[Vor. 8 
52 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
hypha usually obtains entrance at a corner where two cells are 
in contact, in which case the invading hypha frequently grows 
between the cells dissolving the middle lamella. As shown by 
some figures (fig. 5c, fig. 6a-d) made at the time of observation, 
there are also many cases which clearly indicate distortion of 
host cells following the penetration of the hypha. 
d 
Fig. 6. Camera lucida drawings showing penetration of epidermal cells of pea 
roots. 
From these observations I am of the opinion that the penetra- 
tion of cell walls may not take place merely in a chemical way, 
but rather assisted by the mechanical pressure exerted byjthe 
fungus. Penetration of the hyphae of P4 and B1 was also 
noticed to a certain extent, while P7 and B3 seemed to be quite 
unable to penetrate any living tissue. 
Discussion or DATA 
From all the evidence at hand it appears that P1 and H are 
quite identical in their morphological and physiological charac- 
teristics, as well as in pathogenicity, and should properly be 
included under one form of the species Rhizoctonia Solani Kühn. 
This form is a very common type, and the cause of very serious 
diseases of many cultivated plants. It is very interesting to 
notice that these two strains, here shown to be identical, are of 
different geographical origin and from different host plants. I 
am also inclined to believe that this form of the species may be 
