566 KUNKEL: ORANGE RUSTS OF RUBUS 
as to be morphologically indistinguishable. If we consider only 
the life cycles of the two forms we find that they belong in groups 
that are rather widely separated in our classifications of the rusts. 
The short-cycled Caeoma nitens we would place near the genus 
Endophyllum; Gymnoconia interstitialis belongs near Phrag- 
midium. Arthur (1) puts Gymnoconia in the Aecidiaceae while 
Endophyllum he places in the Uredinaceae. When we consider 
the two rusts from a morphological standpoint we find that in 
their Caeoma stage they are alike and we are inclined to consider 
them related forms. Werth (14) believes the aecidiospores of 
Endophyllum Sempervivi are capable of functioning either as 
aecidiospores or as teleutospores, according to the conditions under 
which they germinate. Maire (10) reports a variety of E. Sem- 
pervivi that regularly produces ordinary aecidiospore germ tubes. 
These suggestions are interesting in this connection and they 
deserve consideration in our studies of the two orange rusts. The 
finding of a basidium in cultures of the aecidiospores of Gymno- 
conia interstitialis offers a further suggestion and leads the writer 
to believe that the two rusts may be related. If a strain of the 
orange rust could be found in which some of the aecidiospores 
germinate by ordinary germ tubes while others produce promycelia 
the question as to the relationship of the two forms would be 
much clearer. An effort should be made to find such an inter- 
mediate strain. 
The two Caeomas have undoubtedly been confused in this 
country. There is no way of knowing which rust Burrill (2) 
described as Caeoma nitens since it seems that both occur in the 
vicinity of Urbana, Illinois. Both are reported from Missouri 
and it is impossible to determine which form Newcombe and 
Galloway (11) used in their work. From their drawings of the 
germinating spores, however, one would guess that they had the 
short-cycled form. It is also probable that the material used by 
Olive (12) in his study of sexual cell fusions in the rusts was Caeoma 
nitens, but of this we can not be sure. 
As one looks over the group of host species as given by Arthur 
(1) the question presents itself as to which ones are really host : 
species for Gymnoconia and which ones are the host species of 
Caeoma nitens. This list undoubtedly includes the hosts of both 
