Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: foliose, approximately circular in outline (disintegrating into irregular groups of lobes with age), small-medium-sized, 10-20 cm in diam., adnate lobes: +flattened and elongate (1-1.5 cm wide and up to 4 cm long), often dichotomously branched, imbricate or separate; tips: rounded to subtruncate, often ascending and undulate upper surface: gray or blue-gray to brown when dry, bluish or blackish gray when wet, smooth or cracked, dull or shiny, often pruinose marginally medulla: white, with +loosely interwoven hyphae photobiont: Nostoc lower surface: white near margin, with reticulate flattened abruptly darkening veins, rhizinate rhizines: dark brown to black, irregular, simple to bushy branched Apothecia: +round to oblong, saddle-shaped becoming tubular, on short, ascending lobes, up to 8 mm in diam.; margin: smooth to crenulate disc: flat, dark brown to black, smooth ascospores: colorless to pale brown, acicular, 3(-5) septate, 50-80 x 3-5 µm Spot tests: all negative Secondary metabolites: tenuiorin, methyl gyrophate, gyrophoric acid, hopane-6α,22-diol, 15α-acetoxyhopan-22-ol and unidentified terpenoids. Substrate and ecology: on soil among and over mosses World distribution: temperate and boreal regions of North America, Europe and Asia Sonoran distribution: frequent, in Arizona (2000 -4070 m) and Chihuahua. Notes: If fertile, its ±blackish and (when older) tubular apothecia make P. neckeri rather easy to distinguish. In sterile thalli, its often pruinose margins and its abruptly darkening, somewhat diffuse veining pattern are diagnostic as well as its chemistry.