Flora of New Zealand Series

≡Lecothecium rosulans Th.Fr., Bot. Notiser1863: 12 (1863).

Description : Thallus orbicular, rosette-forming, 2–5 mm diam., occasionally forming confluent patches to 15 mm diam., loosely attached centrally, margins free and lifting from substratum, without a marginal prothallus. Lobes flabellate, narrow, 0.2–0.5(–0.8) mm wide, 1–1.5 mm long, plicate-radiating, contiguous or separated by narrow cracks, convex, surface olive-green to olive-brown, unchanged when moist, matt, emaculate, epruinose, margins slightly blackened, thickened, incised or minutely lobulate, without isidia. Apothecia solitary or occasionally 2(–3)-together, central, sessile, constricted at base, 0.2–0.8(–1.0) mm diam., round to subirregular, disc plane to subconvex, matt or slightly granular-sooty (×10 lens), epruinose, black when dry, dark red-brown when moist; proper margin persistent, entire, raised slightly above surface of disc, slightly shining, concolorous with disc. Epithecium dark brown-black to black, 8–15 μm thick, densely conglutinate, unchanged in K. Hymenium colourless, 65–85 μm tall. Paraphyses simple, septate, 1.5 μm thick, expanding to 3–5 μm at apices, distinctly moniliform with 3–6 terminal cells. Hypothecium densely interwoven, opaque, pale brownish pink, unchanged in K, 80–100 μm thick. Asci cylindrical-clavate, 55–62 × 16–20 μm, 8(–10)-spored. Ascospores simple, ovoid, colourless, contents granular-vacuolate, 11.5–13.5 × 6.5–8.2 μm.

Chemistry : TLC−, all reactions negative.

S: Otago (Poolburn Reservoir). On sloping schist slabs in water seepage trails, associating with the moss Andreaea sp. and the lichens Acarospora, Lecanora lugubris, Lepraria neglecta, Ramboldia petraeoides, Rhizocarpon, Usnea ciliata and Xanthoparmelia (brown). A very small, easily overlooked lichen. Known also from Scandinavia, Greenland and the European Alps (Galloway 2003b; Nimis & Martellos 2003; Santesson et al. 2004).

Bipolar

Illustration : Foucard (1990: pl. 257).

Placynthium rosulans is characterised by: the saxicolous habit; the small, orbicular, dull olive-green to olive-brown thallus, with plicate-radiating, flabellate lobes; the sessile, dark red-brown to black apothecia; dark-brown to black epithecium; colourless hymenium, 65–85 μm tall; 8(–10)-spored asci; simple, ovoid, granular-vacuolate ascospores, 11.5–13.5 × 6.5–8.2 μm; and a restriction to damp, seepage areas of schist outcrops in subalpine grassland.