EFFECT OF TEMPERATURE ON ELECTRICAL RESPONSE 185 



while the temperature was rising from 20 C. to 22 C. the 

 amplitude of the response was increased. After this, however, 

 it fell rapidly in height with rise of temperature and became 

 very small, at or near 60 C. On allowing the temperature 

 to fall, however, the responses revived, with this peculiarity, 

 that during the cooling, as compared with those given during 

 the ascent of temperature, 

 they were markedly en- 

 hanced (fig. 124). 



The heating arrange- 

 ments in this case were 

 such that the temperature 

 was made to rise some- 

 what rapidly. It will be 

 noticed that response had 

 not here disappeared, 

 even at 65 C., though, 

 as we shall see in the 

 next chapter, the death- 

 point is at about 60 C. 

 This apparent anomaly 

 is due to the fact that 

 the plant, which is a bad 

 conductor, was not al- 

 lowed time fully to attain 

 the temperature of its 

 surroundings. We shall 

 see that when the tem- 

 perature is raised at a 

 slower rate about i C. 

 in i '5 minute and when 



the specimen is not too thick, excitatory response disappears 

 with the approach of death, at a temperature very near 60 C. 



I give below a record of the effect of temperature 

 varying from 30 C. to 50 C. on the response of the stem 

 of Amaranth (fig. 125). In order to obtain perfect results, 

 it is necessary that the specimen should not exhibit any 



FIG. 124. Photographic Record of Responses 

 in Eucharis Lily during Rise and Fall of 

 Temperature 



Stimulus constant, applied at intervals of 

 one minute. The temperature of plant- 

 chamber gradually rose on starting current 

 in the heating coil ; on breaking current, 

 the temperature fell gradually. Tem- 

 perature corresponding to each record is 

 given below. 



Temperature rising : (i) 20, (2) 20, (3) 22, 

 (4) 38, (5) 53, (6) 60, (7) 65 



Temperature falling: (8) 60, (9) 51, (10) 

 45, (ii)40 p , (12)38. 



