FLOWERING PLANTS (_continued_).
THE FLORAL AXIS—INFLORESCENCE—FRUIT—SEED—NUTRITION OF PLANTS—ABSORPTION
OF CONSTITUENTS.
There are certain arrangements and mutual relations of the various
portions of the flowers which we have mentioned that it is useful
to consider. The _floral axis_ refers to the position of the
verticils, and _inflorescence_ signifies the arrangement of the
flowers on the stem. Flowers which possess both stamens and pistil
are _hermaphrodite_; those with only stamens are male; those with the
pistil female flowers. If both organs be absent the flower is neutral.
Plants bearing flowers in clusters form several distinct groups, to
which appropriate terms are applied indicative of their respective form
of flora arrangement.
[Illustration: Fig. 777.—(1) Spike. (2) Catkin. (3) Spadix. (4) Cone.]
In the examination of this kind of inflorescence (_indefinite_ or
_axillary inflorescence_), the first object of remark is the general
or primary peduncle, termed _rachis_, and which bears numerous
leaflets called _bracteoles_ or _bractlets_, from whose axils arise the
_pedicellate_ or _sessile_ flowers. The lower bracts often produce no
flower-buds in their axils, and form instead a whorl surrounding the
heads of flowers on the primary axis, and which is called _involucre_
(as in the sun-flower, for instance).
[Illustration: Fig. 778.—Raceme.]
[Illustration: Fig. 779.—Panicle.]
[Illustration: Fig. 780.—Corymb.]
The different varieties of axillary inflorescence are determined
principally by the elongation or depression of the axis, the presence
or absence of stalks to the flowers, and the form and nature of the
bracts. We distinguish—
[Illustration: Fig. 781.—Umbel.]
[Illustration: Fig. 782.—Capitulum or ball.]
1. (1) The _spike_ (fig. 777). In this form of inflorescence, sessile
or short-stalked flowers are arranged along the rachis in the axils
of the bracts; the spike is said to be _compound_ when small spikes
or _spikelets_ arise again from the bracts of the secondary axis. (2)
The _catkin_ or _amentum_ (fig. 777 [2]); a spike, usually pendulous,
which falls off, rachis and all, by an articulation, as in the willow
or hazel. 3. The _spadix_, a thick fleshy spike (fig. 777 [3]);
examples, _arum_ and _calamus_. 4. The _cone_, a fruit-bearing spike,
covered with scales (fig. 777 [4]); examples, the _coniferæ_. 5. The
_raceme_ or _cluster_, a spike with the flowers on longer pedicels
(fig. 778); examples, the _currant_. 6. The _panicle_, a branching
raceme (fig. 779, _Yucca gloriosa_). 7. The _thyrsus_, a dense panicle,
with longer peduncles in the middle than at the extremities; example,
_lilac_. 8. The _corymb_, a raceme, in which the lower flower stalks
are elongated and raised to nearly a level with the upper (fig.
780)—example, _cerasus mahaleb_. 9. The _compound_ or _branching
corymb_, a corymb in which the secondary axis again sub-divides;
example, _Pyrus terminalis_. 10. The _umbel_: in this form the primary
axis is greatly depressed, and the peduncles arise from a common point,
and spread out like radii of nearly equal length, a whorl of bracts
(_involucre_) surrounding the common base. In the _compound umbel_
(fig. 781), _Daucus carota_, the secondary axis ends in small umbels
surrounded by bracts, which is termed an involucel. This is observable
in the umbelliferous plants—carrot, parsley, hemlock, etc.
[Illustration: Fig. 783.—Inflorescence.]
A very peculiar kind of inflorescence, which characterises the great
family of the _compositæ_, is illustrated by fig. 783. We see here the
enlarged floral axis or receptacle, _a_, surrounded by several whorls
or bracts, _b b_, which constitute a general involucre; the membranous
bracts, (_paleæ_), _b´ b´_, seen in the receptacle, bear in their axils
the sessile florets, _c_ and _d_, which either have a calyx, _e e_, or
not. The florets on the receptacle are either all of them _tubular_
(_d_) or _ligulate_ (tongue or strap-shaped); florets (_c_) are
associated with the tubular ones. The receptacle is not always flat,
but frequently presents a convex, globular, conical, concave, etc.,
shape.
In the absence of _paleæ_ the receptacle is said to be naked. The
florets at the margin, or circumference, are termed _marginal flowers_,
or _flowers of the ray_; the florets in the disc (_centre_), _central
flowers_, or _flowers of the disc_.
Some plants bear male and female flowers on the same stem. These are
termed _monæcious_ plants. The oak is an instance. The diæcious plants
are those which bear stamens and pistil, or separately, on different
plants, like willows. We will now glance at the functions of the
stamens and pistil. The ovule has been mentioned as a tiny body in the
ovary, and it consists of a nucleus, and cellular tissue surround it,
leaving a small hole called the _micropyle_, into which the pollen tube
enters after passing through the ovary. As in the animal creation, the
unions of different families succeed best; no close relationship will
fertilize so well as with other flowers.
Fertilization is accomplished in two ways; (1) by the action of the
wind, by which the pollen is carried away to other plants; and (2) by
means of insects—the bee particularly. These flowers have distinctive
qualities relatively. In the case of the pine the pollen is powdery; so
those plants which are thus fertilized are the diæcious species, which
include the poplar, the oak, and the birch, as well as the pines. These
are all wind-carried pollen plants. The nettle is illustrated here with
male and female flowers.
[Illustration: Fig. 784.—Male flower of nettle.]
Plants fertilized by insects are visited by them, and they carry away
upon their heads, or bodies, the pollen, which is then thrust into the
stigma by the insect; or perhaps birds may carry the pollen in the same
way after sipping the nectar, and thus playing an unconscious, but most
important, part in the economy of nature.
[Illustration: Fig. 785.—Female flower of nettle.]
We always find the _ovule_ at the termination of an axis; it is unable
to form a seed alone. The pollen grains must fertilize it, and in
consequence many ovules come to nought. The ovule is produced in the
pistil, which, as before stated consists essentially of two parts—the
_ovary_ and the _stigma_; the latter secretes a fluid to hold the
pollen. We annex the representation of a highly-magnified pistil
(vertical section, fig. 786_a_). The pollen grains are indicated by
_d_, attached to stigma, _c_, projecting through the style, _b_, into
the ovary, _a_, and passing through the ovules.
[Illustration: Fig. 786.—Erect ovule.]
With the transmission of the pollen to the ovary of the pistil, the
functions of the anther and stigma terminate; accordingly these parts
of the flower rapidly wither and decay after fertilization. The
filaments, the style, and the petals speedily participate in the decay,
but the sepals remain sometimes persistent in an altered form. The
ovary and its contents alone proceed in their further development, and
undergo material changes, in which, however, the bracts and the calyx
often participate.
The fully developed and matured ovule, the _seed_, is, of course,
regarded as the _essential_ part of the fruit; the enlarged ovary
forms the _pericarp_, enclosing the seed. The form of the pericarp
determines the external appearance of the denomination of the fruit.
The structure of the fruit, and the arrangement of its parts depends in
a great measure upon the number and position of the carpellary leaves
in the pistil, and the manner and extent of their union, and the extent
to which their edges are folded inwards.
[Illustration: Fig. 787.—Dorstenia.]
[Illustration: Fig. 788.—Dandelion.]
[Illustration: Fig. 789.—Apple.]
[Illustration: Fig. 790.—Follicles of larkspur.]
[Illustration: Fig. 791.—Sycamore fig.]
The carpellary leaves occupy the summit of the floral axis. The axis
terminates either in one single carpel, in which case the ovary is
one-celled, or _unilocular_; or the axis is surrounded by several
carpels, in which case the manner of their union determines the number
of cells in the ovary.
THE FRUIT.
[Illustration: Fig. 792.—Sycamore fig.]
[Illustration: Fig. 793.—Fruit of a composite.]
[Illustration: Fig. 794.—Section of a berry.]
The carpels are the chief agents in the formation of the fruit, and
they form the endocarp (core), and sometimes the whole pericarp, or
seed-vessel. Upon the nature of the various parts and the changes they
undergo during the ripening of the seeds the nature of the fruit
depends. The fruits are classified, some being the produce of a single
carpel, others of several united carpels.
[Illustration: Fig. 795.—Umbelliferous plant and its fruit.]
Fruit, in botany, is by no means limited to the juicy products of
trees or plants which are so refreshing in the summer weather, and so
acceptable in any form. In plant life the herb yielding seed produces
a fruit equally with the orange or the apple. The fruit is the outcome
of the varied processes of the plant. We may trace the plant from
its tiny, sometimes very minute seed, through stem to flower and
seed again. “In the final struggle, even when life is hopeless, and
starvation, in consequence of drought, is imminent—when all is hopeless
and barren, the plant will make an effort to produce its fruit and
flower.” This is a very touching and interesting fact in nature—this
last attempt to beautify the earth and to propagate its species for the
use of man.
[Illustration: Fig. 796.—Three-celled capsule.]
[Illustration: Fig. 797.—Poppy.]
Fruit, then, is not limited to the market and the stall.
This statement scarcely needs proof; but if we consider for a
moment the number of “wild” fruits—the parents, probably, of our
table-fruits—we find many we cannot eat. In short, out of the hundred
thousand plants which bear flowers scarce one two-hundredth part serve
us as producers of edible fruits.
[Illustration: Fig. 798.—Three-celled capsule.]
[Illustration: Fig. 799.—Water melon.]
The fruit is the result of the flower, and if any objection be made
by readers on the part of the common fig, it will be found that this
appreciated fruit really consists of male and female flowers that are
fertilized by the action of minute insects, which enter and depart
(sometimes they die, and are found dead and black in the figs). No
blossom is perceived on the tree, because within the green sac the
so-called “seeds” (really the fruits) are developing. A fig is a sac
full of fruits.
The _legume_ or pod is formed of a single carpel bearing seeds. We
annex illustrations of the pod. The covering is called the _pericarp_,
and the parts when opened separate into valves. Dehiscent fruits
shed their seeds, indehiscent fruits do not; they lie within the
seed-vessel, like the acorns and nuts. These are dry fruits, but there
are others of a soft nature, such as apples or gooseberries.
[Illustration: Fig. 800.—Legume.]
[Illustration: Fig. 801.—Legume opened.]
[Illustration: Fig. 802.—Legume (pea).]
[Illustration: Fig. 803.—Gland (acorn).]
[Illustration: Fig. 804.—Stobule (hop).]
[Illustration: Fig. 805.—Drupe (plum).]
[Illustration: Fig. 806.—Berry (currant).]
Fruits are variously named, and underneath will be found a list. We
have the aggregate, like the mulberry, etc.; the dehiscent fruit of
one carpel like the pea, etc.; the simple fruits as cherry, nettle,
wheat, etc. The dandelion fruit is often a precious object in
children’s estimation, as it is blown away to ascertain the time. There
are indehiscent fruits with many carpels,—the common buttercup, for
instance, and the strawberry. A list is added.
_a._ FRUITS WHICH ARE THE PRODUCE OF A SOLITARY CARPEL.
1. The _gymnospermous_ fruit, where the seed lies naked in the axils of
the ligneous bracts, as in the cone of the fir and spruce tribe.
2. The _legume_ or pod, which is formed of a solitary carpel bearing
seeds on the ventral suture. It characterises the pea and bean tribe
(_leguminosæ_).
3. The _follicle_ is a mature carpel containing several seeds, and
opening by the ventral suture. There are usually several follicles
aggregated together; examples, larkspur, monkshood, evergreen.
_b._ FRUITS WHICH ARE THE PRODUCE OF SEVERAL CARPELS UNITED.
4. The _capsule_ consists of two or more carpels, either simply
laterally united (one-celled or unilocular capsule), or folded inwards
towards the axis, but without reaching it (spuriously multilocular
capsule), or uniting with the axis (bilocular, trilocular, multilocular
capsule). Examples of capsular fruit—mignonette, balsam, violet, poppy,
etc.
5. The _siliqua_ or long pod is formed of two carpels, and
longitudinally divided into two parts by a spurious dissepiment called
the _replum_; examples—cabbages, stock, wallflower, etc. The _silicula_
is a broad and short pod; examples—Iberis, shepherd’s-purse, etc.
6. The _cariopse_ (_caryopsis_, having the appearance of a nut), is
a monospermous or one-seeded fruit, with an indehiscent membranous
pericarp, closely investing the seed or incorporated with it;
examples—rye, wheat, and other grains.
[Illustration: Fig. 807.—Capsule (poppy).]
[Illustration: Fig. 808.—Siliqua (shepherd’s purse, wallflower).]
[Illustration: Fig. 809.—Caryopsis (wheat).]
7. The _achænium_ is a dry, monospermous, indehiscent fruit with one
seed; examples—cashew, ranunculus, strawberry, etc.
8. The _nut_ or glans is a one-celled, indehiscent fruit, with
a hardened coriaceous or ligneous pericarp; examples—hazel-nut,
acorn, etc. The _nucula_, or little nut, is a cariopse, with a solid
coriaceous pericarp; examples—buckwheat hemp, etc.
[Illustration: Fig. 810.—Nut (hazel-nut).]
9. The _berry_ (_bacca_) is a pulpy, succulent fruit, with soft rind;
examples—the gooseberry and the currant. The _pepo_ or peponida
(pumpkin), illustrated by the fruit of the gourd and melon, and the
_hesperidium_, illustrated by the fruit of the orange and lemon, are
modifications of the berry.
[Illustration: Fig. 811.—Strawberry.]
10. The _drupe_ (_drupæ_, unripe olives); the mesocarp is generally
pulpy and succulent, the endocarp hard; examples—the cherry, the peach,
the plum, etc.
11. The _pome_ (_pomum_, or apple); the outer parts of the pericarp
form a thick cellular, eatable mass; the endocarp (core) is scaly or
horny, and encloses the seeds within separate cells; examples—the
apple, pear, etc.
Fruits consisting of the floral envelopes and the ovaries of several
flowers united into one, are termed multiple or anthocarpous; the
_sorosis_ (cluster-fruit: example—the pine-apple, the breadfruit, the
mulberry), the _sycosis_ (fig-fruit), and the _strobilus_ (fir-cone),
form varieties of the anthocarpous or multiple fruit.
NON-FLOWERING PLANTS.
The cryptogamia or acrogens is the botanical term for these plants, of
which we must be very brief in our description,—not that the subject
is not worthy of a much larger space than we can devote to it, but our
pages are not elastic.
There are numbers of plants without pistils or stamens properly so
called. They are hidden from human observation—buried out of sight;
and in the fern, moss, and other primitive plants they are thus
hidden. There are several families of the cryptogamia, but two main
sections include them all—viz., the cormogens and thallogens. These are
sometimes known as cormophytes and thallophytes, but the former will
be our terms, and they include the ferns, algæ, lichens, and mosses,
with many other families, which we do not propose to examine in this
summary sketch. The microscope will here be a great aid if not always
absolutely necessary for any close investigation.
[Illustration: Fig. 812.—Liverwort.]
[Illustration: Fig. 813.—Hypnum.]
We are all familiar with the appearance of ferns, and we may commence
with a few observations concerning them. They are an extensive family
and very beautiful, some of the tropical species being particularly
noticeable for elegance. We are here mostly concerned with the
development of the plant. The polypod ferns fructify under the leaves
or “fronds,” which open from a ball. The seed-cases or _sorri_ are
situated at the back of the fronds in brown spots, and when examined
they will be found to be collections of capsules like tiny cases.
There is a kind of band at the upper part which at the proper time is
extended, and tearing open the capsule releases the seeds. These seeds
or “spores” are very minute, and not properly seeds but buds, every one
of which can generate seeds. So if we try to grasp in imagination the
generating powers of a few fern fronds, we shall miserably fail in the
attempt.
[Illustration: Fig. 814.—Horsetail.]
[Illustration: Fig. 815.—Bryum.]
Some ferns have the “spores” upon the summit of the frond. The osmundas
belong to this family, and are known to all as the “flowering fern,” a
contradiction palpable enough under the circumstances. The beautiful
dust upon some ferns has been mistaken for “spores” by many people,
but it is merely a natural ornament of the plant. The venation and
vernation of ferns are very curious, but in the determination of ferns
the only sure way is to consider the _sorri_ and the venation. The
differences that puzzle may be little or great, but when the sorri have
been examined all doubts will be set aside.
There are about three thousand varieties of ferns known, and we give
a few illustrations of them, although any detailed description is out
of the question, for we have to mention the beautiful mosses of which
there are in Britain more than five hundred different species, all
extremely beautiful, perfectly innocuous, and even beneficial.
THE MOSSES AND ALGÆ.
These plants are extremely lowly in the score of creation, and also in
stature. Very few mosses attain any elevation, only the “sporangia”
shoot up, and the plants are very delicately formed, the leaves being
all of the same pattern. They are common in damp situations, and thrive
in woods, streams, and banks. The _Fontinalis_ is a river moss, while
the _Hypnum_ is found in hedges. The Lycopodiaceæ or the club-moss
family is intermediate between ferns and mosses. They are found in
warm, moist climates, and contain a sort of brimstone. They grow well
with ferns under glass.
[Illustration: Fig. 816.—Diatoma vulgaris.]
[Illustration: Fig. 817.—Club-moss.]
The _Musci_ or moss-family proper are useful in various ways. We have
also the _liverworts_, which bear some resemblance to lichens. They
grow between stones near water, or in damp situations. There are
two distinct families, both beautiful when examined, and are named
Marchantiaceæ, and Jungeramanniaceæ, or scale moss.
[Illustration: Fig. 818.—Scale-moss.]
[Illustration: Fig. 819.—Various diatomaceæ.]
The _Thallogens_ or Thallogenæ include algæ, lichens, and fungi,
which are the lowest of the plants, and all very much alike. The algæ
are termed “protophytes,” and consist of living cells propagating by
subdivision, or union. The thallogens have therefore no distinct axes,
leaves, or stomata.
The algæ are thus simply cellular plants found in salt or fresh water,
hot and cold. They sometimes appear as “slime.” Some contain silicia,
and are termed _Diatomaceæ_, and these propagate by subdivision,
and when they die their shelly covering remains, and we find the
shells or cases in all earthy formations. These diatomaceæ have been
raised from the beds of oceans, and Atlantic soundings have revealed
their presence,—as mud, when examined, proves to be these remains
of vegetable shells. Thus the infinitely little in the animal and
vegetable worlds meet at the bottom of the sea, as well as on dry land.
There are marine and fresh-water algæ—the former familiar to us as
seaweeds which possess air-bladders that children love to explode,
and which assist the algæ to float. They attach themselves to rocks,
generally at the base; the lovely colours of seaweeds are well known.
They will be recognized under the name of “tangle” (fucus), which, when
burned, gives kelp and barilla, which is full of iodide and sodium.
The Sargasso Sea is composed of miles of algæ which live in the open
ocean. The _Carrageen_ or Irish moss is very nutritious and useful in
consumptive cases. Indeed, all algæ, if not absolutely useful, are
certainly not deleterious. The “bladder-wrack” was formerly useful for
the production of soda.
“The life-history of one of these uni-cellular plants in its most
simple form, can scarcely be better exemplified than in the _Palmogeœa
macrococca_, one of those humble forms of vegetation which spreads
itself as a green slime over damp stones, walls, etc. When this slime
is examined with a microscope, it is found to consist of a multitude
of green cells, each surrounded by a gelatinous envelope; the cell
which does not seem to have any distinct membranous wall is filled with
granular particles of a green colour, and a ‘nucleus’ may sometimes be
distinguished through the midst of these. When treated with tincture
of iodine, however, the green contents of the cell are turned to a
brownish hue, and a dark-brown nucleus is distinctly shown. Other cells
are seen, which are considerably elongated, some of them beginning to
present a sort of hour-glass contraction across the middle; in these
is commencing that curious _multiplication by duplicative subdivision_
which is the mode in which increase nearly always takes place
throughout the vegetable kingdom.”[37]
[Illustration: Fig. 820.—Bladder wrack.]
[Illustration: Fig. 821.—Lichen.]
LICHENS are numerous, and may be found upon the bark of trees in dry
forms of grey and yellow growth, and on walls and old stones in our
graveyards. On the hills we find them growing upon the granite, and it
would appear that they prefer stone to any other holding ground. The
Arctic lichens form the principal food of the useful reindeer, and
“Iceland moss” is represented as wholesome for man. Lichen is derived
from the Greek term for “wart.”
The FUNGI are very important, and with them we will close our summary.
They include the favourite mushrooms and poisonous toad-stools, with
many other “fungous growths,” from the “mould” on the jam pot to the
mushroom.
Some of these fungi are peculiar to the substances upon which they
exist, and are in numerous instances destructive. The microscopic
fungus _Puccinea graminis_ is the parasite which fixes itself to corn,
and produces the disease known as mildew, and the _Uredo segetum_
(another microscopic fungus) causes the “smut”; the “bunt” is caused
by the _Uredo fœtida_, and the “spur” or “ergot,” which attacks rye,
is caused by the _Acinula clavis_. These fungi completely destroy the
grain of corn in which they form, and propagate in the most rapid
manner; the ergot is moreover a dangerous poison to those who eat the
bread made of rye infected by it. The truffle is a kind of underground
fungus, and is esteemed a dainty. Mushrooms are also fungi, and several
species are sufficiently wholesome; these are the field mushroom and
the fairy-ring mushroom.
[Illustration: Fig. 822.—_a_ _a_, Mould from an old bone; _b_, Mould
from jam.]
Any organic substance will shortly become covered with this “mould” or
mildew. The air is so full of the germs of animal and vegetable life
that, as it penetrates everywhere, the smallest supply must contain
some germs; and these, under a powerful microscope, present most
beautiful forms and colours. We annex (fig. 822) some of these forms
highly magnified. They are deposited by the air, and the substance
into which they happen to fall determines the kind of life which is to
inhabit it. A few of these spores only come to maturity.
We again take the liberty to quote Dr. Carpenter on this subject. He
says:—
“There are scarcely any microscopic objects more beautiful than some
of those forms of mould or mildew which are so commonly found growing
upon the surface of jams and preserves, especially when they are viewed
with a low magnifying power and by reflected light; for they present
themselves as a forest of stems and branches of extremely varied and
elegant forms, loaded with fruit of singular delicacy of conformation,
all glistening brightly on a dark ground.
“The universality of the appearance of these simple forms of fungi
upon all spots favourable to their development, has given rise to the
belief that they are spontaneously produced by decaying substances,
but there is no occasion for this mode of accounting for it, since the
extraordinary means adopted by nature for the production and diffusion
of the germs of these plants adequately suffices to explain the facts
of the case.
“The number of sporules which any one fungus may develop is almost
incalculable; a single individual of the “puff-ball” tribe has been
computed to send forth no fewer than ten millions. And their minuteness
is such that they are scattered through the air in the finest possible
dust, so that it is difficult to conceive of a place from which they
should be excluded.”
[Illustration: Fig. 823.—Eatable mushroom (_Agaricus campestris_).]
[Illustration: Fig. 824.—Seeds with pappi.]
Pure water exposed to the air does not afford nourishment to the germs
which fall into it, till a sufficient number of them shall have been
deposited to form a food for those which come after them; but if we
mix with the water any soluble vegetable or animal matter, in a short
time the microscope will detect the growth of the germs that are being
deposited, for where nourishment is, there only can they be developed.
These germs are capable of existing for an indefinite period, either
floating in the water, or blown about by the air, and have been
detected hundreds of miles from land; the rigging and sails of ships
far away from shore are often covered with what sailors suppose to be
sand blown from the land, but which are organic substances, either
vegetable or animal. According to Humboldt, the Red Sea has derived its
name from the fact that at certain seasons the surface of the water has
a reddish appearance, and this (as he says) he was fortunate enough
to observe, which colour he found to be due to myriads of red fungi,
which had formed on the surface. The seeds of some plants are furnished
with minute wings or plumes, which cause them to be borne on the air or
floated on the water (fig. 824), to fertilise some barren spot, perhaps
a coral reef, which has at length reached the surface of the water,
and which ascends no higher, for the little creatures which built it
are aquatic, and cannot live exposed to the air; this coral reef now
becomes a receptacle for seaweed and fungi, which float on the surface
of the ocean are washed on to the reef, die, decay, and leave behind
a thin layer of mould, which process being repeated again and again,
forms an elevated edge to the reef, enclosing a lake, or “lagoon” as it
is called, the waters of which evaporate, and the space is filled up
in the same way as the edge was formed, together with the excrements
of birds, etc., forming layer after layer of mould, and the surface
becomes fit for the growth of larger seeds, as the cocoa-nut, banana,
etc., which are drifted on to it by the waves; in this way a coral reef
becomes an island fit to be inhabited by man and other animals.
It is impossible for any person not accustomed to observe the manner
of the propagation of the fungi, to understand a written description,
for the fructification of these plants are very varied in the manner of
the development of the spores. They are not generally hurtful, but much
caution should be observed in the matter of the mushroom, which may
be distinguished by the pale pink and black of the under part. There
are many poisonous fungi, but the greater number are harmless, though
they are not intended for food. They simply clear away the decaying
growths, and act as safety-valves to Nature by carrying away what is
not required, to give it to the air again to be renewed into life.
The vegetable kingdom forms the link between the minerals and the
animals. The vegetable derives food and nourishment from water,
carbonic acid, and ammonia, which are, as we already know, made up
of certain elements, and thus supply us all with food. They give out
oxygen for the use of animals, and are thus, in another sense, the
source of life. The growth of a plant is very interesting, and we may
conclude by following it.
The seed is sown, and the cells of the “cellular tissue” become
developed, passing some upwards, some downwards, to form a radicle
or plumule, as explained. The latter carries up the cotyledon, which
begins to decompose carbonic acid from the atmosphere, and fixing the
carbon as woody fibre. The leaves are then formed and more fibres, and
so on for every leaf; thus the number of woody fibres which form the
trunk of a tree is in proportion to the number of leaves which that
tree has borne, from which we come to the conclusion that the size of
the trunk of a tree is the sum of all its branches. While all this is
going on, the cellular tissue of the downward part or radicle also
becomes developed and divides out into roots, on the surface and at the
extremities of which are minute cellular bodies called “spongioles”
(from their power of absorbing moisture), which take up the fluid of
the earth which surrounds them; this moisture ascends through the
vessels of the plant till it arrives at the surface of the leaves,
where it is exposed to the action of light and sunshine. The ascent of
the moisture of the earth was first correctly explained by Du Trochet,
and is owing to a peculiar power which he discovered, and which is
called “Endosmose”; this consists in the tendency which a fluid has to
penetrate a membrane on the other side of which is a fluid of greater
density than itself. This may be seen by the following experiment:
obtain a piece of glass tubing about a foot long, having the end blown
out into the form of a bell, as in fig. 825, tie a piece of bladder
over the expanded end and fill it partly with syrup or gum-water, so
that this shall rise in the stalk about an inch; place this in a glass
of water with the bladder downwards, and the fluid will be seen slowly
to rise in the stalk, so that in perhaps an hour it will rise to the
top. This apparatus resembles one of the spongioles at the extremity of
the fibre of a root.
[Illustration: Fig. 825.—Endosmose.]
The rain falling through the air carries with it a certain amount of
carbonic acid and ammonia, which the air always contains, and it is
the whole source of the nitrogen which forms a very important part
of the bodies of plants and animals. When the rain arrives at the
surface of the earth, it sinks down into it and carries with it all
soluble vegetable or animal matter which it meets with, together with
any soluble earthy matter which may exist in the soil; this forms
the sap of the tree. When it arrives at the surface of the leaf, the
watery part of it combines with the carbonic acid of the air (through
the influence of light), and appropriating its carbon, gives out the
oxygen; this is the true respiration of plants, and is exactly the
reverse of what takes place during the respiration of animals, in which
case oxygen is absorbed and carbonic acid given off. The carbon thus
retained by the plant combines with the elements of the water to form
the solid green substance called chlorophyl, which is the basis of
all the tissues of the plant; the ammonia is also decomposed, and its
nitrogen combining with the oxygen and hydrogen of the water, and the
carbon of the carbonic acid forms those compounds which constitute the
most nourishing parts of vegetables, such as albumen, gluten, etc.,
and of which all the animal tissues are built up, for the production
of these organic substances takes place in the vegetable only, animals
simply appropriating them for their food. The sap which reaches the
leaf is not all converted into chlorophyl, but also into those peculiar
juices which are found in plants, some of which contain sugar, some
gum, others (as the pine tribe) turpentine, and in the laurel tribe
camphor, all of which are substances containing much carbon; moreover
the solid wood and bark are deposited from these juices as they descend
from the leaf after having been acted on by light (or the actinic power
associated with it). Now, as the water, ammonia, and carbonic acid
which descend with the rain are from the air, and as the vegetable
is formed wholly by their absorption, it may be fairly said that the
vegetable kingdom (and therefore the animal) feeds upon the air, and
that the trees do not grow out of the earth, but into it.
CLASSIFICATION OF PLANTS.
For the groundwork of the system of classification which universally
obtains at present, we are indebted to Linnæus, a Swede, born in
1707. In his classification of plants, Linnæus followed two different
methods. In the one, he based his division of plants in classes and
orders, upon certain peculiarities in the floral organs. This system,
being thus founded on characters taken from certain parts of the plant
only, without reference to others, and having something artificial in
it, has for that reason been termed the _artificial_ system, but it is
now more generally known as the _Linnæan_ system. In the other method,
he arranged the plants according to certain general resemblances and
affinities, in natural orders or families. This system, which is known
as the _natural_ system, has subsequently been much improved.
We use the term _species_, to designate a number of individual plants,
which, in all essential and unvarying characters, resemble each other
more closely than they do any other plant; the term _genus_ or _kind_,
to designate an assemblage of nearly allied species, agreeing with one
another in general structure and appearance more closely than they do
with any other species. Here, too, it must be obvious, that while all
parts of the plant may furnish _specific_ characters, the character of
the _genera_ are taken exclusively from the parts of fructification.
In the name of a plant both the genus and the species are given. The
name designating the genus is called the _generic_ name of the plant,
the one designating the species, the _specific_ or _trivial_ name.
Thus, for instance, we have the genus _Viola_, which includes the
species _Viola odorata_, sweet violet; _Viola canina_, dog violet;
_Viola tricolor_, heart’s-ease.
It is necessary to give the Latin names of plants, as the common name
differs, not only in different countries, but even in different parts
of the same country.
An assemblage or group of allied genera, agreeing in their general
characters, though differing in their special conformation, is called
an _order_ or _family_ of plants.
The sunflower, the daisy, the aster, and the dahlia, are, for example,
plants of different genera, but which, all of them, belong to the same
order or family.
All plants are divided into three primary classes—viz., _Dicotyledons_,
_Monocotyledons_, and _Acotyledons_, as has been stated already.
A proper degree of familiarity with the systematic classification of
plants is of the very highest importance to the student. A successful
pursuit of this branch of the botanical science presupposes a thorough
knowledge of the structure and physiology of plants, and requires,
moreover, the aid of attentive observation, and also some diligence in
collecting and arranging plants.
THE ARTIFICIAL OR LINNÆAN SYSTEM OF CLASSIFICATION.
In this system plants are divided into twenty-four classes;
twenty-three of these contain the _Dicotyledons_ and _Monocotyledons_
indiscriminately; the twenty-fourth class contains the _Acotyledons_.
The first twenty-three classes are founded on the number, position,
relative lengths, and connection of the stamens. The twenty-fourth
comprises the plants with inconspicuous flowers. Every class is
subdivided again into several orders. This division depends, in the
first thirteen classes, on the number of the styles; in classes XIV.
and XV. on the nature of the fruit; in classes XVI. to XVIII. and
XX. to XXII. on the number of stamens; in classes XIX. and XXIII. on
the perfection of the flower. In class XXIV. the orders are formed
according to natural affinities.
TABULAR VIEW OF THE LINNÆAN SYSTEM OF CLASSIFICATION.
A.—FLOWERS PRESENT (_Phanerogamia_).
I. Stamens and pistil in every flower (hermaphrodite).
1. Stamens free.
_a._ Stamens of equal length, or not differing in definite proportions.
Number of Stamens.
1 Class 1. Monandria.
2 ” 2. Diandria.
3 ” 3. Triandria.
4 ” 4. Tetrandria.
5 ” 5. Pentandria.
6 ” 6. Hexandria.
7 ” 7. Heptandria.
8 ” 8. Octandria.
9 ” 9. Enneandria.
10 ” 10. Decandria.
11-19 ” 11. Dodecandria.
20 or} inserted on calyx ” 12. Icosandria.
more } ” receptacle ” 13. Polyandria.
_b._ Stamens of different lengths,
two long and two short ” 14. Didynamia.
four long and two short ” 15. Tetradynamia
2. Stamens united by filaments in one bundle ” 16. Monadelphia.
” ” in two bundles ” 17. Diadelphia.
” ” in more than two bundles ” 18. Polyadelphia.
” by anthers (compound flowers) ” 19. Syngenesia.
” with pistil on a column ” 20. Gynandria.
II. Stamens and pistil in different flowers (unisexual) on the
same plant ” 21. Monœcia.
on different plants ” 22. Diœcia.
III. Stamens and pistil in the same or in different flowers, on the
same or on different plants ” 23. Polygamia.
B.—FLOWERS ABSENT ” 24. Cryptogamia
TABULAR VIEW OF CLASSES AND ORDERS.
---------------------+---------------------------------+--------------
Classes. | Orders. | Examples.
---------------------+---------------------------------+--------------
| |
I.—MONANDRIA | Monogynia one style | Hippuris.
One stamen. | Digynia two styles | Callitriche.
| |
II.—DIANDRIA | Monogynia one style | Syringa.
Two stamens. | Digynia two styles | Anthoxanthum.
| Trigynia three do. |
| |
III.—TRIANDRIA | Monogynia one style | Iris.
Three stamens. | Digynia two styles | Hordeum.
| Trigynia three do. | Holosteum.
| |
IV.—TETRANDRIA | Monogynia one style | Scabiosa.
Four stamens. | Digynia two styles | Gentiana.
| Trigynia three do. |
| |
V.—PENTANDRIA | Monogynia one style | Borago.
Five stamens. | Digynia two styles | Fœniculum.
| Trigynia three do. | Sambucus.
| Tetragynia four do. | Parnassia.
| Pentagynia five do. | Linum.
| Polygynia six and more do. | Myosurus.
| |
VI.—HEXANDRIA | Monogynia one style | Lilium.
Six stamens. | Digynia two styles | Oxyria.
| Trigynia three do. | Rumex.
| Tetragynia four do. | Alisma.
| Polygynia many do. |
| |
VII.—HEPTANDRIA | Monogynia one style | Trientalis.
Seven stamens. | Digynia two styles |
| Trigynia three do. |
| Heptagynia seven do. |
| |
VIII.—OCTANDRIA | Monogynia one style | Daphne.
Eight stamens. | Digynia two styles | Chrysosplenium.
| Trigynia three do. | Polygonum.
| Tetragynia four do. | Paris.
| |
IX.—ENNEANDRIA | Monogynia one style |
Nine stamens. | Trigynia three styles |
| Hexagynia six do. | Butomus.
| |
X.—DECANDRIA | Monogynia one style | Pyrola.
Ten stamens. | Digynia two styles | Dianthus.
| Trigynia three do. | Silene.
| Pentagynia five do. | Lychnis.
| Decagynia ten do. |
| |
XI.—DODECANDRIA | Monogynia one style | Lythrum.
Twelve to nineteen | Digynia two styles | Agrimonia.
stamens. | Trigynia three do. | Reseda.
| Pentagynia five do. |
| Dodecagynia twelve do. | Sempervivum.
| |
XII.—ICOSANDRIA | Monogynia one style | Prunus.
Twenty or more | Digynia two styles | Cratægus.
stamens inserted | Trigynia three do. | Sorbus.
on the calyx. | Pentagynia five do. |
| Polygynia many do. | Rosa.
| |
XIII.—POLYANDRIA | Monogynia one style | Papaver.
Many stamens | Digynia two styles | Pæonia.
inserted on the | Trigynia three do. | Aconitum.
receptacle. | Tetragynia four do. |
| Pentagynia five do. | Nigella.
| Hexagynia six do. |
| Polygynia many do. | Ranunculus.
| |
XIV.—DIDYNAMIA | Gymnospermia four naked seeds | Lavandula.
Two long and two | Angiospermia seeds in capsules | Linaria.
short stamens. | |
Labiate and | |
Personate Flowers. | |
| |
XV.—TETRADYNAMIA | Siliculosa broad and short pod | Capsella.
Four long and two | (silicula), and |
short stamens. | style |
Cruciferous | Siliquosa long pod (siliqua); | Brassica.
Flowers. | stigma sessile |
| |
XVI.—MONADELPHIA | Pentandria five stamens | Erodium.
Stamens united in | Enneandria nine do. |
one bundle. | Decandria ten do. | Geranium.
| Dodecandria 11-19 do. | Malva.
| Polyandria many do. |
| |
XVII.—DIADELPHIA | Pentandria five stamens |
Stamens united in | (two above and three below.) |
two bundles (one | Hexandria six stamens | Fumaria.
generally | (three right, three left, or |
containing nine | three above and three below.) |
enclosed in a | Octandria eight stamens | Polygala.
tube, and one | (four above and four below, |
free). | all united at the base.) |
Papilionaceæ. | Decandria ten stamens | Pisum, Trifolium
| (one above and nine below, | Genista.
| united in a cleft tube |
| surrounding the ovary.) |
| |
XVIII.—POLYADELPHIA | Pentandria five bundles |
Stamens united in | (each bundle bearing five |
more than two | anthers = 25 stamens.) |
bundles. | Dodecandria twelve stamens |
| (each bundle bearing three |
| anthers = 36 stamens.) |
| Icosandria many stamens in | Citrus.
| bundles, inserted on the calyx |
| (20 stamens in bundles bearing |
| an unequal number of anthers.) |
| Polyandria many stamens in | Hypericum.
| three, five, and nine bundles, |
| inserted on the receptacle. |
| |
XIX.—SYNGENESIA | Polygamia æqualia, florets all | Lactuca.
Five stamens, | hermaphrodite. |
filaments free, | Polygamia superflua, florets of | Aster.
anthers united, | the disc hermaphrodite, those |
flower | of the ray pistilliferous and |
monopetalous, | fertile. |
florets united on | Polygamia frustranea, florets | Helianthus.
a disc. Compositæ. | of the disc hermaphrodite, |
In the first four | those of the ray neutral. |
orders only a | Polygamia necessaria, florets | Calendula.
common calyx. | of the disc staminiferous, of |
| the ray pistilliferous. |
| Polygamia segregata, a common | Echinops.
| calyx including all the |
| florets, and a separate |
| involucre for each. |
| Monogamia, anthers united, |
| flowers not compound. |
| |
XX.—GYNANDRIA | Diandria two anthers | Orchis.
Stamens and | Triandria three do. |
pistil united. | Tetrandria four do. |
| Pentandria five do. |
| Hexandria six do. | Aristolochia.
| Decandria ten do. |
| Dodecandria 11-19 do. |
| Polyandria twenty or more do. |
| |
XXI.—MONŒCIA | Monandria one stamen | Arum.
Stamens and pistils | Diandria two stamens | Lemna.
in different | Triandria three do. | Carex.
flowers on the | Tetrandria four do. | Urtica.
same plant. | Pentandria five do. | Amaranthus.
| Hexandria six do. |
| Heptandria seven do. |
| Polyandria more than seven do. | Quercus.
| Monadelphia stamens united | Pinus.
| Syngenesia stamens united by |
| their anthers. |
| Gynandria stamens and styles |
| united |
| |
XXII.—DIŒCIA | Monandria one stamen | Salix.
Stamens and pistils | Diandria two stamens |
in different | Triandria three do. | Ficus.
flowers on | Tetrandria four do. | Viscum.
different plants. | Pentandria five do. | Cannabis.
| Hexandria six do. | Loranthus.
| Octandria eight do. | Populus.
| Enneandria nine do. | Laurus.
| Decandria ten do. |
| Dodecandria 11-19 do. | Stratiotes.
| Polyandria many do. |
| Monadelphia stamens united in | Juniperus.
| one bundle. |
| Syngenesia stamens united by |
| the anthers. |
| Gynandria stamens and styles |
| united. |
| |
XXIII.—POLYGAMIA | Monœcia, hermaphrodite, | Acer.
Stamens and pistil | staminiferous, and |
in the same, or in | pistilliferous flowers on the |
different flowers, | same plant. |
on the same or on | Diœcia on two plants | Fraxinus.
different plants. | Triœcia on three plants |
| |
XXIV.—CRYPTOGAMIA | Filices Ferns | Aspidium.
Organs of | Musci Mosses | Spagnum.
fructification | Hepaticæ Liverworts | Marchantia.
concealed (flowers | Lichenes Lichens | Cetraria.
inconspicuous). | Algæ Seaweeds | Fucus.
| Fungi Mushrooms | Agaricus.
---------------------+---------------------------------+--------------
With all its imperfections, the artificial system has this advantage,
that the character on which it is founded is sufficiently conspicuous
(that is, of course, with the plants in full flower) to render it
generally easy to ascertain the class and order of a plant. At all
events, it may serve as a useful artificial key, and as such may be
combined advantageously with the natural system.
114. NATURAL SYSTEM (JUSSIEU’S).
Classes.
I. Acotyledons 1st Class.
II. Monocotyledons
Mono-hypogynæ (stamens hypogynous) 2nd ”
Mono-perigynæ (stamens perigynous) 3rd ”
Mono-epigynæ (stamens epigynous) 4th ”
III. Dicotyledons.
Monoclines, flowers hermaphrodite.
Epistamineæ (stamens epigynous) 5th ”
Apetalæ (no petals)
Peristamineæ (stamens perigynous) 6th ”
Hypostamineæ (stamens hypogynous) 7th ”
Monopetalæ (petals united)
Hypocorollæ (corolla hypogynous) 8th ”
Pericorollæ (corolla perigynous) 9th ”
Epicorollæ (corolla epigynous)
Synantheræ (anthers united) 10th ”
Chorisantheræ (anthers free) 11th ”
Polypetalæ (petals distinct)
Epipetalæ (petals epigynous) 12th ”
Peripetalæ (petals perigynous) 13th ”
Hypopetalæ (petals hypogynous) 14th ”
Diclines, flowers unisexual, or without a perianth. 15th ”
This system, being likewise founded partly on individual organs, is
also, to a certain extent, artificial; and, strictly speaking, every
natural method of botanic classification must partake more or less of
an artificial character, as many orders of plants merge so insensibly
into others that their respective limits cannot be accurately or
rigorously defined.
FOOTNOTES:
[37] Carpenter on the Microscope.