CLINTON: NORTH AMERICAN USTILAGINEAE. 
337 
means of a septate promycelium producing only infection threads 
or with sporidia formed terminally and laterally near the'Septa; 
sporidia in water usually germinating into infection threads but in 
nutrient solutions multiplying indefinitely, yeast fashion. 
This is the largest genus of smuts and occurs on a great variety 
of hosts, the Gramineae furnishing the greatest number. It is also 
the oldest genus and therefore the type of the Ustilagineae. 
Among its species are found some of the most injurious parasites of 
the cereals. Saccardo describes 248 species and 72 are included 
here from North America. Sphacelotheca, Melanopsichium, and 
Sorosporium are closely related to this genus. B ref eld has divided 
it into Proustilago, Hemiustilago, and Euustilago, groups character¬ 
ized by their types of germination. It is not possible to classify the 
species given here under these because the germination of many is 
not known. The species are arranged as nearly as they can be 
according to their apparent relationships, though it is evidently 
impossible to fully or exactly express these in a linear arrangement. 
* Spores pale to dark reddish brown. 
Ustilago minima Arth. 
Ustilago minima Arth., Bull. Ia. Agr. Coll., Dept. Bot., 172. 1881. 
Exsiccati: Ustilago hypodytes (Schl.) Fr., on Stipa spartea, Seym. & 
Earle, Econ. Fungi, Clinton Ust. Suppl. C 70; Ustilago minima Arth., on 
Stipa spartea , Griff., West Amer. Fungi, 237. 
Sori on stems, linear, usually 3-5 cm. in length, with a conspicu¬ 
ous whitish false membrane composed chiefly of elongated sterile 
fungous threads, upon rupture disclosing dusty black brown spore 
mass surrounding stem as columella; spores light reddish brown, 
chiefly ovoid to subspherical or spherical, smooth, 3.5-4.5 /x, or 
elongated 5.5 g in length. 
Hosts : Oryzopsis cuspidata , Ariz.; Stipa spartea , Ia. (type). 
The writer has previously thought that this species was not dis¬ 
tinct from Ustilago hypodytes and possibly it may not deserve 
separate recognition. Upon receiving the specimens on Oryzopsis 
cuspidata from Arizona, collected by David Griffiths in the Navajo 
Indian reservation last year, the prominence of the sterile membrane 
covering the sorus impressed us, as it did Dr. Griffiths, as separating 
these specimens from the ordinary form of Ustilago hypodytes . 
Upon looking into the subject more carefully it was found that 
