314 THE FUNGI WHICH CAUSE PLANT DISEASE 



spore-balls black, opaque, oblong 

 to spherical or polyhedral, usually 

 containing one hundred or more 

 firmly agglutinated spores, chiefly 

 50-180 M in length; spores from 

 nearly hyaline, to light reddish- 

 brown, outer coat more or less 

 folded in ridges, often spiny, ovoid 

 to subspherical or polyhedral, 

 chiefly 7-10 n or rarely 12 /x in 



Fio. 229. — ^Tolyposporium. Spore length. 



ball germination. After Brefeld. ^ t. • n- • ii^ 



On Panicum crus-galh m the 

 United States east of the Rocky Mountains also in Europe. 

 T. filiferum and T. volkensii, occur on sorghum in Africa. 



TiUetiaceae (p. 302) 



Sori either forming dusty erumpent spore-masses or permanently 

 embedded in the tissues. Germination by means of a short promy- 

 celium which usually gives rise to a terminal cluster of elongate 

 sporidia, that, with or without fusing in pairs, produce similar 

 or dissimilar secondary sporidia or germinate directly into infection 

 threads. 



The American TiUetiaceae embrace nine genera and about one 

 hundred twenty-five species. 



Key to Gexeea of TiUetiaceae 

 Spores single 

 Sori dusty at maturity 

 Spores without a conspicuous hyaline 



appendage 1. Tilletia, p. 315. 



Spores with an elongate hyaline append- 

 age 2. Neovossia. 



Sori permanently embedded in the tissues 



Sori definite, small 3. Entyloma, p. 320. 



Sori indefinite, large 4. Melanotsenium. 



Spores in balls 

 Sori dusty; spore-balls with sterile cor- 

 tex 5. Urocystis, p. 318. 



