224 REPORT OF THE DEPARTMENT OF BOTANY OF THE 
was not an opportunity to make a thorough investigation into the 
cause of the trouble. A few of the dead seedlings which were ex- 
amined microscopically showed traces of Rhizoctonia. 
In a field at Ensenore, N. Y., some alfalfa plants nine inches 
high wilted and died after the manner of plants attacked by Sclero- 
tinia libertiana or Colletotrichum trifolu although neither of these 
fungi was in evidence. ‘There is reason to believe that they were 
killed by Rhizoctonia, with which the roots were thoroughly in- 
fested. 
To what species the above-mentioned Rhizoctoniz belong is not 
known. It can only be stated that the one causing damping off of 
seedlings in the Station greenhouse is different from the one found 
in the Kingsbury field. When grown on potato agar (slightly acid, 
neutral or slightly alkaline) the former produces a conspicuous 
dark-brown discoloration of the medium, whereas the latter dis- 
colors it only slightly. This character may be useful in the identi- 
neation of the damping-off Rhizoctonia. Such discoloration of the 
medium is not common among the species of Rhizoctonia. 
In one instance a box of alfalfa seedlings in the Station green- 
house developed a bad case of damping off due to Pythium de bar- 
yanum Hesse. 
DOWNY MILDEW. 
(Peronospora trifoliorum De By.) 
A few specimens of this fungus were collected on the Station farm 
October 3, 1907. In the forepart of June, 1908, it again occurred 
sparingly in two of the Station alfalfa fields; also, in fields at 
Canandaigua, Potsdam, Earlville and Fayetteville. In Europe, 
Peronospora trifoliorum is a well-known parasite on various species 
of Trifolium, Medicago, Melilotus and some other Papilionacez. 
In America, it appears to be uncommon on alfalfa although speci- 
mens on this host, collected in Colorado, have been distributed in 
Fungi Columbiani, No. 2246, and quite recently it has been re- 
ported from Kansas.” No previous record of its occurrence on 
alfalfa in New York is known to us. It is unlikely to become of 
economic importance. 
The fungus appeared on leaves meee in the upper part of the 
plant, particularly on young leaves at the tips of shoots. Some of 
the leaflets were affected only at the tip, some only on the proximal 
portion and others all over, the affected portion being yellowish, 
“Freeman (32). 
