Mycoblastus sanguinarius f. sanguinarius

Thallus pale to dark grey, often very irregular and uneven, thick and ± coarsely verrucose or papillose-warted, appearing marbled, continuous or ± cracked, more rarely thin with scattered low warty papillae, a pale to dark grey prothallus sometimes present. Soralia rare; when present rounded, scattered, often few or confined to a few areas on a thallus, sometimes becoming confluent, concolorous with or paler than the thallus, convex, efflorescent. Apothecia 0.5–1.7 (–3.0) mm diam., usually frequent, black, becoming convex or hemispherical, sessile or slightly constricted beneath, developing on a bright carmine-red thalline cushion that may be exposed when the thallus is damaged or abraded. Asci 1- (to 3-) spored. Ascospores 70–100 × (28–) 35–45 µm, cylindrical with rounded ends; wall 6–7 µm thick. Pycnidia often present, 40–50 µm diam, wall dark green; conidia bacilliform, 6–9 × ca 1 µm. Cortex C–, K+ yellow, Pd+ yellow; medulla K+ red (in part), UV– (atranorin, chloratranorin, rhodocladonic acid (= mysaquinone), caperatic acid); soralia Pd–; hypothecium and tissue under the apothecium carmine to blood-red, K+ bright red, pigment diffusing into solution.

Mycoblastus sanguinarius and M. sanguinarioides are usually distinguished by the carmine-red tissue under the apothecia. Rarely, this pigmentation is absent, thus leading to confusion with M. affinis. Mycoblastus sanguinarioides was recently recognised as occurring in the northern hemisphere by Spribille et al. (2011). Subsequently M. sanguinarioides was confirmed from Britain, where it appears to be found as an epiphyte in temperate rainforests. It tends to have pruinose young apothecia surrounded by whitish thalline material, and the apothecia are flatter when mature. The only clear separation, however, is by the presence of crystals in the hymenium that are visible in polarised light. These crystals are lacking in M. sanguinarius.

Morphs with soralia are infrequent and have been treated as M. sanguineus f. leprosus, but nearly always also have abundant apothecia. They are mainly confined to upland Scotland. From current knowledge their separation does not appear to be justified.