Arthonia astroidestera Nyl.

    Thallus crustose, to 2-3 cm across, very thin, more or less immersed in bark, cream to cream-yellow, pale greenish, sometimes delimited by a thin prothallus, brownish. Apothecia abundant, 0.5-1 mm across, linear or sinuous, branched or stellate, dark brown, blackish, but seldom seen as such since covered with a thick white pruine, turning waxy when dry and suggesting paraffin wax droplets fallen down from a candle, this coating breaks down in old age while turning yellow and browning. Spores colorless then brownish and finely puncted, long conical-ovoid with a wider end, 4-septate, 18-24 x 6-7 µm according to the literature; 20-25 (27) x 5-8 (9) µm and 2-5-septate according to our measurements. C-, K-, KC-, P- but the pruine of apothecia emits a characteristic orange UV fluorescence. Rather rare and localized species occuring in the shade especially on the smooth bark of deciduous trees (Fagus, Ilex more rarely Quercus) in humid and dark oceanic forests.