240 . Field, Forest, and Wayside Flowers 
In all the leaf-climbers and tendril-bearers whose 
habits have been investigated, the young internodes 
revolve, but there movements are less regular than 
those of the twiners. 
The tender shoots of that familiar leaf-climber, 
the clematis, while growing vigorously in spring, 
make small oval revolutions, moving always in the 
same direction as the hands of a watch. Later 
in the season the vine-tips travel more fitfully 
and slowly through a very small circle, and by 
midsummer their movements have almost ceased. 
But the leaf-stalks have acquired a high degree 
of sensitiveness, as if to make up for the failing 
powers of the shoots. 
While the leaf is yet so young that its blade 
—or flat, green surface—has attained but one-sixth 
of its full size, its stalk is so well developed that 
the whole affair has somewhat the disproportioned 
and lanky appearance of a few-days’-old colt. At 
this stage of growth the sensitiveness of the leaf- 
stalk is at its highest, and the tender blade is 
bent downward, so that the whole leaf has a 
hook-like form (Fig. 67). 
When the growth of the plant or an impulse 
from the wind brings the hook into such a posi- 
tion that it catches on a twig the sensitive stalk 
