July i, 1921 
Pathogenicity of Corticium vagum on the Potato 
467 
seed, (2) from the growth of the fungus from the inoculated to the control 
pots through the moist sphagnum used for insulation, or (3) from the 
basidiospores from the corticium stage of the fungus which occurred 
abundantly during a warm period in all the aerial parts of all the inocu¬ 
lated plants. The last explanation appears the most probable. 
Experiment 2. 1 —The results obtained in experiment 1 indicated that 
the fungus is capable of causing diseases at a temperature much lower 
than 16° C. It was decided for subsequent experiments to include the 
possible temperature range at which the potato plant might be grown 
profitably. This plan resulted in increasing the number of tanks in the 
series to eight. These were maintained approximately at the following 
temperatures: 9 0 , 12 0 , 15 0 , 21 0 , 24 0 , 27 0 , and 30°. The 8 tanks con¬ 
taining 8 cans each were placed side by side, making four series of 16 cans, 
64 in all. Throughout this and subsequent experiments one series of 2 
cans in each tank was used for growing control plants. The other three 
series were used for growing plants in inoculated soil. 
In this experiment two series were run with sterile soil. In a third 
series unsterilized soil was used. The sterilized and unsterilized soils 
were represented separately in the two control cans in each tank. 
Treated southern-grown Irish Cobbler potatoes were used for seed. 
These had begun to sprout and were in good condition for growth. The 
results are presented graphically in figure 2. 
Table II .—Effect of growing Irish Cobbler potatoes {southern seed) in soil inoculated with 
Corticium vagum and held at various temperatures 
EXPERIMENT 2 
Temperature 
(° C.). 
Number 
of sets 
planted. 
Number 
of stems 
grown 
in unin¬ 
oculated 
soil. 
Stems grown in inoculated soil. 
Total 
number. 
Number 
slightly 
injured. 
Number 
severely 
injured. 
Number 
cut off. 
Number 
unin¬ 
jured. 
Per¬ 
centage 
injured. 
Inten¬ 
sity of 
injury 
(points). 
x 
c 
17 
13 
t; 
12 
29. 7 
59*4 
v. 
T T 
x 
j 
A 
2 
J 
II 
15. 0 
1 5 . 3 
TC . 
1 
c 
0 
12 
2 
1 
9 
24. 9 
33 - 2 * * * * 
x J . 
17*4 . 
I 
D 
5 
14 
I 
5 
4 
4 
71. 2 
I 53 - 8 
a t 
1 
6 
10 
I 
6 
3 
70. O 
130. 0 
0*1 1 
l 
8 
14 
3 
11 
21. 4 
21. 4 
1 . 
vl 
26 8 
1 
c 
12 
2 
1 
9 
24. 9 
33 - 2 
'J Cl 'J 
l 
6 
10 
10 
3°*3 . 
At the conclusion of the experiments the plants grown at the tempera¬ 
tures from 15 0 to 30° C. ranged from 2 to 5 inches high. Those grown 
in the 12 0 tank were about 1 inch above the soil line, w r hile but few in the 
1 In an experiment run immediately after experiment i and under conditions as outlined in experiment a 
the inoculum, consisting of the fungus on sand-cornmeal mush, was mixed throughout the first 5 inches of 
soil. The results were so irregular and the root system of the inoculated plants was so unbalanced that 
the data were discarded. The experiment is not given a number in the series of tests. The control plants 
of this experiment were used for the measurements given in Table X and were photographed (PI. 88). 
48495°—21 - 4 
