Micarea lignaria var. lignaria

Thallus of scattered to confluent ± globose whitish, grey-green or bluish grey glossy or matt areoles 80–300 µm diam., sometimes ± immersed; photobiont cells 4–7 µm diam. Apothecia 0.15–0.6 (–0.9) mm diam., black or blue-black, immarginate, convex to ± globose, rarely with a stalk to 1 mm tall; true exciple ± distinct in young apothecia but soon reflexed, brownish in outer parts; hymenium 50–75 µm tall, colourless, or upper part and sometimes lower part olivaceous to blue-green, K–, rarely with a few scattered, minute violaceous (K+ green) granules; hypothecium pale blue-green or olivaceous, K–, but central part often ± colourless or pale brownish; paraphyses 1.3–1.8 µm diam., numerous, aseptate or sparingly branched above; apices often ± swollen and coated in green or greenish brown pigment. Asci 45–50 × 11–19 µm. Ascospores 16–36 (–38) × 4–6 (–7) µm, (0-) 3- to 7-septate, fusiform, straight or slightly curved. Pycnidia ± immersed; walls green (K–) in upper parts: (a) ca 100 µm diam., with macroconidia 16–22 × ca 1 µm, curved or hamate, 0- to 3-septate; (b) 100–140 µm diam., with mesoconidia 4–7 × 1.5–2 µm, ± cylindrical to obovoid; (c) 40–50 µm diam., with microconidia 5–7 × ca 0.8 µm, narrowly cylindrical; only (c) is common. Thallus C–, K–, KC–, Pd+ red (argopsin), the Pd reaction is not always easy to see; apothecial sections C–.

Micarea cinerea and M. peliocarpa differ in having Pd– thalli and C+ red apothecial sections (gyrophoric acid). Gilbertaria contristans has a Pd–, C– thallus and 1-septate ascospores. Protomicarea limosa has a similar Pd+ red thallus, but aseptate ascospores. Rare morphs of M. lignaria with stalked apothecia resemble Pilophorus strumaticus, which differs in having cephalodia, aseptate ascospores and a Pd± faintly yellowish thallus. Often confused with Bilimbia lobulata and B. sabuletorum, which grow in calcareous or base-rich habitats.