HOW PLANTS CLIMB 



131 



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). Ex- 

 amples 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 termi- 

 nal leaflet tendril. The cobea, a common 

 garden climber, has a similar arrangement. 

 In some cases tendrils are stipules, as prob- 

 ably in the green briers 

 (smilax). 



The petiole or midrib 

 may act as a tendril, as 

 in various kinds of clem- 

 atis. In Fig. 172, the 

 common wild clematis 

 or "old man vine," this 

 mode is seen. 



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 sivceps 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. 



Fig. 171. — Leaves of Pea, 

 — very large stipules, op- 

 posite leaflets, and leaflets 

 represented by tendrils. 



