Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus whitish, greenish gray, or bluish gray, thin, sorediate, smooth, or verruculose. Apothecia broadly adnate; margin of same color, disappearing; exciple hyphae radiate, orange, also K+ violet, granular-inspersed; disk flat becoming depressed convex, bare, orange-red; hypothecium hyaline to brownish; epihymenium orange-red, K+ violet; hymenium 65-75 μm, hyaline, upper part inspersed with yellow granules, 1+ blue; paraphyses coherent, not branched, tips not thickened; asci clavate; spores oblong to ellipsoid, 8-12 x 2-4 μm.
Reactions: thallus K+ yellow, C—, P+ red.
Contents: atranorin(in apothecia), fumarprotocetraric acid, especially in the soredia, and an anthraquinone pigment.
This species grows on a variety of trees, including Abies, Picea, Larix, Pseudotsuga, Pinus, and Betula. It occurs in Europe, Greenland, and North America. In the latter, I. M. Brodo informs me that, while fruiting in the West, it also occurs commonly as a sterile lichen in the East, where he has records from New Brunswick, Nova Scotia, Quebec, Newfoundland, Ontario, and Manitoba. Only fruiting specimens are represented in the distribution map.
The collections by J. Vahl on Betula at Tunug-dliarfik in the Julianehaab district were checked by Lynge (1940), who interestingly mentioned that he “would refer this species to Protoblastenia, ” a disposition mentioned also by current authors as a possibility based on the K+ reaction of the epihymenium.