Ch. hi, 9] SPECIAL FL'XCTIOXS OF LEAVES 



simplest case, the petiole acts as the tendril, making a 

 turn around the support, as in our common -wild Clematis 

 (Fig. 51 ). In other cases, as illustrated by our figures, the 

 tendnl is a trans- ^-f,^/^^- 



formed leaflet or 

 leaflets, or else 

 stipule-like struc- 

 tures, or even the 

 entire blade. The 

 typical tendril 

 mo^-es about 

 through the air 

 until it touches 

 some object ; then 

 it bends towards 

 the touched side, 

 and, if the object 

 beofsuitableform, 

 continues the pro- 

 cess, and make 

 several turn 

 around it fFig 

 52). Then the in 

 termecliate part ot 

 the tendril be- 

 comes twisted tj 

 a double spiral 

 dra^^■ing the plant 



closer to the sup jr, ,J_^eru II tr^r D j^a n rr h B. 



port, after which plant «hich catches insects bj sudden closure of its 

 ., 1 , .1 leaf blades; X i. (From Fisurier.) 



it develops tough 



fibrous tissues, thus forming a strong but elastic bond be- 

 tween plant and support. In this definite action of tendrils 

 we have another instance of those automatic self-adjustments 

 made possible by the irritability , of protoplasm (pages 39, 

 55), this particular form being called THiGMOXROPiSii. 



