Birch Woodwart

Fruiting Body

It is one of the stroma-forming Ascomycetes.
The stroma is a 0.5–1.0 cm thick, irregularly cushion-like, lumpy layer, growing horizontally on the bark of birch trees. Originally reddish brown then black. Surface uneven, bumpy (pimple-dotted). Individual stromata could emerge to form a big patch.

FYI:
stroma (singular) or stromata (plural) is a cushion-like mass of fungal hyphae that produces perithecia
hypha (singular) or hyphae (plural) a filamentous thread of fungal mycelium
perithecium (singular) or perithecia (plural) is a cylindrical to flask-shaped hollowed fruiting body which contains the asci
ascus (singular) or asci (plural) is the spore-producing cell of an ascomycete fruit body

Flesh

Tough, brittle, black.

Habitat

Saprotrophic on wood, mostly on Birch, rarely on other hardwoods, such as Alder, Hazel or Poplar. Can be found all year long in parklands, woodlands, and everywhere where dead birch trees are.

Possible Confusion

Beechwood Woodwart (Jackrogersella cohaerens), pictured, looks almost identical, but it grows exclusively on Beech (Fagus).

Frequency

It is very common and widespread in the UK.

Spores

Ellipsoid to bean-shaped, slightly flattened down on one side. Smooth, dark brown with a single oil-like droplet (guttule) within.

Other Facts

Birch Woodwart is the type species of a relatively new genus, Jackrogersella which only contains 6 species worldwide. This new genus was proposed only in 2017, and based on chemical and DNA evidence, it had been accepted. Birch Woodwart was formerly in genus Annulohypoxylon, that had been created from the species of the former Hypoxylon sect. Annulata in 2005.