47. Arthonia] 14. ARTHONIACEAE 85 



23. Arthonia pyrrhuliza Nyl., Flora 68:447. 1885. 



Thallus thin, smooth to slightly rough, whitish, bordered more or less by a 

 narrow, inconspicuous dark line; apothecia minute to small, 0.1-0.2 X 0.4-0.8 mm., 

 irregular and variously elongated, curved and branched, immersed, the disk flat, 

 reddish brown and finally darker; hyaline within; spores oblong-ellipsoid, hyaline 

 to pale brownish, 3- rarely 4-septate, 12-15 X 4-5 /x. 



On trees, New England, and doubtfully New York and Illinois. 



24. Arthonia platyspilea Nyl., Act. Soc. Sci. Fenn. 7:480. 1863. 



Superficial thallus thin, ashy white, often surrounded by a brownish black line; 

 apothecia middle-sized, 0.5-1 mm. across and often 3 mm. long, immersed, irregular 

 and often elongated, sometimes clustered, the disk flat, light or darker reddish 

 brown, or whitish pruinose; tinged brownish within; spores hyaline, ovoid-ellipsoid, 

 7-septate, 21-27 X 8-11 jx. 



On trees, Florida. 



25. Arthonia lecideella Nyl., Mem. Soc. Sci. Nat. Cherb. Suppl. 5:337. 1857. 

 Superficial thallus rather thick, greenish to greenish gray, rough, becoming 



chinky and subareolate; apothecia minute to small, 0.2-0.6 mm., immersed to ad- 

 nate, round, the disk flat to convex, brown to black, or grayish pruinose; hypothe- 

 cium dark brown; hymenium lighter; asci clavate; spores hyaline, slipper-shaped, 

 3-septate, one end cell larger, 16-22 X 5-7 fx. 



On trees, from New England to Maryland, and westward to Iowa and Min- 

 nesota. 



26. Arthonia cupressina Tuck., Gen. Lich. 221. 1872. 



Superficial thallus thin, whitish, smooth to slightly rough, becoming powdery; 

 apothecia minute, 0.2-0.5 mm. across, partly immersed to adnate, round to 

 slightly irregular, the disk convex, pale brown to blackish, at first greenish pruinose; 

 hyaline within; spores hyaline to slightly colored, narrowly ovoid-ellipsoid, con- 

 stricted at the middle septum, 3-septate, two cells at one end larger, 11-16 X 3-5 fx. 



On trees, Massachusetts. 



27. Arthonia albofuscescens Tuck., in Willey, Syn. Arth. 17. 1890. 

 Superficial thallus thin to moderately thick, ashy white, becoming rough; 



apothecia minute to small, 0.1-0.4 mm. across, immersed to semi-superficial, round 

 to irregular or oblong, often reaching 0.6 mm. in length, sometimes clustered, the 

 disk flat, brown to blackish; hyaline or tinged pale brownish within; spores hyaline, 

 ovoid-ellipsoid, 3-septate, 9-13 X 3-5 /x. 

 On trees, Massachusetts. 



28. Arthonia chiodectella Nyl., Flora 52:125. 1869. 



Superficial thallus thin to moderately thick, greenish gray to ashy white, smooth 

 to slightly rough, and finally chinky; apothecia minute to small, 0.1-0.3 mm. across, 

 clustered, round or more commonly somewhat irregular, adnate to semi-immersed, 

 the disk flat, dirty blackish, or obscurely whitish pruinose, at least toward the mar- 

 gin; hymenium hyaline; hypothecium reddish brown'; spores oblong-ovoid, 3-5- 

 septate, 17-21 X 6-8 fx. 



On trees, Louisiana and Texas. 



29. Arthonia impolita (Ehrh.) Borr., in Hook. & Sowerby, Eng. Bot. 1:2692. f. 1. 



1831. 

 Lichen impolitus Ehrh., Plant. Crypt. 274. 1793. A. pruinosa Ach. A. impolita 



var. chiodectonoides Tuck. 

 Superficial thallus thick, ashy white, chinky, rough and crumbling; apothecia 

 minute to small, 0.2-0.9 mm. across, partly immersed to adnate, often clustered, 

 nearly round to irregular, the disk flat, brown to blackish, and whitish pruinose; 

 tinged pale yellowish within; asci pyriform; spores hyaline, oblong-ovoid, 3-5- 

 septate, 12-18 X 5-7 [x. 



On trees, Washington and California. 



