confluens and the Morphology of the A scocarp, 363 
described for Peziza , Lachnea , Ascobolus, and Erysiphe. The 
young asci of Pyronema , like those of the Mildews, contain 
regularly two nuclei. The origin of these nuclei can be readily 
traced in Pyronema, The ascus here is quite regularly an 
outgrowth of the penultimate cell of the ascogenous hypha 
which bears it. Dangeard ( 7 ) has described this method of 
origin quite fully for Peziza vesicidosa , though he still says 
that the ascus may in some cases be the product of the fusion 
of separate hyphae. When the ascus arises from a single 
hypha he finds in the latter at first a single nucleus. This 
divides into two nuclei. Later a second nucleus appears 
which also divides into two. Of these four nuclei two are 
destined to fuse in the young ascus, one remains in the apical 
cell, and one in the cell behind that which develops the ascus. 
I find in general the same phenomena in Pyronema though, 
as will be noted below, the division of the two nuclei always 
occurs simultaneously. 
The tip of the ascogenous hypha pushing up among the 
paraphyses becomes recurved. In this hypha we have a 
period of nuclear division. It at first contains two nuclei 
which divide into four nuclei. The divisions of the two nuclei 
are exactly simultaneous as seen in Figs. 25-29. The 
spindles are so placed that a pair of nuclei are left in the 
bent part of the hypha, a third lies in the recurved tip, and 
the fourth lies farther back in the hypha just below the point 
at which it bends (PI. XXI, Figs. 29, 30). 
The recurved tip is then cut off by a cross-wall (Fig. 31), 
and a second wall is formed parallel to, or at a slight angle with 
the first, and generally at about the same level, cutting off 
the hypha just below the bend. The dome-shaped cell 
formed in this way at the bend in the hypha is to develop 
the ascus. It contains two nuclei, and from the position and 
orientation of the spindles in Fig. 29 it is seen at once that 
they are not sister nuclei, and are each derived from a different 
one of the original pair of nuclei in the tip of the hypha. 
Whether these latter nuclei are formed from a single one 
of the fusion-nuclei by division I have been unable to deter- 
