THE UROMYCES OF EUPHORBIA. 
149 
As the latter species I long ago claimed Uromyces tuberculatus, 
Feld., which Fuckel, in “ Symbol. Mycol.,” p. 64, had combined 
with Uromyces scutellatus ; while this fungus is mentioned in 
“ Grevillea,” No. 23, May, 1874, p. 161, under the supplement to 
the English Fungoflora, as Uromyces excavata (DO.), on Euphorbia 
exigua. But after Dr. Schroeter had, at my request, most kindly 
forwarded this fungus to me, I was able easily to convince myself 
that its appearance on Euph. exigua is quite different to that 
described by Duby l.c. as Uromyces excavatus (DC.), for Uromyces 
tuberculatus grows only in a small and completely separate heap on 
the leaves and more abundantly on the stalk of Euphorbia exigua , 
so that the separate attacked leaves, as also the stalk, bear only a 
few scattered heaps, and the greater part of the attacked leaf, as 
also the whole of the attacked plant, is entirely free from fungus. 
On the contrary, Duby l.c., in his description of Uromyces excavata , 
DO., calls it “ hypophylla, acervulis fuscis parvulis, numerosis ,” &c., 
and in conclusion it is remarked, “ Acervuli frequentes totam pagi- 
nam occupant , sed non deformant .” This cannot, therefore, be the 
Uromyces tuberculatus , Fckl., which grows in separate little heaps 
on the stalk and leaf of Euphorbia exigua. Whereas the descrip- 
tion very well suits the Uromyces which grows on Euph. 
Gerardiana and Euph. verrucosa, in both of which species, 
indeed, the leaves attacked by the fungus do not present so very 
different an appearance from that of the normal leaves, as the 
leaves of Euph. Cyparissias do when attacked by the Uromyces. 
The Uromyces growing on Euph. verrucosa and Euph. Gerardiana, 
I, therefore, hold to be the old Uredo excavata, DC., and describe 
it as Uromyces excavata (DC) It is distinguished from 
Uromyces scutellatus , Lev. (with which, in its characteristic 
growth on Euphorbiaceae, it fully agrees), by the smooth mem- 
brane of the Teleutospores, as also by its association with the 
iEcidium. 
We have here consequently a most highly paradoxical circum- 
stance of two very nearly allied species of Uromyces growing on 
the most nearly related Host plants. Both grow in nearly the 
same very characteristic manner on the Host plants, and are 
accompanied by the same undistinguishable Spermogonia. The 
same Spermogonia accompany the iEcidium belonging to one 
Uromyces. One similar iEcidium, accompanied by similar 
Spermogonia, grows on the Host plants of the other species in 
very nearly the same characteristic way; but this does not belong 
to the circle of evolution of the nearest allied Uromyces, but, in a 
highly remarkable manner, to the circle of evolution of quite a 
different species of Uromyces on another Host plant The two 
associated fruit-forms of a Fungus closely allied to a species of 
Uromyces, growing on the most nearly allied species of Host 
plants to this Uromyces, thus unexpectedly belong to two per- 
fectly distinct fungi. 
It deserves here to be mentioned that Uromyces Pisi, Str., is in 
no way nearly allied to Uromyces excavatus (DC.). Irrespectively 
