Arthopyrenia analepta (Ach.) A. Massal.
Thallus hardly visible or glossy resulting bark, this species probably being not lichenized. Perithecia black, rounded to oval-shaped with a base circled by a blackish belt, 0.3-0.6 mm max. length. Asci cylindrical. Ascospores colourless (but sometimes dark at the end of observation), surrounded by a hyaline perispore, clavate, 1-septate, markedly constricted at septum level, with 1 or 2 vacuoles in each segment, 15-23 x 5,5-8 µm. Chemical spot tests negative. Common and widespread on smooth bark of deciduous trees. N.B. Species close to Arthopyrenia fraxini of which perithecia are smaller, ascospores less enlarged with a less important constriction and issued from pyriform asci. When growing on Betula bark, can easily be confused with Leptorhaphis epidermitis of which ascospores are different (boomerang-shaped). N.B. There are a great number of similar species rather difficult to identify, even with careful microscopic observations.*