110 TENDEIL-BEAEEKS. Chap. III. 



The perfect manner in which the branches arranged 

 themselves, creeping like rootlets over every inequality 

 of the surface and into any deep crevice, is a pretty 

 sight; for it is perhaps more effectually performed 

 by this than by any other species. The action is 

 certainly more conspicuous, as the upper surfaces of 

 the main stem, as well as of every branch to the 

 extreme hooks, are angular and green, whilst the lower 

 surfaces are rounded and purple. I was led to infer, 

 as in former cases, that a less amount of light guided 

 these movements of the branches of the tendrils. 

 I made many trials with black and white cards and 

 glass tubes to prove it, but failed from various causes ; 

 yet these trials countenanced the belief. As a tendril 

 consists of a leaf split into numerous segments, there is 

 nothing surprising in all the segments turning their 

 upper surfaces towards the light, as soon as the tendril 

 is caught and the revolving movement is arrested. 

 But this will not account for the whole movement, for 

 the segments actually bend or curve to the dark side 

 besides turning round on their axes so that their upper 

 surfaces may face the light. 



When the Cobeea grows in the open air, the wind 

 must aid the extremely flexible tendrils in seizing a 

 support, for I found that a mere breath sufficed to cause 

 the extreme branches to catch hold by their hooks of 

 twigs, which they could not have reached by the 

 revolving movement. It might have been thought 

 that a tendril, thus hooked by the extremity of a single 

 branch, could not have fairly grasped its support. 



