EFFECT OF STIMULUS ON LEAFLET 315 



to elapse after the cessation of pulsation. Stimulus applied 

 within a short time of stoppage will give rise to multiple 

 responses ; after a long period, an identical stimulus will 

 be found far less effective. After a still longer interval, 

 which is critical, even a strong stimulus will fail to evoke 

 any response. 



These theoretical considerations will be seen verified in 

 the following series of records. In fig. 158, stimulus of light 

 of two seconds' duration was applied after half an hour of 

 the stoppage of the pulsation of the leaflet. The response is 



Fig. 158. — Effect of stimulus in renewing pulsation of Desmodium 

 brought to standstill through depletion of energy. Note two series 

 of multiple responses due to stimulus of light of two seconds' 

 duration. 



seen to be multiple even under a stimulus of this short 

 duration. The stimulus was applied once more, with similar 

 results. 



In the next series of records, stimulus was applied on a 

 specimen which had been in a state of standstill for five 

 hours. The store of energy here had undergone a consider- 

 able decline. Stimulus of light of two seconds' duration was 

 found ineffective ; it was only after an application lasting 

 for half a minute that a response took place (fig. 159). 

 The response was single, instead of multiple as in the last 

 case. Stimulus was applied a second time, but of still 



