EFFECTS OF RADIATION ON FUNGI 907 



The ability to form sexual organs can be destroyed by X-rays, but 

 the ability to form asexual organs is not so readily suppressed. Nadson 

 and Philippov (133) completely suppressed the formation of zygotes in 

 Mucor genevensis and Zygorhynchus Moelleri, but they could never 

 entirely prevent the formation of sporangia. 



RAYS EMITTED FROM RADIOACTIVE SUBSTANCES 



Studies which have been made of the effects of rays from radioactive 

 substances on fungi have yielded only fragmentary evidence. However, 

 much of it is interesting as a basis for further detailed study. There is no 

 question but that the rays produce effects on fungi provided the dose is 

 sufficiently great. Although no effects were noted by Prescott (149), 

 the preponderance of evidence indicates marked inhibitory action with 

 large doses. 



If the dose is sufficiently great, lethal action occurs. This was 

 reported by Purvis and Warwick (150), Nadson (130), Lacassagne (96), 

 Levin and Levine (103), Miescher (121), Heyderdahl (72), and Glocker, 

 Langendorff, and Reuss (58). Heyderdahl was successful in curing 

 severe cases of facial actinomycosis with gamma rays from radium. 

 According to Glocker, Langendorff, and Reuss lethal action follows a 

 typical S-shaped survival curve when yeast cells are treated with alpha 

 rays from a polonium preparation. The approximate dose necessary to 

 kill yeast cells in beer is expressed by Lacassagne as one in which each 

 square micron receives an alpha particle from polonium once every 

 4.35 sec. He reported that the cells died after one division. Miescher 

 found that a 10- to 14-day exposure to 24.9 mg. of radium with a silver 

 filter 0.1 mm. in thickness and placed at a distance of 15 mm. from the 

 culture is necessary to stop the growth of Achorion gypseum. Lacassagne 

 and Holweck (97) reported that the amount of lethal action is dependent 

 on the total number of alpha particles regardless of the time or the 

 intensity, and Holweck (75) calculated that about 20 times as much 

 energy is necessary to prevent the first as to prevent the second division 

 following irradiation. Nadson (130) observed that there is a latent 

 period following irradiation during which no effect is visible, the length 

 of the period depending on the exposure. He found that, in general, 

 young cultures are more sensitive than older ones, while Lacassagne and 

 Holweck (97) found that cells in a quiescent state are more sensitive than 

 actively dividing cells. Nadson and Zolkevic (136) found, as they had 

 for X-rays, that the harmful action of the rays from radium can be 

 almost balanced by the addition of potassium chloride to the substrate. 

 The antagonism is dependent on a definite ratio between the intensity of 

 radiation and the concentration of potassium chloride. 



Various degrees of injury similar to those produced by other regions 

 of the spectrum are produced with sublethal exposures to radioactive 



