Placopsis macrophthalma
≡Urceolaria macrophthalma Hook.f. & Taylor, Lond. J. Bot. 3: 640 (1844). [For additional synonymy see Galloway (2001a: 57).]
Description : Thallus tartareous, 0.2–1(–1.5) mm thick, smooth, irregularly spreading, often among mosaics of other species of Placopsis, 2–6(–12) cm diam. Margins shallowly scalloped forming very shallow, flat lobes, 1–2 mm wide, to somewhat abruptly delimited, without a marginal prothallus. Upper surface continuous to irregularly cracked to irregularly areolate, minutely roughened to minutely white-papillate, the papillae appearing maculate (×10 lens), and here and there to more widely dispersed patches of delicate, white pruina, most noticeable at margins; pale olive-green to green-grey when moist, pale pinkish white to grey white or off-white when dry, slightly brown-black at margins; without isidia, pseudocyphellae or soredia. Cephalodia mainly immersed, flush with thallus surface and merging gradually into the thallus at their margins, round to irregular, (1–)2–5(–8) mm diam., pale grey-blue to dark purple-blue when moist, concolorous with thallus or slightly paler when dry, minutely wrinkled or irregularly to radially cracked, often difficult to distinguish from thallus in the dry state. Apothecia aspicilioid, immersed, solitary, scattered, rounded, (0.2–)0.5–1(–2, rarely–3) mm diam., rarely 2–4-together and then contorted through mutual pressure; thalline margin concolorous with thallus, 0.05–0.1 mm wide, flush with upper surface and visible as a collar of thalline tissue separated from disc by a narrow, hair-like to gaping, circular crack; proper margin noticeably paler than disc, distinctly puckered or wrinkled and visible when dry, shrinking away from surrounding thalline margin, occluded when moist; disc prominent, bright reddish pink, translucent when moist, dark red-brown to brown-black when dry, subconcave to plane, epruinose. Hymenium colourless, 150–230(–300) μm tall. Paraphyses slender, occasionally branched and anastomosing, apices moniliform, 2–3 μm diam. Hypothecium densely interwoven, 120–150 μm thick. Asci 8-spored, cylindrical, 120–125 × 12–20 μm. Ascospores uniseriate in ascus, thin-walled, broadly ellipsoidal, (15–)20–25(–30) × 12–15(–17) μm. Pycnidia common, scattered, immersed, 250–275 × 130–150 μm, ostiole pale to dark red-brown, slightly depressed, minute, 0.01 mm diam., or less. Conidia filiform, 40–60 × 1 μm.
Chemistry : K−, C+ red; containing gyrophoric and lecanoric acids.
S: Westland (Waitahi Valley), Otago (Teviot River at Lake Onslow), Southland (Henry Saddle between Lake Te Anau and George Sound, Secretary I., near Supper Cove, Mt Hodges, above Cascade Cove, Dusky Sound), C: (Mt Azimuth). On bare rock, in subalpine scrub or grassland, associating with other species of Placopsis (P. cribellans, P. dusenii, P. elixii, P. murrayi, P. subgelida, P. venosa) in very high-rainfall areas, s.l. to 1380 m. Known also from Kerguelen, Heard I., the Crozet Archipelago, and Marion I., Prince Edward Is (Øvstedal & Gremmen 2001; Galloway 2001a; Henssen 2003).
Austral
Illustrations : Lamb (1947: pl. V, fig. 15); Ott et al. (1997: 77, figs 23–27); Henssen (2003: 110, fig. 1D; 111, fig. 2C).
Placopsis macrophthalma is characterised by: a thick (0.2–1.5 mm), spreading, tartareous, creamish or pale whitish pink to greyish buff thallus, which is ±continuous to irregularly cracked, the cracks sharp-edged, 0.05–0.1 mm wide; the surface is minutely roughened, here and there minutely white-pruinose, and ±minutely papillate appearing maculate (×10 lens) in places; by immersed, aspicilioid apothecia (0.2–)0.5–1.0(–2, rarely –3) mm diam., the disc pale to dark red-brown, to somewhat blackish shallowly to deeply urceolate, the thalline margins well-delimited, concolorous with thallus and separated from it by cracks; by immersed, irregularly cracked cephalodia, merging gradually into the thallus at their margins, and distinguished from the thallus only by their colour (pale grey-blue to dark purple-blue when moist, concolorous with thallus or darker to ±pinkish when dry) and texture; a colourless hymenium (150–300 μm tall); and broadly ellipsoidal, colourless ascospores, uniseriate in ascus, (15–)20–25(–30) × 12–15(–17) μm; and long, filiform conidia, 40–60 × 1 μm. It is distinguished from P. murrayi (q.v.) and P. venosa (q.v.), by the morphology of the cephalodia, and by chemistry. The recently described Placopsis stellata (Øvstedal) Henssen (Henssen 2003), from Prince Edward I. differs in having smaller, wart-like cephalodia, a less deeply rimose thallus, hysteroid to lirelliform ascomata, a higher hymenium (160–380 μm tall), smaller ascospores (12–21 × 7–11 μm), and a chemistry of the stictic acid complex.
A recent molecular sudy using sequences from nuclear ITS, LSU and the mitochondrial SSU rDNA of species of Placopsis and related genera (Schmitt et al. 2003) showed that P. macrophthalma and the two known species of Orceolina nest togeher in a well-supported clade within Placopsis, leading the authors to resurrect Aspiciliopsis as a monospecific genus, disinct from Orceolina, which differs in anatomical, morphological and chemical characters, and certainly disinct from other taxa in Placopsis, including P. stellata. Obviously the New Zealand taxa P. murrayi and P. venosa need to be added to a data set with P. macrophthalma to test the robustness of Aspiciliopsis as an independent taxon.
