36 THE CHICAGO ACADEMY OF SCIENCES. 



This species has many forms and has been described under 

 various names. Some of them occur on rocks and mosses, 

 others on trees. It is found on maples in Will County. 

 It is the only species of the genus within our limits so far as 

 known. There are six described varieties in the United 

 States. 



Buellia* (De Not.) Tuckerm. Thallus mostly uniform; apothecia 

 patellaeform. Spores ellipsoid, brown or decolorate. 



96. B. parasema, (Ach.) Th. Fr. Thallus cinerascent or darker, 

 rugose, granulate, glaucescent; apothecia sessile, black; disk 

 flat, often turgid; margin thin. Lecidea, Fr. Tuck. Syn. N. 

 E. 67. L. disciformis, Nyl. 



On oaks near Elgin and elsewhere on dead wood. Occurs 

 everywhere in North America; a variable species. 



97. B. schaerefi. De Not. Thallus granulose, often wanting, cin- 

 erascent; apothecia very small, black, flat; disk turgescent 

 and margin wanting. Lecidea nigritula, Nyl. Scand. 238. 

 Found on an old stump near Lemont, also on old rails; not 



common. Is also found in Grundy and LaSalle Counties. 



TRIBE 3. GRAPHIDACEI. 

 FAMILY 9. OPEGRAPHEI. 



Opegfapha. (Humb.) Ach. Nyl. Thallus hypophlaeous, or, if ex- 

 posed, thin; apothecia normally lirellaeform. 



98. O, atfa, (Pers. ) Nyl. Thallus thin or wanting; apothecia ses- 

 sile, black, simple, flexuose; disk open, canaliculate, proper 

 margin thick, elevated, wavy. 



Throughout our territory on oaks, hickories, cherries, etc. 



99. O, vafia, (Pers.) Fr. Thallus white, pulverulent; apothecia 

 prominent, elongate, oblong, elliptical, attenuate at the ends, 

 brownish-black, dilated in the centre; margin inflexed. 



On various trees in Cook -and Will Counties. 



