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

Life habit: lichenized Thallus: crustose, almost powdery to irregularly granulose, areolate or rarely coralloid and rarely with slightly effigurate marginal areoles, gelatinous when wet surface: black, rarely pruinose, smooth, rough or warty anatomy: ecorticate, small-celled, paraplectenchymatous photobiont: primary one a chroococcoid cyanobacterium, secondary photobiont absent Ascomata: apothecial, orbicular, usually laminal or submarginal on areoles or isolated, semi-immersed, adnate, sessile to stalked, with flat to bulging, persisting thalloid rim ontogeny: hemiangiocarpous, ascogonia arising in a spheroid tangle of generative hyphae beneath the thallus surface proper exciple: lacking or very thin, sometimes apically distinctly widened, hyaline, IKI- epihymenium: pale yellow, yellowish brown, reddish brown, blackish blue green or hyaline, K-, HNO3- or emerald green hymenium: hyaline, IKI+ blue or rarely IKI-; hypothecium: hyaline, IKI+ blue or IKI-, usually extended downwards as a stipe asci: subclavate, prototunicate, thin walled, IKI-, 8(-24)-spored ascospores: simple, hyaline, ellipsoid to broad ellipsoid, 5-20 x 3-10 µm, thin walled Conidiomata: pycnidial, laminal, immersed, pyriform, broad ellipsoid or globose; conidiophores: simple, cells elongated conidia: ellipsoid to subglobose, c. 2.5-4 x 1-2 µm, acrogenous Secondary metabolites: none detected Geography: world-wide, common in arid, semi-arid to warm temperate regions Substrate: on various kinds of rock, occasionally on thin soil crusts. Notes: The genus Psorotichia is in urgent need of a thorough revision. Current synonyms include: Collemopsis Nyl. ex Cromb. [J. Bot. London 12: 332 (1874)] and probably Pyrenocarpon Trevis. [Riv. Acc. Padua 3: 49 (1855)]. Apothecial characters including ascoma ontogeny are mandatory for separation from other genera and species determination. Nomenclatural problems connected to similar genera such as Thelochroa A. Massal. and Pyrenocarpon Trevis. are discussed by Jørgensen and Henssen (1990b). However, the question whether these two genera should be treated separately from Psorotichia has not yet been clarified. Lemmopsis, Porocyphus and Pyrenopsis are similar to Psorotichia in thallus growth form and anatomy. In Lemmopsis the proper exciple is distinctly thickened, the thalline margin soon recedes and the hypothecium is not elongated as a stipe. Porocyphus differs in having a proper and thalline exciple of roughly equal widths, having a different type of ascoma ontogeny (pycnoascocarps), possessing a comparably high hymenium and having elongated asci with a very thin wall that often bulges when mature spores are present. Pyrenopsis differs in its reddish sheath around the photobiont cells, in its ascoma ontogeny (pycnoascocarps) and its relatively thick-walled, narrowly clavate asci. Psorotichia segregata Nyl. ex Hasse from southern California is a species of Lempholemma and P. squamulosa Zahlbr., also from southern California, is a member of the genus Gloeoheppia.