EVOLUTION BY Chlorellu: II 



423 



limited bursts in the previous paper. Since the amount of residual 

 CO2 present from previous dark respiration is far less in this case 

 where the bulk of respiration is anaerobic (in contrast to the aerobic 

 C02-f ree bursts presented in the previous paper) , any question of the 

 role of residual CO2 (see also Figs. 4 and 8) in the burst process is 

 thereby minimized. This CO2 independence of the burst distinguishes 

 the process from that of CO2 fixation. 



16 

 14 



12 



mmzon 



AIR SAT 



90 



3 _ 



80 



I I I I I I I I I I 1 I 



TIME IN MINUTE INTERVALS 



Fig. 4. Effect of interposed dark intervals during C02-limited sustained rate. 

 (Portion of original rate recording with O2 cone, curve dotted in.) Suspension 

 anaerobic dark adapted in "Seaford" N2 (0.002% O2) prior to run. 



Figure 4 shows the effect of interposition of successive short dark 

 intervals of increasing length during the course of C02-limited sus- 

 tained rate. The resulting curvilinear increase of the O2 burst maxi- 

 mum with increasing dark oxidation time is plotted in Fig. 5, which 

 shows the burst response saturating from 18 to 180 seconds. 



In apparent contrast the effects of dark time on C02-nonlimited 



