1921] 
MATSUMOTO— SPECIALIZATION IN RHIZOCTONIA 39 
Fusion or HYPHAE 
Fusion of hyphae is common in this fungus and may be ob- 
served in any culture of the strains studied, especially in the 
young stages. It is generally considered that the fusion of hy- 
phae occurs either between hyphae of the same parent mycelium 
or between hyphae arising from separate colonies of the same 
physiological form. But with regard to fusion between the 
different strains obtained from different plants of the same host 
species, or from different hosts, practically no attempt has been 
made by any of the earlier investigators to determine this point. 
I have obtained some interesting results, so that a brief mention 
of these and of the methods involved is necessary. 
For direct study the ordinary drop-culture method was em- 
ployed, and as a medium 5 per cent maltose in water was used. 
Hyphae or sclerotial aggregates of the same strain or of different 
strains were separately sown at opposite sides of a drop. All the 
cultures were incubated at 27? C., and careful and continual 
microscopical observation was necessary, because the hyphae or 
sclerotia may grow out in a few hours, then branch profusely, 
and readily mingle with the hyphae of the other colony or strain. 
In any case, when two hyphae of the same strain are sown in à 
drop, fusion of hyphae readily takes place. In general, there is a 
slight inhibition of growth at the margin of the two colonies. 
Fusion of hyphae occurs readily when P1 and H are sown in the 
same drop culture. With P1 and P4 the growth rate is about 
the same, and fusion may take place, although it is not so fre- 
quent as in the case of P1 and H. There is no fusion of hyphae 
between P7 and any of the remaining strains. When P1 and 
B1 are sown together and incubated at about 21? C., the growth 
of P1 is much more vigorous than that of B1 and the growth of 
the former inhibits the further growth of the latter; while if the 
cultures are incubated at a higher temperature (about 28-30° C.), 
the result is opposite. In no case does fusion of hyphae occur. 
A precisely similar result is obtained when B1 and H are grown 
together. No fusion of hyphae has been established between 
B1 and any of the remaining strains. When B3 is sown opposite 
to one of the remaining strains, the growth of the first-named is 
always inhibited by the latter, so that up to the present time no 
definite data can be given. 
