They revolve spontaneously, as do the short and non-
sensitive petioles. When rubbed, they slowly bend to the rubbed side
and subsequently straighten themselves; but they are not highly
sensitive. There is something strange in their behaviour: I
repeatedly placed close to them, thick and thin, rough and smooth
sticks and posts, as well as string suspended vertically, but none of
these objects were well seized. After clasping an upright stick,
they repeatedly loosed it again, and often would not seize it at all,
or their extremities did not coil closely round. I have observed
hundreds of tendrils belonging to various Cucurbitaceous,
Passifloraceous, and Leguminous plants, and never saw one behave in
this manner. When, however, my plant had grown to a height of eight
or nine feet, the tendrils acted much better. They now seized a
thin, upright stick horizontally, that is, at a point on their own
level, and not some way up the stick as in the case of all the
previous species. Nevertheless, the non-twining stem was enabled by
this means to ascend the stick.
The extremity of the tendril is almost straight and sharp. The whole
terminal portion exhibits a singular habit, which in an animal would
be called an instinct; for it continually searches for any little
crevice or hole into which to insert itself.
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