58 



UNIVERSITY OF WISCONSIN STUDIES 



TABLE V. OIDIUM 



TABLE VI PENICILLIUM GLAUCUM 



An examination of the above tables shows that the mold 

 spores possess an extraordinarj' resistance to direct sunlight. 

 This resistance was so unexpected that in the earlier trials 

 the cultures were exposed for only a few hours ; this time was 

 gradually lengthened until in the last trials the exposure was 

 continuous for four or five days during the long days of July, 

 and yet Aspergillus niger and nidulam never failed to grow. 

 The other species showed some irregularities, but possessed 

 remarkable endurance. The irregularities may be due to a 

 failure to infect the paper strips, for in no other way can we 

 explain the discrepancy in the case of Aspergillus fumigatus 

 which withstood 42 hours of exposure one time and only 13 

 hours in an earlier trial. 



It is difficult to explain this extraordinary resistance of 

 mold spores as compared with bacterial spores which rarely 

 survive more than five hours. The fact that these spores are 

 colored suggests that this pigment exerts a protective influence ; 



