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Rhizocarpon obscuratum (Ach.) A. Massal.
Family: Rhizocarpaceae
Rhizocarpon obscuratum image
Stephen Sharnoff  
Life habit: lichenized, not lichenicolous Thallus: crustose, warty-rimose to areolate, up to 10 cm in diam.; prothallus: usually distinct, black, sometimes fimbriate areoles: 0.2-0.5(-1) mm in diam., flat to weakly or highly convex, dull, angular to +round surface: brown-gray to gray, dark gray or dark brown, or sometimes white Apothecia: not much projecting above thallus, round, Lecidea like, 0.2-0.6(-1) mm in diam. disc: often +umbonate and roughened, mostly flat, rarely convex, epruinose or rarely +ochraceous pruinose margin: black or appearing pseudolecanorine, thick and persistent or more often thin or disappearing exciple: K-, without crystals epihymenium: red-brown or olivaceous, K-, without crystals hymenium: hyaline, 70-130 µm tall ascospores: hyaline initially but becoming brown, with few to moderately numerous cells, with 3-4 transverse septa and 1 longitudinal septum, 2033(-36) x 9-16 µm Spot tests: medulla I-; thallus K+ yellow or red, C-, KC-, P+ yellow or orange or P- Secondary metabolites: stictic or norstictic acids, or none detected. Substrate and ecology: on smooth, dry, siliceous rocks. World distribution: Europe, North America (mostly northern and eastern), South America and Africa Sonoran distribution: Arizona and Chihuahua. Notes: Rhizocarpon obscuratum is a variable species. One specimen was previously reported as R. oederi (Weber) Körb.
Rhizocarpon obscuratum image
Stephen Sharnoff  
Rhizocarpon obscuratum image
Stephen Sharnoff  
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image
Rhizocarpon obscuratum image