392 
Journal of Agricultural Research 
Vol. XXXI, No. 4 
and 5.88, became more alkaline because of the mycelium; solutions of 
initial P H 7.88, 7.42, and 6.68 became more acid. The lowest final 
P H reached from the alkaline side was 6.21, and the highest P H reached 
from the acid si.de was 6.25. The curves in Figure 1 show very clearly 
how the mycelium of this fungus brought the reaction of the buffer 
mixtures from both the acid and alkaline side toward P H 6.2. 
For the most part, the action of the fungus mycelium in changing 
the reaction of a solution was greater and more rapid than that of 
the potato-tuber tissue or soy-bean root tips. This was also true of 
the other two fungi used. It may be due to the more ready access of 
the liquid to the hyphae of the fungus rather than an actual difference 
in the action of the cell contents. 
The greater rapidity with which equilibrium was reached in the 
phthalate buffer mixture is of interest. Comparing experiments 2 
and 3, it is evident that approximately the same amount of mycelium 
required 65 minutes to shift the reaction of 0.001 M. sodium phos¬ 
phates from P H 4.37 to 6.05 and only 21 minutes to make a greater 
change in a 0.001 M. phthalate buffer mixture. This may be due to 
the cell contents of the fungus being already partially saturated with 
the phosphate ion, since it was grown in a nutrient solution 
containing phosphates, while its reactivity for the phthalate ion would 
be entirely unsatisfied. 
The isoelectric point found in these experiments for Gibberella 
saubinetii is somewhat more alkaline than that which might be 
deduced from the growth experiments and infection experiments 
carried on with this organism by Hopkins (2). He found a minimum 
in the growth curve at P H 5.5 to 6.0 when G. saubinetii was grown in 
solutions of various acidities and a minimum infection of wheat 
seedlings in soils with artificially adjusted reactions at P H 5.5. These 
minima have been interpreted by one of the writers (5) to be due to 
the decreased water absorption which occurs at the isoelectric point. 
The solutions, however, used by Hopkins were complete nutrient 
solutions and much stronger in buffer salts than those the writers 
have used. Moreover, the strain of the fungus was not the same. 
These facts may account for the difference. 
Table V .—Summary of results with mycelium of Fusarium lycopersici. Tissue 
in each case placed in solution indicated , and reaction measured until equili¬ 
brium was reached 
Experi¬ 
ment 
No. 
Weight 
of my¬ 
celium 
Age of 
myceli¬ 
um 
Kind of buffer solution used 
Quan¬ 
tity of 
buffer 
solution 
used 
Initial 
Ph 
Final 
Ph 
Time 
required 
to reach 
equili¬ 
brium 
1 _ ... 
Grams 
0. 71 
Days 
8 
0.01 M. KH phthalate_ 
C.c. 
10 
3.94 
4.88 
Minutes 
30 
2 __. . 
2.14 
14 
0.002 M. Na phosphates_ 
50 
4.03 
5.50 
70 
3_ 
1. 50 
8 
0.001 M. KH phthalate__ 
10 
3. 95 
5.47 
11 
4_ 
1.50 
8 
0.001 M. KH phthalate_ 
10 
3.95 
5.41 
16 
5_ 
5.08 
7 
0.001 M. Na phosphates_ _ 
50 
4. 55 
5.41 
56 
6_ 
4.04 
9 
0.001 M. Na phosphates_ 
50 
5.43 
5.48 
54 
7 
0.635 
5 
0.001 M. Na phosphates.... 
10 
6.66 
5.46 
39 
8 
1.63 
4 
0.001 M. Na phosphates_ 
10 
7.20 
5.52 
34 
9 
1 0.94 
16 
0.001 M. Na phosphates_ 
25 
6.02 
6.16 
20 
10_ 
4.92 
7 
0.001 M. Na phosphates_ 
50 
7.20 
i 
6.00 
60 
1 Autolyzed. 
