PHYLOGENY 81 
Uredinales, as now known, and that attributed by Claussen 
(1912) to Pyronema confluens. In his paper, which is a con- 
clusive reiteration and confirmation of his earlier work, he shows 
that the numerous male nuclei of the antheridium enter the 
ascogonium, and in it pair with the numerous female nuclei, 
but without fusing with them. These synkarya then pass out 
into the ascogenous hyphe, and there multiply by numerous 
conjugate divisions. Finally a pair of descendants of these 
nuclei are seen in the young ascogenic-cell, one being male 
and the other female: here they divide conjugately into two 
pairs, one pair being the ascus-nuclei, and the other pair 
reserve-nuclet which may repeat the process in several ways: 
The two non-sister ascus-nuclei fuse; then the fusion-nucleus 
divides, the first division being heterotypic (meiotic, reducing, 
possessing synapsis and diakinesis stages) and the two following 
ones, by which eight spores are formed, being homotypic. 
There is thus in the life-cycle a single fusion, followed by a 
single reduction. The ascus is a spore-mother-cell, comparable 
to the teleutospore of the Uredinales, but forming an octad, not 
a tetrad of spores. The two “reserve-nuclei,” left after the 
formation of the ascus, answer to the two nuclei Jeft in the 
“basal” cell of the zcidium. Compare in this respect especially 
the process as it takes place in Hndophyllum. The sporophyte 
generation consists then in Pyronema only of the ascogenous 
hyphe, whose cells contain the diploid number of chromosomes 
though arranged within two nuclear membranes. 
In certain species of Laboulbenia (Faull, 1912) there is a 
similar cytological history. The ascogenic hyphe contain two 
nuclei which divide homotypically by conjugate division, and 
two non-sister nuclei pass into each ascus where they fuse; the 
two left in the ascogenic cell may repeat the process. The 
fusion-nucleus of the ascus divides to form eight nuclei of which 
four soon degenerate: the first division is meiotic and the others 
homotypic. There is no double fusion in this group and the 
same statement may justifiably be inferred to be true of other 
Ascomycetes. 
On the other hand, Harper (1900), Blackman, Welsford, 
Fraser, Brooks, Carruthers (1911) and others, maintain that in 
a U. 6 
