130 



PLANT BIOLOGY 



FIG. 169. TENDRIL, to show 

 where the coil is changed. 



distinguished from stem tendrils by their irregular or 

 indefinite position as well as by their mode of growth. 



Tendril climbers. A slender coiling part that serves to 

 hold a climbing plant to a supports known as a tendril. 



The free end swings or curves 

 until it strikes some object, when 

 it attaches itself and then coils 

 and draws the plant close to tlie 

 support. The spring of the coil 

 also allows the plant to move in 

 the wind, thereby enabling the 

 plant to maintain its hold. Slowly pull a well-matured 

 tendril from its support, and note how strongly it holds 

 on. Watch the tendrils in a wind-storm. Usually the 

 tendril attaches to the support by coiling about it, but the 

 Virginia creeper and Boston ivy (Fig. 170) attach to walls 

 by means of disks 

 on the ends of the 

 tendrils. 



Since both ends 

 of the tendril are 

 fixed, when it finds 

 a support, the coil- 

 ing would tend to 

 twist it in two. It 

 will be found, how- 

 ever, that the tendril 

 coils in different di- 

 rections in different parts of its length. In Fig. 169, show- 

 ing an old and stretched-out tendril, the change of direction 

 in the coil occurred at a. In long tendrils of cucumbers 

 and melons there may be several changes of direction. 

 Tendrils may represent either branches or leaves. In the 



FIG. 170. TENDRIL 

 OF BOSTON IVY. 



