TECHNIQUE IN CONTRASTING MUCORS 
ALBERT F. BLAKESLEE, DoNALD S. WELCH, AND J. LINCOLN CARTLEDGE 
(WITH TWO FIGURES) 
For the last two years a more or less intensive study of the 
sexual reactions between different races of mucors has been con- 
ducted. These reactions have been tested by growing the races 
side by side in culture dishes under suitable environmental condi- 
tions and observing the abundance of conjugations which take 
place between the races thus “contrasted.’”’ In making so large 
a number of contrasts, it has been necessary to develop a special 
technique in order to minimize the time consumed in the prepara- 
tion and handling of the cultures, to obtain greater accuracy in 
making observations, and to avoid the various experimental 
errors to which one untrained in the work is liable. As has 
already been shown, the discordant results obtained by different 
investigators working with the same species of mucors may be 
explained by a difference in the technique employed. It has 
seemed desirable, therefore, to give in some detail the methods used 
before presenting the results of the investigations in a series of 
papers which it is hoped to publish shortly. 
GROSS CULTURES.—As a source of races to be investigated, 
gross cultures grown in the laboratory are more convenient than 
natural cultures found out of doors. Certain forms are character- 
istic of certain types of substrata. Most mycologists are familiar 
with the flora obtained from dung cultures made by placing bits 
of dung on filter paper above damp peat moss in a covered crystalliz- 
ing dish. Brazil nuts have been found a constant source of certain 
forms such as Cunninghamella bertholletiae, C. echinulata, Syncephal- 
astrum, and certain other species. In making gross cultures of 
these nuts it was found convenient to use chiefly the shells, since 
the meats furnish too luxuriant a supply of nutrient, so that 
Rhizopus is likely to overgrow the less vigorous forms in the culture. 
The nuts were cracked separately and their shells placed in piles 
Botanical Gazette, vol. 72] [162 
