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Caloplaca borealis (Vainio) Poelt
Family: Teloschistaceae
Caloplaca borealis image
Stephen Sharnoff  
Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus whitish, thin, smooth to wrinkled, K—. Apothecia dispersed, base narrowed, adnate, 0.2-0.4 mm broad; margin thin, conco-lorous with disk or toward the exterior olive-gray to dark gray; exciple markedly radiate; disk flat to slightly convex, waxy or ocher-yellow or yellow-orange, epruinose; hymenium 60 µm; paraphyses with tips not thickened; spores 8 or less, broadly ellipsoid, the center often broadened, 11-14 X 6.5-8 µm, septum 3.5-5 µm.

This species grows on the bark of Alnus, Sorbus, and Salix. It was known from northern Fenno-scandia and was recently reported from a number of localities in Greenland by Hansen, Poelt, & S0chting (1987). It occurs at Cape Parry, Northwest Territories.

This species is quite similar to some specimens of C. cerirm, but the apothecia are tinier, more closely adnate to the substratum, and the margin is more distinct.