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Rhizocarpon amphibium (Fr.) Th. Fr.
Family: Rhizocarpaceae
[Abacina amphibia (Fr.) Norman,  more]
Rhizocarpon amphibium image

Global occurrence: Eurasia – Europe | Arctic.  Substrate: rock – siliceous, siliciferous, acidic.  Life habit: lichenized (mutualistic with algal photobionts).  Thallus: crustose (crustaceous) – episubstratal – unspecified; compartimentized – areolate, squamulate; [th] upper surface: grey(ish); [th upper surface]: epruinose; [th marginal and upper surface] specific structures: absent; [th] morphol substructures (eg areoles, lobes, branches) width [mm]: (low) 0.2 (high) 0.5; [th] morphol substructures (eg areoles, lobes, branches) upper surface: smooth, plane.  Ascomata: absent | present; ascoma: apothecial, apothecioid – hymenial; ascoma [mm]: (min) 0.4 (low) 0.6 (high) 0.8 (max) 1.0; ascoma: immersed, innate; [ascm, if apoth] disc, mazaedium: plane, flat, flattened, expanded; [ascm, if apoth] disc, mazaedium: black(ish); [ascm, if apoth] disc, mazaedium: epruinose; [ascm, if apoth] margin surface; [if perith] periostiolar area, ostiole, involucrellum: black(ish); [ascm, if apoth] subhymenial layers, hypothecium; [if perith] basal excipulum: brown(ish) (if pale: fawn, tan; if mid: cinnamon); [ascm] paraphyses/-oids: present; [ascm] paraphyses/-oid cells width [µm]: (low) 1.5 (high) 2.0; [ascm] epihymenium, epithecium: 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] length [µm]: (low) 23.0 (high) 27.0; [asp] width [µm]: (low) 10.5 (high) 12.0; [asp] septa: present; muriformly septate – muriform, submuriform; [asp] pigmentation: hyaline, colourless; [asp] perispore, epispore: thick, distincly halonate.  Secondary metabolites: absent.  Primary photobiont: present, chlorophytaceous – trebouxiaceous, chlorococcoid.  Secondary photobionts (eg in cephalodia): absent.