Biscogniauxia nummularia (Bull: Fr.) Kuntze.
Stromata applanate, discoid 5-20 mm diam to irregularly ellipsoid
15-50(-120) mm long x 10-22(-60) mm broad x 0.6-0.8 mm thick; surface black, carbonaceous,
when young covered by a dehiscing light brown outer layer; tissue beneath perithecia
Perithecia subglobose to obovoid, 0.4-0.6 mm diam x 0.5-0.7
Ostioles discoid, slightly papillate to nearly at the same
level as the stromatal surface.
Asci short-stipitate, with a discoid
amyloid apical ring.
Ascospores dark brown to blackish, ellipsoid, frequently
with narrowly rounded ends, 11.5 x 13.5 µm, with straight, inconspicuous germ
Specimens examined: FRANCE, Ariège (09): Camarade, Les Moulis, 13
Dec. 2002, JF-02241, on Fagus sylvatica; Montseron, Ousset, 23 Feb.
1995, JF-95010, on Fagus sylvatica; Rimont, Grand Bois, 22 Mar. 1999,
JF-99047, on Fagus sylvatica; Salau, Mines d'Anglade, 09 Jul. 2000, JF-00114,
on Fagus sylvatica.
Notes: Biscogniauxia nummularia is distinctive among other
members of Biscogniauxia with applanate stromata in the combination
of black stromatal surface with slightly papillate ostioles, blackish brown
ellipsoid ascospores 10-13 x 7.5-8.5 µm and specificity for Fagus. The
closest taxon is B. granmoi, thoroughly described by Læssøe et al. (1999).
They pointed out the main differences between these two species: in B. granmoi,
ostioles are pitted and not papillate, stromatal margin is slightly raised, ascospores are medium brown, narrower
(x 5-6.5 µm) and all records were made on Prunus padus (in Europe) and
Prunus padus var. pubescens (in Far Eastern Russia).
Biscogniauxia nummularia, the type species of the genus Biscogniauxia,
is a common fungus specific for Fagus, recorded from all parts of Europe
and Russia, following the distribution of its host.