Flora of New Zealand Series

Description : Thallus rosette-forming, 1–3(–4) cm diam., closely attached from margins to centre. Lobes thin, 0.5–1.2(–2) mm wide, 1–5(–8) mm long, shallowly convex, discrete or adjacent at apices to ±imbricate centrally, apices crenulate. Margins entire, irregularly lobulate, crenate or shallowly incised, here and there with projecting rhizines from lower surface, ±imbricate centrally, not noticeably thickened below, sorediate. Upper surface whitish, creamish to pale-grey, smooth to shallowly undulate, here and there punctate-impressed, matt, white-maculate in older parts (×10 lens), epruinose. Soralia marginal, rather sparse, developed at inner parts of thallus, rounded, 0.5–1.2 mm diam., capitate, callus-like; soredia densely crowded, farinose, white. Lower surface whitish at or near margins, darkening centrally to pale-greyish or brownish, matt or slightly glossy in parts, smooth, rhizinate. Rhizines scattered, simple to squarrose-branched, whitish to grey or brownish, slender, 0.5–0.8 mm long, sometimes projecting from margins. Apothecia rare, immature, to 0.3 mm diam., thalline exciple swollen, persistent, concolorous with thallus, disc plane, matt, brown, epruinose. Ascospores not seen [Pachysporaria type, 20–23 × 9–12 μm (Moberg 1986b: 861)].

Chemistry : Cortex and medulla K+ yellow; containing atranorin and zeorin.

N: Northland (Waitiki Stream, Little Barrier I.), South Auckland (Motuhora (Whale) I.). On exposed rock faces at sea level and on bark of mahoe (Melicytus ramiflorus). Rarely collected in New Zealand from northern, and offshore islands habitats. Earlier ecords of P. tribacoides from New Zealand (Galloway 1985a: 395) refer to P. poncinsii. Known also from Great Britain, southern and western Europe, the Azores, East and South Africa, Socotra, Japan, the Philippines, Argentina, and Australia (Kashiwadani 1975; Moberg 1986b, 2001, 2004b; Swinscow & Krog 1988; Aptroot 1989a; Aptroot & Sipman 1989; Purvis et al. 1992; Nimis 1993; Calvelo & Liberatore 2001; Llimona & Hladun 2001; Coppins 2002b; McCarthy 2003c, 2006; Nimis & Martellos 2003; Mies & Schultz 2004).

Cosmopolitan

Illustrations : Kashiwadani (1975: 38, fig. 7; pl. 4, fig. 2); Moberg (1986b: 849, fig. 8D; 861, fig. 22); Dobson (2005: 342 – as P. tribacioides [sic]).

Physcia tribacoides is characterised by: the corticolous/saxicolous habit; the callus-like soralia; the crenate lobes; the paraplectenchymatous lower cortex with thick-walled cells; and atranorin and zeorin.