370 



MODIFIED CIKCUMNUTATION. 



Chap. Vii 



sink downwards and rotate, so that they stand laterally at night, 

 as may be seen in the figure. Moreover, they move somewhat 

 backwards, so as to point towards the base of the petiole. 



Fig. 154. 



Cassia corymbcsa : A, plant during day ; B, same plant at night. 

 Both figures copied from photographs, 



lu one instance we found that the midrib of a terminal 

 leaflet formed at night an angle of 36°, with a line dropped 



