NO. 5 COLONIAL FORMATION' OF GREKN ALGAE MEIKK 5 



The continuous light was supi)hc(l 1)v four 300- watt Mazda day- 

 Hght lamps so placed that there was a distance of 92 centimeters 

 from the filament to the top of the table on which were the flasks 

 containing the algae. The intensity as measured by the thermocouple 

 was 60 microwatts per square millimeter per second, which is about 

 the same as i/io of noon sunlight in the summer. 



The continuous darkness was provided by placing the flasks of 

 algae in a tightly closed closet in a concrete pier in a basement room 

 that as a rule is kept dark continually, and if lighted is illuminated 

 by a red lamp. 



The intermittent light and darkness were natural da}- and night 

 conditions in March and April in a north window of the flag tower 

 of the Smithsonian Institution. 



RESULTS 



All the results have been tabulated on pages 9-12 for convenient 

 reference. 



CHLOROPHYLL FOR^fATION 



Eleven varieties were equally green in all nine treatments at the 

 end of 30 days. However, in the following cultures a variation in 

 chlorophyll content was indicated by a difference in color : Oocystis 

 naegelii and ClilorcUa vulgaris var., in all nine treatments ; Sccnedes- 

 iiius quadn'cauda, very evident change in the cultures in continuous 

 darkness, slight differences in color in the cultures in intermittent and 

 continuous light ; Chlorococcuui viscosinn in intermittent light and in 

 continuous darkness ; Cystococcus irregularis in continuous light ; 

 Coccomyxa viridis in continuous light and in intermittent light ; and 

 Palmellococcus protothec aides in all cultures except treatment 5. 



After 60 days seven algae showed abundant chlorophyll in all nine 

 treatments. This included the following varieties : Scenedesmus 

 chlorelloides var., Hctcrococcus viridis, Chlorella viscosa, Chlamiy- 

 doiuonas intermedia, Ooeysfis uaegelii, Cystococcus coJiacrens var., 

 and Chlorococcuui viscosuin. 



Six varieties had very little or no chlorophyll in any of the cultures 

 at the end of 60 days. Among these were Chlorella vulgaris, Chlorella 

 vulgaris var., Palmellococcus variegatus, Scenedesmus Havesccns, Pal- 

 mellococcus protothccoidcs, and Coccomyxa viridis. But after the 30- 

 day period, the following were still green: Palmellococcus variegatus 

 and Scenedesmus flavescens in the cultures that had been kept in in- 

 termittent light and in continuous darkness. Palmellococcus proio- 



