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. Pumpkin^ 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. 
Fig. 6. Maple-leaved Passion-flower, with ten- 
drils in various states. 
