DAMPING-OFF TN FOREST NURSERIES. 
59 
figure 18. This suggests, further, that part of the lack of activity 
was due to the failure of the fungus to maintain itself vigorously 
in the soil till the pines reached a stage of sprouting in which they 
could be readily attacked. Direct inoculations after the seed starts 
to sprout are therefore desirable to supplement the experiments 
reported. The survivals in the controls did not show any such 
asymmetrical distribution. 
While the Rheosporangium has given rather definite evidence of 
parasitism on Pinus banksiana under favorable conditions, the 
activity of the strains available has been much less than that of the 
Pythium debaryarmm strains. In view of the fact that the fungus 
has not so far been isolated from pine it can be concluded to have no 
general importance 
in pine seed beds. Its 
very rapid growth on 
prune agar makes it 
very easy to isolate 
when present. 
PHYTOPHTHORA SPP. 
Phytophthora fagi 
R. Hartig has been 
commonly reported 
as the cause of death 
of seedlings of va- 
rious plants in Eu- 
rope, including con- 
ifers and herbaceous 
plants as well as 
beech (5, 8, 15, 55, 
13 16 19 22 25 28 
&EEDUA/GS SUfft//V/A/G PEP POT 
Fig. 17. — Diagram showing the results of inoculation of 
Pinus resinosa seedlings with Rheosporangium aphanider- 
matus, as indicated by the number of seedlings surviving 
in inoculated pots (solid line) and control pots (broken 
line). The shape of the curve for the inoculated pots is 
taken as indicating that a large proportion of them 
were entirely unaffected by inoculation, while those which 
were at all affected suffered considerably. This is a 
frequent result in inoculations with weak parasites added 
at. the time of sowing the seed. 
56, 57, 59, 73, 104.) 
It has been grouped 
with the rather indefinite Phytophthora omnivora and with P. 
cactorum, the enemy of cactus, ginseng, and other plants. Wil- 
son (147, p. 54) considered it distinct, but Rosenbaum (114), 
in his biometric comparison of Phytophthora cactorum and a 
single strain of P. fagi, failed to find significant morphological 
differences. If P. fagi is even physiologically different from 
the American strains of P. cactorum, its introduction into the 
United States is to be guarded against. There is certainly no 
fungus in the United States causing the damage to coniferous 
seedlings which European reports have attributed to P. fagi there. 
As P. fagi attacks roots, it presumably can be carried in soil as well 
as on plant parts. 
