Plectocarpon lichenum (Sommerf.) D. Hawksw.
Lichenicolous ascomycete fungus.
Appears on the host surface as gals containing asci. Gals rounded, to 0.5-5 mm diam., scattered all over the host thallus, on upper as well as lower surfaces, black to blackish, more or less spherical and muriform, narrower towards their base that may somewhat be circled with a pale brown colour, but they also may be flattened and button-shaped with an upper surface plane or slightly convex and verrucose. Ascospores hyaline, then brown, oblong, 3-septate, 18-21 x 5-6,5 µm. Rare, on lobes of Lobaria thalli, notably here on Lobaria pulmonaria (see pictures).*