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Thelidium olivaceum (Schaerer) Korber
Family: Verrucariaceae
Thelidium olivaceum image

Global occurrence: Oceania – Australasia | Eurasia – Europe | Americas – North America (incl Mexico) | Arctic.  Substrate: rock – calcareous, calciferous, basic | rock, stones, pebbles – unspecified.  Life habit: lichenized (mutualistic with algal photobionts).  Thallus: crustose (crustaceous) – episubstratal – unspecified; thallus: continuous, diffuse, effuse | cracked, fissured, fractured, rimose; [th] upper surface: brown(ish) (if pale: fawn, tan; if mid: cinnamon) | brown(ish) black | black(ish) brown; [th marginal and upper surface] specific structures: absent.  Ascomata: absent | present; ascoma: perithecial, perithecioid – hymenial; ascoma [mm]: (median) 0.4; ascoma: subsessile, subimmersed, adnate, semi-immersed, emergent; [ascm, if apoth] margin surface; [if perith] periostiolar area, ostiole, involucrellum: brown(ish) (if pale: fawn, tan; if mid: cinnamon) | brown(ish) black; [ascm, if apoth] margin excipular photobionts: absent; [ascm] paraphyses/-oids: absent.  Asci: fissitunicate – bitunicate; [asc] tholus: thickened; [asc] tholus amyloidity (iodine reaction): absent.  Ascospores: [asp] shape: ellipsoidal | elongate-fusiform, ellipsoidal-fusiform; [asp] length [µm]: (low) 16.0 (high) 22.0 (max) 34.0; [asp] width [µm]: (low) 7.0 (high) 12.0 (max) 14.0; [asp] septa: present; [asp] septa: transversely septate; [asp] transversal septa: (median) 1.0 (max) 3.0; [asp] pigmentation: hyaline, colourless; [asp] perispore, epispore: not apparent.  Secondary metabolites: absent.  Primary photobiont: present, chlorophytaceous – trebouxiaceous, chlorococcoid.  Secondary photobionts (eg in cephalodia): absent.