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turalists, what a prodigious stock of phytological information has been contributed by the labours of Bounet, of Du Hamel, of Gærtver, and, still more recently, of Mirbel, of Humboldt, and of (our own countrymen Knight and Ellis!
In pursuing our studies in any particular department of science, to whichever of the two great branches above-mentioned our faculties may be applied, we shall find much to interest us. A knowledge of a science, systematically, is, no doubt, thre first acquisition in point of order ; since it is hy this method alone, that we can either ourselves become acquainted with the individual characters of the ohjects of our study, or communicate our ideas to others. Much of the power and the wisdom of the Creator, is necessarily unfolded to our view, even when our contemplation of his works is limited to their external conformation, and their more obvious characters. Physiological science is, however, a pursuit of a still higher and more dignified order : while engaged in the investigations to which it conducts, we enter the great laboratory of nature; we lift the veil which hides, from the merely general observer, her more secret and refined operations; we gaze upon the exquisite machinery by which she is preparing, unseen, the fairest of her tints, and the most delicate of her dresses ; and, if we are Christian Philosophers, we shall ever rise from such interesting speculations (not with a vain conceit of the self-agency of material causes, but) deeply impressed with the all-pervading action of that Invisible Hand, which arrays “the lilies of the field” with a greater glory than Solomon's, though “they toil not, “ neither do they spin!"
There is yet another decided advantage which we derive from physiological pursuits, and which is not to be reaped from a merely systematic knowledge. Pursuits of the latter class more immediately lead us to contemplate the objects of nature in their individual characters; in Botany, e. g. it is the difference which we trace between two genera or two species, which teaches us to distinguish them from each other. Investigations of the former description lead us, on the contrary, to a more enlarged view of nature, to the recondite analogies which exist between individuals far removed from each other in the systematical arrangement, and differing widely in their external character. We cannot but observe a similarity of functions, of
. laws, of properties, and of anatomical structure, which links together individuals which we might scarcely have imagined to be connected by any common chain; nor are these physiological analogies confined to a correspondence between the objects of any one department of nature; they are more or less to be traced between many of the works of creation, which, in other respects, are separated from each other by distinct lines of demarcation.
They form, in fact, the harmonies of nature; and they unfold to us the interesting truth, that the most pleasing and inexhaustible variety in the works of God, is not inconsistent with a certain simplicity of design, and uniformity of action, in the laws by which they are governed. As we adinit, however, that the love of tracing natural analogies has often given rise to absurd and fanciful speculations, we must beg permission both to guard our remark with some few cautions, and to obviate an objection which has been urged against one of the most interesting of physiological pursuits.
The propensity to trace real or fancied analogies between the different systems of nature, may be remarked in the history of every science. Such analogies have, sometimes, been founded upon the weakest, and even the most absurd hypotheses. When this is the case, it cannot be doubted that such a method of investigation has a tendency to retard rather than promote the advancement of human knowledge. The very love of our adopted theory, may lead us to reject many facts, as unimportant or doubtful, because they do not conform to the favourite analogy which we have imagined to exist between two particular departments of science; although these facts, had they been pursued, without bias, to their legitimate consequences, would have conducted us to some of the most valuable conclusions. A physiological investigator cannot, therefore, be too much upon his guard, lest he should suffer his fancy to rove without reasonable control, over this enchanting ground; for, undoubtedly, the analogies and harmonies which subsist between objects, which at first consideration appear to be placed in the most opposite parts of the system of nature, constitute some of the most inViting subjects of philosophical study. At the same time it must, we think, be allowed, that the very propensity which is so liable to be abused, is also capable of being made subservient to the most valuable and sublime investigations. The very analogies which he has actually discovered, or has imagined to exist, communicate an ardour to the mind of the investigator, which might otherwise have never been imparted; the stimulus, when once excited, carries bim through many uninviting parts of his subject, upon which he might never even have entered in the simple pursuit of an insulated truth. In fact, however little attachment we might originally have felt for the immediate subject of investigation, the analogy is the offspring of our own mind, and as such we cannot but cherish it; and while we are impelled forward by the desire of establishing our favourite hypothesis, we are necessarily led to view nature in forms under, which she might never otherwise have presented herself to our Dotice. Thus we are insensibly led to the kpowledge of phe
nomena for which, perlaps, we were not in search, and which, probably, we did not even suspect to exist.
Of the truth of these reinarks we cannot forbear noticing a striking instance, in the progress of discovery respecting the laws of the planetary system. Who shall say that the rude analogy which the ancients fancifully supposed to exist between the harmony of the heavenly spheres, and the intervals of a musical chord, did not give the first impulse to those speculations which terminated in the beautiful system established by the Newtonian philosopby? It was in the pursuit of planetary analogies, (somewhat more philosophical, but not less erroneous, than these, that the great Kepler actually discovered the laws by which the heavenly bodies are governed. lle set out upon the false hypothesis of the ancient philosophers, that the path of a planet must be the most simple of all geometrical curves, the circle: in the very endeavour to establish his favourite but false position, he discovered the elliptic orbits. He fancifully inagined that a certain analogy existed between the distances of these masses from the sun, and their respective revolutions around bis centre. In the progress of investigation he learned the beautiful fact, that though his own analogy was not the law of nature, yet a real anulogy did exist;--the cubes of the periodic times being proportional to the squares described upon the mean distances. Kepler was led, by his pursuit of harmonies, to trace the actual conditions of the planetary orbits ; and thus he prepared the way for the physical demonstrations of Newton, who succeeded in establishing the law of universal gravitation.
But we return from this digression, to that particular science to which this article is devoted. Botany is not less indebted to analogies, than astronomy. It was the analogy which Linnæus observed between many of the functions of animals and vegeta. bles, that led him to adopt the sexual system, as the most perfect for classification; and whatever may be thought of the actual harmony which subsists between these two departments of creation, it led to the observation of certain facts, intimately connected with the structure of plants, and most important for the purposes of artificial arrangement. In the physiological part of the science, analogies of the most interesting kind present themselves to our notice, and have always been pursued with avidity, by writers upon the subject. We are not, indeed, among those who imagine that a natural barmony exists between the joints in the stalk of corn, and the number of lunar months which have elapsed between the germination of the seed, and the maturity of the plant; but, undoubtedly, there are many analogical phenomena worthy of notice; they constitute, = 'indeed, a most amusing part of the science. We shall present our readers some examples. * It cannot bave escaped the most cursory observer, that a vegetable, in its general structure, has a considerable correspondence withi a living animal. The trunk (as its name imports) is its body; the bark is its epidermis; the ligneous matter is its flesh; the tubes and sap vessels which abound in its internal structure, are the arteries and the veins by which the circulation of the vital principle is carried on to the remotest extremities, and by which the secretions necessary to the growth of the individual, are conveyed to the appropriate parts; while the leaves subserve the purpose of langs, being the organs by which the plant inhales the gases essential to its existence, or throws off those which are superabundant. Such is the general resemblance, as to organization. From the singular habits of some species, we might be almost led to conclude that plants are endowed with sensibility. The irritability of the Stylidium glandulosum, and of the delicate Mimosa, shrinking from the rude touch of the intruder, is familiar to évery body; nor less so is the singular contraction of the glandular hairs upon the leaves of the various kinds of Drosera (Sun-dew). The most remarkable, however, of the irritable plants, is the curious Dionæu Muscipula (Venus's Fly-trap).
• A fat and somewhat circular process (issues) from the apex of the leaf, which is radical and somewhat battle-dore shaped, and consisting of a mid-rib, which is a prolongation of the mid-rib of the leaf, and of two elliptical lobes strongly toothed at the margin, giving it a slight resemblance to a steel-trap with the wings expanded. This singular appendage, from which the specific name of the plant is derived, is so highly irritable, that if it is but touched with the point of any fine or sharp instrument, or if an insect but alight upon it, the lobes immediately collapse, as if eager to seize their prey and detain the insect captive; so that it resembles a trap, to which it has been compared, not only in form, but in function. (Vol. I. p. 82.)
Many other instances of the existence of a vital principle, bearing all the characters of sensation, might be brought forward, but we shall content ourselves with adducing that of the susceptibility of the Aedysarum gyrans (the Moving-plant). This curious Indian plant grows upon the banks of the Ganges.
• Its leaves are ternate, the middle leafit being larger, and the la. teral leafit smaller. All of them are in perpetual motion up and down, sometimes equally, and sometimes by jerks, but without any unison between each other; the motion being always the most distinct and the most rapid in the lateral leafits. If their motion is temporarily suspended by grasping them in the hand, they quicken it when the hand is removed, as if to make up for lost time, and by-and-by resume their original velocity. This movement does not depend upon
the application of any external stimulus, because it takes place alike by day and by night, in the dark and in the light, and requires only a very warm and čine day to be affected in the best style; the leaves exhibiting then a sort of tremulous motion in addition to that already. described. Such is a phenomenon that puzzles and astonishes every beholder, and still remains inexplicable ; but which participates more of the character of animal spontaneity, than a
any other movement hitherto observed among vegetables.” Vol. II. pp. 464, 465.
. A singular and beautiful instance of irritability, presents itself to our notice in the well-nained plant, Impatiens noli:me-tangere (the Yellow Balsam, or Touch-me-not); a vegetable which, though not a very common native of Britain, is a sufficiently familiar acquaintance in our gardens. If the turgid capsules be touched, even before the seeds are matured, they manifest their delicate susceptibility in an instant; the valves contract with a force truly surprising, and while in the act of coiling up, project the seeds to a cousiderable distance. Some of the species of Cranesbill" (as, Erodium moschatum, E. cicutarium, &c.) present us similarly elegant instances of providential design, in the curious contrivance by which the irritability of the plant iš made subservient to the dispersion of the seeds. The seeds of this genus are each inclosed in a vessel furnished with an irritable appendage or tail, which bas tue property of contracting into a spiral by dryness, and of lengthening by moisture. When the heat of the season has matured the seeds, these appendages contract like a spring, detaching the ripened germs from the parent stem. The various changes in the humidity of the atmosphere, cause this susceptible membrane to become more or less relaxed, and thus the seed is actually locomotive, and continues its wanderings till received by some crevice or depression in the soil, fitted to become the nursery of a new indie vidual ! :
Our Author shall furnish us with another exquisite example of the susceptibility, we had almost said, the sensation of plants, which at the same time brings to our notice, one of the most beautiful contrivances by which the reproduction of the species is effected. No admirer of nature can have strolled along the fields, without observing how busily the insect tribe is cm, ployed about the blossoms of plants. Many of these little re. vellers, whether in quest of food, of honey, or merely of amusement, are the instruments by which the farina is brushed froin the anthers, and scattered over the stigina ; thus, while lurking in the cowslip's bell, or in the tube of the houeysuckle, they are assisting functions essential to the maturity of the seeds. Few persons, however, suspect that some flowers are furnished with the ineans of' forcibly detaining the insect, * until this'auxiliary office has been performed; after which, they VOL. IX. N. S.