Nov. 1, 1925 
807 
Ophiobolus graminis and Take-All of Wheat 
INFLUENCE OF TEMPERATURE ON GROWTH OF THE FUNGUS 
The parasite was grown at different temperatures on 2 per cent 
Dotato-dextrose agar m Petri dishes, and the growth was determined 
)y measuring the diameter of the colonies. The agar used had a 
lydrogen-ion concentration of 7 P H , and in all cases the same amount 
of medium was used in equal-sized Petri dishes. Young, vigorous 
stock cultures growing in Petri dishes were employed for supplying 
the transfer material. In order to insure uniformity among all the 
transfers, blocks of agar 1 mm. square containing mycelium were cut 
at equal distances from the center of the stock colony and placed 
in the center of each Petri dish filled with fresh agar. The dishes 
Fig. 3.—Influence of air temperature on the growth of mycelium of three strains of Ophiobolus graminis* 
Data from Table I 
were then placed in the various temperature compartments of an 
Altmann incubator. The chambers of the incubator were kept as 
nearly as possible under the same conditions, except temperature. 
These chambers excluded all light when closed, hence the growth was 
in darkness. An exception to this was necessary in the case of the 
highest temperature in the first four experiments and in the case of 
the 28° C. temperature in the fifth experiment. These high tem¬ 
peratures were maintained in a separate incubator which contained 
a dim electric light. As this light did not strike the plates, directly, 
and as it was determined, as reported later in this paper, that light of 
that intensity had very little inhibitory influence on mycelial growth, 
it seems evident that this weak illumination did not impair the value 
of the temperature results obtained in this case. 
Ten series with the Oregon strain, and four series each with the 
New York and Arkansas strains, were studied. In each experiment 
