DIURNAL CURVE OF CASSIA 



279 



conclusive in this respect than the remarkable similarity 

 of the diurnal record of Cassia to that of Mimosa. 



Diurnal Curve of the Petiole of Cassia alata 



Experiment 154. — The leaf of Cassia exhibits, as does the 

 leaf of Mimosa, a slight erectile movement after thermal 

 noon at 2 p.m. ; there is then an abrupt fall, due to rapid 

 diminution of light after 5 p.m. ; the movement of fall 



Fig. 1G4. Diurnal record of Cassia leaf. Note similarity 

 to diurnal record of Mimosa. 



continues till about 9 p.m. The leaf then exhibits a con- 

 tinuous rise with the fall of temperature, till the chmax 

 is reached about 6 a.m. in the morning ; the leaf exhibits 

 later a movement of fall with rise of temperature, there 

 being a number of pulsatory movements in the forenoon 

 evidently due to unstable balance under the opposing re- 

 actions to light and to rise of temperature (fig. 164). 



