THE SLEEP OF PLANTS 



201 



Bose was officially informed that ' the palm tree was dead, 

 and that its movements had ceased.' 



Further experiments enabled Bose to show that 

 movements similar to that of the palm tree occur in all 



FIG. 25. Records of the daily movement of the Palm Tree, of 

 Tropaeolum, and of the Palm Leaf. The upper record 

 gives the daily variation of temperature. 



trees and their branches and leaves. 1 He was further 

 able to trace the cause of the movement to the joint effects 

 of geotropism and temperature ; he designates the new 

 phenomenon as therm o-geotropism. Under the action of 

 the stimulus of gravity stems, branches and leaves tend 

 to erect themselves against the force of gravity, and a 



1 Trans. Bose Inst., vol. i., 1918. 



