332 



PLANT RESPONSE 



set of responses in each series gives pulsations at the 

 temperature of the room, while the second set in each gives 

 pulsations of greater amplitude and smaller frequency, 

 due to the lowering of temperature by several degrees 

 (figs. 135, 136). Conversely, as already said, when the 

 temperature is raised, the frequency is increased and the 

 amplitude decreased. This is seen in a general way in the 

 following photographic record (fig. 137), which I took with 



FlG. 135. Photographic Records of Autonomous Pulsations in Des- 

 modiitm, showing Increase of Amplitude and Decrease of Frequency, 

 with Lowering of Temperature 



The pulsations to the left were taken at the ordinary temperature of the 

 room, 29 C. Those to the right were taken when the temperature 

 had been lowered to 25 C. 



Desmodium, the temperature being continuously raised, from 

 30 C. to 39 C. It will be seen how progressive in character 

 is the diminution of amplitude and increase of 'frequency in 

 these responses. 



In another set of experiments in which I took records 

 of the responses of Desmodium at various definite ascending 

 temperatures, I found that at 19 C. the period of a single 

 oscillation was 43 minutes. At 22° C. this was reduced to 



