Classification . i ^ i 



Urocystis. Central resting-spores of a spore-cluster 

 large, tliick-walled, fertile^ peripheral cells smaller, 

 thin- walled, barren. 



Ustilago, Pers. 



Vegetative mycelium spreading in the tissues of 

 the host, soon disappearing; sporogenous hyphge 

 branched, resting-spores formed in the interior of 

 much gelatinized, clustered, terminal branches. On 

 germination the resting-spores give origin to a short, 

 septate promycelium which produces minute terminal 

 and lateral primary sporidia. 



Ustilago, Pers., Sacc. Syll. vii. pt. ii. p. 451 ; Plow. 

 Brit. IJred. and Ustilag. p. 272. 



Many species form long, brown or blackish streaks 

 on leaves or stems, others develop in anthers which 

 then present a blackened, powdery appearance, others 

 again develop in the ovaries of plants. 



A. Resting-s]:iores smooth or wartecl. 

 Ustilago longissima, Tul. 



Forming long, brown, powdery streaks on the 

 leaves ; resting-spores globose or irregularly and 

 broadly elliptical, pale brown, usually with an olive 

 tinge, smooth, 3-4 yu, diameter, or 3-4 x 6-7 /u, ; 

 promycelium fusoid, narrow at the point of origin 

 from the spore, sporidia fusiform. 



Ustilago longissima^ Tulasne, Mem. sur les Usti- 

 lag. Ann. Sci. Nat. 1847, 76; Cke. Micr. Fung. 

 t. V. figs. 105—107 ; Plow. Brit. Ured. and Ustilag. 

 272 ; Sacc. Syll. vii. n. 1637. 



Forming thin parallel streaks, often several inches 



