220 BOTANICAL GAZETTE [MARCH 
aecidium, adopting the generic name established by TULASNE in 1854, 
who applied it to forms without a peridium and having the spores in chains. 
But in the genus Coleosporium it is the uredostage, and not the aecidium, 
that possesses the caeoma structure. Moreover, care must be exercised 
not to confound TULASNE’S caeoma with Linx’s caeoma. For in 1809 
Lryk established a genus Caeoma to cover pulverulent forms of rust, 
whether the spores were borne singly or in chains, which was extensively 
used by mycologists of the time and subsequently, including SCHWEINITZ 
and others in America. But the terminology for the first stage of a rust 
is not yet exhausted. If the stage occurs on a pomaceous host, one is 
usually safe in calling it a roestelia; and if on a coniferous host, it is usually 
styled a peridermium. But there are plenty of instances among the less 
common forms of rust where none of these many terms seems accurate. 
Turning to the second stage of rusts fortunately we do not find so many 
terms in use. The spores are usually borne singly on pedicels, and are 
generally called uredospores, or when borne in chains they are caeomo- 
spores. If the sorus happens to be surrounded or filled with prominent 
paraphyses, the spores become epiteospores, although this term is derived 
from a generic name first applied to an aecidial form. It has seemed to 
me providential that when the uredosorus is surrounded by a peridium, as 
in species of Pucciniastrum and Cronartium, we are not required to have 
some other sort of spore, and are permitted to say simply uredospore. 
I have only cursorily mentioned some of the most obtrusive difficulties 
encountered, when I undertook seriously to record comparative studies of 
the rusts. I should probably never have publicly rebelled against this 
confusion of superfluous and yet inadequate terms, had I not after a time 
become interested in generic nomenclature. So long as there seemed to be 
no impropriety in allowing a generic name to wear out and be cast aside, 
or to be subjected to the menial duty of designating a form of spore, It 
seemed unreasonable to make complaint. But when the conviction 
became firmly established that a uredineous genus Was entitled to as much 
dignity of position as the genus in any other group of plants; and when It 
became evident, moreover, that in the application of the rule of priority 
some of these degraded genera might suddenly assume the place usurped 
by long accepted names, as for instance, Kuntze would have us believe 
that Roestelia should take the place of Gymnosporangium, then I thought 
* ae - look into the possibility of emending, changing, or in some "ey 
improving the terminology of the spore-forms. Pursuing my generic 
studies further, it appeared little short of absurd that one of the earliest 
genera, and until recently one of the largest, which has embodied the mos . 
