Thompson, J. 1984. American Arctic Lichens: The Macrolichens.

Thallus medium-sized, the lobes to 1.5 cm broad, forming rosettes on the substratum; the lobes imbricated and massed; upper side whitish or bluish gray to tan, mottled with black or mainly black, lacking pseudocyphellae, with numerous erect unbranched or rarely slightly branched cylindrical isidia, colored like the surface or tipped with black or all black; lower surface jet black, brown toward the margins, smooth or minutely pitted, lacking rhizines. Upper cortex 18-26 µ; medulla white or partly lavender, 65-240 µ; lower cortex 16-26 µ thick. Apothecia rare, seen only once (Culberson 1965), 3 mm broad, exciple isidiate, the isidia with pyncidia in the tips; spores 8, subglobose to ovoid, 10-13 X 5-8 µ; pycnidia small, immersed in the tips of isidia; conidia straight or slightly curved, 5-10 µ long.

Reactions: medulla K — , C — , KC + red or pink, P— .

Contents: atranorin in upper cortex, alectoronic and a-colatollic acids in the medulla.

This species grows over boulders and less commonly on humus in the tundras. A member of the Beringian Element in the Arctic, its range encompasses Siberia and in North America east to the area of Baker Lake and the mouth of the Back River.