A critical study of certain species of Mucor 
ALFRED H. W. PovaH 
(WITH PLATES 17-—20) 
[Concluded from page 250] 
V. TAXONOMIC 
In the preceding experimental part of this work it has been 
shown that the species of Mucor, with but few exceptions, are 
rather plastic organisms, varying considerably with the external 
conditions, particularly the substratum. This fact, together with 
the lack of emphasis as to its importance, especially in questions 
of taxonomy, has led to a great deal of confusion and often to the 
description of a single species under several names. In view of 
this fact it appeared most desirable to attempt a standardization 
of the cultural requirements and to undertake a detailed study of 
as many forms as possible under such conditions. Early in the 
work it was seen that it would be necessary to limit the field of 
study, and as the genus Mucor is composed of so many species 
which offered difficulty, it was decided to include only this genus 
in the detailed study. In the aggregate, over one hundred col- 
lections (numbering those from which no mucors were isolated) 
have been made during the last three years. A glance at TABLE I 
will show the result: eighty-four collections gave mucors, twenty- 
eight from dung, twenty-two from decaying plant or animal sub- 
stances, twenty-three from soil, etc. Fourteen genera of the 
Mucorales, including thirty-seven species, were isolated: Mucor, 
nineteen species; Absidia, two species; Rhizopus, two species; 
Sporodinia, one species; Phycomyces, one species; Circinella, one 
species; Glomerula, one species; Zygorhynchus, one species; Helt- 
costylum, one species; Thamnidium, one species; Pilobolus, three 
species; Chaetocladium, one species; Cunninghamella, one sot 
and Syncephalis, two species. 
It will be observed (Tasie I) that sixty-six lites of 
Mucor were obtained, which are referred to nineteen species. Of 
these, six species are undescribed, viz.: Mucor abundans, M. 
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