[Vor. 8 
58 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
24. Infection of the host takes place much more easily through 
the root than through any other part. 
25. P1 and H are identical in morphological and physiological 
characteristics and constitute a single form of Rhizoctonia Solani 
Kiihn. This form is a very common type of the species, causing 
serious diseases of many cultivated plants. It may be identical 
with Rosenbaum’s “new” strain. 
26. While P1 and P7 might have been derived from the same 
ancestral origin, some striking physiological specializations have 
been developed. 
7. It is desirable to regard B1 as a physiological strain of 
Rhizoctonia Solani Kühn rather than as a distinct species. 
28. P4 and B1 may be two distinetly specialized forms of 
R. Solani Kühn but cannot be considered distinct species. 
29. P7 is distinct from all other strains studied, and the dif- 
ferences manifested by this strain may be sufficient to be con- 
sidered of specific rank. 
The author wishes to express here his heartiest thanks to Dr. 
B. M. Duggar, under whom this work was prosecuted, for many 
valuable suggestions. Thanks are also due to Dr. George T. 
Moore for the privileges of the laboratory and library. 
Graduate Laboratory, Missouri Botanical Garden. 
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