1921] BLAKES LEE, CARTLEDGE, & WELCH—CUNNINGHAMELLA 197 
Our old test races of C. echinulata (nos. 885 and 886) are able 
to form ‘‘imperfect hybridization” reactions with a number of the 
races of C. bertholletiae, although no sexual reaction between them 
and our race no. 213 has been observed. 
Our race no. 213, which is the same as BURGER’s no, 21 and 
is the strain which furnished the strongest evidence for his theory 
of pseudoheterothallic hermaphroditism, has been tested against 
eighty-eight other races of the same species obtained from Brazil 
nuts from various localities. In all these tests it has reacted, if at 
all, only as a minus. In BuRGER’s experience, although predomi- 
nantly a minus, it produced zygospores in three combinations with 
the seventeen other minus races, a total of 17.5 per cent of the 
contrasts between it and other minus races. If it had reacted in 
‘the same manner we should have expected it to produce zygospores 
with a.minimum of eleven of our sixty-eight other minus races. 
As a matter of fact, it showed reactions with none of these minus 
races. That so great a difference really exists between our minus 
strains and those studied by BURGER seems unlikely. 
BURGER seems not to have observed the imperfect sexual 
reactions between races of C. bertholletiae which failed to carry 
through to zygospore formation. Partly for this reason perhaps, 
despite his own evidence already adduced to the contrary, he failed 
to appreciate the fact that absence of zygospore formation in a 
culture is not a- proof of its freedom from mixture with strains of 
the opposite sex. The imperfect reactions in C. bertholletiae will be 
discussed later. In our experience the plus race no. 465 forms only 
imperfect reactions with the minus race 457. In consequence, 
when these two races are planted mixed in a Petri culture in con- 
trast with the plus race no. 217 and the minus race no. 459, a 
triangular reaction has been obtained, as shown in fig. 1, where the 
mixture is represented as forming zygospores with both the plus 
race no. 217 and the minus race no. 459, while the latter two are 
also forming zygospores together. Although we have obtained 
the triangular reaction shown in fig. 1, which BuRGER considered 
a proof that sexual dimorphism does not exist in Cunninghamella, 
we know in this case that the reaction is due to a mixture of 
strains and not to pseudoheterothallic h phroditi BURGER’S 
