Xanthoria aureola (Ach.) Erichs.

    Thallus loosely attached to the substratum, placodioid and rosette-forming, 10-15 cm across, composed of loose narrow lobes, strap-shaped, indented, radiating from the center, markedly branched, thick, surface uneven, sometimes rough with minute depressions, golden yellow to orange, possibly with green tinge in shaded sections or specimen, to the contrary of other Xanthoria species thriving together. Apothecia absent or scarce, and in that case, scattered and possibly restricted to minute urn-shaped excrescences, disc flat to concave, concolourous or darker. Photobiont: trebouxioid. K+ purple. Common, mostly saxicolous and littoral with a large habitat range: from a level just above Caloplaca thallincola to well-lit coastal rocks subjected to sea-spray. This relatively extensive habitat means that this species seems to appear in several taxa that vary according to the habitat zone but are fairly constant according to our observations, it seems to be only simple forms because there are all possible forms of passage (all these forms are being studied because it is sometimes difficult to separate them from certain forms of Xanthoria calcicola var. calcicola or Xanthoria parietina without sequencing):

1) Xanthoria aureola forme de la frange littorale.

    This form occurs in the black zone of the littoral fringe to Verrucaria (Hydropunctaria) maura. The thallus is pale yellow to golden yellow in color and is highly indented into long, branched, non-continuous, "lace" strips, not covering the entire substrate. N.B. Do not confuse with the sterile specimens of Xanthoria parietina that may grow into this area and which have less vivid and more greenish colorations, the lobes of which are short and broad and not cut into strips.

2) Xanthoria aureola forme de la zone mésique.

   This form occurs in the mesic zone: the lobes are more numerous and dense and cover almost or completely the substrate, the colors are golden yellow, yellow-orange, orange, sometimes with rare apothecia, it seems there is the very common type found in the "orange zone".

3) Xanthoria aureola forme de la zone aérohaline.

    This form occurs from the xeric zone to the aerohaline zone: the thallus is thicker because the lobes in strips overlap each other, bright orange for the thalli in the sun sometimes with rare orange-greenish tones for the thalli in the shade, this taxon makes the transition with the forms of Xanthoria parietina and especially of Xanthoria calcicola var. calcicola, which it is difficult to separate without careful examination and sometimes sequencing.

4) Xanthoria aureola forme ramicole de la zone aérohaline.

    This form occurs in the aerohaline heathlands on the twigs of Erica, Ulex, etc. sometimes on fruticose lichens.

5) Xanthoria aureola forme pseudoisidiée.

   This form which occurs in very exposed and sunny places has been separated from Xanthoria calcicola var. calcicola to which it strongly resembles by sequencing, it can however be recognized in the field by the "embossed" surface of its lobes.