354 Olive . — Sexual Cell Fusions and Vegetative 
throughout the sporophytic development. But here, in the Rusts, Black- 
man would have a doubling to result from a similar origin and to persist 
as well throughout the gametophyte. The nuclei of the vegetative gameto- 
phytic hyphae (Fig. 10 ), as well as those of the spermogonium (Figs. 6 and 
6a), clearly show in some instances this phenomenon. The nuclear fusion 
in the teleutospore and the two promycelial divisions which presumably 
accomplish the reduction processes, have occurred but a short time before 
in the development of the fungus. While Blackman’s conclusion might 
therefore seem to be the natural one under the circumstances, viz. that the 
double character of the nuclei results from the continued association of the 
same nuclear cavity of the chromatin derived from the two nuclei which 
have just fused in the teleutospore, the important bearing of such a theory 
and its lack of harmony with the recent theoretical work on the higher 
plants above mentioned, compels us to await more facts before accepting 
his conclusion. Another view is possible to explain the phenomenon. 
The double centre may be reasonably explained as resulting from a 
precocious division of the centre in each daughter-nucleus, in preparation 
for the next mitotic division — a phenomenon which has already been 
described as taking place in the nuclei of a number of organisms. 
While not yet prepared, as indicated above, to discuss fully the 
important questions which arise as to the mode of origin of the multi- 
nucleated cells at the base of the aecidium-cup, nor as to the part they bear 
in the development of the aecidia, it may be advisable in this place to point 
out a few pertinent facts and theories. Massee (’88) claims to have seen 
such a multinucleated cell at the base of the aecidium-cup, which he thinks 
resulted from the fertilization of an oogonium by an antheridium. Richards 
(’95) has figured in a similar position one, or in large cups often more, large, 
sometimes multinucleated cells, which, according to him, give rise by budding 
to the basal cells at the bottom of the spore-rows. Richards thought that 
the multinucleated cells arose simply by the swelling up and growth of one 
or more special * fertile hyphae ’ at the base of the cup. Blackman (’04 
and ’06) saw a number of cases in young aecidia in which the cells had 
three and four nuclei, but he regarded such isolated instances as abnormal. 
That multinucleated cells are formed, probably as regular occurrences 
during the earlier stages in the development of the young aecidia, is indi- 
cated by their discovery, during the course of this investigation, in at least 
eight or ten species of Rusts. I am therefore convinced that they are per- 
fectly normal occurrences, and that they result simply from the nuclear 
divisions going on much faster and thus getting ahead of cell division. Even 
in the caeoma form — Triphragmium ulmariae — instances, probably of a 
similar nature, have been occasionally noted in which five or six nuclei 
occur in one cell, although but two is the usual number. 
Whether such multinucleated cells result from the stimulated growth 
