INHIBITORY EFFECTS 



141 



Dimond and Duggar (1941) determined the lethal effects of 

 monochromatic ultraviolet radiations 2650 A in wavelength on 

 Aspergillus melleus, Rhizopas minus, and Mncor disperses. They 

 correlated ergs of energy required with volume of the spores, 

 using the volume of A. melleus as unity. Their data, which are 

 presented in Table 11, indicate that resistance is not directly cor- 



TABLE 11 

 Lethal Effect of Ultraviolet Radiations on Three Species of Fungi 



related with the volume of the spore. Pigmentation of spores and 

 differences in the number of spore nuclei are employed as addi- 

 tional factors in accounting for differences in the action of radia- 

 tions. 



Recently Sharp (1938) made certain refinements in methods of 

 studying the effect of ultraviolet light on bacteria that would 

 appear to be adaptable for use with fungi. In attempts to elimi- 

 nate the shielding or screening effects of masses of bacteria and 

 of the medium he atomized broth cultures into the air, passed the 

 bacteria-laden air through a tube where thev were exposed to 

 monochromatic ultraviolet light, and then captured the treated 

 bacteria at the exit on culture media. It should be possible to 

 substitute suspensions of spores in water for broth cultures of 

 bacteria in such an apparatus. 



Several investigators have been concerned with the use of ultra- 

 violet rays as a potential fungicide. Fulton and Coblentz (1929) 

 tested a group of pathogens by use of a 1 10-volt quartz lamp with 

 a mercury cathode and a tungsten anode operated on 320 watts 

 (80 volts, 4 amp). The spores of all organisms were at the sur- 

 face of the agar plates. The investigators eliminated temperature 

 effects and found that the following survived exposure for one 

 minute: Helminthosporium sp., Alternaria sp., Cladosporium sp., 



