4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



Meier (1929) proved that light is not necessary for the formation 

 of chlorophyll and carotin in the cells of Chlorella rubescens Chodat, 

 Sccnedcsmus obtusiusculus Chodat, and Scenedesmus chlorelloides 

 Chodat when an abundant quantity of nitrate and glucose are present 

 in the medium upon which they are growing. 



METHOD 



The medium on which the algae were grown for these experiments 

 was Detmer solution made up in the following proportions : 



Grams 



Calcium nitrate i. 



Potassium chloride 0.25 



Magnesium sulphate 0.25 



Potassium acid phosphate 0.25 



Distilled water 1000. 



Ferric chloride 0.002 



The solution was diluted to ^ for this experiment, then 2 percent 

 dextrose and 2 percent difco-bacto agar were added. 



Nine series of 18 different algae were inoculated in 125-cc Erlen- 

 meyer flasks each containing 75 cc of the above medium. Three in- 

 oculations were made on the surface of the solid medium in each 

 flask by means of a platinum needle. The necessary precautions were 

 taken for strict sterilization. All the algae used were from pure cul- 

 tures, the majority of which had been isolated by the author. 



The following set of nine treatments was given to each alga: 



1. Control in intermittent light (daylight) during 2 months. 



2. Intermittent light for i month, then placed in continuous light (electric 



light) for I month. 



3. Intermittent light for i month, then placed in continuous darkness for i 



month. 



4. Continuous darkness during 2 months. 



5. Continuous darkness for I month, then placed in intermittent light for i 



month. 



6. Continuous darkness for i month, then placed in continuous light for i 



month. 



7. Continuous light during 2 months. 



8. Continuous light for i month, then placed in intermittent light for i month. 



9. Continuous light for i month, then placed in continuous darkness for i 



month. 



The schematic outline of the treatments is as follows: 



Intermittent Continuous Continuous 



light darkness light 



Day I (Inoculation) 



Day 2 123 546 789 



Day 30 I 58 349 726 



Day 60 (End of experiment) 



