1921] 
MATSUMOTO—SPECIALIZATION IN RHIZOCTONIA 51 
way as to leave only the roots in the tubes. Then some of these 
plants were inoculated by placing the mycelium of P1 on the 
surface of the young roots, after which each plant was supported 
in the culture tube by means of a sterilized cork at the base of the 
stem, and the cork was inserted in the tube. To close any air 
connections between the inside and outside of the tube, the cork 
was sealed with melted parafin. The remaining plants were 
also treated as above, except that the plants were inoculated on 
the stems instead of on the roots. All these operations were 
performed in a culture room. The cultures were then removed 
to a greenhouse and placed under a glass hood, and the atmos- 
phere maintained at the saturation point during the infection 
period. 
Owing to the lack of water in the tubes, the observations were 
only continued 2 weeks. A few days after inoculation striking 
brownish discolorations were noticed on the roots inoculated 
with the fungus, while the plants inoculated on the stems ex- 
hibited no positive symptoms. In general, stem infection may 
take place only in cases where the plants are very young (about 
1 or 2 inches high), while the roots are immediately attacked by 
the fungus. Especially do the young rootlets soon fall victim 
to the invading mycelium, as observed by Güssow in his study 
on potato Rhizoctonia. Finally, of course, the aërial parts of 
the plants wilt, because of lack of water supply through the 
affected roots. As a matter of fact, the loss of water from the 
tubes containing plants infected through the roots is extremely 
slight as compared with the others. 
Interest was next centered upon the mechanism of penetration 
of the hyphae after passing through the cuticle. It might be 
assumed that the penetration of the cell wall is effected by en- 
zymatic action, since these fungi are able to secrete an enzyme 
which breaks down pure cellulose. Nevertheless, there was 
still the necessity of determining this point positively. Many 
sections of roots infected by P1 were made by the method de- 
scribed by Vaughan ('14). Evidence was obtained indicating 
that the hypha forms a swelling at the end, as it comes in contact 
with the cell wall, and that it penetrates the wall by a small 
tube, after which the penetrating hypha usually reassumes its 
normal diameter. The most interesting feature was that the 
