CLINTON: NORTH AMERICAN USTILAGINEAE. 
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b. Rather permanent, yellowish or reddish, with markings 
only on free surface of spores . Thecaphora 
c. Quite permanent; spores adhering by folds or thicken¬ 
ings of outer coat . . Tolyposporium 
2. Spore balls with outer sterile cortex . . Urocystis 
B. Forming an agglutinated sorus at maturity. 
1. Spore balls (variable) composed of thick walled spores 
Tolyposporella 
2. Spore balls with peripheral spores and central sterile cells 
Testicularia 
C. Imbedded in plant tissues at maturity. 
1. Spore balls without definite cortex of sterile cells. 
a. Composed entirely of dark colored spores Tuburcinia 
b. Composed of light colored spores and 
* With or without central sterile cells Burrillia 
** With a central network of filaments Tracya 
2. Spore balls with cortex of sterile cells. 
a. Spores light colored (with or without central sterile 
tissue) ...... Doassansia 
USTILAGINACEAE Schl’Ot. 
Krypt. FI. Schles., 3 1 : 266. 1887. 
Sori usually forming exposed dusty or agglutinated spore masses. 
Germination by means of a septate promycelium which gives rise to 
terminal and lateral sporidia (capable of yeast-like multiplication in 
nutrient solutions) or else to infection threads. 
Key to Genera. 
i. Spores single. 
A. Sori dusty at maturity. 
1. Without definite false membrane . . . Ustilago 
2. With false membrane of definite fungous cells 
Sphacelotheca 
B. Sori agglutinated at maturity. 
1. Firmly agglutinated into conspicuous tubercular nodules 
Melanopsi chiwn 
2. Developed around a central columella (rarely dusty) 
Cintractia 
