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1. DEFINITION OF BOTANY - = Res Ae

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3
4,

10.
11
12.

13,
14,
15,

16.

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ELEMENTARY PARTS OF THE PLANT - = be
GENESIS OF THE CELL - = pe a

UNION OF THE CELLS; CHANGES RESULTING FROM THEIR GROWTH

. CHEMISTRY OF THE PLANT - = a =

ABSORPTION AND DISTRIBUTION OF THE PLANT’S FOOD; SEPA-
RATION OF WATER ~ - a a

. PHENOMENA OF ASSIMILATION - ~ =

CONFIGURATION OF THE PLANT, FUNDAMENTAL ORGANS -
THE PLANT CONSIDERED AS A LEAVED AXIS ~ -
LEAF FORMATIONS - - - -
ARCHITECTURAL ARRANGEMENT OF THE PLANT. PHYLLOTAXY
PROPAGATION OF THE PLANT - - -
FORMATION OF SHOOTS - - - -
Unity OF RACE AND OF THE HIGHER CATEGORIES - -

THE PLANT WORLD IN ITS LOCAL DISTRIBUTION. GEOGRAPHY
OF PLANTS - = = = -

CHRONOLOGICAL ASPECT OF THE PLANT, HISTORY OF THE
PLANT WORLD = = ~ =

NATURE OF THE PLANT, ITS POSITION IN THE SCHEME OF
CREATION - - - ~ -

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BOTANICAL LETTERS.

LETTER I.
DEFINITION OF BOTANY.

ir cannot be denied that at the present day the natural sciences
have acquired a prominence in the arena of intellectual activity
superior to any other branches of knowledge, and that they
especially characterise both the spirit and tendency of the age,
as well as the direction in which it is striving to develope itself.
There exists, at the same time, between these sciences a rela-
tionship so intimate; the support which they mutually afford
to each other is so manifold in its nature; their transition into
each other is so frequent ; and they progress with such increas-
ing impetus; that there is, indeed, a difficulty in doubting
that, thus united, they will arrive at some valuable result, sooner
than has hitherto been the case, while cultivated in a different
spirit.

The investigation of nature and its activity is, moreover, so
elevated a field of mental exercise, that, to the healthy and unde-

* praved mind, it affords the most cotigenial and advantageous

preparation for the higher intellectual occupations of life.

Although in former periods of culture the natural sciences
have either been disregarded by the generality of men, or, when
cultivated, were interwoven with many foreign elements, this
must, probably, be regarded as a result rather of the impatience
with which men strove to reach the goal of their thought and
labour, than of any want of conviction that the solution of more
difficult problems must give place to that of the less complicated
ones.

B

ay BOTANICAL LETTERS.

Nevertheless, those branches of knowledge even which are
concerned with the most simple conception of nature in its
material aspect, have shared the same fate as all the other natu-
ral sciences; so that it is impossible to do otherwise than admit
that the former, no less than the latter, are the offspring of
modern time.

In this respect, mineralogy, botany, and zodlogy, are upon
precisely the same footing. Whatever they may be they have
become within a very short and recent period. Since several
other natural sciences have already found their representa-
tives before the general public, I will here venture to discuss
the second of those named above; to examine somewhat more
closely into its present condition; and not only to show in what
kind of connexion it stands to its more immediate congeners,
but likewise to determine what is its position in the general
range of natural science. The interest which has always
been taken in the scientia amabilis will, perhaps, be a sufficient
excuse for my bringing it forward—of course in its holiday
attire.

When we reflect upon the spirit which animated the labours
of a number of investigators, especially during the latter part of
the last century, and led them to seek for some knowledge of
the extent and distribution of the plant world; its rich treasure
of forms ; its phenomena of vital activity ; and even of its seve-
ral phases of creation ; the advance which has been made in bo-
tanical science cannot be regarded as other than satisfactory.
The attainment of this happy result has been contributed to, not
only by botanists, but certainly in an equal degree by physicists,
chemists, geognosts, geologists, etc. New, and hitherto un-
thought-of, questions have not only been raised on all sides, but
they have likewise either met with a satisfactory solution, or the
path to it has already been struck out. The modest demands which
were hitherto made upon the man skilled in the knowledge of
plants have been considerably augmented; and the mere ac-
quaintance with the coiffure, uniform, rank, and merit of the
descendents of Greece’s most fruitful goddess—subjects which
in the age ot Linneus constituted the corner-stone of all botani-
cal erudition—is now, in consequence of the repeated metamor-

BOTANICAL LETTERS. 3

phoses of this science, either entirely put on one side, or employed
only as a groundwork, and that in a very restricted sense.

The botanical science of the present day is constructed upon
an entirely different plan from that of an earlier period, and,
consequently, has a tendency and aim equally distinct and dif-
ferent.

Although the necessity for a knowledge of the names of plants
remains, upon the whole, the same as hitherto, although from
the constantly-increasing material, and continual discovery of
new forms, the distinctions between them are unceasingly mul-
tiplied, and it is requisite that the muster-roll should be main-
tained in good order, still these occupations have not wholly
engrossed the attention of botanists. By an appropriate division
of labour, it has been rendered possible for some to consider
more general questions relating to the actual nature of the things
we call plants; in what consist their life and functions; what
connects them with the outer world; and what may be their
purpose and destiny in the great economy of nature—questions
which lie far beyond the boundaries of the botany of any earlier
period.

When these investigations into the nature of the plant had
once been entered upon, the transition into another department
of science followed as a natural consequence. But, so long as
these questions were considered only in their universal form, the
results arrived at did not amount to much more than abstract
and questionable hypotheses; it was not until, separating the
general from the special point of view, investigators turned their
attention to details, and attempted to reach the solution of the
general problem by the study of particular instances, that their
labours were crowned with anything like success. The fortu-
nate turn thus taken in the cultivation of botany is but of recent
date, and its result is in so far certain that it bids fair to give
rise to a physics of plant organism.

But how far distant we still are from this end may easily be
seen by the most superficial glance at botanical literature which,
with no lack of voluminous works, does not possess one which
accounts for any, even of the most ordinary, phenomena of plant
life ina manner at all satisfactory. All the plant treasures that

B 2

4 BOTANICAL LETTERS.

have been collected by naturalists of every clime; by travellers
in the most remote corners of the world, not unfrequently at
the risk or even sacrifice of their lives, and deposited in mu-
seums, botanical gardens, etc., where they have been studied and
arranged with the most laborious and persevering industry ; all
these can do no more than furnish the raw material for scientific
investigation which has yet to be undertaken. The matter is
in nowise different with regard to the experience which has
been gained in the culture of plants either of one kind or the
other. Neither agriculture, nor forestry, the growth of fruit,
or gardening, is yet advanced beyond the most meagre empiri-
cism, and, unfortunately, occupy time and talents which are
capable of more advantageous application. But we cannot
reasonably be surprised at this, as we have already admitted
being in the dark with regard to the most simple opera-
tions of plant life. It is but a little while that we have
known, and that only in an imperfect manner, how the plant is
nourished, how it grows, increases, and propagates. There is
not a single plant of whose gradual alterations in form and
condition, from the commencement of its growth to the ter-
mination of its existence, we have any knowledge. In this
great field of scientific discovery there is as much to be done
by the botanist as by the geographer in the interior of Africa
or Australia.

But while contemplating that which les before us, we will
not look backwards with disdain; we will not be guilty of in-
eratitude to our predecessors, but congratulate ourselves on the
results of their labours, however deficient they may be, bearing
well in mind that it is only by means of them we are enabled
to make any certain progress. Undoubtedly we shall have
gained much merely in possessing some guide through this un-
known region; and it is no less a saving of time and labour to
be prevented from seeking or forcing an escape from our igno-
rance, where such is impossible. All this has already been
achieved. There is, in this respect, no longer any impediment
to our further progress. If, at the same time, we have returned
again to the point from which we started, still the oppressive
consciousness of an insurmountable obstacle has been removed,

BOTANICAL LETTERS. 5

and we are in a position to press forward with renewed energy
towards the desired object.

In this prospective and retrospective view of what has already
been achieved, and what still remains to be done in this field, I
will now attempt to present my readers with a delineation of
plant life, as well individually as in its entire extent, constituting
a portion of the vital phenomena of our planet.

The plant considered as a most skilfully-planned chemical
laboratory ; a most ingenious mechanism for the play of physical
forces ; as one of the simplest, and, consequently, most sublime
structures ever designed or executed; the extent and distribu-
tion of this form of existence, made up of an indefinite number of
parts; as well as the unity of style, and its developement in
successive ages—these are the subjects which it is my intention
to bring before you in the following letters.

Commencing with that which is most simple in plant life, the
starting-point of our contemplations will be to trace back this
complex structure to its several primary elements; whence
we will follow out the construction of the individual objects ;
the general plan to which, notwithstanding their diversity, they
are all conformable, and, as we shall everywhere recognise, the
same principle of unity ; finally, recombine the primary elements
under a higher general conception.

‘May you possess inclination and patience to accompany me
in the much-trodden, but unfortunately little-known, path [have
marked out, and that not only without fatigue, but, perhaps,
with a gain of intellectual activity.

LETTER II.
THE ELEMENTARY PARTS,OF THE PLANT.

None who have to any degree accustomed themselves to the
contemplation of natural objects, will be disposed to regard the
plant merely as an aggregate of leaves, stalks, flowers, etc., in
which the figure, colour, nature of the substance, etc., have been
determined and arranged by accident. A regular succession of
the several organs, a certain normal developement and unity of
form and colour, must have attracted the notice of all who have
attentively examined even a few plants, and compared together
their respective organs. It is, moreover, impossible to fail in
arriving at a conviction that there is throughout the plant world
a conformity to some general plan; a truth of which a very
striking indication may, without difficulty, be recognized in the
arrangement of the ultimate parts of which all plants are com-
posed.

Before proceeding further in the consideration of this subject,
I must request you to direct your attention for a while to these
ultimate parts of plants, the stones, as it were, with which they
build themselves up, which communicate to them solidity and
durability, utility and beauty, and without which their exist-
ence would be altogether impossible.
_ These ultimate parts of plants are not of such a nature as
to belong to that class of material particles which are scarcely
perceptible by the senses, still less are they analogous to atoms,
but, on the contrary, always possess a definite bulk and a clearly
distinguishable figure, which, although not in all instances per-
ceptible by the naked eye, may by the aid of the microscope be
studied even in their minutest details. It is, however, not only
in the arrangement and connexion of these elementary parts,
that our wonder is excited at the great art and skill which they
display; this is still more evident in the structure of these parts

BOTANICAL LETTERS. Ff

themselves. It is scarcely possible to conceive anything more
wisely and artistically contrived than a cell. A delicate mem-
branous vesicle imperceptible by the naked eye, covering a
nucleus of partly liquid, partly solid substances in one case, and
in another a hollow space, surrounded by a membrane almost
stone-like in its hardness, the one being gradually produced
from the other. The accompa- ee

nying figure is a considerably-
magnified representation of a
roundish somewhat flattened
cell, with its contents partially
visible through the delicate
translucent membrane. How
easy it is thus for the plant, by
an appropriate distribution of
these elements, so dissimilar in
firmness, to employ the one here, the other there, according ag it
may be requisite; and thus on the one hand the firmness and
durability of the plant, on the other, its constant increase and
growth, are rendered possible. The threads which are employed
for making linen and other woven fabrics, the wood of trees, the
hard shells of many fruits, consist of such old, indurated build-
ing-stones of the plant, while the younger and still soft cells,
with their juicy and granular contents, frequently serve as the
food of animals and of men.

The forms which these ultimate parts of plants present in the
different organs of the plant, and in different plants, are not less
remarkable. While one portion
of them maintain their original
globular figure, others become
flattened, and resemble hewn
stones of a square and other
more or less regular figures,
bounded by definite plane sur-
faces. Thus fig. 2 represents a
cell perfectly flattened on all
sides, the original spherical surface being only perceptible at
the corners. It was therefore to some extent pardonable, that

Hig, 2.

8 BOTANICAL LETTERS.

these integral parts of plants should be mistaken for crystals,
and that their formation should be regarded as analogous to
that of the cubes of rock salt and fluor spar, or of the twelve
faced figures of garnet.

Other forms, differing more widely from the vesicular form,
occur in the long cylindrical or
columnar cells, as shown in fig.3,
and the flattened plate-like cells.
The substances which, like wood,
| ; bark fibre, ete., are of such great
utility for all the requirements
of life, are nothing more nor less
hci than such columnar plant-cells,
a with pointed ends, by which
! they are, as it were, welded to
each other, and form those
tough elastic fibres. Fig. 4 is a
magnified representation of seve-
ral contiguous cylindrical cells,
with ends pointed and joined
together. Their thick walls
render them firm and tough, and
likewise communicate these cha-
racters to the bark which they
constitute. It would carry us
much too far to enter into a
description of all those deviations from the primitive-cell form
which, resembling sometimes familiar and sometimes irregular
or variously-distorted figures, take a share in the composition
of the plant organism. There is, however, one form which I
cannot omit to mention, because it is one of the most elegant
of minute forms, the so-called plant vessels.

While all cells, even when resembling pipes and lengthened
cylinders, are closed at their ends, there are cylindrical cells
which burst and form openings at their ends, where they join
other similar cells. Tubes of greater or less length are thus
formed, which, enclosed by other cells, constitute a system of
mutually-communicating pipes, called vessels. A portion of

Fig. 3.

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BOTANICAL LETTERS. 9

such a plant vessel, which, from the net-shaped markings upon
its walls, is termed reticular vessel (vas reticulatum) is shown
on a magnified scale in fig. 5. Generally speak-
ing, a number of such vessels are grouped to-
gether, and surrounded by analogous, although
upon the whole, different utricular cells, the
whole constituting what has been termed vas-
cular fibre.

The cells, according to their figure, form a
kind of masonry, which is sometimes compact,
sometimes porous in structure, consisting in dif-
ferent instances of rounded, quadratic, columnar
or plate-shaped cells of various sizes, and which
the anatomist technically calls cellular tissue.
Thus fig. 6 represents cellular tissue, com-
posed of roundish ellipsoidal and pear-shaped
cells, which are merely in juxtaposition without
being flattened, and consequently form a loose
porous tissue (merenchyma). Fig. 6.
From the transparency of the
cell membrane, the contents,
consisting of green and other
coloured vesicles, are distinctly
perceptible; Fig. 7. Cellular
tissue, composed of polygonal
cells (parenchyma), the interior
of which is exposed at the top
and on one side by section. The
individual cells are somewhat ex-
tended lengthways, and bounded
by twelve planes. Their con-
tents consist of a colourless
watery fluid (cell sap) without
any solid substances. The
vascular fibres, from the cir-
cumstance that they usually
possess greater firmness, may
be compared to a skeleton

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10 BOTANICAL LETTERS,

upon which the softer and more porous parts rest ; but im reality
they do not in any other respect resemble these half-lifeless
parts of the animal organism, at least during that period when
they are still in full activity. When we consider that the

vascular fibres in their form, composition, developement, and —
connexion, appear to exercise a determinative influence in all
formations of cellular tissue, it may be possible to recognize
in them the sketch in conformity with which the details of all
plant structures are carried out. The mere observation of the
_ network of ribs in a leaf might be sufficient to suggest this
idea. Fig. 8 represents a portion of a palm stem, with three
bundles of vessels, of which the two front ones are exposed by

longitudinal, as well as transverse sections. In the larger of
the two, at a, thin-walled wood cells are perceptible, at 6 a
simple, and at c a reticulated spiral vessel, at d a bundle of so-
called true vessels, at e thick-walled bast cells, which likewise
recur in the smaller bundle of vessels. All these bundles of
vessels are surrounded by parenchymatous cells ff.

« If what has already been adduced has served to afford some
little insight into the structure of plants, I may be per-
mitted to direct attention to a few other peculiarities which
may be easily recognized in the arrangement of these elemen-

BOTANICAL LETTERS. 11

tary organs. From the term cellular tissue which has been
applied to the masonry of the plant organism, it is very pro-
bable that those who have not had an opportunity of examining
it by the aid of magnifying lenses, will form the erroneous
opinion that it has in reality a greater resemblance to a tissue
than to a piece of masonry. This, however, is not by any means
the case. It is well known to every one that the peculiarity of
a tissue consists in its being composed of a number of thread-
like parts running in one direction, and united by similar ones
running transversely. There is no kind of cementing substance,
_ but the compactness and strength of the tissue are solely and
alone determined by the interlacing of more or less uniform
fibres.

No such arrangement is found in the so-called tissues of the
plant. Its elementary parts are, without any exception, micro-
scopic; they are simply situated beside and above each other;
they are not interlaced, not even those which are tubular, ex-
cept sometimes in mosses, alge, &c.; consequently the mass
which they form resembles masonry rather than a tissue.

But this circumstance renders it imperatively necessary, in
order that the whole may possess any degree of durability, that
the individual elements should be united to each other. The
cement or mortar by which this junction is effected is some-
thing very remarkable ; and we shall subsequently have occasion
to consider it, for the present merely pointing out the necessity
for it.

But it will be asked, are there not then in the plant organ-
isths, consisting frequently of myriads of cells, arrangements
which support the combination of individual parts as well as the
firm connexion of larger masses? It would seem almost self-
evident that such arrangements are absolutely necessary in all
plants, in order that they may, even for a short period, with-
stand the influence of exterior mechanical violence.

And it certainly is so. The plant builds its secret chambers
and roofs them over with such art—it employs in the construc-
tion of the stem which bears its entire weight, such groundsels,
buttresses, and cramps—that an architect could not proceed
more correctly. Must not the solid vascular fibres, thin above

12 BOTANICAL LETTERS.

and thicker below, which, separately or arranged in circles,
traverse the whole length of the stem, be regarded as actual
buttresses against the storms and wind, with which the slender
plant stem has to contend? Is it not by the most appropriate _
means that the longitudinal fibres of wood are clamped together
by the so-called medullary rays? And when, besides this, we
take into consideration the flexibility and elasticity of the ele-
mentary parts, it becomes intelligible, how, in spite of the
elements, perpetually bent upon destruction, here the oak,
there the feeble reed, wave their heads defiantly in the air.

I have spoken of the secret chambers in the interior of the
plant, and possessing, in almost all instances, a particular form.
These chambers, sometimes large, sometimes small, resembling
regularly-shaped rooms, romantic caves, or even dilapidated
ruins, are termed by the anatomist air-passages. They are
shown on a_highly-maenified
scale in fig. 9, as they appear
in the leaf of Acorus calamus.
In this plant the air-passages
aaaa are bounded by the most
elegant cellular tissue. The re-
gularly-shaped chambers which,
as the above term indicates,
contain nothing but air, are,
for the most part, beautifully
arched, elegantly constructed,
and represent, in fact, micro-
scopic grottoes, columned tem-
ples in the midst of the compact
cellular tissue of the plant. Other larger cavities present, in
their interior, the marks of decay but too distinctly. Much
may be learnt in this respect from every blade of grass.

The most remarkable circumstance connected with these
hollow spaces filled with air is, that they are, for the most part,
connected with each other by means of much smaller passages
which terminate outwards in innumerable open branches.
The mouth of these minute shafts and galleries, leading into the
interior by means of a great variety of channels, is always

Fig. 9.

BOTANICAL LETTERS. 13

delicately formed, and generally of such construction that it
can be closed, and the communication between the atmosphere
and the interior of the plant established or interrupted accord-
ing to circumstances. Such mouth-like openings, which the
botanist calls stomates or stomata, are so numerous, that upon
a single square line of the leaf-surface of the common
monkshood (Aconitum chamarum), nearly one thousand may be
counted, and these do not occupy so much as one-tenth part of
that space.

A piece of this leaf magnified two hundred times in diameter
is represented in fig. 10; a is the exterior layer of cells at the
upper side and consisting of plate-shaped cells; 0 is the ex-
terior layer of cells on the under side, where the stomates are

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situated. At the sections it may be seen how these orifices,
formed by two crescent-shaped cells, open into, with cavities, c,
which communicate with each other throughout the entire
cellular tissue of the leaf; d a layer of cylindrical cells near
the upper surface; e a compound layer of irregular cells. It

14 BOTANICAL LETTERS.

thus becomes intelligible how the atmospheric air penetrates
even to the most remote parts of the plant organism, supplying
it with various substances, and receiving others in exchange.
Nevertheless, we should in vain seek for the air-channels and
passages in those parts of the plant which are still in course of
construction. It is not until after this has been completed
that they are formed; they do not stand in any necessary re-
lation to the new structures, and present the appearance rather
of repositories, where things which are not capable of any
further or immediate use are stored up.

In the plant such substances are represented by the resins,
gum, ethereal oils, etc., which, although incapable of any appli-
cation by the plant, are, nevertheless, of value to us. It thus
frequently happens that we live upon the superfluities of nature,
little suspecting that we are doing her a favour by taking some-
thing from her plenty.

As in all architectural works, requiring any great devas of
accuracy, each stone must be Poy measured, especially
formed and adapted for the position it is intended to occupy ;
so is this equally necessary in the construction of the plant.
There is no cell employed here whose form and dimensions
have not been previously determined as with square and plumb-
line, so that it is suited only to the place it occupies and for
no other, fitting exactly into the depressions or elevations in its
neighbouring cells. In observing a cellular tissue from any
part of a plant, we cannot but be astonished at the beautifully-
constructed compact masonry in which the appropriate elements
are not only arranged in order, but are likewise firmly united
' so as to form one mass. How beautifully, for instance, do the
pointed ends of the columns and cylinders fit into the spaces
left by the juxtaposition of similar elements, both above and
below, thus forming ligneous and bark-fibres!—how close and
tight are the brick-like cells which compose this masonry, which
I ‘bests already compared to buttresses, the purpose of which is
to protect the columnar wall against lateral pressure, and
without which they would not possess that firmness which they
everywhere present! Again, the whole of this is covered with
a protecting mosaic pavement, extending over the entire surface

BOTANICAL LETTERS. 15

of the plant. A portion of this epidermis, consisting of closely-
fitting tabular cells is represented by fig. 11. The upper sur-
face. of several of the cells is removed by section in order to
expose the interior. It is impossible to imagine any roofing
constructed with more closely-fitting tiles or a more delicate
mosaic than the exterior cellular layer of plants, called, in
technical language, the epidermis. Through this neither dust
nor rain can penetrate, no particle of moisture can insinuate
itself; and it is evident that the plant knows how to protect
itself against atmospheric influences better than we can do in
our most splendid and durable buildings.

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But, although by means of these adaptations the plant en-
deavours to maintain, as far as possible, its integrity ; it is not,
on the other hand, entirely shut out from communion with the
exterior world, from which, indeed, as we shall subsequently
perceive, it derives all that is requisite for its existence. It is
by means, partly of the air-cavities present on every part of the
plant’s surface, that it receives whatever supplies it may require,
and discharges its surplus products.

It is not difficult to believe that in a structure so delicate
and well arranged, each part has a particular use and a definite
purpose, so that an harmonious working of all the individual
parts is rendered possible ; but that such a special utility extends
even to the individual elements of the structure, cannot be
inferred otherwise than from strict necessity. It is not until
we know how each separate stone fulfils its functions in the

16 BOTANICAL LETTERS.

perfect whole that we shall be in a position to form an opinion
as to the stability, design, and harmony of the whole; and so
long as there is no attempt made to obtain this knowledge, we
may, indeed, vainly declaim upon the conformity to purpose
and the beauty of the plant structure, but shall never be able,
in accordance with the principles of science and art, to form a
true and adequate conception of the structure of a leaf, or even
a hair. or this reason it is that we cannot too highly esteem
the endeavour, to establish the architecture of the plant upon a
true scientific basis, and to obtain, in the knowledge of its
elementary composition, a key to all that which is now a
mystery to us. The man who has hitherto penetrated the
furthest into this obscure region of research, who has attempted
to examine stone for stone in their production and application,
who has given us both ground-plans and elevations of some
plant structures’ in which each element is marked with the
number its architect intended for it, this man is Karl Nagel.
It is undoubtedly from him that we may look for the unveiling,
not only of the most simple, but likewise of the most com-
plicated structures of the plant organism, which we have hitherto
merely wondered at but not understood.

( Iv)

LETTER III.
GENESIS OF THE CELL.

So far as we have yet proceeded, the comparison of the material
composition of the plant with various parts of buildings has been
of service in rendering our subject familiar and intelligible; but
now the analogy begins to fail, inasmuch as we are about to in-
quire into the origin of the constructing material. Every architect
procures his material from a greater or less distance; stone,
bricks, lime, sand, water, and whatever else he may require, are
brought to the place where the building is to be erected; and
it is with these alone that he is able to carry out his work. But
whence does the plant derive its stone, its mortar, etc., without
which, in this as in the above case,the construction of any edi-
fice of the same or similar elements would be impossible P

It is in this particular that the marvellous character of the
plant economy presents itself most prominently; for we must
remember that although it obtains the materials for all the pur-
poses that it requires from without, still the preparation and
working of these are by no means left to be executed by other
forces; on the contrary, the plant makes its own stones, it burns
and slakes its lime, works it into mortar, and unites in itself, in
short, bricklayer, stone-mason, etc., as well as architect.

It was for a long time supposed that the plant was capable of
effecting more than is really the case, and itwas regarded as a kind
of magician. It was believed that it derived from without only
air and water, and that, by a kind of magical transmutation, it
created everything which it might require, as, for instance, some
alkaline salts, earths, phosphorus, sulphur, etc.: this belief still
lingers in the minds even of some so-called intelligent agricul-
turists, who attach more value to the older chemical analyses than
they merit. Modern chemists consider that it is altogether im-
possible for such a thing as a plant-cell—which, however, as we
shall subsequently see, is the seat of powerful chemical activity

18 BOTANICAL LETTERS.

—to produce from oxygen, hydrogen, or carbon, even a single
atom of phosphorus or sulphur.

Irrespectively however, of this point, we will, in the first
place, direct our attention to the mode in which the plant, during
its construction, continually produces fresh materials upon the
spot, places them in the position they are to occupy, and cements
them together with mortar; then, when we have acquired an
insight into the wonderful operation, we will direct our inquiries
to the preparation of the material substance requisite for the
formation of its stone and cement; thus tracing with the more
searching glance of the chemist that which we first regard only
with the eye of the anatomist.

The insight into the formation of the building materials has
cost the anatomist much toil, and given birth to many contro-
versies. The matter is certainly not presented to us in so ob-
vious a manner that the mere use of our eyes would make us
masters of it. It is true that, unlike the architect who excludes
all uninvited guests from any observation of the progress of his
operations, the plant performs all its functions openly and with-
out disguise ; and if, notwithstanding this, we overlooked many
things, or saw others in a false light, this was rather because, in
our confusion, we did not know where or what to observe, and
was likewise a consequence of our subjective conceptions, as well
as of our inability to face the magic light which the plant pre-
sented to us. In short, it is only after much labour, and rest-
less watching and search, that we have succeeded in arriving
at a knowledge of the simple manipulation which the plant
adapts in its constructive operations, so that now, when we
‘know how this is effected, we feel more astonished at our own
dulness than at this extremely simple process of the plant.

The whole mystery of the production of these building-stones
of the plant consists in the fact that the plant developes each
one that she employs from others previously existing. In this
act these cells must themselves have become larger, to a cer-
tain extent, for otherwise the number of stones would only in-
crease, without the edifice itself becoming larger; and of this
there can be no doubt, as any comparison of a young and old
plant will show.

BOTANICAL LETTERS. 19

Let us now examine, somewhat more minutely, this produc-
tion of building-stones by the plant. As we have already seen,
these building-stones of the plant are, properly speaking, not
solid homogeneous masses, but variously-shaped membranous
utricles, vesicles, etc., filled with soft substances and liquids of
all kinds. Hach vesicle which is employed in the building up
of the plant is, without exception, formed in the interior of an
already-existing cell; when its formation is complete, it is at
once pushed out, and laid in the place which it is destined to
occupy. Neither windlass nor pulley is requisite; the whole
operation takes place so readily, and, as it were, spontaneously,
that we may well be astonished that such a thing is possible.
We will now examine how this is accomplished.

First, the old cell swells up considerably, increases in cireum-
ference, grows; but it must be remembered that it is not a mere
growth that takes place here. As in a pregnant animal, new
cells are formed in its body ; when these have advanced so far
in developement as to possess all the organs requisite for their
independent existence, they are set at liberty ; and the mother-
cell which, during the con- Fig. 12.
tinuance of these processes, not
only devotes the whole of its
contents to the formation of the
brood. of daughter-cells, but
likewise suffers a diminution of
its membranous envelope in con-
sequence of the progressive en-
largement, continues in a kind
of dream existence, and is at last
entirely consumed. Fig. 12 re-
presents a remarkably large bag-
shaped cell from the seed-bud of
the biennial (crepis biennis). It
is situated between parenchy-
matous cells which do not any
longer enlarge. This mother-cell
contains five secondary cells, of which the uppermost is further
developed than the others. The daughter-cells originate, there-

20 BOTANICAL LETTERS.

fore, altogether at the cost of the mother-cells: their existence
involves the death of the latter. Something very analogous is
presented in the propagation of certain insects ; the pregnant
animals gradually increase in size to such an extent that they
appear more like bladders. All the organs, all the functions of
the mother, are directed to the production of her young, and
after their birth there remains scarcely anything more than a
dry, rent membrane. May not, therefore, the formation of
cells by the plant likewise be termed a generation? And
what else is the entire plant formation, with its myriads of
cells, than the result of a continued generation of its ele-
mentary parts ?

After this insight into the progressive developement of the
stones, how different becomes the aspect of the masonry of the
plant perpetually being renewed, and, as it were, growing out of
itself. Here all kind of analogy with architectural operations
ceases; we are unacquainted with any work of human hands or
human invention which is even in the remotest degree similar
to the building up of the plant temple. It is an invisible hand
which inscribes upon its walls words as mysterious as those
once written in the palace of Belshazzar. Nevertheless, we
will follow up the formation of the cell still further.

Even while in the mother-cell, the position is determined
which the secondary cells are to occupy; therefore, after their
separation, no further displacement is necessary. If every cell,
besides the capability of producing new cells, possessed sufficient
energy to do so, only an irregular heap of cells would be pro-
duced ; and, according to the fecundity of one or other of them,
a larger accumulation of cells would be formed at certain points
than at others, and the whole would thus acquire a disfigured
appearance. It is only owing to the single circumstance that
this capability of production is limited, that order and regularity
are maintained, as it were, spontaneously in the formation of
the plant organism.

Two facts here present themselves: on the one hand, it
appears to be a constantly-prevailing normal condition, that
almost all production is limited to the minimum which consists
in the capability of the mother to produce only two secondary

BOTANICAL LETTERS. 21

cells; while, on the other hand, these cells possess altogether
different characters, if not in the first, at least in the last gene-
rations ; so that while the one is active and vigorous, soon pro-
ducing a new generation, the other in modest retirement passes
a mere passive existence. Cells of the latter kind do not con-
tribute to the increase in size of the plant structure, but by
virtue of their more permanent character determine the dura-
tion of the plant, while cells of the other are soon consumed ;
consequently it is of the former cells that the plant is essen-
tially composed. The arrangement of these cells, their mainte-
nance of this permanent character, or the occasional cessation
of it, attended by a renewed capability of reproduction which
may go on indefinitely, determine that part of the whole phe-
nomenon which refers to the dimensions and forms of plants.
These series of generations have not as yet been at all accurately
investigated in their dependence upon each other, or reduced to
definite laws; but it is to be hoped that those investigations
which have already thrown so much light upon the processes of
plant formation which are hidden from the unassisted eye, will
likewise penetrate those labyrinths into which no human eye
has yet reached.

At the present time we only know that the formative cells
exercise their functions chiefly at the outer part of the plant,
as well at the apex as upon the entire surface, so that a conti-
nual elongation as well as a lateral growth is rendered possible.

Jt is at these parts, where, in rapid succession from genera-
tion to generation, such life and activity prevail that, even in
the gigantic works of man, the stir and activity of the multi-
tude of workmen present but a faint reflection of this animated
and vigorous process.

Thus the plant grows gradually, elongating a new layer of
elements after the other encloses the wood of the stem; but
that it should not extend indefinitely, or raise itself to the sky,
there is, as Géthe has remarked, a sufficient provision. In what
manner we shall learn afterwards.

LETTER IV.

UNION OF THE CELLS; CHANGES RESULTING FROM THEIR
GROWTH.

Tue structure of the plant, with the ever-renewed elements of
which it is built up, now stands as a perfected whole before us.
All is well arranged, each stone is laid in its place; but there
is one thing essential to the execution of a durable architectural
work which we have not yet taken into our consideration,—it is
the exterior material union of the individual parts. Since each
cell is in itself a whole, which, notwithstanding its origin from
similar elements, is still destined to pass an independent exist-
ence, the mere bond of family relationship would, without any
other means of union, be quite inadequate to secure the integrity
of the plant, and to prevent the whole structure from being
shattered to pieces like a house of cards by the slightest violence,
or from being, as it were, the means of its own destruction.
To meet this difficulty, Nature has adopted a contrivance for
cementing together the several parts, chaining each cell to its
neighbour in such a manner that even when, from a dissimi-
larity in their character and purpose, there may be any want of
harmony between them, it cannot be attended with any conse-
quences detrimental to the whole. The plant-cells, therefore,
are, as it were, actually built up in their place, and cemented
together with an appropriate mortar.

But the plant prepares for itself not only the stones of which
it is built up, but likewise the cement employed in fastening
them together; and here again it is the cell which not only
performs the work, but likewise appears to be the only source
whence the material itself is derived. The union and cement-
ing together of the cells goes on even simultaneously with the
formation and separation, so that the scarcely-perfect cell is
already unable to change its position; and although furnished

BOTANICAL LETTERS. 25

with life and energy for thousands of generations, resembles a
chained Prometheus remaining during its entire existence
fettered to its neighbour cell.

These phenomena of plant life result from the fact that
this mortar or cement is prepared in the cell itself, and, pene-
trating through its walls, is transferred to the precise spot
where it is required, and where it can exercise its influence
upon the adjoining cell. This mortar or cement is sometimes
more abundant than at others; and at the places where it is
nearly or altogether absent, are Fig. 13.
formed those cavities, arched a @
passages, and mazes running | 7
between the cells (intercellular
passages), of which I have al-
ready spoken. It is natural to |
suppose that this substance
which is deposited between the
several cells should have re-
ceived a special technical de-
nomination; and, indeed, bota-
nists, regarding it as the true
mortar of the plant structure,
have given it the name of inter- \
cellular substance. Fig. 13 re- ©
presents a number of elongated |
parenchymatous cells, distinctly
united together by this inter-
cellular substance, @ a, into a
firm mass.

But the continual increase and arrangement of elementary
parts do not constitute the whole activity of the plant. Not
only the formative cells, but likewise the permanent cells, those
which, after their production, alone continue and insure the
duration of the plant, are subject to further alterations. Ori-
ginally minute delicate utricles, they become gradually larger
and stronger, assuming meanwhile the form which they are
ultimately to retain, and which has already been described as
cubical, polygonal, tabular, columnar, ete.

UW

WU
yy

Y/Y)
a

7
Lil

24 BOTANICAL LETTERS.

The increase in their circumference is, in most instances, at-
tended with a thickening of their exterior membranous boundary
or wall; and it is this process which constitutes the true growth
of the plant, while the increase by multiplication of cells must
be regarded only as a consequence of generative activity. Thus
these two processes mutually associate themselves ; and, while
the increase of cells is not possible without certain operations
of growth, this growth itself appears to be determined by pre-
vious cell formation.

But it is both of these processes conjointly which ultimately
determine the increase of size in the plant; and while the en-
largement of the cell never extends beyond certain and generally
microscopic limits, so, likewise, the multiplication of the cells has,
as we shall subsequently learn, a definite amount and purpose.

Fig. 14.

One phenomenon which, more than any other, is calculated
to insure the duration of the plant as well as to provide for its
sometimes considerable, and even enormous magnitude (as in

BOTANICAL LETTERS. 25

the chesnut dei cento cavalli, the dragon-tree of Oratava, the
Baobab (Adansonia digitata), the cypress of Oachaca) and
to enable it to vie with the most ancient architectural monu-
ments, is the further developement of the cell-membrane after
it has attained, or at least approached very near, its limit of
extension.

Although the original boundary of the cell is in all cases a
thin homogeneous membrane, it frequently happens that at a
later period it becomes thick and solid; and as in this state it
is no longer capable of extension, this progressive thickening
takes place by the deposition of incrusting substance upon the
inner side of the cell-wall. As a consequence of this deposition
the capacity of the cell must necessarily be more and more
contracted, and finally, perhaps, reduced toa minimum. Such
cells which are called thick-walled are distributed here and
there throughout the elevation of the plant, and are generally
of most frequent occurrence wherever there is any part which
requires support or protection. Cells of this kind are conse-
quently not only good as corner-stones, plinths, or paving slabs,
but are especially employed in the construction of the pillars.

Unless the cells which constitute wood had thick walls, even
the most gigantic trees, the most colossal plants, would be borne
down by every blast like a slender blade of grass; and, in fact,
the very existence of such massive plant-organisms as trees
would be impossible if it were not for this character of the cells.

These thick-walled cells are of especial utility likewise at the
exterior of the plant-structure; and when at this part, as is
frequently the case, they even blend together and become
covered with a kind of varnish, they constitute the best pos-
sible protection, resembling a macadamized or asphalt pave-
ment. The same indurated covering is formed around some
fruits and seed-vessels, whose function is to protect the germ.
Judging from the extremely-delicate nature of the elementary
parts, the plant would barely escape destruction, even for a
short period, were it not thus strengthened and protected.

While considering this tendency of the plant, or rather
the cell, to fortify itself against all kinds of antagonistic in-
fluences, and thus to acquire persistence and durability, the

C

26 BOTANICAL LETTERS.

circumstances to which it owes its origin and ch aia
must not be disregarded.

Among these circumstances the most important is undoubt-
edly the ete with which it procures the materials by means
of which it exists, and is capable of further developement.
While the cell strives, as it were, by the excessive formation of
_ wall substance to shut off communication with the outer world,
such provision must be made as will prevent this from becom-
ing perfect, since in that case the further activity of the cell
would necessarily be limited. It is obvious that the communi-
cation, whatever its nature, will be more difficult through thick
walls than through such as are lighter and thinner. But
although the plant is in reality compelled here and there to
build: such thick walls, that is, to make its usually delicate
building materials more massive; it does not any the more
omit to leave openings here and there, or at least to retain in
places the original thinness of the walls.

That this is really the case has already been seen while con-
sidering the exterior cellular layer of the plant; but something
very similar takes place also in the cell itself, that minute and
originally closed space. However much the cells by the
thickening of their walls may separate themselves from each
other and from the outer world, a few, although perhaps closed,
window-like apertures are always left; and although some-
times, deeply sunk in the wall, they may seem like prison
windows, through which liberty can look with only one eye,
still they give animation to the silent space and scare away
death. Such little prison windows are present in some number
in every cell, so tiny that an eye, even with a thousandfold its
ordinary power, is scarcely able to see through them, an achieve-
ment first accomplished by our distinguished plant-anatomists,
Hugo and Mohl. Not only is their singular structure remark-
able, but likewise, and even more so, their direction and commu-
nication with other cavities; strikingly revealing the truth that,
in the body of the plant, one cell cannot exist without the other,
so as to become perfectly independent. Fig. 15 represents
thick-walled cells, united by intercellular substance, from the
fruit of a palm. Upon the upper plane of section may be seen,

BOTANICAL LETTERS. 27

not only the concentric layers of the substance 6 6 coating the
original cell-wall a a from without towards the interior, but
likewise the pit channels ec, intersecting it in all directions, and
opening into the contracted space of the cells d, but producing
on the exterior the appear-
ance of punctures, or as
they are called pits, e.

The arrangement which
by this object is effected
consists in the correspond-
ing situation of these little
windows in the walls of the
cell, so that by meeting
exactly a communicating
passage between the cells is
formed. We shall after-
wards learn how much the
cell, and consequently the
plant, owes to this wise
provision, and that such an
arrangement would not be advisable if perfect separation were
desired.

But when the cell has once advanced so far in its develope-
ment that it has no room either for a marriage-bed or the
apparatus of chemical and physical activity, for retorts, balances,
and pumps, it may well be imagined as little more than a
sepulchre, in which life and love lie buried and motionless for
ever. So in truth it is inethe plant-organism, and in all its
integrant parts ; and it is especially those parts which have, in
the highest degree, enjoyed the pleasure of existence that fall
into a death-slumber from which they never wake again. In
the midst of the beautiful green temple one beam after another
breaks in, one column falls above another, and long before the
proud structure has ceased to wave its leafy crown joyously in
the breeze, the death-worm has been gnawing at its heart.
At last the whole decays; and just as it was built up, imper-
ceptibly making a world of life dependent upon its existence, so
it passes away without leaving a vestige behind.

=

c2

LETTER V.
CHEMISTRY OF THE PLANT.

Tar most wonderful part of the formation of the plant is, and
always will be, the art by which it produces from some few
elements derived from the air and the earth, the whole material
of its structure, which, as we know, is of the most varied cha-
racter. This becomes still more remarkable when it is remem-
bered that this material is in all cases derived from the cell,
and consequently that the great numbers of different substances
met with in the plant-world all originate from this extremely
small microscopic body, and the processes which go on in and
around it. Who would have thought of seeking in this minute
space for a power and energy which, with all our art, we are
unable to command in our chemical laboratories and factories ?

I will now consider the plant, or rather the plant-cell, as an
active, I might indeed say, never-resting spagyric,* labouring,
although in different ways, both day and night, winter and
summer.

From the exterior world the plant derives only a few ele-
mentary substances, the principal of which are carbon, hydro-
gen, oxygen, and nitrogen; for the quantities of sulphur,
phosphorus, chlorine, iodine, as well as of potash, soda, lime,
magnesia, silica, &c., which it likewise requires, are dispro-
portionately small when compared with its consumption of the
former.

One of the greatest necessities of the plant is water, not only
because it is the means by which all other substances are intro-
duced, but likewise because the plant is only able to exercise
its secret art in what is termed the humid way—that is to say,

* The name spagyric, derived from omdeww, to bind, and dyelpew, to com-

bine, was applied in the middle ages to the chemists (alchemists), as those
who were able to dissolve, separate, and combine substances.

BOTANICAL LETTERS. 29

it operates only with aqueous solutions. When we learn from
experiments, which have been made with great accuracy, on the
consumption of water, that 26°910 square feet of meadow-land
or of corn requires six million pounds of water during the period
of vegetation, and an’ equal surface of forest rather more than
less, we cannot but be amazed at the magnitude of this
quantity, and be induced to examine how such a mass of water
can be supplied to such a small surface, and in so short a time.
It is evident that the inexhaustible sources of this supply, upon
which the prosperity of the plant depends, can only lie in the
heavenly gifts of rain, dew, &c.; and that, where the sky does
not afford these gifts, the growth of plants, and even the ex-
istence of a scanty vegetation, are impossible. The absence of
all kinds of plant-life in the deserts of Sahara and Libya, the
sand ocean of Sehamo, or the western coasts of Bolivia, is a
consequence, not of their being sandy or rocky tracts, but of
the want of rain, or any kind of watery deposits, for in these
districts it rains only once in twelve years, and that not
always.

After water and its constituents, carbon is the most im-
portant requisite in the growth of plants, for on examining the
elementary composition of any part of them, this element is
always found to play some part, and, in most instances, the
principal one. But then the question arises, whence does the
plant-world derive the enormous quantity of this substance,
which is far less abundant in the earth than water? It would
almost seem as if the small proportion of carbonic acid con-
tained in the atmosphere (7)¢ of its weight or + 9% oo to
toi00 of its volume) were insufficient for the purpose; but the
chemist has shown that the entire living and dead vegetation
might derive from this source all the carbon they require
without nearly exhausting it.

The fourth substance which must be numbered among the
most indispensable requisites is nitrogen. While the first three
substances above named principally constitute the corporeal
part of the plant, and are especially employed in the formation
of the cell-walls, it appears that throughout the entire con-
structive operation there is a necessity for some substance

30 BOTANICAL LETTERS.

which, so to speak, sets the whole in action, supports its activity,
and ensures its completion. This Archeus, the substance
which fulfils this office in the plant, is nitrogen. It is nitrogen
that sets the work in action, that renders the formation of each
individual cell possible; and it is always to be found wherever
there is anything to be done or made in the plant. While the
activity of carbon, hydrogen, and oxygen, is limited to the
boundaries of the cell-life, the activity of the nitrogen prevails
in the interior in the nucleus of the cell, and gives the initiative
to all the processes which take place.
(Fig. 16). Both the cell nu-
Fig. 16. cleus (cytoblast), that is the
round lenticular-shaped vesicle
with the nucleoli, as well as
the granular substance (proto-
plasm) surrounding it, and dis- _
tributed throughout the entire
cell, consist essentially of nitro-
genous substances. It is not
easy to determine, at the present
time, what may be the purposes
and uses of all the other substances mentioned above, although
it is in some instances plainly evident that they do take a share
in certain operations appertaining to the general constructive
process.

When the elementary substances have been introduced in
the plant-organism into the cell from the exterior world, they
are still by no means in that state which they are to acquire
before becoming actually part of the plant. Even their intro-
duction into the organism is only possible under certain circum-
stances, namely, the conditions corresponding to their nature
and mode of agency; and this is still more the case with regard
to their relation to each other as soon as they have become
constituents of the cells.

The processes by which simple substances unite to form those
new compounds, and by which both the contents of the cells
and the boundaries of their activity—the cell-membrane—are
formed, are still enveloped in deep obscurity. Although we

BOTANICAL. LETTERS. 31

are acquainted with the general chemical laws of their action
upon each other, it has not yet been possible to acquire such a
special knowledge of this mysterious operation of nature as
would enable us to imitate it in our laboratories. The chemical
agency of the cell is, as regards its synthesis, although not as
regards its products, still a problem, and in this point of view
the plant is the only alchemist there is.

By studying the chemical agency of the cell in its products,
we may arrive at the following truths. The substances result-
ing from the combination of the simple elements are of various
kinds as regards their composition, their physical characters,
and their structure. They may, however, very appropriately
be divided into four principal groups, which are, 1, indifferent
substances, destitute of nitrogen; 2, indifferent nitrogenous
substances ; 3, vegetable acids; and 4, substances which per-
form the functions of alkalies.

Of these four principal groups, which comprise a vast number
of substances possessing subordinate differences, only the first
two include the substances which are the most abundant and
frequent in the plant-world, some few of which take a share in
the structure of almost all plants, and appear scarcely ever to
be wanting, while others are of a more or less subordinate im-
portance, and are met with in much smaller quantity, or fre-
quently only in a certain class of plants.

The most frequent non-nitrogenous constituents of plants
are 1, cellulose, or the substance of which the cell-membrane
consists, and which was formerly called igneous fibre; 2, starch
(amylum) ; 3, sugar; 4, gum; 5, plant-gelatine; and a number
of others which possess the most intimate relationship, and
although presenting different external characters, are identical
as regards their chemical nature. The chemist, who from the
time of Hermes, has been accustomed to express himself in a
symbolical language, includes all these substances under the
formula C,, H,, O,, and is able to produce from any one of
them most of the others. A little nitric acid, or sulphuric acid,
or alkaline salt, added to this or that one immediately converts
it into another. The chemist finds no difficulty in converting
starch into sugar, heneous fibre into starch, etc., which is shown

32 BOTANICAL LETTERS.

at fig. 17, as it occurs in the cells of the potato, and at fig.
18, highly magnified. In all the starch granules, a small
nucleus is perceptible, around which are arranged concentric
layers of starch. But this truth does no more than prove that
the plant by its own power may perhaps effect such transform-
ations, and indeed its production of one substance or another,
according as it is required, is one of the most wonderful pheno-
mena of plant life.

An example may serve to render this more intelligible.
There is no plant, which when it developes itself from the seed,
possesses those organs which subsequently furnish it with food.
But the plant requires food during the early period of its exist-
ence, as well as afterwards, and indeed even more; since it is
then about to increase its substance in all directions,—in short,
to produce cells. In order to enable it to accomplish this im-
portant function, upon which alone its further existence depends,
the germ is provided with a larger quantity of superfluous cell
substance, in the form of starch, oil, etc., which it receives from
the mother-plant. When the seed begins to generate, there is
nothing more convenient and appropriate than to convert this
reserve into current coin; and thus, as it were, spontaneously
there is produced—from starch, sugar; from sugar, plant-gela-
tine; and lastly, from this the cell-wall by which the integrity
of the cell is perfected, and one stone after another is added to
the plant structure.

BOTANICAL LETTERS. 33

Many similar examples might be brought forward; for the
transformation of one substance into another is not an unfre-
quent phenomenon of plant-life. The miracle of Cana is an
every-day occurrence.

The chemist calls all substances of this and similar formule
hydrates of carbon, which is as much as to say that they are
compounds of carbon and water, or more properly of carbon (C)
with the constituents of water (H and O). Sometimes there s
an excess of hydrogen (H), or of oxygen (O), giving rise to the
formation in the one case of fat oils, and in the other, of plant
acids, for instance, citric, malic, tannic, and gallic acids. The
agreeable taste and nutritive properties of many plants consist
altogether in the combination of these several constituents of
which the plant produces so great a variety.

The nitrogenous constituents of the plant are likewise either
indifferent, or they present the characters of a base. All the
young parts of the plant contain indifferent nitrogenous sub-
stances in proportionately large quantity. The glutin, albumen,
and legumin, of plants belong to this class. They are all com-
prised under the general term of protein substances.

These protein substances are not only of great importance in
the general process of plant formation, giving rise to every
operation, and regulating its progress, being, as it were, the
actual machinery, without which there would be no activity,
but they are at the same time the substances without which
animal life cannot be conceived, inasmuch as muscle, blood,
milk, etc., the substances by which animals are distinguished
from all other beings, are in reality not made in or by the animal
itself, but are derived ready formed from plants. This deeply
significant relation between two classes of beings apparently so
different, undoubtedly indicates the existence of a more intimate
connexion between them than has generally been suspected.
When, therefore, Liebig says, the animal organism is a higher
kind of plant, whose developement commences with those
materials with whose production the life of the plant ceases,
this is saying no more than what is perceived by the most ordi-
nary experience. ,

The nitrogenous alkaloids, like the plant acids, are to be re-

c3

34 BOTANICAL LETTERS.

garded less as necessary constituents of the plant, than as by-
products of the cell laboratory, and their use, as well as that of
the inorganic bases which are absorbed from the earth, may be
only to establish a chemical neutrality in some parts of the
plant which could not be effected, except by substances of such
decided characters. Wherever it is impossible to bring such
differences into equilibrium, when on the contrary they increase
and accumulate, the further existence of the whole structure is
placed in danger. Without this constant self-protection, the
plant must be destroyed by the strife and ae of its elements
and constituent substances.

When the establishment of this equilibrium is either wholly
or partially impossible, the necessary consequence is disease and
death. Such a permanent sickness from this source is frequently
met with affecting our cultivated plants; consequently both by
the horticulturist and the agriculturist very much remains to
be done before they can avoid this source of error in the treat-
ment of crops. What Liebig has achieved in this direction, as
dietist and prophylactist, is sufficiently known to every one.

If now we once again glance at the interior of the plant, and
consider the various operations which are ever proceeding there
in silence, we cannot adequately express our astonishment at
the series of different chemical processes which take place in
one and the same microscopic laboratory, and at finding that in
the web of cells of even one and the same plant, or part of a
plant, indeed often in adjoining cells, the most diverse chemical
products are formed. Here is a cell filled with watery plant
sap, in which gum or mucilage is dissolved; there is one in
which sugar is lkewise present; this is filled with starch
granules, that with globules of oil,—in one place are whole
groups pe cells filled with green, red, yellow, or blue pigments,
in another they contain bunches or druses of crystals. Fig. 19
represents parenchymatous cells, containing green vesicles
(chlorophyll vesicles) 6, with crystals c, and groups of crystals d.
In some of them the cell-nucleus is still present. It is hardly
possible to conceive anything more varied and manifold than
the picture presented by a section of any kind of plant when
viewed through the microscope.

BOTANICAL LETTERS,

35

How altered appears now the delineation we have hitherto
carried out of a masonry, consisting of homogeneous masses, and

to which we have compared the
plant, in which each stone not
only represents a house in itself,
but also one in which the most
diverse operations are carried
on! It may indeed be said that
a glance into this marvellous
structure, where from story to
story we discover new and un-
known spaces, where, with all
the penetration of the eye, it is
scarcely possible to penetrate
beyond the vestibule of the first
one, reveals to us something
little different from what we
learn by the study of the re-
mote regions of space where
the nebular films of the world
islands hide from us in the same
manner what goes on behind
them.

(=>)

Fig. 19.

YY,

C

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X \\
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i
ly

i
Vj

ll
W.

Yj

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LL

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Li

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Ly

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LETTER VI.

ABSORPTION AND DISTRIBUTION OF THE PLANT’S FOOD ;
SEPARATION OF WATER.

Ir we once again picture to ourselves the cell, we can only
conceive of it as a chamber closed on all sides. In order that
it may exist, increase in size, and even build new chambers in
its interior, the requisite materials for this purpose must be
obtained from without. Carbon, hydrogen, oxygen, nitrogen,
and whatever else may be needed in the shape of alkalies and
earths, can, under the circumstances, be introduced only in the
gaseous or liquid, form: the carbon only as carbonic acid, the
nitrogen as ammonia, the earths and alkalies only as salts, and
always dissolved in water. The cell filled with a greater or
less quantity of liquids can only absorb these raw materials,
constituting its food, when brought into immediate contact with
them. In this circumstance lies the whole mystery of the
absorption of food and its transfer throughout the plant in
those instances in which the plant consists of more than one
cell. Although there is no pump or other engine to effect this
operation, the whole goes on with as much precision as the
work of the most perfect machinery, and, at the same time, so
imperceptibly, that there is in reality no necessity for the ap-
plication of any other force than that which results from the
reciprocal action of liquids of unequal density, or of dissimilar
molecules. Here again is a manifestation of the wisdom of the
plant-architect, who rejects all kinds of apparatus, and yet
arrives more certainly and quickly at the desired end than the
constructor of the greatest monuments of human art. We
have already had occasion to marvel at the achievements of
the plant as a chemist, and our surprise will not be less excited
when we come to consider its physical activity and ingenuity.
The first and most important business of plant-life consists

BOTANICAL LETTERS. ot

in the provision of liquid nutriment with which the plant
almost always comes in contact by means of its lower extre-
mities. The water saturated with small quantities of carbonic
acid, ammonia, and a few saline substances, is there brought into
contact with the outermost cells of the plant filled with liquids
which, though of a different kind, are always saturated.

It is further a general physical law, that when dissimilar
and miscible liquids are brought into contact with each other,
they cannot remain so for an instant without a reciprocal
action.

When a glass containing some water is very slowly and care-
fully filled up with red wine, these liquids will continue for
some time to present sharply-defined boundaries, which gra-
dually become less distinct, and finally disappear altogether,
when it will be found that there is no part of the whole mass
in which the wine and water are not mixed in the same pro-
portions. The same result is brought about, although some-
what more slowly, when two liquids are separated by a mem-
brane, or when a bladder containing one of them is dipped into
the other. The bladder does not hinder the reciprocal action
of the liquids, except with regard to time, for they both con-
tinue to penetrate the bladder, and thus coming in contact, are
finally reduced to equilibrium. When the more-concentrated
liquid is contained in the bladder, a larger quantity of the less-
concentrated liquid will be transferred into the bladder than of
the former into the latter. The bladder will thus become
filled, and finally burst. When, on the contrary, the more-
concentrated liquid is outside the bladder, its contents will
become gradually lessened, and it will finally collapse. Of
these two conditions of action only the former prevails in the
plant, for the cells are everywhere in contact with the dilute
nutritive liquid, which is consequently introduced into the cells ;
or, to express the phenomenon in the language of the physicist,
an endosmose takes place.

From a knowledge of the usual degree of concentration
possessed by the contents of the cells, it is even possible to
calculate that the transfer of liquid into the cell takes place
with a force equal to the pressure of an atmosphere and a

38 BOTANICAL LETTERS.

half, consequently that it is an instance of a very general
physical agency which admits of being estimated and measured.

Again, not only the absorption, but lkewise the further
transport and distribution, of the sap throughout the plant, takes
place in precisely the same manner, provided that the various
cells of which it consists contain liquids of different kinds,
and possessing different degrees of concentration, which is the
case.

Solutions of gum, sugar, and protein substances take a very
different share in this process ; and all other circumstances being
the same, those cells which contain the largest amount of
protein substances receive the greatest quantity of sap. And
as it is the young cells, while in a state of developement, that
contain the protein substances in greatest abundance, it follows
that the flow of the sap is especially directed to them. But
this circumstance is likewise attended by another, which is
directly connected with the developement of the cells, and
consists in this, that if the direction of the sap-current is thus
determined, the developement of the cell must be likewise
dependent upon the same fact. These originally round cells,
through which there is a continual flow of sap in the same
direction, will therefore receive a copious supply of food, and
consequently have a more rapid growth, so that the course of
the sap-stream may be inferred from the increase in size pre-
sented by the cells. All elongated cells, and such as possess
pipe-like, cylindrical, or prismatic forms, obviously owe their
configuration to this circumstance; and the vessels mentioned
above are no other than such cylindrical cells which have soon
become old and inert, but through which at a previous period
the sap-stream flowed most vigorously ; and even in the most
perfectly-developed plant, the bundles of such cells and vessels
(vascular bundles) indicate the former, and, to some extent, the
present course of the sap-current.

When a white-flowered hyacinth is watered while in its pot
with the clear juice of the kermes berry (Phytolacca decandra),
the flowers present a reddish tinge, which cannot be owing
to anything but the absorption of the intensely-red juice of
these berries by the roots of the plant, and its diffusion through

BOTANICAL LETTERS. 39

the stalk into the colourless cells of the floral envelope. When
all these parts of the plant from above downwards are examined
anatomically, the path of the sap-current ‘may be very dis-
tinctly recognized. A magnified
section from the lower part of

Fig. 20.
the floral envelope, represented. Cyan
eas PEEL

in fig. 20, shows that all the
cells marked with arrow-heads aS
contained the red juice of the a2

kermes berries, and have trans-
ferred it higher upwards in the
same direction. Further, it ap-
pears that neither the spiral
vessels, aa, nor the air-passages
b b, take any share in the trans-
fer of sap.

It follows, however, as an
obvious consequence from this
arrangement that the plant does
not stand in need of any such
channels for the circulation of the nutritive liquids as are
necessary in the animal, where the nutrition and the repro-
duction of substance are subject to conditions altogether dif-
ferent.

It will be seen, therefore, from what has been described
above that the entire absorption and distribution of the juices
of the plant, and consequently its nutrition and growth, are
dependent upon the nature of the cell-membrane, and upon the
progressively-increasing degree of concentration of the liquid
contents of the cell. Unless the cellulose, or substance of
which the membrane consists, possessed the property of being
permeated by watery liquids without being dissolved, the cell
could have no permanent existence in contact with water and
moisture, and the introduction of nutriment into the interior
would be impossible. And again, without consecutive incre-
ments in the concentration of the sap contained in the cells,
the transfer from one cell to the other could not be effected.

In order to bring about this latter object, two operations are

ATO
ees Sea, OSS.
: : A ,
©

HONOR TACT

NAAN ACTON

TOT

TTT

40 BOTANICAL LETTERS.

indispensably necessary, one of which constantly regulates the
necessary degree of concentration independently of any che-
mical alteration, the other determines the transformation of the
absorbed liquid, and tends to the same result by chemical
means. Both processes, frequently disturbed by their mutual
reaction, nevertheless prevent any stagnation of the sap-current,
and at all times insure the necessary supply of constructive
materials to every part of the plant. ‘The one process is called
evaporation, the other assimilation.

Plants, with the single exception of those which are aquatic,
even when consisting of only one cell, are always partially ex-
posed to the atmosphere, which cannot remain without influence
upon them. The most striking effect of this influence is the
evaporation of water from the cellular membrane, which is,
however, always kept full by replacement of this liquid from the
interior. The result of this process cannot be any other than
the gradual and progressive concentration of the sap im the
interior, and the further consequence of this is, that the sap-
current is directed to that part where the need of water is
greatest.

If in polycellular plants the cells of the outermost layers
were constructed like those of the interior, it does not appear
that there would be any reason why the replacement of liquid
should not take place to an equal extent in all of them, and why
the sap-current should not be equally directed towards the
periphery of the plant.

However, this is not the case; for the cells constituting the
periphery are furnished with many adaptations which hinder
and retard the evaporation, in consequence of which it becomes
possible for other portions of the cellular tissue to draw up the
sap. It is only by means of this admirable contrivance that
the plant is able to direct the sap-current flowing from cell to
cell precisely to those parts where the developement of sub-
stance especially takes place.

Nevertheless there are some parts of the plant which are
particularly subject to the evaporation of water—for instance,
all those which present considerable surfaces as the leaves.
These organs, inasmuch as they facilitate evaporation, may be

BOTANICAL LETTERS. 4]

regarded as the principal means of renewing the contents of
the cells, and of determining the general mutation of sub-
stances which constitutes assimilation, and consequently as the
prime lever of the plant’s growth. When it is remembered
that a single leaf of moderate size exhales, on the average, from
sixteen to thirty-two grains of water daily, and that this quantity
calculated for the entire plant, or for an acre of land, amounts,
in the first case, to at least two pounds, and in the latter to
60°000 pounds, the statement already made that the consump-
tion of water upon an acre of cultivated land, during the period
of vegetation, amounts to six million pounds, becomes readily
intelligible. Still of this enormous quantity of water scarcely
one-third is actually appropriated by the plant in the formation
of its various constituent substances.

LETTER VII.
PHENOMENA OF ASSIMILATION.

I may probably venture to assume that none of my readers will
infer from the account given of the processes which accompany
the absorption of water, as well as its separation by evaporation,
that the water merely passes through the plant mechanically.
It is indeed true that the water flowing through the plant-orga-
nism is especially the source of its activity ; but it is quite as
true that it carries with it at the same time, in the shape of car-
bonic acid, ammonia, &c., the raw material for the purposes of
construction to which likewise it contributes itself, inasmuch
as it ceases to some extent, at least, to be water, and thus takes
a part in the general mutation of substances. It would at the
present time be a very extravagant proceeding to attempt to
trace the water, or any of the other substances dissolved in it,
throughout either their course in the plant or their several
phases of transformation; so much, however, is certain, that,
having penetrated into the cells, they soon lose their original
character, and that those substances only which are unessential
for the change, 7.e. the production of new substances, travel
from cell to cell more or less in their primitive form, and are
again separated not unfrequently in the same state as they are
absorbed. The sap juices of the plant, from whatever part they
are taken, contain with few exceptions neither carbonic acid nor
ammonia, nor salts of humic acid, but almost solely other com-
binations of the elementary substances, showing consequently
that the former have already been converted more or less into
assimilation substances. A number of phenomena not unim-

BOTANICAL LETTERS. 43

portant for the plant itself, as well as for the general economy
of nature, are referrible to the degree of energy with which this
process of chemical mutation proceeds, and which is naturally
dependent upon external conditions, especially those of temper-
ature and light. The most important of these phenomena is
the relation of the plant to the atmosphere surrounding it.
But here likewise we must not expect to meet with any
processes that are not consistent with chemical and physical
laws.

It may very distinctly be perceived by a comparative exami-
nation of what the plant receives from without, and the sub-
stances which it has subsequently produced, that there is no
inconsiderable surplus of unconsumed oxygen. This oxygen
must be separated, and as the plant-sap itself is able to absorb
only a very minute quantity, the whole of this substance must
be exhaled into the atmosphere. Experiment has indeed proved
that this is really the case; and further it has been observed that
under those conditions which conduce to a more rapid mutation
of substances, and consequently a greater consumption of nutri-
tive substances, the discharge of oxygen is considerably aug-
mented. It may indeed readily be imagined that the activity of
the plant visibly increases under the direct influence of the sun
and diffused light, and under these circumstances the evolution
of oxygen from the plant is considerably increased. When
leaves or any green parts of plants are brought under water and.
exposed to the direct influence of the sun, they soon become
coated with bubbles of air, which, when collected and examined,
prove to be oxygen. Consequently the quantity of oxygen gas
thus disengaged by the grass of meadows, or the trees of a
forest during bright summer days, cannot be inconsiderable.
The shade of the trees invites us not only by its coolness, but
likewise, although without our being conscious of it, by the
agreeable sensations which necessarily accompany the respira-
tion of air richer in oxygen. With this more rapid consumption
of nutriment, the carbonic acid introduced by water is under
the circumstances insufficient, and the various parts of the plant,
wholly deprived of carbonic acid, seek some other means of ob-
taining what that source is inadequate to furnish. For this

44 BOTANICAL LETTERS.

purpose, however, all those parts of the plant which are situated
at its circumference, and are in contact with the atmosphere,
are especially well adapted.

By the examination of what is introduced into the plant from
without, and what it subsequently forms from those substances,
it may be ascertained with the greatest certainty, that there,
is no inconsiderable surplus of oxygen thrown off. This oxygen
must be got rid of by the plant; and as the juices are themselves
only capable of absorbing a very small proportion of it, the
whole excess must pass into the atmosphere.

The sap-juice contained in them becomes charged with car-
bonic acid in the same manner as when water is exposed to the
air. The plant thus obtains a quantity of carbonic acid, which
is frequently equal in volume to its entire liquid contents. It
is evident then that the exhalation of oxygen is accompanied at
the same time by an absorption of carbonic acid, and that both
processes are entirely dependent upon the chemical and physical
agencies in and around the plant. It cannot therefore reason-
ably be regarded as singular, that under altered conditions in
which the influence of light does not play a part, and under
which all the processes of assimilation are retarded, an en-
tirely different and almost opposite result should be brought
about.

Let us examine by night the same plant which during the
day disengaged oxygen, and absorbed carbonic acid from the
atmosphere. Since the activity of the absorbent organs appears
to be the same at all times when there is a sufficient supply of
nutriment, while its consumption and the assimilative process
are lessened, it cannot but follow that the carbonic acid should
accumulate in the juices of the plant to such an extent, that it
can no longer be wholly retained in solution, and that wherever
there is an opportunity it should be disengaged unaltered.

For this purpose again those parts of the plant which are
situated at the circumference, and in contact with the atmo-
sphere, are the best adapted, and the same organs which by day
show a tendency to absorb even the minute quantity of carbonic
acid present in the atmosphere, are the means of discharging
much larger quantities of the same gas during the night. It

BOTANICAL LETTERS. 45

follows quite naturally, from this circumstance, that on account
of the deficiency of free oxygen in the plant-juices, a transfer of
this gas from the air, in other words, an absorption of it, should
necessarily take place ; however, this absorption is always very
minute, and according to experiments which have been made
‘with reference to it, amounts at the utmost to only 4°5 or 65
per cent. of the volume of liquid contained in the whole
plant.

The disengagement of carbonic acid by night is far from being
equivalent to the absorption of this gas during the day. Con-
sequently the plant always consumes more than it returns to
the atmosphere. It follows from this, that the air in valleys,
and at moderate elevations covered with a rich vegetation, is
certainly at times somewhat poorer in carbonic acid than that
of higher regions. But the constant motion of the atmosphere
- immediately tends to restore the disturbed equilibrium, and to
bring its constituents into order.

Thus then we see that even under all conditions, provision
is made for the growth of the plant, that it finds almost
everywhere what it requires, and therefore that its existence
is not in the least degree dependent upon accidental cir-
cumstances.

Although we are still uninitiated and scarcely capable of ex-
plaining the most simple processes which take place in the pro-
duction of plant-substances, we may still perceive that there is
no one of them which has not its laws; and that the formation
even of an atom of sugar or cellulose is preceded by a multitude
of preparatory operations, and gives rise to as many further
processes of vitality in the plant. How it is that from the car-
bonic acid salts absorbed by the plant, there are gradually pro-
duced salts of oxalic, pectic, and other plant-acids, and finally,
after further combination, the bases sugar and the allied hy-
drates of carbon, cannot unfortunately be explained now; but
it is very different as regards the nitrogenous bases and the
protein substances, towards any conception of whose formation
we do not possess the most insignificant data.

But the light which has been thrown upon this hitherto
obscure branch of botanical science by a German physiologist,

A6 BOTANICAL LETTERS.

J. M. Schleiden, crowded as it is with false hypotheses, the
brilliant result which by the acuteness of his intellect he has
secured to science, admits of our entertaining a hope that the
darkness is now dispelled. If the future cultivators of plant
physiology will make it their duty to employ retorts and tests
for themselves, and not leave this task to the chemist, who,
striving towards other objects, furnishes them only with such
results as may happen to present themselves, we may then anti-
cipate more important results for this hitherto-neglected study,
which in return would not remain unproductive, but elevate
agriculture, the most important branch of industry, to the
position of a rational art.

CIS
aw
“I

NY

LETTER VIII.
CONFIGURATION OF THE PLANT. FUNDAMENTAL ORGANS.

By the formation of organic substances from inorganic com-
pounds of elementary substances, the plant is provided with
gum, sugar, cellulose, protein, &c.; but much remains to be done
before these substances can appear in the form in which we
meet with them as parts of the cells. The force, in virtue of
which they acquire a definite form, is certainly different from
what is ordinarily termed chemical affinity ; and without any
more intimate knowledge of it, the term vegetation has been
applied to it. It is this force which determines the aggregation
of protein substances into globular masses, which causes the
deposition upon each of them of a layer of cellulose; thus lay-
ing down the plan of the configuration of the cell. It is the
same force, hkewise, which repeats this operation an infinite
number of times; and thus not only determines the develope-
ment of compound arrangements of cells, but lkewise provides
for the multiplication of them. In short, the vital force, that
force the nature of which has hitherto remained unknown, the
true architect of the plant, is that to which it owes its origin,
its existence, and propagation, and upon which, likewise, ulti-
mately depends the diversity of form, in which the idea of the
plant has clothed itself.

Although we recognise in nature many processes which
resemble the formation of the elementary parts of plants, as, for
instance, the formation of crystals; still on examining them
more closely it is found that the production of the former is
widely different from that of the latter bodies; and conse-
quently that the cell and the crystal, the plant and the mineral,
cannot, upon any ground, be compared with each other.

But when we advance beyond the production of the cells,
the mode of their connection gives rise to so many questions,

48 BOTANICAL LETTERS.

that we willingly devote greater attention to this more accessible
department of the investigation than to those recondite pro-
blems which we are scarcely able to fathom, even with the aid
of the happiest abstractions.

On reviewing the plants of any region of the earth, of any
period of its history, it is only possible to recognise one single
fundamental distinction among all the various differences of
form. All plants, without exception, are either single cells,
that is, they consist of only one cell, or are multiples of a
greater or less number of cells, ‘The former are the unicellular,
the latter the polycellular plants. From the varied configura-
tion of the cell it may easily be foreseen that even unicellular
plants may assume a great number of different forms; but this
diversity of form must always be inferior to that of more com-
plicated individuals.

Since we have already seen that the multiplicity of cells in
the plant is only a consequence of the generative faculty of the
originally individual cell, the question naturally suggests itself,
whether the unicellular plants are destitute of this faculty?
This question may be answered both affirmatively and nega-
tively. Negatively, inasmuch as the unicellular plants are
capable of propagation, and affirmatively, inasfar as there is a
considerable difference between the propagation of the two
kinds of plants ; so that, what the first are able to achieve, as it
were, at the first attempt, the latter can effect only by a series
of generations.

lt is a profoundly wise conception which prevails throughout
the entire range of animated nature, that at the same time
that the individual being is subject to extinction, still its ex-
istence in time is provided for by its capability of putting
forth germs possessing the faculty of developement. Not only
the production of such germs, but likewise their separation
from the maternal body, and their individualization, is deter-
mined by that process which is usually termed propagation.
It is only by the continual formation of self-separating inde-
pendent cells that a plant remains unicellular. When this is
not the case, when the cells which are produced do not separate
from the mother-cell, even when they cease to be further pro-

BOTANICAL LETTERS, 49

ductive (permanent cells) a cell-multiple is formed. But it is
also possible that in such cell-multiples, self-separating cells,
true propagation-cells may be produced, after series of suc-
cessive cells. The entire immense formation of plants, extend-
ing over the whole earth, prevailing throughout all periods,
tends solely and alone to the earlier or later attainment of this
end; and the flood of various configurations, the thousandfold
forms of plants, are in reality nothing more than the expression
of these oscillations between boundaries indefinitely distant.
The only endeavour of the plant is to accomplish the formation
of the propagation-cell; and when it does not rapidly achieve
this end it is compelled to adopt the most manifold means, to
enter upon the most singular preparatory labours, and thus to
give rise to that which we term the plant, and which presents
itself to us under such a vast diversity of aspects.

It would be foreign to the purpose of these letters to follow
up the consideration of the vegetative force in all its phases;
still we must not neglect to glance over at least the most
essential particulars of the plant form. .

It is a circumstance of great
importance as regards the sig-
nificance of the fundamental
form of the plant-structure, that
even in the unicellular plants we
may here and there recognize
an arrangement of certain parts,
similar to that presented in the
most complicated cell-multiples,

In the first instance, the round

vesicle becomes extended in

two opposite directions, form-

ing thus a pipe, with one end

turned towards the earth, and

the other prolonged into the

air, as is shown in Hig. 21 which q
represents an unicellular plant
belonging to the alge (lotry-

dium argillaceum, Wallr.). The presence of nutritive sub-

D

50 BOTANICAL LETTERS.

stances in the soil, and their absorption, on the one hand,
as well as the need of air and light for their assimilation, on
the other, appear to be the principal circumstances which deter-
mine the transformation of the cell into a utricle growing
upwards and downwards, a type of the stem and root or axis.
Nevertheless it does not remain stationary at this point. In
both directions secondary processes are thrown out, as it were,
repetitions of the axis; those at the descending part being
more or less bag-like; those at the part above ground being
also bag-like, though different from the others.

In this simplest of all forms in which the plant appears, may
be recognized all the essential organs which, even in cell-
multiples again tend to make themselves sensible. The first
endeavour is directed towards the building up with cell elements
of an axis, possessed of a tendency to prolong itself in two
opposite directions, a living magnet attracting and repelling at
both poles, the negative pole directed towards the earth, the
positive pole towards the air and the light, and maintaining,
with the earth as well as with the air, a constant interchange
of substances, by means of which it is alone able to exist.

There is scarcely any instance in the plant world of the mere
formation of this axis. The tendency to multiply itself is
always prominent ; and thus similar cell-multiples are put forth
from the primitive series as secondary axes; in the lower stage
of developement imitating the form of the primary axis, and
deviating more or less from the axial form in the more highly-
developed parts of the plant world. Thus are produced upon
one side of the axis, those variously-formed supplementary
organs which are termed leaves; while, at the other side, the
original axial or cylindrical form is maintained with but few
modifications in the radiations of the root.

To this fundamental form of the perfect cell, as it appears in
some alge (botrydium, valonia, caulerpa), etc., which presents
itself in the most simple cell-multiples, all the most varied
and diverse forms of the plant world may be reduced; and
although it sometimes appears as if the linear arrangement of
the elementary parts did not predominate, it is in reality only
hidden, partly by the preponderance of other tendencies of

BOTANICAL LETTERS. 51

developement, and partly by the subsequent developement of
masses which have no causal relation to it; so that even in the
most distorted and decisive plane forms, we are able to detect
the original linear arrangements.

We may therefore say, with perfect justice, that the plant,
divested of all accidental attributes, is, as regards form, essen-
tially a system of axes. This is very distinct and obvious in
all the less highly-developed plants; and from the mosses to
the most perfect plants, the axial configuration presents itself,
so that they have long been characterized by a corresponding
term intended to express the difference between them and all
other plants which have not very happily been termed foliaceous
plants.

Dp 2

(6952) <)

LETTER IX.
THE PLANT CONSIDERED AS A LEAVED AXIS.

I the formation of the plant were limited to the production of
a single axis, upon which sooner or later, and after more or less
numerous generations of elementary parts, the developement of
reproductive cells was ultimately achieved, there can be no
doubt that the greatest monotony would prevail in the plant
world. |
But the emancipation from such restriction, the progressive
developement of the plant, is necessarily attended with the
capability of producing new axes, and consequently of assuming
the greatest multiformity. With the appearance of the secon-
dary axes, the door is opened, through which the unfettered
power of vegetation developes itself in all directions. That
which presents itself to us as diversity of configuration in the
plant world, and produces so pleasing an influence upon our
senses, as well as upon the imagination, is ultimately dependent
upon nothing else but the formation of these secondary axes.
It was certainly a long time before the observing intellect,
the more penetrating judgment, and the power of combining
details into one harmonious whole had broken a way through
the labyrinth of plant forms, and succeeded in uniting under a
few easily intelligible forms that endless multiplicity of confi-
guration which almost overwhelms the power of conception.
Now that this gigantic work has been achieved, it is an easy
matter to recognize even in the most strange and fantastic
forms the one primitive law of formation. With this magic
formula we may wander, not only through the meadows and
woods of our native land, but also among the giant and pigmy
growths of other regions; and in whatever countries, mountains,
or valleys they may occur, we need not be in fear of meeting
with anything inconsistent. If then the supplementary parts

BOTANICAL LETTERS. 53

of the axis perform so important a part in the general pheno-
menon of vegetation, it is certainly worth while to examine
somewhat more closely their influence upon the configuration
of the plant. But this must be done by considering not only
the general mutability of their form and character, but likewise
the sequence of their appearance. We will do this sepa-
rately.

First, as regards the configuration of the secondary axes: this
in the simple cell-multiples, differs less from the form of the
primary axis than in the higher plants; the luxuriance of form
which presents itself in the latter has scarcely any limit, the de-
viation from the original cylindrical form which the leaf under-
goes is here of the most varied kind. Nevertheless it is the plane
form which gradually predominates ; so much so, that the general
conception of the leaf is almost universally associated with this
form. The simple conical cylinder axis of the plant becomes
thus in general a leaved axis. This expression for the more
perfect plant form may be regarded as the most universal, the
most comprehensive. Everything, therefore, which appears
upon the axis, is only leaf. In the leaf the whole configuration
is exhausted, and precisely on this account the greatest luxuri-
ance of form in the plant world is presented by the leaf. There
is nothing beyond the formation of the leaf on the axis, and
whatever the plant is unable to achieve in this is unattainable
by it. However great, therefore, the diversity we recognize in
the axis, this is produced not by itself, but by the leaf.

To form a true conception of the subject of leaf formation,
which will probably appear an intricate maze, you must allow
me to lead you by a somewhat circuitous path to a point from
which, before entering, you may obtain a general view of it.

It was a happy idea of our great poet prince, in order to
comprehend the vast diversity of plant configuration, not to
involve himself in the endless complexity of details, but to con-
template the whole subject from a greater distance, and in a
more general manner. In this way everything presented itself
to him under a different aspect, the apparently essential became
accidental, the accidental essential; in short, he perceived the
forest which before could not be seen because of the trees.

o4

BOTANICAL LETTERS.

In all the higher plants, foliage, flowers, and fruit were re-
garded as essentially different parts. It was Géthe who first
recognized in the flower and fruit the recurrence of the foliage,
so that according to this mode of viewing the subject there is
no essential difference between these three principal parts of

the plant.

When we regard the subject somewhat more definitely, it
becomes evident that it is the leaf, which in its protean capa-
bility of transformation, in the power of gradually assuming

another form, occupies first the
lower, then the upper part of
the axis, and ultimately by com-
bination at the apex, produces
the flower and fruit. The parts
of the fruit, as well as those of
the flower, are certainly not to
be regarded as anything more
than whorls of leaves—leaves
which indeed differ both in
their character and _ position
from other leaves, although in
no other way than in degree,
so that a constant progression
is recognizable throughout all
forms of leaves. This mode of
regarding the plant must be of
essential influence with refer-
ence to the knowledge of its
configuration. It is not the di-
versity of form, but the funda-
mental unity in that diversity
which is here the most promi-
nent feature, Fig. 22.

In order that this may be
perfectly intelligible, let us go
back to the origin of the leaves.

All the rudiments of leaves

originate soon after the formation of the axial point, and

BOTANICAL LETTERS. 55

foilow it continually, so to speak, step by step. As the axis
elongates, they are developed laterally one after the other,
elongating, like the stem at the apex, until perfectly formed, and
then expanding in a contrary direction from the free end
towards the ground. The leaves and axis, therefore, do not
essentially differ from each other, except in the fact that the
growth of the former is limited, while on the contrary, that of
the latter is unlimited. The whole diversity of leaf forms
depends upon the energy and the different directions with
which the cell mass is produced and distributed.

While the leaves are quite young, they are without exception
alike, their diversity is not developed until the period of their
srowth and increase in mass. The young leaves of the flower
and of the fruit have exactly the same appearance as the leaves
of the stem, consequently we are justified in entertaining the
opinion that there is no essential difference between the leaves
of the stem and those of the flowers and the fruit, or between
the respective regions of the axis. Nevertheless it cannot be
denied, that in attaining their perfect developement, differences
become gradually perceptible.

These differences, more or less distinct, frequently present
themselves from leaf to leaf, but in the most striking manner,
after considerable intervals, and more comprehensive alterations.
In this respect the plant resembles a building consisting of
smaller and larger apartments arranged above each other, in
which, although the same character prevails throughout, a con-
stant increase in elegance and decoration is perceptible in the
higher stories, while at the same time it does not the less pre-
sent, as well in the exterior form as in the interior arrangement,
such peculiarities as indicate a different application and a
sharper separation of the parts. Certain leaf structures present
likewise, even externally in the plant, the plinths and other
projecting portions of the masonry separating the successive
stories, and in the interior an equally unmistakable difference
is manifested in the form and contents of the parts correspond-
ing to the exterior.

Tt might indeed almost be said that the analogy between the

56 BOTANICAL LETTERS.

plant and a building does not become distinctly perceptible
until the formation of leaves and their mutual succession take
place, while the upper parts of the axis situated between the
leaf formations would, from their simplicity, scarcely have been
able to give rise to a structure presenting such beautiful and
connected sequence in its arrangement.

man
oe
cad |
~~

LETTER X.

LEAF FORMATIONS.

AFTER what has preceded, it will be evident that it is a matter
of the first importance to become acquainted with these stories
of the plant structure, to point out their peculiarities, and
sufficiently to consider the architectural combination between
them.

In order that this problem may become solvable, it is neces-
sary again to lay aside the idea of a primitive unity of all leaf
organs, and to consider them in accordance with their different
characters, but at the same time to unite under one point of view,
and one form of expression, such objects as are evidently related
and analogous. By thus reviewing the production of leaves
upon the stem or axis, we find that there are seven such groups,
or, as I shall call them, formations.

I speak here only of the more perfect kinds of plants, leaving
out of consideration the less perfect ones, in which the leaf
formations are less numerous. These leaf formations are :—1,
the lower stem-leaf formation ; 2, the true stem-leaf formation ;
3, the upper stem-leaf formation; 4, the calyx-leaf formation ;
5, the flower-leaf formation; 6, the stamen-leaf formation, and
7, the fruit-leaf formation.

Fig. 23 is an ideal representation of a perfect plant, with its
essential organs. The several regions of the leaved axis are
divided into seven formations, the upper ones being artificially
elongated so as to be more clearly distinguishable.

Upon the same principle that the geognost characterizes a
number of different strata as belonging to one formation, inas-
much as they contain embedded organic remains of the same
kind, which indicate a great revolution in the life of our planet,
so the botanist considers under the same denomination a series

of similar leaf forms as a connected; whole for here likewise
D3

58 BOTANICAL LETTERS,

may be recognized a great revolution in the formative tendency
of the plant-—-the completion of one of its stories.

It will perhaps not be without some interest for my readers
to follow me from story to story, from formation to forma-
tion, while I perform the office of an experienced guide, fur-
nishing answers to such questions as may suggest themselves,
directing attention to this or that particular, and generally
assisting them in the considera-
tion of this subject. Neverthe-
less I must confess to being
myself only a student in this
branch of the science, and that
I only repeat to you the words
of a master whose name you
shall learn hereafter.

The lower stem-leaf forma-
tion, which occupies the under-
most story, includes all scale
and sheath-like leaves. Fig. 238,
forma. They are characterized
in form by a broad base and
limited height ; in substance, by
a frequently fleshy cartilaginous
or leathery consistence, and a
dull yellowish or dark colour.
All these characters show that
these leaves are wholly or par-
tially excluded from the influ-
ence of light and air, and have
remained as it were at the low-
est stage of developement, and
nearest to the primitive form.
They thus especially mark the
basement story of the plant
structure; or, in other words,
that part of the axis which
frequently, though tending upwards, remains concealed in the
earth, and like the root, serves for the fastening of the plant.

BOTANICAL LETTERS. 59

This basis of the plant is frequently confounded with the root,
a circumstance solely owing to its situation and striking differ-
ence in external appearance from the other parts of the axis.
All rhizomes, subterranean buds, such as onions, potatoes, &e.,
belong to this formation, and even some parts of the stem
above ground. It not unfrequently happens, moreover, that they
are much contracted in length, so that the leaves appear crowded
and covering each other.

The second formation, that of the true stem-leaves, fig. 23,
form b, corresponds properly to the ground floor of a building.
It is generally a very extensive structure, particularly charac-
terized by the multiplicity of organs which are properly termed.
leaves. They are distinguished by a greater longitudinal ex-
tension, with less breadth of base, expansion at the upper and
contraction at the lower ends, a more membranous nature, and
a green colour. They are moreover divided both longitudinally
and laterally, thus giving rise to such a rich diversity of forms
as is scarcely anywhere else met with. The longitudinal inci-
sion gives rise to the production of the lobes, and the lateral
segments or leaflets, the lateral incision gives rise to the pro-
duction of the most varied and complicated forms of leaf. The
system of veins likewise corresponding to the exterior configu-
ration is very manifold in its character.

The leaves belonging to this formation likewise originate
from very simple forms, cotyledons, which sometimes scarcely
differ from those of the first formation ; but a considerable de-
velopement very soon takes place, and they pass gradually into
the next succeeding formation. A great part even of the more
perfect plants commence their structure with this story, the
basement being wanting; still the structure is not on this
account less durable, less pleasing to the eye, or less imposing ;
I might indeed almost say, that it is essential to its magnifi-
cence to commence immediately with this story, and to leave
the secure fixing of the groundwork to the descending part of
the axis, or, in other words, to the root

The upper stem-leaf formation, fig. 23, form c, follows next
in order, and, as its name indicates, is situated above that last
mentioned. The leaves belonging to this formation approxi-

60 BOTANICAL LETTERS.

mate in some degree both in form and character to those of the
first formation, since both the petiole and the expanded form,
as well as the green colour, disappear, more or less, but they are
distinguished from them by the narrow base and more delicate
structure, which is not much inferior to that of the following
formation. To this class belong sheaths, bracts, glumes, &c.
They present but little that 1s strikingly remarkable, in conse-
quence of their minuteness, and are sometimes even impercep-
tible ; but as regards the general structure of the plant, they are
by no means insignificant, inasmuch as they determine, and are
the means of effecting the construction of the next story, and
thus in a certain degree establish the harmony between the
lower and upper parts of the plant structure.

The most considerable difference in the general production
of leaves occurs in the calyx-leaf formation. Fig. 23, form d.

Here the leaf appears both in its form and position to be
totally altered. Although in general resembling, as to sub-
stance, the stem-leaves, it is considerably smaller ; and perhaps
even by this means renders the approximation of analogous
leaves possible, which henceforth succeed each other vertically,
at scarcely appreciable distances, and therefore reveal their
connexion more distinctly than is the case in the previous leaf
formations. With the calyx leaf commences the extreme anti-
thesis in the plant axis—the flower and the foliage—for the
fruit appears for the most part subordinate to the flower, and
exercises less influence upon the facade of the structure.

The calyx-leaves are more massive, coarser, and greener than
the upper-stem leaves; they have again a broader base, a very
slight or even no expansion, and no petiole; they are equally
destitute of any incision, and thus strikingly present a retro-
eression, an alternation such as frequently occurs in certain
members of one formation.

The following formation, that of the flower-leaves, fig. 23,
form e, presents, on the other hand, a very decisive ad-
vance.

These leaves are especially distinguished from all others by
the delicacy of their tissue, as well as by the purity and diver-
sity of their colour. The flower-leaves situated in the same

BOTANICAL LETTERS. 61

crowded manner as the calyx-leaves, form what is called the
corolla, the most admirable combination of all that constitutes
delicacy and beauty. Deprive the flower of the corolla, and it
sinks at once to mere unheeded foliage ; give to it fragrance and
harmony of colour, and it becomes an incarnation of loveliness.

The art of floriculture consists solely and alone in the en-
largement and decoration of this part of the plant.

The flower-leaves are generally longer than the calyx-leaves,
but narrower at the base ; they present for the most part a con-
siderable expansion, but no decisive developement of petiole.
In consequence of a radiated, forked, or feather-like incision,
they acquire the vast diversity of form, as well as by means of
mouldings, excrescences, duplication of surfaces, &c., which give
rise to the production of the so-called double flowers. Never-
theless the two leaf formations of the calyx and the corolla, do
not always present marked distinctions, but, on the contrary,
blend sometimes in such a manner, that the corolla resembles
a calyx, and the calyx a corolla. However, the more frequent
occurrence is the total, or almost total, subordination of one or
other formation, or the interfusion of both into one; this latter
case occurs, for instance, in a large section of plants as a
general rule, and the resulting formation alternating between
calyx and corolla, is called a perigone.

The corolla is succeeded by the stamen-leaf formation, fig. 28,
form f. The term leaf here does not appear to be a very
appropriately-selected expression, for the leaf-like character dis-
appears here entirely, and it is its function alone which con-
tinues.

The stamen-leaves are the smallest and most remarkable
leaves of the flower, with a decisive developement of petiole, and
small expansion which passes into the bag-like enlargements of
the lateral parts—anthers, It is only in a few instances that
the leaf-like character becomes more prominent, but then it is
at the cost of the production of anthers. The so-called double
flowers, in which there is a malformation of the anthers, com-
municating to them the full appearance of flower-leaves, are
sufficiently indicative of this. Every one is acquainted with
double roses, pinks, ranunculuses, etc., whose increase of flower-

62 BOTANICAL LETTERS.

leaves depends exclusively upon the transformation of stamen-
leaves into flower-leaves.

While the leaves of all other formations have a certain dura-
tion, and are not to be regarded as transient phenomena any
more than the axis, the contrary is generally the case with
regard to the stamen-leaves. Their existence is very precarious,
and dependent upon the more or less rapid developement of the
anthers. But this circumstance indicates that the aim of the
plant, in this direction at least, must be achieved in the deve-
lopement of the stamen-leaves, and especially of the anthers.

Finally there is another formation, that of the fruit-leaves or
carpels, which forms the uppermost story of the plant structure,
fig. 23 a. Here likewise the leaf-like character is less obvious,
and principally because the individual leaves of this formation
are always more crowded together than those of any other, and
generally even grown together, forming a cavity in which the
axis terminates in numerous radiations.

Further the fruit-leaves are thicker, larger, and greener than
the other leaves ; they rise from a smaller base, but expand im-
mediately, while the upper part contracts in a petiolar manner,
forming the style. These leaves have a longer duration than
any others, and still continue to be developed when the others
are for the most part dead. It is these leaves, together with
their enclosures, that in the first instance form what are called
fruit-buds, from which afterwards the fruit is developed.

Whatever else appears upon the axis after the fruit-leaves,
belongs to the ‘last offshoots, or rather breaking up of the axis;
these are the seed-buds upon which neither definite axes nor
parts of leaves can be distinguished, and which consequently
scarce belong any longer to the morphological individuality of
the plant.

Thus with the construction of the fruit-leaf story, the axis,
and consequently the developement of the plant, has attained
its end. In what this end consists, and how attained, shall be
considered in a subsequent letter.

( 63 )

LETTER XI.
ARCHITECTURAL ARRANGEMENT OF THE PLANT PHYLLOTAXY.

Tue study of the structure of the plant as a whole, and in
accordance with the larger and more obvious sections, or, to
keep to our architectural comparison, the various stories, neces-
sarily leads to an examination of the more minute details of the
processes by which the whole structure is raised, as well as of
the relations of measure which must necessarily exist. The
consideration of this point comes so essentially within the
domain of architecture, that we cannot do otherwise than adapt
our mode of contemplation to the laws which obtain in that
art. It is only in this way that it becomes evident that in the
plant world, as in other parts of nature, definite relations, and
an invariable proportionality exist, upon which all phenomena,
and especially those of developement and configuration, are de-
pendent. When, as we have already learnt, the plant builds its
body by its own means, according to a self-projected plan, it
may well be expected that it will do so in accordance as well
with the laws of stability, as with those of architecture.

Although in this respect we have not yet penetrated to the
full depth of the prevailing order and regularity, it has not
escaped observation, that the square and plumb-line have their
application even in the construction of plants.

I will now lead you to a consideration of these geometrical
relations, commencing with the most simple of them.

Whatever plant we examine, we are at the first glance struck
with the truth that the symmetry here prevailing in the arrange-
ment of the several parts, differs from the symmetry of most
architectural structures in the circumstance that it is not made
dependent upon a few predominating directions, but is carried
out with an equal developement in all directions. It is thus
that the plant structure is distinguished in a very striking

64 BOTANICAL LETTERS.

manner, and independently of a few exceptions, from the struc-
ture of the animal body, in which there are always corresponding
members right and left, before and behind. The plant has no
right and left, no front and back, and although this is some-
times apparent in the distichous arrangement of their supple-
mentary parts, and even in the axis, still it is always very
limited, and derived from the predominating mode of arrange-
ment. An uniform disposition of parts on all sides is called
concentric ; and it is such a concentric arrangement that almost
universally prevails in the plant structure, and is especially
evident in the axis and its appendages the leaves. In this
respect, therefore, we cannot compare the plant either to a
palace or any other cubical parallelopiped or pyramidal struc-
ture, but only to one which is round and similar upon all sides,
to a temple or tower. We have already become acquainted
with the various stories succeeding each other at more consider-
able distances. We have now to consider these stories more
closely in their details and respective peculiarities.

Even a superficial glance convinces us that it is not merely
one or other story, as perhaps the calyx or corolla, which presents
an especial regularity in the arrangement of the leaves, but that
sometimes this regularity likewise prevails in the region of the
lower, true, and upper stem-leaf formations. A smaller extent
and a somewhat more crowded situation of these leaves frequently
manifest a symmetry the same as that which generally prevails
in the flower. We cannot therefore avoid ascribing to the lower
regions of the plant the same conformity to law with regard to
the disposition of parts as prevails in the other regions of its
stem.

While the plant was regarded as the result of all manner of
accidental influences, or at least as an inexplicable conjunction
of the most diverse formative tendencies, it may readily be
conceived that there was no probability of recognizing any defi-
nite laws in the elements of the leaves which contain the most
effective expression of constructive differences, and in their suc-
cession.

The penetration of Karl Schimper first dispelled this mystery,
drew from before the eye the veil that had hindered our observ-

BOTANICAL LETTERS. 65

ation, and then the arrangement of the leaves upon the stalk,
as well as in the flower, presented itself as a simple law for the
formal expression of which but little more was requisite.

In the first instance the truth became perceptible, that most
leaf formations do not consist of a succession of leaves situated
at irregular distances from each other, but that a definite pro-
portionality prevails, which though less marked in the vertical
distances, is nevertheless constant and unalterable in the hori-
zontal distances between the leaves; further, that this propor-
tion, though not always the same, is still capable of alteration
only after a definite series of leaf groups; and finally, what is most
important and confirms the unity of the law, that the alterations
of measure likewise bear a certain proportionality among them-
selves. These laws have with endless labour been deduced from
an immense number of facts presented by the most diverse
plant forms, and at the present day we doubt no longer thatthe
same law presents itself in the arrangement of even the smallest
leaves, and in the most different formations. Let us now enter
upon a more extended consideration of this law.

The most distinct and striking advance that the plant makes
in the erection of its tower-like masonry, is undoubtedly the
shooting out of a leaf. The leaf is the stage upon which it
advances in its progress towards the attainment of its aim, and
whence it continues pushing out stage after stage. We perceive
that these stages are not all alike, but that after several immedi-
ately successive stages, there is a point of cessation—an interval
—and the fact that in this way successive series of stages are
formed one above the other, is less distinctly perceptible, and
much laborious observation is requisite before it can be recog-
nized as an universal law. When the series of stages are sepa-
rated by knots, as in the stalks of grasses, and many other
plants, the law is obvious, but such is not always the case, and
these intervals are frequently much concealed, and appear almost
like a continuous succession of stages. But it is at the same
time extremely remarkable that these intervals recur sometimes
even after one stage, though more frequently after 2, 3, 5, 8,
18, 21, sometimes, indeed, not till after 34, 55, 89, 144, 233, and
377 stages. The more numerous the stages in any interval, the

66 BOTANICAL LETTERS.

lower or more compressed they are, generally speaking, but at
the same time broader, so that it takes only one or two stages
of the interval to extend round the whole circumference of the
axis, while in all other cases 2, 3, 5, 8, 18, &c., revolutions are
necessary, a circumstance which communicates to the breadth
of the stages a very definite architectural proportion, which may
be expressed most simply by 4, 4, 2, 3, 3, 1%, 3%, &c. These
intervals have been characterized in technical language by the
term leaf-series, or leaf-cycles; and by means of horizontal pro-
jections, it has been made very clearly perceptible that the ad-
vance from leaf to leaf takes place in every plant, and every part
of a plant, without exception, in a spiral line. When, moreover,
the leaves of numerous leaf-cycles are situated at a small vertical
distance, a spiral arrangement is recognizable in the exterior
appearance, but it is not of this fact that we are now speaking.
While these are characterized as the only true succession of
stages in the arrangement of the leaves by the name of funda-
mental spirals, the others may appropriately be termed secon-
dary spirals.

Fig. 24 represents a plant of the Echinopsis multiplex, Zucc.,
of the natural size. The thorns are removed from the bud

Fig. 24 a,

supports, so that these, as well as the ribs upon whose edges
they are situated, may be better seen. The position of the bud

BOTANICAL LETTERS. 67

supports, or what is the same thing here, the suppressed leaves,
is according to the ;%, order; that is to say, the bud supports
succeeding each other in an ascending direction are so dis-
posed, that the fourteenth is situated exactly over the first, the
fifteenth exactly over the second, the sixteenth over the third,
and so onwards. When, as in the accompanying projection,
fig. 24 5, the outermost numbers 1, 2, 3, 4, &c. are joined by a

willy,
Zw

ANS

Bie
719

Ss Wy

Svs F
“iT

line, a spiral is thus obtained, which is termed the fundamental
spiral. But thisis not the line, which at once strikes the atten-
tion on looking at this plant. The lines formed by connecting
on the one hand the numbers 4, 9, 1, 6, 11, 3, 8, 18, 5, 10, 2,
etc., and on the other by the numbers 6, 1, 9, 4, 12, 7, 2, ete.,
are far more obvious, and are called the secondary spirals. The
former is the less inclined in its ascent, the latter the more in-
clined of the two.

When the construction advances according to any one of
these successions of stages which may be most simply expressed
by the above series of fractions, it does not always remain
confined to that particular order. In every leaf-formation, con-
sisting of one or more such intervals or leaf-cycles, there may
be a change from one proportion to another. Several successive
leaf-cycles with a position of 3 may pass into others of 3%; and
+4 as well as into less complicated ones, for instance, $ and 3

68 BOTANICAL LETTERS.

There can be no doubt that this passage from one order of
succession to another is determined not alone by the specific
peculiarity of the vegetative agency ; but frequently also by its
degree of energy, to which, likewise, must be ascribed the
greater or less vertical distances of the leaves, and the inter-
foliar spaces thus produced upon the stem, with their generally
but not specially definite proportionality.

It is evident from these laws as well as from their more
casual modifications, that a high degree of luxuriance must
prevail in the architecture of the plant; and we cannot, there-
fore, wonder at finding that plants with leaves, even of a similar
or identical form, present the greatest diversity in the exterior
aspect. In this respect, indeed, the plant resembles a Proteus,
changing from one form to another without our perceiving how
it assumes or divests itself of its magic vest.

While this change is less obvious in the passage from interval
to interval, it becomes more prominent in the passage from
one leaf-formation to another, and thus a more marked dis-
tinction is produced than would otherwise be the case from the
form and character of the leaves. In short, the stories of the
plant are thus separated externally, so that the architectural
arrangement of the plant is altered above each cornice without
the style itself being affected. This is least striking in the lower
stories, and much more so in the upper ones. After a simple
order of arrangement in the leaves of the lower and true stem-
formation, there is frequently a very complicated arrangement
of upper stem-leaves, as is the case, for instance, in the com-
posite Dipsacee, Proteacee, Piperacee, Aroide, etc.

The greatest change in the appearance of the plant is always
produced by the passage from the foliaceous part of the stem
to the flower; the complicated arrangements of parts are here
reduced again to the most simple plan, and thus the calyx,
corolla, and stamen-leaf formation, as well as that of the fruit
leaves, are characterised by the simplicity of the order in which
their elements are disposed. Fig. 25 a represents a longi-
tudinal section through the flower of saxifrage, and fig. 25 6
the corresponding ground plan.—/ is the uppermost stem-leaf’;
ce the five calyx-leaves ; p the flower-leaves ; st the 2 x 5 stamen-

BOTANICAL LETTERS. 69

leaves, all in 2 order; lastly, the two fruit-leaves cph (Car-
pophylla) disposed in } order.
Fig. 25a. Fig. 250.
st cph ce
oe se

n I $3 | 8 x
Kay
\

C4
a 3

eats rey!

But here there is still another peculiarity which is seldom
met with in the lower-leaf formation—I allude to the so-
called verticillate arrangement. It is certainly true that whorls
do actually occur in the true foliar region; and, indeed, whorls
consisting of two, three, four, and five leaves. The simple
opposite situation of the leaves, their opposite and rectangular
position, together give rise to whorls, consisting of two and
four leaves; but in all instances this can only result from the
reduction of the vertical distances to a minimum, so that the
spiral line, instead of ascending, runs almost or quite in the
same plane.

This compression of the spiral line, in which the leaves suc-
ceed each other, is to be regarded asa general rule from the
calyx-leaf formation, upwards ; consequently, all the succeeding
leaf-formations appear like closely contiguous rings of leaves,
and the whole thus acquires an entirely peculiar aspect. Be-

sides this, the number of individual leaf-cycles is very small,
~ seldom exceeding two or three, so that the upper stories of the
plant thus acquire an appearance totally different from that of
the lower stories. It is only the all-pervading law of leaf-
sequence which shows the connexion between the upper and
lower parts, and enables us to perceive in the former only a
further perfecting and ennoblement of the lower structure.

There is, however, still one circumstance to which I must
direct your attention, a circumstance by which the archi-
tectural aspect of the flower acquires an especial charm,

70 BOTANICAL LETTERS,

which by no means depends so much upon the multiplicity of
forms in the leaf-organ as upon their arrangement. In the
lower parts of the plant-axis the individual leaf-cycles follow
each other without intermission, and frequently in great
number. After each revolution of the spiral, the next cycle
commences exactly over the commencement of the former one,
and so onwards. The natural consequence of this is, that the
homologous members of each separate cycle are situated exactly
above each other. There must necessarily appear to be as
many vertical series as there are elements in one cycle, thus,
2, 3,5, 8,18, etc. These series certainly appear more distinctly,
in some instances than in others, in a particularly marked
manner in the Echinocactus plants, in which the perpendicular
ribs of the stem are produced by the interfusion of the super-
posed leaf.

The case is different in the flower. Even when only two
similarly membered leaf-cycles follow each other as well as
when dissimilarly membered cycles are associated, there is
never an uninterrupted progression. It is only in this way
that notwithstanding the crowded position of the leaf-cycles,
the leaf-elements do not cover each other. The measure of
progression in the succeeding leaf-cycles is increased exactly
so much that the elements of it come to be situated between
those of the previous cycle; the consequence of which is, an
alteration of the leaves which, as may readily be conceived, is
not without its influence in the agreeable impression which the
flower always produces in us. Thus, then, there presents itself
in the flower, together with the greatest simplicity of elements,
the most beautiful harmony in their arrangement, so much so,
that the architectural aspect of the flower becomes really a
model of perfection in this respect; and, as the history of con-
structive art teaches us, it has always exercised a determining
influence upon all the architectural works of man.

This simplicity, however, does not appear to be universally
prevalent. In some instances more complicated relations of
position present themselves even in the flowers, especially such
as are composed of a great number of elementary leaves. Ex-
amples of this fact are furnished by the cactus plants, the

BOTANICAL LETTERS. 71

nymphe, the Calycanths, ete. Nevertheless, the latter are
especially well adapted to render the unity of the flower
structure recognizable. Fig. 26
represents a flower branch of
Calycanthus floridus. The en-
larged vertical section Fig. 27 a,
with the aid of the ground plan,
fig. 27 b, will enable us to gain
some insight into the somewhat
complicated structure of this
flower; f mdicates the origin
of the true stem leaves which
have been removed; p the co-
loured leaves of the floral en-
velope or perianth; st, the sta-
men leaves; stab, the abortive
staminal organs. Besides these, m represents the pith substance
of the flower-stem, and g the seed-buds, gemule, situated upon
its superior expansion. The diagram, fig. 27 b, will serve to give
a more accurate idea of the relations of position in the flower,

Fig. 27 a, Fig. 27 5.

where, after the two opposite leaves ff there follow from 1 to
28, the leaves of the floral envelope at first reduced in size,

72 BOTANICAL LETTERS.

then larger, and then again becoming smaller, after these, from
29 to 41, the stamen leaves (st), and lastly, from 42 to 55, the
abortive staminal organs in the order pointed out. While in
the first six leaves there is a perceptible tendency towards
lower arrangements of the leaves, all the others stand in definite
positions. This retrogression occurs in almost every flower in
other ways.

There are, indeed, very numerous deviations from this
general regularity in the arrangement of the leaves which has
with good reason been called leaf order or phyllotaxy; still
these deviations do not by any means affect the validity of the
law, but rather soften its iron rigour; so that the plant thus
gains infinitely in expression of liberty. Among these, for
instance, may be named the displacement of the leaves on one
side by the unequal thickening of the stalk sides, the unequal
growth of the leaf base, and a torsion of the axis itself—cir-
cumstances which result from unequal nutrition, unequal in-
fluence of external agents, etc.

LETTER XII.

PROPAGATION OF THE PLANT.

In glancing over the history of botany, it is without difficulty
perceivable, that on no subject within the province of this
science, have so many different theories been held as on the
propagation of the plant. The obscurity of this process, on
the one hand, as well as the influence which it exercises upon
the whole range of developement and configuration on the
other, have at all times led to its being regarded as the most
mysterious, and, likewise, the most important function of plant
life, and sufficiently explain how, as the starting-point of all
botanical knowledge, it should so repeatedly have been a subject
for discussion, and how easy it was to form erroneous views
with regard to it.

Even at the present time science must not flatter herself
with the belief that the veil has been removed from before this
sanctuary of plant life. However, it has at least been possible
to catch a glimpse of the principal points of the external phe-
nomena, to distinguish between the various phases in which this
process presents itself throughout the whole plant world, and
to recognise what is essential in it, and what is more or less
casual.

We have already in treating of the growth of the plant
entered upon the subject of its propagation. We then found
that every increase of mass is the result of reproduction of one
cell from another; but the difference between that propagation
which consists in an increase of mass and propagation in the
more restricted signification of the term, consisting in the for-
mation and separation of germs of new individual life, remained
hidden from us.

We will now attempt to ascertain in what respect these two
processes differ, and likewise describe the various modes in

E

74 BOTANICAL LETTERS.

which the true propagation is effected in the plant world. For
this purpose, it will be advisable, as in all other cases, to direct
our attention to the more simple forms.

My readers will remember that I have frequently spoken of
plants consisting of only a single cell. As might naturally be
supposed, the propagation of these plants is as simple as their
life. One or more cells formed in them separate spontaneously
from the mother-cell which has thus propagated itself. When
the mother-cell is round and tolerably uniform in structure on
all sides, every part of the individual bears an equal share in the
propagation, and the daughter-cells, even at the time of their
separation, perfectly resemble the mother-cell.

But when the mother-cell has passed through a certain pro-
gressive developement, when it has become larger, when it has
experienced opposite changes in configuration, then the indivi-
dual or vegetative life, and the propagation, become more and
more independent of each other. The mother-cell then forms
reproduction cells only after a certain definite time, and at one
particular part ; and, further, these reproductions do not in any
sort resemble the mother-organism in the first instance. As
instances of the former and more simple mode of propagation,
may be mentioned several chroeococcacee, and of the latter mode,
the species ascidium, botrydium, but still more the species vau-
cheria, caulerpa, etc.

It cannot be denied that some plants, almost as simple in
structure, present a somewhat higher mode of propagation, but
then the propagation cells which are separated, do not originate
immediately from the mother-cell, but are produced by means
of one or more intervening generations of cells, which in contra-
distinction to the true propagative generations are called vege-
tative generations. These vegetative generations produce a
multipligity of cells, which adhere together in a more or less
intimate manner, until the last or transition generation suc-
ceeds, which separates and commences the new cycle.. The
cells of the transition generation are, for the most part, of a
different form from the cells of the vegetative generations, and
may very easily be distinguished from them. An example of
this may be found in a small algaceous plant, the Scenedesmus

BOTANICAL LETTERS. 75

acutus, Meyer ; a representation of which, in the transition gene-
ration, is given in Fig. 28.

But even these mediate vege- Fig 28.
tative generations do not remain
alike throughout, but present
differencesat their beginning and
end, so that the transition gene-
ration appears as a third member
in the mode of propagation.

Henceforth, however, even the reproductive cells assume a
dissimilar configuration ; and thus the first impetus is given
towards a dualism which extends to the most perfect plants, and.
certainly is not without a vast influence upon the whole con-
figuration of the plant, and especially upon those parts in
which, after long series of mediate vegetative generations, the
antithesis is developed to the fullest extent.

While in the strictly unicellular plants, and those of the same
kind which are associated together in groups, each cell appears
in the character of a reproductive cell, the possibility of propa-
gation in the’ cell-multiples is transferred solely to the cells
at the apex, while the permanent cells take no part in the
performance of this function. Fig. 29 represents the Gloeocapsa
opaca, Nageli, a very minute
algaceous plant, in the various
stages of propagation from a to
e, in which it forms two, three,
four, and more individuals asso-
ciated together ina group. But
in this antithesis by which each
cell-multiple first acquires its
existence, the heterogeneity of
the reproductive cells of all cell-
multiples is already prefigured,
and we cannot wonder that the
whole propagation of the plant
is subject to this dualism. There
are then two kinds of reproductive cells, which, even in the most
simple unicellular plants, present themselves as conditional to

E 2

76 BOTANICAL LETTERS.

the propagation, and throughout the most diverse forms of cell-
multiples determine in a similar manner the propagation. If
then this dualism in the configuration of the reproductive cells,
except in the most simple forms of plants, is once recognized,
the most important question which suggests itself is indis-
putably that which refers to the mutual relation of these diverse
reproductive cells—is their mutual reaction necessary for the
propagation P—and in what manner does this reaction take
place ?

As far as observation has hitherto extended, a threefold mode
of propagation has been recognised. The different reproductive
cells do not react upon each other immediately. Both forms
may be capable of reproduction, although, in most instances,
only one of them is so, and when separated from the mother-
plant propagates the individual. The second mode of propaga-
tion requires a mutual reaction by immediate contact. While
in this act, the one reproductive cell is exhausted, the capability
of individual developement is first awakened in the other. The
third mode of propagation lastly consists in a complete union of
both kinds of reproductive cells, from which is produced a third,
the germ of anew series. It is remarkable that, in this process,
one of the two reproductive cells frequently acquires an active

Fig. 30. change of position by means of
peculiar motive organs, or that,
at least, an approximation is
effected as a result of growth.
The first indication of this fact
is presented even in the strictly
unicellular plants, whose branch,
or rather leaf-forming protuber-
ances, the seat of propagation,
affect the formation of repro-
ductive cells by their approxima-
tion and mutual union, as is the
case in Vaucheria sessilis, Lyngb.
Fig. 30 represents, according to
Nageli, small fragments of this
plant ; @ is the germ branch, and 4 the reproductive organ before

BOTANICAL LETTERS. ae

their conjunction; c the germ cell in the germ branch after
conjunction; d the empty reproductive organ likewise after
conjunction.

It is here quite indifferent whether this dualism is or is not
regarded as a difference of sex ; so much, however, is certain,
that it is a condition prevailing throughout all instances of pro-
pagation, and which although it does not always present itself
obviously in the phenomenon, does not the less appear to be
the ultimate spring of action. The fact, that, in many instances,
especially among the less highly-organised plants, the one form
of reproductive cells presents both in figure and in power of
motion a great resemblance with the spermatozoa, which de-
termine the propagation of animals, at least admits of the con-
jecture that there is no essential difference between the sexual
propagation of animals and plants. This manifest sexual dif-
ference extends from the fuci, or perhaps, more properly, the
characez onwards throughout the lichens (?), liverworts, mosses,
ferns, and equiseta, or Fig. 31.
horsetails, and becomes oe
less prominent only in
plants of a higher order,
but is not therefore as
such less undoubted.

Fig. 31 represents a
flowerof Jungermania com-
planata. (Partly after
W. Hofmeister). Three
archegones abc, enclosed
in a perianth f, two of
them are not yet impreg-
nated while the third 0 is
just impregnated. The
germ vesicle is still sim-
ple. Beside it is an
antheridium d supported
by a leaf e.

It is already open at
the apex, admittmg of

78 BOTANICAL LETTERS.

the escape of the spermatozoida, some of which are free, while
others are still enclosed in their mother-cells. A part of them
have already attached themselves to the aperture of the ripe
archegonium or sporocarp.

Permit me now to describe, somewhat more minutely, the
mutual reaction of the two kinds of reproductive cells in the
flowering plants. It is these which are almost always before
our eyes, and which attract our attention, most of all, precisely
in this phase of activity during their flowering.

In the greater number of plants the capability of forming
‘reproductive cells appears to be gradually developed through an
indefinite series of cells. The same dualism which is manifested
between the permanent and reproductive cells at the origin of
these series, and which gives rise to the antithesis of axis and
leaves, presents itself ultimately on the apex through an in-
definite gradational succession as reproductive cells, and, as the
aim of the formative agency, terminates the progress of the
plant structure. Two organs of the most extreme antithesis
become the supporters of the reproductive cells, the stamen on
the one, the peripheric side, the seed-bud at apex of the axis
upon the other or central side. The seat of the formation of
reproductive cells in the stamens is situated in the centre of the
stunted leaves. é

Here from one cell there are soon developed series of cells,
in whose interior, and after a transitory cell formation, the re-
productive cells, called pollen-cells, are produced. When they
are perfectly developed, the enveloping cell-membrane — the
anther—is rent, and the reproductive cells set free. It is these
cells which form the pollen.

While this happens in the last stages of the metamorphosis
of the leaf upon the stem, a very similar process is taking place
in the terminal parts of the axis. The axis exhausted by the
continuous formation of leaves, puts forth above the last spiral
of fruit-leaves only one more small continuation, which either
remains simple or divides, and then attaches itself to the fruit-
leaves, and becomes so closely united with them that they can no
longer be distinguished from it. From this continuation of the
axis which generally projects into a cavity formed by the vari-

BOTANICAL LETTERS. 79

ously-convoluted fruit-leaves, and which is termed the placenta,
originate series of cells, which likewise produce in their interior
reproductive cells. The whole apparatus employed in this
process is called the seed-bud, and consists of a nucleus of
cells over which one or more sheath-shaped envelopes are gra-
dually extended, so that, ultimately, there remains only a very
small channel of access to the nucleus: this is called the micro-
pyle. The series of cells from the apex of which this apparatus
is developed, and which soon becomes a support of greater or
less length, called the funiculus, finally assumes a very different
position in relation to
it, according as the
developement of the
former consists In an
equable or one-sided
production of ele-
mentary parts. In
short, there is in the
centre of the appa-
ratus a cell, perhaps
the terminal cell,
which increases con-
siderably in size, and
produces, in its spa-
cious interior, seve-
ral small unconnected
cells, which float in
the liquid contents.
These are and can be
nothing else than re-
productive cells.

The above-named
organs and their ar-
rangement will be
rendered more dis-
tinct by the drawing,
fig. 82, which repre-
sents a magnified sec-

Fig, 32.

80 BOTANICAL LETTERS.

tion of the flower of buckwheat (/agopyrum emarginatum). p
is the floral envelope, s¢ the stamen with the anthers expanded.
Some pollen-cells have attached themselves to the stigma of the
style where they have already become elongated, and penetrated
through the stigma canal into the embryonal sac se.

The accompanying more highly-magnified section of the
upper part of the seed-bud, shows the entire course of the
pollen utricle ¢p, its penetration through the micropyle of the
external coat (integumentum externum) ie—the inner -coat
(integumentum internum) ii—the nucleus into the embryonal
sac se, where it comes into direct contact with the embryonal
or germ cells.

These latter reproductive cells which have originated from
the axis, do not appear to develope themselves spontaneously
any further, and would be dwarfed or entirely broken up if
they did not receive from without some impulse to further
developement. The liberated pollen-cells likewise, although
perfectly formed, share the same fate. It happens, however, that
the detached pollen-cells and the cells of the embryonal sac come
into contact, and then while the former shrivel up and die, the
latter acquire the capability of further developement, which ends
in the separation from the mother-plant of the entire apparatus
above described, and which is now a seed, and places the young
plant in such a position that it can henceforth carry on its
construction independently. This construction naturally goes
on entirely in accordance with the type of the mother-plant.

The reproductive cells of the seed-bud are, generally speak-
ing, enclosed in it, and this is itself enclosed in the cavity of
the blended fruit-leaves, that isin the germen; but this does
not prevent the detached reproductive cells of the stamens
from coming into immediate contact with them.

This happens in the following manner. Even the situation
of the germen is of such a kind, that from among the thousands
of pollen-cells which are set free after the bursting of the
anthers, some few are certain to come in contact with it, and
particularly with its apex. This apex, which is formed by the
blending of the fruit-leaves, and which, according to their form,
is sometimes shorter, sometimes more elongated, forming what

BOTANICAL LETTERS. 81

is then called the style, is expanded into a somewhat broader
part of the stigma.

These pollen-cells, which the stigma receives, are prepared
for a further developement, growth, or germination, by means
of a continually-secreted sap, and, in such a manner, that, in
fact, their exterior membrane is left behind, and a cell utricle
developed from them, which may either remain simple or put
forth branching protuberances. But the thus germinating
pollen-cells would soon come to an end, notwithstanding the
nutrition of the stigma secretion, if they were notin a position,
by means of their penetrating end, to make a way through the
loosened cells of the stigma, and between the series of slightly-
coherent cells of the style. |

This they always succeed in effecting after some time, and
several or at least one pollen cell penetrates even into the cavity
of the fruit. There are then but few obstacles to overcome.
The apex of the growing pollen utricle easily reaches even as
far as the seed-bud, and there finds an unimpeded passage
through the opening of the seed-capsule to the seed itself.
Lastly, however, the cells of the nucleus must be penetrated ;
which is effected the more readily, since they are still very
delicate and pliable, and as meanwhile, also, the embryonal
sac has, by its expansion and the displacement of the upper
cells, in some degree approximated towards the pollen utricle.

In the embryonal sac itself likewise the germ-cells have
drawn near to the surface, and even touch the interior side of
its membranous wall. It is, therefore, easy for the pollen
utricles, which have penetrated thus far to come into direct
contact with the germ-cells, from which they are separated only
by the membrane of the embryonal sac; and, indeed, the pollen
utricle spreads itself out upon the surface of the embryonal
sac, so as expressly to effect this contact wherever it may be
possible. The consequence is, that while the pollen-sac gra-
dually dies from the interior outwards, a further cell-formation
takes place in one of the germ-cells, probably that nearest to
the pollen utricle, and terminates at last in the formation of the
basis of a new plant. Whether, in many instances, during this
process the embryonal sac is not entirely absorbed at the

ES

82 BOTANICAL LETTERS.

point where the two reproductive cells come in contact, so
that they are then brought into direct contact, is, although not
improbable, not yet sufficiently determined by observation.
So much, however, is certain, that in all the more highly-or-
ganized plants, there is nothing beyond a mere contact action
of the two kinds of cells, while in the lower spheres of the
plant-world, a blending of the two is no rare phenomenon.

Thus then the more highly-developed plants manifest, even
in their propagation, a triumph over their material nature; and
while, in other cases, an intimate blending of both elements is
necessary for the production of a new germ in them, a simple
contact and a mere dynamic transfusion is sufficient to effect
the purpose. It is, in fact, a kiss with which the flower-bearing
plant celebrates the most beautiful act of its renewal.

Pe
CO
co

J

LETTER XIII.

FORMATION OF SHOOTS.

Wrru the equalization of the difference of sex, the dualism
which gave a direction to all the functions and activity of the
plant is reconciled, the end of individual life attained. It is
no longer possible for it to achieve anything beyond this; con-
sequently the flower in which this equalization takes place
terminates the formation of the plant completely and finally.

Yet the plant does not always, indeed scarcely ever does,
succeed in attaining this end in the above-mentioned sequence
of its developements. The normal structure of the plant is
in so far only an ideal as that it is seldom realized in nature.
Instead of this ideal, regular indeed and beautiful in and for
itself, but by its nature extremely limited and ephemeral; a
constructive tendency exists in the plant, which is capable of
_ rising above all the limitation of time and space, which bids
defiance to all eventualities, and in magnitude and might
exceeds all the works which human intellect and perseverance
could ever produce. '

But it is only by the power which the plant possesses of
checking itself in its ideal direction and developement, of
opposing obstacles to itself, and being thereby excited to re-
newed efforts, that it, as it were, overpasses its circumscribing
limits, and completes only in a series of spontaneous develope-
ments, that which it would otherwise have reached with only
one effort. The plant, as a series of connected developements,
becomes therefore a vegetative individual in which one phase
succeeds another.

Let us now pass from the consideration of the plant to the
consideration of this vegetative individual. The bluebell shall
here serve us as a guide. i

It would be a great mistake to assume, as would appear on

84 BOTANICAL LETTERS.

a cursory observation, that there is in this plant a simple suc-
cession of leaf-organs, originating from one and the same axis,
up to the seed-bud. This is not the case. The axis which is
developed from the seed-kernel can never achieve the formation

Fig. 33.

of the flower; on the
contrary, its produc-
tive activity entirely
terminates with the
formation of the un-
der-leaf and stem-
leaf series—the latter
being completed in a
few leaf-cycles. With-
out the formation of
a new axis, which
proceeds from the
preceding one, and
completes what the
former leaves incom-
plete, the attainment
of the aim of this
plant would be im-
possible. Now the
second axis, which
begins not with the
under-leaf formations
nor with the stem-
leaf formations, but
immediately unfolds
the upper-leaf region,
bears on its summit
the flower, and brings
to an end the work
begun in the first
axis. This plant may
therefore be legiti-
mately termed bi-

axial. We meet such biaxial plants almost everywhere in the

BOTANICAL LETTERS. 85

vegetable kingdom, but especially among flower-bearing plants ;
nor is it always with a succession of two axes that the plant
terminates, but a series of three, four, and even five, axes is not
unfrequent.

The annexed drawing of a triaxial plant, fig. 33, will serve to -
illustrate what has already been said. In it may be recognized
certain individual elements of existing plants, which are however
combined in an ideal manner, so as to reduce the formation of
shoots to the most simple form. 1. First shoot with lower
stem-leaf formation alone. 11. Second shoot with lower and
true stem-leaf formation. 111. Third shoot with upper stem-
leaf formation, terminated by the flower.

That this succession of axes, like all the formations of the
plant, is a result of generative agency, might be assumed a
priori; but itis likewise confirmed by anatomical investigation,
in so far as they appear to indicate that every formation of
branches proceeds from one cell of the axis, becomes, by its
succeeding generations, a complex of cells which seeks by inde-
pendent developement, as it were, to separate or emancipate
itself from the developement of the mother-axis. This inde-
pendent developement, bringing all the elements of formation
into one direction, it is, which enables such complexes of cells
also to lay claim to the character of independent axes. It
cannot be denied that, in this process, as well as in the gene-
rative functions of the reproductive cells, a propagation of the
plant is achieved. It proceeds, however, and cannot do other-
wise than proceed, from a singleness of activity, and conse-
quently is subordinate to that dualistic generation. The
individuality of the formative tendency, as well as the fre-
quently-occurring division from the mother-plant, distinguishes
it from mere progressive growth.

The phenomena presented by the formation of new axes are
very diverse, and can here only be considered in their leading
characteristics. Each new axis appears originally contracted—
the leaf-elements separated from each other by the smallest
intervals—the whole being, as it were, concentrated. In this
condition they are called buds. After the widening of the
‘intervals, and developement of the supplementary organs, they

86 BOTANICAL LETTERS.

are called shoots or runners. The bud thus indicates only
the youthful condition of the runner; but may, moreover, be
the bearer of the most diverse leaf formations. There are,
therefore, runners with lower stem-leaf, runners with true
stem-leaf, runners with upper stem-leaf, and, finally, runners
with flower-leaf formations. Indeed, even with the flower-
bearing runners, one or other formation of the flower, for
instance that of the stamen-leaves, or that of the fruit-leaves,
may be wanting.

This does not, however, prevent the union of several leaf-
formations in one and the same runner, so that it may, to a
certain extent, become more perfect than another.

Any part of the plant axis, even the descending part, can
produce buds. Their local succession presents no such fixed
law as that of the leaves :—a fact which shows that their forma-
tion consists in something altogether different from the forma-
tion of leaves. Still, it very frequently happens that the point
of origin of the leaf likewise indicates the point whence the
formation of the runner takes its origin. Buds in the axils of
leaves are among the most common phenomena of the plant-
world.

The region of sucker-formation, that is, the section of leaf-
formation, from which the runner is developed, is of great im-
portance and influence with regard to the appearance of the
plant. It is, as regards this point, a general law that all runners
originate only from the lower regions of the axis, never from
the upper. It is, however, very different whether a runner is
thrown out from the lower stem-leaf, the true stem-leaf, or the
upper stem-leaf region. The circumstance that the apparatus
for the female reproductive cell in the higher plants is called
runner and seed-runner arises only from the exterior resem-
blance, and must therefore be passed over for the present as
altogether apart from the nature of the runner.

In the same way that the region of runner developement
exercises a determinative influence upon the vegetative indivi-
dual, so in an equal degree does the succession of runners, or
the order in which the more or less developed runners follow
each other, determine the presentation of the individual in its.

BOTANICAL LETTERS. . 87

perfect integrity. In this succession of shoots, the dependence
of one runner upon another is distinctly recognizable, and the
complete developement of the individual likewise depends upon
the progressive succession of the several runners. A. phenomenon
which is also recognized in the animal world as a succession of
dissimilar generations, tending ultimately to the production of
an individual capable of reproduction.

Although in the animal world this change of reproduction is
met with only in the lower classes of animals, it is found in the
succession of runners in the plant-world as one of the most
general phenomena to which here inversely perhaps only the
lower plants form an exception.

As quite apart from this succession of shoots, which un-
doubtedly appears as an essential feature, since the sexual
propagation of the individual is dependent upon it, must be
distinguished the formation of multiplying shoots which stamp
the individual with the form it actually presents. Thus it
happens by no means exceptionally, but almost as a general rule,
that the formation of a shoot induces the formation of a greater
or less number of co-ordinate shoots equal to it in every
respect. Consequently the functions which would otherwise
devolve upon one individual, are by this adaptation transferred
to a number of similar individuals. If therefore one or other
process should prove abortive in any one of these individuals,
it is taken up again by the succeeding one, and the maintenance
of the plant species is thus by far less perilled than would be
the case if the succession of shoots was simple.

This becomes more distinctly prominent in the shoots of the
last order, whose function is the sexual propagation of the indi-
vidual, and if at the same time the developement of the flowers
is not simultaneous, the influence of exterior conditions, how-
ever antagonistic, will not endanger the existence of the indivi-
dual, still less that of the species. Indeed the reinvigoration
of many plants depends ultimately upon this repetition of
shoots, without which perhaps they would never achieve their
purpose. The formation of the asparagus plants, the vine, the
lime, etc., depends upon such shoots.

88 BOTANICAL LETTERS.

Nature has therefore taken every precaution that the ulti-
mate purpose of the plant may always be attained in the most
perfect manner, and even the apparently-superfluous shoots we
have just spoken of, are not without their utility in its general
economy. But this repetition of similar axes likewise exercises
the most striking influence upon the configuration of the plant,
which thus presents itself as a family of ultimately-related and
mutually-supporting individuals. It is only thus that the plant
becomes a plant stock, upon which thousands of individuals of
different ages live in mutual dependence tending towards the
same end; and when the transitory flower, with its mnumerable
blossoms, unfolds to us a power of charms, such as is found no-
where else in the plant-world, the tree stem with its thousand
branches and twigs, in each of which dwells a dryad, excites in
our feelings the presentment of a majesty and harmony similar
to that which presents itself indistinctly to the mind on the
contemplation of world systems.

Lastly, the actual multiplication of the vegetative being by
the shoot must not be overlooked. Many shoots, for instance
the propagating shoots, possess the peculiarity of separating
while in the young state, as buds from the plant stock, and
thus propagating the biologic individual; others again do this
only after their perfect developement. Man has not been behind-
hand to take advantage of what nature has here suggested with
regard to the plant, and a great number of useful plants are
multiplied by means of the tubers, bulbs, and buds separated
from the mother-plants.

Among the plants whose buds and groups of buds separate
spontaneously are a number of bulbous plants, as for instance,
the fire lly (Likum bulbiferum); and the strawberry potato,
and many others are instances of those in which the connexion
of the buds must be gradually separated. Fig. 34 represents a
young plant of Solanum utile, with six pairs of leaves. From
the axils of the first pair of leaves—the green leaves, two lower
stem-leaf shoots have originated, as well as from the following
pair of leaves, and these have already struck into the ground.
Although not enlarged into tubers, as in the potato, they still

BOTANICAL LETTERS, 89

serve for the propagation of the plant, imasmuch as their con-
nexion with the mother-plant soon terminates.

There can be no doubt that
this formation of propagating
shoots, which have likewise been
called buds, is expressed even in
the lower kinds of plants. The
spores of mosses and liverworts,
the germ-cells of lichens and
aleais, are evidently nothing
more than the result of attempts
at propagation without the anti-
thesis of true reproductive cells.
And thus we find, even back to
the extreme limit of the plant-
world, a provision which secures
the maintenance of the plant
species, even amid the most un-
favourable circumstances, and
although the individuals them-
selves may be very short lived.

With the skill of a master, Alexander Braun has succeeded
in reducing, under one point of view, the whole of this difficult
and intricate subject of shoots-formation, and has, without
doubt, thus introduced more clearness into our conception of
the plant structure and formation, than the most minute ana-
tomical researches have hitherto been able to do. It is to him,
therefore, that we are indebted for the most extensive and im-
portant part of our knowledge of plant architecture.

( 90)

LETTER XIV.
UNITY OF RACE AND OF THE HIGHER CATEGORIES.

Ir is an incontestable fact that the plant reaches its goal only
by a series of renovations. It hovers between the acquisitions
and the effort to acquire, between annihilation and re-birth,
till it succeeds in again uniting the phases of its productive
activity, proceeding one from the other in ever-widening diver-
gence. The fofmation of the cells, the erection in leaf-cycles
and leaf-formations, and finally, production and succession of
sucker, are nothing but wider and narrower circles in which
the death and resurrection of the plant appear. Whilst in the
animal organism the same metamorphosis proceeds, noiseless
and concealed throughout all the organs, in the organism of
plants every member becomes stiff and permanent, and every
new part overlies the old, darts triumphantly beyond the goal
of previous attainment. The whole is therefore not only a
unity, it is also a concrete of unities; so that the entire gra-
dation, the entire transformation and renewal, can be contem-
plated at one glance.

In a similar sequence does the plant proceed in its propa-
gation. Unaltered permanence is no longer possible, and
even if the individual ceases, it reconstitutes itself in the same
manner in its progeny. Hence arises a series of individuals,
locally separate indeed, yet ever connected into a unity, into
a whole, by the course of generation. However life may
fluctuate in the series of these individualizations, all its
members in reality cohere, though the thread breaks which
holds them together in their origin. It is therefore the sum-
total of these apparently distinct individuals which we deno-

BOTANICAL LETTERS, ik

minate species; and it cannot be questioned that this idea
comprehends not merely an aggregate of unities, but a series,
in which every member possesses a certain relation to the
other members. This relation, however, is none other than
the relation in which one cell stands to others, one leaf-cycle
and one leaf-formation to others, and finally one sucker to
others.

From this it follows that the species is in its nature the
same as a series of cells, a succession of leaf-cycles and leaf-
formations, a succession of suckers, 7. e., an organic whole:
Consequently the species must present all those peculiarities
which universally pertain to organic beings. Among these we
reckon above all others—firstly, the production from a germ ;
secondly, the developement into a perfect whole; and thirdly,
the giving-up of individuality after the achievement of their
destiny.

In the life of the species, therefore, all these impulses, which
in individuals frequently follow in quick succession, must again
appear, as equally essential, at longer intervals. In one word,
the species must have a beginning, a succession of further stages
of developement, and an end.

Unfortunately the short space of time which single ob-
servers can devote to the phenomena of this course of life in
the species is far too little for discovering, experimentally,
these stages, even in only one or other species. The cessation
of a species only, or its commencement, could in any degree be
matter of actual experience, as being limited to a shorter space
of time; yet as, even in this, the observations of many gene-
rations must be consumed, while but the smaller number of
plants have, on account of their influence on man, occupied his
attention, and it may easily be conceived that we are altogether
in uncertainty on this point also; only from the animal world
start up here and there significant facts, which admit of our
suspecting analogous phenomena in the plant-world.

But even admitting that the species of plants, like the species
of animals, have their period of existence, that is, an allotted
term of life, it is possible to explain their extinction, as the

92 BOTANICAL LETTERS.

consequence of a constant decrease of productiveness ; but the
source from which they spring, their advent in nature, cannot
be explained, although we may meet with them suddenly
among the already-existing species. The question of the
primordial condition of the species, of its relation to the sub-
sequent species and to nature in general, is not yet solved.

If we conceive the species, as has been customary hitherto,
as an aggregate of similarly-formed (similarly-natured) indi-
viduals—in which not a single quality permanently alters (im-
mutable characteristics), as the experience of our observation
shows—we are inevitably impelled, in the explanation of this
question, to the conclusion that the origin of a species could
not possibly have taken place from any of its precursors.
There is nothing for it, therefore, but to assume that forces
beyond the pale of the organic world co-operate in the produc-
tion of the species—an assumption which, if not in actual con-
tradiction to the universal operation of inorganic forces, yet
sounds at least like a miracle.

Far otherwise does the matter present itself, if, following
the track of analogy, we regard the species as a sum-total of
elements capable of production, and therefore of alteration ; in
which indeed no metamorphoses are to be perceived, except in
lengthened periods, but in which, within the compass of many
centuries (wherein it may be certainly computed that the
generations of existence of every organic being can be com-
prised), the germination, growth, blossoming, fructification,
and ripening, of the species follow none the less.

It would, however, be erroneous to assume that the diversity
of species consisted only in this process of metamorphosis ; but
who can deny that new combinations of the elements arise out
of this permutation of vegetation ever reducible to a certain
law—combinations which emancipate themselves from the
preceding characteristics of the species, and appear as new
species P I must not be asked “ When?’’—nor how such
offshoots from the already-existing species arose. On these
points, nothing but the history of the developement of the
whole plant-world can possibly afford a solution. But this

BOTANICAL LETTERS, 93

much is clear—that this change of generation relating to
species can belong neither to the youth nor to the old age
of the species, but to the period of its greatest strength, its
highest developement, as well in extent as in energy of vege-
tation.

Nevertheless, phenomena strike us, even in our fragmentary
term of observation, which are significant in supporting the
above views, and which, even if they do not, as was supposed,
invalidate the theory of stability of species, still clearly reveal
the great process of metamorphosis of one species into another,
and consequently the comprehension of these within a higher
unity. These phenomena are such as belong partly to normal
life, partly to morbid and uncontrolled vegetation. The devia-

tion of particular characteristics from the normal condition in
the succession of generations is one of the commonest phe-
nomena. According to the greater or less permanence of
these deviations, we call the one a variation (variatio), the
other formation of race. To what an extent these often
proceed our garden plants show, in which we are scarcely able,
often quite unable, to recognize the progenitors. That these
deviations arise not altogether from an alteration of outward
influences, such as from a change of light, air, moisture, soil, or
so on, is demonstrated by the fact, that two similar kinds of
plants frequently become altogether different under these cir-
cumstances.

Whilst the vegetation of both is equally strongly affected, it
is arrested in one, whilst it produces no effects on the other.
The endeavour, therefore, to trace the diversities of species to
the effect of outward influences, such as the nature of the soils,
assuredly misses the true cause. Equally insufficient, though
not without significance, proves the effect which the repro-
ductive activity of one kind of plants exerts over the other,
whereby in the higher, as well as in the lower growing plants,
even in mosses and ferns, arise hybrids, entirely new species as
it were arising from the combination of two pre-existing species.
Their duration, although lasting some generations, is, never-
theless, always short, so that such bastards are never in a con-

94 BOTANICAL LETTERS.

dition to dispute and attain their citizenship among the other
species of plants born their equals.

Finally there remain in the balance the phenomena of ab-
normal vegetation, as not unimportant influences in the constant
presence of a transformative plant-growth. Who is not familiar
with the signs of transformed vegetation which meet him in
every meadow, in every garden P Not only do stem and leaves
expand to an excessive degree, a different texture, other consti-
tuents, etc., appear ; even into the once so regular order of the
leaves diversity enters, the cycles alter, the succession of forma-
tions is disturbed, and transformations of the strangest kind
present themselves. To whom are the so-called double flowers,
perfoliate blossoms, incised fruits, and so on, unknown? It is,
in all cases, the impatient vegetation which here concealed,
there openly, produces these phenomena. Fig. 35 represents
a perfoliate lily (Lilium candidum) in
which all the parts of the flower are
converted into a leafed branch. The
flower-stalk of the plant thus acquires
a perfectly-different appearance.

And how could this spirit of change,
this representative of the unconstant,
of the transitory, fail to transgress the
narrow bounds of peculiarity of species ?
It were scarcely credible. If then we
must dismiss as incorrect all previous
observations on the changes of types of
species, we yet cannot avoid recognis-
ing, in the genius which marks the
species, seeks to preserve its unity

, through all times and localities, and
does in truth preserve it, the strength which not only converts
water into wine, but is able, with similar magic power, to
transmute also one species into another. But if all distinctions
of species sink into nothing before this magic wand, how can it
be doubted, that in the higher categories, the same generic
unity reigns, that they likewise are but the result of propaga-

BOTANICAL LETTERS, G5

tion in distant zones? We should much err if we did not
ascribe a real existence to these unities included in one general
view by the mind. Ifthe universal unity of the plant-body is
rendered possible only by the production of all its single ele-
ments one out of the other, then is this unity in the whole
creation of the plant-world, assuredly in like manner possible
only by the originating of one member from another, one
species from another, one genus, one family from another.
And as in the plant-body, not even a single cell can be pro-
duced from any extrinsic source, equally impossible is it for a
species, a genus, an order, etc., of plants, to be produced from
any extrinsic source, and not to have proceeded from a previous
one.

Thus rises up to our astonished gaze not only the wonderfully-
proportioned structure of the visible plant-form, but this, itself,
extends into regions to which our mortal eye is no longer able
to penetrate. Not only the individual plant, but the whole
plant-kingdom is an edifice—an edifice for which the thousands
and thousands of parts, as leaves and flowers and single cells,
serve as building-stones.

(6)

LETTER XV.
THE PLANT-WORLD IN ITS LOCAL DISTRIBUTION.

(Geography of Plants.)

THE reader will excuse me, if, without reference to the im-
measurable size which the plant-garden of the world presents,
I yet have the courage to escort him round it, and to direct his
glance, if not to all sides, still at least to the most important
points. Everything great appears to us first in its true magni-
tude, when we have formed a correct idea of it ; and I may affirm,
that the green structure of the globe exemplifies the axiom no
less than anything else. We may assume, ad priori, that the
garden which we tread is not a maze in which no track, how-
ever slight, appears to direct the steps. Had not men like
Alexander von Humboldt, Wallenberg, Schouw, Von Martius,
Robert Brown, Wallich, Reinwardt, Blume, Parker, Webb,
Desfontaines, Hooker jun., Griesbach, and others, already
chequered it in so many directions, I would certainly not
venture to be your guide, or dare hope to conduct you to the
desired goal. .

Through whatever gate we enter the park, whatever path we
adopt and follow, the same principle will everywhere im-
press us, that a manifold variety of forms, an intermingling of
the most diverse forms even upon the smallest surfaces, is
the most prominent feature in the character of the vegetable
world. It might almost be supposed, that a conformity to law
in the order of the various members of this part of nature would
not exist at all—would even be utterly impossible on account
of the indefiniteness of developement on the one hand, and the
mutability of extrinsic influences on the other. Yet it is not
so; for there appears, in all respects, a more or less intimate
interweaving of the most diverse forms, so that the glance is
attracted immediately here and there to different plants socially

BOTANICAL LETTERS, rt!

coexistent, attracted together, if not, indeed, in accordance
with their nature, yet, by their mode of life and purposes ; and
here is seen a meadow, there a wood, there a heath and prairie,
there a moor, Indeed in these common localities of similar
tendencies, it frequently happens, that certain closely-allied
species predominate, and in their intimate connexion more or
less exclude everything of a foreign nature. <A pine-forest, a
coast-line of mangle trees (Rhizophora mangle), a heath-country
of Erica, express a far closer community than the flower-carpet
of the Alps, the tree-dotted meadow, or the impenetrable pri-
meval forest. These conditions are not by any means at first
a consequence of the labour of man, whose hand has doubtless
powerfully influenced the state of vegetation—they are much
rather to be considered primitive, or to have been at least settled
long before all influence of that kind was exercised. Although
this original character may be variously influenced by the
cultivation of the soil, in such a manner, that by culture, the
association of particular species is favoured, still, upon the
whole, the alteration is slight; and, as soon as the protection
of culture ceases, it becomes but too soon evident that the
original condition is restored. Man, as the assumed lord of
creation, has, for the use of his habitation, but too often to his
shame experienced that he is in a condition to direct the ex-
isting order of single members of the vegetable world only in a
very limited sense ; and indeed, that, where he sought to wield
exorbitant power, he is confined within narrow limits by a
might to him unknown. It very soon appears that a par-
ticular territory is assigned to every product of the earth,
which it cannot change without perilling its very existence.
See the Alp-rose brought down from the forest-stream into the
valley, how it longs vainly for the pure air; consider the seed
transported from the woods of the West Indies, from the Gulf
Stream to the coast of Norway, how, before it has so much as
germinated, it succumbs already to the inclemency of the
climate. Or is the plant indigenous to the majestic granite
headland, which the storm transports in safety to the neigh-
bouring chalk-rock, better there? Or the grass sprouting in

loose sand which the floods have imbedded in soft clay? In
FE

98 BOTANICAL LETTERS,

vain do even the mightiest powers of nature appear to fight
against the existence of vegetation, without being able to alter
anything whatever that lives; and we are hence compelled to
acknowledge that there are immutable laws by which one place
of location and propagation has been assigned to this plant,
another to that.

The law of dependence on heat has beyond question made
itself sensible as most influential. All plants bow to the iron
sceptre of this influence, whether their cireumambient element be
air or water. Even if a certain degree of temperature does not
actually associate cognate plants, it nevertheless effects the
association of plants, which, in their nature and capacities, are
more than any others similar in their relation to this agent.”
In this manner.the difference of vegetation presents itself in its
most comprehensive features, according to the distribution of
temperature over the earth; and we distinguish most palpably
a vegetation of the polar regions, of the temperate zone, of the
warmer latitudes, and of the tropics, and yet minor gradations
of difference which le between those earth-belts. As, however,
the temperature diminishes all over the earth, according to
elevation, as well as according to latitude, so do the zones of
vegetation, succeeding in horizontal direction, correspond in like
manner to such as present themselves at parts of the earth’s
surface which are in greater or less degree elevated above
the everywhere uniform expanse of water; and we have in
our mountains from below upwards, the same gradation and
diversity of vegetation which the succession of latitudinal
zones presents, only here in quicker succession, just as the
diminution of temperature graduates here in a more rapid
scale than there. We cannot then but subscribe to this posi-
tion, that the vegetation of the polar regions and -of the
loftiest mountain-peaks of the earth, which reach the impreg-
nable boundary of snow and ice, agree in their physiognomy in
like manner as the plants of warmer climates and of the tropics
throughout the whole earth. How much does the vegetation
of Terra di Fuego, of State Island, of the Maldives, of Kergue-
len’s Island, and of the South Pole, the vegetation of the
North Zone, and the vegetation of our central European Alps,

BOTANICAL LETTERS. 99

the Andes, the Himalayas, etc., present a common complexion,
which extends not only to the general habitus, but even to
similarity of order, genus, and species !

As an example, we may cite the universally-spread species of
the Ranunculus, Geranium, Epilobium, Saxifraga, Poa, Festuca,
Carex, etc., whose representatives are met with on the icebound
inhospitable shores of Victoria Land, and of Spitzbergen, as
well as on the desert peaks of the Alps, Andes, Himalayas, ete.
The same observation applies to the other zones.

Next to climate, the nature of the soil, or, to speak more
generally, the support of the plant, has much to do with the
distribution of the vegetable kingdom. If climate marks out
certain regions for the various plants, their support is the arbiter
which has arranged them in certain districts, and even assigned.
them fixed stations. The need for specific means of nourish-
ment, notwithstanding that the materials of nourishment are
distributed everywhere, causes in plants similar in nature a
tendency to congregate in masses more or less closely, according
as the nutritious matter they require is offered them within a
greater or less extent of surface. Hence arise the two great
classes of land and water plants; the second class being sub-
divided into fresh and sea water plants, according to the differ-
ence of their native element; as the land plants are, according
to the physical and chemical nature of the soil, into marsh,
land, and rock plants, into turf-plants, salt-plants, and plants
peculiar to chalk, gypsum, clay-slate, granite, etc. We perceive
in the immense variety of the physical and chemical character
of the earth, the conditions of an equally immense variety of the
districts occupied by peculiar plants. How influential prove
in this matter even the identity and diversity of vegetation,
produced by the greater or less diffusion and change of certain
geologic formations, every land, every mountain, shows.

The quantity of water present in the atmosphere, and the
moisture of the air and earth dependent upon it, present, like
the temperature, certain normal conditions in their distribution
over the surface of the globe; and if, with regard to the quan-
tity of water falling, the zones of periodical deposition are less
regular, still vegetation does not appear on that account to be

F 2

100 BOTANICAL LETTERS.

less influenced. Not only the presence, the strength, and the
luxuriance of vegetation depend on it, but also the periodicity
of its waking and sleeping. As warmth and cold in and
beyond the temperate zone produce a stagnation and resurrec-
tion of vegetation, so do the moisture and the dryness of the
air and the earth, in the warmer latitudes, cause a similar alter-
nation. But, where warmth and moisture are felt equally in a
high degree, a luxuriance of vegetable beauty also follows,

Fig. 36.

which expresses itself as well in multiplicity of form, as in the
large developement of the individuals. Whilst, therefore, we
pass lightly over the mountain vegetation and the meadow lands
of the polar regions, we must hew a path through the inextri-
cabie thickness of the primeval forests of the tropics, as of

BOTANICAL LETTERS, 101

Brazil, the East and West Indies, the Sound Islands, ete., and
even the damp Chonos Islands, and we are not secure against
being held fast and environed by creeping plants, winding, and
parasitic plants, towering one above the other.

Fig. 36 represents a primeval tropical forest in Brazil (Pedra
da Onga) according to the drawings of Benjamin Mary. (v.
Martius, Flora Brasiliensis, fase. x., tab. phys. xxxiv.) This
landscape comprises a group of rocks covered with the most
luxurious vegetation, through the midst of which flows a small
brook. The trees consist of palms and various other tropical
species, upon the living and dead trunks of which flourish
whole swarms of larger and smaller herbaceous plants, among
which the eye is especially attracted by the climbing large-leaved
Pothos and Caladium, the beautiful leaf-bunches of the Bromelias,
and the Tillandsia usneoides hanging from the branches. Here
masses of thirsty plants crowd towards the water, while there
others appear to soar up in the air, twining themselves from
tree to tree, making the jungle still more impenetrable, and
rendering it difficult even for the burning rays of the sun to
reach the ground.

But, although all previous outward influences have appeared
as conditions of similar configuration in the plant-world of
ereater or smaller districts, and always produced, according to
their more or less regular distribution over the earth’s surface,
a vegetation sometimes monotonous, sometimes varied even in
smaller spaces, still there has not by any means been such a
grouping of plants as would have brought the kinds cognate in
their morphologic character into closer contact. The low
carpet-like vegetation of the north is not exclusively marked by
moss in one part, by grass forms in another, in a third place by
umbelliferous plants, nor are the forests of the tropics formed
sometimes by fig species, at others by cisalpine and leguminous
plants. An intimate intermingling even of the plants related
in locality, or in their nature, is everywhere to be remarked,
and constitutes so prominent a feature in the physiognomy of
the various plant formations, that it very rarely occurs that
nearly-related forms either possess themselves exclusively of
the soil, or even predominate largely. On this condition of the

102 BOTANICAL LETTERS.

predominance of certain plants linked together by the laws of
relationship, rest finally the characteristic features which this
or that district, this or that tract of land, possesses, and which,
although they do not always prominently strike the eye, may
yet be detected by observation, and justify us in dividing the
whole surface of the earth into regions according to these
peculiarities of vegetation, in the same manner that is required
in the distinction of the various races of the great human
family. In the same way that we have a region of the Chinese,
the Hindoos, the Athiopians, ete., so are there the regions of
Camellias, Celastrinias, Sertanimias, Stapelias, Mesembrianthema,
Cinchonas, Cacti, ete., although in fact the mass of plants does
not always appear determinative any more than, in the former
case, the nature of prominent races of men. Who can deny
that a dense cloud hovers over the primary cause of the diver-
sity of the races of men ? and who can question that the influ-
ences which effected this and not another classification of plant-
groups over the earth, are quite as obscure to us? At all
events, the key to the understanding of the one secret, as of
the other, must be sought in earlier and departed conditions ;
yet who would not conjecture that here, as everywhere in
nature, the simplest condition formed the basis P

If the plant species in its original appearance is a progeny
of primeeval vegetation, as I have endeavoured to render pro-
bable, and if this assumption leads at length to even fewer and
simpler first types, an equally great difference of all the deriva-
tive types must be recognized as necessary from the ever-in-
creasing districts of diffusion in which the original forms of the
first ages appeared. As therefore the original forms occupied
the whole earth, the derivative types produced in particular
localities are generally distributed over the whole extent of
terra firma and the surface of the earth, It was not possible,
however, that of the cognate forms, some only should be found
at any certain spot, and others in other parts of the globe, but
- the utmost possible diffusion of them must have been the con-
sequence, independently of the fact that external difference of
climate, soil, etc., manifoldly aided and increased the original
distinction.

BOTANICAL LETTERS, 103

If, then, we are no longer in a position to discover the ori-
ginally-created group of plant-forms, this arises truly not from
the deficiency of them, but from the manifold intertwining and
intermixing of their subsequently-changing boundaries, as the
circles produced by bodies falling into smooth water can only,
with the greatest difficulty, be marked according to their
number and the spot at which they originated.

But this complex intermixture of vegetation is of great
advantage to the spiritual as well as the corporeal needs of man.
Whilst, on the one hand, the perception of unity in multiplicity
is thereby awakened and sharpened, the same fact has rendered
it possible for the human race to spread over the whole earth
and to find the conditions of its existence everywhere. The
labyrinth which, to the ignorant, the plant-garden of the world
appears to be, becomes, therefore, to those gifted with insight,
an expression of the most perfect harmony, a veritable Eden,
for the enjoyment of which he lacks only innocence.

( 104 )

LETTER XVI.

CHRONOLOGICAL ASPECT OF THE PLANT.—HISTORY OF THE
PLANT-WORLD.

We have already occasionally referred, on entering upon the
casual conditions of the phenomena of the world of plants, to
the consideration of its earlier stages. The world of plants,
as a many-membered whole, and the grouping of the members
over the surface of the earth, are matters which, without a
conception of their essential process of developement, can never
be known in their true significance. This, and much besides,
compel us to note, not merely the most recent aspect of the
plant-creation of these ages, but also the old age of the time
before. But we must not promise ourselves any great gain
from treating the dual aspect of this Janus-head, were we in a
position to learn in its backward-gazing conntenance aught
even of the state immediately preceding our epoch.
Independently of the fact, that through the want of all his-
toric traditions, of all monuments of the earlier times, no
detailed image would be possible, this would, moreover, teach
us little, for all histuric epochs embrace periods far too brief,
since changes of such a kind as occur in the life of species
cannot possible appear within such narrow limits of time.
Only periods which extend far beyond the historic treatment
of human existence, can afford us ight on such matters, But
inasmuch as we require such an extended epoch, for a pro-
ductive consideration, it is not enough to look back to that
period which immediately preceded the existence of the human
race ; indeed, in order to find remoter data for these conditions
of vegetation, recourse to still earlier epochs is requisite; and
thus, if our view be complete and consistent, we arrive at the
contemplation of a whole series of consecutive periods up to a
time when the first pulsations of life became at all perceptible.

BOTANICAL LETTERS, 105

Only in this succession of the conditions of plant-life lies the
history of their developement, as well as the “ because” to
the “ why,” which we should not be able to utter by any other
process.

If it is to be assumed as a positively-ascertained truth that not
a drop of water sinks lost into earth, not an atom of the all
disappears, that absolutely nothing passes away without a
trace, then there les in this truth the greatest solace for
that science which proposes to itself the contemplation of
events, the changes of things, and their fate in time. For
every condition is the consequence of a previous condition, and
this ever points further to a series of earlier conditions ; so
that we need only a single key to penetrate from the last
secret to the first. This key, however, is not yet found to the
slightest things, and still less to the world of plants. Instead,
therefore, of investigating the earlier stages by means of the
existing stages, so as to show these as necessarily preceding
phases, we have nothing for it but to inquire whether no
monuments exist which precede the succeeding periods of
creation, and which are not yet quite destroyed by the tooth
of Time.

On proposing to ourselves these antiquarian researches, our
labour will not be altogether in vain. By careful investigation
of the various earth-strata and rock-formations, we soon come
to medals with well-preserved inscriptions, soon to utensils
and implements of many a sort, and even to the foundations
of buildings which present to us a not indistinct picture of
once-existing conditions. The medals relating to the history
of the world of plants are the impressions of leaves and other
portions of plants; the utensils are fossils; the foundations of
the building the layers of coal, lignites, and the like. All this,
however, speaks as clearly of a time of an earlier existence of
the plant-world as the phases of its developement are manifested
in their various forms and the succession of them.

The search for metals so useful to man has induced him,
from the most ancient times, to open the secret depths of the
earth; the tendency to improved well-being has further and
further increased the need of them, and has induced man to

EO

106 BOTANICAL LETTERS.

penetrate ever deeper and in all directions. It was inevitable,
if the work was to be of any avail, that even greater advances
should be made in the knowledge of the structure of the earth’s
foundations, or, as we should rather say, of the earth’s surface.
The united experience hence resulting produced what is called
mining, geognosy, geology, and so on.

All antiquity has, nevertheless, produced nothing towards
the history of organic being, nor, consequently, of plants
secreted in the superficial earth-strata. In its eyes, gold
superseded all else ; it overlooked the hidden gold-lumps which
were by those obvious grains. For the first time, some cen-
turies ago, when an inspired and imaginative mysticism sought
to raise the veil of Isis, petrified shell-fish, bones of dragons
and monsters, received attention; and even so was the eye
delighted with the lovely impressions of the foliage of unknown
plants, and prepared from petrified wood, objects of art of
numerous descriptions.

Yet was paleontology, the forerunner of a history of organic
life, scarcely a lisping infant. The greatest progress occurred
first through the necessary opening of the layers of fossil fuel.
Who would have imagined, two hundred years ago, that in
coal, wholly and entirely related to the mineral kingdom, lay
buried nothing less than the remains of an immense vegetation
of the antique world? Who would have conjectured that, in
the impressions of leaves, bark, fruits, seeds, &c., occurring on
the limits of these layers in the barren stone, as well as in its
here-and-there preserved structure, we should succeed in read-
ing the history of its appearance? Who, in fine, would then
have entertained the ardent hope of finding there a standard

-of time, and reckoning the millions of years which elapsed in
the construction of the plant-world of the present time? Though
the geologists have given the historical inquirer a more complete
idea of the succession of rock-strata and of stratification, and
made the mode of their origin intelligible, still the former have,
on the other hand, not neglected, step for step, to collect the
organic remains from the lowest to the uppermost strata, which,
although mostly decayed, are still recognisable, to compare
them together, to arrange them, and by means of these sig-

BOTANICAL LETTERS. 107

nificant vestiges of earlier periods of creation, to form an idea
of all the various kinds of animated beings and their forms.

Hence arose very soon the undoubted principle that the
world of plants, like the world of animals, had, from the earliest
ages till now, suffered a mighty revolution. All doubts con-
cerning the imperfection of our inquiries were solved; and if,
at present, all the materials do not lie before us from which the
extant creations of the world of plants developed their luxuriance,
yet are the essential members of that vegetation, whose origin
is lost in uncalculable ages, assuredly hidden from us no
longer.

From the collection of all contributions hitherto furnished,
from Sternberg and Lindley to Adolphe Brongniart and
Géppert, it results, as a certain fact, in the history of vege-
tation, that, with the seven great geological periods (including
the present one), the world of plants also, which is divided
into seven chief stages, has gradually developed itself step by
step.

The first or transition period is marked by the predominant
character of the most simple forms of plants, so is the coal-
period by the preponderance of the so-called vascular crypto-
gamia, the trias-period by the Monocotyledons, the jura-period
by plants which bare seeds, and so on, till the present seventh
period, which is named after the predominant influence of the
dialypetalous plants. These investigations show, moreover,
very clearly, that even the first of the periods of creation began
with a number of plant-forms which might serve as a standard
for all the rest, that is those in which the germs are to be found
of all the subsequent developements; in a word, with plants
which may in fact be regarded as true primitive forms. Thus
the foundation of the whole plant-world is not by any means a
one-sided lineal progression, but a radiation broadening out on
all sides, and in their primitive shapes is contained the whole
of the existing vegetation, as though in a chalk-drawig made
from meagre outlines.

The plate forming the frontispiece represents a calamite forest
of the coal period. This strange vegetation belongs to the
early age of our planet, in which, although the four principal

108 BOTANICAL LETTERS,

groups of plant-configuration (Thallophyta, Acrobrya, Amphibrya,
and Acramphibrya) were already developed, only the first section
of the latter, the Gymnosperme, existed.

We do not find here any higher plants than the equisetaceous
trees, a few herbaceous and tree ferns, and the singular Stigmaria
ficoides, peculiar to marshy places.

A torrent of water overthrows the lofty, hollow, and brittle
stems of the calamites, and, like the winds in our turf-bogs,
increases the mass of plant substance, which is afterwards
gradually converted into coal. A dreary desert, inhabited by
no higher animal organisms, it appears as if appropriately
selected as a scene of the wildest storms, continuing for cen-
turies.

Could it happen otherwise in this constant spontaneous de-
velopement of vegetation, which gradually became perceptible in
the epochs of creation, than that with the advent of new forms
the earlier should one and all come to this end and extinction ?
Thus proceeds the ideal of the plant, as at first from cell to cell,
from leaf to leaf, from sprout to sprout, from individual to
individual, here also in continuous destruction and new-birth of
genera in unbroken undulation of renewal, one epoch of creation
determining the other, each new, each strange, each proceeding
from the earlier elements modified, but ever ennobled.

How utterly different does the plant-world of the present
period appear to us now that the world of life which, through
thousands of inadequate attempts, ripened to its present per-
fection and general diffusion, reflects in the multiplicity of its
species its whole history! Is it possible that the ultimate sig-
nificance of the hitherto-unexplained impression which a fern, a
pine-wood, a cycada, or a grass-field, produces upon us can re-
main concealed ? Is it not the long-closed grave of the coal-
beds that here opens itself, the mysterious obscurity of the
jurassic period, the trias period, that speaks to us from them ?
As all ruins of fallen grandeur bear an air of lamentation, so the
last remains of those departing forms cannot do otherwise than
speak to us in tones of melancholy.

This language, mixed with the joyous expression of forms
in the state of highest developement, is the most marvellous

BOTANICAL LETTERS, 109

contrast which penetrates through the eye to our ear, and es-
pecially, perhaps, alone explains the pleasure or dislike which,
in sensitive men, is excited by one or other plant; but for the
thinking man it is, and always will be, a duty to penetrate to
the innermost mysteries of their existence and significance.

At the commencement we compared the plant to a piece of
architecture. The elementary construction from cells, their
combination and arrangement into masses, the structure of its
body in the form of superposed stories, all admit of manifold
comparison with the construction of buildings. There is how-
ever yet another comparison which is not less appropriate than
the previous ones, It is the comparison of the various styles of
architecture, and their respective ornamentation with the his-
toric character of vegetation.

In the same manner as the former was developed from the
most simple forms, and gradually passed into the Indian,
Egyptian, Malay, and into the antique style of the classic
nations of the Old World, from out of which, again, the By-
zantine, the Moresque, the Gothic, and all modern styles of
architecture grew up, so we find that the architectural style
of the plant-world has been abundantly altered. And in the
same way as it appears strange to us, when we recognise beside
the half-buried buildings of the Toltek the slender light roof
of the Roman; beside the ruined temples of gods the closed .
cottage ; neaaes pyramids and the graves of kings the mean
straw hut; the impression is no other than that which we
experience on seeing in the shade of dying pine-woods the
laughing-rose; in the oak thicket, grey with age, the smiling little
violet ; and the truth that life must be regarded only as a tran-
sient form of existence forces itself more clearly and promi-
nently upon the perception.

CPO)

LETTER XVII.

NATURE OF THE PLANT.—ITS POSITION IN THE SCHEME
OF CREATION.

THERE still remains one, and indeed the most essential, point
to be considered, in order to complete the picture which we
have endeavoured to give of the plant. This is its position in
the general series of organized beings, of which it is itself
merely a member.

Not only in the organism of the plant as an individual being,
but in the life of the species, as well as the entire plant-world,
does the most intimate interconnexion of all individualities
manifest itself. It appears that this bond of relationship ex-
tends still further, touching and penetrating a class of beings
which reaches far beyond the still self-enveloped plant.

We may in conclusion be allowed to consider somewhat more
closely how intimate is this relation between plants and animals,
how intimate the interpenetration in a material, as well as an
ideal, direction between the two.

The precise boundaries of both kingdoms of life have long
been an important problem to all those who are accustomed to
regard all things according to fixed and definite normals. The
vulgar notions of plant and animal, which are sufficiently defi-
nite in reference to the middle parts of their respective king-
doms, appear to be no longer adequate when the boundaries are
approached. A manifold interlacing of characteristics appeared
to become more distinctly recognizable in proportion to the
ardour with which it was attempted to discover differences both
in structure, chemical constitutions, and the vital functions.
At one time it was believed that a distinction between plant
and animal had been discovered in the elementary organs, and
their mode of reproduction, in the structure and arrangement

BOTANICAL LETTERS. Lit

of the organs. At another time, the relations of material
elements appeared to promise certain boundaries; and, even if
that were not the case, these indications were believed to lie in
the vital phenomena, especially in the phenomena of motion,
which would remove all doubt as to whether the subject be-
longed to vegetable or to animal organism. It may indeed be
said that anatomists, chemists, and physiologists, have, with
united energies, put plants and animals to the rack, in order to
extort some answer to this question. But what was the result ?
While the greatest ingenuity was exercised in the endeavour to
maintain those distinctions which had once been laid down, the
investigations made both by the chemist and by the physiolo-
gist, led to continual encroachments by one or other of them
into the opposite department of science ; so that at the present
time the solution of the problem has not advanced one step.
On the contrary, it has become still more obvious that every
attempt of the kind is a crusade into a region of mystery, where
both parties become embroiled, not only with each other, but
among themselves. I will not therefore desire of my readers
to take any part in this dreary and fruitless controversy, but
rather from some secure retreat to watch the combat, and per-
haps even thence to derive some conception of the means by
which these conflicting views might be reconciled.

In putting an end to any dispute, or in solving any problem,
much depends upon the disputed poimt being stated with as
much simplicity and clearness as possible, upon the avoidance
of any complication likely to divert the attention, and upon
putting the subject in the most naked form possible. To apply
this principle to our own case, we shall do wisely not to con-
front the plant as a perfectly-developed being with the perfectly-
developed animal, much less to seek for points of resemblance
in the still more complicated vital cycles of each. We shall
undoubtedly approach more closely to our aim by prosecuting
our investigation of the elementary parts, and acquiring a more
intimate knowledge of them.

In the previous letters upon the plant-cells, it has been shown
that they are the elements of which all parts of the plant con-
sist, which compose every organ, and govern the whole impulse

112 BOTANICAL LETTERS.

of vital economy in the plant. The cell, as we have already
shown in several places, is the factotum, without which the
existence of the plant would be impossible. But at the same
time the cell is still more than this, if we exclude from consider-
ation the individual. It is in the propagation of plants, the
bond which unites one individual to another, and likewise
renders the life of the species possible; but it is undoubtedly,
at the bottom, the Proteus which determines beyond the species,
the higher organization of the plant-world into families, orders,
etc. In short, the cell is not only the starting point of the
individual life of the plant, but at the same time the starting
point of the life of species and all higher unities ; it is indeed
likewise the starting point of the whole plant-world.

It is therefore in the cell, and nowhere else, that the concen-
tration of the whole being of the plant must be sought.

Hitherto we have only cast a passing glance at the nature
and construction of the cell. It will now well repay our trouble
to penetrate somewhat deeper into the sanctuary of so immense
a series of entities.

The cell is a vesicle imperceptible to the naked eye. When,
however, it is magnified three hundred or four hundred times,
we find not only that it consists of a liquid different from
the solid envelope, that developement of various kinds takes
place both in the interior and on the exterior, which con-
tributes to their anatomical as well as chemical differences,
but under favourable circumstances, we can partly observe the
working of this minute economy.

When the uninjured cell is observed in full operation, as
it appears in its youth, no difference can yet be detected be-
tween its contents and boundary; but in the content itself,
there very soon appears a vital centre, produced in the form of
a tiny vesicle. This leaflet, named nucleus, causes, very soon
after its first appearance, a remarkable separation of the half-
liquid contents. A tough, liquid, granular substance, detaches
itself from the residue, which displays a more watery nature.
This, called protoplasm, unites itself as well to the vital centre
as to the periphery, and thereby binds both together with many
radiating, simple, and branching threads.

BOTANICAL LETTERS, 113

It is a charming spectacle to observe in the so-far per-
fected cell, the active flow of this vital
sap from the centre to the periphery and
back.

The most manifold motions even in the
most opposite directions are seen in close
proximity in the same thread-currents,
All is activity and motion in this proto-
plasm, nevertheless the remaining part re-
mains motionless, and is only here and
there drawn into the current of the stream.
These streams are
moved by no pulsating
veins; there is no
pumping apparatus
which forces them from ¢:
the centre of the cell
and back again. This
marvellous substance,
this self-moving wheel,
is a protein substance, consisting of the

Fig, 37.

oy

same nitrogenous compound that is pre-
sent in every animal.

In some instances (but as far as our ex-
perience yet extends, only in the lower
plants) the de- Me
velopement of pa ae on
this protoplasm ae ee
advances _be- i ee
Wendaethe, ex." eee |
terior bounda- & 9
ries. ae tea ae

1Gs18 "not. 2 pe Se
mere motion of Ce
the liquid mass is
which goes on, but a developement of half-solid thread-like
processes, capable of performing other motions than those of
circulation, When such cells are set at liberty by the opening

114 BOTANICAL LETTERS.

of the mother-cells in which they have been formed, they
commence motions entirely independent of the latter, and when
they are in water, swim about freely in it.

Fig. 87 is a young plant of Vaucheria clavata, Agdh, at the
period of the ripening of the fruit; that is, when the first germ-
cell is pushed out. 8B is the germ-cell after being detached
from the mother-cell, and floating freely. The extremely de-
licate ciliate processes of the membrane by whose vibrations
the motion is effected are shown at o, magnified a thousandfold.
They will be seen to be of equal size, and to cover the whole
surface of the egg-shaped cell. Db is a group of young ger-
minating plants of the same kind, less highly magnified.

The thread-like cilize upon their surface serve at this time the
purpose of rudders, in the same way as the cilie and hairs of
infusoria. Neither the form, the chemical nature, nor the
power of contraction, without which the ciliate or quivering
motion would be inconceivable, distinguish these vegetable cells
from analogous animal forms, and, to connect them even still
more closely with the latter, dots of colour present themselves
as indications of organs sensitive to light.

But this burst of life in the plant-cell is of short duration,
and ceases in the ciliate swarming cells sooner than in others.
After a short time, these feelers, with which they strive to
penetrate further into the exterior world than by the roots, are
drawn in, the cell again becomes smooth, and cellulose is soon
deposited upon its surface, which renders the incarceration
complete. - The vigorous play of motions does indeed continue
for a longer or shorter period, even under the rigid envelope
of the cell-membrane, and it is at this time especially that the
reproduction of the cell goes on by the formation of new vital
centres; but this last spark of life is soon extinguished, and
the victorious forces of molecular attraction, affinity, etc., reduce
the cell gradually within the domain of inorganic nature.

Nevertheless it appears that the manifestation of this vigorous
vital action is reserved to only a few cells in the body of the
plant, although not for its entire duration, at least for some time.
These are the reproduction cells. While all permanent cells
are capable of manifesting their higher nature only in the

-

BOTANICAL LETTERS. 115

motion of their juices, the reproduction cells break all the bonds
which govern the former, and, even although only for a few
moments, enter into the most unrestrained activity.

In some series of the vegetable kingdom, in which, as we have
seen, the duality of sex does not appear to be fully developed,
such reproductive cells become swarming cells in other series ; the
one reproduction cell does not acquire such a degree of freedom,
but the second one moves the more unrestrictedly extended
lengthways, as spermatozoids, whose motions are far from being
understood in respect to their relation to fructification (fig. 39).

A, Fig. 38, represents a spermatozoid of Asplenium septentrionale,
detached from the mother-cell in»
which it was formed, and moving ‘i . ’
rapidly in water by means of the
ciie. It is magnified x 1200fold.
B, Sspermatozoids of Hquzsetum arvense,
magnified x 500fold. 0, a sperma-
tozoid just escaping from the mother-
cell.— ( W. Hofmeister.)

In the intermediate part of the
vegetable kingdom, lastly, comprising
all the more highly-developed plants,
' this primitive vital tendency is almost
entirely stopped under the armour of ie cell-membrane, and
rendered irrecognizable.

Since this higher vital tendency of the cell is, as we have
seen, such a universal phenomenon in germinating organisms,
but appears in such unequal intensity, it may indeed be said
that the developement of the plant rather deviates from than
tends towards a free natural state; and in so far plants and
animals are antagonistic and mutually-deviating manifestations
of a general natural vitality. It is quite as certain that they
are, however, alike in origin, for here all marks of distinction
cease to exist, and there is a gradual transition from one to
the other.

It follows, therefore, obviously from this, that the key to
the mystery of vegetable life lies in the primitively- -similar
foundation of life of the animal and vegetable kingdom, from

116 BOTANICAL LETTERS.

which indeed both have sprung, but have branched off in dif-
ferent directions.

The animal nature is in the plant as it were caged, and this
imprisonment is expressed throughout its entire existence, in
its formation, and relation to the animal kingdom. - They are
the tears of Cypria, the blood of Hyacinth, which in the form
-and colour of the flower whisper to us a melancholy strain.
The complaining Dryad expresses the whole soul of the plant.

Thus in melancholy seclusion does the plant achieve its life-
destiny.. But the fettered and slumbering world-spirit, which
here scarce dares breathe, is the same which in animals bursts
its bonds for ever, and, lastly, sings its hallelujah in man.

We CLOWES AND SONS, STAMFORD STREET AND CHARING CROSS.

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