Feb. 15, 1925 
Inoculation of Coniferous Stems 
335 
experiment with Pinus resinosa and 
caused 100 per cent damping-off 
compared with 7 per cent in the con¬ 
trol plants. This confirms an earlier 
greenhouse experiment in which inocu¬ 
lations with this fungus at the surface 
of the soil killed all the seedlings. 
This is a new host for Pythiacystis. 
PHYTOPHTHORA FAGI 
Seedlings of Pinus resinosa were 
inoculated with Phytophthora fagi in 
three small test-tube experiments. 
The results are given in Table III. 
Table III.— Damping-off of seedlings 
of Pinus resinosa caused by Pythium 
debaryanum and Phytophthora fagi 
First 
experi¬ 
ment, 
per cent 
of damp¬ 
ing-off 
Second 
experi¬ 
ment, 
per cent j 
of damp¬ 
ing-off 
Third 
experi¬ 
ment, 
per cent 
of damp¬ 
ing-off 
Controls _ 
7 
6 
6 
Pythium debarya¬ 
num.. 
80 
100 
100 
Phytophthora fagi. 
50 
47 
67 
PHYTOPHTHORA CACTORUM 
This species which Rosenbaum (7) 
combines with P. fagi caused practically 
no damping-off, but was used only in 
experiments in which, as is shown by 
results with the standard fungi, condi¬ 
tions were less favorable than usual 
for damping-off. Like P. fagi , it was 
obviously less virulent than Pythium 
debaryanum. Further comparative re¬ 
sults with it are greatly to be desired. 
PHYTOPHTHORA SPECIES 
Three lines of a Phytophthora species 
isolated from pine caused 23 per cent, 
43 per cent, and 54 per cent damping- 
off in the above test-tube experiment 
in which P. fagi caused 67 per cent. 
In a single experiment one line caused 
100 per cent of the seedlings to damp- 
off. All three lines caused some 
damping-off of both Pinus resinosa and 
P. banksiana with the platform method 
of inoculation (Table II). 
Obviously Phytophthora cactorum, P. 
fagi and the pine Phytophthora are less 
virulent than Pythium debaryanum. 
They are kept separate in this paper 
because of the need of more extensive 
taxonomic study and because of the 
difference in results. 
Corticium Vagum (Rhizoctonia 
Solani Kuhn) 
The results of inoculating Pinus 
resinosa , P. banksiana and Picea engel- 
manni with Corticium vagum lines are 
given in Table IV. The Corticium 
lines exhibited considerable variability, 
and tests of the same lines at different 
times did not agree very well. One 
possible explanation of this may be the 
fact that most of the lines were used in 
two large experiments, one when it was 
very hot and the other when it was 
very cold. This suggests the theory 
that the virulence of Corticium vagum 
may be closely associated with temper¬ 
ature. Taken as a whole, the Corticium 
vagum lines did not kill half of the 
inoculated seedlings. However, the 
most virulent third killed three-quarters 
of them. In other words, they were 
more virulent than the standard lines 
of Corticium or Fusarium, but less 
virulent than the standard Pythium 
line. The lines isolated from conif¬ 
erous hosts were apparently no more 
virulent from those isolated from other 
hosts. 
The difference between the results 
secured from the use of corn-meal agar 
and rice mush as substrata for Corti¬ 
cium vagum was comparatively little. 
In slightly more than half of the units 
the lines growing on agar caused as 
much or more damping-off than the 
same lines growing on rice. Corn- 
meal agar seemed to be a better sub¬ 
stratum for Corticium than for any 
other fungus tested (fig. 2). A com¬ 
parison of the lines exclusive of the 
standard one (No. 147) used on all 
three hosts gives the following results: 
For Pinus resinosa , 55 per cent damp¬ 
ing-off; for P. banksiana, 49 per cent, 
and for Picea engelmanni, 24 per cent. 
A comparison of all the lines used on 
P. banksiana with the same ones on 
P. resinosa gave, respectively, 50 per 
cent and 49 per cent damping-off. 
From these results one would assume 
that the two pine species are of approxi¬ 
mately equal susceptibility, while the 
spruce is less susceptible. However, 
further experiments are necessary to 
establish relative susceptibility. 
Two preliminary tests in which the 
seedlings were inoculated with several 
Corticium lines at the soil surface in 
general confirmed the results secured 
by the platform method. 
Two lines of Corticium vagum 
killed 7 out of 20 seedlings of Pinus 
caribaea in an experiment in which 
none of the 20 control seedlings damped- 
off. This is a new host for Corticium. 
