Chap. II. TROP^EOLUM. 66 



afterwards much more so. It was nearly straight again 

 in 8 hrs. 



Tropteolum 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 bo 

 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 some- 

 times required 24 hrs. to become straight again. 

 Extremely young leaves have active petioles; one 

 with the lamina only *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. 



Tropseolum minus (?). The internodes of a variety 



named " dwarf crimson Nasturtium " did not revolve, 



4 



