1921] 
MATSUMOTO—SPECIALIZATION IN RHIZOCTONIA 47 
tudinal sections of the diseased potato stem, showed that cells 
of the cortex, vascular bundles, and pith were all found to be 
invaded by mycelium, and finally the vessels became stuffed 
with the fungus so that one might infer a lessening of the trans- 
piration stream, resulting in undersized tubers or curling of the 
leaves, ete. Lastly, he states: Naturally, sometimes infection 
may be slight and no leaf curling will have occurred, but the 
evidence offered is sufficient proof for the stem parasitism of 
the fungus. ” 
Following his work a study of the parasitism of the potato 
Rhizoctonia was also undertaken by Güssow (717). He states 
that tips of the young rootlets fall victim to the invading my- 
celium, the short shoots are destroyed, and the final effect is 
decreased. Moreover, since the growth of the soil tubers is 
precluded the production of aérial tubers may occur. 
Other papers touching upon this aspect of the subject (Duggar 
and Stewart, '01; Fulton, '08; and Barrus, '10) are either of 
minor importance or have been reviewed by Drayton (’15). 
From the facts referred to, it will be inferred that the forms 
here discussed are able to penetrate practically all living plant 
tissue and to cause disease in the host. Concerning the mechan- 
ism of the penetration of the tissue by the hyphae, however, 
praetieally no work has been done on this organism. Well 
known is the work of earlier investigators, especially that of 
DeBary (86) on Sclerotinia libertiana, who used in part the drop- 
lets exuded from the fungus, and concluded that the breaking 
down of the cell walls was due to an enzyme secreted by the 
fungus. Ward ('88), studying the Botrytis on lily, confirmed 
DeBary's view, finding that the fungus excreted relatively large 
quantities of enzyme and dissolved its way into the cell wall. 
The same opinion was maintained by Büsgen (7/93), who main- 
tained that penetration of wall and cuticle by Botrytis cinerea 
is not by mechanical means alone. Nordhausen (98) also agreed 
with DeBary, but he found that under certain conditions oxalic 
acid might play a role in dissolving the cell wall. Smith ('02), 
following the work of Nordhausen, confirmed the responsibility 
of oxalie acid in destroying the cell wall. 
Brown (715), studying Botrytis, affirmed the enzyme viewpoint, 
but at the same time he found that the fungus excreted a toxic 
