(596 CLIMBING PLANTS. 



curvature (cf. fig. 165). When they have reached their full length they begin to 

 move round in a circle just like the apices of twining stems. If by this movement 

 they meet with an object suitable for a support, they grasp and embrace it by their 

 hooked ends. That is to say, contact with a foreign body acts like a stimulus on 

 the tendril; it loops itself over the object with which it is in contact, and then rolls 

 up in a spiral, thus drawing the stem, which bears it, obliquely upwards. Now 



Fig. 165. Tendrils of the Bryony (Bryonia). 



comes the turn of the tendril inserted next above. This behaves exactly in the 

 same way as the first, and in a very short time is succeeded by a third, fourth, &c. 

 It does not much matter if in its nutation one of these tendrils should have found 

 no support, since the successive tendrils are placed so close to one another, and 

 replace each other so quickly, that the shoot is still drawn up uniformly, and is 

 prevented from falling. When whole series of tendrils find no places of attachment, 

 the shoot of course falls down, under which circumstances possibly one of its tendrils 

 may encounter a distant branch to which it can fasten, and which it can use as a 

 support. If this should fail, the tip of the pendent shoot again rises up, sends out 



