64 LEAF-CLIMBEKRS. Cuap. I. 
Tropxolum peregrinum.—tThe first-formed internodes 
of a young plant did not revolve, resembling in this 
respect those of a twining plant. In an older plant 
the four upper internodes made three irregular re- 
volutions, in a course opposed to the sun, at an average 
rate of 1 hr. 48min. It is remarkable that the 
average rate of revolution (taken, however, but from 
few observations) is very nearly the same in this and 
the two last species, namely, 1 hr. 47 m., 1 hr. 46 m., 
and lhr.48 m. The present species cannot twine 
spirally, which seems mainly due to the rigidity 
of the stem. Ina very young plant, which did not 
revolve, the petioles were not sensitive. In older 
plants the petioles of quite young leaves, and of leaves 
as much as an inch and a quarter in diameter, are 
sensitive. A moderate rub caused one to curve in 
10 m., and others in 20 m. They became straight 
again in between 5 hrs. 45 m. 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 ‘82 of a grain 
(53:14 mg.), did not cause any curvature, but a loop 
of double this weight (1°64 gr.) acted. 
Tropzolum elegans—I did not make many obser- 
vations 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 
