GENERA AND SPECIES. 



189 



^. Omphalaria. 



Thallus small, fruticose, lobes flattened, dark. The 

 apothecia are terminal, nearly globose, dark. In fact 

 the genus closely resembles Lichina. The algal sym- 

 biont varies, however. Upon close examination it 

 will be found that the predominating alga is single 

 celled, with a thick, colorless, gelatinous covering, and 

 is evidently Glceocapsa polydermatica. Nostoc is, how- 

 ever, also present, at least in most specimens. 



The spores are simple, colorless, elliptical ; again 

 they are evidently septate. They occur upon rock in 

 the temperate and arctic zones. The genus requires 



further study. 



1. Omphalaria umhella, Thallus small, attached 

 by an umbilicus, branching, lobes flattened and crenu- 

 late, dark to nearly black. Apothecia terminal, 

 globose to discoid. Disk brown. Spores simple, 

 colorless, elliptical, 18/w, X 7.5^. 



5. Polychidium. 



Thallus small, fruticose, branching, lobes cylindrical, 

 dark. There is a cortical tissue present, thus distin- 

 guishing the genus from the genera already described. 

 The algfe are evidently Rivularia or modified Nostoc. 

 The general gross characters of the thallus resemble 

 those of Ephehe. 



The apothecia are small, discoid, and sessile upon 

 the basal portion of the thallus. Disk brown and 

 hypothecium colorless. The spores are oblong, ellipti- 

 cal or spindle-shaped to somewhat curved, two-celled, 

 colorless. This genus also requires further careful 



