66 BULLETIN 934, U. S. DEPARTMENT OE AGRICULTURE. 
For the conifers, no very reliable data on relative importance have 
been published. Numerous European reports emphasize the damage 
due to Fusarium spp., while a smaller number attribute loss to 
Phytophthora fagi or to both. There seems to have been little effort 
to determine the presence or absence of Corticium or Pythium, so 
these reports can not be given great weight. Spaulding's evident 
belief (136) in the importance of Fusarium has more weight, as he 
was on the lookout for the other fungi ; the moist-chamber diagnostic 
method employed in most of this work was, however, not well 
adapted to the detection of either one. The same is true of the work 
of Eathbun (106), in which dilution plates of seed-bed soil were 
employed. Eankin (105) attributes to Fusarium spp. the greatest 
importance in tree seed beds in this country, with Pythium debary- 
anum and Rhizoctonia spp. important in certain cases. Gifford (46) 
emphasizes the importance of Fusarium, while Clinton (28) appar- 
ently found Ehizoctonia (Corticium vagum) especially prevalent 
in the examinations he made. 
On the basis of the data presented or summarized in this bulletin, 
it is believed that of the various organisms which have been con- 
nected with damping-off in coniferous seed beds Pythium debary- 
anum, Corticium vagum, and Fusarium spp. include all of impor- 
tance. The others, either because of low indicated virulence or 
infrequent occurrence, and in most cases both, do not seem to merit 
extensive consideration. 
In order to form an idea of the relative frequency of the parasites 
named above as important, there have been brought together in 
Table IX the results of the examination of 438 damping-off foci in 
untreated beds and 304 foci which have appeared in beds which had 
received various disinfectant treatments. The data are presented 
by foci rather than by individual seedlings, as was done in the census 
reported by Busse and his coworkers. Most of the diagnoses were 
made by planting recently diseased seedlings in plates of solidified 
prune agar, all the seedlings taken from the same focus, or "patch," 
of damped-off seedlings being put into the same Petri dish. The 
resulting growth was in some cases transferred to a tube for later 
examination, but was usually examined directly in the plate. In a 
smaller number of foci the seedlings were macerated and examined 
directly without recourse to culture methods. As Pythium debary- 
anum does not commonly fruit in diseased seedlings of pine or of 
tobacco (81) and its hyphse are both difficult to find and not in 
themselves considered a sufficient diagnostic character, this latter 
method of examination is not so satisfactory for the determination of 
Pythium as it is for Corticium, which is easily recognized by its 
