DAMPING-OFF IN FOREST NURSERIES. 37 
parasitic on pines in preliminary inoculation experiments (62). In 
1910 Spaulding (137) found it on spruce in New York, and Hof- 
mann (76) later made successful inoculations on both pine and spruce 
seedlings, using P. debaryanum cultures both from aerial trap plates 
and from recently damped-off seedlings of cabbage, radish, and 
Russian thistle (Salsola tragus) . Hofmann's work, detailed notes of 
which the writer has been permitted to examine, was done with cul- 
tures which were contaminated by molds, but was checked up by 
microscopic examination of the lesions resulting, which showed the 
affected tissues filled with nonseptate hyphse. His results are taken as 
a rather strong indication that P. debaryanum attacks spruce as well 
as pine and that the fungus attacking conifers is physiologically as 
well as morphologically identical with that causing the damping-off 
of angiosperms. 
There thus appears from the literature to be reason to believe that 
Pythium debaryanum is parasitic on representatives of two groups 
of the Pteridophyta and on gymnosperms, as well as on various 
monocotyledons and dicotyledons, a range of hosts not only remark- 
able but perhaps unequaled in our present knowledge of plant 
parasites. Final published proof of parasitism seems to be available 
for three or four species of dicotyledons only. Additional inocula- 
tions on conifers with strains isolated from various other hosts are 
reported in the present bulletin. Some of the detailed evidence neces- 
sary for complete proof of the parasitism of the Pythium on conifers, 
lacking in experiments previously reported because of the doubtful 
purity of the cultures used and failure to reisolate and reinoculate 
with the organism, is also given here, together with evidence of the 
ability of the parasite to cause root sickness of pines too old to suffer 
from damping-off. 
Descriptive data of interest on Pythium debaryanum have been 
supplied by Hesse (74), De Bary (5), Ward (144), Miyake (89), 
Butler (23), and Butler and Kulkarni (24). An important contri- 
bution to the physiology of the fungus and the factors controlling its 
passage through the tissues of one of its hosts has recently been made 
in the previously mentioned paper of Hawkins and Harvey (71). 
IDENTITY AND ISOLATION. 
The fungus in the writer's cultures referred to Pythium debary- 
anum Hesse has been so called for the following reasons : 
(1) The morphological characters agree with those described and figured for 
Pythium debaryanum by other workers and with those of strains obtained from 
Dr. H. A. Edson under this name. 
(2) The absence of zoospores in the writer's cultures agrees with the experi- 
ence of others with Pythium debaryanum (2, 5, 23, 24, 38, 100), all workers 
with pure cultures having obtained zoospores infrequently, if at all. The 
earliest work by Hesse (74) in which zoospores were apparently produced 
