LETHAL EFFECT OF SHORT WAVE LENGTHS OF 



THE ULTRAVIOLET ON THE ALGA 



CHLORELLA VULGARIS 



By FLORENCE E. MEIER 

 Division of Radiation and Organisms, Smithsonian Institution 



(With Two Plates) 

 INTRODUCTION 



Quantitative investigation of the lethal action of eight wave lengths 

 below the short-wave limit of ultraviolet irradiation in nature on the 

 unicellular green alga Chlorella vulgaris has been reported in two 

 previous papers (Meier, 1932, 1934). A study was made in these 

 papers of the response of the alga to 12 wave lengths of a mercury 

 vapor arc ranging from 2536 A to 3650 A, which was made possible 

 by the use of a fused quartz spectrograph. By means of a crystal 

 quartz spectrograph, the research has now been extended to the lethal 

 effect of 21 wave lengths in the ultraviolet ranging from 2250 A to 

 3 1 30 A on the same alga. 



The spectroscopic manipulations and physical measurements were 

 made by Dr. E. D. McAlister, of the Division of Radiation and 

 Organisms. 



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

 sonian Institution, for his encouragement and assistance in the in- 

 terpretation of the results of the experiments here reported. 



EXPERIMENTAL PROCEDURE 



Chlarclla vulgaris has proved to be well adapted to this type of 

 research because of the spherical shape of its single green cell and 

 the uniformity and speed with which the cells, multiplying by oval 

 or elliptical spores, cover the surface of an agar plate. This uni- 

 cellular green alga consists of a spherical cell containing a parietal 

 chromatophore and one easily visible pyrenoid. The diameter of the 

 cell is usually 3/i, to 5ju., although some giant cells exceed xOjx. This 

 alga has been maintained in pure culture in my collection for 5 years. 



Smithsonian Miscellaneous Collections, Vol. 95, No. 2 



