Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, typically continuous, sometimes scurfy, usually distinctly rimose in thick specimens, even becoming tuberculate, thin to thick, 2-4 cm in diam.; prothallus: white, fibrous, along margin (in thin specimens also elsewhere) surface: pale gray, sometimes with a brownish tinge (in herbarium specimens only?), esorediate medulla: not evident to distinct and white; photobiont: green, up to 18 µm in diam. Apothecia: 1(-2) immersed in thalline verrucae, up to 0.6(-0.8) mm in diam. disc: black or brownish black, plane, usually heavily white pruinose epihymenium: pale yellow to brown, up to 20 µm thick hymenium: up to 210 µm tall; paraphyses: filiform, slender, simple to somewhat branched and anastomosed hypothecium and subhymenium: hyaline to pale brown, together up to 24 µm thick asci: broadly clavate to cylindrical-ellipsoid, with thickened, I- apex, up to 187 x 55 µm, 1-spored (rarely 2-spored) ascospores: hyaline, markedly muriform, cylindrical elongate to narrowly ellipsoid, usually not (but sometimes indistinctly) apiculate, (67-)80142(-180) x 19-45(-53) µm Pycnidia: not seen Spot tests: K+ yellow turning orange-red, C-, KC-, P+ yellow to orange Secondary metabolites: norstictic acid (major), connorstictic acid (usually a trace). Substrate and ecology: on tree bark (Quercus, Lithocarpus) World distribution: endemic to the coastal lowlands of western North America Sonoran distribution: southwestern California (mainland and Channel Islands) at 100-300 m. Notes: The indicated spore sizes are based on specimens throughout the range of the species. Specimens of P. speirea from near the type locality in SW British Columbia (Vancouver Island, Saanich Peninsula) have somewhat larger spores than specimens from the Sonoran region. Phlyctis speirea is distinct from P. agelaea (Ach.) Flot., which has 2(-4) spored asci with short (up to 90 µm long), broadly ellipsoid, distinctly apiculate spores. I have seen no material of P. agelaea from the Sonoran region (but see however Fink 1935).