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that their petals are not special organs, but stamens in an abortive or trans formed state.* .
Plants are also possessed of cutaneous secernents or perspiratory vessels i and in many plants the quantity of fluid thrown off by this emunctory is very considerable. Keil, by a very accurate set of experiments, ascertained that in his own person he perspired 31 ounces in twenty-four hours. Hales, by experiments equally accurate, determined that a sun-flower, of the weight of three pounds only, throws off 22 ounces in the same period of time, or nearly half its own weight. To support this enormous expenditure it is necessary that plants should be supplied with a much larger proportion of nutriment than animals; and such is actually the fact. Keil ate and drank 41b. lOoz. in the twenty-four hours. Seventeen times more nourishment was taken in from the roots of the sun-flower than was taken in by the man.
Plants, nevertheless, do not appear to have the smallest basis for sensation, admitting that sensation is the result of a nervous system; and we are not acquainted with any other source from which it can proceed: notwithstanding that Percival and Darwin, as already observed, have not only endowed them with sensation, but with consciousness also; and the latter, indeed, with a brain, and the various passions and some of the senses to which this organ gives birth.f
Yet, though the vessels of plants do not appear to possess any muscular fibres, we have evident proofs of the existence of a contractile and irritable power from some other principle; and a variety of facts concur in making it highly probable that it is by the exercise of such a principle that the different fluids are propelled through their respective vessels: nor is there any other method by which such propulsion can be reasonably accounted for. Grew ascribed the ascent of the sap to its levity, as though acting with the force of a vapour: Malpighi, to an alternate contraction and dilatation of the air contained in what he erroneously conceived to be air-vessels: Perrault to fermentation: Hales and Tournefort, to capillary attraction: not one of which theories, however, will better explain the fact than another, as Dr. Thomson has ably established; as he has also the probability of a contractile power in the different sets of vessels distributed so wonderfully over the vegetable frame.J
That a contractile power may exist independently of muscular fibres, we have abundant proofs even in the animal system itself. We see it in the human cutis or skin, which, though totally destitute of such fibres, is almost for ever contracting or relaxing upon the application of a variety of other powers; powers external and internal, and totally different in their mode of operation. Thus, austere preparations and severe degrees of cold contract it very sensibly: heat,on the contrary, and oleaginous preparations, as sensibly relax it. The passions of the mind exercise a still more powerful effect over it: for while it becomes corrugated by fear and horror, it is smoothed and lubricated by pleasure, and violently agitated and convulsed by rage or anger. Yet, could it even be proved that the vessels of plants are incapable of being made to contract by any power whatever, still should we have no great difficulty in conceiving a circulatory system in animals or vegetables without any such cause, while we reflect that one-half of the circulation of the blood in man himself is accomplished without such a contrivance; and this too, the more difficult half, since the veins, through the greater extent of their course, have to oppose the attraction of gravitation instead of being able to take advantage of it. It is in the present day, however, a well-known fact, and has been sufficiently ascertained by the late Dr. Parry of Bath, and on the Continent by Professor Dollinger,that the contractile power of the muscular fibres is not called into action even by the arteries in the course of the ordinary circulation of the blood, since, as we shall have occasion to observe, no increase of size or change of bulk of any kind takes place in arteries either in the contraction or dilatation of the heart's ventricles in a state of
* Mtm. da la 8ocKt* i'Arcueil, torn. Hi. t Wiildenow, Princip. of Bowny, $ 226
tSyst. of Clicm. vol. V. p. 388. 1807
health, unless where they are pressed upon by the finger or some other cause of resistance.
In what part of a plant the vital principle chiefly exists, or to what quarter it retires during the winter, we know not; but we are just as ignorant in respect to animal life. In both it operates towards every point; it consists in the whole, and resides in the whole; and its proof of existence is drawn from its exercising almost every one of its functions and effecting its combinations in direct opposition to the laws of chemical affinity, which would otherwise as much control it as they control the mineral world, and which constantly assume an authority as soon as ever the vegetable is dead. Hence the plant thrives and increases in its bulk; puts forth annually a new progeny of buds, and becomes clothed with a beautiful foliage of lungs (every leaf being a distinct lung in itself*) for the respiration of the rising brood; and with an harmonious circle of action, that can never be too much admired, furnishes a perpetual supply of nutriment, in every diversified form, for the growth and perfection of animal life; while it receives in rich abundance, from the waste and diminution, and even decomposition of the same, the means of new births, new buds, and new harvests.
In fine, every thing is formed for every thing; and subsists by the kind intercourse of giving and receiving benefits. The electric fire that so alarms us by its thunder, and by the awful effects of its flash, purifies the stagnant atmosphere above us; and fuses, when it rushes beneath us, a thousand mineral veins into metals of incalculable utility. New islands are perpetually rising from the unfathomable gulfs of the ocean, and enlarging the boundaries of organized life; sometimes thrown up, all of a sudden, by the dread agency of volcanoes, and sometimes reared imperceptibly by the busy efforts of corals and madrepores. Liverworts and mosses first cover the bare and rugged surface, when not a vegetable of any other kind is capable of subsisting there. They flourish, bear fruit, and decay, and the mould they produce forms an appropriate bed for higher orders of plant-seeds, which are floating on the wings of the breeze, or swimming on the billows of the deep. Birds next alight on the new-formed rock, and sow, with interest, the seeds of the berries, or the eggs of the worms and insects on which they have fed, and which pass through them without injury; and an occasional swell of the sea floats into the rising island a mixed mass of sand, shells, drifted sea-weed, skins of the casuarina, and shells of the cocoa-nut. Thus the vegetable mould becomes enriched with animal materials; and the whole surface is progressively covered with herbage, shaded by forests of cocoa and other trees, and rendered a proper habitation for man and the domestic animals that attend upon him.
The tide that makes a desolating inroad on one side of a coast, throws up vast masses of sand on the opposite: the lygeum, or sea-mat-weed, that will grow on no other soil, thrives here and fixes it, and prevents it from being washed back or blown away; to which the lime-grass,f couch-grass,J sandreed,^ and various species of willow lend their aid. Thus fresh lands are formed, fresh banks upraised, and the boisterous sea repelled by its own agency.
Frosts and suns, water and air, equally promote fructification in their respective ways; and the termes, or white ant, the mole, the hampster, and the earth-worm, break up the ground or delve into it, that it may enjoy their salubrious influences. In like manner, they are equally the ministers of putrefaction and decomposition; and liverworts and funguses, the ant and the beetle, the dew-worm, the ship-worm, and the wood-pecker, contribute to the general effect, and soon reduce the trunks of the stoutest oaks, if lying waste and unemployed, to their elementary principles, so as to form a productive mould for successive progenies of animal or vegetable existence. Such is the simple but beautiful circle of nature. Every thing lives, flourishes, and
* On the leafing of trees, there is a curious and valuable paper in the Swodiah Amcenltatea Academic* wl. ul. an. 40, by II. Barck, 1153, entitled Vrrnatio Arborum. f Erymu* arrnoriu* J Trttk-.ura rtpen*. 4 Ajaado arciuni*
decays: every thing dies, but nothing is lost: for the great principle of life only changes its form, and the destruction of one generation is the vivification of the next.* Hence, the Hindoo mycologists, with a force and elegance peculiarly striking, and which are nowhere to be paralleled in the theogonies of Greece and Rome, describe the Supreme Being, whom they denominate Brahm, as forming and regulating the universe through the agency of a triad of inferior gods, each of whom contributes equally to the general result, under the names of Brahma, Visnu, and Iswara; or the generating power, the preserving or consummating power, and the decomposing power. And hence the Christian philosopher, with a simplicity as much more sublime than the Hindoo's, as it is more veracious, exclaims, on contemplating the regular confusion, the intricate harmony, of the scenes that rise before him—
These, as they change, Almighty Father! these Are but the varied God. The rolling year
OH TBI GENERAL ANALOGY OF VEGETABLE AND ANIMAL LIFE.
The perfection of an art consists in the employment of a comprehensive system of laws, commensurate to every purpose within its scope, but concealed from the eye of the spectator; and in the production of effects that seem to flow forth spontaneously, as though uncontrolled by their influence, and which are equally excellent, whether regarded individually, or in reference to the proposed result.
Such is the great art of nature: and he who would study it with success must, as far as he is able, trace out its various laws, and reduce them to general principles, and collect its separate phenomena, and digest them into general classes. This, in many instances, we are able to do; and in such cases we obtain a tolerable insight into the nature of things. But so vast, so unbounded is the theatre before us, so complicated is its machinery, and so closely does one fact follow up and press upon another, that we are often bewildered and lost in the mighty maze, and are incapable of determining the laws by which it is regulated, or of arranging the phenomena of which it is composed.
The zoologist, in order to assist his inquiries, divides the whole animal creation into six general heads or classes: as those of mammals, birds, amphibials, fishes, insects, and worms. Each of these classes he subdivides into orders; of each of his orders he makes a distinct section for a multitude of kinds or genera; and each of his kinds becomes a still more subordinate section for the species or individuals of which the separate kinds consist. But he is perpetually finding, not only that many cases in each of his inferior divisions are so equally allied to other divisions that he knows not how to arrange them, but that even his classes or first divisions themselves labour under the same difficulty; since he occasionally meets with animals that by the peculiarity of their construction seem equally to defy all artificial method and all natural order. Thus the niyxine glutinosa, which by Linnaeus was regarded and ranked as a worm, has been introduced by Bloch into the class of fishes, and is now known by the name of gastrobranchus cceevs, or hag-fish. The siren lacertina, which was at first contemplated by Linnaeus as an amphibious animal of a peculiar genus, was afterward declared by
'See upon this subject the Swedish Amosnitatea Academical, vol. V. art. 60, by J. H. Hagsn, 17»7, enuCamper and Gmelin to be a fish approaching the nature of an eel, and was arranged accordingly. It has since, however, been restored from the class of fishes to that of amphibials, and is in the present day believed by various zoologists to be nothing more than a variety of the lizard. And thus the hippopotamus, the tapir, and the swine, which by Linnaeus were ranked in the fifth order of mammals with the horse, are arranged byCuvierwith the rhinoceros and the sokotyro, that have hitherto formed a part of the second order.
The eel, in its general habits and appearance, has a near similitude to the serpent; many of its species live out of the water as well as in it; and, like the serpent, hunt for worms, snails, and other food,over meadows and marshes.
The platypus anatinus, or duck-bill (the ornithorhyncus paradoxus of Blumenbach), one of the many wonders of New South Wales, unites in its form and habits the three classes of birds, quadrupeds, and amphibials. Its feet, which are four, are those of a quadruped; but each of them is palmate or webbed like a wild-fowl's; and instead of lips it has the precise bill of a shoveler or other broad-billed water bird; while its body is covered with a fur exactly resembling an otter's. Yet it lives, like a lizard, chiefly in the water, digs and burrows under the banks of rivers, and feeds on aquatic plants and aquatic animals. The viverra or weasel, in several of its species, approaches the monkey and squirrel tribes; is playful, a good mimic, and possesses a prehensile tail. The flying squirrel, the flyinglizard, or draco volans, and especially the bat, approach in their volant endowment the buoyancy of birds, and are able to fly by winged membranes instead of by feathers. The exocetus voliians, or flying-fish, and several other fishes, derive a similar power from their long pectoral fins; while the troctilus, or humming-bird, unites the class of birds with that of insects. It is in one of its species, T. minimus, the least of the feathered tribes; feeds, like insects, on the nectar of flowers alone, and like the bee or butterfly, collects it while on the wing, fluttering from flower to flower, and all the while humming its simple accent of pleasure. Its tongue, like that of many insects, is missile. When taken it expires instantly; and after death, on account of its diminutive size, the elegance of its shape, and the beauty of its plumage, it is worn by the Indian ladies as an ear-ring.
Such being the perplexity and seeming confusion that extend through the whole chain of animal life, it is not to be wondered at that we should at times meet with a similar embarrassment in distinguishing between animal life and plants, and between plants and minerals. I gave a cursory glance at this subject in our last lecture, and especially in regard to that extraordinary division of organized substances which, for want of a better term, we continue to denominate zoophytes; many of which, as, for example, various species of the alcyony and madrepore, bear a striking resemblance to crystals, and other mineral concretions; while great numbers of them, and particularly the corals, corallines, and some other species of alcyony, as the sea-fig, seaquince, pudding-weed, and above all the stone-lily (which last, however, is now only found in a petrified state), have the nearest possible approach to a vegetable appearance. Whence, as I have already observed, among the earlier naturalists, who expressly directed their attention to these substances, some regarded them as minerals, and others as vegetables; and it is not till of late years, only, indeed, since it has been ascertained that the chemical elements they give forth on decomposition are of an animal nature, that they have been admitted into the animal kingdom.
Among plants, in like manner, we often meet with instances of individual species that are equally doubtful, not only as to what kind, order, or class of vegetable existence they belong, but even as to their being of a vegetable nature of any kind, till their growth, their habits, and their composition are minutely examined into. But independently of these individual cases, we also perceive, in the general principle of action and animal life, that the more it is investigated, the more it is calculated to excite our astonishment, and to indicate to us, so far as relates to the Subordinate Powers of the animal frame, the application of one common system to both, and to demonstrate one common derivation from one common and Almighty Cause. Having, therefore, in oar last lecture, submitted to your attention a brief outline of the structure of plants, I shall now proceed to point out a few of these general resemblances, and shall endeavour to select those which are either most curious or most prominent.*
Plants, then, like animals, are produced by ordinary generation; and though we meet with various instances of production by the generation of buds and bulbs, or of slips and offsets, the parallelism, instead of being hereby diminished, is only drawn the closer; for we meet with just as many instances of the same varieties of propagation among animals. Thus the hydra, or polype, as it is more generally called, the asterias, and several species of the leech, as the hirudo viridis, for example, are uniformly propagated by lateral sections, or pullulating slips or offsets ;f while almost every genus of zoophytic worms is only capable of increase by buds, bulbs, or layers; and some of these animals, like the houseleek and various grasses, by spontaneous separation. In effect, most of the kinds now referred to, whether animals or vegetables, may be regarded less as single individuals than as assemblages or congeries of individuals; for in most of them every part exists distinctly of every other part, and is often a miniature of the general form. The various branches of a tree offer a similar example, and present a striking contrast with the various branches of a perfect animal. In the latter every distinct part contributes to one perfect whole: the arm of a man has no heart, no lungs, no stomach; but the branch of a tree has a complete system of organs to itself, and is hence capable in many cases of existing by itself, and producing buds, layers, and other kinds of offspring, when separated from the trunk. The different parts of the polype are equally independent, and are hence equally capable of a separate increase. It is owing to this principle that we are able to graft and bud: and M. Trembly, having applied the same kind of operation to the animals we are now speaking of, found that, by numerous grafts of different kinds upon each other, he was enabled to produce monsters as wild and extravagant as the most visionary poet or fabulist ever dreamed of.
The blood of plants, like that of animals, instead of being simple is compound, and consists of a great multitude of compacter corpuscles, globules for the most part, but not always globules, floating in a looser and almost diaphanous fluid. From this common current of vitality, plants, like animals, secrete a variety of substances of different, and frequently of opposite powers and qualities,—substances nutritive, medicinal, or destructive. And, as in animal life, so also in vegetable, it is often observed that the very same tribe, or even individual, that in some of its organs secretes a wholesome aliment, in other organs secretes a deadly poison. As the viper pours into the reservoir situated at the bottom of his hollow tusk a fluid fatal to other animals, while in the general substance of his body he offers us not only a healthful nutriment, but, in some sort, an antidote for the venom of his jaws: so the jatropha manihot, or Indian cassava, secretes a juice or oil extremely poisonous in its root, while its leaves are regarded as a common esculent in the country, and are eaten like spinach-leaves among ourselves; though the root, when deprived, by exposure to heat, of this poisonous and volatile oil, is one of the most valuable foods in the world, and gives bread to the natives, and tapioca as an article of commerce. Its starch is like that of the finest wheatflour, and, combined with potatoes and sugar, yields a very excellent cider and perry, according to the proportions employed. In like manner, while the bark of the cinnamon tree (laurus cinnamomwn) is exquisitely fragrant, the smell of the flowers is highly offensive, and by most persons is compared to that of newly-sawn bones,—by St. Pierre to that of human excrement.J So
* Ooruralt also Mr. Knight's article, Phil. Tram. ISIO, pan il. p. IT9—181.
f Tom Aristotle, upon a subject which is generally tmppoaedto be of modem discovery, "Sltnttp yip rd Qwr& Kai rairi (scilicet) Ivropa fmtpovutva Suvarai ^jv' •' For, like plants, such insects also mamtain lit* after slips or cuttings."—Hist. Anim. lib. Iv. ch. 8.
See a variety of other curious instances in the author's translation of Lucretius, note to b. ii. ver. 880.
; Mr. Marshall's account delivered to the Royal Society. See Thomson's Annals, Sept. p. 242.