EFFECTS OF RADIATION ON FUNGI 909 



Kotzareff and Chodat (94) reported that radiation retards fermentation 

 while Stoklasa (180) and Kayser and Delaval (86) found that small 

 amounts stimulate it. Differences in results are probably caused by the 

 different conditions under which the experiments were performed and the 

 different amounts of radiation to which the cultures were exposed. 

 Nadson (130) reported that Cryptococcus which normally does not pro- 

 duce glycogen, after irradiation forms glycogen and another carbo- 

 hydrate which stains blue or violet with an iodide. Sartory, Sartory, 

 and Meyer (161) found that in an " undissociated " medium irradiation 

 increases the ability of Aspergillus fumigatus to reduce saccharose, while 

 in a "dissociated " medium irradiation decreases it. Suguira and Benedict 

 (183) found that the vitamins in yeast can be partially inactivated by 

 exposure to radon. A positive tropism of the sporangiophores of Phy- 

 comyces nitens to radium after 15 or more hours' exposure was reported 

 by Koernicke (92) and Molisch (123). A rather unusual phenomenon 

 was noted by Guyot (64) who found that a tube of radium applied to a 

 mycelium which is normally phosphorescent but whose phosphorescence 

 has been recently extinguished revives the luminosity. If the mycelium 

 is already luminous and the radium is allowed to act for 2 or 3 hr., the 

 luminosity is gradually destroyed. 



GENERAL SUMMARY 



One of the most outstanding criticisms which might be made of 

 radiation experiments is that the results cannot be easily duplicated. 

 The wave-lengths emitted by the source, the intensity of the source, the 

 nature of any absorbing media interposed, temperature, composition of 

 the medium, hydrogen ion concentration, age of the culture, and inocula- 

 tion technique must all be measured in standard units in order to have 

 results which may be easily confirmed by other workers. Various 

 experiments have shown that all these factors may affect the sensitivity 

 of fungi to radiation. 



Different wave-lengths have been obtained by varying the source 

 and by interposing various absorbing media between the source and the 

 fungus. Often, however, all the absorbing media interposed have not 

 been considered in determining the wave-lengths which the culture 

 received. Cultures placed behind a window do not receive the same sun- 

 light as those placed outside. Water and solid nutrient media absorb 

 radiation selectively with respect to wave-length, so that not only the 

 total intensity but also the quality of the light may be altered. Fungus 

 hyphae may act as an absorbing screen to those hyphae growing below 

 them. For still more quantitative considerations of wave-length there 

 are multiple reflections from the fungus mycelia and from the medium. 



It is quite difficult to control adequately temperature in radiation 

 experiments, especially where the intensities of radiation are large. 



