16 



HOW PLANTS CLIMB. 



23. When, however, the fresh and active 

 - tendril comes in contact with a neighboring 



stalk, or any similar support, it hooks or coils 

 its end round it ; then, having secured a hold, 

 it shortens by coiling up its whole length, or a 

 good part of it. This commonly draws up the 

 , climbing stem nearer to its support, and makes 

 it easier for the younger tendrils above to gain 

 their hold. A tendril which has taken hold 

 and coiled up usually becomes stouter, rigid, 

 and much stronger than it was before. One 

 which would break with an ounce weight be- 

 comes capable of supporting two or three 

 pounds. 



24. There is a difference to be noticed be- 

 tween the coiling of a free tendril and of one 

 which has taken hold. It is plainly shown in 

 Fig. 6. The loose tendril coils up, if at all, 

 from the end, and in a simple spiral or curl. 

 But when attached to a support, both ends be- 

 ing fixed, it cannot coil in this way. It has to 

 coil in the middle ; and the coiling of one part, 

 say from right to left, requires another part to 

 twist as much in the opposite direction. So 

 the coil has a break in the middle, half twist- 

 ing one way and half the other way, as is shown in the lower tendril of the figure. 

 A longer tendril often has three or four, or even five or six, such breaks, the por- 

 tions coiled successively in opposite directions. 



25. Pumpkins, Squashes, and all the Gourd Family furnish excellent examples 

 of these actions of tendrils. Their tendrils are like those of Passion-flowers, ex- 

 cept that they are mostly branched or compound, and, like the claws of a bird, 

 stretch out in several directions. 



Eig. 



. Maple-leaved Passion-flower, with ten- 

 drils in various states. 



