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Rhizocarpon alaxensis J.W. Thomson
Family: Rhizocarpaceae
Rhizocarpon alaxensis image
Thompson, J., 1997. American Arctic Lichens: The Microlichens.

Thallus rusty-ochraceous, thin, areolate, the areolae contiguous but not forming a continuous thallus, not radiate, 0.2-0.4 mm thick, the areole to 0.7 mm broad, angular, flat to slightly convex.

Apothecia immersed and level to slightly above thallus level, single and round or more often grouped and then angular with compression, concave; margin black, thick, smooth, shining, persistent; proper exciple dark red-brown; disk black, shining; hypothecium hyaline to brownish; epithecium blue-black; hymenium 37-50 µm, upper part blue; paraphyses 1-3 µm, clavate-tipped, not moniliform, tips darkened; asci broad-clavate; spores biseriate, 2-celled, brown, halonate, 12-15 X 7-7.5 µm.

Reactions: medulla K-, C-, I-, P-; exciple K+ violet; epihymenium I-, K-; hymenium I+ blue.

This species grows on calcareous rocks.  So far it is known only from the Franklin Bluffs on the Sagavanirktok River.  Alaska, a locality used in the construction of the Alaska pipeline as a source of gravel.