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Constructed on a PLAN,

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Compilel from tbe writings of tbe beft Authors, in several languages ; tbe mosi approved Dictionaries, as well of general science as of its partie

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3

THE THIRD EDITION, IN EIGHTEEN VOLUMES, GREATLY IMPROVED.

ILLUSTRATED WITH FIVE HUNDRED AND FORTY-TWO COPPERPLATES.

.VOL. XV.

IN DOCTI DIS CANT, ET A MENT 11E MINISSE PERITI.

E DIN BURG H.
PRINTED FOR A. BELL AND C. MACFARQU H AR.

MDCCXCVII.

Entered in Stationers Wall in Terms of the gå of Parliament.

1

ENCYCLOPÆDIA BRITANNICA.

Plant

by feeds.

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LANT is defined to be, an organical body, defti- to render them visible. To these ramifications Grew Plant.
PLANT

tute of sense and spontaneous motion, adhering to and Malpighi have given the name of seminal root; be-
another body in such a manner as to draw from it its cause, by means of it, the radicle and plume, before
nourishment, and having a power of propagating itself they are expanded, derive their principal nourishment.

The plume, bud, or germ (fig. 3.), is inclosed in two Plate
The vegetation and economy of plants is one of those small corresponding cavities in each lobe. Its colour CCCXCIV,
subjects in which our knowledge is extremely circum- and consistence is much the same with those of the ra.
scríbed. A total inattention to the structure and eco- dicle, of which it is only a continuation, but having a
nomy of plants is the chief reason of the small progress quite contrary direction; for the radicle descends into
that has been ade in the principles of vegetation, and the earth, and divides into a great number of smaller
of the instability and Auctuation of our theories con- branches or filaments; but the plume ascends into the
cerning it; for which reason we shall give a short de- open air, and unfolds itself into all the beautiful va.
fcription of the structure of plants, beginning with the riety of ftem, branches, leaves, flowers, fruit, &c. The
feed, and tracing its progress and evolution to a ftate of plume in corn shoots from the smaller end of the grain,
maturity.

and among maltsters goes by the name of acrospire.
1. Of Seeds.] The seeds of plants are of various The next thing to be taken notice of is the substance
figures and sizes. Most of them are divided into two or parenchymatous part of the lobes. This is not a
lobes ; though some, as those of the cress-kind, have mere concreted juice, but is curiously organized, and
hx; and others, as the grains of corn, are not divided, consists of a vast number of small bladders resembling
but entire.

those in the pith of trees (fig. 4.)
But as the essential properties of all seeds are the Besides the coats, cuticle, and parenchymatous parts,
fame, when considered with regard to the principles of there is a substance perfectly distinct from these, diftri-
vegetation, our particular descriptions shall be limited buted in different proportions through the radicle, plume,
to one feed, viz. the great garden-bean. Neither is the, and lobes. This inner substance appears very plainly in
choice of this feed altogether arbitrary; for, after it be- a transverse section of the radicle or plume.' Towards
gins to vegetate, its parts are more conspicuous than the extremity of the radicle it is one entire trunk; but
many others, and consequently better calculated for in- higher up it divides into three branches; the middle
vestigation.

one runs directly up to the plume, and the other two This feed is covered with two coats or membranes. pass into the lobes on each side, and spread out into The outer coat is extremely thin, and full of pores; great variety of small branches through the whole bobut may be easily separated from the inner one (which dy of the lobes (fig. 4.) This substance is very pro

Plate is much thicker), after the bediebas been boiled, or lain perly termed the seminal root: for when the feed is fown, CCCXCI. a few days in the soil. At the thick end of the bean the moisture is first absorbed by the outer coats, which

there is a small hole visible to the naked eye, immedi- are everywhere furnished with fap and air-vessels ; from Platcately over the radicle or future root, that it may have these it is conveyed to the cuticle ; from the cuticle it cccxciv a free passage into the foil (fig. 1. A). When these proceeds to the pulpy part of the lobes ; when it has

A
coats are taken off, the body of the feed appears, which got thus far, it is taken up by the mouths of the small
is divided into two smooth portions or lobes. The branches of the feminal root, and passes from one branch
{moothness of the lobes is owing to a thin film or cu- into another, till it is all collected into the main trunk,
ticle with which they are covered.

which communicates both with the plume and radicle,
At the basis of the bean is placed the radicle or fu- the two principle involved organs of the future plant.
ture root (fig. 3. A). The trunk of the radicle, juft After this the fap or vegetable food runs in two oppo-
as it enters into the body of the seed, divides into two site directions : part of it ascends into the plume, and

capital branches, one of which is inserted into each promotes the growth and expansion of that organ; and Plate

lobe, and sends off smaller ones in all directions through part of it descends into the radicle, for nourithing and CCCXCI, the whole fubitance of the lobes (fig. 4. AA). These evolving the root and its various filaments. Thus the

ramifications become so extremely minute towards the 'plume and radicle continue their progress in opposite di.
edges of the lobes, that they require the finest glasses rections till the plant arrives at maturity.
Vol. XV. Part I.

A

It

Plant.

a

These rays

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Plant. It is here worth remarking, that every plant is really renchymatous part of the radicle, but greatly augment

possessed of two roots, both of which are contained in ed. The bark is of very different sizes. In molt trees
the seed. The plume and radicle, when the feed is first it is exceeding thin in proportion to the wood and pith.
deposited in the earth, derive their nourishment from the On the other hand, in carrots, it is almost one-half of
seminal root ; but, afterwards, when the radicle begins the femidiameter of the root; and, in dandelion, it is
to shoot out its filaments, and to absorb some moisture, nearly twice as thick as the woody part.
not, however, in a sufficient quantity to supply the ex- The bark is composed of two fubitances ; the paren-
igencies of the plume, the two lobes, or main body of chyma or pulp, which is the principal part, and a few
the seed, rise along with the plume, assume the appear- woody fibres. The parenchyma is exceedingly porous,
ance of two leaves, resembling the lobes of the feed in and has a great resemblance to a sponge ; for it shrivels
size and shape, but having no resemblance to those of considerably when dried, and dilates to its former di-
the plume, for which reason they have got the name of mensions when infused in. water. These pores or vef-
di similar laves.

sels are not pervious, so as to communicate with each
These dissimilar leaves defend the young plume from other ; but consist of distinct little cells or bladders,
the injuries of the weather, and at the same time, by scarcely visible without the aflistance of the microscope.
absorbing dew, air, &c. assist the tender radicle in nou- In all roots, these cells are conftasitly filled with a thin
rishing the plume, with which they have still a connec- watery liquor. They are generally of a spherical figure;
tion by means of the seminal root above described. But though in some roots, as the buglofs and dandelion, they
when the radicle or second root has defcended deep are oblong. In many roots, as the horse-radish, peony,
enough into the earth, and has acquired a sufficient asparagus, potatoe, &c. the parenchyma is of one uni-
number of filaments or branches for absorbing as much form itructure. But in others it is more diversified,
aliment as is proper for the growth of the plume; then and puts on the shape of rays, running fru• the centre
the feminal or diffimilar leaves, their utility being en- towards the circumference of the bark.
tirely superseded, begin to decay and fall off.

sometimes run quite through the bark, as in lovage;
Plate
CCCXCIV Fig. 1. A, the foramen or hole in the bean through and sometimes advance towards the middle of it, as in
which the radicle shoots into the foil.

melilot and most of the leguminous and umbelliferous Fig. 2. A transverse section of the bean ; the dots plants. Thefe rays generally stand at an equal dilance being the branches of the seminal root.

from each other in the same plant; but the distance vaFig. 3. A, the radicie. B, the plume or bud. ries greatly in different plants. Neither are they of Fig. 4. A, a longitudinal section of one of the lobes equal fizes : in carrot they are exceedingly small

, and of the bean a little magnified, to show the small bladders scarcely discernible; in melilot and chervil, they are of which the pulpy or parenchymatous part is compo- thicker. They are likewise more numerous in fome plants sed.

than in others. Sometimes they are of the same thickFigs. 5. 6. A, a transverse section of the radicle. B, ness from one edge of the bark to the other; and some a transverse section of the plume, showing the organs or grow wider as they approach towards the fkin. The veslils of the seminal root.

vessels with which thete rays are amply furnished, are Plate Fig. 4. A view of the feminal root branched out up- supposed to be air-vefels, because they are always found CCCXCI. on the lobes.

to be dry, and not so transparent as the veľfels which Plate Fig. 7. The appearance of the radicle, plume, and se- evidently contain the fap. CCCXCIV minal root, when a little further advanced in growth. In all roots there are ligneous vessels dispersed in dif

Having thus briefly described the feed, and traced its ferent proportions through the parenchymna of the bark.
evolution into three principal organic parts, viz. the These ligneous veffels run longitudinally through the
plume, radicle, and feminal leaves, we shall next take an bark in the form of small threads, which are tubular, as
anatomical view of the root, trunk, leaves, &c. is evident from the rising of the sap in them when a

2. Of the rool.] In examining the root of plants, root is cut transversely. These ligneous fap-vessels do
the firit thing that presents itself is the skin, which is not run in direct lines through the bark, but at small
of various colours in different plants. Every root, after distances incline-towards one another, in such a manner
it has arrived at a certain age, has a double skin. The that they appear to the naked eye to be inofculated;
first is coeval with the other parts, and exists in the but the microscope diieuvers them to be only contigu-
feed: but afterwards there is a ring sent off from the ous, and braced together by the parenchyma. These
bark, and forms a second skin ; e... in the root of the braces or coarctations are very various both in fize and
dandelion, towards the end of May, the original or number in different roots; but in all plants they are
outer skin appears Thrivelled, and is easily separated most numerous towards the inner edge of the bark.
from the new one, which is fresher, and adheres more Neither are these vessels fingle tubes ; but, like the
firmly to the bark. Perennial plants are supplied in nerves in animals, are bundles of 20 or 30 small conti-
this manner with a new skin every year; the outer one guous cylindrical tubes, which uniformly run from the
always falls off in the autumn and winter, and a new extremity of the root, without sending off any branches
one is formed from the bark in the fucceeding spring. or suffering any change in their fize or shape.
The skin has numerous cells or vessels, and is a.conti- In some roots, as parsnep, especially in the ring next
nuation of the parenchymatous part of the radicle. the inner extremity of the bark, these vessels contain a
However, it does not confift folely of parenchyma; for kind of lymph, which is sweeter than the sap contained
the microscope hows that there are many tubular lig- in the bladders of the parenehyma. From this circum-
peous veffels intersperfed through it.

stance they have got the name of lymph-dues.
When the skin is removed, the true cortical substance These lymph-ducts fometimes yield a mucilaginous
or bark appears, which is also a continuation of the pa- lymph, as in the comphrey; and sometimes a white

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Plant. milky glutinous lymph, as in the - angelica, fonchus, The trunk, like the root, consists of three parts, viz. Plane.

burdock, scorzonera, dandelion, &c. The lymph-ducts the bark, wood, and pith. These parts, though sub-
are supposed to be the vessels from which the gums and stantially the same in the trunk as in the root, are in
balsams are fecerned. The lymph of fennel, when ex- many cases very different in their texture and appear-
posed to the air, turns into a clear transparent balsam;
and that of the scorzonera, dandelion, &c. condenses in-

The skin of the bark is composed of very minute
to a gum.

bladders, interspersed with longitudinal woody fibres,
The situation of the vessels is various. In some plants as in the nettle, thistle, and most herbs. The outside
they stand in a ring or circle at the inner edge of the of the skin is vilibly porous in some plants, particularly
bark, as in asparagus ; in others, they appear in lines the cane.
or rays, as in borage; in the par nep, and several The principal body of the bark is composed of pulp
other plants, they are most conspicuous towards the outer or parenchyma, and innumerable vessels much larger
edge of the bark; and in the dandelion, they are dispo- than those of the skin. The texture of the pulpy part,
fed in the form of concentric circles.

though the fame fubftance with the parenchyma in
The wood of roots is that part which appears after roots, yet seldom appears in the form of rays running to-
the bark is taken off, and is firmer and lefs porous than wards the pith ; and when these rays do appear, they
the bark or pith. It consists of two distinct subitances, do not extend above half way to the circumference.
viz. the pulpy or parenchymatous, and the ligneous. The vessels of the bark are very differently situated, and
The wood is connected to the bark by large portions of defined for various purposes in different plants. For
the bark inserted into it. These insertions are mostly in example, in the bark of the pine, the inmost are lymph
the form of rays, tending to the centre of the pith, which ducts, and exceedingly small ; the outmost are gum or
are easily discernible by the eye in a transverse fection of resiniferous vessels, destined for the secretion of turpen-
most roots. These insertions, like the bark, contist of tine; and are so large as to be distinctly visible to the
many vessels, mostly of a round or oval figure.

The ligneous vefsels are generally disposed in collateral The wood lies between the bark and pith, and conrows running longitudinally through the root. Some fists of two parts, viz. a parenchymatous and ligneous. of these contain air, and others fap. The air-vefsels are In all trees, the parenchymatous part of the wood, so called, because they contain no liquor. These air- though much diversificd as to fize and consistence, is univessels are distinguished by being whiter than the others. formly disposed in diametrical rays, or insertioils run.

The pith is the centrical part of the root. Some ning betwixt similar rays of the ligneous part.
roots have no pith, as the stramonium, nicotiana, &c.; The true wood is nothing but a congeries of old dried
others have-little or none at the extremities of the roots, lymph-ducts. Between the bark and the wood a new
but have a considerable quantity of it near the top. The ring of these ducts is formed every year, which gradu,
pith, like every other part of a plant, is derived from ally loses its softness as the cold season approaches, and
the seed; but in some it is more immediately derived towards the middle of winter is condensed into a solid
from the bark : for the insertions of the bark running ring of wood. These annual rings, which are distinctly
in betwixt the rays of the wood, meet in the centre, and visible in most trees when cut through, serve as natural
constitute the pith. It is owing to this circumstance, marks to distinguish their age (fig. 10. 11.) The rings Plate
that, among roots which have no pith in their lower of one year are sometimes larger, sometimes less, than CCCXCIV.
parts, they are amply provided with it towards the top, those of another, probably owing to the favourableness
as in columbine, lovage, &c.

or unfavourableness of the season.
The bladders of the pith are of very different sizes, The pith, though of a different texture, is exactly of
and generally of a circular figure. Their position is the fame substance with the parenchyma of the bark,
more uniform than in the bark. Their fides are not and the insertions of the wood. The quantity of pith
mere films, but a composition of small fibres or threads; is various in different plants. Instead of being increased
which gives the pith, when viewed with a microscope, every year like the wood, it is annually diminished, its
the appearance of a piece of fine gauze or net-work. vessels drying up, and affuming the appearance and struc-

We thall conclude the description of roots with ob- ture of wood; infoinuch that in old trees there is scarce
serving, that their whole substance is nothing but a con- such a thing as pith to be discerned.
geries of tubes and fibres, adapted by nature for the ab- A ring of sap-vessels are usually placed at the outer
forption of nourishment, and of course the extension and edge of the pith, next the wood. In the pine, tig, and
augmentation of their parts.

walnut, they are very large. The parenchyma of the Place

Fig. 8. A transverse section of the root of worm- pith is composed of small cells or bladders, of the same CCCXCIV wood as it appears to the naked eye.

kind with those of the bark, only of a larger size. The
Fig. 9. A fection of fig. 8. magnified. AA, the general figure of these bladders is circular; though in

' .
skin, with its vessels. BBBB, the bark.. The round some plants, as the thistle and borage, they are angu-
holes CCC, &c. are the lymph-ducts of the bark : All lar. Though the pith is originally one connected
the other holes are little ceils and fap-vessels. DDD, chain of bladders, yet as the plant grows old they shri.
parenchymatous insertions from the bark, with the cells, vel, and open in different directions. In the walnut, afe
&c. EEEE, the rays of the wood, in which the holes ter a certain age, it appears in the form of a regular
are the air-vessels. N. B. This root has no pith. transverse hollow division. In some plants it is alto-

3. Of the Trunk, Stall, or Stem.] In describing the gether wanting ; in others, as the fonchus, nettle, &c.
trunks of plants, it is necessary to premise, that what there is only a transverse partition of it at every joint.
ever is said with regard to them applies equally to the Many other varieties might be mentioned; but these
branches.
: muit be left to the ybservation of the reader.

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