Biscogniauxia marginata (Fr.: Fr.) Pouzar.
Stromata gregarious, orbicular to broadly ellipsoid, 3-8 mm diam x
3-4 mm thick, cupulate with raised margins, with the
base broadly attached to the underlying wood; surface carbonaceous, dark grey
to dull black, on immature stromata hidden under an operculum-like ochreous
outer layer which dehisces as a whole; the tissue beneath the perithecia
2-3 mm thick, of whitened host tissue in places mixed with melanized tissue.
Perithecia obovoid to tubular, 0.4-0.5 mm diam x 0.6-1.2 mm high, ostiolar canal lined
with greyish tissue.
Asci short stipitate, with apical ring discoid, amyloid.
Ascospores blackish brown, broadly ellipsoid to subglobose, 12-14.5 x
8-12.5 µm, with a sigmoid germ slit spore-length.
Specimens examined: FRANCE, Ariège (09): Camarade, Les Moulis, 13
Dec. 2002, JF-02240, on Sorbus aria; Durban sur Arize, Fajal, 23 Sept.
1995, JF-95009, on Sorbus aria; Rimont, Las Muros, 04 Jul. 1999, JF-99141,
on Malus sylvestris. Haute Garonne (31): Vigoulet Auzil, 21 Mar. 2000, JF-00030,
on Fraxinus excelsior.
Notes: in the field, B. marginata is distinctive thanks
to its gregarious small-sized rounded and cupulate stromata, spreading over
large areas on dead standing stems or branches. Biscogniauxia marginata
shares with B. simplicior the combination of raised stromatal margins
and umbilicate ostioles. Its ascospores are blackish brown and subglobose with
a sigmoid germ slit, while those of B. simplicior are brown, narrowly
with a straight germ slit.
Biscogniauxia marginata is widespread in Europe and North America,
mostly associated to the Rosaceae.