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THE

PRINCIPLES OF BOTANY,

CRYPTOGAMIA.

FOR THE USE OF SCHOOLS AND COLLEGES.

BY

HARLAND COULTAS.

PHILADELPHIA:
LINDSAY AND BLAKISTON,
1853.

MS tA
cise

Qe.
SOs
a,
eae

Entered sealing’ to the Act of # Cbnivienss in the year 1853, iis
LINDSAY AND BLAKISTON,

in the Office of the Clerk of the District Court of the United States
in and for the Eastern District of Pennsylvania.

PAILADELPHIA:
T. K AND DP. G. COLLINS, PRINTER*

TO

T. 8. ARTHUR, Esq.,

AS

A TRIBUTE OF ESTEEM FOR HIS TALENTS AND VIRTUES,

Chis Little Bonk

1g
RESPECTFULLY DEDICATED,
BY

THE AUTHOR.

INTRODUCTION.

THERE is no department of natural history which is more
important, beautiful, and interesting than Botany, or the natu-
ral history of plants. Let us take, not a costly exotic from
the conservatory, but any common wild flower or weed. What
exquisite symmetry and elegance of form! The choicest
works of art, the most finished productions of genius, are but
as the poor efforts of savages when contrasted with this won-
derful work of nature! We know that this humble flower
grows when fanned by winds, watered by rains, warmed by
the sun, and that it must derive some portion of its substance
from the soil. But how does Nature form this green leaf
and this beautiful blossom? We see her constantly engaged
in building up these living forms, and weaving the air, the
earth, and the water into every imaginable variety of vegeta-
ble fabric. The whole earth is, in fact, one vast chemical
laboratory or workshop, where Nature is ever operating with
an untiring industry in fabricating living forms out of lifeless
inorganic matter. Let us endeavor to trace the movements of
this glorious mechanism framed by the hand of the Almighty ;
let us ‘ consider the lilies of the field, how they grow.”

And let it not be assumed, at the outset of this investiga-
tion, that the intelligence of man is incapable of searching out

vi INTRODUCTION.

the mysteries of vegetation. Before the time of Newton,
there were many men who had seen apples fall to the ground
without ever reflecting on the cause of their fall. Newton
saw the same, and thought. The result of his reflections was
the production of his immortal work, the Principia, and the
development of the theory of gravitation. He showed with
what small means Nature attains the most magnificent results.
It was the mutual attraction subsisting between the earth and
apple that brought the apple to the earth’s surface; and the
game mutual attraction retains the moon and planets in their
orbits, causing them to sweep out in immensity those sublime
curves with which the mind of the geometer is familiarized.
It is by the attraction of other suns that our own sun, or rather
star, is upheld in space; whilst all the stars that sparkle on
the roof of night, and whose light comes to us from the most
distant regions of the universe, are upheld by mutual attrac-
tion. Such was the sublime discovery of the illustrious New-
ton. What though the means which Nature employs in the
construction of the various forms of plants is at present only
imperfectly understood—if the law that regulates the motion
of masses of matter has been discovered, why not the law
which governs the motion of atoms of matter, and causes them
to collect around every germinating seed or growing plantlet,
so as to develop it with such unchanging constancy and regu-
larity into the same definite form of life and beauty? Man
is not destined to continue forever hopeless and helpless
amidst the forces of nature. It is his prerogative “ to subdue
the earth,” and “have dominion.”

The law of material attraction may be thus expressed : Mat-

INTRODUCTION. vil

ter may attract matter at all distances from zero to infinity.
This attraction takes place with a force varying directly in
proportion to its quantity, and inversely as the square of the
distanee. Now when matter collects into masses, as we see
it has done in the case of the starry heavens and planetary
bodies, two or more bodies, thus mutually attracting each other,
separate sometimes to distances all but infinite, but according
to a fixed and determinate mathematical law, the distance
being in exact proportion to the ratio of their respective mag-
nitudes and quantities of matter. We call the name of this
species of attraction, gravity. But when matter retains its
elementary condition, and exists in the form of those invisible
particles called atoms, two or more mutually attracting par-
ticles must be brought by the same law infinitely near to
each other before they can exercise any mutual influence ;
and we give the name of chemical affinity to this kind of at-
traction.

To apply this philosophy to plants. They are the result,
principally, of the atomic or chemical affinity, combined with
other agents, and are a beautiful pile of matter borrowed from
the atoms in the earth and air, and united together by the
operation of natural laws for alittle space of time. Fabricated
by nature as material for the building up of higher or-
ganic forms, they perform their part in the ever-shifting
scenery of life, and either become incorporated as food into
animal bodies, or else, retaining their state as plants, they are
the instruments used by nature to extract fertilizing princi-
ples from every falling shower and passing breeze, which they
impart to the soil on which they finally decay. The end of

viii INTRODUCTION.

being accomplished, their beautiful and evanescent forms de-
cay, they become disorganized, the pile of matter falls, and is
restored by the operation of the common laws of chemical at-
traction to the earth and air from which it was taken.

We are accustomed to admire the magnificent spectacle of
the starry heavens; but let us look on the earth, at the splen-
dors of the vegetable creation. From the lowly Moss which
raises its little sporangia hardly an inch above the ground, and
covers with its minute, but exquisitely beautiful foliage, the
rugged rocks and the bark of trees, to the noble arborescent
Ferns of the tropics, from whose lofty summit a magnificent
bouquet of gigantic fronds is gracefully pendent; from the
little inconspicuous aquatic plant, called the Duckmeat, which
covers the surface of the pools and stagnant waters with its
scumlike vegetation, to the splendid Victoria Regia, the queen
of water-lilies, cradled in the rolling billows of the mighty
Amazon—what differences in size! what an advance in organic
development! Yet nature has every intermediate variety of
organization, passing, as we shall presently show, from the
utmost simplicity to the sublimest grandeur of vegetable
structure, through a beautiful and highly instructive series of
transition-forms.

The forms of life called Plants deserve every attention.
Botany is not a mere accomplishment, but an important
branch of education. If it be true, as some philosophers have
asserted, that the whole chain of organic being, from man
down to the humble spire of grass, is only a manifestation of
life in different degrees of development, then are we all per-

sonally interested in this inquiry. Itis in plants that mineral

INTRODUCTION. ix

matter first becomes endowed with life. It ig there that we
meet with its earliest, humblest indications. We know that
every plant is formed out of the mineral matter of the earth
and atmosphere, and that the vegetable world is formed out of
mineral matter for the support of animal life. Thus the plant
connects the animal with the mineral. He who would suc-
cessfully study the laws of life as developed in the animal
world certainly ought not to neglect the investigation of plants
on which animals depend for food, or rather for their very
existence.

It must be clear, to reflecting minds, that plants and animals
exercise a great many of the functions of life in common.
Both are nourished by food and air, are subjected to disease,
decay, and death, and have the power of self-reproduction, or
of continuing their species. Plants appear to be subject to
similar organic laws to animals, in the development of their
tissues, and the life in them is probably only a modification of
the same universal principle of action which pervades all or-
ganic being. In the prosecution of physiological researches, it
is therefore of the utmost importance that we should become
conversant with the phenomena of vegetable vitality. In the
development of living nature, there is too evident a system of
dependency, and no link in the great chain of being can be
dispensed with. Human physiology will progress, and the
noble art of healing be better understood, in proportion as we
understand the expression of life in inferior organic forms. If
we would understand the higher manifestations of life in our-
selves, we must neglect the study of nothing that has life,

x INTRODUCTION.

however humble may be its manifestations of vitality or simple
its organic structure.

And let me suggest that the study of the simple plants ought
to take the precedence of those whose organization is more com-
plex and intricate, as being the simplest expression of the laws
of vegetable life. It is now certain that the growth of plants,
and, in fact, of every organic being, is the result of the opera-
tion of certain fixed and immutable laws. All who have no-
ticed the phenomena of the life of plants must be satisfied
that this is the case. Thus, all have a period of life assigned
them, more or less limited, during which we see them, as it
were, by successive increments, slowly elaborated out of the
earth and atmosphere, arrive at the full perfection of their
growth and beauty, reproduce themselves, and then die. The
period of time during which these phenomena take place varies
according to the peculiar structure of each plant. Thus plants,
whose structure is very simple, as ferns, mosses, and many of
our flowering-plants, grow, reproduce themselves, and then die,
and this all in a single season. In other instances, where the
organization is higher, the duration of life is much longer.
But the forest-tree, lifting its massive stem for centuries to the
light of day, has also an appointed period to its life, as regular
as the lowly moss that grows beneath its shade. A few months,
however, suffice to perfect the one, and many centuries are re-
quired by nature before she can build up the other. Now it
is evident that the growth of the humble moss is only a sim-
pler expression of that same law which operates in the produc-
tion of the forest-tree ; and if we can explain the law of deve-
lopment in the one case, we can in the other.

INTRODUCTION. xi

The science of Botany has not yet received that attention to
which it is justly entitled, on account of that forbidding array
of dark technicalities which has been but too frequently pre-
sented to the minds of those seeking instruction. But much
pleasing, wonderful, and instructive truth may be communi-
cated about plants in plain ordinary language, and by thus
studiously avoiding the use of scientific terms, and keeping to
the simplicity of nature, the approach of the student to the
study of them may be greatly facilitated. Linneeus and his
scholars have generally written in Latin. They addressed
themselves to anatomists, physicians, and philosophers, and
not to the people, or they would have adopted a different lan-
guage as a means of communicating thought. I shall endeavor
to copy Nature in her simplicity, and to conduct my readers,
by a plain and easy pathway, to the noble temple of Flora;
and, when they shall catch a glimpse of the glorious interior,
of the play of those magnificent laws of life of which man is
the highest expression, and which operate in the production
of the vast chain of organic being beneath him, there is no
difficulty which they will not attempt to surmount, in order
to learn more about those beautiful forms of life called plants,
and to solve the problem of their growth and reproduction.

PAR? 1.

ON THE

SIMPLE ELEMENTARY ORGANS OF PLANTS.

PAW Tol:

ON THE SIMPLE ELEMENTARY ORGANS OF PLANTS.

1. Wuen the structure of plants is examined, parts of that
structure are found to have peculiar functions assigned them ;
these parts are called organs, and the structure is said to be
organized. The lower tribes of plants possess fewer separate
organs, and the functions exercised are more general and less
restricted than in the higher tribes of plants in which the
organs are more numerous and complicated. The organization
of a plant is considered to be complex or simple, highly de-
veloped or the contrary, just in proportion to the number of
distinct organs of which it is composed, and of separate and
peculiar functions exercised by its tissues.

2. The organization of plants, when examined with the
microscope, is seen to consist of a united mass of cella or
vesicles, tubes, and fibres. These cells, tubes, and fibres,
which in some of the lower forms of vegetation are developed
as separate and independent plants, gradually unite together
ag organization advances in complexity of structure, and con-
stitute the substance of the more highly organized plants.

16 ELEMENTARY ORGANS OF PLANTS.

3. The cells, tubes, and fibres, thus associated, constitute
what botanists call the cellular, vascular, and woody tissues of
plants. The first is of universal occurrence; the other two
kinds of tissue are only partially introduced or wholly absent
from the structure of a great many plants, such as mosses and
seaweed, which consist of cellular tissue alone.

4, That all the parts of plants are fabricated out of cells is
evident from the fact that the cellular nature of the vegetable
substance invariably manifests itself when sections of that
substance are examined by means of transmitted light under
the microscope; the growth or extension of the parts of plants
must therefore be the result of the development of new cells,
and the size and form of plants must depend on the number
and nature of the arrangement of the new cells thus developed.
It is therefore proper to begin these investigations by first
considering the cells or simple elementary organs of plants
separately, and their mode of development into the different
tissues; we may then study more profitably the tissues as com-
bined together in the form of root, stem, and leaves, which
have been very properly termed the compound organs of
plants. We shall first show that all the different forms of
tissue are only modifications of the cellular, and that they all
originate in the simple cell as a point of departure.

CHAPTER I.
CELLULAR TISSUE.

5. Tuts consists of a number of vesicles or bladders, with
thin transparent sides adhering together, and containing fluid.
A piece of honey-comb gives a very good idea of this tissue
when it is at all regular, which is seldom the case, the walls
of the cells in the honey-comb representing the sides of the
cells in plants, and the inclosed spaces the cavities formed by
the union of the cells themselves. To become familiar with
this tissue, it is only necessary to examine a thin slice of any
of the succulent plants with the microscope, or the pulpy part
of an orange, where these cells may be readily distinguished
by the naked eye, and separated from the mass of the fruit.
When the body is sufficiently transparent, its internal struc-
ture may be perceived with the aid of the microscope, without
examining it in section. We may sometimes see this cellu-
lar structure very distinctly in a piece of thin transparent sea-
weed, or “in a young and delicate rootlet,” and “ observe the
closed cavities entirely circumscribed by nearly transparent
membranous walls.”*

6. Each cell is in itself a distinct and separate cavity; the
wall or partition between two cells is therefore double, being

* Gray’s Botanical Text-Book.
2%

18 ELEMENTARY ORGANS OF PLANTS.

produced by the cohesion of their sides. The double nature
of the cell-wall may be readily detected by boiling the tissue
for a short time, when the cells will separate. In ripe pulpy
fruits, the cells may be separately picked out, and examined
without boiling. Hence, when pulpy fruits are cut into pieces,
there is very little flow of fluid from them, the juices of the
fruits being retained in the little membranaceous sacs or cells
of which the pieces are composed.

7. The primitive or typical form of the cells is supposed to
be spherical or globular (Fig. 1), and this form the cells

Fig. 1.

retain in the lax tissues of succulent plants, in the pulpy parts
of fruits, where they do not impress each other, and where
growth takes place equally in all directions. But when any
part of the plant grows more rapidly in one direction than in
another, the cells commonly elongate in that direction, and
become elliptical, oblong, or even tubular if free from all adja-
cent pressure, and prismatic if laterally compressed, as is the

case in young shoots and branches. In the pith and in the

CELLULAR TISSUE. 19

parenchyma or green stratum of vegetable matter in the leaf,
where the cells are globular by mutual compression, they

assume an hexagonal or honey-comb like structure (Fig. 2).

The form of the cells, therefore, depends entirely on the cir-
cumstances in which they are placed, varying greatly in dif-
ferent parts of the same plant, their form being modified by
the growth and peculiar functions exercised by the organs of
the plant.

8. In the simpler tribes of plants, such as mosses and algee,
the cells depart but slightly from their primitive form, which
they retain throughout the entire life of the plant. But in
the more highly organized and complex plants, although the
mass of the plant at first consists wholly of cellular tissue, yet
as soon as the embryo plant begins to germinate, even whilst
the cotyledons or first pair of leaves are yet developing above
the carth’s surface, certain cells are seen rapidly to depart
from their primitive form, and to assume an elongated or

tubular appearance; the septa, or walls, or partitions between

20 ELEMENTARY ORGANS OF PLANTS.

contiguous cells are wholly absorbed in the process of growth,
and woody fibre and vascular tissue enter into composition.
It will be easy to perceive, from these facts, how, from so sim-
ple an element as a cell, may proceed a countless number of
different forms of tissue.

9. The substance out of which the cells of plants are formed
is called Cellulose, which is of universal occurrence in all
plants. This cellulose is formed out of a viscid mucilaginous
fluid termed by vegetable physiologists cambium, or organiz-
able matter, which fluid always precedes the appearance of
the cells, and is ever present when vegetable matter is in a
state of growth.

10. A stratum of cambium appears in the young and vitally
active tissues of plants in the spring of the year, and renders
the bark so easily separable from the stem of plants at this
season ; this fluid matter is gradually organized into cells, and
by the addition of these to their previously developed tissue,
the growth of the plant is effected. In autumn, this cambium,
or fluid matter, gradually disappears, the cells cease to form,
and the parts of plants to elongate and enlarge, and the bark
and stem again become firmly adherent.

11. True cellulose is always excessively thin and plastic
when first developed, so as to be easily impressible into any
form whatever. To this first layer of cellulose the well-contrived
term Protoplasm (wedros first, and waacua formative matter),
first proposed by Professor Mobl, is now applied. The thick-
ness and rigidity afterwards acquired by cellulose are owing
to the internal deposition of layers of incrusting matter which

CELLULAR TISSUE. 21

has received the name of Lignine (/gnum, wood), or sclerogen
(oxaygos hard, and yevvdew to generate).

12. In the lax parenchyma or tissue of plants, where the
cells retain in part their spherical or cylindrical figure, in
proportion as they retain that figure when they mutually
impress each other do they necessarily touch each other at
certain points only, leaving vacant spaces formed between
the cells; which, when they occur as separate cavities, are
called intercellular spaces; but when they follow the course
of the tissue, and occur as continuous and tubular sinuosi-
ties, they are termed intercellular passages.

13. Sometimes these intercellular spaces become the re-
ceptacles of the peculiar secretions of the plant. The trans-
parent dots seen in the leaves of the orange, the myrtle, and
the St. John’s-wort, when they are held up to the light, are
produced. by the presence of oil in the intercellular spaces
of the parenchyma, whilst the transudation of the milky
secretions into the intercellular passages forms the so-called
vessels of the latex.

14. These consist of long, irregularly-branching, and anas-
tomosing tubes, of extreme tenuity and transparency, having
a diameter of about 1-1400th of an inch, and forming, by
their union, an anastomosis or network, like the veins of
animals. They are visible only under a powerful microscope,
and were formerly thought to be cells united in a linear
series, their septa being obliterated; but, at a very early
period, the milky secretions of the plant may be seen circu-
lating through the intercellular passages, and from these
secretions the membrane forming the continuous and anasto-

22 ELEMENTARY ORGANS OF PLANTS.

mosing tubes of the latex is ultimately developed. The
secretion of the latex may be readily seen in dandelion,
euphorbia, or celandine, by breaking any leaf or shoot of
these plants.

15. Besides the intercellular spaces and passages already
described, other cavities exist in the parenchyma or cellular
tissue, which are usually filled with air, and are called lacunz
or air-cells. In aquatic plants large lacunz or air-celly are
formed in the parenchyma of the stem and leaves, by the
rupture or absorption of the septa between a number of con-
tiguous cells. These lacuna, in the pond-weeds, assume a
regular form, which is constant in each species; their forma-
tion, therefore, cannot be attributed to accident; on the con-
trary, they seem to be organically necessary to the healthy
exercise of the functions of these plants, giving them the
requisite degree of buoyancy in the water.

16. More frequently, however, the lacunz are very irregu-
lar in their form, and are produced by the rapid growth of
the parts resulting in the irregular destruction or distension
of the cellular tissue. In these instances, their formation is
in some sort accidental. The hollow stems of grasses and of
the umbelliferee are produced in this way.

17. After the first layer of protoplasm has been formed
from the cambium and the cells constructed, as growth pro-
gresses, the cells, at first extensible and compressible, ulti-
mately assume fixed and unyielding forms, owing to the
internal deposition on their walls of sclerogen. The de-
posited matter includes all the various substances introduced
into the circulatory system of the plant, and left by evapora-

CELLULAR TISSUE. 23

tion in its cells; and every degree of its deposition may be
seen from a slight increase of thickness of the cell-wall to
the entire filling up of the cavity of the cell. The difference
between sapwood and heartwood is caused, in fact, by a dif-
ference in the amount of the incrusting matter in the cells,
and by an increase of which the former is converted into the
latter. The indurated tissue which forms the cells of the
stones of the peach, cherry, and other fruits is produced in
this way.

18. Sometimes nearly the whole of the interior surface of
the cells is thus thickened, the stratification of the matter
being distinctly visible on the cross-section, as is well seen in
the woody cells of the liber of the birch (Fig. 3), the cells

Fig. 8.

being nearly filled with a deposit of solid matter in concentric
layers; occasionally, however, certain parts of the primitive
layer of protoplasm only have the power of attracting from the
fluid contents of the cells the incrusting matter, and of becom-
ing thickened. This produces those dots and lines which are
seen to mark the cell-walls of many species of plants, and
which have been taken for pores or slits in the cell-wall; but
the primitive membrane of the cell-wall is never perforated

24 ELEMENTARY ORGANS OF PLANTS.

or slit except accidentally ; and these apparent pores and slits
are, in reality, pits and chinks left by the non-deposition of
sedimentary matter at that particular part of the cell-wall,
and consequently visible by the greater amount of trans-
parency there.

19. The chinks and pits in contiguous cells usually corre-
spond, and hence one reagon for this peculiar deposition of
the sclerogen is very obvious. By it the lateral communica-
tions between the several cells composing the tissue are kept
open, notwithstanding this thickening of their walls, the sap
permeating through the vegetable tissues at these particular
parts. These lateral passages and their nature are clearly
shown in Fig. 4, which is a transverse and longitudinal

Fig. 4.

section of a portion of four cells of the woody tissue of Pla-
tanus occidentalis, or the Buttonwood, “highly magnified,
showing the canals or deep pits in the thickened walls, and
their apposition in adjoining cells; on the cross-section the
layers of deposit are more plainly visible.’’*

* Gray’s Botanical Text-Book.

CELLULAR TISSUE. 25

20. Although these pits and chinks are not real pores or
openings in the cell-wall, yet they often become so with age,
by the breaking away of the thin primitive membrane after
the cell has lost its vitality.

21. By what power the sedimentary matter left on the sides
of such tissue as this is prevented from choking up the pits
and chinks is at present unknown. The sedimentary matter
left by the evaporation of the fluid contents of the cells is
certainly not deposited mechanically, as in the ordinary cases
of evaporation; but it appears to be controlled in its dispo-
sition by the higher vital and physiological action in the cell-
walls.

22. Sometimes, however, the secondary deposit itself is
restricted to a delicate thread, which either occurs in rings or
fragments of rings, or winds about the interior of the cell in a
spiral (Fig. 5). The delicate membranous walls of such cells

Fig. 5.

are sometimes ruptured at maturity, by the elastic expansion

of the spiral fibre within them. This takes place in the

fructification of the hepatic mosses, which consists of spindle-

shaped cells inclosing spiral threads called elaters, which, by

their elastic expansion, burst the cell-walls and scatter the
3

26 ELEMENTARY ORGANS OF PLANTS.

spores. By a similar mechanism, the pollen is dispersed
from the anther-cells of Cobaea scandens.

23. When the cell-walls of cellular tissue are composed of
membrane without fibre, it is called membranous cellular tis-
sue; but when the cell-walls consist of membrane and fibre
combined, it is designated as /ibro-cellular tissue. Some
writers have recently distinguished other differences in the
figure assumed by the cells, by the employment of a variety
of technical terms expressive of those figures. But this is
only multiplying unnecessarily the technicalities of the
science. The general term, parenchyma, will suffice to dis-
tinguish a tissue composed of cells, from a fibrous tissue, or
that which is composed of fibres or tubular vessels.

24. Cellular tissue enters largely into the composition of
all plants, forming the pith of trees, the pulp of fruits, and
filling up the interstices between the fibrous network of the
leaves. There is an extensive tribe of plants which are
wholly composed of this tissue, and as they produce no
flowers, they have been for these reasons called by botanists
cellulares or flowerless plants. The orders comprised in this
division are the fungi, lichens, alge, liverworts, and mosses.
Of this tissue all plants in their earliest stage of development
are entirely composed. Indeed, plants, however complex
their organization, may all be traced by observation nearly
or quite to a single cell; which cell, endowed with the power
of self-propagation equally with the fully developed plant,
gives rise to other cells, each being individually possessed of
the same powers, and so forms the whole mass of the plant.

CELLULAR TISSUE. 27

The woody and fibrous tissue which is so beautifully spread
out horizontally in the framework of the leaves of plants,
and which constitutes the substance of their more solid parts,
is, therefore, only a peculiar transformation of cells which
are, in fact, the basis and origin of all the other forms of
tissue.

CHAPTER II.
WOODY AND VASCULAR TISSUE.

25. Iv has been shown (4) that every plant consists of a
series of cells aggregated together, having a certain arrange-
ment, and developing into a certain regular form, according
to fixed natural laws. The cells thus aggregated together con-
stitute what botanists call a tissue, which tissue, according to
the forms which the cells assume, is designated as cellular,
vascular, and woody tissue. These are the three leading
forms; but, in the study of nature, we must accustom our-
selves to consider that there are transition forms, and never
to believe that one and the same type remains unchanged.
With this qualifying remark, we can now very properly in-
vestigate,

26. Woody tissue, or, as it is termed by some writers, fibrous.
tissue, or Pleurenchyma (waevpa a rib, and zevya anything
effused or spread out), Fig. 6, consists of vesicles of cellular
tissue drawn out into fusiform tubes of extreme tenuity and
toughness, which lie close together and overlap each other at
their tapering extremities, so that they are, as it were, spliced
together. These tubes, united together in bundles, constitute
the wood of the stem, and form those long coarse fibres which
stretch through the plant lengthwise. Issuing from the side
of the stem in distinct fasciculi or bundles, this woody fibre

WOODY AND VASCULAR TISSUE. 29

forms the more solid parts of the petioles or stalks of the
leaves; it is seen spread out horizontally in their frame-
work, and in consequence of its constant tendency to anasto-
mose, its subdivisions or branchlets, which are ramified out

Fig. 6.

amidst the green cellular parenchyma, even to the minutest
visible fibre, and continued beyond the limits of unassisted
vision, run into each other, forming that delicate and beauti-
ful network which is visible to the eye in the leaf. It is
owing to the vertical development of woody fibre that a
piece of wood splits more readily in the direction of the stem
(longitudinally) than when broken across (transversely).

27. Woody fibre, in the earlier stages of its growth, con-
tains fluid, which it carries from the roots, through the stem
and branches, into the leaves and extremities of the plant.
In the progress of growth, however, its walls become thick-
ened by deposits of sclerogen; the caliber of the tubes di-
minishes, until, at length, as in the heartwood of trees, their
tubular character is wholly obliterated.

28. The sclerogen thus deposited is generally spread out
uniformly over the interior parietes of the tubes, so that bands,
lines, and other markings are seldom seen in the walls of the
cells of woody fibre. It is necessary, however, to except the
fibre of pine woods, which exhibit large saucer-like depressions

in the outer walls of the tube, with a dot in the centre, where
8*

30 ELEMENTARY ORGANS OF PLANTS.

the sclerogen has not been deposited, and, consequently, visi-
ble by the greater transparency of the tubular walls in that
part. The disks, or saucer-like depressions on the walls of two
contiguous tubes, are applied to each other, whereby a small
space is left between them, similar to the cavity left between
the concave surfaces of two watch-glasses. In some fossil
woods, pieces of silica, like double convex lenses, have been
removed from these cavities, so as to leave no doubt as to the
nature of these interspaces between the fibres, of which they
were clearly the casts.

29. These circular markings in the fibres of pine woods are,

Fig. 7.

therefore, caused by cavities formed by the concave depres-
sions or lenticular cavities, 7, c, between the walls of two con-
tiguous tubes, the centre of each depression being thin and
transparent, and producing the dot seen in the centre of the

WOODY AND VASCULAR TISSUE. 31

disk. These circular markings or disks are found in single,
double, and triple rows. When there is more than one row,
the individual disks are either opposite to each other, as in
ordinary pine wood, or they alternate with each other, as in
Araucarias. Mr. William Nichol, of England, and Prof.
Bailey, of West Point, were the first to apply these characters
to the determination of fossil woods, thus revealing the true
nature of some of the earliest vegetation of the earth.*

30. Plants are durable and strong in exact proportion to
the amount of woody fibre which enters into their composition.
The lowly mosses and other orders of cellular plants scarcely
rise more than a few inches above the ground; but when
woody fibre begins to form amongst the cells, additional
strength is given to the vegetable fabric, and plants are de-
veloped into herbs, shrubs, and assume the noblest arbores-
cent forms.

31. Vascular tissue.—This consists of a series of vesicles of
cellular tissue, having fibre generated spirally in their inside,
drawn out into membranous tubes tapering to either extremity,
the walls of the tubes being absorbed at the points where they
overlap each other, so as to allow of direct communication be-
tween them. More frequently, however, these tubes, instead
of tapering, terminate abruptly at their extremities, and when
this is the case, their origin from a series of elongated cells,
placed end to end, is often beautifully apparent in the remains
of the persistent parietes of the cells which are seen along the
cavity of the tube, and by which its continuity is not unfre-

quently interrupted.

* Balfour’s Class-Book of Botany.

32 ELEMENTARY ORGANS OF PLANTS.

32. As the vascular tissue in plants is only a modification
of the cellular, we find in it all those characters which we
have already described in the cells of the cellular tissue.
Vascular tissue sometimes assumes the appearance of dotted
or pitted ducts, which are continuous tubes of very conspicu-
ous caliber or bore, which have been formed out of a series of
porous cells, placed end to end, the walls of which have been
absorbed in the progress of growth. The open mouths of
these ducts are conspicuous to the naked eye on the cross sec-
tion of the stems of the oak, poplar, and willow, rendering
apparent the limits of each year’s growth in‘ the successive
rings of the stem. The tubular tissue, formed by porous ves-
sels, is termed Bothrenchyma (o6pos, a pit). Fig. 8 is a
portion of a dotted duct from the vine, evidently made up of
a short series of cells. Fig. 9 is part of a smaller dotted duct,
showing no appearance of such composition.

33. When cells containing spiral deposits of sclerogen are

Fig. 8. Fig. 9.

placed end to end, and their parietes absorbed, then vascular
tissue takes the form of scalariform, annular, and spiral ducts,

WOODY AND VASCULAR TISSUE. 33

which are simply open membranous tubes containing spiral
fibre lying together in close coils in the tube, or with the coils
more or less separated, or broken into rings or bars, by the
elongation of the tube after the formation of the spiral. All
these different forms of the spiral deposit may be seen in the
common garden balsam, very frequently in the same duct.
This form of vascular tissue is called Trachenchyma (trachea,
the windpipe), on account of its resemblance in appearance
and in functions to the trachea or air-tubes of animals.

The annexed illustrations are taken from the Botanical Teat-

Book of Dr. Gray :—

Figs. 10.

Cm

SERS

os

OO CU

Ta

D000 0900000000000

Fig. 10. A simple spiral vessel, torn across, with the thread uncoiling.

Fig. 11. Two such vessels joined at their pointed extremities.

Fig. 12. A compound spiral vessel, partially uncoiled, from the Banana.

Fig. 13. A portion of a duct from the leafstalk of Celery; the lower part annular,
the middle reticulated, and the thread at the upper part broken up into short pieces.

Fig. 14. Duct from the Wild Balsam or Jewel-weed; the coilsof the thread distant;
a portion forming separate rings.

Fig. 15. Scalariform ducts of a Fern, rendered prismatic by mutual prossure.

Fig. 16, Similar duct of a Fern, torn into a spiral band.

84 ELEMENTARY ORGANS OF PLANTS.

84. Spiral fibre usually consists of a single filament, but
sometimes numerous fibres are united together, assuming the
aspect of a broad ribbon or band, as may be seen in the stems
of the banana or the asparagus. When the spiral coil re-
mains unbroken, it is so strong and tough, in comparison with
the delicate cell-wall on which it is deposited, that it may be
torn out and uncoiled when the vessel is pulled asunder, the
membrane being destroyed in the operation. This capability _
of being unrolled characterizes the true spiral fibre.

35. Spiral fibre is soon known, and familiarized to the
mind, by breaking asunder almost any young shoot or leaf-
stalk (as for instance that of the geranium or strawberry),
and gently separating the broken ends, when a number of
white glistening fibres of extreme delicacy, and not unlike
the threads of the spider’s web, will be seen running from
one portion to the other. If these threads be placed under
the microscope, it will be evident that they had lain in spiral
coils, which are partially straightened through being drawn
out, just as when a spiral spring is strained. These vessels
were first discovered by Henshaw, in the year 1661.

86. Vascular tissue is never wholly filled up by deposits
of sclerogen, the spiral fibre within it keeping the canal of
the tubes constantly open. The accurate experiments of
Bischoff have led to the conclusion that the perfect spiral
duct or spiral vessels are filled with air which contains a large
amount of oxygen in its composition. This oxygen, the
result of the chemical compositions and decompositions going
on in the interior of the plant, spiral vessels convey from the
central part of the plant to its young shoots and leaves, the

WOODY AND VASCULAR TISSUE. 35

network of which consists of woody fibres inclosing spiral
vessels as a protecting sheath, and through the pores of the
leaves and young shoots this oxygen escapes into the atmo-
sphere. The other kinds of vascular tissue, particularly the
porous, convey fluid which they distribute horizontally and
longitudinally through the vegetable system. Spiral fibres
are abundant in young plants and shoots; in the hard stems
of trees and shrubs, they chiefly surround the pith.

87. The cell has now been shown to be the type of all the
tissues of plants, and to be the basis of the vegetable struc-
ture. To the elongation of cells and to the deposition of
thickening layers in their interior, the various kinds of vessels
owe their origin. In the lower tribes of plants, such as
mosses and algee, the cells multiply in their primitive form,
which they retain during the life of the plant ; in vegetation
of a higher grade, some of the cells early undergo the transfor-
mations already described, and become elongated into tubes of
vascular and woody tissue, which tubes, imbedded in the
parenchyma or cellular tissue, impart additional strength and
solidity to the vegetable structure, conveying fluids and air
to every part of it. The beautiful researches of Treviranus
and M. Mirbel have proved that these vessels are only a
series of superposed vesicles of membranous and fibro-mem-
branous cellular tissue, the septa of which have been absorbed
in the process of growth. These facts may be verified by
direct observation on the young and growing tissues of plants,
if those tissues be placed beneath the microscope. All the
different forms of tissue which we have described, pass insen-
sibly one into the other through intermediate gradations, and

36 ELEMENTARY ORGANS OF PLANTS.

in this manner the origin of the whole of them from the
simple cell may be distinctly traced. Such are the beauty and
simplicity of those laws which govern the development of
plants! Such are the simple means with which nature accom-
plishes the sublime results of vegetation !

CHAPTER III.
ON THE DEVELOPMENT AND FUNCTIONS OF CELLS.

38. As all the parts of plants are fabricated out of cells,
it follows that growth, or the extension of their parts, is the
result of the development of new cells, and that the size and
form which plants assume must be owing to the number and
nature of the arrangement of the cells thus developed. All
the varieties in the size, form, and duration of plants are,
therefore, simply the result of different degrees of cell-
evolution, and the same plan and principle of structure per-
vade the whole of them. To show that this is really the
case is the object of the present chapter.

89. In all plants which consist of more than one cell, or
of a series of cells united together, a distinction must be
made between Vegetative cells, or those which aid in nutrition
and growth, and Reproductive cells, or those which continue
the species. All such plants continue to grow or extend in a
given direction so long as their vegetative cells continue to
develop; but when the reproductive cells make their appear-
ance, the growth or extension of their parts in that direction
ceases. Now the endless variety of form and size amongst
plants is owing to peculiar modifications in their common
organs of vegetation and reproduction. ach species of
plant appears to be governed by peculiar organic laws, which

4

38 ELEMENTARY ORGANS OF PLANTS.

are probably only a modification of one universal principle of
vital action.

40. In Forest-trees, the process of growth, or cell-evolution,
continues for centuries; in shrubs, for a much shorter space
of time: hence, the vast size to which the former attain, and
the dwarfed growth of the latter. In these plants, the cells,
as they increase in number, become specialized, or arrange
themselves into definite parts, such as root, stem, and leaves,
each having distinct functions to perform in the vegetable
economy, whilst their reproductive cells are contained in
certain metamorphosed and terminal leaves termed anthers,
and are the final results of the physiological action of an
exquisite floral apparatus bright with the most resplendent
hues and colors. Forest-trees and shrubs are the highest
forms of vegetable development on the face of the earth.
Not only do they surpass the herbaceous plants, that grow
beneath their shade, in size and in the duration of their life,
but they are to a considerable extent more composite in their
mode of growth. The forest-tree is not a simple individual,
as is usually supposed, but a community of individuals.
Properly speaking, the simple plant consists only of a stem,
root, and the first pair of leaves. The succeeding evolution
of leaves is only a continuation of the first process of growth,
whilst each bud is an actual repetition of the plant, the only
difference being that the bud or new plant has no free radical
extremity, like the parent plant, developed on the soil, its
root being intimately blended with and contributing to the
formation of the wood of the stem on which it grows.

41. In Shrubs and herbaceous annuals and perennials, there

DEVELOPMENT AND FUNCTIONS OF CELLS. 39

is a similar development of buds or new plants on the stem,
but not to the same extent; hence they do not attain the
same elevation above the ground. In the lower forms of
herbaceous vegetation, the buds or stem-plants become suc-
cessively less and less evolved, until at length they disappear
altogether from the stem, which itself is so contracted in its
growth as to be hidden in the earth. This is the case with
the hyacinth, lily, and other bulbous-rooted plants. The
bulbs of these plants are considered by botanists to be subter-
ranean buds or undeveloped stems, to which they are in every
respect similar. The outer leaves of these buds retain their
rudimentary scalelike appearance, and form a protective
covering to the inner leaves, which grow in a tuft on the
ground, the flower-stem rising from their centre.

42. In all these instances, the parts consist of millions of
vegetative and reproductive cells, especially when the plants
attain any considerable degree of elevation above the earth’s
surface, as in the case of forest-trees, where the evolution of
cells goes on for centuries. In the lower forms of vegetation,
the vegetative and reproductive cells become successively less
and less evolved, until at length, by successive degrees of
simplification of structure, all distinction into organic parts
gradually and finally vanishes.

43. In the beautiful and interesting tribe of plants called
Ferns, we have a still greater simplification of vegetable struc-
ture. Stem and leaf are now blended into what is designated
a frond, which appears to partake of the nature and office of
both, whilst in place of the beautiful flower there is only a

40 ELEMENTARY ORGANS OF PLANTS.

collection of mere dustlike spots or lines of reproductive mat-
ter, situated on the margin or under surface of the frond.

44. But the structure of Ferns is complexity itself when
contrasted with the beautiful simplicity of the tribes of plants
beneath them. When we come to examine the Mosses—those
miniature representations of the arborescent forms of nobler
plants—we are struck with the extreme delicacy, simplicity,
and exquisite beauty of their structure. There is a certain
degree of solidity about the organization of forest-trees, flow-
ering-plants, and ferns, the result of different amounts of
ligneous matter or woody fibre entering into their composition.
These substances impart strength and stability to the vegeta-
ble fabrics, and plants so organized will grow to a considerable
height. But mosses are wholly cellular in their organization,
and, for this reason, never rise more than a few inches above
the ground. They usually possess a sort of stem, around
which their minute leaves are arranged with the greatest regu-
larity. These minute leaves, when examined carefully with
a microscope, are seen to have an entire and sometimes serrat-
ed margin, and to contain condensed cells in the form of ribs
or nerves. Their fructification is contained in little capsules,
or urn-shaped bodies, which are borne on the summit of their
filiform fruit-stalks or setae. These capsules contain the mi-
nute spores or reproductive matter. The beautiful mechanism
by which its dispersion is effected will be described another
time. Few common objects appear more interesting than the
little mosses growing on the bark of trees or barren rocks,
amidst the gloom and desolation of winter, which require neither
skill nor the assistance of instruments for the detection of

DEVELOPMENT AND FUNCTIONS OF CELLS. 41

their beauties. The same distinction of parts into root, stem,
and leaves is therefore still seen in these minute, but exquisite-
ly beautiful plants, although the root no longer springs from
one extremity of the axis of growth, but from every part of it.

45. In the Liverworts, the leaves are reduced to mere im-
bricated scales, and in the lower forms~become blended into
a continuous expansion of vegetable matter called a frond.

46. In the Lichens, vegetation is reduced to its last degree
of simplicity. Root, stem, and leaves have now disappeared,
and the whole plant is blended into a flat expansion or bed of
vegetable matter, called a thallus. The thalli of the higher
forms of lichens are foliaceous, consisting of several layers of
cells radiating out on all sides; some of these cells are repro-
ductive, and exhibit the spores in the shape of powdery heaps
called soredia, or else they become organized into saucer-like
bodies called sh¢elds, in which the spores are imbedded. In
the lower forms, the thalli of these plants are crustaceous or
even pulverulent, the whole plant assuming the appearance of
mere powder. In this case the cells no longer remain together,
but are free and unformed, any cell being capable of originat-
ing a new individual. The plant and cell are now identical.

47. Nature passes through the same transitions in the Sea-
weed tribe. Certain Algse or sea-weed are of-a frondose,
others of a filamentous structure, whilst some appear as mere
scum on the surface of the waves. In these instances, the
plants consist of cells developing in length and breadth, of
cells developing in length only, or of a single cell. The same

remark applies to the Fungi, where nature only finishes with
4*

42 ELEMENTARY ORGANS OF PLANTS.

plants of a single cell. Here then we have vegetation reduced
to its simplest terms. The basis of the superstructure of the
whole vegetable world is a single cell.

48. We have seen that the fabric of plants is wholly made
up of cells, and that growth is simply the result of the evolu-
tion of new cells. The process of cell-growth, which is really
the key to much that remains mysterious in the fabrication of
plants, may be most successfully studied in these simple
plants. A review of the life of the cell, and of very simple
plants consisting of a few cells, must necessarily precede any
successful attempt at the comprehension of higher and more
complex vegetation. This has been felt to be the truth, and
hence this subject has recently taxed the powers of the ablest
minds. Much remains involved in obscurity; but scientific
and microscopical investigation of these humble plants has
already revealed many deeply interesting discoveries in refer-
ence to cell-growth, tending to throw light on the wonders and
beauties of the vegetable creation.

49. Now as the plan of structure in the more highly organ-
ized and complex plants can only be understood by studying
the operations of nature in detail, as exemplified in the simpler
vegetable forms, we shall commence with these first, this being
plainly the most natural and philosophical method of investi-
gation. Let us begin, then, with

50. Plants composed of a single cell—Some of the lower
forms of the Alge and Fungi furnish us with examples of
plants thus organically simple, and they are especially inte-
resting, as furnishing us with the simplest indications of those
processes of cell-growith and reproduction, on an accurate

DEVELOPMENT AND FUNCTIONS OF CELLS. 43

knowledge of which rest the very foundations of scientific
botany.

51. The Plant-cell, as it is termed by Dr. Schleiden, con-
stitutes an entire vegetable, without organs, imbibing its food
by endosmosis through every part of its surface, which it con-
verts into the materials of its own enlargement and growth,
and finally into new cells which constitute its progeny. Being
without lateral compression of any kind, the plant-cell neces-
sarily takes a globular form. We select, as an illustration of
the plant-cell, the Protococcus nivalis, or red snow-plant,
found in the arctic regions, and which also occurs on damp
ground in much lower latitudes. In Fig. 17, 1, we have

Fig. 17.

several individuals of this plant slightly magnified to show the
nature of the reproductive process. New cells are seen to
originate in the interior of each plant-cell, which gradually
take their place, and the new generation thus produced enlarges
and gives rise to a new progeny in their interior as before.
In this manner, this simple vegetation grows on from age to
age: 4 represents a more highly magnified individual of the
Protococcus nivalis, showing more distinctly the new cells

44 ELEMENTARY ORGANS OF PLANTS.

forming in its interior. The green pulverulent matter which
appears on old walls, and on the bark of trees, consists of an
unformed mass of free globular cells, which grow and repro-
duce in this simple manner. Here we have the starting-
point of vegetation, the beginning of the formation of those
vegetable elements which, in their future development, shall
clothe the earth’s surface with the richest forms of life and
beauty. In other species of plant-cells, the mode of repro-
duction is somewhat different. In Chroococeus rufescens, 2,
the plant-cell takes an oval form; a partition then appears
across its cavity, as represented at 3, dividing it into two cells.
These two cells are again subdivided by the formation of
another septum at right angles to the first partition, as is seen
at 5. The four cells thus formed enlarge and ultimately sepa-
rate, constituting four new individuals, which propagate in like
manner. In Oscillaria, the plant-cell becomes elongated, or it
may become elongated and branched, as is the case with the
species Vaucheria, which forms one kind of those delicate and
flossy green threads abounding in fresh water, and which are
popularly known in some places as brook-silk. Fig. 18 is a
magnified view of Vaucheria clavata, which consists of a sin-
gle cell of unbroken caliber, furnished with branches. In one
of these branches, at a, a spore is forming. 0 represents the
end of the branch more magnified, with the spore escaped
from its burst apex. In this instance, the ramifications of the
cell foreshadow, as it were, the elongation and ramification of
cells in the stem and branches of more highly organized

plants.

DEVELOPMENT AND FUNCTIONS OF CELLS. 45

Fig. 18.

52. Plants composed of a single row of cells.—In this
instance, the cell is multiplied by division combined with sub-
sequent expansion which takes place in one direction only. A
cell is first elongated, and a partition is seen to project across its
middle, by which it is divided into two cells; one of these cells
again elongates, and is again subdivided in a similar manner ;
in this way, a plant is produced consisting of a simple or branch-
ing series of cells placed end to end. Such plants can be seen
in any shallow stream of water which is exposed to the light.
They appear like threads of vegetable matter, and collectively
form that bright-green ooze which attaches itself to the stones
and pebbles of the stream. The extension of the parts of
plants, or their growth, in all ordinary cases is effected by this
mode of cell-multiplication.

53. In the simplest plant in nature, the plant-cell, both the
reproductive and nutritive processes are carried on by the same

46 ELEMENTARY ORGANS OF PLANTS.

cell. So also in the Diatomaceze, a species of marine alge,
where the union of plant-cells ts only temporary, the organs
of nutrition and reproduction are still identical. The cells of
these plants are at first united, but afterwards spontancously
disarticulate and break up, exhibiting well-marked spontane-
ous movements, insomuch that some naturalists have referred
them to the animal kingdom, to which they certainly approxi-
mate. Fig. 19 shows this process of disarticulation in Dia-

toma marinum after the consummation of the reproductive
process. The cells thus separated, under suitable conditions,
individually develop into new and independent plants.

54. But when plant-cells unite together permanently, as
they do in the higher forms, the organs of nutrition and repro-
duction are no longer identical or confined to the same cell;
on the contrary, some of the cells are specialized or set apart
for nutrition, and others for reproduction.

This is beautifully exemplified in the Mucor, or bread-
mould (Fig. 20), which consists, as to the creeping part at its
base, of long, threadlike and branching cells, the partitions
of which have been wholly absorbed, so that they form con-
tinuous tubes, whilst its upright portion, or stem, is composed
of a single row of cells, formed by the process of division

DEVELOPMENT AND FUNCTIONS OF CELLS. AT

already explained, the terminal cell containing the reproduc-
tive matter or spores. In Fig. 21, the Penicillum glaucum,

Fig. 20. Fig. 21.

another mould, we have a somewhat different arrangement of
the reproductive cells, which, instead of being inclosed in a
solitary terminal cell, are arranged side by side, forming a
number of beadlike branches at the summit of the stem.
These cells ultimately separate, and grow into new indi-
viduals.

55. When plant-cells unite together permanently, as in the
bread-mould, their union with each other evidently corre-
sponds to the union of phytons on the stem of flowering-
plants, and forest-trees. It has been shown (p. 40) that a tree
“ig not a simple individual, as is usually supposed, but a com-
munity of individuals.” Every bud which develops into a
branch is in fact a phyton (voy, a plant), or new plant, and
is actually capable of becoming such when taken off from the
stem and introduced into the soil as a cutting. A tree is the
regult of the evolution of a countless number of these super-

48 ELEMENTARY ORGANS OF PLANTS.

posed phytons or buds which are developed successively on its
stem or axis of growth, and differ only from ‘‘the parent plant
developed on the soil,”’ in having “no free radical extremity ;”’

their roots commingling with and “contributing to the forma-
tion of the wood of the stem on which they grow.” Fig. 22 is

DEVELOPMENT AND FUNCTIONS OF CELLS. 49

a diagram illustrating the development of a monocotyledonous
plant by superposed phytons; a—y, the successive phytons.
Sometimes the lower phytons develop adventitious roots from
the side of the stem, as represented at 6, which roots are in-
tended to act as props or mechanical supports. This is well
seen in the lower joints of the stem of the Zea Mays, Indian
corn. Now. these buds or phytons, although capable of
growing independently, remain through life united to the
parent stem on which they develop and form by their united
growth the individual tree. In like manner, when plant-cells
unite together in a linear series to form the individual plant
called the bread-mould, each plant-cell in the series is capable
of propagating the species when separated from the others
(which it actually does, as we have already seen, when this
separation takes place naturally), and each plant-cell is also
only a repetition of the same process of growth which took
place in the development of the primary plant-cell. The
bread-mould is therefore a composite plant formed by the
union of plant-cells, each of which is capable of forming the
germ of an independent existence, and of propagating the
species, although it remains through life in union with the
parent plant-cell forming the individual bread-mould, just as
the permanent union and development of a superposed series
of phytons form the individual tree.

56. It is therefore clear that the little bread-mould which
nature constructs from decaying organic matter in a few short
hours, consisting of a few united vegetative cells and a single
terminal reproductive cell, is only a simpler expression of the

same law which operates in the production of the forest-tree.
5

50 ELEMENTARY ORGANS OF PLANTS.

The extent of cell-development in forest-trees and flowering-
plants is alone different; the phenomena themselves are pre-
cisely analogous. In forest-trees and flowering-plants, the
vegetative cells, as they develop in countless millions, assume
distinct organic parts, as root, stem, and leaves, whilst the
reproductive cells are seen in the form of beautiful and highly
organized flowers. In the bread-mould, all such distinctions
vanish, and the organization of the parts is reduced to the
utmost degree of simplicity.

57. Let us pause for a few moments, and reflect on the sim-
plicity and beauty of these admirable productions of nature.
Think of the Liriodendron tulipifera, or tulip-tree, the pride
of the American forests. Its wide-spread and powerful roots,
its tall and massive stem, its glorious and far-extended canopy
of foliage and flowers—this is the result of centuries of assimi-
lation from inorganic matter, of the evolution of countless
myriads of cells. Now look at the little bread-mould, which
nature constructs from decaying organic matter. A few inter-
woven tubular filaments form the root, a single row of verti-
cal cells the stem, whilst a solitary terminal cell is the humble
representative of the flower. Here, then, we have the whole
of the vegetative and reproductive process, seen as it were in
miniature beneath the microscope, and brought within the
compass of a few short hours.

58. Yet, though nature has thus simplified her operations,
how little do we in reality know about them! We do not
know how the cells of the bread-mould originate, why they
develop in this particular form, and why, after a certain num-
ber of vegetative cells have been developed, a solitary termi-

DEVELOPMENT AND FUNCTIONS OF CELLS. ° 51

nal reproductive cell should make its appearance. Could we
but answer these simple questions, we could explain the form-
ation of vegetable out of mineral matter, the laws which
govern the evolution and special arrangement of cells into the
specific forms assumed by plants, and the mechanism of the
entire vegetable creation. But, although the subject of cell-
development has recently taxed the powers of the ablest
minds, it is still confessedly obscure. A more thorough
investigation of the simpler forms of vegetation seems to be
necessary to the understanding of this important subject.

59. It would seem, from the facts already brought to light,
that there are two methods of cell-multiplication by which
growth and reproduction are effected, which are but modifica-
tions of one and the same process of division: 1. The cell is
multiplied by the formation of a partition across its cavity by
which it is divided into two cells; one of these cells elongates,
and is again subdivided in a similar manner, the original wall
of the cell remaining. In this way, a single cell gives rise to
a row of connected cells, when the division takes place in one
direction, and to a plane or solid mass of cells, when it takes
place in two or more directions. This is the ordinary mode of
increase in all growing or vegetating parts. 2. The cell is
propagated by division of its interior cavity into two, four, ora
greater number of free new cells, the original cell-wall being
absorbed or perishing in the operation. By this method the
reproductive cells of pollen formed in the anthers of all flower-
ing plants, and the spores or reproductive cells of flowerless-

plants, originate.

PART II.

ON THE

COMPOUND ORGANS OF PLANTS.

THE CRYPTOGAMIA, OR FLOWERLESS PLANTS.

5*

PART II.

ON THE COMPOUND ORGANS OF PLANTS.—THE CRYPTO-
GAMIA, OR FLOWERLESS PLANTS.

CHAPTER IT.
CELLULARES, OR CELLULAR PLANTS.

60. Tum cells have now been separately considered, and the
student has been made acquainted with such facts respecting
their origin and anatomical peculiarities as are afforded by the
present state of science. We are now about to investigate the
phenomena of the cells in a state of combination, or when
united together into those masses of tissue which constitute
definite organs.

61. In the lower forms of vegetation, such as alge or sea-
weed, lichens, and mosses, the cells retain, to a great extent,
their primitive form, being but slightly altered by the com-
pression and growth of the parts. For this reason, these plants
have been called by botanists cellulares or cellular plants.

62. These cellular plants commence the vegetable series,
and are by far the most interesting in the vegetable kingdom.

56 COMPOUND ORGANS OF PLANTS.

In them we see organization brought, by successive degrees of
simplification, to the utmost degree of structural simplicity.
We have seen that all the different forms of tissue found. in
plants are only modifications of the cellular, all originating in
the simple cell as a point of departure; and in like manner,
when we look on the plants themselves individually, and fol-
low the operations of nature in detail, as seen in the lower
vegetation, it may be truly said that the same simple cell is
the starting-point of the plants themselves, considered ag indi-
viduals.

68. It is not necessary for cell-development to be carried to
any great extent in order to constitute the fabric of a true and
perfect plant. All the organs which constitute the most com-
plete vegetable concur in the exercise of one or the other of
two general functions, nutrition and reproduction, and we have
seen that these functions may be exercised by plants composed
of a single row of cells strung end to end, or may be confined
to one and the same cell, ag in the Protococcus and the various
species of leprarias or pulverulent lichens (51), which are
plants composed of a mass of free spherical utricles, or cells
filled with granulations of various colors.

64. It is at this point that the Vegetable makes the nearest
approach to the Animal kingdom, which also has for its start-
ing-point a single spherical utricle or cell, which differs only
from the vegetable cell in that it possesses the property of
motion. The two series, the animal and vegetable, there-
fore, commence in the same manner, and hence it is not in
plants which are the most perfect, but, on the contrary, in

CELLULARES, OR CELLULAR PLANTS. 57

those which are the most simple, that we meet with the near-
est analogies to the animal kingdom.

65. It is in the alge: that the vegetable makes the nearest
approach to the animal kingdom. It is amongst these plants
that we observe the curious phenomena of zoospores (fads liv-
ing, and omced, a spore), movable spores, which enjoy truly an
animal life at the moment when they are emitted from the
tube which contains them, and afterwards germinate and de-
velop into a vegetable, fixed and immovable. In Vaucheria
(51), Fig. 18, the production of spores takes place in a cell
situated at the extremities of the filaments, which becomes
swollen so as to acquire a clavate form, is densely filled with
granular matter, and finally bursts at the apex and discharges
the spore 6. The spores thus emitted are furnished with
vibratile appendages resembling cilize (cilium, an eyelash),
which enable them to swim about in the water; and in this
state they have been actually figured by Ehrenberg as animal-
culeo!! In the course of a few hours, however, after their
emission, the cilize are absorbed, the spontaneous movements
cease, they become attached to some immovable substance in

Fig. 23.

the current, and begin to germinate, elongating and under-
going division by septa in the usual manner. In Fig. 23, we

58 COMPOUND ORGANS OF PLANTS.

have represented, a, spore of Conferva glomerata ; b, Prolifera
rivularis; c, Vaucheria ungerii, after Thuret.

66. In plants composed of a cell or a single row of cells,
even at this stage of vegetation, a process of great physiologi-
cal importance is observed, the evident equivalent of bi-sexu-
ality in the higher orders. In Zygnema and other Confervas,
which consist of plants composed of rows of cells, the cells, at
a certain period, bud out laterally, and coming in contact with
similar buds on contiguous filaments, the septa become ab-
sorbed, a free communication is opened between the cells of
the two filaments, the contents of one cell then pass into the
other, and the result is the production of the germinating
spore. The common fresh-water plant, called the Hydro-
dicton utriculatum or water-net, is composed of filaments
which have united in this manner, and in this case with so
much geometrical regularity as to give the plant the appear-
ance of a green net, inclosing hexagonal and pentagonal spaces.
The process is termed conjugation. In Fig. 24, a, we have a

Fig. 24.

CELLULARES, OR CELLULAR PLANTS. 59

magnified view of an elongated plant-cell, the Closterium acu-
tum, after Ralfs. 6 shows two of these plants in a state of
conjugation, and the granular contents of one cell passing into

Fig. 25.

the other; c, the contents of the two cells in a more highly
condensed state ; d, the fully formed spore. In Fig. 25, we

Fig. 26.

60 COMPOUND ORGANS OF PLANTS.

have two filamentous plants of Zygnema, showing the differ-
ent stages in the process of conjugation, which are seen from
below upwards. Fig. 26 is a portion of the network of Hy-
drodicton utriculatum.

THE LICHENS.

67. Plants composed of a tissue of cells combined in one
plane.—In this case, the cell is multiplied, as before, by divi-
sion, which takes place in two or more directions, giving rise
to a plane or solid mass of cells, some of which are specialized
for nutrition, and some for reproduction, as already explained.
Only the simplest forms of these plants consist of a single
layer of cells. Most frondose sea-weeds, as well as lichens
and liverworts, are made up of several such layers.

68. The term frond, or, as it is called in the lichens, thal-
lus, is applied to those simple expansions of vegetable matter
which are neither leaf nor stem, but combine the appearance
and the office of both.

69. The thalli of lichens are composed wholly of cellular
tissue, and are either pulverulent, crustaceous, foliaceous, or
arborescent; these different forms depending, of course, on
the different ways in which the cells are developed and com-
bined together. Those portions of the thallus which contain
the sporules are called apothecia (from azo6qxn, a repository).
In the lowest forms of lichens, the pulverulent thallus over-
spreads the surface of rocks and the bark of trees, in the form
of an inert leprous crust, resembling on the rocks stains of
color. Sometimes the fructification is included within the

crust and depressed below its surface. The cortical layer or

CELLULARES, OR CELLULAR PLANTS. 61

outer bark of the lichen nearly covers the apothecia thus im-
mersed, and air and light are admitted only through a small
aperture called an ostiole (os, oris, a mouth). In other spe-
cies of pulverulent lichens, the fructification reaches the sur-
face, and is seen in the form of a dark convex nucleus of cells.
In the crustaceous and foliaceous lichens, the fructification
rests on the surface, or is situated on the margin of the’ thal-
lus in saucer-like bodies or shields, the cortical matter of the
thallus forming a border round the nucleus.

70. In the higher developments of lichens, the thallus
rises into a kind of axis, the cortical matter forming a pode-
tium or stalklike process containing the apothecia at its sum-
mit; or it assumes an arborescent appearance, as in Cladonia
rangeferina, the reindeer-moss, or in Usnea, the beard-moss,
which at first grows upright, but afterwards becomes pendu-
lous with age, and forms those long gray tufts of vegetable
matter which hang from the boughs of trees. In these
instances, the fructification is contained in little circular
shields at the extremities of the branches.

71. The annexed illustrations, from the Botanical Text-
Book of Dr. A. Gray, convey a very good idea of the organi-
zation of the different species of lichens. Fig. 27, 1, is a
stone covered with several species of pulverulent, crustaceous,
and foliaceous lichens. In the centre of this stone, we have
Sticta miniata, a lichen whose apothecia are immersed in
the substance of the thallus; 2 is a piece of its thallus
magnified, in which the ostioles and immersed apothecia are
seen more distinctly. On the right-hand margin of the stone,
we have crustaccous lichens, the fructification being visible on

6

62 COMPOUND ORGANS OF PLANTS.

their surface in the form of dark nuclei or spots; and on the

left-hand margin we have a foliaceous lichen, Parmelia con-

spersa, with its fructification in shields or cups, the cortical
matter of the thallus forming a rim or border round the
nucleus; 3 is a piece of the thallus of Parmelia conspersa
with a section through the apothecium; 4 is a magnified
section of an apothecium, showing the young asci or sacs
which contain the spores imbedded in the substance of the
apothecium; 5 is a representation of two of these asci or
sacs, with their contained spores and accompanying fila-
ments highly magnified; 6 shows the podetium or stalk-

CELLULARES, OR CELLULAR PLANTS. 63

like thallus of Cladonia coccinea, a beautiful lichen found on
the decaying stumps of old trees, and which bears its fructifi-
cation in rounded red masses at the summit of its podetium.

72. It not unfrequently happens that the reproductive
matter of lichens appears on the surface or margin of the
thallus in the form of irregularly-shaped powdered masses of
spores, soredia (sorws, a heap), which propagate either on the
original thallus, forming foliaceous or squamulous expansions,
or external to the original thallus, forming new individuals
of the species. ;

73. The thallus of lichens, when it exists under the form
of a membrane, is composed of three superposed beds or
layers of cellular tissue; the cortical layer, which is formed
of spherical utricles, containing interiorly granules of various
colors. These cells have received the name of Gonidia, and
constitute the soredia or masses of spores, which, when de-
tached from the plant, form new individuals of the species.
The medullary layer is situated immediately beneath the
cortical, and is composed of both rounded and filamentous
cells. The hypothallus or under surface of the lichens is
composed of cellules elongated and cylindrical, the analogues
of roots by means of which the plant attaches itself firmly to
the substance on which it grows.

74, The limits of the three great families of cellular
plants, the lichens, the fungi, and the algz, have not yet
been distinguished; and some naturalists, who have studied
these tribes with great attention, are of opinion that a spore
from any one of them will develop into a fungus, alga, or
lichen, according to the medium in which it happens to be

64 COMPOUND ORGANS OF PLANTS.

placed at the time that its vegetative powers are called into
action.

75. Algee have been considered by some to be lichens
growing in water, and in the Synopsis of the Lichenes, re-
cently published by Edward Tuckerman, A. M., of Boston,

“perennial, aerial alge’? It is true

lichens are defined to be
that the hard, dry, scaly, and almost indestructible thallus of
such species of lichens as grow on the surface of exposed
rocks, old fences, or the bark of trees, is very unlike the soft,
easily decomposed, and leaflike frond of the algee or sea-weed ;
nevertheless, when lichens grow in moist situations, they
approximate towards the alge in point of organization, and
in some cases, as in the genus Collema, it is difficult to fix
the group to which they belong. Certain it is that this tribe
of plants deserves the closest investigation of the physiologist.
In them we have the simplest expression of the laws of vege-
table life, and they are probably the best starting-point in the
study of the vegetable creation.

76. Hitherto, the plants investigated have been stemless,
leafless, and rootless, presenting to the eye the appearance of
powdery, filamentous, or flat foliaceous expansions of vegetable
matter, having the reproductive cells imbedded on the surface
or restricted to the extremities. These plants, which are
without any distinct root, stem, or foliage, have been called
collectively Thallophtes, because they consist of a thallus or
bed of vegetable matter; and the name is very appropriate,
for the greater part of these rootless, stemless, and leafless
vegetable bodies consist of a collection of cells commonly

aggregated so as to make up a stratum or bed of vegetation

CELLULARES, OR CELLULAR PLANTS. 65

more or less compact, and which is without any definite
figure. We are now about to enter on the examination of a
higher type of vegetation.

HEPATIC, OR LIVERWORTS.

77. Planis composed of a distinct axis and foliage, and
which develop into root, stem, and leaves.—This distinction of
parts is first visible in the higher forms of the Hepaticee or
liverworts. The thallus, or vegetative part of the lower forms
of these plants, is a lobed and continuous mass of green vege-
table matter lying on the ground, and emitting root hairs
from every part of its under surface; but in the higher forms
of the Hepaticee the vegetative part is distinctly foliaceous,
although the organization of their minute leaves is of the
simplest character, which resemble in some species a two-
ranked series of imbricated scales, with an imperfect or rudi-
mentary row of leaves (amphigastria) on the under side. In
both kinds of Hepaticee, the reproductive matter is no longer
imbedded in the thallus or vegetative part; on the contrary,
it is contained in special and distinct organs. A capillary
peduncle, the type of a true stem, rises above the surface of
the frondose, scalelike vegetation, bearing on its summit a
valvular brown case or capsule, which contains the repro-
ductive matter or sporules. This capsule is without an oper:
culum or lid, and in most of the genera without a columella,
dchiscing at its apex, and opening by four spreading valves.

78. Fig. 28 is an illustration of the workmanship which
nature exhibits in the formation of Jungermannia complanata,

a species which is common on the bark of trees in moist
6*

66 COMPOUND ORGANS OF PLANTS.

Fig. 28.

a. Jungermannia complanata in fruit, natural size. 0b. The fruit magnified,
showing the pericheetium or sheath, at the base, the peduncle rising from it, and the
capsule at its summit not yet burst. c. The capsule split at its apex, and discharging
its spores. d. The capsule empty, showing its four valves.

situations, and which may be found in fruit from January to
April.

79. The spores of these plants are often mixed with spiral
filaments called elaters. Spores are now generally regarded as
produced by the agency of certain bodies analogous to the
stamens and pistils of flowering-plants, called antheridia and
pistillidia. These organs have been demonstrated more or
less in all the orders of the Cryptogamia or flowerless plants.

80. In the hepaticee, or liverworts, the antheridia appear on
the fully developed plant. In the frondose species they are
imbedded in the substance of the frond or thallus, and in the
foliaceous species they are situated in the axils of the leaves.

MUSCI, OR MOSSES.

81. It is, however, in the mosses that the higher type of
vegetation is fully realized. In them we have plants possess-
ing a distinct axis and foliage; that is to say, a stem which
rises from the soil growing onward from its apex, and which
is symmetrically clothed with distinct leaves as it advances.

CELLULARES, OR CELLULAR PLANTS. 67

82. Few common objects are more interesting than mosses,
which require neither skill nor the assistance of instruments
for the detection of their beauties. The term moss is applied
not only to the true mosses, but also to many lichens. The
true mosses may, however, be always distinguished by their
green color, whilst the lichens are generally grayish in their
aspect, or of some other hue than green.

88. In the algee and lichens there are no fixed forms as-
sumed by these plants; they are also, generally, without any
local habitat. Some of the lichens vegetate indifferently
anywhere, on rocks, or the bark of trees, or on the ground,
and vegetate in all climates, and at all seasons of the year.
These plants certainly exhibit a low degree of life as well as
simplicity of organization. They are amongst the slowest
in growth of all plants, and the least subject to alteration
from decay. Whilst alive, they scarcely exhibit any change
through’a long series of years; and, when dead, their forms
and colors are scarcely altered by being dried.

84. But we are ascending the scale; and now commences
the unfolding of a more elaborate erganization, in which the
conditions of development are necessarily more restricted,
and a higher degree of life is manifested. The plants now
about to be described grow only in certain soils, at certain
seasons of the year, and are peculiar to certain climates,
whilst they retain the same specific form from age to age.

85. Mosses generally affect a cool, moist, shady situation,
and appear to be for the most part developed under the in-
fluence of humidity, accompanied with a low degree of tem-
perature. Hence they prefer the shade of woods and rocks

68 COMPOUND ORGANS OF PLANTS.

facing the north, and are most abundant in the temperate
regions of the earth. In tropical climates, they are found
chiefly on the summit of mountains, where the heat and dry-
ness of the climate are moderated by the elevation of the
land. In summer, they are seldom seen, except in moist,
shady spots, such as grow in tufts on the tops of walls, or the
surface of exposed rocks, being burnt up, or as it were dried
to dust, so that they escape our notice. Yet even at this
season, a shower of rain will revive them and cause them to
burst forth into verdure. But their beauty is evanescent;
and they soon wither and disappear from the wall or rock on
which they were seen. In autumn, as the temperature de-
clines, the mosses make their appearance, and in winter
they are found in perfection, beautifying this desolate season
of the year.

86. The mosses are plants having a distinct stem or axis
of growth, around which their minute leaves are arranged with
the greatest regularity and beauty. These leaves, and, in
fact, the whole plant, assume a regular specific form, being,
as to their margin, entire, serrate, or denticulate, with con-
densed cells in their centre, which form a sort of midrib or
nerve. Occasionally, however, the leaves are nerveless, as
in Hypnum purum, a British species.

87. Sometimes the stem is procumbent, or creeps along the
ground; the branches fork and spread, emitting rootlets from
every part of their under surface, which doubtless perform
their part in absorption; and the capsules or fruit come out
laterally, or from the side of the branches. In other species,

the stem takes an ascending direction, the rootlets are con-

CELLULARES, OR CELLULAR PLANTS. 69

fined to the lower extremities of the axis of growth, and the
fructification is terminal, or comes out at the summit of the
branches. Such mosses are evidently the higher represent-
atives of the family. This is well seen in the genus Cli-
macium dendroides, which has an arborescent growth, and
presents the appearance of a beautiful tree in miniature.

88. Such mosses as have lateral fruit are called Pleuro-
carpi (waevpa side, and xapmdg fruit); those in which the fruit is
terminal are called Acrocarpi (ox*pa summit, and xapzés fruit).

89. If we carefully examine a moss in fructification, we
shall soon see a number of urn-shaped bodies, sporangia
(onopa a spore, and dyyos a vessel), supported on capillary
peduncles, which rise from amidst the foliage. Surrounding
the base of the peduncle, a number of leaves will be perceived
somewhat different in exterior configuration from the rest,
which serve as a kind of calyx, inclosing the fructification
in the earlier stages of its growth, and which are called the
pericheetial leaves (wept around, and zoven a bristle).

90. The sporangia are at first covered by a membranaceous
body called a calyptra (xaava¢pa, a covering), and enveloped
in the perichetial leaves in the axilla or summit of the
branches. When first elevated above the perichetial leaves,
nothing is apparent but a number of stiff bristle-like pro-
cesses, each rising from its own perichzth. From this, how-
ever, we must except Dicranum undulatum, which has several
setee originating in the same pericheth, and the fruit of which
appears in clusters. The young fruit of mosses is called, for
this reason, setae (seta, a bristle). As the seta of mosses

elongate, the reproductive cells at their summit begin to

70 COMPOUND ORGANS OF PLANTS.

swell and the sporangia to form. By the expansion of the
sporangium, the calyptra which incloses it is separated, or
rather torn from its base, and carried upwards on the apex of
the sporangium. If, when this happens, the calyptra is torn
away equally on all sides from the base of the sporangium,
so as to hang over it vertically, the calyptra is said to be
mitriform, or mitre-shaped. If, on the contrary, the rupture
takes place unequally, by the adhesion of part of the mem-
branaceous matter of the calyptra to the base of the sporan-
gium, the sporangium, in swelling, necessarily splits up the
calyptra on one side, so that when the adhesion is overcome
the calyptra is ultimately carried up, and has an angular in-
clination to the surface of the sporangium; in. this case, the
calyptra is said to be cuculliform (cucudlum, a hood). When
the calyptra has fallen, the sporangium is seen to be inclosed
by an operculum or lid, which assumes different shapes in
different species, being convex, conical, or rostrate (rostrum,
a beak). As fructification ‘advances, the operculum or lid
falls, and the peristome (wep: around, coxa mouth) or mouth
of the sporangium is revealed, which, in some species, presents
to the eye the appearance of a beautiful fringe, the organiza-
tion of which can only be distinguished by the microscope.

91. As an illustration of the parts already described, Fig.
29 is given, which is taken from Dr. Gray’s Botanical Teat-
Book.

92. When the peristome of different species of mosses is
examined, it is found to consist in some of an inner and
outer peristome, which is, in fact, a peculiar organic modifi-

cation of the inner and outer membrane of the sporangium.

CELLULARES, OR CELLULAR PLANTS. 71

Fig. 29.

«, Bryum cuspidatum in fruit, natural size. b. The cuculliform calyptra detached
from the sporangium. ¢. Magnified sporangium, from which the operculum or lid
(@) has been removed to show the peristome or mouth of the sporangium. e. A por-
tion of the inner and outer peristome highly magnified. f. Physcomitrium pyriforme
in fruit, showing the mitriform calyptra, g. The calyptra detached from the spo-
rangium (h). 7. The operculum or lid removed from the sporangium, showing it to
be destitute of a peristome.

The outer peristome usually exhibits a number of broad,
short, lanceolate processes called teeth, and the inner is
developed into long filamentous cilia (ciléwm, an eyelash).
Sometimes there is only one peristome or fringe, or the
membrane, instead of being developed into teeth or cilic,
may stretch across the mouth of the sporangium and close
it altogether, as in the genus Atrichium; or, perhaps,
neither of the membranes is developed, and the sporangium

is without a peristome, as in the genus Physcomitrium.

2 COMPOUND ORGANS OF PLANTS.

93. The teeth of mosses are a- beautiful object beneath
the microscope, and follow a regular geometrical law in their
numerical relations, being either four, or multiples of that
simple number, 8, 16, 32, or 64; and from their absence, and
differences in their number and degree of cohesion when
present, the generic character of mosses is wholly taken.

94. The teeth of mosses are exceedingly hygrometrical, or
easily affected by moisture. When the sun shines bright
and warm, and the atmosphere is dry, the mosses on ten
thousand rocks and hills expand and spread abroad their
teeth, which may be seen then at right angles to the mouth
of their sporangia; the sunlight pours down into the spo-
rangia, and the young spores speedily ripen under its influence.
But when clouds shade the sun, and the air becomes sur-
charged with moisture, the teeth of the peristome imme-
diately curve over the mouth of the sporangium, fitting
together in the most beautiful manner, and effectually closing
it, so that not one particle of moisture can enter the spo-
rangia to injure the young spores. This beautiful mechanism
may be seen in operation on the top of almost any stone wall,
or on the surface of rocks, in the winter months, by those
who will only search for it.

95. However philosophers may attempt to explain these
movements on mechanical principles, and it is probable that,
with the progress of science, all vital phenomena will be
ultimately resolved into physical laws, yet have we not in
these phenomena the first faint foreshadowings, as it were, of
the powers of a higher vitality? Is there not manifest a
shrinking away of the young life of mosses from what would

CELLULARES, OR CELLULAR PLANTS. 73

injure it, and do not mosses modify their organs to protect
themselves? Let us look at the evident design of these
movements. Surely the life thus manifested is only part of
the system of life which pervades all organic matter, the same
in kind, but inferior only in degree.

96. The pedicel or stalk of the sporangium, continued
through the middle of the sporangium, forms a central cellu-
lar axis or support called the columella, around which the
spores are agglomerated ; enlarged under the sporangium, it
forms an apophysis (dzopvecs, excrescence).

97. The antheridia of mosses are produced like the cap-
sules in the midst of little rosettes of leaves, which differ
from those of the stem in appearance; they are minute,
cylindrical, clavate, cellular sacs, which discharge from their
apex a mucilaginous fluid containing numerous cellules, in
each of which a spiral phytozoon (ovroy a plant, and @Sov an
animal) is seen. These exhibit active movements in water,
at certain periods of their existence, similar to the zoospores
of the algee!! Here again the vegetable appears to approach
the animal kingdom. Whilst the highest classes of animals
and plants are widely separated from each other, the lowest
members of each kingdom approximate so closely that it is
impossible to draw a line of demarcation between them.

98. The antheridium-bearing plants of Polytrichium, or
the common hair-cap moss, are very conspicuous, and are
selected as most suitable for the purpose of illustration. In
Fig. 30, at a, we have represented the antheridium-bearing
plant of the Polytrichium. It will be seen that the leaves

at the apex are different in form from those on the side of the
7

74 COMPOUND ORGANS OF PLANTS.

stem; this difference is owing to the peculiar functions
assigned them. They surround the antheridia or male organs

of the plant, which are the analogues of stamen, together
with certain cellular filamentous bodies called paraphyses
(xaegcovors, an offset), which are considered to be abortive
antheridia. Fig. 31 is a magnified view of an antheridium
a, which is composed of quadrangular cells c, each of which

CELLULARES, OR CELLULAR PLANTS. 75

Fig. 31.

contains a phytozoon. Surrounding the perfect antheridium,
there are abortive filaments or paraphyses p.

CHAPTER ITI.
VASCULARES, OR VASCULAR FLOWERLESS PLANTS.

99. Every plant germinating from the spore or seed has a
tendency to develop in three directions, upwards, downwards,
and horizontally, according to the nature of the tissues of which
it is composed. The fibrous and vascular system is developed
vertically, in an ascending and descending direction, except-
ing in the case of the leaves, where it takes a horizontal
spread; the cellular system, on the contrary, is developed for
the most part horizontally. In the lower tribes of crypto-
gamic plants, the structure is wholly cellular, and the plants,
therefore, are wholly stemless and leafless, the greater part
of them consisting of flat expansions of vegetation, spreading
centrifugally in one plane, increasing by additions of cellular
matter to their periphery or circumference, so as to form
a thallus, or bed of vegetable matter; hence these plants have
been called Thallophytes (602205 a frond, and @vrov a plant).

100. In the higher tribes of cryptogamic plants, the fibrous
and vascular tissues enter into the composition of their structure,
and these plants necessarily develop vertically as well as horizon-
tally. These two systems of tissue, I mean the vascular and
fibrous vertical system and the horizontal cellular system,
cross each other at right angles, become interwoven with each

other, and form a common axis of vegetation or stem. Part

VASCULAR FLOWERLESS PLANTS. 77

of the vascular and fibrous tissues of the stem take an
ascending direction, and associated with the horizontal cellular
tissues forms the branches and leaves; the other part take a
descending direction, and contribute to the formation of the
roots and fibres in the soil.

101. It is true that in the mosses we have the higher type
of vegetation fully realized. We have an ascending axis or
stem clothed with symmetrically arranged leaves, and a
descending axis or root, in these humble plants, although
their structure is wholly cellular. It is not surprising, how-
ever, that in this instance the cellular system should take a
vertical development, since we have shown that the vascular
and fibrous vertical system is only a modification of the cell-
ular. The cells of the sphagnums or bog-mosses contain
spiral fibre, and woody fibre seems to be faintly foreshadowed
in those elongated cells which form the nerves of the leaves
of many mosses. Mosses, owing to their cellular structure,
seldom rise more than a few inches above the ground. Not
so with the

LYCOPODIACEZ, OR CLUB-MOSSES.

102. In these plants we have a most decided advance in
organic development. In their general appearance, they
resemble mosses to which they are closely allied, although
they are much larger; for, owing to the strength imparted by
the bundles of woody fibre running lengthwise through their
stem, they are enabled to rise to a greater elevation above the

ground, some of them growing two or three feet high.
7q*

78

COMPOUND ORGANS OF PLANTS.

Fig. 32.

Lycopodium clavatum. a. Scale of a spike with a capsule (magnified).

103. The genus Lycopodium (Fig. 32), which forms the
type of this little family, appears to occupy an intermediate
position between the Ferns and the Mosses, and in some
respects seems to be allied to the Coniferee.

104. It is in these plants that vascular tissue first makes
its appearance in the form of woody and annular vessels,
which form a bundle in the centre of the stem, and which is
encompassed with cellular tissue; from this vascular central
axis smaller bundles of woody tissue communicate with the
imbricated subulated leaves, which have an epidermis pierced
with true stomates, and are disposed spirally about the stem.

105. The roots are still of a secondary character, that is,

VASCULAR FLOWERLESS PLANTS. 79

they spring from all parts of the stem in contact with. the
earth, and are not confined to one of its extremities.

106. The reproductive capsules are situated in the axils of
the metamorphosed leaves of the stem, which form long,
yellow, clavate spikes in Lycopodium clavatum; whilst, in
other species, as in Lycopodium lucidulum, these leaves
retain their usual green color and appearance, being appa-
rently unaffected physiologically, by being in the immediate
neighborhood of the fruit.

107. These plants abound in warm, moist, insular climates,
and are especially interesting as being allied especially to the
fossil plants called Lepidodendrons. The Lepidodendrons are
very abundant in most English coal-mines, where some have
been found nearly entire from their roots to their upper
branches, one specimen being forty feet high and thirteen
feet in circumference. These fossil plants are called Lepi-
dodendrons, or scaly trees, because their cylindrical stems are
covered with marks left by the fallen leaves. In their struc-
ture, they accord with the Lycopodiums; they are, in. fact,
gigantic club-mosses.

108. The Lycopodium squamatum, of Brazil, exhibits a
very interesting case of locomotive power. This plant, when
deprived of water during the dry season, unroots itself from
the ground, rolls itself into a ball, and becoming withered,
and apparently devoid of life, is driven hither and thither by
the wind, until it reaches a moist situation, when it speedily
unrolls itself, sends down its roots into the soil, and spreads
out its leaves, which from a dingy brown speedily change to
the bright green hue of active vegetation.

80 COMPOUND ORGANS OF PLANTS.

FILICES, OR FERNS.

109. The Ferns are the most highly developed of the Cryp-
togamia, or flowerless plants. The higher representatives of
the family possess roots, conspicuous stems and leaves, whilst
almost every kind of vascular tissue enters into their compo-
sition.

110. We give the name of frond (frons, a bough) to the
foliaceous appendages of the stem of ferns, because they
appear more analogous to branches enlarged into leaves (as
for example to the foliaceous and flattened branches of Phyl-
lanthus amongst flowering-plants), than to leaves, properly
speaking.

111. The lower representatives of the family of ferns are
found in Europe and in all temperate climates, and are deve-
loped as perennial, herbaceous plants, from a rhizome or pros-
trate stem, which either creeps horizontally along the ground,
or burrows beneath its surface the fronds which it produces,
annually perishing, without producing an elevated trunk.
These herbaceous ferns seldom rise more than three or four
feet above the ground. They prefer moist, shady situations,
and are found overhanging the margin of streams and rivulets,
or springing from the crevices of rocks which they cover and
adorn with their bright green feathery fronds.

112. A considerable degree of heat as well as humidity ap-
pears to be requisite to the complete development of ferns.
Beneath the warm bright sun of the tropics, they attain the
noblest arborescent forms. The united and persistent basis
of the decayed and fallen fronds forms an aerial stem, which

VASCULAR FLOWERLESS PLANTS. 81

sometimes attains an altitude of from 50 to 60 feet above the
earth’s surface, crowned at its summit by a magnificent bou-

quet of gigantic fronds finely and clegantly divided. Fig. 83

Fig. 33.

82 COMPOUND ORGANS OF PLANTS.

represents the Alsophila armata, a tree-fern of Brazil.* As the
lower fronds decay and drop off, the young upper fronds gra-
dually unroll and become pendent, and in this manner con-
tinual additions are made to the height of the stem, and the
growing point is carried upwards, the stem increasing in alti-
tude, but not in diameter.

113. It is for this reason that these plants are called Acro-
gens (dxpos a summit, and yévydew to produce) or summit-
growers, because they increase by additions of cellular and
vascular matter to their extremities, and have no provisions
for any subsequent increase in diameter.

114. Ferns, in their infancy, resemble the adult liverworts,
having a green, flat, pro-embryo like the thallus of the frondose
liverworts. This pro-embryo or pro-thallus afterwards gives
rise to the proper stem and frond of the fern. In Fig. 34, s is

Fig. 84.

the spore ofa fern, the Pteris longifolia, sprouting and giving off
a rootlike process 7, and a flat cellular expansion p, called the
pro-thallus or pro-embryo. It is on this expansion that the
antheridia and pistillidia occur, and the former having fulfilled

* Richard’s ‘Précis de Botanique,” pt. i., Paris, 1852.

VASCULAR FLOWERLESS PLANTS. 83

their function, the latter develop into the frond. These bodies
are, therefore, only found on these plants whilst in a young
and nascent state; in the mosses, on the contrary, antheridia
and pistillidia are found on the fully developed plant.

115. The fronds of the different species of ferns are circi-
nate, or rolled up from the apex to the base in the bud, in a
beautiful spiral. This disposition of the plant is analogous
to that of the Droseracese and Cycadaceze amongst flowering-
plants. Ophioglossum vulgare is, however, an exception, as the
fronds are straight, and never rolled up or circinate in the bud.

116. The young unrolled fronds are copiously covered with
membranaceous, chaffy scales, but, as the heat and light of the
sun increase, the scales fall off, and the fronds gradually un-
roll, until at length their entire surface is spread abroad in
the atmosphere.

117. After the vegetative functions of the plant have been
exercised for a certain length of time, and the frond has ac-
quired its maximum growth, certain parenchymatous cells
situated along the margin or on the under surface of the
frond begin to manifest their reproductive functions. These
cells develop into regular organized bodies called thecxe (Gexy,
a repository), which contain the spores or reproductive mat-
ter. The thece invariably spring in clusters from the nerves
or veins of the frond. The spores are ordinarily very small,
and are free in the interior of the thece at every epoch of
their development.

118. The clusters of thecee are called, botanically, sort (sorus,
a heap), presenting to the naked eye the appearance of circu-
lar or oblong masses, or heaps of powder. This pulverulent

84 COMPOUND ORGANS OF PLANTS.

appearance only shows itself in the more advanced stages
of development, the thecze being at first concealed by the
cuticle, which they raise up like a blister, and ultimately rup-
ture and detach from the parenchyma of the frond in a variety
of ways, which serve as characteristics of the genera. It is
necessary, however, to except Polypodium vulgare, or the
common polypody, the thecse of which are formed above the
cuticle.

119. The cuticle which is thus ruptured from the frond ig
called the indusium. Generic and specific characters de-
pending on the peculiarities of its form, and the nature of its
rupture from the parenchyma of the frond, can only be detect-
ed in early spring. Later in the season, the indusium withers
away, and the sori or heaps of thecee are alone visible.

120. In Fig. 35,* at a, we have represented two of the pin-

ne of Polypodium thelypteris covered with sori, having an
indusium; is a magnified view of one of these sori, show-
ing the clusters of annulate thecse and the partially withered

* Richard’s “ Précis de Botanique,” pt. ii, Paris, 1852.

VASCULAR FLOWERLESS PLANTS. 85

indusium 7; ¢ one of the thece taken from the cluster, and
more highly magnified. It consists of a flattened bag of cellu-
lar tissue, which is partially surrounded by an elastic ring of
cells, annulus, having a special structure. The walls of the
cells of the annulus are much thicker than the walls of the cells
which they surround; and, as the annulus has a continual
tendency to straighten itself, when the theca becomes dry and
the spores matured, it is suddenly torn open by the elastic
straightening of the annulus, as shown at d, and the spores e,
contained in its cavity, scattered. This beautiful contrivance
of nature may be seen in operation in the ripened sori situated
on the back of any dorsiferous fern.

121. The thece attached to the frond beneath the indu-
sium appear to produce all the peculiarities of its rupture, by
their different modes of development. In Polystichum acrosti-
choides, the marginal thecee of each sorus are the first to de-
velop, and the indusium ig thus ruptured from the paren-
chyma and the epidermis, all round the margin, whilst it
remains attached to the frond by its centre. In Woodsia, on
the contrary, the central theese of the sori are the first to de-
velop and effect a corresponding rupture in the cuticle, for
the indusium is ruptured at its centre and forms a sort of
cup-shaped involucre around the thece, being continuous with
the epidermis of the frond at the margin. Sometimes the in-
dusium is a mere fold of the margin of the frond, as in Pteris
and Adiantum.

122. We stated that the thecee or spore-cases of ferns were
developed from the parenchyma of the frond. In some genera,
the sori, or clusters of thecee, are developed at the expense of

8

86 COMPOUND ORGANS OF PLANTS.

the parenchyma, the whole of which disappears, leaving no-
thing but the naked nerves all covered with sori. A striking
instance of this kind is not uncommon in bogs in the form of
a plant called the Osmunda spectabilis, or flowering-fern. The
lower pinne of this fern present the usual leaf-like appear-
ance, whilst the upper are entirely changed into sori.

123. The morphological changes of the frond into sori are
well seen in Osmunda Claytonia. Some two to five pairs of
the middle pinne of the frond of this fern are usually meta-
morphosed into sori. An occasional specimen may be found
bearing pinnz, in which the metamorphosis has been only
partially effected, the pinnee being partly parenchymatous and
partly soriferous. In such specimens, nature herself teaches
us her own process.

124. When the sori are moderately dispersed over the un-
der surface of the frond; or, when developed in great num-
bers, if they are confined to its under surface; or, when only
a part of the frond is metamorphosed into sori, then the same
frond can still continue to exercise the functions of vegetation
as well as of reproduction; but this ceases to be the case when
the whole frond is metamorphosed into sori. Other fronds
are then developed from the same rhizome to carry on the
vegetative functions, which are barren and without sori, as
we see exemplified in the barren and fertile fronds of Osmund
cinnamomea, and Onoclea sensibilis.

\EQUISETACES, OR JOINTED FERNS.
125. This family of plants is remarkably different from all
the other Cryptogamia. It differs from the rhizomatous ferns
in the structure of its stem and that of its reproductive

VASCULAR FLOWERLESS PLANTS. 87

organs, and in sending up erect branches instead of leaves
from the rhizoma. Dr. Lindley has placed this family near
the Coniferze, in the class Gymnosperme, on account of the
analogy subsisting between their reproductive organs and
those of the coniferee; but they are so totally different from
the coniferze in every other respect that this classification is
somewhat objectionable, and has not been generally adopted,
so that they still retain that place which Linnzeus assigned
them amongst cryptogamous plants.

126. The stems of these plants are cylindrical, simple, or
branched, as in Equisetum sylvaticum (Fig. 36), striated
longitudinally, tubular, and articulated; the cavity of the
stem being closed at the articulations or joints, which are
readily separable and surrounded by a membranaceous-toothed
sheath s. The stems are, in this respect, somewhat analogous
in organization to those of the grasses which are solid at the
nodes (nodus, a knot), or joints, and tubular between the
internodes; but they are without leaves, as we are unable to
consider as such the membranaceous sheaths which surround
their nodes n, or articulations above the verticillate branches;
for the branchés should be developed between the sheath and
the stem, if the sheath were a circle of abortive and united
leaves, whereas the sheath is, in reality, situated in the axilla
of the branches, and appears to be only the termination of the
external portion of the stem, the continuity of which is
broken by the formation of the nodes or articulations. The
whorls of branches at the nodes are jointed, striated, and
tubular, being solid and sheathed at the joints, like the stem
from which they spring.

88 COMPOUND ORGANS OF PLANTS.

127. The organs of fructification consist of an ovate or
more or less elongated spike composed of thick peltate, pe-
dicellate, polygonal scales, very similar to those of the male
flowers of the Taxus baccata, or common yew-tree, each scale
having several thecze or sporangia attached to its lower sur-
face longitudinally dehiscent, and discharging a multitude of
little bodies termed spores, each of which is embraced by four
hygrometrical clavate filaments called elaters, by which the
mechanical dispersion of the spore is effected. In Fig. 36

we have represented the summit of the stem of Equisetum
sylvaticum (Dr. Gray’s Botanical Text-Book); e shows the
cone of fructification; m is a magnified view of part of this
cone, exhibiting the peltate polygonal fructification. One of

VASCULAR FLOWERLESS PLANTS. 89

these organs is more highly magnified at p, and exhibited so
as to show the attachment of the thecse to its lower surface ;
z, a separate theca, still more magnified; 7 and v are the
spores, with the clavate filaments, which are shown rolled in a
‘spiral around the spore 7, and spread out from the spore v.

128. Struck by the analogy of form which exists between
the reproductive organs of the Equisetacece and the stamens
of some Coniferee, Linnzeus named these clavate filaments
stamens, without indicating those which he regarded as pistils.
Hedwig, on the contrary, considered these bodies as herma-
phrodite flowers, the globular part being the pistil and the
filaments the stamens, the pollen being situated on their ex-
terior surface. But these filaments are certainly analogous
to the elaters of Jungermannia. These spores are first
formed in the interior of the cells, the walls of which, in
place of being absorbed, remain attached to the spores in the
form of elaters.

129. When moist, these filaments are twisted spirally
around the central spore; but, when dry, they unroll and
expand elastically, thus moving the spore along with them in
various directions. Ifa spike of the Equisetum, when ripe, be
shaken over white paper, the spores will appear like brown
powder on its surface; and if we gently breathe on them, and
examine them at the same time with a magnifier, they will
be seen crawling about the paper like so many little spiders.
This circumstance arises from the hygrometric property of
the elaters which are affixed to the spores and possess this
property in order to effect their dissemination,

130. All the species of Equisetacese are, with us, perennial
8*

90 COMPOUND ORGANS OF PLANTS.

herbaceous plants, growing in moist places, with stems about
half an inch in diameter and two feet high, which is increased
to a maximum of twelve feet in equinoctial marshes, and are
remarkable for the quantity of silex which enters into their
composition. The equisetum is well known under the name
of horse-tail.

131. The cellular Cryptogamia are seldom met with in a
fossilized condition. One or two instances are mentioned of
mosses being found fossil in the upper and tertiary deposits
only; but there is a general paucity of plants of this cha-
racter, whilst on the other hand there is a decided preponder-
ance of ferns and of the higher orders of the cryptogamia.

132. Fossil Equisetaceze abound in the coal-measures and in
strata far more ancient; indeed, they appear to belong to the
earliest terrestrial flora of which any traces remain. Some of
them attained an enormous size, being from one to three feet
in diameter, and from thirty to forty feet high. In most in-
stances when these plants are found, their stems are pressed
flat, but specimens have been met with in a vertical position,
and retaining their cylindrical character.

133. Fossil Ferns seldom exhibit any traces of fructification,
and are chiefly distinguished by the shape and forked venation
of their fronds. About one hundred and fifty species of fossil
ferns have been detected in the carboniferous strata in Eng-
land alone. The originals of many of these species were un-
doubtedly arborescent. Fossil fern-stems are rarely found,
yet a few have been discovered bearing all those characteristic
marks by which the tropical arborescent fern-stems are dis-

tinguished. Cicatrices, or scars, are left by the fallen fronds

VASCULAR FLOWERLESS PLANTS. 91

on the stem of tree-ferns, and these cicatrices are very con-
spicuous in the fossil fern-stems, and form a valuable and ac-
curate indication of their true character.

134, Certain conditions necessarily produce certain phe-
nomena. This philosophical axiom is especially applicable to
the phenomena of vegetation. Certain plants require certain
conditions of temperature, air, light, and moisture, in order to
insure their development from the gpore or seed. But these
fossil arborescent ferns and Hquisetacese, although analogous
in their growth to the existing arborescent species in tropical
countries, are altogether specifically different. They have had
their final development, and are now extinct. The earth, once
their home, is now their sepulchre. Hence it is evident that
the conditions under which they were developed exist no
longer; and when, along with these extinct plants, we find the
remains of animals equally low in the scale of organization, and
which have no living representatives in the zoology of any
country, we have indubitable evidence of a system of organic
change, which has been probably contemporaneous with the
changes which have undoubtedly taken place in inorganic
nature.

135. The history of the earth has been written by the
Author of nature in characters the most striking and impres-
sive, in its strata, which have been justly termed the “leaves
of the stone book.”’ But these characters can only be inter-
preted by a careful and accurate study of the living creation,
and the existing laws which govern inorganic matter. Not
only every world in space, but every atom in the universe,
moves according to fixed and unchanging laws, and the inte-

92 COMPOUND ORGANS OF PLANTS.

resting facts revealed by geologists prove that the mutable
and perpetually changing system of wonders by which we are
surrounded is under the control of a sublime and mysterious
Providence.

136. We have seen that every plant which consists of
more than one cell or of a series of cells, which are permanently
united together, may be divided into two distinct parts, to
which the functions of nutrition and reproduction are respect-
ively assigned (54). In like manner, all the organs which
compose the structure of the most highly organized vegeta-
tion concur in the exercise of either one or other of these
functions. In the compound organs of plants, we have addi-
tional complexity of structure, but no essential change of
plan. The same distinction may be made of them into
organs of vegetation and reproduction.

137. In the lower orders of the cryptogamia or flowerless
plants, the organic parts which concur in the exercise of these
functions are reduced to the utmost degree of structural
simplicity, being at first confined to a single cell, as exempli-
fied in the Protococcus, and certain confervoid plants (51),
in which the union of the plant-cells is but temporary. But,
as we advance in the scale of vegetable organization, we find
these plant-cells remaining permanently united to each other,
and developing into filamentous or foliaceous expansions, and
finally into distinct organic parts, designated as root, stem,
and leaves: so also the reproductive matter is at first confined
to the same vegetative cell, then concentrated in certain special-
ized cells as in the bread-mould, and finally contained in regular

VASCULAR FLOWERLESS PLANTS. 93

organs named apothecia in the lichens, wrns or capsules in the
mosses, and thecee in the ferns.

138. The recent discovery, within the last few years, of
antheridia or organized bodies, analogous to the stamens or
male sexual organs in the flowering-plants, in the different
tribes of the Cryptogamia, proves that these organized
receptacles of the spores are produced by a similar process of
fecundation, and hence they have been very properly termed
pistillidia. Like the pistils or female organs of flowering-
plants, they contain within their cavities fecundated germs or
spores, which have equally the power as well as the highly
elaborated seed of developing themselves into new cells, con-
formably to the arrangement of the cells of the plants in
which they originated, and thus of continuing the same vege-
table form in the earth.

139. This discovery of the analogues of sexual organs in the
cryptogamia (yevrros concealed, and yduos union or mar-
riage) renders the term, as formerly understood, inapplicable
to the present state of science. There is now no longer
any doubt as to the existence of these organs. The only
difference between the antheridia and pistillidia of Crypto-
gamous plants or flowerless plants, and the stamens and
pistils of the Phanerogamous (paveecs conspicuous, and yapos
union or marriage), or flowering-plants, is in the degree of
their development, the stamens and pistils of flowers being
antheridia and pistillidia in a more highly developed condi-
tion, and the same remark applies to the seeds or embryos

which are contained in the cavity of the germen; these are

94 COMPOUND ORGANS OF PLANTS.

probably only spores which have arrived at a higher degree of
development.

140. We have seen how beautifully nature has simplified
the laws of vegetation and reproduction, in the lower tribes of
the Cryptogamia or flowerless plants; these plants afford us
the best facilities for investigating questions of anatomical
structure, and showing us what is really essential to vegeta-
tion and reproduction. At some future time, we may call
attention to the manner in which the’same laws are expressed
in the higher series of the Phenogamous or flowering-plants,
as the beauty and simplicity of these laws will be more readily
appreciated and understood, and can only be fully revealed by
the study of the manifold varieties of form assumed by the
vegetative and nutritive organs of plants, in the completed

type of vegetation.