154 A. W. BENNETT. 
cell, whether by constriction as in Chalara, or by the 
formation of a septum as in Oitdium lactis, is however still 
uncertain. There is also this fact in support of the identity 
of these two organisms ; that Chalara branches are sometimes, 
though rarely, found so intimately attached to Ozdium conidia, 
as to suggest the explanation that they must have been pro- 
duced by the germination of the latter; but further investi- 
gations are wanted to determine this point. 
Brefeld’s researches! relate mainly to the Mucorini. 
Referring to the fact already known, that the spore of a 
Mucor produces a unicellular mycelium, from which is usually 
developed a single asexual sporangiophore, terminating in a 
sporangium (zygospores being occasionally produced in 
addition by a process of conjugation), he points out that in 
one respect different phenomena are presented by the minute 
Mucor racemosus. 
If the spores of this species are sown on soaked bread or 
some other solid but moist substratum, the normal mycelia 
and sporangiophores are produced, butmuch more rapidly than 
in other species, the mycelium becoming separated into a great 
number of divisions, each producing a sporangiophore. If, on 
the other hand, the Mucor is plunged into a fluid, a modified 
developmental form results. Mycelia are first of all produced 
from the spores, which, after from twelve to twenty-four hours, 
become divided by septa, placed very irregularly, commencing 
from the ends, the cells thus produced being of very various 
forms and sizes. These cells rapidly become rounded off, their 
connection at their points of contact remaining very slight or 
being altogether destroyed. Their contents at the same time 
undergo a change ; the vacuoles disappear ; the protoplasm no 
longer consists of granules, but become homogeneous and 
strongly refractive ; the cell-walls also become thicker ; and the 
prevention of the formation of sporangiophores thus causes the 
uni-cellular mycelium to break up into a number of resting- 
spores which apparently replace them. ‘They do not, how- 
ever, long retain this condition; but after six hours or less 
put out germinating filaments resembling those produced 
from the ordinary spores ; these filaments again break up into 
resting-spores, and the process is repeated as long as the 
supply of nutriment lasts. But in the later generations the 
germinating filaments become gradually shorter, passing 
gradually into a state closely resembling what we know as 
yeast (Saccharomyces). If the amount of nutriment is limited, 
only some of the cells assume the character of resting-spores, 
1 ¢ Flora,’ 1873, No. 25, Sept. 1st. 
