348 RESEARCHES ON IRRITABILITY OF PLANTS 



application is attended by quick abolition of excitability 

 followed by the death of the plant (p. 94). 



Death-spasm in Plant 



One test by which a dead plant may be distinguished 

 from a living one is that of electric response. The response 

 of galvanometric negativity characteristic of living condi- 

 tion is abolished at death. When the plant is subjected 

 for a time to a temperature of 60^ C. its electric response, 

 generally speaking, disappears. This temperature is, there- 

 fore, fatal for most plants. 



When the leaf of Mimosa is continuously raised in tem- 

 perature there is produced a progressive erectile movement ; 

 but at a critical temperature the erectile movement is 

 suddenly reversed into a spasmodic contraction. This 

 inversion takes place under standard conditions at or about 

 60° C, after this the response of the plant is permanently 

 abolished. The death record is a V-shaped curve, the 

 point of inversion being the death-point. After death 

 a repetition of experiment shows no further inversion. 

 Various other plants, sensitive and ordinary, exhibit this 

 characteristic death-spasm at or about 60° C. In radial 

 organ this movement consists of an abrupt longitudinal 

 contraction. In taking an electrical record it is found 

 that an electric-spasm also takes place at the critical tem- 

 perature which is very near 60° C. 



The death contraction in plants is similar to that seen 

 in the animal. The death-point is found lowered under 

 physiological depression. Thus, in a certain case, fatigue 

 lowered the death-point of the plant from the normal 

 60° C. to 37° C. In another case dilute solution of poison 

 lowered the death-point by 18° C. (p. 106). 



Polar Effects of Electrical Current in Excitation 



The fundamental unity of excitatory phenomena in 



the animal and plant finds a striking illustration in the 



characteristic effects induced at the kathode and anode. 



