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Australian Biological Resources Study

Checklist of the Lichens of Australia and its Island Territories
Introduction | A–D | E–O | P–R | S–Z | Oceanic Islands | References
Trichothelium oceanicum P.M.McCarthy
  Lichenologist 33: 395 (2001). T: c. 2 km SSW of airport, off North–South Baseline Rd, Christmas Island, Indian Ocean, disused forest track, 10°28.23'S, 105°40.83'E, alt. 240–250 m, on living leaves in moderately dense primary forest, 31 July 2000, P.M.McCarthy 1426; holo: CANB; iso: Herb. R.Lücking.  
  Thallus crustose, foliicolous, epicuticular, scattered and diffuse to coalescing and determinate, pale greenish grey or pale to medium green, 10–15(–20) µm thick, continuous, smooth to minutely uneven, usually matt, ecorticate, K–. Algae Phycopeltis; filaments loosely aggregated; branching irregular, not forming radiating plates; cells angular-rounded, short-rectangular or oblong, 6–10 × 3–6 µm. Hyphae 1–2 µm wide. Prothallus not apparent. Perithecia usually moderately numerous, scattered, superficial, hemispherical to subglobose and slightly or strongly attenuated at the base, (0.14–)0.19(–0.24) mm diam. (not including setae), often covered by a thin layer of thallus up to the point of attachment of the setae, greenish black, matt. Apex ± plane to convex. Ostiole inconspicuous or in a hemispherical, 25–35 µm wide papilla. Setae (5–)8(–12), 0.05–0.2(–0.35) mm long, 20–40 µm thick, ± evenly spaced in a crown just below the ostiole, narrowly acute, occasionally lanceolate, at first angled obliquely upwards, becoming horizontal and, eventually, strongly decurved, uniformly hyaline to whitish, usually remaining discrete, rarely coalescing, sometimes with torn, ragged edges at maturity, composed of elongate, agglutinated hyphae 2(–3) µm wide. The setae of some post-mature perithecia are greenish to brown due to being coated with chlorococcoid algae and cyanobacteria. Involucrellum contiguous with and extending to the base of the excipulum, occasionally incurved beneath it, uniformly 12–20 µm thick, greyish black, greenish black or purple black in thin section, K– (when greyish or greenish black) or intensifying purple; space between the base of the involucrellum and the excipulum with a loose reticulum of blackish, 2–3 µm thick hyphae. Excipulum greyish black, greenish black or purple-black, 10–12(–15) µm thick. Subhymenium 10–15 µm deep. Centrum globose, subglobose or depressed-ovate, 0.1–0.2 mm diam. Paraphyses simple, 0.5–0.7 µm thick. Periphyses absent. Asci elongate-cylindrical to elongate-obclavate, 8-spored, 90–110 × 15–19 µm, usually with a subtruncate apex; apical ring present. Ascospores colourless, 7(–11)-septate (c. 15–25% of mature ascospores with more than 7 septa), elongate-fusiform or oblong, often tapering more noticeably towards the proximal end, straight or slightly curved, irregularly biseriate in the asci, (29–)43(–53) × (5–)7(–8.5) µm; contents clear to guttulate; perispore 1–1.5 µm thick or not apparent. Pycnidia not seen.
  This foliicolous species is endemic to Christmas Island where it is common.  
  McCarthy (2001k)  

Checklist Index
Introduction | A–D | E–O | P–R | S–Z | Oceanic Islands | References

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