flower stalk, and, on reaching the ground, strike root, and detaching themselves, become new individuals. Budding animals still further resemble plants in being propagated, also, by ova, or impregnated bodies, as well as by buds. Thus, in the hydra, the ova appear on the cylindrical body of the animal, the ovaries being seated there, and the ova are readily distinguished from the buds, by their hard horny shell.

The bisexuality of the greater number of plants forms no better distinctive feature between them and animals than those characters already noticed: many of the echinodermata, the infusoria, the radiata, and the annelida contain both male and female organs in the same individual. A still more striking affinity may be traced in the existence of those animalcules termed spermatozoa, in the male fecundating organs of plants as well as in those of animals, although they are more rare in the vegetable kingdom. In the anthers of the moss called spagnum exist cells, each of which contains a filament with an elongated ellipsoid head rolled up in a spiral form, and which moves whilst within the cells, and continues its movement when it escapes from them. This is still more curiously displayed in Chara. Each of the pollen particles is an articulated thread, within each of the joints of which a single spermatic animalcule is enclosed. It is at first like a small grain, which gradually assumes a curved appearance, and ultimately that of a spiral convolution. Until this occurs it is motionless; after a time, it breaks through the walls of the cell, and moves very briskly in the water.

2

3

This diagram displays, 1, 2, a mucus molecular substance in each cell of the early pollen thread; 3, the first irregular form of the spermatozoa; and 4, their complete development, and the escape of two of them, from the cells which contained them.

Plants, like animals, possess excitability, or the faculty of being acted upon by external stimuli, impelling them to the exertion of their vegetative powers. Light acts on plants, directing the growth of the stem-vigour and colour of the plant-the direction of branches-position of leaves-the opening and shutting

of flowers, as seen in the Calendula, Taraxacum, Daisy, and Anagallis. Is light the sole agent? Certainly not, for some flowers blow at night, as, for instance, the night-flowering Cereus. Heat influences the protrusion of buds; and other stimulants also influence the vegetable irritability; so that cut plants which have faded revive when placed in water impregnated with camphor. Plants, also, like animals, have their excitability exhausted by over-stimulus, and are acted upon by sedatives (such as Hydrocyanic acid) and Sulphuretted hydrogen, in the same manner as animals.

Besides the physical and physiological distinctions that have been pointed out as marking the line between an animal and a plant, some also are furnished by Chemistry. Thus, through its means we perceive, that one of the great functions of the plant is to decompose water, and assimilate its components to the vegetable tissue, whilst it is one of the properties of animal life, constantly to reform it from its elements. The oxygen, derived from the atmosphere, by whatever means it is introduced into the animal system, is consumed in producing carbonic acid and water, both of which are thrown off as excretions. It is true that water is exhaled in great quantity from the surfaces of plants, but it is that fluid which has been taken into the system of the plant and has not undergone decomposition; it is not actually formed in the body of the vegetable as in that of the animal. It is in the process of vegetation that proteine, also, is formed from the constituents of water, carbonic acid, and ammonia, and it is this proteine which forms the blood and muscular flesh of animals.

The close affinity between plants and animals is demonstrated even in the chemical nature of their products. Thus, MM. Dumas and Cahours have ascertained that vegetable albumen has the same composition as 'the albumen of serum and of eggs-that caseum, which has the same composition as albumen, does not differ whether it is procured from animal milk or from the juices plants-and that fibrine, whether from the blood or from the preper juice of plants, has always more nitrogen and less carbon than albumen or caseum. The influence, indeed, which Chemistry has lately displayed in unfolding the exact relation of composition between vegetable and animal matter, has given a new impulse to the study of the vegetable kingdom, and in this augmented interest, the study of Botany is more or less involved.

If plants and animals agree in so many particulars, it may, justly, be demanded in what does the differences between them consist? The most striking, and those that appear most obvious, are, undoubtedly, sensation and voluntary motion, which are the attributes of animals but not of plants.

Those motions of animals which we term voluntary, differ most

materially from those of plants, by resulting in the voluntary operation of a single organ-namely, that of the mental facultiesand not merely in accordance with the harmonious action of the whole organism. The movements of the Hedysarum gyruns approach nearer to those of volition than any others in the vegetable kingdom with which I am acquainted. The leaves of the plant are trifoliate, or consist of a large middle leaflet, and two small lateral leaflets. When the sun beams full upon the central leaflet, it moves, but here we have a cause adequate to the effect, without referring any part of it to volition: the two lateral leaflets, however, display an incessant rising and falling, independent of the influence of external stimuli. It is also asserted that, if these movements be stopped by holding the leaflets between the fingers for a short space of time, and then withdrawing the fingers, they will move more rapidly, as if to make up for the constrained quiescence which they had suffered. This certainly has somewhat of the character of volition. Some of the movements of plants, also, seem to indicate sensibility. Dutrochet directed the focus of a burning-glass on a single leaflet of a mimosa or sensitive plant-the impression was propagated gradually to the other leaflets. But sensibility must not be confounded with irritability, a principle which plants possess in common with animals; but, with the exception of the solitary observation of Dutrochet, which I have mentioned, we cannot affirm that any of the movements of plants manifest consciousness, without which they cannot exert voluntary movements. The simplest animals manifest both sensation and volition, even those that are fixed to rocks and other bodies, and which present a ramified and vegetable form, for instance the compound polypes; for each individual polype displays both sensation and volutary motion. It is difficult to explain satisfactorily the movements of some plants to simple. irritability. Thus we find that plants placed in an apartment with light admitted at one side only, not only turn the upper surface of their leaves to the light, but bend their stems and branches towards it. The florets of the White Clover are so aggregated as to form a globular head; after the lower circle of florets is impregnated, the whole of that circle turns down, as if to admit light and air to the next circle, which in its turn gives place to the third, and to on until all the florets have been impregnated. This succession of acts for an obvious purpose has, assuredly, a close resemblance to consciousness; yet we cannot affirm that it is so, or that the movements are voluntary. Many similar examples might be mentioned, but none of them, not excepting the movements of the Oscillatoria, and some of the lower vegetables, which more closely resemble volition than those of some of the simpler animals, can be referred to volition.

Plants, again, differ from animal sin having no nervous system.

I was formerly believed, that the functions of apparent sensation, of motion, and of digestion, in the lower and simplest animals, were performed independently of nerves: but more recent investigations have discovered a nervous system in many of these singular beings; and Ehrenberg has described and represented very distinctly, a trace of both vessels and nerves in the more perfect rotatoria, and in some infusoria, animals so minute as to evade our unassisted vision. Indeed, every succeeding day's experience renders it more and more probable that all animals, without distinction, have a nervous system; whilst nothing of the kind has ever been detected in any member of the vegetable kingdom.

Another obvious distinction between plants and animals is connected with the function of digestion, and the digestive apparatus. The simplest animals, those which may be turned outside in and, nevertheless, perform their functions as well as in their natural condition, have an internal cavity, into which their food is taken at intervals; but vegetables are nourished by the surface, not at intervals, but by continual imbibition. It must not, however, be overlooked, that some plants seem to require the aid of solid food, or at least the results of the decomposition of solid matter; and are furnished with an apparatus for entrapping animals evidently for this purpose. This is beautifully exemplified in the leaf-appendages of Dionæa Mucipula; and in the flowers of Leersia lenticularis* To both of these singular plants the decomposed animal matter seems to be a requisite stimulus for maintaining the health of the plant; and this opinion receives support from the fact, that when the plants have languished in hot-houses, where there were no flies, they have been revived by placing fibres of meat upon the fly-traps. Still, however, this food does not enter a stomach-the act of closing upon the fly is not an act of volition; and the fact does not invalidate this point of distinction between plants and animals.

It has been supposed that, because the sap rises in plants, and in the interior of some internodia, and cells of some simple plants, a rotatory motion of fluid can be perceived, plants like animals, have a circulation of fluids. But the opinion is at least disputable, the sap in plants ascend only once, for that which is termed the descending sap of the plant is the proper juice prepared in the leaf, and the fact of currents being observed in opposite directions in the leaf of Chelidonium majus is no proof of the existence of a circulation. But it may be asked, Is the motion in the chara first noticed by Professor Corti, or

This species of Leersia was found by Mr. Pursh growing on the islands of Roanoak River, in North Carolina. Its flowers have appendages on the corolla, similar to those attached to the leaves of Dionæa mucipula; and it uses them in the same manner as the Dionæa, for catching flies.

that discovered in the cells of Valisneria spiralis, or in the hairs of the radicle fibres of frog's bit, Hydrochares morsus rane, any proof of a circulation? I reply, that the motion of a fluid in the cells of a plant, effected in a manner at present not understood, is very different from a general circulation of the sap. The true circulation in animals is derived from an internal impelling power, not from external influences. But whilst we contend for this distinction between animals and plants, we must admit that in some of the former, in many simple animals, neither heart nor vessels, nor circulation, have been discovered.

A more distinctive character is obtained in the products of the respiratory function in plants. Respiration is performed by many simple animals by the entire surface, as by plants, but the products even in this case are different. In plants the process consists chiefly in the conversion of carbonic acid and water into vegetable matter; hence oxygen is exhaled by the leaves, and carbonic acid absorbed by them from the atmosphere; and it is by the decomposition of that acid in the leaf, that the greater part of the oxygen is restored to the air. And although plants exhale carbonic acid during the night, and in the shade, yet the quantity is small; and plants are, in reference to their respiration, a balance in the opposite scale to animals—they remove from the air the carbonic acid exhaled from the lungs and spiracula of animals, and re-supply the oxygen requisite for their respiration. Without the vegetable tribes, the atmosphere would soon cease to be fitted for the present race of animals; without the carbonic acid formed by animal respiration, plants would lose the greater part of their nutriment; by their reciprocal action the atmosphere is preserved nearly absolutely unchanged. Upon the whole we may sum up this comparative view of plants and animals by saying, that whilst they are endued with many properties and functions common to both, they possess others, sufficiently distinctive, which prevent them from being regarded as parts of the same link in the great chain of vital existence.

PROVINCIAL TRANSACTIONS.

BATH BRANCH OF THE PHARMACEUTICAL SOCIETY.

THE Committee of the Bath Royal Literary and Scientific Institution having granted the use of their lecture-room for the purpose, an arrangement has been made with Mr. HENRY M. NOAD (Member of the Chemical and Electrical Societies of London, Author of Lectures on Chemistry, &c., &c.) to deliver an evening course of TWELVE LECTURES ON PRACTICAL AND EXPERIMENTAL CHEMISTRY, which commenced on Friday, May 5th, at eight o'clock p.m., and is continued on the succeeding Fridays and Tuesdays at the same hour. (Terms 10s).