Rhizocarpon superficiale (Schaer.) Malme
Lecidea superficialis Schaerer, Lich. helv. spic.: 125 (1828).
Thallus crustose, spreading, 2-10 cm diam., prothallus conspicuous. Areolae close together, widely dispersed, usually separated by black strips of prothallus, some specimens with a distinct border formed of young areolae of characteristic shape, 0.3-2.5 mm diam., angular, concave to plane to convex, or rounded- angular to rounded and convex, yellowish-white to yellow to greenish-yellow, surface smooth, matt or glossy or scabrid. Apothecia 0.6-2 mm diam., round to angular, usually higher than surrounding areolae, plane to subconvex, with a distinct persistent margin, surface matt, minutely papillate, "sooty". Hymenium 70-100 µm tall, colourless to brownish, dark reddish or greenish in upper parts. Asci clavate, 60-80 × 15 µm. Hypothecium brown, 60-150 mm tall. Ascospores 8 per ascus, 1-septate, small, 11-18 × 6-8 µm. Chemistry: Medulla K+ red, Pd+ yellow, or K+ yellow and Pd+ brick red (rarely K-, Pd-). Rhizocarpic, stictic or norstictic acids, rarely psoromic acid.
S: Otago. On alpine rocks. Collected only once from summit of Bold Peak, Humboldt Mountains by G.E. and G. Du Rietz in 1927. Probably more widely distributed in alpine areas of South I.
Cosmopolitan
