SMITHSONIAN MISCF:LLANE0US COLLECTIONS VOL. 92 



CONCLUSIONS 



1. Intermittent light gives more favorable results than continuous 

 light. 



2. In continuous illumination better results were obtained by the 

 weaker light (at a distance of 40 centimeters). 



3. Agitation is favorable to a more equal distribution of cells and 

 hence a more uniform lighting condition. It also favors multiplica- 

 tion, as the cells do not collect in large masses. 



4. Detmer ^ is a favorable solution for the growth of the algae 

 under the controlled conditions described above. 



5. Rubber stoppers serve as well as cotton plugs in 300-cc flasks 

 containing 100 cc of solution for an experimental period of a month. 



SECOND EXPERIMENT 



A second experiment was carried out with cultures of the follow- 

 ing 15 algae: Coccamy.va simplex, Chlorclla viscosa, Scencdesmus 

 flavesceus, Chlorella vulgaris, Stichococcus hacillaris, Palmellococcns 

 protothecoidcs. Oocyst is nacgclU, Cystococcus irregularis, Chlamy- 

 dotnonas intermedia, Palmelococcus variegatus, Chlorococcum vis- 

 cosum, Scenedesmus chlorelloides var., CJdorella vulgaris var., Cysto- 

 coccus cohaereus, and Heterococcus viridis. Three sets of the cul- 

 tures were illuminated each by a 300-watt Mazda daylight lamp at a 

 distance of 40 centimeters from the glass bottom of the bath to the 

 top of the filament of the lamp. The fourth was kept in darkness. 



Of the three illuminated culture sets, one received intermittent 

 light for 6 hours. All the cultures were constantly agitated with the 

 exception of one of the two receiving continuous illumination. The 

 experiment was in progress from July 28 to August 18. 1931. Detmer 

 7!) solution was used for each alga. 



The cultures that were agitated continuously and lighted intermit- 

 tently and the cultures that were stationary and lighted continuously 

 produced the most satisfactory results at the end of the experimental 

 period. In the stationary cultures, the algae had formed a film on 

 the bottom of the glass flasks that shielded those in the solution 

 from the intense light. The first seven algae listed above were green- 

 est and in the best condition. The next six listed were less green 

 probably because the light was too intense, while the last two listed, 

 that is, Cystococcus cohaereus and Heterococcus viridis. were killed 

 by the intense light in all three of the baths. 



The cultures which were continually agitated and kept as closely 

 as possible in continuous darkness gave the following results : all 



