Classification . 185 



Calamogrostis, Bactylis, Festuca, Bromus, Agrostis, 

 Lolium. Not uncommon. 



TJrocystis, Rabenli. 



Sori erumpent, coarsely pulverulent, blackisli ; 

 spore-clusters consisting of one or several large, thick- 

 walled resting-spores capable of germination and 

 surrounded more or less completely by smaller, thin- 

 walled, sterile cells; on germination the slender 

 promycelium produces sporidia at the apex only. 



Urocystis, Rabenh. in Klotzsch, Herb. Myc. ed. ii. 

 no. 393; Sacc. Syll. vii. ii. p. 515; Plow. Brit. Ured. 

 and Ustilag. p. 285. 



Polycystis, Lev. 



Readily distinguished by the spore-clusters con- 

 sisting of large, thick walled, dark resting-spores 

 surrounded by thin walled, pale, sterile cells. 



Urocystis occulta, Rabenh. 



Sori forming long streaks on leaves, leaf-sheaths, 

 stems, and glumes, at first covered by the epidermis, 

 becoming powdery and black ; spore-clusters globose 

 or elliptical, 17-24 X 15-20/^, central fertile spores 

 9-17 fji diameter, spherical or angularly compressed, 

 smooth, obscure opaque brown, 1 — 3 in number, 

 rarely more ; sterile peripheral cells in a single, 

 interrupted layer, globose or flattened, pale brown, 

 4-6 fi diameter ; promycelium slender, bearing at 

 the apex 2 — 6 cylindrical sporidia. 



Urocystis occulta, Rabenh. in Klotzsch, Herb. Myc. 

 ii. n. 393; Sacc. Syll. vii. ii. n. 1891; Plow. Brit. 

 Ured. and Ustilag. p. 285. 



