NUCLEAR DIVISIONS AND NUCLEAR FUSION IN 
COLEOSPORIUM SONCHI-ARVENSIS, LEV. 
E. J. HOLDEN AND E. A. IIAEPEE. 
The study of tlie nuclear phenomena in the rusts has led to 
some very interesting and unexpected results. Sappin-Trouffy 
(1) has shown that the mycelial cells are regularly binucleated 
through a large portion of the life history of the fungus. 
He investigated some ten genera of Uredineae and his results 
on this point cannot be questioned. Dangeard and Sappin- 
Trouffy (2) have shown that these pairs of nuclei lie side by 
side in division and in such a fashion that the daughter nuclei, 
for each new cell formed, are not sister nuclei, but maintain a 
separate and distinct line of descent through the vegeta¬ 
tive growth of the fungus, including the formation of uredo- 
spores and aecidiospores. This method of division has been 
called conjugate division by Poirault and Raciborski (3). 
As far back as 1880 Schmitz (11) observed that the vegeta¬ 
tive cells and the uredospores of the Uredineae were binucle¬ 
ated. He regarded the binucleated condition of these spores 
as analogous to that of the pollen grains of phanerogams. 
Rosen (12) in 1892 found that the binucleated condition ex¬ 
tended to the other spores. The “basidium” which bears the 
aecidiospores he describes as uninucleated. The nuclar phe¬ 
nomena connected with the formation of the aecidiospores as he 
observed them are as follows. The nucleus of the “basidium” 
divides and the daughter nuclei separate in the direction of the 
long axis of the cell. The upper of the daughter nuclei, thus 
produced, then divides again. The spore is cut off by a wall 
separating the upper portion of the “basidium,” containing the 
two nuclei, from the lower portion, which is uninucleated. 
