Mycoglaena myricae (Nyl.) R. C. Harris
Arthopyrenia aeruginella (Nyl.) Arnold
Thallus immersed in the bark and probably not lichenized because photobiont absent. Perithecia (or better: perithecioid formation) at bark level or barely prominent, circular to elliptical from 0.2 to 0.4 mm in diameter, blackish and typically surrounded by a circular silvery-white halo which gives them a cockade aspect. Asci with 8 spores, club-shaped, 50-70 x 10-18 µm according to our measurements. Long ovoid spores with pointed ends, in the ascus first 1-septate and delimiting 2 slightly triangular alveoli, these alveoli then tighten towards their center giving the impression of a septum delimiting 2 alveoli of different size, which makes the spore appear as 3-septate, but it is rather an incomplete false septum and the spore could be considered only as 1-septate, 16-20 x 4.5-7 µm according to the literature, 15 -18 x 5-7 according to our measurements. Rare species typically coming from old branches of Myrica gale and more rarely from small twigs of Betula, etc. Species theoretically frequent on its host but which in practice is rare (or which goes unnoticed?), To be sought in marshes and peatlands with Myrica gale which is a fairly common wetland species in Brittany, but so far we have only found Mycoglaena myricae on Myrica gale in peat bogs not far from the sea.