THE FUNGI WHICH CAUSE PLANT DISEASE 



315 



Sori rather permanently embedded in 

 tissues 

 Spore-balls without sterile cortex 

 Spore-balls consisting entirely of 



dark-colored spores 6. Tuburcinia. 



Spore-balls consisting of light-colored 

 spores 

 Spore-balls with or without central 



sterile cells 7. Burrillia. 



Spore-balls with central network of 



filaments S. Tracya. 



Spore-balls with sterile cortex 9. Doassansia, p. 322. 



Neovossia occurs on Phragmites; Tuburcinia on Convallariacese, 

 Primula, Trientalis and Geranium in Russia; Burrillia on Limnan- 

 themum, Echinodorus and Sagittaria; Tracya on Spirodela. 



TiUetia Tulasne i"'" (p. 314) 



Sori in various parts of the hosts, usually in the ovaries, forming 

 dusty spore-masses; spores single and usually formed singly in 

 the ends of the mycelial threads 

 which disappear more or less 

 completely through gelatiniza- 

 tion, germination usually by a 

 short promycelium wliich bears 

 a terminal cluster of elongate 

 sporidia that in nutrient solu- 

 tions, with or without fusing in 

 pairs, may give rise to a con- 

 siderable mycelium bearing sec- 

 ondary air-sporidia. 



The genus closely resembles 

 Ustilago except in its larger Fig. 230.— t. 

 spores and mode of germination. 



Twenty-two American species are listed by Clinton. Only three 

 are of economic importance. 



T. pancicii Bub. & Ran. is reported on barley heads in Servia.^' 



T. glomerulata. Cocc. & Mor. is a doubtful species on aKalfa. 



fcetens, spores. Photo- 

 micrograph. After Clinton. 



