Virginia creeper and grape they are branches; they stand opposite the leaves in the position of fruit clusters, and sometimes one branch of a fruit cluster is a tendril. These tendrils are therefore homologous with fruit-clusters, and fruit-clusters are branches.
In some plants tendrils are leaflets (Chap. XI). Examples are the sweet pea and common garden pea. In Fig. 171, observe the leaf with its two great stipules, petiole, six normal leaflets, and two or three pairs of leaflet tendrils and a terminal leaflet tendril. The cobea, a common garden climber, has a similar arrangement. In some cases tendrils are stipules, as probably in the green briers (smilax).
The petiole or midrib may act as a tendril, as in various kinds of clematis. In Fig. 172, the common wild clematis or "old man vine," this mode is seen.
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Fig. 171.—Leaves of Pea,—very large stipules, opposite leaflets, and leaflets represented by tendrils.
Twiners.—The entire plant or shoot may wind about a support. Such a plant is a twiner. Examples are bean, hop, morning-glory, moon-*flower, false bittersweet or waxwork (Celastrus), some honeysuckles, wistaria, Dutchman's pipe, dodder. The free tip of the twining branch sweeps about in curves, much as the tendril does, until it finds support or becomes old and rigid.
Each kind of plant usually coils in only one direction. Most plants coil against the sun, or from the observer's left across his front to his right as he faces the plant.
