I have, however, seen tendrils of the Bryony which had
temporarily caught other tendrils, and often in the case of the vine.
Tendrils of which the extremities are permanently and slightly
curved, are sensitive only on the concave surface; other tendrils,
such as those of the Cobaea (though furnished with horny hooks
directed to one side) and those of Cissus discolor, are sensitive on
all sides. Hence the tendrils of this latter plant, when stimulated
by a touch of equal force on opposite sides, did not bend. The
inferior and lateral surfaces of the tendrils of Mutisia are
sensitive, but not the upper surface. With branched tendrils, the
several branches act alike; but in the Hanburya the lateral spur-like
branch does not acquire (for excellent reasons which have been
explained) its sensitiveness nearly so soon as the main branch. With
most tendrils the lower or basal part is either not at all sensitive,
or sensitive only to prolonged contact. We thus see that the
sensitiveness of tendrils is a special and localized capacity. It is
quite independent of the power of spontaneously revolving; for the
curling of the terminal portion from touch does not in the least
interrupt the former movement.
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