Umbilicaria grisea
Description : Thallus monophyllous, ±orbicular, (2–)3–15(–25) mm diam., attached by a central umbilicus, pliable and rather flabby when wet, very fragile, brittle when dry. Margins of lobes entire to torn, notched or incised to irregularly lobulate here and there, commonly reflexed and thinly to thickly parasorediate. Parasoredia dark, olive-green to dark-brownish or brown-black, coarsely granular to minutely lobulate, isolated parasoredia sometimes becoming distinctly phyllidiate when developed centrally above umbilicus. Upper surface shallowly undulate to rarely convex, pale to dark olive-greenish when moist, pale-grey to grey-black when dry, distinctively pale grey-white, minutely scabrid-areolate centrally (×10 lens), darkening to grey-black towards margins. Lower surface smooth, minutely scabrid-areolate (×10 lens), pale-creamish or whitish tan to brownish or grey, to brown-black sometimes distinctly grey- or white-pruinose (×10 lens) in patches at margins, with or without rhizinomorphs. Umbilicus compressed, 2–3 mm diam., concolorous with lower surface or darker. Rhizinomorphs rather infrequent, concolorous with lower surface, to 1 mm long and 0.01–0.02 mm diam., simple or sparingly branched towards tips, when present developed below reflexing parasorediate margins and often obscured by these. Apothecia and pycnidia not seen.
Chemistry : Gyrophoric (major), lecanoric and umbilicaric (minor) acids (Posner et al. 1992; Narui et al. 1996).
S: Canterbury (Godley Valley, Lake Tekapo, Lake Ohau), Otago (St Marys Ra., Poolburn Reservoir, Flagstaff, Dunedin), Southland (S. Mavora Lake). Closely attached, on flat, sloping or sometimes vertical faces of schist outcrops and tors, in full sun, generally N-facing, in or near water runnels and drainage cracks, to the top of schist tors and rock outcrops in tussock grassland. Occasional, to locally common. Associating with Aspicilia cinerea, Caloplaca rubelliana, Cladia aggregata, Coccocarpia palmicola, Collema durietzii, Flavoparmelia haysomii, Lecanora farinacea, L. rupicola, Massalongia carnosa (in pads and tufts of moss), Physcia tribacia, Ramboldia petraeoides, Toninia bullata, Umbilicaria cylindrica, and U. vellea. Known also from the Channel Is, Europe, Scandinavia, the Ukraine, Macedonia, Romania and Greece (Galloway 2001c: 23; Nimis & Martellos 2003).
Bipolar
Illustrations : Wirth (1987: 483; 1995b: 935); Lumbsch & Mietzsch (1990: 75, fig. 3D); Thor & Arvidsson (1999: 334).
Umbilicaria grisea is characterised by: the saxicolous habit; monophyllous, rounded thalli with reflexed margins; a distinctive marginal zone of dark, olive-green to brown-black parasoredia [derived from the upper cortex and not from medullary layers (Codogno et al. 1989)]; a characteristic pale, grey-white, minutely scabrid (×10 lens) central area of the upper surface which contrasts with the darker, parasorediate, marginal zone; a pale-tan to dark-brown to grey or blackened lower surface, which is generally also minutely scabrid-areolate (×10 lens), and commonly distinctly grey- or white-pruinose at or near the margins; and absence of apothecia; and sparse or absent rhizinomorphs.
