Slideshow image
Rhizocarpon geminatum Korber
Family: Rhizocarpaceae
[Rhizocarpon concretum Elenk.,  more]
Rhizocarpon geminatum image
Stephen Sharnoff  
Life habit: lichenized, not lichenicolous Thallus: crustose, areolate, verrucose; prothallus: black among the areoles areoles: rounded, flat to more often convex, 0.3-0.8 mm in diam. surface: usually gray, sometimes gray-brown, somewhat pruinose cortex: thin, 5-15 µm thick, overlain with an epinecral layer 5-15 µm thick medulla: white or yellow due to rhizocarpic acid Apothecia: black, adnate or among the areoles, 0.4-0.6(-1) mm in diam. disc: black, flat or becoming convex, dull, epruinose margin: at first +thick, then mostly absent epihymenium: brown to brownish black, 15-25 µm thick, K+ red hymenium: hyaline, 100-140 µm tall; paraphyses: coherent, scarcely branched; hypothecium: brown asci: clavate, 2-spored ascospores: pale green initially, becoming olive-brown to brown, muriform, ellipsoid, (28-)35-60(-67) x (13-)1828(-35) µm, halonate Pycnidia: frequent, black, almost globose, on the prothallus conidia: hyaline, filiform, 8-12 x 0.3-0.6 µm Spot tests: medulla K+ weak yellow or occasionally K+ red, rarely K-, C-, KC-, P+ yellow to red, P- Secondary metabolites: rhizocarpic, stictic and +norstictic acids. Substrate and ecology: in cold and wet regions World distribution: throughout western and northern North America and Greenland, Europe and South America Sonoran distribution: Arizona and southern California. Note: A chemotype with yellow, K-, P- medulla usually has dark brown, small, plane, angular areoles and is restricted to +calciferous rocks in the lowlands may represent a distinct taxon.
Rhizocarpon geminatum image
Stephen Sharnoff  
Rhizocarpon geminatum image
Stephen Sharnoff  
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image
Rhizocarpon geminatum image