23. Pyrenula] 4. PYRENULACEAE 57 



D. Thallus an ashy coloration 2. P. farrea 



C. Thallus very thin but distinct 



D. Thallus dull to bright orange 6. P. cerina 



D. Thallus ashy or greenish brown to brown 7. P. Herrei 



B. Perithecia larger, rarely less than 0.4 mm. across 



C. Thallus commonly indicated by a coloration of the substratum 



D. Thallus a greenish or grayish brown coloration . . . 4. P. mamillana 

 D. Thallus a grayish or yellowish white coloration . . . .3. P. laevigata 



C. Thallus very thin, but distinct, greenish gray to grayish brown . 5. P. nitida 

 A. Spores 4-7-septate 2. P. farrea pluriloculata 



1. Pyrenula aspistea (Afz.) Ach., Ges. Naturf. Freund. Mag. 6:17. pi. 2, f. 18. 



1814. 



Vermcaria aspistea Afz., in Ach., Meth. Lich. 121. 1803. 



Thallus rudimentary, the superficial portion thin, sometimes absent, the im- 

 bedded portion indicated at the surface by a whitish or yellowish area; perithecia 

 minute to small, 0.2-0.35 mm. across, partly immersed, sometimes clustered or 

 conglomerate, the superficial portion subhemispherical, becoming black, the ostiole 

 minute, rarely visible, the wall very thin, complete; spores 3-septate, ellipsoid, 

 20-28 X 8-12 ix. 



On trees, Massachusetts, Delaware, and Florida. 



2. Pyrenula farrea (Ach.) Branth. & Rostr., Bot. Tidss. 3:260. 1869. 



Verrucaria farrea Ach., Meth. Lich. 115. 1803. P. leucoplaca (Wallr.) Koerb. 



Thallus ashy or whitish, rudimentary, the superficial portion smooth, very thin, 

 often disappearing, the imbedded portion indicated at the surface by an ashy colora- 

 tion; perithecia minute to small, 0.15-0.35 mm. across, the superficial portion hemi- 

 spherical, becoming depressed, black, the ostiole rarely visible, the wall very thin, 

 complete; spores ellipsoid or pointed-ellipsoid, 3-septate, 14-25X5-9/*. (Plate 

 2 a.) 



On trees, New England, New York, arid westward to Iowa and Minnesota. 

 var. pluriloculata (Fink) Zahlbr., Cat. Lich. Univ. 1:430. 1922. 



P. leucoplaca var. pluriloculata Fink, Minn. Bot. Stud. 2:709. 1902. 



Perithecia somewhat larger than in the species, 0.2-0.45 mm. across; spores 

 4-7-septate. 



On trees, Minnesota. 



3. Pyrenula laevigata (Pers.) Arm, Flora 68:158. 1885. 



Verrucaria laevigata Pers., Ann. Wet. Ges. 2:11. 1811. P. glabrata (Ach.) 

 Mass. 



Thallus rudimentary, the superficial portion sometimes absent and the imbedded 

 portion indicated at the surface as a dull grayish or yellowish white coloration ; 

 perithecia middle-sized to large, 0.4-0.8 mm. across, the superficial portion hemi- 

 spherical to conical, black, the ostiole minute, visible, usually indicated by a 

 whitish area, the wall very thin, complete; spores ellipsoid, 3-septate, 18-25 X 

 6-9 ;u. 



On trees, from New England to Florida and westward to Louisiana and Iowa, 

 recurring in Washington. 



4. Pyrenula mamillana (Ach.) Trev., Conspect. Verruc. 13. 1860. 

 Verrucaria mamillana Ach., Meth. Lich. 120. pi. 3, f. 2. 1803. P. mamillana var. 



santensis (Nyl.) Trev. P. santensis (Nyl.) Mull. Arg. 



Thallus rudimentary, often bordered by a black hypothallus, the superficial 

 portion sometimes absent and the imbedded portion indicated at the surface as a 

 greenish or grayish brown coloration; perithecia middle-sized to large, 0.35-1 mm. 

 across, the superficial portion subhemispherical, becoming depressed, black, the 

 ostiole papillate, the wall dimidiate; spores ellipsoid to ovoid, 3-septate, 12-20 X 

 7-8.5 fi. 



On trees, from South Carolina to Florida and westward to Texas. 



