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Rhizocarpon subgeminatum Eitner
Family: Rhizocarpaceae
Rhizocarpon subgeminatum image

Global occurrence: Eurasia – Europe | Americas – North America (incl Mexico) | Arctic.  Substrate: rock – siliceous, siliciferous, acidic | rock, stones, pebbles – unspecified.  Life habit: lichenized (mutualistic with algal photobionts).  Thallus: crustose (crustaceous) – episubstratal – unspecified; compartimentized – areolate, squamulate; [th] upper surface: brown(ish) (if pale: fawn, tan; if mid: cinnamon); [th marginal and upper surface] specific structures: absent; [th] morphol substructures (eg areoles, squamules): contiguous, coherent (throughout the thallus) | distantly discontiguous; [th] morphol substructures (eg areoles, lobes, branches) upper surface: smooth, plane.  Ascomata: absent | present; ascoma: apothecial, apothecioid – hymenial; [ascm, if apoth] disc, mazaedium: plane, flat, flattened, expanded | subconvex, slightly convex; [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: green(ish) | brown(ish) (if pale: fawn, tan; if mid: cinnamon) | yellow(ish) green.  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) 25.0 (high) 50.0 (max) 60.0; [asp] width [µm]: (low) 13.0 (high) 28.0; [asp] septa: present; muriformly septate – muriform, submuriform; [asp] pigmentation: hyaline, colourless | greenish grey; [asp] perispore, epispore: thick, distincly halonate.  Secondary metabolites: absent.  Primary photobiont: present, chlorophytaceous – trebouxiaceous, chlorococcoid.  Secondary photobionts (eg in cephalodia): absent.