310 PovaH: A CRITICAL STUDY OF 
white bread, such as is readily obtainable at any grocery store. It 
is thought that the use of bread is simpler than employing such 
complex media as Lendner’s “‘ mout gelatinisé.”’ 
VII. SUMMARY 
1. From over one hundred collections, thirty-seven species 
representing fourteen genera of the Mucorales have been obtained. 
2. After having tried various substances, bread was adopted 
as a standard culture medium for taxonomic purposes. 
3. The carbohydrates with regard to their availability as a 
source of food supply for the mucors, as exhibited by their growth, 
may be arranged as follows, the best being given first: levulose, 
dextrin, glucose, lactose, maltose, inulin, and saccharose. 
4. Organic nitrogen compounds are better than ammonium 
nitrate. 
5. Seventeen species of Mucor were found capable of fermenting 
dextrose-peptone solution. 
6. Mucor griseosporus and Mucor coprophilus can oxidize 
tyrosin in a maltose-tyrosin-peptone solution, with the production 
of a red coloration of the solution and the formation of a dark 
brownish black precipitate. 
7. The terms racemose and cymose should not be employed 
to describe branching in this group, because of the confusion which 
has arisen through their use, not to mention the lack of homology 
between a sporangiophore and a branch of one of the higher plants. 
8. Sixty-six collections of the genus Mucor have been studied 
in great detail under uniform conditions in standard bread cul- 
tures, and they have been referred to nineteen species, six of which 
are new: Mucor griseo-lilacinus, M. varians, M. coprophilus, 
M. aromaticus, M. griseosporus, and M. abundans. 
CRYPTOGAMIC LABORATORY, 
UNIVERSITY OF MICHIGAN 
