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

Thallus: endosubstratic, non-lichenized Apothecia: 0.5-0.6 mm tall, dark brown to black, epruinose stalk: 0.04-0.06 mm in diam., olivaceous brown, occasionally forked; hyphae: periclinally arranged, brown throughout, slightly intertwined, 2-3 µm in diam. capitulum: cup-shaped to obconical, not flattened exciple: brown, formed by 6-9 layers of periclinallly arranged, hyaline (in the inner part) to sclerotized hyphae; hypothecium: hyaline to brown, consisting of periclinally arranged, thin-walled, short-celled hyphae asci: cylindrical, 8-spored, 75-95 x 4-5 µm, strongly but uniformly thickened at the apex, with uniseriate spores ascospores: predominantly 1-septate to rarely 3-septate, elliptical to elongate, brown when mature, 1318 x 5-7 µm; surface: papillate to areolate (but appearing smooth under light microscope), subtly to conspicuously constricted at septa; larger spores with cracks Pycnidia: not seen Spot tests: all parts of the apothecia K-, N-; stalk K-, N- Secondary metabolites: none detected. Substrate and ecology: on bark near the base of dead main stem of a Rhus World distribution: boreal and north temperate zones of North America Sonoran distribution: southern California. Notes: Phaeocalicium curtisii is extremely similar to P. populneum, but differs in having a K- stalk, in the anatomy of the stalk (P. curtisii lacking a layer of hyaline, swollen hyphae at the surface) and in having Rhus rather than Populus as host.