812 
Journal of Agricultural Research 
Vol. XXXI, No. 9 
These results vary somewhat from those obtained by Kirby (7). 
He obtained maximum growth of the New York strain on potato 
agar at a concentration of about P H 9.0, and growth was inhibited at 
about P H 3.2. The latter figure agrees very closely with the writer’s 
results. However, the hydrogen-ion concentration for optimum 
growth obtained by Kirby is considerably more alkaline than that 
obtained in the present studies. Using corn-meal agar as a sub¬ 
stratum he found the maximum growth at about P H 9.2. The 
writer’s cultures were kept in the light, while those studied by Kirby 
were kept in the dark. This may be a factor of importance. How¬ 
ever, the writer is convinced that the strains of the fungus which he 
has been studying will grow better, in the media employed, at less 
alkaline reactions than those reported by Kirby. In this connec¬ 
tion it may be said that Kirby (7) obtained less disease in wheat 
plants when the soil in which they were growing was made acid by 
addition of certain fertilizers than when it was made alkaline, and 
likewise more disease was obtained in untreated soil than in limed 
soil. Kirby made no hydrogen-ion determinations on the soils 
treated in different ways; at least no data were published to this 
effect, so it is impossible to correlate the data for the growth of the 
organism in pure culture with those for the occurrence and intensity 
of the disease of plants growing in such soils. These were only pre¬ 
liminary studies, but it is evident that more work is necessary on 
this phase of the problem. 
INFLUENCE OF LIGHT ON GROWTH AND SPORULATION OF THE 
FUNGUS 
Cultures of Ophioholus graminis in Petri dishes kept under glass 
bell jars in the diffuse light of the laboratory grew slightly less than 
cultures kept under darkened bell jars, as shown in Table IV. Al- 
