548 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
trate was determined in order to compare the changes in the reaction of the 
media due to the growth of the fungus. The results are given in table 5. 
Table 5. Influence of the Reaction of Culture Medium on the Growth 
of Fusarium lycopersici 
No. of Flask 
Initial Approximate 
Adjustment of Me¬ 
dium 
H-ion Concentration 
after Sterilization 
Relative Growth in is 
Days 
H-ion Concentration 
of Medium after is 
Days 
pH 
pH 
pH 
I 
2.0 
1.8 
No growth 
1.8 
2 
3-0 
2.8 
Heavy 
3-0 
3 
4.0 
4.4 
Very heavy 
4.4 
4 
5.0 
5-0 
Heavy 
4.6 
5 
5-6 
6.0 
Moderate 
4.8 
6 
6.2 
6.4 
Moderate 
5-4 
7 
7.0 
7.0 
Moderate 
5-6 
8 
7.6 
7.6 
Light 
5-6 
9 
8.2 
8.2 
Light 
5-0 
10 
9.0 
8.4 
Moderate 
5-8 
It will be noted from the table that relatively small changes occurred in 
the pH value as a result of sterilization. No germination occurred at pH 
1.8. A moderate growth was produced from pH 6.0 to 8.4, accompanied 
by considerable changes toward greater acidity. The heaviest growth of 
mycelium took place at pH 2.8 to 5.0, without much change in the reaction 
of the medium. 
Experiment 2 
The culture medium was made and adjusted as in experiment 1. In 
this case, however, the culture flasks were sterilized at five pounds’ pressure 
for twenty minutes on two successive days. They were then inoculated 
and incubated in the greenhouse as before. The period of incubation was 
coincident with the time of the growth of the plants in experiment 3, hence 
the cultures were subjected to the same temperature changes as were the 
plants. The results of the experiment are shown in table 6. 
Table 6. Influence of the Reaction of Culture Medium on the Growth 
of Fusarium lycopersici 
No. of Flask 
Initial Approximate 
Adjustment of Me¬ 
dium 
H-ion Concentration 
after Sterilization 
Relative Growth in is 
Days 
H-ion Concentration 
of Medium after is 
Days 
pH 
pH 
pH 
I 
2.0 
2.2 
Very light 
2.2 
2 
3-0 
3-6 
Light 
3 .o 
3 
4.0 
4.4 
Light 
34 
4 
5 -o 
5 -o 
Moderate 
4.2 
5 
6.0 
6.2 
Moderate 
5.2 
6 
6.8 
6.6 
Light 
5 -o 
7 
74 
7.0 
Light 
5-0 
8 
8.2 
7.2 
Heavy 
6.4 
9 
8.8 
7.6 
Heavy 
6.6 
10 
9.6 
8.0 
Heavy 
6.6 
