1921] 
MATSUMOTO—SPECIALIZATION IN RHIZOCTONIA 9 
(18) later identified the Corticium causing disease as the common 
Corticium vagum B. & C., reducing the variety to synonymy. 
My material was examined by Dr. Burt and determined to be 
identical with Corticium vagum B. & C. For the isolation of the 
fungus Rolfs suspended the fruiting layer over a Petri dish con- 
taining agar, covering stem and dish with a sterile bell jar. If, 
however, a fruiting stage is too young or too old, this method is 
unsatisfactory and the dilution method is preferable. The 
method applied by me consists in touching the hymenial layer 
with a sterile platinum needle which is immediately removed 
into sterile water before transfer to melted agar. 
Fig.2. a, sclerotial and hyphal cells of P7; b, sclerotial and hyphal cells of B1 
(camera lucida drawings). 
From the preliminary work it appeared that among the 
strains mentioned above P1, P2, P3, L1, and E1 are very closely 
related to each other in general morphological characters, in 
reaction on potato agar, in shape and color of sclerotia, in myce- 
lial characters, etc. Likewise, the group of cultures P4, P5, and 
P6 are also apparently identical; while another group of similar 
forms includes B1, L2, and B3. 
Therefore, for further extensive studies concerning the phys- 
iological specialization of the strains a single representative of 
each group is considered, namely, P1, P4, P7, B1, B3. In addi- 
tion to these, H is also included. The last-named strain seemed 
identical with P1 in every respect, but for the reason that the 
strain was obtained from a different host and was of different 
geographical origin, it was decided to use it in the present ex- 
periments. 
