426 
Journal of Agricultural Research ... 
Vot. EX, No. » 
advance of the fungal filaments. This might lead one to suspect that 
part of the action is due to a toxin that is secreted by the fungus. 
(6) Actual cell-wall penetration by the Rhizoctonia hyphae apparently 
may occur, but this seems to be the exception rather than the rule. 
PLATE 27 
A-D.—Various stages of the “ dry core ’' of potato tubers. 
E-F.—Cross sections of a tuber badly affected with Rhizoctonia. Figure F shows 
two of the cores joined together. Compare with figure E of Plate 28, which illustrates 
a similar core taken bodily out of a boiled potato. 
