sand
answers the same purpose as placing the root end of
the cutting in contact with the pot, and is an ingeni-
ous device for doing that with small cuttings, which
cannot be conveniently done otherwise except with
large ones.

5. The cuttings are eventually placed in a hot-
bed. This is for the purpose of giving them a stimu-
lus at exactly that time when they are most ready to
receive it. Had they been forced at first in bottom
heat, the stimulus would have been applied to cut-
tings whose excitability had not been renovated
(118), and the consequence would have been a deve-
lopement of the powers of growth so languid, that
they probably would not have survived the coming
winter: but, the stimulus being withheld till the cut-
tings are quite ready for growth, it tells with the
utmost possible effect.

In addition to these comments upon an excellent
mode of striking cuttings of many kinds, it is neces-
sary to add some observations upon the object of
additional precautions often taken by gardeners.

Cuttings are covered by bell glasses, whose edge is
pressed into the earth. This is for the purpose of
preserving a uniform degree of humidity in the
atmosphere breathed by the cuttings. It is gene-
rally necessary to leave one or more leaves upon
a cutting, in order to generate organisable matter,

204 APPLICATION OF PRINCIPLES.

and to assist in the formation of roots; but this is a
very delicate operation, for, if the leaf is allowed
to suffer by excessive perspiration, the cuttings must
necessarily perish (75). To maintain a steady saturat-
ed atmosphere around a cutting stops this
danger, and hencetheuse of abell glass. A
double glass has been lately recommended
(fig. 21); butif this precaution is of any
value, it must be, not because it main-
tains an even temperature, which is
injurious rather than useful, but because it prevents
condensation upon the inner bell glass, and the con-
sequent abstraction of atmospheric moisture, and pro-
bably acts at the same time as a kind of shade.

Notwithstanding the precaution of covering cut-
tings with a bell glass, shade is also necessary, as a
further security against perspiration ; for light acts as
a specific stimulus (71), whose effects are very diffi-
cult to counteract. It must, however, be employed
with great caution; for, if there is not light enough,
the leaves attached to the cuttings cannot form that
organisable matter out of which roots are produced.

All gardeners know that the root end of a cutting
should be close below a leaf-bud; this is to facilitate
the emission of roots by the buds, which emission
must necessarily take place with greater or less diffi-
culty in proportion as their exit is facilitated or imped-
ed by the pressure of bark on them.*

* [The amateur will find it advantageous to take off the cutting,
when delicate or short, close up to the main stem, so as to preserve
the collar or enlarged portion of wood at the base of the branch.

OF PROPAGATION BY CUTTINGS. 205

No further precautions are taken with cuttings,
nor does it at first sight appear possible to suggest
any; nevertheless, the enormous constitutional dif-
ference among plants is such, that, while numerous
species will strike without any difficulty under almost
any circumstances, with the wood ripe or half-ripe,
just formed or aged, there are many others which no
art has yet succeeded in converting into plants; and
it is-by no means uncommon to find that, out of a
potful of cuttings of the same species, apparently all
alike and subjected to exactly the same treatment,
one will grow and the remainder fail. Itis, therefore,
one of the most probable of all things, that the prin-
ciples of striking cuttings are still very imperfectly
understood, and that this is one of the points of
horticulture in which there is the greatest room for
improvement.

It may be worthy of inquiry whether bell glasses
of different colours will not produce different effects
upon cuttings, in consequence of their different power
of transmitting light. It has been shown by Dr.
Daubeny, in a very interesting paper in the Philoso-
phical Transactions for 1836, page 149, that glass of
different colours exercises very different effects upon
the plants exposed to the rays of solar light passing
through it; that both the exhalation and absorption
of moisture by plants, so far as they depend upon the
influence of light, are affected in the greatest degree

This consists of a collection of latent buds or fibres, from which
roots are emitted with much greater facility than from any other
portion. A. J. D.]

206 APPLICATION OF PRINCIPLES,

by the most luminous rays; and that all the functions
of the vegetable economy, which are owing to the
presence of this agent, follow in that respect the same
law. In these experiments, it was ascertained that
the glass employed admitted the passage of the rays
of light in the following proportions:

Transparent. Orange. Red. Blue. Purple. Green.

Luminous rays 7 6 4 4 3 5
Calorifie rays q 6 5 8 4 2
Chemical rays vi 4 0 6 6 3

M. Decaisne found, during some experiments to
ascertain the effect of light in causing the production
of colouring matter in the Madder plant, that when
the lower parts of a plant were inclosed in cases
glazed at the side with transparent green, red, or yel-
low glass, the leaves and stem of the part surrounded
by red glass became pallid, and exhibited signs of
suffering in a greater degree than under the other
colours, but all were affected more or less.* (Hecher-
ches sur la Garance, p. 23.)

We, however, require very different experiments
from any yet instituted, before we can proceed to draw
practical conclusions as to the relative effects upon
plants of glass of different colours. We do not know
what the effect is of the calorific and chemical rays,
and therefore we cannot say what may be the advan-
tage or disadvantage of their action upon plants.
As, however, the object of the cultivator is to protect

* The nature of these experiments has been misapprehended in
the translation, by Mr. Francis, of Meyen’s Report on Vegetable
Physiology, for 1837, p. 51.

OF PROPAGATION BY LAYERS AND SUCKERS. 207

his cuttings from too much light, and at the same
time to give them enough to enable them to perform
their digestive functions steadily, there can be little

doubt that transparent glass is inferior to that of ano-
ther colour.

Ula Pilar gobs
OF PROPAGATION BY LAYERS AND SUCKERS.

Wirt regard to layers, there is but little which it
is necessary to say regarding them, if what has been
stated respecting eyes, leaves, and cuttings, has been
rightly understood and well considered. A layer isa
branch bent into the earth, and half cut through at
the bend, the free portion of the wound being called
“a tongue.” Itis, in fact, a cutting only partially se-
parated from its parent.

The object of the gardener is to induce the layer to
emit roots into the earth at the tongue. With this
view he twists the shoot half round, so as to injure
the wood-vessels ; he heads it back so that only a bud
or two appears above ground; and, when much nicety
is requisite, he places a handful of silver sand round
the tongued part; then pressing the earth down with
his foot, so as to secure the layer, he leaves it without
further care. The intention of both tongueing and
twisting is to prevent the return of sap from the layer

208 APPLICATION OF PRINCIPLES.

into the main stem, while a small quantity is allowed
to rise out of the latter into the former; the effect of
this being to compel the returning sap to organize it-
self externally as roots, instead of passing downwards
below the bark as wood. The bending back is to
assist in this object, by preventing the expenditure of
sap in the formation, or rather completion, of leaves ;
and the silver sand is to secure the drainage so neces-
sary to cuttings.

In most cases, this is sufficient; but it must be
obvious that the exact manner in which the layering
is effected is unimportant, and that it may be varied
according to circumstances. Thus, Mr. James Munro
describes a successful method of
layering brittle-branched plants
by simply slitting the shoot at
the bend, and inserting a stone
at that place (Gardener's Maga-
zine, ix. 302): and Mr. Knight
found that, in cases of difficult
_ rooting, the process is facilitated
by ringing the shoot just below
the tongue, about midsummer,
when the leaves upon the layers
had acquired their full growth
(Hort. Trans., 1. 256); by which
means he prevented the passage
, of the returning sap further
downwards than the point in-
tended for the emission of roots.

It will sometimes happen that

OF PROPAGATION BY LAYERS AND SUCKERS. 209.

the branch of a plant cannot be conveniently bent
downwards into the earth; in such cases, the earth
may be elevated to the branch by various contri-
vances, as is commonly done by the Chinese. (jig.
22.) When this is done, no other care is necessary
than that required for layers, except to keep the earth
surrounding the branch steadily moist.

Suckers are branches naturally thrown up by a
plant from its base, when the onward current of
growth of the stem is stopped. Every stem, even the
oldest, must have been once covered with leaves;
each leaf had a bud in its axil; but, of those buds,
few are developed as branches, and the remainder
remain latent or perish. When the onward growth of
a plant is arrested, the sap is driven to find new out-
lets, and then latent buds are very likely to be deve-
loped; in fact, when the whole plant is young, they
Inust necessarily shoot forth under fitting circum-
stances; the well-known effect of cutting down a tree
is an exemplification of this. Such branches, if they
proceed from under ground, frequently form roots at
their base, when they are employed.as a means of
propagation ; and, in the case of the Pine-apple, they
are made use of for the same purpose, although they
do not emit roots till they are separated from the pa-
rent. Gardeners usually satisfy themselves with tak-
ing from their Pine-apple plants such suckers as are
produced in consequence of the stoppage of onward
growth by the formation of the fruit: but these are
few in number, and not at all what the plant is

capable of yielding. Instead of throwing away the

210 APPLICATION OF PRINCIPLES.

“stump” of the Pine apple, it should be placed in a
damp pit, and exposed to a bottom heat of 90° or
thereabouts, when every one of the latent eyes will
spring forth, and a crop of young plants be the re-
sult. Mr. Alexander Forsyth, a very sensible writer
upon these subjects, pointed this out some years since
in the Gardener’s Magazine (xii. 594); and there can
be no doubt that his observations upon the folly of
throwing away stumps are perfectly correct both in
theory and practice.

The practice of scarring the centre of bulbs, the
heads of Echinocacti and such plants, and the crown
of the stem of species like Litteea geminiflora, in all
which cases suckers are the result, is explicable upon
the foregoing principles.

CHAPTER XIL
OF PROPAGATION BY BUDDING AND GRAFTING.

THESE operations consist in causing an eye or a
cutting of one plant to grow upon some other plant,
so that the two, by forming an organic union, become
a new and compound individual. The eye, in these
cases, takes the name of bud, the cutting is called a
scion, and the plant upon which they are made to
grow is named the stock.

Propagation by eyes and cuttings is, therefore, the
same as budding and graftmmg, with this important

OF PROPAGATION BY BUDDING AND GRAFTING. 211

difference, that in the one case the fragments of a plant
are made to strike root into the inorganic soil, and to
grow on their own bottom, as the saying is, while in
the other they emit the equivalent of roots into liv-
ing organic matter. In like manner, the operation of
inarching, or causing the branch of one plant to
remain attached to its parent, and at the same time to
grow upon the branch of another tree, is analogous
to layering.

The objects of these operations are manifold. Many
plants, such as the Pear and the Apple, will bud or
graft freely, but are difficult to strike from cuttings.
Species which are naturally delicate become robust
when “worked” on robust stocks; and the conse-
quence is a more abundant production of flowers and
fruit; thus the more delicate kinds of Vines produce
larger and finer grapes when worked upon such coarse,
robust sorts as the Syrian and Nice. The Double
yellow Rose, which so seldom opens its flowers, and
whieh will not grow at all in many situations, blos-
soms abundantly, and grows freely, when worked
upon the common China Rose. (See Hort. Trans. v.
370.) The peculiar qualities of some plants can only
be preserved by working: this is especially the case
with certain kinds of variegated Roses, which retain
their gay markings when budded, but become plain
if on their own bottom. (Jb. 492.) Fruit may be ob-
tained from seedling plants by these processes much
earlier than by any others, and thus many years’ un-
certain expectation may be saved : indeed, Mr. Knight
ascertained that it is possible to transfer the blossom-

212 APPLICATION OF PRINCIPLES.

buds of one plant to another, so as to obtain flowers
or fruit from them immediately. He thus fixed on
the Wild Rose the flower-buds of Garden Roses,
“and these buds, being abundantly supplied with
nutriment, afforded much finer roses than they would
have done had they retained their natural situation.”
He repeated many similar experiments upon the
Pear and Peach trees with similar success; but, in
the case of the Pear, he found that if the buds were
inserted earlier than the end of August or begin-
ning of September, they became branches and not
flowers.

The manner in which these operations may be
practised is exceedingly various, and an abundance
of fanciful methods have been devised, for an account
of which the reader is referred to Thouin’s Mono-
graphie des Greffes; to the article “Greffe” by the
same author, in the Nouveau
Cours complet d’ Agriculture,
&c., edition of 1822; to Lou-
don’s Encyclopedia of Garden-
ing, part ii.; and to the Gar-
dener’s Magazine, vol. x. p.
305. I shall only -here de-
scribe the commoner and more
important methods.

BuDDING consists in intro-
ducing a bud of one tree, with
a portion of bark adhering
to it, below the bark of ano-
ther tree. In order to effect

OF PROPAGATION BY BUDDING. 218

this, a longitudinal incision is made through the bark
of the stock down to the wood, and is then crossed at
the upper end by a similar cut (fig. 28, a), so that the
whole wound resembles the letter T. Then from the
scion is pared off a bud with a portion of the bark
(fig. 28, 6), and the latter is pushed below the bark
of the stock until the bud is actually upon the naked
wood of the stock; the upper lips of the wound in
the stock and that of the bud are made to coincide,
the whole are fastened down by a ligature, and the
operation is complete.

By these means we gain the important end of
bringing in close contact a considerable surface of
young organising matter. The organisation of wood
takes place on its exterior, and that of bark on its
interior surface, and these are the parts which are
applied to each other in the operation of budding;
in addition to which the stranger bud finds itself, in
its new position, as freely in communication with ali-
mentary matter, or more so, than on its parent branch.
A union takes place of the cellular faces, or horizon.
tal system, of the stock and bark of the bud, while
the latter, as soon as it begins to grow, sends down
the woody matter, or vertical system, through the
cellular substance. In consequence of the horizontal
incision, the returning sap of the scion is arrested in
its course, and accumulates a little just above the new
bud, to which it is gradually supplied as it is required.
Sometimes the whole of the wood of the bud below
the bark is allowed to remain; and, in that case,
coniact between the organising surfaces of the stock

214 APPLICATION OF PRINCIPLES.

and scion does not take place, and the union of the
two is much less certain: as it is, however, usually
practised with tender shoots before the wood is con-
solidated, the contact spoken of is of less moment.
Tn all cases, a portion of the wood of the bud must
be left adhering to it, or the bud will perish ; because
its most essential part is the young woody matter in
its centre, and not the external surface, which is a
mere coating of bark.*

In the Agricultural Journal of the Pays Bas for
October, 1824, it is recommended to reverse the
usual mode of raising the bark for inserting the buds,
and to make the cross cut at the bottom of the slit,
instead of at the top, as is generally done in Britain.
The bud is said rarely to fail of success, because it
receives abundance of the descending sap, which it
cannot receive when it is under the cross cut. This
explanation is unintelligible, and there is no ap-
parent advantage in the method; it is, however,
practised by the orange-growers of the South of
France.

Mr. Knight was accustomed on some occasions to
employ two distinct ligatures to hold the bud of his
Peach trees in its place. One was first placed above
the bud inserted; and upon the transverse section

* [This is the universal opinion, but it is not always practically
true; for if the operation be performed at a favorable period, when
the tree abounds with sap, the space left by extracting the woody
matter will be almost immediately filled by a new deposit. But
leaving the wood in the bud, in working fruit-trees, is the general
and most successful practice. A. J. D.]

OF PROPAGATION BY BUDDING. 215

through the back; the other, which had no further
office than that of securing the bud, was employed in
the usual way. As soon as the bud had attached
itself, the ligature last applied was taken off: but the
other was suffered to remain. The passage of the

, sap upwards was in consequence
much obstructed; and buds inserted
in June began to vegetate strongly
in July: when these had afforded
shoots about four inches long, the
remaining ligature was taken off to
permit the excess of sap to pass on*
and the young shoots were nailed to
the wall. Being there properly ex-
posed to light, their wood ripened
well, and afforded blossoms in the
succeeding spring.

Flute-budding (fig. 24) is not
practised in this country, but de-
serves to be mentioned. It consists
of peeling off a ring of bark from
the stock, just below a terminal
bud; replacing it by a similar ring,
with a bud or two upon it, taken

* Nurserymen and others find this tyifg with double ligature of
great service in budding the plum. The difficulty in working this
tree arises from the tendency of the upper part of the bud to curl up
and detach itself after the ordinary single tie is taken off, and the
union apparently complete. By leaving on the upper ligature a
fortnight after the lower one, this tendency to rupture is prevented,
and the upper bandage may then be removed with safety, and
before the bud has been excited into growth. A. J. D.

216 APPLICATION OF PRINCIPLES.

from a scion; and binding down the whole. This
is performed only in the spring, and has the advan-
tage of being so contrived that the stranger bud
is placed immediately below that part of a branch
where processes of organisation are most active,
namely, below a central bud of the stock; and from
occupying all the circumference, it must necessarily
receive the whole of the alimentary and organised
matter sent downwards by that bud. It isemployed
in Bavaria for the Mulberry.* (See Gard. Mag. v.
425.)
In GRAFTING no attempt is made to apply the inner
surface of the bark of a scion to the outer sur-
™, face of the wood of the stock ; but the contact
m™ is effected by the wood of the two, and their
@ bark only joins at the edges. Whip-grafting
(fig. 25) is the commonest kind; it is per-
formed by heading down a stock, then paring
one side of it bare for the space of an inch
or so, and cutting down obliquely at the
upper end of the pared part, towards the pith;
the scion is levelled obliquely to a length
corresponding with the pared surface of the
stock, and an incision is made into it near
the upper end of the wound obliquely up-
wards, so as to form a “tongue,” which is
forced into the corresponding wound in the
stock ; care is then taken that the bark of the
scion is exactly adjusted to that of the stock,
and the two are bound firmly together.

* [The success of thia practice will be found to depend mate-

OF PROPAGATION BY GRAFTING. 217

Here the mere contact of the two enables the sap
flowing upwards through the stock to sustain the life of
the scion until the latter can develope its buds, which
then send downwards their wood; at the same time
the cellular system of the parts in contact unites by
granulations ; and, when the wood descends, it passes
through the cellular deposit, and holds the whole toge-
ther. The use of “tongueing” is merely to steady the
scion, and to prevent its slipping. The advantage of
this mode of grafting is the quickness with which it
may be performed; the disadvantage is, that the sur-
faces applied to each other are much smaller than can
be secured by other means. It is, however, a great
improvement upon the old crown-grafting, still em-
ployed in the rude unskilful practice of some Conti-
nental gardeners, but expelled from Great Britain ;
which consists of nothing more than heading down a
stock with an exactly horizontal cut, and splitting it
through the middle, into which is forced the end of
a scion cut into the form of a wedge; when the whole
are bound together. In this method the split in the
stock can hardly be made to heal without great care:
the union between the edges of the scion and those

rially upon choosing the exact time or seasgn for performing the
operation. In some trees, if it be attempted a few days earlier
or later than « certain period, the operator will experience great
difficulty in effecting that which might have been done with the
greatest ease at a more favourable moment. The bark of the stock
should part very readily on introducing the budding-knife; the
young wood from which the buds are taken should also be in pro-
per condition, not too young, as it would not have sufficient consis-
tency, but just when assuming the appearance of ripening. A. J, D.]

10

218 APPLICATION OF PRINCIPLES.

of the stock is very imperfect, because the bark
of the former necessarily lies upon the wood of
the latter, except just at the sides; and, from the
impossibility of bringing the two barks in contact,
neither the ascending nor descending cur-
rents of sap are able freely to intermin-
ja gle. This plan, much improved by cut-
= ting out the stock into the form of a wedge,
instead of splitting it, may, however, be
advantageously employed for such plants
as Cactaceze (fig. 26), the parts of which,
owing to their succulence, readily form a
union with each other.
A far better method than whip-graft- 27
ing, but more tedions, is saddle-graft-
ing (fig. 27); in which the stock is
pared obliquely on both sides till it be-
comes an inverted wedge, and the scion
is slit up the centre, when its sides are
pared down till they fit the sides of
the stock. In this method, the great-
est possible quantity of surface is
brought into contact, and the parts are
mutually so adjusted, that the ascend-
ing sap is freely received from the
stock by the scion, while, at the same
time, the descending sap can flow
freely from the scion into the stock.
Mr. Knight, in describing this mode of operating, has
the following observations :
“The graft first begins its efforts to unite itself to

OF PROPAGATION BY GRAFTING. 219

the stock just at the period when the formation of a
new internal layer of bark commences in the spring ;
and the fluid which generates this layer of bark, and
which also feeds the inserted graft, radiates in every
direction from the vicinity of the medulla to the
external surface of the alburnum. The graft is, of
course, most advantageously placed when it presents
the largest surface to receive such fluid, and when
the fluid itself is made to deviate least from its natu-
ral course. This takes place most efficiently when
(as in this saddle-grafting) a graft of nearly equal size
with. the stock is divided at its base and made to
stand astride the stock, and when the two divisions
of the graft are pared
extremely thin, at and
near their lower extre-
mities, so that they
may be brought into
close contact with the
stock (from which but
little bark or wood
should be pared off)
by the ligature.” (Hort.
Trans. v. 147.) To ex-
ecute saddle-grafting

properly, thescion and ¥
stock should, be of
equal size: and, where |}
that cannot be, a se-
cond method, in which |
the scion may be much ‘a

rll

220 APPLICATION OF PRINCIPLES.

smaller than the stock, bas been described by the
same great gardener. This (jig. 28) is practised
upon small stocks almost exclusively in Here-
fordshire; but it is never attempted till the usual
season of grafting is past, and till the bark is rea-
dily detached from the alburnum. The head of
the stock is then taken off, by a single stroke of
the knife, obliquely, so that the incision commences
about the width of the diameter of the stock below
the point where the medulla appears in the section,
and ends as much above it, upon the opposite side.
The scion, or graft, which should not exceed in dia-
meter half that of the stock, is then to be divided
longitudinally, about two inches upwards from its
lower end, into two unequal divisions, by passing the
knife upwards, just in contact with one side of the
medulla. The stronger division of the graft is then
to be pared thin at its lower extremity, and intro-
duced, as in crown-grafting, between the bark and
wood of the stock; and the more slender division is
fitted to the stock upon the opposite side. The graft,
consequently, stands astride the stock, to which it
attaches itself firmly upon each side, and which
it covers completely in a single season. Grafts of
the Apple and Pear rarely ever fail in this method
of grafting, which may be practised with equal success
with young wood in July, as soon as it has become
moderately firm and mature.*

* A very neat and satisfactory mode of propagating fruit trees
when large stocks are not at hand, is to take small pieces of the
roots of the proper kinds of stocks and graft the scions on these

OF PROPAGATION BY GRAFTING. 221

In all these methods, and in every other that could
be named, it is indispensable that similar parts should
be brought as much as possible into contact; for the
more completely this is accomplished, the more cer-
tain is the operation to succeed. It is undoubtedly
true, that, as the cellular system of a tree is diffused
through its whole diameter (43, 46), it is impossible
to apply a scion to a stock without their cellular sys-
tems coming in contact; and, therefore, it might ap-
pear indifferent whether bark is applied to bark and
alburnum to alburnum, or whether the bark is adapt-
ed to the wood and the latter to the liber. But it is
always to be remembered that each of these parts has
special modifications of its own, which modifications
require contact with parts similarly modified, in or-
der to unite readily and firmly; and also, that, al-

roots, by common whip grafting. Then plant them at once, cover-
ing the point of union about two inches under the surface of the
soil. Small seedling apple stocks, one year old, even if only the
thickness of the graft, answer perfectly well in this manner.

The apple tree is propagated in American nurseries, by millions
every year, by grafting the roots, or rather the stocks headed down
to an inch or so above the crown of the root, splitting them, and
inserting the scion sloped to a wedge shape in the common mode of
cleft grafting. The two year seedling stocks used for this purpose,
are usually lifted in the autumn, and buried in a cellar for this pur-
pose. The grafts are inserted in winter by the fire-side; when
grafted, the scion is held firm by a bit of matting bound round the
stock, the latter is then packed away in the cellar till spring. Then
the grafts are planted out in rows in the nursery, and by autumn
they have grown from three to six feet high. As the earth covers
the graft-wound no grafting clay or wax is needed, and the whole,
except planting, is done in winter, when labor is least valuable.

AJ. D.

222 APPLICATION OF PRINCIPLES.

though the cellular horizontal system, through which
union by the first intention takes place, may be alive
on all parts of the section of a branch, yet that it isin
the bark, and in the space between the bark and
wood, that its developement is most rapid, and its
tendency to growth most easily excited and main-
tained.

It is not, however, to be supposed that these opera-
tions can be performed indifferently, between any two
species, although such was formerly so general a
belief that it was asserted that roses became black
when grafted on Black Currants, and oranges crim-
son if worked on the Pomegranate.* In point of
fact, the operations are successful in those cases only
where the stock and scion are very nearly allied ; and
the degree of success is in proportion to the degree of
affinity. Thus, varieties of the same species unite the
most freely, then species of the same genus, then
genera of the same natural order; beyond which the
power does not extend, unless, in the case of parasites
like the Mistletoe, which grow indifferently upon
totally different plants. For instance, Pears work
freely upon Pears, very well on Quinces, less willing-
ly on Apples or Thorns, and not at all upon Plums
or Cherries; while the Lilac will take on the Ash,
and the Olive on the Phillyrea, because they are
plants of the same natural order. M. De Candolle

* Et steriles platani malos gessére, valentes
Castanez fagos, ornusque incanuit albo
Flore pyri, glandemque sues fregére sub ulmis,
Georg. lib. ii.

OF PROPAGATION BY GRAFTING. 223

even says that he has succeeded, notwithstanding the
great difference in their vegetation, to work the Lilac
on the Phillyrea, the Olive on the Ash, and the
Bignonia radicans on the Catalpa; but plants so ob-
tained are very short-lived. For some curious parti-
culars upon this subject, see Physiologie Végétale, p.
788, &e.

There are two cases apparently at variance with
this law; both of which require explanation.

1. Columella asserts that, by a particular manner
of grafting, the Olive may be made to take upon the
Fig tree, and his words have been repeated by many
writers; but Thouin proved, experimentally, that no
such union will take place, and that where success
appears to attend Columella’s operation, it is owing
to the scion rooting into the soil, independently of
the Fig stock (see Mémoire sur la prétendue Greffe
Columelle), and becoming a layer.

2. Mention is made by Pliny of a tree in the gar-
den of Lucullus, which was so grafted as to bear pears,
apples, figs, plums, olives, almonds, grapes, &c.; and
at this day the gardeners of Italy, especially of Genoa
and Florence, sell plants of Jasmines, Roses, Honey-
suckles, &., all growing together from a stock of
Orange, or Myrtle, or Pomegranate, on which they
say they are grafted. But this is a mere cheat, the
fact being that the stock has its centre bored out, so
as to be made into a hollow cylinder, through which
the stems of Jasmines and other flexible plants are
easily made to pass, their roots intermingling with
those of the stock; after growing for a time, the hori-

224 APPLICATION OF PRINCIPLES.

zontal distension of the stems forces them together,
and they assume all the appearances of being united.
Such plants are, of course, very short-lived.

From what has been now stated, it may be easily
conceived that the choice of the stock on which a
given plant is to be worked is by no means a matter
of indifference, but that the operation may be serious-
ly affected by the skill with which the most suitable
stock is selected. If, indeed, we had no other object
in view in grafting than to unite one plant to ano-
ther, that object would doubtless be best attained by
using the same species, and even a similar variety of
the same species, for both stock and scion; the ends
of grafting and budding are, however, much beyond
this, and it often happens that the species to which a
scion belongs, or the nearest variety, is the worst on
which it can be worked. It is, indeed, sometimes
asserted that the stock exercises little influence over
the scion, but this is so great an error that it cannot
be too distinctly contradicted. This subject has al-
ready been adverted to, but it now requires more
special consideration.

One of the first objects of budding and grafting, is
to multiply a given species or variety more readily
than is possible by any other method. If this is the
only purpose of the cultivator, that stock will obvi-
ously be the best which can be most readily procur-
ed; and hence we see, in the ordinary practice of the
nurseries, the common Plum taken as a stock for
Peaches and Apricots, the Wild Pear and Crab for
Pears and Apples, and so on. When there is a diffi-

OF PROPAGATION BY GRAFTING. 225

culty in procuring a suitable stock, pieces of the roots
of the plant to be multiplied are often taken as a sub-
stitute, and they answer the purpose perfectly well;
for the circumstance which hinders the growth of
pieces of a root into young branches ‘s merely their
want of buds: if ascion is grafted upon a root, that
deficiency is supplied, and the difference between the
internal organisation of a root and a branch is so
trifling as to oppose no obstacle to the solid union of
the two.

Mr. Knight was the first to show the possibility of
grafting scions upon roots. An account of his me-
thod of doing this was given at a very early period
of the existence of the Horticultural Society (June,
1811), and he at the same time suggested the possibi-
lity of the practice being applied to grafting scarce
herbaceous plants upon the roots of their commoner
congeners; an operation now commonly practised
with the Dahlia, Peony, and other plants of a similar
kind; and lately a method of multiplying Combre-
tum purpureum by similar means has been pointed
out in the Proceedings of the Horticultural Society, i.
40.

Mere propagation is, however, by no means the
only object of the grafter; another and still more im-
portant one is, to secure a permanent union between
the scion and stock, so that the new plant may grow
as freely and as long as if it were on its own bottom
under the most favourable circumstances. If this is
not attended to, the hopes of the cultivator will be
frustrated by the early death of his plant.

10*

226 APPLICATION OF PRINCIPLES.

Whenever the stock and graft or bud are not per-
fectly well suited to each other, an enlargement is
well known always to take place at the point of their
junction, and generally to some extent either above
or below it. Thisis particularly observable in Peach
trees which have been budded, at any considerable
height from the ground, upon Plum stocks; and it
appears to arise from the obstruction which the de-
scending sap of the Peach tree meets with in the bark
of the Plum stock; for the effects produced, both
upon the growth and produce of the tree, are simi-
lar to those which occur when the descent of the
sap is impeded by a ligature, or by the destruc-
tion of a circle of bark. In course of time this
difference between the scion and stock puts an
end to the possibility of the ascending and de-
scending fluids passing into each other, and the
death of the scion is the result. In all the cases I
have seen, this has arisen from the power of hori-
zontal growth in the stock and scion being different;
and I doubt whether it ever proceeds from any other
cause. For example: the Hawthorn and the Pear
are so nearly allied that the latter may be easily work-
ed upon the former; the Hawthorn is, however, a
slow-growing bush or small tree; the Pear is a large
forest tree of rapid growth; and the Pear will grow
an inch in diameter while the Hawthorn is growing
half an inch.

This last circumstance, if the difference in the rate
of growth or in other respects is not excessive, may
be taken advantage of for particular purposes. When

OF PROPAGATION BY GRAFTING. 227

trees grow too large for asmall garden, it is desirable
to dwarf them; and when they are naturally unfruit-
ful, to render them productive; both which effects
result, at the same time, from grafting them upon
stocks that grow slower than themselves. Thus the
Apple is dwarfed by grafting on the Paradise stock,
and the Pear by the Quince. The physiological ex-
planation of trees dwarfed by being compelled to
grow upon a stock which compels their descending
sap to accumulate in the branches has been already
given (85). Instead of repeating it here, I take the
following paragraph from the paper by Mr. Knight,
“ On the Effects of Different Kinds of Stocks in Graft-
ing,” published in the Horticultural Transactions, ii.
199.

“The disposition in young trees to produce and
nourish blossom buds and fruit is increased by this
apparent obstruction of the descending sap; and the
fruit of such young trees ripens, I think, somewhat
earlier than upon other young trees of the same age,
which grow upon stocks of their own species; but
the growth and vigour of the tree, and its power to
nourish a succession of heavy crops, are diminished,
apparently, by the stagnation, in the branches and
stock, of a portion of that sap which, in a tree grow-
ing upon its own stem, or upon a stock of its own
species, would descend to nourish and promote the
extension of the roots. The practice, therefore, of
grafting the Pear tree on the Quince stock, and the
Peach and Apricot on the Plum, where extensive
growth and durability are wanted, is wrong; but it is

228 APPLICATION OF PRINCIPLES.

cligible wherever it is wished to diminish the vigour
and growth of the tree, and where its durability is
not thought important.

“When,” adds this great gardener, ‘much diffi-
culty is found in making a tree, whether fructiferous
or ornamental, of any species or variety, produce
blossoms, or in making its blossoms set when pro-
duced, success will probably be obtained in almost all
cases by budding or grafting on a stock which is
nearly enough allied to the graft to preserve it alive
for a few years, butnot permanently. The Pear tree
affords a stock of this kind to the Apple; and I have
obtained a heavy crop of Apples from a graft which
had been inserted in a tall Pear stock only twenty
months previously, in a season when every blossom
of the same variety of fruit in the orchard was destroy-
ed by frost. The fruit thus obtained was externally
perfect, and possessed all its ordinary qualities; but
the cores were black and without a single seed; and
every blossom had certainly fallen abortively, if it
had been growing upon its native stock. The expe-
rienced gardener will readily anticipate the fate of the
graft; it perished in the following winter. The stock,
in such cases as the preceding, promotes, in propor-
tion to its length, the early bearing and early death
of the graft.”

It is sometimes desirable to increase the hardiness
of a variety, and grafting or budding appears to pro-
duce this effect to a certain extent, not, indeed, by
the stock communicating to the scion any of its own
power of resisting cold, but by the stock being better

OF PROPAGATION BY GRAFTING. 229

suited to the soil of latitudes colder than that from
which the scion comes, and consequently requiring a
lower bottom-heat to arouse its excitability. Mr.
Knight, indeed, denies the fact, because “the root
which nature gives to each seedling plant must be
well, if not best, calculated to support it;” and it is so,
under the circumstances in which the species was first
created; but, without this addition, the paragraph
quoted in inverted commas is specious only, not just.
Probably, in Persia, the native country of the Peach,
that species, or its wild type the Almond, is the best
stock for the former fruit; because the temperature
of the earth (see 117, 118, 119, and Book II. Ch. L.)
is that in which it was created to grow. But ina
climate like that of England, the temperature of
whose soil is so much lower than that of Persia, the
Plum, on which the Peach takes freely, is a hardy
native, and suited to such soil, and its roots are
aroused from their winter sleep by an amount of
warmth unsuited to the Peach. And experience, in
this case, completely confirms what theory teaches;
for, although there may be a few healthy trees
in this country growing upon Almond stocks, it is
perfectly certain that the greater part of those which
have been planted have failed; while, in the warm
soil of France and Italy, it is the stock upon which
the old trees have, in almost all cases, been budded.
Tn determining upon what kind of stock a given
fruit tree should be grafted, it is important to be
aware that certain species prefer particular soils and
dislike others, for reasons which are not susceptible

230 APPLICATION OF PRINCIPLES.

of explanation. In the case of the common stocks
employed for the propagation of the Apple, Pear,
Peach, and Cherry, it was found by Mr. Dubreuil,
an intelligent gardener at Rouen, that in the chalky
gardens about that city neither the Plum nor the
wild Cherry would succeed for stone fruit, nor the
Doucin or Quince stock for Pears and Apples; but
that the Crab suited the Apple, the wild Pear the
cultivated Pear, the Almond the Peach, and the Ma-
haleb the Cherry. I formerly witnessed the result of
those experiments while in progress, and I well
remember the sickly state of his peaches and Cherries
grafted on Plum and Cherry stocks in the calcareous
borders of the rampart gardens of Rouen, and the
healthiness of the same fruit trees in the same garden,
when worked upon the Almond and the Mahaleb,
while the latter were unhealthy in their turn in the
borders composed artificially of loam. The result
of this experiment has been mentioned in the Hort.
Trans.., iv. 566, and is as follows :—

Loamy Soil. Chalky. Light.*
Apple Doucin Crab Doucin.
Pear Quince Wild Pear Quince.
Plun Plum Almond Almond.
Cherry Wild Cherry Mahaleb Wild Cherry.+

As this work treats exclusively of those operations
in gardening which can be explained upon known

* That is, with an admixture of sand and decayed vegetable
matter.

+ By Wild Cherry here is meant Mazzard, and not our Wild Cherry.
A. J.D,

OF PROPAGATION BY GRAFTING. 231

principles of vegetable physiology, all further refer-
ence to the question of stocks ought, in strictness, to
be dismissed at this stage. It may be as well, however,
to add that there are some well-attested facts relating
to the preference of particular varieties for one kind
of stock rather than another, which we cannot explain,
but which are so important in practice as to deserve
to be studied carefully. There appears to be no
doubt that, as is asserted by Mr. Knight and others
(Hort. Trans., ii. 215; Gard. Mag., vii. 195), the Apri-
cot succeeds better on its own species than on the
Plum. The nurserymen know very well that what
they call French Peaches, such as the Bourdine, Belle
Chevreuse, and double Montague, will only take on
the. Pear Plum, while other varieties prefer the
Muscle Plum; and a variety called the Brompton
suits them all equally well, making handsome trees,
which are, however, uniformly short-lived.* The
Lemon is also found to be a better stock for the
Orange than its own varieties.

It is not merely upon the productiveness or vigour
of the scion that the stock exercises an influence; its
effects have been found to extend to the quality of
the fruit. This may be conceived to happen in two
ways—either by the ascending sap carrying up with
it into the scion a part of the secretions of the stock,
or by the difference induced in the general health of
a scion by the manner in which the flow of ascending
and descending sap is promoted or retarded by the

* See G. Lindley’s Guide to the Orchard and Kitchen Garden, p.
299.

232 APPLICATION OF PRINCIPLES.

stock. In the Pear, the fruit becomes lighter coloured
and smaller on the Quince stock, than on the wild
Pear, still more so on the Medlar; and in these two
instances the ascent and descent of sap is obstructed
by the Quince more than by the wild Pear, and by
the Medlar more than by the Quince. Similar effects
are produced in the Apple by the Paradise and Sibe-
rian Bittersweet stocks. Mr. Knight mentions such
differences in the quality of his Peaches. His garden
contained two trees of the Acton Scott variety, ‘one
growing upon its native stock, the other upon a Plum
stock, the soil being similar and the aspect the same.
That growing upon the Plum stock, afforded fruit of a
larger size, and its colour, where it was exposed to the
sun, was much more red; but its pulp was more
coarse, and its taste and flavour so inferior that he
would have denied the identity of the variety, had he
not with his own hand inserted the buds from which
both sprang.” (Hort. Trans., v. 289.)

In addi:ion to a judicious adaptation of the bud or
scion to the stock, there are other circumstances to
which it is necessary to attend, in order to insure the
success of the operation. It has already been seen
(p. 180), that the youngest buds of the Potato are more
excitable than those more completely matured; and
the same appears to be true of the bud im other fruits.

‘The mature bud,” says Mr. Knight, “ takes imme-
diately with more certainty, under the same external
circumstances: it is much less liable to perish during
winter; and it possesses the valuable property of
rarely or never vegeteting prematurely in the sum-

OF PROPAGATION BY GRAFTING. . 233

mer, though it be inserted before the usual period,
and in the season when the sap of the stock is most
abundant. I have, in different years, removed some
hundred buds of the Peach tree from the forcing-
house to luxuriant shoots upon the open wall; and I
have never seen an instance in which any of such
buds have broken and vegetated during the summer
and autumn; but when I have had occasion to
reverse this process and to insert immature buds from
the open wall into the branches of trees growing in a
Peach-house, many of these, and in some seasons all,
have broken soon after being inserted, though at the
period of their insertion the trees in the Peach-house
had nearly ceased to grow.” (Hort. Trans., iii. 136.)

This property was turned to practical account by
Mr. Knight in budding the Walnut. Owing to the
excitability of its buds, this tree is difficult to work,
because its buds exhaust all their organisable and ali-
mentary matter before any adhesion can be formed
between themselves and the stock; but by taking the
small, fully matured, and little developed buds, found
at the base of the annual shoots of this plant, time is
given for an adhesion between them and the albur-
num before they push forth, and then they take freely
enough. (See Mort. Trans., iii. 135.)

Buds should either be inserted when the vegeta-
tion of a plant is languid, or growth above the place
of insertion should be arrested by pinching the ter-
minal bud; otherwise the sap, which should be
directed into the bud, in order to assist in its adhe-
sion, is conveyed to other places, and the bud

234 APPLICATION OF PRINCIPLES.

perishes from starvation. For similar reasons, when
a bud begins to grow, having firmly fixed itself upon
the stock, the latter should be headed back nearly as
far as the bud, so as to compel all the ascending cur-
rent of sap to flow towards it; otherwise the buds of
the stock itself will obtain that food which the
stranger bud should be supplied with.

In grafting also it is always found that a union be-
tween the scion and the stock takes place most readily
when the latter is headed down ; but thisis not the only
point to attend to. The scion should always be so pre-
pared that a bud is near the point of union between
itself and the stock, because such a bud, as soon as it
begins to grow, proceeds to furnish wood which assists
in binding the two together. The scion should be more
Lackward in its vegetation than the stock, because
it will then be less excitable; otherwise its buds may
begin to grow before a fitting communication is esta-
blished between the stock and scion, and the latter
will be exhausted by its own vigour: if, on the con-
trary, the stock is in the state of incipient growth, and
the scion torpid, granulations of cellular tissue will
have time to form and unite the wound, and the scion
will become distended with sap forced into it from
the stock, and thus be able to keep its buds alive
when they begin to shoot into branches. In order to
assist in this part of the operation, a “ heel” is some-
times in difficult cases left on a scion, and inserted
into a vessel of water, until the union has taken
place; or, for the same purpose, the scion is bound
round with loose string or linen with one end steeped

OF PROPAGATION BY GRAFTING. 235

in water, so as to secure a supply of water to the
scion by the capillary attraction of such a bandage.
IndvsJ, the ordinary practice of surrounding the
scion snd stock at the point of contact with a mass of
grafting clay is intended for the same purpose; that
is to say, to prevent evaporation from the surface of
the scioa, and to afford a small supply of moisture ;
and henw, among other things, the superiority of
clay over tue plasters, mastics, and cements, occasion-
ally employed, which simply arrest perspiration, and
can never assiss in communicating aqueous food to
the scion.

Here also muss be noticed certain practices, which
experience shows to be important, of which theory of-
fers no obvious explanation. Mr. Knight, for exam-
ple, asserts that cutungs taken from the trunks of
seedling old trees grow much more vigorously than
those taken from the extremities of bearing branches;
and it is an undoubted fact that the Beech, and other
trees of a similar kind, cannot be grafted with any
success, unless the scions are made of two-years’-old
wood; one-year-old wood generally fails.

What is called herbaceous grafting, or Tschudy
grafting, depends so entirely upon the same princi-
ples as common grafting, that a separate notice of it
is hardly necessary. Nevertheless, as itis sometimes
very useful, a few words may be given to it. When
two vigorous branches cross each other, and press
together, so as not to move, they will often form an
organic union ; if two apples press together, or if two
cucumbers are forced to grow side by side in a space

236 APPLICATION OF PRINCIPLES.

so small] as to compel them to touch each other firmly,
they also will grow together; and herbaceous graft-
ing is merely an application to practice of this power
of soft and cellular parts to unite. In order to secure
success, the scion and stock, being pared so as to fit
together accurately, are firmly bound to each other,
without being crushed; parts in full vegetation, and
abounding in sap, are always chosen for the opera-
tion, such as the upper parts of annual shoots, near
the terminal bud; perspiration is diminished by the
removal of some of the leaves of both stock and scion,
and by shading (71); and by degrees, as the union
becomes secured, buds and leaves are removed from
the stock, in order that all the sap possible may be
impelled into the scion. This method, if well managed,
succeeds completely in about thirty days, and is use-
ful as a method of multiplying lactescent, resinous,
and hard-wooded trees, which refuse to obey more
common methods. Baron de Tschudy succeeded in
this way in working the Melon on the Bryony (both
Cucurbitaceous plants), the Artichoke on the Car-
doon (both Cynaras), Tomatoes on Potatoes (both
Solanums), and so on. The following account of
managing Conifer, where herbaceous grafting is
used, is taken from the Gardener's Magazine, vol. il.
p. 64, and sufficiently explains the practice :—

“The proper time for grafting pines is when the
young shoots have made about three quarters of their
length, and are still so herbaceous as to break like a
shoot of asparagus. The shoot of the stock is then
broken off about two inches under its terminating

OF PROPAGATION BY GRAFTING. 237

bud; the leaves are stripped off from twenty to
twenty-four lines down the extremity, leaving, how-
ever, two pairs of leaves opposite, and close to the
section of fracture, which leaves are of great import-
ance. The shoot is then split with a very thin knife
between the two pairs of leaves (jig. 29, a,) and to
the depth of two inches. The scion is then prepared
(0): the lower part, being stripped of its leaves to the
length of two inches, is 29

cut, and inserted in the
usual manner of cleft-
grafting. They may also
be grafted in the lateral
manner (c.) The graft is
tied with a slip of woollen,
and a cap of paper is put
over the whole, to protect
it from the sun and rain.
At the end of fifteen days
this cap is removed, and
the ligature at the end of
a month; at that time also
the two pairs of leaves (a), which have served as
nurses, are removed. The scions of those sorts of
pines which make two growths in a season, or, as
the technical phrase is, have a second sap, produce a
shoot of five or six inches in the first year ; but those
of only one sap, as the Corsican Pine, Weymouth Pine,
&c., merely ripen the wood grown before grafting, and
form a strong terminating bud, which in the following
year produces a shoot of fifteen inches, or two feet.”

238 APPLICATION OF PRINCIPLES.

With regard to INARCHING, which was probably
the most ancient kind of grafting, because it is that
which must take place accidentally in thickets and
forests, it differs from grafting in this, that the scion
is not severed from its parent, but remains attached
to it until it has united to the stock to which it is tied
and fitted in various ways; the scion and stock are
therefore mutually independent of each other, and
the former lives uponits own resources, until the union
is completed.

In practice, a portion of the branch of a scion
is pared away, well down into the alburnum; a cor-
responding wound is made in the branch of a stock ;
tongues are made in each wound so that they will fit
into each other; and the liber and al-
burnum of the two being very accu-
rately adjusted, the whole are firmly
bound up; grafting clay is applied to
the wound, and the plants operated
upon are carefully shaded; in course
of time the wounds unite, and then
the scion is severed from its parent.
Gardeners consider this the most cer-
tain of all modes of grafting, but it is
troublesome, and only practised in dif-
ficult cases. The circumstances most
conducive to its success are, to stop the
branch of both stock and scion under
operation, so as to obtain an accumula-
tion of sap, and to arrest the flow of sap
upwards; to moderate the motion of

OF PRUNING. 239

the fluids by shading; to head back the stock as far
as the origin of the scion, as soon as the union is
found to be complete; and at the same time to re-
trench from the scion a part of its buds and leaves, so
that there may not be a too rapid demand upon the
stock, while the line of union is still imperfectly con-
solidated.

A method of propagating Camellias, (jig. 30,) by
putting the end or heel of a scion into a vessel of
water, mentioned in the Gardener's Magazine, ii. 33,
is essentially the same as inarching. The water
communicated to the scion through the wounded end
supplies it with that food which, under natural cir-
cumstances, would be derived from the roots of the
plant to which it belongs.*

CHAPTER XIII.
OF PRUNING.

“Ta taille est une des opérations les plus import-
antes et les plus délicates du jardinage. Confiée

* One of our most experienced gardeners propagates the camellia
with great facility, by whip grafting small seedling stocks and
plunging the pots in the bone-black of the sugar refineries, covering
the graft entirely with this fine loose material. This not only pre-
serves an uniform state of moisture about the graft, but it seems to
exert some specific action upon the growth of new wood, doubtless
from the action of the phosphate of lime in the bone-black. The
luxuriance of the young grafts raised in this way is very remark-
able. A. J.D.

240 APPLICATION OF PRINCIPLES.

communément a des ouvriers peu instruits, observée
dans les résultats d’une pratique trop souvent irré-
fiéchie, elle a di nécessairement trouver des détrac-
teurs méme parmi les physiologistes. Tl en efit sans
doute été autrement, si on l’avait étudiée dans les jardins
du petit nombre de praticiens qui ont su de nos jours
la bien comprendre. Sagement basée sur les lois de
la végétation, elle contribue, entre leurs mains, non
seulement 4 régulariser la production des fruits, 4 en
obtenir de plus beaux, mais encore 4 prolonger l’ex-
istence et la fécondité des arbres.”

Nothing can be more just than these words,
addressed to the Horticultural Society of Paris, by
their President, M. Héricart de Thury; and, if they
do not apply with as much force to our gardeners as
to those of France, they do most fully to our forest-
ers.

The quantity of timber that a tree forms, the
amount and quality of its secretions, the brilliancy of
its colours, the size of its flowers, and, in short, its
whole beauty, depend upon the action of its branches
and leaves, and their healthiness (64). The object of
the pruner is to diminish the number of leaves and
branches; whence it may be at once understood how
delicate are the operations he has to practise, and how
thorough a knowledge he ought to possess of all the
laws which regulate the action of the organs of vege-
tation. If well directed, pruning is one of the most
useful, and, if ill-directed, it is among the most mis-
chievous, operations that can take place upon a
plant.

OF PRUNING. 241

‘When a portion of a healthy plant is cut off, all
that sap which would have been expended in sup-
porting the part removed is directed into the parts
which remain, and more especially into those in the
immediate vicinity of it, Thus, if the leading bud of
a growing branch is stopped, the lateral buds, which
would otherwise have been dormant, are made tosprout
forth; and, if a growing branch is shortened, then
the very lowest buds, which seldom push, are brought
into action: hence the necessity, in pruning, of cut-
ting a useless branch clean out; otherwise the remo-
val of one branch is only the cause of the production
of a great many others. This effect of stopping does
not always take place immediately; sometimes its
first effect is to cause an accumulation of sap in a
branch, which directs itself to the remaining buds,
and organises them against a future year. In ordi-
nary cases, it is thus that spurs or short bearing-
branches are obtained in great abundance. The
growers of the Filbert, in Kent, procure in this way
greater quantities of bearing wood than nature unas-
sisted would produce; for, as the filbert is always
borne by the wood of a previous year, it is desirable
that every bush should have as much of that wood as
can be obtained, for which everything else may be
sacrificed; and such wood is readily secured by
observing a continual system of shortening a young
branch hy two thirds, the effect of which is to call
all its lower buds into growth the succeeding year;
and thus each shoot of bearing wood is compelled to
produce many others. The Peach, by a somewhat

11

242 APPLICATION OF PRINCIPLES.

similar system, has been made to bear fruit in unfa-
vourable climates (Hort. Trans., ii. 366); and every
gardener knows how universally it is applied to the
Pear, Apple, Plum, and similar trees.* LEveni the
Fig-tree has thus been rendered much more fruitful
than by any other method. ‘ Whenever,” says Mr.
Knight, “a branch of this tree appears to be extending
with too much luxuriance, its point, at the tenth or
twelfth leaf, is pressed between the finger and
thumb, without letting the nails come in contact with
the bark, till the soft succulent substance is felt to
yield to the pressure. Such branch, in consequence,
ceases subsequently to elongate; and the sap is
repulsed, to be expended where it is more wanted.
A. fruit ripens at the base of each leaf, and during the
period in which the fruit is ripening, one or more of
the lateral buds shoots, and is subsequently sub-
jected to the same treatment, with the same result.
When I have suffered such shoots to extend freely to
their natural length, I have found that a small part
of them only became productive, either in the same

[* Nothing is more general, of late years, than complaints of the
short period of productiveness in the Peach tree, throughout the
Middle States, Although this is often owing tothe worm, which
girdles the tree at the root, yet the almost total neglect of pruning
is a frequent cause of sterility and decay. When left to itself the
interior of the head of the tree becomes filled with small dead
branches, and the trunk and larger limbs bark-bound and moss-
covered: the whole tree is enfeebled; leaves are only produced at
the extremity of the long branches, and the fruit borne, if any, is
comparatively worthless. By pursuing the practice reeommended
in the text, the trees may be preserved for a long time in a high
state of vigour and productiveness, <A. J. D.]

OF PRUNING. 243

or the ensuing season, though I have seen that their
buds obviously contained blossoms. I made several
experiments to obtain fruit in the following spring
from other parts of such branches, which were not
successful; but I ultimately found that bending
these branches, as far as could be done without danger
of breaking them, rendered them extremely fruitful ;
and, in the present spring, thirteen figs ripened per-
fectly upon a branch of this kind within the space
of ten inches. In training, the ends of all the shoots
have been made, so far as practicable, to point down-
wards.” (Hort. Trans., iv. 201.)

The effect produced upon one part by the abstrac-
tion of some other part, thus shown in the develope-
ment of buds which would otherwise be dormant, is
seen in many other ways. [If all the fruit of a plant
is abstracted one year when just forming, the fruit
will be finer and more abundant the succeeding year,
as happens when late frosts destroy our crops. If of
many flowers one only is left, that one, fed by the
sap intended for the others, becomes so much finer.
Tf the late figs, which never ripen, are abstracted, the
early figs the next year are more numerous and
larger. If of two unequal branches, the stronger
is shortened and stopped in its growth, the other
becomes stronger; and this is one of the most useful
facts connected with pruning, because it enables a
skilful cultivator to equalise the rate of growth of all
parts of a tree; and as has been already stated, this is
of the greatest consequence in the operation of bud-
ding. In fact, the utility of the practice, so common

244 APPLICATION OF PRINCIPLES.

in the management of fruit trees which are very
young, turns entirely upon this. A seedling tree hasa
hundred buds to support, and consequently the stem
grows slowly, and the plant becomes bushy-headed :
but being cut down so as to leave only two or three
buds, they spring upwards with great vigour, and,
being reduced eventually to one, as happens practi-
cally, that one receives all the sap, which would other-
wise be diverted into a hundred buds, and thrives
accordingly, the bushy head being no longer found,
but a clean straight stem instead. In the Oak and
the Spanish Chesnut this is particularly conspicuous.

Nothing is more strictly to be guarded against than
the disposition to bleed, which occurs in some plants
when pruned, and to such an extent as to threaten
them with death. In the Vine, in milky plants, and
in most climbers or twiners, this is particularly con-
spicuous; and it is not unfrequently observed in
fruit trees with gummy or mucilaginous secretions,
such as the Plum, the Peach, and other stone fruits.
This property usually arises from the large size of the
vessels through which sap is propelled at the periods
of early growth, which vessels are unable, when cut
through, to collapse sufficiently to close their own
apertures, when they necessarily pour forth their
fluid contents as long as the roots continue to absorb
them from the soil. If this is allowed to continue,
the system becomes so exhausted as to be unable to
recover from the shock, and the plant will either
become very unhealthy, or will die.* The only

* [A solution of Gum Shellac in aleohol, of the consistence of thin

OF PRUNING. 245

mode of avoiding it is to take care never to wound
such trees at the time when their sap first begins
to flow; after a time, the demand upon the system
by the leaves becomes so great that there is no sur-
plus, and therefore bleeding does nottake place when
a wound is inflicted.*

All these things show how extremely necessary it
is to perform the operations of pruning with care and
discretion. But, in addition to the general facts
already mentioned, there are others of a more special
kind that require attention. The first thing to be
thought of is the peculiar nature of the plant under
operation, and the manner in which its special habits
may render a special mode of pruning necessary. For
example, the fruit of the Fig and Walnut is borne by
the wood of the same season; that of the Vine and
Filbert by that of the second season ; and Pears,
Apples, &c., by wood of some years’ growth; it is

paste (put on with a brush,) is an admirable application to wounds
of stone-fruit trees, and others, which are disposed to bleed pro-
fusely. It is readily applied, adheres closely, excludes the air com-
pletely, and is less offensive to the eye than large plasters of clay,
composition, de. A. J. D.]

* “The Vine often bleeds excessively when pruned in an impro-
per season, or when accidentally wounded; and, I believe, no mode
of stopping the flow of the sap is at present known to gardeners. I
therefore mention the following, which I discovered many years ago,
and have always practised with success :—If to four parts of scraped
cheese be added one part of calcined oyster shells, or other pure cal-
careous earth, and this composition be pressed strongly into the
pores of the wood, the sap will instantly cease to flow; so that the
largest branch may, of course, be taken off at any season with
safety.” (Knight in Hort. Tyans., i. 102.)

246 APPLICATION OF PRINCIPLES.

clear that plants of these three kinds will each require
a distinct plan of pruning for fruit.

The pruner has frequently no other object in view
than that of thinning the branches so as to allow the
free access of light and air to the fruit; and if this
purpose is wisely followed, by merely removing super-
fluous foliage, the end attained is highly useful; it is
clear, however, that in order to arrive at this end,
without committing injury to the tree which is operat-
ed on, it is indispensable that its exact mode of bear-
ing fruit should be in the first instance clearly ascer-
tained.

The period of ripening fruit is sometimes changed
by skilful pruning, as in the case of the Raspberry,
which may be made to bear a second crop of fruit in
the autumn, after the first crop has been gathered.
In order to effect this, the strongest canes, which
in the ordinary course of things would bear a quan-
tity of fruiting twigs, are cut down to within two or
three eyes of the base; the laterals thus produced,
being impelled into rapid growth by an exuberance
of sap, are unable to form their fruit buds so early as
those twigs in which excessive growth is not thus
produced; and, consequently, while the latter fruit
at one season, the others cannot reach a bearing state
till some weeks later. Autumnal crops of summer
roses, and of strawberries, have been sometimes pro-
cured by the destruction of the usual crop at a very
early period of the season; the sap intended to
nourish the flower buds destroyed is, after their
removal, expended in forming new flower buds,

OF PRUNING. 247

which make their appearance at a later part of the
year.

The season for pruning is usually midwinter, or at
midsummer ; the latter for the purpose of removing
new superfluous branches, the former for thinning and
arranging the several parts of a tree. It is, however,
the practice, occasionally, to perform what is called
the winter pruning early in the autumn, as in the case
of the Gooseberry, and of the Vine when weak; and
the effect is found to be, that the shoots of such plants,
in the succeeding season, are stronger than they would
have been had the pruning been performed at a much
later season. This is necessarily so, as a little reflec-
tion will show. During the season of rest (winter) a
plant continues to absorb food solely from the earth by

its roots (81); and, if its branches

are unpruned, the sap thus and then
- introduced into the system will be

Va distributed equally all through it; let

31

us say from 0 to ¢ d and ¢ in the
accompanying diagram. If late pru-
ning is had recourse to, and the
branches from a toe d and e are re-
o moved, of course a large proportion
of the sap that has been accumulat-
ing during the winter will be thrown
away, and 6 to ¢ will retain no more
of it than the exact proportion which
that part bears to the part abstracted.
When, however, early or autumnal pruning is employ-
ed, a toc d ande are removed before the sap has

oo ®

248 APPLICATION OF PRINCIPLES.

accumulated in them, and then all which the roots are
capable of collecting during the period of repose will
be deposited in the space from @ to a, and conse-
quently branches from that part will necessarily
push with excessive vigour. As, however, pruning
is by no means intended at all times to increase the
vigour of a plant, late or spring pruning, if not de-
ferred till the sap is in rapid motion, may be the more
judicious.

With regard to pruning plants when transplanted,
there can be no doubt that it is more frequently inju-
rious than beneficial. It is supposed, or seems to be,
that when the branches of a transplanted tree are
headed back, the remaining buds will break with
more force than if the pruning had not been perform-
ed; but it is to be remembered that a transplanted
tree is not in the state supposed in the case put at
page 235, jig. 31. Its roots are not fully in action,
but from the injuries sustained in removing they are
capable of exercising but little influence on the
branches. The great point to attain, in the first in-
stance, is the renovation of the roots, and that will
happen only in proportion to the healthy action of the
leaves and buds (81): if, therefore, the branches of a
plant are removed by the pruning knife, a great ob-
stacle is opposed to this renovation; but, if they re-
main, new roots will be formed in proportion to their
healthy action. The danger to be feared is, that the
perspiration of the leaves may be so great as to ex-
haust the system of its fluid contents faster than the
roots can restore them, and in careless transplanting

OF PRUNING. 249

this may doubtless happen: in such cases it is cer-
tainly requisite that some part of the branches should
be pruned away; but no more should be taken off
than the exigency of the case obviously requires:
and, if the operation of transplanting has been well
performed, there will be no necessity whatever. In
the case of the transplantation of large trees, it is al-
leged that branches must be removed, inorder to re-
duce the head, so that it may not be acted upon by
the wind; butin general it is easy to prevent this ac-
tion by artificial means.*

* The first impulse of every young planter is to leave the entire
head of a transplanted tree untouched ; and we fear such novices will
find too abundant authority for this exercise of their sympathies in
the foregoing paragraph. But sound as the advice is, for a damp
climate, we are forced by experience to adopt the continental mode
in this country, and reduce the heads of all trees, more or less, on
transplanting them. The demand upon the roots in our dry sum-
mers, especially the first season after removal, is usually much greater
than they can supply, and we have seen numberless cases where
they have put outa fine show of green leaves and commenced a
tolerable growth at first, only to wither and die in mid-summer ;
while others, treated precisely like them in all other respects, except
that their branches were shortened back, grew freshly and luxuri-
antly all the season, Certainly nothing appears more foolish and
unnecessary than to wantonly spoil the fair proportions of a young
tree whose branches have begun to assume something of graceful
symmetry : but when the experience of all old planters conclusively
proves that transplanted trees whose heads have been shortened
back somewhat at the extremity of every branch, have succeeded
almost without exception, and have always grown more vigorously,
and, in a few seasons, have always regained more beautiful heads
than those left untouched by the knife, the novice must be
stubborn who will plant his tree, in this climate, and see it fail
because he will not reduce the top sufficiently to restore the balance
of action between the roots and the leaves. A. J. D.

250 APPLICATION OF PRINCIPLES,

In the nurseries it is a universal practice to prune
the roots of transplanted trees; in gardens, this is as
seldom performed. Which is right? If a wounded
or bruised root is allowed to remain upon a trans-
planted tree, it is apt to decay, and this disease may
spread to neighbouring parts, which would otherwise
be healthy; to remove the wounded parts of roots is
therefore desirable. But the case is different with
healthy roots. Wemust remember that every healthy
and unmutilated root which is removed is a loss of
nutriment to the plant, and that too at atime when
it is least able to spare it; and there cannot be any
advantage in the removal. The nursery practice is
probably intended to render the operation of trans-
planting large numbers of plants less troublesome;
and, as it is chiefly applied to seedlings and young
plants with a superabundance of roots, the loss in
their case is not so much felt. If performed at all,
it should take place in the autumn, for at that time
the roots, like the other parts of the plants, are com-
paratively empty of fluid; but, if deferred till the
spring, then the roots are all distended with fluid,
which has been collecting in them during winter,
and every part taken away carries with it a portion
of that nurture which the plant had been laying up
as the store upon which to commence its renewed
growth.

It must now be obvious that, although root-pruning
may be prejudicial in transplanting trees, it may be
of the greatest service to such established trees as are
too prone to produce branches and leaves, instead of

OF PRUNING. 251

flowers and fruit. In these cases the excessive vigour
is at once stopped by removal of some of the stronger
roots, and consequently of a part of the superfluous
food to which their ‘‘rankness” is owing. The opera-
tion has been successfully performed on the wall trees
at Oulton, by Mr. Errington, one of our best English
gardeners, and by many others, and, I believe, has
never proved an objectionable practice under judi-
cious management. Its effect is, pro tanto, to cut off
the supply of food, and thus to arrest the rapid
growth of the branches; and the connexion between
this and the production of fruit has already been ex-
plained (85). It is by pushing the root-pruning to
excess that the Chinese obtain the curious dwarf trees
which excite so much curiosity in Europe. Mr.
Livingston’s account of their practice is so instructive,
aud contains so much that an intelligent gardener
may turn to account, that I think it worth repeating
here.

“When the dwarfing process is intended, the
branch which had pushed radicles into the surround-
ing composition in sufficient abundance, and for a
sufficient length of time, is separated from the -tree,
and planted in a shallow earthenware flower-pot, of
an oblong square shape; it is sometimes made to rest
upon a flat stone. The pot is then filled with small
pieces of alluvial clay, which, in the neighbourhood
of Canton, is broken into bits, of about the size of
common beans, being just sufficient to supply the
scanty nourishment which the particular nature of the
tree and the process require. In addition to a careful

252 APPLICATION OF PRINCIPLES.

regulation of the quantity and quality of the earth,
the quantity of water, and the management of the
plants with respect to sun and shade, recourse is had
to a great variety of mechanical contrivances, to pro-
duce the desired shape. The containing flower-pot
is so narrow, that the roots pushing out towards the
sides are pretty effectually cramped. No radicle can
descend ; consequently it is only those which rur to-
wards the sides or upwards that can serve to convey
nourishment properly, and it is easy to regulate those
by cutting, burning, &c., so as to cramp the growth
at pleasure. Every succeeding formation of leaves
becomes more and more stunted,—the buds and
radicles become diminished in the same proportion,—
till at length that balance between roots and leaves
is obtained which suits the character of the dwarf re-
quired. Insome trees this is accomplished in two or
three years, but in others it requires at least twenty
years.” (Hort. Trans., iv. 229.)

We have still to consider that peculiar kind of pru-
ning which is technically called ringing (fig. 32.)
This consists in removing from a branch one or more
rings of bark, by which the return of sap from the
extremities is obstructed, and it is compelled to accu-
mulate above the ring. Mr. Knight explains the
physiological nature of the operation so well, that I
cannot do better than quote his words.

“The true sap of trees is wholly generated in their
leaves, from which it descends through their bark to
the extremities of their roots, depositing in its course
the matter which is successively added to the tree;

OF PRUNING. 253

whilst whatever portion of such
1m Sap is not thus expended sinks

fp into the alburnum, and joinsthe
ascending current, to which it
communicates powers not pos
sessed by the recently absorbed
fluid. When the course of the
descending current is intercept-
ed, that naturally stagnates and
accumulates above the decorti-
Py cated space; whence it is re-
pulsed and carried upwards, to
be expended. in an increased
production of blossoms, and of
fruit: and, consistently with
these conclusions, I have found
that part of the alburnum which
is situated above the decorticat-
ed space to exceed in specific
gravity, very considerably, that
which lies below it. The re-
pulsion of the descending fluid,
therefore, accounts, I conceive,
satisfactorily, for the increased
production of blossoms, and
more rapid growth of the fruit
upon the decorticated branch: but there are causes
which operate in promoting its more early maturity.
The part of the branch which is below the decorti-
cated space is ill supplied with nutriment, and ceases
almost to grow; it in consequence operates less ac-

254 APPLICATION OF PRINCIPLES.

tively in impelling the ascending current of sap,
which must also be impeded in its progress through
the decorticated space. The parts which are above it
must, therefore, be less abundantly supplied with
moisture ; and drought, in such cases, always operates
very powerfully in accelerating maturity. When
the branch is small, or the space from which the bark
has been taken off is considerable, it almost always
Operates in excess; a morbid state of early maturity
is induced, and the fruit is worthless.

“Tf this view of the effects of partial decortication,
or ringing, be a just one, it follows that much of the
success of the operation must be dependent upon the
selection of proper seasons, and upon the mode of
performing it being well adapted to the object of the
operator. If that be the production of blossoms, or
the means of making the blossoms set more freely,
the ring of bark should be taken off early in the sum-
mer preceding the period at which blossoms are re-
quired: but, if the enlargement and more early ma-
turity of the fruit be the objects, the operation should
be delayed till the bark will readily part from the
alburnum in the spring. The breadth of the decorti-
cated space must be adapted to the size of the branch ;
but I have never witnessed any except injurious
effects, whenever the experiment has been made upon
very small or very young branches, for such become
debilitated and sickly, long before the fruit can ac-
quire a proper state of maturity.”

The effects of ringing in altering the appearance of
the fruit is very striking. In the Horticultural Trans-

OF PRUNING. 2590

actions, ili. 867, the following cases are reported.—In
a French Crab, the fruit, by ringing, was increased to
more than double the size, and the colour of it was
much brightened. In a Minshull Crab the size was
not increased, but the appearance of the apple was so
improved as to make it truly beautiful; its colours,
both red and yellow, were very bright. In the Court-
pendu Apple the improvement was still more conspi-
cuous, the colours being changed from green and dull
red, to brilliant yellow and scarlet. Many others of a
similar kind are to be found recorded in books on hor-
ticulture, It is, however, by no means’ alone to the
maturation or production of fruit that this operation
is applicable ; it will, of course, induce also the pro-
duction of flowers, and it has occasionally been used
for that purpose, as in the Camellia. It is best per-
formed in the early spring, when the bark first sepa-
rates freely from the wood.

This operation has, however, the disadvantage of
wounding a branch severely; and, if performed ex-
tensively upon a tree, it is very apt, if not to kill it,
at least to render it incurably unhealthy ; for if the
rings are not sufficiently wide to cut off all communi-
cation between the upper and lower lips of the wound
they produce little effect, and if they are, they are
difficult to heal. For these reasons the operation is
but little employed, other means being used instead.
By some persons ligatures are made use of, and they
would be preferable if they answered the purpose cf
obstructing the sap to the same extent as the abstrac-
tion of a ring of bark. In Malta, one of the objects

256 APPLICATION OF PRINCIPLES.

of ringing, that of advancing the maturation of the
fruit, is practised upon the Zinzibey, or Jujube tree, by
merely fixing in the fork of a branch a very heavy
stone, made fast with bandages; its weight forces the
branches a little into a horizontal direction, and thus,
independently of the pressure it exercises upon the
parts it touches, obstructs the free circulation of the

sap.

CHAPTER XIV.
OF TRAINING.

TRAINING is one of the most artificial operations
that gardeners are acquainted with, its object being to
place a plant in a condition to which it could never
arrive under ordinary circumstances. The practice
of it forms one of the most complicated parts of the
art of horticulture, each species demanding a method
peculiar to itself; but the principles on which it
depends are few andsimple. These will be best con-
sidered with reference to. the objects the gardener
wishes to attain in performing the operation.

It is probable that the intention of the first gar-
dener who trained a tree was to gain some advantage
of climate, by placing the tree close to a wall or other
screen; and this is still one of the greatest objects ;
partly with a view to guard the flowers in spring
from cold, and especially cold winds, partly to expase

OF TRAINING. 257

the leaves and fruit to a hotter temperature than
would otherwise be gained, and in some measure to
ripen wood with more certainty.

That training a tree over the face of a wall will
protect the blossoms from cold must be apparent,
when we consider the severe effect of excessive eva-
poration upon the tender parts; a merely low tempe-
rature will produce but little comparative injury in a
still air, because the more essential parts of the flower
are very much guarded by the bracts, calyx, and
petals, which overlie them, and, moreover, because
radiation (see page 186) will be intercepted by the
branches themselves placed one above the other, so
that none but the uppermost branches which radiate
into space will feel its full effects; but, when a cold
wind is constantly passing through the branches and
among the flowers, the perspiration, against which no
sufficient guard is provided by nature, becomes so
rapid (see page 129) as to increase the amount of cold
considerably, besides abstracting more aqueous mat-
ter than a plant can safely part with. This being one
of the great objects of training trees, it is inconceiv-
able how any one should have recommended such
devices as those mentioned in the Horticultural Trans-
actions, ii. Appendix, p. 8, of training trees upon a
horizontal plane; the only effect of which would be
to expose a tree as much as possible to the effect
of that radiation which it is the very purpose of train-
ing to guard against.

The actual temperature to which a tree trained
upon a wall facing the sun is exposed is much higher

258 APPLICATION OF PRINCIPLES,

than that of the surrounding air, not only because it
receives a larger amount of the direct solar rays, but
because of the heat received by the surrounding earth,
reflected from it and absorbed by the wall itself.
Under such circumstances the secretions of the plant
are more fully elaborated than in a more shady and
colder situation ; and, by aid of the greater heat and
dryness in front of a south wall, the period of matu-
rity is much advanced. In this way we succeed
in procuring a Mediterranean or Persian summer
in these northern latitudes. When the excellence of
fruit depends upon its sweetness, the quality is ex-
ceedingly improved by such an exposure to the sun;
for it is found that the quantity of sugar elaborated
in a fruit is obtained by an alteration of the gummy,
mucilaginous, and gelatinous matters previously
formed in it, and the quantity of those matters will
be in proportion to the amount of light to which the
tree, if healthy, has been exposed. Hence the greater
sweetness of plums, pears, &c., raised on walls from
those grown on standards. It has been already
stated (page 138) that an increase of heat has been
sought for on walls by blackening them ; and we are
assured in the Horticultural Transactions (iii. 330) that,
in the cultivation of the Grape, this has been attended
with the best effects. But, unless when trees are
young, the wall ought to be covered with foliage dur-
ing summer, and the blackened surface would scarcely
act; and in the spring the expansion of the flowers
would be hastened by it, which is no advantage in
cold late springs, because of the greater- liability of

OF TRAINING. 259

early flowers to perish from cold. That a blackened
surface does produce a beneficial effect upon trees
trained over it, is, however, probable, although not in
insuring the maturation of fruit; it is by raising
the temperature of the wall in autumn when the
leaves are falling, and the darkened surface becomes
uncovered, that the advantages are perceived by a
better completion of the process of growth, the result
of which is ripening the wood. This is, indeed, the
view taken of it by Mr. Harrison, who found the
practice necessary, in order to obtain crops of pears
in late seasons at Wortley in Yorkshire (see Hort.
Trans., 1. 330, and vi. 453.) It hardly need -be
added that the effect of blackening will be in propor-
tion to the thinness of the training, and vice versd.
Another object of training is, to place a tree in such
a state of constraint that its juices are unable to cir-
culate freely, the result of which is exactly that
already assigned to the process of ringing (see p.
254). If a stem is trained erect, it will be more
vigorous than if placed in any other position, and its
tendency to bear leaves rather than flowers will be
increased; in proportion as it deviates from the per-
pendicular is its vigour diminished. For instance, if
a stem is headed back, and only two opposite buds
are allowed to grow, they will continue to push
equally, so long as their relation to the perpendicular
is the same; but, if one is bent towards a horizontal
direction, and the other allowed to remain, the growth
of the former will be immediately checked; if the
depression is increased, the.weakness of the branch

260 APPLICATION OF PRINCIPLES.

increases proportionally ; and this may be carried on
till the branch perishes. In training, this fact is of
the utmost value in enabling the gardener to regu-
late the symmetry of a tree. It however by no
means follows that, because of two continuous
branches, one growing erect and the other forced
into a downward direction, the latter may die, that all
branches trained downwards will die. On the con-
trary, an inversion of their natural position is of so
little consequence to their healthiness, that no effect
seems in general to be produced beyond that of
causing a slow circulation, and the formation of
flowers. Hence the directing of branches downwards
is one of the commonest and most successful contri-
vances employed by gardeners to render plants fruit-
ful. Mr. Knight was the first to recommend the
practice in the following account of his recovery of
an old and worthless Pear tree :

“An old St. Germain Pear tree, of the spurious
kind, had been trained in the fan form, against a
north-west wall in my garden, and the central
branches, as usually happens in old trees thus train-
ed, had long reached the top of the wall, and had be-
come wholly unproductive. The other branches
afforded but very little fruit, and that never acquiring
maturity was consequently of no value; so that it
was necessary to change the variety, as well as to
render the tree productive. To attain these purposes,
every branch which did not want at least twenty de-
grees of being perpendicular was taken out at its
base ; and the spurs upon every other branch, which

OF TRAINING. 261

I intended to retain, were taken off closely with the
saw and chisel. Into these branches, at their sub-
divisions, grafts were inserted at different distances
from the root, and some so near the extremities of the
branches, that the tree extended as widely in the au-
tumn after it was grafted, as it did in the preceding
year. The grafts were also so disposed, that every
part of+the space the tree previously covered was
equally well supplied with young wood.

“« As soon, in the succeeding summer, as the young
shoots had attained sufficient length, they were train-
ed almost perpendicularly downwards, between the
larger branches and the wall, to which they were
nailed. The most perpendicular remaining branch
upon each side was grafted about four feet below the
top of the wall, which is twelve feet high; and the
young shoots, which the grafts upon these afforded,
were trained inwards, and bent down to occupy the
space from which the old central branches had been
taken away; and therefore very little vacant space
remained: any where in the end of the first autumn.
A few Dlossoms, but not any fruit, were produced by
several of the grafts in the puptendioe spring; butin
the following year, and subsequently, I have had
abundant crops, equally dispersed over every part of
the tree; and I have scarcely ever seen such an ex-
uberance of blossom as this tree presents in the pre-
sent spring.” (Hort. Trans., ii. 78.)

The practice was then followed by Sir Joseph
Banks, whose fruit trees, trained downwards over the
walls of his gardeu at Spring Grove, and facing the

262 APPLICATION OF PRINCIPLES.

high road, long excited the astonishment of passers-
by; and it has now been generally applied to other
cases. What are called Balloon Apples and Pears,
formed by forcing downwards all the branches of
standard trees till the points touch the earth, are an
instance of this; and they have the merit of produc-
ing large crops of fruit in a very small compass: their
upper parts are, however, too much exposed to ra-
diation at night, and the crop from that part of the
branches is apt to be cut off. One of the prettiest
applications of this principle is that of Mr. Charles
Lawrence, described in the Gardener's Magazine, viii.

33

ee
(As.
NR S Ms

OF TRAINING. 263

680, by means of which standard Rose trees are con-
verted intu masses of flowers. The figure given in
that work, and here reproduced (fig. 33), represents
the variety called the Bizarre de la Chine, “ which
flowered most abundantly to the ends of its branches,
and was truly a splendid object.”

The last object of training to which it is necessary
to advert is that of improving the quality of fruit, by
compelling the sap to travel to a very considerable dis-
tance. The earliest notice of this, with which I am
acquainted, is the following by Mr. Williams of
Pitmaston.

“Within a few years past,” he says in 1818, “I
have gradually trained bearing branches of a small
Black Cluster Grape, to the distance of near fifty feet
from the root, and I find the branches every year
grow larger, and ripen earlier as the shoots continue
to advance. According to Mr. Knight's theory of
the circulation of the sap, the ascending sap must
necessarily become enriched by the nutritious par-
ticles it meets with in its progress through the stems of
the alburnum; the wood at the top of tall trees, there-
fore, becomes short-jointed and full of blossom buds,
and the fruit there situated attains its greatest perfec-
tion. Hence we find Pine and Fir trees loaded with
the finest cones on the top boughs; the largest acorns
grow on the terminal branches of the Oak, and the
finest mast on the high boughs of the Beech and Chest-
nut; so likewise apples, pears, cherries, &c., are al-
ways best flavoured from the top of the tree.” (Hort.
Trans., iii. 250, 251.) The merit of the Fontainbleau

264 APPLICATION OF PRINCIPLES.

mode of training the Vine (fig. 34), in which many
of the stems are carried to very considerable distances,
seems to depend in some measure upon this principle;

34

WU le

LOAPLOL AEDT ——_ BSE ez

and there is a well-known Black Iamburg Grape at
Bath, growing in a garden formerly belonging to Mr.
Farrant, the stem of which, owing to local circum-
stances, is necessariby conveyed to a very considera-
ble distance before it is allowed to produce its bearing
branches, the quality of whose fruit is of very un-
usual excellence. These facts seem capable of being
applied to many important improvements in fruit ma-
nagement.

OF TRAINING. 265

The foregoing are the principal advantages: which
arise from training plants; let us next consider what
disadvantages there may be. The only trees which
at all approach in nature the state of trained plants are
climbers and creepers, whose stems, unable to support
themselves, cling for a prop upon whatever they are
near; some of them enclose the stem of another plant
in their convolutions ; others simply attach themselves
by means of tendrils as the Vine, by hooks as the
Combretum, or by other contrivances; and some,
like the Ivy, lay hold of walls, rocks, or the trunks
of trees, by their minute roots. To none of these
can that motion be necessary to which plants are
naturally exposed, and which, as has been already
seen (p. 157), is of so much importance to the healthy
maintenance of their functions. Hence it is, that
among fruit trees the Vine never suffers from being
trained: indeed its anatomical structure is especially
suited to such a mode of existence; while all erect
trees, of whatever kind, whose branches nature
intended to be rocked by the storm, and perpetually
waved by the currents of air to which they are
exposed, in all cases suffer more or less.

One of the commonest and worst diseases induced
by training is a gradual impermeability of tissue
to the free passage of sap, which appears to stagnate,
so that in time the branches become debilitated and
juiceless; the obstruction to the flow of the sap
tends to produce coarse shoots from various parts of
the branches, and especially from the roots. The
cause of this seems to be the too rapid deposit

12

266 APPLICATION OF PRINCIPLES.

of the sedimentary matter of lignification,* and to
be induced by want of motion and excessive expo-
sure of the leaves and branches to the sun. The effect
of the latter is to inspissate all the juices, and to pro-
mote their formation ; while the former increases the
evil by not keeping the fluids in rapid circulation :
just as we know that a slow stream, from a muddy
source, deposites its impurities much more copiously
than a rapid stream. As this evil arises out of the
operation of training, and seems to be inseparable
from it, there will be no expectation of a remedy
being discovered.

The increase of the saccharine quality of fruit is by
no means an advantage in all cases; it improves the
peach, the nectarine, the pear and the plum, in which
sweetness is the great object; but it deteriorates the
apple and the apricot, which are chiefly valued for
their peculiar mixture of acidity and sweetness.

The protection received in the spring by trees
trained upon walls exposed to the sun, while it
advances the period of flowering, at the same time
causes it to take place at a season when they are not
sufficiently secure from spring frosts ; and hence the
necessity of protecting such plants artificially by
coping, screens, bushes, curtains, and other contri-
vances. It is on this account that the utility of fiued
walls is so much diminished, and that they are found,
in practice, more valuable for ripening wood in
autumn, than for guarding blossoms in the spring.

* See Introduction to Botany, ed. 3, p. 3

OF POTTING. 267

CHAPTER XV.
OF POTTING.

WHEN a plant is placed to grow in a small earthen
vessel like a garden pot, its condition is exceedingly
different from that to which it would be naturally
exposed. The roots, instead of having the power
of spreading constantly outwards, and away from their
original starting point, are constrained to grow back
upon themselves; the supply of food is comparatively
uncertain; and they are usually exposed to fluctua-
tions of temperature and moisture unknown in a
natural condition. For these reasons, potted plants
are seldom in such health as those growing freely
in the ground; but, as the operation of potting is one
of indispensable necessity, it is for the scientific gar-
dener, firstly, to guard against the injuries sustainable
by plants to which the operation must be applied ;
and, secondly, to avoid, as far as may be possible,
exposing them to such an artificial state of existence.
That the latter may be done more frequently than is
supposed will be sufficiently obvious, when we have
considered what the purposes really are that the gar-
dener needs to gain by potting.

The first and greatest end attained by potting is,
the power of moving plants about from place to place
without injury; greenhouse plants from the open air
to the house, and vice versd ; hardy species, difficult
to transplant, to their final stations in the open ground

268 APPLICATION OF PRINCIPLES.

without disturbing their roots; annuals raised in heat
to the open borders; and so on: and, when this
power of moving plants is wanted, pots afford the
only means of doing so. It also cramps the roots,
diminishes the tendency to form leaves, and increases
the disposition to flower. Another object is, to effect
a secure and constant drainage from roots of water ;
a third is, to expose the roots to the most favourable
amount of bottom heat, which cannot be readily
accomplished when plants of large size are made to
grow in the ground even of a hot-house ; and, finally,
it is a convenient process for the nourishment of deli-
cate seedlings. Unless some one of these ends is to
be answered, and cannot be effected in a more natu-
ral manner, potting is better dispensed with.

That it may be advantageously dispensed with, in
many cases, is evident from several facts more or less
well known. The nurserymen prefer ‘ pricking out”
their delicate seedlings into pans, or movable bor-
ders, instead of pots ; and they always thrive the bet-
ter. In conservatories, the necessity of shifting plants
from place to place may be often avoided; while,
under judicious management, those which are planted
in the open soil have greatly the advantage of others,
both in healthiness and easiness of management; and
there is no doubt that Pine-apples will succeed better
unpotted, if planted freely in soil exposed to a proper
amount of bottom heat. This was first asserted by Mr.
Martin Call, one of the Emperor's gardeners at St.
Petersburgh (Mort. Trans., iv. 471), and has been since
practised very successfully by others. In the year

OF POTTING. 269

1830, a pine-apple, obtained by this treatment, weigh
ing 9b. 40z., was sent to the King of England by Mr.
Kidwards of Rheola; and the success of other growers,
in the same manner, has been remarkable. (See Hort.
Trans., un. s., i. 888.)

The exhaustion of soil by a plant is one of the most
obvious inconveniences of potting. The organisable
matter in a soluble state, contained in a garden pot,
must necessarily be soon consumed by the numerous
roots crowded into a narrow compass, and continually
feeding upon it. The effects of this are seen in the
smallness of leaves, the weakness of branches, the
fewness and imperfect condition of flowers, &c.; and
the gardener remedies them by applying liquid ma-
nure, by frequent shifting, or by placing his plants in
pan-feeders, shallow earthen vessels containing ma-
nure, to which the roots have access through the
holes in the bottom of a pot. It is, however, to shift-
ing, more particularly, that recourse is had for reno-
vating the soil; and this, if skilfully performed, with-
out giving a sudden and violent shock to the plant,
is probably the best means; because the roots are
thus allowed more liberty of distribution, and the
earth is kept more open (more permeable) than when
consolidated by repeated applications of liquid ma-
nure. There is, however, a difficulty in shifting
plants without injury to their roots, in the midst of
full vegetation ; and at such times the application of
liquid manure is preferable, when the soil requires
renovation.

It is not, however, by mere exhaustion that potted

270 APPLICATION OF PRINCIPLES.

plants render the soil unfit for their support. Every
one knows that the soil of a farm will not bear, year
after year, the same kind of crop, but that one kind
of produce is cultivated on a piece of ground one
year, and is succeeded by some other kind; which
practice, in part, constitutes the important system of
rotation of crops. Not, however, to refer to matters
extra-horticultural, it is notorious that an apple
orchard will not immediately succeed upon the site
of an old orchard of the same kind of fruit, and that
no amount of manuring will enable it to succeed; a
wall border, in which fruit trees have been long
grown, becomes at last insensible to manure, and re-
quires to be renewed; and, not to dwell upon an un-
disputed fact, Dahlias do not ‘‘like” the soil in which
Dahlias were grown the previous year. This class
of phenomena cannot be explained upon the principle
of soil being exhausted, because that exhaustion is
made good and yet to no purpose, unless we assume
that land contains something mineral which each
species prefers to feed on, and which is not contained
in manure. But the slender power of selection pos-
sessed by the roots of plants (85) would be unfavour-
able to this supposition, even if it were open to no
other objections. It has of late years been thought
that the excretory functions of the root (39) would
explain the deterioration of soil, and that the reason
why plants cannot grow year after year in the same
soil, if it and their roots are disturbed, is, that, under
such circumstances, they are perpetually brought into
contact with the matter of which nature had previous:

OF POTTING. 271

ly relieved them; this matter being assumed to be
unsuitable to themselves, although harmless to differ-
ent species, The subject has been hitherto so little
investigated that it is not safe, perhaps, to take it as
the basis of a theory; but it certainly appears to offer
amore probable explanation of the deterioration of
soil than any other yet proposed. There are those,
indeed, who seem willing to deny altogether that soil
is deteriorated; and cases are adduced of Peach trees
not repotted for twenty years, which did not die; of
Strawberry beds not renewed for a long series of
years, which still bore fruit: but I do not know that
any one ever asserted that trees would perish if re-
planted in their own deteriorated soil; it has only
been said that they would become unhealthy and un-
productive, and I think few gardeners will deny that.
Neither has it been pretended that the root-secretions
of every plant are deleterious at all. It is quite con-
ceivable that one plant may secrete a deleterious mat-
ter that is very slowly decomposable, but which may,
nevertheless, be soluble enough to enter into the food
of other roots; and in such a case an injurious effect
may be produced : while, in another case, the secreted
matter may be rapidly decomposable, when it will
enter into new combinations, and lose whatever dele-
terivus property it originally possessed, ifany. At
all events, be the theory what it may, it is an un-
doubted fact that soil is deteriorated by a plant
which has grown in it for a long time; and that, to
be maintained in a healthy condition, that soil must
be changed. This explains why potted plants, care-

t

272 APPLICATION OF PRINCIPLES.

fully attended to and often shifted, are so much more
healthy than those treated otherwise. It is not, how-
ever, merely for the purpose of removing deterio-
rated earth or adding manure, that shifting is impor-
tant; all potted plants have, in time, their ball of
earth, by the continual passage of water through it,
reduced to a state of hardness and solidity unfavour-
able to the retention of moisture or the growth of
roots; and this is of course cured, if the operation of
shifting is judiciously performed. I must, however,
confess, I have seen gardeners contented with lifting
a plant, with a hard old matted ball, out of one pot
into another of a little larger size, shaking some par-
ticles of fresh earth in between the ball and the side
of the pot, and pressing the whole down with as much
force as the thumbs can give.

It is found that the roots of potted plants invariably
direct themselves towards the sides of the pot, as must
indeed necessarily happen in consequence of their dis-
position to grow horizontally. Having reached the
sides, they do not turn back, but follow the earthen-
ware surface, till at last they form an entangled stra-
tum enclosing a ball of earth; then, if not relieved
by repotting, they rise upwards towards the surface,
or they attempt to force themselves back to the centre.
The greater part, however, are always found in con-
tact with the porous earthen side of the vessel; and
especially all the most powerfully absorbent, that is,
youngest parts. They are, therefore, in contact with
a body subject to great variations of temperature and
moisture, in consequence of exposure to the sun, or to

OF POTTING. 273

a dry air in motion, unless in those rare cases where
the air is kept by artificial means shaded, and uni-
formly damp. By these means, in a dry summer day,
when the leaves are perspiring freely, and therefore
requiring an abundance of water from the roots, the
latter are placed in contact with a substance whose
moisture is continually diminishing; or in a green-
house where the pots are syringed, the heat of the
earth in contact with the roots is lowered by a copious
evaporation from the sides of the pot, just when, in
nature, the bottom heat should be the greatest. The
evil consequences of this are well known to gardeners,
who however seldom take any sufficient precautions
to prevent it. Greenhouse plants exposed to the
open air in summer always suffer severely from the
irregular condition of the sides of the pots; whence
the common practice of plunging them in the earth,
for:the purpose of bringing them into the condition
of plants growing in the open ground.

This is, however, attended with some disadvan-
tage; for the plants root, through the bottom of the
pots or over the edges, among the earth in which
they are plunged; and, when taken up in the autumn
for removal into the greenhouse, they must have all
such roots cut off again; for there are no means of
bringing them within the limits of a pot. For these
and similar reasons, no good gardener will expose his
greenhouse plants to the open air in summer, ¢f he can
help it, unless they are duplicates, or unless there is
some object to be attained very different from the
strange notion that they are hardened by this pro-

12*

274 APPLICATION OF PRINCIPLES.

cess. The effect that is really produced upon them
is, to give them a sort of artificial winter in summer,
that is, to expose them to a period of comparative
rest from growth, which, in many cases, is useful.
The best method of counteracting the injurious
35 effects of exposure to the air is
m by employing double pots (fig.
35), as recommended in the
Gardener's Magazine, ix. 576,
and by Captain Mangles, in his
Floral Calendar, p.44; the space
(5) between the two pots being
filled up with moss, or any other
substance retentive of moisture.
Of course the inconveniences now alluded to are
principally sustained by plants in small pots: when
the quantity of earth is considerable, as in tubs or
the largest kinds of pots, the loss of water through
the sides is of little moment; and the variation of
temperature is more than counteracted by the large
surface exposed to the direct influence of the solar
rays. In these cases, the perfect drainage of super-
fluous moisture is often of the greatest service. Mr.
Knight, indeed, assures us that “ plants of every
species are more or less affected, but not all inju-
riously, by having the sides of their pots exposed
fully to the air. The taste and flavour of the peach
and nectarine, and still more of the strawberry, are
greatly improved; and the Fig-tree, in the stove,
is made to afford a longer succession of produce,
owing to the succession of young shoots, which are

OF POTTING, 275

caused to spring from its larger branches and stems;
and, in all cases when trees can be made to retain their
health in exposed pots, the period of the maturity of
their fruit is very considerably accelerated. (Hori.
Trans., vii. 258.)

It seems to be nothing but the complete drainage
to which they are then exposed, that makes the
Orange and all its tribe, naturally inhabitants of the
hill-sides of the temperate parts of Asia, thrive
best when the roots come in contact with the sides of
the pots, &c., in which they grow. In all cases, the
drainage should be most carefully secured, by placing
an abundance of broken tiles, potsherds, &c., in the
bottom of a pot, so as to prevent the stagnation of
water (page 119) about the roots.

Mr. Macnab, in his excellent practical treatise upon
the cultivation of Cape Heaths, points out very forci-
bly the value of good draining to that class of plants.
There is scarcely any danger, he says, of giving too
much draining; and, in order to effect this essential
object still more perfectly, he, in shifting his Heaths,
constantly keeps the centre elevated above the gene-
ral level of the earth in the pot or tub, so that at.
last each plant stands on the summit of a small hillock.

In order to counteract the risk of excessive drain-
age, without in reality diminishing it, great advan-
tage is derived from the introduction into the earth
of fragments of some absorbent stone. Mr. Macnab
uses ‘coarse soft free-stone, broken into pieces from
one inch to four or five inches in diameter ;” because
in summer these stones retain moisture longer than

276 APPLICATION OF PRINCIPLES.

the earth, and in winter allow a free circulation of
any superabundant moisture.

If woody plants are allowed to remain growing in
the same pot for many years, as is sometimes the
case, one of two things must happen; either the
roots, matted into a hard ball, become so tortuous
and hard as to be unfit for the free passage of sap
through them, or they acquire a spiral direction. In
either case, if such plants are turned out of their
pots in a conservatory, or in the open ground, with a
view to their future growth in a state of liberty, new
roots will be made with difficulty, and it will be
a long time before the effects of growth in the free
soil will be apparent. Where the spiral or corkscrew
direction has been once taken by the roots, they are
very apt to retain it during the remainder of their
lives; and if, when they have become large trees,
they are exposed to a gale of wind, they readily
blow out of the ground, as was continually happen-
ing with the Pinaster some years ago, when the nur-
serymen kept that kind of Fir for sale in pots. In
all such cases as these, the roots should be carefully
disentangled and straightened at the time when trans-
plantation takes place.

If, however, a potted plant is managed in the most
perfect manner, no such entanglement or coiling up
will take place. To be managed perfectly, a plant,
when young, should be placed in as small a pot as it
will grow in, and it should be gradually and succes-
sively transferred to larger pots as it advances in
size. If this is done, the warmth to which the pot

OF POTTING. 277

is exposed will be more immediately felt by the roots;
the latter, as they grow, will ramify regularly all
through the mass of earth, which, moreover, will
be thoroughly drained: but if, on the other hand, a
very small young plant is placed at once in a large
pot, and left to grow there, the drainage will be less
perfect, the large mass of earth will be less sensible
of the heat to which it is exposed, the roots will from
the first take a horizontal direction towards the ou:-
side of the pot, and, once there, will follow its surface

"as has been already stated, exhausting the small
quantity of earth with which they are then in con-
tact, and profiting little or nothing by the main body
of soil in the interior of the pot. As the proper
manner of managing potted plants is of the first con-
sequence, I transcribe the following mode of treating
the Balsam, from a very sensible paper by the Rey.
William Williamson.

“ As soon as they have got four leaves, I trans-
plant them singly into the smallest pots Ican procure,
and in such a manner that the stem of the plant may
be covered somewhat more than it was at first, and
then all are to be again placed in the frame. Ina
short time, if there be a sufficiency of heat, that part
of the stem which is covered with the mould puts
forth fibres, by which nourishment is conveyed more
immediately to the principal stem of the plant. As
soon as the plants are a little advanced in growth,
they are again removed (if possible without disturb
ing the earth) into somewhat larger pots, still plant-
ing them rather deeper than before. The same process

278 APPLICATION OF PRINCIPLES.

is repeated five or six times, till, at last, they are
removed into their final pots. I have found it best
to give them their last removal after they have
opened their first blossoms, as it gives additional
brilliancy and size to the flowers. By following this
method the plant acquires extraordinary vigour,
throwing out its branches from the surface of the
mould, exhibiting flowers nearly as large as a full-
blown rose, and a stem measuring two, and some-
times three, inches in circumference.” (Hort. Trans.,
i. 128).

The plan of continually sinking the stem with
every succeeding potting is useful to the Balsam,
because it puts forth roots in abundance from its
stem; and to all plants having the same property,
the same practice is desirable: but not to others,
which, if their stems do not root as fast as they
are buried, will suffer injury by the sinking.

It is by paying constant attention to the shifting
of the growing plant, by the employment of a very
rich stimulating soil, and by a thorough knowledge
of the kind of atmosphere which suits them best, that
have been obtained those magnificent Pelargoniums,
Cockscombs, Balsams, and similar flowers, which
have so often and so justly excited the admiration of
even the most experienced gardeners.

OF TRANSPLANTING. 279

CHAPTER XVI.
OF TRANSPLANTING.

AS soon as man attempted to beautify his residence
with trees planted around it, he would naturally
obtain them from the forest ; and he then would find
that, of many that he removed, all or some at least
would die: if however he persevered, he would
at last discover that while constant failure attended
his efforts at one time, comparative success would
crown them at another; and he would thus be led to
investigate, according to his skill, the causes of suc-
cess and failure. Out of this would grow in time the
art of transplanting, among the most important busi-
ness of the gardener.

I fear, however, it is too generally practised as an
empirical art, without sufficient attention being paid
to the principles on which its success or failure
depend; at least, one hardly knows how to draw any
other conclusion from the opposite opinions held by
planters, the dogmatical manner in which they are
too often expressed, and the obscure and unintelligi-
ble phraseology of what are called explanations of the
practice by amateurs, to whom it is not necess ry to
allude more particularly. If there is any one part of
the art of Horticulture in which post hoc has been
mistaken for propter hoc more commonly than ano-
ther, it is surely in what concerns transplantation.*

* It is scarcely necessary to say that these remarks do mot, in any

280 APPLICATION OF PRINCIPLES.

And yet the rationale is simple enough, if we do not
labour to render it confused by imaginary refine-
ments.

When a plant is taken out of the ground for trans-
planting, its roots are necessarily more or less injured
in the process, and consequently it is less able to sup-
port the stem than it was before the mutilation took
place; its loss of this power will also be in proportion
to the extent of the mutilation, which may be carried
so far as to amount to destruction.

But the importance of their roots to plants is not
alike at all seasons; in the summer, when there is the
greatest demand upon them in consequence of the
perspiration of the foliage (70, &c.), they are most
essential; in winter, when the leaves have fallen,
they are comparatively unimportant, as is evident
from avery common case. Let a limb of a tree be
felled in full leaf in June; its foliage will presently
wither, the bark will shrivel and dry up, and the
whole will speedily perish ; but, if a similar limb is
lopped in November, wher its foliage has naturally
fallen off, it will exhibit no sign of death during win-
ter, nor till the return of spring, when it may make a
dying effort to recover; but the means it takes to do
so, namely, the emission of leaves, only accelerates
its end.

These two propositions really include all the most

way apply to Mr. Macnab’s Hints on the Planting and General
Treatment of Hardy Evergreens in the Climate of Scotland; an
excellent treatise, which it is impossible to recommend too strongly
to the attention of the planter.

OF TRANSPLANTING. 281

essential parts of the theory of transplantation, as
will presently be seen: it is necessary, however, that
they should be applied in some detail; for which pur-
pose it will be convenient to consider, first, the seasun,
and, secondly, the manner, in which transplanting
can be best effected.

It is the powerful perspiratory action of the leaves
of deciduous trees which renders transplanting them
in a growing state so difficult, that for practical pur-
poses it may be called impossible; for the operation
is necessarily* attended by a mutilation of the roots
which feed the leaves. At no period, then, can the
operation be performed if such plants are growing.
Even if the buds are only pushing, the process should
be avoided, because immediately after that period
the demand upon the roots is greatest; for although
in consequence of the smallness of the surface of the
young leaves the action of perspiration may seem to
be feeble, yet the thinness of the newly formed tissue
will not enable it to resist the drying action of the
atmosphere unless there is a most abundant afflux of
sap from the roots. In England, too, the months
when buds begin to burst forth are objectionable,
not only on account of their dryness (see the tables
at page 133), but of their coldness, which prevents
the free circulation of sap; and their evil effects are
felt not only by the roots through the foliage, but

* Transplanting from garden pots, in which the roots are pre-
served artificially from injury, may be performed equally well at
any time if care is taken, and is, of course, not included in this
statement.

282 APPLICATION OF PRINCIPLES.

directly, as will be shown hereafter. The season,
then, which ought to be chosen is the period that
intervenes between the fall of the leaf in autumn and
the earliest part of spring, before the sap begins
to move and the dry cold winds of that season to pre
vail. I entirely agree with Mr. Macnab, that the
earliest time at which planting can be effected is,
upon the whole, the best; a conclusion to which he
has come from his extensive practice, in which my
own observation of a great deal of planting for the
last twenty-five years coincides, and which is, in all
respects, conformable to theory. As soon as a plant
has shed its leaves, it is as much at rest for the season
as it will be at any subsequent period, unless it is
frozen; its torpor, indeed, is greater at that time,
because its excitability is completely exhausted by
the season of growth, and it has had no time to reco-
verit. If, at that time, a root is wounded, a process
of granulation or cicatrisation will commence, just as
it does in cuttings (page 200); and from that granu-
lation, which is a mere developement of the horizon-
tal cellular system (45), roots will eventually proceed.
Now, it is obvious that since roots must be wounded
in the process of transplantation, the sooner the wound
is made the better, because it has the longer time in
which to heal ; and therefore the earlier in the autumn
transplanting is effected, the less injury will be sus-
tained by the plant submitted to the process; in the
technical language of the gardener, ‘‘it has the more
time to establish itself.”

Autumn and mid-winter are, moreover, the best

OF TRANSPLANTING. 283

seasons, because of their great dampness. It will be
seen. by reference to Mr. Thompson's tables (page
1383), that the air is very generally in a state of satura-
tion in the months of October, November, December,
January, and February, and that it is seldom in that
condition at any other season. Now, although the
perspiration of plants is greatly diminished by the
removal of the leaves, it is not destroyed, for they
also perspire through their young bark; and there-
fore a saturated atmosphere, which prevents much of
the perspiratory action which remains from being ex-
ercised, is a conditio., even when plants are leafless,
much too beneficial 19 be overlooked. Nor is the ac-
tion upon the perspi atory power of the stem the only
mode in which a sa:urated atmosphere is important
at the time of transplantation ; it exercises a directly
favourable influences on the roots themselves, Roots,
at their spongivles, or most absorbent points, are ex-
tremely delicate psrts, unprotected by a fully organis-
ed epidermis (223, dastined to exist in a moist medium,
and capable of being easily killed by exposure to dry-
ness as well as by actual violence. The accidents to
which the roots of transplanted trees are liable, from
the very nature of the operation, are of such kind that
it is impossible to prevent their being exposed to the
air, sometimes for considerable periods of time; it is
therefore obviously a point of the first importance,
that the air should be as nearly of the humidity of
the soil from which the roots have been extracted as
can be secured. How unfavourable, in this point of
view, the months of March, April, and May are for

284 APPLICATION OF PRINCIPLES.

planting, is apparent from Mr. Thompson’s tables
above referred to; how little the matter is attended
to by nurserymen, gardeners, and labourers, all great
planters know to their cost. Mr. Macnab, who
thoroughly understands all this, prefers a moist
rainy day; although, as he says, he has “at times
been as wet in planting evergreens, as when exposed
for hours on the windy side of Ben Nevis in a wet
day, without greatcoat and with a broken umbrella.”
It may be very true that good plantations have been
made in March and April; it may be equally true
that no such care as I have described is necessary for
all plants; but no wise man would, on that account,
neglect the precautions which the nature of plants
shows to be necessary to insure success with all things.
Very wet and late springs may prevent the loss of
any considerable proportion of the trees planted in
March and April, especially if succeeded by a dull,
warm, wet summer; and a Willow may be planted
with success at midsummer: but we cannot tell be-
forehand what sort of spring is coming, and all
plants have not the tenacity of life possessed by a
Willow.

If the months of November and December are the
most favourable for transplanting deciduous trees,
and March and April the worst, how much more im-
portant must be those periods to evergreens. An
evergreen differs from a deciduous plant in this ma-
terial circumstance, that it has no season of rest; its
leaves remain alive and active during the winter, and
consequently it isinastate of perpetual growth. Ido

OF TRANSPLANTING. 285

not mean that it is always lengthening itself in the
form of new branches, for this happens periodically
only in evergreens, and is usually confined to the
spring; but that its circulation, perspiration, assimi-
lation, and production of roots are incessant. Such
being the case, an evergreen, when transplanted, is
liable to the same risks as deciduous plants in full
leaf, with one essential difference. The leaves of ever-
greens are provided with a thick hard epidermis (61),
which is tender and readily permeable to aqueous ex-
halations only when quite young, and which becomes
very firm and tough by the arrival of winter, whence
the rigidity always observable in the foliage of ever-
green trees and shrubs. Such a coating as this is
capable, in a much less degree than one of a thinner
texture, such as we find upon deciduous plants, of
parting with aqueous vapour; and moreover its
stomates (61) are few, small, comparatively inactive,
and chiefly confined to the under side, where they are
less exposed to dryness than if they were on the upper
side also. But although evergreens, from their struc-
‘ture, are not liable to be affected by the same external
circumstances as deciduous plants, in the same de-
gree; and although, therefore, transplanting an ever-
green in leaf is not the same thing as transplanting a
deciduous tree in the same condition, yet it must be
obvious that the great extent of perspiring surface
upon the one, however low its action, constituteg
much difficulty, superadded to whatever difficulty
there may be in the other case. Hence we are irre-
sistibly driven to the conclusion, that whatever care

286 APPLICATION OF PRINCIPLES.

is required in the selection of a suitable season, damp,
and not too cold, for a deciduous tree, is still more es-
sential for an evergreen. It is, therefore, most extra-
ordinary that it should ever have been the practice to
defer the planting evergreens till late in the spring,
upon the supposition that it is the very best season
for them, and that midsummer even is a proper pe-
riod; as if cold winds, accompanied by from 20° to
30° of dryness in the air, which is not more than
500 or ‘357 of moisture, with a bright sun beating
on the roots which are exposed, and exciting the ac-
tion of the perspiring surface to the utmost exteut of
its power, were external conditions with which the
gardener has no concern: and yet, as Mr. Macnab
justly observes, half a day’s sun in spring and autumn
will do more harm immediately after planting, than a
whole week’s sun from morning till night in the mid-
dle of winter.

The Holly, says the writer in the Horticultural
Transactions, does not succeed well, if transplanted at
any other season of the year than the end of April
or beginning of May; at this time the buds are just
breaking open into leaf, and I have rarely failed of
success in transplanting small, or even very large old,
trees (ii. 8357). Although such statements cannot be
too strongly contradicted as guides to practice, yet it
is not difficult to explain their origin. As evergreens
are never deprived of their leaves, so they are never
incapable of forming roots; on the contrary, they
produce them abundantly all winter long, and rapid-
ly at any other period of the year which is favourable

OF TRANSPLANTING. 287

to their growth: so that they are capable of making
good an injury to their roots much more speedily than
deciduous plants; especially as in the majority of
cases the roots are numerous and fibrous, and not so
liable tv extensive mutilation when transplanted.
Now, if an evergreen is planted in the month of May,
and the weather happens to be cloudy, mild, and
damp, as the plant is just then commencing the re-
newal of its growth, and is forming fresh roots abun-
dantly, if such a state of weather lasts for a week or
two, there is no doubt that the plant will succeed very
well; and so it will if removed at midsummer. In
the year 1822, in the month of August, there were
planted in the garden of the Horticultural Society of
London above 6000 Hollies from two to three feet
high, for the purpose of forming fences: few plants
in all thas number ever exhibited any traces of hav-
ing been removed, and I do not believe that a hun-
dred died. The weather was dry; but the plants
were deluged with water when placed in their holes,
and they had been obtained from the Regent’s Park,
where they grew in the stiff plastic clay of that side
of London; the consequence of which was, that, when
taken out of the ground, so much earth adhered to
them, that they were almost in the state of plants re-
moved from pots. Now, is this a case to justify
planting Hollies in the month of August? Surely
not; it only shows that it may be done under a com-
bination of very propitious circumstances. There
may be local conditions of a permanent nature, owing
to the peculiarity of climate, in which those advan-

288 APPLICATION OF PRINCIPLES.

tages may be calculated upon; but they do not justify
the gardener in taking a season of great risk, instead
of a season of perfect certainty. I have seen tens of
thousands of Hollies planted late in the spring in the
county of Norfolk, and in the quarters, too, of nur-
series, where, from the plants shading each other, they
are far more likely to succeed than if exposed singly ;
and although it sometimes happened that a good
many lived, it is not too much to say that three-fifths
at least would die; and it is perfectly well known
that if planted in the beginning of November no such
loss is sustained. In short, I am certain that if ex-
perience is looked to only, it will give the same an-
swer as theory to the question of what season is the
best for planting evergreens, namely, that which is
best for other trees; and such cases to the contrary
as may appear to exist will always be found excep-
tions to the rule, in consequence of some peculiar cir-
cumstances attending them; not unfrequently, I be-
lieve, from the operation having been performed upon
a very small number of plants, to the removal of
which a degree of care was given wholly incompatible
with general and extensive practice.*

* [These remarks must be received with great modification,
especially in the Northern and Eastern States, The moist or rainy
winters of England are the exact opposite of our cold and dry ones,
during which, for two months at least, the soil is severely frozen,
and vegetation is nearly or quite dormant. Our whole experience
goes to prove that the practice of transplanting evergreens in
autumn is, for this country, extremely injudicious; as the damage
which the trees sustain in their removal greatly increases their
susceptibility to injury by the cold of winter. The early spring

OF TRANSPLANTING. 289

Mr. Macnab rightly adverts to the importance of
choosing a suitable day, as well as season, for the
operation; and it must be evident from what has now
been stated, and this is very necessary: as, however,
the theory of this is the same as that of the season, it
will be sufficient to quote this excellent practical gar-
dener’s rule. In winter, you may plant with perfect
safety in a dull calm day, whereas in spring or autumn
a moist rainy day is preferable to any other; but
where a person has not the choice of such weather,

is the most favourable period for the purpose; since the abundant
and long-continued rains which occur from the vernal equinox to
the middle of April enable the plant to recover itself, and emit
new roots with rapidity. We have been very successful in May,
but then so much depends upon the occurrence of rainy weather,
that the risk is greatly increased; Next to the selection of the
proper time, the preservation of the roots in a moist condition is
the most essential point, in removing all evergreen trees.—These
remarks are not applicable to a different mode of transplanting
large evergreen and other trees, which is very successfully prac-
tised in this country; that of removing them with large frozen
balls of earth in midwinter. The trees to be removed are selected,
and the holes prepared for their reception in autumn, while the
ground is yet open. When the ground is slightly frozen, the ope-
rator proceeds to dig a trench around the tree, at some distance
from its trunk, gradually undermining it, and leaving the princi-
pal mass of roots embodied in the ball of earth, which is left to
freeze pretty thoroughly. At a favourable time during the win-
ter, the tree with the ball of frozen earth is rolled upon a sled
drawn by oxen, by which it is readily transferred to the hole
previously prepared for its reception, and placed in the proper
position; and as soon as the weather becomes milder, the earth
is properly filled in around the ball. In this way, a tree twenty-
five feet high may be transplanted, so as scarcely to exhibit, during
the ensuing season, any ill effects from the change of location. A. J. D,

13

.

290 APPLICATION OF PRINCIPLES.

then the work should be performed in the evening,
when the sun gets low, especially in spring or autumn
planting.

Next in importance to the selection of a fitting sea-
son, is the preservation of the roots of transplanted
trees; the former is of little consequence, if the latter
is not more carefully attended to. We know, indeed,
that some plants will live with the rudest treatment,
and bear the most severe mutilation without much
suffering ; but those are special instances of extreme
tenacity of life, and do not affect general principles.
The value of great attention to the roots, in the ope-
ration of shifting, has already been pointed out (p.
269), aud transplanting is only shifting in another
manner. It would be the duty of the gardener to
save every minute fibre of the roots, if it were prac-
ticable ; but, as that is not the case, his care must be
confined to lifting his trees with the least possible
destruction of those important organs; remembering
always that it is not by the coarse old woody roots
that the absorption of food is carried on, but by the
younger parts, and especially the spongioles (23,2+.)
The mechanical means by which this is best effected
do not belong to the present subject; I may, how-
ever, remark, without quitting the limits of theory,
that, as the greater part of the young fibres is pro-
duced at the circumference of the circle formed by
the root, the earth should be first removed at some
distance from the stem, so as to insure, as far as pos-
sible, their being taken up entire; if this is not done,
but the spade is struck into the earth near the stem,

OF TRANSPLANTING, 291

or if the rude nursery practice, justly enough called
drawing, is employed, a large part of the most valua-
ble roots must necessarily be cut off or destroyed by
tearing. The greatest difficulty, beyond that of
mechanical removal, in transplanting trees of consi-
derable size, is this preservation of roots; and, if it
were possible to carry without injury such heavy
masses as old forest trees, there is no physical obstacle
to transplanting them, if the extrication of the fibrous
part of the roots be secured, which is not impracti-
cable. As, however, the latter is a troublesome and
very difficult operation, even when trees are only ten
or twelve feet high, it has been, from time out of
mind, the custom of skilful planters to prepare such
trees for removal by cutting back their main roots
one year before they are to be transplanted ; if this
very simple operation is properly performed, al] the
principal limbs, so amputated, will emit young fibres
in abundance from their extremities, and the gardener,
from knowing where to find those roots, can easily
take them up without material injury. In order to
effect the same end, but in another way, the following
expedient has been occasionally employed for large
trees. A deep trench has been opened, in midwinter,
round a stem, at such a distance as to be clear of the
principal fibres; the tree has then been carefully
undermined, till, at last, the earth belonging to it has
formed a huge ball; upon the approach of frost,
water has been freely poured over the ball so that ite
whole surface may be converted into an icy mass; in
that state it has been raised by powerful tackle, and

292 APPLICATION OF PRINCIPLES.

conveyed without disturbance to its intended site.
This operation, which is the best possible for hardy
trees of great size, but expensive, and therefore only
capable of application in a limited degree, owes its
success entirely to the young and tender fibres being
placed in such a position that they cannot be injured
by the act of transport.

Under all ordinary circumstances, the roots must
necessarily be injured more or less by removal; in
that case, all the larger wounds should be cut toa
clean smooth face; not in long ragged slivers, as is
often the case, and which is only substituting one
kind of mutilation for another, but at an angle of
about 45°, or less. If the ends of small roots are
bruised, they generally die back a little way, and
then emit fresh spongioles; but the larger roots, when
bruised, lose the vitality of their broken extremity,
their ragged tissue remains open to the uncontrolled
introduction of water, decays in consequence of being
in contact with an excess of this fluid, and often
becomes the seat of disease which spreads to parts
that would otherwise be healthy. When, however,
the wound is made clean by a skilful pruner, the ves-
sels all contract, and prevent the introduction of an
excess of water into the interior; the wound heals by
granulations formed by the living tissue, and the
readiness with which this takes place isin proportion
to the smallness of the wound. It may be sometimes
advantageous to remove large parts of the coarser
roots of a tree, even if they are not accidentally
wounded when taken up, the object being to compel

OF TRANSPLANTING. | - 298

the plant to throw out, in room of those compara-
tively inactive subterranean limbs, a supply of young
active fibres. This is a common practice in the nur-
series in transplanting young Oaks and other tap-
rooted trees, and is one of the means employed by
the Lancashire growers of Gooseberries, in order to
increase the vigour of their bushes; in the last case,
however, the operation is not confined to the time
when transplantation takes place, but is practised
annually upon digging the Gooseberry borders. The
reason why cutting off portions of the principal roots
causes a production of fibres appears to be this: the
roots are produced by organisable matter sent down-
wards from the stem (81); that matter, if uninter-
rupted, will flow along the main branclies of the
roots, until it reaches the extremities, adding largely
to the wood and horizontal growth of the root, but
increasing, in a very slight degree, the absorbent
powers: but if a large limb of the roots is ampu-
tated, the powers of the stem remaining the same,
all that descending organisable matter which would
have been expended in adding to the thickness of the
amputated part is arrested at the line of amputation ;
and, unable to pass further on, rapidly produces gra-
nulations to heal the wound, and immediately after-
wards young spongioles, which soon establish them-
selves in the surrounding soil, and become the points
of new active fibres.

The question of pruning the branches of trans-
planted trees has been already sufficiently adverted
to (see p. 248).

294 APPLICATION OF PRINCIPLES.

By many excellent planters, the advantage of de-
luging the roots with water, when newly planted, is
much insisted on; and in the case of large plants,
particularly evergreens, it is, undoubtedly, an essen-
tial process, partly because it causes the flagging and
injured roots to be immediately surrounded by an
abundant supply of liquid food, which, if the opera-
tion be skilfully performed (see Macnab’s Treatise, p.
24 and 25), will not subsequently fail them; and
partly because it is the only means we possess of
embedding with certainty all the fibres in soil.
When the earth is reduced to the state of puddle, it
will settle round the finest roots, and place them as
nearly as possible in the same condition, with regard
to the soil, that they were in before the plants were
removed. But the operation of puddling is unneces-
sary to small plants, if removed at a proper season
of the year, especially to deciduous trees of all kinds;
and it may be very injurious. This was long ago
stated by Mr. Knight (Hort. Trans., ii. 159), who
found by experience that when trees are very much
out of health, in consequence of having become dry,
excess of moisture to the roots is often fatal. This
appears to arise from the languid powers of the
plant being insufficient to enable it to decompose aud
assimilate the water rapidly introduced into its system
through the wounds in its root, and by the hygrome-
trical force of that part; under such circumstances,
water will dissolve the mucilaginous and other mat-
ters intended for the support of the nascent buds,
which matters then putrefy, lose their nutritive qua-

PRESERVATION OF RACES BY SEED. 295

lity, and rapidly destroy the tissue. The substitute
for root-watering contrived by Mr. Knight in such
cases was, to keep the plants in a situation shaded
from the morning sun, and to moisten their bark fre-
quently; by these means, water is presented to them
very slowly through the young cortical integument
(48); which, partaking of the nature of a leaf (63),
slowly absorbs it, probably decomposes it, and trans-
mits it laterally (57) through the liber into the albur-
num, where it finds itself in the ordinary channel for
the ascending sap, and thus enters the system of
circulation. In this way Mr. Knight originally pre-
served American Apple trees, which reached him in
the middle of April, in so bad a state that they seemed
“perfectly lifeless and dry, and much better fitted for
firewood than for planting.”*

CHAPTER XVII.
OF THE PRESERVATION OF RACES BY SEED.

THE manner of preserving the domesticated races

* For the same reason, the best possible mode of reviving trees
that have become dry and shrivelled by long transportation is to
unpack them and bury them for a few days in light soil, covering
both roots and branches with earth. The parched bark will absorb
moisture gradually from the earth, and the trees may be entirely
restored to freshness and vitality, when immersing them in water, or
planting them with the branches dry, would only insure their death.
A. J.D.

296 APPLICATION OF PRINCIPLES.

of plants by the ordinary means of propagation, such
as cuttings, layers, grafts, and so on, has already been
explained; there are, however, some other topics con-
nected with this important subject which require to
be touched upon.

Propagation by division is inapplicable to annuals
or biennials, or at least can be practised upon only a
very limited scale, and for such plants the gardener
has to trust to seeds alone. But it is an axiom in
vegetable physiology that seeds reproduce the species
only, while buds (that is, propagation by division)
will multiply the variety; and this is undoubtedly
true as a generalrule. But the skill and care of the
gardener often enable him to perpetuate by seed the
many races of cultivated annuals, varieties of the same
species, improved and altered by centuries of domes-
tication, with as much certainty as if he were operat-
ing with cuttings. In a well managed farm we see the
various breeds of Turnips and Corn preserving each
its own peculiar character unchanged year after year,
and yet they must all be propagated by seed alone;
and in gardens the varieties are innumerable of Peas,
Lettuces, Cabbages, Radishes, &c., whose purity is
maintained by the same means. ‘The manner in
which this is effected is of the first importance to be
understood.

Although it is the general nature of a seed to per-
petuate the species only to which it belongs, and it
cannot therefore be relied upon, in ordinary cases, to
renew a particular variety of species, yet there is al-
ways avisible tendency in it to produce a seedling

PRESERVATION OF RACES BY SEED. 297

more like its parent than any other form of the
species. Suppose, for example, the seed of a Ribston
Pippin apple were sown; if untainted by intermixture
with other varieties, it would produce an apple tree
whose fruit would be large, sweet, and agreeable to
eat, and net small, sour, and uneatable, like the
Wilding Apple or Crab. The object of the gardener
is to fix this tendency, and he does it by means not
unlike those employed in the preservation of the races
of domesticated animals, namely, by “breeding in and
in,” as the phrase is. An example of this will be more
instructive than a dissertation. The Radish has, when
wild, a long pallid root; among many seedlings one
was remarked with roots shorter and rounder, and
more succulent than the remainder; this was a “sport”
to which all plants are subject. Had that Radish
been left among its companions, and the seed saved
from them all indifferently, the tendency would have
disappeared for that time; but its companions were
all eradicated, and the better one produced its seed in
solitude. The crop of young plants produced from
this Radish was, for the most part, composed of indi-
viduals of the wild form, but several preserved the
same qualities as the parent, and some, perhaps
one only, in a higher degree: in this one, then, the
tendency was beginning to fix. Again were all
eradicated, except the last-mentioned individual,
whose seeds were carefully preserved for the succeed-
ing crop; and, by a constant repetition of this prac-
tice for many years, at last the habit to produce a.
round and suceulent root became so fixed, that all the
13*

298 APPLICATION OF PRINCIPLES.

Radishes assumed the same appearance and quality,
and there were none left to draft or ‘rogue.’ Every
variety of annual crop, not still in its wild state, must
have gone through this process of fixing; and thus
the varieties of earliness, lateness, and productive-
ness, colour, form, and flavour, observable in garden
plants, have been secured for our enjoyment.

But to fix a new habit in annual plants is not the
only care of the cultivator, whose patience and skill
would be ill employed if it could not be preserved.
If a plant has some tendency to vary from its origi-
nal condition, it has much more to revert to its wild
state ; and there can be no doubt that, if the arts of
cultivation were abandoned for only a very few years,
all the annual varieties of our gardens would disap-
pear, and be replaced by a few original wild forms.

For the means of preserving the races of plants
pure, the means vary according to the nature of the
variety. As far as concerns early and late varieties,
it often happens that, as in Peas, the tendency in such
plants to advance or retard their season of ripening
was originally connected with the soil or climate in
which they grew. <A plant which for years is culti-
vated in a warm dry soil, where it ripens in forty
days, will acquire habits of great excitability; and,
when sown in another soil, will, for a season or so,
retain its habit of rapid maturity: and the reverse
will happen to an annual from a cold wet soil. But,
as the latter will gradually become excitable and
precocious, if sown for a succession of seasons in a dry
warm soil, so will the former lose those habits, and

PRESERVATION OF RACES BY SEED. 299

become late and less excitable. Hence, the best
seedsmen always take care that their early varieties
of annuals are procured from warmer and drier lands
than those on which they are to be sown; our earliest
Peas, for example, are obtained from France, and the
next in time of ripening from the hot dry fields of
Kent, the Suffolk coast, and similar situations. Thus,
also, the Barley grown on sandy soils, in the warmest
parts of England, is always found by the Scotch
farmer, when introduced into his country, to ripen on
his cold hills earlier than his crops of the same kind
do, when he uses the seeds of plants which have
passed through several successive generations in his
colder climate; and Mr. Knight found that the crops
of Wheat on some very high and cold ground, which
he cultivated, ripened much earlier when he obtained
his seed-corn from a very warm district and gravelly
soil, which lies a few miles distant, than when he em-
ployed the seed of his vicinity. It would seem as if
this were in some way connected with the mere size
of aseed, the smallest seeds of a given variety pro-
ducing plants capable of fructifying quicker than
those of a much larger size. We have, at present,
but little information upon this subject; but there
are some most curious experiments relative to it by
Messrs. Edwards and Colin, who found that, although
Winter Wheat cannot, in France, be made to shoot
into ear, if sown in the spring, provided the largest
grains of the variety are employed, yet that, if the
smallest grains are picked out, some will ear like
Spring Wheat (see Annales des Sciences Naturales, v.

800 APPLICATION OF PRINCIPLES,

1). Out of 530 grains of Winter Wheat, sown on the
23d of April, and weighing 7 ounces 52 grains, not
one pushed into ear; they tillered abundantly, but the
tillers were excessively stunted, and concealed among
the tufts of leaves; in short, they formed nothing but
turf: on the other hand, of 530 other grains, weiglh-
ing 3 ounces 56 grains, and sown on the same day,
60 pushed in ear.

It would seem as if many of our most esteemed
garden plants were the result of debility, and that the
succulence, the sweetness, or the excessive size, which
render them so well suited for food, were only marks
of unhealthiness. At least, it is almost necessary to
assume this to be the case, in order to account for
the efficacy of one of the modes of maintaining races
genuine. It is perfectly well known, that, if such an
annual as a Turnip is transplanted shortly before it
runs to seed, the characters of its variety will remain
more strongly marked, and have far less tendency to
vary, than if, all other circumstances remaining the
same, the seed is saved without the process of trans-
plantation having been observed. Now, the only
effect of transplanting, at the season immediately pre-
ceding the formation of a flower-stalk, would seem to
be that of checking the luxuriance of the individual
operated on; or, upon the above assumption, of in-
creasing its debility of constitution. And the same
explanation appears applicable to a strange custom
mentioned by Mr. Ingledew as being practised in the
Dekkan, to prevent the rapid deterioration, in that
climate, of the Carrot, the Radish, and the Parsnep,

PRESERVATION OF RACES BY SEED. 301

the favourite table vegetables of the inhabitants. He
states that the Indian gardeners, in the first place,
prepare a compost of buffaloes’ dung, swine’s dung,
and red maiden earth, mixed with water till they have
the consistence of paste, and scented with a small
quantity of assafoetida, the Jatter of which seems to be
perfectly useless.

“The vegetables for this operation are drawn,
when wanted, from the beds, when they have attain-
ed about one third of their natural growth, and those
plants are chosen which are the most succulent and
luxuriant; the tops are removed, leaving afew inches
from their origin in the crown upwards; and a little
of the inferior extremity, or taproot, is cut straight
off likewise, allowing nearly the whole of the edible
part to remain, from the bottom of which to within
about an inch of the crown, are made two incisions
across each other entirely through the body of the
vegetable, dividing it into quarters nearly to the up-
per end. They are then dipped into the compost
until they are well covered by it, both externally and
internally, and are immediately placed in beds, pre-
viously prepared for their reception, at the distance
of fifteen or sixteen inches from each other, and so
deep in the ground that the upper extremities only
appear in sight. They are afterwards regularly
watered; and when they take root, and fresh tops
have made some advance in growth, they require but
little attention. The tops speedily become large, and
grow into strong and luxuriant stalks, the blossoms
acquire a size larger than ordinary, and the seed they

302 APPLICATION OF PRINCIPLES,

produce is likewise large and vigorous, and supera-
bundant in quantity. Innumerable roots are thrown
out from the incised edges of these plants; they con-
sequently receive a greater abundance of nourishment,
which occasions their luxuriant growth, causes them
to yield not only a more than ordinary crop of seed,
but also of a superior quality. (Hort. Trans., v. 517.)
The operation is performed at the beginning of the
dry season.

Besides “roguing out” (i. e. eradicating) all indivi-
duals having the slightest appearance of degeneracy
from among the plants intended for seed, care must
be taken that the crop is so far from any other of a
similar kind as to incur no risk of being spoiled by the
intermixture of its pollen (88). This substance is
conveyed to considerable distances by wind and in-
sects ; and it is scarcely possible to be secure from its
influence, if similar crops are cultivated within some
miles of each other; whence we find certain villages,
in different parts of Europe, celebrated for the purity
of the seed of particular varieties ; this usually happens
in consequence of the villagers cultivating that
variety and no other, as happens at Castelnaudary
with Beet, at Altringham with the Carrot, and in
Norfolk with different kinds of Turnip.

It is, however, to be observed, that the deteriora-
tion of seed by bastardising happens to a greater
extent to single plants than to large masses of them ;
and it seldom happens that good seed can be saved
in a garden, or near gardens, from a single indivi-
dual. Solitary specimens of the Turnip, the Cauli-

PRESERVATION OF RACES BY SEED. 803

flower, and such plants, have been frequently selected
on account of their perfect characters, and been care-
fully planted in gardens for a stock of seed, but their
produce has as frequently been of the worst descrip-
tion, bearing no resemblance to the parent. In such
cases as these, it would seem as if bees and other
insects were attracted from all quarters by the gay
colours, or odour, of such isolated individuals, and,
arriving from a hundred flowers which they had pre-
viously visited, bring with them so many sources of
contamination.

When, however, the action of other flowers can be
prevented, as in the Melon and other unisexual
plants, by “setting,” the largest, healthiest, and most
cultivated varieties will yield seed of the purest and
finest quality. The tendency of Persian Melons to
degenerate in this country was remarked soon after
their introduction; and, for a long time, it was
thought impossible to preserve them for many
generations. Mr. Knight, in his numberless experi.
ments upon this fruit, found that to be the case ; for
his fruit, at one time, became less in bulk and weight,
and -deteriorated in taste and flavour. But when he
came to consider that “every large and excellent
variety of Melon must necessarily have been the pro-
duction of high culture and abundant food, and that
a continuance of the same measures which raised
it to its highly improved state must be necessary
to prevent its receding, in successive generations,
from that excellence,” the cause of his Persian Melons
deteriorating became apparent ; and he found that by

304 APPLICATION OF PRINCIPLES.

bringing the cultivation of the plants to a state
of great perfection, he succeeded completely in ren-
dering the original quality hereditary, so long as
those precautions were observed. No man was more
successful in the cultivation of the Melon than Mr.
Knight; and it is in the memory of many persons,
that the quality of his Sweet Melons of Ispahan has
very rarely been equalled. The peculiar methods
that he adopted appear to have been the complete
and most careful preservation of the leaves from
injury of whatever kind, the full exposure of their
surface to light, and the augmentation of the ordinary
warmth of a Melon bed by availing himself of the
heat reflected from brick tiles with which his bed
was paved. To such an extent was his care of the
leaves carried, that he would not allow even the
watering to be performed “ over-head,” but he caused
his gardener to pour water, from a vessel of proper
construction, upon the brick tiles between the leaves,
without touching them. (See various papers upon
the Melon in the Horticultural Transactions, and espe-
cially that in vol. vii. p. 584.)

While, however, such are the general principles
upon which the preservation of the peculiar qualities
‘ of the many races of cultivated annuals necessarily
depends, it must be confessed that, according to
report, there are circumstances upon which science
can throw no light, and which, if true, must depend
upon conditions as yet unsuspected to exist. Of this
class is the following, respecting the Brussels Sprouts
Cabbage, given upon the authority of M. Van Mons.

PRESERVATION OF RACES. BY SEED. 805

“Much has been said of the disposition of this
plant to degenerate. In the soil of Brussels it
remains true, and I have lately observed it to do the
same at Louvain; but at Malines, which is the same
distance from Brussels as Louvain, and where the
greatest attention is paid to the growth of vegetables,
it deviates from its proper character, after the first
sowing; yet it does not seem that any particular soil
or aspect is essential to the plant, for it grows equally
well and true at Brussels, in the gardens of the town,
where the soil is sandy and mixed with a black moist
loam, as in the fields, where a compact white clay
predominates. The progress of deterioration at
Malines was most rapid; the plants raised from seed
of the true sort, which I had sent there, produced the
sprouts in little bunches or rosettes, in their true
form ; seeds of those being saved, they gave plants in
which the sprouts did not form into little cabbages,
but were expanded; nor did they shoot again at the
axils of the stem. The plants raised from the seeds
of these last mentioned only produced lateral shoots
with weak pendant leaves, and tops similar to the
shoots, so that in three generations the entire charac-
ter of the original was lost. From a plant in the state
last described, seed was saved at my request, and
sent back to me. I had it sown by itself, and care-
fully watched the plants in their growth; I was not
long in discovering that they retained the same cha-
racter of degeneration they had assumed at Malines,
and preserved it throughout the whole course of their
growth, yielding pendulous leaves with long petioles,

306 APPLICATION OF PRINCIPLES.

and having no disposition to cabbage. I suffered
these plants to run to seed at a great distance from
my true Sprouts, which the extent of my garden
allowed me easily to do. The second sowing brought
them back a good deal to their true character; the
plants yielded small cabbages regularly at each axil,
but not generally full or compact, and they did not
shoot a second time, as the true sort does. J again
suffered these to run to seed, using the same precau-
tion of keeping them by themselves. I sowed the
seed, and this time the plants were found to have
entirely recovered their original habits, their head,
and rich produce.” (Hort. Lrans., iii. 197.) I must
confess, however, that, although tne passage merits
quotation, for the sake of exciting attention to the
subject, it appears to me very doubtful whether the
case has been fully, if correctly, stated.

CHAPTER XVIII.
OF THE IMPROVEMENT OF RACES.

Wuar has been stated in the preceding chapter,
concerning the preservation of the races of domes-
ticated plants, is in some measure applicable to their
improvement, because the very means employed
to preserve those peculiarities of habit which render
them valuable, will, from time to time, be the cause
of still more valuable qualities making their appear-

OF THE IMPROVEMENT OF RACES. 307

ance. There are, however, other points of great
importance on which the gardener has dependance.

A fixed improvement in the quality of the produce
of a plant can only be obtained in one of two ways;
either directly, by accidental variations in itself, or
indirectly, by the process of muling.

Direct alterations in the quality of seedling plants
often occur from no apparent cause, just as those ac
cidental changes, called ‘‘sports,” in the colourorform
of the leaves, flowers, or fruit, of one single branch
of a tree, occasionally break out, we know not why.
Of these things, physiology can give no account; but
it is known that, when those sports appear, they in-
dicate a permanent constitutional change in the action
of the limb thus affected, which changes may be
sometimes perpetuated by seed, and always by pro-
pagation of the limb itself, when propagation is prac-
ticable. Itisin this way that many of our fruits have
probably, and several of the Chinese Chrysanthemums
have certainly, been obtained. It was apparently
thus that the Nectarine emanated from the Peach. It
is possible that many new forms of shrubs might be
procured'by keeping these facts in view, and that
climbers might be deprived of their climbing habits ;
for it is known that the handsome evergreen bush
called the Tree Ivy, which grows erect, with scarcely
the least tendency to climb, has been procured by
propagating the fruit-bearing branches of trees of con-
siderable age,

But we are by no means destitute of the power of
procuring, with considerable certainty, improved.

308 APPLICATION OF PRINCIPLES.

varieties, by an application to practice of physiologi-
cal principles. In the last chapter has been shown
the importance of securing the production of seed by
plants in the most healthy state possible, because a
robust parent is likely to afford a progeny of similar
habits to itself. In annuals, however, this is appa-
rently restrained within narrower limits than in woody
plants, from the great difficulty of fixing a new
peculiarity in the former, and the facility with which
it may be effected in the latter case, by means of
buds, cuttings, grafts, and similar modes of propaga-
tion. The great object of the scientific gardener who
desires to improve the varieties of plants upon prin-
ciple will be, then, by artificial means, to bring the
parent from which seed is to be saved as near as pos-
sible to that state at which he desires the seedling to
arrive.

It is well known that the abstraction of fruit and
flowers augments the vigour of the branches, or of the
parts connected with them, and that the removal
from the former of any part which takes up a portion
of the food employed in the support of the flowers in-
creases their efficiency. Thus those varieties of the
Potato, which will neither flower nor fruit otherwise,
may be made to do both by stopping the develope-
ment of tubers; and, on the other hand, the size
and weight of the tubers themselves are increased by
preventing the formation of flowers and fruit. The
course, then, to take, in obtaining the largest possible
tubers in a new variety of the Potato, would be, in
the first place, to effect that end temporarily, but dur-

OF THE IMPROVEMENT OF RACES. 809

ing several successive seasons, by abstracting all the
flowers and fruit, and by such other means as may
suggest themselves; and then to obtain the most per-
fect seed possible by a destruction of the tubers dur-
ing the season when seed is finally to be saved. Mr.
Knight found, in raising new varieties of the Peach,
that, when one stone contained two seeds, the plants
these afforded were inferior to others. The largest
seeds obtained from the finest fruit, and from that
which ripens most perfectly and most early, should
always be selected (Hort. Trans., i. 89); and, in his
incessant ‘efforts to obtain new varieties of fruit of
other genera, he had reason to conclude that the trees,
from blossoms and seeds of which it is proposed
to propagate, should have grown at least two years in
mould of the best quality; that during that period
they should not be allowed to exhaust themselves by
bearing any considerable crop of fruit; and that the
wood of the preceding year should be thoroughly
ripened (by artificial heat when necessary) at an early
period in the autumn; anc, if early maturity in the
fruit of the new seedling plant is required, that the
fruit, within which the seed grows, should be made to
acquire maturity within as short a period as is consis-
tent with its attaining its full size and perfect flavour.
Those qualities ought also to be sought in the parent
fruits, which are desired in the offspring; and he
found that the most perfect and vigorous progeny was
obtained, of plants as of animals, when the male and
female parent were not closely related to each other.
(See the Horticultwr:! Transactions, i. 165.)

310 APPLICATION OF PRINCIPLES.

There are no processes known to the cultivator so
efficacious in producing new varieties as that adverted
to in the last paragraph, that is to say, muling or cross
breeding (88); and it is to these operations, more than
to any thing else, that we owe the beauty and excel-
lence of most of our garden productions; more, how-
ever, I think, to cross breeding than to muling. It
was entirely by the first of these processes that have
been so greatly multiplied and improved our fruits
for the dessert, and the gay flowers that adorn our
gardens. The Pelargonium, the Calceolaria, the
Dahlia, the Verbena, and a thousand others—what
would they be but simple wild flowers, without the
power of man exercised in this way? “To the cul-
tivators of ornamental plants,” says Mr. Herbert,*
“the facility of raising hybrid varieties affords an
endless source of interest'and amusement. He sees
in the several species of each genus that he possesses
the materials with which he must work, and he con-
siders in what manner he can blend them to the best
advantage, looking to the several gifts in which each
excels, whether of hardiness to endure our seasons,
of brilliancy in its colours, of delicacy in its mark-
ings, of fragrance, or stature, or profusion of blossom;
and he may anticipate, with tolerable accuracy, the
probable aspect of the intermediate plant which he is
permitted to create; for that term may be figurative-

* See much the most valuable and practical account of cross
breeding and muling which has been yet published in regard to
horticulture, in the -Amaryllidacew of the Hon. and Rey. W.
Herbert, p. 335, et seq.

OF THE IMPROVEMENT OF RACES. 311

ly applied to the introduction into the world of a na-
tural form which has probably never before existed
in it. In constitution the mixed offspring appears to
partake of the habits of both parents; that is to say,
jt will be less hardy than the one of its parents which
bears the greatest exposure, and not so delicate as the
other; but, if one of the parents is quite hardy, and
the other not quite able to support our winters, the
probability is, that the offspring will support them,
though it may suffer from a very unusual depression
of the thermometer, or excess of moisture, which
would not destroy its hardier parent.”

In the many successful attempts made by Mr.
Knight to improve the quality of fruit trees by rais-
ing new varieties, his method was to obtain cross-
breds by fertilising the stigma of one variety of
known habits with the pollen of another also of
known habits. But, in doing this, his experiments
were not conducted at random, and without due con-
sideration; on the contrary, we learn from himself
that he was very careful in selecting the parents from
which his crossbreds were obtained. He found that
the genéral opinion, that the offspring of crossbred
plants as well as crossbred animals usually presents
great irregularity of character, is unfounded; and
that if a male of permanent habits, and of course not
crossbred, be selected, that will completely overrule
the disposition to sport, “the permanent character
always controlling and prevailing over the variable.”
He tells us that he usually propagated from the seeds
of such varieties as are sufficiently hardy to bear and

812 APPLICATION OF PRINCIPLES.

ripen their fruit, even in unfavourable seasons and
situations, without the protection of a wall, because,
in many experiments made with a view to ascertain-
ing the comparative influence of the male and female
on their offspring, he had observed in fruits, with few
exceptions, a strong prevalence of the constitution
and habits of the female parent. Unfortunately,
however, this is precisely the reverse of the result at
which Mr. Herbert has arrived in the very great
number of experiments performed by himself on that
subject, he believing that the male parent generally
influences the character of the foliage, and the female
that of the flowers (Amaryllidacee, p. 848, 877); and
although it does appear to me that, in the majority
of cases, Mr. Herbert’s opinion is the more correct of
the two, yet I fear there is too little certainty in the
results of hybridising to justify the establishment of
any axiom upon the subject.

This power of muling, properly so called, is con-
fined within very narrow limits, and can hardly be
said to exist at all between species of different genera,
unless under that name are comprehended some of
the spurious creations of inconsiderate Botanists.
There are, indeed, many cases of species very closely
allied to each other which it is either impossible
to mule, or so difficult that no one has yet succeeded
in effecting it. Mr. Knight never could make the
Morello breed with the common Cherry. I have in
vain endeavoured to mule the Gooseberry and Cur-
rent, and we do not possess any garden production
known to have been produced between the Apple

OF THE IMPROVEMENT. OF RACES. 313

and the Pear, or the Blackberry and the Raspberry;
any of which might have been expected to intermix.
As to mules obtained between plants of distinct
genera, we have, no doubt, upon record, some experi-
ments said to have been performed successfully in
crossing a Thorn-Apple with Tobacco, the Pea with
the Bean, the Cabbage with the Horse-radish, and so
on; but Mr. Herbert regards these cases, and I think
with great reason, as apocryphal, and not to be relied
on; the fact being, as he truly states, “that in this
country, where the passion for horticulture is great,
and the attempts to produce hybrid intermixtures
have been very extensive during the last fifteen years,
not one truly bigeneric mule has been seen.”

On the other hand, cross breeding (89) will take
place quite as readily among plants as among ani-
mals, and it is difficult to estimate the alteration
which this process has really produced, although
unperceived by us, in the amelioration and advantage
of long-cultivated plants. We cannot reasonably
doubt that a process so simple as that of dusting the
stigma of one plant with the pollen of another, which
must be continually happening in our gardens, either
through the agency of insects or the currents in the
air, and which, where it takes place between two
varieties allied to each other, must necessarily pro-
duce a cross,—we cannot suppose, I say, that this
occurs in our crowded gardens and orchards at that
time only when we perform it artificially.

The operation itself, although so simple, consisting
in nothing more than applying the pollen of one

14

314 APPLICATION OF PRINCIPLES.

plant to the stigma of another, nevertheless requires
to be guarded by some precautions. In the first
place, it is requisite that the flower whose stigma
is to be fertilised should be deprived of its own
anthers before they burst, otherwise the stigma will
be self-impregnated, and although superfcetation is
not, by any means, impossible, yet it is not very
likely to occur. Then, again, the application of the
stranger pollen should be made at the time when the
stigma is covered with its natural mucus; if not, the
pollen will not act, either in consequence of the
necessary lubrification of itself being withheld, from
the stigma being too young, or because the stigma,
from age, has lost its power of receiving the action
of the pollen. Neither should the stigma be in any
way injured after fertilisation has apparently taken
place. The art of fertilisation consists in the emission,
by the pollen, of certain tubes of microscopical tenuity,
which pass down the style, and eventually reach the
young seed, with which they comein contact ; and, un-
less this contact takes place, fertilisation misses. Now
the transmission of the pollen tubes from the stigma
to the ovule, through the solid style, is often very
slow, sometimes occupying as much as a month or six
weeks, as in the Misletoe.

Those who occupy themselves in attempts at
improving the quality of cultivated plants should be
aware of this: namely, that the real quality of either
the fruit or the flower of a seedling cannot be ascer-
tained when they are first produced; for it is only as
plants advance in age that the secretions necessary

OF THE IMPROVEMENT OF RACES. 815

for the perfect production of either the one or the
other are elaborated. Of this fact, the first produce
of the Black Eagle Cherry tree afforded a striking
example. <A part of it was sent, with other cherries,
to the Horticultural Society; and it was then, in the
Fruit Committee, pronounced good for nothing. It
was so bad, that Mr. Knight, who raised it, would
most certainly have taken off the head of the tree
and employed its stem as astock, but that it had been
called the property of one of his children, who sowed
the seed which produced it, and who felt very anxious
for its preservation. It has now become one of the
richest and finest fruits of its species which we pos-
sess.

It may be expected that some mention should here
be made of double flowers, and of the manner in
which they are to be obtained. But I confess myself
unable to discover, either in the writings of physiolo-
gists, or in the experience of gardeners, or in the
nature of plants themselves, any sufficient clue to an
explanation of the causes to which their origin may
be ascribed. There are, however, several facts ap-
parently connected with the subject, which deserve
mention.

A double flower, properly so called,* is one in
which the natural production of stamens or pistils is

* What is called a Double Dahlia is misnamed; and so are
all so-called double Composite flowers. The appearance of doubling
is ‘caused in these plants by a mere alteration of the florets of
their disk into the form of florets of the ray; a very different
thing from double flowers, (83.)

3816 APPLICATION OF PRINCIPLES.

exchanged for petals, or in which the number of the
latter is augmented without any disturbance of the
former; in other words, it is a case of the loss, on the
part of a plant, of the power necessary to develope its
leaves in the state of sexual organs (88, 84). But
what causes that loss of power we do not know. It
can hardly be a want of sufficient food in the soil;
for double flowers (the Narcissus, for instance) be-
come single in very poor soil. On the other hand, it
can scarcely be excessive vigour; for no one has ever
yet obtained a double flower by promoting the health
or energy of a species. When plants are excessively
stimulated by unusually warm damp weather at the
period of flowering, their flowers in such cases some-
times became monstrous: but the effect of this is to
lengthen their axis of growth, and to form true leaves
instead of floral organs (84, jig. 14), just the reverse
of what occurs in a truly double flower; the varieties
of Rosa gallica often exhibit this kind of change. In
damp cloudy summers, some flowers assume the ap-
pearance of being double, by the change of their
sexual organs into small green leaves, as occurred
very generally to Potentilla nepalensis in the summer
of 1839, a representation of which is given at page
61; but there was, at the same time, scarcely a trace
of any tendency, on the part of those leaves, to assume
the colour or texture of petals.

There is, evidently, a greater tendency in some
flowers to become double than in others, and especial-
ly in those having great numbers of stamens or pistils.
All our favourite double flowers, Hepaticas, Peeonies,

OF THE IMPROVEMENT OF RACES. 317

Camellias, Anemones, Roses, Cherries, Plums, Ranun-
culuses, belong to this class; and, in proportion as
the natural number of stamens diminishes, so do both
the disposition to become double, and the beauty of
the flowers when altered. The Pink and Carnation
with ten stamens are the handsomest race next to
those just mentioned; while the Hyacinth, the Tulip,
the Stock, and the Wallflower with six stamens, and
the Auricula and Polyanthus with five, form altoge-
ther an inferior race, if symmetry of form, and regu-
larity of arrangement in the parts of the flower, are
regarded as beauties of the highest order. If the
mere circumstance of a plant having but a small num-
ber of stamens be a bar to its beauty when made
double, how much greater an obstacle to it must be
the natural production of unsymmetrical flowers.
This occurs in the Snapdragon, which, with a
five-lobed corolla, has but four stamens; and the
consequence is, that, when it becomes double, the
flower is a confused crowd of crumpled petals issuing
from the original corolla.

I have heard of attempts to produce double flowers
by artificial processes, but I never heard of the
smallest success attending such cases, unless the ten-
dency to their production had already manifested
itself naturally ; as in the Stock, which will frequent.
ly become single from having been double, in which
case its original double character may be recovered.
A mode of effecting this has been described by Mr.
James Munro (Gard. Mag. xiv. 121). Having a
number of Single Scarlet Ten-week Stocks, he de-

318 APPLICATION OF PRINCIPLES.

prived them of all their flowers as soon as he found
that five or six seed-vessels were formed upon each
spike, by which means he compelled all the nutritive
matter that would have been expended upon the
whole flower-spike and its numerous seed-vessels to be
concentrated in the small number which he left; and
the result, he says, was, that from the seed thus saved
he had more than 400 Double Stocks in one small bed.

There can, J think, be no doubt that, if any original
change to a double flower can possibly be effected by
art, it will be more likely to occur with respect to
those species which have an indefinite number of
stamens, where the tendency to this monstrosity al-
ready exists. Itis not many years since the Chryseis
(Eschscholtzia) Californica, a polyandrous plant, was
introduced to our gardens; and I, at one time, made
some attempts to render it double, conceiving it a
good subject for experiment on that account, but
I had no success; it has, however, accidentally be-
come semi-double in Mrs. Marryat’s garden, at Wim-
bledon; and I entertain no doubt that seed skilfully
saved from that plant would present its flowers in a
still more double condition.

CHAPTER XIX.
OF RESTING.

A GARDENER is said to rest a plant when he ex-
poses it to a condition in which it cannot grow, and

OF RESTING. 819

which is analogous to its winter state. For many
parts of gardening, especially what relates to forcing
and the management of exotic plants, this is a subject
of the first importance.

If we look over the different climates of the world,
we shall find thatin each there are a season of growth,
and a season in which vegetation is more or less sus-
pended; and that these periodically alternate, with
the same regularity as our summer and winter. I do
not know that there is in nature any exception to this
rule: for, even in the Tierra templada of Mexico,
where it is said that, at the height of 4000 to 5000
feet, there constantly reigns the genial climate of
spring, which does not vary more than 8° or 9°, in-
tense heat and excessive cold being alike unknown,
and the mean temperature varying from 68° to 70°,
we cannot suppose that, even in that favoured region,
a season of reposeis wanting; for it is difficult to con-
ceive how plants can exist, any more than animals, in
a state of incessant excitement. Indeed, it is pretty
evident that these countries have a period when vege-
tation ceases; for Xalapa belongs to the Tierra tem-
plada, and we know that the Ipomcea purga, an inha-
bitant of its woods, dies down annually like our own
Convolvuli.

But, although all plants have naturally a season
of repose, their winter is not in allcases cold. In the
tropics it is marked by coolness and dryness, while
the summer is rainy and very hot; and in extra-tro-
pical countries the two seasons vary in their charac.
ter, according to latitude and local circumstances.

320 APPLICATION OF PRINCIPLES.

In some parts of Persia, Armenia, and Mesopc-
tamia, the summer heats are excessive, while the win-
ters are rendered cold by the proximity of moun-
tains. Bagdad is described as having a cold winter,
because of the proximity of the mountains of Koor-
distan; yet its heats are intense: in August, 1819,
the thermometer stood at 120° in the coldest parts
of the house, and at 108° at midnight in the open
air. This was preceded by heavy rains, which raised
the Euphrates 7% feet above the ordinary level: the
whole country was like a vapour bath, and multi-
tudes of persons dropped down dead: twenty-two in
three days in a single caravan. In the northern pro-
vinces of Mexico the winters are of German rigour,
while the summers are those of Naples and Sicily
the Tierra fria of that country has, however, a very
different climate, the mean heat of the summer being
76°, and the winters so mild that the thermometer
only oceasionally falls below 32°.

At the Cape of Good Hope there are districts
in which the period of wet is long and very severe;
and many of the favourite flowers of our gardens are
produced by those districts. The Karroos are plains
of great extent, destitute of running water, with a soil
of clay and sand, coloured like yellow ochre by the
presence of iron, and lying on the solid rock. Dur-
ing the dry season the rays of the sun reduce: the
soil nearly to the hardness of brick; Fig Marigolds,
Stapelias, and other fleshy plants, alone remain green ;
nevertheless, the bulbs and tribes of Iridaceous and
other plants are able to survive beneath the sun-

OF RESTING. 821

scorched crust, which appears indeed to be necessary
to their nature. But in the wet season these bulbs
are gradually reached by the rain; they swell beneath
the earth; and at last develope themselves so simulta-
neously that the arid plains become at once the seat
of acharming verdure. Presently afterwards, myriads
of the gay flowers of the Iridaceze and Mesembryan-
themums display their brilliant colours; but in a few
weeks the verdure fades, the flowers disappear, hard
dry stalks alone remain; the hot sun of August,
when in those latitudes the days begin to lengthen,
completes the destruction of the few stragglers that
are left, the Karroo again sinks into aridity and deso-
lation, and the desert reappears. What succulents
survive are covered with a grey crust, and derive
their nourishment only from the air. In other parts
of the Cape of Good Hope the mean range of the
thermometer in winter is 48° to 98°, with cold rain,
while that of the summer is from 55° to 96°, with
dry days and damp nights.

In the Canaries we have the season of growth from
November to March, when rains fall like those of
Europe, and the mean temperature is 66°; and the
period of rest is April to October, when it never
rains, and the mean temperature is 73°.

In Brazil the seasons are thus described by Mr.
Caldcleugh :—‘‘ The summer begins about the months
of October or November, and lasts until March or
April. This is the wet season; but the rains by no
means descend from morning till night, as in some
other: tropical countries, but commence, generally,

14*

822 APPLICATION OF PRINCIPLES.

every afternoon about four or five o'clock with a
thunderstorm. The heaviness of the rain can only
be conceived by those who have been in these lati-
tudes. This fall naturally arrests the sea breeze, and
the succeeding night is dark and cloudy. Formerly
these diurnal rains came on with such regularity that
it was usual, in forming parties of pleasure, to arrange
whether they should take place before or after the
storm. During this period of the year there is sel-
dom, if ever, a deposition of dew. From April until
September very little rain falls; vegetation almost
stops, and, to the eye of every one who has not just
arrived from Europe, a wintry appearance is discern-
ible. The land and sea breezes do not succeed each
other with the same regularity, and are, besides,
more frequently disturbed by violent gusts from the
8. W., imagined to be the tails of those destructive
winds, the Pamperos of the River Plate. The nights
are beautifully clear; Venus casts a shadow, and the
southern constellations are seen in all their beauty.
The dews, as might be expecigd, are at this season
very copious.” (Brande’s Journal, No. 27, p. 41.)

In other parts of the tropics the seasons of growth
and rest are equally marked. In Ava, during the
rainy season, which lasts from May to October, the
mean temperature varies from 78° to 915°; while,
in the dry season, from November to April, it falls to
from 68° to 80°. At Calcutta, in the growing season,
from April to October, 58 inches of rain commonly
fal], with a mean temperature of 79° to 86°; while,
during the season of rest, from November to March,

OF RESTING. 823

there is not perhaps above an inch of rain, and the
thermometer sinks to from 66° to 80°. At this
time vegetation is said, in such countries, to “ labour
under a deadly languor; but one night’s rain con-
verts an arid plain into a verdant meadow.”

In most of the West India Islands situated under
the tropic of Cancer, there is said not to be much dif
ference in the climate, so that accurate observations
made on any one of them may be applied with little
variation to them all. Malte Brun gives the follow-
ing sketch of their seasons. ‘The spring begins
about the month of May; the savannas then change
their russet hue, and the trees are adorned with
a verdant foliage. The periodical rains from the
south may at this time be expected; they fall gene-
rally about noon, and occasion a rapid and luxuriant
vegetation. The thermometer varies considerably ;
it falls sometimes six or eight degrees after the diur-
nal rains; but its medium height may be stated at
78° Fahrenheit. After these showers have continued
for a short period, the tropical summer appears in all
its splendour. Clouds are seldom seen in the sky;
the heat of the sun is only rendered supportable
by the sea breeze, which blows regularly from the
south east during the greater part of the day. The
nights are calm and serene; the moon shines more
brightly than in Europe, and emits a light that ena-
bles man to read the smallest print; its absence is in
some degree compensated by the planets, and, above
all, by the luminous effulgence of the galaxy. From
the middle of August to the end of September, the

324 APPLICATION OF PRINCIPLES.

thermometer rises frequently above 90°, the refresh-
ing sea breeze is then interrupted, and frequent calms
announce the approach of the great periodical rains.
Fiery clouds are seen in the atmosphere, and the
mountains appear less distant to the spectator than at
other seasons of the year. The rain falls in torrents
about the beginning of October, the rivers overflow
their banks, and a great portion of the low grounds is
submerged. The rain that fell in Barbadoes in the
year 1754 is said to have exceeded 87 inches. The
moisture of the atmosphere is so great, that iron and
other metals easily oxidated are covered with rust.
This humidity continues under a burning sun; the
inhabitants (say some writers) live in a vapour bath.”
(Malte Brun’s Geography, vol. v. p. 569, Engl. ed.)
It is evident, from what has been said, that the
natural resting of plants from growth is a most
important phenomenon, of universal occurrence, and
that it takes place equally in the hottest and the
coldest regions. It is, therefore, a condition neces-
sary to the well-being of a plant, not to be overlooked
under any circumstances whatever ; and there cannot
be any really good gardening where this is not at-
tended to in the management of plants under glass.
Rest is effected in one of two ways; either by a very
considerable lowering of temperature, or by a degree
of dryness under which vegetation cannot be sustained.
The way in which the physical powers of vegeta-
tion are affected by this has been already explained
(114); and, in practice, it is found a point of the utmost
consequence. The early fruit-gardener draws his

OF RESTING. 325

Vines out of the vinery, and takes the sashes from his
Peach and other forcing-houses, when the artificial sea-
son of growth is over, in order to prepare them for the
duty of a succeeding season ; although this operation
is performed in summer, its effect is to expose them
to dryness, which arrests their growth, and favours
the deposit in their wood of the matter required for
the produce of a succeeding year.

The effects of a very dry atmosphere are necessa-
rily an inspissated state of the sap of the plant; and
this in all cases leads to the formation of blossom
buds and of fruit. It thus operated upon some
Pine-apple plants in Mr. Knight’s garden, to such an
extent as to cause even the suckers from their roots
to rise from the soil with an embryo pine-apple upon
the head of each, and every plant to show fruit, in a
very short time, whatever were its state and age.
Very low temperature, under the influence of much
light, by retarding and diminishing the expenditure
of sap in the growth of plants, comparatively with its
creation, produces nearly similar effects, and causes
an early appearance of fruit.

The operations of forcing are essentially influenced
by these facts; and, by a skilful alteration of the
periods of rest, we are enabled to break in upon the
natural habits of plants, and to invert them so com-
pletely, that the flowers and fruits of summer are
obtained to load our tables even in winter. Of this,
the following instance, taken from a paper by Mr.
Knight, in the Horticultural Transactions (v1. 232), is
a sufficient illustration.

826 APPLICATION OF PRINCIPLES.

‘A Verdelho Vine, growing in a pot, was placed
in the stove early in the spring of 1823, where its
wood became perfectly mature in August. It was
then taken from the stove and placed under a north
wall, where it remained till the end of November,
when it was replaced in the stove; and it ripened its
fruit early in the following spring. In May it was
again transferred to a north wall, where it remained
in a quiescent state till the end of August. It then
vegetated strongly, and showed abundant blossom,
which, upon being transferred to the stove, set very
freely; and the fruit, having been subjected to the
influence of very high temperature, ripened early in
the month of February.”

The strawberries of February and March are in like
manner procured by exposing the plants to such an
amount of dryness and heat as can be obtained by
presenting them unwatered, in pots, to the sun, at an
early period of summer; so as to cause a sufficient
accumulation of excitability by the end of autumn,
instead of the month of May.

It must be manifest that the operations of the flower-
gardener should be regulated by the same principles,
although it must be confessed that they are often
little considered ; a circumstance the more strange,
from the indispensable necessity of resting fruit
trees being universally known. It is to the giving
their plants the proper kind of rest that some gar-
deners owe the magnificent blossoming of their
Chinese Azaleas, Cacti, Camellias, and other forced
flowers, much more than to any peculiarity in the com-

OF RESTING, 827

post they employ, which is often a point of subordi-
nate interest, although generally regarded as of the
first importance. If but little progress has yet been
made by art in altering the time of flowering of parti-
cular races, so as to invert their seasons, this is cer-
tainly very far from being beyond the reach of attain-
ment; and there is apparently no more reason why a
Chinese Chrysanthemum should not be compelled to
flower at midsummer instead. of November, or a
Dahlia at Christmas, than that Vines and Strawberries
should ripen fruit in February. The great difficulty
to contend against in obtaining winter flowers is want
of light; but, by the employment of slender iron sash-
bars and large glass, a sufficient amount of this im-
portant vital agent may be obtained in England even
at that season of the year.

But it is not merely the periodical rest of winter and
summer that plants require; they have also their
diurnal repose: night and its accompanying refresh-
ment are as necessary to them asto animals. In all
nature the temperature of night falls below that of
day, and thus one cause of vital excitement is dimi-
nished; perspiration is stopped, and the plant parts
with none of its aqueous particles, although it con-
tinues to imbibe them by all its green surface as well
as by its roots; the processes of assimilation are sus-
pended; no digestion of food and conversion of it
into organised matter takes place; and, instead of
decomposing carbonic acid by the extrication of oxy-
gen, they part with carbonic acid, and rob the air of
its oxygen, thus deteriorating the air at night, al-

828 APPLICATION OF PRINCIPLES.

thouzh not to the same amount as they purify it dur-
ing the day. It is, therefore, nost important that the
temperature of glass houses should, under all circum-
stances whatever, be lower than that of theday; and
it is probable that this ought totake place to a greater
extent than is generally imagined by even the best
practical gardeners. We are told that, in Jamaica
and other mountainous islands of the West Indies,
the air upon the mountains becomes, soon after sun-
set, chilled and condensed, and, in consequence of its
superior gravity, descends and displaces the warm air
of the valleys; yet the sugar-canes are so far from be-
ing injured by this decrease of temperature, that the
sugars of Jamaica take a higher price in the market
than those of the less elevated islands, of which the
temperature of the day and night is subject to much
less alteration. At Fattehpitr, in the East Indies, the
difference in temperature between night and day
amounts to as much as 78°, on an average of the
whole year; in April the greatest heat by day is 110°,
that of night is only 65°; in January the thermometer
falls to 88° at night, while the day is 76°; and there
are 40 degrees of difference between the day and night
in May, one of the hottest months, when the thermo-
meter ranges as high as 115°. At Calcutta, in May,
the thermometer averages 98° in the day, and 79° at
sunrise; while in January the temperatures are 77°
and 56° respectively, for those two periods.

When we compare these facts with the habits of
plants just adverted to, we must, I think, see that it
is the purpose of nature to reduce the force which

OF RESTING. 829

operates upon the excitability of vegetation at that
period of twenty-four hours, when, from other causes,
the powers of digestion and assimilation are suspend-
ed. As far as is at present known, that power is
heat; and therefore we must suppose that, to main-
tain at night in our hot-houses a temperature at all
equal to that of the day, is a practice to be much con-
demned. Plants will no doubt lengthen very fast at
night in a damp heat, but what is at this time produced
seems to be a mere extension of the tissue formed
during the day, and not the addition of any new part;
the spaces between the leaves are increased, and the
plant becomes what is technically and very correctly
called drawn ; for, as has been justly observed, ‘the
same quantity only of material is extended to a greater
length, as in the elongation of a wire.”

Mr. Knight has pointed out another ill effect of
high temperature during the night, namely, that it
exhausts the excitability of a tree much more rapidly
than it promotes its growth, or accelerates the matu-
rity of its fruit; which is, in consequence, ill supplied
with nutriment at the period of its ripening, when
most nutriment is probably wanted. The muscat of
Alexandria, and other late grapes, are, owing as he
thinks to this cause, often seen to wither upon the
branch in a very imperfect state of maturity; and
the want of richness and flavour in other forced fruits
is often attributable to the same cause. “There are
few peach-houses,” he adds, “or indeed forcing-houses
of any kind, in this country, in which the tempera-
ture does not exceed, during the night, in the months

830 APPLICATION OF PRINCIPLES.

of April and May, very greatly that of the warmest
valley in Jamaica in the hottest period of the year.
There are probably as few forcing-houses in which
the trees are not more strongly stimulated by the
close and damp air of the night, than by the tempera-
ture of the dry air of the noon of the following day.
The practice which occasions this cannot be right: it
is in direct opposition to nature.” In the same paper
from which the foregoing is an extract (Hort. Trans.,
ii. 185), the same great experimentalist records the
result of his own management of a peach-house, where
a due regard was had to the preservation of a suffi-
ciently low temperature at night. ‘As early in the
spring as I wanted the blossoms of my Peach trees to
unfold, ny house was made warm during the middle
of the day ; but towards night it was suffered to cool,
and the trees were then sprinkled, by means of a large
syringe, with clear water, as nearly at the tempera-
ture at which that usually rises from the ground, as
I could obtain it; and little or no artificial heat was
given during the night, unless there appeared a pros-
pect of frost. Under this mode of treatment, the
blossoms advanced with very great vigour, and as
rapidly as I wished them, and presented, when ex-
panded, a larger size than I had ever before seen of
the same varieties; which circumstance is not unim-
portant, because the size of the blossom, in any given
variety, regulates, to a very considerable extent, the
bulk of the future fruit.”

OF SOIL AND MANURE. 831

CHAPTER XX.
OF SOIL AND MANURE.

NOTWITHSTANDING all that has been written upon
these substances, and the endless accounts we possess
of their real or supposed action upon vegetation, I
must confess that the contradictions are so numerous,
the exceptions to supposed rules so frequent, and phy-
siology is so insufficient to account for the greater
number of well ascertained facts, that it does not
appear to me possible to construct any tolerable
theory relating to them.*

Mr. Knight has observed that varieties of the same
species of fruit tree do not succeed equally in the
same soil, or with the same manure: the Peach in
many soils acquires a high degree of perfection,
where its variety, the Nectarine, is of comparatively
little value; and the Nectarine frequently possesses
its full flavour in a soil which does not well suit the
Peach. The same remark is also applicable to the
Pear and the Apple; and, as defects of opposite
kinds occur in the varieties of every species of fruit,
those qualities in the soil which are beneficial in some
cases will be found injurious in others. In those dis-

[* These remarks were perfectly applicable when this work was
publishel (early in 1840); but the treatise on Organic Chemistry in
its applications to Agriculture and Physiology, by the distinguished
Professor Liebig, which appeared a few months later, has greatly
elucidated the whole subject. ]

332 APPLICATION OF PRINCIPLES.

tricts where the Apple and Pear are cultivated for
cider and perry, much of the success of the planter
is found to depend on his skill or good fortune in
adapting his fruits to the soil. (Hort. Trans., i. 6.)
Rhododendrons and Kalmias are usually cultivated
in peat earth mixed with sand, and yet they grow as
well in fresh hazelly loam, without any mixture
whatever; and, than these two kinds of soil, none
can be apparently more dissimilar. The fine Ame-
rican cottons are grown in a calcareous sand, those
of India in deep black saponaceous earth: the Ame-
rican cotton will not thrive in the latter, nor that of
India in the former, as has now been ascertained ;
and yet the species of Gossypium producing the two
qualities have no organic differences which can, so
far as has yet been ascertained, explain in the smallest
degree the necessity, under which it is evident that
they labour, of being provided with different kinds
of food. The Alnus glutinosa, or Common Alder,
flourishes in wet clayey meadows; while Alnus
incana, or Upland Alder, is equally suited to a dry
and high land: we are totally ignorant of the reason
of such a case as this. Rhododendron hirsutum and
Erica carnea are, in their wild state, confined to cal-
careous soil; while Rhododendron ferrugineum grows
exclusively on granite, and Erica vagans on serpen-
tine. We are informed by Beyrich (@ardener’s
Magazine, iii. 442) that ‘the Pine-apple, in its wild
state, is found near the sea-shore; the sand accumu-
lated there in downs serving for its growth, as well
as for that of most of the species of the same family.

OF SOIL AND MANURE. 333

The place where the best Pine-apples are cultivated
is of a similar nature. In the sandy plains of Praya
Velha and Praya Grande, formed by the receding of
the sea, and in which no other plant will thrive, are
the spots where the Pine-apple grows best. The
cause of this lies evidently in the composition of the
sand, which chiefly consists of salt, lime from decom-
posed shells, and a very little vegetable mould.
‘Warmth, lime, salt, and moisture, seem therefore
to be the principal ingredient in which the Pine-apple
thrives. Sand will take a very high and continued
degree of warmth, being often heated by the sun so
much as to scorch vegetation, and yet it seldom dries
to a greater depth than from eight inches to one foot.
Sea salt is well known for its property of attracting
the nocturnal damps, and retaining them a long
time. The lime of the shells seems to be the princi-
pal manure, which has also been proved by the Eng-
lish here, who, by manuring their Pine-apples with a
mixture of stamped oyster-shells and vegetable earth,
produce very large fruit. The natural mould, usually
slightly mixed with sand, is partly of a vegetable,
and partly of a mineral origin.” But it is well known
that the Pine-apples of England are much superior to
those of South America, and yet English gardeners
grow their plants neither in sand, nor saline nor cal-
careous soil, As to manures, some plants bear them
in almost any quantity, others suffer from the access
of only a small quantity. The Vine and the Mul-
berry can hardly be over-manured, no soil was ever
found too rich for Roses: but Coniferous plants can

334 APPLICATION OF PRINCIPLES.

scarcely bear any manure, and the Peach is often
greatly injured by excess of it in a solid state: yet
this same plant will bear a very considerable quantity
in a liquid form.

The application of soils and manures to plants must,
therefore, remain at present exclusively within the
domain of art. There are, however, some general
remarks which it is possible to offer with tolerable
confidence.

Soil, considered without reference to the organisable
substances it contains, appears to act upon plants
chiefly by its power of absorbing and parting with
heat and moisture. When soil is tenacious, or plastic,
it absorbs heat slowly, and it parts with its water with
great difficulty, as is the case in the London clay;
the number of cultivated plants to which this is suit-
able is so small that it is almost expelled from gar-
dens, where the object is to expose the cultivated
Species to conditions more favourable than those
afforded them by nature. The small amount of bot-
tom heat afforded by clay, and the impossibility of
effectually draining it, sufficiently explain the badness
of its quality for gardening purposes, even without
taking into account the difficulty experienced by
plants in rooting in it, from the resistance afforded to
the passage of the spongioles by so compact a sub-
stance. On the other hand, loose sand, whose par-
ticles have no cohesion, although it imbibes water with
great facility, parts with it as readily, and, being easily
heated by the sun's rays, becomes so soon dried up
as to be for that reason as unsuitable to most plants

OF SOIL AND MANURE. 835

as plastic clay itself. It is by obtaining a mean be-
tween these two extreme cases that the soil is formed
most favourable to the growth of plants in general ;
hence the mixtures of peat, loam, and sand, which
are so continually employed. These substances
counteract each other's influences, the loam by conso-
lidating the sand, and the sand by lightening the
loam, and the peat by binding them all together, and
preserving their perfect admixture, independently of
its manuring qualities. It is, however, a well ascer-
tained fact, that loam containing a considerable quan-
tity of calcareous matter is in general much better
suited to cultivation than such as is destitute of it:
the reason for which seems to be, in part, that calcare-
ous earth enters largely into the organisation of all
plants, in which it is deposited in the state of the
oxalate and phosphate of lime; and, in part, because,
as was shown by Davy, there is a strong action be-
tween the lime and vegetable matter contained in
soils, the result of which is a compost partly soluble
in water.*

* [The extensive beds of marl distributed over « considerable
portion of this country are just eoming into use, and will ultimately
prove valuable in the highest degree to the cultivator. We have
found this substance peculiarly adapted to promote the growth and
productiveness of the Peach and the Vine. In New Jersey, thou-
sands of acres of sandy soil formerly sterile and worthless have been
rendered fertile and productive by the application of marl. In other
districts it is now used to a considerable extent for top-dressing
grass-land, corn fields, de. From ten to forty loads per acre, ac-
cording to the quantity of calcareous matter contained, are generally
applied, A J. D.]

[It is easy to understand the rationale of the favourable effects

336 APPLICATION OF PRINCIPLES.

Doubtless one of the safest rules for a gardener, in
determining the soil required for.a given plant, would
be, if practicable, to ascertain what amount of mineral
matters it contains, and to select earth in which those
substances abound. For, although it may be asserted
that the presence of iron, copper, or other substances,
in plants, in minute quantities, is accidental and un-
important, yet such a supposition is gratuitous, if not
altogether unfounded ; for-I do not know what war-
rant we have for saying that any of the constant
phenomena of nature, however minute they may seem
to be, are accidental. This at least is certain, that,
where mineral substances occur abundantly in plants,
they are part and parcel of their nature, just as much
as iron and phosphate of lime are of our own bodies;
and we must no more suppose that grasses can dis-
pense with silica in their food, or marine plants with
common salt, than that we ourselves could dispense
with vegetable and animal food. Flint is found on
the exterior of the whole Graminaceous order, with-
out exception; it forms the polished surface of the
Cane Palm, the grittiness of many kinds of timber ;
sulphur abounds in Cruciferous plants, especially
of the New Jersey marl, when we consider its chemical composition.
According to the numerous analyses of Mr. Rogers, the marl from
various localities contains from 9 to nearly 13 per cent. of potash,
and seldom more than one-half per cent. of lime: and Mr. Rogers*
very correctly states “that the true fertilising principle in marl is

not lime but potash.” On this subject see the note commencing on
p- 337. G.J

* Final Report on the Geology of the State of New Jersey; by Henry D. Rogers,
1840.

OF SOIL AND MANURE. 337

Mustard; copper in Coffee,* Wheat, and many other
plants (it is believed in the state of a phosphate);
iron, as a peroxide, in Tobacco. John, in his experi-
ments upon these matters, found that the Ramalina
fraxinea and Borrera ciliaris, two lichens, contained
a great quantity of the last metal, although he could
not find a trace of it in the Fir tree, on the topmost
branches of which the lichens grew. We cannot sup-
pose iuat such things are the result of accident, and
that it is unimportant to the plants containing mine-
rals thus constantly, whether such substances are pre-
sent in their soil or not.t

* Seventy millions of kilogrammes of coffee arrive annually in
Europe ; of these, 560 kilogrammes consist of copper, according tc M.
Sarzeau, The weight of copper consumed in bread in France is 3650
Kilogrammes annually. (De Candolle, Physiologie Végétale, p. 889.)

¢ [The quantity of earthy or saline matters which different plants
absork 's probably nearly uniform, under the same circumstances,
since their roots possess little if any power of selection. But the
quantities which are retained vary according to the constitution of
each species, and the chemical composition of its products. The
ashes of Pine and Fir trees, ne matter on what soil they may have
grown, contain a much smaller quantity of alkalies than the ashes
of the Oak, Beech, or Maple. Hence the former are found to thrive
upon sandy or sterile soils, which do not furnish sufficient alkali for
the latter. All plants of the grass kind require a considerable por-
tion of silicate of potash, which is deposited in their stems; and of
phosphate of magnesia, which is a constituent of their seeds. The
quantity of both varies in different species. “One hundred parts of
the stalks of Wheat yield 15°5 parts of ashes; the same quantity of
the dry stalks of Barley 8°54 parts; and one hundred parts of the
stalks of Oats only 4°42; the ashes of all these are of the same com-
position.” These several crops, therefore, extract the potash of the
soil in different degrees; and upon a field which will yield but one
harvest of Wheat, two crops of Barley or three of Oats may be

15

338 APPLICATION OF PRINCIPLES.

Manures act apparently in one of three ways,
either by merely stimulating the vital forces, as com-

raised. Peas, and many other leguminous plants, take very little
alkaline or earthy matter from the soil: they contain no potash,
and only a trace of phosphate of lime or magnesia. This explains
their utility as fallow-crops: they return to the soil a certain portion
of vegetable mould, while they scarcely if at all diminish the potash
or the phosphates of the soil, which are required for the succeeding
wheat crop. ‘“ When we grow in the same eoil, for severai years in
succession, different planta, the first of which leaves Yehind that
which the second, and the second that which the third, may require,
the soil will be a fruitful one for all the three kinds of produce. If
the first plant, for example, be Wheat, which consumes the greatest
part of the silicate of potash in a soil, while the plants which sue-
ceed it are of such a kind as require only smal] quantities of potash,
as is the case with the Leguminose [Pea tribe], Turnips, Potatoes,
&e., the wheat may be again sowed with advantage after the fourth
year; for, during the interval of three years, the soil will be render-
ed capable of again yielding silicate of potash in suffiuent quantity.”
(Liebig, Organic Chemistry, p. 170.) The alkaline constituents of
the soil, except when added in the form of manure, are derived from
the slow disintegration and decomposition of the rocks which com-
pose it, and particularly the argillaceous earths. According to
Liebig, the quantity of potash contained in alayer of soil formed by
the disintegration of 40,000 square feet of the following rocks to the
depth of 20 inches, is as follows ;
Felspar contains Ve Ate te - . « «+ 1,152,000 Ibs.
Clinkstone contains oe ata feorn 200,000 to 400,000 Ibs.
Basalt contains . . . . . . from 47,500to 75,000 Ibs.
Clay-slate contains . . . . . from 100,000 to 200,000 Ibs.
Loam contains . . from 87,000 to 300,000 Ibs.
“A thousandth part of lane, wiheal with the quartz in new red
sandstone, or with the lime in the different limestone formations,
affords as much potash to a soil only 20 inches in depth as is sufficient
to supply a forest of pines growing upon it for a century. A single
cubic toot of felspar is sufficient to supply a wood, covering a surface
of 400,000 square feet, with the potash required for five years.”

OF SOIL AND MANURE. 339

mon salt; or by their power of absorbing moisture
from the atmosphere, as salt and the muriate of lime,

(Tiebig, op. cit. p. 146.) “A soil which has been exposed for cen-
turies to all the influences which effect the disintegration of rocks,
but from which the alkalies have not been removed, will be able to
afford the means of nourishment to those vegetables which require
alkalies for their growth during many years; but it must gradually
become exhausted, unless those alkalies which have been removed
are again replaced: period therefore will arrive when it will be
necessary to expose it, from time to time, to a further disintegration,
in order to obtain anew supply of soluble alkalies. For small as is
the quantity of alkali which plants require, it is nevertheless quite
indispensable for their perfect developement. But when one or more
years have elapsed without any alkalies having been extracted from
the soil, a new harvest may be expected. The first colonists of Vir-
ginia found a country, the soil of which was similar to that mention-
ed above; harvests of Wheat and Tobacco were obtained for a cen-
tury from one and the same field, without the aid of manure; but
now whole districts are converted into unfruitful pasture land, which
without manure produces neither Wheat nor Tubaeeo. From every
acre of this land there were removed, in the space of 100 years, 1200
lbs. of alkalies in leaves, grain, and straw; it became unfruitful,
therefore, because it was deprived of every particle of alkali which
had been reduced to w soluble state, and beeause that which was
rendered soluble again in the space of one year was not sufficient to
satisfy the demands of the plants. . . . It is the greatest possible
mistake to suppose that the temporary diminution of fertility in a
soil is owing to the loss of humus [vegetable mould]; it is the mere
consequence of the exhaustion of the alkalies.” (Op. cit. p. 148.)
This proposition is very perfectly made out by this distinguished
organic chemist; and the true theory of the operation of manure,
of the interchange of crops, &c., is thence readily and satisfactorily
deduced. The limits of a note will not allow us to enter farther into
the consideration ot this subject, so important to agriculture and
horticulture; which is the less necessary, now that an American edi-
tion of the work from which these observations are drawn has been
announced. G.]

3.0 APPLICATION OF PRINCIPLES.

obtained by mixing together equal parts of salt and
lime; or by supplying the plant with soluble carbon
and nitrogen. It is in proportion to their power of
furnishing these principles, and to the length of time
during which they continue to do so, that manures are
active or sluggish, and durable or ephemeral in their
operation. Carbonic acid, when decomposed, fur-
nishes an essential part of the starch and other sub-
stances secreted by plants; and nitrogen seems, from
its great abundance in their system, at least when
young, to be indispensable to their existence: the
first is a fact of universal notoriety, the latter has been
ascertained by modern chemists to be also apparently
2, constant phenomenon. (See Introduction to Botany,
Ed ed. p. 870, 379, &., and Appendix.) For these
ressons every description of putrefying animal or
vegetable matter, from putrid yeast and malt-dust to
horses’ hoofs and feathers, have been used for the
purpose of fertilising land, the nature of whose differ-
ent actions constitutes a study of itself, very obscure,
but of the highest degree of importance.

In the more delicate of horticultural operations,
liquid manure, prepared by steeping dung in water,
and drawing it off when clear ar.1 of the colour of
porter, is most generally now employed, and is
undoubtedly the best form in which it can be admi-
nistered, in consequence of its concentration, the faci-
lity of its administration in any quantity, and its con-
taining nothing but soluble matter. It was first used
by Mr. Knight, who not only applied it with great
advantage to Fruit trees, but also to the Heaths and

-- OF SOIL -AND MANURE. 841

other flowers; and it is, with the exception of bone
dust, the form of manure best adapted to all plants
in pots.*

What most concerns the subject of this work is,
not the nature of manure, but the proper time and
manner of applying it to garden plants. Provided
manure is of a permanent character, it does not very
much matter at what time it is administered, because,
if it does not act at first, it will sooner or later; but
when it is of such a nature as to be easily dissipated,
like malt-dust, or soot, or yeast, a knowledge of the pro-
per season becomes extremely necessary. Plants will
not receive the influence of manure so readily at any
season as when they are in the most rapid and steady
growth; because at that time the absorbing force of
their roots, and their vital energies, are all greatest.
It is for this reason that a top-dressing is almost use-
less to a lawn at midsummer, but better in the spring,
and best of allin October. If applied at midsummer,
the ground is dry, the herbage closely shorn, and the
vegetation extremely Janguid, partly in consequence
of the constant operation of the mower, and partly
because our summertide is the winter of herbage
grasses, which only flourish in the cool and damp

* The efficacy of liquid manure, applied out of doors, is doubled by
applying it in damp weather or before rain, when the plants are in
a growing state. The same remark applies to guano and other con-
centrated manures that require a large amount of water to make
them soluble. Hundreds of persons have been entirely disappointed
in the use of guano, and animal manures generally, because they
applied them so late in the spring that they were never rendered
sufficiently soluble to be taken up by the roots of plants. A. J.D

842 APPLICATION OF PRINCIPLES.

seasons of the year. When a top-dressing is applied
in the spring, the lawn profits by it so long as it con-
tinues to grow vigorously; but the quick approach
of summer daily interferes with the force of this kind
of vegetation, and diminishes the effects of the
manure. On the contrary, if October is the season
chosen for the operation, the grasses are then begin-
ning to grow steadily, the operations of the mower
are, or should be, suspended, and there are seven clear
months at least during which the effects of the
manure continue to be felt.

It may be indifferent at what season such manure
as bones, and other kinds of matter which decompose
very slowly, are employed; yet there can be no
doubt that upon every known principle they also
should be given at a time when vegetation is most
active; hence the every-day practice of digging
manure into the borders of a garden in spring, or
shortly before an annual crop is about to be commit-
ted to the soil.

As to the manner of applying manure, it must be
obvious that it can be of no use unless it isin contact
with the absorbing parts of the roots; now those
parts are the young fibres and spongioles, as has been
already stated (23, 24), and, when plants have arrived
at any considerable size, the roots form the radii of
a circle whose circumference is the principal line of
absorption. This being so, if a plant has arrived at
the state of a bush or tree, it is useless to apply
manure at the base of the stem, because that is pre-
cisely where the power of absorption is the weakest,

OF SOIL AND MANURE. 348

if it exists at all; and, as the circle formed by the
roots is generally greater than that of the branches,
the proper manner of applying manure is to introduce
it into the ground at a distance from the stem about
equal to the radius formed by the branches. And,
yet, although this is so evidently right, I have seen
a gardener, who ought to have known much better,
sedulously administering liquid manure, by pouring
it into the soil at the base of the stem; which is’
much the same thing as if an attempt were made
to feed a man through the soles of his feet.

INDEX.

A.

Axsorrtion, force of, in spongelets, 16.

Acetate of lime, solution of, rejected by roots, 18, _

Air, deterioration of, by plants at night, 327—introduction of heated,
to plant compartments, 153—purification of, by plants, during
the-day, 328—of plant-houses, ventilation a means of drying, 153.

Air passages penetrate plants in all directions, 102.

Alburnum, 26—its connexion with the spongelets, 12—offices per-
formed by it, 82—its importance, 83—its quantity proportionate
to the number of buds, 187.

Alburnous substance, 187.

Ammonia employed to promote germination, 166.

Amylaceous substance, 188.

Annuals, oleraceous, 114,

Annual rest of plants, 319.

Anther, 56.

Aquatic plants, 114—necessity of maintaining a due degree of tem
perature in the water in which they are grown, 109.

Aqueous matter, necessity of its excess being decomposed in fruits
during the process of ripening, 115.

Aqueous particles in plants, effects of their being frozen, 86.

Arid regions, 321,

Atmosphere, temperature of, at various places, 100—unfavourable
state of, a cause of sterility in flowers, 171—dry, produces an
inspissated state of the sap, 325.

Atmospheric dryness, or moisture, extremes of, 132, 138—averages
of, 183—moisture, 125.

Axil, 80.

Axils of leaves, the situation where leaf-buds are formed, 30.

B.
Balloon training, 262.
Bark, 28—its production, 26—its distinct parts, in trees and shrubs,
27—its anatomical relation to leaves, 387—of the root, its offices,
15*

846 INDEX,

12—its absorbent property, 13—its rind and epidermis in some
eases perform the office of leaves, 40.

Bell glasses, their use in propagation by cuttings, 203—of different
colours, 205.

Bleeding, 244—of vines, preventive against, 245.

Blossom-buds, their identity with leaf-buds in the first stage of
organisation, 62.

Bottom heat, 102—its effects different from those resulting from
solar radiation, 93—its natural amount, 108—necessary for the
flowering of many tropical plants, 107—degree of, communicated
to plants in pots, from the atmosphere of a stove, 111—its va-
riation agreeably to that of the soil of countries, 112.

Branches, their vigour augmented by the abstraction of flowers and
fruit, 309—effects of their being subjected to a widely different
temperature from that of the roots, 50.

Budding, propagation by, 210—mode of operation, 212.

Buds, the origin of branches, 15—not the origin of roots, 15—ad-
ventitious in roots, 22—embryo, 30—their relation to bulbs, 30—
latent, 37—-mature, preferable to immature for the purpose of
propagation, 232—the youngest most excitable, 232.

Bulbs, 31, 114—a species of bud, 87—in arid regions, 820—effect of
scarring their centre, 210.

Cc

Callus, 26

Calyx, its situation and colour, 55—its use, 67.

Camellias, a method of propagating them, 239,

Canker, 106.

Cape heaths, drainage for, 275.

Capillary tubes give hygrometrical force to tissue, 17.

Carbon, excess of, in seeds, 8—its conversion into carbonic acid dur-
ing the process of germination, 9—a component of the food of
plants, 18—proportions of, in certain vegetable secretions, 76
—in seeds, 175, 179—necessary to preserve their vitality, 179—
requires its proportion altered before germination can be effect-
ed, 78.

Carbonic acid, its formation during the process of germination, 9—
its decomposition in plants by solar light, 41—its mode of in-
troduction into the system of plants, 41—its decomposition in

INDEX. 347

plants during the day, 42—its formation by plants during the
night, 42—its digestion and decomposition in the system of
plants, 42—period at which leaves cease to decompose it, 53—
conditions under which it is slowly formed, 167—formation of,
in seeds, 180—decomposed, furnishes an essential part of the
secretions of plants, 340.

Carburetted hydrogen gas, 118.

Cellular system, 217—horizontal, 282.

Cellular tissue combined with woody fibre, 24.

Charcoal, packing seeds in, 181.

Chemical changes in seeds, 159.

Cherries, foreing of, 109.

Chinese mode of dwarfing trees, 251

Chlorine employed to promote germination, 167.

Cicatrisation, 282.

Circulation of sap, 32.

Climate, uniform, 819.

Climates, extreme, 820—extreme, imitation of, 107.

Climbers, 265.

Colour of leaves influenced by light, 52—the natural green in planta,
circumstances which prevent its being acquired, 34—green, in
plants, how produced, 84—yellow, in plants, cause of its oceur-
rence, 84,

Colouring matter, green, decomposed by frost, 86.

Colours of plants, cause of their formation, 84.

Cormi, 29.

Corolla, its nature, 55—its use, 67.

Cortical integument, 27.

Cotyledons, 10—supply nourishment to the plumule, 23.

Creepers, 265.

Crops, change of, 270, 388, 339

Cross-beds 68—are generally fertile, 68.

Cross-breeding, 310—process of, 314.

Cucumbers, advantage of growing them in foreing-houses, instead of
pits, in winter, 155.

Curl in potatoes, 73.

Cuttings, propagation by, 195—conditions required in order to en-
able them to become young plants, 195—double pots employed
in striking them, 202.

348 INDEX.

D.

Damping off, 149.

Deciduous plants, 73—trees, season for transplanting, 282.

Degeneracy, means of preventing it in seed crops, 302.

Degeneration of varieties, 302.

Deleterious matter thrown off by roots, 20—substances, when
attenuated, are most likely to prove injurious to plants, 18.

Dew-point, 126.

Digestion, a function of the leaves, 40.

Diurnal rest of plants, 327.

Drainage, 118—of pots for plants, 119, 275—of soil in pots by frag-
ments of absorbent stone, 275.

Dryness, atmospheric, table of, with regard to the direction of the
wind, 133, 184—causes of, in hothouses, 143.

Double composite flowers, 315.

Double Dahlias not truly double flowers, 315.

Double flowers, 315—conditions under which they may and may not
produce seed, 173.

Double pots employed for striking cuttings, 202—for plants, 274.

Double Stocks, 318.

Dung-heat, Grapes and Nectarines forced by it, 146.

Dwarfing trees, Chinese mode of, 251.

E

Earth, temperature of, at various places, 91, 92.

Earths, certain of them enter into the composition of the food of
plants, 17.

Easterly winds, their dryness, 180.

Embryo buds, 30.

Endogens, 24, 29—mixed arrangement of their tissue, 29.

Envelopes, not a necessary part of a flower, 55.

Epidermis, in its young state, highly sensible to the stimulus ot
light, 115—regulates the amount of perspiration, 53—of leaves,
88—an extension of the outer bark of the stem, 40—o: the
leaves of evergreens, 285—of plants inhabiting shaded situation,
44,

Evaporation, an important vital function of plants, 125—affected by

elevation, 129—affected by wind, 129—from the surface of
ecions, 285.

INDEX. 849

Evergreen plants, 53.

Evergreens, season for transplanting, 284—epidermis of their leaves,
285.

Excitability diminished by lowness of temperature, 87.

Excrementitious matter of plants poisonous, 20, 21—matter of plants
superfluous, 20.

Exeretory functions of roots, 270.

Exogens, 24, 29—their pith central and distinct, 24

Exposure of green-house plants, 273,

Eyes, propagation by, 184.

F.

Fall of the leaf, 54.

Fertilisation, 68—of the Mistletoe, 314.

Fibrous roots, production of, by root-pruning, 292.

Fibre, woody, originates in the leaves, 24.

Field crops, germination of, in wet seasons, 176.

Fig-trees, mode of pruning, 242.

Filament, 55.

Floral envelopes, 565.

Flowers, their action, 55—their structure, 55—essentially constituted
only by the presence of the sexes, 66—double, 57—their parts
are modified leaves, 62—their metamorphoses, 57—their - pro-
duction induced by ringing, 253—tendency in some to become
double, $16—causes of their not expanding, 84.

Flower-buds, their production depends upon the presence of nutritious
matter, 64,

Flues, 143.

Fluids, ascending, their channel in plants, 27—their mode of descent,
27—their lateral transmission, 33—are attracted into the sys-
tem of plants, during the night, 49.

Flute-budding, 215.

Food, natural, of plants, 18. ;

Frost, its effects on plants, 84—its physiological effects on vegetables
accounted for, 140—its accumulation in valleys, 138.

Fructification, period of its commencement in plants, 63—may be
advanced or retarded artificially, 64—means of advancing its
period, 64—influenced by ringing, 65—its removal in a young
state strengthens the functions of the leaves, 79—induced by
an inspissated state of the sap, 325.

350 INDEX.

Fruit, its maturation, 69—its ripening affected by pruning. 246—its
physiological action analogous to that of a leaf, '71—its physio-
logical use, 71—derivation of its food, 70—is an advanced stage
of a flower, 69—differs from leaves in its appropriation of the
sap which it receives, 73—attracts food from the surrounding
parts, 70—its secretions, 74—changes which it undergoes, 74—
aqueous matter in, requires decomposition, 116—succulent,
ripening of, 116—effects produced on, by ringing, 254—method
of obtaining improved varieties of, 8311—superior and inferior,
table of, 71—on what its size and excellence depend, 72—cause
of the weaker portion of it being generally thrown off, 72—the
secretions of, partly changed by heat, 74—influenced by light,
44—the decomposition or dissipation of water by, '76—the ripen-
ing of, retarded by an excessive supply of water, 76.

Functions of leaves, termination of their performance, 57.

Fungi, deleterious parasitic, 149, 155.

G.

Garden, choice of soil for a, 187-—situation for a, 187

Gases, their destructive effects on vegetation, 152.

Geothermometrical averages, 94.

Germination, 7—conditions required to produce it in seeds, 8—why
best effected in the absence of light, 9—requires communication
with the atmosphere, 8—requires different degrees of heat in
different species, 9—causes of, 78—degree of heat required fot
seeds of tropical trees, 103—is assisted by the absorption of
water, 8—interrupted, 160.

Germination, means of promoting it, 163—means of assisting it in
cases of seed with very hard integuments, 164.

Glass, the coldness of its surface condenses the enclosed atmospheric
vapour, 144,

Glass roofs, their coldness a cause of dryness in the state of the in-
ternal air, 143.

Glazed houses, means of applying temperature and moisture to the
atmosphere of, 142.

Grafting, propagation by, 216—modes of operation, 216, 219—de-
grees of affinity within which the operation may be performed,
222—deceptions practised with regard to it, 228—on roots, 224
—herbaceous plants, 286—pines, 287.

INDEX. dol

Grafting clay, its use in preventing evaporation and affording
aqueous food for the scion, 235.

Grafting plasters, their unfitness to supply aqueous food to scions, 235.

Grass, its fibrous texture favourable to the emission of heat, 137.

Granulation, 282.

Granulations of cellular tissue, 235--formed by the living tissue, 293

Grapes, a cause of their shrivelling, 106.

Greenhouse plants, their exposure, 273.

Growth by the stem, 22.

Growing point, 22.

H.

Heart-wood, its mode of formation, 27—the oldest formation, 27.

Heat, its impulse to the vital principle, 9—necessary to produce
germination, 8—produces a distension of all the organic parts, 9
—degree of, most conducive to germination, is variable, 9—its
agency in changing the secretions of fruits, 74—the stimulus of
excitability, 87—acts as a stimulus to the vital forees, 107.

Herbaceous grafting, 236.

Horizontal plane, bad effects of training on a, 257—system, 214.

Horizontal cellular system, 282—syatems of stocks and scions, neces-
sity for their correspondence in growth, 222.

Hothouses, causes of atmospheric dryness in, 143.

Hot springs, their effects on surrounding vegetation, 103.

Hybrids, their origin, 68—are generally sterile, 69.

Hydrogen, fixed in the tissue of plants, 8—excess of, in certain vege-
table secretions, '76—incorporated in the tissue of plants, deri-
vation of its supply, 18.

Hygrometers, 126—Daniell’s, 126.

L

Improvements in the races of plants by direct means, 307—by indi
rect means, 309.

Inarching, 288—circumstances conducive to its suceess, 239,

Inner bark, 24.

Insects, 124—their ravages on vegetables, preventive of 124-—con-
ducive to fertilisation, 172.

Iron roofs for plant-houses, light afforded by, $26.

352 INDEX.

K.
Knaurs, propagation by, 189.

L,

Latex, its destruction by frost, 85.

Layering, Chinese mode of, 209.

Layers, propagation by, 207.

Leaf, an expansion of the bark, 37.

Leaf-buds, their reproductive properties different from that of seeds,
7—locality of their formation, 30—adventitious, 31—their pro-
perties, 30—their formation on stems, 30—their importance, 32
—the parents of wood, 30.

Leaf-buds, their presence universal, either latent or developed, in
the axils of leaves, 37—instances of their formation on leaves, 55
—their identity with blossom-buds in the first stage of organi-
sation, 62—on cuttings, 196, 204.

Leaves give origin to woody tissue, 23—their action, 37—attraction
of, causes the flow of sap, 36—their nature, 37, 41—their modi-
fications have leaf-buds in their axils, 37—have universally
leaf-buds, either latent or developed in their axils, 37—their
epidermis, 88—number of stomates on the surface of, in various
species, 389—particular offices of, 40—their free action essential
to the health of plants, 40—their action reciprocal with that of
the roots, 49—their absorption of moisture from the air, 50—
their action forms the peculiar secretions of plants, 51—their
colour influenced by light, 52—period at which they cease to
decompose carbonic avid, 54—ultimately become incapable of
performing their functions, 54—are organs of digestion and
respiration, 54—their temporary nature, 54—instances of leaf-
buds being formed on them, 55—modified, constitute the parts
of flowers, 62—their physiological action analogous to that of
the fruit, 71—their functions strengthened by the early removal
of the fructification, 75—propagation by, 189—conditions most
favourable for propagation by, 195—their action forms roots,
195—of evergreens, 285.

Liber, its consistence, 2i—its situation, 26—the internal part of the
bark, 26 —offices performed by the, 32—its importance, 33.
Ligatures for buds, 215—objects of their application with regard to

the fertility of trees, 255.

INDEX. 353

Light, detrimental to the germination of seeds, 9—its absence con-
ducive to the formation of carbonic acid, 9—conducive to the
formation of roots, 14,

Light, by its action on the leaves a principal agent in forming secre-
tions, 52—its effect. on the colour of leaves, 52—its agency in
changing the secretion of fruits, 74—its stimulating effects, 115
—its effect in altering and decomposing the fluids of plants, 115
—an abundance of, with low temperature, tends to inspissate
the sap, 325—solar, its influence on vegetable life, 41—effects a
decomposition of carbonic acid in plants, 41—occasions the ex-
trication of nitrogen in plants, 41—promotes insensible perspi-
ration in plants, 41, 48—its full intensity can be safely borne by
some species but not by others, 53—more necessary than change’
of air in imparting flavour to fruits, 152.

Lights of fruiting-houses, their removal, 156.

Lignification depends on the action of leaves, 23—sedimentary mat-
ter of, 265.

Lime, applied for the germination of seeds, 166—enters into the
organisation of plants, 335.

Liquid manure, 340.

M.

Male flowers in unisexual plants, 82. ;

Manures, 388—their application, 840—principles of their eonstitu-
tion, 889—their action, 340—time of their application, 341—
manner of their application, 842—liquid, 340.

Marsh plants, 114.

Maturation of fruit, 69.

Medullary rays, 27.

Melons, preservation of the purity of their races, 303—effects of their
roots being immersed in water, 116.

Metallic substances in plants, 335, 336.

Metamorphoses of the parts of plants, 57—-example of, 67, 61, 178.

Mildew, 51, 123—in wheat, attributed to a superabundant absorption
of moisture, 51.

Mineral substances in plants, 336.

Moisture, atmospheric, when amounting to saturation, occasions a
cessation of perspiration in plants, 48—its absorption by leaves,
51—connected with temperature, 125—its range, 127—ita mean

354 INDEX.

near London, 128—effeet of, on pollen, 171—necessary to pro
duce germination, 8—of the soil, 118—abundant supply of, re
quired by plants in a growing state, 114—effects of an exces-
sive supply of, 115—of hothouses, its regulation, 142—an excesa
of, prejudicial to plants in a rapid state of growth, 148—rules
for its adaptation, 149—preserved by means of oiled paper, 155
—necessary to germination, 160—its tendency to produce decay
in seeda, 168—should be sparingly applied to the roots of trees
previously too much dried, 294.

Monstrosity » cause of sterility, 178—causes inducing it, 316.

Mules, their origin, 68.

Muling, 310.

Muling, limits of its operation, 312.

Muriate of lime, its use for the preservation of seeds, 176,

Muriate of soda, its free absorption by roots, 17.

N.

Nitrogen, in spongioles, 13—in seede, accelerates their vegetation, 19
—indispensable for the first formation of tissue, 19—a compo-
nent of the food of plants, 18—in plants, is extricated by solar
light, 41—its abundance in young tissue, 18.

Night, diminution of the functions of plants in the, 327.

Nodules in the bark of trees, 31.

Nutritious matter, in plants, influences the production of flower-
buds, 65.

oO.

Oleraceous annuals, 115.

Orange tree, natural temperature of the soil for, 104.

Orange tribe, drainage for their roots necessarily beneficial, 275.

Ovary, and ovules, 56. 7

Oxalic acid employed to promote the germination of old seeds, 167.

Oxygen is absorbed from water during the process of germination, 8
—in plants, 18—derivation of its supply, 18—excess of, in
certain vegetable secretions, 75—employed to promote germi-
nation, 167—is absorbed by leaves when their functions become
languid through age, 54.

P.
Pan feeders, 269.
Parasitical fungi supposed to lay hold of diseased tissue only, 51.

INDEX. 855

Paving the soil, 120.

Peas, securing a late ercp of, 124.

Pendulous training, 260.

Perspiration of plants supplied chiefly by the action of the spon-
gioles, 183—a function performed by the leaves of plants, 40—is
promoted by solar light, 41—its amount in various species, 47-
49—experiments on, 47-49—entirely obstructed when the air
is saturated with moisture, 49—its amount is in proportion to
the intensity of the solar rays, 49—commencement of its action,
114—an important vital function of plants, 126—affected by
wind, 129—prevented by damp, 148—exeessive precautions
against, 204—cold produced by, 257—through young bark, 283

Pine-apple, its habitat in a wild state, 232.

Pine-apple stools, 210.

Pines, grafting of, 237.

Pistil, its parts and situation, 56.

Pith, 28—its production, 24—in endogens is intermingled with thie
woody fibre, 24—distinct and central in exogens, 24.

Placenta, 76.

Plant, its nature, 5—mode of its birth detailed, 10.

Plants, their power of producing roots from various parts, 14—liable
to injury from contact with deleterious matters in the soil, 17—
cannot exist long on pure water, 19—the channel through which
all their ascending fluids are conducted, 27—their healthiness
depends on the free action of the leaves, 40—decompose car-
bonie acid during the day, 42—form carbonic acid during the
night, 42—inhabiting shady situations, reason of their not en-
during full exposure to the sun, 44—imbibe an excess of fluid
during the night, 49—their capacity of bearing direct light is
variable in different species, 53—deciduous, 54—commencement
of the period of their fructification, 63—their limits of endurable
temperature, 80—are penetrated in all directions by air passages,
102—require a correspondence of temperature with that of the
countries of which they are natives, 105—of extreme climates,
112—growing on grass, 138—growing below projecting shelter,
188—in sitting-rooms, 148—their cultivation in confined air,
151—have universally a season of rest, 319—their resting, 319
—their annual rest, 319—diurnal rest, 327—their rest. neces
sary to flowering, 827—some grow equally well in different

356 INDEX.

soils, and others will uot, 332—aphyllous, office of leaves per
formed in, by the rind and epidermis, 40.

Plumule, 22—derives its nourishment partly from the cotyledons and
partly through the agency of the rc ot, 22.

Plurging of petted plants, 273.

Poisonous substances fatal to man prove equally so to plants, 17.

Poisons, alkaline, their destructive effects, 18—metallic, destructive
to plants, 18. ;

Polien, agents which affect its fertilising powers, 171—deficiency of,
a cause of sterility in seeds, 171.

Potash, employed to promote germination, 166—as a component of
manures, 335, 338.

Potato, tubers of, early varieties, their appropriation of nutritive
matter, 173—means of obtaining improved varieties of, 308—
unequal periods of its maturity from different eyes, 189.

Potatoes, disease of, curl in the leaves of, 73—propagation of, from
eyes, 185.

Pots for plants, their drainage, 119—double, for plants, 274—neces-
sity of their being proportioned to the size of the plants, 277.

Potting, 267—objects attained by, 267—cases in which it may be
advantageously dispensed with, 268.

Preservation of races by seed, 295.

Pricking out seedlings, 268.

Principles upon which the operations of horticulture essentially
depend, 101.

Productiveness, 64.

Propagation by budding and grafting, only successful within certain
degrees of affinity, 222—its objects, 224, 228—its rationale ex-
plained, 199, 225—by cuttings, 195—by knaurs, 189—by layers
and suckers, 207—by leaves, 189—by eyes, 184—by eyes and
cuttings, difference of, from that by budding and grafting, 211
—by roots, depends on the formation of adventitious buds, 20.

Protection afforded by walls, 266.

Pruning, 289—its objects, 239—its effects, 248—seasons for, 247—of
transplanted trees, 248—of roots, 249.

R.
Races of plants, means of their preservation by seeds, 297—means
of fixing their habits, 297—accidental alterations in, 307.

INDEX. 857

Races of plants, improvement of, 306.

Radiation, 138.

Radicle, 10.

Rain, amount of, at various places, 128.

Repotting, 272.

Reproduction, property of, in leaf-buds, 7—properties of, in seeds, 7.

Respiration, a function performed by the leaves, 40.

Rest of plants, 118—periods of, in tropical regions, 321—in tropical
regions, how imitated, 326."

Resting plants, 319.

Rind, 26.

Ringing, an operation by which the production of roots is accele-
rated, 15—experiments on, 34—physiological nature of the
operation, 252—its effects on fructification, 65—its use in facili-
tating the production of roots, 208—proper seasons for, 254—
its effects with regard to fruit and flowers, 254—its ultimate
consequences, 255.

Ripening of seeds, 175.

Root, substance from which it first derives its means of accretion,
10—is the part soonest developed, 10—mode of its increase in
length after it passes the embryo state, 11—at first grows by a
general distension of its tissue, 11—offices of its bark, 12—its
proportion to the stem variable, 15.

Roots lengthen at their points only, after passing their embryo
state, 11—why their extreme points are called spongelets, 11—
delicacy of their extreme points, 11—their hygrometrical pro-
perties, 11—local motions of their spongioles in quest of fresh
food, 18—immediate cause of their formation involved in
obscurity, 14—produced from various parts of plants, 14—aug-
ment in diameter simultaneously with the stem, 14—growing in
air, 13—growing in water, 13—their formation, an elaboration
of organisable matter furnished by the leaves, 15.

Acots perish if their formation be not speedily followed by the
development of leaves, 14—most readily formed in darkness, 14
—produced by removing a ring of bark, 15—differ from
branches in not being the development of previously formed
buds, 14—their incessant activity arrested only when frozen, 16
—their principal office, 15—their feeding property depends
upon the hygrometrical force of their tissue, 16—absorb gene-

858 INDEX.

rally whatever is fluid and sufficiently attenuated, 16—their
property of throwing off secreted, deleterious, or superfluous
matter, 19—necessity of their advancing into fresh soil, 20—in
general have no buds, 20—of some species, their power of
forming adventitious buds, 20—their fitness for propagation
depends on their power of forming adventitious buds, 20—
effects of their being situated in a widely different temperature
from that of the branches, 49—their action reciprocal with
that of the leaves, 49—bad effects of their being deeply
covered by soil, 105—their deep penetration into cold soil, a
cause of canker, 106—are naturally placed in a higher mean
temperature than branches and leaves, 107—instances of their
production by leaves, 190—emitted into the air, 198—are
formed by the action of leaves, 199—may be grafted, 225—
renovation of, 248—pruning of, 249, 293—their deleterious
excretions, 270—their slender power of selecting food, 270—
their direction in pots, 272—matted, 806—bruised, 292—of
trees retain the powers of life longer than branches, 19,
Rose, double yellow, expansion of its flowers, 84.

8.

Saddle-grafting, 219.

Salts, certain of them enter into the composition of the food of
plants, 18.

Sand, employed in propagation by cuttings, 203.

Sap-wood, its mode of formation, 27.

Sap, its constituents, 32—its transmission through the stem, 32—its
changes during the course of its circulation, 32—of plants may
be made to deviate from its usual course, 33—cause of its flow,
86—motion of, different from its flow, 36—its ascending and
descending currents communicate with different systems of
veins in leaves, 36—ascending, its force, 47—-derangement of its
course, 49—accumulation of, 72—its circulation affected by
motion communicated to plants by wind, 157—may be com-
pelled to organise itself externally as roots, 208—direction
given to, by pruning, 241—its return obstructed by ringing,
252—an inspissated state of, produced by a dry atmosphere, 325,

Saturation, hygrometrical, 127.

Searring the centre of bulbs, 210.

INDEX. 859

Scion influenced by the stock, 224.

Screens, 187—their importance in moderating the dryness of the air,
129—of oiled paper, 155.

Seasons of opposite extremes of moisture and dryness, 320.

Secretion, saccharine, formed by the germinating seed, 10.

Seeretions of plants, formative agents of, 52—an essential part of
them formed by the decomposition of carbonic acid, 8389—of the
fruit, 76—changes which they undergo, 76—result from the ac-
tion of their leaves, 52—table of the proportions of carbon and
water in various, 75—their formation favoured by a high tempe-
rature, with dryness, 83—deeomposed by frost, 84—of roots, 270.

Seedlings, pricking out of, 268.

Seed, its nature, 7—its properties of reproduction, 7—are different
from those of leaf-buds, 7.

Seeds contain an excess of carbon, 8—manner of their germination, 8
—conditions required to produce their germination, 8.

Seeds, germinating, form a saccharine secretion, 9—those germinate
quickest which contain the most nitrogen, 20—will renew the
epecies, 68—will not produce the identical peculiarities which cha-
racterise varieties of the same species, 68—origin of their food, 76
—their longevity, 77—its cause, 77—destruction of their vitality,
77—remain dormant whilst their proportion of carbon is undis-
turbed, 77—difference in their vigour, 77, 161—of tropical trees,
degree of heat required for germination, 108—length of time
which some species of, will lie in the ground, 168—consequences
of gathering them in an unripe state, 175—close packing of, in-
jurious in hot climates, 182—containing oily matter, 184—ex-
treme temperature which various species will bear, 162—tem-
perature required for their germination, 162—cause of their rot-
ting in the ground, 164—vital energy of, 164—with very hard
integuments, means resorted to for assisting their germination,
164—old, of spruce fir, germination promoted in, 167—germi-
nating, effects produced upon, by alkaline substances, 166—
subjected to boiling, 165—weak, produce weak plants, 174—of
composite plants, 174—period of their retention of the power
of germination, 175—ripeness in, 175—invigorated, 175—their
preservation, 177—reproduce species only with certainty, 296—
preservation of races by, 296—influence of cireumstances under
which they are matured extends to the progeny, 299.

360 INDEX.

Seed-packing, 177.

Seed-saving, 169.

Seed-sowing, 159—depth of seeds in the soil, 161.

Sexes, the essential parts of a flower, 56.

Shade necessary for cuttings, 205.

Shifting plants in pots, 269.

Shoots, young, their susceptibility of frost, 86—“ unripe,” their di
minished capability of resisting frost, 84.

Silex in solution absorbed by the Wheat plant, 17—rejected by the
Pea, 17.

Situation of a garden, 137.

Soil, necessity of roots advancing into fresh, 20—sterile, its effects in
accelerating fructification, 64—its temperature and moisture
more important than its mineralogical quality, 108—moisture
of the, 118—its superior heat at top taken advantage of for the
cure of canker, 106—effects of one too wet, 115—effects of rapid
evaporation from, 120—choice of, 137—for seeds, 160—its ex-
haustion in pots, 269—its deterioration by excretions of roots,
270—necessity of its being changed, 271.

Soils, appropriation of stocks to, 280—different, requisite for different
varieties, 332.

Solar light, difference of its effects on plants when transmitted
through different coloured media, 205.

Solar radiation cannot be imitated by bottom heat, so as to produce
a similar effect, 94.

Solar rays, their exhausting effects on plants, under certain cireum-
stances, 58—the immediate cause of perspiration in planta,
126.

Spongelets, their consistence, 11—reason of the extreme points of
roots being so called, 11—act as absorbenta, 12—are not special
organs, 13—their force of absorption, 15.

Spongioles abound in nitrogen, 13—chiefly supply the waste occa-
sioned by perspiration, 18—their importance, and the danger
of destroying them, 18—are not protected by a fully organised
epidermis, 283.

Succulent plants, their small proportion of roots, 15.

Succulents, 321.

Suckers, propagation by, 207—their production, 209—of the Pine-
apple, 209

INDEX. 361

Sulphuric acid, employed in drying air for the preservation of seed,
176.

Sulphurous acid gas, its eseape from brick flues, 152—its destructive
effects, 152.

Sun’s rays, foree of, 93.

Supertluous matter thrown off by roots, 19.

Stagnation of water about the roots of plantsin pots, 275.

Stamens, their parts and situation, 66—their use, 68.

btarch, its accumulation in seeds, 175.

Stem bears a variable proportion to the roots, 13—its origin, 21—
growth by the, 21—is at first merely a small portion of cellular
tissue, 24—its parts, 25, 28—its horizoutal system, 24—its per-
pendicular system, 24—its property of forming leaf-buds, 30—its
office, 82.

Stems, processes by which wounds in them are healed, 25—those
freely emitting roots may be more moulded up than others not
possessing such power, 278.

Sterility, 65—from cold and moisture, 84—in seeds, causes of, 170—
remedy for, 173.

Stigma, 56.

Stocxs, appropriation of, to soila, 280—their influence on grafts, 224
—necessity of a correspondence in growth between their hori-
zontal system and that of the graft or bud, 225—their effects in
modifying the growth of the tree, 226—their effects on fruetifi-
cation, 227—heading down, 234.

Stomates, 38—their number and size proportionate to the natural
nabits of plants, 39—number of, in a square inch of the leaves
of various species, 89—their position and adaptation, 51—per-
mit the escape of vapour, 115.

Stones, utility of, in soil, 119.

Strontian, rejected by certain plants, 17.

Structure of flowers, 55.

Style, 56.

Syringing, 51.

System, horizontal, of stems, 24, 26—horizontal cellular, 24—perpen-
dicular, of stems, 24, 26.

T.

Temperature, effzets uf great discrepancy in, as regards different por-

862 INDEX.

tions of a plant, 49—limits of, endurable by plants, 80—limit
of, below which plants will not grow, 81—effects cf one toe
high on plants, 81—unnaturally low, its effects, 83—relatively
high, conjoined with dryness, favours the formation of secre
tious, 883—at which different fluids become frozen, 85—its laws
with respect to its influence on vegetation, 87—its alternations
necessary to plants, 88—of the earth at various places immeur
ately below the surface, 91—effects of its diurnal alternations,
87—effects of its annual alternations, 88—of the earth, 90, 9s—
at various places, comparatively with that of the atmosphere,
91—at various depths, 92—of the hottest and coldest months at
various places, 100—importance of insuring a proper one tor
plants, 108—of soils, its important influence on vegetation, 1U%
—with regard to the direction of the wind, 130, 134—of hot-
houses, its regulation, 142—effects of a high one at night in nov-
houses, 145—effeets on pollen of one too low, 171—which grain
will bear, 181—seasons of extreme, 320—uniform, 320—low.
with much light, its effects on the sap, 325—of plant houses, ne-
cessity of lowering it during the night, 328—diurnal extremes
of, 328.

Tissue, general distension of, in the embryo state of roots, 9—general
distension of, in roots growing in air and water, 13—ids hygro-
metrical foree depends on the action of capillary tubes, 16.

Tissue, its first formation requires nitrogen, 18—disorganisation of,
117—impermeability of, indaced by training, 265—cellular, is
the component of the first rudiments of the stem, 21.

Tonguing, 217.

Training, 257—on a horizontal plane, bad effects of, 257—its elfecta
on the circulation of the juices, 259—pendulous, 260—its disaa-
vantages, 265.

Transplanted trees, their pruning, 248—languid from previous dry
ness, effects on, by the too rapid absorption of water, 294.
Transplanting, 279--its rationale, 281—season for, 283—of deciduous
trees, 280—manner of performing the operation, 290—prepara-

tion of old trees for, 291.

Trees and shrubs, distinet parts of their bark, 2¢.

True sap, wholly generated in the leaves, 252.

Tubers, 29.

INDEX. 863

U.
Unisexual plants, effects of temperature on, 82

Vv.

Valleys, superior general warmness of, 189—their liability to sudden
cold, 139.

Vaporous impurities, 152.

Varieties not absolutely permanent through propagation by seeds,
296—ineans of fixing them, 297—contamination of, 302.

Vegetation, relative advancement of, in stocks and scions, 284—in
forcing houses, mode of resting it, 330.

Veins of leaves consist of two systems, 37—their structure, 37.

Ventilation, 150—under some circumstances injurious, 151—cireum-
etances which render it necessary, 152.

‘Vine, its cultivation in the open air in England, cause of the general
want of success in, 99—great power of its ascending sap, 47—
preventive against its bleeding, 245

Vine borders, their preparation, 119.

Vines, a cause of their not setting, 106.

Vital forces of vegetation, 40—principle is stimulated by heat, 9, 107
—principle in seeds, 175—force in plants decomposes water, 40
—functions of plants, 125.

Vitality in seeds, causes of its destruction, 111.

Ww.

Walls, effect of blackening, 188—importance of, with regard to
shelter, 131.

Walnut, propagation of, by budding, 233.

Water, a vehicle by which oxygen is supplied during the process of
germination, 9—in various respects conducive to germination, 9
--enters into the composition of the food of plants, 18—pure,
eannot solely support vegetation for a long period, 18—is de-
composed by the vital action of plants, 18, 41—proportions of,
in certain vegetable secretions, 96—an excessive supply of, re-
tards the ripeuing of fruits, 76—its decomposition or dissipation
by fruits, 76—in a tepid state applied to roots, 109—in which
aquatics are grown, necessity of regulating it to a due degree of
temperature, 109—in the soil, should be diminished when suecu-
lent fruit is ripening, 116—stagnation of, 275—absorption of,

364 INDEX.

by dried roots, effects of, 294—effects of immersing roots in
116.

Watering, 113—its effects on stiff soil, 122—has the effect of lower-
ing the temperature of the soil, 122—newly planted trees, 294
—of roots, substitute for, under particular circumstances, 295.

Water plants, flowering of, 109.

Weights applied to branches, 255

Wet borders, 118.

Whip-grafting, 216.

Wind, its effect in increasing the dryness of the air, 129—its effects
with regard to fertilisation, 171—its effect on the circulation of
sap, 157.

Winds, table of, with the corresponding temperatures and dryness,
183, 134,

Winter of plants, not in all cases cold, 319.

Wood formed by the combination of cellular tissue and woody fibre,
23—of exogens, 24—the channel for the ascent of all the fluids
of plants, 27—of stems, 27—central, its importance compared
with that of the alburnum and liber, 38—central, example of
its removal, 33, 35.

Woody matter, its first appearance, 24.

Worms, injury occasioned by them to plants in pots, 120.

Wounding of plants to be avoided when the sap first begins to flow,
244.

Wounds, processes by which they are healed, 25, 292.

THE END.