L I E) R.ARY

OF THE

UNIVERSITY

Of ILLINOIS

634
J63p

Wtter

<♦

SCIENCE AND PRACTICE

GARDENING.

London:

GEORGE WOODPALL AND SON,

ANGEL COURT, SRINNER STREET.

THE

PRINCIPLES

OF

PRACTICAL GARDENING.

BY

GEORGE W. JOHNSON, ESQ.

FELLOW OF THK -AGRI-HORTICt'LTURAL SOCIETY OF fXDrA;

CORREfePO.VDIVG -MEMBER OF THE ROYAL CALEDONIAN AND

MARYLAND HORTICVLTCRAL SOCIETIES,

ETC. ETC.

LONDOxN :

ROBERT BALDWIN, 47, PATERNOSTER ROW.

1845.

PREFACE,

For nearly twenty years the Author of these pages
has laboured to make the gardeners of England
more generally aware than they are, even at pre-
sent, of the principles on which their practices are,
or ought to be, founded. The results of his early
researches have, from time to time, been made
public, and those, together with more that are new,
he now offers to his readers in a collected and
orderly form.

He has thus laboured to impart the reasons for

horticultural practice, because it is certain that

gardening is no exception to the rule, that the

worst of ignorance is an ignorance of the reasons

for our conduct ; and if this volume aids in some

j degree to remove such ignorance from the gardener,

-^ the Author ^ill be happy in the consciousness that

^ he has helped the advance of plant- culture from

^ mere empiricism into the class of the rational

^ sciences.

304427

CONTENTS.

Introduction

Chapter I. — Sowing

Chapter II. — The Root

Chapter III. — The Stem and Branches

Chapter IV. — The Leaves

Chapter V,— The Sap . . .

Chapter YI. — The Flower

Chapter VIL — The Fruit and Seed .

Chapter VIII, — The Diaeases of Plants

Chapter IX. — Death and Decomposition

PAGE

1
8

49
125
135
152
185
212
243
309

THE

PRINCIPLES OF GAEDENING.

INTRODUCTION.

Gardening or Horticulture has for its objects, the
production of the fiTiits, flowers, and culinaiy vege-
tables of any climate, in any habitable place, in the
greatest perfection, and at the least possible expense.

Like all other human occupations, gardening is di-
visible into the science which teaches the principles
and circumstances on which the attainment of the de-
sired objects is founded ; and the art or practical skill
which enables the practitioner to secure those cir-
cumstances, and effectuate those principles.

It is to the first of these departments of knowledge
that the following pages are devoted: their prime
subject being the guidance afforded to the gardener
in the practice of his art by chemistry, vegetable
physiology, and other sciences.

If any one asks what those sciences have done for

2 PEINCIPLES OF GARDENING.

gardening, I point to the discoveries of the late Mr.
Knight. The opinion of that most scienced horti-
cultuinst is also recorded in a letter from him now in
my possession, — the words should be engraved over
the portal of every garden : " Physiological know-
ledge CAN ALONE NOW DIRECT THE GARDENER TO IM-
PROVEMENT, FOR HE possesses ALL THAT MERE PRAC-
TICE IS LIKELY TO GIVE." Scicnce, it is time, can
never supersede the necessity for a practical ac-
quaintance with the operations of the spade, the
knife, and the hoe ; but it is their best guide, — a
pilot needed even by the most experienced, and let
it be remembered, that to botanists we owe nearly
the whole of our flowers, as well as our knowledge
of their habits; and that to information drawn
from their discoveries, we are indebted for the ma-
jority of oui' numerous varieties of fruits and culinary
vegetables, as well as for a laiowledge of their ana-
tomy and functions. Botany also affords the best
nomenclature for our plants ; and thus, to it we are
indebted for an enlightened practice, and a language
universally intelligible. But for another science,
chemistiy, the true nature of soils, of manures, of
the food and functions of plants, would be unknown
to us, and many of our simplest gai'den operations
would be inexplicable.

The gro\Ni:h of horticultural science has been slow;
for, although its dawn was in the Elizabethan age.

INTRODUCTION. 3

yet it never afforded any distinct light to gardening
until the beginning of the present centmy.

It is undoubtedly tme. that in much earher ages
there were suiinises bom of inquiiing minds, that
are startlingly in accordance with the results afforded
by modern vegetable chemistiy and physiology ; but
they were no more than sm'mises ; fortunate guesses
that, among many totally erroneous, happened to sa-
vour of ti-uth. Thus Pythagoras forbade the use of
beans as food, because he thought that they and human
flesh were created from the same substances, and
modern research has rendered it certain that that
pulse has among its constituents more animo-vege-
table matter than most other seeds. Empedocles
maintained that plants are sexual ; that they possess
life and sensation ; and that he remembered when
he was a plant himself, previously to being Empe-
docles.

Theophrastus and Pliny wrote more voluminously
upon plants, but not ^vith more knowledge of their
physiolog}^ ; and little or no improved progress is
really visible until the sixteenth centurj^ was well
advanced; for this branch of science was no bright
exception from the darkness enveloping all human
knowledge dming the middle ages, and it was not
until that period in which Bacon lived, that the
human mind threw off the trammels of the school-
men, and instead of arguing as to what must be,

B '2

PEINCIPLES OF GARDENING.

proceeded to examine and search out what is. The
Reformation, the spirit of the age, was then not con-
fined to rehgion. By dehvering the human mind
from thraldom, and teaching man to search all things,
hut to retain only that which is good because true,
it gave an impetus to improvement which no tyrant
opposition has ever since been enabled to check.

Such men as Bacon, Peiresc, Evelyn, Grew and
Malpighi arose. Bacon was the first to teach aloud
that man can discover truth in no way but by observ-
ino- and imitating the operations of natm'e ; that
truth is born of fact, not of speculation ; and that
systems of Imowledge are to be founded not upon
ancient authority, not upon metaphysical theories,
but upon experiments and obsen-ations in the world
around us.

Peiresc was a munificent man of letters, whose
house, whose advice, and whose purse were opened
to the students of eveiy art and science. His library
was stored with the literature of every age, and his
garden with exotics from exerj clime, from whence
he delighted to spread them over Em'ope^.

Grew in England, and Malpighi in Italy, de-
voted themselves to the anatomical examination of
plants, and these were followed by Linnaeus, Gaertner,
and others, who, trusting only to the dissecting knife
and the microscope, soon precipitated into mins all
* History of English Gardening.

INTRODUCTION. 5

the fanciful fabrics of the Aristotelians. They were
the founders of that science of vegetable physiology,
which, enlarged and carried into practice by the
late Mr. Knight and others, has advanced horti-
culture to a degree of improvement, undreamed of
by their immediate predecessor, Heresbach, when
he informed the world that, if the powder of rams'
horns is sown, and well watered, " it will come to be
good aspai'agus."

The researches of Hales upon the circulatory
power of the sap-vessels, of Bonnet upon the func-
tions of the leaves, and of Du Hamel, Priestley,
Ingenhousz, Sennebier, Saussure, and others, upon
the action of hght, and the nature of the gases de-
veloped during the respiration of plants, imparted
still more useful knowledge to the gardener, and
rendered his art still less empirical.

The same philosophers directed their attention
also to the food of plants imbibed by their roots,
and to the examination of their various secretions ;
but here they were joined by another band of na-
ture's students, and no one conversant with the phi-
losophy of plant-culture but will remember the debt
he owes to Vauquelin, Lavoisier, Johns, Da^y, Liebig,
Lindley, Johnston, and Low.

It has been my endeavour to concentrate and arrange
the results of the researches of the above-named disci-
ples of nature in the following pages, — adding such rays,

6 PEINX'IPLES OF GARDENING.

derived from lesser lights, as aid to render the whole
more luminous, and such links of experiments and
obsen'ations from similar sources as make the work
more connected than it w^ould be without their aid.

In the arrangement of this work I might have fol-
lowed the more obvious plan of commencing with a
description of the seed, and the promotion of its pro-
duction ; but I found that the order adopted enabled
me to pursue more readily, and more progressively,
the phenomena and practices to be explained and
illustrated.

A few gardeners may still exist who venture to
think science useless — as there once existed a de-
votee of fashion who wondered w4iy it was not alwaj^s
candle-light ; but the great majority of gardeners
are now men of science, endeavouring thoroughly
to understand the reason of eveiy practice, and the
supposed cause of each effect. To those differing
from them I might name, if it would not be invi-
dious, nearly all the most successful of our modern
gardeners. To a man, these are w^ell acquainted with
gardening's relative sciences. I forbear from men-
tioning names, but I may remind my readers, with-
out fearing to offend, of two departed savans, M.
Lavoisier, and our fellow^-countrjmian, Mr. Knight.
Lavoisier, the Linnaeus of chemistiy, cultivated his
grounds in La Vendee on scientific principles, and
in a few years their annual produce doubled that from

INTRODUCTION. I

equal spaces of his' neighbours' soil. Mr. Knight has
scai'cely left a department of our horticulture unim-
proved, by that combination of scientific ^vith prac-
tical knowledge which he, perhaps more than anv
other man, had united in his own mind.

It behoves every gardener to follow in theu" steps,
for though the great men who have gone before
have done much for gardening, yet still more remains
to be accomplished. We still, on most points, do
and must ever see through a glass dai'kly ; but that
is no reason why any one should refrain from the
efifort to elicit a ray towards diminishing the obscu-
rity— and we may all, without fear of misspending our
laboui', continue to act as if botany could still fur-
nish something new, and as if chemistry and phy-
siology had still some secret to reveal to the en-
quirer.

CHAPTER I.

SOWING.

That the seed should have a perfectly developed em-
bryo, and have arrived to nearly perfect ripeness, is
essential to its being able to germinate. The rea-
son for this is obvious : the young plant requires for
its earliest nourishment a peculiar compoimd, usually
saccharine matter ; and this compoimd, in accordance
with that universal fitness of things which demon-
strates the wisdom of God, is always generated by
the combined agency of heat, moistm'e, and oxygen
gas, from the substances most abmidant in the fully
ripened seed. Let barley be the example. Saccha-
rine matter is essential for the first nourishment of
the radicle and plumule,^ and into such saccharine
matter is starch converted, by the combined agency I
have named. It is starch, therefore, that is the chief
constituent of the seed. But if barley be gathered
immature, and dried, the chief ingredient is mu-
cilage or gum ; and this, if exposed to the essentials
for germination, heat, moisture and oxygen gas, in-

^ The thread-like sprouts, becoming afterwards the root and
stem, are so named.

CH. I.] SOWING. 9

Stead of passing into saccharine matter, is converted
into acetic acid.

As it is imperative that eveiy seed should have
nearly attained to ripeness before it acquii'es the power
of germinating, and that the more perfect the ripeness
the more perfect and the more healthy that germina-
tion, so is it equally ceitain, that the length of time it
retains the power of germination differs in almost every
plant. The seed of the coffee shrub loses all vege-
tative power, unless sown within a few weeks after it
has been gathered, whilst that of the melon improves
by being stored for one or two years, and celery re-
mains capable of germinating for five times the last-
named period ^. These and all other instances within
my knowledge demonstrate, that the more starchy
and other matters into which nitrogen^ does not enter
as a constituent, which a seed contains, the longer v61\
it retain vitality ; and two familiar instances are com-
mon rice and the kidney bean. Eice contains 85 per
cent, of starch, and will retain its vegetative powers
for many years ; whilst kidney beans, which contain

* Melon seeds^ by keeping, improve only in the sense in which
gardeners consider the plant improved, viz. less of stem is produced,
and the fruit is matured earlier. Whatever checks the develop-
ment of the early organs, the radicle and plumule, produces this
effect, and this is effected by age in the melon seed ; its starchy
component diminishes in quantity, being gradually converted into
albumen. This is less easily transmuted to the soluble matters
necessary for the nourishment of the parts first developed.

^ Nitrogen, a gas present in most animal matters.

10 PRINCIPLES OF GARDENING. [CH. I.

one-third their weight of animo-vegetable matter and
other constituents, of which nitrogen is a component,
will not vegetate healthily a second season.

Carolina, Rice.

Water 5.00

Starch 85.07

Parenchyma 4.80

Gluten 3.60

Uncrystallizable sugar . . . 0.29
Grummy matter, approaching

starch 0.71

Oil 0.13

Phosphate of lime . . . . 0.13

99.73^
Kidney Beans.

Skins 288

Starchy fibrous matter . . . 425

Starch 1380

Animo-vegetable matter . . . 799

Extractive 131

Albumen and vegeto-animal mat-
ter 52

Mucilage 744

Loss SI

3840 b

* M. Braconnot, in Ann. de Chym. iv. 370.
'' Einhof in Gehlen's Journ. vi. 545.

CH. I.] SOWING. ' 11

This speedy loss of \-itality in seeds abounding in
nitrogenous matter, is just what the chemist would
predict ; for all bodies so constituted are most prone
to decomposition and decay.

The following list, furnished by the late Mr. Lou-
don, shows the greatest age at which some of our
common garden seeds germinate freely ; and this
result of experience is quite concuiTent ^vith our
knowledge of their chemical constitution : —

One year. Peas, beans, kidney beans, carrot, par-
snip, oraches, herb-patience, rhubarb, elm, poplar,
and willow.

Tivo years. Radish, salsafy, scorzonera, purslane,
the alUums, cardoon, rampion, alisander, love apple,
capsicum, egg-plant.

Three years. Sea-kale, artichoke, lettuce, mari-
gold, rue, rosemaiy.

Four years. Brassicas, skirret, spinach, asparagus,
endive, mustard, tarragon, borage.

Five and six years. Burnet, sorrel, parsley, dill,
fennel, chervil, hyssop.

Ten years. Beet, celery, pompion, cucumber, melon.

Now in this list generally, as already observed,
those with the most of nitrogenous matters among
their component parts, are the first to decompose,
and consequently lose their \-itahty ; and those with
the greatest amount of starch and lignin, or more
carbonaceous constituents, retain their germinating

12 EKINCIPLES OF GARDENING. [CH. I.

power the longest, and for the evident reason, that
such ai'e less prone to decay.

At the same time, let me guard myself from being
misconceived to say, that such are the only chemical
causes for a seed's curtailed or protracted vitality.
On the contrary, I am "well awai'e there are others,
and for example may be taken many seeds abounding
with expressed oil. These, exposed to the free ope-
ration of the air, gradually lose their \'itality, as the
oil they contain becomes rancid. Presented from the
action of the air, no seeds are more retentive of vi-
tality, apparently because when so preserved, the oil
they contain will remain sweet and unchanged for
ages. This is the reason that in earth excavated
from great depths below the sui-face, charlock, mus-
tard, and such like plants, ha\ing oleaginous seeds,
are found to have retained their embiyo ^^tality.

In considering this subject, let it ever be kept in
mind, that almost every species of seed has a peculiar
degree of heat, and a peculiar amoimt of moisture,
at or approaching to which its vitality will be excited
into action. Therefore, in all obsei'vations on the
life-retaining power of seeds, and in conclusions
deduced from experiment, it must be carefully
secured that they have not been excited to those
initiatory steps of germination, which being taken and
then checked, invariably cause the destruction of a
seed's vital powers.

CH. I.] SOWING. 13

This brings me to the consideration of the con-
tingencies necessaiy to cause a seed's germination.

A certain degi'ee of warmth is essential, for no
known plant has seeds that will genninate below or
at the freezing point of water. A temperature above
32° of Fahrenheit's thermometer, therefore, is
requisite ; and the plants whose seeds will germinate
nearest to that low degree of temperature, in this
country, are the winter weeds. For example, I have
found the seeds of the Poa annua, the commonest
grass of our gravel walks, germinate at SS"^, and the
seeds of groundsel (Senecio vulgaris) would probably
requii'e no higher temperature. But, on the other
hand, the temperature must not be excessively high.
Even no tropical seed, probably, will germinate at a
temperature much above 120^ F., and we know from ' tl^^f.i ix^
the experiments of MM. Edwards and Colin, that ' ^

neither wheat, oats, nor barley will vegetate in a
temperature of 113°.^

Every seed differing in its degree of excitability,
consequently has a temperature without which it
will not vegetate, and from which cause arise the
consequences that different plants require to be so"uti
at different seasons, and that they genninate with
various degrees of rapidity.

For example, two vaiieties of early pea, sown on a
south border on the same day, and treated strictly

^ Jour, de Pharmacie, xxii. 210.

14

PRINCIPLES OF GARDENING.

[CH. I.

alike throughout their growth, were about a fortnight
differing in all their stages of vegetation.

Sown In bloom Gathered from

Cormack's Prince

Albert . . Jan. 4. April 1. May 14-

Warwick . Jan. 4. April 13. May -28.

Adanson found that, under the most favourable
circumstances, various garden seeds might be made
to germinate in the following veiy different spaxies of
time.

Spinach, Beans, Mustard . 3 days.

Lettuce, Aniseed .... 4

Melon, Cucumber, Cress . 5

Eadish, Beet 6

Orache 8

Purslain 9

Cabbage 10

Hyssop 30

Parsley 40 or 50 do.

Almond, Chesnut, Peach . 1 year.

Rose, Hawthorn, Filbert . 2 do.^

In one instance M. Adanson certainly must have
experimented with old seed, for I have fomid good
new parsley seed, sown on fresh fertile soil in May,
had germinated in two days, and its leaves were
above the surface within a week from the day of
" Families des Plantes, i. 85.

CH. I.] SOWING. 15

sowing. Then again in the case of rose seed, — at all
events, in the case of that of the dog rose, — if the hips
he allowed to endure the frosts of winter before they
are gathered, their seed vail geiToinate in much less
time than is named by M. Adanson. This lesson
was probably taught the gardener by nature, for the
hips of roses never shed their seed in this country
until they have been frosted.

The gardener should always bear in mind, that it
would be a very erroneous conclusion, because a seed
does not geiTuinate at the accustomed time, that
therefore its vegetating powers ai'e departed. No
two seeds taken from the same seed-vessel ger-
minate precisely at the same time ; but, on the
contrary, one will often do so promptly, while its
companion seed will remain dormant imtil anotlier
year. M. De Candolle relates an instance where
fresh tobacco seedhngs continued to appear annually
for ten years on the same plot, though no seed was
sown after the first sowing ; and the same phenomenon
usually occurs for two or three years, when the seed
of either the peony or hawthorn are sown. Why
one seed is more easily excited than another is as
yet unexplained, but the wisdom of this one of many
pro-visions for avoiding the accidental extinction of a
species in any given locality is readily discerned.
An ungenial spring may destroy the plants from
those seeds which first germinated, but this could

16 PBINCIPLES OF GAEDENING. [CH. I.

scarcely occur also to those of the second and third
year, or even to those which were only a few weeks
later in their vegetation.

It is not possible to enunciate a general rule

I relative to germinating temperatures requiring no
exceptions, but in general, for the seeds of plants
natives of temperate latitudes, the best germinating
temperatiu'e is about 60° ; ^ for those of half-hardy
plants 70° ; and for those of tropical plants about
SO'^; and the necessity for such temperatui'es
depends upon the same causes that prevent the
incubation of eggs unless they be kept for a certain
period at a temperatui'e of about 100^. The
requisite changes are not produced either in the seed
or in the egg, miless it be submitted to the pro-
pitious temperature — but why this is requisite to
develope the forms, and effect the changes, without

' wliich there is no vitality, is a secret at present
witlilield from man s understanding by the Almighty

I architect, and w^e must rest satisfied with the
approximate Imowledge that heat is the vast and all
pen^ading agent he employs to call life into existence.
Although temperatm'es ranging between 60° and
80"^, are those most usually propitious to germina-
tion, yet a much higher temperature can be endured
by seed without its vitality being destroyed, and

* Except where otherwise stated, Fahrenheit's thermometer is
referred to in the temperatures particularized.

CH. I.] SOWING. 17

indeed may be employed Avith great advantage,
when the seed from age or other cause geinninates
A\-ith difficulty. Dr. Lindley foimd the seeds of a
raspberr}^ germinate, though they must have endured
a temperature of 230'^ in the boiling synip of the
jam, -whence they were taken ; and other instances
are known where peas submitted to a temperature
of 200°, and, left in the water for twenty-four
hours until cool, germinated more readily than
other peas not so treated. The seeds of Acacia
lophantha also produced seedlings after being boiled
in water for five minutes. The effects produced by
this high temperature, are to permanently soften the
cuticle of the seed, and render it more readily per-
meable by the air ; also aiding the conversion of the
starchy components of the seed into saccharine
matter ; but if the boiling be contmued until the com-
position of the germen is altered, the germinating
power of the seed is destroyed.

These facts lead to the verj- important inquiry,
whether the soil has any influence over the tempera-
ture occurring to the seed, and to the roots of plants
placed beneath its surface. The researches of M.
Schluber answer this query in the affirmative. This
distinguished German chemist fomid that when the
temperature of the upper sui'face of tlie earth was 77°
in the shade, various soils, exposed to the sun from

c

18 PRINCIPLES OF GARDENING. [CH. I.

eleven to three, in vessels four inches square and
half an inch deep, attained the temperatures shewn
in this table.

Wet. Dry.

Siliceous Sand, bright yellowish gray 99.1 11 '2. 6

Calcareous Sand, whitish gray . . 99.3 112.1

Gypsum, bright w^liite gray . . . 97.3 110.5

Sandy Clay, yellowish 98.2 111.4

Loamy Clay, yellowish . . . , 99.1 112.1
Stiff Clay, or Brick Earth, yellowish

gray 99.3 112.3

Fine bluish gray Clay 99.5 113.0

Lime, white 96.1 109.4

Magnesia, pure wiiite 95.2 108.6

Garden Mould, blackish gray . . 99.5 113.5

Arable Soil, gray ...... 97.7 111.7

Slaty Marl, brownish red .... 101.8 115.3

The results of M. Schluber's experiments demon-
strate that which our knowledge of the laws of caloric
would have induced us to pre-suppose, namely, that
light coloured earths by reason of their reiiecting
most rays of heat, are warmed much more tardily
than dark coloured earths. It was this conclusion
which induced me, some years now past, to try the
effect of sprinkling coal ashes over rows of autumn
sown peas. The peas invariably appeared above
"the soil some days before those in rows not similarly

CH. I.]

SOWING.

19

treated. This acceleration of vegetation continued
equally marked throughout their growth, and is
further explained hy other experiments of M.
Schluber, which testify that those soils in the above
table which absorbed the heat most readily, retained
it most tenaciously, and consequently were longest
coohng. Magnesia cooled in one hour and twenty
minutes as much as the garden mould did in two
hours and sixteen minutes, and the slaty marl in
three hours and twenty-six minutes.

From more recent experiments made in the Hor-
ticultural Society's garden at Chiswick, and in other
parts of England, Ave have the following results, con-
firming M. Schluber's experiments.

In the Chiswick garden,

1844.

Minimum
Temp, of air.

Earth
1 foot deep.

Earth
2 feet deep

)ec. 4 .

2-2 .

40 .

43

5 .

U .

38 .

43

6 .

U .

37 .

42

7

20 .

37 .

41

8 .

26 .

36 .

41

9 .

•28 .

36 .

40

10 .

28 .

36 .

40

11 .

22

36 .

39

In a stiffish loam on a gravelly subsoil near
Sheffield, after a fortnight "s exposure to a minimum

c 2

20 PRINCIPLES OF GARDENING. [CH. I,

temperature, var^-ing between 21° and 31°, the soil
had frozen to a depth of 4 J inches, but at lower
depths the temperatui'es w^ere as follow : —

At 6 mches . . 34°

— 12 „ . . 36i

— 24 „ . . 39

In every instance the lighter soils were frozen
to a less depth than the more tenacious. The for-
mer in no case having the frost penetrate lower than
six inches, but in hesi\j soils two inches deeper.*

The following table, kept by Mr. Shai-p, the scien-
tific manager of the Winchester gas works, shows
the lowest temperature of the air at night, and its
highest temperature by day during the January of
the present year, as well as the temperature of the
soil at six inches and at twelve inches below its sur-
face. The soil is black, rich, and siliceous, resting
on a chalky subsoil : —

^ Gardeners' Chronicle.

CH. I.]

SOWING.

^1

Ground.

Jan.

Night.

Day.

6 in.

12 in.

Jan.

1

35

44

39

39

1

2

34

38

371

39

2

3

25

40

34

37

3

4

32

47

35

36

4

5

38

51

38

381

5

6

42

52

41

40

6

7

45

50

421

411

7

8

35

42

40

41

8

9

32

39

371

40

9

10

35

39

371

391

10

11

43

50

42

41^

11

12

39

45

42

42

12

13

38

45

41

414

13

14

36A

49

40

4l|

14

15

38

46

40

41

15

16

38

46

40

41

16

17

39

45

40

41

17

18

38

48

40

41

18

19

32

46

38

401

19

20

34

45

38

40

20

21

30

42

36

39

21

22

25

47

35

39

22

23

35

49

40

391

23

24

36

49

40

40t

24

25

29

51

37

39

25

26

42

47

41

41

26

27

34

46

38

39

27

28

281

40

35

3'i

28

29

27

39

34

37

29

30

31

39

38

37

30

31

25

35

33

36

31

These facts, and the frequent failure of our potato
crops have led Dr. Lindley to the very judicious sug-
gestion of planting these crops in autumn, which must
be the best time, if practicable, for it is pursuing the
dictate of nature. That it is practicable, I have no

22 PEINCIPLES OF GARDENING. [CH. I.

doubt, for no frost -would injure the sets if a little
coal ashes were put over them in each hole, for coal
I ashes are an excellent non-conductor of heat, and
1 consequently opposed to the admission of cold, and
/ are, at the same time, a good preservative from ex-
' cessive moisture.

The fact that the earth, in regions not eternally
ice-boimd, never is reduced in temperature, at a few
inches from the surface, so low as the exterior air in
winter, nor is elevated at a similar depth to an equal
degree of warmth in summer, suggests the necessity
for more attention to the temperature of the soil
in our horticultural houses than it has hitherto ob-
tained.

Attention is more awakened to it now than for-
merly, and by hottom-heat our gardeners now intend
something more than a mass of fermenting matter
for forcing cucumbers or pine-apples.

It is quite certain, that eveiy plant, when growing
in a favourite soil in its native climate, has its roots
growing in the temperatui'e which is best accordant
with that in which its branches are delighting. Under
no circumstances, if the plant is flourishing, will the
temperature in summer, at 12 inches from the sur-
face, be found to be less than 2"", nor more than 5°
loiver than the average temperature of the atmo-
sphere ; and in winter, that temperature at the same

SOWING. 23

depth will be found to range similarly above the at-
mospheric temperatiu'e. There is no doubt that in
tropical climates, the bare exposed soil becomes heated,
for a few inches in depth, to a degree higher than
that of the air incumbent upon it. But this is not the
case about the roots of plants ; for their fohage, and
the herbage naturally clothing the soil, preserve this
from such a pernicious elevation of temperature. That
such an excessive elevation is injmious, is known to
every obseiTer of plants, whether the plants are grow-
ing in the tropics or in a stove. The roots are stimu-
lated to imbibe moisture faster than the foliage can
digest sufficiently the sap thus forced to them, and
that foliage is expanded wider and more weakly m
the vain effort to keep pace with the supply. This is
only one among many instances of that property, so
wisely given to organised beings by their Creator, of
adapting themselves to circumstances ; and it is only
when the vicissitudes of those circumstances are too
violent, or too long continued, that they fail in their
effort at conformity.

If the temperature of the soil be unnaturally below
that in which the branches are vegetating, the effects
are equally, though differently, disastrous. The sup-
ply of sap is too much diminished in quantity, and
the edges of the leaves consequently die, or the blos-
soms fall, or disease attacks some part of the fruit,
according to the nature of the plant, or the stage of

24 PRINCIPLES OF GARDENING. [CH. I.

growth in which it occurs. The shanking in grapes
appears traceable to this cause.

Then again, a soil abounding in supei'fluous \Yater
is always colder than a soil of siinilai' constitution
that has been well drained. The reason for this is
obviously that the same quantity of caloric which will
heat the earth four degrees will only heat water one
degree ; or, to use the language of the chemist, tlie
capacity for heat of water is four times greater than
that of the earth s. In every day experience, we see
the low lying and consequently the wettest portions
of a field, are always those on which the even-
ing mist or fog first appears ; for at one season of
the year it becomes colder than the air, and the at-
mospheric moisture always precipitates first on the
coldest surface. At other seasons of the year, eva-
poration from the wettest portion of a field is tlie
most abundant ; and, at those seasons, mists ai'e
formed by the temperature of the aii* being much
below that of the earth, and consequently condensing
its watery exhalations. The greater the difference
of temperature, the denser is the mist, the condensa-
tion being more complete.

I will observe, as on a former occasion, that the
time will probably anive when gi'eater precision will
be attained as to the time when om' various seeds
may best be committed to the soil. We shall owe
that advance to a more complete knowledge of what

CH. I.] SOWING. 25

mav be termed the coincidences or sjniclironisms of
natiu'e.

The attempt to attain knowledge on this subject is
not new, for nearly a centmy since Harald Barck and
Alexander Berger, in Sweden, made many observ-
ations directed to this object, and in later years,
Stillingfleet and Martyn have done the same in
England.

The first named of these botanists thus expresses
himself upon the subject : "If botanists noted the
time of the foliation and blossoming of trees and
herbs, and the days on which the seed is sown,
flowers, and ripens, and if they continued these
observations for many years, there can be no doubt
but that we might find some inle from which we
might conclude at what time grains and culinary-
plants, according to the nature of each soil, ought to
be sown ; nor should we be at a loss to guess at the
approach of winter ; nor ignorant whether we ought
to make our autumn sowing later or earlier."

M. Barck would derive his intimations from the
vegetable tribes alone, but I think the other king-
doms of organic nature might be included — as the
appearances of certain migratory birds, and the birth
of certain insects. For example, in the east of
England, it is a common sapng among gardeners —
confirmed by practice — AMien you have seen two
swallows together, sow kidney beans.

26 PRINCIPLES OF GAP.DENING. [CH. I.

This s}Tichronical mode of regulating the opera-
tions of the cultivator of the soil is no modem sug-
gestion, but the efforts of Barck and his successors
have only been to find such indications in our north-
em clime that would be of the same utility, and
similarly admonitory as others adopted by the an-
cients in more simny latitudes. Thus Hesiod says,
If it rain three days together when the Cuckoo sings,
then late sowing will be as good as early sowing ;
and in another place, when snails begin to move and
climb up plants, cease from digging about vines, and
take to pruning.

That our operations may be made justly s}ti-
chronical vdth certain appearances in nature is sup-
ported even by our present limited knowledge. " It
is wonderful," says Mr. Stillingfleet, " to observe
the conformity between vegetation and the arrival of
certain birds of passage. I will give one instance as
mai'ked down in a diary kept by me in Norfolk, in
the year 1755. 'April ICtli. Young Figs appear;
the 17th of the same month the Cuckoo sings.'
Now the word xo-^iv^ signifies a Cuckoo and the
young Fig, and the reason given for it is, that in
Greece they appeared together. I will just add,
that the same year I first found the Cuckoo Jioicer in
blossom the 19th of April."

"Linnaeus says, that the Wood Anemone blows
when the Swallow arrives. In my diary for the year

CH. I.]

SOWING.

27

1755, I find the swallow appeared April 6th, and the
Wood Anemone was in blow on the lOtli of the same
month. He says that the Marsh Marygold blows
when the Cuckoo sings. Accordingly in my diary
that flower was in blow April 7th, and the same day
the Cuckoo sang."

Then, again, whatever may be the character of the
season, whether it be unusually cold or preter-
naturally mild, the same order prevails in the leafing
of plants.

1. Honeysuckle.

2. Gooseberry.

3. Currant.

4. Elder.

5. Birch.

G. "Weeping "Willow.

7. Raspberry.

8. Bramble.

9. Briar.

10. Plum.

11. Apricot.

12. Peach.

13. Filbert.

14. Sallow.

15. Alder.

16. Sycamore.

17. Elm.

18. Quince.

19. Marsh Elder.

20. Wych Elm.

21. Quicken Tree.

22. Hombean.

23. Apple.

24. Abele.

25. Chestnut.

26. WiUow.

27. Oak.

28. Lune.

29. Maple.

30. Wahiut.

31. Plane.

32. Black Poplar.

33. Beech.

34. Acacia Piobinia.

35. Ash.

36. Carolina Poplar.

28 PRINCIPLES OF GARDENING. [CH. I.

This invariable simultaneous change, this con-
sistent adherence to the same order of time, seems to
demonstrate that the same circumstances, the same
variations of cold and moisture endured, produce this
general similar effect ; they make all plants delay or
accelerate their leafing to the most favourable time
for vegetating. It seems to follow, therefore, that if
it be found one year that the best potato crop was
obtained by planting on the 15th of March, being
the first day the gooseberr}^-leaves opened, and that
the following year the leaves of the same tree did
not open until the 7th of April, that in such case the
potato planting ought until then to be delayed, for,
as M. Barck observes, " No one can deny but tliat
the same influences which bring forth the leaves
of trees, will also make grain vegetate ; and no one
can justly assert that a premature sowing will always
and everywhere accelerate a ripe harvest."

I beg leave to explain that my illustration by
potato planting is a mere assumption, and that I do
not intend to advance that the leafing of the goose-
berry and potato planting ought to be simultaneous.
I only throw out the suggestion for others to confirm
or to refute by observation and ex})eriment, adding
only thus much, that Mr. Stillingfleet, one of the
most careful of Nature's observers says, that in his
time " the prudent gardener never ventured to put

CH. I.] SOWING. 29

his house-plants out until the mulberry leaf was of a
certain growth."

As no seed ^^ill germinate unless a certain degree
of heat is present, so also does it require that a cer-
tain quantity of water is in contact ^^ith its outer
skin or integument, and this is required not only to
soften this covering, and thus permit the enlarge-
ment of the cotyledons (seed lobes) always preceding
germination, but also to afford that water to the in-
ternal components of the seed, without which the
chemical changes necessary for the nutriment of the
embryo plant will not take place.

Pure water, or some other liquid of which it is
a large constituent, is absolutely necessary ; no other
fluid will advance germination a single stage. The
quantity of water, necessaiy to be present before
germination will proceed, varies much. The seeds
of aquatic plants require to be completely and con-
stantly submerged in water; others, natives of dry
soils and warm climates, \vill germinate if merely
exposed to a damp atmosphere, of which the Spanish
and Horse chestnut afford ready examples ; but the far
larger majority of seeds require and germinate most
healthily in contact with that degree of moisture
wliich a fertile soil retains only by its chemical and
capillary attraction. If the soil be inefficiently
drained, and there be, consequently, a superfluity of

30 PEINCIPLES OF GARDENING. [CH. I.

stagnant water, the seeds either decay without ger-
minating or germinate unhealthily. This arises
neither merely from its keeping them in an ungenial
temperature, nor only from the usual tendency of
excessive moisture to promote putrefaction ; but also
because the vegetable decomposing matters in a soil,
where water is superabimdant, give out carburetted-
hydrogen with acetic and gallic acids — compounds
unfavourable to the vegetation of most cultivated
plants, whilst the evolution of carbonic acid and
ammonia is prevented, which two bodies are bene-
ficial to the embryo plant.

x\s water is essential to germination, and only a
certain quantity is required for its healthy progress,
so is it by no means a matter of indifference what
matters it holds in solution. Until germination has
commenced, no liquid but water at common tempera-
tures \sill pass through the integuments of a seed.
So soon as germination has commenced, this power
to exclude foreign fluids ceases, but the organs start-
ing into activity, the radicle and the plumule, are so
delicate, that the weakest saline solutions are too
acrid and offensive for them. So utterly incapable
are the infant roots of imbibing such solutions, that
at first they are absolutely dependent, themselves,
for their \ery existence, upon the seed-leaves ; and if
these be removed, the plant either makes no further
advance, or altogether perishes. Many years since I

CH. I.] SOWING. 31

tried various menstrua, to facilitate the germination
of seeds ; but, with the exception of those which pro-
moted the decomposition of water, and the conse-
quent more abundant evolution of oxygen, I found
none of any efficiency. xVs to keeping the seeds in
saline solutions until they germinated, I never, cer-
tainly, carried my experiments so far as that; and
shall be most astonished, if any other effect than
injury or death to the plant is the consequence.
Such has been the result in the Horticultural So-
ciety's gardens, where the seeds of Lupinus Hartwegii
were made to germinate in a weak solution of phos-
phate of ammonia.

No liquid in which water does not preponderate
will enable a seed moistened ^vith it to germinate ;
for I have treated broad beans, Iddney beans, and
peas with pure alcohol, (spiiit of wine), ohve oil,
alcohol and water, in equal proportions by measure,
and with a solution of carbonate of ammonia, but in
no instance did they germinate.

It may be noted as a warning to those who em-
ploy steeps for seed, with the hope of promoting the
%igour of the future plant, that they must keep the
seed in those steeps a very few hours. In foity-eight
hom's, if the temperatui'e be 60^ or more, putrefaction
commences, and germination is weakened, or entirely
destroyed.

M. Vogel, of Munich, has published an extended

32 PKINCIPLES OF GARDENING. [CH. I.

course of experiments upon this subject ; and they
fully confii'm my opinion, that salts, innoxious when
the plant is of robust and advanced growth, are fatal
to it at the time of germination; for he found that seeds
germinate without injury in carbonate of lime, (chalk),
carbonate of strontian, litharge, red oxide of lead,
phosphate of lead, black oxide of manganese, calo-
mel, and cinnabar. That they germinate feebly in
carbonate of magnesia, copper filings, sulphuret of
antimony, red oxide of mercury, and aqueous solution
of iodine. Lastly, that they refused to germinate at
all in carbonate of barytes, hydrate of barytes, iodine
pulverised and moistened, kermes mineral, golden
sulphur of antimony, oxide of bismuth, arseniate of
lead, and green oxide of chromium ^. These are facts
which explain the result of practice, that saline ma-
nures are generally injurious if applied with the seed,
though they may be beneficial if applied long before
the seed time, or subsequently, when the plants are
of advanced gro\vth.

Nothing is so injurious to a germinating seed as
^dcissitudes of temperature and moisture, or a length-
ened exposure to excess of the latter ; in either case,
the awakening vitality is frequently entirely extin-
guished. Nothing is more dreaded by the maltster
than a sudden check to his germinating barley ; and,
as a chill to the incubatmg egg effectually prevents the

^ Joum. de Pharmacie. xvi. 406.

CH. I.] SOWING. 33

formation of the cluck. To preserve the seeds of our
winter crops from such vicissitudes, they should in-
variably be sown upon and covered with a thin stratum
of coal ashes — these are an excellent drainage, as well
as a good non-conductor of heat.

The preceding facts afford a warning to those
who have to pack seeds for lengthened transport in
tropical regions. They cannot be kept too dry — for
heat alone will have no influence over their germina-
tion ; and they should, therefore, be put into small,
open, canvas bags, and suspended from the beams of
the upper cabins, where a current of air mil keep the
seeds as free as possible from damp. Close packing
in paper, in boxes, and in tin cases, stowed away in the
hot hold of a ship, causes such a heating of the seeds,
such an extrication of moisture from them, as is just
enough to commence their germination ; and which,
only carried through its first stage, ceases, and then
decomposition ensues, which effectually destroys the
arousing vitality.

Water being such an essential application to the
seed as well as to the growing plant, it may be at
once observed, that the source from whence it comes
is by no means immaterial. The best for the gar-
dener's purpose is rain water, preserved in tanks
sunk in the earth, and rendered tight either by pud-
dling, or bricks, covered with Parker's cement. To
keep these tanks replenished, gutters should run

34 PRINCIPLES OF GARDENING. [CH. I.

round the eaves of every structure in the garden, and
coramimicate with them. Every 100 cubic inches of
rain water contains more than 4 cubic inches of air, of
wliich more than half are carbonic acid gas, and the
remainder nitrogen and oxygen, in the proportion of
62 of the fonner to 38 of the last named. Liebig,
from actual experiment on a large scale, states that
both rain and snow contain ammonia; and its
importance appears from the fact that, if there
be only one-fourth of a gi'ain in each pint of water,
the annual deposition from the atmosphere would be
more than sufficient, on half an acre of ground, to
give all the nitrogen contained in the vegetable albu-
men of 150 cwt. of beet root. Ram water also
contains a peculiar substance, analogous to the ex-
tractive matter and gluten of plants, though dif-
fering from them chemically. To this substance Dr.
Daubeny has given the name of Pyrrhine. Traces of
salts and oxides have also been found in rain water ;
but compared ^vith all other naturally produced, it is
so pure, and so abounds with the gases beneficid to
plants, that none other can equal it for their service.
That obtained from ponds or sprmgs invariably con-
tains matters offensive or deleterious to plants. That
known as hard water, containing in excess salts of
lime or magnesia, is invariably prejudicial, and pond
water is scarcely less so. If it be stagnant and loaded '
with vegetable extract, it is even worse than hard

CH. I.] SOWING. 35

spring water, for it then contains carburetted hydrogen
and other matters noxious to vegetables. These last
named waters, if obHged to be employed to tender
plants, should have a pint of the ammoniacal ivater
of the gas-works, mixed thoroughly with every sLxty
gallons, an hour or two before they are used.

The presence of .one of the constituent gases of the
atmosphere, oxygen, is also essential to germination.
Ray proved that lettuce seeds would not germinate in
the exhausted receiver of an air pump, though they
did so when the air was re-admitted ^ ; and though
the experiments of Homberg throw some doubt upon
this conclusion b, yet it was fully confirmed by the re-
searches of Boyle, Muschenbroek, Boerhaave and
Saussure, for they showed that Homberg must have
employed an imperfect apparatus, and their expe-
riments embraced many other seeds than those of
the lettuce. So soon as pneumatic chemistry de-
monstrated that the atmospheric air is composed of
several gases, \iz. :

Oxygen 21

Nitrogen 79

100
with about one per cent, of aqueous vapour in the
driest weather, and about one part in every thousand
of carbonic acid gas, the question then arose which

^ Phil. Trans. No. xiii. »> Mem. French Acad, for 1693.

D 2

36 PRINCIPLES OF GARDENING. [CH. I.

of these gases is necessary for germination, and
Scheele was the first to demonstrate that it is the
oxj'gen. Achard afterwards proved that seeds will
not germinate in nitrogen, carbonic acid, or hydrogen
gases, unless mixed with oxygen ; and though Carra-
dori doubted the correctness of his experiments, his
doubt was sho"\Mi to be groundless by the more accu-
rate researches of Gough, Cruickshank, Saussure and
others^. Senebier carried his experiments still fur-
ther, and has determined that although seeds will
germinate in an atmosphere not containing at least
one-eighth of its bulk of oxygen, yet that the propor-
tion most favourable to the process is one-fouith. Ger-
mination will proceed in an atmosphere of pure oxy-
gen, but not so readily as when it is mixed ^rith
other gases. The same phenomena attend the incu-
bation of eggs — they will not hatch in the vacuum of
an air pump, nor will the process proceed so satis-
factorily in any other mixtm'e of gases than atmo-
spheric air.

It is necessary that the oxygen should penetrate

^ Althougli seeds will not germinate in an atmosphere of nitro-
gen, yet they all absorb a small quantity of this gas when ger-
minating. It is a constituent of most young roots^ especially of
their spongioles, or extreme points. There is reason to believe
that by its aid ammonia is fonned during germination, and that
this acts as a stimulant and food to the young plant. Seeds con-
taining nitrogen germinate more rapidly than seeds of the same
genus which do not contain this gas.

CH. I.] SOWING. 37

to the cotyledonous parts of the seed, as is e\-ident
by the changes which take place during gennination :
and it is fmlher proved by experiment. TMien
healthy seed is moistened and exposed in a suitable
temperature to atmospheric air, it absorbs the oxygen
only. This power of separating one gas from the
others, appears to reside in the integuments of the
seed, for old seeds lose the power of absorbing the
oxygen and consequently of germinating ; yet they
will frequently germinate if soaked in an aqueous
solution of chlorine — a gas wliich has the power of
attracting hydrogen from water, and others of its
compounds, and releasing the oxygen, doing so in
the case of seeds ^vithin their integuments as well as
withoutside. Humboldt and Saussure have also
she\vn that the application of chlorine to seed ac-
celerates its gennination, and cress seed, which, under
ordinaiy cu'cumstances, requires some days to com-
plete the process, they found e£fected it in no more
tlian three houi's. The late Mr. George Sinclair,
author of the excellent Hortus Gramineus Wo-
hurnensis, also informed me that he employed
chlorine with singular success. He obtained it by
mixing a tablespoonful of miu-iatic acid ^vith a similar
quantity of black oxide of manganese, and half a pint
of water. After allo^^ing the mixtm'e to remain two
or three hours, the seed is to be immersed in the
liquid for a similar period, and then sown. Another,

38 PRINCIPLES OF GARDENING. [CH. I.

and I consider the most eligible mode of applying
the chlorine, was also suggested to me by the same
distinguished horticulturist. In this way he said he
made tropical seeds vegetate, which refused to ger-
minate by other modes of treatment. He placed
the mixed ingredients mentioned above in a glass
retort, inserting its bulb in the hot bed, and bringing
its beak mider the pot in which the seeds were so^mi
connecting it with the draining aperture of the pot.
The chlorine gas is gradually evolved, passing
through the earth of the pot to the seeds, with more
or less rapidity according to the heat employed.

This absolute necessity for the presence of oxygen
is a reason why seeds will not germinate if buried
beyond a certain distance from the earth's surface ;
and why clayey soils often fail of having a good plant,
an impervious coat of the clay enveloping the seed,
and preventing the airs access.

M. Bm'ger foimd that seeds of lye buried one inch
below the sui'face had their leaves above it in eight
days and a half, whereas those at a depth of sL\ inches,
had only just sprouted at the end of twenty-two days.

But too deep sowing inflicts another injury ; though
it be not at such a depth as entirely to prevent ger-
mination, yet it so consumes the matter of the seed
in forming the useless elongation of stalk necessary
to bring the leaves above the surface, that all further
progress in vegetation has been prevented. M.

CH. I.] SOWING, 39

Bui-ger found that rye seeds sown five inches and
a half deep, forced thek blades to the surface in
seventeen days and a half, but these remained green
only for six days and then \Nithered ; and that in
evei7 instance, the most shallow sown seeds pro-
duced the most stalks. I have observed the same in
the case of kidney beans, Windsor beans, and peas of
various vaiieties ; those seeds, buried one and a half
inch below the surface, invariably grew higher and
were more prolific than those buried at greater depths.

From Saussure's experiments we leam that, weight
for weight, wheat and barley during germination
absorb less oxygen than peas, whilst these consume
less than beans and kidney beans. This explains
why, in proportion to their size, the two first may be
so^^•n at a greater depth below the soil's surface than
the three last named, without vegetation being pre-
vented.

Seeds deposited at great depths, or similarly ex-
cluded from the air '\\ithin the Egyptian mummy
cerements, mil often retain their vegetative power
for an apparently unlimited time. Hence, earth
taken from far below the surface ■will often become
covered with charlock. This is an oleaginous-seeded
plant, and such, when thus excluded from the air,
retain their \itality most pertinaciously for reasons
already assigned.

The atmosphere contains rather more than one-

40 PRINCIPLES OF GARDENING. [CH. I.

^ fifth of its weight of oxygen gas, and this is the pro-
portion most favourable to the germination of the
majority of fresh seeds. Indeed few seeds will ger-
minate when this proportion is much reduced. Ra-
dish seed refuses to do so when it amounts to no
more than one-fortieth part, and lettuce seeds require
in it at the least one-sixth, when it amounts to only
one-eighth, they refuse to germinate. This is a reason
why of all kitchen garden seeds the lettuce requires
the most shallow sowing.

So far are plants at their first germination from
being benefited by the application of stimulants, as
is supposed by the advocates of those menstrua, that
if the air supplied to them during that process is
contaminated by stimulating vapours, such as that of
sulphuric aether, camphor, spirits of turpentine, or
ammonia, germination is always in some degree
retarded and injured.

Old seeds are alone those which require the addi-
tional stimulus of more oxygen to enable them to ger-
minate, and this as just stated is most readily aff'orded
by moistening them with a solution of chlorine, which
slowly extracts the hydrogen from water, and sets at
liberty its oxygen \rithin the integuments of the seeds.

How oxygen operates in aiding the seed to develope
the parts of the embryo plant we cannot even guess
— we only know that most seeds have more carbon
(pure charcoal) in their composition than other parts

CH. I.] SOWING. 41

of their parent plant, that the oxygen absorbed by
the seeds combines with a portion of that extra carbon,
and is emitted in the form of carbonic acid. These
are the attendant phenomena, but we can penetrate
the mysteiy no farther.

I have never been able to discover that light has
any injurious influence over germination, and in
those experiments apparently proving the contraiy,
due care was not taken to prevent the seed being
exposed to a greater degree of dryness as well as to
light. If seed be placed on the surface of a soil,
and other seed just below that surface, and care be
taken to keep the former constantly moist, it will ger-
minate just as speedily as the bui'ied seed, and if ex-
posed to the blue rays only of the spectrum, by being
kept under a glass of that colour, even more rapidly.

M. Saussui'e found that when the dii'ect rays of
the sun were intercepted, though light was admitted,
seeds geiTiiinated as fast as when kept in the dark^.

Therefore the object of so^^Tng the seed below the
surface, is for the purposes of keeping it in a
state of equable and salutary moisture, as well as to
place the radicle in the medium necessary for its
gro^vth into a root, immediately it emerges from the
integument of the seed.

A seed placed in a situation where it is supplied
with the desirable degrees of heat, moisture, and air,
* Recherches sur la Vegetation, 23.

42 PRINCIPLES OF GARDENING. [CH. I.

begins immediately to enlarge in size. Tliis is
occasioned by its absorbing moistiu'e, %vliich, passing
into the Cotyledons, causes their immediate increase
in size. The rapidity of tliis process is remai'kable,
and warns the gai'dener from distui'bing the seed
after it is once committed to the ground. A few
choice peas, from -which to raise stock, being sown
accidentally in ground devoted to another crop, were
removed after twenty-four hours, and were not again
committed to the ground for some days. Not one
of them produced a fniitfid plant, and only two or
three vegetated.

This is in no degree surprising, because in the ma-
jority of healthy seeds cultivated in our open gi'ound
departments, the embryo will be found swollen
within three hours ; within six hours the radicle
will be preceptible ; in from one to six days the
radicle will have burst the integuments of the seed ;
within from two to seven days the pi nutlet will have
similarly escaped ; and in from four to twenty-four
da3's perfect roots will have been developed, and
the leaves appear above the surface.

Moistui'e, as already stated, is absorbed and causes
the immediate enlargement of the parts of the seed,
and this moisture though it will and does penetrate
through the suiiace of the integuments, yet is chiefly
imbibed through the hilum or scai\ It passes to the
cotyledons, causing their enlargement, and settmg in

CH. I.] SOWING. 43

motion their elaborating powers for the nutriment of
the radicle and plantlet, for if thej are removed, or
if thev have been injured bv insects, the seed does
not germinate, and if they are removed even after
the radicle is developed into a root, the plants
vegetation ceases.

No sooner has the radicle escaped from the seed's
integument, tlian it immediately proceeds to elongate
in the dii'ection of the matters most promotive of the
future plant s growth. If the seeds of carrots, pars- ■■
nips, beets, and other fusiform-rooted plants are
sown in a soil with its surface richly manured, and its
subsoil deficient in decomposing organic matters,
the plants will have forked and abundant lateral
roots, keeping within the fertile surface soil. On the
other hand, if the surface stratum is only moderately
rich, but some manure is trenched in with the bottom
spit so as to be about sixteen inches below the ,seed,
the roots \vill strike down straight to this superior
source of nutriment.

From the same cause the roots of orchidaceous
plants, grown upon wood only partially charred, will be
found to have their roots clamber up, and around, and
along the wood, but always directing their course most
numerously towards the charred portion. Again,
the seeds of the misletoe placed upon the under
surface of a bough, always have their radicles grow
upwai'ds to penetrate the bark, and thus secure to

44 PRINCIPLES OF GARDENING. [CH. I.

themselves the moisture without which they could
not exist. Lastly, if seeds of plants loving a fertile
soil be somi along the partition, dividmg a vessel
into two portions, of which one portion is filled with
rich earth, and the other with sand, though both
portions are equally moist, equally loose, and equally
wann, all the radicles will direct their course into
the fertile soil.

These facts, with many others, all demonstrating
that roots travel in the direction where the most
acceptable food is presented, overturn, beyond all con-
troversy, Mr. Knight's hypothesis, that the descent
of the root is a consequence of the laws of gravitation,
for these laws will not explain why roots mil grow
sidewise, and even upwards, if their best source of
nourishment is so placed as to require it — Gravita-
tion could only influence them to a downward direc-
tion, and in a fluid medium. To maintain that the
laws of gravitation will make the tender radicle of a
seed piejce the hardest soil, appears to be a self-
evident absurdity.

As the radicle always advances in the direction
most suited to its nourishment, and in which it can
best exercise its functions, so does the plantlet as
invariably direct itself towards the surface of the soil,
where its leaves and stem and other superior organs
can alone develope themselves and perform the
functions bestowed upon them at their creation.

CH. I.]

SOWING.

45

The necessaries in search of which their upward
course is directed, are air and hght, but especially
the first, for the plantlet rises above the surface
though the seed is genninated in a totally dark room,
but if the seed of an aquatic plant be germinated in
water under a double glass receiver, one compartment
of wliich is filled with hydi'ogen or nitrogen, and the
other compartment with atmospheric air, the plantlet
invariably dii'ects its growth into the latter. We also

know that germinated seeds placed in vacuo refuse
to advance any further in vegetation.

The absorption of moisture and the consequent en-
largement of the cotyledons is followed by another
change in them. Oxygen gas is absorbed and carbonic
acid is evolved, the farinaceous natiu'e of the seed being
completely changed — it usually becoming saccharine,
though sometimes it attains acidity — but in every
case its components become soluble in water, more
liquid, and adapted to the nutriment of the embryo

46 PRINCIPLES OF GARDENING. [CH. I.

plant. The quantity of oxygen absorbed by seeds
differs in every species, but they entirely agree in
emitting it all again in the form of carbonic acid ; it
is absorbed therefore for the purpose of diminishing
the seed's carbon.

The seeds of beans and lettuce absorb one-hun-
dredth part of their weight of oxygen to enable them
to germinate ; purslain, onion, and radish seed one-
thousandth only, and the weight absorbed is always
proportionate to the weight of the cotyledon.

The fact of carbonic acid being extricated aids to
explain why germination proceeds more slowly in
clay soils, and in soils rolled firm, even mider other-
wise favom'able contingencies, than it does in porous,
well pulverized soils ; not only does the atmospheric
air get to the seed in the former soils vdih more
difficulty, but in these the carbonic acid emitted
during germination is confined in immediate contact
with the seed, and M. Saussure found that carbonic
acid, almost in any proportion, retards the com-
mencement of germmation.

That the atmospheric air is that mixture of oxygen
and nitrogen gases which is most favourable to the
due progress of germination, is proved by the experi-
ments of M. Saussure, for he found that seeds ger-
minating in it always absorbed a portion of the
nitrogen, but which they did not do if the proportion
of oxygen was increased.

CH. I.] SOWING. 47

These facts hold out some beacons worthy of being
attended to, as guides for the operation of sowing.
They point out that eveiy kind of seed has a par-
ticular depth below the sui'face, at which it germi-
nates most \dgorously, as securing to it the most
appropriate degree of moisture, of oxygen gas, and of
warmth. From a quarter of an inch to two inches
beneath the siuface, appear to be the limits for the
seeds of plan.s usually the objects of cultivation;
these, howev r, must x-ary for the same seeds in
different grounds and countries. It must be the least
in aluminous soils and dry climates. In general, sow-
ing should be performed in dry weather, especially on
heavy soils, not only because of the greater saving of
labour, but because it prevents the seed being
enveloped with a coat of earth impermeable by the
air, " which,"' says Sir H. Davy, " is one cause of the
miproductiveness of cold, clayey soils." Perhaps the
time at which any ground may be raked with the
greatest facility, is as good a practical criterion as
any, to judge when it is most fit for sowing. In
general, if clay does not predommate in its constitu-
tion, a soil rakes best just after it has been turned
up with the ^] ade. If clay does predominate, it
usually rakes ^rith most facility after it has been dug
two or three days, and then immediately after a gentle
rain. But it is ceitain that the sooner seed is sown
after the soil is dug for its reception, the earlier it

48 PRINCIPLES OF GARDENING. [CH. I.

germinates. In the di'oughts of summer, water is
often required to newly sown beds. Such applica-
tion must not be very limited or transitory ; for, if
the soil is only moistened at the immediate time
of sowing, it induces the projection of the radicle,
which in veiy parcliing weather, and in clayey
caking soil, I have known wither away, and the crop
be consequently lost from the want of a continued
supply of moisture.

CHAPTER II.

THE ROOT.

The root is present in all cultivated plants. The
truffle, which, however, can scarcely be considered as
belonging to cultivated vegetables, having hitherto
defied all attempts to subjugate it, maybe considered
as consisting of nothing but root^.

A root is annual, biennial, or perennial. In the
two former instances, if the individuals to which
they belong be allowed to perfect their seed, no care
can protract their existence beyond the ensuing
winter, however genial the temperature, &c., in
which they are made to vegetate ; but, if the ri-
pening of seed be prevented, it is undetermined
how long in most instances they may be sustained
in life. I have kno\vn mignionette continued in
healthy vegetation for four years by this pre-
caution. In all roots, and under any mode of ma-
nagement, the fibrous parts (radiculse) are strictly
annual ; they decay as winter approaches, and are
produced with the returning vigour of their parent

* In Prussia it is said the gardeners succeed in cultivating this
subterraneous fungus, but their mode of treatment is a secret.

E

50 PRINCIPLES OF GARDENING. [CH. 11.

in the spring. Hence the reason that plants are
transplanted with most success during the season of
their decay : for, as the root almost exclusively im-
bibes nourishment by the mouths of these fibres, in
proportion as they are injured by the removal, so is
the plant deprived of the means of support ; that
sap which is employed in the formation of new
fibres, would have sensed to increase tlie size of
other parts.

The quantity of root I have always observed to
increase with the poverty of the soil in which it is
growing. Duhamel found the roots of some young
oaks in a poor soil to be nearly four feet long, though
the stem was not more than six inches. Every one
may have noticed this familiarly instanced in Poa
annua growing on a gravel walk, its stem minute, its
root a mass of widely extending fibres. The cause
of this is evident : the nourishment which is required
for the growtli of the plant, can only be obtained by
an increased, widely extending surface of root, and,
to form this, more sap is often required than the
plant, owing to the poverty of the earth, can obtain
for itself ; in that case, a soil is sterile, for the plant
must evidently perish.

A root always proceeds in that direction where
food is most abundant, and, from a knowledge of
this fact, we should be circumspect in our mode of
applying manures, according to the crop and object

CH. II.] THE ROOT. 51

we have in ^-iew. The soil in my own garden being
shallow, never produced a carrot or a parsnip of any
size ; but almost every root consisted of numerous
forks thickly coated with fibres : digging two spades
deep produced no material advantage, the gardener
applying as usual manure to the surface ; but, by
trenching as before, and turning in a small quantity
of manure at the bottom, the roots always spindled
well, grew clean, and had few lateral fibres. For
late crops of peas, which mildew chiefly from a
deficiency of moisture to the root, it is an object to
keep their radiculae near the surface, for the sake
of the light depositions of moisture incident to their
season of growth ; hence it will always be found
of benefit to cover the earth over the rows with
a little well rotted dung, and to point it in hghtly.

If it be desirable to prevent the roots of any
plant travelling in a certain direction, the soil on
that side should be excavated and the cavity refilled
with sand or some other unfertile earth, whilst the
soil on those sides of the plant whither the roots are
desired to tend should be made as fertile as is per-
missible with its habits.

To keep the roots of trees near the surface,
gardeners make an impervious substratum beneath
their borders, either by ramming a bed of chalk at
the requisite distance from the sui'face, or by placing
there an asphaltic mixture of hot coal tar and lime

E 2

llNlveRSlTY OB ■
ILLINOIS LIBRARY

•s

bH PRINCIPLES OF GARDENING. [CH. II.

rubbish. Roots coming in contact with these do not
tuni aside, but immediately cease extending in
length, and produce laterals.

It may be accepted as an universal maxim, that

whatever causes an excessive developement of root

prevents the production of seed ; and vice versa, the

production of seed, especially in tuberous-rooted

plants, reduces the amount of root developed. Thus,

, frequent transplanting the young plants of the*

lettuce, brocoli, and cauliflower causes the production

of nmnerous fibrous roots, and is found effective in jire-

■ venting the mature plants advancing early to seed.

: The early varieties of the potato do not naturally

produce seed; but if their tubers are removed as

soon as they are formed, these early varieties blossom

and bear seed as freely as the later kinds, a fact

suggesting many experiments to the cultivators of

sin'-blooming tuberous-rooted flowers. Again, if

. the blossoms of these later varieties are plucked ofl"

\as they appear, the weight of tubers produced will be

very materially increased.

According to the usual acceptation of the term,
the roots of plants do not emit excrements, yet it is
quite certain that in common with all the other parts
of a plant they perspire matters differing in their
amount and composition in every species. The
earth in contact with the tubers of a potato fully
ripe contains mucilage, and has the peculiar odour of

CH. II.] THE ROOT. 53

the root ; that in contact ^vith the roots of peas is
also mucilaginous, and smells veiy strongly of that
vegetable ; and the freshly up-turned soil where
cabbages have been growing always smells offensively.

In addition to this, every gardener knows that the
vigour and luxmiance of a crop is influenced remark-
ably by that which immediately before pre-occupied
the ground on which it is growing, and this does not
arise entirely from the previous crop having robbed
the soil of constituents requu'ed by its successor, but
from that crop ha^'ingleft something offensive. Thus
brassicas will not grow healthily upon soil where the
immediately previous crop was of the same tribe, but
if the ground be pared and burnt they will grow Iilxu-
riantlv ; and the same occurs to crroimd exhausted bv
strawberries : ^ if it be burnt and manured, straw-
berries will grow as vigorously as upon fresh gi'ound,
but they will not do so if manure only is applied. It
has also been observed that the roots of plants placed
in water give out their characteristic flavours to the
liquid, but on this, as evidence that they emit excre-
ments, no great rehance can be placed, for some of the
roots during removal from the soil must be wounded.

The fact that the roots of plants do give out peculiar
and varying matters to the soil which sustains them,
aids to explain why one rotation of crops is superior
to another, as well as why fallovsing is beneficial.

Fallowing gets rid by decomposition of any offen-
sive excrementitious matters, as well as accumulates

54 PRINCIPLES OF GARDENING. [CH. II.

that which is desirable to plants ; and one crop suc-
ceeds better after some predecessors than others, be-
cause their exuvise is more salutar}'. Upon similar
principles is explained the association which, centu-
ries since, was first observed to prevail between some
plants. Thus, in 1570, Conrad Heresbach wrote thus :
" Because there is a natural friendsliip and love be-
tween certain trees, you must set them the nearer
together, as the "sdne and the olive, the pomegranate
and the myrtle." Others, he adds, have a natural
hatred, " as the \Tne with the filbert and the bay, &c. ;"
and Cato says that the vine is at enmity with the
cabbage.

That some plants are benefited by being grown in
the vicinity of others, seems established by obsen^a-
tion, and might be rationally expected. Thus the
blue bottle {Centaurea cyanus) is rarely found flourish-
ing, except in company ^itli a com crop. The bene-
fit arising from such associations is probably the con-
sequence of the cereal grasses emitting the usual gases
in proportions and at times grateful to the Centaurea,
or from their excreting something in the soil that is
acceptable to its roots. Then, again, the fragrance
of the rose is said to be increased by having the onion
or some other allium grown in its vicinity. Phillips,
in his poem entitled " Cider," alludes to this result :

" The Paestan rose unfolds

\

Her bud more lovely near the foetid leek,
(Crest of stout Britons,) and enhances thence
The price of her celestial scent."

CH. II.] THE ROOT. 65

This increase of fragrance, if it be a truth, probably
arises from the same cause that ammonia increases
the pungent perfume of snuff. Flavours and scents,
we all know, are often made more intense by com-
bination.

Plants are very much benefited by having oxygen
applied to their roots, being found to consume more
than their own volume of that gas in twenty-four
hours ; and when applied by Mr. Hill to the roots of
melons, hyacinths, &c., the first were found to be im-
proved in flavour, the second in beauty, and all in
vigour. Everything, therefore, that promotes the
presentation of oxygen to the roots of plants, must be
beneficial ; thus we find, that frequently stirring the
ground about them promotes their growth; for, in
proportion as the soil is loose can the atmosphere
more easily penetrate it. Moist earth rapidly ab-
sorbs oxygen from the atmosphere, as Humboldt has
demonstrated, but diy soil does not ; this affords an-
other reason for frequently stirring the earth about
plants during the di'oughts of summer ; for well pul-
verized soils admit the evening dews, more freely than
others more consolidated, and consequently dews will
be deposited more within their texture, and moisture
is more firmly retained in such pulverized soils, in as-
much as that they are not so much heated by the
sun's rays, being more pervaded by the air, which,
like all gases, is one of the worst conductors of heat.

56 PRINCIPLES OF GARDENING. [CH. II.

M. Schluber has more recently published experi-
ments upon this subject, and their results confirm
those of M. Humboldt. No earth, in the follo"«ing
table, absorbed any oxygen from the air in which they
were confined, so long as they were dr>'' ; but when
moist, and confined in a similar bulk of atmospheric
air for thirty days, they had absorbed its oxygen in

the following proportions :

Per cent.

Siliceous sand l.G

Calcareous sand 5.6

Gypsum in powder . . . . 2.7

Sandy clay 9.3

Loamy clay 11.0

Stiff" clay or brick earth . . . 13.6

Grey pure clay 15.3

Fine lime 10.8

Magnesia 17.0

Humus '20.3

Garden mould 18.0

Arable soil 16.2

Slaty marl 11.0

The decomposing parts of animals and yegetables
contained in a soil are also highly absorbent of mois-
ture : hence the more freely the air is exposed to
them, the more eff'ectually will they be enabled to
exert tliis power. By being freely exposed to the
influence of the air, such substances are more rapidly

CH. II.] THE ROOT. 57

decomposed, which leads to a consideration of the
practice of exposing soils as much as possible, to the
action of the atmosphere by ridging, &c. WTien a
soil is tenacious, or abounding in stubborn vegetable
matters, as in heath lands, it cannot be too com-
pletely exposed to the action of the air ; but to light
soils, "^vhich are in general deficient in organic de-
composing matters, chemistry would say that ridging
is accompanied by e^'ils more injmious than can be
compensated by the benefits obtained ; for such light
soils are easily pulverized whenever occasion requires,
are so porous as at all times freely to admit the per-
vasion of the atmosphere ; and therefore, by this
extra exposure the vegetable and animal remauas are
hastened in decomposing, and much of their fertile
constituents evolved in the state of gas, or carried
away by the rains, &c., ^rithout there being any crop
upon them to benefit by them. Thus theory argues,
and practice certainly seems to support, in this in-
stance, her doctrines. Switzer, one of our horticul-
tural classics, says, " Rich, heavy ground cannot well
be ploughed too often to make it light, and the
better manure by killing the weeds ; as poor, light ,
gromid cannot be ploughed too seldom, for fear of /
impoverishing it."' — (Ichnographia Rustica, vol. iii.
p. 237.)

The benefit derivable from the access of the atmo-
spheric gases to the roots of plants, and the knowledge

/ r

I

58 PRINCIPLES OF GARDENING. [CH. II.

that fertile pulverized soil absorbs and retains from
them moisture, explains why plants are benefited
by having their lateral roots kept near the surface,
and by lla^•ing that surface frequently loosened by
the fork. This is no mere imagination of theory,
for as long since as the days of Cato, half a century
before the Christian era, the importance of pulver-
izing the soil was duly appreciated. "What is
good husbandry ? " inquires that writer. To plough.
•' What is the second point?" To plough. The
third is " to manure." In later days, Mr. Barnes,
one of the best practical gardeners of the present
age, in a letter to me, dated August, 18-44, says, —
" To secure good crops of carrots, parsnips, and
onions, I make it a standing rule to trench the
ground well in winter, tliro\\-ing it into rough ridges,
forking and turning it over during frosty mornings,
which not only sweetens and pulverizes the earth,
but eradicates insects, for I prefer a good prepara-
tion to early sowing ; and practice has proved to me
^ that a good season for sowing is any time between
?the 15th March and the 10th April. My practice
is, sow every thing in drills ; hoe as soon as the
plants can be seen breaking the suiface, continuing
the hoeing throughout the season at eveiy opportunity
when the weather will permit, but not duiing rain,
or when the ground is full of water, — not for the
sake so much to destroy weeds and insects, which

CH. II.l THE ROOT. 59

are rarely to be seen by following up hoeing with
spirit, but with a desire to keep one unifoiTu pulver-
ization and moisture throughout, which is the
means of not only continuing the present crop in
the greatest of health and luxuriance, but at the
same time is making a beautiful preparation for the
succeeding crop. No season, for some years, has
proved this practice to be efficient more than that
of 1844, in proof of which, I have the great satis-
faction of hearing, from many practical gardeners
from various parts of the countiy, who have carried
out the system of my practice, recommended in the
" Gardener s Magazine," and elsewhere. For my
own part, I never had more abundant or healthier
crops of vegetables of all kinds than I have this
season, although in this neighbourhood (Sidmouth)
we were eighty-nine days without any rain, after the
5th April, and then only partial showers for a few
days ; and then drought set in again for some
time, more rigorously than it had previously been.
Onions \rith me are astonishingly large, weighty, and
somid.

" I keep all ground, as soon as a crop is done
with, well trenched, burning all the refuse I possibly
can in a green state, casting the earth into rough
ridges, tumbling those ridges over with a strong
fork on frosty mornings in winter and spring, and

60 PRINCIPLES OF GAEDENIKG. ^CH. II.

during hot sunny days in summer; continually
changing the crops ; keeping the hoe at work at all
seasons in suitable "weather ; forking up all odd
comers and spare ground without loss of time. By
this management, I find the ground is always in
good condition, and never tired by cropping ; some
judgment only being exercised in applpng such
properties again to the soil that have been taken
from it, or that are likely to be required by the
succeeding crop. To rest or fallow groimd for any
length of time, is only loss of time and produce ;
more benefit will be obtained by trenching and
forking, in frosty or hot sunny weather, in a few
days, than a whole season of what is erroneously
called rest or fallow. Trench, fork, and hoe ;
change every succeeding crop; return to the earth
all refuse that is not otherwise useful in a green
state, adding a change of other manm^es occasionally,
especially charred refuse of any kind, at the time of
putting the crop into the ground. Every succeeding
crop will be found healthy and luxmiant, suffering
but little either from drought, too much moisture, or
vermin."

The benefit derived from keeping the roots near
the surface is more apparent in fruit trees and
other perennials than in our annual crops, inasmuch
as that the roots of trees being thus kept within the

CH. II.] THE ROOT. 61

influence of the solar rays, they always vegetate
early, and ripen well their young wood, yet the quan-
tity of oxygen absorbed by the roots of annual plants
is very large, being, in the instances of the radish,
carrot, and others, not less than their own bulk in
the course of twenty-four hours.

Digging, hoeing, and trenching are employed for
facilitating the access of the air to the roots of plants,
by rendering the texture of the soil easily perme-
able, and they are practices requiring a separate
consideration.

Very few people ever consider in detail the
expenditui'e of labour required from the gardener
when digging. It is a labour above all others call-
ing into exercise the muscles of the human frame,
and how great is the amount of this exercise may
be estimated from the following facts : —

In digging a square perch of ground in spits of
the usual dimensions, (seven inches by eight inches,)
the spade has to be thrust in 700 times, and as each
spadeful of earth, if the spade penetrates nine
inches, as it ought to do, ^rill weigh on the average
full seventeen pounds, eleven thousand nine hun
dred pounds of earth have to be lifted, and the
customar}' pay for doing this is S^tZ. !

As there are 160 perches or rods in an acre, in
digging the latter measure of ground, the garden
labourer has to cut out 112,000 spadefuls of earth,

V"^

62 PRINCIPLES OF GARDENING. [CH. II.

■weighing in the aggregate 17,000 cwl., or 850 tons,
and during the work he moves over a distance of
fourteen miles. As the spade weighs between eight
and nine pounds, he has to lift, in fact, during the
work, half as much more weight than that above
specified, or 1,278 tons. An able-bodied labourer
can dig ten square perches a-day.

A four-pronged fork, with the prongs twelve
inches long, and the whole together forming a
head eight inches wide, is a more efficient tool for
digging than the common spade. It requires the
exertion of less power; breaks up the soil more
effectually ; and does not clog even when the soil
is most wet. It is less costly than the spade, and
when worn can be relaid at a less expense.

The following table, being the results of the ex-
periments of M. Schluber, exhibits the comparative
labour required in digging various soils, and the
same soil in various states. Thus if to penetrate
with a spade, when dry, grey pure clay, required
a force represented by 100, then to penetrate an
arable soil in the same state would require a force
equal only to 33, or about one-third ; so in a wet
state the clay would adhere to the blade of the
spade with a force equal to 29.2 lbs. the square foot,
while the arable soil would only adhere to the same
surface with the force of 6.4 lbs.

CH. II.]

THE ROOT.

63

Siliceous sand
Calcareous sand
Fine lime
Gypsum powder
Humus
Magnesia
Sandy clay
Loamy clay
Brick earth
Grey pure clay
Garden mould
Arable soil .
Slaty marl .

Firmness
when dry.

0

0

5.0

7.3

8.7
11.5
57.3
68.8
83.3
100.0

7.6
33.0
23.0

Adhesion to a square
foot of iron when wet,

3.8 lbs.

4.1
14.3
10.7

8.8

5.8

7.9
10.6
17.3
27.0

6.4

5.8

4.9

The preceding observations and facts are appli-
cable to Jweing, an operation beneficial in conse-
quence of its loosening the soil, as much, or more, as
by its destroying weeds. Moisture abounds in the
atmosphere during the hottest months, and it is
absorbed and retained most abundantly by a soil
which is in the most friable state. Professor
Schluber found, that 1000 grains of stiff clay ab-
sorbed in twenty-four hours only thirty-six grains of
moisture from the air ; whilst garden mould ab-
sorbed in the same time forty-five grains ; and fine
magnesia seventy-six grains. Then, again, pulver-
izing the soil enables it better to retain the

64 PRINCIPLES OF GARDENING. [CH. II.

moisture absorbed. This I demonstrated some years
since, and the reason is, ob^dously, because a hard
soil becomes heated by the sun's rays much more
rapidly than one with a loosened texture. The
latter is better permeated by the air, which is one
of the worst conductors of heat. I am glad to find
my opinions confinned by so practical and so intelli-
gent a man as Mr. Barnes, gardener to Lady Rolle,
at Bicton Gardens, DeA^onshire. He says, (Gard.
Mag. Sept. 1843,) " I do not agree with those who
tell us, one good weeding is worth two hoeings ; I
say, never weed any crop in which a hoe can be got
between the plants ; not so much for the sake of
destroying weeds and vermin, which must necessa-
rily be the case, if hoeing be done well, as for
increasing the porosity of the soil, to allow the
water and air to penetrate fi'eely through it. I am
well convinced, by long and close practice, that
oftentimes there is more benefit derived by crops
from keeping them well hoed, than there is from
the manure applied. Weeds, or no weeds, still I
keep Stirling the soil ; well knowing, from practice,
the very beneficial eff'ect which it has.

" Baking the surface fine, I have almost wholly
dispensed with in eveiy department. By hoeing
with judgment and foresight, the surface can be left
even wholesome, and porous ; and three hoeings
can be accomplished to one hoeing and raking.

CH. II.] THE ROOTS. 65

Much injury is done by raking the surface so very
much. It is not only the means of binding and
cakincf the surface, but it clears the stones o£f as well'".
The eaith, in its natui'al state, has stones, &c., to
keep it open and porous, &c. If the earth be
sufficiently di'ained, either naturally or othei-wise, '
and the surface kept open, there is no fear of suffer-
ing either from drought or moistui'e."

Exposing the soil in ridges during the winter is
usually practised by gai'deners for the pui'pose of
destroying predatory vermin, but it is also beneficial
by aiding the atmosphere to pen-ade its texture,
which textui'e is also rendered much more friable
by the frost. M. Schluber says that freezing re-
duces the consistency of soils most remarkably, and
that in the case of clays and other adhesive soils,
the diminution of this consistency amounts to at
least 50 per cent. In hoeing clay he found it re-
duced from sixty-nine to forty-five of the scale already
stated, and in the ordinary arable soil from thirty-
three to twenty. He satisfactorily explains this
phenomenon, by obsendng that the crystals of ice
pervading the entire substance of the frozen soil
necessarily separate the particles of earth, rendering
their points of contact fewer.

We have seen that plants seai'ch after and acquire

* A finely pulverized even surface cakes after rain much more
than a surface rather rough.

F

66 PRINCIPLES OF GARDENIXG. [CH. II.

food by the agency of their roots ; and the extremi-
ties of these appear to be the chief, if not the only
parts employed, in the intro-susception of all food not
in a gaseous state, for M. Duhamel observed that
that portion of a soil was soonest exhausted in which
the greatest number of the extremities of the roots
were assembled. — [Physique des Ai'bres, vol. iii.
p. 276.)

M.M. Sennebier and Carradori brought this to the
test of direct experiment, and fomid that if roots of
the carrot, scorzonera, and radish are placed in
water, some mth only their extremities immersed,
and others with their entire surfaces plunged in,
except the extremities, the foimer imbibe the
water rapidly, and the plants continue vegetating ;
but the others imbibe no perceptible quantity, and
speedily wither. It suggests also the reason why
the gardener, in applying water or manure to trees
or shrubs, does so at a distance from their stems.
A good rule for ascertaining the proper distance for
such applications, seems to be to make them beneath
the circumference of the head of the tree ; for, as M.
De Candolle observ^ed, there is usually a relation
between that and the length of the roots, so that
the rain falling upon the foliage is poured off most
abundantly at the distance most desirable for reach-
ing the extremities of the roots.

This explains why the fibrous points of roots are

CH. II.] THE ROOTS. 67

usually annually renewed, and the caudex (or main
limb of the root) extended in length : by these means
they each year shoot forth into a fresh soil, always
changing their du'ection to where most food is to be
obtained. If the extremity of a root is cut off, it
ceases to increase in length, but enlarges its circle of
extension by lateral shoots.

The distance to which the roots of a plant extend
is much greater than is usually imagined; and one
reason of the stunted growth of plants in a poor soil
is, that the sap collected and elaborated by them has
to be expended in the extension of the roots, which
have to be larger in proportion as the pasturage near
home is scanty. An acorn accidentally deposited on
a wall produced a young oak ; but this made no pro-
gress until its root had descended the whole height
of the wall, and had penetrated the soil at its base.

In deep, poor siliceous soils I have traced the roots
of trees from twelve to fourteen feet perpendicidar
without reaching their tennination. Those of the
Canada thistle, seven feet ; common fern, eight feet ;
wheat, thirty inches; oats, twenty-four inches;
potatoes, eighteen inches ; onions, twenty inches ;
caiTots, parsnips, and beet, two feet. The distance
to wliich roots will travel, and their tenacity of life,
render them, often, veiy obnoxious to the gardener.
Thus the common couch_grass (TriUcum rej)jim^)-is — ■'
the most troublesome of weeds, for every fragment of

F 2

68 PRINCIPLES OF GARDENING. [CH. II.

its far-spreading roots will vegetate ; and the Sweet-
scented coltsfoot and Lemon mint are not less to be
avoided, for the same cause renders them extremely
difficult of extirpation, and they never can be kept
within moderate bounds. Yet these creeping rooted
plants are not to be condemned without exception;
for whoever has grounds under his care bordering
upon the sea-shore, the sands of which are trouble-
. somely light and shifting, may have them effectually
'bound down by inoculating them with slips of the
root of these grasses, Elymus arenarius, Carex aren-
iaria, and Arundo arenaria.

The roots of plants, unless frozen, are constantly
imbibing nourishment, and even developing parts ;
for if the roots of trees planted during the winter be
examined after an interval of a few weeks, they will
be found to have emitted fresh radicles. The food
they imbibe is slowly elaborated in the vessels of the
stem and branches, and there deposited.

It is by their extremities, then, that roots imbibe
food ; but the orifices of these are so minute, that
they can only admit such as is in a state of solution.
Carbon, reduced to an impalpable powder, being
insoluble in water, though offered to the roots of
several plants, mingled with that fluid, has never
been obsened to be absorbed by them ; yet it is one
of their chief constituents, and is readily absorbed in
anv combination which renders it fluid.

TH. II.] THE ROOTS. 69

Roots then must obtain from a soil nomishmeut to
plants in a gaseous or liquid state : we may next,
therefore, consider "what constituents of soils are
capable of being presented in such foims. Water
can be the only solvent employed ; indeed, so essen- .
tial is this liquid itself, that no plant can exist wheiNfe/
it is entirely absent ; and, on the other hand, many^
will exist ^vith their roots in vessels containing
nothing but distilled water. Plants with a broad
surface of leaves as mint, beans, <tc., I have always
found increase in carbonaceous matter, whilst thus
vegetating; but onions, hyacinths, &c. with small sur-
faces of foliage, I, as invariably, have found to decrease
in solid matters. The first, at all times, obtain
nourishment by decomposing the carbonic acid gas of
the atmosphere : the latter do so in a much smaller
proportion: hence the reason why the latter are so
much more impoverishing crops than the former,'
inasmuch as that they acquire nearly all their solid
matter by means of their roots. These obsei*vations
explain the conflicting statements of Saussure and^^
Hassenfratz on this point: the fomier experimented^
with broad-leaved plants ; the latter on such as have ;
small foliage. The first maintained that plants in;^;
crease in solid content when their roots are supplied^ i
with water only ; the latter denied the fact.

It has been advanced that water is the sole food of
plants ; but all experiments are inconclusive which

70 PEINCIPLES OF GARDENING. [CH. II.

are presented as supporting the theory. In the first
place, all waters contain earthy, saline, and organic
matters : even distilled water is not pure, as Sir H.
Davy has proved; and rain water, Margraaf has
demonstrated to be much less so. No plants, grow-
ing in water only, will ever perfect seed ; and the
facts, that different plants affect different soils, and
that a soil will not bear through a series of years the
same crop, whereas it will bear a rotation of different
ones, demonstrate that they each take different kinds
of food from the earth, and not that imiversal one,
water, which is ever present and renewed.

So far, indeed, from water being the sole food of
plants, they are injured and destroyed by its super-
abundance in the soils sustaining them. Such soils
are always colder than well-drained soils, inasmuch
as that the same quantity of caloric which vdW heat
^the earth four degrees, will only heat water one
degree — or, to use the language of the chemist, the
capacity for heat of water is four times gi'eater than
that of the earths. Secondly, the vegetable decom-
posing matters in a soil, where water is superabimd-
ant, give out carburetted hydrogen, acetic, gallic,
and other acids, instead of carbonic acid gas and
ammonia — products essential to healthy vegetation.
Palliatives for such evils are the application of lime,
or its carbonate (chalk), to the soils in which these
acids have been generated ; and indeed after they

CH. II.] THE ROOTS. 71

have been formed, such an application is essential,
though the radical cure and preventive of recurrence
— thorough draining, be adopted. It is not an extrava-
gant assertion, that there is scarcely a garden exist-
ing, that "would not be benefited by under-draining.
Every gai'dener knows the absolute necessity for a
good drainage under his wall-trees and vines ; but
few gardeners ever think, for a moment, whether
there is any escape, any outfall, for the water he
has drained from immediate contact with the roots
of the above-named favom^ed trees. Every garden
should have di'ains cut, vaiying in depth from two
to three feet, according to the depth of the soil,
A^ith an intenal of twenty-four feet between the
drains. At the bottom of the drains, should be
placed one-inch pipes : these should be well puddled \
over, six inches deep, with clay, and then the earth
returned^. They should have an outfall into a ditch,
at the least elevated side of the garden. By having
the pipes with a bore no larger than an inch, moles
cannot creep in, and they are large enough to carry
off all the water, after even the heaviest rains.

The expense is, comparatively, nothing, varying
from 3/. to 61. per acre ; and I shall not stop to argue
with any one, who doubts for an instant the advan-

* If the subsoil be clayey, the drains should be only twelve
feet apart, and the draining tiles covered with stones.

/-

72 PRINCIPLES OF GAEDENING. [CH. II.

tage consequent upon removing all water from a soil
not retainable by its own absorbent powers ; and I
will only state one relative fact, viz., that at Lord
Hatherton's residence, Teddesley Hay, in Stafford-
shire, four hundred and sixty-seven acres, formerly
letting for an average rental of 12s. per acre, were
all drained for an outlay of M. 4s. Id. per acre,
and their rental now averages more than 31s. per
acre !

To plants in pots good drainage is not less
essential than to those in oui' borders.

To secure this not only should at least two inches
of rubbly charcoal be placed beneath the soil put
into the pots, but the soil itself should be allowed to
retain its pebbles, instead of hav-
ing them sifted out, as was the an-
cient practice. Hunt's pots, re-
presented in the annexed figures,
are well calculated to facilitate
drainage, and, by permitting the
passage of air beneath the pots,
they also admit it more readily to
the roots.

Drainage, however, is not the only desideratum to
potted plants, for they have many other difficulties
to contend against, from which those in the open soil
are presei'ved. The soil, at a few inches below its

CH. II.] THE ROOTS. 73

surface, is always, during -vs-inter, some degrees
wanner than the exterior air ; but, owing to the
evaporation from the sides of garden pots, this
is rarely the case with the soil
in them. To presence this salu-
tary warmth to the roots, a double
pot has been suggested, as re-
presented in the accompanying
sketch.

The importance of following the dictate of nature
to keep the roots of plants, natives of the torrid and
temperate zones, as warm or waimer than the
branches, has been too much neglected by the gar-
dener in his forcing department. In the vinery, for
example, the stem and roots are too often absurdly
exposed to the rigour of winter ; whilst the buds are
expanding within the glass shelter in a temperature
of 60°. A vine so treated, is like the felled elm,
which, allowed to retain its bark, though rootless, puts
forth its leaves in the spring ; expands its buds, and
advances through the first stages of growth merely
from the inspissated sap stored within its stem and
branches. This is no mere suggestion of fancy ; for
repeated experiments have showTi that hot-house
vines, with their roots thus kept torpid by exposure
to cold, had not their buds burst ; whilst other ^dnes,
treated in all respects similarly, but vdih their roots
kept genially warm, were actually in bloom.

74 PRINCIPLES OF GARDENING. [CH. II

Although an excess of water applied to the roots
of plants is injurious to them, yet all of them are
benefited by a due supply of that liquid, and the
supply has to be regulated by the amount of their
daily transpiration. The gardener knows that this
differs in every species, and dui'ing different seasons.
For instance, in a dry hot day, a sunflower three
feet and a half high transpired lib. 4ozs., being
seventeen times more than the human body ; during
a hot dry night, 3ozs. ; during a dewy night there
was no transpiration ; and during a rainy night
the plant absorbed 3ozs.

Therefore the gardener finds it best to apply
water during dry weather, early in the morning, just
before the chief demand occui's, which is from sLx a.m.
till two in the afternoon ; and duiing moist weather
he refrains from the application entirely. Then,
again, the gardener keeps his agaves and other fleshy-
leaved plants in a diy stove, for they transpire but
sparingly in proportion to their mass, and require
watering but seldom, and then abundantly ; for they
take up, as in their native siliceous habitats, a large
supply, and retain it pertinaciously in defiance of the
long-protracted droughts to which they are exposed.
In the same species I have always found varieties
transpire abundantly, and requii'e a lai'ger supply of
water in proportion to the extent of their transpiring
surface. Thus the broad-leaved fuchsias and pelar-

CH. II.] THE ROOTS. 75

goniums transpire from t^-o to three times as much
as those varieties ■which have smaller and less
abundant foliage.

The want of a few suggestions for the cultivation
of plants in rooms has been so often brought to my
notice that the subject may be here glanced over,
especially as it \nll afford the opportunity for a few
remarks upon potting generally.

Plants growing in pots, placed in our dwelling-
houses, may be as successfully cultivated as other
plants placed in green houses. It is quite time that
they very rarely are so cultivated ; but this does not
prove that such success is impossible — it demon-
strates no more than that either the cultivation is
more difficult, or is less judiciously attended to, or
that both these sources of failure attend upon our
room plants ; and that they do suffer from both, is
the actual truth.

As the plants are placed in or near ^vindows, there
is no injurious deficiency of light, but as it comes to
them most intensely on one side, they should be half
turned romid eveiy day, that their heads may have a
uniform appearance, and the leaves be not directed
only in one direction. If the window faces the
south, the intense heat and light should be mitigated
during the middays of the summer months by lower-
ing the blind.

Whenever the outdoor temperature is not below

76 PKINCIPLES OF GARDENING. [CH. II.

34", the plants will be benefited by having the

window and door of the room open. They cannot

have too much fresh air at any season of the year, if

j they are not grown under a Wardian case ; for the

I exterior air always contains a due proportion of

'moisture, whilst the air of a room is as invariably

drier than is beneficial to plants.

A due supply of moisture in the air, as well as in
the soil, is absolutely necessary to our room plants.
To obtain this in the best available degree, little
porous troughs constantly filled with water should be
kept on the stand among the pots ; and the saucers
of the pots themselves, if made according to Hunt s
plan, may always have a little water remaining in
them. The application of water to the soil requires
far more attention than it usually receives. Room
plants mostly are the proteges of the ladies, who ad-
minister the water with their own hands ; and so long
as the novelty and leisure prompt to this attention,
all goes well ; but no room plant ever existed, per-
haps, which was not at some period of its existence
left to the tender mercies of a housemaid, with the
frequent usual consequence of a deluge of water, cold
from the pump, after the roots had become heated
and parched by days of total abstinence. Plants so
treated cannot flourish. The water should be allowed
to stand in the kitchen for some hours before it is
applied to the plants, so that it may be as warm or

CH. II.] THE ROOTS. 77

warmer than the soil to which it is to be added. It
may be given in diy hot weather eveiy second day,
and in such abundance as to pass slightly through
the earth into the saucers. These must be emptied
as often as water appears in them, unless they be
Hunt's saucers, in which case a little water may be
allowed to remain, as before mentioned. These are
general rules, to be modified only in the instances of
plants requiiing peculiar treatment. Among the
exceptions are the different kinds of mimulus,
hydrangea, and some others, which are benefited by
the saucers being constantly filled with water.

If the thennometer does not fall below 60° during
the day, nor to less than 34° at night, the usual room
plants may be kept in healthy growth during the
\sinter. There is a much greater variety of tempe-
ratui'e at command, even in a small room, than is
generally imagined. Thus, in one twelve feet
square, with a fire burning, and having the door
open, I have observed the thennometer on the
floor 59° ; at six feet from the floor, 67° ; and at nine
feet, 74°. During severe frosts, the higher plants
are placed from the floor the less liable will they be
to suffer during the night, when the fire has become
extinguished.

The soil varies according to the nature of the
plant ; but whatever be its quality, instead of being

78 PRINCIPLES OF GARDENING. [CH. II.

sifted fine, as gardeners formerly directed, let all the
small pebbles remain, and pieces of charcoal, none
smaller than nuts, be mixed so as to pei'vade the earth
at distances of about two inches. Let the whole rest
upon a di'ainage composed entirely of charcoal, the
pieces not less than small walnuts. This treat-
ment, suggested by nature, but first recommended,
by Mr. Barnes, of Bicton Gardens, secures ac-
ceptable food to the roots, and prevents the occur-
rence to them of that fatal evil, stagnant water.
Let the plants once a year be taken out of their
pots, their heads reduced in size, and a portion of
the exterior roots be removed. Let them be re-
turned into the same pots, with similar attention to
the soil and drainage, for it is an inconvenience
mostly growing out of error, to give them larger
pots annually. Mr. Knight grew even a nectarine
tree for more than nine years in the same pot.
This restriction to small-sized pots cannot be always
effected ; and when shifting is necessary, it is ad-
\'isable to remove, as much as possible, the old
soil, of coui'se without injurmg the roots. This is
generally best effected by soaldng the ball of earth
in water ; and thus it may be washed almost entirely
away, and the roots be left coated with a mud that
is beneficial to them, and preserves them from
drying, until the fresh soil is well settled about them.

CH. II.] THE ROOTS. 79

The number of roots within a given space of soil is
much larger than when the plants grow in the open
soil ; for, being restrained by the side of the pot, they
fork mto numerous fibres, spread over its surface and
even turn inwards again in search of food, they being
gifted with the power of forming an extra number
of radicles whenever deficiency of food renders such
compensatory power necessaiy. The gardener en-
deavours to render it needless by supplying the
plants with liquid manure ; but this richness of pas-
ture can only be permitted to a certain extent, for if
a plant is so well supplied with food as not to render
a certain consumption of its proper juices in forming
roots requisite, so much more of those juices is
stored in the stem and branches, rendering the
plant over-luxuriant, and consequently unproductive
of flowers and fruit.

Mr. Barnes, in a letter dated September 9th, 1844,
observ^es, that the common earth-worm is too gene-
rally regarded as an enemy, whereas by its perfora-
tions of the earth it facilitates the admission of air!
to the roots of plants ; and we have found that thrust-
ing a knitting needle down through the soil of potted
plants, as well as stirring its surface, is highly bene-
ficial.

I am not an advocate for putting room plants out
of doors whilst rain is falling ; it is a practice origi-

80 PRINCIPLES OF GARDENING. [CH. II.

nating in idleness, the cultivator alloAving his plants
to be overdosed with moistui'e, in order that the
trouble of cleansing their leaves ^ith the syringe and
sponge may be avoided. With these implements the
cleansing is much more effectual than when the rain
is allowed to be the agent; and it is a process pro-
moting the plant's health, if repeated once a week,
during a morning, when the weather is mild.

Returning to the consideration of the food obtained
by a plant from the soil by the agency of its roots,
we find that silica, or the pure substance of flint, is
present in all soils ; is soluble in water, requiring
one thousand times its weight of this liquid to dis-
solve it [Kirwans Mineralogy, vol. i. p. 10); is found
in many plants, and in all the grasses that have been
analysed. Alumina, or the basis of clay, present in all
soils, is so soluble in water as to be inseparable by
the filter, and is much more so when any of the acids
are present {Sennehier's Physiolog. Veget. vol. iii.
p. 18); it is found in plants in minute quantities,
especially in the grain of barley, oats, wheat, &c.
(Schrceder, in GehlensJourn. vol. iii. p. 5*25.) Lime
is found in almost all soils ; it is easily soluble in
water, and there is but one plant that is not known to
contain some of it as a constituent, the Salsola Soda.
[Ann. de Chimie, vol. xviii. p. 76.) Magnesia, gene-
rally present in soils, is soluble in water, and is

CH. II.] THE EOOT. 81

found in many plants. Iron is present in all soils,
in all natural waters, and in all plants. Manganese
is found in some soils, is soluble in water containing
acids, &c., and is found in a few plants. But none
of those substances in a state of purity, either simply
or combined, have ever been found capable of perfect-
ing a plant through all its stages of growth, when
moistened only with distilled water ; the contraiy is
the case, however, when the water contains in solution
vegetable or animal matters, as the dimg of animals.
Now these matters contain carbon, hydro^ren, oxvgen,
nitrogen, and various salts : the three first are abso-
lutely necessary for the existence of all plants, every
part of which is chiefly composed of them; nitrogen
is found in most plants ; and the importance of salts
to vegetation is demonstrated by the facts, that clover
will not flourish where there is no sulphate of lime ;
that nettles follow the footsteps of man for the nitrate
of potass, which always abounds near the walls of his
habitation, and that marine plants linger for the com-
mon salt of their native haunts. Salts of some kind
or other are found in every species of plant, but none
of which the constituents have not also been detected
in soils. During decay, vegetable and animal matters
exhale various gases. Carbonic acid, hydrogen, car-
buretted hydrogen, ammonia, &c. are of the number,
all of which have been applied to the roots of plants
with great benefit by Sir H. Davy and others.

a

82 PRINCIPLES OF GARDENING. [CH. II.

Although plants ^^■ill uot grow u2:)on soils com-
posed of the earths only, yet these have a great in-
fluence over plants, not merely by their secondare
powers of regulating the amount of moisture, heat, &c..
but by entering directly into the constitution of the
plant ; for it is a result of experience, to which I
know of no exception, that a plant contains more of
any given earth if gro^Mi in a soil where it predomi-
nates, than if grown in a soil where it is in less pro-
fusion. This fact was first pointed out by Saussure,
who found that the Rhododendron ferrugineum, when
growing on the calcareous formation of Mount Jura,
contained in its ashes 43.25 per cent, of carbonate of
lime, but only 0.75 of silica. On the other hand,
the ashes of the same plant, from the granitic dis-
trict of Mount Brevere, contained 2.0 per cent, of
silica, but only 16.75 of carbonate of lime.

However vai'}ang in the proportions, yet every soil
is composed of silica, alumina, lime, magnesia, oxide
of iron, salts, and animal and vegetable remains.
The most important consideration is, what propor-
tions those are which constitute a fertile soil.

The heau ideal of a fertile soil is one which con-
tains such a proportion of decomposing matter and of
moisture, as to keep the crop gro\^ing upon it always
supplied wdth food in a state fit for introsusception,
yet not so superabundantly as to render the plants
too luxuiiant, if the object in view is the production

\

CH. II.] THE ROOT. 8:1

of seed : but, for the production of those plants whose
foliage is the part in request, as spinach, or of edi-
ble bulbous roots, as onions, which have a small
expanse of leaves, so as to be almost entirely de-
pendent upon the soil for nourishment, there can
scarcely be an excess of decomposed matter presented
to their roots. Spinach, on rich soils, will yield sue- (
cessive cuttings ; the same as asparagus : the latter,
especially, demands abundant applications of nou-
rishment to its roots ; since, like the onion, it has
little foliage and slightly fibrous roots, at the same
time that, like the spinach, it has to afford re-
peated cuttings ; and thus, requiring a repeated deve-
lopement of parts, it needs abundant food in its im?
mediate neighboui'hood.

A soil with a just proportion of decomposing matter,
will be capable of absorbing moisture during the
droughts of summer from the atmosphere, for the
most fertile soils are always the most absorbent, yet
it must not be too retentive of moistui'e, which is
the case in such soils as contain too much alumina ;
neither must it too easily part with moisture, a fault
which is a characteristic of those soils which contain
an excess of silica. A subsoil of gravel mixed with
clay is the best, if not abounding in oxide of iron, for
clay alone retains the moistui'e on the arable surface
in too great an excess ; and sand, or chalk, on the
contrary carries it away too rapidly. It is, however,

G 2

84 PEIN'CIPLES OF GARDENING. [CH. II.

evident, that to insure these desiderata in any soil, at
all seasons, is impossible ; and it is as manifest that
a soil that would do so in one climate would fail in
another, if the mean annual temperature of them
should differ, as vrell as the amount in inches of rain
■which fall duiing the same period. Since, in the
western parts of England, more than t^\•ice as much
rain occurs as in the most eastern counties, or in the
proportion of 42 to 19, a soil in the east of England,
for any given crop, may be richer and more tenacious
than the soil required for it on the westeiTi coast.

Alumina, or clay, imparts tenacity to a soil when
applied ; silica, or sand, diminishes that power ;
whilst chalk and lime have an intermediate effect.
They render heavy soils more friable, light soils
more retentive. These simple facts ai'e impoi*tant :
two neighbouring gardens, by an interchange of soils,
being often rendered fertile, which, before, were in
the extremes of tenacity and porosity.

From these statements it is evident, that no uni-
versal standard, or recipe, can be given for the
fonnation of a fertile soil, but a soil, the constituents
of which approach in their proportions to those of
the follo-\ring, cannot be unproductive in any cli-
mate. It is a rich alluvial soil, which Mr. Sinclair,
in his invaluable '' Hortus Gramineus Woburnensis,''
gives as being the most fertile for the grasses :

" Fine sand, 115; aluminous stones, 70; carbonate

CH. II.] THE ROOT. 85

of lime, 23 ; decomposing animal and vegetable mat-
ter, 34 ; silica, 100; alumina, 28 ; oxide of iron, 13 ;
sulphate of lime, 2 ; soluble, vegetable, and saline
matter, 7 ; loss, 8, total, 400."

I have already stated what fonns it a fertile soil ;
it may be added, that, to constitute it eminently
such, its earthy particles must be in a minute state
of di^dsion ; the more so the more fertile it will be.
In the above analysis, 185 parts only were separable
by sifting through a fine scarce, 215 parts were im-
palpable ; whereas poorer soils will often have 300
parts coarse matter to e\ery 100 of finely pulverized
constituents.

In affording wannth to plants, we have seen that
the earth is of considerable importance, and the
power of accumulating and retaining heat vaiies as
much in soils as the proportions of their constituents.
Sir Humphrey Davy found that a rich black mould,
containing one-fouith of vegetable matter, had its
temperature increased in an hour from 65° to 88°
by exposure to the sunshine, whilst a chalk soil was
heated only to 69° under similar circumstances ; but
the first, when removed into the shade, cooled in
half an hour 15°, whereas the latter lost only 4''.
This explains why the crops on light coloured tena-
cious soils are, in general, so much more backward
in spring, but are retained longer in verdm'e dm'ing

86 PRINCIPLES OF GARDENING. [CH. 11.

autumn, than those on black light soils ; the latter
attain a genial warmth the more readily, but part
from it with equal speed.

Different plants affect different soils. Every gar-
dener must have observed that there is scarcely a
kitchen-garden but has some paiticular crop which
it sustains in luxuriance far superior to any other
garden in its neighbourhood, or to any other crop that
can be grown on it. A gai'den I once cultivated,
would not produce, without the preparation of an
artificial soil, the common garden cress, [Lepidium
sativum,) whilst the raspberiy was remarkably luxu-
riant ; and we have seen that the composition of a
soil has a main influence in these peculiarities.

It is certain that a soil is often considered unpro-
ductive, and the unproductiveness attributed to some
deficiency in its staple, when, in tmth, the defect
arises from erroneous management. I have before
stated an instance of tap-rooted plants being produced
of superior size and fonn, by means of applying the
manure deep below the surface. In another instance,
some parsneps being of necessity sown in a poor soil,
hav-ing turned in some manure by trenching full
twelve inches deep, I would not allow any to be
applied to the surface ; but, at the time of thinning,
I set half the bed out at an average of twelve inches
distance between each plant, the other half at nine

CH. II.] THE ROOT. 87

inches : wlieu taken up for storing, the whole were
aHke perfectly fusifoim, but those grown at twelve
inches apart were the finest, as four and a-half is to
three. If manure had been applied to the surface,
the fibrous roots, I calculated, would be multiplied at
the expense of the caudex, to its much greater detri-
ment, than by making the few, usually produced by
this root, extend in length by enlarging the circuit
of their pasturage.

Agaui, a more siliceous, darker-coloured soil should
be employed for the growth of an early crop of any
given plant, than is required by the main crop ; be-
cause such soil will more readily get rid of the su-
perfluous moisture, and earlier acquire a genial
warmth, two gi'eat desiderata for vegetation in spring.
On the contrary, in autumn, for a late crop of peas,
for instance, the soil should be more aluminous ;
because in August and September, atmospheric
moisture, in the form of night-dews, abomids, the
foliage is therefore perpetually subject to alternate
extremes of moistui"e and dijness, whilst the root
is liable to a state of exceeding drought. The soil,
therefore, should be rich ; and kept in a minute state
of division by frequent hoeing, that moisture may be
absorbed; and it should be more aluminous, that such
moisture may be retained.

I may now proceed to consider manures, a class of

88 PRINCIPLES OF GARDENING. [CH. II-

bodies of the first importance to the cultivator of the
soil, yet of the economy of which he is generally most
ignorant, inasmuch as that their judicious employ-
ment requires considerable chemical acquirements.
Eyery substance increasing the fertility of a soil,
when incorporated ^^ith it, is a manure ; henc^,
the earths, when applied to regulate its retentive
powers, are actually manures. Manures are ani-
mal, vegetable, and mineral ; they directly assist
the gro^\i:h of plants ; first, by entering into their
composition ; secondly, by absorbing and retaining
moisture from the atmosphere ; thirdly, by absorbing
the gases of the atmosphere ; fourthly, by stimu-
lating the vascular system of the plants. Manures
ajjproximately assist vegetation : firet, by killing
predatory vermin and weeds ; secondly, by pro-
moting the decomposition of stubborn organic re-
mains in the soil ; thirdly, by protecting incumbent
plants from violent changes of temperature.

AH these properties seldom, if ever, occur in one
species of manure, but each is usually particularized
by possessing one or more in a superior degree.
That is the most generally applicable manure which
is composed of matters essential to the growth of
plants ; the chief of these are carbon, hydrogen, and
oxygen; therefore all animal and vegetable sub-
stances ai'e excellent manui'es. It would evidently

CH. II.]

THE EOOT.

89

be of great benefit, if eveiT plant could be manured
•with the decapng parts of its o^vn species ; the
ancients made this a particular object. We read
that those vines were the most fruitful, which were
manured Avith their own leaves and pmnings, and the
skins of expressed grapes^. This rule might be so
far followed, as that the stems of potatoes, peas, &c.,
could be dug respectively into the compartments
where those crops are intended to be groA^Ti in the
following year.

The foUo^nng table shews the relative constitu-
tion of common stable manure and our usual
crops : —

Stable manure.

Carbon . . ,
Hydrogen
Oxygen . . .
Nitrogen . . .
Carbonate of lime
Carbonate of soda.
Benzoate of soda.
Muriate of potash
Muriate of soda
Sulphate of soda.
Sulphate of potash

These are the chief components
of all plants.

In some vegetables.
In almost all plants.

In cucumbers, garlic, &c.
Perhaps in all.

In cucumbers, garlic, &c.

Crescentius Agric, sect. 2, c. 6.

90 PRINCIPLES OF GARDENING. [CH. II.

' Magne^a . ... lu all com and many other plants. |

Phosphate of lime Potatoes, onions, &c. &c.

Oxide of iron . . In most plants .

Alumina . . . ] ^

^„. rin most plants.

Silica .... J

! Stable manure, and for the same reason every

other manure composed of animal or vegetable I
remains, is evidently valuable to plants, by affording
them such matters as they are composed of. But
this is not the only reason that manures are beneficial :
for in that case mere decayed parts of theii" o\\7i
species should be the most fertilizing applications.
There is no doubt that plants are essentially benefited
by such applications ; but why do potatoes, for ex-
ample, grow more luxuriantly on ground manured
by sprats, than on ground manured vdx\i the dung
of horses, and still more superior to the same crop
grown on a plot manured with the decayed parts
of its own species ? Apparently, but only partly,
because the manures mentioned decompose ^\'ith a
rapidity exactly proportioned to the order of benefit.
Sprats decompose, and their parts become soluble
and capable of introsusception, first and most ra-
pidly ; then the dimg of animals ; lastly, the vege-
table remains. All the less solid animal matters
decompose with greater rapidity than vegetable mat-
ters: hence the dung of such animals as are car-

CH. II.] THE ROOT. 91

nivorous is the most prompt in benefiting vegeta-
tion : witness night soil, pigs' dung, &c. ; but such
manures are not the most permanent. Hassenfratz
manured two portions of the same soil, No. 1 with
a mixture of dung and straw highly putrefied ;
No. '2, with a similar mixture, newly made. He
observed that during the first year the plants in
Xo. 1 produced the best crop, but the second and
third years (no more dung being added) No. Q, pro-
duced the best crop ; after which, both seemed alike
exhausted^. The same chemist found, that a soil
manured with wood-shavings did not, dui'ing the two
succeeding years, produce a superior vegetation to
the same soil without any manure ; the third year,
however, it was better, but it was not mitil the filth
year that it reached the maximum of fertility. The
site of a wood stack, and the newly cleared lands of
America are eminently fertile, from the gradually
decomposing vegetable remains they contain.

These facts and obsen^ations teach us that the
most prompt manures are the reverse of economical.
Vegetable remains, incorporated with a soil, will
insure an average produce dming several years;
animal matters and dungs highly putrescent are
powerfully but transiently beneficial. Putrefaction
is evidently the means of rendering these substances
available to plants : hence, thoroughly decayed stable
* Ann. de Chimie, xiv. 57.

92 PEINCIPLES OF GARDENING. [CH. II.

manure is usually employed by gardeners, as being
of immediate benefit, admitting of clean liusbandr}',
and as economy is not, in private estaldisliments, the
generally presiding genius of the gardens. If stable
dung or other manure be allowed to putrefy in an
uninclosed heap, the loss is immense ; all the gases
which pass off during decomposition, all the soluble
matters which drain away, are highly nutritious to
plants, as has been proved by Davy and othei-s. If
the decomposition be thus allowed to proceed until
the heap becomes a saponaceous mass, the loss can-
not be less than 50 per cent. Notmthstanding all
the reasoning of chemists, however, putrefied dung
will continue to be used ; it admits of clean workman-
ship, \nth less labour, and insures a good immediate
crop : to prevent as much loss as possible, therefore,
the dmig-heap should be in a brick cistern, and
covered over with eaith at 'least nine inches deep,
with a well at one comer to retain the drainage,
which from time to time, should be returned over
the heap.

The chief component of plants is carbon, and we
shall not be far wrong if we estimate it as constituting
50 per cent, of eveiy vegetable : it is the decayed!
organic remains of the soil which supply a consider-
able portion of this to the growing plants. It is a
subject of debate amongst chemists, how the carbon of
manures is imbibed by plants. Carbon, say they, is

CH. II.] THE ROOT. - 93

insoluble, and experiment has demonstrated that the
roots cannot absorb it in a solid state. Sennebier,
having obsened that water impregnated with car-
bonic acid, "svhen applied to the roots of plants, was
beneficial, concluded that the carbon of manures is
converted into carbonic acid, and is in that state
imbibed by them^.

Thomson, in an early edition of his System of
Chemistry, gave a still more elaborate theory; which,
being in subsequent editions omitted, we have no
occasion to demonstrate absurd. I consider that the
facts of which we are in possession, if progressively
estimated, place the subject in a very clear light.
Saussure fomid that a soil deprived of its soluble
matters, by repeated decoctions with water, would not
support vegetation so well as that portion of the same
soil not so deprived of its soluble constituents^. The
extract thus obtained was e\'idently composed of
sacchaiine matter, mucilage, extractive principle, &c.
These we know are nutritive to plants, and are
elaborated and assimilated by them after introsuscep-
tion. Now, vegetable substances, as straw, &c.,
gradually yield these soluble matters as they decay.
Straw, wood, leaves, &c., consist chiefly of woody
fibre : to convert this into saccharine and mucila-
ginous matters is the work of putrefaction ; to effect

^ Phys. Yeg. v. iii. p. 55.

*» Recherh. sur la Yeg. cv. sect. 11. p. 170.

P4 PRINCIPLES OF GARDENING. [CH. II.

this, oxygen must be absorbed, and the extra pro-
portions of carbon be got rid of, as is evident from the
following table of constituents : —

Woody Fibre.

Gum.

Sugar

Carbon

. 52.53 .

42.23

27.5

Oxygen .

. 41.78 .

50.84

64.7

Hydrogen

. 5.69 .

6.93

7.8

100.00 100.00 100.0

That such processes actually do occur, Saussure
has demonstrated by experiment : he fomid that
moist wood, exposed to the air, absorbed oxygen,
evolved carbonic acid, and water was evidently de-
composed. Thus, then, putrefaction seems to render
organic matters fit for the nourishment of plants, by
converting them into saccharine and mucilaginous
compounds, capable of solution in water. Hence
the phenomenon of wood, which is slow of decom-
position, being a permanent manure ; animal matters
which rapidly putrify, being transient, though tempo-
rarily powerful : hence the economy of using partially
decomposed composts is also rationalized ; when com-
pletely decomposed, their soluble matters, being more
than can be consumed at the time by the crop, pass
away with the drainage water, much is lost in the
state of gas, and all that is left, are a few earthy.

CH. II.] THE ROOT. 95

saline, and carbonaceous paiticles, of comparatively
little value.

The quantity of soluble matter obtainable from a
soil at any one time is veiy small, seldom exceeding
a one-thousandth part of its weight ; and even pure
vegetable mould, the debris of entirely putrefied
plants, was found by Saussure to yield only one-
eleventh of soluble matter. This mould was too
rich for horticultural purposes, peas and beans groAvn
in it being too luxuriant, and they were more pro-
ductive in a soil containing only one-twentieth of
organic constituents dissolvable by water. Small in
amount, however, as is the soluble constituents of
the most fertile soils, they are necessary for the
\-igorous vegetation of plants, for when a soil is
deprived of those constituents by frequent washings
^ith boiling water, it is much less fertile than before.
Liebig and others have most illogically concluded
from the smallness of the soluble extract contained
in a soil, that, therefore, it is of trivial impoitance ;
but they forget that, as fast as this extract is removed
from a soil by the roots of the crop, it is generated
again by the decomposition of the animal and vege-
table remains within its bosom. This is one reason
why fallowing is beneficial, the most easily de-
composing matters have been exhausted by successive
crops ; and by a year s rest, and exposure to the
putrefactive agency of the air, the more stubborn

96 PRINCIPLES OF GARDENING. [CH. II.

and more slowly decomposing exuvias have time to
resolve into and accumulate soluble compounds in
the soil.

The mucilaginous and saccharine mattei's formed
by manures, during their decomposition in the soil,
are unquestionably absorbed by the roots along with
its moisture ; for if the whole of the branches of a
vine or maple be cut away close to the surface of the
ground, it vdW continue to bleed for many days, and
to the last its sap will continue to afford the same
amomit of those matters. But their saps, and that
of all plants as yet sul)jected to analysis, abound
with cai'bonic acid gas, and there is no doubt that
decomposing organic manures are veiy largely bene-
ficial to plants by affording that gas to their roots, a
subject which will be further considered when we
are examining the phenomena attendant upon vege-
table decomposition.

Of tlie less general manures, which benefit plants
by entering into their composition, a few words will
suffice. Sulphate of lime (gypsum) is a component
of clover, lucerne, turnips, &c. ; hence it has been
applied -^ith benefit to these crops, on such soils
as did not already contain it. Bones, broken small,
have lately become a very general manure; their
benefit, which is ver}^ permanent, is easily accounted
for. The bones of oxen contain about fifty per c«nt.
of gelatine, which is soluble in water, and rapidly

CH. II.] THE ROOT. 97

becomes putrescent ; the remainder is chiefly phos-
phate and carbonate of lime, salts which are com-
ponents of wheat, r}'e, barley, oats, peas, beans,
vines, cucumbers, potatoes, garlic, onions, truffles, &c.
Common salt, also, is employed as a manure, and is
beneficial, partly in consequence of entering into the
constitution of plants.

The day has long passed when it was disputed
whether saline bodies ai-e promotive of the gro\^1:h
of plants. It is now deteiTained that some plants
will not even live without the means of pro-
curing certain salts. Borage, the nettle, and parie-
taria will not exist except where nitrate of potash is
in the soil ; turnips, lucerne, and some other plants V
will not succeed where there is no sulphate of lime.
These are facts that have silenced disputation. Still
there are found persons who maintain that salts are
not essential parts of a plant's stiiicture : they assert
that such bodies are beneficial to a plant by absorb-
ing moisture to the \icinity of its roots ; or by
improving the staple of the soil ; or by some other
secondar}' mode. This, however, is refuted by the
fact that salts enter as ultimately into the con-
stitution of plants as do phosphate of lime into
that of bones, and carbonate of lime into that of
egg-shells. They are part of their very fabric,
universally present, remaining after the longest
washing, and to be found in the ashes of all and of

H

08 PRINCIPLES OF GARDENING. [CH. II.

any of their parts, when subjected to incmeration.
Thus Saussui'e observes that the phosphate of
lime is universally present in plants^. The sap
of all trees contains acetate of potash ; Beet-root
contains malate and oxalate of potash, ammonia
and lime ; Rhubarb, oxalate of potash and lime ;
Horse-radish, sulphur ; Asparagus, super-malates,
chlorides, acetates, and phosphates of potash and
lime ; Potatoes, magnesia, citrates and phosphates
of potash and lime ; Jerusalem Artichoke, citrate,
malate, sulphate, chloride, and phosphate of pot-
ash ; Garlic, sulphate of potash, magnesia, and
phosphate of lime ; Geraniums, tartrate of lime,
phosphates of lime, and magnesia ; Peas, phosphate
of lime ; Kidney beans, phosphate of lime and pot-
ash ; Oranges, carbonate, sulphate, and muriate of
potash ; Apples and Pears , malate of potash ; Grapes,
tartrate of lime ; Capsicums, citrate, mmiate, and
phosphate of potash ; Oak, carbonate of potash ; and
the Lilac, nitrate of potash. Let no one fancy that
the salts are a very trivial proportion of the fabric of
plants. In the Capsicum, they constitute one-tenth
of its fruit ; of carrot juice, one-hundredth ; of
Elmbarb, one-eleventh ; of Potatoes, one-twentieth ;
whilst of the seed of the Lithospennum officinale,
they actually form more than one-half: their con-
stituents being as follows.

=* Sur la Veget. c. 8. s. 4.

CH. II.] THE ROOT. 99

Carbonate of Lime 43.7

Silica 16.5

Vegetable Matter, Phosphate of Lime, &c. . 39.8

100.0

These amounts of earthy saline matters are
nearly as much as exist in human bones ; but if we
turn to the marrow, it only contains one-twentieth
of saline matters ; the blood only one-hundredth ;
muscle, only one-thirty-fourth ; yet no one will argue
that these saline constituents, though smaller than
those in -vegetables, are trivial and unimportant.

The preceding facts shew why some saline manures
are generally beneficial, and often essential. An
important consideration, therefore, is contained
in the answer to the query, so often put, — How
should saline manures be applied? The answer
is, that, when practicable, they ought to be in very
small quantities and frequently, during the time of
the plant's growth. No plan can be worse than soak-
ing seed in a saline solution, for the purpose of giving
such salt to the plant of which it will be the parent.
It is soddening the embrj-o with a supeiiluity totally
useless to it, and, if it does not injure the germina-
tion, it will be washed away most probably before the
roots begin to absorb such nutriment.

I may observe here, appropriately, that to arrive
at a con-ect knowledge of manures by means of expe-

H -2

100 PRINCIPLES OF GARDENING. [CH. II.

riments, far more forethought and care are requisite
than are usually bestowed upon them. 1. A space
should be left without any manure being applied,
othei'wise there will be no satisfactoiy basis of
comparison.

2. The larger the space subjected to experiment
for each manure, the more entitled to confidence
vdW be the result. The reason for this is, ob^-iously,
that no two seeds will produce plants of precisely
equal prolificacy. Imperfect ripening of the parent
seed, yariance in the depth at which the seed is
buried, and many other circumstances, will be more
liable to have a controlling effect over the weight of
the produce from a small plot of crop than from a
larger. A dozen super-prolific, or defective plants,
on a square rod of gromid, v,i.\\ have an influence
on the result when calculated per acre, that would
be scarcely appreciated, if the experiment were
made on an eighth of an acre.

3. If manures in solution are employed for soak-
iuo- the seed, a similar quantity of seed of the same
sample should be soaked for a similar length of time
in simple water. If liquid manures are given expe-
rimentally to plants during their growth, other
plants of hke number and growth, and in every
respect treated similarly, should at precisely the
same time have simple water applied to them.

4. There should be a certainty tliat the manure

CH. II.] THE ROOT. 101

employed be pure. Xo wonder that experiments are
discrepant, when Mr. E. Solly has detected adultera-
tions in fertilizers to the amount of 97 per cent. !
Even when the dung of animals is employed, it
varies most essentially, and according to the food on
which tliey are kept The richer their nourishment
the more abouncUng are their excrements in the salts
of ammonia and other fertilizing matters.

Some manures ameliorate a soil by absorbing
moisture from the atmosphere. This property is at
least as beneficial to ground that is aluminous, as to
that which is siliceous ; for it is equally useless to
either duiing such periods of the year as are charac-
terised by a plentiful deposition of rain ; but in the
drought of summer, when moistui'e is much wanting
to plants, it is beneficial to both : m very dry
seasons it is even of greater importance to clayey
than to light soils ; for vegetation on the former
suffers more from long continued drought than
on the latter, inasmuch as that moisture being
equally exhaled from each, the surface of the clayey
soil becomes caked and impervious to the air, the
only grand source of compensatoiy moisture that is
available to the languishing plants, and which is more
open to those which grow on light and, consequently,
more pervious soils.

The following table of the comparative absorbent
powers of many manui'es is extracted chiefly from

102 PRINCIPLES OF GARDENING. [CH. II.

An Essay on the Uses of Salt in Agriculture, by my
brother, Mr. Cutlibert Johnson.

Parts.
^Horse dung evaporated previously to
dryness, at a temperature of 100°,
absorbed during an exposure of three
hours to air saturated with moisture

at 62^ 145

Putrefied tanners' bark, under similar

circumstances, (66 ') 145

Unputrefied tanners' bark . . . . 115

Cow dung 130

Pig ditto 120

Sheep ditto 81

Pigeon ditto 50

Refuse marine salt (60^) 49 J

Soot (68°) 36

Burnt clay 29

The richest soil (in one hour) . . . 23*

Coal ashes 14

Lime (part carbonate) 11

Crushed rock salt 10

G}^sum , 9

I Chalk 4

O
O

o

The absorbing power of a manure is much influ-
» Sir H. Davy.

CH. 11.] THE ROOT. 103

enced by the state in which it is presented to
the atmosphere. In a finely divided state, mere
capillary attraction assists it : hence, as before in-
sisted, the importance of keeping the soil fre-
quently stirred, by hoeing, &c. But a mere mass of
cotton, by means of capillary attraction, will absorb
moisture from the aii', yet it parts with it at a very
slight elevation of temperature ; it is of importance,
therefore, to ascertain which are the manures that
not only absorb but retain moisture powerfully The
following results of my experiments throw some
light on this point : —

Minutes,
^ Pig dung evaporated to diTuess at a

temperature of 106°, and then mois-
tened with 6 parts of water, required
for being reduced to diyness again, at

the above temperature 135

Horse dung, under similar circumstances 90

o
n

^ \ Common salt .75

v

Soot 75

Rich Soil 32

Chalk 29

Poor soil (siliceous) 23

Gypsum 18

These experiments point out a criterion by which
we easily ascertain the comparative richness of any

]04 PRINCIPLES OF GARDENING. [CH. II.

two given soils or manures : the most fertile "vvill -be
the most absorbent and retentive.

Some persons have argued that the moisture-re-
tentive powers of manures must be injurious to
plants, by withholding that moisture from their
roots; but these theorists argue without an acquaint-
ance with facts. Such manures have a greater at-
traction for moisture than is possessed by atmo-
spheric air ; but it is much less powerful than the
po\^er of suction possessed by roots. There is no
saline body which they will not deprive of the mois-
ture it has absorbed — nor \rill any be surprised at
this, when they know that the root of a pear-tree,
half an inch in diameter, absorbs water with such
force and rapidity as to cause mercury to rise up
an attached tube eight inches in sL\ minutes ^.

Some manures increase the growth and \igour of
plants, by stimulating their absorbent and assimi-
lating organs. This will only be admitted by those
who, like myself, allow that plants are gifted with
sensation — a topic more fully discussed in a future
chapter ; but a few illustrative facts may be here
stated. The Venus 's fly trap [Dioncea muscipula)
has jointed leaves, which are furnished on their
edges with a row of strong pricldes. Flies, attracted
by honey which is secreted in glands on their surface,

* Hale's Veg. Statics. Exp. xxi.

CH. II.] THE ROOT. 105

veutm-e to alight upon tliem : no sooner do their legs
touch these parts than the sides of the leaves spring
up, and loclving their rows of prickles together,
squeeze the insects to death. The well known
sensitive plant (Mimosa sensitivaj shrinks from the
shghtest touch. Oxalis sensitiva and Smithia serisi-
tiva are similarly irritable, as are the filaments of
the stamens of tbe berbeny. One of this irritable
tribe, Hedysaruni gyrans, has a spontaneous motion ;
its leaves are frequently mo^'ing in various dh'ections,
without order or co-operation. When an insect
inserts its proboscis between the converging anthers
of a kind of dog's bane ( Apocynum androsscemifoliwnj
they close with a power usually sufficient to detain
the intiiider mitil death. The more I study the
phenomena of vegetation the more I feel convinced
on this point. How often have I heard a farmer
reply to an obseiTation upon the tardy growth of
turnips, " They will not grow apace, until their
leaves are large enough for the wind to take hold of
them;" and this is only because plants cannot be
healthy and vigorous ^rithout exercise. Mr. Ivnight
found that trees which were regularly shaken every
day in his green-house, grew more rapidly and were
stronger than others which were kept still.

The stimulating powers of excrementitious manures
arise from the salts of ammonia they contain. Sir
H. Da\-y foimd vegetation assisted by solutions of

106 PRINCIPLES OF GARDENING. [CH. II.

muriate of ammonia (sal-ammoniac), carbonate of am- ,
monia (volatile salt), and acetate of ammonia. Night I
soil, one of the most beneficial of manures, surpasses '
all others in the abundance of its ammoniacal con-
stituents in the proportion of 3 to 1 . It may be ob-
served, that the nearer any animal approaches to
man in the nature of its food, the more fertilizing is
the manure it affords. I have no doubt that a lan-
guishing plant one, for example, that has been kept
very long with its roots out of the earth, as an orange
tree recently imported from Italy, might be most
rapidly recovered, if its stem and branches were steeped
in a tepid, weak solution of carbonate of ammonia,
and, when planted, an uncorked phial of the solution
were suspended to one of the branches, to impreg-
nate the atmosphere slightly \\ith its stimulating
fumes.

Manures are also of benefit to plants, by affording
some of the gases of the atmosphere to their roots,
in a concentrated form. A soil, when first turned up
by the spade or plough, has generally a red tint, of
various intensity, which, by a few hours' exposure to
the air, subsides into a grey or black hue. The
first colour appears to arise from the oxide of iron,
which all soils contain, being in the state of the red or
protoxide ; by absorbing more oxygen during the ex-
posure, it is converted into the black or peroxide.
Hence one of the benefits of frequently stirring soils :

CH. II.] THE KOOT. 107

the roots of incumbent plants abstract the extra dose
of oxygen, and reconvert it to the protoxide. Coal
ashes, in common with all carbonaceous matters, have
the po^wer of strongly attracting oxygen. Every gar-
dener may have observed how rapidly a bright spade ;
of iron left foul with coal ashes becomes covered with
rust, or red oxide. All animal and vegetable ma- |
nures absorb oxygen from the air during putrefa^- j
tion. If it be inquired, of what benefit this property
is to plants, since the gases are frequently presented
to them in the atmosphere, it admits the ready an-
swer, that they enjoy the additional quantity which
is thus collected to the vicinity of their roots, with-
out the latter source being diminished; and, that
plants are benefited by such additional apphcation to
their radiculae, has been proved by the experiments
of Mr. Hill, already quoted. The question may also
be asked, whether the roots have the power to ex-
tract the oxygen from its combination. That they
have this power admits of little doubt, since Saussure
found that they were able to extract various saline
bodies from their combinations ; not only extracting,
but selecting in those cases where several salts were
in the same solution. Dr. Daubeny, the Oxford Pro-
fessor of Agriculture, has also shown that Strontian
is rejected by barley, pelargoniums, and the vringed
pea.

Carbonic acid is also of benefit to plants, when ap-

1 iN

108 PRINCIPLES OF GARDENING. [CH. II.

plied to their roots in an advanced stage of their
crro\vth. Animal and vefretable matters evolve this
gas whilst putrefying ; and I am not aware of any
manure that absorbs it from the atmosphere, so as to
be for that reason beneficial to vegetation. Lime
attracts it rapidly ; but combines with it so strongly.
that it is useless to the plant, imtil the carbonate of
lime so formed is imbibed and elaborated.

Manures assist plants, by destropng predatory
vermin and weeds. This is not a property of animal
and vegetable manures — they foster both those ene-
mies of oui' crops. Salt and lime are veiy efficient
destroyers of slugs, snails, grubs, &c. It is astonish-
ing how ignorantly neglectful are the cultivatoi*s of
the soil, when their crops are devastated by the slug,
not to dress them Avith caustic lime, so as to render
the surface of the soil quite white, duiiiig the pro-
mise of a few days' diy weather : it is instant destruc-
tion to eveiy slug it falls upon ; and those that it
misses, are destroyed by their coming in contact A\-ith
it when moving in search of food.

It is a common practice to bum couch-grass, docks,
gorse, and other vegetables, which are veiy retentive
of life, or slow in decay : a more uneconomical, un-
scientific method of reducing them to a state bene-
ficial to the land of which they were the refuse, can-
not be devised. In breaking up heaths, such exuviae
are very abundant ; but, in all cases, if the weeds,

CH. 11.] THE ROOT. 109

leaves, ttc, were conveyed to a hole or pit, and, -^ith
every single horse load, and with barrow loads in
proportion, a bushel of salt and half a bushel of lime
were incoi-porated, it would, in a few months, form a
mass of decayed compost of the most fertilizing qua-
lity ; the Hme retaining many of the gases evolved
during the putrefaction of the vegetable matter, and
the salt combining with the lime to destroy noxious
animals, which might form a nidus in the mass. By
this plan, nearly all the carbonaceous matters of the
refuse vegetables are retained ; by burning, nearlv all
of them are dissipated. The forming of a compost,
such as that recommended, is justified and approved
by the experience of many.

Stable manure, and all decomposing animal and
vegetable substances, have a tendency to promote
the decay of stubborn organic remains in the soil, on
the principle that putrescent substances hasten the
process of putrefaction in other organic bodies \\-ith
which they come in contact. Salt, in a small pro-
portion, has been demonstrated by Sir I. Pringle, to
be gifted \\dth a similar septic property ; and that
lime rapidly breaks down the texture of organized
matters is well kno^n.

There is no doubt that rich soils, or those abound-
ing in animal and vegetable remains, are less liable
to change in temperature with that of the incumbent
atmosphere, than those of a poorer constitution.

110 PRINXIPLES OF GARDENING. [CH. II.

This partly arises from causes already explained
when treating of the influence of the colour of soils
upon vegetation. Some manures, as salt, protect
plants from suffering by sudden reductions of tem-
perature, by entering into their system, stimulating
and renderuig them more - vigorous, impregnating
their sap, and consequently rendering it less liable to
be congealed^.

Every cultivator of the soil, by certain empirical
signs, may be able to determine that ceitain appli-
cations are required to render his land produc-
tive: for example, he knows when chalk may be
applied to advantage ; but no lengthened practice has
yet enabled any one to judge of the quality of a chalk
by its exterior appearance. ChemistiT alone can do
this. The fanners of a district in Yorkshire having
experienced the benefit of lime, procured some from
a neighbouiing kiln, and were astonished to behold
the injury it caused to their crops, and it remained
an anomaly of their experience, until chemistry
demonstrated that the lime near home contained a
very large proportion of magnesia, which, absorbing
carbonic acid very slowly, remained in a caustic state,
to the injuiT of the roots of the plants, and the diminu-
tion of benefit from the carbonic acid evolved by the
decomposing constituents of the soil.

The experiments of Saussure demonstrate the
^ Cuthbert Johnson's valuable work on Fertilizers.

CH. II.] THE ROOT. Ill

benefit accruing to cultivated plants from animal and
vegetable manures decomposing in the soil ; but they
do more, for they afford additional evidence to that
already given, how erroneously those persons argue
who recommend the seed to be soaked in powerfully
stimulating manures, for no other reason than because
they are grateful to the adult plant. Carbonic acid gas,
though an efficient promoter of a plant s growth when
mature, is a check to its progress whilst the root ls
forming. Saussure placed peas so that their just deve-
loped radicles were immersed, some in distilled water,
and others in water impregnated with carbonic acid.
The radicles when the experiment commenced were
two lines and a half in length, and in ten days those
in distilled water were five inches longer than those
in the acidulated water, and the stalks and leaves
were equally superior. But when a month had
passed, the relative superiority was reversed, and in
six weeks the plants fed with carbonic acid were in
eveiy respect most vigorous. Ruckert obtamed
nearly the same result when beans were grown in
earth, some being watered with distilled water, and
the others mth water impregnated with carbonic
acid.

Every farmer, in districts where marl is to be
obtained, is aware that it is highly beneficial when
applied to the land ; few of them, however, know, that
this various-coloured compound of earths contains

11*2 PEINXIPLES OF GARDENING. [CH. II.

always chalk, often to the amount of 50 per cent. They
leaiiDjfrom experience, that the marl of one district is
most beneficial to their hea^T soils ; that of a second
district is productive of most benefit upon light land :
yet they are ignorant, in the first instance, that the
first marl contams silica or sand ; that the second has
alumina, or clay, as a component, and if a new pit of
marl is opened, they have to wait the result of some
years' practice before they ascertain its quality. The
chemist can inform them in an hour, and this
naturally leads to a consideration of the indications
of a soils steiility or productiveness.

Xo soil is absolutely barren — not an instance is
known of land, penetrable by the spade or by the
ploughshare, that ^ill not support some species of
plant seniceable to man. By the use of the term
barren, therefore, in these pages, I intend no more
tlian that the soil, in its present state, "svill not
repay its cultivator for his expenditui*e of money
and labour.

By the term fertility. I intend the exact converse.
Wlien a soil is spoken of as fertile, it must not be
understood (unless so stated) that it is rich and
largely remunerating ; but merely that it is suffi-
ciently productive to reward its cultivator for his
expenditure, and to induce him to contmue the appli-
cation of his capital upon it.

Now the natural indications which mav enable the

CH. II.] THE BOOT. 1 I 3

inspector to pronounce, at once, upon the quality of
the soil exhibiting them are obviously arrangeable
under four heads. First, the vegetation on the
soil; secondly, the soil itself ; thii'dly, the drainage
water; fourthly, the meteorological phenomena;
and on these heads I shall proceed to offer some
observations in the order mentioned.

I. The Plants produced by the Soil. — If the com-
mon fern fPteris aquilina,) furze fUlex EuropcBus, )
and heaths f Erica,) prevail, either separately or
conjmictively upon a soil, they afford a certain indica-
tion that it is the most improductive and unreclaimable
of all light soils — a siliceous surface resting upon a
sandy or gravelly subsoil. When I say unreclaim-
able, it is not intended that such a soil cannot be
rendered productive, if clay, aluminous marl, or
chalk be in the vicinity with which to improve its
staple, but that it cannot be improved from its own
bowels — that it has not the remedy for its sterility
within itself.

In the east of England the Pteris aquilina, there
known as the Brake, is estimated as the indicator of
the most evil, and a common story is current amongst
the Essex farmers expressive of this opmion. An old
cultivator who was blind, when upon a farm that was
to be let, being told that he might tie his horse to
one of the brakes, replied " Nay, nay, then I'll go on
fiuther — the brakes shan't break me."

I

114 PRINCIPLES OF GARDENING. [cil. II.

It is certain, that where the brake flourishes, the
siliceous nature of the soil invariably prevails to a
very considerable depth. I have frequently seen the
stem of this cryptogamous plant followed four or five
feet into the soil without reaching its extremity.
Some authorities say that the stem is often eight or
nine feet long. When a frond of the brake is pulled
up, the blackened portion of it must not be mistaken
for root, it being merely the stem discoloured by ex-
posure to the ferruginous soil, which strikes a black
colour with the gallic acid and tannin in the bark of
the plant, where the air can gam access.

Rooting to so great a depth, and each fragment of
root being reproductive, it is extirpated with extreme
difficulty. This renders it most obnoxious to the
cultivator; but the depth of light unretentive soil it
indicates, is also especially to be deprecated in the
eastern comities of England, for such soils more ra-
pidly become dry than any others ; and the annual
depth of rain in inches in that district is never more
than half as compared with the same atmospheric
deposition in the western counties of England, and
on an average of years much less.

I have not the tables by me ; but I ^rill quote two
instances, from first-rate authorities, showing the dif-
ference of rain monthly in inches duriniT one year
only, 1842. The observations were made at Tliet-
ford and Hereford, places nearly equidistant from the

CH. II.]

THE ROOT.

115

sea, and in the same parallel of latitude. I give
them, because they demonstrate that a soil equally-
light may be much less unproductive in the west
than in the east of England, o^^ing to its being better
supplied with moisture.

January
Februaiy
March
April .
May .
June .
July .
August
September
October .
November
December

Thetford.
0.13
0.76
1.40
0.50
1.Q3
1.70
3.08
0.64
■2.90
1.43
2.53
0.75

Hereford.
2.94
1.87
2.70
0.21
2.45
2.29
2.36
1.99
3.56
1.06
7.38
1.11

17.05

29.92

The brake will not live upon a rich soil : but the
next plant to be mentioned, the furze, will live upon
rich light land, although it speedily reduces it to
steriHty. I think it is a greater exhauster of a soil
then any plant native of England. Xor is this diffi-
cult of explication ; for being almost destitute of
leaves, it has to derive its chief nutriment from the
soil, which it does by its widely extending and enor-

i2

116 PRINCIPLES OF GARDENING. [CH. II.

mously disproportioned roots. So exhausting is its
nature, that it absolutely seems to change the veiy
staple of the soil on which it is planted. I remem-
ber this fact, most strikingly illustrated by a bank,
on which a hedge of the furze was gro\Mi in the
county of Essex. I had, unfortunately, no analysis
of the soil previously to its being thus planted ; but
after the furze had grown upon it for some ten or
more years, the colour and texture of the soil was
completely changed ; it appeared a mere effete sand,
with but the smallest power of adhesion remaining.

Heath is another infallible demonstration that the
surface soil is barren and siliceous ; but it is not in-
dicative of the subsoil being gravelly or porous. I
have seen it abounding where a stiff brick earth
was not many inches from the surface. The fine-
leaved heath [Erica cinerea) is the most insepa-
rably associated mth sterility. The cross-leaved
heath {Erica tetralix) will flourish in richer and
better stapled soil than the preceding. The Erica
tetralix is that which has waxen-looldng flowers, var}^-
ing in colour from almost pure white to the deepest
pink.

Another infallible inchcation of a barren siliceous
soil is the heath-grass [Triodia decumbens). Gromid
where it is found may be boggy, and disguised by the
superfluity of its undrained water, but the staple will
invariably be found to have a large excess of silica.

CH. II.] THE EOOT. ]17

The rest han-ow or caanmock (Ononis arvensis and
Ononis spinosaj is also indicative of barrenness and
lightness of soil. I have gathered them on such
land where clay pits were in the immediate vicinity.
But where the \>voom.( Spa rtiumscopariunij abounds,
we may be certain that no clay will be found ^\-ithin
reach of its deeply penetrating roots. It thrives only
in hungiy deep gi'avels or sands.

The common nettle ( Urtica urens) I have always
considered indicative of fertility, and this will be
found, I believe, to be the fact, except in accidental
cases. Thus was I once startled from such conclu-
sion by seeing immense beds of this plant gro-uing
upon that most sterile of sandy soils, the rabbit war-
rens near Brandon, in Norfolk. But the explanation
of this was easy upon remembering that the urine of
the rabbit contains an excess of the salts of potash, —
salts absolutely necessary for the nettle's A^gorous
growth, — salts found, also, near old brick walls, and
inducing the nettle to be so constant an attendant on
the dwellings of man in temperate latitudes^.

Wherever the elm (Ulmus campestris) grows
* Vauquelin found in the urine of the rabbit.

Carbonate of lime.

magnesia,
potash.

Sulphate of lime.

Chloride of potassium.

Urea.

Mucus and sulphur.

Sulphate of potash.

Its milkiness arises from carbonate of lime, — (Tfiot/uon's
AniiKKiL Ckeiiiistry, 496.)

118 PRIN'CIPLES OF GARDENING. [CH. 11.

rapidly and to a large size, it is well kno\^-n that the
soil is rich and open, and capable of producing
abundant crops of almost any plant subject to the
Fanner's care.

If the birch (Betula alba J be the most flourishing
tree upon the land, it is most certainly light and poor.

Where the oak flourishes, wheat and beans, with
good tillage, are sure to succeed, for the staple of
the soil must be hea^7 and deep. A very marked
illustration of this is to be seen in a valley be-
tween East Grinsted and Lewes, near the resi-
dence of the Earl of Shefiield. In this valley the
oak, the wheat, and the beans, flourish, whilst not
one of the uplands around peld any thing approach-
ing to an average growth. Again, near Littleton, the
residence of Captain Dunn, not far from Himgerford,
in Berkshire, I know an oak standing in a hollow,
probably an old clay pit. The tree is of gigantic
gro^nh, and the field itself almost invariably grows
better beans and wheat than any other inclosure on
the estate.

Wherever the common way tliistle, or saw-wort
fCarduus arvensis of Smith, Serratula arvemis of
Linnseus) grows luxuriantly, it is usually an intima-
tion that the soil is fertile, and that the plant is
rejoicing in its being rather aluminous. This weed
will live and annoy the cultivator on almost any soil,
but if a vein of soil somewhat heavier than the rest

CH. II.] THE ROOT. ] 19

of tlie land crosses a field, the "vs'av thistle will be
found on that part to be remarkably the most
luxuriant and robust.

If the colts-foot (Tussilago farfara) is prevalent
and luxuriant, it may be considered certain that the
soil is fertile ; it may indicate that the land has
been ill-farmed, and that under- draining, especially,
is required; but the staple of the soil ^^■i^l generally
be fomid to reward the judicious cultivator.

Where femiel {Meum fcenicidum of Smith, AncB-
thumfcenicuhinio{ljmn2exis)is obseiTed upon land, it
indicates not only that the soil will reward the efforts
of the cultivator, but that chalk (carbonate of limej
will in some form be fomid in the vicinity.

Com mint (Mentha an'ensisj is never found upon
unfeitile soils, but it is a certain indication that
underdraining is required. It will not live except
where there is more moisture habitually in the soil
than is requu'ed for the healthful vegetation of
cultivated crops.

The scaly stalked spike-rush (Eleocliaris ccEspitosa)
is indicative of a soil not very easily reclaimable, %-iz. ;
the bog resting upon a retentive subsoil.

Common knot grass (Polygonum aviculare ), black
grass f Alojtecunis agrentis), and the smaller leaved
creeping bent (Agrostls stolonifera angustifoUaJ, are
very far from being indicative of barrenness. They
are most noxious weeds, injuiious to the legitimate

1'20 PRINCIPLES OF GARDENING. [CH. II.

crops, and most difficult of eradication, but I do not
know that I ever observed them upon any soil that
would not amply reward the careful cultivator. It is
also quite certain that they are never found prevail-
ing upon well cultivated land.

I know some farmers w^ho class unsparingly
together " Poppies and Poverty," but this conclusion
ought not to be without reservation. There is no
doubt that this weed (Papaver rhceasj prevails and
seeds most abundantly upon very poor sandy or
gravelly soils, but I know it will be in profusion also
even in the best land, with the exception of that
which is veiy heavy. On the latter I do not re-
member having ever seen the poj)py veiy numerous.
Sprit fJimcus articulatusj. Purple sandwort (Aren-
aria rubra), and Sweet Gale (Myrica gale), are un-
erringly indicative of a poor siliceous soil resting on
a porous substratum.

II. The soil itself. — The most fertile soils have the
greatest difference of colour between the extreme
surface, after it has been exposed for some days to the
atmosphere, and that portion which is taken fresh
from a few inches below that surface.

I am not aware of having ever met with a fertile
soil that retained, after exposure to the dry air, the
same coloiu*, after the lapse of forty eight hours, that
it had when freshly turned up. Such a soil mvariably
becomes much lighter coloiu'ed.

^

CH. II.] THE ROOT. 121

Not SO barren soils, for I know many that are
nearly the same colour at all times, and some boggy
soils that are even darker upon the dry surface than
beneath.

Eveiy one knows the fresh earthy smell peculiar
to a fertile soil newly dug. This smell is never
given forth by boggy or sandy soils that are baiTen,
neither is it emitted by chalk. It does not indeed
appear to be perceptibly emitted by any soil not con-
taining five per cent, of alumina. It is totally absent
from the soil on the most barren portions of Bagshot
Heath, and is always most powerful upon the heaviest
soils. The smell arises in fact fi'om the alumina.

I have never known a black sandy soil, containing
a multitude of white pebbles, that ever repaid the
expense of cultivation; especially if it was on the
side of a decli\dty, and, I may add, that all the most
fertile soils of England have a specific gravity not
exceeding 2.4. I have never yet examined a pro-
ductive soil ^ith a specific gravity above 2.5.

Although a black sandy soil, as last described,
is invariably infertile, yet a dark coloured soil, if of
con-ect staple, will always bear better crops than one
lighter coloured. I know two soils, the specific
graxities of which are the same ; they have nearly the
same amount of aluminous and decomposing matters,
but one has much less silica and has much more
chalk in its composition than the other. The chalky

122 PRINCIPLES OF CtARDENING. [cH. II.

soil is lighter coloured, and although they both rest
upon porous subsoils, yet vegetation is always later,
and harvest backwarder, on this than upon the other
field. So much indeed has colour to do ^vith forwai'd
vegetation, that, if the surface of one stetch in a field
where wheat is so^^'n be sprinkled thickly with
coal ashes, it will be found to be earlier in every
stage of growth than the com growing around. This
result of obsen-ation is readily explicable upon the
fact demonstrated by Leslie and others, that dark
surfaces absorb more heat from the sun than light
coloured ones. The latter reflect its rays.

The sensation imparted to the hand when damp
portions of various soils are grasped is very ditferent.
The greasy feel of the clayey ; the grittiness of the
sandy; and the cold softness of the chalky, are
easily recognizable by those accustomed to §uch
examinations.

There are two tests connected with handling damp
soils that are fer from bad criteria, whereby to judge
of their fertility. Let a handful be grasped firmly
of each soil under examination, and let each con-
solidated handful be placed upon a sheet of paper on
a table m the same room, out of the sunshine. The
handful which dries first and crumbles do\ra the
most easily will be the least fertile.

Take equal proportions of different equally damp
soils, and expose them side by side, each on a

CH. II.] THE EOOT. 1^3

separate sheet of paper, to the sun's rays for an hour,
and then put them into a dark cold closet for another
houi'. Handle them in succession, and that which
feels the warmest will be the most fertile. This is
easily explicable from the fact that a fertile soil, that
is, one haWng a due proportion of alumina and de-
composing matter, is always slower in cooling than
one that is deficient in these constituents.

III. The drainage ivater. — Upon this I shall
merely observe, that I have never been able to find
that it affords any satisfactory criterion whereby to
judge of the fertility of a soil. A red, ocherous
deposit from such water shews that the subsoil
through which it percolated is an irony gravel or sand.
The dark film exhibiting the dove's-neck varying
colours, often seen on the surface of drainage water,
indicates its having passed through peat, bog, or
wood, for that film arises from the vegetable extract
it contains. Virgil tells us (Georg. ii. 245) to wash a
soil, and that if the water employed becomes con-
sequently nauseous and bitter, it indicates a salt soil
unsuited to the growth of com. I have never met
with such a soil, except where soda was a product of
the land, and this is not the case in England.

IV. Meteorological j^heriomena. — Under this head
I have only to remark that, wherever fogs or mists
settle, or become apparent in the evening earlier
than upon neighbouring soils, it is a certain indica-

124 PRINCIPLES OF GARDENING. [CH. II.

tion that that part is colder, and ^^•ill be usually more
unproductive and certainly later in its vegetation.
I once saw a remarkable proof of this. On one
portion of a field the evening mist-cloud was always
obsen-ed to settle sooner than on the other parts.
This portion also always bore the lightest part of the
crops grown. It was under-drained, and the early
mists and unproductiveness simultaneously ceased.

i

CHAPTER III.

THE STEM AND BRANCHES.

Although even- member of the vegetable form,
from the minutest root to the most fragile flower,
have their epidermis, cellular integument, bark,
woody fibre, and medullary matter, yet as these are
most apparent in the stem and branches, they can
be commented upon most readily in tliis chapter,
devoted to the consideration of those vegetable
members.

The first of these, the epidermis, is analogous to
the human cuticle, or scarf skin, being the external
envelope of the whole surface. It is commonly
ti'ansparent and smooth, sometimes hairy ; in other
instances hard and rugged, occasionally so abounding
-with silica or flint as to be employed as a polisher for
wood, and even brass. In every instance it is a net-
work of fibres, the meshes of which are filled ^^ith a
fine membrane. The epidermis appears to be de-
signed as a preservative from the injurious effects of
the atmosphere, to regulate the quantity of gaseous
matter and moistm'e respired, and as a shield from
the attacks of animals, &c. It is certainly devoid of

126 PEINCIPLES OF GARDENING. [CH. III.

sensation. The texture of the membrane between
the meshes varies much in different species of plants.
In ver}' succulent plants, it is so contrived, tliat it
readily allows the absorption of moisture, but pre-
vents perspiration. Such plants are, consequently,
well qualified to inhabit hot climates and diy soils.
Neither is it at all impossible, that it possesses the
quality of allowing the passage of some gases, and
rejecting others, as the bladder of animals permits
water to pass through its textm'e, but is impendous
to alcohol. In old trees it cracks, and in many
cases becomes obliterated, the dead layers of bark
performing its offices. Its growth is slower than
that of other parts, and its powers of expan-
sion, though great occasionall}^ cannot equal the
rapid enlargement of the parts it incloses and de-
fends. This is very frequently the case with
the stem and branches of the cherry ; the tre€
is then said by gardeners to be hide-hound, and is
relieved by making longitudinal incisions. It is
still more apparent in the fruit of the clierr}' and
plum : when rain falls abundantly during their state
of ripeness, their pulj) swells so rapidly, that in an
hour or two the epidermis of eveiy ripe dimpe upon
a tree ^^'ill be cracked. Gardeners are very prone to
scrape ^^ith no gentle hand the bark of their fruit-
trees ; whereas every care should be taken not to
wound its surface unnecessarily, and never to reduce

CH. III.] THE STEM AND BRANCHES. \'i7

its tliickuess until all danger of severe frosts is
passed.

The epidermis regulates the evaporation from a
plant, and preserves it in some degree from the de-
trimental sudden changes of temperature to which
our climate is liable. The birch {Betulus alba), has
more films of epidermis than any other European
tree ; and it ascends to greater heights in the Alps,
and approaches nearer to the frozen zone than other
trees of the same climates.

Immediately below the epidermis occurs the cellu-
lar integument (otherwise known as the parenchyma
and pulp.) It is a juicy substance ; and, being the
seat of colour, is analogous to the rete 7nucosum
of man, which is red in the white, and black in
the negro : the flesh of fruits is composed of it.
Leaves are chiefly formed of a plate of it, inclosed
by epidermis. In herbs, succulent plants, leaves
and fruits, if it is destroyed, like the epidermis of
the same, it remains unrestored ; but in the case of
trees and shiaibs, it is regenerated after each re-
moval. In leaves it is generally gi'een ; in flowers
and fiTiits, of eveiy hue. It is alwa^'s cellular, and
evidently acts a part in the secretory system of plants.

Under the cellular integument occurs the hark,
which, in annual plants, or branches of one year s
growth, consists of a single layer, scarcely distin-
guishable from the wood ; in older stems and branches,

128 PRINCIPLES OF GARDENING. [CH. III.

it is composed of as many layers as tliey are years of
age. It is in the innermost of these, which is called
the liber, that the vital returning circulation and se-
cretions are carried on for the time being almost ex-
clusively. These layers are concentric, or, as they
are usually termed, cortical layers; they are thicker
in feeble plants than in more vigorous plants of the
same species ; they are formed of wa\dng longitudi-
nal fibres, the meshes of the net- work they thus con-
stitute being filled with pulp. If the outer bark is
destroyed, but the wound does not penetrate below
the liber, the wound is healed up, otherwise the re-
moved part is unregenerated. In some roots, al-
though only annuals, the bark is composed entirely
of liber, and is \ery thick, as in the carrot and pars-
nep, in which it is remarkably separated by a light-
coloui'ed annular mark, from the central or woody
part. The liber is composed of various longitudinal
tubes, m which the true sap of the individual de-
scends after elaboration in the leaves : consequently
here are found in the most concentrated state the sub-
stances that are the peculiar products of each plant,
as the resin of the fir, the bitter principle of the cin-
chona, or Peruvian bark, &c.

I will here pause, to remark upon some of the
remedies which have been recommended for the re-
moval of insects from the bark of trees. Oil has
been directed to be smeared over them, for the de-

CH. III.] THE STEM AND BRANCHES.

129

struction of the aphis lanigera, moss, &c. TMiether
this appUcation "will answer such piii'pose, I ^sill not
stop to argue, but >vill content myseK with observing,
that a more deleterious one is scarcely possible ; for
on the same principle that it destroys the parasites,
namely, by closing their spiracles and pores, and thus
suffocating them, it in a like manner clogs up the pores
of the infected tree, and. in every instance, insures a
weak and unhealthy vegetation ; for it is not a tran-
sient remedy, that will cease in its effects as soon as
it has attained the desired end. The oil dries, and,
as it were, forms a varnish over the epidermis for
years, unremoved by exposure to the atmosphere ;
and this effect is more decidedly insured by linseed
oil being the kind recommended, it being one of the
most unctuous and quick-drying of the oils. The
most effectual, most salutary, and least disagreeable
remedy is of trivial expense, and which a gardener need
but try upon one indi%adual to insure its adoption.
It is with a hard sci-ubbing brush, dipped in a strong
brine of common salt, as often as necessary, to insure
eaxih portion of the bark being moistened with it, to
scrub the trunks and branches of his trees at least
every second year. It most effectually destroys in-
serts of all kinds, and moss ; and the stimulating
influence of the application and the friction are pro-
ductive of the most beneficial effects. The expense
is not 80 much as that of dressing the tnmks ^vith a

K

h

130 PRINCIPLES OF GARDENING. [CH. III.

solution of lime, which, however efficient in the de-
struction of moss, is not so in the removal of insects
— is highly injurious to the trees, by filling up the
respiratory pores of the epidermis, and is decidedly
a promoter of canker. Let my remedy be brought
by every orchardist to the test of experiment under
his own eye, that it may be effectually done, and he
will not require me to theorise. Facts are stubborn
opponents.

The injury inflicted by stopping the pores of the
epidermis, on the stem and branches of a tree, is at
once evident from the fact, that oxygen and water
are absorbed, and carbonic acid evolved from them,
the same as in the leaves, which operations are all
parts of the process of elaborating the sap. It is no
trivial inspiration of oxygen ; for in twenty-four hours,
the branch of an apple-tree has been found to inhale
five times its own volume.

If the fibres emitted by the ivy, by which they
cling to other trees for support, do not aid it in ob-
taining nourishment, yet by fillmg their respiratory
pores, they ai'e injurious, and should never be al-
lowed to cling around serviceable trees.

Immediately beneath the bark is situated the wood,
which forms the chief bulk of trees and shrubs. It
is formed of concentric layers, one of which, at least,
is added annually. These layers are formed of a tissue
of longitudinal fibres, resembling net-work, the in-

i

CH. III.] THE STEM AND BRANCHES. J 31

terstices of which are filled up with soluble matter,
differing in each vegetable genus, but closely resem-
bling its parenchj-ma The layer immediately in
contact with the bark is the softest and palest in
colour, and thence is called the alburnum. It is in
this that the vessels which convey the sap from the
roots to the leaves are chiefly situated. This layer is
annually renewed, that of the previous year becoming
more complete wood. Although the chief part of the
sap vessels, as just observed, is situated in the albur-
num, yet others, though more scantily, are dispersed
through the whole of the w^ood. Wherever situated,
they extend from the extremity of the minutest root
to the leaves. The idea that the annular layer of
wood is rendered more dense and firm by severe
winters, is denied by reason, and demonstrated to be
false by actual obsei-vation. The layers are thickest
on those sides of a tree where the largest branches
occur, and are, throughout, of greater size, in such
years as afford the most genial period to vegetation.
Wood is consolidated fastest m those plants which
are most freely exposed to the influence of light and
air, and those plants grow in height the slowest.
This teaches a lesson to the gardener he often may
remember with advantage ; for it is often desirable
to have specimens of the same shrub, varying in
height ; and he may often increase their stature, yet
preserve them in health, by keeping them in a moist,

k2

lo'2 PRINCIPLES OF GARDENING. [CH. Ill,

shaded locality, during the early stages of growth ;
and he may as certainly render them more dwarf, by
exposing them to a drier, and the brightest atmo-
sphere that they will healthily endure, and he can
command. By the former treatment, I have seen
heliotropes clustering round the pillars of a conserva-
tory to the height of fifteen feet.

From the extension of the woody fibre being greater
and longer continued on one side of a stem or branch
than on its opposite side, it frequently becomes con-
torted. Gardeners usually endeavour to remedy this
by making an incision on the inner side of the cun^a-
ture, and then employing force to restore it to a rec-
tilinear form, causing a gaping wound, and mostly
failing to attain the object. If the incision be made
on the outer side of the curve, thus dividing the
woody fibres that continue to elongate most rapidly, the
branch or stem, \vith but slight assistance, will recover
its due form, and there will be no open wound.

From the fact that there is invariably more wood}'
matter deposited on the side of a stem or branch which
is most exposed to the air and light, gardenei-s have
explained to them why those sides of their trained
trees which are nearest the wall, ripen, as they term
it, most slowly ; and are benefited by being loosened
from the wall so soon as they are relieved from tlieir
fruit. If they require any demonstration that tliis
explanation is correct, they need only examine the

CH. III.] THE STEM AND BRANCHES. 138

trees in clumps and avenues ; their external sides
will be found to enlarge much more rapidly than
their internal or most shaded sides.

In the centre of the wood is situated the medulla
or pith. It is a soft, cellular, membranous substance,
juicy when young, and extendmg from the ends of the
roots to the extremities of the branches. In the first
stages of vegetation, it occupies but a small space : it
gradually dilates ; and in shoots of a year old, and in
young trees, it is of considerable diameter; as their
age increases, it gradually diminishes and at length
becomes totally extinct, its place being occupied by
perfect wood. Its functions are little understood.
It appears to be connected with the production of
young shoots ; for, as soon as it becomes extinct in
a branch, that member loses, in a great degree, the
power of producing them ; that power apparently
being transferred to those younger branches which
still retain their pith in perfection.

The stem is by no means an essential part of the
plant, since many are destitute of it ; to such trees as
naturally are gifted with one, it is somewhat injurious
to prevent its formation. Standard fruit trees, under
similar circumstances of soil, season, and culture,
generally, produce finer flavoured fruit than either
dwarf standards or espaliers. This fact appears to be
accounted for by the discoveries of the indefatigable
Knight, which evince that plants, duiing the latter

134 PRINCIPLES OF GARDENING. [CH. III.

part of the summer, are employed in preparing
nourishment for the production of the foliage and
blossom in the succeeding spring ; this nourishment
is perfected and deposited in the alburnum, and
mixes with the saj) dming its ascent in that season.
Of a consequence it is found to increase in density-
proportionate to the height at which it is extracted.

I

CHAPTER IV.

THE LEAVES.

The leaves are highly vascular organs, in Tvhicli are
performed some of the most important fmictions of a
plant. They are very general, but not absolutely
necessary organs, since the branches sometimes per-
fonn their offices ; such plants, however, as naturally
possess them, are destroyed, or greatly injured by
being deprived of them. The duration of a leaf is,
in general, but for a year, though in some plants,
they survive for t^^'ice or thrice that period. These
organs are generally of a green colour. Light seems
to have a powerful influence in causing this, since,
if kept in the dark, they become of a pale yellow, or
even white hue, unless uncombined hydrogen is
present, in which case they retain theii' verdure
though light be absent. Hence their etiolation would
seem to arise from their being unable to obtain this
gas, ujider ordinaiy circumstances, except when light is
present. Now, the only source from which they can
obtain hydrogen, is by decomposing water; and how
light assists in the decomposition may perhaps be

136 PRINCIPLES OF GARDENING. [CH. IV.

explained by the disoxygenizing power ^ntli which it
is gifted. The violet rays of the spectrum have this
power iu the greatest degree; and Sennebier has
ascertained by experiment, that those rays have the
greatest influence in producing the green colour of
plants. ^Yhen leaves are of any other hue than
green, they are said to he coloured. This variegation
is often considered to be a symptom either of tender-
ness or debility ; and it is ceitain, when the leaves of
a plant become generally white, that that mdividual
is seldom long lived. Mr. Knight, however, has
demonstrated that variegation is not a certain indica-
tion of a deficiency of hardiliood.

The functions of the leaves appear to be a com-
bination of those of the lungs aiid stomach of animals ;
they not only modify the food brought to them from
the roots, so as to fit it for increasing the size of the
parent plant, but they also absorb nourishment from
the atmosphere. The sap, after elaboration in these
organs, difi'ers in every plant, though as far as experi-
ments have been tried, it appears to be nearly the
same in all vegetables when it first arrives to them.
The power of a leaf to generate sap is in proportion
to its area of surface, exposure to the light, and con-
genial situation.

Leaves throw off a veiy considerable quantity of
water. Dr. Hales found that a cabbage emitted
daily nearly half its weight of moisture, a sunflower,

CH. IV.] THE LEAVES. 107

three feet high, perspired lib. 14 oz., and spearmint
exhales 1^ times its weight in the same period. But
of all the plants the diumal perspiration of vrhich
has been ascertained, the coiTieHan cheriy f Coniiis
masculaj transpires the most ; the exhalation amount-
ing to nearly twice the weight of the plant in twenty-
foui' hours. This aqueous expiration takes place
chiefly duiing the day ; is much promoted by heat,
and checked by rain, or a reduction of temperature.

On the free-performance of this function of plants,
their health is dependent in a very high degree ; and
I believe that half the epidemics to which they are
subject arise from its derangement. That consequence
of the clubbing of the roots of the brassica tribe called
fingers and toes arises, I consider, entu*ely from it.
In the drought of summer, when the moisture sup-
plied to a club-rooted cabbage by its root does not
nearly equal the exhalation of its foliage, to supply
this deficiency the plant endeavours, by forming a
kind of spurious bulbous root, to adapt itself to the
contingency ; in the same manner that in dry situa-
tions, the fibrous roots of Phleum pratense, Alopecu-
rus geniculatus, &c., acquire a tuberous form, because
bulbous or tuberous-rooted plants, it is well known,
will exist in a soil so deficient in moisture as to de-
stroy all fibrous-rooted vegetables.

Evergreens transpire less moisture than deciduous
plants ; which would lead to the expectation that

138 PRINCIPLES OF GARDENING. [CH. IV.

they are more capable of Imng in dry situations,
wliich, in general, is really the case. The matter
transpired by a healthy plant is nearly pure water,
5,000 grains of it never containing more than one
grain of solid matter, and this is constituted of resin-
ous and gummy matter, with carbonate and sulphate
of lime. It appears to be nearly the same in all
plants. The quantity, however, we have seen, varies
in every species, probably in eveiy indi^ddual — and
is greatly influenced by the quantity of water applied
to the roots. Under precisely similar circumstances,
Sennebier obtained the following results :

Grs. Grs.

A peach branch, imbibing 100 exhaled 35

210 . . 90

220 . . 120

710 . . 295

I have found the branch of a pelargonium, that,
whilst growing on the parent stem, exhaled only
twenty grains in twenty-four hours, more than trebled
that quantity, in the same time, when cut from the
stem, and placed \^ith the di^dded end in water.
This increased transpiration is attended by a propor-
tionate reduction of temperature ; for a collection of
pelargoniums, in the midst of which Fahrenheit's
thermometer stood at 55*^, fell to 48° ^rithin two
hours after a plentiful watering to their roots only,

CH. IV.] THE LEAVES. 139

though the water vras of the same temperature as the
greenhouse.

The transpiration of plants decreases with that of
the temperature to wliich they are exposed, as well
as with the period of their growth. This explains
why the gardener finds that his plants do not require
so much water in cold weather, nor during the time
that elapses between the fall of their blossom and
the ripening of their seed. Duiing this period they
do not transpire more than one-half so much as
during the period preceding and attending upon their
blooming. The transpiration takes place from the
upper surfaces of the leaves ; and, if these surfaces
are coated with varnish, the leaves gradually decay
and fall, and the growth of the plant ceases until
fresh leaves are produced. Hence arises the benefit
which plants derive in rooms, gi'eenhouses, and
other confined inclosures, from keeping those sur-
faces cleansed with the sponge and syringe. Some
plants are particularly sensitive to injury from any
check to their transpiration, among wliich are the
tea-scented roses ; and it thence arises, that they
cannot now be cultivated in nurseiy-gardens near
London, where they once flourished when that me-
tropolis was less extensive. The advantage derived
by plants from having their leaves cleansed, was ex-
emplified by the following experiment : —

Two orange trees, weighing respectively 18 and

140 PRINCIPLES OF GARDENING. [cH. IV.

'20 ozs., were allowed to vegetate without their leaves
being cleansed for a whole twelvemonth ; and two
others, weighing 19 and 20 1 ozs. each, had their
leaves sponged mth tepid water once a week; the
two first increased in weight less than half an ounce
each; whilst of the two latter, one had increased
two, and the other nearly three ounces. In all other
respects they had been treated similarly.

It must be remembered, however, in using the
sponge and the syringe, that the under side of leaves
is an absorbing surface, benefited by being kept
clean, and by the application of moisture. The kid-
ney bean, sunflower, cabbage, and spinach, absorb
moisture equally by their under and upper surfaces ;
the cockscomb, pui'ple-leaved amaranth, heliotrope,
lilac, and balm, absorb most freely by their upper
surfaces ; and the vine, pear, cheriy, apricot, walnut,
mulberry, and rose, absorb most by their under sur-
faces.

The transpiration from the leaves of plants is ef-
fected through pores or stromates, varying in number
and size in every species, but being, usually, either
largest or most numerous in plants inhabiting moist
or shady localities. This is a wise provision ; for
such plants, consequently, have an abundant supply
of moist food to their roots, requiring a competent
provision for its elaboration and reduction from su-
perfluous water. Those plants which are natives of

CH. IV.] THE LEAVES. 141

sandy, exposed soils, have, on the other hand, either
fewer or smaller stromates. Criniim amahile, an in-
habitant of swamps near Calcutta, has 40,000 of the
largest known stromates on ever}^ square inch of its
leaves ; whilst an aloe from the exposed sands of the
Cape of Good Hope, has 45,000 of the smallest, and
not equal in transpiring power to half the same num-
ber of stromates in the leaves of the Crinum. I
have not been able to test their relative transpiring
powers ; but of two similarly constnicted plants, of
nearly similar size, the rate of perspiring in July,
both in a temperature of 65°, but not exposed to the
sunshine, was as follows. In six hours, Mesemhry-
anthemum Deltoides, native of an arid soil, exhaled
eight grains, whilst Caltha palustris, found only in
marshy places, exhaled twenty-five grains. In the
absence of certain information, therefore, the gardener
may conclude, as a guide for his treatment of a new
plant, that, if its stromates are large, it will require
abundance of water.

Another circumstance most influential in control-
ing the transpiration of plants, is the hygrometric
state of the atmosphere in which they are growing.
The drier the air, the greater is the amount of
moisture transpired ; and this becomes so excessive,
if it be also promoted by a high temperatui'e, that
plants in hothouses, where it has occui'red, often djj
up as if burned. The justly-lamented Mr. Daniell

142 PRINCIPLES OF GARDENING. [CH. IV.

has well illustrated this by showing, that if the tem-
perature of a hot-house be raised only five degrees,
viz. from 75° to 80'', whilst the air within it retains
the same degree of moisture, a plant that, in the
lower temperature exhaled 57 grains of moisture,
would, in the higher temperature, exhale 120 grains
in the same space of time.

Plants, however, like animals, can bear a higher
temperature in diy air, than they can in air charged
with vapour ; animals are scalded in the latter, if the
temperatiure is veiy elevated ; and plants die under
similar circumstances as if boiled. MM. Edwards
and Colins found kidney beans sustained no injury
when the air was dry at a temperature of 167" ; but
they died in a few minutes if the air was moist.
Other plants, under similar circumstances, would
perish, probably, at a much lower temperature ; and
the fact affords a warning to the gardener to have
the atmosphere in his stoves very dry, whenever he
wishes to elevate their temperatui'e for the destruc-
tion of insects or other pui'poses.

Though growing plants can bear an elevated tem-
perature without injury, a very different effect is
produced upon them by even a lower heat, after they
have been separated from their roots. This has to
be borne in miud in the diying of potherbs, which,
though it is a process very simple and veiy important
for the winter's cuisine that it should be conducted

CH. IV.] THE LEAVES. 143

correctly, is usually more neglected and more
thoughtlessly practised than any other in the varied
range of the gardener's duties. To demonstrate this,
will only require to have pointed out how it ought to
be managed. The flavoui' of almost every potherb
arises from an essential oil which it secretes, and
this being in the greatest abundance just pre-
viously to the opening of its flowers, that is the time
which ought to be selected for gathering. Potherbs
ought to be dried quickly, because, if left exposed
to winds, much of the essential oil evaporates, and
mouldiness occurring, and long continuing, destroys
it altogether, for nearly eyerj plant has its pecu-
liar mucor, (mould,) the food of which is the charac-
teristic oily secretion of the plant on which it vege-
tates. A dry brisk heat is therefore desirable ; and
as the fruit store-room ought always to have a stove,
and is untenanted when herbs require drying, no other
place can be more efficiently employed for the purpose.
The temperature should be 90°, for if it exceeds this,
the essential oils are apt to burst the integuments
of the containing vessels, 6ind to escape. Forty-eight
hours, if the heat be kept up steadily, are sufficient
to complete the process of diying. The leaves, in
which alone the essential oils of potherbs reside,
should then be carefully clipped ^dth scissors, not
crushed, from the stalks, and stored in tightly corked
wide-mouthed bottles. Each will thus preserve its

144 PRINCIPLES OF GARDENING. [CH. IV.

peculiar aroma, not only through the winter, but for
years, and be infinitely superior to any specimens
producible in the forcing department, for these are
unavoidably deficient in flavour.

Leaves have the power of absorbing moisture as
well as of emitting it, which power of absorption
they principally enjoy during the night.

During the day leaves also absorb carbonic acid
gas, which they decompose, retaining its carbon,
and emitting the greatest part of the oxygen that
enters into its composition. In the night this ope-
ration is in a certain measure reversed, a small
quantity of oxygen being absorbed from the atmo-
sphere, and a yet smaller proportion of carbonic acid
emitted.

Carbonic acid gas in small proportions is essential
to the existence of leaves, yet it only benefits them
when present in quantities not exceeding one-twelfth
of the bulk of the atmosphere in which they are
vegetating ; though one twenty-fifth is a still more
favourable proportion; and as hot-beds, heated by
fermenting matters, rapidly have the air within their
frames contaminated to a much greater extent than
the proportions above-named, thence arises the injury
to the plants they contain, from a too long neglected
ventilation. The leaves turn yellow from the excess
of acid, which they are unable to digest, and which
consequently effects that change of colour which also

CH. IV.] THE LEAVES. 145

occurs in autumn, and wliich will be more fully con-
sidered when the decay of plants is detailed.

It is the accumulation of carbonic acid and other
gaseous matters, such as sulphurous acid and am-
monia, which renders ventilation so essential to the
health of plants in forcing-pits and hot-houses.
They cannot inhale air, overloaded with these con-
taminations, without being speedily injured, and the
proportions of those gases which rapidly cause dis-
ease, or even death, are much less than the gardener
usually suspects, for if the sulphurous acid amounts
to no more than one cubic foot in ten thousand of
the air in a hot-house, it will destroy most of its
inhabitants in two days. To avoid such destruction,
for the comfort of visitors, and, above all, for the
sake of the plant s vigour, air should be admitted as
freely as the temperatui'e will permit. The foul
warm air can be easily allowed to escape through
ventilators in the most elevated parts of the roof, and
fresh warm air can be as readily supplied, through
pipes made to enter near the flooring of the house after
passing through hot water, another source of heat.

I am quite aware that Mr. Knight has stated that
he paid little attention to ventilation, and that plants
Avill be vigorous for a time in Wardian cases ; but
this does not prove that their Creator made a mis-
take when he placed vegetables in the open air.
Plants confined in houses or other close structures

L

146 PRINCIPLES OF GARDEXING. [CH. IV.

may be made to grow in spite of such confinement,
but all experience proves that other favourable cir-
cumstances, such as heat, light, and moisture, being
equal, those plants are most ^-igorous and healthy
wliich have the most liberal supply of air.

Though an excess of carbonic acid eras is detri-
mental, yet its partial absence from the atmosphere
is equally fatal to a plant's leaves, for without it they
witlier and fall. It is not a matter of indifference,
therefore, whether a gTeen-house or hot-house be
whitened with a solution of lime, which absorbs that
gas from the air, a fortnight or only a day or two before
plants are introduced or forcing commenced ; for it
is the infliction of several tri\dal injuries to a plant that
prevents its successful cultivation; no one who is
entitled to practise in the higher departments of his
art ever makes such great blunders as at once to
destroy the plants under liis care. That fresh-limed
walls do injui-e plants is beyond dispute, for the
plants in a row of small pots next the back wall in a
propagating house W'hich had been thus whitened
only the day before, have been more than once
observed to be the only plants that acquired a sickly
hue, and shed nearly all their leaves. Fleshy leaved
plants would not be so liable to injury if obliged to
be brought into a house fresh limed, for these require
much less carbonic acid daily than thin leaved plants.
Five plants of Cactus sj^eciosmimus in the injured

CH. IV.] THE LEA\'ES. 147

row just noticed, were not apparently affected.
Thin leaved plants consume daily from five to ten
times their own bulk of carbonic acid gas, whilst
fleshy leaved plants, such as the cacti, aloes, agaves
and mesembiyanthemums, do not consume more
than their owa or double their ovm. bulk of that gas.
Plants and their leaves if excluded from light
become of a white or pale yellow colour, in which
state they are said to be blanched or etiolated. This
is occasioned by their being neither able to decom-
pose the water they imbibe, nor to inhale cai'bonic
acid. In the dai'k, plants can only inhale oxygen,
and thus, deprived of free hydrogen and carbon,
on the due assimilation of wliich by the leaves all
vegetable colours depend, and satm*ated with oxygen,
they of necessity become wliite. An excess of
oxygen has uniformly a tendency to whiten vege-
table matters ; and, to impart it to them is the prin-
ciple upon which aU bleaching is conducted. An
over-dose of oxygen causes in them a deficiency of
alkaline, or an excess of acid matter, and light
enables plants to decompose the acid matter and
to restore that predominancy of alkalinity on which
their green colour depends. Sennebier and Davy
found most carbonic acid in etiolated leaves ; and all
green leaves contain more alkahne matter than the
rest of the plant which bears them. Ever}- cook
knows that a little alkali, carbonate of soda, added

l2

148 PRINCIPLES OF GARDENING. [CH. IV.

to the water improves the green hue of her boiled
vegetables. That this is the cause of the pheno-
menon is testified by direct experiment. Blanched
celeiy and endive, and the -white inner leaves of the
cos-lettuce, contain about one-third more water than
the same parts when green ; and if submitted to
destructive distillation do not yield more than half
so much carbon. Then, again, if a plant of celerj-
is made to vegetate in the dark, under a receiver
containing atmospheric air, with the addition of not
more than one-twentyfifth part of its bulk of a mix-
ture of carburetted hydrogen, and hydrogen such as
is afforded by the distillation of coal, that plant,
though it becomes paler than when grown in the
daylight, still retains a verdant colour.

So effectual is the metamorphosis of plants
effected by excluding them from the light, that Pro-
fessor Robinson brought up from a coal-mine, near
Glasgow, some whitish-looking plants of wliich no
one could detect the name or character. Aft^er
exposure to the light, the white leaves decayed, and
were succeeded by green ones, which speedily re-
vealed that the plants were tansy. They had found
their way into the mine in some sods from a neigh-
bouring garden ; but though they had retained life
in its dark galleries, they had entirely lost their
natural colour, odour, and combustibility. This is
only in accordance with the gardener s yearly expe-

CH. IV.] THE LEAVES. 149

rience, for his blanched sea-kale, endive, and lettuce
are totally dissimilar in flavour and appearance to
the plant left in its natui'al state.

Sir H. Daxj excluded a cos-lettuce from the light.
In six days it was rendered very pale, and, at the
end of another week, it was quite white : the growth
of the plant was checked, and the analysis of its
leaves shewed that they contained more carbonic
acid and water, but less hydrogen and residual
cai'bon, than an equal weight of green leaves.

It deseiTes notice, that it has been proved by the
experiments of Dr. Hope and others, that light from
artificial sources may be concentrated so as to
enable plants to absorb oxygen and perfect those
elaborations on which their green colour depends ;
and the light of the moon has a similar influence.
A similar concentrated light will make the pim-
pernel and other flowers which close until sun-rise
open their petals, and rouse from their rest ; a fact
which gives another reason why plants in rooms
frequented at night become weak and exhausted
sooner than those that remain, as nature dictates,
unexcited at night.

The yellow, red, and light brown tints wliich
render the fohage of our plants so beautiful in
autumn, arise from the absorption of an excess of
oxygen gas. When the reduced temperature of the
season deprives a leaf of the power to elaborate the

150 PEINCIPLES OF GARDENING. [CH. IV.

sap, and, indeed, stops the circulation to it of that
fluid, the absorbent powers of the organ are re-
versed, and instead of carbonic acid it inhales
oxygen. The effect is speedily perceptible. Gallic
acid forms, and this, modified by the differing saline
constituents of different leaves, changes the hue of
their green colouring matter, called chlorophyllite or
chromulite, into various tints of yellow, red, and
bro^\Ti. This is the general effect of acids acting
upon vegetable greens, and that it is the cause of
the autumnal change of colour in leaves, is proved
by the fact, that if a green leaf be dipped into an
acid it assumes the same hue, and if a red or yellow
leaf be dipped into an alkaline solution, it is ren-
dered green — the alkali, evidently, neutralizing the
acid that had wrought the unnatural change of
colour.

The hints and warnings which these facts suggest
to the mind of eveiy reflecting practitioner are nu-
merous. They explain and enforce the necessity of
a regular, and by no means, as to quantity, indiscri-
minate, supply of water to plants ; the importance
of shading after their transplanting, and of a free
circulation of air, &c. ; and the necessity of keeping
the leaves as clean and as free from injuiy as
possible. The leaves of plants must often be re-
moved ; and in some instances this is done mth
essential benefit ; but the horticulturist should con-

CH. IV.] THE LEAVES. 151

stautly keep in mind that, with eveiy leaf that he
removes, he deprives the plant of a primary organ of
its existence.

Light, it has just been stated, is the cause of the
green colour of plants ; but it should be obseiTed that
its full power is only beneficial when directed upon
their upper surface. This is evidenced by the posi-
tion they always maintain. Trees nailed either to a
north or south wall, or trained as espaliers, always turn
the upper surfaces of their leaves outwards, to where
there is most light. Plants in a hot-house uninflu-
enced by the direction from whence proceeds the first
supply of air or the greatest degree of heat, turn not
only their leaves but their very branches towards
the source of brightest light, and if not turned
almost daily, entirely lose their sjTnmetrical form.

If the branches of a tree trained against a wall, or
other support, are so moved when their leaves are
completely expanded, that the under side of the
foliage is the most exposed to the light, they are
always found to regain their natural position in a
day or two. If the experiment is often repeated on
the same individual, the leaves to the last continue
to revert, but become gradually weaker in the effort,
partially decay, and their epidermis peels off. Suc-
culent leaves are particularly sensible of light, but
those of pinnated, legTiminous plants, as the pea and
French bean, are still more so.

CHAPTER y.

THE SAP.

As there is a ver^^ close similarity in the blood of all
animals, so does the same resemblance obtain in the
sap of plants. Uniformly it is limpid as water, its
chief constituent, and contains an acid, salts, and
mucilage or saccharine matter. The proportions of
course vaiy.

The basis of this sap is the moisture of the soil
and atmosphere absorbed by the roots and other
organs ; and that that power of absorption is veiy
great has been observed in a previous chapter.
Neither is it an indiscriminate power : for if the
roots of a plant are placed in water containing two
or more salts in solution, they will abstract different
portions of those salts, and will reject some of them
entirely. Thus, when 100 grains of each of the
follomng salts were dissolved in 10,000 grains of
water, and plants of Polygonum persicaria, Mentha
jnperita, and Bidens camiah'ma were made to grow
in it, they took up six grains of sulphate of soda
(glauber salt), and ten grains of chloride of sodium
(common salt), but not a grain of acetate of lime.

CH. v.] THE SAP. 153

The moistui'e from the soil absorbed by organs
ha\'ing such powers of intro-susception and dis-
crimination passes up vessels situated in the wood,
but especially in the alburnum, impelled by their
contractile power, a power so great that it drives
the sap from the extremity of a cut vine branch
with a force capable of sustaining a column of mer-
cury thirty-two inches and a half high. If a proof
of their contractile power, evidently resembling the
peristaltic motion of the animal power, be required,
Dr. Thomson justly refers for such proof to the
evidence afforded by milky-juiced plants like the
Euphorbia peplis. If the stem of this plant be
divided in two places, the juice flows out at both ends
so completely, that if it be again bisected between the
two former cuts, no more juice will appear. Now it
is impossible that these phenomena could take place
^rithout a contraction of the vessels ; for the vessels
in that part of the stem which has been detached
could not be more than full; and their diameter is
so small, that if that diameter continued imaltered,
the capillary attraction would be more than sufficient
to retain their contents, and, consequently, not a
drop would flow out. Since, then, the whole liquid
escapes, it must be driven out forcibly, and, con-
sequently, the vessels must contract*.

Thus propelled, the sap is distributed along each
' Thomson's Organic Chemistrj', 988.

154 PRINCIPLES OF GARDENING. [CH. V.

branch, to every leaf, and to every finiit of the
plants, gradually acquiring during its passage a
greater specific gravit}^ not only by exlialation, but
by dissolving the peculiar secretions of the plant
formed during its previous year's growth, and de-
posited in the alburnum from the sap, during its
downward course in the inner bark from the leaves.
It is in the leaves that the chief elaboration of the
sap takes place, and those peculiar juices are formed
characteristic of the plant, and which are found
deposited there, or in the bark, or still further altered
in the fruit and seed.

Although the sap increases in specific gi'avity, and
consequently obtains an accession of solid matter
duiing its progress up the stem, yet the matter thus
obtained is not of paramomit importance, nor abso-
lutely controlling the subsequent changes to be
effected, for in such case the greengage would be
altered by its plum stock, and the nonpareil by its
crab stem. So far from this being the case, the
old gardener's maxim, "the graft overruleth the
stock quite " is consonant with truth, though it is to
be taken with some reservation. The graft prevails
and retains its qualities, yet the stock has the power
of influencing its productiveness as well as the
quality of the fruit. Thus, a tree having an expan-
sive foliage and robust growth, indicative of large
sap vessels and vigorous circulation, should never be

CH. v.] THE SAP. 155

grafted upon a stock oppositely characterized, for the
supply of sap Avill not be sufficient: illustrations
are afforded by the codlin never succeeding so well
on a crab, nor a bigoureux on a wild cherrv^ as they
do on freer growing stocks. Indeed, I have no
doubt that exerj tree and shrub succeeds best, is
most productive, and freest from disease, if it be
supplied A\ith sap from roots and through a stem of
its own particular kind. This is evident to common
sense, nor would any fruit-scion be grafted upon a
stock of another species or variety, if it were not
that such stocks are most easily obtainable. For
example, our choicest cherries are, for the reason
assigned, grafted or budded upon the wild cherry ;
and eveiy one must have noticed the frequently
occurring consequence, an enlargement, appearing
like a wen, encircling the tree just above where the
graft and the stock joined; — the growth of the
former ha\ing far outstripped that of the latter. If
a tree could be nourished from its ovm. roots, — from
organs assigned by its Creator as those best suited
to supply the most appropriate quantity and quality
of sap, there can be no doubt that it would be pro-
ductive of benefit ; and this desideratum seems to
be secured by the plan suggested by M. Aibret. In
the instances of apples and pears, and I see no
reason forbidding its adoption to any other grafted
tree, he recommends the grafts always to be inserted

156 PRINCIPLES OF GARDENING. [CH. V.

close to the surface of the gi'ound, or they might
be even rather below the surface, by scooping out
the earth around the stems of the stocks. When
planted out, the lowest extremity of the graft should
be about four inches below the surface. After two
or three years, at the close of June, the soil should
be removed, and just above the junction of the graft
and stock, with a gouge, one-fourth of the bark
removed, by four cuts on opposite sides of the stem.
The cuts being deep enough to remove the inner
bark, and the wounds covered immediately viixh
rich soil, formed of one part putrescent cow-dung,
and two parts maiden loam. If kept constantly
moist with water, and occasionally ^nth liquid
manure, roots will usually be speedily emitted, espe-
cially if the place where a bud once was formed
be thus kept moist beneath the soil.

But the stock has some other influence over the
sap, besides limiting the quantity of sap supplied to
the scion, an influence not only arising from the size
of its vessels, but upon its susceptibility to heat. It has
a further influence over the scion by the sap becoming
more rich, indicated by its acquiring a greater specific
gravity in some stocks than in others, during its
upward progress. The specific gravity of the sap of
a black cluster vine stock on which a black Ham-
burgh had been grafted was, when obtained six
inches from the ground, 1,003, and at five feet from

CH. v.] THE SAP. 157

the ground 1,006; but the same black Hamburgh,
gro^-ing upon its o^vn roots, had specific gravities
at corresponding heights of 1,004 and 1,009. This
increase is of great importance to a tree's gro^^th,
when the quantity of sap passing annually through
its vessels is considered. The exact amount of this,
it is perhaps impossible to discover, but its extent
may be appreciated by the quantity of moisture their
roots ai'e kno^ii to imbibe, and by the facts that
a small \me branch has poui'ed out sixteen ounces
of sap in twenty-four hours ; a birch tree a quantity
equal to its own weight during the bleeding season ;
and a moderate sized maple about two himdred pints
duiing the same period.

The habit of the stock also is of much more im-
portance than is usually considered. If it grows
more rapidly, or has larger sap vessels than the
scion or bud, an enlargement occurs below these ;
but if they grow more rapidly than the stock, an
enlargement takes place just above the point of
union. In either case the tree is usually rendered
temporarily more prolific, but in the case where the
stock grows most slowly, the productiveness is often
of very short duration, the supply of sap annually
becoming less and less sufiicient to sustain the
enlai"ged production of blossom and leaves. This
veiy frequently occurs in the freer growing cherries
when inserted upon the wild species; and still more

158 PKINCIPLES OF GARDENING. [CH. V.

frequently to the peach and apricot upon stocks of
the slower growing plums. It is highly important,
therefore, to employ stocks, the growth of which is as
nearly similar as may be to that of the parent of the
buds or scion.

The earlier vegetation of the stock than of the bud
or graft is also important ; for if these are earliest in
developement, they ai'e apt to be exhausted and die
before the flow of sap has enabled granulation and
union between the faces of the wounds at the junc-
tion to occur. Mr. Knight's observations upon this
point are the results of experience, and are so con-
sonant with the suggestions of science, that I vnll
quote them in his own words without comment :

*' The practice 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 eligible wherever it is wished to
diminish the vigour and growth of the tree, and where
its durability is not thought important. The last
remark applies chiefly to the Moor-park apricot — the
Abricot-peche, or Abricot de Nancy of the French.

" When great difficulty occurs in making a tree,
whether fructiferous or ornamental, of any species
or variety, produce blossoms, or in making its blos-
soms set when produced, success, probably, \\ill be
obtained, by budding or grafting upon a stock nearly
enough allied to the graft to preserve it alive for a

CH. v.] THE SAP. 159

few years, but not pemianently. Tlie pear-tree
affords a stock of tliis kind to the apple, and I have
obtained a heaAy crop of apples from a graft inserted
in a tall pear stock only twenty months pre\dously,
when every blossom of the same variety of fruit in
the orchard was destroyed by frost. The fruit thus
obtained was perfect externally, and possessed all its
ordinary qualities ; but the cores were black and
without a single seed ; and exery blossom, ceitainly,
would have fallen abortively, if it had been growing
upon its native stock. The graft perished the ^\'inter
following.

" My own experience induces me to think very
highly of the excellence of the apricot stock for the
peach or nectarine ; but whenever that or the plum
stock is employed, I am confident the bud cannot be
inserted too near the gromid, if ^-igorous and durable
trees are required.

" The form and habit which a peach-tree of any
given variety is disposed to assume, is very much
influenced by the kind of stock on which it is budded.
If upon a plum or apricot stock, its stem will increase
in size considerably as its base approaches the stock,
and it will be much disposed to emit many lateral
shoots, as always occurs in trees whose stems taper
considerably upwai'ds. Consequently, such a tree
will be more disposed to spread itself horizontally,
than to ascend to the top of the wall, even when a

160 PEINCIPLES OF GARDENING. [CH. V.

single stem is suffered to stand perpendicularly. On
the contrary, where a peach is budded upon a stock of
some cultivated variety of its own species, the stock
and the budded stem remain very nearly of the same
size at the point of junction, as well as above and
below. No obstacle is presented to the ascent or
descent of the sap, which appears to arise more
abundantly to the summit of the tree. It appears,
also, to flow more freely into the slender branches,
wdiich have been the bearing wood of preceding years,
and these extend consequently veiy ^ndely, com-
pared "v\'ith the bulk of the stock and large branches.
" "V\Tien a stock of the same species, A^"ith the grtift
or bud, but of a variety far less changed by cultiva-
tion is employed, its effects are very nearly allied to
those produced by a stock of another species or
genus. The graft, generally, overgrows its stock ; but
the form and durability of the tree generally are less
affected than by a stock of a different species or
genus. Many gardeners entertain an opinion, that
the stock communicates a portion of its own power
to bear cold without injury to the species, or variety
of fiTiit, which is grafted upon it : but I have ample
reason to believe that this opinion is wholly errone-
ous ; and this kind of hardiness in the root alone,
never can be a quality of any value in a stock, for the
branches of every species of tree are much more
easily destroyed by frost than its roots.

CH. v.] THE SAP. 161

Many believe, also, that a peach-tree, when
grafted upon its native stock, veiy soon perishes,
but my experience does not further support this
conclusion, than that it proves seedling peach-trees,
when growing in a veiy rich soil, to be greatly
injured, and often killed, by the excessive use of
the pmning-knife upon their branches, when these
are confined to too narrow limits. I think the
stock, in tliis instance, can only act injuriously by
supplying more nutriment than can be expended ;
for the root which nature gives to each seedling
plant must be well, if not best, calculated for its
support ; and the chief general conclusions which
my experience has enabled me to draw safely, ai'e,
that a stock of a species or genus, different from
that of the fniit to be grafted upon it, can be used
rarely with advantage, unless where the object of
the planter is to restrain and debilitate ; and that
where stocks of the same species ^rith the bud, or
graft, are used, it will be found advantageous, gene-
rally, to select such as approximate in their habits
and state of change, or improvement, from cultiva-
tion, those of the variety of fmit which they are
intended to support^.

The only situation in which I can believe that the
stock of another species can be advantageously em-
ployed, is where the soil happens to be unfriendly
^ Trans. Hort. Soc. of London for 1816.

M

162 PRINCIPLES OF GARDENING. [CH. V.

to the species from which the bud or scion is
taken. This is justified bj my observing that in a
garden so low-lying as to be veiy subject to an
ovei'flow of water, the only pear-trees which were at
all productive were those grafted upon quince stocks
— and the quince is well knovra to endure water
much better than either the apple or pear.

The ascent of the sap, like the circulation of the
blood, is increased in rapidity by an addition to the
temperature in which the plant is vegetating, and
when it is flowing from incisions made in a stem at
various heights from the ground, a sudden reduc-
tion of temperature will cause a cessation of the
flow from the upper wounds whilst it continues from
those below.

These facts indicate most satisfactorily why the
gardener finds his vines, peaches, and other plants
in the forcing-houses injured by keeping them in a
high temperature during the night. It is then, as
in the animal economy, that the individual functions
are renovated by a temporary repose, and if left to
the dictates of healthy nature, the sap, like the blood,
flows at night with a much diminished velocity.

That plants do become exhausted by too unre-
mitting excitement is proved to eveiy gardener who
has a peach-house under his nile, for if the greatest
care be not taken to ripen the wood by exposure to
the air and light during the summer, no peach-tree

OH. v.] THE SAP. 163

wHl be fniitful if forced during a second successive
winter, but -will require a much more increased tem-
perature than at fii'st to excite it even to any ad-
vance in vegetation.

Mr. Barnes, one of the best practical gardeners of
the day, has very justly observed that there is more
judgment required in thoroughly ripening the wood
of forced fmit trees, than in ripening their finiit^.
It is too generally an error to think that when the
fruit is off no further trouble is required ; that the
wood has got to be hardened, — and that no other
care is necessaiy until the times for pruning, forcing,
&c., come round. This is a mistake fraught with
failm*e. "VMien the finiit is off, the whole vegetative
power of the tree is employed, until the leaves begin
to fall, in imbibing and elaborating the sap which is
to be the source from whence next year's growth
and produce are to arise. The hurry some gardeners
are in to expose the forced trees to the full influence
of the air, and allo^ving them to remain without the
shelter of glass at night, after the ariival of frosts,
are all errors, sources of injury and loss. A far
more judicious plan is to promote the lengthened
vigorous vegetation of the trees, by sheltering
them during inclement weather ; by not reducing
the temperature of the house suddenly ; by gi\ing
liquid manure occasionally, and never allowing the

^ Grard. Mag. 604.

m2

164 PRINCIPLES OF GARDENING. [CH. V.

trees to be subjected to a freezing tem2:»erature. It
v,il\ be found, generally, that the forced tree that is
kept longest vegetating healthily after its finiit is
gathered, \\ill be the most vigorous next season.

The experiments of Hai'ting and Munter upon
\ines growing in the open air, and those of Dr.
Lindley upon \dnes in a hothouse, coincide in testi-
fying that this tree grows most duiing the less light
and cooler houi's of the twenty-four. But the hours
of total darkness were the period when the vine
grew slowest. This, observ^es Dr. Lindley, seems
to show the danger of employing a high night tem-
perature, which forces such plants into growing fast
at a time when nature bids them repose ^.

That the elevation of temperature at night does
hurtfully excite plants, is proved by the fact, that
the branch of a vine kept at that period of the day
in a temperature not higher than 50'', inhales from
one-sixteenth to one-tenth less oxygen than a simi-
lar branch of the same vine during the same night
in a temperature of 16°. The exlialation of mois-
ture and carbonic acid is proportionably increased by
the higher temperature.

The e^■idence of the vine's growth being most

rapid during the hours of diminished light, but not

of entire darkness, is curiously coincident with the

observation of Moses, that, though fruit is brought

^ Hort, Trans. 109.

CH. v.] THE SAP. 165

forth by the sun, yet that the plant itself is put
forth by the moon ^.

The sap, after ascending the stem, and being dis-
tributed along the various branches, is poured by
their vessels into their leaves and there undergoes
that elaboration, the phenomena of wliich have been
described in the last chapter. The sap vessels are
ramified from the wood of the branches along the
upper side of the leaf-stalks, are minutely subdi^'ided
so as to form a web resembling lace work, on their
superior sm'faces, and unite at the edge of the leaf
with equally minute vessels, forming a similar web
on then lower sm'faces. These fall into larger
vessels, which return the sap along the under side
of the leaf-stalks into vessels traversing the inner
bark of the branches, stem, and roots, and the sap
is found to be converted, during its elaboration in
the leaves, into the peculiar juices of the plant. The
limpid insipid sap has been converted into the
austere Gallic acid and tannin of the oak; the
acrid perfumed oil of the lemon ; the insipid gum
of the cheriy ; the starchy matter of the potato,
and the pimgent resin of the pine tribe.

In its descent in trees and shrubs it deposits

between the bark and the wood that juice, known as

cambium, from which the year's increase or enlarged

growth is obtained, and a superfluous store is depo-

^ Deut. xxxiii. 14.

166 PRINCIPLES OF GARDENING. [CH. V

sited ready to be communicated to the sap in its
upward course the following spring, as it may be
required for the developement of the next year's
foliage, flowers, and fi-uit. In the potato, dahlia, and
other tuberous-rooted plants, it is deposited in the
tuber ; in the bulbs of the onion and tulip, and in the
fibrous roots of the ranunculus and grasses.

A knowledge of these facts suggested to the
gardener that if the return of the sap were checked
by a ligature so tight as to compress the vessels of
the bark, the fruit above the ligature would be
rendered finer and more abundant. Practice has
shewn that this is the desired result ; and it may
be taken as a rule, that whatever mechanical means
check the downward flow of the sap, causes the
enlargement of buds or the production of new. If it
be practised upon the artichoke, a ligature being
twisted round the stem, about three inches below the
head, its size will be very much increased. If a similar
ligature be passed round the branch of a fiiiit-tree
just previously to the bursting of its buds in the
spring, the fiTiit will set more abundantly and be of
finer growth. -When the fruit is beginning to ripen,
the ligature should be removed, that the refliLx of the
sap to the inferior parts may be less impeded, and
the growth of those parts be, consequently, less
checked. The power to do this renders a ligature
much superior to another mode of producing the

CH. v.] THE SAP. 167

same effect, first introduced in Germany, \dz., by
removing an entire zone of bark, about an inch wide
around the branch to be rendered more fruitful, and
taking care that the bark be completely removed
down to the very wood. This was designated the
ring of Pomona, but it certainly was not auspiciously
received by that deity, for although it renders the
part of the branch superior to the woimd more
fruitful for two or three seasons, yet it renders the
branch unsightly, by the swelling which occurs
around the upper lip of the wound, and is always
followed by disease and unfmitfulness.

If the branch of a tree be cut off; or if an inci-
sion be made so as to remove entirely not only a
section of its bark, but also the alburnum of the
wood beneath it, one bud or more, if the tree be
vigorous, usually will be put forth below the incision.
Lateral vessels are formed from the alburnum, com-
municating with the bud, and ha\dng a similar
return communication with those of the bark, it
speedily enlarges into a perfect branch, with its
necessary leafy organs. If instead of leaNing the
portion of the branch above the incision exposed
to the air it be covered with moist earth, which is
easily effected by the aid of a layering pot, roots will
be protruded from the lips of the wound, and as
these are furnished, like the bud produced from
below, with vessels from the alburnum and bark, it
is evident that the plant has the power of producing

168 PRINCIPES OF GARDENING. [CH. V.

branches or roots accordingly as the medium, air
or earth, renders the production appropriate. This
may be proved in two ways ; for if a gooseberry bush
be trimmed, and then its head is buried in the earth
with the roots exposed to the air, these will put forth
leaves whilst the branches will emit roots. On the
other hand, if a root be induced by the layering
pot in the mode mentioned, and subsequently it is
gradually introduced to the air, by removing the
soil and filling the pot Arith moist moss, and then
by removing the moss and giving only moisture,
it may eventually be left exposed, and will put forth
leaves. The experiment mil succeed with the
codlin, and probably with the June-eating apple.

Buds contain the rudiments of a plant, and it
very early suggested itself to the gardener that they
might be employed advantageously as a means of
propagation ; and budding has now become the most
prevalent mode. In performing the operation, as
the nourishment has to be afforded to the bud from
the albiu-num of the stock Avith which it is brought
in contact, this should not be exposed to the air for
one minute longer than is necessai-y to insert the
pre\dously prepared bud, for if the surface becomes
dry in the slightest degree, vegetation on that part is
permanently destroyed. The alburnum of the stock
only supplies sap, which is elaborated in the bud
and its developed leaves ; and through its bark is
returned the peculiar juice from whence the woody

CH. v.] THE SAP. 169

matter is formed that unites it to the stock. A con-
fused line marks the point of union, but all the
deposit of wood is between that line and the bud,
and is always the same in character as the tree
from which the bud is taken.

A bud, with almost the solitary exception of that
of the walnut, succeeds best when inserted on a
shoot of the same year's growth, and apparently
for the reason that the sap and juice it yields are
most nearly of the same state of elaboration as they
were in the parent of the bud ; and because, as
in the animal frame, repair of injuiy, the healing of
wounds, is always advanced most favourably by the
\^tal energy of youth.

The more mature any part of a plant the less easy
is it excitable ; a branch from which the leaves have
fallen in autumn requires a higher temperature to
induce vegetation, than does a similar branch in the
spring. So is it with a bud ; and, as was suggested
by Mr. Knight, it appears to be occasioned by those
parts having passed into a state of repose ; a de-
creased degree of ^'ital energy occurring preparatoiy
to their -winter sleep. Let no man scoff at the idea
of this vital energy continuing in a bud after a sepa- ^
ration from the parent, for even the head of a poly-
pus may be cut off and grafted, ^\'ithout injuiy, upon
the decapitated body of another. The mature bud

•^-^i-i

S^-^At^.

is consequently always inserted with more success f^i, ^

l^A

^p^e^^e^-iT^

a

170 PRINCIPLES OF GARDENING. [CH. V.

in a stock, the buds of which are less mature, for
it does not commence vegetating until the supply
of sap is abundant, nor until the union between the
bark and alburnum have had time to be completed.
WTien Mr. Knight reversed this comparative state
of the stock and the bud, by inserting immatui'e
buds from a wall peach, upon peach trees in a forcing
house, which had nearly completed their gro^\th for
the season, the buds broke soon after their insertion,
and necessarily perished for w^ant of sufficient
nouiishment.

Whatever promotes an over-luxuriant production
of leaf buds, proportionately diminishes the pro-
duction of flower buds, and the reason is obvious.
A luxuriant foliage is ever attendant upon an over-
abmidant supply of moist nomishment to the roots,
the consequent amount of sap generated is large,
requiring a proportionately increased surface of leaf
for its elaboration, and for the transpiration of the
supei^uous moisture, and as the bud becomes a
branch or a root accordingly as circumstances re-
quire, so does it produce, as may be necessary for
the plant s health, either leaves or flowers. This is
ascertained by the universal fact that a tree or
shi-ub, if headed down, throws out leaf-producing
buds only, but never flower buds; the former are
required for the plant's existence, but the latter
are only needful for the propagation of its species.

CH. v.] THE SAP. 171

A cloud of other testimonies might be produced,
shewing the alteration of vegetable form to accommo-
date the individual to altered circumstances. Place
some aquatic plants in a running stream, the water
cress, for instance, and its submerged leaves will be
very small, thus giving the stream less power to
force them from their rooted hold ; but plant them
in still water, and the leaves are uniform in size.
Momitain plants have, for a similar reason, the
smallest foliage near then- summits, thus giving less
hold to the boisterous ^inds which sweep over them.
Nor is this contrary to reason, as some persons
would have us believe ; for the petals, and even the
minuter parts of eveiy flower, are only different
forms of the same alburnum, parenchyma, and bark,
which takes another shape in the leaf. And it
is only one other instance of that power of adapta-
tion to circumstances so wisely given by God to all
organized beings, which makes the wool of the
sheep become scanty hair m tropical tempera-
tures, and the brown fur of our hare become white
amid the snows of the arctic regions. In the
case of plants, it is familiar to eveiy gardener ; and
he knows, that by differing modes of treatment, he
can make, according to his pleasure, his plants pro-
duce an exuberance of leaves or of flowers, and a
well-known instance is the Solandra grancUflora.
This native of Jamaica had for many years been
cultivated in our hot-houses, had been propagated

17Q PRINCIPLES OF GARDENING. [CH. V.

by cuttings, and eacli plant put forth annually
shoots of surpassing luxuriance ; but no flower had
ever been produced : accidentally one plant was left
for a season in the dry stove at Kew, and this plant
had only a moderately luxmiant foliage, but a flower
was produced at the extremity oi every shoot. It
now blooms every season in our stoves, a drier and
less fertilizing course of treatment being adopted.

Those who ridicule the idea of the leaf, the flower,
and the fruit being only different developements of
the same parts, which take different forms as the ne-
cessities of the plant render them desirable, surely
forget that the leaf naturally takes such vaiying
shapes, as in many instances to have more the ap-
pearance of fruit than of that usually assumed by
foliage. Of this number are many of our fleshy-
leaved plants ; and the tubular vessel at the ex-
tremity of the leaf of the Nepenthes distillatoria . In
the calyx of the strawbeny-spinach, (i^Z/ttwi,) and in
that of the mulberry, the transformation is still more
complete ; for here it actually changes colour when
the flowering is over, becoming the edible part of the
fruit, and inclosing the seed like a genuine berry.

The difference of colour usually existing between
leaves and petals is a veiy unsubstantial distinction.
Many flowers are altogether green ; many leaves are
brilliantly coloured, as those of melampyiiim, ama-
ranthus, begonia, &c. Then again, gi'een leaves be-
come vellow, red, and bro\\ii, in autiunn ; and M.

CH. v.] THE SAP. 173

Macaire has slio\vn, that the chromule, or colouring
matter of leaves and flowers is identical, being only
more oxygenised in the latter.

There are cii'cumstances, there are certain degrees
of nouiishment, of heat, and of light, though our
knowledge is too limited to assign them with arith-
metical precision, which have a tendency to promote
the developement of some vegetable organs rather
than others. Accordingly, as those circumstances
prevail, we find the pistils increased in number at
the expense of the stamens, as was obsen^ed by Mr.
Brown, in the case of the wallflower, and in the Mag-
nolia fuscata; and by M. Pioeper, in the Campanula
Rapunculoides ; or the pistils changed into stamens,
as was noticed by the same botanist in Euphorhia
palustris and Gentiana campestris ; so the petals have
been observed converted to calyx in the Ranunculus
abortivm, and the calyx into petals in Primula caly-
canthema ; petals changed to stamens in the black
currant, and in Capsella bursa pastor is ; and stamens
to petals in double flowers. But all the parts of a
flower have been observed changed into leaves : nor
is this matter of sui^prise, for these are the organs
most necessary for the well-being of a plant ; and
when the production of blossom fails, it is only be-
cause more foliage is required, for the elaboration of a
superabundant sap. Illustrations of these changes
of the floral organs into leaves have been obsen-ed

174 PRINCIPLES OF GARDENING. [CH. V.

by M. de Candolle and others, in a variety of the
gilUflower (Hesperus Matronalis), in varieties of the
anemone, ranunculus, and fraxinella {Dlctamnus
alius) ; in Ranunculus philonotis ; Campanula rapun-
culoides, Anemone nemorosa, Erysimum officinale,
and Scahiosa columbaria.

To promote the production of blossoms, and the
maturity of the fruit they engender, is the usual ob-
ject of pruning and training — confessedly two of the
most difficult practices of the gardener's art ; for if
the branches are too much reduced in number, or
are unfavourably trained, the developement of leaves
is induced, and the production of blossom as propor-
tionately prevented. The reason for this has al-
ready been explained ; and in these pages, devoted to
the science rather than the practice of gardening, I
can add little more than a few hints upon the sub-
ject. The season for pruning must be regulated in
some degree by the strength of the tree ; for al-
though, as a general mle, the operation should not
take place mitil the fall of the leaf indicates that
vegetation has ceased, yet if the tree be weak, it
may be often performed mth advantage a little ear-
lier, but still so late in the autumn as to f)revent the
protmsion of fresh shoots. This reduction of the
branches before the tree has finished vegetating, di-
rects a greater supply of sap to those remaining, and
stores up in them the supply for increased growth

CH. v.] THE SAP. 175

next season. If the production of spurs is the ob-
ject of pmning, a branch should be pinned so as to
leave a stump ; because, as the sap supplied to the
branch vdW be concentrated upon those buds remain-
ing at its extremity, these will be productive of
shoots, though othenvise they would have remaineii
dormant, it being the general habit of plants, first to
develope and mature parts that are furthest from the
roots. It is thus the filbert is induced to put forth
an abundance of young bearing wood, for its fruit
is borne on the annual shoots, and similar treat-
ment to a less severe extent is practised upon wall
fmit.

With regard to the practice of budding, the gar-
dener finds it essential to insure success, that the
bud should be sheltered from the direct rays of the
sun, and the wound, where it joins the stock, from
the air and from wet.

Moist bast is usually employed for closing the
womid of the stock ; but it is far preferable to use
worsted, and over this a coating of the grafting wax,
made according to the following recipe :

Ozs.

Burgundy pitch 1

Common pitch 4

Yellow wax 4

Tallow 2

Nitre (carbonate of potash, powdered) . 1

176 PRINCIPLES OF GARDENING. [CH. V.

These must be melted slowly in an earthen pipkm,
and applied whilst warm. Common diachylon, sold
in rolls by chemists, answers as well as the above.
A laurel leaf, fastened at each end by a ligature round
the stock, so as to arch over the bud, will complete
the arrangement.

If the rays of the smi are not excluded from the
scion for some time after its insertion, it is dried uj)
by the transpiration from it being greater, owing to
the uniting vessels being unformed, than can be sup-
plied by its iutrosusception from the stock. If wet
from the rains and dews be not excluded, the water
from them settles in the wound, and, by mere capillaiy
attraction, is absorbed between the bark of the bud
and the alburnum of the stock, so diluting the sap as
to prevent their organic union. If the air be not
excluded sufficiently, a diyness of the parts, and
consequent collapse of the vessels so as to prevent
the requisite supply of sap is induced, equally fatal
to the desired connexion.

Grafting is a more difficult mode of multiplying
an individual, because it is requisite so to fit the
scion to the stock that some portion of their albur-
nums and inner barks must coincide, otherwise the
requisite circulation of the sap is prevented. No
graft will succeed if not immediately grafted upon a
nearly kindred stock — I say immediately, because it
is possible that by grafting on the most dissimilar

CH. v.] THE SAP. 177

species on which it will take, and then moving it,
with some of the stock attached to another stock
still more remotely allied, that a graft may be made
to succeed, though supplied with sap from roots of
a very dissimilar species. Thus some pear scions
can hardly be made to unite with a quince stock ;
but if they be gi^afted upon a young shoot of a pear
that can be so united to the quince, and this young
shoot be aftei-wards inserted in a Cjuince stock,
they grow as freely as if inserted in a seedling pear
stock.

The reason for this unusual difficulty in the way
of uniting kindred species arises from one or more of
these causes. First, the sap flowing at discordant
periods; secondly, the proper juices being dis-
similar ; or thirdly, the sap vessels being of inappro-
priate calibre.

It is quite certain that the ancient Romans were
skilful gi'afters, for Cato, in his De Re Paisticd, gives
very full and accurate dkections on the art. If
it be true, as he asserts, in common with Varro,
Palladius, Virgil, Columella, Pliny, and other writers,
contemporary as well as more ancient, that they en-
grafted any kind of tree upon any stock, though of an
entirely different genus, as the apple upon the plane,
and the \due or the fig on the cherry, then, indeed, is
there another added to the list of lost arts. But
there is just reason for concluding that the ancients

N

178 PRINCIPLES OF GARDENING. [CH. V.

never possessed the Imowledge thus claimed — not
only because it is denied by modem experience and
science; but because we know that by stratagem
such unions may be made to appeal' as if effected,
and none of the ancient writers on the soil s culture
were practical men. Moreover, in considering this
question, it must not be forgotten that it was denied
that such grafting was possible, even by some of their
contemporaries. Columella, in his treatise on trees,
has a chapter maintaining by argument the possibility
of promiscuous grafting in opposition to some other
authors who denied its practicabiUty. Arguments
would have been needless if there were examples of
success ready for reference.

Inarching differs from grafting only in having
the scion still attached to its parent stem whilst the
process of union -with the stock is proceeding. It is
the most certain mode of multiplying an indi\'idual
that roots or grafts with difficulty, but is attended
with the inconvenience that both the stock and
the parent of the scion must be neighbours. The
most ingenious application of inarching is one
suggested by Mr. Knight. If a fruit-bearing branch
becomes denuded of its leaves above the fruit it
has produced, this either falls, or remains stunted
and deficient in flavour, owing to bemg thus de-
prived of a supply of the elaborated sap or proper
juice. In such case a branch having leaves of the

CH. v.] THE SAP. 179

same or of a neighbouring tree, may be inarched to
the denuded portion of the branch, and the fruit will
then proceed to maturity. Mr. Knight's experiment
was tried upon a peach tree, the fruit of which he
was anxious to taste, but which produced that season
only two peaches, and from the branch bearing which
all the leaves had fallen.

Cuttings for multiplying any individual may in
general be taken either from the stem, branch, or
root, and are, in fact, grafts, which by being placed in
the earth, a medium favourable to the production
of roots, expend their juices in the formation of ra-
dicles instead of aiding the stock to effect that
developement of vessels necessary for their union
to it had they been grafted. A due degree of mois-
ture in the soil is all that is absolutely required
from it by cuttings, for these will often produce
roots if placed in water only. The time for taldng
off cuttings from the parent plant for propaga-
tion, is when the sap is in full acti\'ity, the vital
energy in all its parts is then most potent for the
developement of the new organs their altered circum-
stances require. Well-matured buds are foimd to
emit roots most successfully, and apparently for the
same reason that they are least liable to failure when
employed for budding, viz., that being less easily
excitable, they do not begin to develope until the
cutting has the power to afford a due supply of sap.

n2

ISO PRINCIPLES OF GARDENING. [CH. V.

Therefore, in taking a cutting it is advisable to remove
a portion of the wood having on it a bud, or joint, as it
is popularly called, of the previous year's production.

Many plants can be multiplied by cuttings with the
greatest facility, but others only with the greatest
difficulty, and after every care has been taken to
secure to the cutting eveiy circumstance favourable to
the developement of roots.

Those plants which vegetate rapidly, and delight
in either a moist or rich soil, are those which are
propagated most readily by this mode, and such
plants are the willow, gooseberry, and pelargonium —
a budded section of these can hardly be thmst into
the ground without its rooting.

Cuttings of those plants which grow tardily, or, in
other words, form new parts slowly, are those which
are most liable to fail. These are strildngly instanced
in the heaths, the orange, and ceratonia.

A rooted cutting is not a new plant, it is only an
extension of the parent, gifted with precisely the
same habits, and delighting most in exactly the
same degrees of heat, light, and moisture, and in the
same food.

A cutting produces roots either from a bud or eye,
or from a callus, resembling a protuberant lip, which
forms from the alburnum between the wood and the
bark round the face of the cut which divided the slip
from the parent stem.

CH. v.] THE SAP. 181

If tlie atmospheric temperature is so liigh that
moistm-e is emitted from the leaves faster than it
is suppUed, they droop or flag, and the growth of the
plant is suspended. If a cutting be placed in water,
it imbibes at first more rapidly than a rooted plant
of the same size, though this power rapidly decreases ;
but if planted in the earth, it at no time imbibes so
fast as the rooted plant, provided the soil is similarly
moist ; and this evidently because it has not such an
extensive imbibing surface as is possessed by the
rooted plant : consequently the soil in which a cutting
is placed, should be much more moist than is
beneficial to a rooted plant of the same species ; and
evaporation from the leaves should be checked by
covering the cuttings Avith a bell glass, or a Wardian
case would be still better. The temperature to
which the leaves are exposed should be approaching
the lowest the plant ^^ill endure.

The wanner the soil within the range of tempera-
ture most suitable to the plant, the more active are
the roots, and the more energetically are caiTied on
all the processes of the vessels buried beneath the
surface of the soil: 50'^ for the atmosphere, and
between 65° and 75° for the bottom heat, are the most
effectual temperatures for the generality of plants.

The cutting should be as short as possible con-
sistently ^^•ith the objects in \'iew.

182 PEINCIPLES OF GARDENING. [CH. V.

Three or four leaves, or even two, if the cutting be
very short, are abundant. They elaborate the sap
quite as fast as required, and are not liable to exhaust
the cutting by super-exhalation of moisture.

Cuttings taken from the upper branches of ajjlant
flower and bear fmit the earliest, but those taken
from near the soil are said to root most freely.

Cuttings which reluctantly emit roots, may be
aided by ringing. The ring should be cut romid the
branch a few weeks before the cutting has to be
removed; the bark should be completely removed
do^vn to the wood; and the section dividing the
cutting from the parent be made between the ring
and the parent stem, so soon as a callus appears
round the upper edge of the ring.

The soil is an important consideration. The
cuttings of orange-trees and others which strike
^vith difficulty if inserted in the middle of the earth
of a pot, do so readily if placed in contact ^^ith its
side. The same effect is produced by the end of
the cutting touching an under-drainage of gravel or
broken pots. Why is this ? and my obsen-ations
justify me in concluding that it is because in these
situations — the side and the open-drainage of the
pot — the atmospheric air gains a salutaiy access.
A light porous soil, or even sand, which admits
air the most readilv, is the best for cuttings ; and so

CH. v.] THE S.O*. 183

is a shallow pan rather than a flower-pot, and appa-
rently for the same reason. I have no doubt that
numerous perforations in the bottom of the cutting
pan would be found advantageous for cuttings which
root shyly.

Some plants may be successfully propagated by
means of the leaves ; and among those whose num-
bers are thus most commonly increased are the
Cacti, Gesnerge, Gloxiniae, and other fleshy-leaved
plants. Lately, the suggestion has been revived,
that the majority of plants may be thus propagated,
a suggestion first made by Agiicola, at the commence-
ment of the last century. He states that M. Mandi-
rola had raised a lemon tree in this mode ; and
thence concludes, rather too rashly, " that all exotic
leaves may, at any time, be converted into trees."
Since that was written, in 1721, it is certain, that
plants have been raised from leaves that previously
had been considered totally incapable of such exten-
sion. Thus Mr. Neumann has succeeded with the
Theophrasta latifolia; and, going a step further, he has
even bisected a leaf, and raised a leaf from each half.
Mr. Knight has also recorded, in the Horticultural
Transactions of 182Q, that leaves of the peppermint,
{Mentha piperita,) without any portion of the stem
upon which they had grown, lived for more than
twelve months, increased in size, neai'ly assumed

184 PRINCIPLES OF GAEDENING. [CH. V.

the character of evergreen trees, and emitted a mass
of roots.

That leaves may be made almost universally to
emit roots, there appears little reason to doubt ; for
the same great physiologist had long before proved,
that the roots of trees are generated from vessels
passing from the leaves through the bark ; and that
they never, in any instance, spring from the albur-
num. But the question arises, will they produce
buds '? and, at present, the answer derived from prac-
tice is in the negative. Orange leaves, Rose leaves,
leaves of Statice arborea, have been made to root
abundantly ; but, like blind cabbage-plants, they ob-
stinately refused to produce buds. Dr. Lindley thinks
that a more abmidant supply of richer food, and ex-
posure to a greater mtensity of light, would have re-
moved this deficiency^; and I see every reason for
concurring with so excellent an authority ; for buds
seem to spring from the central vessels of plants,
and these vessels are never absent from a leaf. If
an abundant supply of food were given to a well-
rooted leaf, and it were cut do^\-n close to the callus
from whence the roots are emitted, I think buds would
be produced, for the very roots themselves have the
same power.

* Gardeners' Chronicle, January, 1845.

CHAPTER VI.

THE FLOWER.

The organs of fmctification are absolutely neces-
sar}% and are always producible by garden plants
properly cultivated. They may be deficient in
leaves, or stems, or roots, because other organs may
supply their places; but plants are never incapable
of beaiing flowers and seeds, for without these they
can never fully attain the object of their creation —
the increase of their species.

Eveiy flower is composed of one or more of the
following parts, viz., the calyx, which is usually
green and enveloping the flower whilst in the bud ;
the corolla or petals, leaves so beautifully coloured,
and so delicate in most flowers; the stamens, or
male portion of the flower secreting the pollen, or
impregnating powder; the pistils, or female portion,
impregnatable by the pollen, and rendeiing fertile
the seeds ; and lastly, the pericarp, or seed-vessel.

It is not within the scope of this work to trace
these parts through their various forms, — a research
belonging to the botanist, — but we may profitably
consider Ihek structure.

186 PEINCIPLES OF GARDENING. [CH. VI.

Their organization closely resembles that of the
branch by which they are borne, and they are only
its parts taking other fonns. Tracing, says the
late Mr. Ivnight, the progress of the organization in
the full grown finiits of the apple and pear, I found,
as Linnaeus has described, that the medulla, or
pith, appeared to end in the pistils. The central
vessels diverged round the core, and approaching
each other again in the eye of the fniit, seemed to
end in ten points at the base of the stamens, to
which I believe they give existence. The spiral
tubes, which are, in all other parts, appendages to
these vessels, I could not trace beyond the com-
mencement of the core ; but as the vessels them-
selves extend through the whole fruit, it is probable
that the spiral tubes may have escaped my observation.

xUthough the medulla is traced to the base of the
pistils, the central vessels to the part enveloping
the seed, and to the stamens, and the spiral ves-
sels tlu'oughout the fniit, yet over eveiy part is
extended the parenchyma and epidermis, and the
sap circulates through the entii'e of the flower and
fmit — ascending, being elaborated, and descending —
as regularly as through other parts of the plant.
Coloured infusions may be traced through the ves-
sels in the stem to the fmit, and if a ligature be
passed round a peach or an apple, the enlargement
is greatest above, that is between the ligature and

CH. VI.] THE FLOWEK. 187

the footstalk ; and Mr. Knight succeeded, by inter-
grafting, in proving that the leaf-stalk, the tendril of
the vine, the fniit stalk, and the succulent point of
the annual shoot, may be substituted for each other —
a bunch of gTapes grew and ripened when grafted
upon the leaf-stalk ; and a succulent voung shoot of
the \me, under the same circumstances, acquired a
growth of many feet.

The stamens are the only portion of a flower
which can be removed without preventing the form-
ation of fertile seed, and their loss must be sup-
plied by the introduction to the pistils of pollen
from some kindred flower.

The calyx is not useless so soon as it ceases to
envelope and protect the flower, for the flower-stalk
continues increasing in size until the seed is per-
fected, but ceases to do so in those plants whose
caljTes remain long green if these be removed. On
the other hand, in the poppy, and other flowers
from which the calvx falls early, the flower-stalk
does not subsequently enlarge.

The corulla or petals, with all their varied tints
and perfumes, have more important oSices to per-
form than thus to delight the senses of mankind.
Those bright coloiu's and their perfumed honey
serve to attract insects, which are the chief, and
often essential, assistants of impregnation ; and
those petals, as obsened by Linnaeus, sen-e as

188 PRINCIPLES OF GAEDENING. [CH. VI.

wiugs, giving a motion, assisting to effect the same
impoitaiit process. But tliey have a still more
essential office, for although they are absent from
some plants, yet, if removed from those possessing
them before imj)regnation is completed, the ferti-
lization never takes place. They, therefore, per-
form in such cases, an essential part in the vegetable
economy ; and that they do so is testified by all the
phenomena they exhibit. They turn to the sun
open only when he has a certain degree of poAver.
and close at the setting of that luminaiy ; their
secretions are usually more odorous, more saccha-
rine, and totally differing from those of the other
organs of plants ; and in the absence of light those
secretions are not formed.

The corolla is not always short-Hved, for, although
in some, as the cistus, the petals which open Avith
the rising sim, strew the border as it departs ; so
some, far from being ephemeral, continue until the
fiiiit is perfected. The dm'ation of the petals, how-
ever, is intimately connected with the impregnation
of the seed, for in most flowers they fade soon after
this is completed; and double flowers, in which it
occm's not at all, ai*e always longer endming than
single flowers of the same species. Then, again, in
some flowers they become green, and perform the
functions of leaves after impregnation has been
effected. A familiar example occurs in the Christr

CH. VI.] THE FLOWER. 189

mas rose {Helleborus ni(/er), the petals of wMch are
white, but which become green so soon as the seeds
have somewhat increased in size, and the stamens,
and other organs connected with fertility, have
fallen off.

It is quite tme that some fiiiit ^vill not ripen if
the part of the branch beyond is denuded of leaves ;
but this only shews that those fniits cannot advance
when deprived of leaves as well as of calyx and
corolla — the only organs for elaborating the sap ; and
there are some flowers, as the Daphne mezereon,
autumn crocus, and sloe, that have their flowers per-
fected and- passed away before the leaves have even
appeared.

That the petals perform an important part in elabo-
rating the sap supplied to the fruit, is further proved
by the flower being unable to bloom or to be fertile
in an atmosphere deprived of its oxygen ; and by
their absorbing more of that gas, and evolving more
carbonic acid than even a larger sur&ce of leaves of
the same plant.

So essential is oxygen to the fertility of a flower,
that we shall find, in a futui'e chapter, that the sta-
mens of one plant absorb 200 times their bulk of the
gas at the time of impregnation ; and Saussure found
that double, or imfertile flowers, do not absorb so
much oxygen as those which are productive. The
following table shows the number of volumes of this

190 PEINCIPLES OF GAEDEXING. [CH. VI.

gas inspired by one volume of the flowers and
leaves :

Cheirantlius incanus, 6 p.m. . .

Ditto double-flowered

Poljantlies tuberosa, 9 a.m. .

Ditto double-flowered

TropEeolum majus, 9 a.m. . . .

Ditto double-flowered

Datura arborea, 10 a.m.
Passiflora serratifolia, 8 a.m. .

Daucus cai'ota, 6 p.m

Hibiscus speciosus, 7 a.m.
Hypericum calicinum, 8 a.m. .
Cucurbitamelo-pepo, male flowers,

7 A.M

Ditto female ditto, 7 a.m.
Lilium candidum, 1 1 a.:m. .

Typha latifolia, 9 a.m 9.8 . 4.25

Fagus castanea, 4 p.m 9.1 . 8.]

As the flowers inhale more oxygen than the leaves,
so do they exhale more carbonic acid than these or-
gans ; and, unlike leaves, they pour it forth not only
during the night, but in the sun-light — at least,
Dr. Priestley, Dr. Ingenhouz, and M. Saussure found
this was done by the rose, marigold, and honey-
suckle.

It is upon the oxygen combined with their paren-

By the

By the

flowers.

leaves.

11.0 ,

. 4.0

7.7

9.0 .

, 3.0

7.4

8.5 .

8.3

7.25

9.0 .

5.0

18.5 .

5.25

8.8 .

7.3

8.7 .

5.1

7.5 .

7.5

12.0 .

6.7

3.5

5.0

2.5

CH. VI.] THE FLOWER. 191

chyma, that the coloui' of a petal depends ; foj sul-
phiu'ous acid, (the fume aising from a bmiiing match,)
which has a most powerful affinity for oxygen, destroys
the hue of all coloui-ed flowers, though it leaves that of
white flowers unchanged. Mr. Smithson's experi-
ments, and those of M. Schluber, seem to indicate
that the coloming matter of flowers and fruits is fun-
damentally blue — rendered red by acids or the ad-
dition of oxygen, or yellow by the presence of an al-
kali or the subtraction of oxygen. Mr. Smithson
says, that the coloming matter of the violet is the
same in the ruddy tips of the daisy, geranium, blue
hyacinth, hollyhock, lavender, and vaiious plums, in
the leaves of the red cabbage, and in the lind of the
salmon radish. The acid which causes the red tint
seems to be usually the carbonic.

No seed ever attains the power of germinating,
unless the pollen from the stamens in the same, or
some nearly-allied flower has reached and impreg-
nated its pistils. This was known to the most an-
cient of the Greeks ; for Herodotus relates that the
cultivators of the date (Phoenix dactilifera) brought
the flowers of the barren plants, which they called
the males, and attached them to the finiitful trees,
that theii' produce might not fall without attaining
matmity, a phenomenon explained both by Anaxa-
goras and Empedocles, who flourished in the fifth
century before the Christian era, by claiming for

192 PRINCIPLES OF GARDENING. [CH, VI.

vegetables the same sexuality as animals. Subse-
quent researches have established the fact beyond
the reach of reasonable doubt.

In favourable seasons, when genial warmth and
gentle winds prevail, impregnation is readily affected
by the plant's own provision. The pollen is never
shed from the anther of the stamen, until the stigma
of the pistil is fully developed ; and this soon withers
after the contact. The gaping of the stigma when
the pollen is about to fall, and at that time only,
may be observed in the heart's-ease [Viola tricolor) ;
and every morning, on the summit of the stigma of
the Jacobean lily [Amaryllis forviosissima), a drop of
viscous hquid protrudes, to be re-absorbed as regu-
larly at noon, with the pollen shed upon it, until
impregnation is completed — the drop then exudes no
more. But, as was first observed by Sir J. E. Smith,
the process, as it is effected in the berberry [Berheris
vulgaris), is the most curious. In the flowers of this
shrub the six stamens, spreading moderately, are
sheltered under the concave tips of the petals, until
some extraneous body, as the feet or tnmk of an in-
sect searching for honey, touches the inner part of a
filament near the bottom. The irritability of that
part is such, that contracting and thrown forward
spasmodically, it dashes the anther, full of pollen,
against the stigma.

The above are only a few of the modes by which

CH. VI.] THE FLOWER. 193

plants are, by their own powers, enabled to effect the
impregnation of then- seed ; but where there is any
more than ordinar}' difficulty, theu' all-pro^ddent
Creator has invariably provided efficient assistance.
The agents usually called in are insects : these, in
their search after honey and wax, visit the inmost re-
cesses of flowers, and bear from the anthers to the
stigma, and from flower to flower, the fecmidating
dust. Here, too, I may remai'k upon another in-
stance of that Providence, which makes all things
fitting and appropriate ; for those who have made the
bee their study relate, that though this insect does
not confine itself to one species of flower, yet it re-
stricts its visits dming each ramble to that kind
which it first ^'isits. How this facilitates impregna-
tion is obvious, when it is remembered, that no
flower can be fecundated but with pollen from a
kindred species.

The most remarkable instance of the agency of in-
sects, and of the aitifice, if the tenn be permissible,
employed to render them efficiently semceable, oc-
curs in the Aristolochia Clematitis ; and is thus de-
scribed by Willdenow^ The corolla is tubular, ter-
minating in a globiilai' extension at the base. The
tubular part is lined with stiff hairs, pointing down-
wards, like the wii*e entrances to some mouse-traps.
The globular part contains the pistils, surrounded by
the stamens ; but the latter bemg veiy much the

o

194 PRINCIPLES OF GARDENING. [CH. VI.

shorter, and as the flower always holds itself erect,
the pollen cannot reach the stigmas, but would fall
to the bottom of the corolla, if it were not for the
agency of a particular insect. This diminutive vi-
sitant is the T'qmla pennicornis, which entering the
tube in search of honey, in vain tries to repass the
phalanx of hairs which easily yielded to it an en-
trance ; in its search for a way of escape, it carries
the pollen to the stigma, and impregnation being ef-
fected, the hairs lose their rigidity, sink to the side
of the tube, and the prisoner easily escapes.

The efficient agency of insects suggested that in
hot-houses from whence they are almost totally
excluded, other artificial means might be adopted
with success to render fertile flowers that had
hitherto failed in producing seed. One of the
earliest instances on record of the experiment being
tried with a prosperous result was on the Abroma
augusta, which had bloomed unfertilely for several
years in a hot-house at Berlin. The gardener by
the aid of a hair pencil applied a little pollen to the
stigma, and for the first time perfect seed was pro-
duced, from which plants were raised. This practice
is now very generally adopted to all plants cultivated
under glass from which a produce of either fruit or
seed is desired ; for fruit rarely attains its full size if
the seeds within it are unfertilized. Thus the gar-
dener always finds the advantage of using the camel

4

CH. XI.] THE FLOWERS. 105

hair pencil to apply pollen to the stigmas of his
forced melons, cucumbers, cherries, and peaches.

That seed can be rendered fertile by the agency
of other flowers than their o^Yn parent has long
been known, for it had come within the obseiwation
of the IsraeHtes, some three thousand four hundred
years now past, as may be gathered from Deutero-
nomy, xxii. 9 ; Jeremiah, ii. -21 ; and Le^^ticus,
xix. 19 ; but it was not rendered useful knowledge,
until the late President of the Horticultui'al So-
ciety, Mr. Knight, commenced his experiments in
1787. Mr. Bradley, seventy years before, had de-
monstrated that hybrid plants may be grown, par-
taking of the qualities of both their parents ; but to
Mr. Knight first occurred the happy thought that
the good characteristics of one parent might thus be
employed to correct deficiencies which would other-
wise occui- in the offspring of another parent of the
same species. Since his time, this system of cross-
breeding has been practised by gardeners upon
almost every genus of plant that comes under their
care, and by its agency the size, colour, and form
of flowers have been improved and varied ; the mag-
nitude and flavour of fruits have been increased;
and tender plants have been made to bring forth
a hardy progeny.

Bradley had only carried out the suggestions of
others, for both Lawson and Evelyn, half a century

o2

196 PRINCIPLES OF GARDENING. [CH. VI-

previously, had related that new apples ad infinitum
might be raised from kemjels ; and Bacon, whose
penetrating eye pierced the most dark recesses
of nature, had observed that " The compounding
and mixture of plants is not found out, which, never-
theless, if it be possible, is more at command than
that of living creatures ; wherefore, it were one
of the most noble experiments touching plants to
find this out ; for so you may have a great variety
of new plants and flowers yet unkno^ai. Grafting
doth it not : that mendeth the fruit, or doubleth the
flower, but it hath not the power to make a new
kind." My own observations, and those of others,
justify the following statements, as affording some
guide to the raiser of varieties.

1. The seed-vessel is not altered in appearance by
impregnation from another plant ; therefore, no
hasty conclusion of failure is justified by that want
of change.

2. The colour of the future seed, not of that first
hybridized, seems to be most influenced by the male
plant, if its seeds and flowers are darker than those
of the female. Mr. Knight found, that when the
pollen of a coloured blossomed pea was introduced
into a white one, the whole of the future seeds were
coloured. But when the pollen of a white blossom
was introduced to the stigma of a coloured blossom,
the whole of the future seeds were not white. Capt.

i

CH. VI.l THE FLOWER. 197

Thurtell, from his experiments on the pelargonium,
also informs me, that he has always fomid the colour
and spot of the petals to be more influenced by the
male than by the female parent. Indeed, all ex-
perience proves that the progeny usually, though not
invariably, most resembles in colour the male parent.

3. Large stature and robustness is transmitted to
the offspring by either parent. It does not abso-
lutely matter, for obtaining this characteristic,
whether it be the male or female w-hich is large ;
but Mr. Knight generally found the most robust
female parent produced the finest offspring.

4. Capt. Thurtell, from lengthened obser^-ation
and experiment, ha§ ascertained that the form of the
petals follows most closely that of the female parent.

5. Mr. Knight says that the largest seed from the
finest fruit that has ripened earliest and most per-
fectly should always be selected. In stone fruit, if
two kernels are in one stone these give birth to
inferior plants.

6. The time which elapses before seedlings attain
a bearing age is very various. The pear recjuires
from twelve to eighteen years; the apple, five to
thirteen ; plum and cherry, four to five ; \dne, three
to four ; raspberiy, two ; and the strawberiy one.

7. The most successful mode of obtaining good
and very distinct varieties is to employ the pollen
from a male in a flower grown on another plant than

19B PRINCIPLES OF GARDENING. [CH. VI,

that bearing the female parent. To avoid previous
and undesired impregnation, the anthers in the
female parent, if they are produced in the same
flower with the pistils must be removed by a sharp-
pomted pair of scissors, and the flower enclosed in a
gauze bag to exclude insects, mitil the desired
pollen is ripe. Another effectual mode of avoiding
undesii'ed impregnation is biinging the female parent
into flower a little earlier than its congeners, and re-
moving the anthers as above described ; the stigma
will remain a long time vigorous if unimpregnated.

8. Although the fertility of all the seed in one
seed-vessel may be secured by applying pollen only
to one style, even where, there are several, yet the
quantity of pollen is by no means a matter of in-
difference. Koelreuter found that from fifty to sLxty
globules of pollen were required to complete the
impregnation of one flower of Hybiscus Syriacus :
but in Mirabilis Jalapa and il/. longijiora, two or
tliree globules were enough-^, and in the case of
pelargoniums, Capt. Thurtell says, two or three
globules are certainly sufficient.

9. M. Haquin, a distinguished horticulturist at
Liege, has impregnated flowers of the Azalea mth
pollen kept sL\ weeks ; and Camellias -svith pollen kept
sixty-five days. He gathers the stamens just pre-
viously to the anthers opening, wraps them in writing

^ Willdenow, 323.

CH. VI.] THE FLOWER. 199

pajDer, places them in a warm room for a day, collects
the pollen they emit, and presences it in sheet lead
in a cool diy place. M. Godefroy suggests that two
concave glasses, like those employed for vaccine "\-inis,
would be better. The globules of the pollen must
not be crushed. M. Haquin thinks the pollen of
one year mil be effective if preserved imtil the year
following. Mr. Jackson of Cross Lanes Xiu-ser}',
near Bedale, says, he has found the pollen of the
Rhododendron Smithii tigrinum retain its fertilizing
power even for twelve months.

1(J. It is easy to discern whether impregnation has
been effected, as in such case the stigmas soon wither.
The stigmas which have not received the pollen
remain for a long time green and vigorous.

" By the aid of the Stanhope lens," obsen^es Capt.
Thurtell, in a letter now before me, " 1 fancy I can
discover the seed of the pelargoniimi being closed
over in the space of four hours after impregnation."

11. When double flowers are desired, if a double
flower should chance to have a fertile anther or two,
these should be employed for fertilization, as their
offspring are almost sure to be very double.

\'Z. Many analyses of the pollen of various plants
have been made by chemists, ^^ithout throwing
any light upon hybridizing. M. Grotthus found the
components of twenty-six grains of the pollen of the
tulip were : —

200

PRINCIPLES OF GARDENING.

[CH. VI.

Vegetable albumen . . .
Malates of lime and magnesia
Malic acid .,,...
Malate of ammonia . . .
Colouring matter ....
Nitrate of potash ....

20.-25
3.50
1.00

1.25^

26.00

13. Superfoetation has been doubted, but as it
occui's in the dog, we see no reason for disbelieving
its possibility in plants. Capt. Thurtell thinks it
may be done by the bee introducing mmgled pollens
at the same instant. Then why not, if a similar
mixture is inserted by the camel's hair pencil of the
cultivator ? I think it quite possible, that different
seeds in the same pericarp, may be fertilized by pollen
from more than one different male species ; but
nothing but the strongest evidence will convince me
that the same seed can be effectually fertilized by
more than one pollen. M. Foulard gravely asks us
to believe that his Rosa perpetuosissima had four
male parents, the Bengal, the tea, the hundred-
leaved, and the noisette !

14. Plants nearly related, that is, closely similar
in the structure of their various parts, are those only
which will immediately impregnate each other ; but
it is impossible, at present, to say what families of

* Schweigger's Jouni. xi. 281.

CH. VI.] THE FLOWER. QOl

plants may or may not be brought into fertile union
through intermediate crosses. A very short time ago
the azalea and rhododendron were thought incapable
of such union, but this opinion is now exploded, for
rhododendron ponticum has been fertilized with the
pollen of azalea sinensis, and the progeny, between
that evergreen and this deciduous shiiib, is the pre-
viously unknown phenomenon a yellow rhododendron.
Though such unions may be effected, I entirely agree
with Mr. Knight in anticipating that the progeny will
be mules, incapable of producing offspring. Jt is
quite time that many plants, said by botanists to be
distinct species, have between them produced fertile
seeds, but I incline decidedly to the opinion, that this
fact demonstrates that they are not distinct species, but
only deviations from a common origin. For example,
the peach and almond are considered distinct species
by botanists, yet the fruit of both and of the nectarine
have been borne spontaneously by the same tree. " I
cannot," says Mr. Knight, " by any means admit that
plants ought to be considered of originally distinct
species, merely because they happen to be found to
have assumed somewhat different forms or colours in
an uncultivated state. The genus Prmius contains the
P. ai'meniaca, P. cerasus, P. domestica. P. insititia,
P. spinosa, P. sibirica, and many others. Of these
I feel perfectly confident that no art will ever obtain
offspring (not being mules) between the Pnuius

202 PRINCIPLES OF GARDENING. [CH. VI.

armeniaca, P. cerasus, and P. domestica ; but I do
not entertain much doubt of being able to obtain an
endless variety of perfect offspring between tlie
P. domestica, P. insititia, and P. spinosa; and still
less doubt of obtaining an abundant variety of offspring
from the P. armeniaca and P. sibirica. The former,
the common apricot^, is found, according to M. Reg-
nier, in a wild state in the oases of Africa. It is there
a rich and sweet fruit of a yellow colour. The fruit
of the P. sibirica, seeds of which came to me last year
from Dr. Fischer of Gorenki, is, on the contrary',
I understand, black, veiy acid, and of small size : but
nevertheless if these apparently distinct species will
breed together, and I confidently expect they ^rill,
without giving existence to mule plants, I shall not
hesitate to pronounce these plants of one and the
same species, as I have done relatively to the scarlet,
the pine, and the chili strawberries. Botanists may
nevertheless, if they please, continue to call these
transmutable plants, species; but if they do so,

* The early period at which the apricot unfolds its flowers leads
me to believe it to be a native of a cold climate : and I suspect
the French word abricot, the English aprico^, and the African
berrikokka, to have been alike derived from the Latin word
praicocia, which the Romans (there is every reason to believe)
pronounced praikokia, and which was the term applied to early
varieties of peaches, which probably included the apricot. The
Greeks also wrote the Latin word as I suppose the Romans to
have pronoxmced it. — Hardouins ed. of Pliny, lib. 15. sec. xi.

CH. VI.J THE FLOWER. 203

I think they should find some other term for such
species as are not transmutable, and which will either
not breed together at all, or which breeding together
give existence to mule plants.

" If hybrid 2)lants had been foiined as abimdantly
as Linnaeus and some of his followers have imagined,
and such had proved capable of affording offspring, all
traces of genus and species must snrely long ago have
been lost and obhterated; for a seed vessel even of a
monogynous blossom often affords plants which are
obviously the offspiing of different male parents ; and
I beheve I could adduce many facts which would
satisfactoiily prove that a single plant is often the
offspiTQg of more than one, and, in some instances,
of many male parents. Under such circumstances,
every species of plant which, either in a natural state
or cultivated by man, has been once made to sport
in varieties, must almost of necessity continue to
assume valuations of fonn. Some of these have often
been found to resemble other species of the same
genus, or other varieties of the same species, and
of permanent habits, which were assumed to be
species ; but I have never yet seen a hybrid plant
capable of affording offspring, which had been proved,
by any thing like satisfactory- eridence, to have
sprung from two originally distinct species ; and
I must therefore continue to believe that no species
capable of propagating offspring, either of plant or

204 PEINCIPLES OF GARDENING. [CH. VI.

animal, no-^ exists, which did not come as such
immediately from the hand of the Creator."

Hybridizing, aided by cultivation, gives birth to
those splendid objects of the gardener's care, gene-
rally designated double flowers, which are such beau-
teous ornaments of our borders and parterres. To
the uninitiated it seems incredible that the double
moss-rose should be a legitimate descendant from
the briai' ; neither do the flowers of the Fair maid of
France appear less impossible derivatives from those
of the Ranunculus platanifoUus ; nor Bachelor's
buttons from the common buttercup, yet so they
are. Double flowers, as they are popularly called,
are more correctly discriminated as the full flower,
the multiplicate flower, and the proliferous flower.

The full-flower is a flower with its petals aug-
mented in number by the total transformation into
them of its stamens and its pistils. One-petiilled
flowers rarely undergo this metamorphosis ; but it is
very common in those having many petals, as in the
carnation, ranunculus, rose, and poppy. But this
is not the only mode in which a flower becomes full :
for, in the columbine {Aquilegia) it is eff'ected in
three difl'erent ways, \az., by the multiplication of
the petals to the exclusion of the nectaries ; by the
multiplication of the nectaries to the exclusion of
the petals ; and by the multiplication of the necta-
ries whilst the usual petals remain. Piadiated

CH. VI.] THE FLOWER. 205

flowers, such as the sunflower, dahlia, anthemis,.
and others, become full by the multiplication of the
florets of their rays to the exclusion of the florets of
their disks. On the contraiy, various species of the
daisy, matricaria, &c., become full by the multiplica-
tion of the florets of the disks.

The multiplicate flower has its petals increased
by the conversion of a portion of its stamens, or of
its cal}^, into those forms. It occui's most fre-
quently in poh^etallous flowers. Linnaeus gives
the only instances I know of the conversion of the
calyx into petals, and these are to be observed in
the pink [Dianthus caryophyllus) and a few of the
Alpine gi'asses.

A proliferous flower has another flower, or a shoot
produced from it. This is most strikingly exem-
plified by that variety of the daisy popularly known
as The-hen-and-chickens. It occurs also more rarely
in the ranunculus, pink, marigold, and hawk-weed.
A leafy shoot often appears in the bosom of the
double-blossomed cherry, anemone, and rose.

The influences regulating the production and
developement of leaves and flowers are these : — If
an excess of water to the roots, or too little light to
the superior parts of plants be appUed, they produce
an increased surface of leaf, and few or no flowers ;
for it is a wise power given to them by their
Creator, that those parts shall increase in size.

206 PRINCIPLES OF GARDENING. [CH. VI.

which circumstances render most necessary'. An
excess of moisture requires an increased transpira-
tory surface, as in the case of Solandra grandiflora
before mentioned.

This knowledge that flower-buds and leaf-buds are
mutually convertible is no novel discovery, much less
a visionaiy theory, for, as long ago as the beginning
of 1817, the late Mr. Knight thus expressed the
results of his experience, when writing to the Lon-
don Horticultural Society relative to the pruning of
peach-trees : — " The buds of fmit-trees, which pro-
duce blossoms, and those which afford leaves only,
in the spring, do not at all differ from each other, in
their first organization, as buds. Each contains the
rudiments of leaves only, which are subsequently
transformed into the component parts of the blos-
som, and, in-some species, as the fruit also." And
he then proceeds to state his experience that leaf-
buds of the apple and pear have been thus trans-
formed, and of his ha\'ing succeeded in obtaining
every gradation of monstrous transfonnation, adding,
that " eveiy bunch of grapes commences its forma-
tion as a tendril, it being always within the power of
every cultivator to occasion it to remain a tendril,"
either by removing a considerable portion of the
leaves, or reducing the temperature and light to
which the vine is exposed.

A deficiency of light decreases the decomposing

CH. YI.] THE FLOWER. '207

power of the leaves. For this reason the best glass
should always be employed in the sashes of the
hothouse, conservatory, and other stnictures of the
forcmg department. But the benefit sought for is
frustrated if that glass be not constantly well
cleansed. Tlie best glass, if dirty, allows fewer
rays of light to pass through than inferior glass if
kept bright.

A thorough cleansing should be given both to
the outside and inside twice annually, during the
first weeks of March and of October, and a third
cleansing, on the outside only, at the end of June.
In proportion to the deficiency of hght, does the
plant under glass become, in the gardener "s phrase-
ology, drawn. That is, its surface of leaves be-
comes unnaturally extended, in the vain effort to
have a suf&cient elaboration of the sap effected by
means of a large suiface exposed to a diminished
light, for which a less surface would have been
sufficient if the light were more intense. The
plant with this enlarged sui'face of leaves becomes
unfniitful, the sap being expended in their produc-
tion, which should have been appropriated to the
formation of fruit.

Mr. Williams made some experiments intended
to illustrate this point, and he found that varieties
of the vme, when grown under white, or crown
glass, under green glass and in the open air, had

^08

PRINCIPLES OF GARDENING.

[CH. VI.

the diameters of their leaves, in inches, altered as
in the following table : —

Name.

1 White. ! Green.

1 1

Open Air.

\Yhite Muscat . . .
Malmsey Muscadine

Syrian

White Sweet Water . .
Black Hamburgh . .
Wliite Frontignac . .
WTiite Muscadine . .

8

?

' 6

! 8

1 6

6

l--i
12

9
131
11
11

6

6

b
6

A due supply of moisture, but rather less than
the plant most delights in when the production of
seed is the desu-ed object, a superabundant supply
of decomposing organic matter to its roots, and an
exposui'e to the greatest possible degree of sun-
light, are the means successfully employed to pro-
mote that excessive developement of the petals
which characterize double-flowers.

By these means a greater amount of sap is sup-
plied to the flower than the natural extent of petal
can elaborate, and, following the laws of nature
already specified, those parts required for the extra
elaboration are developed at the expense of those
not demanded for the pui-pose. The chief office of
tlie petals is this preparation of nourishment for the
stamens, and, for the most part, they fade together,
usually enduring until impregnation has been effected,

i

CH. VI.] THE FLOWER. 209

or has altx)getlier failed. In double flowers, too, as
was observed by the late Sir J. E. Smith, the
corolla is much more durable than in single ones of
the same species, as anemones and poppies, because,
as he conceived, in such double flowers the natural
functions not being performed, the vital principle of
their corolla is not so soon exhausted. Advantage
may be taken of this to prolong the duration of
flowers by cutting away the pistils, or stamens,
whichever are least conspicuous, with a sharp pair of
pointed scissors.

The transmutation of the stamens into petals is
most readily traceable in the water-lily {NymphcEa
alba) and the common China rose. Sometimes, as
is justly observed by a writer in the Gardeners
Chronicle, sometimes a stamen is half changed, and
then half an anther is found on one side, while the
other is expanded into the thin texture of the petal.
Sometimes the anther seems to struggle with the
petal for mastery, and resolutely maintains its
ground at the point while the filament as resolutely
expands, till at last it rises above the anther on
each side, as if to smother that w^hich it cannot
otherwise destroy.

Although an abundant supply of nourishment is
absolutely necessaiy for the production of double
flowers, it is quite as certain that such supply will
not, of a certainty, cause their appearance — there.

p

210 PRINCIPLES OF GARDENING. [CH. VI.

must be some tendency in the parent thus to sport,
otherwise the superfluity of food will not have the
desired influence. That abundance of nourishment
is necessary appears from the fact, that if the double-
daisy, or the double-narcissus be grown in a poor
soil they speedily produce none but single flowers,
yet, if they again be restored to a rich soil, they
may, with care, be made to produce an unnatural
profusion of petals. Mr. D. Beaton's estimate of a
double flower is original. He says that cultivation
having enlarged all the parts of a plant, the consti-
tutional vigour thus obtained is transferred to the
next generation, and to some of the seedlings, in a
measure, even greater than that possessed by the
parent. Extraordinary supplies of nourishment,
under favourable circumstances, invigorate still fur-
ther the improved race, and so on through many
generations. During this time cultivation produces
the very opposite of double-flowers, and Mr. Beaton
thinks it would continue to do so if it were possible
to keep up every member of each generation to the
same degree of health and vigour; but accidents
and diseases overtake some of the plants, and double-
flowers are the produce from these decrepits. Cul-
tivation, according to this idea, is only indirectly
the cause of double-flowers, and these a retrograde
step from a liigh state of developement.

CH. VI.] THE FLOWER. 'ill

Whether my own opuiion or Mr. Beaton's be
correct, it is quite certain that in practice the plants
from which double-flowered varieties are sought
must be kept in the highest state of developement
by supplpng them abundantly with all the as-
sistants to ^dgorous growth, and when the seed-
vessels are formed these should be reduced in num-
ber, in order to make the seed in these remaining
as large and perfect as possible. In the course of a
few generations seedlings appear having flowers, with
an excess of petals and seeds being obtained from
these, or from other flow^ers impregnated by their
stamens, and the same high cultivation continued,
the excess of petals increases, and becomes a perma-
nent habit.

CHAPTER VII.

THE FRUIT AND SEED.

When the blossom begins to fade, " tlie joy of the
plant" is departing, but other beauties and parts
more important to the animal world are advancing
to succeed the decapng inflorescence. The fruit
and the seed are then entering on the season of
maturity ; will soon offer to the palate some of our
most delicious luxuries, nor will beauty of colour be
altogether wanting. "The ripened tints of autumn
are equally pleasing with the bloom of spring, and
the colours of the peach and apricot, the plum
and cherry, are in nothing inferior to the blossom
which preceded them."

The petals, stamens, pistils, and frequently the
calyx having performed their destined functions,
fall and leave the oyslyj or embiyo seed-vessel, re-
maining attached to the parent plant. This in-
creases in growth and becomes the fruit, which title
is not restricted merely to such as ai-e edible, but
includes every matured ovary with its contents, and
which matured ovary, in botanical language, is kno^ii
as the pericarp. This takes various distinct forms.

CH. VII.] THE FRUIT AND SEED. '213

and as ail are subjects of interest to the gardener,
eacli may liave advantageously a separate notice.

1. The capsule is diy, woody, or membranous,
containing one or more cells, as in the poppy, cle-
matis, ash, and paeony.

'2. The siliqua or pod, is long, diy, and has two
valves separated by a linear receptacle, along the
edges of which are ranged the seeds alternately.
Instances are hi the stock, wall-flower, and cabbage.

3. The legume has tsvo dr}" long valves united by
a seam at their edges, having no dividing receptacle
as in the pod, but with the seed attached to one
edge, as in the pea, bean, laburnum, and other legu-
mmous plants.

4. The drupe or stone fruit is usually soft and
fleshy, not separating into valves ; but enclosing a
woody nut to which it is attached, as in the peach,
plum, olive, and cherry; but sometimes more diy,
as in the almond and cocoa nut.

5. The pome, or apple, is usually fleshy like the
drupe, but enclosing a capsule \\'itli several seeds,
instead of a nut, as in the common apple and pear.

6. The berry is pulpy and has its seed embedded
in its substance as in the asparagus, currant, goose-
beiTy, strawberiy, raspbeny, potatoe, orange, melon,
cucumber, and medlar.

7. The strobile or cone is scaly, tough, and woody,
formed of the catkin or calyx which has become

214 PRINCIPLES OF GARDENING. [CH. YII.

indurated. It is the seed-vessel of the pine tribe,
the plane tree, and comptonia.

Though thus vai-jdng in form, they have all one
common office, the protection and maturing of the
seed they contain. To effect this they require a
due supply of sap as well as of the peculiar juice of
the parent plant ; for they make no further advance,
if the entire wood^ be cut through below them, so
that they are only attached to the parent by a strip
of bark ; neither will they advance though fully
supplied with sap, if the peculiar juices are cut off
from them by removing the leaves that are above
them on the branch. The loss of such leaves, as
stated in a preceding page, may be supplied by in-
arching to the denuded branch one stUl retaining its
foliage. I have also shewn that the application of a
ligature to a peach or apple, shews by the enlarge-
ment on one side of the ligature, that the sap really
circulates through them.

Yet each fruit has a peculiar elaboration of its owii
to perform, for though the fluids afforded by the
branches and leaves be nearly similar, yet each fruit
differs from another in fragrance and flavour: six
different varieties of the peach and of the apple
budded upon the same branch, still retain unaltered
their times of ripening, and their distinctive colours
and flavours. Now the processes going on at dif-
ferent periods of a fruit s growth are very opposite

CH. ^TI.] THE FRUIT AND SEED. 215

in their character. During their green and growing
state they are usually converting gummy matter into
an acid ; but during ripening they, as commonly, are
convertincr an acid into su^ar.

To convert gum or mucilage into tartaric acid, as
in the early growth of the grape, oxygen in excess
should be absorbed, for their relative components

stand thus :

Grum. Tartaric Acid.

Carbon . . . 42.23 . . 24.05

Oxygen . . . 50.84 . . 69.32

Hydrogen . . . 6.93 . . 6.63

100.00 100.00

They might therefore be expected to absorb more
oxygen than the leaves, and this is actually the case,
for though a vine branch will continue to vegetate
in a glass globe hermetically sealed, yet the grapes
upon it will not increase in size unless oxygen gas
be from time to time admitted. The same phe-
nomenon occm^s duiing the ripening of the grapes ;
oxygen has to be absorbed during the conversion of
the tartaric acid into sugar, but a larger volume of
carbonic acid has to be evolved, and this is coincident
with the result of well established experiments,
uniformly testifying that carbonic acid is given out
abundantly by ripening fruit. " Six equivalents of
tartaric acid," saysLiebig, " by absorbing six equiva-

216 PRINCIPLES OF GARDENING. [CH. VII.

lents of oxygen from the air, form grape sugar,
separating at the time twelve equivalents of carbonic
acid."

This, however, is not the only decomposition taking
place whereby sugar is formed in ripe fruit, but there
is sufficient reason to believe that its mucilage and
starchy constituents are converted into saccharine
matter by the combined agency of warmth and the
acids. It is thus that apples are rendered so much
sweeter by baldng, and M. De Candolle states that
the pulp of apple dissolved in water with a vegetable
acid is converted into sugar ; that gummy matter
obtained from starch and mixed with tartaric acid
aided by warmth effects a similar transmutation ;
and M. Kirchoff proved long since that starch,
digested at a gentle heat ^\ith diluted sulphuric acid,
became sweet.

During the ripening process, both of fruit and seed,
all plants give out more carbonic acid and less oxygen
than during the earlier stages of their growth, and
thus is given a reason why room plants should be
removed when once past their meridian vigour.

Now to effect these changes, to ripen perfectly,
that is to generate its best proportions of sugar and
aroma, every plant requires a certain amount of sap,
light, heat, air, and moistui'e ; and how these are best
secured to them, so far as training and the atmosphere
around them is concerned, may be here appropriately

CH. VII.]

THE FRUIT AND SEED.

217

considered. These circumstances, so far as the roots
and leaves were also concerned, have heen examined
in previous chapters.

Sap. — The more rapidly and consequently the
greater the amount of this poui-ed into the branches,
the greater suiface of leaf is required for its elabora-
tion ; and, as the plant has power given it of increas-
ing most freely, and even at the expense of others,
those organs which are most necessary, the leaves of
such abundantly supplied branches are increased
both in number and size, whilst the blossom is pro-
portionately dimmished in number, or is obliterated
entirely. A plant propels its sap with greatest force
perpendicularly, so much so that the sap rising in a
vine branch growing in a right line from the root with
a force capable of sustaining a column of mercuiy
twenty-eight inches high, will, if the branch be bent
do^\Ti to a right angle, support
barely twenty-three inches, and if
bent a few degrees below the hori-
zontal, the column sustained will
not be more than tv/enty one
inches. This is the reason why, at
such angles, gardeners find the
trained branches of their wall trees
rendered more productive of blos-
soms, and furnished with a smaller
smface of leaves. A similar effect

*218 PEIKCIPLES OF GARDENING. [CH. VII.

is produced by training a branch in a waving form,
for two thirds of its length are placed horizontally as
in the accompanying outline. Other modes of inter-
rupting the rapid flow of the sap by checking its
return has been noticed in a previous chapter.
Among which modes are ligatures and wounds round
the bark.

Light and heat are so combmed, and so equally
essential for the ripening of fniit, that they may be
considered conjointly. They are both diminished in
ungenial summers, and in such, finiit ripens indiffer-
ently, or not at all, being, if it does ripen, deficient in
colour, as well as flavour. In our latitudes, however,
warmth is more deficient than light for the matui'ing
of exotic plants — therefore, by securing to them a
higher temperature, we have the peach, the melon,
the mango, and the pine-apple as richly flavom-ed,
and even superior to the excellence they attain in
their native climes.

It must be remembered, in considering this branch
of our subject, that all cooling is occasioned either by
the heat being conducted from a body by a colder, which
is in contact with it, or by radiating from the body
cooled, though circumstances accelerate or retard the
radiation, and whatever checks the radiation of heat
from a body keeps it warmer. For example, — a ther-
mometer placed upon a grass-plat, exposed to a clear
sky, fell to 35°, but another thermometer witlun a

CH. VII.] THE FRUIT AND SEED. 219

few 3'ards of the preceding, but with the radiation of
the rajs of heat from the grass checked by no other
covering than a cambric pocket-handkerchief, decHned
no lower than 42°. Xo difference of result occurs,
whether the radiating surface be parallel or per-
pendicular to the horizon ; for when the mercury in
a thermometer, hung against an openly exposed wall,
fell to 38", another thermometer against the same
wall, but beneath a web of gauze stretched tightly at
a few inches distance, indicated a temperatui'e of 43°.

These results explain the beneficial operation of
apparently such slight shelter to our wall-fruit when
in blossom. A sheet of canvas, or of netting, pre-
vents the direct radiation of heat from the wall — the
cooling goes on more slowly, and is not reduced to
that of the exterior air at night before the return of
day begins to re-elevate the external temperature.

The colder the body surrounding another body, the
more rapid the radiation from the latter ; for it is a
law of heat that it has a constant tendency to be
diffused equally, and the greater the diversity of
temperatui'e between two bodies in contact with
each other, the greater is the rapidity with which the
progi'ess towards equihbrium goes on. This is one
reason why a temperatm'e of 32° with a brisk wind
attending it -^dll injure plants to a far greater extent
than a temperature many degrees lower with a still
atmosphere, but it is aided by the operation of

^20 PRINCIPLES OF GARDENING. [CH. VII.

anotlier law of heat, viz. that aeriform bodies convey
it from a cooling hodj, as a wall or a tree, hy an actual
change in the situation of their own particles. That
portion of the air which is nearest to the cooling
body is expanded, and becoming specifically lighter,
ascends, and is replaced by a colder portion. This,
in its turn, becomes heated and dilated, and gives
place to another colder portion, and thus the process
goes on imtil the cooling body is reduced to the
same temperatui'e as the air. In a still atmosphere
this goes on slowly, the air in contact with the wall
and tree rises very gradually as it imbibes warmth
from them, but if there be a brisk wind, a constant
current of air at the lowest temperature then occur-
ing is brought in constant contact with them, and
the cooling is rapid in accordance ^^ith the law of
equilibrium just noticed. A shelter of netting, or
even the sprays of evergreens are of the greatest
service in preventing the sweeping contact of cold
air at such times.

It is not altogether immaterial of what substance
netting is formed. Worsted is to be preferred, not
only because it is the most durable, but because it is
the best preventive of a wall's coolhig. I have found
the thermometer under a hemp net sink during the
night from two to four degrees lower than that under
a net of worsted, the meshes being small and of equal
size in both nets. This can only be because worsted

CH. VII.] THE FRUIT AND SEED. 221

is a known worse conductor of heat than hemp, and
not absorbing moisture so easily, is not so liable to
the cold always produced by its drying.

Snow is a protection to plants from the three fore-
going reasons — it prevents heat radiating from them —
protects them from the chilling blasts — and is one of
the worst conductors of heat. I have never known the
surface of the earth below a covering of snow colder
than 3-2°, even when the temperature of the air above
has been 28°. A similar protection, though less effec-
tual, is afforded by straw.

Strange as it may appear, yet it is nevertheless
true, that a shelter is more beneficial in preseiwing
the temperature of trees, when from three to six
inches from them, than when in immediate contact
with their surfaces. When a woollen net was
suspended four inches from the wall, on which a
peach-tree was trained, the thermometer fell very
slowly, and the lowest degree it reached was SS'^;
when the same screen was twelve inches off, it
fell to 34° ; and when draAvn tightly over the tree,
it barely kept above 32", the temperatiu'e of the
exterior air. When at twelve inches from the wall,
it permitted the too free circulation of the air;
and when in immediate contact with the polished
bark of the peach, perhaps another law of cooling
came into operation. That law is, that polished
surfaces radiate heat slowest. Thus if two glass

222 PRINCIPLES OF GARDENING. [CH. YII.

bottles, equal in size and thicknes of glass, and of
the same shape, be filled with warm water, and one
of the bottles be covered with an envelope of fine
muslin, this bottle will give out heat to the sur-
rounding air with much greater rapidity than the
other bottle : so that in a given time the bottle with
the envelope will be found colder than the one which
has no covering.

Shelters such as the preceding, or the slighter
agents, sprays of evergreens, placed before the
branches of wall-trees, or other plants, as already
noticed, operate beneficially in another way — check-
ing the rapid passage of the air over them — such
passage is detrimental in proportion to its rapidity,
for the more rapid it is, the greater is the amount
of evaporation, and consequently of cold produced.
Mr. Daniell says, " That a surface which exhales
100 parts of moisture when the air is calm, exhales
125 parts when exposed to a moderate breeze,
and 150 parts when the wind is high. During
all high winds, but especially when blowing from
points varying between the east and the south — for
they are the driest in this country — the gardener will
always find shelters beneficial to his plants whether
in blossom or with fruit in its first stages of growth,
for these winds cause an evaporation much exceeding
in amount the supply of moisture afforded by the
roots." In March, such shelters are much required.

CH. VII.] THE FRUIT AND SEED. 223

for the winds are then violent and diy even to a
proverb ; but it is during the days of its successor,
April, that sets in the only periodical wind, known
in this island. It comes intermittingly, and A-sith
variable force, from points ranging from e. to n.e.,
and is one of the most blighting winds we have. It
continues until about the end of the second week in
May, though often until its close ; and it is a good
plan to have the trees during the whole period, by
day as well as by night, protected. This periodical
wind is occasioned, probably, by Sweden and Norway
remaining covered with snow, whilst England is
some 20° or more warmer; an upper current of warm
air is consequently flowing hence to those countries,
whilst a cold under current is rusliing hither to
supply its place. This wind, and its consequent
cold weather, is so regular in its appearance, that
in Hampshire and some other parts of England the
peasantry speak of it as " the blackthorn winter," that
bush being in blossom durmga part of its continuance.
Colour has very considerable influence over a body's
power of absorbing heat. If a thennometer on a hot
summer's day be exposed to the sun, it will indicate a
temperature of about 100°, but if the bulb be black-
ened with Indian ink, or the smoke of a candle, it
wiU rise from ten to twenty degrees higher. The '
reason for this is, that the polished surface of the
glass reflects some of the sun's rays, but the blackened

224 PRINCIPLES OF GARDENING. [CH. VII.

surface absorbs them all. Blue absorbs all but the
blue rays — red all but the red — green and yellow,
all but those of their own name, and white reflects
all the rays. The lightest coloured rays are the
most heating, therefore light coloured walls, but
especially white, are the worst for fruit trees. The
thermometer against a wall rendered black by
coal tar rises 5° higher in the sunshine than the
same insti-ument suspended against a red brick
structure of the same thickness ; nor will it cool
lower at night, though its racUating power is increased
by the increased darkness of its colour, if a proper
screen be then employed. The elevation of the
temperature of a dark coloured fniit compared
with that of a lighter coloured of the same kind is
often remarkable, as in the instance of the muscle
plum and greengage, growing on standard trees. But
there are other causes than colour for fmit often
remaining of a cool temperature m the hottest
weather, and among these causes is then- covering.
Ever}^ one must have noticed the delicious coolness
of the peach s flesh compared with that of the nec-
tarine grovm on the same wall and in the same
bright sunshine ; and the reason of this is, that the
dense woolly cuticle of the first, hke all other dowiy
coveiings, is one of the worst conductors of heat.
Similar coverings are found on Mexican and Cretan
plants which have to endure exposui*e to a torrid
temperature.

CH. VII.] THE FRUIT AND SEED. 225

Despite all the contrivances for rencleiing more
effectual the natural sources of temperature offered
by oui' climate, these can never obtain duiing the
twelve months, by night as well as by day, a heat
sufficient for the successful cultivation of most tro-
pical plants. Hence arises the necessity for employ-
ing hothouses and other shelters of that description.
In these, fuel has to be employed to elevate the
temperatm'e, and some transparent medium as a
covering, to prevent the radiation of the heat thus
obtained, as well as to shut out the colder atmo-
sphere, without excluding the hght. But few words
^Yill suffice relative to the fuel employed, this being
so generally coal ; yet there are some facts ascer-
tained by the chemist, which afford guides to the
gardener in the selection of his fuel, as well as tests
to enable him to judge whether he employs it eco-
nomically.

The heating quality of the different coals known
in Great Britain are in the following proportions :

Scotch Cannel 199

Lancashire Wigan 196

Yorkshire Cannel 188

Newcastle (best Wallsend) . . . 169

Gloucestershire (Forest of Dean) . 108

Welsh (common) 25

Hence, if the Scotch Cannel coal cost 19s., when the

nv Tiarrl ona} \

3.13

226 PRINXIPLES OF GARDENING. [CH. VII.

Gloucestershire could be had for 10s. per chaldron,
the latter would be no cheaper ; for the heating
powers of the first is as 199 to 108 of the latter.
In other words, 108 chaldrons of Scotch would
afford as much heat as 199 chaldrons of Stafford-
shire.

The following are the quantities of the fuels
named, required to heat eight gallons of water, from
52'^ to 2 12°:

lbs.

Caking coals 1.2

Splint, or hard coal
Cannel coal .

Cherry, or soft coal 1.5

Wood of lime 3,10

beech 3.16

elm 3.52

" oak (chips) 4.20

ash 3.50

maple 3.00

" service 3.00

cherry 3.20

" fir 3.52

poplar 3.10

" hornbeam 3.37

Peat (average, not compressed) . . 7.6

Charcoal of w^ood 1-52

j " peat 3.28

CH. VIT.] THE FRUIT AXD SEED. 2*27

The specific heat of water being 1, and that of at-
mospheric air 0.00035, or o-rV*)^^' ^ *'^^ quantity
of fuel which will heat a cubic foot of water one de-
gree be multiplied by 0.00035, the product will be
the quantity of fuel requh'ed to heat a cubic foot of
air one degree., and twenty times that quantity vn\\
heat it twenty degrees, thhty times will heat it
thuty degrees, and so on. Xow 0.0075 lbs. of best
coals will heat a cubic foot of water one degree, there-
fore, 0.0000026-25 lbs. of coal vdW heat a cubic foot of
air one degree.

It is essential to good and profitable fuel that it
should be free from moisture ; for unless it be dry,
much of the heat which it generates is consumed in
converting that moisture into vapour ; hence the su-
perior value of old, dense, dry wood, to that which is
porous and damp. A pound of dry will heat thirty-
five pounds of water from 32° to 212', but a pound
of the same wood in a moist or fresh state, vdW not
similarly heat more than twenty-five pounds. The
value, therefore, of different woods for fuel is
nearly inversely as their moisture ; and this may
be readily ascertained, by finding how much a
pound weight of the shavings of each loses by
drying, during two hours, at a temperature of
212^2

^ C. Johnson's Fanner's Encyc. p. 512.

q2

228 PRINCIPLES OF GARDENING. [CH. VII.

The above are the average of results obtainable in
a common well-constiTicted furnace. By a compli-
cated form of boiler, perhaps, a small saving of fuel
in obtaining the same results may be effected ;
but it mil be foimd, generally, that the original
cost of appai'atus, and the current additional ex-
penses for repairs will more tlian exceed the economy
of fuel.

Flues for imparting heat to hot-houses are, for the
most part, superseded by either tanks or hot-water
pipes ; but where retained, the top should be formed
of iron plates, these admitting the heat most readily
into the house, and consequently requiring a less
consumption of fuel. If it be desirable to have a
covering for the flues that will retain the heat
longer, as when the fires are made up at night, this
may be readily accomplished, by putting a row of the
thick square paring tiles on the top of the whole
length of the flue, an hour or two before the houses
are finally closed.

The power of retaining heat, or, in other words,
of cooling slowly and gradually, wliich renders the
covering of paving tiles desirable, renders the tank
system of heating by hot-water still more efficient.
It is a scientific operation throughout, and will
be best appreciated by a reference to the annexed
diagram, borrowed from Mr. Rendle's pamphlet,

CH. VII.]

THE FRUIT AND SEED.

a-29

entitled the " Tank System of communicating
Heat:"

It is a law of fluids, that their hottest portions
rise to the surface of the containing vessel, and the
coldest portions as invariably subside to the lowest
suiface ; because heat makes them expand, and con-
sequently diminishes their specific gravity ; and the
abstraction of heat makes them contract, and, as con-
sequently, increases that gravity. When the boiler
A and the tank g are filled with water, as well as
their connecting pipes, and a fire is lighted in B, the
hottest portions rise to the top, pass up c, flow along
the surface of g, and getting cool, sink to its bottom,
and passing down d, enter A again at the lower part,
to be once more heated and pass through the same

230 PEINCIPLES OF GARDENING. [CH. YII.

circulatory system. A very small boiler will speedily
raise the heat of the water, in a very large tank, to
1 80 degrees ; and if this heat be imparted late in
the evening, it will retain its heat but little di-
minished until the morning. The smoke, by means
of a flue, /, may be made to impart heat to the house,
by passing through it, or may at once enter the chim-
ney or pipe attached to the summit of the boiler.

Hot water in a tank is superior to the same source
of heat in pipes, because it is not liable to freeze ;
and it is preferable to steam, because its heating
power continues, until the whole mass of water is
cooled down to the temperature of the house, whereas
steam ceases to be generated as a source of heat the
moment the temperature falls below 212°.

If steam be employed, Mr. Tredgold has given
the following niles for calculating the surface of pipe,
the size of the boiler, the quantity of fuel, and the
quantity of ventilation required for a house thirty
feet long, twelve feet mde, with the glass four feet
high in front ; vertical height of the glass roof eight
feet ; length of the rafters foiu'teen feet ; height of
the back wall fifteen feet. The surface of glass
in this house will be 720 feet supei-ficial, viz." 540
feet in the front and roof, and 180 feet in the ends.
Now, half the vertical height, 7 ft. 6 in., multiplied
by the length in feet, and added to Ij time the

CH. VII.] THE FRUIT AND SEED. 231

area of glass in feet, is equal to the cubic feet of air
to be wanned in each minute, when there are no
double doors. That is 7.5 x30 + 1| X 720 = 1305
cubic feet. But in a house ^ith wooden bars and
rafters, about -J^th of this space will be occupied
with wood-work, which is so slow a conductor of heat,
that it will not suffer a sensible quantity to escape,
therefore 130 feet may be deducted, leading the
quantity to be warmed per minute ==1175 cubic
feet.

To ascertain the surface of pipe required to warm
any given quantity of air, multiply the cubic feet of j
air to be heated per minute by the difference be- j
tween the temperature the house is to be kept at, 1
and that of the external air in degrees of Fahren- \
heit s thennometer, and divide the product by 2.1,
the difference between 200, which is the temperature
of the steam pipes, and the temperature of the
house ; the quotient will be the surface of cast iron
pipe required.

Now in the house, the dimensions of which are
above given, if the lowest temperatm^e in the night
be fixed at 50°, and lO'^ are allowed for winds,
and • the external air is supposed to be at zero,
or 0 of Fahrenheit, then 1175 multiplied by 60,
and the product divided by 2.1, the difference
between 200 and 60, will give us the quotient 236
=to the surface of pipe required. Now the house

•23'2 PRINCIPLES OF GARDEXINO. [CH. VII.

being thirty feet long, five pipes of that length, and
five inches in diameter, will be about the proper
quantity.

If hot water be employed instead of steam, the
following proportions and information, ol>tained from
Mr. Rendle, may be adopted confidently as guides.
In a span roof propagating house forty feet long,
thirteen feet broad, seven feet high in the centre,
and four feet high at the two fronts, having a super-
ficial surface of glass amounting to 538 square feet,
Mr. Rendle has a tank eighty-three feet long,
running round three sides of the house, four feet
mde and about eight inches deep, and consequently
capable of containing nearly 300 cubic feet of hot
water, though only half that quantity is used. This
is closely approaching to the size pointed out accord-
ing to Mr. Tredgold's formida. The mean tem-
perature of a hot water tank will never be much
above 160 \ so that for the sized house mentioned by
that slvilful engineer, the divisor must be '2.1 times
the diff"erence between 160' and 60", which gives as
the quotient 335 cubic feet.

The tank in Mr. Rendle s propagating house is
built of bricks lined ^vith Roman cement, and if the
temperature at the time of lighting the fire be 90",
the temperature of the atmosphere of the house 67°,
and the temperature out of doors 50°, the quantity
of small coal, or breeze, required to raise the tern-

CH. Tir.] THE FRUIT AND SEED. 233

perature of the -water to 10,6^ is SSlbs. In twelve
hours the water cools, after the fire has been ex-
tmgiiished, from 125° to 93°.

"WTien steam is employed, the space for steam in
the boiler is easily found by multiplying the length
of the pipe in feet, by the quantity of steam in
a foot in length of the pipe.

T . • J- Decimal parts of

Intenor dia- ■>■ r ^ r

r • a cubic toot ot

meter ot pipe ^ . ,

. . xf ^ steam m eacn

in inches. r ^ r •

toot ot pipe.

1 00545

U 01225

2 02185

2i 034

3 049

4 0873

5 1363

6 1964

7 267

8 349

9 442

10 545

In the above noticed house the length of pipe,
5 inches in diameter, is 150 feet, and these mul-
tiplied by 1.363=20.5 cubic feet of steam; and as
the pipe will condense the steam of about one cubic
foot and one third of water per hour, therefore the
boiler should be capable of evaporating 1| cubic feet

234 PRINCIPLES OF GAEDENIKG. [CH. VII.

of water per hour, to allow for unavoidable loss. In
the extreme case of the thermometer being at zero,
the consimiption of coals to keep up tliis evaporation
will be 12|lbs. per hour^.

These calculations are all founded upon the sup-
position that the condensed water is returned to the
boiler whilst hot ; but if this cannot be effected,
then one-twelfth more fuel will be required. The
boiler for the supply either of steam or hot- water
should be covered ^^ith the best available non-con-
ductor of heat, and this is either charcoal or sand.
A case of brick-work, -with pulverized charcoal be-
tween this and the boiler, is to be preferred to any
other. A boiler ha\ing a surface of seventy feet
exposed to the air in a temperature of S'Z^ requires an
extra bushel of coals to be consumed per day, to
compensate for the heat radiated and conducted
from that surface ; and the smaller the boiler the
greater is the proportionate waste.

The surface of the pipes should be painted black,
because sui'faces of this colour give out more heat
in a given time than any other.

Solar light is essential to the ripening of all fruit ;
it ^^•ill not ripen in the dark, and the greater the
light's intensity and the longer its daily endiu'ance, the

* For these rules I am chiefly indebted to ]\Ir. Tredgold's
valuable work on " Warming and Ventilation/' which will well
repay the gardener for the perusal.'

CH. VII.] THE FRUIT AND SEED. 235

sweeter and the higher is the fniit's flayoiir. Xo
fiiiits are so luscious as those grown witliin the
tropics, and the fruits of the temperate zone are excel-
lent in proportion to the brightness of its seasons.

That light is essential in causing the colour of
the leaves and other parts of plants has been noticed
already ; and it aids the ripenmg process of fruit in
a similar manner, to convert their acid and mucila-
ginous constituents into sugar ; much carbon and
hydrogen have to be got rid of, and this is effected, if
light be admitted, by the evolution of cai'bonic acid
and watery vapour. How light operates in pro-
moting this and other decompositions which are
effected by the vegetable organs is at present a
mysteiT, but so it is ; and the gardener promotes its
access as much as lies within his power by removing
overshadowing leaves, by employing the best glass in
his hot-houses, and by havmg their interior whitened,
for white surfaces reflect all the rays of light back
upon the objects those smfaces enclose.

The angle formed by the glass roof of the hot-house
is of veiy considerable importance, because rays of
light are reflected in proportion to the obliquity with
which they fall upon any given smface ; those which
fall upon it pei-pendicularly from the source of light
pass through \vith very slight diminution, but those
falling upon it in a slanting or oblique direction are
reduced in number in proportion to the obliquity of

236

PRINCIPLES OF GARDENING. [CH. VII.

that direction. To ascertain how a glass roof may
be constructed so as to receive the greatest number
of rays of light from the sun pei-pendicularly or
near to perpendicularity at any given time of the
year, it is necessary to know the latitude of the
place where the hot-house is erected, and the sun's
declination at the period when most light is required.
The latter information may be obtained from most
almanacks, and if it be subtracted from the latitude,
the remainder will be the angle desired.

If London be the place, and May the 6th the
time about when the most light is desired, the
latitude being .51° 31' and the smi's declension then
16° 36' north, therefore the roof ought to slope at an
angle of 34° 55^

CH. Yll.] THE FRUIT AND SEED. 237

In latitude 52°, Mr. Knight found, from lengthened
experiment, that the best angle is about 34°, con-
sidering the services of a hot-house through the year ;
and to illustrate this, he gave the preceding diagram.

About the middle of May, the elevation of the sun
at noon, corresponds nearly with the asterisk a ; in
the beginning of June, and early in July it will be
vertical at *&, and at midsummer at c, only six
degrees from being vertical. The asterisk d points
out its position at the equinoxes, and e its position
at midwinter ^

If the best glass be employed it is an excellent
plan to have it put double in each sash, an interval
of half an inch being left between the two panes, and
a small hole at the comer of the inner one to pre-
vent the glass being broken by the expansion or con-
traction of the air between. This confined air is one
of the worst possible conductors of heat, keeping the
house from being rapidly cooled during the coldest
weather ; and thus is effected a very great economy
of fuel, whilst little or no extra interruption is
caused to the entrance of light.

Moisture. — Every fruit-bearing tree requires a
larger supply of moisture during the growth of its
fruit, and in proportion to its abundance, than at
any other season, and for the obvious reason that, as
the fruit is a reservoir of accumulated and elaborated

'' Hort. Society's Trans.

238 PRINCIPLES OF GARDENING. [CH. VII.

sap, that sap requires for its formation an extra
supply of moisture, inasmuch as that its chief in-
gredient is "water.

Though ahundance is required it must not be
excessive, for if this does occur, the sap poured into
the fruit is so abundant that it cannot elaborate it
sufficiently fast ; and instead of exhalmg the super-
fluous moisture, its cells enlarge, and the fruit
greatly increases in size, but at the expense of its
flavour. In veiy wet seasons the supply of moisture
is so great that the cells of the parenchymous or
fleshy part of the fruit swells faster than its epidermis
can expand, and this consequently bursts. This is
continually occurring to the plum and cherry. When
this happens to the greengage, and its extremely sax:--
charine juice is exposed to the air, vinous fermentation
speedily takes place, and an appreciable quantity of
spirit of wine (alcohol) is formed, a discovery to which I
was led by observing, what every gardener must have
observed, that wasps, after feeding plentifully upon
the juice that has been thus exposed, usually fall to
the ground stupified and inebriated.

Finiit has also the power of imbibing water through
the pores of its epidermis, a power taken ad^'antage
of by those gooseberiy growers, who aim at size
rather than flavour. They keep the calyx end of the
berry dipped in a saucer of water.

Fruit for storing should be gathered before it is

CH. YII.] THE FRUIT AND SEED. 239

qiiite matiu'e, for the ripening process, the formation
of sugar, with its attendant exhalation of carbonic
acid and water, goes on as well in the fruit-room as in
the open air, at the season when the functions of the
leaves have ceased, and the fmit no longer enlarges.
In gathering fruit every care should be adopted to
avoid bruising, and to this end, in the case of apples,
pears, quinces, and medlars, let the gatheiing basket
be lined throughout -with sacldng, and let the con-
tents of each basket be carried at once to a floor
covered with sand, and taken out one by one, not
poured out, as is too usual, into a larger basket, and
then again from this into a heap ; for this systematic
mode of inflicting small bruises, is sure to usher in
decay, inasmuch as that it bursts the di^dsional
membranes of the cells containing the juice, and
this being extravasated speedily passes from the
stage of spirituous feimentation to that of putrefac-
tion. To avoid this is the principal object of fruit
stoiing, whilst, at the same time, it is necessary that
the fruit shall be kept firm and juicy.

Now it so happens that the means required to
seciu'e the one also effects the other. To presence
the juiciness of the fruit, nothing more is required
than a low temperature and the exclusion of the
atmospheric air. The best practical mode of doing
this, is to pack the fniit in boxes of perfectly dried
pit-sand, employing boxes or bins, and taking care

240 PEINCIPLES OF GAEDENING. [CH. VII.

that no two apples or pears touch. The sand should
be thoroughly dried by fire-heat, and over the upper-
most layer of fi-uit the sand should form a covering
nine inches deep.

Putrefaction requires indispensably three contin-
gencies,— moisture, warmth, and the presence of
atmospheric air, or at least of its oxygen. Now
burying in sand excludes all these as much as can be
practically effected. The more minutely divided into
small portions animal or vegetable juices may be, so
much longer are they preserved from putridity, —
hence one of the reasons why biniised fi*uit decays
more quickly than sound — the membranes of the
pulp dividing it into little cells are niptured, and a
larger quantity of the juices are together ; but this
is only one reason, for bruising allows the air to
penetrate, and it deranges that inexplicable vital
power which, whilst uninjured, acts so antiseptically
in all fruits, seeds, and eggs. Bruises the most
slight, therefore, are to be avoided ; and instead of
putting fruit in heaps to sweat, as it is ignorantly
termed, but in fact to heat, and promote decay, fiiiit
should be placed one by one upon a floor covered
witli diy sand, and the day follo^ving, if the air be
dry, wiped and stored away as before directed. Fruit
for storing should not only be gathered during the
midday hours of a dry day, but after the occurrence
of several such.

CH. VII.] THE FEriT A^'D SEED. 241

Although the fniit is stored in sand, it is not best
for it to be kept there up to the very time of using,
for the presence of light and air are necessary for the
elaboration of saccharine matter. A fortnight's con-
sumption of each sort should be kept upon beach,
birch, or elm shelves, with a ledge all round to keep
on them about half an inch in depth of dry sand.
On this the fruit rests softly, and the vacancy caused
by every day's consumption should be replaced from
the boxes as it occui's. If deal is employed for the
shelving, it is apt to impart a flavour of turpentine
to the fruit.

The store-room should have a northern aspect, be
on a second floor, and have at least t^wo "windovrs to
promote ventilation in diy days. A stove in the
room, or hot -water pipe mth a regulating cock, is
almost essential, for heat will be required occasionally
in veiy cold and in damp weather : the windows
should have stout inside shutters. Sand operates
as a preservative, not only by excluding air and mois-
ture, but by keeping the fruit cool, for it is one of the
worst conductors of heat, and moreover, it keeps car-
bonic acid in contact with the fruit. All fruit in
ripening emits carbonic acid, and this gas is one of
the most powerful preventives of decay known.

The temperature of the fruit-room should never
rise above 40°, nor sink below 34° of Fahrenheit's
thermometer, the more regular the better. Powdered

242 PRINCIPLES OF GARDENING. [CH. VII.

charcoal is even a better preservative for packing
fruit than sand, and one box not to be opened until
April, ought to be packed with tliis most powerful
antiseptic. If it were not from its soiling nature,
and the trouble consequent upon its employment.
I should advocate its exclusive use. I have kept
apples perfectly sound in it until June.

It is not unworthy of observation, that the eye or
extremity fuithest from the stalk is invariably the
first to ripen. This is most perceptible in pears,
especially in the Chaumontelle. That end, therefore,
should be slightly embedded in the sand, as thus ex-
cluding it from the light, checks its progress in
ripening.

The perfecting of seed is a process very similar to
the matui'ation of fniit — indeed, for the most part,
whatever advances the one promotes the other. The
chief difference is that, if seed be the exclusive object,
less moisture and rich food should be supplied to the
plants, inasmuch as that an abundant supply of
these increases excessively the developement of the
succulent part of the fniit, and yet tlie vessels from
this to the seed ^ritlier and render it abortive. A
similar defective fertility occurs if the female parent
in animals is over-stimulated and fat. In the gai'-
dener s department it is most apparent in the pine
apple.

CHAPTER VIIL

THE DISEASES OF PLANTS.

De. Good, the distingiiislied medical wiiter, has
remarked, that the morbid affections to -^-hich the
vegetable part of the creation is liable, are almost
as numerous as those which render decrepid and
destroy the animal tribes. It would be difficult,
perhaps, whatever system of nosology is followed,
to place a finger upon a class of animal physical
diseases, of which a parallel example could not be
pointed out among plants. The smut, which ravages
our com crops ; the mildew, which destroys our
peas ; the curl that is annually infecting more
destructively our potatoes; the ambur}% or club-
root, to which oiu' turnips, and other species of
brassica, are liable ; the shanking, or ulceration,
which attacks the stalks of our grapes, are only
a few of the most commonly observed diseases to
which the plants we cultivate are liable.

Numerous as are the vegetable diseases, and de-
structive as they are to the interests of the culti-
vator, yet no subject connected with his art has
obtained so little attention, and never was even
trivial attention followed by benefit less important.

r2

244 PRINCIPLES OF GARDENING. [CH. VIII.

The reason of this deficiency of benefit is not dif-
ficult of detection.

Common experience teaches us that diligence
and perseverance, directed by judgment, are the
essential preliminaries of success : and these are
more particularly requisite in examining, in search-
ing for the causes of the diseases and decay of
vegetables, because we have fewer guides, less as-
sistance from the vegetable affected, than Tve have
from a diseased animal ; fewer symptoms marking
the commencement, or seat of the evil. Yet where
is the cultivator who ever took a fraction of the
care, or a decimal of the attention to discover the
cause, progress, or remedy of one disease, some-
times bringing destruction upon his harvests, as he
does to detect the disorder or discover the panacea
for some miserable pig ?

The subject is one beset mth difficulties, but it
is commensurately important. Difficulty, however, is
veiy distinct from impossiljility ; and the importance
of the research is a stimulus to exertion. Human
knowledge being acquired by observation and expe-
rience, by conversing mth the things about us,,
—that is by noticing them attentively, and re-
cording and reflecting upon the facts they reveal, —
eveiy gardener should do this, especially whenever
he finds his crops diseased. He should record from
what soil he obtained his seed ; how and in what

CK. Vni.] THE DISEASES OF PLANTS. *245

weather it was committed to the ground : the subse-
quent culture of the crop : the crops which preceded
it; the thermometrical and hygrometrical registries
of the seasons through which it has grown; the
treatment of the soil ; its drainage ; with the ma
nures employed ; the wateiings ; the piiming ; and
any other miscellaneous observations his owa com-
mon sense may dictate. If this were done, vegetable
medicine would soon advance more in one year
towai'ds that state of reasoned knowledge, which
alone desen^es the name of science, than it has done
during the last century.

As observations multiply, the adjutant sciences,
chemistr}^ and physiology, will contribute and apply
their improved stores of information, and if but few
specifics for the diseases of plants resulted, yet I am
quite satisfied that the causes of diseases would be
more accurately ascertained : and every one is aware
that to know the cause of an evil is the most im-
portant step towards the prevention of its occur-
rence.

It is a very important preliminaiy to the study
of the diseases of plants, that the nature of these be
understood — for our ignorance of, or inattention to,
the nature of these organized creatures, is one of the
causes from whence arises the little progress made
in this branch of natural philosophy.

Its students ought fully to understand that this

246 PRINCIPLES OF GARDENING. [CH. VIII.

part of the creation, even the commonest weed they
uproot, is so highly organized, so exhibiting intima-
tions of the fimctions, circulations, and secretions
more highly developed in the superior animals, that
it is not possible to point out where animal life
terminates, and where vegetable life begins : the
zoophytes connect the two kingdoms. It is abso-
lutely necessaiy, I think, for this to be understood
and felt by those who enter upon the investigation
of vegetable diseases, because I have a strong opinion
that these, in veiy many instances, are caused by
the plants which they infect being treated as if they
were totally insentiate matter, scarcely more suscep-
tible of injury at some periods of their growth than
the soil from whence they partly derive their sus-
tenance.

To determine the question, whether plants possess
a degi'ee of sensation, is not so easy as the cursory
inquirer may believe ; and Mr. Tupper is much
nearer to tinith when observing that it is as difficult
to ascertain the nature of vegetable existence as to de-
termine what constitutes the li\dng principle in
animals.

Dr. Darwin, by the aid of imaginaiy Jbeings simi-
lar to the Dryads and other minor deities of the
heathen mytholog}', has raised plants to a position,
in the order of nature, superior even to that to
which animals are entitled. Other philosophers

CH. VIII.] THE DISEASES OF PL-\^•TS. 247

adopting a totally antagonist opinion, estimate vege-
tables as bodies, only somewhat more organized
than crystals, but like these entirely and micon-
troledly subject to chemical and mechanical changes.

Each of the foregoing extreme opinions is simi-
larly eiToneous, as ^^ill have been gleaned from the
facts mentioned in preceding pages, and as vrill more
clearly appear from those -^'hich now follow. The
gradation from reason to instinct, from instinct to
inanimation, might easily be she^Ti to be as gradual
as are the transitions of light in om* climate from the
noontide to the midnight of a summer's day. But
we must, in this volume, confine our attention to
that section of creation commencing from the close
of the animal classes in the zoophyte, and termi-
nating where inorganic matter commences in the
crystal, and the details here given must be directed
specially to demonstrate how closely it approaches,
how indistinctly it is divided from, the former.

Let us first consider the comparative composition
of animals and plants as revealed by the researches
of the chemist, and it must be somewhat startling
even to the most sceptical to find that their consti-
tuents are identical. Carbon, hydrogen, oxygen,
nitrogen, sulphm', phosphoiTis, acids, alkalies, earths
and metals are the components of both.

Nitrogen was considered as a constituent, mark-
ing, by its presence, animal from vegetable matters ;

248 PEINCIPLES OF GARDENING. [CH. VIII.

but this distinction is now admitted to fail ; for
although in the former it is usually most abundant,
yet later researches shew it to be present in all
seeds, it is abundant in yegetable gluten, and per-
vades the whole frame of the tobacco plant, yet is
absent from some animal substances.

If we follow the above-named chemical bodies
through their combinations, we shall find that the
similarity between animals and plants still obtains,
and are equally numerous and intricate in each.

Of the acids there are contained in

Animals, Vegetables.

1. Sulplumc, 1. Sulphuric,

2. Phosphoric, 2. Phosphoric,

3. Miuiatic, 3. Muriatic,

4. Carbonic, 4. Carbonic,

5. Benzoic, 5. Benzoic,

6. Oxalic, 6. Oxalic,

7. Acetic, 7. AcetiC;

8. Malic, 8. Malic,

besides others still more numerous, peculiar to
each.

Of the earths and alkalies, lime, magnesia, silica,
soda, and potass are found in both classes ; and of
the metals, iron and manganese are their conjoint
constituents. If we follow the two orders of organized
creatures through their more compound constituents »

CH. YIII.] THE DISEASES OF PLANTS. 249

we shall find the close analogy still continues, for
they contain in common, sugar, mucus, jelly, colour-
ing matters, gluten a, fibrin, oils, resins, and ex-
tractives.

The fimctions of animals and plants ai'e in a like
degree analogous. Animals take in their food by the
agency of the mouth, and prepare it for -digestion
either by various degrees of mastication, or by attri-
tion, as in the gizzards of birds. In this they differ
from plants ; but these have a sufficient compensa-
tion, inasmuch as that they imbibe their food in a
fluid foi-m, liquid or aeriform, and consequently in a
state already of the finest possible dirision. Animal
and vegetable remains ai'e their common food, and
salts of various kinds are their condiments and stimu-
lants ; plants having this advantage over animals,
that as they absorb only the soluble and finer parts
of their nutriments, and their absorbing organs have
the power of rejecting that which is offensive, they
have no offensive matters to sepai'ate such as appear
in the excrements of animals.

In the animal stomach the food undergoes an ex
tensive change, being reduced to a pulp of greater
specific gravity, and being altered entirely both in
taste and odoui'. In the sap vessels of plants, which
may be tinily considered as their primary organ of
digestion, their food or sap undergoes a change pre
* The gluten of plants is the albumen of animals.

250 PRINCIPLES OF GARDENING. [CH. VIII.

cisely similar ; its colour and flavour are altered, and
its specific gravity increased.

From its stomacli the animal's food passes into the
intestines, is there subjected to the action of the
bile, and the chyle or nutritive portion separated
from that which is excrementitious. In its pas-
sage through the intestines, the chyle is absorbed by
the lacteal vessels, and conveyed into the blood ; and
these mingled liquids are propelled by the heart into
the lungs, to be there exposed to the action of the
air. The vital liquid now changes its pui'ple hue to
a florid red, loses a portion of its carbon and watery
particles, the former combining with the oxygen of
the atmospheric air in the lungs, and being breathed
forth in the form of carbonic acid gas. As plants
take in as food no gross, imneeded ingredients, it is
obvious that no process like the biliaiy operation is
required in their course of digestion. But in them
the food or sap, proceeding at once along the branches,
is poured into the leaves, which are the very lungs of
the vegetable world. Here, as is the blood, its
colour is changed, and oxygen emitted from it dur-
ing the light hours of the twenty-four ; but carbonic
acid is breathed forth during the night, and, at all
periods, a considerable amount of wateiy vapour is
emitted.

From the lungs, by the agency of the heart, the
blood is propelled through the arteries over the whole

CH. VIII.] THE DISEASES OF PL^^'TS. 251

animal frame, supplying noimshment and warmth to
all the parts, and where, by those being abstracted,
it is again converted into purple or venous blood, and
is returned by the veins to imdergo a repetition of
those changes already noted as being effected in the
lungs. In plants the sap, after exposure to the ac-
tion of the air in their leaves, is returned by another
set of vessels, situated in the bark, ministering to
the growth and support of the whole plant. It is
true, that only under certain circumstances, detailed
in another chapter, is heat evolved duiing the pro-
cesses of vegetation ; but the cumulation of the sap in
plants, beyond all doubt, enables them to resist the
intense colds and heats of their native chmates. In
frosts, the most intense and prolonged, we find the
interior of trees remain unfrozen ; and, under the
meridian sun of the tropics, the sap of the palm and
all other trees retain temperate coolness. This power
to resist extremely elevated and depressed tempera-
tures is characteristic of all animated nature.

Such is the close similarity in the digestive and
circulatory processes characterising the members of
the two great kingdoms of organized nature, a resem-
blance which obtains in all the other functions en-
joyed by them in common. During respiration, the
air inhaled by animals through the mouth and nos-
trils proceeds immediately to the lungs, and acts
upon the blood ; in plants, the air inhaled by their

252 PRINCIPLES OF GARDENING. [CH. VIII.

leaves operates instantaneously upon the sap. The
changes which occur have been detailed in pre^dous
pages, and there it has been shown, that as oxygen is
the vital air of animals, so that gas and carbonic acid
gas are equally essential to plants. If animals be
placed in a situation where they inhale pure oxy-
gen, their functions are highly excited and mcreased
in rapidity ; but it is an exhilaration speedily termi-
nating in exhaustion and death, if the inhalation be
contmued for a protracted time. So plants will
flourish with increased vigour in an atmosphere con-
taining -/irth of carbonic acid, but even this brings
on prematui'e decay ; and if it exceeds that pro-
portion, destruction is still more rapidly induced.
During sleep, animals exhale less carbonic acid
than during their waking hours, so plants emit a
much diminished amount of oxvgen duiing the
night.

We might now proceed to enumerate the obsen-a-
tions and facts demonstrative that plants are gifted
with sensation, if these had not already been re-
corded at p. 104. In addition to those I mil only ob-
serve, that plants are obviously stimulated by light.
Everybody must have observed, that they bend to-
wards the point whence its brightest influence pro-
ceeds. M. Bonnet, the French botanist, demon-
strated this by some very satisfactory experiments, in
which plants, growing in a dark cellar, all extended

CH. VIII.] THE DISEASES OF PLANTS. 253

themselves towards the same small orifice admitting
a few illuminating rays.

Almost every flower has a particular degree of
light requisite for its full expansion. The blossoms
of the pea and other papilionaceous plants, spread
out their wings in fine weather, to admit the solar
rays, and again close them at the approach of night.
Plants requiring powerful stimulants do not expand
their flowers until noon, whilst some would be de-
stroyed if compelled to open in the meridian sun — of
such is the night-blooming Cereus, the flowers of
which speedily droop, even if exposed to the blaze of
light attendant on Indian festivities.

From these and other facts incidentally mentioned
in the preceding chapters, without belie"STng that
the}' demonstrate sensation to exist in plants as acute
as that possessed by the superior or more perfect
classes of animals, yet they certainly are satisfactory
e\ddence that plants possess it to a degree nearly as
high as that with which the zoophytes, or even the
polypus and leech, are gifted. Some of these ani-
mals may be cut into pieces, and each section will be-
come a perfect individual ; of others, their heads
being taken off, may be grafted upon other bodies ;
and a third class of them may be turned with their
insides outwards, without any apparent inconvenience.
If plants be endowed with no more or even less sens-
ation than must be that of such animals as these, it

254 PRINCIPLES OF GARDENING. [CH. VIII.

explains the causes, and throws light upon the pre-
vention of many diseases affecting those which we
cultivate, and warns the cultivator from the late per-
formance of many of his operations, as Avell as from
being needlessly violent in his treatment. If a grape-
vine be pinmed too late in the spring, the bleeding
or effusion of sap has been known to be so excessive,
that the tree has died from absolute exhaustion.
Stone-fruit trees, if severely bruised, are frequently
destroyed by the inroads of a disease, resembhng, in
all its characteristics, the cancerous affections of ani-
mals ; and I have known a whole crop of wheat af-
fected with a swelling of the stem or culm, evidently
caused by an extravasation of the sap from its rup-
tured vessels, owing to a hea\7- roller being passed
over the crop, Avhen of a forward growth.

I shall now proceed to the consideration of a
few of the most usual diseases affecting cultivated
plants, but without any attempt at classification, for
our knowledge is too imperfect as yet to justify an
attempt to form a system of vegetable nosology. It
is readily perceivable that plants have their epi-
demics, for at certain seasons a disease, such as the
mildew, will devastate a whole neighbourhood. They
have their endemics for some diseases, as the
Amhury is often confined to a single compartment
in a garden ; but these and other detached portions
of similar knowledge are too slight and uncoimected

CH. VIII.] THE DISEASES OF PLANTS. 255

to enable me to attempt a classification of their dis-
eases. Neither shall I attempt in this volume to
enter upon the consideration of the injuiies to which
plants are subjected either from predatoiy insects, or
from parasitical plants : my space will not permit
this, and I regret it the less because they ai'e now
the subjects dwelt upon by master minds in the
pages of the Gardeners Chronicle.

The Curl. — Xo disease appears to me to arise
from impau'ed vital energy in the plant more
clearly than the curl, that of late years has made
such extensive ravages upon our potato crops ^. Any
one can insure the occurrence of this disease, at
least I have found it so in the county of Essex, by
keeping the sets in a situation favourable to their
vegetation, as in a warm damp out-house, and then
nibbing off repeatedly the long shoots they have
thrown out. Sets that have been so treated, I have
invariably found produce curled plants. Is not the
reason very apparent. The vital energy had been
weakened by the repeated efforts to vegetate; so
that, when planted in the soil, their energy was
unequal to the perfect developement of the parts ;
for the curl is nothing more nor less than a distorted

* The opinions of Mr. Monro, of Brechin Nursery, coincides
with mine. He considers " weakness is the cause " of the dis-
ease.— Gardeners Magazine, xi. 417.

256 PRINCIPLES OF GARDENING. [CH. VIII.

or incomplete formation of the foliage, preceded by
an imperfect production of the fibrous roots.

The following experiment I consider as very de-
cisive : it was made in the year 1830, in my garden at
Great Totham, in the coimty of Essex. The soil in
this case, and in all others that will be stated here-
after, unless otherwise specified, is light, deep,
moderately fertile, resting on a substratum of sili-
cious gravel, and is constituted as follows :

Water 30.5

Stones and coarse sand , . . . 15.5

Vegetable fibres 5

Saline matters 4.5

Oxide of iron 2.5

Carbonate of lime 17.5

Decomposing matter 7

Alumina 15

Silica 102.5

200

The variety employed was the early Shaw. An
equal number of whole moderately-sized potatoes that
had been treated in three different modes, were
planted the last week of March. No. 1! Twenty
sets that had been carefully kept cold and diy through-
out the mnter, firm, unshrivelled, and with scarcely
any symptoms of vegetation. No. 2. Twenty sets

CH. VIII.] THE DISEASES OF PLANTS. 257

that had been kept warm and moist, and from which
the shoots, after attaining a length of six inches,
had been thrice removed. No. 3. Twenty sets that
had been kept warm and moist for about half the
time that No. 2 Had, and from which the shoots,
three, inches in length, had been removed only twice.

All the sets were planted the same morning, each
exactly six inches below the smface, and each with
an unsprouted eye upwards. The spring was genial.

Of No. 1, nineteen plants came up. The twen-
tieth seemed to have been removed by an accident.
Of the mneteen not one was curled. The produce
a ftdl average crop.

Of No. 2, all came up, but from ten to fourteen
days later than those of No. 1, and three of the
plants sixteen days later. Fourteen of the plants
were cm-led.

Of No. 3, all came up, but from ten to fourteen
days later than those of No. 1. Fom' plants were
as severely curled as those in No. 2, eight were less
so, and the remainder not at all ; but of these the
produce was below an average, and a full fortnight
later in ripening.

Dickson, Crichton, Knight^, and others have found,
that tubers, taken up before they are fully ripened,
produce plants not so liable to the curl as those

" Caledonian Hort. Mem., Horticultural Trans,, Loudon's Gar-
dener's Mag., &c.

S

S58 PEINCIPLES OF GARDENING. [CH. VIII.

that have remained in the ground until completely
perfected ; and I believe, under ordinaiy treatment,
this to be the fact, for it is rational. The process
of ripening proceeds in the potato, as in the apple,
after it has been gathered, and until that is per-
fected, it is accumulating vigour, shews no appetency
to vegetate, consequently is not exhausting its
vitality, which is a great point, considering the
careless mode usually adopted to store them through
the winter ; for this energy commences its decHne
from the moment it begins to develope the parts of
the future plant. Tubers taken from the soil before
perfectly ripe, never are so early in shewing sjinp-
toms of vegetation. Crichton, Hunter, and Young,
in some of the works before referred to, have also
agreed, that exposing the sets to light and air,
allomng them to become diy and shrivelled, also
induces the curl in the plants arising from them.
This result of experience also confirms my con-
clusion, that the disease aiises from deficient vital
energ}^; for no process more than this drying one of
exposui'e to the light and air, tends to take away from
a tuber the power of vegetating altogether. A farmer,
Mr. G. Allaker, residing in the same village that I
did, employed in the year 1836 rather small sets :
cutting a moderate-sized potato into at least two
pieces. Unfavourable weather, other business, and
a somewhat dilatory habit, caused him to leave those

4

ji

CH. VIII.] THE DISEASES OF PLANTS. Q59

sets Upon a bam floor, dndng for more than a week.
He planted with them a two-aere field, and not more
than three-fifths vegetated ; of which three-fifths, a
fourth was in various degrees ciu'led.

Similar results were obtained in the experiments
of Mr, Wright, a market gardener of Westfield.
When the sets were allowed to ferment in a heap,
allowed to sprout, &c., he had a crop, one-fifth of
which was curled^.

Every one acquainted with the cultivation of the
potato, is aware of the great difference existing in
the varieties as to their early and rapid vegetation ;
those that excel in this quality are, of course, the
most easily excitable, A consequence of this is,
that they are always planted earliest in the spring
before their vital power has become veiy active :
and of all crops, practice demonstrates that these
early ones are least liable to the cui'l. But what is
the consequence on the contraiy, if an early variety
is planted for a main crop later in the spring, when
extraordinaiy pains in keeping them cold and
dry have not been employed to check their vegeta-
tion, and consequent decrease of vital energy ? Such
crop then is, more than any other, liable to tlie
disease ; and a good preventive has been suggested
by Dr. Lindley, namely, that of planting the tubers
in autumn immediately after they have ripened.
* Grardener's Mag, x. 436,

s2

260 PRINCIPLES OF GARDENING. [CH. Till,

The statements of a practical man in the Gar-
deners Magazine, vol. x. 433., entirely support my
views of the disease. He remarks that in 1836,
through the prevalence of rain, the late crops of
potatoes never sufficiently ripened so as to be
marketable. They were resei'ved for planting the
next season, and the consequence was, that the curl
affected the crops that year to a great extent ; but
those who planted well ripened tubers had crops
free from the disease, and as productive as usual.
Now we all know that the ^dtal energy is always the
most powerful in a bulb or seed that is perfectly
ripened.

The results of my view of the disease, sustained
by numerous experiments, are, that it will never
occur if the following points are attended to : — First,
that the sets are from tubers that exhibit scarcely
any symptoms of incipient vegetation. To effect
which, they ought, throughout the winter, to be
preserved as cool, and as much excluded from the
air as possible. Secondly, that the tubers should
be perfectly ripened. Thirdly, that they should be
planted immediately after they are cut. Fourthly,
that the manure applied should be spread regularly,
and mixed with the soil, and not along a trench in
immediate contact "VN-ith the sets. Fifthly, that the
crop is not raised for several successive years on the
same area.

CH. Tin.] THE DISEASES OF PLANTS. *26l

The Amhury ^, Anbury, Hanhury, or club root.
The deficiency of knowledge relative to the diseases
of plants, is well illustrated by the imperfect and
inaccui'ate observations that have been adventured
upon this disease. Where there is much difference of
opinion there is little real knowledge, and both these
are certainly the case in the instance before us.
Some cultivators assert that the disease arises from
a variableness and unfavourable state of the seasons ;
a second 2)arty of theorists advance, that it is caused
by insects ; and a third, that it is owing to a too fre-
quent growth of the same crop upon the same site.

Every man having formed an opinion, usually
clings to it pertinaciously, and sets its estimate far
above its real value, or correctness,

" *Tis with our judgments as our watches ; none
Gro just alike^ yet each believes his own."

The chief error appears to be in considering any
of the above enumerated causes as the exclusive one,
for, beyond doubt,, they each contribute, either im-

• This, the correct name, is evidently derived from the Saxon
word atmhre, a wart suffused with blood, to which horses are
subject. In Holdemess, a district of Yorkshire, this disease is
known as " Fingers and Toes," from its causing the tap-root of the
turnip to be divided into swollen fibres, resembling those members
of the human body. On this Mr. Spence, the entomologist, wrote a
very sensible pamphlet, entitled " Observations on the Diseases in
Turnips termed in Holdemess, ' Finger and Toes.' Hull, 1812."

262 PEINCIPLES OF GARDENING. [CH. VIII,

mediately or remotely, to induce or exasperate the
attacks of the ambuiy.

I am about in the first place to consider the
disease exclusively as aifecting the cabbage, and
secondly, as it operates upon the turnip, though
other species of brassica, the hollyhock, &c., are sub-
ject to its attacks. Its progress has invariably ap-
peared to me as follows :

Cabbage-plants are frequently infected with ambury
in the seed-bed, and this incipient infection appears
in the form of a gall or wart upon the stem, im-
mediately in the vicinity of the root's. If this wart
is opened, it will be found to contain a small white
maggot, the lan^a of a little insect called the weevil.
If the gall and its tenant being removed, the plant is
placed again in the earth, where it is to remain, unless
it is again attacked, the wound usually heals, and
the growth is but httle retarded. On the other hand,
if the gall is left undisturbed, the maggot continues
to feed upon the alburnum or young woody part of
the stem, until the period arrives for its passing into
the other insect form, previously to which it gnaws
its way out through the exterior bark. The disease
is now almost beyond the power of remedies. The
gall, increased in size, encircles the whole stem;
the alburnum being so extensively destroyed, pre-
vents the sap ascending ; consequently, in dry wea-
ther, sufficient moisture is not supplied from the roots

CH. Vni.] THE DISEASES OF TUlSTS. 263

to counterbalance the transpkation of the leaves, and
the diseased is veiy discernible amongst its healthy
companions, by its pallid hue and flagging foliage.
The disease now makes rapid progress, the swelling
continues to increase, for the vessels of the alburnum
and the bark continue to afford their juices faster
than they can be conveyed away ; moisture and air
are admitted to the interior of the excrescence
through the perforation made by the maggot; the
wounded vessels ulcerate: putrefaction super^'enes,
and death concludes the stinted existence of the
miserable plant. The tumom' usually attains the
size of a large hen's egg ; has a rugged, ichorous,
and even mouldy surface, smelling strong and offen-
sively. The fibrous roots, besides being. generally
thickened, are distorted and monstrous from swell-
ings, that appear throughout their length, and
which appai'ently arise from an effort of nature to
form receptacles for the sap, deprived as it is of its
natui-al spissation in the leaves. These swellings do
not seem to arise immediately from the attacks of the
weevil ; for I have never observed them containmg
its larva.

Mr. Marshall very correctly describes the form
which this disease assumes when it attacks the
turnip. It is a large excrescence appearing below
the bulb ; growing to the size of both hands, and as
soon as the hard weather sets in, or it is by its own

264 PRINCIPLES OF GARDENING. [CH. VIII.

nature brought to matmitv, becoming putrid, and
smelling very offensively. On the last day of
August, when the bulbs of the turnips were about
the size of walnuts in the husk, the amburies were
as big as a goose's egg. These were irregular and
uncouth in their form, with inferior excrescences,
resembling the races of ginger, hanging to them. On
cutting them, their general appearance is that of a
hard turnip ; but on examining them through a mag-
nifier, there are veins or string-like vessels, dispersed
amongst the pulp. The smell and taste somewhat
resemble those of turnips, but without their mildness,
having an austere and somewhat disagreeable flavour
resembling that of an old stringy turnip. The tops of
those much affected turn yellow, and flag with the heat
of the sun, so that, in the day-time, they are obviously
distinguishable from those that are healthy. These
distortions manifest themselves veiy early in the
turnip s growth, even before the rough leaf is much
developed. Observation seems to have ascertained,
that if the bulbs have attained the size of a wal-
nut unaffected, they do not subsequently become
diseased.

Mr. Spencer has already shewn, from established
facts, that the ambury does not arise from any im-
perfection of the seed sown ; for experience demon-
strates, that, in the same field and crop, the attax^ks
are very partial ; and crops in two adjoining fields,

CH. VIII.] THE DISEASES OF PLANTS. 265

sovm with seed from the same growth, will one be
diseased and the other healthy.

Secondly, It does not arise from an unfavourable
time of sowing, or from dry unpropitious seasons dur-
ing their aftergi'owth ; " for, on this supposition, we
might expect that in all turnip districts the disease
would occasionally make its appearance, in conse-
quence of variations in the period and mode of sow-
ing, or from following droughts ; yet we know that
in many parts of the country it has never been
heard of."

Thirdly, It does not arise from the quality of the
soil ; for Sir Joseph Banks suffered from its infecting
thin stapled sandy fields, whilst all Holdemess,
which is generally a strong loamy soil, was found
equally liable to the disease. But a stiU more
decisive e\ddence on this point is, that it makes its
appeamnce at uncertain intervals upon the same
soil ; the turnips upon it being in some years greatly
injured by the disease, and in other years entirely
free.

Fourthly, Although it is certain from the observa-
tions of Sir Joseph Banks, and from general experience,
that the disease occurs most frequently in soils tired
of the crop, that is soils upon which it has been grown
for a long course of years ; yet, that this is not the
immediate cause of the disease is proved by the
fact, that often only patches in the same field are

S66 PRINCIPLES OF GARDENING. [cH. VIII,

affected; and the same observers record, that it
appears in soils that have not produced turnips for
a long series of years. The diseased specimens
examined by Mr. Marshall, were from an old orchard
that had not borne turnips ^rithin the memory of
man.

Mr. Spence concluded, that the disease is occa-
sioned by the poisonous wound inflicted by some un-
ascertained insect upon the turnip in an eai'ly stage
of vegetation, or by its insinuating its egg into it,
infusing at the same time a liquid, causing a morbid
action in the sap vessels, and the consequent forming
of excrescences. This correct opinion was afterwards
confiiined by the actual discoveiy of the insect,
and that there actually is a maggot generated
from the egg, of which fact, at the time, he was
entirely ignorant.

The maggot fomid in the turnip ambury, is the
larva of a wee\il called Curculio pleiirostigma by
Marsham, and Rhynchcenus sulcicollis by Gyllenhal.
" I have bred this species of weevil " says Mr. Kirby,
"from the knob-like galls on turnips, called the
ambury, and I have little doubt that the same insects,
or a species allied to them, cause the clubbing of
the roots of cabbages ^.

Marsham describes the parent as a cleopterous
insect, of a dusky black colour, with the breast
' Kirby and Spence's Introduction to Entomology, i. 450.

CH. VIII.] THE DISEASES OF PLANTS. QG7

Spotted with white, and the length of the body one
line and two-thirds^.

The general experience of all the farmers and
gardeners with whom I have conversed upon the
subject, testified that the ambuiy of the turnip and
cabbage usually attacks these crops when grown for
successive years on the same soil. This is precisely
what might be expected; for the parent insect
always deposits her eggs in those situations where
her progeny ^^ill find their appropriate food ; and in
the fragments of the roots of preceding crops, some
of these embryo ravagers are to be expected. That
they never attack the plants upon a fresh site is not
asserted. Mr. Marshall's statement is e\'idence to
the contraiy; but it is advanced that the obnoxious
weeN-il is most frequently to be observed in soils
where the turnip, or cabbage, has recently and
repeatedly been cultivated.

" He adds, subtus albido squamosus ; inter thoracem et elytro-
rum basin puncto albo pectus notatur. Thorax utrinque obsolete
dentatus, postice et antice fossula intermedia exaratur. Femora
omnia denticulata. Entomologia Brit. 282. A very full de-
scription of this insect is in the " Insecta Suecica Descripta" of
Gyllenhal, vol. iii. p. 229, under the name of Rhynchcenns sulci-
collis. It is the Curculio affinis of Panzer's Faunae Insectorum
Germanicce initia ; the Curculio sulcicollu in PaykuU's Suecica,
the Falciger suldcollis of De Jean's Catalogue des Cleopteres ;
and the Cryptorhynchus alanda of Germar's Insectorum species
novae, &c.

268 PRINCIPLES OF GARDENING. [CH. VIII.

Another general result of experience is, that the
ambury is most frequently observed in dry seasons.
This is also what might be anticipated, for insects
that inhabit the earth, just beneath its surface, are
always restricted and checked in their movements by
its abounding in moisture. Moreover, the plants
actually affected by the ambuiy, are more able to con-
tend against the injury inflicted by the lan-a of the
weevil by the same copious supply. The dev elope-
ment of their parts, their growth, is more rapid ;
consequently the maggot has not to extend its
ravages so extensively in search of food, as in drier
seasons, when the stem is less juicy, and of smaller
growth. In wet periods also the affected plants
shew less the extent of the injury they have sus-
tained; for their foliage does not flag, because
their transpirations of wateiy particles are less, and
their supply of nutriment from the soil is more free.
In wet seasons I have, in a veiy few instances,
known an infected cabbage plant produce fresh
healthy roots above the swelling of the ambuiy.

These facts, being premised, better qualify us for
the consideration of the best modes of preventing
the occurrence of the disease and pdliating its
attacks. It is apparent that any addition to the
soil that renders it disagreeable to the weevil, will
prevent the visits of this msect. The gardener has

CH. YIII.] THE DISEASES OF PLANTS. 269

this in his poTver ^ith but little difficulty, for he can
keep the ^-icinity of his cabbage, cauliflower, and
brocoli plants soaked with water.

Mr. Smith, gardener to M. Bell, Esq., of Wool-
sington, in Northumberland, expresses his conviction
after several years' experience, that charcoal-dust,
spread about half an inch deep upon the suiiace, and
just mixed with it by the point of a spade, effectually
prevents the occurrence of this disease^. That this
would be the case we might have surmised from
analogy, for charcoal-dust is offensive to many in-
sects ; and is one of the most powerful preventives of
putrefaction known. Soot, I have reason to believe,
from a slight experience, is as effectual as charcoal
dust. Judging from theoretical reasons, we might
conclude that it would be more specifical, for in
addition to its being like charcoal, finely di\-ided
carbon, it contains sulphur, to which insects have
also a great antipathy.

Mr. Drurey, a practical farmer at Erpingham, in
Norfolk, considered marl a certain preventive of this
disease. He and several other judicious farmers
also thought that teatJiing, that is, giving sheep and
cattle their green food, turnips, &c., upon the barley-
stubbles intended for turnips as the succeeding
crop, would cause the ambur}^^. It is ver}' evident

^ Trans, of London Horticultural Soc. vi. art. 2.
^ Marshall's Rural Economy of Norfolk, ii. 33-35.

270 PPJXCIPLES OF GAEDENING. [CH. VIII.

that it would mLx fragments ■with the soil that
would be liable to contain the eggs of the weevil.
The marl approved by Mr. Drurey is probably
the calcareous marl which occui's at Thorp Mar-
ket, in the hundred of North Erpingham ; but
as there is a slight doubt owing to the defici-
ency of accuracy in the statement, it affords me
an opportunity to impress upon cultivators in
general the great importance of employing more
certain terms than they usually do. What can be
more indefinite than the statement, that marl is a
certain preventive of the ambury ? For the very
first question suggested to the readers mind is,
what marl is intended? Is it a chalky-marl, or
a clay-marl ? Is it a mixture of chalk and clay,
or of chalk and silicious sand ? for all these va-
rieties of marl are known. The want of a cor-
rect nomenclature is one of the drawbacks and
deficiencies checking the improving progi'ess of the
soil's cultivation. Few have ever thought much upon
this point, and still smaller is the number who
duly appreciate its importance. Yet it is an in-
controvertible fact, that no art or science can
advance rapidly imtil its technical terms are fixed,
terse, expressive, and generally understood. Che-
mistry attained a greater aid to its advancement
by the introduction of its new nomenclature by
Lavoisier, than by any series of discoveries that

CH Vm.] THE DISEASES OF PLANTS. '271

have since been made on its rapid and brilliant
progress. If a sulphate, an acid, or a metal is
mentioned, a chemist immediately has a definite
idea of the nature and properties of the substance
alluded to, but if a loam or marl is spoken of,
would any t^ro cultivators of the soil agree in their
idea of what description of earthy compound was
intended? To make it well understood, a long
detail must be added, and nothing checks the im-
parting of knowledge more than the person capable
of imparting it being conscious that he must define
every term as he goes on, and that even then it is
doubtful whether he shall succeed in making himself
intelligible. The veiy name (ambmy) usually ap-
plied to the disease which is the subject of our present
consideration, is another proof of the necessity of a
reformed horticultm^al and agricultural nomenclature ;
for, LQ Suffolk, the same title is given to another dis-
ease, which merely affects the leaves of the tui'nip.

Sir Joseph Banks, Mr. Baker, of Norfolk, and
others, agree that marl is the best preventive of am-
bury, and another evidence of the efficacy of appli-
cations to the soil, is afforded by a gentleman in
Holdemess, a Mr. Brigham, who had a highly ma-
nui'ed clayey ridge, which he had levelled the year
before, and which grew turnips entirely free from the
disease, whilst, in the natural rich loam of the field,
they were much infected.

272 PRINCIPLES OF GARDENING. [CH. VIII.

Francis Constable, Esq., of Burton Constable,
had a field that had been in grass twenty years :
this he pared, burned, and sowed ^vith turnips,
obtaining a crop perfectly free from the disease.
Two white crops were then taken, after which
turnips were again sown ; and a considerable portion
of the crop was then infected ^.

I have myself tried the efficacy of common salt
in preventing the occurrence of this disease. Its
tendency to keep the soil moist, and to irritate the
animal frame, certainly checks the inroads of the
weevil, and its generally beneficial effects as a
manure enables the plants better to sustain them-
selves under the weakening influence of the disease ;
but it is not a decisive preventive. The following
results of one of my experiments was read to the Hor-
ticultural Society of London, October 16, 1821 : —

*' Some cauliflowers were planted in a light sili-
ceous soil, which had pre\dously been manured with
well putrefied stable maniu'e ; and over one-third of
the allotted space was sown salt, at the rate of twenty
bushels per acre ; immediately before the planting,
in the beginning of July, 1821, the previous crop
had been brocoli ; fifty-four plants were set on the
two-thirds unsalted, and twenty-six on the one-third
salted ; the result has been, that of the fifty-four un-

^ Spence's Observations on the Disease in Turnips, tenned in
Holdemess, " Fingers and Toes."

CH. VIII.] THE DISEASES OF PLANTS. Q73

salted, fifteen have been diseased and unproductive,
but of the twenty-sk salted, only two.

" Some more cauliflowers were planted on a plot of
ground which had previously borne a crop of savoys,
and half of which ground had been sown with salt
four months previous to planting ; in this the un-
salted and the salted were alike nearly destroyed,
evincing that the salt was not present in a sufficient
proportion to produce the desired effect.

" With regard to the use of salt as a cure for the
disease, I am inclined to think, from the results of
experiments which I have instituted, that unless the
salt be applied very early it would be useless, for the
root soon becomes so diseased as to be entirely past
recovery." a

I have a strong opinion that a slight dressing of
the surface soil, with a little of the docj hydro-sul-
phuret of lime, that may be now obtained so readily
from the gas-works introduced through England,
would prevent the occurrence of the disease, by
driving the weevils from the soil. It would, pro-
bably, as effectually banish the turnip-fly or flea,
if sprinkled over the sui'face immediately after the
seed is sown. I entertain this opinion of its effi-
cacy in preventing the occurrence of the ambury,
from an instance when it was applied to some brocoli,
ignorantly grown upon a bed, where cabbages had as

* C, \V. Johnson's Essay on Salt, p. 136.

T

274 PRINCIPLES OF GARDENIXG. [CH. VIII.

ignorantly been endeavoured to be produced in suc-
cessive crops. These had invariably failed, from the
occuiTcnce of the ambury ; but the brocoli was unin-
fected. The only cause for this escape that I could
trace was, that just previously to planting, a little of
the hydro-sulphuret of lime had been dug in. This
is a very fetid, powerful compound. \Vhere dry
lime purifiers are employed at gas works, it may be
obtained in the state of a diy powder ; but where
a liquid mixture of lime and water is employed,
the hydro-sulphuret can only be had as a thick
cream. Of the diy hydro-sulphuret, I recommend
eight bushels per acre to be spread regularly by
hand upon the surface, after the turnip seed is sown,
and before harrowing. If the liquid is employed,
I recommend thirty gallons of it to be mixed
with a sufficient quantity of earth or ashes, to
enable it to be spread over an acre in a similar
manner.

For cabbages, twelve bushels or forty-seven gallons
per acre, would not, probably, be too much, spread
upon the surface, and turned in with the spade or
last ploughing. To effect the banishment of the
turnip flea, I should like a trial to be made of six or
eight bushels of the dry, or from twenty-two to
twenty-eight gallons of the liquid hydro-sulphuret
being spread over the surface, immediately after the
sowing, harrowing and rolling are finished. Although

CH. YIII.] THE DISEASES OF PLANTS. '275

I specify these quantities as those I calculate to he
the most correct, yet in all experiments it is best to
try various proportions. Three or four bushels may
be found sufficient, perhaps twelve, or even twenty
may not be too much.

Frequent hoeing has been recommended as a pre-
ventive of this disease ; but I believe tliis to be un-
sustained by either reason or practice. Hoeing, like
any other stirring of the surface soil, assists the ad-
mission of the atmosphere to the incumbent plants,
and so far promotes then- general health ; but I have
never yet found, or even heard any one advance, that
a frequently hoed part of a crop was free from the
ambury, which affected the more rarely hoed portion.

It would be fortunate if our white turnip crops
could be sown as early as our Swedes, for they would
then, probably, be as little liable to the ambur}' as
these are. The reason of this seems to be, that the
weevil does not emerge into that state in which it is
capable of injuring the young plants until the sum-
mer is far advanced, and by that time the Swedish
turnips have attained a size which secures their
safety. I conclude this to be the case from my own
slight, very slight, observ^ations upon the habits of
the insect ; for, unfortunately, we are veiy deficient
in knowledge upon this point. It is to be regretted,
that entomologists are not more attentive to what
may be termed the private and particular histor}^ of

t2

276 PRINCIPLES OF GARDENING. [CH. VIII,

their study. To define and describe tlieir specific
cliaracters is very useful ; but it is chiefly so, be-
cause it is like a good index to an intricate volume.
It is of far more utility to ascertain their habits, and
their periods of gestation and transformation, be-
cause such knowledge is that which often affords us
one of the best means of avoiding their ravages.

In cabbages, the ambury may usually be avoided
by frequent transplan tings, for this enables the work-
man to remove the excrescences upon their first ap-
pearance, and renders the plants altogether more ro-
bust and ligneous ; the plant, in its tender, sappy
stage of growth, being most open to the insect's
attacks.

The sap of the turnip and cabbage thus diseased
undergoes a considerable change. Its specific gravity
is much increased, arising from an excess of mu-
cilage, vegetable extract, and saline constituents,
which it naturally contains, caused probably by its
being in a concentrated state ; for it is very con-
siderably reduced in quantity, compared with what
the same plant contains when healthy. The increase
of the saline components unquestionably exasperates
the disease. They consist chiefly of chloride and
carbonate of potass, which, by the corroding power of
the last-named, and the irritating qualities of both,
must increase the sanious discharge, by stimulating
the already lacerated and morbidly sensitive vessels.

CH. Tin.] THE DISEASES OF PLANTS. '^77

Probably the occasional application of diluted acids,
such as the dregs of beer, ^vould mitigate the spn-
ptoms, and check the progress of the ulceration ; but
the application could not be expected to effect a cure,
nor is it available, even if proved to be a specific.

The warts or galls that may so frequently be no-
ticed on the bulbs of turnips, must not be mistaken
for the ambury in a mitigated foiTQ. If these are
opened, they "will usually be found to contain a yel-
lowish maggot, the larva, probably, of some species of
c}'nips. This insect deposits its eggs in the turnip
when of larger growth than that when it is attacked
by the weevil, and the vegetable, consequently, suf-
fers less from the injmy; but from slight observa-
tions, I am inclined to conclude, that the turnips thus
infested suffer most from the frosts of winter, and
are the earliest in decay. This is what might be an-
ticipated ; for when the maggot has escaped from its
cell, the hollow of this admits the exterior air to the
wounded vessels, and forms a resen'oir for moisture,
agents which promote the progress of putrefaction,
and assist the penetrating influence of the freezing
temperature.

Canker. "Wliatever may be the disease under which
a plant is suffering, it is too usual for the cultivator
to confine his attention to the part immediately af-
fected. It is looked upon as a strictly local derange-
ment, and the remedies are as erroneously topical.

278 PRINCIPLES OF GARDENING. [CH. VIII.

To consider that because a bud, a brancli, or a root
is diseased, that the cause of the disorder is to be
sought for there, is as sensible as to suppose that
every local pain endui'ed by the human frame arises
from a disorganization of that part. On the con-
traiy, we Imow that the diseases of animals arise al-
most universally from the stomach; and, as Addi-
son remarked, " that physic is generally the substi-
tute for temperance or exercise." The functions of
the stomach, by whatever cause deranged, render di-
gestion imperfect, and the secretions defective ; the
bile is superabimdant or deficient in quantity, and
head-ache is the result ; the liver is diseased, and it
causes a pain the most acute between the shoulders ;
the blood is ill elaborated, and eruptions are thrown
out on the surface of the body. With plants it is
the same. It may be laid do-«ii as an axiom, ^rith-
out exception, that all vegetable diseases, unpre-
ceded by external injmy, arise from the unhealthy
state of the sap — a state brought about conjointly or
separately by the improper food imbibed, and the de-
ranged digestive power of the leaves and other or-
gans. That this is so will not appeal' strange, when
we reflect, that from the sap all parts of the plant
are formed, and are continually increased in number
and size. The solid substance of the wood, and the
temporaiy tender blossoms are alike extracted from
that circulating fluid. If the constituents for tliese

I

CH. VIII.] THE DISEASES OF PLANTS. 279

are wanting, or if improper components are intro-
duced, disease is the necessaiy consequence. Dis-
ease, which in youth and manhood usually arises
from intemperance and over-excitement, visits old
age as a consequence of its decayed \dtal powers;
and, " if the silver cord has not been loosed," or
" tlie golden bowl broken" by the short-sighted indul-
gence of early years, man gradually declines into the
■ grave, as the vital organs cease to perfonn their of-
fices, because the limit of existence natui'al to his
species has been attained. Some diseases pecidiar
to old age are prematurely induced in the usually
vigorous period of life by licentious indulgences, in-
di\idual or hereditaiy. Ossification of the vascular
system is an example. In the vegetable part of the
creation, the canker or ulcer, to which our apple,
pear, elm, and other trees are subject, is a somewhat
parallel instance. This disease is accompanied by
different symptoms, according to the species of the
tree which it infects. In some of those whose tme
sap contains a considerable quantity of free acid, as in
the genus Pyms, it is rarely accompanied by any dis-
charge. To this dry form of the disease it would be
well to confine the term canker, and to give it the
scientific name of Gangrana sicca. In other trees,
whose sap is characterized by abounding in astringent
or mucilaginous constituents, it is usually attended
by a sanious discharge. In such instances, it might

280 PRINCIPLES OF GARDENING. [CH. VIII.

strictly be designated ulcer, or Gangrana saniosa.
This disease has a considerable resemblance to the
tendency to ossification which appears in most aged
animals, arising from their marked appetency to se-
crete the calcareous saline compounds that chiefly
constitute their skeletons. The consequence is an
enlargement of the joints, and ossification of the cir-
culatory vessels and other parts, phenomena very ana-
logous to those attending the cankering of trees. As
in animals, this tendency is general throughout their
system; but, as is observed by Mr. Knight, " like
the mortification in the limbs of elderly people,'" it
may be determined as to its point of attack, by the
irritability of that part of the system. This disease
commences with an enlargement of the vessels of the
bark of a branch, or of the stem. This swelling in-
variably attends the disease, when it attacks the
apple tree. In the pear the enlargement is less, yet
is always present. In the elm and the oak some-
times no swelling occurs ; and in the peach I do not
recollect to have seen any. I have never observed
the disease in the cherry tree, nor in any of the pine
tribe. The swelling is soon commmiicated to the
wood, which, if laid open to view on its first appear-
ance, by the removal of the bark, exhibits no marks
of disease beyond the mere unnatural enlargement.
In the course of a few years, less in number in pro-
portion to the advanced age of the tree, and the un-

CH. VIII.] THE DISEASES OF PLANTS. 281

favourable circumstances under which it is vege-
tating, the swelling is greatly increased in size, and
the albumiun has become extensively dead ; the su-
perincumbent bark cracks, rises ia discoloured scales,
and decays even more rapidly than the wood beneath.
If the caries is upon a moderately-sized branch, the
decay soon completely encircles it, extending through
the whole alburnum and bark. The circulation of
the sap being thus entu'ely prevented, all the parts
above the disease necessarily perish. In the apple
and the pear the disease is accompanied by scarcely
any discharge ; but in the elm this is veiy abundant.
The only chemists who have examined these morbid
products are Sir H. Davy and Vauquelin ; the former s
obseiTations being confined to the fact, that he often
fomid carbonate of lime on the edges of the canker
in apple-trees^.

Vauquelin has examined the sanies discharged
from the canker of an elm with much more precision.
He found this liquor nearly as transparent as water,
sometimes slightly coloured, at other times a blackish
bro^vn, but always tasting acrid and saline. From
this liquor a soft matter, insoluble in water, is de-
posited upon the sides of the ulcer. The bark over
which the transparent sanies flows attains the ap-
pearance of chalk, becoming white, friable, cr}'stal-
line, alkahne, and effervescent mth acids. A

* Elements of Agric. Chemistry, 2nd ed. p. 246.

282 PRINCIPLES OF GARDENING. [CH. VIII.

magnifier exhibits the crj^stals in the forms of
rhomboids and four sided prisms. When the liquid
is dark coloured, the bark appears blackish, and
seems as if coated \^dth varnish. It sometimes is dis-
charged in such quantities as to hang from the bark
like stalactites. The matter of which these are
composed is alkaline, soluble in water, and with acids
effervesces. The analysis of this dark slimy matter
shews it to be compounded of carbonate of potass
and ulmin, a product peculiar to the elm. The white
matter deposited round the canker was composed of —

Vegetable matter . . . 60.5

Carbonate of potass . . 34.2

Carbonate of lime . . 5.0

Carbonate of magnesia . 0.3

100.0
Vauquelin calculated from the quantity of this
white matter that was found about the canker of an
elm, that 5001b. weight of its wood must have been
destroyed a. There is no doubt that such a discharge
is deeply injurious to the tree, but the above learned
chemist appears to have largely erred, for he calcu-
lated from a knowledge of the amount of the saline
constituents in the healthy sap, whereas in its
diseased state these are much and unnaturally
increased. I once was of opinion, that this disease

' Annales de Chimie, xxi. 30.

CH. Yin.] THE DISEASES OF PLANTS. 283

does not arise from a general diseased state of the
tree, but that it is brought on by some bruise or
injury, exasperated by an unhealthy sap consequent
to an unfavourable soil, situation, and culture : but
more extensive and more accurate examinations con-
vince- me that the disease is in the tree's system ;
that its juices are vitiated; and that disease ^ill
continue to break out independent of any external
injur}% so long as these juices continue peccant and
unaltered. This conclusion will be justified, I think,
by the preceding facts, as well as by those distributed
through the following pages.

The disease is not strictly confined to any par-
ticular period of the tree's age. I have repeatedly
noticed it in some of our lately introduced varieties
that have not been grafted more than five or six
years ; and a writer in the Gardener's Magazine,
vol. V. p. 3, states, that the trees in his orchard,
though " only of four years' growth, are sadly troubled
\sith the canker." Although young trees are liable
to this disease, yet their old age is the period of
existence most obnoxious to its attacks. It must be
remembered, that that is not consequently a young
tree which is lately grafted. If the tree from which
the scion was taken be an old variety, it is only the
multiplication of an aged individual. The scion may
for a few years exhibit signs of increased vigour,
owing to the extra stimulus of the more abundant

284 PRINCIPLES OF GARDENING. [CH. VIII.

quantity of healthy sap supplied by the stock ; but
the vessels of the scion vdW, after the lapse of that
period, gradually become as decrepid as the parent
tree. The unanimous experience of naturalists
agrees in testifying that eveiy organized creature
has its limit of existence. In plants it varies from
the scanty period of a few months, to the long
expanse of as many centuries ; but of all, the days
are numbered ; and although the gardener's,' like the
physician's skill, may retard the onward pace of
death, he will not be permanently delayed. In the
last periods of life, plants shew every symptom that
accompanies organization in old age, — not only a
cessation of growth, but a decay of former develope-
ment, a languid circulation, and diseased organs.

The canker, as already observed, attends especially
the old age of some fruit trees, and of these the
apple is most remarkably a sufferer. " I do not
mean" says Mr. Knight, "to assert that there ever
was a time when an apple tree did not canker on
unfavourable soils, or that higlily cultivated varieties
were not more subject to the disease than others,
where the soil did not suit them. But I assert,
from my omti expeiience and obsen^ation within the
last twenty years, that this disease becomes progres-
sively more fatal to each variety, as the age of that
variety, beyond a certain period, increases : that if
an old worn-out orchard be replanted with fruit trees,

CH. VIII.] THE DISEASES OF PLANTS. 285

the varieties of the apple which I have found in the
catalogues of the middle of the seventeenth century,
are unproductive of fruit, and in a state of dehility
and decay. "^

Among the individuals particularly liable to be in-
fected, are those which have been marked by an ex-
cessively vigorous growth in their early years. I had
one in my garden at Great Totham, which for the first
twelve years of its existence was remarkable for the
unnaturally large size and abundance of its annual
shoots. It then became grievously affected by canker
which at length destroyed it.

Trees injudiciously pruned, or growing upon an
uugenial soil, are more frequently attacked than those
advancing under contrary circumstances. The oldest
trees are always the first attacked of those similarly
cultivated. The golden pippin, one of the oldest
existing varieties of the apple, is more frequently
and more seriously attacked than any other.

The soil has a very considerable influence in
inducing the disease. If the subsoil be a ferruginous
gravel, or if it is not well drained, and the soil be
aluminous, and effective means are not adopted to
free it of superabundant moisture — the canker, under
any one of these circumstances, is almost certain to
make appearance amongst the trees they sustain,

* Some doubts as to the Efficacy of Mr. Forsyth's Plaster, by
T. A. Knight, Esq. P. L. H. S., &c., 1802.

286 PRINCIPLES OF GARDENING. [CH. VIII.

however young and vigorous they were when first
planted.

How inductive of this disease is a wet retentive
subsoil, if the roots penetrate it, appears from the
statement of Mr. Watts, gardener to R. G. Rus-
sell, Esq., of Chequer's Court, in Bucldughamshire.
A border beneath a south wall had a soil three feet
and a half in depth, apparently of the most fertile
staple, twice re-made imder the du'ection of the
late Mr. Lee, of the Vineyard, Hammersmith. In
this the trees, peaches and nectarines, flourish for the
next three or four years after they are planted, but ai'e
then rapidly destroyed by the canker and gum. The
subsoil is a stiff sour clay, nearly approaching to a
brick eaith ; and the disease occm-s as soon as it is
reached by the roots of the trees ^. Mr. Forsyth
concluded that the soil is not always the soui'ce of
the disease, because it universally and invariably
appears at first in the branches, and proceeds thence
towards the roots of the tree. But this is certainly
not a conclusion waiTanted by the premises, because
the acridity of the sap, whatever may be its soirrce,
would be likely to injiu'e and corrode, in the first
instance, those parts where the vessels are the most
weak and tender ; now these, past dispute, are in the
branches. Moreover, we generally see the youngest
branches the earliest sufferers.

" Grardener's Magazine, vi. 617.

CH. YIII.] THE DISEASES OF PLAKTS. 287

Pruning has a povrerful influence in preventing
the occuiTence of the canker. I remember a standard
russet apple tree, of not more than twenty years'
growth, with a redundancy of ill-arranged branches,
that was excessively attacked by this disease. I
had two of its three main branches and the laterals
of that remaining carefully thinned ; all the in-
fected parts being at the same time removed. The
result was a total cm'e. The branches were annually
regulated, and for sLx years the disease never re-
appeared. At the end of that time the tree had to be
removed, as the gi'omid it stood upon was required
for another pm'pose. John Williams, Esq. of Pit-
maston, from long experience, concludes that the
golden pippin and other apples may be presented
from this disease, by pnining away every year that
part of each shoot which is not perfectly ripened.
By pui-suing this method for sLx years, he brought a
dwarf golden pippin tree to be as ^dgorous and as
free from canker as any new variety^.

All these facts unite in assuring us that the
canker arises from the tree's weakness, from a de-
ficiency in its \ital energ}', and consequent inability
to imbibe and elaborate the nourishment necessary to
sustain its frame in "sdgoui', and much less to supply
the healthy developement of new parts. It matters
not whether its energ}' be broken down by an unna-
tural rapidity of growth, by a disproportioned excess
^ Trans. London Horticultural Society, vi. Art. 61.

288 PRINCIPLES OF GARDENING. [CH. VIJI.

of branches over the mass of roots, by old age,
or by the disorganization of the roots in an ungenial
soil ; they render the tree incapable of extracting
sufficient nouiishment from the soil, consequently
incapable of developing a sufficient foliage^, and
therefore unable to digest and elaborate even the
scanty sap that is supplied to them.

The reason of the sap becoming unnaturally saline
appears to be, that in proportion as the vigour of
any vegetable declines, it loses the power of select-
ing by its roots the nourishment congenial to its na-
ture. M. Saussure found in his experiments, that
the roots of plants, growing in saline solutions,
absorbed the most of those salts that were injurious
to them, evidently because the declining plant lost
the sensitiveness and energy necessary to select and
to reject.

M. Saussure also found, that, if the extremities of
the roots were removed, the plants absorbed all
solutions indiscriminately^.

An imgenial soil would have a debilitating influ-
ence upon the roots in a proportionate, though less
violent, degree than the sulphate of copper, and as
these consequently would absorb soluble bodies more
freely, and Avithout that discrimination so absolutely
necessary for a healthy vegetation, so the other

* No sjinptoms of a cankered tree is more inYariable than a
deficiency of leaves.

•» Saussiire's Recherches Chimiques sur la Vegetation^ 260.

CH. VIII.] THE DISEASES OF PLANTS. 289

most essential organs of nutrition, the leaves, of the
weakened plant, would promote and accelerate the
disease. These, reduced in number and size, do
not properly elaborate the sap ; and I have always
found that, under such circumstances, these stimted
organs exhale the aqueous particles of the sap veiy
abmidantly, whilst their power of absoi-ption is
greatly reduced. The sap, thus deficient in quan-
tity, and increased in acridity, seems to corrode,
and affect the vascular system of the tree in the
manner already described.

These facts afford us most important guides in
attaining the desired objects, the prevention and
cure of the disease.

If superluxuriance threaten its introduction, the
best remedy is for the cultivator to remove one of
the main roots of the tree, and to be particularly
careful not to add any fertile addition to the soil
^^ithin their range. On the contraiy, it will be
well if the continued exuberant gro\\1;h shews its
necessity for the staple of the soil to be reduced in
fertility by the admixture of one less fertile, or even
of drift sand.

If there be an excess of branches, the saw and
the pruning knife must be gradually appHed. It
can be only trees of very weak vital powers, such
as is the golden pippin, that \\ill bear the general
cutting of the annual shoots, as pursued by Mr.

u

290 PRINCIPLES OF GARDENING. [CH. VIII.

Williams. A new \dgorous variety would exhaust
itself, the following year, in the production of fresh
wood. Nothing beyond a general rule for the
pruning can be laid doMH, and it amounts to no
more than the direction to keep a considerable
vacancy between every branch, both above and be-
neath it; and especially to provide, that not even
two twigs shall chafe against each other. The
greater the intensity of light, and the freer the
circulation of air amongst the foliage of a tree,
the better the chance for its healthy vegetation.

If the disease be in a fiiiit tree, it is probably
a premature senility, induced by injudicious ma-
nagement, for very few of our varieties are of an
age that insure to it decrepitude. I have never
yet known a tree, unless it was in the last stage
of decay, that could not be recovered by gi^ing it
more air and light, by careful heading in, pruning,
improvement of the soil, and cleansing the bark.

If the soil by its ungenial character induces the
disease, the obvious and only remedy is its ame-
lioration, and if the subsoil be the cause of the mis-
chief, the roots must be prevented strildng into it.
In all cases, it is the best practice to remove the
tap-root. Many orchardists pave beneath each tree
with tiles and broken bricks. If the trees are
planted shallowly, as they ought to be, and the sur-
face of the soil kept duly fertile, there is not much

CH. VIII.] THE DISEASES OF PIANTS. 291

danger of the roots striking into the worse pasturage
of the subsoil. On this point, the experience of Mr.
W. Nichol, the gardener at Newick Place, in Sussex,
agrees Anth my own. He says that the canker
may he avoided in most instances by paying proper
attention to the soil in which the tree is planted.
Canker, he thinks, will seldom occur if the surface-
soil is good, for in that case the roots aatII never
descend into the prejudicial subsoil, but spread out
their radicles near the surface, where they find food
most abundant. If this is not kept up, the roots
descend into the obnoxious substratum, and the
disease assuredly follows^.

It remains for me to detail the course of treat-
ment that I have always found successful in effecting
a cure in any variety not decrepit from age, if the
canker has not spread to the roots.

Having completely headed down, if the canker is
generally prevdent, or duly thinned the branches,
entirely removed every small one that is in the
least degree diseased, and cut away the decayed
parts of the larger, so as not to leave a single speck
of the decayed wood, I cover over the sm'face of
each wound with a mixture, whilst in a melted state,
of equal parts tar and rosin, applying it vdth a

* Baxter's Library of Agric. and Hortic. Knowledge, 3rd
Edit. 22.

u2

29'3 PRINCIPLES OF GARDENING. [cU. VIII.

brush immediately after the amputations have been
performed, taking care to select a diy day. I prefer
this to any composition with a basis of cow-dung
and clay, because the latter is always more or less
absorbent of moistui'e and is liable to injury by rain
and frost, causing alternations of moisture and dry-
ness to the wounds, that promote decay rather than
their healing, by the formation of new wood and bark.
The resinous plaster seldom or never requires re-
newal. Mr. Forsyth, the arch advocate of earthy
and alkaline plasters, finding that they promoted
decay, if applied to the wounds of autumn-pruned
trees, recommends this important act of cultivation
to be postponed to the spring. Such a procrastination
is always liable to defer the pruning until bleeding
is the consequence. If a resinous plaster be em-
ployed, it excludes the wet, and obviates the objection
to autumnal pnming. Mr. Fors}'th's treatment of
the trunks and branches of trees, namely, scraping
from them all the scaly, dry exuvite of the bark, is
to be adopted in every instance. He recommends
5 them to be brushed over with a thin liquid com-
pound of fresh cow-dung, soap-suds, and urine ; but
I veiy much prefer a brine of common salt. Each
acts as a gentle stimulus, which is their chief cause
of benefit ; and the latter is more efficacious in de-
stro}dng insects, and does not, like the other, obstruct

CH. VIII.] THE DISEASES OF PLANTS. Q93

the respiratoiy vessels of the tree. The brine is
advautageously inihbed in with a scrubbing, or large j
painter's biiish. Some persons recommend a liquid
wash, containing, as prominent ingredients, quick-
lime and wood ashes, which, as the disease arises
from an over-alkalescent state of the sap, cannot but
prove injurious, and aggravate the disease. Mr.
Forsyth, formerly gardener at Kensington Palace,
made a considerable sensation at the close of the
last, and at the commencement of the present cen-
tury, by the wonderful effects produced upon trees,
as he asserted, by the following composition, used as
a plaster over the womids from which the decayed
or cankered parts had been cut out : —

One bushel of fresh cow dimg.

Half a bushel of lime iTibbish ; that from ceilings of

rooms is preferable, or powdered chalk.
Half a bushel of wood ashes.
One sixteenth of a bushel of sand ; the three last to

be sifted fine. The whole to be mixed and beaten

together until they form a fine plaster 3.

Mr. Knight, in a very able and sarcastic pamphlet
published in 180^, entitled " Some Doubts relative
to the Efficacy of Mr. Forsjlh's Plaster," fully
exposed tlie quackeiy, perhaps falsehood may not be
too harsh a term, of this horticulturist's statements.
* Forsyth's Observations on Fruit Trees, p. 68.

204 PRINCIPLES OF GARDENING. [CH. VIII.

Mr. Forsyth received a pai'liamentary grant of
money for his discovery ; but this, as Mr. Ivnight
obsen-es, " affords a much better proof that he -was
paid for an impoitaut discovery than that he made
one."

" Should the pubhc," continues this distinguished
physiologist, " believe that an old dying tree can be
restored to youth and vigour, merely by being
plastered with lime, cow-dung, and wood ashes, and
that a piece of such tree may by such means be
made immortal, I think it would be a good spe-
culation for some enterprising genius, in imita-
tion of the quack doctors of the sixteenth century,
to bring forward a nostnim to restore and per-
petuate youth in the human subject. Should such
a projector join Mr. Forsyth, and the one imder-
take the animal, and the other the vegetable world,
under Dr. Andersons patronage, I will ventm'e
to predict that the success of each in the cures
they perform will be equal."
j It has been very ingeniously suggested, that, if a
1 destruction of the bark by external violence, txnd
consequently, likely to terminate in canker, has
1 occurred, it would be a good plan to insert, as in
budding, a piece of living bark, exactly correspond-
ing to the excision, from a less valuable tree.

In conclusion, I would enforce upon the or-
chai'dist s attention the importance of obtaining his

CH. VIII.] THE DISEASES OF PL.A.NTS. 295

grafts or buds from trees not affected by the disease,
because, apparently, it is hereditary ; and, although
after-culture may eradicate the malady, it is always
far better to avoid the infection than to have to
employ a specific.

Having noticed the gangrene as it appears in
various forms upon our trees, we may now turn to a
few of the many instances where it occurs to our
fruits and flowers, for it is not too much to say that
scarcely a cultivated plant is within our enclosures
that is not liable to its inroads. It assumes dif-
ferent aspects, and varies as to the organs it assails,
yet still in some mode and in some of their parts all
occasionally suffer, for it is the most common form of
vegetable disease.

The canker in the auricula is of this nature, being
a rapidly spreading ulcer, which, destroying the whole
texture of the plant where it occurs, prevents the rise
of the sap. Some gardeners believe it to be infectious,
and therefore destroy the specimen in which it
occurs, unless it be very valuable; but this I believe
to be an erroneous opinion, the reason of its appear-
ing to be infectious or epidemic, being that it occurs to
many when they are subjected to the same injurious
treatment which gives birth to the disease.

It appears to be caused by the application of too
much water, especially if combined with superabund-
ant nourishment. Therefore, although cutting out

296 PRINCIPLES OF GAPvDENIKG. [CH. VIII,

the decaying part when it first appears, and appljdng
to the wound some finely powdered charcoal, will effect
a cure if the disease has not penetrated too deeply,
yet it mil he liahle to return immediately if a less
forcing mode of culture he not adopted. No auricula
mil suffer from this disease if it he shifted annually,
and the tap-root at the time of moving be shortened,
a thorough system of draining being adopted, either
by using one of the pots suggested in a previous part
of this work, or by having the pot used one-fourth
filled with pebbles ; and excessive damp during the
winter being prevented by proper shelter.

Parsley grown in a poor soil is also liable to canker
in the winter. Mr. Barnes says he never found any
application w^ich eradicated this disease so effectu-
ally as a mixture in equal parts of soot and slacked
lime sown over the plants. The cure is complete in
a few days, and the vigour of the plants restored,
indicating that this species of ulceration, like that
which is found in the dwellings of the poor, arises
from deficient nourishment.

The spot, as it is technically termed, occurring on
the leaves of the jwlargoniiim, is a dry gangrene,
occasioned by an irregularity in the supply of
moisture, and vicissitudes of temperature, but espe-
cially if one of the extremes is much below the
degree of heat most favourable to the healthy growth
of that plant. The reason of this is very obvious.

CH. VIII.] THE DISEASES OF PLANTS. 297

If a pelargonium, or any other plant, be placed in a

highly stimulating heat, and is abundantly supplied

with root-moisture, it immediately increases its sur-

face of leaf to elaborate and digest the large amount

of sap forwarded from the roots. If this amount of

sap is subsequently suddenly reduced, by lowering the

temperature and adding water to the soil less freely.

the increased suiface of leaf is no longer required,

and it is a law pervading all the vegetable creation,

that the moment any of the parts of a plant are

unnecessaiy to it, that moment it begins to decay.

I placed a plant of the Manuel of Peru, or Heliotrope,

in a high temperature, and supplied it abundantly

"\nth water until its leaves were much increased in

size ; the temperature and moisture were then much

reduced, and the leaves in a few days were completely

decayed round their edges and in spots upon their

surfaces. The extent of leaf was accommodated to the

amount of sap to be elaborated.

The tubers of the potato also are liable to the
speck, black spot, or diy gangrene ; a disease which
I once thought was occasioned by the calcareous
earth (lime, or chalk) contained by the soil, but more
lengthened observation has con\dnced me of my
error ; and having obsen^ed it in all soils, and in
seasons characterized by opposite extremes of wet-
ness and dryness, I am induced to consider that the
disease arises from some defect in the sets employed ;

20S PRINCIPLES OF GARDENING. [CH. VIII,

or to potatoes being grown too often on the same
site. It is quite certain from my own experience,
that in ground tired of potatoes, the disease invari-
ably and most extensively appears. This suggests
that it is occasioned by a deficiency of some con-
stituent in the soil required by the tubers, a sug-
gestion confirmed by the fact that in the fields of the
market gardeners near London, which are supplied
without stint with the most fertilizing manure, this
disease of the potato comparatively is unknown.

The stems of succulent plants, such as the cacti,
mesembryanthemums, and the balsam, as well as
the fruit of the cucumber and melon, and the stalk
of the grape, are all liable to moist gangrene ; all
requiring for the developement of the disease exces-
sive moisture in the air, though the immediate cause
of its outbreak is usually a sudden reduction of tem-
perature.

Extravasated Sap. — Under tliis general name I
puq)ose to include the consideration of gumming,
bleeding, and other injurious affections under which
plants occasionally labour, on account of their sap
escaping from the properly containing vessels. The
extravasation proceeds either from the albumnm or
from the inner bark, and may arise from five causes :
1. The acrid or alkaline state of the sap, which
has been considered already, when treating of the
canker. 2. From plethora, or excessive abundance

CH. VIII.] TnE DISEASES OF PLANTS. 299

of the sap effused. 3. From tlie unnatural contrac-
tion of the circulatory vessels. 4. From wounds.
5. Heat and dryness.

1. With regard to the alkaline state of the sap,
it may be observed, additionally, that the excessive
alkaline quality of the sap, imparting to it the power
of destroying the fibre of its containing vessels, is
placed on the basis of chemical experiment. A weak
alkalme solution dissolves woody fibre, Avithout altera-
tion ; and it may be thrown down again by means of
an acid. By this property we are enabled to sepa-
rate wood from most of the other vegetable princi-
ples, as few of them are soluble in weak alkaline leys^.
It is tiTie that the vital principle may counteract
powerfully this chemical action ; but it will not con-
trol the corrosive effect of an active agent in excess,
if repeated for any length of time. The blood of the
human system contains, when in a healthy state, a
portion of common salt ; yet if this saline constituent
is in excess, it induces inflammation and organic de-
rangement.

'2. Plethora is that state of a plant's excessive
vigour, in which the sap is formed more rapidly than
the circulatory vessels can convey it away. When
this occurs, inipture must take place ; for the force
with which it is propelled during circulation, and
cons^equently, the force acting to burst the vessels

^ Thomson's System of Chemistry, vol. iv. p. 180. 6th ed.

300 PRINCIPLES OF GARDENING. [CH. YIII.

during any check, is very much greater than coukl
have been expected, before Mr. Hales demonstrated
it by experiment. This distinguished vegetable
physiologist found, that in the vine this furce Avas
able to raise 19 lbs. weight. To the stem of a vine
cut off about two feet and a half from the ground, he
fixed a mercurial gauge, and luted it to the sides of
the stem with mastic. The gauge was in the form of
a syphon, so contrived, that the mercmy might be
made to rise in proportion to the pressure of the as-
cending sap. In this instance it raised the mercury
to a height of thirty-eight inches^. The branch of
an apple-tree was separated from the parent trunk,
and placed in water. When the leaves were upon it,
the force with which it propelled its sap, raised the
mercur}' four inches, in a tube attached as to the
vine; but a similar branch, deprived of its leaves,
scarcely raised the mercury a quarter of an inch.
The pear, quince, cherry, walnut, peach, gooseberry,
and sycamore, had a power equal to elevating the
mercur)% varying from three to six inches. The elm,
the oak, chesnut, hazel, sallow, and ash, elevated it
variously from one to two inches. The laurustinus,
laurel, and other evergreens, scarcelv raised the mer-
cury at all ^.

The experiments made with a separated branch do

* Hale's Vcget. Statics, vol. i. p. 107.
b Ibid. p. 114, &c.

CH. VIII.l THE DISEASES OF PLANTS. 301

not give the full amount of the parent tree s power,
because the exhaustion incident to amputation neces-
sarily diminishes the vigour, and every minute the
power in the branch is reduced, because it is so
much the nearer to death.

Now we know that a much less pressure than any
of those above mentioned would be capable of burst-
ingf the delicate membranes of anv of their exterior
descending sap vessels ; and it is in such outer ducts
that the injuiy first occurs. ^Yhen one exterior ves-
sel is ruptured, that next beneath it, having the sup-
porting pressure removed, is enabled to follow the
same course at the same locality ; and in proportion
to the length of the time that the sap continues in
excess, is the depth to which the mischief extends,
and the quantity of sap extravasated.

If the extravasation proceeds from this cause, there
is but one course of treatment to be pursued : sever
one of the main roots, to afford the tree immediate
relief, and reduce the staple of the soil, by remo\dng
some of it, and admixing less fertile earthy compo-
nents, as sand or chalk. This must be done gra-
dually, for the fibrous roots that are suited for the
collection of food from a fertile soil, are not at once
adapted for the introsusception of that from a less
abundant pasturage.

Care must be taken not to apply the above reme-
dies, before it is clearly ascertained that the cause is

302 PRINCIPLES OF GARDENING. [CH. VIII.

not an unnatural contraction of the sap vessels — be-
cause, in such case, the treatment might be injurious
rather than beneficial. I have ahvays found it aris-
ing from an excessive production of sap, if the tree,
when afflicted by extravasation, produces at the same
time superluxuriant shoots.

3. Local contraction of the sap vessels. If the ex-
travasation arises from this cause, there is usually a
swelling of the bark immediately above the place of
dischari^e.

I had a cherry tree in my garden, in Essex, of
which the stock grew very much less freely than the
graft. Consequently, just above the place of union,
a swelling, resembing a wen, extended round the
whole gii'th of the tree, from which swelling, gum
was continually exuding. In the stem below it
I never observ^ed a single extravasation. In a case
such as this, the cultivators only resource is to
reduce cautiously the amount of branches, if the
bleeding threatens to be mjuriously extensive, other-
wise it is of but little consequence, acting like tem-
porary dischaiges of blood from the human frame,
as a relief to the system.

4. The extravasation of the sap from a wound is
usually the most abundant, and therefore the most
exhausting ; and as the wound, whether contused
or cut, is liable to be a lodgement for water and
other foreign bodies, opposed to the healing of the

CH. VIII,] THE DISEASES OF PLANTS. 308

injured part, the discharge is often protracted. This
is especially the case, if the wound he made in
the spring, hefore the leaves are developed, as in
performing the vrinter pruning of the vine later
than is proper. In such case the vine is always
weakened, and in some instances it has been destroyed.
The quantity of sap which may be made to flow from
some trees is astonishing, especially in tropical
climates. Thus from a cocoa-nut palm, fi'om three
to five pints of sap will flow dming eveiy day for
four or five successive weeks.

The best mode of checking such exudations, is by
placing a piece of sponge dipped in a solution of
sulphate of iron, upon the discharging place, covering
the sponge with a piece of sheet lead, and binding
it on firmly. The sulphate acts as a styptic, pro-
moting the contraction of the mouths of the vessels ;
the sponge encourages cicatrization, and the lead
excludes moisture.

5. Heat, attended by dryness of the soil, as during
the drought of summer, is very liable to produce an
unnatural exudation. This is especially noticeable
upon the leaves of some plants, and is popularly
known as honey-dew. It is somewhat analogous to
that out-burst of blood which, in such seasons, is
apt to occur to man, and arises from the increased
action of the secretory and circulatory systems to
which it affords relief. There is this great and

304 PRINCIPLES OF GARDENING. [CH. VIII.

essential difference, that in the case of the plants
the extravasation is upon the surface of the leaves,
and consequently, in proportion to the abundance of
the extruded sap is their respiration and digestion
impau'ed.

Azaleas sometimes, hut rarely, have the impubes-
cence on their leaves, especially on their lower sur-
face, beaded as it were with a resinous exudation.
This can scarcely he called a disease. It is never
found but upon plants that have been ke2)t in a
temperatiu'e too high, and in a soil too fertile. It is
an effort to relieve the surcharged vessels, and occurs
in various forms in other plants.

The honey-dew was noticed by the ancients and is
mentioned by Pliny ^ by the fanciful designation of
the " sweat of the heavens," and the '• saliva of the
stars," though he questioned whether it is a deposition
from the air, purging it from some contracted im-
purity. More modem philosophers have been quite
as erroneous and discordant in their opinions relative
to the diseases nature. Some, with the mostunmi-
tigatable asperity declare that it is the excrement of
aphides : others as exclusively maintain that it is an
atmospheric deposit ; and a third party consider that
it arises from bleeding consequent to the woimds of
insects. That there may be a glutinous, saccharine
liquid found upon the leaves of plants arising from

^ Hist. Natur. xi. 12.

CH. VIII.] THE DISEASES OF PLANTS. 305

the fii-st and third named causes is probable, or
rather certain, but this is by no means conclusive
that there is not a similar liquid extravasated upon
the surface of the leaves, o^^ing to some unhealthy
action of their vessels. It is vrith this description of
honey.dew that we are here concerned. The error
into which writers on this subject appear to have
fallen, consists in then* having endeavoui'ed to assign
the origin of every kind of honey-dew to the same
cause. Thus the Rev. Gilbert White seems (Natu-
ralist's Calendar, 144) to have had a fanciful and
comprehensive mode of accountuig for the origin of
honey-dew: he tells us, "June 4, 1783. Vast honey-
dews this week. The reason of this seems to be,
that in hot days the effluvia of flowers are dmvm. up
by a brisk evaporation, and then in the night fall
down with the dews with which they are entangled."

The objection ui'ged to this theoiy by Ciu'tis
(Trans. Linn. Soc. vi. 82) is conclusive. " If it fell
from the atmosphere, it would cover every thing on
which it fell indiscriminately, whereas we never find it
but on certain liviug plants and trees ; we find it also on
plants in stoves and green-houses covered -svith^lass."

Curtis had convinced himself that the honey-dew
was merely the excrement of the aphides ; and he
supported his theoiy Ts-ith his usual ability, although
he justly deemed it a little " wonderful extraordin-
ary," that any insect should secrete, as excrementi-

X

306 PEINCIPLES OF GAKDENING. [CH. VHI.

tious matter, sugar, — he even thought it possible
that if the ants, wasps, and flies, could be prevented
from devouring the honey dew " almost as fast as it
was deposited," to collect it in considerable quantities
and convert it into the " choicest sugar and sugar
candy." The bees, however, he found totally disre-
garded the honey dew which came imder his observ-
ation. With the opinion of Mr. Curtis I do not
agree, any more than does the Abbe Boissier de
Sauvages, who, in a memoir read before the Society
of Sciences, at Montpelier, gives an account of '* a
shower of honey- dew," which he witnessed imder a
lime tree in the King's garden at Paris.

The various successful applications of liquids to
plants, in order to prevent the occurrence of the
honey-dew, and similar diseases, would seem to
indicate that a morbid state of the sap is the chief
cause of the honey-dew, for otherwise it would be
difficult to explain the reason why the use of a solu-
tion of common salt in water, applied to the soil in
which a plant is growing, can prevent the appearance
of a disease caused by insects. But if we admit that
the irregular action of the sap is the cause of the
disorder, then we can understand that a portion of
salt introduced into the juices of the plant woidd
natm'ally have a tendency to correct or vary any
morbid tendency, either correcting the too rapid
secretion of sap, stimulating it in promoting its

CH. VIII.] THE DISEASES OF PLA^'TS. 307

regular fomiation, or presenting its fluidity. And
that, by such a treatment, the honey-dew may be
entirely prevented, I have myself often witnessed in
my own garden, when experimentalizing with totally
different objects. Thus I have seen plants of various
kinds which have been treated with a weak solution
of common salt and water totally escape the honey-
dew, where trees of the same kind, growing in the
same plot of ground, not so treated, have been ma-
terially injured by its ravages. I think, however,
that the solution which has been sometimes employed
for this purpose is much too strong for watering
plants. I have always preferred a weaker liquid,
and am of opinion that one ounce of salt (chloride of
sodium) to a gallon of water is quite powerful enough
for the intended purpose. I am in doubt as to the
con'ectness of Knight's opinion as to the mere water
having any material influence in the composition of
such a remedy, since I have noticed that standard
fruit trees, around which, at a distance of six or eight
feet from the stem, I had deposited, at a depth of
twelve inches, a quantity of salt to promote the
general health and fniitfulness of the tree, according
to the manner fonnerly adopted to some extent in
the cyder counties for the apple orchards ; that these
escaped the honey-dew (which infected adjacent trees)
just as well as those which had been watered with
salt and water. It is ^rith much diffidence that I

x2

308 PRINCIPLES OF GARDENING. [CH. VIII.

doubt the correctness of any of the opinions of such
a man as the late lamented President of the Horti-
cultural Society, for to him is vegetable physiolog;^'
most deeply indebted for many highly scientific,
accm'ate, and interesting researches : he seemed, too,
on all occasions, to introduce into his experiments
an elegance of research and ingenious management,
worthy of the great class of organized substances to
which he devoted his valuable life. Will not some-
thing be done towards shewing the gratitude of his
contemporaries? Cannot some nook be found at
Westminster for his tablet?

CHAPTER IX.

DEATH AND DECOMPOSITION.

As in the animal creation the period of life varies
from a few hours in the ephemeron, to hundreds of
years in the tortoise, so among the vegetable tribes,
though it is circumscribed to a few months in some of
our annuals, yet it extends to centuries in the oak, the
chestnut, and the adansonia. But however varied in
space, each has its limit of existence ; and death,
though its inroad may be delayed, finally effects a
conquest over all.

Now, wliat is the death of a plant ? — and though
this queiy admits of the ready answer that it is a
want of the power to vegetate, though the requisites
for vegetation are present — yet one question more
difficult of solution follows upon this reply — what
is that power of wliich death is the negation ? — and
although neither the chemist nor the physiologist
have ever succeeded — probably never will succeed —
in penetrating further than to an acquaintance witli
the phenomena of that power, yet these we have
already seen are intimately connected with the gar-
dener s art, and the phenomena attending its absence
are not less worthy of his study.

310 PEINCirLES OF GARDENING. [CH. IX.

The phenomena of that power — which is justly
called vegetable life — have been traced in pre^'ious
pages from germination through all the stages of
growth, the developement of parts, the circulation
of the sap, the mysteries of the impregnation
and the matuiing of the fruit; and we will noAT
trace the phenomena of the plant's decline and final
decay.

The first symptom of that decline is a deficiency
of the usual annual developement of parts. A perma-
nently lessened production of shoots, or leaves, or
fruit — or of all these — becomes apparent ; and this
non-production arises from a diminished power in
the roots to imbibe, and of the vessels of the stem
and branches to impel, the sap.

Thus Hales always found that the two, three, and
foul' years' old branches of trees imbibed water with
much greater force than those of greater age ; and
that young A-igorous vines usually exuded their sap
with much oreater force than the older and less

o

robust. So I have found that our annuals, such as
the dwarf kidney bean, mignionette, clarkias, and
others, imbibed water with more than twofold ra-
pidity when in full bloom, than other plants of the
same species and size did in the autumn, though
they were still growing and verdant.

Now, w^hat is the cause of this deficient power —
this decline of vigour ? — To me there appears little

CH. IX.] DEATH AND DECOMPOSITION. 31 1

doubt that it is the exhaustion consequent upon
the production of seed. Scarcely an annual exists
which usually dies at the close of the season, after
ripening its seed, but may be made to retain a vigorous
existence if its inflorescence be removed as speedily
as formed. Mignionette is a very familiar example,
for this may be allowed to bloom, but if its flower
stalks be cut down before the seed-vessels are per-
fected, it becomes woody and shrubby, and ^^ill live
and bloom for three or more successive years. If
allowed to ripen its seed, it dies the same autumn.
The common nasturtium is an annual, but the
double nasturtium, says M. De Candolle, has be-
come a perennial, because its flowers, deprived of
the faculty of producing seeds, do not exhaust the
plant, and it is probable that every annual, rendered
double by cultivation, will become a perennial.

This explains why fniit trees are weakened, or
rendered temporarily improductive, and even killed,
by being allowed to ripen too large a crop of fniit,
or to " overbear themselves," as it is emphatically
tenned by the gardener.

The thinning of fruit is, consequently, one of the |
most important operations of the garden, though \
one of the least generally practised. On the weaker
branches of the nectarine and peach, an average
space of nine inches should be between each
brace of fruit, and on the most \'igorous wood

312 PRINCIPLES OF GARDENING. [CH. IX.

of the most healthy trees, they should not be
nearer than six inches. This enforcement of the
importance of thinning fruit, is not intended to be
confined to the two trees specified; it is equally
important to be attended to in all other finiit-bearers,
but especially the vine, apricot, apple, and pear. It
should be done with a bold, fearless hand — and the
perfection of that which is allowed to remain will
amply reward the grower in the harvest time for
the apparent sacrifice now made. But he will not
reap his reward only in this year ; for the trees thus
kept unweakened by over-production, will be able to
ripen their wood and deposit that store of inspis-
sated sap in their vessels, so absolutely necessary
for their fniitfulness next season.

The berries of the grape-vine are best thinned
from the branches with a sharp-pointed pair of
scissors, care being taken to remove the smallest
berries. This increases the weight and excellence
of the bunches, for two berries will always outweigh
four grown on the same branchlet of a bunch,
besides being far handsomer, and having more juice
as compared with the skins. The average weight of
the bunches on a ^ine may be taken, when ripe, at
half a pound each, and with this data it is easy to
carry into practice Mr. Clement Hoare's excellent
rule for proportioning the crop to the size of the
vine.

CH. IX.] DEATH AND DECOMPOSITION. 313

If its stem, measured just above the ground, be
three inches in cii'cumference, it may bear five
pounds weight of grapes.

3i inches 10 lbs.

i 15

^ 20

5 25

And so five pounds additional for eveiy half inch of
increased circumference.

Although fiTiit bearing is the most influential
curtailer of a plant's longevity, there are others of
scarcely less fatal efficiency, among which are im-
proper supplies of moisture, obnoxious soils., dele-
terious food, uncongenial temperatures, and deficient
light. These all tend to shorten a plants existence,
or even at once to destroy it if administered in a
violent or protracted degi'ee.

Excessive moisture induces that over succulency
which is ever attended by weakness, unnatural
growth, and early decay. Such plants more than
any others are sufferers by sudden \acissitudes, in the
hygrometric state of the atmosphere, and are still
more fatally visited if exposed to low reductions of
temperature.

Soils containing obnoxious ingredients are certain
introducers of disease and premature death. An
excess of oxide of iron, as when the roots of the

314 PRINCIPLES OF GARDENING. [CH. IX.

apple and pear get into an ii'ony red, gravelly
subsoil, al-ways causes canker to supervene. In the
neighboui'liood of copper-smelting furnaces not only
are cattle subjected to swollen joints, and other
unusual diseases, causing decrepitude and death, but
the plants also around are subject to sudden visit-
ations— to irregular growths, and to unwarned
destruction : and a crop once vigorous ^^•ill sud-
denly wither as if swept over by a blast. There is
no doubt of this arising from the salts of copper
which impregnate the soil irregularly as the winds
may have borne them sublimed from the furnaces,
and the experiments of Sennebier have she^vn, that
of all salts those of copper are the most fatal to
plants.

That they can be poisoned, and by many of those
substances, narcotic as well as corrosive, which are
fatal to animals, has been she^ii by the experi-
ments of M. F. Marcet. The metallic poisons being
absorbed are conveyed to the different parts of the
plant, and alter or destroy its tissue. The vege^
table poisons, such as opium, stiychnia, prussic
acid, belladonna, alcohol, and oxalic acid, which act
fatally upon the nenous system of animals, also
cause the death of plants. Does not this fa-
vour the opinion of those who believe that there
is something in plants analogous to the nerves in
animals? is the natui'ally suggested inquiiy made

CH. IX.] UEATH AND DECOMPOSITION. 315

bv Dr. Thomson, the Glasgow Regius Professor of
Chemistry.

The poisonous substance is absorbed into the
plants system, and proves injmious when merely
applied to its branches or stem, almost as much as
if placed in contact with the roots. Ulcerations and
canker ai*e exasperated if lime be put upon the
wounds : and when Dr. Hales made 'a golden rennet
apple tree absorb a quart of camphorated spuits of
wine through one of its branches, one half of the
tree was destroyed.

An uncongenial heat is as pernicious to vege-
tables as to animals. Every plant has a particular
temperatiuT, without which its functions cease, but
the majority of them luxuiiate most in a climate
of which the extreme temperatures do not much
exceed o'2'^ and 90°. No seed t,\tL1 vegetate, no sap
will circulate, at a temperature at or below the
freezing point of water, yet the juices of the plant are
not congealed even at a temperature fai' more de-
pressed, and I know of no other more satisfactory
proof, that like a cold-blooded animal, the frog and
the leech for example, it becomes torpid though life
is not extinct, imless excited by a genial temperature.
No cultivation will render plants, natives of the torrid
zone, capable of beaiing the rigoiu's of our ^^inters,
although their offsprmg raised from seed may be

316 PRINCIPLES OF GARDENING. [CH. IX.

rendered much more hardy than their parents.
When a new plant arrives from such tropical lati-
tudes, it is desirable to use eveiy precaution to
avoid its loss, but so soon as it has been propagated
from, and the danger of such loss is removed, from
that moment ought experiments to commence, to
ascertain whether its acclimatization is attainable.
That this should be done is self-evident ; for the
nearer such a desirable point can be attained, the
cheaper will be its cultivation, and consequently the
greater will be the number of those who mil be able
to derive pleasure from its growth. Hence, it is
very desirable that an extended series of experi-
ments should be instituted, to ascertain decisively
whether many of our present green-house and stove
plants would not endure exposure to our winters, if
but slightly or not at all protected. It may be laid
do\Nai as a rule, that all Japan plants mil do so in
the southern coast counties of England, but it
remains unascertained to what degree of northern
latitude in our islands this general power of endur-
ance extends. " Foregone conclusions" should have
nothing to do with this matter. Experiment, and
experiment only, ought to be relied upon ; for we
know that the larch was once kept in a green-house :
and within these few months, such South American
plants as Tro^aolexmi 'pentaphyllum and Gesnera

CH. IX.] DEATH AND DECOMPOSITION. 317

Doiiglasii have been found to sumve our \\-inters in
our garden borders ; the first in Scotland and Suf-
folk, and the second in Herefordshire ^.

Another fact is, that many tropical plants of
every order and species have been found to re-
quire much less heat, both during the day and
during the night, than gardeners of a previous
century believed. Other plants than those already
noticed have passed from the tropics to our par-
terres, and even to those of higher noitheni lati-
tudes. The horse chestnut is a native of the tropics,
but it endui'es uninjured the stem climate of Sweden,
Auciiba Japonica, FcEonia Moutan, we all remember
to have, passed from our stoves to the green-house,
and now they are in our open gardens.

Every year renders us acquainted with instances

of plants being acclimatized ; and, in addition to

those already noticed, we iind that Mr. Buchan,

Lord Bagot's gardener, at Blithfield House, in

Staffordshire, has an old cinnamon tree {Laurus

Cinnamonum) under his care, which ripens seed:

from these many plants have been raised that

endure our winters in a consers'^atory without any

artificial heat^. Then, again, there is no doubt that

all the conifercB of Mexico, which flourish there at

an elevation of more than 8000 feet above the sea's

level, will survive our winters in the open air.

^ Gard. Chron. 824. *• Lond. Hort. Soc. Trans.

318 PRINCIPLES OF GARDENING. [CH. IX.

Among these are Pinus Llaveana, P. Teocote, P. pa-
tula, P. Hartivegll, Cupressus thurifera, Jumperus
flaccida, Abies religiosa, and some others a.

Closely connected with the consideration of accli-
matization of plants is the fact that they retain
habits long after their removal to situations in which
these habits are unsuitable. Thus the hyacinth, a
native of Southern Asia, begins to shew symptoms
of vegetation here in autumn, wliich answers to the
spring of its long-left native clime. So the fuchsia,
although it accommodates itself to our hemisphere,
and submitting to remain dormant during the
winter, will revive in the spring, yet the season
duiing which it ^ill grow most vigorously, if placed
in a suitable temperatui'e, is the winter, for this is
the spring-time of its native countiy, Chili. This.
I consider, is the rationale of what Mr. Ayres justly
calls the whole secret of fuchsia management^. It
should be placed at the end of December, in a suit-
able temperature, and duly supplied with moisture
and manure, and it ^Nill have attained a growth in
April far larger than it would during twice the
number of months, if the growth were not per-
mitted to commence until the spring.

In the next place, let us consider what cir-
cumstances render a plant most liable to suffer
from frost, and let it be observed once for all, that
" Gard. Chron. 315, &c. " Gard. Cliron. 821.

CH. IX.] DEATH AND DECOMPOSITION. 319

to avoid such circumstances, is by so much to render
plants capable of enduring our climate.

First. Moisture renders a plant susceptible of
cold. Every gardener knows this. If the au' of his
green-house be dry, the plants -within may be sub-
mitted to a temperature of 3-2=^ without injuiy,
provided the return to a higher temperatm'e be
gradual.

Secondly. Gradual decrements of temperature are
scarcely felt. A myrtle may be forced, and sub-
sequently passed to the conservatoiy, cold pit, and
even thence to an open border, if in the south of
England, -without enduring any injury fi'om the cold
of winter, but it would be killed if passed at once
from the hot-house to the border.

Thirdly. The more saline are the juices of a
plant, the less liable are they to congelation by
frost. " Salt presences vegetables from injury by
sudden transitions in the temperature of the atmo-
sphere. That salted soils freeze with more reluctance
than before the salt is apphed is well known, and
that crops of turnips, cabbages, cauliflowers, &c., are
similarly preserved, is equally well established a.

Fourthly. Absence of motion enables plants to
endure a lower degi'ee of temperature. Water may
be cooled down to below 3-2o without freezing, but it
solidifies the moment it is agitated.

* Cuthbert Johnson on Fertilizers, 381.

320 PRINCIPI-ES OF GARDENING. [CH. IX.

Some plants like some animals are able to endiu'e
a veiy higb degree of temperatiire. Sir Joseph
Banks and others have breathed for many minutes
in an atmosphere hot enough to cook eggs, and I
have myself travelled in Bengal breathing air with-
out inconvenience, which rendered the silver mount-
ings of my green spectacles too hot to be bonie
without their occasional removal. So do certain
plants flourish in hot water springs of which the
temperature varies between the scalding heats of
from 150° to 180° of Fahrenheit's thermometer, and
others have been found growing freely on the edge
of volcanoes in an atmosphere heated above the
boiling point of water. Indeed it is quite certain
that most plants will better bear for a short time an
elevated temperature which, if long continued, would
destroy them, than they can a low temperature.
Thus a temperature much above the freezing point
of water to orchidaceous and other tropical plants
is generally fatal if endui'ed by them for only a few
minutes, whereas a considerable elevation above a
salutaiy temperature is rarely injurious to plants.
But this is not universally the case, for the elegant
Pnmula marginata is so impatient of heat, that
although just about to bloom, it never opens a bud if
brought into a room in which there is a fire.

Plants, generally, have the power of preventing
tlieir sap attaining to the unnatural elevation of

CH. IX.] DEATH AND DECOMPOSITION. 321

temperature of the atmosphere around them. This
in some degree may depend upon the bark and wood
being bad conductors of heat, but they have a power
of resisting heat quite independent from that; for
the pine apple, though growing for months in a
minimum temperature of 60°, never has that of its
flesh, whilst growing, elevated above 50°. Now the
worst of conductors would have conveyed heat
through them in that time. This is only analogous
to what occurs in the animal economy. Sir Joseph
Banks, Sir Charles Blagden, and Dr. Solander, in
the case already alluded to, remained several minutes
in a room heated to 212°, the boiling point of water,
and though unpleasant sensations were produced,
yet the air was easily borne, and the temperature of
the body was very little elevated. If they breathed
on the thermometer it sank several degrees ; every
expiration was cool to the nostrils, previously heated
by the air inspired ; the body felt cold as a corpse to
the touch of the fingers, and the heat of the skin
under the tongue was only 98°. A dog was exposed
to a temperature of 220° for ten minutes, but its
body's heat did not rise above 1 1 0°, being only nine
degrees above its natural warmth. In these rooms
an egg was cooked quite hard in twenty minutes.

But though plants have the power of preserving an
internal temperature, differing from that of the ex-
ternal air in which they are vegetating, yet they have

Y

322 PEINCIPLES OF GAKDENING. [CH. IX.

no more power than have animals to escape from the
injurious excitement occasioned by being compelled to
live for any protracted time in a temperature uncon-
genially elevated. In such a temperature, youthful
and growing animals are stimulated to an excessive
rapidity of growth, so attenuating, that nothing but
removal to a colder climate can preserve them from
premature death ; and the same phenomena attend
upon plants. These, over-excited by heat, acquire
rapidly an unnaturally elongated growth, attended
by a weakness of texture, that hastens them to decay,
unless checked by a gradual reduction of tempera-
ture. The roots in such a heat absorb water with
unnatural rapidity, and this is commensurately
hurried through the sap vessels of the stem and
branches, so that the over wateiy sap arrives at the
leaves much too fast for them to elaborate it suffici-
ently, though an extra effort is made by preternatur-
ally enlarging the leaves. The water transpired is
excessive, but very little carbonic acid is inhaled, and
consequently the quantity of carbon assimilated is
very deficient. The whole structure of the plant is
therefore wateiy and weak ; and if a supply of water
to the roots is withheld but for a few hours, the leaves
mther and shrivel past revival. These organs not
only lose the power to decompose carbonic acid, but
also to decompose water, though the light to which
they are exposed be the brightest sunshine ; and

CH. IX.] DEATH AND DECOMPOSITION. 323

thus deficient of carbon and hydrogen, the chief
constituents of their colouiing matter, they become
unnaturally pale.

It must not be omitted to be observed, that all
plants have a great power to resist the reduction, as
well as the elevation, of their internal temperatm-e,
however low may be that of the air which suiTounds
them. In the polar regions, and even in those of
less northern latitudes, they have to endure a tem-
perature ten and more degrees below the freezing
point of water — yet their sap is never known to
freeze. If water does congeal in the texture of a plant
it rifts it, but this never occurs unless extraneous
moisture has penetrated through some wound or
decayed part. I have seen trees so torn, but never with-
out finding a mass of ice within the trunk or branch
traceable to some outward fissure. This is entirely
in accordance with the the experiments of Mr. John
Hunter; and other experiments which I have tried,
confirm me in acceding to the conclusion to which
that distinguished anatomist, as well as Sprengel,
Schluber, and others have arrived, that the sap of
healthy plants never congeals, however low the tem-
perature to which they are exposed. Even in a
temperature fifteen degrees below that at which the
sap, if taken from the tree, would freeze, yet, in the
living plant, it remains uncongealed. This has been
tried upon the vine, walnut, elm, and red pine.

y 2

824 rniNCiPLEs of gardening. [ch. ix,

Tliese experiments also determine that plants have
but a slight power of generating heat ; for the
thermometer, placed mthin their stems, in -sWnter
sinks gradually nearly to the temperature of the
exterior air ; and in the spring or summer, that instru-
ment so placed does not follow implicity the atmo-
spheric variations, hut this is not merely hecause
wood is a bad conductor of heat. It is evident
that a hving plant has the power of preventing the
congelation of its juices, and it is impossible to
account for this phenomenon without connecting it
ydih the plant's vitality ; and I see no reason for
concluding that plants, differing from animals, do
not, during their respiratory function, convert oxy
gen into carbonic acid, set free its latent heat,
and thus presen-e their temperature. It is beyond a
doubt, that, by this chemical change, some plants at
one period of their vegetation generate a considerable;
degree of heat. The stamens of Arum cordifolium
emit so much heat at the time they shed their pollen,
that twelve of them placed by M. Hubert round a
thermometer raised the mercury from 79° to 143°.
Under similar circumstances, M. Sennebier observ^ed
the stamens of the Arum maculatum were nearly 16°
hotter than the surrounding air. The flowers of
Caladium j;mnaf«/z\Zi<?«, when emitting a strong
ammoniacal smell, were obsened by Dr. Schultz to be
as hot as 81°, though the atmospheric temperature

CH. IX.] DEATH AND DECOMPOSITION. 3'25

•vvas but 6l.*25'^. The stamens of the ^Pompion,
Bignonia radiccms, and Polyanthus tuberosa have also
been observed to elevate the mercury at the time of
shedding their pollen, but in a much slighter degree.
In every instance this evolution of heat is occasioned
by a proportionate absorption of oxygen gas by the
stamens and pistils at the instant of fecundation.
The stamens oHhe Aru7nma€ulatum, forinstance, have
been shewn by M. Saussure to absorb at that time
'200 times their bulk of oxygen gas, converting it
into carbonic acid. But, although some plants thus
cause a great extrication of heat, and others are
capable of resisting the greatest Imown cold to ^vliich
they can be exposed, yet all have degrees of tem-
perature most congenial to them, and if subjected to
lower temperatures are less or more injured propor-
tionately to the intensity of that reduction. If the
reduction of temperature be only slightly below that
which is congenial, it only causes the growth of the
plant to diminish, and its colour to become more
pale ; this effect being now produced by the plant "s
torpidity or want of excitement to perform the
requisite elaboration of the sap, as it is by over
excitement when made to vegetate in a temperature
vrhich is too elevated. If blossoms are produced at
all, they are unfertile, and the entire aspect of the
plant betrays that its secretions are not healthy, and
its functions are deadened. Mr. Knight says, that

3'26 PRINCIPLES OF GARDENING. [CH. IX.

melon and cucumber plants, if groTNii in a tem-
perature too low, produce an excess of female blos-
soms ; but if the temperature be too bigli, blossoms
of the opposite sex are by far too profuse.

If a plant be frozen, and though some defy the at-
tacks of frost, others are \ery liable to its fatal influence,
death is brought upon them as it is in the animal
frame, by a complete breaking down of their tis-
sue, their vessels are ruptured, and putrefaction
supervenes wdth unusual rapidity. As already
observed, when considering the means of acclimatiz-
ing plants, the more abundant is the water present
in their vessels, the more apt are they to be in-
jured by frosts, w^hence the young shoots are often
destroyed, whilst the older branches remain un-
injured, and crops on ill-drained soils suffer more
severely in ^vinter than those where the drainage is
more perfect.

Deficiency of light is another contingency most
influential in promoting the decline and death of
plants. In proportion as they are deprived of this
stimulus, they become unable to elaborate their
juices, and, deficient in colour, weak, and of unnatural
height, they die prematurely, and decompose more
rapidly than those whose fibres, more firm and
robust, are less combined with an excess of watery sap.

Finally, the unhealthy vicissitudes to which plants,
in common with all other orGjanized forms, are ex-

CH. IX.] DEATH AND DECOMPOSITION. 327

posed, inevitably bring upon them death ; and it
would be mere waste of time to argue against those
physiologists who maintain that, in favourable circum-
stances, the life of plants may be prolonged in-
definitely. Those vrho choose to surmise that some
plants would endure throughout all time, if unfail-
ingly preserved from all things offensive, and sup-
plied without failure with all things agreeable,
amuse themselves with imaoining what would occur
under circumstances of impossible attainment.

A plant must be subjected to unfavourable con-
tingencies, and the greater the amount and frequency
of their occurrence, the more speedily do they bring
its life to a close — for the more do they aid chemical
affinities in breaking down that resistance of
their efforts, wliich is the chief characteristic of
vitality.

So long as a plant lives, it triumphs over those
affinities. Its roots overcome the affinity of the
soil and take from it its moisture ; its leaves over-
come the affinity of the atmosphere, and deprive it
of the wateiy vapour it has in solution ; the inter-
nal vessels overcome numerous affinities, and, by the
decomposition of carbonic acid and water, perform
within their simple tubes that which can only be
effected by the chemists most powerful agents.
These triumphs over chemical affinities — and that
most characteristic of triumphs, its avoidance of pu-

328 PRINCIPLES OF GARDENING. [ciI. IX.

trefaction, endure in the same individual, often fur
centuries of years ; it is the most marked of the
triumphs of vittdity; its prime distinction as a
creature, capable, for a time, of defying the laws
which doom all organic matters to return to the
dust from which they were created ; for no sooner
does that vitality cease, than the heat, the mois-
ture, and the gases which \T.tality compelled to
minister to the plant's luxuriance and health, now
triumph in their tuni, and serve to destroy that
form which they had aided to sustain.

That heat is necessaiy to putrefaction appears
from the fact, that no vegetable matter kept at the
freezing temperature of water will decay. Advan-
tage of which is taken by the gardener occasionally
to preserve his summer fmits and vegetables in the
ice-house ; and apples, pears, and grapes are borne
unchanged half round the globe in the ice ships
which annually visit India from North America.

That dryness effectually prevents vegetable pu-
trefaction we see every day, in the fact, that our
furniture does not decay ; and the gardener knows
that moisture is fatal to his stores in the fruit-
room.

Putrefaction is also prevented by the exclusion of
the atmospheric air, or if it proceeds, it is by very
slow degrees. An example of this is familiarly
presented in a very effective mode adopted to pre-

CH. IX. "i DEATH AND DECOMPOSITION. 329

serve green peas. These are put into diy glass bot-
tles, and the bottles placed in water, then gradually
made to boil. The chief part of the air is thus driven
from the bottles and they are corked do^vn tightly,
and the cork rosined over whilst thus heated. What
little oxygen remains in the bottles is absorbed by
the peas, and these remain green and unaltered for
months, requiring only the addition of a little soda
to the water in which they are boiled, to be as
tender nearly as when first gathered.

When a temperature of 45^, moistui'e, and atmo-
spheric air occur to dead vegetable matters, they ab-
sorb large quantities of oxygen, evolving also an equal
volume of carbonic acid. If composed of carbon,
hydrogen, and oxygen only, the fumes they emit are
not offensive ; but if, as in the case of onions and
the cabbage tribe, they contain a considerable por-
tion of azote, the smells emitted are disgusting.

As in all other instances where vegetable sub-
stances absorb oxygen gas in large quantities, much
heat is evolved by them when putrefying ; and advan-
tage is taken of this by employing leaves, stable
litter, and tan, as well known sources of heat in the
gardener's forcing department.

^^^len the putrefactive process of plants is com-
pleted, there remains a soft black mass, known as
vegetable mould, or humus. One hundred parts of
the humus of wheat straw have of extractive or

330 PRINCIPLES OF GARDENING. [CH. IX.

apotlieme, rather more than twenty-six parts, and
the residue is lime, peroxide of iron, phosphate of
lime, and carbonaceous matter. This apotheme
is identical with the humic acid of Liebig, the
ulmic acid of Braconnot, and the geic acid of
Berzelius. It contains

Carbon 46.6

Hydrogen 20.0

Oxygen 33.4

100.0

It was once believed, indeed is still believed, by a
few men of science, that this apotheme is the imme-
diate fertilizing component of organic manures,
being soluble under some circumstances, and enter-
ing at once into the roots of plants dissolved in the
moistui'e of the soil. But every relative research
of more modern chemistrv is a^^ainst this conclu-
sion, and it is now tolerably certain that a chief
nutritive portion of vegetable manures are their
carbon converted into carbonic acid, absorbed, either
in solution with the earth's moisture, or in a gaseous
foi*m, by the roots. Apotheme is only one of the
products formed during the progress of putrefaction,
and is in its turn a source of carbonic acid. Car-
bonic acid has been long since shewn to be beneficial
if applied to a plant's roots. It abounds in the
sap of all vegetables, though this be drawn from

CH. IX.] DEATH AND DECOMPOSITION. 331

their veiy lowest parts, whereas apotheme is inju-
rious to them if they are gro-^ii in a solution of it,
and the minutest analyzers have failed to detect it
even within the extreme vessels of roots.

Acids ai'e antiseptic, and retard the decay of
vegetable matters, which explains why the woody
fibre in peat soils remain.' so long unchanged, for
those soils abound in gallic and other acids.

Alkalies, on the other hand, accelerate vegetable
decomposition; and these being present in calca-
reous soils, is one reason that manures are sooner ex-
hausted in them than in any other. Another reason
for this rapid consumption is, that in calcareous and
siliceous soils, the air easily penetrates, and the rapid
progress of decay depends in a great measure upon
the free access of oxygen gas. Such access is less easy
to manures buried in clayey soils ; and, as a conse-
quence, manures in them are much more permanent.

Such is the progress, such the phenomena, attend-
ant upon the death of plants ; and but one more re-
lative question remains for our consideration — Can
death be averted from plants ? Can they be made,
by mans devices, an exception to that decree of
limited existence, which extends over all other or-
ganized creatures ?

Those who assert that grafting completely renovates
the scion, maintain the affirmative. From these I
totally differ ; for though it is happily true that

33-2 PRINCIPLES OF GARDENING. [CH. IX.

grafting upon a voung and \igorous stock imparts to
the scion a supply of sap of wliich the parent stem is
incapable, yet this failure is only premonitory of the
departure of power which will, after a transient in-
crease of strength, occur to its removed member.
Every subsequent scion, however frequently, and
whilst in apparent health , removed to another youth-
ful stock, ^ill be found to have a period of renewed
^dgour and productiveness of shorter duration than
its predecessor. The golden pippin is occasionally
quoted as a contrary proof : but this example has no
such weight ; for, supposing that this fruit yet exists,
still it has not passed the age beyond which the pe-
riod of unproductiveness and death in the apple-tree
may be delayed by grafting ; for we have no mention
of this finiit that at all justifies the conclusion, that
the golden pippin existed much more than three
centuries ago. A peannain apple is mentioned in
records as old as King John (a. d. 1-205); but the
pippin is not noticed by any authority earlier than
the reign of Henry the Eighth (1509). Lambard
mentions that Tenham in Kent, famous for its cherry-
gardens and apple-orchards, was the place where
Ptichard Harris, or Haines, that king's fmiterer. first
planted cherries, pippins, and the golden renate.

Supposing, then ; that the golden pippin of our
days is a genuine portion of the Tenham trees,
handed down to us by successive graftings, yet still,

CH. IX.] DEATH AND DECOMPOSITION. 333

though in extreme decrepitude, it has not exceeded
the age assigned by naturalists as that beyond which
the life of the apple does not extend. But then
another question will arise, supposing our golden
pippin does appear to survive the allotted period, —
Who will undertake to demonstrate that the golden
pippin of Tenham still exists ? It is quite certain
that a majority of the apples for which the title of
golden pippin is claimed have no pretensions to the
distinction, and more than one old person with whom
it was once a favourite fniit now declare that it is no
longer obtainable.

Be this as it may, even if the tree in question
has not already departed, yet even those who main-
tain that it is still to be found lingering in our fruit
gardens, acknowledge that it is in the last stage of
decrepitude and decay ; it is following the imiversal
law of nature, no organized creature shall endure
through all time. Grafting may postpone the arrival
of death, as the transfusion of blood will revive for
a while the sinking animal, but the postponement
cannot be for a time indefinite : the day must
come in both the animal and the scion, when its
vessels shall be without the energ}^ to propel or
to assimilate the vital fluid, though afforded to it
from the most youthful and most vigorous source.

INDEX.

Abroma augusta, 194

Absorbent power of soils, 63

power of manures, 101

Acacia lophanta, 17

Acclimatizing plants, 316

should be gradual,

319

Acids antiseptic, 331

Acridity of sap, 281, 299

Adaptation to circumstances, 171

Adhesion of soils, 63

Agrostis, 119

Alburnum, 131

Alkalies promote putrefaction, 331

Alopecurus agrestis, 119

Alumina, 84

in soils, &c., SO

Amaryllis formosissima, 192

Ammoniaan rain, &c., 34

from gas works, 35

formed during germina-
tion, 36

to roots, &c., 105

Anaethum foeniculum, 119

Angle for hot-house glass, 235

Animal manures, 91

Apocynum androsssemifolium, 105

Apotheme, 330

Apple, 213, 332

trees, canker in, 284

Apricot, derivation of, 202

Arenaria rubra, 120

Aristolochia clematis, 193

Artichoke, to enlarge, 166

Arum cordifolium, 324

maculatum, 325

Association of plants, 54

Atmosphere, its components, 35

Auricula ulcers, 295

Autumn tints, 149

Azalea cross with rhododendron,

201
, disease of, 304

Bachelor's buttons, 204

Backward soils, 85

Bacon, 4

Bark of plants, 125, 127

Barren soils, characteristics of, 112

Beaton's theory- of double tlowers,

210
Bees honey-seeking, 193
Berberris vulgaris, 192
Berr^', 213

Betuia alba, 118, 127
Biarnonia radicans, 325
Birch, 118, 127
Black grass, 119
Blackthom-winter, 223
Blanching, 147
Blind cabbages, 184
Bones, 96

Borders, flooring, 181
Bottom-heat, 22
Brake, 113

Branches of plants, 125
Brine destroys moss, 129
Broad-leaved plants, soil for, 83

nSG

INDEX.

Broad-leaved plants, water for, 75
Brooin, 117
Budding, 168, 175
Buds, to promote, 1G7

, their convertibility, 206

Bulbous roots, 137

Btiming weeds wasteful, 108

Cabbages, blind, 184
Calyx,^185

, its use, 187

Cambium, 165

Canker, "277

Capsule, 213

Carbon, abundant in seeds, 40

in plants, 82

Carbonic acid beneficial to plants,

93, 107, 111
evolved bv the stem

and branches, 130

quantity consumed

by plants, 147

— exhaled by flowers,

190

often the cause of

red colours, 191
Carduus arvensis, 118
Cellular integument. 127
Chalk, 84

Charcoal, its A-alue as fuel, 226
Charlock, 39
Chlorine promotes serraination, 33,

37 ^

Cinnamon tree, 317
Clay, 84
Clayey soils, why germination slow

in, 46
Club-root, 137
Coal, relative value of, 225

. its heating power, 226

Coal-ashes, 18, 22, 107

Coffee, seed of, 9

Cold, to preserve plants from, 319

plants can exclude, 323

Colour of soils, 18, 3 20

Colour of leaves, 135, 149

of flowers, 190

of fruit, consequences. 223

of walls, 223

Coltsfoot, 119

Compost, 109

Cone, 213

Coniferse of Mexico, 317

Contortions, how ciired, 132

Contraction of sap vessels, 302

Cooling, laws of, 218

Corn-mint, 119

Corolla, 185

, its use, 187

Cortical layers, 128
Creeping roots, useful. 68

bent, 119

Crops affect different soils, S6
Cross-breeding, 195
Cucumber blossoms, 325
Curl in potatoes, 256
Cuttings, 179

Death of plants, 309
Decline, symptoms of, 310
Decomposing matters absorb mois-
ture, 56
Decomposition of dead plants, 308
Depths for sovN'ing, 39, 47
Digging, labour required by, 61
Diontea muscipula, 104
Diseases of plants, 243
Double flowers most enduring, 188
. to obtain, 199, 204.

208

theory of, 210

Drainafje, how necessary, 30, 71

~ water, 123

Draining, expense of, 71
Drilling, 58
Drupe,"213
Dungs, 89, 105

Early and late crops, soil for, 87
Earths, their influence, 82

INDEX.

337

Earth-worms, 79
Eleocharis ccespitosa, 119
Elm, 117

ulcerous discharge from, 2 SI

Empedocles, 3
Endemics of plants, 254
Epidennis of plants, 125, 254
Ericce, 116
Etiolation, 147

Evergreens tiTinspire little, 137
Excrements of plants, 52
Exercise of plants, 105
Exhalation, most when the air is

agitated, 222
Experiments, how to try, 100
Extravasated sap, 298

Fair maid of France, 204

Fallowing, 53, 60

Female tiowers, to produce, 326

Fennel, 119

Fern, 113

Fertile soil, 82, 84

Filbert pruning, 175

Fingers and toes, 137

Fish as manure, 90

Flower, the, 185

its organization, 186

its uses, 187

absorbs oxygen, 189

its colour, 190

Flues, 228

Fogs, cause of, 24

on undi-ained soil, 123

Food of plants, tluid, 68, 330
Fork preferable for digging, 62
Form of plants accommodated to

circumstances, 171
Forsyth's plaster for trees, 293
Forward soils, 85
Freezing soils, its effect, 65

plants, its effect, 328

Frcst, to prevent its being inju-
rious, 318
, its effect on rose seed, 15

Frost, depth it penetrates, 20
Fruit, 212 .

process of ripening, 214

intluence of its colour, 223

influence of its skin, 224

influence of moisture, 237

why it cracks, 23 S

storing, 239

Fruitfulness, to promote, 166
Fuchsia gro%ving, 318

Fuel, comparative value of, 225

heating power of, 226

should be dry, 227

Full flowers, 204
Furze, 115

Grangra;na sicca, 279

saniosa, 280

Grardening defined, 1
Grases applied to roots, 81
Gathering fruit, 239
Geic acid, 330.
Germination, essentials for, 8

heat required, 13

prevented by heat, 13

periods of, differ, 14,

42

temperatures for, 16

water required, 29

quantity necessar}',

quality impoitant, 30
promoted by chlorine,

injured by some salts,

does not occur in
some liquids, 31

injured b}' sudden

29

31

31

changes, 32

46

reqmres oxygen, 35
in the light, 41
not to be checked, 42
evolves carbonic acid.

338

INDEX.

Glass should be double, 237

why best to be used, 207

Golden pippin, 332

renate, 332

Gooseberries, to grow large, 238
Grafting, 176

— to hasten fertility, 158

wax, 175

■ not done indiscriminately,

177

by the ancients, 177

■ on different organs 187

does it prolong life? 331

Grapes, shanking in, 298

thinning, 312

Grasses for sands, 68

Gravitation does not guide roots, ii

Grew, 4

Groundsel, 13

Growing time of plants, 164

Gum, 94

its components, 215

Gypsum, 81, 96

Habits, plants acquire, 318
Hawthorn seed, 15
Heading down, its effects, 170
Heat, effects of its excess, 13, 315,

320, 325
• effects of its reduction, 325

endured bj^ plants, 142, 320

plants have the power to

exclude, 321

plants produce, 324

its radiation, 218

required for germination, 13

-ripeningfruit, 218

the agent to arouse life, 16

Heaths, 116

Hedysarum gyrans, 105

Height of plants, how influenced,

132
Helleborus niger, 189
Hide-bound, 126
Hilum of seed, 42

Hoeing, 58, 64
Honey-dew, 303
Horse chestnut, 317
Hot-beds, cause of their heat, 329
Hot-houses, proper angle for their
glass, 235

why needed, 225

their ventilation, 145

Hot water for heating, 228

House plants, when to put out, 29

Humic acid, 330

Humus, 329

Hunt's pots, 72

Hyacinth, 318

Hybridizing, 195

influence of parents

in, 196

modes of, 197

Hybrids, parents of some, 204
Hydro-sulphuret of lime as a
remedy, 273

Impregnation, 191

symptoms of, 199

■ produces heat, 324

Inarching, 178

Insects aid impregnation, 193

to destroy,^ 108, 128

Iron in soils, See, 81
Ivy injures trees, 130

Japan plants will endure our
climate, 316

Kidney beans, 9.

rule for sowing, 25

Knight (T. A.). 2,6,308
Knot-grass, 119
Lavoisier, 6
Leafing, time of, 27
Leaves, 135

absorb moisture, 144

cause of colour, 135

influence of light on, 135

their functions, 136

INDEX.

330

Leaves, transpiration how influ-
enced by, 139, 2S9

transpire water, 137

to be cleansed, 139

their pores or stromates,

140

170

absorb carbonic acid, 144
their colours in decay, 149

direction, 151

in excess prevent flowers,

required by fruit, 178

propagating by, 183

expand, when light is de-
ficient, 207

variegated, 136

Legume, 213

Liber, 128

Life, vegetable, what is. 309

conquers chemical affinities,

327

can it be prolonged in-
definitely, 331

Light, influence on germination, 41

influence over colour, 135.

149

consequences of deficient,

206, 326

required to ripen fruit, 218,

234
particular degrees of required,

252
Lime, 71, 108, 109, 110
Lime in soils, &c., 80

Magnesia in soils, &c., 80

when injurious, 110

Male flowers, to produce, 325
Malpighi, 4

Manganese in soils, &c., 81
Manures, why useful, 81, 88

rendered soluble by

decay, 93

fresh, economical, 94

how to try, 100

Manures absorb moisture, 101

retain moisture, 103

rules for inserting, 43, 87

stimulate plants, 104

yield gases, 106

destroy vermin, 108

promote decay, 109

influence a soil's tempera-
ture, 109
Marl, 111
Marvel of Peru, decay of its leaves,

297
Medulla, 133
Melon seed, 9

blossoms, 326

Mentha piperita, 183

arvensis, 119

Mexican coniferse, 317
Mimosa sensitiva, 105
Mists, cause of, 24

on undrained soil, 123

Moisture required by fruit, 237

excessive, injurious, 313

-: . — renders a plant susceptible

of cold, 319
Morphologj', 170, 206
Moss, to destroy, 129
Motion aids cold to be injurious, 319
Mules produced by intermixing

species, 202
Multiplicate-flowers, 205
Myrica-gale, 120

Nectarine thinning, 311
Nerves ] Have plants, 314
Netting, why useful, 219

which best, 220

Nettle, 117

Night temperature, 162
Nitrate of potass, 81
Nitrogen in seeds, 9, 11
absorbed during germina-
tion, 36
Nyraphoea alba, 209

340

INDEX.

Oak, 118

Oil injurious to trees, 129

Oily seeds, 12

Onions, soil for, 83

Ononis, 117

Ovary, 212

Over-production, its consequences,

311
Oxalis spnsitiva, 105
Oxide of iron, its effect on roots,

313
Oxyofen required for germination, 35
proportions necessary, 36,

41, 45

appli d to roots, 55

moist earth absorbs, 55

quantity al>sorbed, 5(i

absorbed by roots, 60

inhaled by the stem and

branches, 130

essential to flowers, 189

quantity the}' absorb, 190

Packing seed, 33
Papaver rhceas, 120
Parenchyma, 127
Parslev seed, 14

canker, 296

Parsnip, 87

Peach, stocks for, 158, 161

thinning, 311

Pearmain, 332
Peas, early, 16

to preserve, 328

Peat, its value as fuel, 226

soil, 331

Peculiar juices, 165
Peiresc, 4

Pelargonium spotting, 296
Peony seed, 1 5
Pericarp, 185, 212

its office, 214

Petals, 185

their use, 187

Phoenix dactilifera, 191

Phosphate of lime, 97

Physiology, its progress, 4

Pis'tils, 185

Pith, 133

Plants, their nature, 245

constitUv?nts, 247

functions, 249

proofs of sensation in, 1 04,

9n9

Plethora in plants, 299

Poa annua, 13, 50

Pod, 213

Poisons, their effect on plants, 313

Pollen, 185

its use, 192

quantity necessary, 198

time it continus good, 198

analysis of, 200

essential to fertility, 191

Polyanthus tuberosa, 325

Polvgoniim aviculare, 119

Pome, 213

Pomona's riuff, 167

Poppy, 120

Potato, autuum planting, 21

Potatoes, deprived of blossom, 52

ulcers in, 297

cui'l in, 255

Pot-culture, 75

Potherbs, drying, 143

Pots, their form, 72

Primula marginata, 320

Proliferous flowers, 2{i5

Pruning, 174

Prunus, various species of, 201

Pteris aquilina, 113

Pulp, 127

Putrefaction, 327

of manures, 92

causes heat, 329

its requisites, 24«")

Pyrrhine in rain, 34
Pythagoras, 3

Rabbits' urine, 117

INDEX.

341

Radiation, to prevent, 218

Rain water to be preferred, 33

ammonia in, 34:

Rain in England, 84, 114

Raking, 47, 64

Rendles system of heating, 229

Rest-haiTow, 117

Retentive power of manures, 103

Rhododendron, cross with azalea,
201

■ — ferrugineum, 82

Rice, ^

Ridging, its benefits, 55, 59, 65

Ring of Pomona, 167

Ripening wood, 132, 162

Room plants, their culture, 75

Rooms-, their temperature, 77

Roots, temperature they like, 22

effect of heat and cold upon,

23, 73

effects of salts on, 30

v.hy they descend, 43

their duration, 49

most abundant in poor soils,

5' I

how to guide, 50

excess of, checks the pro-
duction of seed, 52

oxygen to, 55

whv to be near the surface,

58

their power of selection, 107

their extremities, 6Q

renewed annually, 67

their extent, 67

reqiiire a certain suppl}' of

water, 74

a plant's own best, 155

to promote produce of, 1G7

Rosa pcrpetuosissima, 200

Rose, increasing its fragrance, 54

seed 15

Rotation of crops, 53

Salt (common), 81, 109

Salt, as a remedy, 273, 807, 319

Saltpetre, 81

Salts as manures, 97

in plants, 98

■ when to be used, 99

their effect on roots. 30

Sand, 84

Sandv soils, grasses for. 65

Sap, 152

power v.'ith which it rises,

153, 300

its elaboration, 154

its descent, 1 5

checking its return, 166

required by fruit, 217

checking its ascent, 217

extravasated, 295

Saw-wort, 118

Scar of seed, 42

Science of Gardening, 2

Scion, hov.- influenced bv the stock,

154—160
and stock must be related,

177
Seedlings, time before they bear, 197
Seed-packing, 33
Seed-producing shortens the life

of a plant, 49
Seed-vessel, its office, 214
Seeds, 212
time they retain A'itality, 9,

11

containing nitrosen, 9, 11

oil, 12

differ in excitability, 13

time of germinat-

ing, 14

some bear great heat, 16

their germination accele-
rated, 31

depths to bur}-, 39, 47

abound with carbon, 40

why buried in the soil, 41

time germinating, 42

how fertilized, 191

34Q

INDEX.

Seeds, sap they require, 217

ripening, 242

Sensation in plants, 104. 252
Shanking of grapes, 24, 298
Sheltering, laws of, 218
Shoots, to promote, 167
Silica, 84

in soils, &c., 80

Siliqua, 213

Skin of fruit, its influence, 224

Small-foliaged plants, soil for, 83

water for, 75

Smell of soil, 121
Smithia sensitiva, 105
Snow useful as a shelter, 221
Soil in pots, 78

poisonous components of, 313

temperature of, 17

influence of colour, 18

rate of heating, 18, 55

cooling, 19, 85

depth it is frozen, 20

wet and cold, 24

when moist absorbs oxygen,

55

stirring beneficial, 55, 64

how regulated, 57

force required to dig, 63

with which it adheres,

63, 122

composition, 82

fertile, 82

relation to moisture, 83

will not grow some crops, 86

for early and late crops, 87

its soluble matters, 95.

specific gravity, 121

smell, 121

feel, 122

Solandra grandiflora, 171
Soluble matter in soil, 95
Sowing, 8
guides for time of, 25

- proper depths for, 39
rule for, 47

Spartium scoparium, 117
Spiked rush, 119
Spinach, soil for, 83
Specific gravity of soils, 121

— heat of water and air, 227

Speck in potatoes, 297

Spot in pelargonium, 296

Sprit, 120

Stable manure, its components,

89
Stamens, 185

absorb oxygen, 189

Standards produce best fruit, 133
Steam as a source of heat, 230
Steeping seed, 31, 111
Stem of plants, 125

pores of the, 130

absorbent, 130

not essential, 133

Stems, W'hy they rise out of the

soil, 45
Sterile soils, their characters, 112
Sterility, 86 ,

Stillness preserves a plant from |

injury by cold, 319 '

Stimulating manures, 104
Stock, its influence over the scion,

154—160
Storing fruit, 239

room, 241

Strawberries, 53
Strobile, 213
Subsoils, 83
Sugar, 94

its formation, 215

Sulphate of lime, 81, 96
Sulphurous acid destroys colour of

flowers, 191
Superfoetation, 200
Sweet-gale, 120
Synchronisms of nature, 25

Tank system of heating, 228
Tap-rooted vegetables, to grow fine,
51

INDEX.

:34H

Tartaric acid, its components, 215
Temperature for cuttings, 181

- internal, of plants,

221

142, 320

— for germination, 16

— endured by seed, 16

— of soils, 18
endured by plants,

— '■ at night, 162

its influence over

transpiration, 139, 164
Theophrasta latifolia, 183
Thinning fruit, its importance,

311
Tipula pennicomis, 194
Tobacco seed, 15
Training, 174
to check the progress of

the sap, 217
Transformations, 173
Transpired matter, 198
proportioned to

that imbibed, 138

decreases with

the temperature, 139, 164

— influenced by

the dryness of air, 141
Transplanting, its effects, 50

why in autumn, 68

Trenching, 51, 58, 86

Tropical plants which endure our

climate, 316
Tniffie, 49
Tuberous roots, 137
Tulip pollen, 200
Turnip flea or fly, 273

warts, 277

Turnips secured from the fly by

■early sowing, 275
Tussilago farfara, 119

Ulcers, 279

, analysis of discharge from,

282
Ulex europaeus, 115
Ulmus campestris, 117
Urtica urens, 117

Varieties, raising, 196
Vegetable manures, 91

mould, 329

Ventilation, why needed, 145
Vine, increase of its leaves, 208

training vigorous, 217

when it grows, 164

Vines, their roots vv^hen forced, 73

Viola tricolor, 192

Vital power of plants, 309 — 333

Wall fruit, sheltering, 219

Warts on turnips, 277

Water required for germination, 29

quality important, 30, 33

— not sole food of plants, 69,

81

-- salts in, 70
— not to be

in excess, 70,

313
— when to be applied, 74

Wax for budding and grafting, 175
Way-thistle, 118

White-washing, how injmious, 116
Wind, why cooling, 222

periodical, 223

Wood, its construction, 130

promotion of its growth, 131

promoting its ripening, 132,

162

value of as fuel, 226

Woody fibre, 94
Wounds of plants, 302

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