Climbing Plants 241 
feels the pressure and begins to curve. Darwin 
experimented upon one species of clematis with a 
aS 
or 
Bioriitenrsce 
SUL Rare np awe SUS 
aN, 
Fic. 67.—Scaling-hooks of the Virginia creeper (Ampelopsis quin- 
quefolia) and of the wild clematis (Clematis Virginiana). 
stick placed so as to press lightly against one of 
its young leaf-stalks. He found that the leaf-stalk 
