I62 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
greatly facilitated by the addition of 40 to 50 cubic centimeters of 95 percent 
alcohol to the contents of the flask. The mats were washed five or six 
times with 50 percent alcohol after being thrown on the filter. The results 
of this experiment are presented in table i. 
Table i. Hydrogen-ion Concentration and Growth of Gibberella Sauhinetii in Liquid Media 
in which the Reaction was Adjusted with Sulphuric Acid and 
Sodium Hydroxide. 
Temperature, 26° C. 
pjj (Before) 
Ph (After) 
pj^ (Average) 
Milligrams Dry Weight 
3-85 
4.4 
4.12 
1.6 
4.8 
3.6 
4.2 
30.4 
5-37 
4-5 
444 
54-2 
4.8 
6.0 
5-4 
48.0 
5-5 
5-5 
5-5 
60.8 
5.8 
6.2 
6.0 
60.0 
7-5 
5-2 
6.3 
34-8 
7.5 
5-2 
6.35 
27.0 
7.4 
5.6 
6.5 
36.8 
7.5 
5-7 
6.6 
46.8 
76 
5-9 
6.75 
50.4 
8.25 
7-5 
7.5 
79.6 
6.9 
7-57 
74.2 
If the average hydrogen-ion concentration expressed as pn is plotted 
on the abscissa and the dry weight of the fungus is plotted on the ordinate 
as in figure i, it is seen that with decreasing acidity from pn = 4.0 the 
growth of the fungus increases to a maximum at about 5.5 and then falls 
sharply to a minimum at 6.3. It then rises again to about 7.5. 
Fig. I. Relation of hydrogen-ion concentration of liquid culture solution and growth 
of Gibberella Saubinetii — sulphuric-acid-sodium-h}^droxide series. 
