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Darwin, Charles, 1809-1882

"The Movements and Habits of Climbing Plants"

5). But it is a little larger, and in a young plant
was about half an inch in length. It is curiously like the leg and
foot of a small bird, with the hind toe cut off. The straight leg or
tarsus is longer than the three toes, which are of equal length, and
diverging, lie in the same plane. The toes terminate in sharp, hard
claws, much curved downwards, like those on a bird's foot. The
petiole of the leaf is sensitive to contact; even a small loop of
thread suspended for two days caused it to bend upwards; but the sub-
petioles of the two lateral leaflets are not sensitive. The whole
tendril, namely, the tarsus and the three toes, are likewise
sensitive to contact, especially on their under surfaces. When a
shoot grows in the midst of thin branches, the tendrils are soon
brought by the revolving movement of the internodes into contact with
them; and then one toe of the tendril or more, commonly all three,
bend, and after several hours seize fast hold of the twigs, like a
bird when perched. If the tarsus of the tendril comes into contact
with a twig, it goes on slowly bending, until the whole foot is
carried quite round, and the toes pass on each side of the tarsus and
seize it.


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