64 LEAF-CLIMBERS. Chap. II 



Tropseolum i^eregrinum. The first-formed internode3 

 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. 48 niin. 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 1 hr. 48 m. The present species cannot twine 

 spirally, which seems mainly due to the rigidity 

 of the stem. In a 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. 



Tropseolum 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 17m.; and 



