EXPERIMENTS WITH WINTER-SPECIMENS 



37 



Experiments with Winter-Specimens 



The results obtained with winter-specimens are given 

 below in Table VI. 



Table VI. — Photosynthetic Activity under Increasing Intensity 

 of Pointolite. (Winter-specimens) 



For purposes of comparison, two curves are given in the 

 same figure (fig. 7), one for a spring-specimen (I.) and the 

 other for a winter-specimen (IV.). The curve for the spring- 

 specimen, s, is the more erect, indicating greater sensitive- 

 ness. The effect of season in modifying activity is further 

 shown by the different minimal effective intensities of light. 

 In spring, photosynthesis occurred at an intensity lower than 

 300 lux, but in winter the minimally effective light was 450 lux 

 or even much higher. The two curves otherwise bear a 

 general resemblance with each other. In both we notice 

 a turning-point, beyond which the curves tend to become 

 horizontal. The middle part of the curve, from about 100 

 to 1200 lux, is practically straight ; and a method will be 

 presently described for the determination of the coefficient 

 in this middle range. 



Formula for determination of activity for a given intensity 



