Bloody-heart Lichen

The thallus of Mycoblastus sanguinarius ranges in colour from pale to dark grey. The thallus is often very irregular, thick, and has a coarse, wart-like (verrucose or papillose-warted) texture, giving it a marbled appearance. It can be continuous or somewhat cracked, and sometimes a pale to dark grey prothallus (the initial growth stage) is present. Soralia (propagules for asexual reproduction) are rare but, when they do appear, they are rounded, scattered, often few in number, and can be the same colour as or paler than the thallus. These soralia are convex and have an efflorescent (powdery) appearance. The apothecia (sexual reproductive structures) are usually frequent and measure between 0.5 and 1.7 mm in diameter, occasionally up to 3.0 mm. They are black, becoming convex or hemispherical as they mature, and can be sessile (sitting directly on the thallus) or slightly constricted at the base. These apothecia develop on a bright carmine-red thalline cushion that becomes visible when the thallus is damaged or worn. The asci (spore-producing cells) typically contain 1 to 3 spores. The ascospores themselves are cylindrical with rounded ends, measuring 70–100 μm in length and 35–45 μm in width, with a thick wall of about 6–7 μm. Mycoblastus sanguinarius also commonly has pycnidia, which are small asexual reproductive structures. …

Mycoblastus sanguinarius grows in a variety of habitats, primarily growing as an epiphyte on tree bark in cool, moist environments. It is found in temperate forests across North America, Europe, and Asia. This lichen is particularly abundant in boreal and montane forests, where it often grows on the bark of coniferous trees such as spruce and fir. The species is also known to colonise decaying wood and, less frequently, mossy rock surfaces.