8 BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. 
dence of the relatively small amount of actual investigation carried 
on there on this disease in the nurseries. A number of references to 
the damping-off of conifers in the English horticultural and botani- 
cal literature yield even less definite information as to the causal 
fungi than do the German articles. 
With the awakening of interest in reforestation in the United 
States between 15 and 20 years ago and the first efforts to grow 
pines in quantity for forestry purposes, attempts were made to de- 
termine the cause of the disease in this country and to develop direct- 
control methods. Duggar and Stewart (32) made what appears to 
be the first report of Rhizoctonia in connection with the damping-off 
of conifers. Spaulding (136, 137), in work begun in 1905, con- 
tributed much to our knowledge of the etiology of the damping-off 
of pine in this country, especially in relation to Fusarium, and origi- 
nated the sulphuric-acid method of control. The writer in 1910 re- 
ported preliminary inoculations on conifers with both Rhizoctonia 
and Pythium deharyanum (62). The work of Gifford (46) and 
Hofmann (77) added to the information on the causal relation of 
Fusarium spp. and P. deharyanum, respectively. Hartley, Merrill, 
and Rhoacls (68) have recently established the parasitism of a num- 
ber of strains of the Corticium vagum type of Rhizoctonia on pine 
seedlings under inoculation conditions, have confirmed Spaulding's 
conclusions as to the parasitism of Fusarium moniliforme Sheldon, 
and have given preliminary data on other fungi. They consider P. 
deharyanum and G. vagum more important in pine seed beds than any 
single Fusarium species. Hartley and Hahn (69) have announced 
successful inoculations on pines with P. deharyanum and Rheospo- 
rangium aphanidermatus Edson, with less satisfactory evidence of 
the parasitism of Phytophthora sp. and a fungus tentatively referred 
to Pythium artotrogus. Hartley and Pierce (67) report the finding 
of P. deharyanum in Tsuga mertensiana and Pseudotsuga taxifolia 
as well as in the pines. In damped-off pine seedlings they find P. 
deharyanum more commonly than C. vagum, especially in beds which 
have received disinfectant treatments. Other considerations, how- 
ever, keep them from concluding that the former is necessarily the 
more important of the two. Both of these latter papers and all of 
the reports of Pythium with the exception of Hofmann's are brief 
notes, presenting no evidence in support of the statements made. 
DESCRIPTION. 
The symptoms of damping-off in conifers have already been de- 
scribed in some detail (68). In the paper cited, injury due to exces- 
sive heat of the surface soil and injury caused by high wind, both of 
which may easily be confused with damping-off, are described and 
accompanied by colored illustrations both of different types of damp- 
