Flora of New Zealand Series

≡Lecidea platycarpoides Bagl., Nuovo Giorn. Bot. Ital. 11: 99 (1879).

Description : Thallus pale greyish white to dark-grey or olivaceous, to somewhat blackened in parts, spreading in irregular patches or forming interlocking mosaics with other crustose lichens, 2–6 cm diam., without a marginal prothallus. Upper surface lumpy–warted, areolate, the areolae angular to irregular, separated by narrow to deeply gaping cracks. Medulla I−. Apothecia scattered, common, 1–3 per areole, semi-immersed, aspicilioid, round to irregular or deformed through mutual pressure, (0.2–)0.5–1.5(–2.5) mm diam., disc black, subconvex to plane, matt, roughened-papillate to striate-auriculate or umbonate at maturity, epruinose or with occasional patchy white pruina. Epithecium densely granular, olive-greenish to dark-brown, 15–20 μm thick. Hymenium colourless, 100–120(–140) μm tall. Asci, 8-spored, broadly clavate, 85–92 × 25–30 μm, with a massive apical tholus and tube structure. Ascospores broadly ellipsoidal to ovoid, contents oily-granular, (16.5–)20–30(–32) × 11–13.5 μm, distinctly halonate.

Chemistry : Medulla, K+ yellow or + yellow→red, C−, KC−, Pd+ orange, UV−; containing stictic acid (major) and occasionally also norstictic acid.

S: Nelson (Mt Arthur), Otago (Poolburn Reservoir, Lake Onslow), Southland (Piano Flat Waikaia River, S Mavora Lake). On dry, exposed rock outcrops in tussock grassland, on riverside rocks, and on rocky outcrops in subantarctic fellfield and on cliffs. Associating with species of Aspicilia, Placopsis perrugosa, Rhizocarpon geographicum, R. grande, R. lecanorinum, and Xanthoparmelia. Probably much more widespread than records currently show. Known also from Great Britain, Europe, Scandinavia, North America and Brazil (Nimis & Poelt 1987; Galloway & Coppins 1992b; Nimis 1993; Esslinger & Egan 1995; Aptroot 2002e; Coppins 2002b; Nimis & Martellos 2003; Fryday 2005).

Bipolar

Illustration : Dobson (2005: 362).

Porpidia platycarpoides is characterised by: the saxicolous habit; a greyish to olivaceous, rather thick, lumpy or papillate, areolate thallus; subimmersed, aspicilioid apothecia; an exciple with a pale interior and wide hyphae (6–8 μm diam.); a bluish tinge to the hymenium in section (Fryday 2003); broadly ellipsoidal to obovoid ascospores, (16.5–)20–30(–32) × 11–13.5 μm, distinctly halonate; and the presence of stictic/norstictic acid. It is closely similar to P. macrocarpa but differs in the above characters and especially in the K+ reaction.