CHAPTER XV 



EFFECT OF TEMPERATURE ON ELECTRICAL RESPONSE 



General observation of effect of temperature on plant Effect of fall and rise of 

 temperature on autonomous response of Desmodium Effect of frost in abolition 

 of electrical response After-effects of application of cold, in Eucharis, Ivy 

 and Holly Effect of rise of temperature in diminishing height of response 

 This not probably due to diminution of excitability Similar effect in auto- 

 nomous motile response of Desmodium Enhanced response as after-effect of 

 cyclic variation of temperature Abolition of response at a critical high 

 temperature. 



WE have now seen that the physiological activity of a living 

 tissue may be gauged by means of its electrical response. 

 We know further that the influence of temperature is of 

 importance in the maintenance of a proper physiological 

 condition. There is a certain range of temperature which is 

 favourable to this, and above or below these limits physio- 

 logical efficiency is diminished. If the plant be kept too long 

 at or above a certain maximum temperature, it is liable to 

 undergo death. Similarly, there is a minimum point at which 

 physiological activity is arrested, and below which death is apt 

 to occur. The plant has thus two death-points, one above the 

 maximum and the other below the minimum temperature. 

 Some can resist these extremes better than others, and 

 length of exposure is also a factor which should not be for- 

 gotten in the question of the ultimate survival of the plant 

 under the given unfavourable conditions. Certain species 

 are hardy, while others succumb easily. 



An unmistakable indication of the effect of temperature 

 on physiological activity is found in the variations induced 

 by it in the autonomous motile pulsations of the telegraph 

 plant, Desmodium gyrans. Here, too great a lowering of the 



