47. Arthonia] 14. ARTHONIACEAE 79 



irregular, sometimes branched, single or united in a stroma, the exciple absent or 

 very poorly developed; paraphyses branched and interwoven. 

 The algal hosts are Palmella, Trentepohlia, and Phyllactidium. 



A. Spores transversely 1-several-septate 47. Arthonia 



A. Spores transversely and longitudinally septate 48. Arthothelixtm 



47. Arthonia Ach., Neu. Journ. Schrad. 1 3 :3. pi. 4. 1806. 



Thallus rudimentary, without cortical tissues, partly or wholly within the sub- 

 stratum, appearing as a grayish coloration of the bark, becoming crustose to rarely 

 areolate; apothecia minute to small, round to irregular, linear or star-shaped, more 

 or less immersed to adnate, the disk flat to slightly convex, brownish black to black 

 or rarely reddish brown or grayish pruinose; hypothecium rarely hyaline to more 

 commonly brownish to dark brown; hymenium hyaline to brown; paraphyses 

 usually branched; asci pyriform; spores 8, hyaline to rarely brownish, oblong-ovoid 

 or ovoid-ellipsoid, 1-3 or rarely more septate, the cells cylindrical, often unequal. 



The algal hosts are Trentepohlia and Palmella. 



A. Apothecia colored, but not black 

 B. Spores 1- or rarely 2-septate 



C. Disk reddish brown to darker 



D. Spores 1-septate, cells equal 1. A. carneorufa 



D. Spores 1-2 -septate, one cell larger 2. A. incarnata 



C. Disk dark brown or brownish gray to black or rarely yellowish 

 D. Disk dark brown or brownish gray to black 

 E. Thallus thin, smooth, greenish gray or ashy 



F. Spores 1-septate, 10-15 X 4-5 /x 3. A. lurida 



F. Spores 1-septate, 16-20 X 5.5-7.5 /* 4. A. floridana 



E. Thallus thicker, rough, creamy to ashy white . 6. A. lecanactidea 



D. Disk yellowish 5. A. ochrodiscodes 



B. Spores 1-3 or more septate 



C. Disk yellow, red, flesh-colored to reddish brown 

 D. Disk yellow, flesh-colored, or light brown 

 E. Spores 1-3-septate 



F. Apothecia linear and more or less branched . . . 7. A. impallens 

 F. Apothecia irregular and often elongated . . . 8. A. ochrolutea 

 E. Spores more than 3 -septate 



F. Spores 4-5-septate 9. A. gyalectoides 



F. Spores 7-11-septate 10. A. fissurina 



D. Disk red or reddish brown or darker 



E. Spores 5-7-septate 11. A.pyrrhula 



E. Spores 3-5-septate 



F. Disk with an ochre-red margin 13. A. ochrocincta 



F. Disk without a margin 



G. Disk reddish brown to black or pruinose . . 12. A. gregaria 



G. Disk violet-brown 12. A. gregaria adspersa 



C. Disk reddish brown to black 

 D. Spores 3-7-septate 



E. Spores large, 44-50 ai in length 18. A.subrubella 



E. Spores less than 30 ai in length 

 F. Thallus whitish or ashy white 



G. Apothecia irregular and often elongated . . 24. A. platyspilea 

 G. Apothecia elongated, curved and 



rarely branched 14. A. Ravenelii 



F. Thallus pale yellow 22. A. perminuta 



D. Spores 3-5-septate 

 E. Spores 3-5-septate 



F. Spores 25-35 ai in length 



G. Thallus becoming granular or chinky .... 17. A. rubella 

 G. Thallus slightly rough, surrounded 



by a black line 16. A. caribaea 



F. Spores less than 25 n in length 

 G. Apothecia irregular to oblong 



H. Spores 12-15 n in length 23. A.pyrrhuliza 



