Psoroma durietzii P.James & Henssen
Thallus foliose-lobate, rosette-forming to irregularly spreading, 2-3(-5) cm diam., closely attached, with a blue-black, byssoid prothallus extending beyond lobe margins. Lobes irregularly divided, larger and radiating at margins, 2.0-3.5 mm wide, smaller and ± imbricate centrally, usually contiguous for most of their length but sometimes remaining discrete and widely separated on prothallus. Upper surface plane or concave, shining, smooth or rarely slightly roughened, bright lettuce-green when wet, yellowish or golden-brown when dry. Cephalodia frequent, laminal, originating at margins, to 1 mm diam., at first ± suborbicular, flattened, often becoming unequally lobed with indented margins, pale brown, yellowish-flesh-coloured or concolorous with thallus, at first with numerous blue-grey, granular soredia on underside and at margins, finally spreading to upper surface, conspicuously dark grey-blue when wet. Lower surface pale ochraceous, ± densely rhizinate. Rhizines blue-black to black, simple, in a ± uniform felt to the margins. Apothecia rare, when present abundant, crowded, ± central, variously contorted-angular through mutual pressure, 0.5-1.5 mm diam., globose, sessile, ± cupuliform, constricted at base, disc pale pink to red-brown, ± white-pruinose, often with faint, pale concentric lines, often fissured, thalline margin well-developed, involute or radially crenate, often ± fissured. Ascospores oval or rounded 12-15 × 10-13 µm, epispore roughened or irregularly ridged 2.0-2.5 µm thick. Chemistry: Medulla K+ yellow, C-, KC+ yellow, Pd+ red. Pannarin, zeorin and two unidentified pigments.
N: South of lat. 38°S. S: Nelson to Fiordland, close to and west of Main Divide. A: C: Characterised by the blue-grey sorediate cephalodia. A conspicuous epiphyte of Leptospermum, Nothofagus, Dacrycarpus, Phyllocladus and several other trees and shrubs, s.l. to 1000 m.
Australasian
Holotype (fide James and Henssen loc. cit. ): New Zealand. Westland, South Hokitika Experimental Station, on Weinmannia racemosa. G.E. and G. Du Rietz 1570c, 1927, OTA.
