1 86 



COMPARATIVE ELECTRO-PHYSIOLOGY 



fatigue, and I have found that this plant is but little subject 

 to it. It will be noticed how the response is continuously 

 depressed, as the temperature rises from 30 C. upwards. 

 In this case, the thermal ascent took place at the rela- 

 tively slow rate of i C. in 1*5 minute, so that there was 

 time for the plant to attain the temperature of its sur- 

 roundings. A tabular statement is given below, showing 

 the effect of temperature on amplitude of response, in two 

 different specimens of Amaranth \ 



SPECIMEN I. 



SPECIMEN II. 



The same fall in amplitude of response, when a certain 

 point has been reached in the thermal ascent, to which I 



have already referred, in the 

 case of Eucharis lily, has 

 also been noticed in that of 

 muscle. From this it might 

 be concluded that rise of 

 temperature beyond 30 C. 

 or so, induced depression of 

 excitability. But here we 

 are met by an anomaly. 

 For growth, which I have 

 50 shown to be a phenomenon 

 of excitatory response, in- 

 creases, in the case of 

 FIG. 125. Diminished Amplitude of the plant, throughout the 



Response with Rising Temperature, thermal ascent, Up to an 

 (Stem of Amaranth) 



optimum point at or near 



35 C. Conductivity, again, which is, to a certain extent, 

 correlated with excitability, undergoes enhancement with 



3U 



I 



