A moderate rub
caused one to curve in 10 m., and others in 20 m. They became
straight again in between 5 hrs. 45m. and 8 hrs. Petioles which have
naturally come into contact with a stick, sometimes take two turns
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.
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