TENDRIL CLIMBERS 



111 



The tendril is carried round by a revolving move- 

 ment similar to that of a twining stem, and if thus, 



FIG. 23 

 BIGNONIA GRACILIS 



Showing tendrils 



or by the wind, it is brought into contact with some 

 thin stem that is not too smooth, coils round it, 

 because the stimulus of contact with a rough surface 

 (it won't round a smooth glass rod) causes the outer 

 side to grow more quickly than the inner. Most ten- 

 drils are branched at the top with three curved prongs, 

 which easily catch on any rough objects. When 

 several coils have been formed, the tissues become 

 woody and tough, so that the coils are made fast and 



