NO. 2 EFFECT OF ULTRAVIOLET ON ALGAE MEIER 1 7 



DISCUSSION 



The radiotoxic spectral sensitivity curve for the green alga Chlorella 

 vulgaris in figure i is of the same general type in the region 2600 to 

 3130 A as the curves representing bactericidal action and virus in- 

 activation as found by Duggar and Hollaender ( 1934) ; the lethal 

 effect on yeast by Oster (1934) ; the lethal effect on paramoecium by 

 Weinstein (1930); and bactericidal action and protein coagulation 

 by Sonne (1928), and Rivers and Gates (1928). 



Fig. 2. — Radiotoxic virulence determined from Chlorella vulgaris. The 

 abscissae are wave lengths in angstroms. The ordinates are radiotoxic virulence 

 in arbitrary units. 



Very little study has been made of the effect of wave lengths of 

 the ultraviolet below 2600 A on algae. Lucas (1934) has given us an 

 idea of the actual effect of an ultraviolet ray on an individual algal 

 cell. By means of a specially designed ultraviolet microscope with a 

 monochromatic system, Lucas has photographed living cells of the 

 blue-green alga Gloeocapsa. Wave lengths 2573 A and 2750 A showed 

 good definition of the cells, although the absorption of the cell in- 

 creased at 2573 A. At 2300 A, the absorption of the cell was very 

 strong, but the photographs were not sharp or distinct. No photo- 

 graphs were possible with wave length 2265 A, as, for a second or 

 two while under visible observation with the fluorescent ocular, the 

 cells seemed agitated or strained and then suddenly increased to 5 



