round it. After they have clasped a support, they become rigid and
hard. They are less sensitive to a weight than in the previous
species; for loops of string weighing 0.82 of a grain (53.14 mg.),
did not cause any curvature, but a loop of double this weight (1.64
gr.) acted.

Tropaeolum elegans.--I did not make many observations on this
species. The short and stiff internodes revolve irregularly,
describing small oval figures. One oval was completed in 3 hrs. A
young petiole, when rubbed, became slightly curved in 17 m.; and
afterwards much more so. It was nearly straight again in 8 hrs.

Tropaeolum tuberosum.--On a plant nine inches in height, the
internodes did not move at all; but on an older plant they moved
irregularly and made small imperfect ovals. These movements could be
detected only by being traced on a bell-glass placed over the plant.
Sometimes the shoots stood still for hours; during some days they
moved only in one direction in a crooked line; on other days they
made small irregular spires or circles, one being completed in about
4 hrs. 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