Rhizocarpon submodestum
≡Lecidea submodesta Vain., Meddel. Soc. Fauna Fl. fenn. 10: 137 (1883).
Description : Thallus areolate, spreading in orbicular to irregular patches, 2–6(–8) cm diam., delimited at margins by a thin, black prothallus. Areolae minute, 0.05–0.4 mm diam., angular to rounded, separated by narrow cracks, grey-brown to dark-grey or olive grey-green, rarely somewhat blackened, smooth. Apothecia scattered, or in small groups, rounded to angular, 0.1–0.6 mm diam., generally somewhat larger than areolae, disc plane to subconvex, black, matt, epruinose, with a thin, concolorous proper margin. Epithecium green-grey to greenish brown. Hymenium colourless, 80–120 μm tall. Asci clavate, 8-spored, 80–100 × 20– 30 μm. Ascospores 3-septate, slightly constricted at septa, colourless, 16–25(–28) × 8–10 μm.
Chemistry : Thallus K−, C−, KC−, Pd−; without any secondary chemistry.
N: Wellington (Ruapehu). S: Canterbury (Waimakariri riverbed close to Christchurch), Southland (S Mavora Lake). C: On exposed rocks in subalpine fellfield, on rocks in old riverbed, and on rocks in grassland. Associating with Buellia macularis, R. geographicum, R. lecanorinum, Lecanora rupicola, Xanthoparmelia. Known also from Great Britain, Europe, Scandinavia, and North America (Feuerer 1978; Santesson 1993; Esslinger & Egan 1995; Scholz 2000; Hafellner & Türk 2001; Llimona & Hladun 2001; Coppins 2002b; Santesson et al. 2004).
Bipolar
Illustrations : Feuerer (1978: 99)
Rhizocarpon submodestum is characterised by: the dark-grey to grey-brown, areolate thallus, delimited by a thin, black prothallus; scattered or grouped, minute black apothecia; a green-grey to greenish brown epithecium; 8-spored asci; and colourless 3-septate ascospores, 16–25(–28) × 8–10 μm; and no secondary chemistry.
