CHAPTER XX. OF PLANTS. I THINK a defigned and ftudied mechanism to be, in general, more evident in animals, than in plants and it is unneceffary to dwell upon a weaker argument, where a stronger is at hand. There are, however, a few obfervations upon the vegetable kingdom, which lie fo directly in our way, that it would be improper to pass by them without notice. The one great intention of nature in the ftructure of plants feems to be the perfecting of the feed; and, what is part of the fame intention, the preferving of it until it be perfected. This intention fhews itself, in the first place, by the care which appears to be taken to protect and ripen, by every advantage which can be given to them of fituation in the plant, thofe parts which most immediately contribute to fructification, viz. the antheræ, the stamina, and the stigmata. These parts parts are ufually lodged in the centre, the receffes, or the labyrinths of the flower; during their tender and immature ftate, are fhut up in the ftalk, or theltered in the bud: as foon as they have acquired firmnefs of texture fufficient to bear expofure, and are ready to perform the important office which is affigned to them, they are difclofed to the light and air, by the bursting of the ftem or the expansion of the petals after which they have, in many cafes, by the very form of the flower during its blow, the light and warmth reflected upon them from the concave fide of the cup. What is called also the sleep of plants, is the leaves or petals difpofing themselves in fuch a manner as to shelter the young ftem, buds, or fruit. They turn up, or they fall down, according as this purpose renders either change of position requifite. In the growth of corn, whenever the plant begins to fhoot, the two upper leaves of the ftalk join together; embrace the ear; and protect it till the pulp has acquired a certain degree of confiftency. In fome water plants, the flowering and fecundation are carried on within the ftem, which afterwards opens to let loofe the impregnated seed *. The pea or papilionaceous tribe in close the parts of fructification within a beautiful folding of the internal bloffom, fometimes called from its fhape the boat or keel; itself alfo protected under a penthouse formed by the external petals. This ftructure is very artificial; and, what adds to the value of it though it may diminish the curiosity, very general. It has alfo this further advantage (and it is an advantage ftrictly mechanical) that all the bloffoms turn their backs to the wind, whenever the gale blows ftrong enough to endanger the delicate parts upon which the feed depends. I have obferved this a hundred times in a field of peas in bloffom. It is an aptitude which results from the figure of the flower, and, as we have faid, is ftrictly mechanical; as much fo, as the turning of a weather-board or tin cap upon the top of a chimney. Of the poppy, and of many fimilar fpecies of flowers, the head, while it is growing, hangs down, a rigid curvature in the upper part of the ftem giving to it that pofition; and in that pofition it is impene Phil. Tranf. part ii. 1796, p. 502. trable When the head trable by rain or moisture. has acquired its fize, and is ready to open, the ftalk erects itself, for the purpose, as it thould feem, of presenting the flower, and, with the flower, the inftruments of fructification, to the genial influence of the fun's rays. This always ftruck me as a curious property; and specifically, as well as originally, provided for in the conftitution of the plant: for, if the stem be only bent by the weight of the head, how comes it to ftraighten itself when the head is the heavieft? Thele inftances fhew the attention of nature to this principal object, the fafety and maturation of the parts upon which the feed depends. In trees, especially in those which are natives of colder climates, this point is taken up earlier. Many of thefe trees (obferve in particular the ab and the horse chefnut) produce as the embryos of the leaves and flowers in one year, and bring them to perfection the following. There is a winter therefore to be got over. Now what we are to remark is, how nature has prepared for the trials and feverities of that feafon. These tender embryos, are, in the first place, wrapped up with a compactnefs, which no art can imitate: in which ftate, ftate, they compofe what we call the bud. This is not all. The bud itself is inclofed in fcales; which scales are formed from the remains of paft leaves, and the rudiments of future ones. Neither is this the whole. In the coldeft climates a third preservative is added, by the bud having a coat of gum or refin, which, being congealed, refifts the Atrongest frofts. On the approach of warm weather this gum is foftened, and ceafes to be a hindrance to the expanfion of the leaves and flowers. All this care is part of that system of provifions which has for its object and confummation, the production and perfecting of the feeds. The SEEDS themselves are packed up in a capfule, a veffel compofed of coats, which, compared with the reft of the flower, are Atrong and tough. From this veffel projects a tube, through which tube the farina, or fome fubtle fecundating effluvium that iffues from it, is admitted to the feed. And here alfo occurs a mechanical variety, accommodated to the different circumftances under which the fame purpofe is to be accomplished. In flowers which are erect, the piftil is fhorter than the flamina; and the pol len, |