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Rhizocarpon oederi (Weber) Korber
Family: Rhizocarpaceae
[Aspicilia oederi (Ach.) A. Massal.,  more]
Rhizocarpon oederi image
Stephen Sharnoff  

Global occurrence: Eurasia – Europe | Americas – North America (incl Mexico) | Arctic | Antarctic – Southern Subpolar Islands, Subantarctic Islands.  Substrate: rock – siliceous, siliciferous, acidic | rock, stones, pebbles – unspecified.  Life habit: lichenized (mutualistic with algal photobionts).  Thallus: crustose (crustaceous) – episubstratal – unspecified; cracked, fissured, fractured, rimose | compartimentized – areolate, squamulate; [th] upper surface: brown(ish) (if pale: fawn, tan; if mid: cinnamon) | red(dish) | red(dish) brown (if pale: orange brown); [th marginal and upper surface] specific structures: absent; [th] medulla amyloidity: present.  Ascomata: absent | present; ascoma: apothecial, apothecioid – hymenial; ascoma [mm]: (median) 0.6; ascoma: immersed, innate | subsessile, subimmersed, adnate, semi-immersed, emergent | sessile, superficial; [ascm, if apoth] disc, mazaedium: plane, flat, flattened, expanded; [ascm, if apoth] disc, mazaedium: black(ish); [ascm, if apoth] margin surface; [if perith] periostiolar area, ostiole, involucrellum: black(ish); [ascm, if apoth] margin excipular photobionts: absent; [ascm, if apoth] subhymenial layers, hypothecium; [if perith] basal excipulum: brown(ish) (if pale: fawn, tan; if mid: cinnamon) | black(ish) brown; [ascm] paraphyses/-oids: present; [ascm] epihymenium, epithecium: blue(ish) black | green(ish) black.  Asci: lecanoralean; [asc] tholus: thickened; [asc] tholus amyloidity (iodine reaction): present; [asc] tholus amyloidity pattern: with amyloid cap (= Icmadophila-, Lecidea-, Pertusaria-types etc).  Ascospores: (median) 8.0; [asp] shape: ellipsoidal; [asp] length [µm]: (low) 12.0 (high) 18.0; [asp] width [µm]: (low) 3.0 (high) 7.0; [asp] septa: present, transversely septate | muriformly septate – muriform, submuriform; [asp] transversal septa: (median) 3.0; [asp] pigmentation: hyaline, colourless; [asp] perispore, epispore: thick, distincly halonate.  Primary photobiont: present, chlorophytaceous – trebouxiaceous, chlorococcoid.  Secondary photobionts (eg in cephalodia): absent.