69 



P. M. COOK 



pump, recycles medium through a cell enclosed in a black cylin- 

 der containing a constant-intensity light source and a photoelec- 

 tric cell (See Figure 3). Constant dilution is obtained in the same 

 manner as in the inside column. A photograph of the column 

 in operation is shown in Figure 4. 



Experiments have been made with this apparatus since Sep- 

 tember, 1949. Variables affecting rates of growth and production 

 have been studied. Light in this case is not, of course, a constant 

 condition and all data therefore must be interpreted on a basis of 

 varying light conditions. 



AIR 

 FILTER 



WATER 

 AND 



STEAM 



MEDIUM SUPPLY 



CULTURE TANKS 



CENTRIFUGE 



Fig. 5 — Chlorella culture pilot plant, continuous culture process. 



