50. Opegrapha] IS. GRAPHIDACEAE 97 



adnate, 1-several on each wart, round to irregular or elongated, sometimes 

 1-3 times short-branched, the disk closed to open and concave, pale to darker 

 brown, the exciple thin, colored like the disk; spores oblong-ellipsoid, 11-16 X 

 3-5 [a. 



On old wood, along the coast of New England. 



50. Opegrapha Humb., Fl. Friberg. 57. 1793. 



Thallus forming a crust upon the substratum, and partly or rarely wholly within 

 the substratum, devoid of differentiation into layers; apothecia linear, fusiform, 

 ellipsoid, oblong, or rarely circular or irregular in outline, rarely branched, super- 

 ficial or more or less immersed, usually black, the disk commonly closed and indi- 

 cated by a black or blackish depressed line, but sometimes becoming open and 

 black, the exciple usually black; hypothecium commonly brownish black in section; 

 paraphyses interwoven and branched; asci commonly clavate with thin wall; 

 spores usually 8, commonly hyaline but becoming brownish in some species, sev- 

 eral- to many-septate with cylindrical cells, from oblong or ovate to ellipsoid, 

 fusiform, or finger-shaped. 



The algal host is Trentepohlia. 



A. Spores constantly 3 -septate 

 B. On trees 



C. Hypothecium hyaline 5. O. Umbellulariae 



C. Hypothecium brownish to brown or black 

 D. Spores less than 20 /x in length 

 E. Thallus white or whitish 



F. Spores 11-13X4-5^ 8. O. Candida 



F. Spores 15-21 X 4-5 y. 1. O.atra 



E. Thallus greenish gray to ashy or brownish gray 

 F. Thallus smooth to slightly rough 

 G. Apothecia short and wide, 



0.4-1 X 0.3-0.6 mm 4. O. diaphoroides 



G. Apothecia longer and narrower, 



0.5-2.5 X 0.2-0.3 mm 2. O. agelaea 



F. Thallus minutely granulose 7.0. microcyclia 



D. Spores more than 20 y in length 



E. Apothecia 1 or 2 times branched . . . . 6. O. herpetica subocellata 



E. Apothecia very rarely branched 3.0. betulina 



B. On rocks 



C. Spores 12-16 X 3.5-5 p. 10. O. calcarea 



C. Spores 18-28 X 5-7 /x 9. O. saxicola 



A. Spores 3-5- or more septate 

 B. Spores 3-5- or 7-septate 

 C. On trees and old wood 

 D. Hypothecium hyaline 



E. Apothecia closely aggregate, usually straight ... 20. O. longissima 



E. Apothecia scattered, frequently curved 11. O. filicina 



D. Hypothecium brownish black 

 E. Thallus smooth 



F. Apothecia not branched or rarely so 

 G. Apothecia short and wide, 



0.5-1 X 0.15-0.35 mm 15. O. lichenoides 



G. Apothecia longer and narrower, 



0.4-2 X 0.15-0.25 mm 14. O. cinerea 



F. Apothecia often branched 13. O. astraea 



E. Thallus becoming chinky, scurfy, scaly, or powdery 

 F. Disk closed 



G. Thallus white, with plainly marked margins . 17. O. leucoplaca 

 G. Thallus light greenish gray to ashy white 



or brownish 19. O. vulgata minor 



F. Disk more or less widely open 



G. Apothecia not more than 2 mm. long 



