810 
Journal of Agricultural Research 
Vol. XXXI, No. 9 
Table II .—Influence of hydrogen-ion concentration of potato-dextrose agar on the 
growth of the mycelium of three strains of Ophioholus graminis, as shown by 
measurements of diameter of colonies 
Diameter of colonies in centimeters 
Initial Ph 
value of 
agar 
Oregon strain 
New York strain 
Arkansas 
strain 
Series 
Series 
Series 
Series 
Series 
Series 
Series 
Series 
Series 
Series 
Series 
Series 
a 
lb 
1c 
2a 
2b 
2c 
3a 
3b 
3c 
3d 
3e 
3f 
3.0. 
0.0 
0.0 
0.0 
0.5 
fl t u 
0.0 
3.2.. 
.0 
.0 
.5 
.5 
.0 
.0 
3.4. 
.0 
.0 
2.0 
1.0 
1.0 
1.0 
3.8.___ 
0.5 
0.5 
0.5 
4.0. 
1.5 
1.5 
1.0 
4.2.. 
2.0 
2.5 
3.0 
2.0 
2. 5 
6.0 
6.0 
4.5 
3.5 
4.4_____ 
3.0 
3.5 
3.5 
4.6. 
5.0 
6.0 
4.5 
3.6 
3.0 
3.0 
i 
6.0. 
5.5 
6.5 
6.5 
3.6 
3.0 
7.0 
7.0 
.0 
6.0 
5.2.. 
6.5 
6.5 
5.4. 
4.0 
8.0 
7.0 
7.0 
7.0 
5.6. 
7.0 
7.0 
7.0 
5.8.. 
6.5 
7.0 
6.0 
7.0 
7.0 
6.0. 
6.0 
6.6 
9.0 
9.0 
6.0 
6.0 
6.2.. 
6.0 
6.6 
6.4.. 
6.5 
6.0 
6.6__ 
7.0 
5.5 
6.8. 
9.0 
9.0 
8.0 
8.5 
8.0 
7.2... 
3.0 
3.5 
7.4... 
4.0 
4.0 
3.0 
7.6.. 
1 
4.5 
6.0 
6.0 
8.0 
8.0 
7.8.. 
3.5 
2.5 
2.0 
8.0.. 
1.5 
2.0 
1.5 
2.5 
2.5 
8.2. 
4.5 
4.5 
6.0 
4.5 
5.0 
5.5 
5.0 
7.0 
7.0 
8.4.. 
4.0 
4.0 
4.5 
3.0 
3.0 
3.0 
3.5 
- 3.0 
4.0 
3.0 
2.5 
3.0 
8.8.. 
7.5 
7.0 
7.0 
3.0* 
2.5 
2.0 
9.0. 
3.5 
2.0 
4.0 
2.0 
2.0 
3.0 
2.5 
2.0 
9.2.. 
3.0 
9.4. 
1.5 
3.0 
2.0 
1.5 
2.0 
9.6.. 
3.0 
1.0 ( 
1.0 
10+_. 
1.5 
1 
.5 
.5 
.5 
1.0 
.5 
. 5 
! 
It will readily be seen from these results that the three strains of 
the fungus varied somewhat in the amount of growth at the various 
hydrogen-ion concentrations. With the Oregon strain, the highest 
acidity allowing growth was P H 3.8 in potato-dextrose agar. Growth 
increased rather regularly with decrease in acidity until a maximum 
was obtained at from P H 5.6 to P H 6.8. Beyond this, as the acidity 
diminished, mycelial growth of this strain decreased until it was 
checked at P H 10.0+ . The Arkansas strain exhibited growth at a 
concentration of P H 3.4 and reached its maximum growth at P n 6.8 
to P H 7.6. The most alkaline reaction permitting growth of this 
strain was just above P H 10.0. The New York strain grew at all 
concentrations from P H 3.0 to P H 10.0+ , with maximum growth at 
P H 6.0. 
In addition to the experiments with potato-dextrose agar, two 
experiments were conducted with the Oregon strain of the fungus 
in nutrient broth and Czapek’s full nutrient solution. The results 
are given in Table III and represented graphically in Figure 5. In 
both, growth occurred at all reactions employed. However, the 
nutrient broth proved to be a more favorable medium at all hydro¬ 
gen-ion concentrations than did the Czapek’s full nutrient solution. 
In fact, the latter medium was found to be decidedly unfavorable for 
making these studies. Growth was comparatively feeble in the most 
