EFFECT OF TEMPERATURE 



145 



will be seen to be exactly parallel to those already given in 

 electrical response. 



The responses are seen to be very much diminished at 35°C, 

 and almost to disappear at 55 C, v/hich, as will be shown later, 

 is near the death-point. Heat-rigor began to manifest itself 

 a few degrees above this point, in the contracting of the speci- 

 men as a whole. This last phenomenon will be treated at 

 greater length in a subsequent chapter. I have already alluded 

 to the experiment in which, when the plant is killed by ex- 

 cessively high temperature, the response disappears altogether. 



Effects of cyclic variation of temperature : (a) on 

 electrical response. — I detected another very curious result 



19" C 



30 C 



25 C 



50 C 



Temperature 

 falliruj 



Temperature rising >■ 



Fig. 80. Effect of Rising and Falling Temperature on the Electrical 

 Response of Scotch Kale (stimulus constant) 



in the course of my investigations on the effect of temperature 

 by means of electrical response. This was, a marked increase 



L 



