32 SPERMOGONES 
SPERMOGONES. 
While ecidia are always subepidermal, and in the higher 
forms sunk rather deeply in the tissues of the host, the 
spermogones are in certain genera subcuticular and in others 
subepidermal, but always shallow. This doubtless corresponds 
to the primitive form of the ecidium, when the trichogynes 
protruded through a stoma in order to catch the spermatia. 
When fertilisation was dropped, it became possible for the 
wcidia to be surrounded for protective purposes by a continuous 
and firm peridium and to be more deeply sunk within the host: 
the spermogones, being outside the range of selective evolution 
on account of their uselessness, have retained more or less of 
their original character. The description of those of P. Caricis 
applies essentially to nearly all, except that in certain genera 
they are flat, not flask-shaped, and open by a wide pore, not 
by an ostiole, and in these and others there are no protruding 
filaments. 
Spermogones never appear alone; they are always accom- 
panied or closely followed by some other spore-form, either 
ecidio-, uredo-, or teleutospores. In comparatively few cases, 
as in P. Malvacearwm, have the spermogones disappeared en- 
tirely. 
UREDOSPORES. 
Uredospores are usually distinguished from wcidiospores by 
being produced singly at the apex of a short pedicel from 
which they easily fall off: this pedicel is the homologue of the 
intercalary cel] of the ecidiospores, as was shown by Christman. 
In certain genera, however, e.g. Coleosporium and Chrysumyxa, 
the uredospores are produced in short chains. Uredospores can 
reproduce uredospores for an indefinite number of generations. 
Occasionally there are two kinds, primary and secondary uredo- 
spores; in such cases the primary ones arise from fusion-cells 
and take the place of ecidiospores. So far as is known true 
uredospores never arise from a uninucleate mycelium, though 
they may spring from a mycelium which was at first uninu- 
cleate, but became binucleate at some point in its development. 
