ARTHUR: IMPORTANCE OF THE SPERMOGONIUM 119 
ing teleutospores, there will appear spermogonia, without any 
regard to the kind of spore that is to follow. The spermogonium 
is clearly the first fruiting structure to arise in the cycle of de- 
velopment, that is, the first to follow nuclear fusion, which we 
may assume to be the sexual act. If we are, therefore, to regard 
the spermogonium as having any necessary association with other 
spore-forms, it must be with what precedes, that is, with the 
sporidium of the teleutospore, rather than with the conidia which 
follow. That this is physiologically as well as morphologically 
true is shown by the fact that the conidia closely following the 
spermogonia are usually larger and in many ways more vigorous 
than those conidia which arise from the germination of conidia, 
and thus are further removed from the reinvigoration of nuclear 
fusion. In some species with primary and secondary uredo, as for 
example, Puccinia suaveolens, and Phragmidium Potentillae on 
Potentilla Canadensis, the primary uredo when fresh can be told at 
a glance by the richer coloration and the larger and more compact 
sorus. It may be argued that the reason why the primary uredo 
is larger and stronger is because of its association with the 
spermogonium, which may be true, but if so, the explanation of 
it can not now be shown or even clearly conjectured. It is evi- 
dent, however, that assuming the nuclear fusion in the teleutospore 
to be an invigorating process, and that position seems fairly unas- 
Sailable, the effect of the fusion must be most marked in the 
earliest fruiting-bodies, and grow less and less the greater the 
number of removes, and hence the difference between the primary 
and secondary uredo. 
Before reaching the chief feature of this paper there is one 
more phase of cyclar development that should be presented. It 
is the relation of the repeating conidia to the succession of spore- 
forms. The incompleteness of knowledge of full life-histories is 
especially felt in making generalizations regarding this feature of 
development. All that can be claimed is probable correctness. 
Both tabular and diagrammatic methods of illustration may be 
employed as before. When the uredo occurs in the series, the 
uredospores by germination give rise to a mycelium that at once 
Produces more uredospores, and these may repeat the process, 
and so on indefinitely, or until the favorable season for growth 
