124 



Mycologia 



of Pyronema, (b) the extract of heated-soil is itself so favorable 

 as a culture medium that it is at once attacked by the fungus 

 while the extract of the same soil unheated remains uninfected, 

 (c) heated-soil watered with the extract of another heated-soil is 

 much more favorable to Pyronema growth than similar soil 

 watered with distilled water, the former producing mycelium and 

 fruit in much greater abundance. 



4. Distillation of heated-soil extract does not remove the prop- 

 erties favorable to Pyronema, both the colorless distillate and 

 the highly colored distillation residue being favorable to its 

 growth, the distillation residue, however, appearing to" be more 

 favorable than the distillate. 



5. Excessive heating of soil in a combustion-tube renders it 

 unfavorable to Pyronema growth. The distillate has a very 

 offensive odor but is apparently neutral to Pyronema growth 

 when applied to heated-soil. 



6. It has been impossible to render unheated-soil favorable to 

 the growth of the fungus by the introduction of the extract of 

 heated-soil, this being apparently due to the fact that the nutrient 

 materials in the extract are rendered insoluble by the action of 

 unheated-soil. 



7. Not only is the extract of heated-soil a favorable nutrient 

 medium for Pyronema, but for other fungi as well, indicated by 

 the fact that the extract is attacked by fungi of various kinds. 



8. Soil subjected to steam or dry heat (either in a closed oven 

 or by burning over the surface of the soil), becomes a very favor- 

 able nutrient medium for fungi of various kinds, by reason of 

 the large quantity of food material rendered available through the 

 heating of the materials in the soil. 



We wish to acknowledge our indebtedness to Dr. W. J. Gies, 

 of the Department of Biological Chemistry of Columbia Uni- 

 versity and Consulting Chemist to the New York Botanical 

 Garden, for his oversight and aid throughout the course of the 

 present work. We also extend thanks to Dr. Oswald Schreiner, 

 of the Bureau of Soils, Washington, for numerous suggestions 

 on various questions which have arisen pertaining to matters of 

 soil fertility. 



Fred J. Seaver, New York Botanical Garden. 

 Ernest D. Clark, Columbia University. 



