304 



PHY 



THE UNIVERSAL HERBAL; 



P H Y 



panded, adducent vessels, and a few air vessels, and is 

 covered with the vascular cutis. The most careful cultivation 

 cannot convert a prickle into a shoot, as its air vessels become 

 very rapidly ligneous, and separate from the inner bark, 

 and it is therefore only kept from dropping off by the cover- 

 ing cutis. Prickles have sometimes a peculiar shape ; they 

 are almost of the shape of contorted tendrils in Nauclea 

 aculeata, and other plants. Even the stipulse of some plants 

 are converted into prickles ; for instance, Robinia pseuda- 

 cacia, Berberis vulgaris, &c. Tendrils have the same struc- 

 ture of vessels, in herbaceous stems. They are, in fact, 

 petioli, without the leafy expansion, but which, having not 

 wasted their sap in the formation of leaves, have grown 

 longer, and on this account have become too feeble to keep 

 their straight direction. Hence arises their twisted shape. 

 It appears, as if the diminished force of the current of air 

 had a particular influence upon the tendril. For each plant 

 that supports itself by tendrils, when distant from a wall, 

 tree, or shrub, sends out all its tendrils towards that side on 

 which the plant is to attach itself. At least this phenomenon 

 can scarcely be explained in any other way. The pith which 

 is found in the centre of stems, is a spongy cellular texture, 

 which commonly is of a remarkably splendid white colour. 

 It is not the least different from cellular texture, and in no 

 respect like the spinal marrow of animals. Nature seems to 

 have provided plants with it on purpose to deposit in it a 

 store of moisture, that they may not suffer during drought. 

 Hence all trees and shrubs have it; but as soon as they grow 

 older, they need it no longer, the wood being an excellent 

 substitute. On the same account it is unnecessary in water 

 plants, as they very rarely suffer from drought; all of them 

 have a hollow stem, without any pith. The gem or bud is 

 the embryo of a future branch, and its anatomy therefore 

 perfectly coincides with the anatomy of the stems and leaves, 

 as they are inclosed in it in small compass. The period of 

 their formation differs in different plants. In cold regions 

 the bud is formed in autumn, covered with a great many 

 scales, and so prepared for the mild spring. In warm and 

 hot regions this is different; there no pernicious frost 

 destroys the blossoms of the spring, and cold does not impair 

 the vital power of the vegetable creation, therefore no pre- 

 caution was necessary. The buds unfold themselves imme- 

 diately from the bark into branches, without having remained 

 there in the form of buds for any length of time. However, 

 we meet with exceptions to this rule. Hot climates too, have 

 some bud-bearing plants; and we possess a few shrubs, espe- 

 cially the Rhamnus/r</M/a, which never buds. Each bud 

 unfolds a branch with leaves, which at the base of each 

 petiole again produces buds. In this manner their growth 

 continues. But this evolution of buds from buds, would 

 continue without stopping, were it not so regulated, that 

 each bud, as soon as the blossoms and fruits are perfectly 

 formed, decays. The evolution of the flowers, and after- 

 wards of the fruit, constitutes the invincible barrier to the 

 growth of the branches. Each bud, like all vegetable pro- 

 ductions, is formed by the spiral vessels. Cutting a bud in 

 a transverse direction, a white spot appears, continued to 

 the very extremity of the bud, and this snow-white conti- 

 nuation is nothing else than a bundle of air vessels. If 

 the same is done at an early period, an elongation of a 

 small bundle of the spiral vessels is found. The leaves 

 are composed of the same vessels of which the root, 

 stems, and other parts of vegetables, consist. But the 

 manner in which they arc disposed presents a remarkable 

 difference. A great bundle of vessels enters the base of the 

 leaf, and divides on its surface in a rcticular manner, anas- 



tomosing like plants. On this anastomosing of the vessels 

 of leaves depends their form ; and as it differs in each plant, 

 we need not be surprised at the diversity of leaves. If the 

 large vascular fascicle divides into three great divisions, a 

 triangular leaf is formed; if it divides into more, then we see 

 all the species of compound leaves arise. If, for instance, 

 the vascular fascicle at the base of the leaf splits into smaller 

 ones, a nerved leaf is formed. But if it run straightforward, 

 emitting single fascicles on its sides, then we have a veined 

 leaf. If there are on the margins of the leaf numerous anas- 

 tomoses, such a leaf is then called folium integerrimum. 

 But if the fascicles spread in small unconnected branches 

 towards the margin, the leaf becomes, according to circum- 

 stances, serrated, dentated, crenate, and so forth. These 

 bundles of vessels in leaves are composed of air and addu- 

 cent vessels. The net-work they form, is in both its surfaces 

 covered with cellular texture, in which the reducent vessels 

 lie. And the external membrane, or cutis, which on both 

 sides invests the cellular texture, is provided with innumer- 

 able lymphatic vessels, and their exhaling pores. The foot- 

 stalk of leaves resembles in its structure that of the stem, 

 except that the air vessels on its base by their convolutions 

 form a knot, which serves for the evolution of the bud, their 

 direction being thus changed. This knot is of the same 

 nature as the supporter of a bulb. In rooty plants, radicles 

 are observed to shoot out ; as also in sessile leaves, or such 

 as want the footstalk, we seldom find such a knot, and 

 therefore they will not always produce buds at their base. 

 Of all the parts of plants, the leaves shew a particular irri- 

 tability ; especially in compounded leaves. Merely by touch- 

 ing the leaves of Mimosa pudica, sensitiva, casta, Oxalis 

 sensitiva, Smithia sensitiva, and many others, they instantly 

 contract. If single leaves, or the .main footstalk, be touched, 

 they remain contracted for some minutes. Almost all trian- 

 gular leaves, and leaves which are composed of several small 

 ones, contract at night, like the above plants, in such a 

 manner that one leaf covers the other, and the whole becomes 

 compressed. Whoever will take the trouble to examine the 

 plants of a garden at night-time with a lantern in his hand, 

 will find several of them in this state, which has been called 

 sleep. There are plants which, at a certain hour in the day, 

 open and close their leaves. Du Hamel made experiments 

 with the Mimosa sensitiva, which at a certain hour in the 

 evening shuts its leaves, and again at a certain time opens 

 them. He put this plant in a leathern trunk, covered with 

 woollen blankets, and found that its leaves opened at a cer- 

 tain hour in the morning, and again were shut up in the 

 evening. It has been alleged, that this phenomenon varies 

 in its period, when going on in vacuo. A South American 

 shrub (Porliera hygrometrica,) uniformly contracts its fea- 

 thered leaves whenever it is going to rain, and is the surest 

 foreteller of the weather that one can have. A plant which 

 grows in the marshes of South Carolina, Dionoea muscipula, 

 has a singularly constructed leaf. At the apex of a lanceo- 

 late leaf an elongation is seen armed with short prickles, 

 which as soon as an insect or other small body is put upon 

 it, shuts itself, and does not open till the body caught 

 by it becomes quiet. The species of Drosera rotundifolia 

 and lonr/ifo'lia, the leaves of which are planted on their mar- 

 gins and surfaces with petioled glands, contract, according 

 to Roth's observations, when stimulated, though very slowly. 

 A species of Filix in No th America, the Onoclea sensibilis, 

 has got this appellation merely from the circumstance, that 

 its young leaves, when they begin to unfold themselves, 

 shrink upon the least touch. In other respects, this plant 

 shews no symptoms of irritability. The Nepenthes distilla- 



