The extreme points reached by the apex of the shoot were only
about one or one and a half inches asunder; yet this slight movement
brought the petioles into contact with some closely surrounding
twigs, which were then clasped. With the lessened power of
spontaneously revolving, compared with that of the previous species,
the sensitiveness of the petioles is also diminished. These, when
rubbed a few times, did not become curved until half an hour had
elapsed; the curvature increased during the next two hours, and then
very slowly decreased; so that they sometimes required 24 hrs. to
become straight again. Extremely young leaves have active petioles;
one with the lamina only 0.15 of an inch in diameter, that is, about
a twentieth of the full size, firmly clasped a thin twig. But leaves
grown to a quarter of their full size can likewise act.
Tropaeolum minus (?).--The internodes of a variety named "dwarf
crimson Nasturtium" did not revolve, but moved in a rather irregular
course during the day to the light, and from the light at night. The
petioles, when well rubbed, showed no power of curving; nor could I
see that they ever clasped any neighbouring object.
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