Muellerella lichenicola (Sommerf.) D. Hawskw.
Muellerella atricola (Linds.) Sacc. & Sacc. ?
Parasitic fungus of saxicolous lichens.
Parasite visible in the form of black perithecia, immersed in the thallus of the host and very rarely superficial, subglobose 80-150 µm in diameter with a more or less regularly rounded and sometimes papillate ostiole. Asci sometimes difficult to observe because of the very fragile walls which disintegrate at maturity, 60-70 x 20-26 µm according to the literature, 55-65 x 18-25 according to our measurements, polysporous with more than 64 spores. Ascospores broadly elliptical, brown, smooth, 1-septate, 5.5-7 x 3-3.5 µm according to literature, 5-8 x 3-4 according to our measurements. Fairly common species, parasitic on saxicolous crustose lichens of the genera: Lecanora, Rhizocarpon, Lecidea, etc.
N.B. Species whose parasitism can sometimes considerably alter the host by making its thallus sterile and unrecognizable.
N.B. Very variable species depending on the host. Would be the sexual form (teleomorph) of Lichenodiplis lecanorae.
N.B. May make one think macroscopically in some cases of Cecidonia xenophana but the latter species has superficial and even sessile apothecia and its spores are simple.