Mycological Notes, i 13 
Some years later, Brefeld—owing to want of direct evidence as 
to the nature of the nominal sexual organs when present, and to 
their apparent absence in the higher forms—was led to put forward 
the view, which held sway for some time, that the Ascomycetes 
were a group entirely wanting in sexuality. He derived the 
Ascomycetes from the Zygomycetes, believing that the ascus was 
nothing more than a sporangium, like that of the Mucorini, 
which had become definite in form, size, and the number of spores 
it produced. From later researches it soon, however, became clear 
that to homologise the ascus and sporangium was a matter of some 
difficulty. From the observations of Dangeard and others, it became 
clear that the single nucleus of the young ascus was the product 
of fusion, usually of two nuclei; it had also been known for some 
time that the ascospores were produced within the ascus by free 
cell formation. Both these characters distinguish the typical ascus 
from the sporangium. 
The discovery by Harper, in 1895, of actual fertilisation (i.e, 
nuclear fusion) in Sphaerotheca , at once placed the sexuality of the 
Ascomycetes on a firm footing. This occurrence of undoubted 
sexuality in such a form would appear to lend great support to 
De Bary’s view of the relation of the Ascomycetes to the Oomycetes. 
Harper himself, however, was not able to support this idea; a 
comparison of the cytological characters of the sporangium and 
ascus had so impressed him with their differences that he was 
unable to consider them as homologous structures. The 
question of the ancestry of the Ascomycetes he believed to be a 
very difficult one, but that, at all events, their relationships should 
be sought elsewhere than among the Phycomycetes. 
The elucidation later of the sexual process in Pyronema 
revealed a new type of fertilisation. Whereas in Sphaerotheca 
the ascogonium was uninucleate and there was only one male 
nucleus, in the form under consideration both the ascogonium 
and antheridium contain numerous nuclei and there is a 
process of multiple fertilisation, numbers of male and female 
nuclei fusing in pairs within the ascogonium. In so far as the 
sexual organs were multinucleate, Pyronema obviously shewed a 
closer similarity to the Oomycetes than did Sphaerotheca ; but so 
far as was then known, all the Oomycetes possessed uninucleate 
oospheres. Shortly afterwards, however, Stevens made the inter¬ 
esting discovery that in Albugo (Cystopus) Bliti there was also 
multiple fertilisation ; the well-defined oosphere of the usual type 
