602 
Brooks. — The Development of 
in this species only a single nuclear fusion takes place. 1 It would seem that 
the sexual fusion which doubtless originally occurred in the ascogonia of 
Gnornonia has been replaced by a fusion immediately before the formation 
of the asci. There is a slight indication that a period in which the nuclei 
may be conjugately arranged precedes the actual fusion. If this is really 
the case, the commencement of the sexual process must be looked upon 
as beginning with the association of nuclei in pairs, as Blackman ( 1 ) has 
pointed out for the Uredineae. It would be premature at present to discuss 
the possible means by which the transference of the sexual process might 
have been brought about in the course of phylogeny. Only a single process 
of reduction in the ascus of Gnornonia has been observed. This harmonizes 
with the single nuclear fusion which has alone been seen. 
The nuclear phenomena described for Gnornonia seem to indicate 
a closer parallelism between Gnornonia and the Uredineae than has yet 
been determined for other Ascomycetes. The origin of the binucleate 
phase in the Uredines has been shown to take place in more than one way, 
and in some forms possessing deeply-seated aecidia it is possible, from the 
recent work of Olive, 2 that the binucleate phase originates in multinucleate 
cells at the base of the aecidium. If this prove to be the case, the cytological 
behaviour would appear to be somewhat similar to that of Gnornonia. Such 
a similarity between the nuclear phenomena of some of the Uredineae and a 
member of the Ascomycetes is of great interest, but in the present state of our 
knowledge it can hardly be made the basis for phylogenetic speculations as 
to the relationship of these two groups. On the other hand, the closest 
relationships of the Uredineae are certainly with the other Basidiomycetes. 
It is recognized that expressions of opinion on the phylogeny of the fungi 
must be highly speculative from the very nature of these organisms. 
Therefore one hesitates to state the possibility that the Uredineae—true 
Basidiomycetes as they undoubtedly now are—may have been connected 
with the Ascomycetes in the course of phylogeny. 
Summary. 
1. The vegetative mycelium consists of multinucleate cells. It is 
intercellular. Haustoria are not developed. 
2. The spermogonia are similar in structure to those of the Uredineae. 
The spermatia are long and thread-like, and possess the cytological cha¬ 
racters of male cells. They are considered to be now functionless, there 
being no evidence that fertilization is effected by their agency as Frank 
supposed. 
3. The trichogynes arise in tufts of 2-5, and do not invariably arise in 
1 It is possible that an earlier fusion has been missed, though in view of the careful search made 
for such a process this is unlikely. 
2 Olive, E. W. : Sexual Cell Fusions and Vegetative Nuclear Divisions in the Rusts. Ann. 
13 ot., xxii, 1908. 
