358 



MODIFIED CIEUUMNUTATION. 



Chap. VIl. 



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 31 m. (temp, 

 91° P.) 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 le.aves asleep. 

 Copied from a photograph ; figurfes 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. Pfeffer 

 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- 



