Flora of New Zealand Series

≡Psora albescens Hoffm., Dtschl. Fl. 2: 165 (1796).

?=Lecanora pulvinaris Zahlbr., Denkschr. Akad. Wiss. Wien math.-naturwiss. Kl. 104: 340 (1941).

Lecanora pulvinaris. Lectotype: New Zealand. Southland, Clifden, on limestone, J.S.Thomson A3 – CHR 345803 [fide Galloway (1985a: 218)]. Isolectotype – OTA.

Description : Thallus on mortar, concrete, limestone rock, 0.5–1.5 cm diam., in usually discrete rounded rosettes, but also coalescing into larger patches to 5 cm or more diam., surface hummocky, convex, whitish or creamish, sometimes white-pruinose (×10 lens), thick, tartareous, margins plicate to somewhat placodioid. Apothecia crowded centrally or spreading over entire thallus, rounded to somewhat angular or deformed through mutual pressure, 0.1–1(–2) mm diam., sunk in thallus at first, sessile, constricted at base at maturity, disc subconcave to plane at first, plane to subconvex at maturity, pale yellow-brown to tan or pale red-brown, with or without a thin to dense, white to grey-white pruina; margins 0.05 to 0.1 mm thick, persistent, raised, subcrenulate, concolorous with thallus. Hymenium 50–80 (–95) μm tall, I+ blue; epithecium pale brownish. Paraphyses branched and anastomosing, 1–2 μm thick, apices capitate to 3 μm thick. Ascospores ellipsoidal, apices rounded, 8–11(–15) × 4–7 μm.

Chemistry : Thallus K−, C−, KC−, Pd−; containing 2,7-dichlorolichexanthone (Fröberg 1997: 30).

N: Wellington. S: Marlborough (Kaikoura Peninsula), Canterbury (Cave Stream, Castle Hill, Weka Pass, Opihi River, Kimball), Otago (Matanaka), Southland (Gore, Borland Stream, Clifden). On painted concrete walls, mortar, calcareous sandstone and limestone (both coastal and inland), in sunny, high-light situations, together with other Northern Hemisphere calcicolous lichens such as Caloplaca holocarpa, Candelariella sp., Diplotomma alboatrum, Lecanora flotoviana, Leptogium plicatile, Placynthium nigrum etc. Known also from Great Britain, Europe, Scandinavia, and North America (Purvis et al. 1992; Nimis 1993; Santesson 1993; Esslinger & Egan 1995; Fröberg 1997; Scholz 2000; Brodo et al. 2001; Coppins 2002b; Laundon 2003; Nimis & Martellos 2003; Santesson et al. 2004).

Bipolar

Illustrations : Foucard (1990: pl. 123); Dobson (1992: 171; 2000: 187 ; 2005: 213); Poelt et al. (1995: 305, fig. 5H; 315, fig. 7C); Fröberg 1997: 32, fig. 1A, B).

Lecanora albescens is characterised by: the saxicolous habit (basicolous substrata see above); the thick, tartareous, white or creamish, hummocky thallus that is somethimes white-pruinose, and with distinctive, plicate to somewhat placodioid margins; crowded, central apothecia with pale yellow-brown, tan or pale red-brown discs, with or without a thin to dense white or grey-white pruina; a thick, persistent, raised, subcrenulate thalline exciple, concolorous with thallus; ellipsoidal ascospores, 8–11 × 4–7 μm; and 2,7-dichlorolichexanthone.