42 CHAP. IV. VARIATION OF TEMPERATURE 



to be SO effected as to eliminate this source of error. A 

 continuous record of growth under uniform rise of tem- 

 perature gives a Thermocrescent Curve, from which 

 the absohite rate of growth at different temperatures can 

 be found. 



Different plants exhibit characteristic differences in 

 their cardinal points of temperature. In the tropical plant 

 Kysoor the minimum temperature for arrest of growth is 

 22-5° C, the optimum is about 34° C. The growth-rate 

 declines as the temperature rises further, and becomes 

 arrested at or about 55° C. A sudden spasmodic death- 

 contraction occurs at 60° C. 



