140 CHAP. XVII. EFFECT OF VARIATION OF TEMPERATURE 



The photosynthetic curve plotted from the data for 

 Specimen I. is given in fig. 39. It is seen that the curve is 

 practically straight from 17 up to 28 C. ; there is a sharp 

 decline. The straight portion of the curve when produced 



Fig. 39 FlG - 4° 



Fig. 39. Photosynthetic Curve under Variation of Temperature 

 The curve is straight from 17 to 28 . Note abrupt fall of curve 



after the optimum temperature of 28 (under stronger light 



the optimum is 33 ). 



Fig. 40. Curve of Growth under Variation of Temperature 

 Ordinate represents growth in /* per second. 



backwards cuts the abscissa at 9 -2 C, which will be shown 

 in a later chapter to be the physiological zero point. The 

 activities coi responding to the three temperatures of 17°- 5. 

 21 , and 24°- 5 are shown in the record. We will presently 

 determine the temperature coefficient. 



