7 As there are in nature many contrasts, there are, also, many resemblances, though there are no likenesses. Some of these resemblances constitute the best media, by which the several portions of nature may be associated, or contrasted, with each other. The sciences become simplified by this method. Since illustrations of excursion, if the term may be allowed, impart beauty to strength; colour to form; variety to monotony; and render more evident Nature's unison of systematic accordance. The perfume of the citron may be imparted to less favoured fruits, by infusing its essence into the sap of their roots. Plants claim some affinity with animals. The stalk of the former resembles the body of the latter; VOL. III. B the root the stomach; the bark the skin; the pith the marrow; and the juice the blood. Like animals, too, plants are subject to a great variety of disorders. They imbibe air and moisture by their leaves; and food by their roots ;-both being transubstantiated into their own substance: as theirs is afterwards employed in the structure of animals. For the entire frame of animated being derives its form and its consistence from vegetable organizations. Some writers confound sensation with the power of motion: and if no motion is perceived, they cannot imagine the existence of sensation. Oysters have no more the locomotive power than thistles; and they can no more forsake the beds, in which they are deposited by the tide, than fishes can swim without water, or birds and insects fly without air. Vegetable sensation, however, is not animal sensation; and it is no superficial mode of supporting this argument to observe, that, as Nature has given compensations to all, she would never have ordained so cruel a result as animal sensation to plants, without giving in return the power of defence. A few plants, it is true, seem to be endued with this faculty: some by the noxiousness of their qualities; and others by the peculiarity of their structures: as the nettle, the thistle, the noli me tangere, the thorn, the rose, the holly, the kamadu of Japan, with the deadly nightshade, and other poisonous plants. Yet these plants, armed as some of them are against attacks, and as others are against animal use, support innumerable insects. Some plants open their petals to receive rain: others avoid it. Some contract on the approach of a storm; and others at the approach of night; while some expand and blossom only to the evening air. Near the Cape, certain flowers form a species of chronometer. The Moræa unguiculata' and undulata open at nine in the morning, and close at four; the Ixia cinna monea opens at the time the other closes; and sheds a delicious perfume during the night. The Mexican marvel of Peru3 also closes at four. II. The stamina of the flowers of sorrel thorn are so peculiarly irritable, that, when touched, they will incline almost two inches; and the upper joint of the leaf of the Dionæa is formed like a machine to catch food. When an insect, therefore, settles upon its glands, the tender parts become irritated; the two lobs rise up, grasp the insect, and crush it to death. The sensitive plant shrinks back and folds its leaves upon being touched, after the manner of a snail; and a species of the hedysarum of Bengal has its leaves during the day in continual motion; on the approach of night these leaves sink from their erect posture and seem to repose. Nor is this motion confined to the time of being in full perfection; for if a branch is cut off and placed in water, the leaves will, for the space of an entire day, continue the same motion; 1 Bot. Mag. 712. Hesperantha, ibid. 1054. Mirabilis dichotoma. and if any thing is placed to stop it, no sooner is the obstacle removed, than the plant resumes its activity with greater velocity than it did before; as if it endeavoured to recover the motion it had previously lost. Mons. Descernet' and other writers suppose, that this irritability is ordained by nature for promoting generation. As the motion is constant during the day, this reason is insufficient: unless we can suppose, that the organs of generation are in a constant state of irritable excitement. But these instances are exceptions to the general rule, and form links serving to connect the sensation of vegetables with those of animals; for it is not unreasonable to suppose, that plants may differ in feelings as well as in appearance; and that trees, shrubs, flowers, and roots, may have distinct gradations of sensation. The plane-tree exhibits the power of exercising a sagacity for securing food, not unworthy of an animal. Lord Kaims relates, that among the ruins of New Abbey, in the county of Galway, there grew, in his time, on the top of one of its walls, a plane-tree, upwards of 20 feet in height. Thus situated, it became straightened for food and moisture, and, therefore, gradually directed its roots down the side of the wall, till they reached the ground, at the distance of ten feet. When they had succeeded in this attempt, the upper roots no longer shot out fibres, but united in one; and shoots vigorously sprung up from the root, that had succeeded in reaching the earth. 1 Annales de Chimie, No, 86. |