Flora of New Zealand Series

Description : Thallus rosette-forming to irregularly spreading, closely attached, 1–3 cm diam., often confluent with neighbouring thalli and forming irregular patches 5–8 cm diam. Lobes irregularly branching, 0.5–1(–1.2) mm wide, 2–6(–8) mm long, discrete at margins, soon imbricate to complex-imbricate centrally, plane to subconvex. Margins rarely entire, to variously notched, incised to minutely lobulate, slightly thickened and ridged below, generally paler than upper surface (especially at lobe apices), commonly obscured at centre by generous development of confluent soredia; non-sorediate areas generally white-pruinose. Upper surface smooth to shallowly undulate, matt, glabrous centrally, commonly white-pruinose and appearing "frosted" towards and at apices, pale-green when moist, off-white, grey-white, pale olivaceous-buff to pinkish in parts when dry, sorediate. Soralia marginal, labriform–undulate, developing towards inner parts of lobes and around sinuses between lobes, eroding extensive areas of both lower and upper surfaces; soredia delicate, farinose, greenish when moist, olivaceous to greenish white or off-white when dry and on storage. Lower surface ecorticate, white at margins, pale-tan or brownish centrally, with conspicuous red-brown to brown-black, ribbed or nerve-like longitudinal striations, rhizinate. Rhizines conspicuous, frequent, simple, occasionally with a short squarrose tuft at apices, slender, 0.02–0.05 mm wide, 0.5–1.2(–1.5) mm long, brown or black. Apothecia and pycnidia not seen in New Zealand collections.

Chemistry : Upper cortex and medulla K+ yellow; containing atranorin, zeorin and several unidentified triterpenoids.

N: Northland (Ririwha I., Onerahi, Tawharanui Peninsula). On bark of Avicennia marina and Pittosporum umbellatum. Known also from from East and South Africa (Moberg 1986b, 2004b; Swinscow & Krog 1988), Socotra (Mies & Schultz 2004), South America where it appears to be rare (Moberg 1990; Scutari 1995b; Galloway & Quilhot 1999; Calvelo & Liberatore 2001), Hawai'i, and Australia (Hale 1963; Elix & McCarthy 1998; Moberg 2001; McCarthy 2003, 2006).

Pantropical

Illustrations : Moberg (1986: 846, fig. 5; 847, fig. 6E, F; 849, fig. 8A; 853, fig. 12); Aptroot (1987: 36, pl. 8); Swinscow & Krog (1988: 224, fig. 108); Brodo et al. (2001: 551, pl. 661).

Physcia atrostriata is characterised by: the corticolous habit; a pale grey-white upper surface which is delicately white-pruinose appearing "frosted"; by the marginal soredia best developed in the sinuses between lobes; and the brown-black striations on the lower surface.