10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. CJ2 



in the next two light intensities, and numerous green cells with red 

 eye spots and a number of completely orange-red cells in the highest 

 light intensity. 



II. EFFECTS OF DIFFERENT WAVE LENGTHS 



THE PLANT USED 



Stichococciis hacillaris Naegeli, the green alga used in this experi- 

 ment, consists of a single cylindrical cell with rounded ends usually 

 partially filled with the chloroplast. The dimensions of the cell vary 

 from 2 to 2.5 [X in diameter and from 4 to 8 /x in length. Multiplica- 

 tion takes place by transverse division of the protoplast and the 

 formation of cross walls. The nucleus usually lies near the center 

 of the cell. (See pi. 2.) Filaments of cells were rarely observed in 

 my cultures. The alga develops rapidly, soon forming a green deposit 

 in Detmer 7^ containing 0.005 percent to 0.02 percent ferric chloride. 



The cells multiply very slowly on a solid medium such as Detmer J, 

 agar, and after two months' time small green buttons about 4 to 7 

 millimeters in diameter are present on the agar. If dextrose from 1.5 

 to 2 percent is added to the medium, the flat regular dark green disks 

 may grow to over i centimeter in diameter. 



This alga does not liquefy gelatine but forms a slight dark green 

 growth on the surface of the culture medium. 



My cultures have remained green in the dark for two months on 

 Detmer -J agar plus 2 percent dextrose. The colonial formations, al- 

 though greener, are smaller when grown in darkness than correspond- 

 ing cultures in the light, owing to the less rapid development and 

 exhaustion of the nutrient medium. Artari (1899), Radais (1900), 

 Matruchot and Molliard (1902), and Chodat (1913), have also 

 grown green cultures of Stichococcus hacillaris in darkness. Cultures 

 illuminated continuously by electric light for two months were a 

 , brownish-gray color and the individual cells were abnormally shaped. 

 Corresponding cultures in sky illumination showed normal cells but 

 were beginning to discolor at the center of each colonial disk. 



APPARATUS 



A metal table somewhat similar to the one used for experimenting 

 on the effects of light intensity was constructed for experimental 

 work on the effect of light of different wave lengths on one variety 

 of alga. (See pi. i, fig. i.) 



