500 



Plant Physiology 



Roots and leafy shoots appear to possess this power to a 



very limited extent. 



Plants producing ten- 

 drils are particularly well 

 equipped to climb aloft, 

 supporting themselves by 

 the attachment of these 

 to any small supports, 

 especially to those hori- 

 zontally placed. By this 

 means such plants as the 

 grape vine, wild cucum- 

 ber, Passiflora, and many 

 others are enabled to climb 

 through trees and lay- 

 ered vegetation, whereas 

 twining plants commonly 

 require a support which 

 is more or less vertical. 

 The tendrils are com- 

 monly axillary or super- 

 numerary branches devoid 

 of leaves, or leaf-parts 

 entirely lacking blades. 

 Sometimes, however, pet- 

 ioles of normal leaves or 

 extended leaf tips may 

 function as tendrils. 



FIG. 144. Demonstration khnostat, 



after Ganong, vertical arrangement. These structures COm- 



[Illustration from Bausch and Lomb monlv exhibit dorsi- 

 Optical Co.] 



ventrality , and a right and 



