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Darwin, Charles, 1809-1882

"The Movements and Habits of Climbing Plants"

When
rubbed, it curves and subsequently straightens itself; and it can, as
is shown in the drawing, securely clasp a support. I have seen an
object as soft as a young vine-leaf caught by one.
The lower and naked part of the sub-peduncle (C) is likewise slightly
sensitive to a rub, and I have seen it bent round a stick and even
partly round a leaf with which it had come into contact. That the
sub-peduncle has the same nature as the corresponding branch of an
ordinary tendril, is well shown when it bears only a few flowers; for
in this case it becomes less branched, increases in length, and gains
both in sensitiveness and in the power of spontaneous movement. I
have twice seen sub-peduncles which bore from thirty to forty flower-
buds, and which had become considerably elongated and were completely
wound round sticks, exactly like true tendrils. The whole length of
another sub-peduncle, bearing only eleven flower-buds, quickly became
curved when slightly rubbed; but even this scanty number of flowers
rendered the stalk less sensitive than the other branch, that is, the
flower-tendril; for the latter after a lighter rub became curved more
quickly and in a greater degree.


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