Massariosphaeria compositarum  

Anamorph: not known.
Teleomorph: ascostromata perithecial, 200-300 µm diam., scattered, black, the ostiolar region to 60 µm in height and 50 µm diam., conical, minutely erumpent through the plant epidermis, the neck composed of dark very thick-walled cells 10-12 µm long and 8-10 µm broad. Peridium  in the base only 10-12 µm thick, consisting only of 2-3 layers of pale yellowish, rather thin-walled flattened cells 8-10 µm in diam., gradually increasing in thickness in the lateral parts, where the cells are thicker-walled and darker. Interascal tissue of filamentous pseudoparaphyses. Asci 140-160 x ca 20 µm, numerous, clavate, broadly rounded at the strongly thickened apex, the base gradually narrowing, fissitunicate, 8-spored. Ascospores arranged biseriately above and uniseriately below, 42-50 x (7-) 8-10 µm, broadly fusiform, the ends obtuse, often slightly curved, with 6-7 transverse septa, constricted at the septa, the third cell from the apex slightly inflated, hyaline but often becoming pale yellowish-brown when senescent.