306 PovaH: A CRITICAL STUDY OF 
is no differentiation of the plant body into a specialized apical 
cell, such as is found in the higher plants. There may be, how- 
ever, a correlation between the relatively simple plant body and 
the lack of a fixed branching system. 
The vegetative condition may continue for a brief period or 
indefinitely, depending upon experimental conditions. Under 
usual laboratory conditions the vegetative period is short (twenty- 
four to thirty-six hours), and sporangiophores are produced as 
perpendicular branches arising from the thallus. In some species 
the growth of the sporangiophore stops with the formation of the 
apical sporangium; in other species, after the formation of a 
terminal sporangium, growth starts again, with the production of 
a lateral branch from some part of the sporangiophore, and con- 
tinues until a sporangium is formed at the tip of this branch. On 
one hypha or branch the same process may be again repeated. 
(De Bary, 1887, p. 46.) 
This account of the development of the sporangiophore ap- 
parently does not harmonize with De Bary’s (1887) statement 
that “both growth and branching follow the laws which prevail 
generally in the vegetable kingdom.’’ For it may be said that a 
comparison of the development of branching systems in the higher 
plants with those in the genus Mucor shows little similarity 
between them. Although, perhaps, the stems and inflorescences 
of the higher plants may be analogous to the sporangiophores 
and sporangia of Mucor, it can scarcely be maintained that there 
exists a homology between them. It appears then advisable not 
to apply the terms used to describe the branching of the higher 
plants to the sporangiophores of Mucor. Even if the writer’s 
views on this matter can not be accepted, the impracticability of 
using the terms is sufficient reason for discarding them. 
The characters which experience has proven reliable for specific 
determination are as follows: turf, columella, spores, sporangium, 
sporangium wall, and chlamydospores. These are given in the 
relative order of their importance. The height, color, and nature 
of the turf must be considered. Inasmuch as the term turf in- 
cludes only the aerial part of the plant, the height of the turf is 
the length of the sporangiophores, and is expressed either in milli- 
meters or in centimeters. Contrary to current opinion, there is 
