102 RESEARCHES ON IRRITABILITY OF PLANTS 



temperature had reached 6o° C. there was an abrupt 

 inversion, and the spasmodic contraction took place at a 

 very rapid rate. The successive dots in the up-portion of 

 the curve are at intervals of • 2 of a degree. The point of 

 inversion, as we shall see, indicates the death-point, and 

 the curve giving the death-record we shall call the death- 

 curve. It should be remembered that the particular 



Fig. 58.— Death-curve of Mimosa. Successive dots in down 

 or expansive part of curve represent rise of temperature 

 of i° C. Spasmodic contraction causing inversion of 

 curve takes place at 6o° C. 



electric response characteristic of living condition of the 

 tissue is found to disappear after the tissue had been 

 subjected to the temperature of 6o° C. 



If the sudden contraction that takes place at 6o° C. 

 should prove to be the death-spasm, then this should 

 be the last response given by the plants. If we raise the 

 temperature of the plant short of the death-point, say to 

 45 C, we get a continuous responsive expansion ; when 

 cooled the leaf recovers, to a greater or less extent, its 



