Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Life habit: lichenized Thallus: squamulose, crustose or peltate; margin: appressed or raised upper surface: olive, brownish, gray, or blackish, plane to deeply concave, smooth, corrugate or cracked cortex: when present composed of predominantly anticlinally oriented hyphae; cells: cylindrical, globose or isodiametric medulla: normally not separated from the algal layer, primarily composed of anticlinally arranged hyphae photobiont: primary one a filamentous, heterocyst-containing cyanobacterium (Syctonema-like), secondary photobiont absent lower surface: paler than upper surface, attached to substrate by numerous rhizoidal hyphae Ascomata: apothecial, immersed ontogeny: developing from a hyphal web of generative tissue with numerous ascogonia; disc: red or red-brown, urceolate, flat or slightly convex; exciple: sometimes present, then 20-60 µm thick; hymenium: 100-195 µm high; paraphyses: well developed, short-celled at the base, slightly branched in the upper part with characteristically enlarged top cells in older material; subhymenium: 10-60 µm asci: prototunicate, cylindrical to obovoid, 70-170 x 15-30 µm, (4-)8-spored ascospores: simple, frequently with a central plasma-bridge, often mistaken as a central septum, ellipsoid to fusiform, 14-32 x 4.5-13 µm Conidiomata: pycnidial, immersed, solitary, simple to cerebriform in shape, 190-280 µm tall and 150-330 µm wide conidia: simple, fusiform to bacilliform, terminally produced, hyaline, 2.5-3.5 x 1-1.5 µm Secondary metabolites: none detected Geography: predominately in arid and semi-arid regions of the world, but occurring wherever arid microclimates are found Substrate: acidic or calcareous rocks or soil. Notes: Although he recognized much of the variation used to distinguish the species below, Wetmore (1970) recognized only one species, H. lutosa, which was circumscribed broadly. Heppia occurs in similar habitats to those in which Peltula occurs. Differences in spore number (8/ascus in Heppia and 16-100+/ascus in Peltula) and ascus structure are definitive ways to tell the genera apart.