214 BOTANICAL GAZETTE [OCTOBER 
fewer than five differences in reaction are shown both in the plus 
and minus strains chosen to form table IX. A graded series is 
indicated which might indefinitely be expanded as more and more 
races were tested. 
“IMPERFECT HYBRIDIZATION’? BETWEEN SPECIES 
Tables IV to VIIA deal with sexual reactions between races 
within the individual species concerned. In tables II, VII B, X, 
and XI are given the results of contrasting individual races of one 
species with those of another species. Many of the contrasts were 
made before the species Cunninghamella A was separated from 
TABLE Ix 
ARRANGEMENT OF SELECTED RACES FROM TABLE VIIA SHOWING 
TRASTED: CAPITAL LETTERS INDICATE GRADES OF ZYGOSPORES, 
SMALL LETTERS GRADES OF IMPERFECT SEXUAL REACTION. 
Plus races 
Minus races 
217 227 456 779 234 
SOB. ee A B C D b 
BEG. re B B c D c 
Seo. ee B B D O b 
ay a a gn B C b O b 
eas Pome NRG Se € c d O b 
C. echinulata and C. bertholletiae. Those between the testers H 
and D and the races of Cunninghamella A were made merely for 
the purpose of identifying the sex of the latter, and were not graded, 
since they were not originally intended for publication. It has 
seemed best, however, to include these and the reactions in table 
VII B, since they furnish cumulative evidence in regard to sexual 
dimorphism in Cunninghamella. Two races of C. elegans (nos. 496 
and 506, respectively plus and minus) failed to show reactions with 
the old plus and minus testers of C. echinulata (nos. 885 and 886). 
In table VII B certain combinations are starred because in them | 
the imperfect hybridization reactions led to the production of 
parthenospores (a-zygospores). When certain races of high sexual 
vigor are contrasted, gametes which have been formed but which 
have been unable to unite may develop into thick-walled sculptured 
