CULTURE FOR PHYSIOLOGICAL RESEARCH 51 



active carbon Fager (1949) has developed an aquarium-like tank 

 one meter high by one meter wide by 10 cm. thick. Illumination 

 by banks of fluorescent lamps allows a production of a pound of 

 Scenedesmus per week. Another development for quantity pro- 

 duction is that of Ketchum and Redfield (1938, 1949) as modi- 

 fied by Scott (1943). A five gallon carboy is adapted as a culture 

 vessel. A similar development is that of Spoehr and co-workers 

 (1949a) who used five-gallon carboys under daylight illumina- 

 tion in a greenhouse. An extension of culture methods to large 

 scale algal farming is being explored by Paul Cook of the Stan- 

 ford Research Institute, who will describe in another paper of 

 this symposium his experience in development of really large 

 scale mass culture. 



Finally, brief comment well may be made on the problems of 

 selection of culture media. Innumerable formulae are available in 

 the literature and have been variously selected by different labora- 

 tories in the fine tradition of ancestor worship. It is our experi- 

 ence that the problem of culture media may be broken down 

 into a series of specific choices with respect to (i) concentration 

 of the major salts, (2) pH, (3) nitrogen source, (4) the provision 

 of iron and other micro-elements, (5) the provision of organic 

 materials or growth factors for certain forms. 



I hope that I have not implied in any way that culture meth- 

 ods have become cut and dried. Actually, most of the methods 

 which I have described have been developed for hardy and easily 

 grown forms such as Chlorella. A great deal of ingenuity needs 

 to be applied to the culture of a number of algae which should 

 prove highly interesting for physiological work. 



