140 EFFECTS OF RADIATION ON FUNGI 



evaluated. The methods employed by Oster (1934) in his study 

 of Sac char omyces cerevisiae appear to be well suited to similar 

 studies of other fungi. He used monochromatic light and found 

 that inhibition of colony size could be obtained at a low energy 

 level. Under such conditions few new buds were formed, giant 

 cells were sometimes produced, and the metabolic functions were 

 retarded, as was shown by lowered 2 consumption. At a wave- 

 length of 2652 A, 457 ergs/mm 2 were required to kill 50% of the 

 cells, but at 3022 A, 23,500 ergs/mm 2 were necessarv. The shape 

 of the curves for lethal action at different wavelengths suggests 

 that more factors than single quantum hits on a sensitive region, 

 that is, adsorption of energy by the nucleoproteins, are responsible 

 for these effects. Oster suggests that the age of the cells at the 

 time of exposure is also a factor in the energy relations involved. 

 The effect of temperature must always be taken into considera- 

 tion in experiments of this type. 



Ultraviolet radiations of wavelengths between 2537 and 2650 A 

 were found most effective in killing Trichophyton mentagroph- 

 ytes [Hollaender and Emmons (1939)]. They suspended the 

 spores in physiological salt solution, using wavelengths in the 

 range 2280 to 2950 A in measured quantities. In a subsequent 

 report these investigators [Emmons and Hollaender (1939) | cor- 

 related time of exposure of spores of this same species to mono- 

 chromatic light of 2650 A with energy required to cause death 

 and with percentage survival. Their experimental data on these 

 points are contained in Table 10. 



