1921] 
MATSUMOTO—SPECIALIZATION IN RHIZOCTONIA 57 
14. The growth relations of B1 on liquid media were changed 
after successive transfers on artificial culture media. 
15. No definite cultural characterization of B3 is possible from 
the results thus far obtained. 
16. The presence of trypsin and erepsin was observed in the 
mycelium of all the strains studied. 
17. Examined as to hydrogen-ion concentration all strains 
show increased growth on the acid side of neutrality. In gen- 
eral, all yield well on media with an exponent somewhat larger 
than Pa 3.8. P4 and P7 exhibit a somewhat narrower range 
on the acid side, while B1 has the widest acid range. 
18. In these fungi the general tendency is to increase the 
active acidity during growth, and this increase seems to be 
proportional to the increase of growth. 
19. Fusion occurs between hyphae arising from the different 
mycelia of the same strain. Fusion is also observed when P1 
and H are sown in a drop culture, also between P1 and P4, 
although this is not so frequent as in the case of Pl and H. No 
fusion occurs between B1 or P7 and any one of the others. 
From the experiments it is inferred that fusion may take place 
only between the hyphae from strains which are rather closely 
related, or which have rather recently originated from the same 
ancestral type. 
20. The effect of inadequate aération is to repress the growth 
of mycelium and sclerotial formation in all strains. 
21. From the inoculation experiments it is concluded that 
P1 and H may attack all the plants studied, generally causing 
“damping off." B1 also attacks certain hosts, but it is less 
virulent than the others mentioned. The virulence of P4 is 
slight. In no case has direct infection by P7 and B3 been ob- 
served. 
22. The pathogenicity of the strain P1 was more or less modi- 
fied by a transfer to a host plant different from that on which 
it was originally found, but the highest pathogenic capacity of 
the strain is always manifest when inoculation is made on plants 
belonging to the same species of host as that from which the 
culture originated. 
23. The hyphae of these fungi may enter the host tissue 
directly through the cuticle, and the penetration of such hyphae 
is chiefly a mechanical process. 
