Seaver: Studies in Pyrophilous Fungi 135 



to high temperatures is a question concerning which little is known 

 and one which is of vital importance to the problem under con- 

 sideration. While the heating of the soil destroys the fungi 

 already present, there is every reason to believe that it prepares 

 the way for the growth of those species which may be introduced 

 subsequent to sterilization. The experimental work of the pres- 

 ent paper has been based mainly on the one species, Pyronema 

 omphalodes (Bull.) Fuckel, but the question of the effect of the 

 heating of soils on the production of fungi is doubtless a large 

 one and it is the intention of the writer to extend these investi- 

 gations to other forms when fresh material can be secured for 

 experimental work. 



Some of the observations in support of the above conclusion 

 are : in its occurrence on sterilized soil the fungus usually appears 

 at a very early date and is mature before other forms of vegeta- 

 tion have had time to make any considerable growth ; after matur- 

 ing one crop of ascocarps the fungus gradually disappears, indi- 

 cating that the most favorable time for its growth is immediately 

 after sterilization; soil sterilized, moistened and allowed to stand 

 for a week appears to be as unfavorable for the growth of 

 Pyronema as soils which have never been sterilized, notwithstand- 

 ing the fact that the soil is entirely free from other forms of vege- 

 tation so far as the eye can detect. 



In its occurrence in nature on burnt ground, no notes have been 

 made as to the relative time between the burning of the substratum 

 and the appearance of the fungus. This would doubtless depend 

 upon conditions of moisture. A place having been thoroughly 

 sterilized would remain so until the return of moisture, when the 

 Pyronema avails itself of the favorable conditions of sterilization 

 and moisture and matures its crop of spores. So far as can be 

 recalled, this species has been found on burnt places only when 

 bare and apparently devoid of other forms of vegetation, indi- 

 cating that it appears soon after burning or soon after the return 

 of moisture to the burnt places. 



In its occurrence on agar, the Pyronema grows rapidly, cover- 

 ing the surface of the agar in a three-inch petri dish in about 

 four days. All of the cultures have been slightly contaminated 

 with other fungi in the center of the dish, but fruit has not been 



