198 
BOTANICAL GAZETTE 
[OCTOBER 
conclusions, therefore, are not justified from ‘his own data, and 
the few races which it has been possible to retest from among 
Mixture of : 
“he 46504) & 467(-) a 
seer 
459(-) 217(+) 
G. 1.—Diagram Edens 
a dish culture: at lower right 
and left were planted secidini 
those studied by him have shown 
either reactions which he considered 
impossible or have failed to show the 
reactions which he found and upon 
which his theory of pseudohetero- 
thallic hermaphroditism in Cunning- 
hamella was based. It must be em- 
phasized, however, that despite the 
necessity for considering the evidence 
for sex intergrades in heterothallic 
mucors open to serious criticism, there 
is no proof at hand that such inter- 
grades do not exist. A somewhat 
detailed consideration of the evi- 
dence for them in Cunninghamella has 
been given to indicate a few of the 
dangers into which even one with some 
experience with cultural methods is 
likely to fall. The data already pub- 
lished (10) and to be presented in 
the following pages show that sex intergrades must be extremely 
rare in the mucors, and place the burden of proof on observers 
who think they have found evidence for their occurrence. 
h are formin 
(represented by dots at line of con- 
tact between them); in upper third 
was planted a mixture of plus and 
minus races 465 and 457 which 
fail to form zygospores with each 
other, but form them with the re- 
spective opposite sexes 459 and 
217. 
New data on Cunninghamella 
Tests of the sexual condition in Cunninghamella were made with 
202 races of four species; forty-two races of C. elegans, eighteen races 
of C. echinulata, eighty-nine races of C. bertholletiae, and fifty-three 
races of a species as yet unidentified.4 The method of running the 
4 The discrepancy between the number of races given here and that listed in a 
previous publication (10) is due to the separation of Cunninghamella A from the other 
species and the omission of four races ftom the tables on account of infection in the 
stock tubes, because of incomplete records or for other reasons. All told; including 
tests with other genera, a considerably larger number of contrasts has been made with 
Cunninghamella than is reported. 
