134 



Mycologia 



tion. That the spores might not only be able to withstand the 

 process of sterilization, but might even be stimulated to germina- 

 tion by high temperatures was suggested, since it is claimed that 

 the spores of some of the coprophilous fungi must be subjected 

 to the body temperature and other influences of the alimentary 

 canal of animals in order to induce their germination. 



In order to test the matter of the effect of heat on the spores of 

 the fungus, mature ascospores were heated to various tempera- 

 tures and later planted in hanging drop cultures. The heating 

 was accomplished both with dry heat and by heating in a drop 

 of water. In no case could the spores which had been heated to 

 any considerable temperature be made to germinate. On the 

 other hand, mature ascospores which had not been heated germi- 

 nated readily in drop cultures, proving that if high temperatures 

 have anything to do with the appearance of this fungus the effect 

 is on the substratum only, the spores themselves being as sensitive 

 to heat as are those of other species of fungi. 



This species is not sufficiently common to expect that the air of 

 the laboratory is saturated with the spores at all times, but from 

 later experiments it is evident that these cultures were inoculated 

 from the air. The fact that the fungus occurred in cultures in 

 which the agar had been poured over filter paper previously heated 

 to no° C. for purposes of sterilization again raised the question 

 of the relation existing between this fungus and the heating of 

 the substratum. Cultures of agar were later tried, leaving out 

 the filter paper, and the fungus was found to grow fully as well 

 as in the preceding case. The luxuriant growth of this species 

 on agar is evidence that high temperatures are not necessary in 

 all cases to its growth. Soils sterilized with dry heat require a 

 higher temperature to bring about favorable conditions for the 

 growth of this fungus than are necessary for the sterilization 

 of agar. 



From our own observations and experiments there is little 

 doubt that this fungus occurs on burnt places as a result of steril- 

 ization of such places by fire. However, it is probable that steril- 

 ization means much more than the simple elimination of compe- 

 tition by the destruction of bacteria and other fungi present in the 

 soil. The nature of the changes brought about in soil by heating 



