With respect to the sensitiveness of the foot-stalks of the leaves and
flowers, and of tendrils, nearly the same remarks are applicable as in the
case of the revolving movements of twining plants. As a vast number of
species, belonging to widely distinct groups, are endowed with this kind of
sensitiveness, it ought to be found in a nascent condition in many plants
which have not become climbers. This is the case: I observed that the
young flower-peduncles of the above Maurandia curved themselves a little
towards the side which was touched. Morren found in several species of
Oxalis that the leaves and their foot-stalks moved, especially after
exposure to a hot sun, when they were gently and repeatedly touched, or
when the plant was shaken. I repeated these observations on some other
species of Oxalis with the same result; in some of them the movement was
distinct, but was best seen in the young leaves; in others it was extremely
slight. It is a more important fact that according to the high authority
of Hofmeister, the young shoots and leaves of all plants move after being
shaken; and with climbing plants it is, as we know, only during the early
stages of growth that the foot-stalks and tendrils are sensitive.
It is scarcely possible that the above slight movements, due to a touch or
shake, in the young and growing organs of plants, can be of any functional
importance to them.
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