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Staurothele discedens (Nyl.) Zahlbr.
Family: Verrucariaceae
Staurothele discedens image
Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus of scattered dark gray-green to blackish areolae or granules covered with calcareous nodules or crystals giving a gray appearance; thallus covering the perithecia with Pertusaria-like globular verrucae, constricted at base. Perithecia adnate on substratum, subcompound with the involucrellum dark at the tip and embedded in a thalloid coating; exciple 100 µm thick, dark with a broadening at the base to cup the base of the major part of the exciple; some old perithecia losing the thalloid coating and appearing black; hymenium 1+ blue; spores 8, hyaline and becoming pale brown, muriform with numerous cells; 37-45 x 15-23 µm.

This species grows on calcareous rocks which are at least periodically irrigated, including those in the spray area of waterfalls. It was described from Port Clarence, Alaska, and recently rediscovered by Barbara Murray at several localities in Alaska. It was also collected by C. D. Bird and G. D. Benson in the Mackenzie Mountains, Northwest Territories.