910 BIOLOGICAL EFFECTS OF RADIATION 



There is no good literature on the effects of sudden changes in temperature 

 on fungi, and it may be that very sUght sudden changes may produce 

 very pronounced results. In the problem of temperature not only infra- 

 red radiation emitted by the source but also light absorbed by the fungus 

 and by the medium and transformed to heat must be considered. This 

 effect can be minimized somewhat by the use of liquid media and a water 

 bath whose temperature is regulated. However, in many instances a 

 liquid medium is not desirable since it often leads to a thicker mycelial 



mat. 



The vigor of the fungus as affected by its age, nutrition, acidity, and 

 previous light treatment probably determines very largely its sensitivity 

 to radiation. If the effect of light on a fungus in which there are no other 

 limiting factors is to be considered, then preliminary experiments should 

 be made to establish the fact that other conditions are favorable. 



Because environmental factors have been so largely neglected in the 

 experiments, there are very few general conclusions which may be 

 drawn. It has been well established that some fungi will carry on a 

 normal life cycle in complete darkness. Others need light for different 

 stages in their development. Most fungi require light for the formation 

 of large amounts of pigment. Short wave-lengths are in general more 

 harmful to vegetative development than long wave-lengths. But even 

 such generalizations as these may be open to question. It seems quite 

 certain that a great many phenomena which have been attributed to the 

 action of light are due not to light alone but to light linked with some other 

 varying environmental factor. 



REFERENCES 



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2. Bailey, A. A. Effects of ultraviolet radiation upon representative species of 

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3. Bary, a. de. Recherchcs sur le dcveloppement de quelques champignons 

 parasites. Ann. Sci. Nat. Bot. Ser. 4, 20: 5-148. 1863. 



4. Becquerel, p. L'action abiotique de I'ultraviolet et I'hypothese de I'originc 

 cosmique de la vie. Compt. Rend. Acad. Sci. [Paris] 151: 86-88. 1910. 



5. Berde, K. von. Das Verhalten von Fadenpilzkolonien unter der Wirkung des 

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6. Bessey, E. A. tlber die Bedingungen der Farbbildung bei Fusarium. Flora 

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7. Bie, V. Uber das Vermogen des Lichtes Spross, und Schimmelpilze zu toten. 

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8. BiSBY, G. R. Zonation in cultures of Fusarium discolor sulphureum. Mycolo- 

 gia 17: 89-97. 1925. 



9. Blaauw, A. H. Lichtund Wachstum I. Zeitschr. Bot. 6: 641-703. 1914. 



10. Blaauw, A. H., and W. van Heyningen. De radiumgroeireactie van een eel. 

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 173-188. 1925. 



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