GENERA AND SPECIES. 139 



The apotliecin belong to the tlialline type, and are 

 discoid, sessile, small to medium in size. The disk is 

 dark in color. There is no yellow or orange colora- 

 tion in this genus. It may also be mentioned that 

 spermagonia occur upon many species. The spores 

 are typical of the family, closely resembling those of 

 Rinodina. 



The Physcias have a wide range ; the higher forms 

 are somewhat southern. They occur upon bark and 

 rock. 



Formerly the PJiyscias were quite generally com- 

 bined with Parmelia, from which group they are, how- 

 ever, readily distinguished by the spore-characters and 

 by the differences in the appearance of the thallus. 



1. Physcia adglutinata. Thallus crustose, thin, 

 very closely adnate to the substratum, central portion 

 areolate, warty, margin lobed, lobes of uniform width ; 

 dark colored. Apothecia small to medium. Disk dark- 

 brown, margin slightly crenulate. Spores brown, 

 typical, 15/x X 8.. 5 /a. 



2. Physcia obscura. Thallus comparatively small, 

 branching, firmly attached to the substratum, green- 

 ish-gray above, black beneath, with numerous rhizoids. 

 Apothecia small to medium, margin extending above 

 the dark-brown disk. Spores brown, typical, 24/x 

 X 10.5/x. 



3. Physcia setosa. Thallus much as in P. obscura, 

 lobes broader, often bearing soredia, black below, with 

 densely crowded black rhizoids. Apothecia rare; none 

 have come to my notice. 



4. Physcia ccesia. Thallus comparatively small to 



