OF THE FULCRA, OR APPENDAGES OF PLANTS.
There are various appendages to the herbage of plants, all of which are com prehended by Linnxus under the term of fulcrum, a prop or support, which term in its literal sense, however, applies but to a few of these organs.
1. Stipula. This is a leafy appendage to the true leaves, or to their stalks, for the most part in pairs, more or less con stant even in the same genus or species: in roses they are invariable ; in willows very much the contrary. Some species of Cistus have stipulas, others none. The peculiar stipula of grasses is a membrane, crowning the sheaths of their leaves and embracing their stem, but it is not found in all the species. Plate 1. fig. 18.
2. Bractea, is a leafy appendage to the flower or its stalk, conspicuous in the lime-tree, beautifully coloured in the pur ple or pink-topped Clary, and very much diversified in different plants. Fig. 19.
3 Spina, a thorn, proceeds from the wood itself, as in the wild pear-tree, which loses its thorns by cultivation. This is fancifully expressed by Linnzeus, who calls such garden plants tamed, or de prived of their natural arms.
4. Aculeus, a prickle, proceeds from the bark only, having no connection with the wood, as in the rose, bramble, &c. It might be expected that this should be less permanent than the foregoing, but the reverse is the case, for prickles are not effaced by culture. They rather abound most upon the most luxuriant stems. Plate II. fig. 21.
5. Cirrus, a tendril or clasper, is really intended as a support for weak stems, by which they are enabled to climb rocks, or the trunks of lofty trees. These organs are either simple or branched, straight in the first instance, but soon becoming spi ral, and thus are rendered capable of ta king hold of any thing that comes in their way ; especially as many of them are so constructed, that,after having made a cer tain number of turns, they perform as many in a contrary direction. Some at
tach themselves by a dilatation of their extremities to the smoothest and hardest stone. Thus, the vine, the passion-flow er, and the family of vetches, are elevated to a considerable height above the ground. Such tendrils differ essentially from roots, in never imbibing nourishment, any more than the short fibres of the ivy. The gloriosa, or superb lily, has a spiral ten dril at the end of each leaf, and in some few plants the flower stalks produce ten drils. Plate I. fig. 22.
6. Glandula, a gland, is a small tumour secreting a sweet, resinous, or fragrant liquor, as on the calyx of the moss-rose, the foot-stalks of passion-flowers whose glands are like little cups, and the leaf of salix pentendra : which last being pressed between pap er,leaves the impres sion of an elegant row of yellow dots. Fig 23.
7. Piles, a hair. Fig. 24. Under this are included all the various kinds of pu bescence ; bristles, wool, &c some of which are curious objects for the micros cope. Some few of these bristles dis charge a poison, as in the nettle, causing great irritation, whenever they are touch ed in such a manner as for their points to wound the skin. Hence arose the fol lowing hoes : "Tender handed touch a nettle, And it stings you for your pains ; Grasp it like a man of mettle, And it soft as silk remains."