170 British Fungi, 



Ustilago. Sori pulverulent at maturity. 



ft Sporidia numerous, produced at apex of pro- 

 mycelium. 



§ Sori pulverulent at maturity. 



Tilletia. Resting-spores with the epispore generally 

 reticulated. 



§§ Sori not pulverulent at maturity. 



a. On stems or leaves. 



Entyloma. Sori pale or brown. 



Melanotcenium. Sori broadly expanded, black. 



h. On roots. 



Entorrhiza. 



B. Sori covered witli an involucre formed of 

 liyplise. 



Sphacelotheca. 



II. Resting-spores aggregated in clusters. 



A. All the spores in a cluster of uniform size. 



t Sporidia mostly apical on the septate pro- 

 mycelium ; sori forming brownish spots, generally on 

 leaves. 



* Sporidia numerous. 



Doassansia. Sori covered with a continuous layer 

 of sterile cells. 



Tuhurcmia. Sori not covered with a special layer 

 of sterile cells. 



** Sporidia solitary. 



Tliecapliora. Sori rufescent ; generally in the fruit 

 or seed. 



ft (Sporidia unknown), promycelium very slender. 



Sorosporium. Sori black. 



B. The cells or spores of different sizes, forming 

 clusters. 



