confluens and the Morphology of the Ascocarp. 365 
case being the basal cell of the lateral branch bearing the 
second ascus. I doubt, however, whether such a series could 
be found. The ascogenous hyphae produce such numerous 
short branches in Pyronema that I have never been able to 
find more than two asci connected in the fashion shown in 
Fig. 31. Such a system is doubtless itself a lateral branch. 
The formation of the asci is, however, clearly basipetal, as has 
been pointed out many times, and this makes it still more 
improbable that the apical recurved cell develops further after 
the first ascus is formed. 
In brief, then, of the four nuclei formed by the divisions of 
the two fusion-nuclei, two in the case described undergo no 
further development. The other two, lying in the young 
ascus, fuse to form the nucleus of the ascus. Such a pair of 
fusing nuclei are shown in Fig. 33. The nuclei become 
somewhat enlarged before fusion occurs, the dome-shaped cell 
in which they are enclosed at first pushes out at its apex 
into a club-shaped process, which grows rapidly in length and 
becomes the ascus, which is thus supported on two cells at its 
base (Figs. 31 and 32). The two nuclei lie side by side or 
one above the other in the young ascus when they fuse. They 
become slightly flattened upon each other, their membranes 
disappear at the point of contact, and they form thus a 
single nucleus which is first oblong and becomes gradually 
spherical or oval (Fig. 34). This behaviour of the nuclei at 
the time of the formation of the ascus has not been as yet 
satisfactorily explained. Dangeard’s hypothesis, that the ascus 
is an oogonium, is certainly not established, and as it was 
developed by its author without any investigation of the origin 
of the ascocarp or knowledge of the existence of nuclear 
fusions in its early stages, it can hardly be considered as 
applying to Pyronema . I shall further discuss the question 
of the significance of these fusions later on. 
The phenomena of nuclear division and spore-formation in 
the ascus of Pyronema differ only in details from what I have 
already described for a number of forms. As it seems worth 
while, however, to have a complete account of the develop- 
