134 TENDRIL-BEARERS. Cuar. 1V. 
with its extreme point, can work itself onwards until 
it has passed twice or even thrice round the stick, 
and has permanently grasped it. 
Hanburya Mexicana—Tbhe young internodes and 
tendrils of this anomalous member of the family, revolve 
in the same manner and at about the same rate as those 
of the Echinocystis. The stem does not twine, but can 
ascend an upright stick by the aid of its tendrils. 
The concave tip of the tendril is very sensitive ; after 
it had become rapidly coiled into a ring owing to 
a single touch, it straightened itself in 50 m. The 
tendril, when in full action, stands vertically up, with 
the projecting extremity of the young stem thrown a 
little on one side, so as to be out of the way; but the 
tendril bears on the inner side, near its base, a short 
rigid branch, which projects out at right angles like 
a spur, with the terminal half bowed a little down- 
wards. Hence, as the main vertical branch revolves, 
the spur, from its position and rigidity, cannot pass 
over the extremity of the shoot, in the same curious 
manner as do the three branches of the tendril of the 
Echinocystis, namely, by stiffening themselves at the 
proper point. The spur is therefore pressed laterally 
against the young stem in.one part of the revolving 
course, and thus the sweep of the lower part of the main 
branch is much restricted. A nice case of co-adaptation 
here comes into play: in all the other tendrils observed 
by me, the several branches become sensitive at the 
same period: had this been the case with the Hanburya, 
the inwardly directed, spur-like branch, from being 
