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

Thallus: foliose, large, 5-10(-15) cm in diam., adnate lobes: +flattened and elongate (up to 3 cm wide and up to 4 cm long), often dichotomously branched, imbricate or separate; tips: rounded to subtruncate, often ascending and undulate upper surface: brown but with a bluish tinge when dry, deep bluish green to olive green when wet, smooth, dull, thinly scabrid-tomentose with small, erect hairs especially towards margin, without isidia or soredia medulla: white, with +loosely interwoven hyphae photobiont: Nostoc lower surface: whitish or pale tan, +uniformly tomentose, veins and rhizines almost absent, pale interstices few or absent Apothecia: frequent, +round, sessile, marginal, up to 7 mm in diam.; margin: smooth to crenulate disc: flat, red-brown to brown, smooth ascospores: colorless to pale brown, elongate fusiform, 3-5 septate, 55-70 x 5-6 µm Pycnidia: not seen in Sonoran material Spot tests: all negative Secondary metabolites: tenuiorin, methyl gyrophorate, gyrophoric acid and unidentified terpenoids. Substrate and ecology: among mosses over soil in moist habitats at relatively high elevations World distribution: temperate and boreal regions of North America, Europe and Asia Sonoran distribution: infrequent at higher elevations in Arizona. Notes: Thick thalli with erect tomentum at least marginally and a non-veined lower surface characterize P. malacea and help to distuinguish it from e.g. P. elisabethae and P. neckeri, both of which have a glossy non-tomentose upper surface. When moist, it has a characteristic blue-green color.