Flora of New Zealand Series

Description : Thallus rosette-forming to irregularly spreading, 0.5–2(–3) cm diam., closely to loosely attached to substratum, rather small and fragile. Lobes convex to plane, rather narrow, (0.2–)0.5–1(–1.5) mm wide, 2–8 mm long, discrete from margins to centre or imbricate both at margins and centrally, apices rounded to truncate to irregularly notched or incised. Margins entire to notched, incised or crenulate, slightly to markedly raised, conspicuously sorediate, especially towards centre of thallus at base of lobes and around sinuses separating lobes, generally free of soredia at apices. Soralia marginal, linear, undulate, eroding margins and extending to lower surface, at times appearing somewhat labriform; soredia coarsely granular, greenish when moist, white when dry and on prolonged storage. Upper surface matt, smooth to shallowly undulate, pale lettuce-green when moist, on drying soon becoming pale green-white to clean grey-white, delicately white-pruinose and appearing "frosted" especially at apices (×10 lens), sometimes white-maculate centrally (×10 lens). Lower surface whitish to greyish at margins, pale buff-brown centrally, never brown-black-striate; rhizinate. Rhizines ±prominent at margins, more sparse and scattered centrally, simple with a squarrose tuft at tip, stout, 0.1–0.2 mm wide, 0.4–0.8 mm long, whitish to grey-black or brownish. Apothecia and pycnidia not seen in New Zealand collections.

Chemistry : Cortex and medulla K+ yellow; containing atranorin, zeorin and leucotylin (Moberg 1990: 341).

N: Northland (Waitiki Stream) to Wellington. S: Canterbury (Hawdon Shelter, Waipara River, Christchurch, Lincoln, Rakaia Gorge), Otago (Queenstown, Warrington, Dunedin, Beaumont), Southland (Mataura, Forest Hill, Otautau). On introduced trees in parks, gardens and on roadsides where it appears to be able to tolerate moderate pollution. Possibly an introduced species. Known also from Portugal, Spain, the Azores, the Sudan, East and South Africa, Central and South America, Arizona and Mexico, and Australia (Aptroot 1989a; Moberg 1986b, 1990, 2001, 2002b, 2004b; Scutari 1995; Galloway & Quilhot 1999; Calvelo & Liberatore 2001; Llimona & Hladun 2001; McCarthy 2003c, 2006).

Palaeotropical

Illustrations : Moberg (1986b: 862, fig. 23); Scutari (1995b: 225, fig. 6A, B).

Physcia undulata is characterised by: the corticolous habit; the rather small, fragile, rosette-forming to at times somewhat straggling thalli; the marginal, ±undulate soralia; the delicately white-pruinose upper surface (especially at the lobe apices) giving a "frosted" appearance to the upper surface (×10 lens); the pale whitish to buff lower surface without any trace of brown-black striation; and atranorin and zeorin (cortex and medulla K+ yellow). It may be confused with the widespread saxicolous species P. nubila, but is distinguished from it by having more irregular, undulating lobes, a thinner thallus, and a different chemistry. P. atrostriata is similar in a number of aspects of its morphology but is distinguished from P. undulata by its distinctive brown-black striations on the lower surface.