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 Thallus: umbilicate, monophyllus, rarely polyphyllus, pustulate; pustules: raised on upper side, hollow below upper surface: whitish gray or light brown to dark brown, dull or somewhat shiny to strongly areolate or areolate-echinate, with or without isidia upper cortex: paraplectenchymatous medulla: white, variable thickness, decreasing to nearly disappearing when deepening into pustules, composed of two layers; upper layer: arachnoid, loosely arranged composed of leptodermatous hyphae; lower layer: prosoplectenchymatous, composed of pachydermatous hyphae photobiont: primary one a Trebouxia, secondary photobiont absent; forming a continous layer lower cortex: paraplectenchymatous to scleroplenctenchymatous, sometimes with a strongly necrotic lower layer lower surface: smooth to tiny papillose to areolate or strongly areolate, whitish gray or creamy to dark brown or black Ascomata: lecideoid or superlecideoid, sessile to stipitate; disc: flat to undulate, dark brown to black; epithecium: pale brown to dark brown; hymenium: hyaline; paraphyses: simple to slightly branched, apices clavate, pale brown with a dark brown cap; hypothecium: brown asci: clavate, 1-2-spored, with a well developed amyloid cap ascospores: pale to dark brown, muriform, large Secondary metabolites: gyrophoric acid, papulosin, anthraquinone pigments Geography: world-wide with highest diversity in the Northern Hemisphere, mainly temperate Substrate: non-calcareous rocks. Notes: Lasallia differs from the umbilicate genus Umbilicaria in having pustules, that are raised on upper side and hollow below, and in its spores, that are large or very large, consistently muriform and only 1 or 2 per ascus.