904 BIOLOGICAL EFFECTS OF RADIATION 



from a mercury- vapor lamp for 50 min. An average of 13 saltants was 

 produced for each 100 colonies subcultured. Most of the saltants showed 

 no tendency to vary, even though many of them were cultured through 

 several generations. There is no essential difference between the 

 characters exhibited by saltants induced by X-rays and those induced 

 by ultra-violet radiation. 



PHYSIOLOGICAL PROPERTIES 



Respiration, Transpiration, and Synthetic Processes. — There is still 

 some doubt as to the possible effects of radiation on the respiration of 

 fungi. Detmer (28), Elfving (39), and Lowschin (107) all reported no 

 effects. Bonnier and Mangin (11), however, made extensive study of a 

 number of fungi under controlled temperature conditions and found that 

 respiration is retarded by radiation. This retardation may have been 

 masked in the earlier work by the acceleration produced by a rise in 

 temperature when temperature was not controlled. The problem is 

 complicated, however, by the results of Surdnji and Vermes (184) 

 which indicate a temporary increase in respiration. No mention is 

 made of any temperature control so that the acceleration may again be 

 due to temperature. Maximow (118) found that age may be a factor. 

 He reported that light from an electric lamp exerts no influence on the 

 respiration of young cultures of Aspergillus niger, but it furthers the 

 respiration of older cultures. With regard to the effective wave-lengths, 

 Bonnier and Mangin found that the blue end of the sun's spectrum causes 

 more carbon dioxide to be released than the red. 



According to Bonnier and Mangin (11), transpiration is accelerated by 

 diffuse light when the water loss from a number of different fungi was 

 studied under constant temperature conditions. The synthetic processes 

 in fungi were reported by Elfving (39) to be retarded by light, especially 

 by blue light. 



Fermentation. — A number of investigations have been made to deter- 

 mine the effects of light on the fermentation activities of yeast in the 

 making of wine and beer (36, 42, 45, 46, 47, 48, 49, 62, 63, 73, 108, 113, 

 114, 115, 117, 144). In view of the difficult conditions under which 

 most of this work was done, it would be hazardous to discuss it critically. 



X-RAYS 



It has been rather conclusively shown that X-rays exert positive 

 effects on green plants. The evidence is not so convincing perhaps for 

 the fungi, but nevertheless there have been a number of clear-cut experi- 

 ments in which definite effects of X-rays have been observed. 



Some explanation, however, seems to be necessary for the large 

 number of negative results which have been obtained. In some cases 

 perhaps too small intensities were used. This is a possible explanation 



