46 LEAF-OLIMBEES. Chap. IL 



obserred, in order to see what amount of difference 

 in the manner of climbing existed within the same 

 genus ; and the differences are considerable. 



Clematis. — G. glanduhsa. — The thin upper inter- 

 nodes revolTe, moving against the course of the sun, 

 precisely like those of a true twiner, at an average 

 rate, judging from three revolutions, of 3 hrs. 48 m. 

 The leading shoot immediately twined round a stick 

 placed near it; but, after making an open spire of 

 only one turn and a half, it ascended for a short space 

 straight, and then reversed its course and wound two 

 turns in an opposite direction. This was rendered 

 possible by the straight piece between the opposed 

 spires having become rigid. The simple, broad, ovate 

 leaves of this tropical species, with their short thick 

 petioles, seem but ill-fitted for any movement; and 

 whUst twining up a vertical stick, no use is made of 

 them. Nevertheless, if the footstalk of a young leaf 

 be rubbed with a thin twig a 'few times on any side, 

 it will in the course of a few hours bend to that side ; 

 afterwards becoming straight again. The under side 

 seemed to be the most sensitive ; but the sensitiveness 

 or irritability is slight compared to that which we 

 shall meet with in some of the following species ; thus, 

 a loop of string, weighing 1-64 grain (106"2 mg.) 

 and hanging for some days on a young footstalk, 

 produced a scarcely perceptible effect. A sketch is 

 here given of two young leaves which had naturally 

 caught hold of two thin branches. A forked twig placed 

 so as to press lightly on the under side of a young 



