Flora of New Zealand Series

≡Lecanora constans Nyl., Mém. Soc. Sci. nat. Cherbourg 3: 199 (1855).

Description : Thallus closely attached, pale green-grey to brownish, granular, orbicular, in ±neat rosettes or spreading, 1–3 cm diam., corticolous. Apothecia sessile, to 1.5 mm diam., rounded, ±central, disc red-brown to dull-black, matt, epruinose, margins crenulate, concolorous with thallus or paler. Epithecium brown, 10–15 μm thick, K+ violet-brown. Hymenium colourless, 60–80(–90) μm tall, inspersed with oil droplets, I−. Hypothecium colourless, 30–75 μm thick. Asci I+ blue, 40–60 × 9–15 μm containing 80–100 spores. Ascospores colourless, simple to 1-septate, 3–6(–8) × 2.5–3 μm.

Chemistry : Thallus K−, C−. KC−, Pd−; containing sekikaic acid with traces of homosekikaic acid and 4'- O -demethylsekikaic acid (Kantvilas 2001: 187).

S: Canterbury (Canterbury Plains), Otago (Dunedin). On bark of Magnolia, Quercus, Sorbus etc., on wayside trees and in parks and gardens. Probably more widespread than records show and possibly often mistaken for a species of Lecanora or for Caloplaca homologa (q.v.). Known also from Europe where it is apparently declining (Magnusson 1934, 1936; Poelt 1969; Nimis 1993; Scholz 2000; Hafellner & Türk 2001; Llimona & Hladun 2001; Nimis & Martellos 2003), in Sweden where it is rare or even extinct (Magnusson 1934: Santesson1993; Thor & Arvidsson 1999), in North America (Magnusson 1934; Esslinger & Egan 1995; Harris 2006), India (Singh 1980), Ecuador (Kalb 1988:10); Thailand (Wolseley et al. 2002), Australia and Tasmania (Kantvilas 1990c, 2001, 2004h; McCarthy 2003c, 2006).

Cosmopolitan

Illustrations : Haffelner (1984: 279, fig. 24; 1995a: 103, fig. 15); Wirth (1995a: 568); Thor & Arvidsson (1999: 284); Kantvilas (2001: 187, fig. 5A); Lumbsch et al. (2001: 8); Flora of Australia56A (2004: 106, pl. 54); Harris (2006: 66, fig. 2).

Maronea constans is characterised by: the corticolous habit; the neat, rosette-forming crustose thallus; red-brown apothecial discs with pale margins; a brown epithecium reacting K+ violet-brown; a hyaline hymenium 60–100 μm tall, inspersed with oil droplets; a colourless hypothecium inspersed with oil droplets; and polysporous asci (walls I+ blue) containing 80–100 ascospores.