88 BULLETIN 934, U. S. DEPARTMENT OF AGRICULTURE. 
satisfactory, though the acid treatment has now been in successful 
use for several years at some nurseries. At most nurseries, if the 
minimum effective quantity of acid is used, there is no need of any 
special precautions to prevent injury to the seedlings. It is not 
expected that any single treatment can be found that can be uni- 
versally applied without change in details irrespective of differences 
in soil characters and in fungous flora. 
(7) Corticium vagum and Fusarium spp. have been previously 
shown to be parasitic on pine seedlings. Different strains of C. 
vagum are found to vary considerably in their ability to cause damp- 
ing-off, certain strains being consistently destructive and others 
much less active in tests conducted on different species of pine and 
several years apart. The differences in activity between strains 
were greater, and apparently rather more constant from one ex- 
periment to the next, than with Peltier's strains in his carnation ex- 
periments. Comparison of the results on pine with those of Edson 
and Shapovalov on potato gives some indication that strains vigor- 
ously parasitic on one of these hosts are likely to be parasitic on the 
other also. 
(8) Pythium debaryanum, reported on many hosts and proved to 
be parasitic on few, is shown by repeated inoculation, reisolation, 
and reinoculation to be capable of causing the damping-off of seed- 
lings of pine species. The identity of the fungus causing the damp- 
ing-off of conifers with that attacking dicotyledons has been estab- 
lished by cross-inoculations as well as by morphological comparison. 
Inoculations on unheated soil are much less destructive than on 
heated soil. Pythium debaryanum has been obtained in culture from 
Picea engelmanni, P. sitchensis, Tsuga mertensiana, Pinus banksiana, 
P. nigra austriaca, P. ponderosa, P. resinosa, and Pseudotsuga taxi- 
folia. In addition, fenugreek {Trigonella foenum-graecum) , cowpea 
(Yigna sp.), and rice (Oryza sativa) are reported as apparently new 
hosts among the dicotyledons. In inoculations the fungus has been 
successfully used on Pinus banksiana, P. ponderosa, P. resinosa, and 
in a preliminary experiment on Pseudotsuga taxifolia. It had 
already been successfully used in preliminary inoculations on Picea 
canadensis by Hofmann (77). 
Differences in parasitic activity on pine are found between differ- 
ent strains of Pythium debaryanum. These differences are not as 
large and partly for this reason their constancy is not quite as con- 
clusively demonstrated as in the case of the strains of Corticium 
vagum. 
(9) Rheosporangium aphanidermatus Edson, a parasite of radish 
and sugar beet, in many ways closely resembling Pythium debary- 
anum, has killed seedlings of Pinus banhsiana and P. resinosa in 
certain experiments, and reisolations and reinoculations have been 
