J natural 



r ORY 



GROWTH OF A GREEN ALGA IN ISOLATED WAVE- 

 LENGTH REGIONS 



By FLORENCE E. MEIER 

 Division of Radiation and Organisms, Smithsonian Institution 



(With One Plate) 

 INTRODUCTION 



The importance of experimentation with isolated narrow ranges 

 of light for the determination of the effectiveness of specific wave 

 lengths on cell multiplication and chlorophyll formation in green 

 algae was manifested in a previous paper by Meier (1934 b). In the 

 research reported in that paper, 11 short wave length cut-off filters 

 were used to transmit light of progressively shorter and shorter wave 

 lengths from one transmitting only deep red, 6000 A, to one at the 

 other extreme, 3700 A, where most of the visible region is included. 

 Chlorophyll was formed in the unicellular green alga, Stichococcus 

 bacillaris Naegeli, under all the filters but in best condition where the 

 wave lengths of the blue-violet region were included. A multiplica- 

 tion of algal cells ranging from twofold to fourfold was obtained in 

 the cultures. It was evident that some ranges of wave lengths seemed 

 to inhibit cell multiplication and chlorophyll formation and that others 

 seemed to favor them. Considering the complexity of the bands of 

 radiation from the short wave length cut-off filters, it was clear that 

 the effectiveness of restricted wave-length regions could be deter- 

 mined conclusively by experimentation in the isolated narrow ranges 

 of light such as can be provided by Christiansen filters. 



I am very grateful to Dr. C. G. Abbot, Secretary of the Smith- 

 sonian Institution, for his encouragement and helpful criticism dur- 

 ing the accomplishment of this research. The Christiansen light 

 filters were made by Dr. E. D. McAlister, of the Division of Radia- 

 tion and Organisms, as described in his paper, " The Christiansen 

 Light Filter: Its Advantages and Limitations" (1935). W. H. 

 Hoover, of the Division of Radiation and Organisms, made the 

 nephelometer measurements, as described by Meier (1934 b). Both 

 Dr. McAlister and Mr. Hoover made the intensity measurements, 

 and with the combined helpfulness and watchfulness of Dr. E. S. 

 Johnston, assistant director of the Division of Radiation and Organ- 



Smithsonian Miscellaneous Collections, Vol. 94, No. 17 



