126 CLIMBING PLANTS. 



always bend towards the side which is pressed or 

 touched, at different rates in different species, 

 sometimes within a few minutes, but generally 

 after a much longer period. After temporary 

 contact with any object, the petiole continues to 

 bend for a considerable time ; afterwards it slowly 

 becomes straight again, and can then re-act. A 



FIG. 35. TROP/EOLUM MINUS. (Sachs). 



petiole, excited by an extremely slight weight, some- 

 times bends a little, and then becomes accustomed 

 to the stimulus, and either bends no more, or be- 

 comes straight again, the weight still remaining 

 suspended. Petioles which have clasped an object 

 for some little time cannot recover their original 

 position. After remaining clasped for two or three 

 days they generally increase much in thickness, 



