Flora of New Zealand Series

Holotype: New Zealand. South I. Canterbury, Arthur's Pass, roadside in the forest, on a boulder, 12.i.1927, G. Einar & Greta Du Rietz 1515e : 1 – UPS. Isotypes – S, UPS.

Description : Thallus crustose, very closely attached, 2–5 cm diam., often among mosaics of other crustose lichens, 150–250 μm thick, distinctly areolate, irregularly microphylline or squamulose at margins, and delimited from neighbouring lichens by a narrow, brown-black line of prothallus. Areolae angular, 0.5–2 mm diam., separated by rather narrow cracks. Upper surface pale greyish brown to pinkish brown, minutely velvety-pruinose (×10 lens), smooth, to minutely irregular, without maculae, isidia, pseudocyphellae or soredia. Cephalodia angular, polygonal, 1–3 mm diam., subimmersed to mainly level with thallus surface, dark purple-blue when moist, dark olive-brownish and contrasting with thalline areolae when dry, surface smooth to noticeably and deeply cracked. Apothecia clustered in small groups, widely scattered or absent, 0.1–0.5 (–1) mm diam., subimmersed at first becoming sessile but very little raised above surface of thallus, rounded to contorted through mutual pressure; disc shallowly concave, matt or slightly shining, red-brown to brown-black, epruinose, translucent when wet (and then reminisent of Gyalidea hyalinescens); with a thin, entire, slightly raised proper margin, concolorous with disc or darker; thalline margin prominent, crenate-striate, sometimes slightly wavy, raised above disc, concolorous with thallus or distinctly whitish. Epithecium granular, pale yellow-brown to olive-brown, 15–27.5 μm thick. Hymenium colourless, 175–200 μm tall. Hypothecium densely opaque, colourless, 125–150 μm thick. Asci cylindrical, 8-spored, 150–170 × 15–20 μm. Ascospores uniseriate in ascus, ovoid to subglobose, colourless, without oil droplets, (12.5–)20–27.5 × 10–15(–17.5) μm. Pycnidia minute, immersed at first, with a brown-black, depressed ostiole, 1–5 per areolae, margins whitish, swollen at maturity. Conidia filiform, curved, 20–40 × 0.5 μm.

Chemistry : Thallus K−, C+ red, KC+ red, Pd−; containing gyrophoric acid.

S: Canterbury (Arthur's Pass). It is presently known from several sites at Arthur's Pass where it grows on greywacke rocks associating with Aspicilia sp., Labyrintha implexa, Placopsis macrophthalma, P. perrugosa and species of Porpidia.

Austral

Illustration : Galloway (2004b: 111, fig. 5).

Placopsis durietziorum is characterised by: the saxicolous habit; the closely attached, areolate thallus that is irregularly microphyline or squamulose at the margins, and forming irregular mosaics, delimited by a narrow, black prothallus; the upper surface is pale greyish brown to pinkish brown and minutely velvety pruinose; the cephalodia are angular, 1–3 mm diam., subimmersed to plane with thallus surface; the apothecia are small, 0.1–0.5(–1) mm diam., clustered in small groups, subimmersed to sessile, the disc red-brown to brown-black, epruinose; the colourless hymenium, 175–200 μm tall; cylindrical, 8-spored asci, 150–170 × 15–20 μm; ascospores uniseriate in ascus, ovoid to subglobose, colourless, (12.5–)20–27 × 10–15(–17.5) μm; and filiform, curved conidia, 20–40 × 0.5 μm. The specific epithet commemorates the Swedish lichenologists G. Einar and Greta Du Rietz, who travelled widely throughout New Zealand in 1926–27 (Galloway 2004e), and who made the first collections of the species.