Slideshow image
Rhizocarpon norvegicum Rasanen
Family: Rhizocarpaceae
Rhizocarpon norvegicum image
Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus areolate, the areolae dispersed or contiguous, to 0.7 mm broad, angular to roundish, usually very convex; yellow to bright yellow, dull or glossy; hypothallus black, present or only under the areolae. Apothecia to 0.7 mm broad, rounded-angular to round, slightly to strongly convex; margin thin, disappearing; exciple reddish brown, radiate; hypothecium brown; epithecium dark, with granules; hymenium 60-90 µm, hyaline or faintly reddish brown, upper part dark reddish brown; paraphyses capitate, tips dark; spores 8, 1-septate, dark, with halo, 9-15 x 6-7 µm.

Reactions: medulla K—, P—, or P+ yellow, 1+ dark blue; exciple K+ reddish violet; upper part of hymenium K— or K+ reddish violet.

Contents: rhizocarpic acid with or without psoromic acid.

This species grows on schists and slightly calcareous rocks. It is known from Scandinavia and the Alps in Europe, and from Greenland and Siberia, as well as from North America.