Graphis scripta (L.) Ach.
Thallus crustose, 2-8 cm long, often forming ovoid 'banners', perpendicular to trunk axis, smooth or slightly uneven, pale grey-greenish, grey-whitish, the var. limitata being surrounded with a prothallus black line. Apothecia lirelliform, 5-25 x 1-2 mm, more or less immersed but always slightly prominent and embossed, discontinuous in depth, leaving a white scar after falling down, simple and curved, forked, branched, stellate, etc., with raised, unfurrowed, carbonaceous margins, disc narrow, hardly visible (except for some varieties), blackish with whitish pruinose. Ascospores colourless or brownish when old, markedly elongate, fusiform, 5-10-septate, but not muriform, (insect larva appearance), 25-70 x 6-10 µm. Photobiont: Trentepohlia. Chemical spot tests negative. Common, on moderately shaded, smooth bark of a wide range of trees. Highly variable species, many varieties and morphs have already been described, based on questionable criteria, and they hardly can be considered here. See Graphis elegans of which the apothecia are shorter and less numerous and thallus K+ red, Pd+ yellow-orange (sometimes faint). N.B. Often difficult to distinguish on the field from Graphis britannica of which lirellifrom apothecia are more immersed and less embossed and ascospores muriform. Frequently found with the parasitic species Stigmidium microspilum visible as black spots possibly with perithecia.*