[Vor. 8 
240 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
to increase the active acidity during growth, though there were 
exceptions. They call attention to the fallacy of combining the 
results obtained from a few organisms and drawing general con- 
clusions as to the relation of hydrogen-ion concentration and 
growth of a group of fungi. Duggar, Severy, and Schmitz (717) 
stated that Aspergillus niger shifts the reaction of certain plant 
decoctions to a hydrogen-ion concentration of about 10°. 
Gillespie (18) has shown the limiting acidity for Actinomyces 
scabies (chromogenus) to be between Py 4.8 and 5.2. Growth 
was accompanied by a marked decrease in the acidity. 
Ayers and Rupp (18), in an explanation of reversions of reac- 
tion of culture media by organisms of the colon-aerogenes group, 
ascribed the simultaneous production of acid and alkali in an 
inorganie medium to the production of organie acids from the 
sugar with the subsequent formation of alkaline carbonates or 
bicarbonates from the organic acids. Waksman and Joffe (720) 
are of the opinion that Actinomycetes are not able to produce any 
appreciable quantities of acid from the carbohydrates which they 
employed, but that the change in reaction of the medium is due 
to the source of nitrogen. Their explanation of the alkalinity 
produced in a nitrate medium is that in the reduction of the 
nitrate to nitrite, the oxygen split off is united with the hydrogen 
or other reducing substances of the medium, thus tending to re- 
duce the hydrogen tension of the medium. Boas and Leberle 
(18, "18a, 719, '20), in a series of articles on the production of 
acid by molds and yeasts, have found that both the carbon and 
nitrogen sources may influence the hydrogen-ion concentration 
resulting from metabolism, that with the same carbon source and 
different sources of nitrogen, for example, the greatest hydrogen- 
ion concentration of the solution on which Aspergillus fumigatus 
has grown may vary between Py 1.56 and 5.79. 
METHODS 
The methods employed in the part of this work which was 
completed in 1915-17 (see page 242) and in that completed in 
1919-20 are essentially the same. The cultures during the first 
part of the work were grown in 100-cc. Jena flasks, using water 
doubly distilled from glass, which usually gave a conductivity 
test from 1.0 to 1.3 x 10 5, with .8 x 10? the best obtained 
at any time. The water used during the latter part of the ex- 
periments was doubly distilled from glass and most of it was 
