1921] 
MATSUMOTO—SPECIALIZATION IN RHIZOCTONIA 53 
more or less closely related to Rosenbaum's new strain, as shown 
by contrast with his data. 
Unfortunately no direct comparison 
could be made with his material. 
ROSENBAUM’S NEW STRAIN 
(1) More pathogenie on the 
stems of potato than other strains 
or isolations from that host; able 
to produce a distinct necrosis of 
the tissues of the potato tuber. 
(2) On potato agar this strain 
produces in 7-10 days a marked 
discoloration (dark brown to 
black) of the medium; while other 
strains, if they produce color at 
all, never approach the intensity 
produced by this strain. 
(3) On corn-meal agar, there 
are produced light gray, loosely 
formed sclerotia, as compared 
with the darker, brownish, and 
more compact sclerotia of other 
strains. 
(4) On Uschinsky’s solution, 
after 10 days, the strain covered 
the surface and was growing on 
the side of the flask, while in 
the other growth was still sub- 
merged. 
(5) The diameter of the hy- 
phae varies from 4.7 to 8.84, 
with 7.8 was the average meas- 
urement. 
(6) Selerotia: cells measure in 
length —13.6-30.6 à, averaging 
21.6 u; in width, 8.3-20.4 u, with 
an average of 12.3 u. 
P1 OR H 
(1) The strains are more patho- 
genic on stem of potato, lettuce, 
egg-plant, and bean than the 
remaining strains. 
(2) On potato agar, these 
strains produce a blackish dis- 
coloration, by which means the 
strains may be easily distin- 
guished from the others studied. 
(3) The characteristics referred 
to by Rosenbaum are not only 
observed on corn meal agar, but 
also on potato agar, bean agar, 
rice meal agar, and other media. 
(4) Unfortunately these strains 
were not cultured on Uschinsky's 
solution, but the tendency ob- 
served by Rosenbaum is strik- 
ingly noticed on all liquid media 
used. 
(5) The diameter of the hy- 
phae of these varies from 7 to 
12u, with 9u as the average meas- 
urement. 
(6) Sclerotia: cells measure in 
length 17-59 u, averaging 38 u; in 
width, 8-20 u. 
It is thus shown that with the exception of minor differences 
in the dimensions of sclerotia the characteristics presented are 
concordant. Again, it may also be inferred that Rosenbaum’s 
“other strain” may be identical with either B1 or P4. 
