Micarea peliocarpa

Thallus greenish white or grey-white to blue-grey, of shallowly convex to subglobose areoles 40–200 µm diam; thallus occasionally poorly developed and ± immersed; photobiont cells 4–7 µm diam. Apothecia 0.14–0.4 (–0.6) mm diam., to 1 mm diam. if tuberculate, appressed, flat to convex, whitish (in shade) or blue-grey to black; true exciple well-developed, colourless; hymenium 40–55 µm tall, usually greenish to blue-green (K-, N± red) in the upper part; hypothecium ± colourless; paraphyses 1–1.5 µm diam., numerous, branched especially above; apices often thickened to ca 2.5 µm diam. by green pigment. Asci 40–55 × 12–17 µm, clavate, without ring-structure. Ascospores (11–) 15–23 (–24) × 3–5 (–6) µm, fusiform or cylindrical, ± curved, (1-)3(-5)- septate. Pycnidia frequent (especially on bark or wood): (a) 0.14–0.2 mm diam., immersed, white or greenish around often gaping ostioles, the macroconidia 21–40 (–50) × 1–1.5 µm, curved or sigmoid, often faintly 1- to 5-septate; (b) 50–80 µm diam., ± sessile, whitish, the microconidia 6–7 × 0.5–1 µm, fusiform–cylindrical. Thallus, apothecia and pycnidia C± red, K–, Pd– (gyrophoric acid).

Very variable and often confused with Micarea lignaria, which has C– apothecial sections. M. nitschkeana has smaller ascospores and a K+ violet epithecium. Micarea leprosula has similar apothecia but a Pd+ red, sorediate thallus. See also M. alabastrites and M. cinerea. Lecania naegelii has unbranched paraphyses with swollen apices, is C– and occurs on basic or nutrient-enriched bark.