Chapter 6 



EFFECTS OF RADIATION ON FUNGI 



Although students of fungi have long been interested in the 

 reactions to light of this group of organisms, little progress in this 

 field was made until after the beginning of the present century. 

 The primary reason for this state of affairs is that the existence of 

 radiations other than visible light was unknown until approxi- 

 mately 1900. From physical researches it is now known that 

 radiations of the following groups exist, some of them possessing 

 wavelengths in excess of those of visible light and others being 

 shorter. 



1. Hertzian rays, the wavelengths of which range from 1 X 10 6 

 to 3 X 10 14 Angstrom units, an Angstrom unit (A) being 1/10,- 

 000,000 of a millimeter. Those waves in the upper portion of the 

 range between 1 X 10 11 and 3 X 10 14 A are used in radio com- 

 munication. 



2. Infrared or heat rays, the wavelengths of which range from 

 8000 to 4 X 10 6 A, thus overlapping the lower end of the range 

 of Hertzian waves. 



3. Visible light rays, the wavelengths of which range from ap- 

 proximately 4000 to 8000 A. 



4. Ultraviolet rays, the wavelengths of which range from 136 

 to 4000 A. 



5. X-rays, the wavelengths of which range from 0.06 to 1000 A, 

 thus overlapping the lower end of the ultraviolet range. 



6. Gamma-rays, the wavelengths of which range from 0.01 to 

 1.4 A. 



7. Cosmic rays, the wavelengths of which range down to 

 1/10,000 A. 



Of these groups, infrared rays, visible light rays, ultraviolet 

 rays, and X-rays have been used in experimentation with fungi. 

 Such studies have been concerned mainly with the morphogenic 

 effects of radiation, the fungicidal effects, and the modifying 



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