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Omphalodiscus krascheninnikovii (Savicz) Schol.
Family: Umbilicariaceae
Omphalodiscus krascheninnikovii image
Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Thallus to 5 cm broad, monophyllus, rigid, umbo with a coarsely granulated crystal covering, with sharp reticulate ridges running to the margins, the ridges weakening toward the margins; upper surface dull (shining in var. dar-rowii in SW United States), ashy to ashy brown or ashy black, pruinose; underside with a dark spot around the umbilicus, dove gray or paler peripherally, the lower cortex nearly smooth or slightly granulose to rimulose; occasionally there may be a few cylindrical simple or branched rhizinae near the margins. Thallus 200-500 µ thick; with upper dead material zone 50-100 µ, a thin upper cortex 18-30 µ thick, a discontinuous algal zone, a very loose medulla, a lower cortex 66-100 µ, scleroplectenchymatous. Apothecia to 3 mm, sessile to substipitate, common; disk flat, black, with central sterile button and many secondary fissures; hypothecium brown, 40-50 µ; hymenium 55-65 µ; paraphyses simple, septate, tips to 3.4 µ; spores 8, simple, hyaline, ellipsoid, 5-7 x 3.8-4 µ.

Reactions: K—, C+ red, KC+ red, P— .

Contents: gyrophoric acid (Krog, 1968).

Growing on acid rocks, this is a circumpolar arctic and alpine species, in North America growing south to California and Arizona in the west and Mt. Kataadn in Maine in the east.