Flora of New Zealand Series

≡Lichen caesius Hoffm., Enum. lich. eur.: 65 (1784).

Description : Flora (1985: 393).

Chemistry : Upper cortex and medulla K+ yellow; containing atranorin and zeorin.

N: Northland (Karikari Peninsula) to Wellington. S: Nelson (Mt Owen) to Southland. St: (Port Pegasus). Ch: (SW of Waitangi). Widespread, s.l. to 1900 m. on both acidic and basic rocks, in full sun (often very common and forming large, confluent, grey-white swards covering large areas on dry, vertical schist faces in Central Otago), to partial shade, on concrete fenceposts, bridges, gravestones etc., and on asphalt footpaths and along concrete curbing. Known from all major landmasses including Antarctica (Awasthi 1960; Thomson 1963; Moberg 1977, 1986b, 1990, 1997, 2001, 2002b, 2002g, 2004b; Redon 1985; Swinscow & Krog 1988; Purvis et al. 1992; Nimis 1993; Santesson 1993; Esslinger & Egan 1995; Hansen 1995; Egea 1996; John 1996; Kondratyuk et al. 1996a; Seaward 1996; Elvebakk & Hertel 1997; Esslinger 1997; Elix & McCarthy 1998; Galloway & Quilhot 1999; Diederich & Sérusiaux 2000; Scholz 2000; Calvelo & Liberatore 2001; Hafellner & Türk 2001; Llimona & Hladun 2001; Øvstedal & Lewis Smith 2001; Coppins 2002b; Elvebakk & Moberg 2002; McCarthy 2003c, 2006; Kurokawa 2003; Nimis & Martellos 2003; Santesson et al. 2004; Søchting et al. 2004).

Cosmopolitan

Illustrations : Martin & Child (1972: 125, pl. 35); Filson (1974a: 5, pl. 2A–D); Moberg (1977: 65, fig. 29); Jahns (1980: 245, pl. 615); Moberg & Holmåsen (1982: 200); Thomson (1984: 354); Phillips (1987: 174); Dobson (1992: 264; 2000: 303; 2005: 339); Goward et al. (1994b: 110, fig. 8B); Hansen (1995: 54); Wirth (1995b: 731); McCune & Geiser (1997: 230); St. Clair (1999: 147); Brodo et al. (2001: 553, pl. 663); Øvstedal & Lewis Smith (2001: pl. 63); Nordic Lichen Flora Vol. 2 (2002: 98); Sérusiaux et al. (2004: 137).

Physcia caesia is characterised by: the saxicolous habit; the rather narrow convex lobes; maculae on the upper surface (×10 lens) imparting a distinctive spotted or marbled appearance; and the marginal capitate soralia; and the thick, blackish, simple rhizines often projecting from the lower surface at lobe apices. It may sometimes be confused with P. poncinsii but the distinctly crateriform soralia of the latter species are characteristic. Specimens from coastal habitats from Northland (Karikari Peninsula) to southern Stewart I. (Port Pegasus) are sometimes parasitised by the lichenicolous fungus * Polycoccum pulvinatum (Eitner) R.Sant. (Galloway et al. 1999), which is characterised by its distinctive laminal, erumpent galls on the upper surface of P. caesia, and its brown, 1-septate ascospores, (16–)17–20(–21) × 7–9 μm, the upper cell larger.