1894.] The Homologies of the Uredineae. 989 
THE HOMOLOGIES OF THE UREDINEAE 
| (THE RUSTS). 
By CHARLES E. Bessey. 
The place of the parasitic plants constituting the Order Ure- 
dineae (The Rusts), in a natural system of classification, has long 
been in doubt, botanists not being fully agreed as to the hom- 
ologies existing between these and other fungi. In a study 
of this group, extending over many years, I have been led to 
a view of the homologies between these plants and the Asco- 
myceteae and Basidiomyceteae, somewhat at variance with the 
theories of most recent writers; and itis probable that the time 
has come for a more definite statement of this view than has 
yet been given. 
GENERAL STRUCTURE. 
The Uredineae are parasitic within the tissues of higher 
plants, for the most part Anthophyta. They consist of sep- 
tated branching threads which vegetate for some time within 
the host, and eventually produce spores (conidia) in chains, by 
abstriction. These spores develop upon numerous, crowded, 
parallel, terminal branches, within the tissues of the host, at 
length bursting through the epidermis. The outer conidial 
branches are modified into a “ peridium,” which surrounds 
the erumpent spore-mass like a tiny cup, whence the common 
name, “ Cluster-cup,” in allusion also to the fact that the spore- 
cups usually appear upon the leaf in clusters. For a long | 
time these cluster-cups were supposed to have no connection 
with the rusts, and they accordingly were described under the 
generic names Aecidium and Roestelia. The first of these 
names is preserved in the term “ aecidiospore,” by which the 
spores are often designated. (Figs. I and II of Plate XXXII.) 
Somewhat later, spores of another kind are produced singly 
upon the ends of other branches in the tissues of the host. 
These, while occurring in clusters, are by no means as closely 
