98 IS. GRAPHIDACEAE [50. Opegrapha 



H. Apothecia 0.3-1 X 0.1-0.2S mm., 



usually scattered 16. 0. diaphora 



H. Apothecia 0.4-2 X 0.16-0.4 mm., 



scattered or clustered 18. O. varia 



G. Apothecia 0.4-5 mm. long 19. O. vulgata 



C. On rocks 



D. Thallus thin, smooth 12. O. lithyrga 



D. Thallus thicker, becoming chinky to subareolate, 



crumbling or powdery 21. O. Hassei 



B. Spores 7-1 5 -septate 



C. Spores not more than 45 fi in length 



D. Thallus very thin; spores 20-42 X 3.5-7.5 n .... 23. O. Bonplandi 



D. Thallus somewhat thicker; spores 24-32 X 6-11 /j. . . . 22. O.prosodea 



C. Spores 35-70 X 4.5-7.5 it 24. O. viridis 



1. Opegrapha atra Pers., Ann. Bot. Usteri 7:30. pi. 1, f. 28. 1794. 



O. atra var. hapalea (Ach.) Nyl. 



Thallus thin, smooth, whitish, infrequently tending to disappear, rarely lim- 

 ited by a blackish line; apothecia moderately long and wide, 0.5-2.5X0.2-0.3 

 mm., oblong-ellipsoid, adnate, usually numerous, straight to curved or flexuous, 

 very rarely branched, the disk closed to narrowly open and black, the exciple 

 black; hypothecium brownish black; spores finger-shaped, 3-septate, 15-21 X 4-5 /x. 



On trees, throughout the United States. 



2. Opegrapha agelaea Fee, Mem. Mus. Hist. Nat. Strasb. 2"':23. 1835. 

 Thallus thin, smooth, pale greenish gray, varying toward ashy or olivaceous; 



apothecia of moderate length and width, 0.5-2.5 X 0.2-0.3 mm. with ends rather 

 obtuse, slightly immersed to adnate, scattered to clustered, straight to curved or 

 rarely and obscurely flexuous, very rarely branched, the disk closed to narrowly 

 open and black, the exciple dull black; hypothecium black; spores 3-septate, 

 14-18 X 5-7 /x. 



On trees, Florida. 



3. Opegrapha betulina J. E. Smith, in Sowerby, Engl. Bot. 32: pi. 2281. 1811. 



O. atrorimalis Nyl. 



Thallus thin, smooth, ashy, varying toward yellowish or brownish, often mar- 

 gined by a blackish line; apothecia rather short and wide, 0.5-2 X 0.25-0.45 mm., 

 ellipsoid, adnate, numerous, scattered or clustered, straight to curved, very rarely 

 branched, the disk soon open and black, the exciple black; hypothecium brownish 

 black; spores ovoid-ellipsoid, 3-septate, 19-25 X 6-8.5 /x. 



On trees, Orange County, California. 



4. Opegrapha diaphoroides Nyl., Flora 61:453. 1878. 



O. varia var. diaphora f. diaphoroides Boist. 



Thallus thin, smooth to slightly rough, greenish gray to ashy or brownish; 

 apothecia short and wide in proportion, or even subrotund, 0.4-1.4 X 0.3-0.6 mm., 

 adnate, usually scattered, straight to rarely and obscurely curved, the disk soon 

 widely open and black, the exciple black; hypothecium thick and brownish black; 

 spores finger-shaped, 3-septate, 12-17 X 3-4 /x. 



On trees, Florida. 



5. Opegrapha Umbellulariae Zahlbr., Beih. Bot. Cent. 13:154. 1902. 

 Thallus thin, smooth, finally and obscurely chinky, pale greenish gray to whitish, 



occurring in small roundish to irregular areas; apothecia rather short and narrow, 

 0.4-0.8 X 0.15-0.25 mm., narrowly oblong, subsessile, commonly scattered, straight 

 to curved or obscurely flexuous, sometimes branched, the disk closed to open, 

 concave to flat, dull black, the exciple black and of medium thickness; hypothe- 

 cium hyaline; spores oblong-dactyloid, 3-septate, 12-15 X 3.5-4 /x, obscurely con- 

 stricted, especially at the middle septum, sub-biseriately arranged. 

 On Umbellularia californica, Santa Monica Range, California. 



