ARTIFICIAL DARKNESS 277 



for more than 6 hours. In order to remove all misgivings 

 in regard to possible modification of the result by variation 

 of temperature I carried out the following experiments, 

 which were completed in a relatively short time. I have 

 already explained how the duration of experiment can be 

 shortened by suitable increase of the intensity of light. The 



Fig. 161. Fig. 162. Fig. 163. 



Fig. 161. Pre-maximum after-effect of light on Mimosa. 



Fig. 162. After-effect at maximum. 



Fig. 163. Post-maximum after-effect exhibiting an overshooting 



below position of equilibrium. 



In the above record light was applied at arrow, and stopped at 

 the second arrow enclosed in a circle. 



following experiments were commenced inside a room at 

 noon and completed by 2 p.m., so that the temperature 

 variation during this period did not exceed i° C. 



Experiment 151. After-effect at pre-maximum. — Light 

 from a loo-candle-power incandescent lamp was focused 

 on the upper half of the pulvinus of Mimosa for 8 minutes, 

 after which the light was turned off. The after-effect was 

 a persistence of previous movement followed by recovery 

 to normal (fig. 161). 



