[Vor. 8 
286 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
Steinberg (719), using Pfeffer’s solution as a medium, conducted 
experiments dealing with the relation of 7 different acids to the 
growth and spore production of Aspergillus niger. The addition 
of acid to the normal nutrient solution, which initially tests Px 
3.0-4.0, produced an acceleration of growth; the addition of 
alkali to the normal nutrient solution resulted in a diminution 
in yield. The effect of the increased acidities of the cultures 
was to cause a retardation or suppression of spore formation as 
contrasted with the effect of decreased acidity, which failed to 
exhibit the same phenomenon. All 7 acids gave similar results, 
indicating that the results are primarily due to the hydrogen 
ions rather than to the anions. 
Zeller, Schmitz, and Duggar (719), growing various wood- 
destroying fungi on Czapek's solution, Dunham's solution, a 
pine decoction, Reed's solution, Richards’ solution, and sap 
from Acer saccharinum, whose reactions were adjusted by means 
of mono-, di-, and tri-basie potassium phosphate, found that there 
is a decided indication of the advisability of selecting a specific 
medium for each fungus. The hydrogen-ion concentration did 
not seem to be the only limiting factor in growth, and the shifting 
of the hydrogen-ion concentration due to metabolism depended 
both upon the medium and the fungus. No general statement, 
in their opinion, could be made concerning the relation between 
hydrogen-ion concentration of the culture media and the growth 
of wood-destroying fungi as a group. 
Thiel and Weiss (’20) report that acetic acid in aqueous solu- 
tion exerts a pronounced stimulating effect on the germination 
of teliospores of Puccinia graminis. Other acids and chemical 
agents in various concentrations were employed by them. but 
all gave negative results. Although no hydrogen-ion determina- 
tions were made, or at least published, the authors are inclined 
to believe that the process is not one of hydrogen-ion catalysis, 
but one of a specific activator. 
Zeller (20) obtained a high percentage of spore germination 
of Lenziles saepiaria upon the shavings of short-leaf pine sap- 
wood when the humidity of the air was sufficiently high to supply 
free water as a film on the wood surface. A decoction prepared 
by steaming such shavings with distilled water in a reflux tested 
