Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Primary thallus: squamulose, persistent; squamules: up to 6 mm long and 4 mm wide, unevenly dentate to crenate-lobate or sinuate, coarsely sorediate (especially under margins), sometimes breaking into masses of soredia podetia: 6-30 (-40) mm tall, 1-2 mm wide, green to whitish gray, unbranched, with trumpet-shaped cups forming at apices; cups: 2-6 mm wide; margins: entire or minutely dentate surface: ecorticate or persistently corticated at the base (sometimes cortex extending up to cup bases); soredia: abundant, farinose, sometimes enlarging, later disintegrating and exposing the white medulla Apothecia: uncommon, brown, up to 1.5 mm diam ascospores: oblong, 8-14 x 3-4.4 micro meter Pycnidia: at cup margins, subglobose, with hyaline gelatin conidia: 7-8 x 1.5-2.5 micro meter Spot tests: K- or K+ dingy yellow to dingy brown, C-, KC-, P+ brick red, UV- Secondary metabolite: fumarprotocetraric acid. Habitat and ecology: on wood, tree trunks, soil or mosses over rocks, usually in deep shade; mainly temperate-boreal World distribution: on all continents Sonoran distribution: Arizona, southern California, Baja California and Chihuahua. Notes: This species is widespread in Arizona but rare elsewhere in the Sonoran Region. Earlier reports from southern California belong either to Cladonia subfimbriata, which has narrower, dentate cups (sometimes cups are missing) and more elongate, whitish podetia, or C. nashii, which has very short podetia with wide cups, like those in C. humilis (see discussion under that species). Cladonia fimbriata is characterized by the green (grayish when exposed so sun), thick, persistent layer of very fine soredia on podetia. The cups are generally symmetrical and often bear fimbriate proliferations on the margin.