GRIFFITHS: West AMERICAN FUNGI 291 
by a hyaline envelope about 24 thick; epispore rather thin but 
often appearing thick on account of the tubercles, 13-18, in 
diameter. (Fig. 2.) 
Affecting the culms of Agropyron occidentale Scribn. (311), 
Aberdeen, S. D., August 10, 1896. The host grew on ground 
heavily fertilized with refuse from the city on high and dry banks 
of the Moccasin a short distance below the mouth of a sewer. 
The species is easily recognized by its method of attack as well as 
by its color which is more like that of some of the species of Soro- 
S g@ 5 @ 
FIG. 1. Spores of Tilletia externa. >X 630. 
: IG, 2. Spores of 7; tlletia Earlei, 630. 
1G. 3. Spores of Ustilago elegans. X 630. 
Fic. 5- Spores of Sorosporium Williamsii, and outline o 
Mass, bd 730. si 
f the cylindrical spore 
‘Porium which affect the Compositae. It was very destructive to 
the host during 1896, ’97 and '98 in this very circumscribed area 
of not Over an acre in extent. There were square rods where the 
ost grew to the exclusion of almost all else, having every culm 
