456 BOTANICAL GAZETTE : [DECEMBER 
are subjected to different conditions and a rigorous selection prac- 
ticed. In view of what has been said, we would not expect the 
relationship of fusing nuclei to make any difference if they were all 
in the same plant, and especially if they were all derived from a 
single nucleus with the haploid number of chromosomes. When 
therefore the ascogonium and antheridium, as in Pyronema con- 
fluens (HARPER 16), came to be derived from a single hypha, it 
would not seem to be a matter of great significance if the fusion of 
the nuclei derived from the ascogonium and antheridium should 
be replaced by the fusion of more nearly related or even sister nuclei, 
as seems sometimes to be the case in Leotia chlorocephala. It may 
be that the tendency toward the loss of sexual organs which is 
shown by a large number of the higher fungi is connected with 
the fact that there is in so many of them no provision for the fu- 
sion of nuclei derived from different individuals. 
Conjugate division 
In the first process of multiplication of asci described in Leotia 
chlorocephala there is a series of conjugate divisions comparable 
_to those in the rusts. When the hook gives rise to a binucleate 
penultimate cell and a uninucleate ultimate and antepenultimate 
cell, and then the ultimate cell fuses with the antepenultimate, 
there result two binucleate cells in which the two nuclei are derived 
one from each of two pairs of sisters. This is of course the rela- 
tion that exists in the rusts. The processes in the rusts and in 
Leotia are compared diagrammatically in fig. 47. If in Leotia the 
nuclei divided side by side rather than one in the tip and the other 
nearer the base of the hypha, and the walls still came in between 
the sister nuclei, there would result a series of binucleate cells 
resembling very closely those in the rusts. Such a division in an 
ascomycete has been described by Marre (20) in Galactinia 
succosa. : 
The cells which fuse in the rusts are often derived from separate 
hyphae, but BLackMAN (3) says that in some cases the fusing 
cells may be sisters, while OLtvE (22) figures two cases in which 
one nucleus is apparently migrating into an adjoining cell. The 
fusion of the ultimate and antepenultimate cells in the hooks of 
