Generations , and General Cytology of the Uredineae. 347 
As the spermatia have no power to act as male cells and appear quite 
incapable of causing infection, there would seem to be no escape from the 
view that they are now functionless 1 . It becomes evident then that a study 
of their structure is the only means by which one can hope to obtain 
evidence as to their primitive nature, for originally they must have acted 
either as male cells or as conidia. Strangely enough, their histological 
characters have never been considered from this point of view, though 
they appear to give very definite evidence for a decision of the disputed 
question. 
As the observations detailed earlier show, the spermatia, in both the 
forms investigated, are small, uninucleate cells, with a thin wall, apparently 
no reserve-material, a very dense nucleus without a distinct nucleolus, and 
a very small amount of cytoplasm (Figs. 47, 59) 2 . That these characters 
are general throughout the whole group is shown by a glance at the figures 
of Sapin-Trouffy (48), diagrammatic as they are ; though this observer, 
assuming that the spermatia were conidia, passed over these characters 
without particular comment. It is obvious, however, that these characters 
are not those of conidia nor of any regular asexual reproductive cells ; on 
the other hand they are to a very striking degree the characters of male cells, 
in which, as is well known, there is usually little or no reserve-material, 
the nucleus is often very dense, and the cytoplasm is nearly always much 
reduced in amount. 
The reduction in cytoplasm is very well marked in the small sper- 
matia of Phragmidium and Gy mno sporangium, but it is just as clearly shown 
in the comparatively large spherical spermatia of Coleosporium Senecionis , 
Fr., where, according to the figure of Sapin-Trouffy, the diameter of the 
nucleus is more than two-thirds of that of the whole cell. Such a struc- 
ture is certainly without parallel in any known asexual reproductive cell, 
and sufficiently explains the inability of the spermatia to develop in water, 
for the volume of cytoplasm is insufficient to form a germ-tube of any length. 
When one considers the peculiar structure of the spermatia of the 
Uredineae, their total incapacity, as far as is at present known, to bring 
about infection, their feeble power of development even in nutritive solu- 
tions, their usual close association with the aecidium, there seems no escape 
from the view that the spermatia are male cells which have now become 
functionless. The peculiar process of fertilization in the fertile cells of the 
aecidium of Phrag. violaceum , which one can hardly but consider as a reduced 
process, seems only explicable on the view that the spermatia formerly 
acted as fertilizing agents in connexion with the aecidia. 
1 It is satisfactory to note that Klebahn (27) in his recently published work, though unable 
to throw any light upon their nature, also arrives at the conclusion that they act neither as conidia nor 
male cells ; he thinks they may in some way be useful to the plant as an excretory product. 
2 I have also observed the same structure in the spermatia of Puccinia Poarum , Niels, 
P. Phalaridis, Plowr., and Uromyces Poae, Rabh. 
