RELATION BETWEEN TEMPERATURE AND GROWTH 449 



approach the optimum point, which in the present case is 

 35-5° C. After this there is a steep fall, and growth is almost 

 abolished at a maximum temperature at or near 45 ° C. This 

 arrest of growth does not mean arrest of internal activity. I 

 have in the last chapter (fig. 176) explained why, in spite of 

 the persistence of internal activity, there is in this case no 

 resultant growth. It is to be borne in mind that as the curve 

 of growth in fig. 183 is continuous, the rate of growth at 



Fig. 184. Curve showing Relation between Temperature and Rate of 

 Growth, as deduced from the Thermo-crescent Curve in fig. 181 



points intermediate to those specified may be determined 

 from it. 



From a large number of experiments which I have carried 

 out on Crinum Lily, I find that the optimum temperature is 

 very constant, not varying by as much as one-tenth of a 

 degree from the mean value of 35'5° C. as the optimum tem- 

 perature. In the first portion of the curve, as the temperature 

 rises from 30 C. to 3 5 "5° C. the rate of growth is seen to 

 increase, from -004 to -01125 mm. per minute, or to nearly 

 three times its first value. The fall, beyond the optimum, is 

 steeper than this rise. At S7° C. the rate of growth has 



G G 



