Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Habit: lichenized Thallus: crustose, not lobate, ±pruinose cortex: absent, but with a 15-20 µm thick epinecral layer photobiont: primary one a chlorococcoid green alga, secondary one absent; algal layer: 50-80 µm thick medulla: with hyphae extending into the substrate Ascomata: apothecial, aspicilioid, zeorine, with a hemiangiocarpous ontogeny, deeply immersed in thalline verrucae, with a thalline exciple exciple: thin but well delimited, hyaline or pale straw colored, composed of strongly conglutinated, vertically aligned, short-celled, highly reticulated hyphae covering the whole hymenium and continuing into the basal part of the apothecium, thus forming a cupulate exciple epihymenium: brownish green, N+ bright green and K+ green hymenium: colorless, I+ blue (±yellowbrown according to Lumbsch, et al. ), K/I+ blue; paraphysoids: richly branched and anastomosing, not swollen at apices, strongly conglutinate, septate, forming a kind of epithecial tissue; hypothecium: not distinguishable; ascogenous layer: hyaline, c. 20 µm thick asci: clavate or cylindrical-clavate, thin-walled except towards the apex (thickwalled according to Lumbsch et al. 1994), with a K/I pale apical dome, the outer wall I+ faint blue, (4-)8-spored ascospores: hyaline, simple, globose to broady ellipsoid; wall: uniformly thick, 2-layered Conidiomata: pycnidial, immersed in the thallus, unilocular; conidiophores: type III of Vobis (1980) conidia: filiform, up to 12 µm long Secondary metabolites: no lichen metabolites found by TLC or HPLC Geography: Europe, Macaronesia, Asia, northern Africa, and North and South America Substrate: on soil or more frequently mosses and plant remains, or sometimes wood or bark, circumboreal-montane to alpine. Notes: Megaspora is an aspicilioid segregate from Lecanora, characterized by its large, thick-walled spores, thin, numerous, anastomosing paraphyses, and growth on non-rock substrates. It differs from Aspicilia especially by its thallus lacking a cortex, its apothecia being zeorine with a well developed, cupular true exciple, by having reticulately branched and non-moniliform paraphysoids, by having hemi-amyloid (rather than non-amyloid) hymenial gel, by having thick-walled, two-layered ascospores, and by having type III (rather than type IV) conidiophores. In addition, the conidia of Megaspora are never bacilliform, and the apothecial ontogeny is more distinctly hemi-angiocarpous. Megaspora is similar to some Pertusariae (e.g. P. saximontana) in several ways, but differs by its hymenial gel being hemi-amyloid (rather than non-amyloid in Pertusaria), by only pale amyloid asci (versus K/I-) that lack an ocular chamber; and by having type III (rather than type IV) conidiophores and in usually having smaller spores. The two varieties keyed below are recognized as separate species by some authors (Ozenda and Clauzade, 1970), but we accept the use of varieties here, pending the recognition of better characters to separate them. As far as we know, no molecular investigations has been attempted, and such studies might help resolve whether specific status is merited. The var. verrucosa is not currently known from the Sonoran region but may be found in our very limited alpine areas, as it is known from Colorado.