389 
All rusts at present known fall into one of these two classes: the 
sporophytie generation gives rise either to a single spore-form, or else to 
initial and final spore-forms, with usually intermediate repeating forms. 
Whether one or more than one spore-form arises between the cell fusion 
and final nuclear fusion, constitvting the sexual period, all such spores, of 
whatever morphological structure, are of a sexual nature, the initial form 
(whether of the «cidiuim-type, caoma-type, primary uredo-type, or when 
none of these is produced, the teleuto-type) being the one which most 
clearly shows the stimulus of fertilization. 
The above facts, especially when taken in connection with the highly 
differentiated structures associated with the initial and repeating spores, 
often being quite equal or superior to those of the teliospores, show every 
reason that may be based upon morphology and development for consider- 
ing the initial and repeating spores as practically of equal taxonomic 
rank with the teliospores. To illustrate, a genus founded upon a repeat- 
ing stage, like the genus of imperfectly known fern rusts, Milesia, should 
be as valid as if founded on the telia. This genus has recently been re- 
christened Milesina on the ground that the original name, given in 1870. 
is invalid because it was only applied to the uredinia and not to the telia. 
Again, now illustrating with a specific name, the hetercecious rust which 
was first specifically called poculiforme was described in its cial stage 
under d4fcidium, and according to the preceding argument on the impor- 
tance of the initial spores, this name having priority, although not at the 
time made to include the telia, should be used, whatever genus name be 
considered the best, as e. g., Dicwoma poculiforme or Puccinia poculiformis, 
not Puccinia graminis. 
From the foregoing it will be seen that for purposes of taxonomy 
names applied to the pycnia (spermogonia) may properly be ignored, on 
the ground that they apply to asexual or conidial structures, but that 
names applied to «cia and uredinia (cidium, Caoma, Peridermium, 
Uredo, and other such forms) should haye the same standing as names 
applied to telia (teleutospore stage). 
I have tried to show that the main features in the life cycle of all 
rusts exhibit essential uniformity, there being two large groups, one with 
a single form of spore (teliospore) in the sporophytic generation, and the 
other with additional initial and (usually) repeating spores, and that the 
great diversity lies in the details of their structural development. It is 
