Chap. IV. PASSIFLOBACEiE. 157 



quickly when nearly full-grown. A plant was placed 

 in front of a window, and, as with twining stems, the 

 light accelerated the moTement of the tendril in one 

 direction and retarded it in the other ; the semicircle 

 towards the light being performed in one instance in 

 15 m. less time and in a second instance in 20 m. less time 

 than that required by the semicircle towards the dark 

 end of the room. Considering the extreme tenuity of 

 these tendrils, the action of the light on them is 

 remarkable. The tendrils are long, and, as just stated, 

 very thin, with the tip slightly curved or hooked. 

 The concave side is extremely sensitive to a touch — 

 even a single touch causing it to curl inwards ; it 

 subsequently straightened itself, and was again ready 

 to act. A loop of soft thread weighing y^th of a grain 

 (4"625 mg.) caused the extreme tip to bend ; another 

 time I tried to hang the same little loop on an inclined 

 tendril, but three times it slid off; yet this extra- 

 ordinarily slight degree of friction sufficed to make the 

 tip curl. The tendril, though so sensitive, does not 

 move very quickly after a touch, no conspicuous move- 

 ment being observable until 5 or 10 m. had elapsed. 

 The convex side of the tip is not sensitive to a touch 

 or to a suspended loop of thread. On one occasion I 

 observed a tendril revolving with the convex side of 

 the tip forwards, and in consequence it was not able 

 to clasp a stick, against which it scraped ; whereas 

 tendrils revolving with the concave side forward, 

 promptly seize any object in their path. 

 Passiflora quadrcmgularis. — This is a very distinct 



