47. Arthonia] 14. ARTHONIACEAE 87 



37. Arthonia lapidicola (Tayl.) Branth & Rostr., Bot. Tidssk. 3:245. 1869. 

 Lecidea lapidicola Tayl., in Mack., Fl. Hib. 2:124. 1836. 



Superficial thallus thin and disappearing, ashy white to olive-brown; apothecia 

 minute to small, 0.1-0.3 mm. across, adnate, round, the disk flat to convex, black; 

 tinged pale brownish within; asci pyriform; spores oblong-ovoid, hyaline or tinged 

 brown, 1-septate, 12-17 X 5-7 fx. 



On sandstone, New York, Indiana, Illinois, and Nebraska. The algal host is 

 Palmelloid, and some workers recognize the genus Allarthonia based on difference 

 in host. 



38. Arthonia terrigena Nyl., Flora 68:448. 1885. 



Thallus grayish brown, thin and inconspicuous, widespread; apothecia very 

 minute. 0.06-0.08 mm. across, round, the disk brownish black; flat to slightly con- 

 vex; hymenium tinged brown; hypothecium light brown; spores hyaline to pale 

 brown, oblong-ovoid, 1-septate, 11-12.5 X 3-4 jx. 



On soil, near New Bedford, Massachusetts. 



39. Arthonia rupicola Fink; Hedrick, Mycologia 25:310. 1933. 



Thallus very thin, smooth, widespread, pale greenish gray to ashy, finally dis- 

 appearing; apothecia minute, 0.1-0.25 mm. across, adnate, round to irregular, the 

 disk convex, black; hypothecium tinged brownish; hymenium hyaline; paraphyses 

 indistinct, appearing interwoven and branched; asci broadly clavate to sub-ovoid; 

 spores hyaline, oblong, 1-septate, constricted at the septum, the upper cell larger, 

 10-15 X 4.5-6 [x, irregularly arranged. 



On limestone rock, near Oxford, Ohio. 



40. Arthonia patellulata Nyl., Nya Bot. Notis. 1853:95. 1853. 



A. patellulata var. pallidiuscula Willey. Allarthonia patelhdata (Nyl.) Zahlbr. 



Superficial thallus thin, whitish, rough, often mealy, becoming chinky, some- 

 times disappearing; apothecia minute to small, 0.15-0.5 mm. across, adnate, round, 

 the disk flat to convex, black; hypothecium pale brown; hymenium hyaline; asci 

 subpyriform; spores hyaline, oblong-ovoid, 1-septate, 10-14 X 3.5-5 /x. 



On trees, Massachusetts, Illinois, Iowa, Minnesota, and California, 

 var. caesiocarpa Zahlbr., Bull. Torr. Club 27:646. 1900. 



Allarthonia patelhdata var. caesiocarpa (Zahlbr.) Hasse. 



Apothecia from grayish white pruinose to naked and black; spores 12-17 X 

 5-6 fi. 



On trees, southern California. 



41. Arthonia subdispuncta Nyl.; Hasse, Bull. Torr. Club 24:448. 1897. 

 Superficial thallus thin, dirty white, smooth; apothecia minute, 0.08-0.12 mm. 



across, slightly immersed to adnate, round, angular or oblong, reaching 0.3 mm. 

 long, the disk flat, bluish black to black; brown within; asci pyriform; spores 

 tinged brownish, oblong-ovoid, 1-septate, one cell larger, 9-12 X 4-5^.. 

 On Leptosyne gigantea, Santa Monica Range, California. 



42. Arthonia convexella Nyl., Act. Soc. Linn. Bord. 21:415. 1856. 



Thallus thin, smooth, becoming chinky, pale greenish gray to whitish, often 

 disappearing; apothecia minute to small, 0.2-0.4 mm. across, adnate, round or 

 varying toward oblong, convex and often obscurely rough, black; hypothecium 

 dark brown; hymenium lighter brown; asci subpyriform; spores oblong-ellipsoid, 

 hyaline to light brown, 1-septate, 11-14 X 4-6 /x. 



On trees, northern Minnesota. 



43. Arthonia exilis (Floerke) Anzi, Cat. Lich. Sondr. 94. 1860. 



Lecidea synotheca var. exilis Floerke, Deutsche. Lich. 187. 1821. Allarthonia 

 exilis (Floerke) Sandst. 



Superficial thallus thin, dark gray, inconspicuous, and disappearing, on trees 

 thicker and becoming slightly rough and chinky; apothecia minute, 0.1-0.3 mm. 

 across, adnate, round to slightly irregular, sometimes clustered, the disk convex 



