ASCOMYCOTA | ARTHONIOMYCETES > ARTHONIALES > Arthoniaceae

Genus Arthonia, meaning 'to sprinkle' referring to the scattered apothecia

Common name:            -

Synonym:                     Opegrapha atra

Habitat:                         Woodland, wayside trees

Substrata:                     Bark

Growth form:                Corticolous

Thallus:                 Crustose

Apothecia:                    Lirellate

BLS identity rating:        Graded 1/5 (identification should be straightforward)

Thallus thin, smooth, delimited or sometimes almost evanescent, typically 2-4cm across; silver-white, cream to pale greenish-grey, sometimes with a yellowish tinge; lirellae short, usually no more than 2mm long, slightly raised, simple or forked, rarely stellate, blackish with central narrow, seldom open slit, more often than not in clusters or as a network of dense meshes, particularly at the centre of the thallus, sometimes arranged parallel like 'writing lines'.

Arthonia atra is a common and generally widespread species, occurring on the trunk, branches and twigs of mainly smooth- barked trees in lightly shaded locations; often found mosaic-forming on young trees with other smooth-barked species.

Could be confused with Graphis scripta, although the smaller, prominent and usually more densely packed lirellae should help to distinguish.

All of the photos featured below have been checked and confirmed by an experienced lichenologist.