70 BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. 
weak strains of C. vagum than in the case of Pythium. In inocula- 
tions on Pinus banksiana and P. ponderosa in Kansas sand treated 
with acid followed by lime, the average Corticium was very much 
more destructive than even the strongest Pythium strains, allowing 
practically no germination in most cases. On the other hand, in ex- 
periments in which the inoculum was applied directly to Pinus 
resinosa and P. ponderosa seedlings, either immediately after germ- 
ination or after the older parts had become resistant, the Pythium 
has been the more effective. The inoculation evidence so far avail- 
able justifies so nearly equal emphasis on the two that it can prac- 
tically be eliminated from the calculations. It is the writer's opinion 
that the Corticium strains are probably rather less virulent on the 
average than the Pythium strains, but perhaps better able to main- 
tain themselves and spread from one seedling to another in most 
soils. The evidence of Table IX that the Corticium seemed less fre- 
quent in the damping-off foci is more or less counterbalanced by the 
apparent larger size of many of the disease patches which it seems 
to cause in the seed beds. Nearly all the large clean areas such as 
are shown in figures 7 and 8 have been found to contain abundant 
Corticium hyphse. The evidence on the whole seems to indicate a 
very nearly equal importance for the two fungi. The Pythium is 
probably somewhat the more important for the stations at which 
most of the cultures in Table IX were made, but the Corticium has 
received more emphasis from other observers in this country and is 
indicated by the writer's observations to be more important in the 
western mountains than any other damping-off fungus. 
The inoculation evidence for Fusarium spp., though less complete 
than for Corticium and Pythium, is nevertheless rather helpful in 
indicating their importance rating. None of those so far tested in 
inoculations at sowing have shown the destructiveness of the aver- 
age strains of Pythium or of the stronger strains of Corticium ; while 
this is only in part a test of virulence and in part a test of the 
ability of the fungus to grow saprophytically in the soils used, the 
indication is that no one Fusarium species is the equal in destructive 
capacity of either Corticium vagum or Pythium debaryanum. How- 
ever, when all of the Fusarium species which occur in the seed beds 
are considered, the group as a whole may proA T e quite as important 
or even more important than either of the other two fungi. The data 
already at hand rather definitely indicate considerable importance for 
all three. 
DAMPING-OFF FUNGI AS CAUSES OF ROOT-ROT AND LATE 
DAMPING-OFF. 
As has been already stated, root-rot, often with frequent recovery, 
has been commonly observed in seedlings several weeks old. It has 
been especially common in the vicinity of old damping-off foci in 
