Verrucaria prominula
Description : Thallus superficial, often poorly-developed, white to pale-grey, always with a mauvish tinge, discontinuous, soft and crumbling, scabrid, not gelatinous when moist. Prothallus indistinct. Perithecia semi-immersed to almost superficial, 0.4–0.8 mm diam., black, prominent, sometimes 2–3-together, apex flat or depressed. Involucrellum closely attached to exciple. Exciple black, even at base. Ascospores ellipsoidal, the apices abruptly truncate, 12–15 × 7–10 μm.
S: Otago (Taieri Mouth). On vertical shaded faces, under overhangs, or in dry crevices on soft siliceous rocks, especially schist, commonly in mesic to xeric-supralittoral zones on seashores. Known in the Northern Hemisphere from France, Great Britain, Norway, North America and Taiwan (Clauzade & Roux 1985; Hawksworth et al. 1992; Aptroot 2003a; Santesson et al. 2004), and in the Southern Hemisphere from Tasmania (McCarthy & Kantvilas 2000a; McCarthy 2001j: 192, 2003c).
Cosmopolitan
Illustrations : Zschacke (1934: 189, fig. 83); Dobson (1992: 354; 2005: 451); McCarthy & Kantvilas (2000a: 33, fig. 2).
Verrucaria prominula is characterised by: the pale thallus; rather large, prominent perithecia that are frequently clustered; and the characteristic habit of soft maritime rocks in dry, shaded sites. It may be confused with V. muralis (q.v.) but is distinguished from it by the thallus colour, perithecial characters, ascospore shape and substratum preference.
