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: crustose, sometimes embedded in substrate and nearly invisible, or smooth or rimose-areolate to bullate areolate, sometimes with radiating marginal areoles, some species very dendroidly arranged upper surface: gray or various shades of brown, smooth upper cortex: lacking or rudimentary, algae often found within upper thallus layers medulla: white photobiont: primary one an alga (Stichococcus), seconddary photobiont absent; cells: irregularly distributed throughout lower cortex: absent hypothallus: present or absent (most North American species) Ascomata: perithecial, simple (without a separate involucrellum) or compound (with darker involucrellum covering the exciple to the base), or subcompound (with a small involucrellum limited to the ostiole region), either embedded in substrate, sessile on the substrate, or within areoles of thicker thalli; apical ostioles: present; periphyses: present; paraphyses: lacking; hymenial gelatin: usually I+ blue in 2-spored species, I+ yellow or red in 8-spored species; hymenium: containing photobiont (Stichococcus mirabilis Lagerheim) which may be spherical or elongate asci: saccate, verrucarioid, without a distinct ocular chamber, 1-(-8)-spored (when 2-spored the distal spore is usually larger than the basal one) ascospores: hyaline or becoming brown, muriform, with many cells Conidiomata: pycnidial, laminal, of Dermatocarpon-type conidia: bacilliform, simple, colorless Secondary metabolites: none detected Geography: widespread in temperate to polar regions wherever open rock surfaces occur; sometimes submerged Substrate: on or in various rocks (including calcareous and siliceous rocks) and made-made substrates (bricks, mortar, etc.).