166 



L. N. M. DUYSENS 



10 



37 



160 



350 quanta 

 _i I 



1 2 3 it minutes 



Fig. 1. Changes in optical density upon illumination of a RhodospiriUum sus- 

 pension in anaerobic peptone at 430 (top figure) and 530 mju (bottom figure). 

 Onset of illumination is indicated by an upward pointing arrow and darkening 

 by a downward pointing arrow. The numbers written at the bottom of the figure 

 are the approximate nimaber of quanta absorbed per minute per bacteriochlorophyll 

 molecule. 



Fig. 2. Difference s])ectra of RhodospiriUum. strain 1 in anaerobic peptone (top 

 figure) and in aerobic distilled water (bottom figure). The left part in aerobic 

 water is for strain 4, the right part for strain 1 , and the middle part for an aqueous 

 extract of strain 1 ; two parts were multiplied by factors to get an approximately 

 continuous connection between the curves. 



