208 BOTANICAL GAZETTE [OCTOBER 
TABLE VI—Continued 
Minus testers Plus testers 
Grade Races 
269 a0 257 515 242 181 
Minus races 
Po Da i aor dee lpn ie rg O O O Cc O O 
O.67 brit. oa O O O C O Oo 
O67 81655 a O O O C O oO 
O07 PSth es O O O . O O 
ragty sy Rl Gh (oie mele eyes oO oO O c O oO 
O69} 9Ae oO O O c oO O 
OF) Tha coe eee O O O Cc oO oO 
OOF teeter yee, O O oO 5 oO oO 
OOF P7Ges ee yt O oO oO c O O 
O07) O4F 2. 5. O oO O c O O 
O07 Set ec oO 0 O c O O 
O55 | Soh es. oO oO oO D O O 
Oss PelOe ee. O oO O O O d 
Grades (all combinations) .} 1.91 1.86 1.82 2.50 0.07 163 
in any of the combinations tested, have been provisionally listed 
as neutral. 
C. bertholletiae seems to differ from the other species of Cunning- 
hamella investigated except species A, and in fact from all the 
other mucors which have been studied in the same manner, in that 
between certain races imperfect sexual reactions have been found 
which do not lead to zygospore formation. It is possible that 
such reactions may occur more frequently than is realized. In 
contrasting the first few. testers of a given species, the practice has 
been to look for imperfect reactions at an early stage of develop- 
ment, and, if none are found, to examine the culture dishes in later 
series only at the end of the growth period when imperfect reactions 
would not readily be recognized. It is thus possible that some of 
the zero records for the contrasts of species A in table VI would be 
replaced by grades of imperfect sexual reaction if they had all 
been retested and inspected at an early growth period. Imper- 
fect reactions are graded in the tables by small letters instead of 
by the capitals used for zygospore formation. The reaction might 
readily be confused with the early stages of zygospore formation 
or the final stages of ‘‘imperfect hybridization.” Imperfect 
hybridization has heretofore been found to occur only between the 
opposite sexes of different species. When dealing with races of 
