crystalline and nearly circular shell, without either incision or teeth,
though towards the apex it falls in so as to form a smooth notch; the
body is affixed to the middle of the shell; a double glittering organ,
with ciliated edges, is projected from the apex; both these organs are
of a conical figure, appearing to stand on a pellucid substance, which
is divided into two lobes; between these and the rotatory organ there is
a silver-coloured crenulated membrane; two small claws may be discovered
near the mouth. It is reckoned as one of the rarer species of
vorticella, and is found in stagnant waters in the month of May.
361. BRACHIONUS CLYPEATUS. B. univalvis, testa oblonga, apice
emarginata, basi integra, cauda mutica. Univalved brachionus, the shell
oblong, the apex notched, the base smooth, and the tail naked.
362. BRACHIONUS LAMELLARIS. B. univalvis, testa producta, apice integra,
basi tricorni, cauda bipili. Univalved brachionus, the shell extending
considerably beyond the body; the base divided into three small horns,
with two hairs at the end of the tail.
363. BRACHIONUS PATELLA. B. univalvis, testa ovata, apice bidentata,
basi emarginata, cauda biseta. Brachionus with a univalve oval shell,
two teeth at the apex, the base notched; two bristles at the tail.
The shell plain, oval, orbicular, crystalline, with the anterior part
terminating in two acute points on both sides, though the intervening
space is commonly filled up with the head of the animal. The head, the
tail, and the trunk are very distinct; the bottom of the trunk is
terminated in a semicircle, the fore-part marked with two transverse
lines; it occupies the disc of the shell. The intestines are indistinct,
and the tail affixed to the trunk; it is short, annulated, flexible, the
middle projecting beyond the shell, the apex diverging into two very
fine bristles; it fastens itself by these, and whirls about with the
body erect; the rotatory cilia are not perceptible without great
difficulty. It is found in marshy water all the winter.
364. BRACHIONUS BRACTEA. B. univalvis, testa suborbiculari, apice
lunata, basi integra, cauda spina duplici. Univalved brachionus, the
shell rather orbicular, lunated apex, smooth base, and the tail
furnished with two spines.
365. BRACHIONUS PLICATILIS. B. univalvis, testa oblonga, apice
crenulata, basi emarginata. Univalved brachionus, with an oblong shell,
the apex hairy, and the base notched.
366. BRACHIONUS OVALIS. B. bivalvis, testa depressa, apice emarginata,
basi incisa, cauda cirro duplici. Bivalved brachionus, with a flattened
shell, the apex notched, a hollow part at the base, the tail formed of
two tufts of hair.
367. BRACHIONUS TRIPOS. B. bivalvis, testa apice mutica, basi tricorni,
cauda duplici. Plate XXVII. Fig. 59. Bivalved, the apex of the shell
beardless, three horns at the base, and double tail.
The body is pellucid, nearly triangular, bivalved, and open on the back
of the animalculum; from the orifice proceed two little laminæ larger
than the rotatory cilia; at the bottom are three or four rigid points,
_e f e_, and a moveable tail, _g_, between them, divided into two
filaments, which the little creature opens and shuts at pleasure; by
these it fixes itself to objects. _a a_, the lateral cilia; _b_, two
small laminæ; _c_, a deglutatory muscle; _d_, an opake mass.
368. BRACHIONUS DENTATUS. B. bivalvis, testa arcuata, apice et basi
utrinque dentata, cauda spina duplici. Bivalved brachionus, with an
arched shell; the apex and the base are both toothed, and the tail
formed of two spines.
369. BRACHIONUS MUCRONATUS. B. bivalvis, subquadrata, apice et basi
utrinque mucronata, cauda spina duplici. Bivalved, somewhat of a square
form; the base and apex pointed; the tail consisting of two spines.
370. BRACHIONUS UNCINATUS. B. bivalvis, testa ovali, apice integra, basi
mucronata, cauda rugosa biseta. Plate XXVII. Fig. 55. Bivalved
brachionus, with an oval shell, the apex even, the base pointed, two
thick bristles for the tail.
This is one of the smallest bivalved animalcula, muscular, the apex and
anterior part round, the hinder part straight, terminating in a point,
furnished with a hook on the fore-part, a small rotatory organ, a long
tail composed of joints, and divided at the end into two bristles. It
can open its shell both at the fore and hind-part. _a_, the shell when
close; _c_, the posterior point; _d_, the animalculum; _h_, the tail;
_i_, the bristles.
371. BRACHIONUS CIRRATUS. B. capsularis, testa apice producta, basi
curti bicorni, cauda biseta. Larger than the preceding, ventricose,
somewhat pellucid, the head conical, with a bundle of hairs on both
sides; it has likewise a rotatory organ.
372. BRACHIONUS PASSUS. B. capsularis, testa cylindracea, frontis cirris
binis pendulis, setaque caudali unica. Capsular brachionus, in a
cylindric shell, with two long pendulous locks of hair proceeding from
the front; the tail consists of a single bristle.
373. BRACHIONUS QUADRATUS. B. capsularis, testa quadrangula, apice
bidentata, basi bicorni, cauda nulla. Capsular brachionus, in a
quadrangular shell, with two small teeth at the apex, two horns
proceeding from the base, and no tail.
374. BRACHIONUS IMPRESSUS. B. capsularis, testa quadrangula, apice
integra, basi obtusi emarginata, cauda flexuosa. Capsular brachionus,
the shell quadrangular, a smooth undivided apex; obtuse base; notched
margin, and a flexuous tail.
375. BRACHIONUS URCEOLARIS. For a full description of this animalculum,
being the same as the vorticella urceolaris, the reader will please to
refer to page 408. Views of the animal in its different positions will
be found in Plate XXII. Fig. 36, 37, 38, and in Plate XXVII. Fig. 56 and
57. Fig. 56, _a a_, are the two fibrillæ; _b_, the head; _f_, the
intestines; _i_, the aperture from which the tail is protruded; _i k_,
the tail; at the end, _k_, is a cleft, enabling the animal to affix
itself more firmly to any substance. Fig. 57, at _a c a_, are seen the
fibrillæ; _d_ shews the moveable intestine, supposed to be the heart or
lungs; _f_, the intestines; _h i k_, the tail.
376. BRACHIONUS BAKERI. B. capsularis, testa ventricosa, apice
quadridentata, basi bicorni, cauda longa bicuspi. Plate XXVII. Fig. 58.
Capsular brachionus, the shell ventricose, four teeth at the apex, two
horns at the base, and a long tail terminating in two short points.
This differs considerably from the foregoing in the shape of the shell,
from each side of which there is a curved projection, _f f_, inclining
towards the tail, nearly of the same length with it, and terminating in
a point, _h h_. The upper part also of the shell is of a different form,
having in general four longer spiculæ, and two shorter ones. From the
head two arms or branches, _e e_, are frequently extended; the circular
end of each is furnished with a tuft of little hairs, which sometimes
move in a vibratory manner, at other times have a rotatory motion. The
eggs are either affixed to the tail, or the curved part of the shell;
they have from one to five hanging from them. Müller has likewise
discovered in this animalculum two small feelers, and a kind of tongue.
_a a_, the rotatory organs; _b_, the tongue; _c c_, the feelers; _d d_,
a ciliated part on the side of the shell; _g_, the heart or lungs; _m
k_, the tail; at the extremity, _k_, two sharp points.
377. BRACHIONUS PATULUS. B. capsularis, testa ventrosa, apice
octodentata, basi lunata quadricorni, cauda brevi bicuspi. Capsular
brachionus, the shell ventricose, eight teeth at the apex, the base
lunated or hollowed into the form of a crescent, and furnished with four
horns; the tail short, with two small points at the end.
ADDITIONAL ANIMALCULA INFUSORIA, EXHIBITED IN PLATE XXVI.
378. Fig. _A A A_. An animalculum found in ditch water in the month of
September, represented in three different forms which it assumed.
379. Fig. _B B B_. A species of testaceous wheel-animal; _a_, its
appearance when protruded; _b_, when in the shell; _c_, another
appearance of the same.
380. Fig. _C_, shews one of the same species; and
381. Fig. _D_, exhibits another of the same kind; they both appear as
protruded from the shell. The above are all drawn as they were found
adhering to a vegetable substance.
382. Fig. _E E E_. Several appearances of an animalculum found in
stagnant water in September, about the one-hundredth part of an inch in
length; it moved slowly, and there appeared a wheel-like motion in
certain fibrillæ in the head. The double-forked part of the tail had a
similar motion to the tail of the pulex aquaticus; the intestines
appeared of different colours, as brown, yellow, and reddish, and had a
quick irregular motion; the external parts were very transparent.
383. Fig. _F F F F_. Several animalcula in a drop of water from a leaden
cistern; of different sizes, but apparently of the same species. They
moved either end foremost, without any undulating motion, but very
uniform and slow; each end appeared alike, and very transparent; the
middle clear, brown, with a blackish list nearly the whole length of
the animal. The large one, _a_, lay sometime bent, as in the drawing,
the others, both when in motion and at rest continuing quite straight.
Some of the very small ones were transparent; others appeared as at _b_
and _c_.[128]
[128] In the former edition of this work, owing to an error in the
numeration, it appeared that 379 of these animalcula were described,
though in reality it contained only 377, or the number which has
already been given.
Previous to the publication of Mr. Adams’s edition, a friend
communicated to him drawings and descriptions of several of these
minute beings which had fallen under his observation; but they were
received too late for insertion. Mr. A. having at that time favoured
me with a copy of the drawings and manuscript, they are now added,
with the hope that they will not prove unacceptable to the curious
reader. EDIT.
Having in this and the preceding chapter described an extensive variety
of those minute and wonderful productions of nature, the hydræ,
vorticellæ, and animalcula infusoria, I shall take my leave of the
subject with remarking, that though by the assistance of the microscope
myriads of animated beings, roving in the smallest drop of water as if
it were a sea, have been exhibited to the astonished eyes of attentive
observers, it surely cannot be deemed an unreasonable supposition, that
the ADORABLE CREATOR, who has filled the immensity of extent with suns
and worlds, has also peopled every particle of fluid with beings far
more minute than any apparatus of ours can perceive; and however
insignificant many of the smaller parts of the creation may appear to
the uninformed bulk of mankind, there cannot exist a doubt, but that
they were all, collectively and individually, formed for the wisest
purposes; and, though in many instances these designations are to us
incomprehensible, let us not on that account rashly withhold our
admiration. These sentiments are beautifully enforced in the following
expressive lines of Thomson:
Gradual from these what num’rous kinds descend,
Evading ev’n the microscopic eye!
Full nature swarms with life; one wond’rous mass
Of animals, or atoms organized,
Waiting the vital breath, when parent heaven
Shall bid his spirit blow. The hoary fen,
In putrid streams, emits the living cloud
Of pestilence. Thro’ subterranean cells,
Where searching sun-beams scarce can find a way,
Earth animated heaves. The flowery leaf
Wants not its soft inhabitants. Secure,
Within its winding citadel, the stone
Holds multitudes. But chief the forest boughs,
That dance unnumber’d to the playful breeze,
The downy orchard, and the melting pulp
Of mellow fruit, the nameless nations feed
Of evanescent insects. Where the pool
Stands mantled o’er with green, invisible,
Amid the floating verdure, millions stray.
Each liquid too, whether it pierces, soothes,
Inflames, refreshes, or exalts the taste,
With various forms abounds. Nor is the stream
Of purest crystal, nor the lucid air,
Tho’ one transparent vacancy it seems,
Void of their unseen people. These, conceal’d
By the kind art of forming heaven, escape
The grosser eye of man:---------
Let no presuming impious railer tax
Creative Wisdom, as if aught was form’d
In vain, or not for admirable ends.
Shall little haughty Ignorance pronounce
His works unwise, of which the smallest part
Exceeds the narrow vision of her mind?
As if upon a full-proportion’d dome,
On swelling columns heav’d, the pride of art!
A critic fly, whose feeble ray scarce spreads
An inch around, with blind presumption bold,
Should dare to tax the structure of the whole.
And lives the man, whose universal eye
Has swept at once th’ unbounded scheme of things;
Mark’d their dependance so, and firm accord,
As with unfaultering accent to conclude
That this availeth nought? Has any seen
The mighty chain of beings lessening down
From infinite perfection to the brink
Of dreary nothing, desolate abyss!
From which astonish’d thought, recoiling, turns?
Till then alone let zealous praise ascend,
And hymns of holy wonder, to that Power,
Whose wisdom shines as lovely on our minds,
As on our smiling eyes his servant sun.
CHAP. IX.
ON THE ORGANIZATION OR CONSTRUCTION OF TIMBER, AS VIEWED BY THE
MICROSCOPE.
The subject of the following chapter opens an extensive field for
observation to the naturalist, in which the labour of a life may be well
employed: it is a branch where the observer will find the microscope of
continual use, and without which he will scarce be able to form any just
idea of the organization of trees and plants, or of the variations in
the disposition, the number, nature, and offices of their several parts.
Vegetables are beautiful and perfect in their kind, wonderful in their
growth, beneficial in their uses. “Herbs and flowers may be regarded by
some persons as objects of inferior consideration in philosophy; but
every thing must be great which has God for its author. To him all the
parts of nature are equally related: the flowers of the earth can raise
our thoughts up to the Creator of the world as effectually as the stars
of heaven; and, till we make this use of both, we cannot be said to
think properly of either. All trees and herbs in their place and seasons
speak the same language from the climates of the north to the torrid
regions of the south, and from the winter to the spring and the harvest,
they join their voices in the universal chorus of all created beings,
and to the ear of reason celebrate the wisdom of the Almighty Creator.”
Malpighi, Grew, Duhamel, Hill, Bonnet, and De Saussure, are almost the
only writers who have treated on the interior structure of vegetables;
and, if we consider the imperfection of the instruments used by some of
them in these anatomical researches, and the little attention paid by
the rest to the advantages their favourite pursuits might have derived
from the use of the microscope, as well as the dissecting knife, we find
greater cause to wonder at what has been done, than at what remains to
be performed. To the general inattention to the structure of plants, we
may, amongst other causes, also ascribe the instability and fluctuation
of the different theories on the principles of vegetation. We are,
however, so little acquainted with the steps which Providence takes to
lead intellectual, but free agents, to the knowledge of truth, and the
various difficulties, errors, and prejudices, necessary to be removed,
before it can shine in its native colours, that it is our duty to
encourage every humble effort towards the advancement of science, that
thus we may co-operate with our Creator and Redeemer in promoting that
vast plan to which all things are now converging, the bringing all his
creatures to a state of truth, goodness, and consequent happiness, an
end worthy of the best and wisest of beings.[129]
[129] See the Bishop of Exeter’s Sermon before the Society for the
Propagation of the Gospel.
As Dr. Hill is the first writer who has treated this part of natural
history in an orderly and scientific manner, I shall use the names he
has adopted for characterizing the different parts of trees, &c. which
are, 1. the rind; 2. the bark; 3. the blea; 4. the wood; 5. the corona
or circle of propagation; 6. the pith. These are placed immediately
within or under one another; they are the essential parts upon which the
strength of the tree depends: in, among, and between these, the various
vessels are placed, which nourish the whole, and maintain and carry on
the vegetation of the tree, and from which it obtains its peculiar
qualities and virtues. These vessels are of five kinds:
1. The Exterior }
}
2. The Interior } Juice Vessels.
}
3. The Intimate }
4. The Sap Vessels.
5. The Coronal.
Of these, the first are placed between the rind and bark; the second, in
the substance of the bark; the third, in the substance of the blea; the
fourth, in the substance of the wood; the fifth, in the corona.
More accurate instruments, or a more minute investigation of the parts,
may probably discover new vessels in a system which appears to be
entirely vascular, and brings us more thoroughly acquainted with the
nature of vegetation.
OF THE RIND.
The exterior covering of all trees is a thin, dry, parched substance,
which has been compared by many writers to the skin of animals, and
called by names analogous thereto; thus it is called the epidermis by
Duhamel, the skin by Grew, the rind by Hill.
When a tree is full of sap, this membrane may be easily detached from
the part it covers; it may be separated from green branches which are
not in sap, by boiling them in water; large pieces of it may also be
obtained from rotten branches; the rind of the leaves of many trees is
detached with singular dexterity from the other parts, by some of the
mining caterpillars; artificial methods for effecting this purpose have
been described in page 160 of this work. Though the rind may at first
sight be thought to be of little use, it will be found to be a principal
organ in the process of vegetation. The part which covers the root has
the most important offices assigned to it.
Many are of opinion that the rind is formed of dried vesiculæ; and
Malpighi says, that we may see in the vascular texture of the bark of
the cherry and plumb-trees an arrangement of the parts proper to form
the rind, and this arrangement is occasioned by the endeavour of the
vascular part to extend itself to the circumference, and the resistance
it meets with from the rind; and that hence the vessels are flattened,
and assume a membranaceous form.
The rind is a general covering to the young trunks of trees, to the
branches, the roots, the leaves, the fruit, the flowers, &c. Upon the
trunks of large trees some pieces only of the rind are to be found,
having probably been broken by the increased size of the tree. The rind
of some species of trees will bear being stretched much further than
those of others, and remain for a considerable time uniformly spread
over the bark. Du Hamel asserts, that the rind of vigorous healthy,
trees remains longer whole than on those that are more languid,
notwithstanding that the growth of the last is slower, and therefore
makes less efforts against the rind. This circumstance is much in favour
of the distinct organization of the rind, and against the opinion of
those who only suppose it to consist of dried bladders.
Thin as the rind is, it is formed of many coats, adhering closely to
each other, which in some species may be separated with ease, in others,
with difficulty. Du Hamel says, that he has divided the rind of the
birch into six distinct coats, and that he had no doubt but what the
division might have been carried much further. Dr. Hill says, that
unless some of these coats be obtained in a state of separation from the
rest, the true construction of the rind cannot be discovered, for the
connection and form of the parts are lost by the confusion in which they
appear while they lie one upon another.
The following experiments may throw a little light upon this obscure
subject.[130] All the rind was taken from the trunk of a cherry-tree,
and the tree thus skinned exposed to the air; a part of the bark which
was next to the rind dried up and exfoliated; the part next to this did
the same; after two or three exfoliations, a farinaceous substance
covered the superfice of the trunk, soon after which a new rind
appeared. Some pieces of rind were taken from a few young branches, and
the wounds were covered with a cloth that had been soaked in wax and
turpentine; on these the rind appeared in a very little time, without
any apparent exfoliation. From some other branches, not only the rind,
but a part of the bark was also taken away, and the wounds covered as
before; a slight exfoliation was observed here, which was soon followed
with a new rind. The bark was taken entirely off from a vigorous
cherry-tree, while it was in full sap, so that the wood appeared the
whole extent of the trunk. This was protected from the rays of the sun,
and from the air. A new bark and rind formed themselves upon the trunk,
but they did not originate from the bark that was left on the branches
and the root, but extended from different spots, which were first formed
at considerable distances from each other. After a lapse of fifteen
years, this new rind did not appear like the natural rind of the
cherry-tree. From these experiments we learn, that the rind regenerates
more readily in some cases than in others, and that it preserves and
prevents in a degree the bark from becoming dry too soon, and in
consequence thereof exfoliating.
[130] Du Hamel Physique des Arbres, tom. 1, p. 12.
Aided by the microscope, a number of luminous points may be discovered
in the rind;[131] these are so many minute holes for other purposes of
transpiration. In the cane these holes are visible to the naked eye. A
few oval holes may also be perceived in it; these are, however, no more
than a separation of the parts, occasioned by the extension of the vasa
interiora.
[131] Du Hamel Physique des Arbres, tom. 1, p. 9.
Dr. Grew supposed the rind to be formed of small vesicles, or bladders,
clustered together, and intermixed with ligneous fibres or vessels,
which run through the length of the rind; these are conjoined by other
transverse ones, but that as the rind dries, the bladders or blebs
shrink up and disappear. This account does not differ much from that of
Dr. Hill, who says, that the rind is formed of a series of longitudinal
vessels, and a filmy substance, between them, which, when viewed in a
transverse section, form small circles, the sides of which are supported
and made up of these longitudinal fibres; that the transverse vessels
are only a deception, occasioned by the spaces between them and part of
the film. The mode of obtaining an accurate view of the organization of
this part, by conveying coloured liquors into the several vessels
thereof, has been already described in page 160 of these Essays; by
these means, together with the microscope, we find that the vessels are
everywhere pierced with small dots or openings: of the use of these, the
following conjectures have been formed.[132]
[132] Hill’s Construction of Timber, &c. p. 37.
The root, which is equal in surface to a third part of the tree above
ground, is covered with a pierced rind. The cold of winter contracts
the whole of this, the parts are drawn closer together, and the mouths
of these innumerable vessels are shut or nearly so, by this contraction;
a very little of the half-congealed moisture of the ground gets into
them, but this suffices for the service of the tree, when there is
little heat to cause any perspiration, and at a time when in the
deciduous trees, the very organs of the greatest perspiration, the
leaves, do not exist.
The warmth of the spring arrives, the fluids of the earth grow thinner,
every part of the root expands; this opens the mouths of the vessels,
and the torrent of nutrition rushes in. By these means, every coat of
the rind, and the interstitial spaces thereof, are rendered supple, and
may be easily separated from the under coverings.