In like manner, if the petiole comes into contact with a
twig, it bends round, carrying the tendril, which then seizes its own
petiole or that of the opposite leaf. The petioles move
spontaneously, and thus, when a shoot attempts to twine round an
upright stick, those on both sides after a time come into contact
with it, and are excited to bend. Ultimately the two petioles clasp
the stick in opposite directions, and the foot-like tendrils, seizing
on each other or on their own petioles, fasten the stem to the
support with surprising security. The tendrils are thus brought into
action, if the stem twines round a thin vertical stick; and in this
respect the present species differs from the last. Both species use
their tendrils in the same manner when passing through a thicket.
This plant is one of the most efficient climbers which I have
observed; and it probably could ascend a polished stem incessantly
tossed by heavy storms. To show how important vigorous health is for
the action of all the parts, I may mention that when I first examined
a plant which was growing moderately well, though not vigorously, I
concluded that the tendrils acted only like the hooks on a bramble,
and that it was the most feeble and inefficient of all climbers!
Bignonia Tweedyana.
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