

^^^N^^r 



Fig. 5. Section of Rhodopseudomouas spheroides growing photosyntheti- 

 cally at a light intensity of 50 foot-candles. The cytoplasm is packed '^ith 

 membrane-bounded vesicles (v) of relatively uniform dimensions, 500 A in 

 diametet-. Main fixation 2 hours, post staining with lead hydroxide. 

 X 120,000. 



Fig. 6. Section of Rhodopseudomouas spheroides growing exponentially 

 under photosynthetic conditions at a light intensity of 9500 foot-candles. 

 Internal membranes (arrows) can be distinguished at the periphery of the 

 cell; in this section, only one irregularly shaped, membrane-bounded 

 vesicle (v) is visible. The very electron-dense structure in the middle of 

 the cell is polymetaphosphate. indicates areas originally occupied by 

 poly-y8-hydroxbutyric acid. Several deposits of glycogen (g) are also vis- 

 ible in this section. Main fixation 2 hours, post staining with lead hydrox- 

 ide. X 120,000. 



