(-.2 



PltACTICAL BOTANY 



Tfiidfil cliinhers attach themselves to the stems or branches 

 of other plants or to inanimate objects by means of special, 

 slender, tlrread-shaped, leafless organs called tendrils. These 

 are modified leaves or parts of a leaf, as in the pea (Fig. 306) ; 

 or modified branches, as in the grape, the Virginia creeper 

 (Fig. 48 ), and the ]^^)assi()ii flower. ^\"hen a living and active 

 tendril comes into contact with a support, this contact causes 

 growth tu take place more rapidly on the exterior side of the 



Fig. 49. A tropical Smikii, a tendril climber 



o, tendril coiled about a portion of the stem ; I, tendril coiled about ;> leafstalk ; 

 br, a young branch; (, young unattached tendrils 



tendril (that side which does not touch the foreign object), 

 and thus the tendril is made to coil about the support. The 

 sensitiveness of some tendrils is almost inconceivably great. 

 Those of the star, wild, or bur cucumber QSicijnx) are stimu- 

 lated to curve by a moving weight of ^ oo^oiyo ^^ ^ grain, or 

 one eighth of the smallest amount which can be perceived 

 by the most sensitive part of the human skiir (the face). 

 After a tendril has become attached the free portions are also 

 thrown into coils and tlius the plant is drawn closer to the 

 support. As a result of its attachment the tendril liecomes 

 stronger and often eoiisideral)ly thicker. In some plants, 

 as the Vhginia creeper, the tendrils are enabled to fa.sten 



