1921] BLAKESLEE, WELCH, & CARTLEDGE—MUCORS 169 
of empty stacks in the inoculating room ready for pouring. A 
tube of alcohol is seen at the right holding the inoculating needles. 
EXAMINATION OF CULTURES.—The cultures were examined under 
the binocular microscope by the transmitted light of a substage 
electric lamp. In some species the mycelium and spores above the 
substratum hid any zygospores which might be present, and neces- 
sitated manipulating the culture before examination. Wetting 
with alcohol, pressing down the aerial growth with the finger, and 
even washing the spores away under a jet of water occasionally 
Fic. 1.—Inoculating chamber with stacks of culture dishes ready for pouring 
was found necessary. The relative abundance of zygospores when 
present is shown by the grades A to D. A indicates about the 
maximum number of zygospores to be expected of the species under 
the given environmental conditions, while D indicates generally less 
than a dozen zygospores in the whole culture. Absence of zygo- 
spores is indicated by O. Naturally the zygospores would be 
expected to form in greatest numbers at the line of €ontact between 
the opposing mycelia, and in some species produce a sharply defined 
dark line. In forms like Rhizopus and Cunninghamella, in which 
the zygospores are produced on branching aerial filaments, the 
zygospores may spread from this median line until ultimately 
