136 TENDRIL-BEARERS. Cuar. IV. 
arrested. As soon as the tendril with its three 
branches begins to stiffen itself in this manner and to 
rise from an inclined into a vertical position, the 
revolving motion becomes more rapid; and as soon 
as the tendril has succeeded in passing over the ex- 
tremity of the shoot or point of difficulty, its motion, 
coinciding with that from its weight, often causes it to 
fall into its previously inclined position so quickly, 
that the apex could be seen travelling like the minute 
hand of a gigantic clock. 
The tendrils are thin, from 7 to 9 inches in length, 
with a pair of short lateral branches rising not far 
from the base. The tip is slightly and permanently 
curved, so as to act to a limited extent as a hook. The 
concave side of the tip is highly sensitive to a touch; 
but not so the convex side, as was likewise observed 
to be the case with other species of the family by 
Mohl (p. 65). I repeatedly proved this difference by 
lightly rubbing four or five times the convex side of 
one tendril, and only once or twice the concave side 
of another tendril, and the latter alone curled inwards. 
In a few hours afterwards, when the tendrils which 
had been rubbed on the concave side had straightened 
themselves, I reversed the process of rubbing, and 
always with the same result. After touching the 
concave side, the tip becomes sensibly curved in one or 
two minutes; and subsequently, if the touch has been at 
all rough, it coils itself into a helix. But the helix 
will, after a time, straighten itself, and be again ready 
to act. A loop of thin thread only one-sixteenth of 
