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, areolate to squamulose, often with effigurate or placodioid margin, rarely lobate or subfruticose, gelatinous when wet surface: black or blackish brown, dark olive, rarely light gray pruinose, smooth, furfuraceous, rimose to tessellate, plane or uneven, sometimes granulose or isidiate anatomy: ecorticate, homoiomerous, fan-shaped (i.e. symbionts arranged in vertical rows) or paraplectenchymatous, basally often distinctly paraplectenchymatous with gelatinized cells, rarely with internal cavities photobionts: primary one a usually small celled chroococcoid cyanobacterium with yellowish brown or rarely reddish/purplish gelatinous sheath, secondary photobiont absent Ascomata: apothecioid, laminal, orbicular, semi-immersed to sessile, sometimes with constricted base; margin: usually distinct and prominent, with thin, with a persisting thalloid rim ontogeny: hemiangiocarpous, pycnoascocarps with ascogonia beneath pycnidia or ascogonia free or in a spheroid tangle of generative hyphae exciple: hyaline or apically becoming faintly yellowish brown epihymenium: yellowish brown or pale hymenium: hyaline, often divied by intrusions; hypothecium: hyaline asci: prototunicate, wall uniform but relatively thick, not amyloid but with thick amyloid outer coat (hymenial gelatin), 8-24-spored ascospores: hyaline, simple, globose to subglobose or ellipsoid to broadly ellipsoid; 4-18 x 4-10 µm; wall: thin but sometime thick with age, hyaline Conidiomata: pycnidial, laminal, immersed to sessile; wall: simple to convoluted; conidiophores: simple, with elongated cells conidia: ellipsoid, 3-5 x 1-1.5 µm, acrogenous Secondary metabolites: none detected Geography: world-wide in arid to semi-humid regions Substrate: on various kinds of rocks. Notes: The genus is in need of thorough revision. It exhibits substantial variability in thallus growth form, thallus anatomy, ascospore size and number, and ascoma ontogeny, as well as ecological preferences. Therefore, genus boundaries are hard to define and separation from other crustose genera in the Lichinaceae is difficult. Currently the following are considered generic synonyms: Enchylium A. Massal. [Flora 39: 213 (1856)] and Forssellia Zahlbr. [in Engler and Prantl, Nat. Pfl.fam., 1(1): 161 (1906)].