8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



had wrinkled disks but brilliant, smooth ones in the other six treat- 

 ments. Scenedesmns chlorclloides var. had moist colonies in i, 5, 8, 

 and dull, dry ones in the other six treatments. 



SUMAIARY 



Of 18 varieties of unicellular green algae, 11 developed chlorophyll 

 while growing for 30 days in continuous light, in natural conditions 

 of intermittent light and dark, and in continuous darkness. The other 

 7 varieties showed individual reactions to the different treatments ; 

 3 showed poor development in all of the conditions ; 2 algae had the 

 best chlorophyll formation in continuous darkness and in intermittent 

 light ; I grew best in continuous light ; and i variety developed best 

 in continuous darkness. Seven of the 1 1 algae still maintained their 

 chlorophyll at the end of 60 days, although the growth and develop- 

 ment of each colony had attained its maximum at the end of 30 days. 

 Decoloration was manifested in all the cultures of i alga and in 

 some treatments of 6 other algae. 



Five of the 18 algae formed carotin, 2 of the 5 in all the treatments, 

 the greatest amount being formed in intermittent light. 



Haematochrome was formed in i variety to the largest extent in 

 continuous light and least in those cultures exposed to intermittent 

 light during the last 30 days of their development. 



The colonies dififered greatly in morphological appearance. 



