1220 Wisconsin Academy of Sciences, Arts, arid Letters . 
may not in all cases extend far back of this, or even may be 
characteristic of it; still in Entyloma Nymphaeae the entire 
mycelium is binucleated. In general it may be said at present 
as to the nuclear conditions in the smut mycelium that in the 
genus Ustilago the cells are multinucleated up to the time of 
spore formation; in some of the Tilletia group the cells are cer¬ 
tainly binucleated while in others they are probably so, at least 
to the extent that many binucleated cells are present. 
The question arises for the smuts as for the rusts and Ba- 
sidiomycetes as to the point of origin of this binucleated condi¬ 
tion. Eor the rusts it is now generally agreed according to the 
work of Blackman (2) and Christman (7) that it arises in some 
way in the aecidium, or in the primary uredo, if the aecidium 
is lacking. In the Basidiomycetes Miss Nichols (32) found 
the binucleated condition arising irregularity at almost any 
point in the mycelium which formed the carpophore. 
As described above we have a fairly complete life history of 
one of the types with multinucleated cells in Ustilago levis and 
there are a number of points of interest here to which it is 
necessary to call attention. The divisions which the nucleus 
undergoes in forming the nuclei for the promycelium should 
perhaps be assumed to be the reduction divisions on analogy 
with the rusts. Usually there are two of these divisions in the 
genus Ustilago while in Tilletia there are at least three, one of 
which must be on this hypothesis only a vegetative division. 
The promycelial cells on this hypothesis have the reduced num¬ 
ber of chromosomes and the conidia that come from them also 
have the reduced number and hence are gametophytic. When 
the nucleus of this conidium divides without the conidial cell 
dividing, has the cell now become necessarily sporophytic? 
Certainly not, since the condition is evidently unstable and the 
nuclear divisions may continue till the cell contains twenty or 
thirty sister nuclei. The sporophytic generation cannot be as¬ 
sumed to begin until the binucleated condition is definitely es¬ 
tablished and it is very difficult to say at just what point this oc¬ 
curs. There seems to be no possibility that the binucleated con¬ 
dition in Ustilago is established by any thing in the nature of 
cell fusion or nuclear migration. 
