872 
Journal of Agricultural Research 
Vol. XXIV. No. lo 
Table V .—{Experiment j) Showing the hydrogen-ion concentration of the control 
solution {sweet-potato decoction) at the beginning and end of the experiment, also of 
the inoculated solution, and the time required by the solution and mycelium to 
macerate sweet-potato disks 
Ph of 
control 
at end of 
experi¬ 
ment. 
Ph of in¬ 
oculated 
solution 
at end of 
experi¬ 
ment. 
Ph of 
control 
at begin¬ 
ning of 
experi¬ 
ment. 
Time required to complete maceration. 
In in¬ 
oculated 
un¬ 
steamed 
solution. 
In inoculated steamed 
solution. 
In uninoculated solution. 
By 
hyphae 
H gm. 
in 25 cc. 
H2O. 
I. 27 
I. 27 
I. 28 
Hours. 
Hours. 
Hours. 
A 2 ... 
Hours. 
2 
2. 25. 
48. 
2.05 
2. 67 
3-80 
4.66 
5. 06 
6.14 
2.10 
2.10 
7-24 
2. 25 
2. 00 
2. 00 
2. 25 
2. 2$ 
2. 25 
2. 50 
4 °. 
04 ... . 
Slight in 48... 
5-0 
2 - 55 
2. 71 
3-83 
4.69 
5* 20 
None in 48. 
4.0 
3. 12 
4 * 5 . 
.do. 
4. 0 
3. 20 
3*36 
3-48 
.do. 
5 *o 
24. 
aR . 
.do. 
5*0 
D. 17 
XTrfcTick tn 4ft . . 
.do. 
7.12 
7 - 58 
3 * 57 
3. 60 
7. 19 
7.67 
Q 
1 do. 
. . 1 . 
5 - 5 
8. 28 
3-09 
o- 33 
2* 5^ 
. 
1 
Table Wl .— {Experiment 4) Showing the hydrogen-ion concentration of the uninocuhted 
sweet-potato decoction at the beginning and end of the experiment, also of the inoculated 
solution, dry weight of mycelium produced, and time required to macerate sweet-potato 
disks 
Ph of 
Ph of 
control 
at end 
of ex¬ 
peri¬ 
ment. 
Ph of 
inocu¬ 
lated 
solution 
at end 
of ex¬ 
peri¬ 
ment. 
Time required to complete maceration. 
control 
at be¬ 
ginning 
of ex¬ 
peri¬ 
ment. 
Dry 
weight 
of my¬ 
celium. 
In inoculated un¬ 
steamed solution. 
In inoculated 
steamed solution. 
In uninoculated 
solution. 
By 
hyphae 
H gm. 
in 25 cc.. 
HjO. 
I. 24 
. I. 24 
1. 27 
Gm. 
Hours. 
3-00. 
Hours. 
6. 
Hours. 
18. 
18. 
Hours. 
2.01 
2.01 
2.63 
2.02 
0.0965 
24* 00... 
48. 
None in 48. 
4 * 75 
2.69 
2. 54 
3 * 25. 
04 ___ 
.do. 
3 - 50 - 
3-63 
3-57 
3 -17 
. 0115 
. 1268 
2. 50. 
•^4 .... 
3 - 75 
4 - 33 
4-31 
3 - 29 
3* 00. 
4. 00 
5 * 13 
5 - OS 
3-51 
. 1214 
. 1186 
. 1388 
• 1280 
3* 00. 
-^ 4 - ••T. . 
04 ___ 
.do. 
4.50 
6.05 
6.02 
3-51 
3-58 
3-00. 
^ 4 - ..*. 
48 . 
.do. 
4. so 
7. 29 
6. 32 
3 * 25... 
4 - 75 
7*99 
7 - 53 
3* 72 
3-86 
8. 14 
3 * 25 . 
do. 
.do. 
4 * 75 
8.30 
9.12 
8. 21 
8.86 
• 1297 
.0693 
3 * SO--;. 
None in 48. 
.do. 
.do. 
5-50 
In experiment 4, the fungus felts from five flasks were collected and 
the dry weight determined. The average weight is given in Table VI. 
The mycelium from the other flasks was used in determining the rate 
of maceration. . . r ^ -..i. 
An examination of Tables III to VI shows some interesting facts with 
respect, first, to the changes in hydrogen-ion concentration of the solution 
produced by the fungus; second, to the influence these changes have on 
the production of pectinase; third, to the consumption of sugar (in 
Czapek’s solution); and fouth, to the amount of mycelium produwd. 
It will be seen that growth was entirely inhibited at a Ph of 1.7. Ihe 
maximum limit of alkalinity for growth was not obtained, since the 
alkali in the solutions prepared to be about Ph h o appeared to react 
with the sugars, thereby reducing the alkalinity. It was found in general, 
however, that the growth was best in the most alkaline solutions so long 
