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Rhizocarpon atroflavescens Lynge
Family: Rhizocarpaceae
Rhizocarpon atroflavescens image

Global occurrence: Eurasia – Europe | Americas – North America (incl Mexico) | Arctic.  Substrate: rock – siliceous, siliciferous, acidic | rock – calcareous, calciferous, basic | 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: white(ish) yellow; [th marginal and upper surface] specific structures: absent.  Ascomata: absent | present; ascoma: apothecial, apothecioid – hymenial; ascoma [mm]: (low) 1.0 (high) 1.2; [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: brown(ish) (if pale: fawn, tan; if mid: cinnamon) | red(dish) brown (pale: orange brown).  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) 23.0 (high) 38.0; [asp] width [µm]: (low) 13.0 (high) 20.0; [asp] septa: present, transversely septate; [asp] transversal septa: (median) 3.0; [asp] pigmentation: dark brown | greenish grey; [asp] perispore, epispore: thick, distincly halonate.  Secondary metabolites: present, rhizocarpic acid.  Primary photobiont: present, chlorophytaceous – trebouxiaceous, chlorococcoid.  Secondary photobionts (eg in cephalodia): absent.