Bacidia rubella (Hoffm.) Massal.
Thallus crustose, effuse, not well delimited, consisting of small granules 60-120 µm diam., aspect often isidiate-like, grey-green when dry to yellow-green or green when moist. Apothecia variable in number, sometimes clustered, sessile and usually distinctly constricted below, 0,5-1,2 mm diam., discs flat to slightly convex, pale to dark red-brown, thick margin, smooth or white pruinose, hyaline or pale orange-red, in general persistent. Ascospores needle-shaped (acicular), 3-7(13)-septate, 40-70 x 2,5-4 µm. Photobiont : Chlorophycea. Chemical spot tests negative. Rare in our prospection area, on trunks of old or wounded trees, mainly aligned or in parklands (Fraxinus, Platanus, Ulmus, etc).*