Stigmidium microspilum  (Körb.) D. Hawksw.

  Graphis scripta parasitic Ascomycota

    Colonies are easily recognizable in irregular blackish carbonaceoous (or brown-violet) patches, 2-5 mm across, regularly scattered over the pale grey-greenish or pale greenish thallus of host. Towards the center of the main black spots, small clusters of perithecia may be observed. Perithecia blackish with small ostioles sit on the top, leaving small cupules when falling down. Ascospores colourless, elongate, ellipsoid, sometimes curved, 1-septate, 13-18 x 2-4 µm, conidia 3-5 x 1 µm. Rather common, but understated, grows on thalli of Graphis scripta  mainly in very humid woodlands and forests. Not to be confused with  Polymorphum rugosum, the anamorph (imperfect form) of Ascodichaena rugosa  that is rather similar, at least macroscopically, but devoid of perithecia, found on smooth bark of trees, notably Fagus, and above all, not parasite of Graphis scripta.*