166 FUNGI. 
enlarges, the wall of the arcuate cclls becomes coloured brown. 
This colouring is more marked on the convex side, and it shows 
itself first in the cell on which the dichotomous branches are 
first produced, and which retains the darker tint longer than the 
other. The zone from whence the processes issue, and also the 
processes themselves, have their walls blackened deeply, while 
the walls of the conjugated cells, which continue to clothe thy 
zygospore during the whole of its development, are bluish-black. 
By pressure, the thin brittle coat which envelopes the zygospore 
is ruptured, and the coat of the zygospore exposed, formed of a 
thick cartilaginous membrane, studded with large irregular warts. 
The germination of the zygospores in this species has not as 
yet been observed, but it is probably the same or very similar to 
that observed in other species of Mucor. In these the rough 
tuberculate epispore splits on one side, and its internal coat 
elongates itself and protrudes as a tube filled with protoplasm 
and oil globules, terminating in an ordinary sporangium. 
Usually the amount of nutriment contained in the zygospore 
is exhausted by the formation of the terminal sporangium, ac- 
cording to Brefeld ;* but Van Tieghem and Le Monnier remark 
that in their examinations they have often seen a partition 
formed at about a third of the length of the principal filament 
from the base, below which a strong branch is given off, and 
this is also terminated by a large sporangium. 
De Bary has given a precise account of the formation of the 
zygospore in another of the Mucors, Rhizopus nigricans, in which 
he says that the filaments which conjugate are solid rampant 
tubes, which are branched without order and confusedly inter- 
mingled. Where two of these filaments meet each of them 
pushes towards the other an appendage which is at first cylin- 
drical and of the same diameter. From the first these two 
processes are applied firmly one to the other by their extremities; 
they increase in size, become clavate, and constitute together 
a fusiform body placed across the two conjugated filaments. 
Between the two halves of this body there exists no constant 
difference of size; often they are both perfectly equal. In each 
* Brefeld, ‘‘ Bot, Unt. uber Schimmelpilze,” p, 31. 
