Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Life habit: lichenized; a number of species lichenicolous (but not known from the Sonoran region) Thallus: crustose to subsquamulose, rimose, areolate, bullate or (slightly) squamulose prothallus: often well developed, (greenish) black, dendritic (especially in high alpine morphodems), rarely white or often inconspicuous or indistinguishable surface: white, ivory, pale to rather dark gray, pale yellow or greenish gray to dark red brown or rusty colored (due to interspersed iron oxides), dull to glossy (due to a thick transparent epinecrotic layer); extremely rarely sorediate, isidia unknown medulla: white, I+ or I- photobiont: primary one a green trebouxioid alga, secondary one absent; cephalodia unknown Ascomata: apothecial, usually sessile (with an often well constricted base), rarely sunken between the areoles, black (discs rarely becoming blackish brown when fully moistened) or with a (bluish gray) pruinose disc; true exciple: usually persistent, with a small greenish or brownish black epihymenioid cortex and an usually unpigmented, opaque medullary part, composed of +radiating hyphae with subglobose to elongated cells, without algae epihymenium: bright green (pigment cinereorufa-green), olive, brown or black hymenium: hyaline, faintly green or very pale brownish violet, I+ blue or (in living material only) I+ reddish brown, 35-90 µm tall; paraphyses: simple or occasionally branched and anastomosing, apical cells usually markedly swollen; conglutinated subhymenium: hyaline or pale bluish green, 20-90 µm thick hypothecium: unpigmented, or pale ochre to dark blackish brown asci: clavate, Lecidea-type, moderately thick-walled, apically thickened, outermost gelatinous layer I+ blue, 8-spored ascospores: hyaline, constantly simple, often pseudodiblastic (due to a central plasma bridge), bacilliform, oblong, slender to broadly ellipsoid (rarely subglobose), smooth, lacking a perispore Coniomata: pycnidial, immersed, with usually lens-shaped to graphidoid ostioles conidia: hyaline, simple, bacilliform to (rarely) filiform Secondary metabolites: p-depsides of the orcinol-type with long aliphatic side-chains, ß-orcinol depsidones, and dibenzofurans Geography: Northern and Southern Hemisphere, often in temperate to cold habitats, preferentially in humid areas, or in semiarid climates Substrate: almost exclusively on acid and (more rarely) on calcareous rocks, rarely on consolidated sandy soil (exceptionally on hard timber, as old railway ties) or on gypsum. Notes: The name Lecidea derives from the Greek lekis (small shield) and eidos (shape), in reference to the appearance of the apothecia. A number of species (e.g. Lecidea atrobrunnea , L. fuscoatra, L. tessellata) are extremely variable. Damaged specimens (especially by snail-feeding) very often occur. Subsequent regeneration leads often to aberrant morphodems. Determination of specimens without well developed ascospores requires prior familiarity with the taxa. In addition to the 100 species of Lecidea s.s., there is quite a number of taxa of unclear taxonomic position described as Lecidea, including many taxa on bark and wood. Species in the latter group occurring in the Sonoran region are keyed ("Lecidea") and described below under B - s. lat (sensu Zahlbruckner). Research beyond the scope of this flora is required to establish proper taxonomic classification of them. The generic description above applies only to Lecidea s.s. (A) Lecidea, sensu stricto

I. Lecidea subg. Lecidea

This subgenus comprises non-alpine, mostly thermophilous species with relatively short conidia and (in freshly collected material), a red brown hymenium and a non-amyloid medulla (see Rambold 1989).

II. Lecidea subg. Rehmiopsis

This subgenus comprises species of temperate and cool, mostly humid climates with relatively long conidia and (in freshly collected material too) I+ blue hymenium (see Rambold 1989). The name Rehmiopsis means "similar to Rhemia" [Rehmia Kremp. = Rhizocarpon] and Müller-Argovensis described Patellaria heterodaxa as similar to Rhemia coeruleoalba in gross morphology.

III. Lecidea subg. Cladopycnidium

This subgenus comprises a few species of temperate and cool (humid as well as arid) climates with relatively long conidia (mean values: 9-13µm) and (in freshly collected material too) I+ blue hymenium and short, bluntly ellipsoid spores with relatively thick (up to c. 1.5µm) spore walls (see Rambold 1989). The name "Cladopycnidium" means "ramified pycnidia", because the pycnidia here do not appear as little dots on the thallus surface, but instead as ramified lines ("graphidoid"), a common character in Lecidea, but usually less conspicuously developed.

(B) Lecidea s.l. (sensu Zahlbruckner)

This is an artificial unit and includes all those taxa of still unclear generic position, that were described as members of the genus Lecidea, as circumscribed by Zahlbruckner and based primarily on the occurrence of hyaline, non-septate spores within lecideine apothecia. Finding a phylogenetically proper placement for the species is a project well beyond the scope of the development of this flora.