122 



Mycologia 



unheated-soils that we found in the case of dry heat at i8o° C. 

 He also calls attention to the same disappearance of this soluble 

 organic matter when soils were allowed to stand after steam 

 sterilization, that we had noted in our work on Pyronema. All 

 this shows that either dry or steam heat may cause very important 

 changes in soils and that it is to the effect of these changes on 

 plants, as well as to the destruction of bacteria, etc., that we 

 must ascribe the cultural results often noted in our experiments 

 with heated-soils. 



VIII. Products of Dry Distillation of Soil 

 In order to see if the heating of a soil would drive off sub- 

 stances toxic to Pyronema, we filled a combustion tube with soil, 

 put it in the furnace, fitted to the tube a smaller glass tube opening 

 under a receiver of distilled water and heated the soil. Steam 

 came over first and then more and more of a yellowish oil 

 which was partially suspended in the water and partially formed 

 a scum on the surface. The oily substance had an intensely 

 irritating and nauseating odor like that of an old, stale pipe and 

 recalled pyridine or its allies. The liquid in the receiver was 

 alkaline to litmus. All of this seemed to indicate pyridine bases. 

 We watered some heated-soil with this liquid and inoculated it 

 with Pyronema. In a week, the growth on this soil was as good 

 as that on the control watered with distilled water. 



The soil left in the tube was black. This was watered with 

 distilled water and inoculated with the spores of Pyronema but 

 proved to be unfavorable to its growth, although some mycelium 

 was produced. 



IX. Identity of the Fungus 

 The fungus which we have been cultivating in the laboratory 

 had been determined by us as Pyronema omphalodes (Bull.) 

 Fuckel, although its appearance in the laboratory differed slightly 

 from specimens of this species previously observed by us in the 

 field. In nature the ascocarps of this species give rise to dense, 

 confluent masses in which it is difficult to recognize the individual 

 ascocarps, while in the laboratory the plants are thickly gregarious 

 but not confluent to the extent that they are in nature. It there- 

 fore occurred to us that the species might be distinct. 



