120 CHAP. XV. C0 2 -SUPPLY AND PHOTOSYNTHESIS 



but by the end of February the activity was initiated at as 

 low a value as I mg I give the following results of 

 observations made with a spring-specimen, the light being 

 maintained constant at 1200 lux from the Pointolite. 



Table XV. — Photosynthetic Activity under Variation of 



C0 2 -CONCENTRATION (POINTOLITE) 



(Spring-specimen) 



The curve obtained from the above data is similar to 

 that given in fig. 33. It is straight up to the turning-point 

 at about 9 mg. After this the curve becomes rounded, the 

 maximum being attained gradually and not abruptly. A 

 reversal often occurs above a concentration of 12 mg. per 

 100 c.c. The curve of spring-specimens is more erect than 

 that of winter-specimens. 



Determination of the coefficient of spring-specimen : 



Specimen IV. C0 2 -concentrations of 2 mg. and 5 mg. : 

 Activity for 2 mg. = 142 -2 

 5mg. =355-5 



K= 355-5 --142-2 



5-2 



71-1 



The average coefficient for the winter-specimens is 39-9, 

 that for the spring-specimens is 71-1. The ratio of the 

 coefficients for spring- and winter-specimens is therefore 1 • 8 

 or nearly 2. This was the ratio which we also found in 

 the enhancement of the coefficient for light under variation 



