indeed, a most amusing part of the science. We shall present bur readers some examples.

It cannot have escaped the most cursory observer, that a vegetable, in its general structure, has a considerable correspondence with 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 lungs, 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 every 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 Dionau Muscipula (Venus's Fly-trap).

A flat 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 upón 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 Hedysarum 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 latéral 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 fine 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 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-named 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 considerable 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 is 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 has the 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 individual! ;

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 employed about the blossoms of plants. Many of these little revellers, whether in quest of food, of honey, or merely of amusement, are the instruments by which the farina is brushed from the anthers, and scattered over the stigma; thus, while lurking in the cowslip's bell, or in the tube of the honeysuckle, they are assisting functions essential to the maturity of the seeds. Few persons, however, suspect, that some flowers are furnished with the means of forcibly detaining the insect, until this auxiliary office has been performed; after which, they VOL. IX. N. Š.

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have the power of releasing their little prisoner. This is the singular structure of Aristolochia Clematitis, (Common Birthwort,) a native of Britain.

The corolla of this flower, which is tubular, but terminating upwards in a ligulate limb, is inflated into a globular figure at the base. The tubular part is internally beset with stiff hairs pointing downwards. The globular part contains the pistil, which consists merely of a germen and stigma, together with the surrounding stamens. But the stamens being shorter than even the germen, cannot discharge the pollen so as to throw it upon the stigma, as the flower stands always upright till after impregnation. And hence without some additional and peculiar aid, the pollen must necessarily fall down to the bottom of the flower. Now the aid that nature has furnished in this case, is that of the agency of the Tipula pennicor nis, a small insect. which entering the tube of the corolla in quest of honey, descends to the bottom, and rummages about till it becomes quite covered with pollen; but not being able to force its way out again, owing to the downward position of the hairs, which converge to a point like the wires of a mouse trap, and being somewhat impatient of its confinement, it brushes backwards and forwards, trying every corner, till after repeatedly traversing the stigma, it covers it with pollen sufficient for its impregnation; in consequence of which, the flower soon begins to droop, and the hairs to shrink to the side of the tube, effecting an easy passage for the escape of the insect.' Vol. II. pp. 353, 354.

None of the investigations of the physiological botanist appear to be more difficult and intricate, than those which are directed to the explanation of the excitability of the vegetable structure. In some cases, as we have seen, mere contact with the glandular hairs, or irritable membrane of the plant, is a sufficient stimulus for the production of the most striking phenomena. These cases appear to approach most nearly to the nervous action upon the animal system, and would almost induce us to believe that vegetables are endued with sensation as well as vitality. In by far the greater number of instances of vegetable susceptibility, the immediate exciting cause is light, or temperature, or humidity: these stimulate the plant in proportion to their degrees of intensity. Here, the manner of action is either chemical, or mechanical, and is much more conformable to the changes produced in unorganized matter when operated upon by similar circumstances. Temperature and humidity doubtless produce their effects chiefly in a mechanical way, by the various degrees of tension or relaxation of the vegetable fibre. The presence or absence of light, combined with the above-mentioned causes, is productive of a great number of phenomena principally to be referred to chemical agency. During the darkness of the night, the numerous tribes of plants, as well as of animals, sink into repose. The great Linnæus has even ventured to trace the

analogy further, and to assert that vegetables sleep! Whatever be the real nature of the changes which they undergo, certain it is that, during the night, the functions of plants are, in some species, materially different from those which they perform during the day, and in others are totally suspended. While the sun is above the horizon, carbonic acid gas is inhaled by the vegetable, and oxygen gas is evolved. When the light has departed, a precisely contrary elaboration of these two gases commences; the carbonic being given out, and oxygene taken in. As soon as the dews of the evening begin to fall, a universal change takes place throughout the vegetable world. The flower hangs its head, as if pensively awaiting the return of the holy light' which no longer sheds its genial influence; the corolla closes, as if unwilling to expand its delicate structure to te illuminated by no sun-beam, and to be painted by no ray of heaven. Even the leaves appear to sympathize in the gloom which prevails over the face of nature; those of many species folding themselves back upon the stalk, or drooping till the return of day! Such are the analogies between the vegetable and animal creation, which not only poets, but philosophers delight in tracing. To call this alteration or suspension of vegetable functions, their sleep, is doubtless to assume that they, are sentient, and is to give a plausible name to a phenomenon, the rationale of which is but ill understood. If, however, the analogy be fanciful, it is innocent; it is scarcely possible that it should mislead; and it conducts us to a more extended observaion of an order of facts both important and interesting.

Analogies between the condition of the merely organized and he intellectual world, have been traced not only in their funcions, but in accidental circumstances with which they are conjected. Our readers may, perhaps, smile when we tell them hat, if men have clocks, so have flowers:

'Although many plants open their flowers in the morning and shut hem again in the evening, yet all flowers do not open and shut at the ame time. Plants of the same species, are, however, pretty regular > an hour, other circumstances being the same; and hence the daily pening and shutting of the flower has been denominated by botanists, he Horologium Flore. Flowers requiring but a slight application of timulus open early in the morning, while others requiring more, pen somewhat later. Some do not open till noon, and some, whose xtreme delicacy cannot bear the action of light at all, open only at ight, such as the Cactus grandiflora, or night-blowing Cereus.' I. p. 445.

We have vegetable weather-gages also, and of very delicate ructure. That the changes in the state of the atmosphere are dicated by corresponding effects in the habits of certain plants, a fact which suggests itself to the notice of the most trivial

observer. Indeed, some of the most sensible of our philosophi cal instruments bave been constructed upon this very principle. The hygrometer is an instance in point. The most delicate of these instruments, is that which has been constructed by Major Kater, from the beard of an Indian grass, the Andropogon contortum (twisted Andropogon), which, from its zero of perfect dryness, to the saturation by moisture, twists around its own axis ten or twelve times :* if, therefore, one end of the beard be fixed, and the other be attached to an index pointing to a circumference divided into one hundred equal parts, we have the enormous scale of 1000 or 1200 degrees. Human skill, however, is not absolutely necessary to the existence of a vegetable weather-gage; and yet we can scarcely subscribe implicitly to all the following assertions :'

The opening or shutting of some flowers, depends not so much on the action of the stimulus of light, as on the existing state of the atmosphere, and hence their opening or shutting betokens change. If the Siberian Sow-thistle [Sonchus Sibiricus+] shuts at night, the ensuing day will be fine; and if it opens it will be cloudy and rainy. If the African Marigold [Tagetes erecta] shuts after seven o'clock in the morning, rain is near at hand. And if the Convolvulus arvensis [the Corn Bind-weed,] Calendula fluviatilis C. pluvialis? we presume the Small Cape Marygold,] or Anagallis arvensis [the Scarlet Pimpernell, are even already open, they will shut upon the approach of rain, the last of which, from its peculiar susceptibility, has obtained the name of the Poor Man's Weather-glass. Vol. II. p. 446.

If we were inclined to pursue these accidental analogies, between the productions of art and the spontaneous results of unassisted nature, we might amuse our readers with a thousand popular examples. Dionaea muscipula (Venus's Fly-trap) has been before quoted; this curious plant is not only an example of irritability analogous to the nervous affections of animated beings, but the very machinery by which it entraps the unwary fly, bears a striking similarity to a rat-trap. The North Ame rican Saracenia purpurea (the Purple side saddle flower) has its leaves furnished with an anomalous appendage somewhat funnelshaped, forming an artificial bucket adapted to contain water. Nepenthes distillatoria (the Ceylon Pitcher-plant) is still more sportively imitative. From the end of the leaf issues a slender.

*See an interesting memoir on the hygrometric properties of this curious, plant (the Oobeena Hooloo of the Mysore country) in the Asiatic Researches, Vol. IX. It was first brought to England in 1806; but the mechanical construction of the instrument has been much improved by Mr. Jones, Optician, Charing Cross. Rev.

+ Throughout this article, wherever either the Scientific or the Trivial name has been omitted by our author, we have inserted it.

Rev.