--The internodes do not move, but the tendrils
revolve regularly. A half-grown and very sensitive tendril made
three revolutions, opposed to the course of the sun, in 3 hrs. 5 m.,
2 hrs. 40 m. and 2 hrs. 50 m.; perhaps it might have travelled more
quickly when nearly full-grown. A plant was placed in front of a
window, and, as with twining stems, the light accelerated the
movement of the tendril in one direction and retarded it in the
other; the semicircle towards the light being performed in one
instance in 15 m. less time and in a second instance in 20 m. less
time than that required by the semicircle towards the dark end of the
room. Considering the extreme tenuity of these tendrils, the action
of the light on them is remarkable. The tendrils are long, and, as
just stated, very thin, with the tip slightly curved or hooked. The
concave side is extremely sensitive to a touch--even a single touch
causing it to curl inwards; it subsequently straightened itself, and
was again ready to act. A loop of soft thread weighing one
fourteenth of a grain (4.625 mg.) caused the extreme tip to bend;
another time I tried to hang the same little loop on an inclined
tendril, but three times it slid off; yet this extraordinarily slight
degree of friction sufficed to make the tip curl.
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