Heterodermia obscurata (Nyl.) Trevisan ss. auct. brit.

    Thallus shaped in rosette, 2-5 cm diam., well attached on its substratum, formed by notched lobes 1-2 mm wide, more or less radiant with rolled-up ends bearing white-greyish labriformes soralia, dull ivory upper side, creamy slightly glaucous when dry, grey-greenish when moist, sometimes with some tiny orange spots here and there ; lower side typically stained ochre-orange (at least towards the center of the thallus) or also with large ochre-orangy spots, K+ purple, some simple and tight rhizines can occur toward margins, black. Not fertile under our climate, elsewhere with a dark brown disc and a margin of the same colour than thallus, crenelated. Ascospores with a thick wall, ellipsoid, brown, 1-septate, 21-31 x 12-17 µm according to literature. Cortex and medulla : C-, K+ yellow, KC+/- yellow, Pd-. Rare, oceanic, growing among other foliose lichens on mushy trunks on trees in temperate and wet oceanic forests. Formerly identified as Heterodermia japonica but the interpretation of this latter was too wide. Cf. Heterodermia subneglecta lighter and of which lower side is not colour in ochre-orangy, growing in aerohaline heaths very exposed, and Heterodermia speciosa of which lower side is dull whitish.

NB The ocher-orange underside character is very unreliable and the examples presented here are given in the sense of the British authors, they are also subjected to sequencing as part of a review of European species very variously interpreted from this genera difficult.