TYPE. ITALY. “Sui muri di mica-schist, senza cemento e ombreggiati, tra il borgo di Suna, e il villaggio di Cavandòne (Lago Maggiore).” (Anzi 1864); Anzi, L. Lang. exs. n. 402 (M, isotype)
Description. Life form: lichenized fungus.
Thallus epilithic or rarely endolithic, whitish to dark or olive gray, occasionally weakly oxidized orange; surface thin to patchily disappearing, rarely continuous or rimose; prothallus sometimes distinct, black. Vegetative diaspores absent. Photobiont chlorococcoid alga. Ascomata lecideine apothecia, 0.4-1.8(-2.5) mm diam., sessile, abundant; disk red-brown to black, convex, epruinose; margin thin to moderately thick. Exciple cortical zone dark blue-black, internally paler yellow-brown in thin section, K+ crimson; epithecium brown to olive-brown; hymenium hyaline, 80-120(-130) μm high; hypothecium brownish. Asci clavate, Porpidia-type, 8-spored; ascospores oblong, hyaline, simple, 14-17(-20) x 5-9 μm.
Chemistry. K+ yellow, PD+ red; stictic acid with cryptostictic acid sometimes present.
Substrate and Habitat. On siliceous rocks.
Distribution. Asia, Europe, North America, South America (Chile); in North Carolina found in the Blue Ridge ecoregion.
Note. Similar to P. macrocarpa, of which it is sometimes considered a forma (Fryday 2005), and from which it differs in the yellowish, K+ crimson inner exciple (A.M. Fryday, pers. comm. 13.III.2023).
Anzi, M. (1864) Symbola lichenum rariorum vel novorum Italiae superioris. Commentario della societa crittogamologica Italiana 2: 22-28 (original description as Lecidea nigro-cruenta).
Fryday, A.M. (2005) The genus Porpidia in northern and western Europe, with special emphasis on collections from the British Isles. Lichenologist 37(1): 1-35.
Jablonska, A. (2010) The lichen genus Porpidia in Poland III. Herzogia 23: 217–228.