curvature; but they were never closely clasped, as were the far
lighter loops of thread by the petioles.

In the nine vigorous plants observed by me, it is certain that
neither the slight spontaneous movements nor the slight sensitiveness
of the flower-peduncles aided the plants in climbing. If any member
of the Scrophulariaceae had possessed tendrils produced by the
modification of flower-peduncles, I should have thought that this
species of Maurandia had perhaps retained a useless or rudimentary
vestige of a former habit; but this view cannot be maintained. We
may suspect that, owing to the principle of correlation, the power of
movement has been transferred to the flower-peduncles from the young
internodes, and sensitiveness from the young petioles. But to
whatever cause these capacities are due, the case is interesting;
for, by a little increase in power through natural selection, they
might easily have been rendered as useful to the plant in climbing,
as are the flower-peduncles (hereafter to be described) of Vitis or
Cardiospermum.

Rhodochiton volubile.--A long flexible shoot swept a large circle,
following the sun, in 5 hrs. 30 m.; and, as the day became warmer, a
second circle was completed in 4 hrs. 10 m. The shoots sometimes
make a whole or a half spire round a vertical stick, they then run
straight up for a space, and afterwards turn spirally in an opposite
direction. The petioles of very young leaves about one-tenth of
their full size, are highly sensitive, and bend towards the side
which is touched; but they do not move quickly. One was perceptibly
curved in 1 hr. 10 m., after being lightly rubbed, and became
considerably curved in 5 hrs. 40 m.; some others were scarcely curved
in 5 hrs. 30 m., but distinctly so in 6 hrs. 30 m. A curvature was