22 BOTANICAL GAZETTE [JANUARY 
each individual through at least a considerable part of its life- 
history, leading up to the formation of basidia, while no such 
binucleated cells are found in the Ascomycetes either in vegeta- 
tive or ascogenous hyphae, shows that the two groups are widely 
separated phylogenetically. In the face of such differences, 
resemblance of outer form and method of spore-formation 
between conidiophores and basidia must be regarded as super- 
- ficial and of uncertain value, and as wholly inadequate evidence 
for the conclusion Massee wishes to draw. On the other hand, 
it is quite clear that the binucleated condition in the hyphae of 
both groups stlll further strengthens the evidence for the rela- 
tionship between the rusts and Basidiomycetes. The nuclear 
fusions occurring in the teleutospore and basidium are seen also 
to be directly comparable processes, and there is a strong pre- 
sumption that in the Basidiomycetes, as in the Uredineae, this 
fusion is not between sister nuclei, but nuclei which by the 
process of conjugate division have remained distinct through 
long periods of vegetative growth. Maire affirms unequivocally 
the existence of conjugate division in all the forms he has 
studied. a 
It must not be assumed without further evidence that the 
rusts are primitive Basidiomycetes. Their parasitic habit is 
against this view, and the evidence from the resemblance of a 
sorus of Coleosporium to a true hymenium cannot be considered 
as very conclusive. Still, the binucleate condition of the hyphal 
cells suggests very strongly that rusts and Basidiomycetes must 
have arisen from some ancestral type characterized, at least in | 
some stage of its development, by the possession of binucleate 
instead of uninucleated or multinucleated vegetative cells. How 
this binucleated condition arose originally is not at all clear. The 
view of Raciborski that the binucleated cells of the rust repre- 
sent a prolonged vegetative stage interposed between two phases — 
of a sexual act, namely the cell fusion and the nuclear fusion, iS~ 
suggestive as a hypothesis, but it is nothing more. 
The question as to the nature of the spermogonia and their 
relation to the aecidia of the rusts remains still unsettled, and — 
ipecamelea eS: 
