48 4. PYRENULACEAE [ 15. Arthopyrenia 



hemispherical with papillate ostiole, brownish black to black; spores 1 -septate, 

 oblong-ellipsoid, somewhat constricted at the septum, 32-60 X 14-21 /*, uniseri- 

 ately or obliquely uniseriately arranged. 

 On trees, Minnesota. 



9. Arthopyrenia alba (Schrad.) Zahlbr., Cat. Lich. Univ. 1:315. 1922. 



Verrucaria alba Schrad., Spic. Fl. Germ. 1:109. 1794. Pyrenula gemmata (Ach.) 

 Naeg. A. gemmata (Ach.) Mass. 



Thallus usually imbedded, indicated at the surface by a moderately wide- 

 spread whitish to ashy gray area, superficial portion very thin when present, 

 smooth or somewhat powdery; perithecia small to middle-sized, 0.3-0.65 mm. 

 across, the wall dimidiate, superficial portion depressed-hemispherical, black, the 

 ostiole minute, not always visible; spores 1 -septate, ellipsoid, 12-22 X 7-13 /i, 

 uniseriately arranged. 



On trees, from New England to Florida and westward to Illinois, Minnesota, 

 and Washington. 



10. Arthopyrenia analepta (Ach.) Mass., Ric. Lich. 165. 1852. 

 Lichen analeptus Ach., Lich. Suec. 15. 1798. 



Thallus thin, smooth to obscurely scurfy, greenish gray to olivaceous, some- 

 times disappearing; apothecia minute to small, 0.2-0.5 mm. across, partly im- 

 mersed, black, dimidiate, the superficial portion subcorneal; the ostiole indicated 

 by a whitish area; asci cylindrical; spores ellipsoid, 1 -septate, constricted, one 

 cell larger, 16-25X6-8/*, irregularly arranged. 



On trees, Santa Cruz Peninsula, California. 



11. Arthopyrenia leucochlora Mull. Arg., Flora 66:287. 1883. 



Thallus greenish to ashy white, thin, smooth, or becoming chinky; apothecia 

 minute, 0.2-0.5 mm. across, hemispherical, black and shining, the apex finally per- 

 tuse, the ostiole minute, sometimes indicated by a whitish area, dimidiate, the 

 basal portion immersed in a thallus; asci broadly clavate; spores ovoid-ellipsoid, 

 1 -septate, 14-21 X 5-7 p, irregularly arranged or roughly biseriate. 



On trees, Massachusetts and Ohio. 



12. Arthopyrenia conoidea (E. Fries) Zahlbr., in E. & P., Nat. Pfl. 1:65. 1907. 

 Verrucaria conoidea E. Fries, Lich. Eur. 432. 1831. 



Thallus a whitish or minutely powdery crust, or absent and indicated only by 

 an ashy or pinkish coloration of the substratum; perithecia small to middle-sized, 

 0.3-0.7 mm. across, partly immersed, superficial portion convex, black, the wall 

 dimidiate, the ostiole minute, rarely visible; spores 1 -septate, oblong-ellipsoid, 

 13-20 X 8-10 //-, uniseriately arranged. 



On calcareous rocks, Minnesota. 



13. Arthopyrenia rhyponta (Ach.) Mass., Ric. Lich. 166. 1852. 



Verrucaria rhyponta Ach., Vet. Akad. Nya Handl. 150. 1809. Pyrenula rhy- 

 ponta (Ach.) Trevis. 



Thallus rudimentary, the imbedded portion indicated by a moderately wide- 

 spread, brownish black coloration; perithecia small, 0.25-0.3 mm. across, super- 

 ficial portion subhemispherical, black; spores 3-septate, oblong-ellipsoid, 18-24 X 

 6-8/*. 



On trees, Massachusetts. (Not certainly algicolous.) 



14. Arthopyrenia prospersella (Nyl.) Zahlbr., Cat. Lich. Univ. 1:288. 1921. 

 Verrucaria prospersella Nyl., Lich. Jap. 108, 109. 1890. 



Thallus very thin, dull, smooth, greenish gray to whitish, usually tinged rose- 

 colored; apothecia minute, 0.1-0.2 mm. across, semi-immersed, black and conical, 

 dimidiate, the ostiole minute, rarely visible; hyaline within; spores oblong- 

 ellipsoid, 1-2-septate, one cell slightly larger, 12-18 X 5-5.5 /t, irregularly arranged. 



On rocks, northern Illinois. 



