190 BOTANICAL GAZETTE LOCTOBER 
BURGER’S CONCLUSIONS COMPARED WITH NEW DATA 
It will be remembered that of the cultures used by BURGER, 
Cunninghamella echinulata plus and minus, C. elegans plus, Mucor 
V plus and minus, and his race no. 21 of C. bertholletiae were obtained 
from us. These races are still running, and it has been possible 
therefore to compare their behavior with the observations of 
BURGER on the same material. 
The second conclusion in his summary, to the effect that neither 
the sexual strains of our C. echinulata nor those of our Mucor V 
are able to form progametes with any one of twenty-six cultures 
of C. bertholletiae, is contrary to our experience. Table II shows 
TABLE II 
“IMPERFECT HYBRIDIZATION” BETWEEN RACES OF Cunninghamella bertholletiae AND 
Mucor V pus AND MINUS; Mucor V PLANTED 4:00 P.M., 11/19/19; C. berthol- 
nested PLANTED I1:00 A.M., 11/20/19; RECORDS seas 2:00 TO 4:00 P.M 
11/22/19; NUTRIENT NO. 380 (BURGER’S OATMEAL AGAR); c AND d_ INDICATE 
GRADES OF IMPERFECT HYBRIDIZATION; O INDICATES ABSENCE OF OBSERVED 
REACTION 
Neutral . 
Plus races oe Minus races 
C. bertholletiae 
217 | 227 | 268 | 234 | 464 | 456 | 215 | 452 266 | 457 | = 213 ose 
ssa aa O101.01-0101,0) 6104 tie ci8 
cor V minus..| c c eroro, oro; 0 3 01 0 
the results of contrasts between the sexual races of Mucor V and 
testers from the collection of races of C. bertholletiae grown on 
oatmeal agar made up according to BURGER’s method of prepara- 
tion. The majority of the races (including no. 213, which is 
BURGER’S no. 21) showed “imperfect hybridizations” with the 
opposite sex of Mucor V. The nutrient chosen does not appear 
to be the best for the reaction, but was used to make the conditions 
of the experiment so far as possible comparable with those reported 
in the paper under discussion. ‘Imperfect hybridization’’ between 
Mucor V plus and our race no. 213 has been obtained on other 
nutrients, but the reaction with this particular race has never been 
strong and might readily have been missed had we employed @ 
less successful method of observation (12). 
