Generations , and General Cytology of the Uredineae . 363 
The existence of immotile male cells (spermatia) and of a sterile cell 
(in Phvagmidium ) which may possibly have formerly had the function 
of a trichogyne certainly points to a relationship of the Uredineae with the 
Florideae, a relationship which has been suggested by Meyer (35), chiefly 
on anatomical grounds, for all the higher Fungi. It is possible that an 
alternation of generations may yet be found in this algal group, for 
tetraspore-formation suggests a process of chromosome-reduction; the 
fact that in the majority of forms there is a distinction of sexual and asexual 
plants is also very striking in this connexion. Such a discovery — and it 
must be remembered that Williams (59 and 60) has already observed this 
alternation in the Dictyotaceae with chromosome reduction in the tetra- 
spore-mother-cell — -would certainly lend strong support to a view of a 
relationship between the Florideae, Uredineae, and Basidiomycetes. 
Summary. 
The peculiar nuclear cycle described by Sapin-Troufify for the 
Uredineae was confirmed in the case of Phragmidium violaceum , Wint., 
and of Gy mno sporangium clavariaeforme , Rees. In this cycle, the mature 
teleutospore is uninucleate and gives rise to four uninucleate sporidia, from 
which a mycelium is developed with the nuclei arranged singly, usually in 
separate cells. The spermatia produced on this mycelium are uninucleate, 
but in the young aecidium the nuclei become paired (forming binucleate 
cells) and divide together in very close association. This paired condition 
is then persistent throughout the rest of the life-cycle (aecidiospores, 
uredospores, and mycelia produced from them) up to the formation of the 
teleutospores, which in the young state are binucleate, but when mature 
become uninucleate by the fusion of the two paired nuclei. This cycle of 
development seems common to all the Uredineae (except Endophyllum ) 
which have an aecidial stage in their life-history. 
A study of the structure of the spermatia of the Uredineae shows that 
they have the characters not of conidia but of male cells , for they exhibit 
a large dense nucleus, very little cytoplasm, no reserve material, and a very 
thin cell-wall. These characters, together with their usual association with 
the aecidia, their absence of function, and the peculiar, apparently reduced, 
form of fertilization to be observed in the aecidium of Phragmidium 
violaceum y point clearly to the view that the spermatia are male cells which 
formerly took part in a process of fertilization in connexion with the 
aecidium, but have now become fiinctionless. 
The aecidium of Phrag. violaceum is developed immediately beneath 
the epidermis of the leaf and has a very simple structure. It consists 
of a layer of special cells, each of which cuts off a sterile cell above, which 
soon disorganizes, while the lower, the fertile cell, increases in size and shows 
abundant protoplasm, and after a pause in its development is fertilized by 
