DEATH-SPASM IN PLANTS 107 



Summary 



The electric response of galvanometric negativity is 

 characteristic of the living condition of the vegetable 

 tissue. Dead plants do not exhibit this characteristic 

 electric-response. 



When a plant is subjected for a time to a temperature 

 of 60° C. its electric response disappears, such abolition 

 being indicative of the death of the plant. 



A leaf of Mimosa subjected to abrupt variation of 

 temperature — either sudden cooling or sudden warming — 

 exhibits excitatory reaction. But if the temperature be 

 gradually raised, there is a progressive erectile movement 

 of the leaf ; gradual cooling induces a depression of the leaf. 



When the leaf of Mimosa is continuously raised in 

 temperature, then at a critical point the erectile expansive 

 movement is suddenly converted into one of spasmodic 

 contraction. This inversion takes place under standard 

 conditions at or about 60° C. After this the response of 

 the plant is permanently abolished. 



Various other plants, sensitive and ordinary, exhibit this 

 characteristic death-spasm at or about 60° C. 



In taking an electric record it is found that an electric- 

 spasm also takes place at the critical temperature, which is 

 very near 60° C. 



The death-point of the plant is lowered under physio- 

 logical depression. Thus under fatigue induced by tetanising 

 electric-shocks, the death-point was lowered from the 

 normal 60° C. to 37° C. 



Poisonous reagents also lower the death-point. In a 

 particular case poisonous solution of copper sulphate 

 lowered the death-point by 18° C. 



