358 MODIFIED CIKCUMNUTATICXN CHAP. VII. 



Circumnutation. The circumnutating movements of four 

 young shoots were observed during 5 h. 15 m. ; and in this time 

 each completed an oval figure of small size. The main petiole 

 also circumnutates rapidly, for in the course of 31m. (temp, 

 91 F.) it changed its course by as much as a rectangle six times, 

 describing a figure which apparently, represented two ellipses. 



Fig. 149. 



Desmodium gyrans : A, stem during the day ; B, stem with leaves asleep. 

 Copied from a photograph ; figures reduced. 



The movement of the terminal leaflet by means of its sub- 

 petiole or pulvinus is quite as rapid, or even more so, than that 

 of the main petiole, and has much greater amplitude. Pfenx-r 

 has seen* these leaflets move through an angle of 8 in the 

 course of from 10 to 30 seconds. 



A fine, nearly full-grown leaf on a young plant, 8 inches in 

 height, with the stem secured to a stick at the base of the leaf, 

 'vas observed from 8.30 A.M. June 22nd to 8 A.M. June 24th. 



' Die Period. Beweg.,' p. 35. 



