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Acarospora hospitans H. Magn.
Family: Acarosporaceae
Acarospora hospitans image
Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus squamulose or areolate, dispersed or contiguous, making small areas or lines over or between the areolae of other crus-tose lichens, the areolae to 1.5 mm broad, reddish brown, dull or slightly shining, nearly convex; lower side dark brown to black. Apothecia usually 2-5 per squamule; exciple 15-20 µm; disk to 0.5 mm broad, slightly or deeply impressed, of same color as thallus and with thick thalloid border; hypothecium hyaline; epihymenium red-brown; hymenium 60-90 µm, 1+ blue; paraphyses 2 µm, not capitate; spores numerous, broadly ellipsoid, 3-4 x 2-2.5 µm.

Reactions: K—, C —, P—.

This species grows upon other lichens on either granitic or slightly calciferous rocks, principally along stream margins at the water's edge. It is known from Siberia, northern and alpine Europe, Iceland, and eastern Greenland but has not yet been found in the American Arctic.

Another species also growing over other crus-tose lichens, especially Aspicilia cinerea, is Acarospora insignis Magnusson. This likewise occurs in Europe and Greenland but has not yet been found in the American Arctic. It differs mainly in the C+ red reaction of the thallus.