84 14. ARTHONIACEAE [47. Arthonia 



16. Arthonia caribaea (Ach.) Mass., Mem. Lich. 114. f. 149. 1853. 

 Graphis caribaea Ach., Lich. Univ. 272. 1810. 



Superficial thallus thin, ashy white, slightly rough, surrounded by a black line; 

 apothecia minute to small, 0.5 X 0.05-0.15 mm., immersed, dendroid-branched and 

 reaching 1 or 2 mm. long, the disk pale brown to brownish black; hyaline or tinged 

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

 septate, end cells larger, 25-35 X 13-16 /x. 



On trees, Texas. 



Spore measurements of Nylander and Miiller Arg. are 42-50 X 16-22 /u,, and 

 our material is doubtfully included. 



17. Arthonia rubella (Fee) Nyl., Mem. Soc. Sci. Nat. Cherb. 4:89. 1856. 

 Graphis rubella Fee, Essai Crypt. 43,44. pi. 11, f. 5. 1824. 



Superficial thallus thin, greenish gray to ashy white, rough, becoming granular 

 or chinky; apothecia minute to small, 0.1-0.2 X 0.5-1.5 mm., immersed, elongated 

 and branched, the disk flat, reddish brown; tinged faintly brownish within; asci 

 pyriform; spores hyaline, ovoid-ellipsoid, 3-5-septate, end cells larger, 25-34 X 

 10-14 fi. 



On trees, from South Carolina to Florida, and westward to Alabama, Louisiana, 

 and Texas. Spores large and like those of Arthothelium. 



18. Arthonia subrubella Nyl, Act. Soc. Sci. Fenn. 7:479,480. 1863. 

 Superficial thallus grayish white, of moderate thickness, becoming rough and 



chinky; apothecia minute, 0.07-0.15 mm. across, adnate, irregular, elongated and 

 often much-branched, the disk flat, light and darker brown; hypothecium tinged 

 brown; hymenium hyaline; asci ovoid; spores hyaline, ellipsoid to slightly ovoid- 

 ellipsoid, sometimes curved, 5-7-septate, one or both end cells larger, 44-50 X 

 16-18 fi. 



On trees, Florida. Thallus scarcely visible according to Nylander, and our 

 plant may have to be referred elsewhere. 



19. Arthonia polygramma Nyl., Act. Soc. Sci. Fenn. 7:480. 1863. 

 Superficial thallus thin, ashy white, rough, becoming powdery; apothecia minute 



to small, 0.1-0.3 mm. across, often elongated to 0.8 mm., somewhat immersed, ir- 

 regular to oblong, sometimes stellate, scattered or clustered, the disk flat, brownish 

 black and thinly white-pruinose ; tinged pale yellowish within ; asci pyriform ; spores 

 hyaline, ovoid-ellipsoid, 3-5-septate, 16-22 X 5-7.5 /a. 

 On trees, Florida and southern California. 



20. Arthonia varia (Ach.) Nyl., Mem. Soc. Sci. Nat. Cherb. 5:132. 1857. 

 Opegrapha abnormis var. varia Ach., Lich. Univ. 259. 1810. 



Superficial thallus thin, ashy, often absent; apothecia minute, 0.09-0.13 mm/ 

 across, often elongated to 0.5 mm., round to irregular or oblong, the disk flat, dark 

 brown to black; hyaline within; asci globose-ovoid; spores hyaline, ovoid-ellipsoid, 

 3-septate, one end cell larger, 12-17 X 4.5-6 /x. 



On trees, Florida. 



21. Arthonia erubescens Willey, Int. Stud. Lich. Suppl. 53. 1887. 

 Superficial thallus thin, greenish gray, smooth; apothecia minute, 0.05-0.15 mm. 



across, immersed to subadnate, round to irregular, or lobed, the disk flat, reddish 

 brown; hyaline or tinged pale yellowish within; spores hyaline, oblong-ovoid, 3- 

 septate, 13-18 X 5-7.5/*. 

 On trees, Texas. 



22. Arthonia perminuta Willey, Syn. Arth. 14. 1890. 



Thallus very thin to thin, widespread, pale yellow; apothecia minute, 0.08-0.15 

 mm. across, adnate, round to irregular or rarely becoming oblong, the disk flat, 

 dark brown to black, lighter when wet; hypothecium hyaline; spores oblong-fusi- 

 form, 5-6-septate, 18-23 X 4-5.5 it. 



On trees, Florida. 



