Buellia aethalea
≡Gyalecta athalea Ach., Lichenogr. universalis: 669 (1810).
Description : Thallus crustose, areolate cracked, spreading in irregular patches, (0.5–)1–3 cm diam., with a prominent black prothallus visible at margins and between areolae, often forming mosaics. Areolae small, 0.1–0.6(–1) mm diam., flat, angular, white to grey-white or discoloured brownish. Apothecia immersed, cryptolecanorine or zeorine, round to somewhat angular, 0.2–0.5(–0.8) mm diam., disc plane to subconcave, black, epruinose, with or without a thin proper margin, concolorous with disc. Epithecium greenish to olive-brown, 8–13 μm thick. Hymenium colourless, 60–80 μm tall. Hypothecium colourless to brownish. Ascospores greenish to dark-brown when over-mature, broadly oblong with rounded apices, slightly constricted at septum, 12–15 × 6.5– 8.5 μm.
Chemistry : K+ yellow-orange, C−, KC−, Pd+ yellow-orange; containing norstictic and ±stictic acids.
S: Otago (Old Man Ra.). On quartz veins in schist outcrops in tussock grassland. Associating with * Rhizocarpon pusillum and Sporastatia testudinea (Galloway 2003b). Known also from Great Britain, Europe, Scandinavia, North America, Australia, Antarctica (Purvis et al. 1992; Nimis 1993; Santesson 1993; Schiedegger 1993; Scholz 2000; Øvstedal & Lewis Smith 2001; McCarthy 2003c, 2006; Nimis & Martellos 2003; Bungartz & Nash 2004b; Santesson et al. 2004).
?Bipolar
Illustrations : Foucard (1990: 91); Dobson (2000: 80; 2005: 87); Bungartz & Nash (2004b: 444, fig. 1).
Buellia aethalea is characterised by: the saxicolous habit; small, mosaic-forming, white thalli clearly delimited by a black, marginal prothallus; 1-septate, greenish to brownish ascospores slightly constricted at septum, 12–15 × 6.5–8.5 μm; and norstictic acid in the medulla.
