Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Life habit: lichenicolous, often gall-inducing, usually commensalistic, non-lichenized Ascomata: stromatic, single, more rarely grouped, generally rounded, immersed to prominent, flattened to strongly convex, reddish brown, dark brown or black, in most species reaching more than 1 mm diam.; surface mat to shiny, smooth to warted; often inducing the formation of galls by deforming the host thallus; galls sometimes with a thalline pseudo-margin (host tissue surrounding the Plectocarpon hymenium) stroma: multilocular, the hymenium usually divided in several loculi separated by sterile stromatic tissue; sterile stromatic tissue brown to blackish or reddish, often lighter in the middle part, often with characteristic pigments hymenium: hyaline to brownish, I+ red or I+ blue, entirely filling the loculi; hymenial gel K/I+ blue, epihymenium hyaline, brownish to reddish, I+ red or blue paraphyses: branched or anastomosing, end cells enlarged or not asci: Opegrapha type, clavate, wall K/I-, except for an apical K/I+ blue ring, 2-8-spored ascospores: hyaline, smooth, oblong or ellipsoid to fusiform, 2-6(-7)-septate, often slightly constricted at the septa; perispore at first hyaline, becoming sometimes brown at maturity with brown granules appearing on the ascospore wall (supposedly resulting from a change in the perispore) Pycnidia: known in some species, immersed, intermixed with the ascomatal loculi and indistinguishable from them externally; microconidia bacilliform, aseptate, hyaline; macroconidia bacilliform, 1-septate, hyaline, known only from one species (P. nashii) Geography: cosmopolitan Substrate: thallus of macrolichens (Brodoa, Bunodophoron, Cladonia, Lobaria, Lobarina, Melanohalea, Nephroma, Niebla, Peltigera, Pseudocyphellaria, Sticta, Usnea), many species on Lobariaceae.