DICOTYLEDONOUS, OR EXOGENOUS PLANTS.
IN Endogenous plants the seeds have but one lobe, and the growth is
invariably from the interior. In the Exogenous class, on the contrary,
the seeds have two lobes, and the increase in growth is external: hence
the botanical distinction of Exogenous plants. Although the distinctive
character of the highest class of vegetables is to have seeds with two
lobes, yet the structure and position of the seeds are extremely
diversified. Many have horny coats, such as the pips of apples and
oranges; or hard ones, as nuts, and the stones of plums and cherries.
They are sometimes on the outside of the fruit, as in strawberries, but
oftener within it, as in the melon, the pear, and a variety of others.
These succulent substances nourish the young seeds for a time, but, when
they are matured, the light and heat which ripened the fruits now
combine to accelerate their decay and decomposition, in order to set the
seeds free.
Whatever be the size or form of the seeds, whether large or microscopic,
they invariably contain two seed lobes or primary leaves, consisting of
cellular tissue, between which the miniature plant, with its radicle,
stem, and terminal bud lies concealed. At the end of the first year
there is little difference in the structure of a young woody plant,
whether from a one or two lobed seed; the distinction begins the second
year. In herbaceous plants, the stem, which is in general annual, is of
loose cellular tissue, with separate bundles of fibro-vascular tissue
running from the roots upwards, and passing at last into the leaves,
where they form the ribs or veins. Many of the higher forms of plants
have fleshy underground stems, as instances of which may be named the
Corm, as seen in the crocus and colchicum, the Tuber, as in the potato,
the Rhizome, as in the fleshy rootstock of Iris florentina, which yields
the violet powder of the shops, and indeed most bulbs may be considered
as modifications of stems, though they are more strictly analogous to
buds. The edible parts of the carrot, turnip, parsnip, and radish are
not stems, but highly developed succulent roots, the unusual development
of which is a direct result of cultivation.
A young tree, at the end of the first year of its growth, has
subterranean roots, with their branches and fibrils, and an aërial stem,
often more or less branched, formed of bark, wood, and pith, with a few
leaves at its extremity, all exceedingly tender. Every succeeding year a
new cylinder of woody fibre and vascular tissue is formed between the
wood and the bark, both in the stem and branches. It follows from this
manner of growth, that the stem of a tree, consisting of bark, wood, and
pith, is formed of a series of cylinders or extremely elongated
concentric cones closely united, so that a transverse section exhibits a
series of concentric circles or zones from the surface of the bark to
the central pith. The structure of the branches is similar, but the
number of zones depends upon the age. Since all the tissues that have
been described are combined to form the organs of nutrition and
reproduction in a full-grown tree, it affords the best general
illustration of the organization of the highest class of vegetables.
Every part of a tree or plant, except the top of the stigma and
extremity of the roots, is covered by an extremely delicate film of
cellulose, closely pressed down upon one, two, or three layers of
transparent colourless cellular tissue compressed into a tubular form,
which constitutes the cuticle. These flattened cells, which are firmly
united to one another by their edges, differ in shape in almost every
tribe of plants. In the monocotyledons they are elongated in the
direction of the parallel ribs of the leaves; in the highest class they
differ little from circular discs, but they have large sinuosities in
their edges, which make their junction very irregular. The upper cells
of the cuticle are lined with a waxy substance, which protects the plant
from damp; and in many cases it contains more or less silex.
This general covering, or cuticle, is perforated by numerous pores,
especially on the under-side of the leaves, and the green tender parts
of the branches; they are the organs of respiration. These pores, or
stomata, are usually formed of two crescent-shaped cells, joined
together by their points or horns, so as to leave an open space like a
mouth, through which the plant breathes. These, however, are only the
guardians: the opening between them leads into a cavity full of air,
which is the antechamber to an interior cavity. The valves of the
stomata open and shut according to the humidity or dryness of the
atmosphere. All plants of both classes, woody or herbaceous, have
stomates, except water plants, fungi, fuci, and others of the lowest
class. They are generally very abundant on the under-surface of leaves.
They are sometimes in vast numbers on both sides of the leaves, and are
essential to the life of the plant. According to MM. Payen and Liepner,
silex and azote, together with calcareous and alkaline salts, are
invariably found in the cells forming the skin of the roots, stems,
leaves, fruits, hairs, and spines. The strong cohesion of the skin,
together with the presence of these substances, becomes a defence
against the wearing effect of the weather, without diminishing the
transparency of the tissues.
The bark is divided into three regions, or zones. The external coat,
lying immediately under the skin, is formed of one or many layers of
cubical or oblong cells, elongated horizontally. They are transparent
and colourless at first, but become brown and opaque with the colouring
matter of cork as they grow older. On that account it is called the
suberous zone, and sometimes acquires great thickness, as in the Quercus
Suber, or cork tree.
The green cellular envelope comes next to the corky layer, and consists
of prismatic cells and laticiferous tubes, which form an irregular
wide-meshed network, elongated in the direction of the axis of the tree,
and sometimes constituting the chief thickness of the bark. This zone,
as well as the succeeding, increases imperceptibly by new layers added
to its interior, while the exterior coats of the bark perish annually.
In some trees they are annually cast off in plates and large flakes, as
in the Oriental plane, whose stem and branches look as if they had been
peeled in autumn.
The liber, which is the third and innermost zone of the bark, generally
consists of several layers of cellular tissue, traversed longitudinally
by bundles of woody fibre and laticiferous tubes.
The generating layer of cambium, in which all the phenomena of growth
takes place, is a semi-fluid mucilaginous substance, which comes between
the liber and the wood. It is most abundant in the spring, and is the
origin of all horizontal growth. This mucilage is really made up of a
vast multitude of cells, with cell-walls as delicate as those of a soap
bubble, which gradually undergo transformation into woody fibre,
laticiferous ducts, spirals, &c., thence called the cambium zone. The
whole of this matter spontaneously divides into two parts: one forms a
new layer of liber on the interior of all those which precede it, and
the other a new ring of young sap-wood, exterior to all its
predecessors. A portion of the cambium, in its unchanged or liquid
state, always remains between the wood and the bark, which are never in
absolute contact.
As a new cylinder of wood enclosing all its predecessors is annually
formed, the section of a stem perpendicular to its axis exhibits a ring
of woody fibre, alternating with a ring of spotted and rayed vascular
tubes, which constitute the silver grain of the wood. The rings are more
and more crowded, and narrower towards the centre, and at last become
impervious to the sap, which only rises through the younger part of the
sap wood. In fact, a large portion of the solid fibres of most plants
have ceased to take any active share in the performance of vital
functions, and, like the solid heart of an oak, retain their integrity
simply because they are not exposed to influences which would cause
their decomposition. A vegetable tissue exposed to ordinary chemical
action, can only remain entire so long as it is performing vital
functions. The arrangement of the woody fibre and ducts in the different
orders and genera is much varied. The breadth of the rings of wood shows
the effect of good and bad seasons; and in extra-tropical latitudes,
where there is alternately a period of growth and repose, their number
frequently indicates the number of years’ growth; so that the age of a
tree may be approximately, if not exactly, learned from a critical
examination of a section of its stem.
The innermost cylinder of wood is lined by the medullary canal or tube
containing the pith. It is a delicate membrane, entirely formed of
hollow spiral tubes. The pith, which fills the canal, is of greenish
cellular tissue when young, full of sap, and occasionally, though
rarely, mixed with vascular and spiral tissue. It passes uninterruptedly
to the end of every branch, leaf bud, and flower. Perpendicular plates,
called medullary rays, radiate from the medullary sheath and end at the
bark, dividing the whole mass of the wood into triangular or
wedge-shaped sections. They are thin plates of cellular tissue,
stretched horizontally between the central pith and the bark. In each
family of trees and shrubs they have a different arrangement, but in all
they keep up a horizontal communication between the centre and the
circumference, though they do not all extend throughout the whole length
of the stem; some do, others do not. Thus the cellular tissue forms a
horizontal system, while the fibro-vascular ducts constitute a
perpendicular system of tissues. In some trees the pith is scarcely
perceptible, and in others it diminishes or vanishes with age, as in the
oak. In the alder and other plants it dries up, breaks into pieces, and
the canal is filled with air.
In the stem and branches of the Coniferæ, there is scarcely any mixture
of vessels amongst the woody fibre, the vascular system generally
consisting exclusively of glandular woody tissue, except in the
medullary sheath, where spiral vessels are found in small numbers.
The subterranean growth, or descending axis of trees consists of large
branches, sometimes tending downwards, but more frequently spreading in
extensive ramifications, not far from the surface of the earth. Their
growth and structure are similar to those of the stem, but the cylinders
of wood are less apparent; they have medullary rays, but no pith; they
merely connect the active roots with the stem, and fix the plant firmly
in the ground, for they have few or no pores, and contribute little to
the nourishment of the plant, except by conveying liquids from the
fibrous roots to the upper growth. The active feeding roots spring from
them in the form of bunches of white fibres, like cords or threads,
which sink straight down into the ground. These real roots are of
cellular tissue enclosed in vascular tubes and spiral vessels, which
terminate at a little distance from the extremity, leaving a point of
loose spongy cellular tissue, called the spongiole, which absorbs from
the ground the liquids that nourish the plant. These root fibrils are
temporary organs; they die on the older parts of the subterranean
branches, and are succeeded by others on the new.
The various tissues which form the stem of a tree form, in the same
manner, though in diminished numbers, the complicated ramifications of
the branches and the leaf-stalks, and terminate in the leaves
themselves. Under the transparent film which forms the skin on the
upper-surface of a leaf, there is a layer of soft thin-walled
cylindrical or prismatic cells, closely pressed together, and full of
green vegetable matter, or chlorophyll. Several layers of thick-walled
cells follow, each more loosely aggregated than that which precedes it,
and fuller of void spaces, till in the last green layer on the
under-side of the leaf the cells are globular, with numerous large
irregular void spaces, united in a reticulated system filled with air,
and in direct communication with the atmosphere by means of the
innumerable stomata, which are to be found in the under-surface of the
leaves of all land plants of the higher classes, and which are their
organs of respiration.
The form of the leaf is determined by the arrangement of the vascular
bundles, which are in communication with those in the interior of the
stem, and branch out in various directions through the green layers:
these branches unite again, and form the skeleton of the leaf, which is
often a delicate maze of the finest lacework of nerves. The vascular
system is double, consisting of an ascending and descending portion. The
ascending portion, which is continuous with the medullary sheath,
becomes continuous at the apex of each nerve of the leaf with the
descending portion, which is beneath and in contact with it throughout
its ramifications. This descending portion at the base of the
leaf-stalk, or petiole, becomes continuous with the bundles of the
liber. In the upper part of the nerves of the leaf there are spotted
vascular ducts, in the lower part there are laticiferous vessels. Those
on the upper side carry the rising sap to the green matter, where it is
elaborated and matured, and then it passes into the vessels on the
under-side of the nerves or veins, which carry it down the liber.
Buds are generally formed of scales closely imbricated round the young
leaves, which are variously folded and firmly packed; they contain the
rudiments of the whole plant, and as in a large tree they are renewed
every year, the sources of life are all but infinite.
The spines with which many plants are armed are of two kinds; one is
permanent, being an excrescence from the wood, as in the blackthorn; the
other proceeds from the bark, and may be stripped off, as in the rose;
both contain silex, and are covered by the skin common to the whole
plant.
Few plants of any kind are without hairs, which are chiefly found on the
young shoots, and on the under surface of the leaves. They are either
formed of a transparent elongated hollow cell, or consist of a number of
transparent colourless superimposed cells, sometimes jointed, but more
frequently rectilinear. When they sting, as in the nettle, they are set
upon a kind of bulb composed of cells which secrete the acrid colourless
liquid which causes the irritation, and when slightly pressed send it
through the hair, the point of which breaks off as it enters the skin of
the hand.
The hairs are so transparent that the gyration of the azotized liquid,
called protoplasm they contain, has been distinctly traced, a motion so
universal in some part of the structure of plants that according to the
observations of Mr. Wenham, the difficulty is to find a plant, aquatic
or terrestrial, in which it does not take place at some period of its
growth. The gyration in any given cell preserves a uniform direction; in
different cells the direction is different. It will persist in a
detached part of a plant for several days or even several weeks. It is
arrested by cold, and recommences its gyration when the temperature is
raised.
It has been mentioned that in the primordial cell the solid coloured
particles often form a nucleus in the centre of the viscid liquid called
protoplasm, which is continually diminished by the increase of the
watery vegetable sap. At length the protoplasm in the hairs is reduced
to mere threads extending from the cell wall to the nucleus, so that the
latter looks like a spider in the middle of its web. These threads are
really streams of the viscid protoplasm flowing through the more liquid
cell sap from the nucleus to the cell wall, where they turn and flow
back again in another thread. When there are several currents in the
same cell, the nucleus, which is the common point of departure and
return, is the centre of the vital activity of the cell, though it does
not always maintain a central position; in the cells of the leaves of
the Vallisneria spiralis the nucleus even follows the protoplasm, which
flows in a broad stream up one side of the cell and down the other, as
in the Chara. In most plants the gyration is transitory, for the nucleus
which always exists in young cells is dissolved as the cell advances in
age, and the protoplasm is so much diminished in quantity, that its
motion is imperceptible. There are exceptions, however, as in the hairs
of the nettles and some other plants, where it is persistent.
The motion is in general very slow. The thinness and minuteness of the
currents may be imagined, since they and the cells containing them are
microscopic objects, and the solid particles carried by the liquid,
which afford the means of tracing its course, are not more than between
the three and the five thousandth part of an inch in diameter. M.
Schleiden ascribes the motion to changes in the form of the cells
produced by an internal vital action, while Professor Karsten believes,
from observations he made on the rotation of liquids in the hairs of the
common nettle, that it is a phenomenon of diffusion, depending upon the
chemical changes taking place in the cells of the hairs independent of
any contractibility, not referable to them.
The whole of the tissues that exist in a well-grown tree are not to be
met with in each of the numerous woody and herbaceous plants of the
first class; some may be wanting, and those that do exist may be, and
generally are, much modified both in form and size. All the trees in the
temperate zone, and most of those in the tropics, belong to the class of
Exogens; but the annual rings of wood are less distinct in the latter,
the periods of repose and activity depending upon the dry and wet
seasons not being so decided as our winter and summer. The leaves of
tropical plants have a thicker skin than in colder climates, to defend
them from an ardent sun. The structure of herbaceous plants in all
countries is lax and juicy, they have abundance of pith, large medullary
rays, and zones of fibro-vascular tubes, which separate the pith from
the bark. In fact, each herbaceous and ligneous family has a structure
and properties peculiar to itself; but although there is almost an
infinite diversity of form and character, the general type of the class
may be traced in all.
Vegetable matter consists of carbon, hydrogen, oxygen, and nitrogen, yet
no plant can combine these simple elements into organic substances; they
imbibe them by their roots and leaves under the form of carbonic acid,
water and ammonia: these they have the power of decomposing, and
recombining their simple elements into new compounds. Carbon forms the
hard part of plants, and enters extensively into their most delicate
structure; but it is never found free. Combined with hydrogen and oxygen
it not only constitutes the cell wall cellulose, which may be regarded
as the skeleton of the vegetable world, but hundreds of compounds
differing decidedly in their properties, yet consisting only of these
three elements united with one another in different quantities and
proportions. Proteine, a compound of all the four simple elements, is a
mucilaginous substance, which lines the primordial cell, is homogeneous
at first, and afterwards more or less granulated. It is present wherever
the vital energy is in activity.
Although these four primary elements form the basis of vegetation,
plants require other substances which they absorb from the ground in a
state of solution, such as silex, or rather silicious salts having a
base of potash or soda, the carbonates, sulphates, and phosphates of
lime, the phosphate of manganese, and the oxides of manganese and iron,
with various other metals and substances in a state of combination and
solution. A few are universal constituents, as the earths and alkalies;
in general each race of plants only absorbs such as are peculiar to
itself. Soda abounds in the Algæ and is found in the Liliaceæ,
Cruciferæ, and other plants that are indigenous on the sea-coast, or in
brackish marshes. Potash exists in land plants, and cannot be replaced
by soda, for however rich the soil may be in soda, they do not thrive in
it. The ashes of land plants consequently contain the metal potassium,
while most of the Algæ yield sodium; they also yield chlorine, iodine,
and bromine in a state of combination. It is proved by spectrum
analysis, that every plant, with the exception of the very lowest,
contains a variety of metals in infinitesimal quantities, as lithium,
rhodium, and others; but they are not essential to the welfare of the
plants. Iron is the most frequent constituent in very small quantities;
there are also occasional deposits of soda, lime, and a little
manganese. All the various substances which enter the vegetable system,
are combined in definite proportions into an infinite variety of organic
compounds in different plants, and in different parts of the same plant,
for the decomposed matter is carried by the ascending sap to every part
even of the highest trees. Throughout the whole process the law of the
division of labour prevails; to each part of a plant, and to each group
of cells, its own duty is allotted.
The vegetable sap, consisting of water, carbonic acid, ammonia, and
other substances, which enter the spongy extremities of the roots in a
liquid state, rises in the form of a crude fluid through the whole loose
texture of herbaceous plants, through both the wood and pith of trees
under two years’ growth, and in older trees and shrubs it rises through
the sap-wood of the stem into the branches, and thence into the leaves,
the limit of ascent in all plants, so that in spring, all the cells are
full of sap. The vascular ducts are capillary tubes, and the cellular
tissue is an assemblage of closed cells or sacs, whose wall or
cell-membrane is permeable by liquids; hence the imbibition of the roots
and the rise of sap in the plant are essentially due to capillary
attraction acting contrary to gravitation. The ascension of the liquid
is inversely as the diameter of the capillary tubes and cells in the
stem and branches; the quantity raised is the same at all heights, and
the velocity of ascent is inversely as the height.[79] As soon as the
leaves are expanded, they evaporate a quantity of water through their
stomata during the day, so that in a tree or any plant, an enormous
extent of evaporating surface aids in raising the sap by creating a
vacuum in all the upper cells and vessels, by which the force of suction
and the rapidity of ascent are increased. It appears that the water
evaporated by the leaves is in exact proportion to that taken up by the
roots to supply its place; but as soon as the young branches are formed,
the buds for the following year produced, and when the leaves are full
of the chlorophyll which they have consolidated during the summer, the
evaporation is less, the sap ceases to rise, the spirals and vascular
ducts in the medullary canal and sap-wood are left dry, and fill with
air, which they convey to every part of the plant except the bark, to
assist in assimilation, that is, in the formation of organic compounds.
During the whole of this process the leaves and other green parts, which
are the organs of vegetable respiration, are most active. They absorb
carbonic acid gas from the atmosphere by day, and exhale oxygen. For by
the direct action of solar light the carbonic acid gas and ammonia in
the crude sap are decomposed, part of the oxygen is set free and
exhaled, and the rest, with part of the remaining elements, combine to
form chlorophyll, which is a compound of starch and a little nitrogen.
The oxygen inhaled by plants during the night, combined with other
elements in the sap, forms oxidized vegetable compounds.
M. Kosmann, of Strasburg, observed that both the leaves of plants and
their corollas give out a ponderable quantity of ozonized oxygen, much
more than that which exists in the air, and that the quantity is less in
the night.
All parts of plants that are _not green_ exhale carbonic acid gas, and
inhale oxygen, like animals, night and day; if prevented from inhaling
oxygen they lose their vital power, are soon suffocated, and the plant
dies. The expiration of oxygen by the leaves is connected with the
nourishment of a plant, the inspiration of that gas is connected with
its life.
When the sap is completely organized by respiration, evaporation, and
the chemico-vital agency of light, it descends chiefly through the
cambium, lying between the liber and the wood. From this layer the sap
distributes to each organ capable of increase, the requisite nutritious
liquids, deposits various organic compounds, and annually renews the
cambium. Part of the sap in its descent runs into the wood through the
horizontal medullary rays, in the cells of which it deposits starch. The
descent of the sap is no doubt due to gravitation.
The latex is a general name for those white or coloured juices peculiar
to some plants. It is separated in the leaves from the descending sap,
which is always colourless, and consists of a clear liquid, thickened
and coloured by white, yellow, reddish-brown, or green globules floating
in it; it does not turn blue under the action of iodine, therefore it
does not contain starch. These proper juices differ as much in quality
as in colour; some contain fatty matters, others substances of a totally
different nature, as caoutchouc; a few are bland and nutritious, many
acrid and poisonous; some contain alkaloids, others have none. These
juices are by no means essential to the life of the plant, for sometimes
they are wanting in their most essential parts, and they are found in
certain species and not in others most nearly allied. Certain it is,
that tropical lactescent plants which do not produce their proper juices
when brought to a cold climate, still produce their milk vessels.
These vessels follow the ramifications of the veins of the leaves in the
highest class, and also in some of the monocotyledons. In the stem the
milk vessels belong especially to the layers of the bark, where they
take the form of long reticulated perpendicular ducts, through which the
proper juices descend towards the roots.
Each plant has its own system of milk vessels, and M. Lestiboudois has
found that the coloured liquids have a rapid motion; the movements are
very complicated, not from point to point, but in such a manner that the
granules are carried by the liquid into all the ramifications of a
complicated network.
The septa, or divisions between the primordial cells, exert a powerful
influence upon the substances contained in the sap as it permeates
through them, no doubt acting as a dialysing membrane, which separates
the gelatinous from the crystalloid matter. The latex is probably
separated from the sap by the septa in the cells of the leaves, and sent
into the vessels peculiar to it, and then, while the sap is descending
and passing through the cambium, it is likely to be dialysed by the
septa between the cells of that layer, arresting the protein, and other
gelatinous substances, and allowing sugar, starch, and other crystalloid
matter to pass freely, and form deposits of organic compounds for the
following year. For perennial plants in extra-tropical countries remain
in a dormant state during the winter; their cells are then full of
organic compounds under the form of protein, as well as sugar, gum, &c.,
but especially starch, which is converted into sugar or dextrine, when
spring awakens the plants to renewed life and activity.
The composition of inorganic matter is very simple; there are
comparatively few radicals, and the substances are compounded of few
equivalent atoms, at most eight or ten, sometimes only two or three.
Carbonic oxide is formed of one atom of carbon and one of oxygen;
carbonic acid is formed of one atom of carbon and two of oxygen; and
acetylene, M. Bertholet’s base of synthetic compounds, contains two
atoms of carbon and two of hydrogen, chemically united; but no organic
compound contains less than three equivalent atoms, generally a great
many more. For example, citric acid, which is lemon juice, contains 12
atoms of carbon, 5 of hydrogen, and 11 of oxygen; while strychnine
contains 44 atoms of carbon, 23 of hydrogen, 4 of oxygen, and 2 of
nitrogen. Experiment has proved that the powers which maintain stability
among the numerous and complex constituents of organic substances
decrease in energy as the number of the equivalent atoms augments; hence
such compounds are in less stable equilibrium than those of inorganic
bodies, and are more liable to be disturbed and changed into new and
more stable forms.
As the chemical functions are not the same in all the cells, situated as
they are in different parts of a plant, they elaborate different
substances from the same materials. Besides, new substances are
introduced with the growth of the plant, to be acted upon by the light
and heat of the different seasons, so that numerous compounds may be
formed out of a given number of the primary elements. For example, the
ultimate elements of wheaten flour, or a grain of ripe wheat, are
carbon, the three elementary gases, sulphur, phosphorus, calcium,
magnesium, and silex; but during the germination and growth of the
plant, its flowering, forming the seed, and ripening the grain, certain
portions of these elements chemically combine in definite proportions to
form cellulose, starch, sugar, gum, gluten, fibrin, albumen, casein, and
fat, all of which are found in wheaten flour.
However much plants may differ in their organic products, they all agree
in producing protein, which takes an active part in the formation of
cells; and all produce neutral hydrates of carbon, such as cellulose,
starch, sugar, gum, &c., which consist of carbon, combined with hydrogen
and oxygen in the exact proportion that forms water. Many of them have
precisely the same quantity of carbon, and only differ in the quantity
of the aquatic element, as for example, lignin, starch, and cane-sugar,
which consist of 12 parts of carbon, in a state of combination with 8,
10, and 11 parts of water respectively; indeed the affinity between many
of these neutral hydrates is of a most intimate character. Some of their
varieties are isomeric, that is to say, they contain the same
ingredients in the same proportions, and yet they differ essentially in
regard to their properties.
Next to cellulose, starch is the most universal and distinctive of
vegetable productions, being a constituent of all plants, except the
fungi. It abounds in the grains and other seeds, and supplies the young
plant with food till it can feed itself. In both of the flowering
classes it occurs in small colourless transparent grains, either
floating in the sap, attached to the walls of the cells, or accumulated
within them. Starch globules of very small size are imbedded, either
singly or in groups, in the granules of chlorophyll, or leaf green; the
manner in which the green coating takes place is unknown. Starch is an
organic substance, varying from grains of inappreciable minuteness to
such as are visible to the naked eye, and of such a variety of forms
that it can be ascertained with tolerable certainty by what plant a
grain of starch has been produced. The small grains are generally
globular, but whatever the form may be, each consists of a series of
superimposed layers of different densities, which exhibit coloured rings
and a black cross in polarized light.
Starch is an early and transient product of young plants, which is
destined to be changed into nutritious substances at a later period, but
being insoluble in cold water it is unfit to travel with the sap.
However a ferment called diastase produced during the incipient
germination of the grains and seeds, in the tubers of potatoes, &c.,
being in a state of change, imparts that state to the starch, and
converts it into a sweet soluble matter known as dextrine or starch-gum
which is capable of being carried throughout the plant with the sap, and
which is itself ultimately changed into sugar. Dextrine is an ingredient
in the primordial cell. Starch, dextrine, and cellulose are isomeric:
consisting of the same elements with different characters.
The woody part of trees and shrubs, the fibres of hemp, flax, of the
Agave, and many other plants, are formed of cellulose, the purest form
of that substance being bleached flax and linen. During the progress of
vegetation, the cells of the ligneous tissue of trees, also those of
woody and fibrous plants, which are transparent and colourless when
young, become internally coated or filled with sclerogen, the colouring
matter of wood, a substance of various hues. In extra-tropical countries
it is generally some shade of brown, sometimes dark, sometimes so pale
as to be almost white with a yellowish or reddish tinge; and
occasionally it is beautifully marked as in the wood of the olive. In
tropical countries the colours are more vivid and varied, deeper and
even black, as in ebony. This colouring matter has the same quantity of
oxygen as cellulose, but it contains hydrogen and more carbon, hence
wood is combustible in proportion to the quantity of sclerogen it
contains. In beech it forms half of the wood, in oak two thirds, and in
ebony nine tenths, so it is the most highly combustible of the three.
The additional carbon is obtained by increased respiration, the hydrogen
by decomposition of water in the sap.
Sugar is almost as universal a constituent of the higher classes of
plants as cellulose and starch, for besides the saccharine juice of
innumerable plants, starch, the acids of unripe plants, and even the
acrid juice of the fig and other plants, is turned into sugar as the
plant advances to maturity, and the fruits ripen. Manna and other
saccharine exudations from the leaves or stems of trees, as the lime
tree, are probably intercepted by the dialysing septa of the cells, and
exude to the exterior through the pores of the skin. The sweet juice
found in the nectaries of flowers is formed in other parts of the plant,
and rarely flows to the flower before it is full blown; the quantity is
at its maximum during the emission of the pollen, and ceases when the
fruit is formed. In diœcious plants and that singular and beautiful race
the Orchideæ, it is evidently intended to attract insects for their aid
in fertilization.
Vegetable oils, resins, and wax, consisting of the same simple elements
as the hydrates, form a large class of inflammable organic substances in
which hydrogen predominates. Olive oil is a rare instance of a fixed oil
being obtained from a fruit; some laurels have that property also, but
the fixed oils are chiefly found in seeds, as the walnut, hazel nut, and
the almond, in which the principle of oil is in its greatest purity. It
is particularly abundant in hemp seed, and in a great variety of plants
the starch in the seed is changed into oil to nourish the embryo, till
the seed lobes are above the ground, and the true lobes appear.
Resins, gums, and wax, being colloid substances, are dialysed and
ejected from the system either through the fissures in the bark, or by
pores in the leaves. The resins exude through the bark from canals that
run between the cells of the plant, in solution, and are consolidated by
the oxygen on coming into the air. The herbaceous zone in the bark of
the fir and pine family furnish an abundant supply of resins and
balsams; the camphor tribe and the Amyrids are rich in them, as
frankincense, myrrh, balm of Mecca, and the Olibanum, supposed to be the
frankincense of scripture.
Wax is a frequent vegetable production, especially in the torrid zone,
where many of the wax-bearing plants supply the natives with light. An
exudation through the pores of many plants coats their surfaces with
resin or wax. Young buds are often covered with resin to protect them
from cold and wet during the winter and early spring, as those of the
horse-chestnut and balsam poplar. It is wax that gives the bloom to the
plum, cherry, and grape, and the rain drops lie on the waxy surface of
the cabbage leaf, like balls of diamond, from the total reflection of
light at their point of contact. Wax protects plants from damp in a
rainy climate, and prevents too strong perspiration from the fleshy
leaves of the aloe, cactus, and other inhabitants of the parched and hot
regions in the tropics.
The vegetable substances hitherto under consideration are neutral, but
the remarkable compounds albumen, fibrin, and casein, already mentioned
as constituents of wheaten flour, not only contain carbon and hydrogen
with a little oxygen, but azote and small quantities of sulphur and
phosphorus. Each of these three organic compounds is the same, whether
derived from animal or vegetable matter. Thus albumen is chemically the
same, whether obtained from wheat and other grains, from arrowroot,
dahlia roots, the serum of blood, or the white of an egg. As it
constitutes the film or thin coating of the primordial cell, and
combines with dextrine in its internal viscid lining, it not only forms
an ingredient in all vegetable organisms, but plays an important part in
the growth of the whole vegetable world. Fibrin is chemically the same
in the juice of plants and in blood, in which it exists as a liquid
during the life of the animal, and as a fibre after death. It forms the
basis of the muscular system in animals, and that extracted from the
juice of plants coagulates spontaneously like blood. Casein is
chemically identical, whether derived from the curd of milk, or from
peas and beans. Azote is a very important principle in these substances
as well as in the gelatinous substance gluten. It forms an essential
part of the animal structure, and is either highly nutritious or
deleterious in the vegetable, being at once one of the most valuable,
contradictory and powerful agents in nature.
Chemists have formed by synthesis compounds identical with all the fixed
and essential oils, for confectioners can now give the flavour of the
pear, orange, quince, pine apple and other fruits by means of artificial
chemical compounds. All the saccharine substances have not yet been
artificially obtained, nor the albuminous substances, albumen, fibrin,
and casein.
It cannot be a matter of surprise, when chemists form organic substances
out of inorganic elements, that they should succeed in transforming
compounds produced by living plants into new compounds, as that of
changing the vegetable acids into alcohols, which is now done. But some
of the acids themselves are synthetically formed out of inorganic
elements; as for example the oxalic, the most common of all the
vegetable acids, which is found most abundantly in the Oxalis or wood
sorrel, and is a frequent constituent of the highest and lowest plants.
The formic acid, which is the acrid stinging principle in ants, is also
synthetically formed; it is found in the juice of the stinging nettle
and in decaying pine leaves, and contains hydrogen like all the other
vegetable acids. These acids result from an augmentation of oxygen
during nocturnal respiration, which penetrates deeply into the vegetable
structure.
Octahedral, prismatic, and stellar microscopic crystals formed by the
chemical combination of the natural acids with bases imbibed by the
roots, are deposited in the cells under the skin, and in all parts of
plants. However, they appear most frequently as bundles of needle-shaped
crystals of carbonate of lime, lying side by side in the hollow of a
cell. They are known as raphides, from _raphis_ a needle, and may be
easily seen under the skin of the medicinal squill. Large single
crystals of oxalate of lime, octahedral or prismatic, are found in the
cells under the skin of the onion and other plants; and stellar crystals
of the same substance abound so much in the common rhubarb that the best
specimens of the dry medicinal root contain as much as thirty-five per
cent. of them; while certain aged plants of the cactus tribe have their
tissues so loaded with them as to become quite brittle. The calcareous
base in some instances is combined with tartaric, citric, or malic acid.
The crystals of some raphides are 1/40th of an inch long, others are not
more than the hundredth; they are brought into view by polarized
light.[80] Spherical raphides between the 1/2000th and 1/4000th of an
inch in diameter have been discovered scattered profusely through the
tissues of the leaves, and those parts of plants which are modifications
of the leaves; they may be seen under the skin of Pelargoniums and other
plants, and it is supposed that few if any orders of plants are without
them.[81]
Although azote forms 788 thousandth parts of the atmosphere, none, or at
least no appreciable quantity of it, is absorbed by the vegetable world;
that great principle of nourishment is entirely supplied by ammonia and
nitric acid, imbibed by the roots, and decomposed by the chemico-vital
power. Here it shows its capricious character by combining with other
simple elements in the bark, to produce the most precious medicines in
some plants, and in others the most deadly poisons, while no vegetable
substance is perfectly nutritious without it.
The milk sap, when exposed to the air, coagulates into a tenacious
viscid solid. The white juice is generally acrid, or narcotic, or both,
and for the most part extremely poisonous, though exhibiting strong
contrasts even in nearly allied species. In the order Euphorbiaceæ or
Spurgeworts, comprising nearly 1,500 species, a large proportion are
hurtful; but there is a gradation from mere stimulants to the most
formidable poisons. This order furnishes the Ethiope and the native
Brazilian with poison for their arrows. It contains the Manchineel, and
Excœcaria Agallocha, the most poisonous of plants; even the smoke from
the burning branches of the Excœcaria affects the eyes with insufferable
pain. The white juice of the Fig, one of the Morad order, is violently
poisonous; in many, as in the common fig, it is acrid and irritating.
The Antiaris toxicaria, the celebrated Upas-tree of Java, which is of
the Artocarpeæ or Bread-fruit order, owes its virulence to its milky
juice, which contains strychnia, the most fatal of drugs. Dangerous and
acrid as these orders are, the Bread-fruit, abounding in starch,
supplies the inhabitants of the East Indian islands with excellent food;
the milky juice of the Cow-trees, chiefly of the Bread-fruit and Fig
orders, furnishes a wholesome beverage to the South Americans; and the
Manihot or Cassava, a poisonous spurgewort when raw, yields when roasted
nutritious food to whole nations, the heat driving off the dangerous
principle. Caoutchouc, a most harmless substance, is the solid produce
of many of the most acrid and virulent juices of plants belonging to the
preceding orders; the poison is probably left in the liquid. The
chemico-vital power is strikingly illustrated by the number of safe and
excellent fruits produced by trees full of the most deleterious juices,
whether milky or not. Some of the finest fruits in the Indian
Archipelago are products of eminently dangerous species of the
Sapindaceæ or Soapworts. The acrid juices of the leaves and branches,
are so much diluted with water in the fruits, that they become
innocuous, or they may be changed into sugar, as in the common fig.
Nothing can surpass the virulence of the juice of the Upas-tree, yet its
nuts are eaten with impunity, and the pulpy contents of the fruit of the
Strychnos nux vomica is food for birds. The leaves and berries of the
potato are so strongly narcotic, that an extract from them is
intermediate in power between that from deadly nightshade and hemlock,
yet the potato itself, like the cassava, is rendered wholesome by being
boiled or roasted.
The alkaloids are alkaline substances formed in the bark and milky
juices of plants, always combined with an acid during the life of the
plant. The chemical structure of this class of substances is very much
alike, and chemists have succeeded in forming many of them
synthetically; they all contain azote, and have a great affinity for
acids. The bark of the different species of Cinchoneæ, especially the
Cinchona cordifolia and C. Condaminea, yield three alkaloids—namely,
cinchonine, quinine, and cusconine—they are all formed of carbon,
hydrogen, and azote in the same proportions; but the first has one atom
of oxygen in addition, the second has two atoms in addition, and the
third has three; so that in these alkaloids the carbon, hydrogen, and
azote combine to form an organic radical, which is oxidized in three
different degrees. Six of the alkaloids have been obtained from opium,
which is the solid portion of the milk juice of the poppy; of these,
morphine seems to be the narcotic principle; and the orange-coloured
milk sap of the Chelidonium, a very poisonous and acrid plant of the
poppy order, has furnished chelidonine. The Colchicum order, containing
the meadow saffron or autumnal crocus, and Veratrum album or white
hellebore, as well as many other plants, yield alkaloids, all of which
are medicinal or poisonous, according to the dose.
There is scarcely a people, however savage, that has not discovered some
exciting narcotic. Opium is almost universally smoked or eaten among
Eastern nations; and bhang, a strong narcotic, obtained from the leaves
of Indian hemp, is in equally universal use among the Brazilian savages
and Hottentots, but especially among the Malays, who are excited to
madness when they smoke it too freely. The same intoxicating effect is
produced by a strong liquor prepared from the Datura sanguinea, a
species of stramonium; and its congener tobacco, now all but a necessary
of life among civilized mankind, was smoked by the natives of the
American continent, before the arrival of the Europeans, as a relief
from hunger.
Coffee has been long in use on account of its stimulating principle
caffeine, which is now discovered to be the same with theine, the
latter, however, being less exciting, unless the tea plant grows in a
very hot climate. In countries where nature furnishes few narcotic
principles, wine, beer, and spirits supply their place, especially in
the far north, where animal heat is rapidly carried off by the cold, and
carbon must be furnished to satisfy the all-devouring oxygen which we
draw in at every breath.
Caffeine, the highly azotized principle of coffee, obtained from tea
leaves and coffee beans, is one of the substances known as neutral
crystallisable principles. Similar substances are found in asparagus,
pepper, almonds, the bark on the roots of the apple, pear, plum, and
cherry trees, as well as in the bark of the willow. The two last are
especially analogous, and contain no azote, as the others do.
The colouring matter of flowers is a fluid contained in cells, situated
immediately under the skin, which itself is perfectly transparent and
colourless. The whiteness of the white Camellia, rose, lily, and other
flowers, is supposed to be owing to the total reflection of light from
the cells immediately below the skin, which are either full of air, or
of a colourless liquid. The predominating colours are yellow, red, and
blue, with the various intermediate tints. Sometimes these colours are
converted one into another in the petal after fertilization, at which
period the colours are brightest. The chemical nature of these liquids,
the cause of their variety, and their definite arrangement in one and
the same petal, do not seem as yet to be ascertained.
The parts of plants that are not green inhale oxygen from the
atmosphere, and exhale carbonic acid gas exactly like animals. During
the chemical combinations of the oxygen with the carbon derived from the
nutriment to form the carbonic acid gas, heat is necessarily evolved,
especially in the flower, the point of maximum heat varying with its
expansion. The blossoms of the Aroideæ, or Arums, are remarkable for the
evolution of heat. According to Saussure, a blossom of the common Arum
maculatum consumes five times its volume of oxygen in twenty-four hours
previous to its evolution of fruit, so it is not wonderful that the
chemical combination of such a quantity of oxygen should produce a
strong development of specific temperature. By M. Dutrochet’s
observations, the heat evolved by the Arum maculatum has a maximum in
the day and a minimum in the night, and he found that it exceeded the
heat of the surrounding air by between 25° and 27°. The heat of the
Colocasia odorata, another Arad, was determined by several observers to
be even 50° above the warmth of the air. The heat evolved by germinating
seeds when in a heap is not from fermentation; it is owing to their
consumption of oxygen and expiration of carbonic acid gas. The
temperature of all vegetating parts of plants, the roots, leaves, young
juicy shoots, &c., is far superior to that of their flowers. It arises
from the nutritive process, and has a maximum at noon, and a minimum at
midnight, like that of the flower. The growth of plants is most vigorous
at noon; consequently there is then a greater evolution of heat.
Water in small quantities is secreted night and morning from the points
of the leaves of many plants, probably to relieve them from a
superabundance of liquid, which evaporation is insufficient to carry
off. The arums are remarkable for the quantity they eject. It falls in
drops from the points of the leaves. About half a pint is given out
every night by the enormous leaves of the Caladium distillatorium, a
species of Arad. In that plant, and in the Colocasia, the water flows in
canals along each rib into a general duct, which runs along the border
of the leaf, and terminates in an orifice upon the surface.
Since electricity is developed by chemical action in unorganized matter,
it may be inferred that it is also developed within the vegetable cell
where so many organic compounds are formed; but it is probably given off
from the points of the leaves or by evaporation from their surfaces.
Professor Fleming ascertained by actual experiment, that the sap of a
leaf, and its surface, are in different electric states; he also found
that the surface of the spongioles of the roots of plants and the
ascending sap have opposite electricities. Both of the preceding cases
the Professor ascribes, in part at least, to organic changes which take
place during vegetation. Slight currents of electricity were obtained
from the petioles of flowers, but fruits and tubers give powerful
electrical currents due to the reaction of different vegetable juices
upon one another. The tuberose is said to emit scintillations and dart
small sparks of light in a hot electric evening, and gardeners have long
been aware that mushroom spawn is most prolific in stormy weather.
The irritability of the tissues of plants which renders them liable to
be acted upon by external causes, has occupied the attention of many
celebrated botanists. From experiments by Professor Ferdinand Cohn and
his pupil M. Krabsch upon the irritability of the stamens in the florets
on the discs of composite flowers, more especially the Centaureas, they
have come to the conclusion that susceptibility to the excitement of
light, as well as to that of mechanical and probably electrical impulse,
is possessed by all young vigorous tissues, and upon comparing the
phenomena of these with those of animal irritability, they further
conclude that the faculty of responding to external irritation by
internal movements and change of form, belongs to cells, and holds good
in the vegetable as in the animal kingdom. To be irritable, to change
its normal form as a vessel of excitation, and to revert to the normal
form after a while by its internal elasticity, are characteristics of
the living cell. In plants these properties are met with only when the
vital processes are in full activity, and therefore are particularly
noticed during the period of flowering, when the processes are at the
maximum. And it may be remarked that the stamens, in which irritability
is most frequently noticed, are the only organs in which an elevation of
temperature measurable by the thermometer occurs, although a certain
degree of heat is generated in all plant cells by the chemical process
going on within them. It is to be supposed that irritable properties
belong to all parts of plants, but that they exist in an intensified
degree, and for a certain epoch, in those parts where their results
arrest attention, as in the stamens of the Centaurea, berberry, cactus,
Cistus, nettle, &c., and in the anthers of the Stylideæ, the leaves of
Dionæa muscipula, and many others, all of which are more or less
affected by the external action of mechanical force and electricity; for
it is scarcely possible that plants should not be under the influence of
atmospheric electricity, since every shower of rain forms a perfect
conductor between the clouds and the earth. The motion does not always
immediately follow the excitement; plants often require to be rudely
shaken before the movement begins. M. Hofmeister has observed that all
young shoots and leaves become curved by mechanical shaking.
Light is the most universal and important exciting cause in the
vegetable world. The mouths of the stomata are opened by the influence
of light. The leaves, young shoots, and tendrils turn to the light; it
regulates the sleep of plants, as well as the diurnal motions of the
daisy and sunflower. The opening of blossoms and of folded leaves which
had been closed in sleep during the night, shows the susceptibility of
their tissues to the influence of light, an influence beautifully
exhibited by the orange-coloured Eschscholtzia, which shuts its golden
blossoms under every passing cloud.
All M. Cohn’s experiments prove that in the Mimosa pudica, which is
highly sensible to the action of light, heat, electricity, and touch,
‘the propagation of the external excitement, proceeds in the same mode
as in animals, and there is little doubt that the vascular tissue (which
contain spiral vessels) constitute the special bundles adapted for the
purpose, and that the phenomena of contractibility depend upon a
muscular tissue.’[82]
From Professor Franklin’s experiments it appears that ‘the motions
resulting from external causes are owing to vital contractibility, and
that they are governed by the same laws which regulate similar action in
the animal kingdom. Their energies vary with the vigour of the plant;
they are exhausted by over exercise, and require rest; and like animals
they are lulled and put to sleep by chloroform and narcotics.’
END OF THE FIRST VOLUME.
LONDON: PRINTED BY
SPOTTISWOODE AND CO., NEW-STREET SQUARE
AND PARLIAMENT STREET
Footnote 1:
Professor Faraday.
Footnote 2:
Professor Helmholtz.
Footnote 3:
The address of the president, Sir William Armstrong, C.B., to the
British Association at Newcastle-on-Tyne, 26th August, 1863.
Footnote 4:
J. Tyndall, Esq., on Force.
Footnote 5:
The Law of Exchange was independently proved by Messrs. Tyndall,
Kirchhoff, Angström, and Balfour Stewart.
Footnote 6:
Tyndall on Heat.
Footnote 7:
Analogous to transparent media which receive their colour by stopping
or absorbing some of the colours of white light and transmitting
others.
Footnote 8:
‘Connection of the Physical Sciences.’
Footnote 9:
‘Connection of the Physical Sciences.’
Footnote 10:
They are called vacuum tubes, and are filled while open by putting one
end in communication with the vessel in which the gas is generated,
and the other end in communication with an air pump. As soon as the
atmospheric air is pumped out, the gas rushes in and fills the tube,
the communication with the vessel containing the gas is cut off by
fusing up that end of the tube, and as soon as the gas is sufficiently
rarefied the other end is fused up also. An electrical discharge that
will not pass through one inch of air, will pass through thirty or
forty inches in a vacuum tube.
Footnote 11:
‘Connection of the Physical Sciences.’
Footnote 12:
Lectures of much interest by Dr. William Odling in the _Chemical News_
of 1862.
Footnote 13:
M. H. Kopp.
Footnote 14:
Lectures by Dr. Crace Calvert on improvement and progress of calico
printing and dyeing since 1851.
Footnote 15:
This prediction, made in his Treatise on Light published in 1826, has
been completely fulfilled by the discovery of four new metals by
spectrum analysis.
Footnote 16:
Phil. Mag. vol. iv. 1834, p. 114.
Footnote 17:
‘On the Spectrum of the Electric Spark in Compound Gases,’ by Mr. J.
M. Seguin. Comptes Rendus.
Footnote 18:
The light of the electric lamp is produced by an apparatus which
successively makes and breaks an electric current, whereby the
terminal charcoal points become red-hot.
Footnote 19:
‘On the Means of Increasing the Intensity of Metallic Spectra.’ By Mr.
W. Crookes.
Footnote 20:
_The Chemical News and Journal of Physical Science_ for July 4, 1863.
Footnote 21:
Dr. W. A. Miller has shown that these invisible highly refrangible
rays exist in the vapours of all metals, and has obtained photographs
of their spectra (see Phil. Trans. 1862, p. 876), which correspond to
the spectra of fluorescence.
Footnote 22:
In γ Cassiopeiæ, Mr. Huggins has detected a second _bright_ line in
the red part of the spectrum. He has also found that these two bright
lines agree in position with the two brightest lines of the spectrum
of hydrogen, and may therefore be considered due to luminous hydrogen.
Footnote 23:
Sir John Herschel, who is of the highest authority with regard to the
nebulæ in both hemispheres.
Footnote 24:
Since this observation, Mr. Huggins discovered that two small comets
give an analogous spectrum.
Footnote 25:
From further observations Mr. Huggins is of opinion that the red
colour of this planet is not due to its atmosphere, but is peculiar to
certain parts of its surface.
Footnote 26:
‘Quarterly Journal of Science,’ April 1864.
Footnote 27:
Jan. 7, 1865.
Footnote 28:
On the latest discoveries concerning the sun’s surface, by Balfour
Stewart, Esq., in the ‘Chemical News and Journal of Physical Science’
of April 1865.
Footnote 29:
According to Payen. Like starch, it is stained blue by iodine.
Footnote 30:
‘On the Functions of the Nitrogenous Matter of Plants.’ By M. L.
Garreau, ‘Annales des Sciences naturelles,’ t. xiii. 1860.
Footnote 31:
‘Remarks on the Vessels of the Latex, the Vasa Propria, and the
Receptacles of the elaborated Juices of Plants.’ By M. Lestiboudois,
‘Comptes rendus,’ 1863.
Footnote 32:
The author is indebted throughout many parts of this section to the
excellent work of Dr. Carpenter, and to the ‘Cryptogamic Botany’ of
the Rev. M. J. Berkeley, from which also many of the cuts are derived.
Footnote 33:
Mr. Berkeley’s ‘Cryptogamic Botany.’
Footnote 34:
‘Dr. Carpenter’s Microscope.’
Footnote 35:
These motions were discovered, and are described by Dr. Harvey, in his
‘Manual of British Marine Algæ.’
Footnote 36:
‘Cryptogamic Botany.’ By the Rev. M. J. Berkeley.
Footnote 37:
‘Cryptogamic Botany.’ By the Rev. M. J. Berkeley.
Footnote 38:
‘The Microscope.’ By Dr. Carpenter.
Footnote 39:
‘Cryptogamic Botany.’ By the Rev. M. J. Berkeley.
Footnote 40:
‘British Seaweeds.’ By Mrs. Alfred Gatty.
Footnote 41:
‘Flora Italica Crypta.’
Footnote 42:
Mr. Berkeley’s ‘Cryptogamic Botany.’
Footnote 43:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 44:
Mrs. Gatty’s ‘British Sea Weeds.’
Footnote 45:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 46:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 47:
‘Voyage of the Adventurer and Beagle,’ by Mr. Darwin.
Footnote 48:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 49:
In the Fuci each kind of fruit is discharged on the surface of the
receptacle before fructification.
Footnote 50:
Hooker’s ‘Flora Antarctica.’
Footnote 51:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 52:
Berkeley’s ‘Introduction to Cryptogamic Botany.’
Footnote 53:
‘Des Myxomycetes,’ par M. Antoine de Bary; et Mémoires par MM. Tulasne
et Hermann Hoffman, ‘Annales des Sciences Naturalles,’ 4me séries.
Footnote 54:
‘Introduction to Cryptogamic Botany,’ by the Rev. M. J. Berkeley.
Footnote 55:
‘Sur des Isaria et Sphæria Entomogens,’ par MM. L. et H. Tulasne, de
l’Institut, ‘Annales des Sciences Naturelles,’ 4me série, 1857.
Footnote 56:
‘On the Geographical Distribution of Fungi,’ by M. E. P. Fries, of
Upsala, Sweden.
Footnote 57:
Memoir by M. Hermann Hoffmann, upon Fermentation, in the ‘Ann. des
Sciences Naturelles,’ 4me série, 1860.
Footnote 58:
‘The Microscope,’ by Dr. Carpenter.
Footnote 59:
M. Hoffmann.
Footnote 60:
‘Comptes rendus,’ Nov. 12, 1860.
Footnote 61:
‘Geographical Distribution of Fungi,’ by M. Fries.
Footnote 62:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 63:
Berkeley’s ‘Introduction to Cryptogamic Botany.’
Footnote 64:
Berkeley’s ‘Introduction to Cryptogamic Botany.’
Footnote 65:
Dr. Carpenter’s ‘Microscope.’
Footnote 66:
Dr. Carpenter’s ‘Microscope’
Footnote 67:
‘Anatomy and Physiology of the Vegetable Cell,’ by M. Hugo von Mohl.
Footnote 68:
M. von Mohl, on the ‘Vegetable Cell.’
Footnote 69:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 70:
Dr. J. D. Hooker on the ‘Distribution of Ferns,’ in Berkeley’s
‘Cryptogamic Botany.’
Footnote 71:
‘Index Filicum,’ by Thomas Moore, F.L.S.
Footnote 72:
Moore, in ‘Treasury of Botany.’
Footnote 73:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 74:
Charles Johnson, Esq.
Footnote 75:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 76:
Berkeley’s ‘Cryptogamic Botany.’
Footnote 77:
Inflorescence and fructification are fully explained, and applied to a
vast number of plants, in ‘Structural and Physiological Botany,’ by
Arthur Henfrey, Esq.,—a work of great research and merit.
Footnote 78:
Messrs. Hooker, Darwin, and Brongniart.
Footnote 79:
Professor Matteucci.
Footnote 80:
Dr. Carpenter, ‘Microscope.’
Footnote 81:
Annals of Natural History for 1863.
Footnote 82:
Annals and Magazines of Natural History for 1863.
Transcriber's Note
This book uses inconsistent spelling and hyphenation, which were
retained in the ebook version. Some corrections have been made to the
text, including correcting the errata and normalizing punctuation.
Further corrections are noted below:
p. 29 heat indedendent matter -> heat independent matter
p. 166 next the visual center-> next to the visual center
p. 179 in dependently -> independently
p. 251 isr eproduced -> is reproduced
p. 343 ig 56 -> Fig 56
p. 351 the fonds are articuled -> the fonds are articulated