Verrucaria phaeoderma
Description : Thallus epilithic, sparingly to richly rimose, rarely areolate, smooth, matt, medium grey-green to greenish black or grey-black, darker thalli becoming reddish brown when moist, paler thalli becoming intensely green, all forms becoming somewhat gelatinous, usually delimited by a black prothallus, lacking a dark basal layer, 40–120 μm thick. Areolae 0.3–0.8(–1) mm wide, angular, irregular, plane. Cortex paraplectenchymatous, 8–10(–14) μm thick. Photobiont cells subglobose to globose, 1–17(–20) × 7–16 μm, scattered. Perithecia ⅓–⅔ immersed, very numerous; apex rounded or somewhat flattened, becoming irregularly fissured with age. Ostiole usually in a shallow depression 40–80(–100) μm wide. Involucrellum 0.16–0.27 mm diam., brown-black, K+ greenish black, contiguous with exciple and extending to exciple-base level, 40–50 μm thick. Centrum globose to depressed-ovate, 0.1–0.18 mm diam. Exciple 12–15 μm thick, outer layers greenish black, internally colourless, Periphyses sparingly branched, 15–30 × 1.5–2.5 μm. Asci clavate to cylindrical-clavate, 53–70 × 18–26 μm. Hymenial gel I+ brownish red. Ascospores ellipsoidal, narrowly ellipsoidal or subcylindrical, irregularly massed in asci, 14–24 × 5–10.5 μm, contents clear or finely granular and guttulate.
S: Southland (Borland Valley), Otago (Nenthorn, Three O'Clock Stream). On streamside rocks close to waterline. Known also from SE Australia and Tasmania and recently from Taiwan (McCarthy 1995f; 2001j: 191; 2003c; Aptroot 2003).
Australasian
Illustration : McCarthy (1995f: 117, fig. 5).
Verrucaria phaeoderma is characterised by: the saxicolous (aquatic rocks) habit; a dark and scarcely cracked thallus; comparatively large photobiont cells; small perithecia, and ascospores 14–24 × 5–10.5 μm.
