Fertilisation in Ascobolus furfuraceus Pers. 159 
emptied of its contents, though a little vacuolate cytoplasm with 
scattered nuclei remains for a time. The empty scolecite eventually 
collapses. The ascogenous hyphae develop rapidly, their apices 
bend over, a terminal and a penultimate cell are cut off and the 
two nuclei in the latter fuse to form the definitive nucleus of the 
ascus from which the spore nuclei are derived. 
The development of the ascus was not studied in detail, as it 
has already been fully described by Harper (8). 
General Conclusions. 
Among Ascomycetes the union of the pronuclei in fertilization 
was first observed by Harper (10) in 1896 for Sphaerotheca humuli. 
The sexual organs are here uninucleate and the fertilized oogonium 
gives rise to a row of cells. These with the exception of the 
penultimate binucleate cell, are uninucleate ; they are regarded 
by Harper as an “ ascogonium,” but by Blackman and Fraser (3) 
as a single ascogenous hypha. 
A similar fertilization occurs in Erysiphe communis, Harper (8) 
and in Phyllactinia Corylea, Harper (11). The oogonium in these 
species gives rise to a row of cells, but here several ascogenous 
hyphae grow out from the penultimate cell and, in Phyllactinia at 
least, may arise from the other cells also. 
In Pyronema confluens (9) the male and female cells are 
coenocytic and fusion between a very large number of nuclei takes 
place in the ascogonium which without further development 
branches freely to form the ascogenous hyphae. 
Among parthenogenetic forms, a reduced fertilization has been 
observed in Humana granulata, and Lachnea stercorea. In Lachnea 
stercorea, Fraser (7) a trichogyne and antheridium are present 
but not functional; fusion takes place between the nuclei of the 
ascogonium. 
Humaria granulata, Blackman and Fraser (2), probably shows 
a further stage of reduction since a trichogyne and antheridium are 
not developed. 
In view of the above facts it seems obvious that the nuclear 
fusions occurring in the ascogenous cell of Ascobolus furfuraceus 
constitute a reduced sexual process. Here, as in Humaria granulata, 
an antheridium is not present. Though no definite knowledge 
could be obtained of the relationship of the fusing nuclei or indeed 
as to whether they necessarily came from the different cells of 
the scolecite, yet it seems probable that they are more distantly 
