350 K. EMERSON AND R. V. CHALMERS 



whose respiration differed by a factor of about seven. In the case of 

 the cells with low respiration, photosynthesis exceeded respiration. 

 Whereas, in the case of the cells with high respiration, photosynthesis 

 was less than respiration. The calculated efficiency was essentially 

 the same in the two cases. 



TABLE I. Comparison of I'^^fficicncy of Photosynthesis above and below Com- 

 pensation of Respiration 



In these experiments, the light intensity decreased from the inci- 

 dent value and approached zero as the light penetrated the cell 

 suspension. Thus the statement that photosynthesis was above com- 

 pensation in one case and below in the other, means only that the sum 

 of respiration for all cells exceeded or was less than the sum. of photo- 

 synthesis. Certainly, the rate of photosynthesis in the full intensity of 

 the incident beam must have been sufficient to produce photosyn- 

 thesis above compensation, even in the case of the high respiration 

 cells. This effect was counterbalanced by the cells exposed to loAver 

 intensities as the light penetrated the suspension and by the cells 

 which were in darkness outside the periphery of the light beam, 

 which was smaller than the area of the reaction vessel. The experi- 

 ment therefore does not show whether there would be a difference 

 in efficiency above and below compensation, under conditions of 

 continuous illumination of all cells with approximately uniform light 

 intensity. 



In our opinion, comparison of quantum requirements of different 

 samples of cells on the basis of measurements with thin suspensions 



