216 BOTANICAL GAZETTE [Marca 
Many other investigators, however, maintain that the nuclear 
fusion in the ascus constitutes the only fusion in the life cycle, and 
state that the third division in the ascus is a typical vegetative 
mitosis. Fautt (26 Hydnobolites, Neotiella) and CLAUSSEN (17 
Pyronema confluens) state that the same number of chromosomes 
is found in each of the three divisions in the ascus, and HARPER 
(40 Pyronema confluens, 41 Phyllactinia Corylea), who describes a 
double fusion, also finds the chromosome number remaining con- 
stant. 
Although many Ascomycetes have been examined in the 
endeavor to reach a satisfactory solution of the questions involved 
in this controversy, investigators are now as far as ever from agree- 
ment. The minute size of the sexual nuclei and the consequent 
difficulty encountered in demonstrating fusion renders misinter- 
pretation easy. It is possible, as suggested by Brown (12), that 
nuclear division in the ascogonium has been mistaken for fusion. 
Moreover, the presence of V-shaped chromosomes in the third 
division in the ascus in some species at least probably explains the 
differences in chromosome counts made by different investigators. 
It is possible also that coalescence of degenerating nuclei has been 
mistaken for a sexual fusion. 
It will be admitted also that two lines of a priori argument have 
contributed to the general disagreement concerning the essential 
facts in the nuclear history of the Ascomycetes. One group of 
investigators maintains that two successive nuclear fusions in a 
single life cycle, resulting in the production of a fusion nucleus with 
the 4x chromosome number, followed by a double reduction embra- 
cing the remarkable process of brachymeiosis, constitute a phenome- 
non so unusual as to warrant skepticism and to demand absolute 
proof. Since no similar variation has been found in any other group 
of organisms they doubt its occurrence in the Ascomycetes. 
The other school of workers lay great stress upon the presence 
of 8 spores in the ascus of so many Ascomycetes, and point out that 
even in asci containing fewer spores than 8 the production of 8 nuclei 
as the result of the triple division of the fusion nucleus has been 
described in practically every species investigated. This almost 
universal occurrence of the triple division in the ascus is ascribed 
