312 Wisconsin Academy of Sciences^ Arts, and Letters. 
egg. Each egg has a centrosome which may function like the cen¬ 
tral body of the Ascomycetes described by Harper. 
In a later work Clausen (1912) confirms the results of his earlier 
research on Pyronema confluens. He agrees with Harper as to 
migration of nuclei from the antheridium to the ascogonium, but 
does not believe that nuclear fusion takes place in the ascogonium. 
The nuclei pair and migrate into the ascogenous hyphae. The 
ascogenous hyphae becomes septate and the cell nearest to the asco¬ 
gonium may have eight pairs of nuclei, the other cells only one pair. 
The penultimate cell lying in the hook usually forms an ascus and 
the two nuclei lying in the hook fuse to form the primary ascus 
nucleus. In some cases the apical cell at the extremity fuses with 
the stalk cell and another ascus is formed. The cell usually form¬ 
ing an ascus may in some cases by budding produce a hook-like 
structure which forms another ascus in the usual way. 
The first division in the ascus is heterotypic and the nuclei con¬ 
tain twelve chromosomes after the division. The second division 
is homotypic, twelve chromosomes appear at the equatorial plate 
and twelve pass to the poles. During the third division the astral 
rays appear at the poles, and twelve chromosomes pass to each pole. 
Clausen finds no centrosome as described by Harper in Phyllactinia. 
He believes the delayed fusion in Pyronema confluens may be due 
to toughness of the nuclear membrane. Clausen adheres to the 
idea of sexuality in Erysiphe and Sphaerotheca and holds that the 
ascus is a spore mother cell as stated by Harper. In accordance 
with the views of Clausen the Ascomycetes are similar to the 
Basidiomycetes and their phlogeny must be conceived from a new 
standpoint, preferably from some oomycete. It is simpler to con¬ 
sider the Ascomycetes from the viewpoint of Clausen but to do so 
we must disregard the work of so many investigators who believe 
they have observed nuclear fusion in the ascogonium, especially the 
critical work of Harper, that more evidence is necessary before 
these facts can be considered established. 
Another point of view which may be considered as a reversion to 
the ideas of Brefeld has been brought out by Blackman and Wels- 
ford (1912) working with Polystigma rubrum. They maintain 
that the sexual organs have degenerated and that the ascogonium 
develops but does not function. The asci arise from the vegetative 
hyphae and the development then proceeds as described by Harper, 
Clausen, and others. 
