Verrucaria compacta
≡Placidium compactum A.Massal., Misc. Lich.: 62 (1856).
Description : Thallus on rocks, areolate to subsquamulose, dark olive-green, dark-brown or greenish black, matt, smooth. 0.2–0.3 (–0.5) mm thick, corticate; areolae or squamules plane to convex, normally contiguous, 0.1–1.0 m diam., often slightly attenuated at base. Prothallus and basal layer not apparent. Perithecia ±immersed, 1–3 per areole or squamule, apex rounded or somewhat flattened, to 0.2 mm diam., ostiole inconspicuous or in a minute depression. Involucrellum absent. Exciple 30–40 μm thick, hyaline at base and sides, darkening to brown-black at apex. Centrum 0.18– 0.25 mm wide. Periphyses 25–35 × 1.5–2.0 μm. Asci 50–65 × 15– 23 μm. Ascospores subglobose to globose, 8–13 × 8–11 μm. Pycnidia immersed, 70–120 μm diam. Conidia bacillar, 1.5–3.0 × 0.5 μm.
S: Otago (Ngapara). On limestone. Known also from Europe, Scandinavia, and Australia (McCarthy 2003c, 2006).
Cosmopolitan
Verrucaria compacta is characterised by: the basicolous (limestone) habit; dark olive-green to dark-brown or greenish black, areolate to subsquamulose thallus; immersed perithecia; exciple colourless at base and sides, brown-black at ostiole; ascospores subglobose to globose, 8–13 × 8–11 μm.
