1S2 



Professor Jagadis Ch under Bose 



[May 29, 



of seiisil>ility, I made it record its ansAver to uniform questioiiinor 

 shocks, repeated every hour of the day and night. The amplitude of 

 the answering twitch gave a measure of the " wakefulness " of the 

 plant during twenty-four hours. The results obtained were quite 

 unexpected. The plant is found to keep up very late, and fall asleep 

 only at the early hours of the morning. It makes up for its late 

 hours by gradually waking up by noon (Fig. 6). It then remains in 

 a condition of uniform sensibility all the afternoon. This period of 

 uniformity is chosen for investigations on the effect of changed 

 external conditions on excitability. 



Effect of Ijight and Temperature. 



Does the plant feel the depressing effect of darkness ? The 

 the effect of a passing cloud (Fig. 7). It is 



following record show 



Fig. 7. — Effect of Cloud. Dotted up-curve indicates responsive fall, and 

 continuous down-line exhibits slow recovery. First four responses 

 normal ; next three show depression due to diminuticn of light brought 

 on by cloud, the duration of which is indicated by horizontal line below. 

 Last'^three records show restoration of excitability brought on by clearing 

 of sky. All records read from left to right. 



the sadden change which exerts a marked depressing effect. The 

 plant partially regains its sensibility when accustomed to darkness. 



