Rosellinia helvetica L. Petrini, O. Petrini & S. M. Francis.
Stromata densely gregarious on blackened wood, uniperitheciate,
at times fused in a few peritheciate stroma, dark brown to black, when young with
a greyish tomentose coating, subglobose with a conical apex, 0.6-0.8 mm high x 0.6-0.8 mm diam;
ectostroma carbonaceous, brittle; subiculum brown to dark brown, abundant,
felty, persistent at least at the base of mature stromata, usually conspicuous.
Ostioles papillate, conical.
Asci cylindrical, long-stipitate, with apical apparatus 5.5-6 x 4-4.5
µm, slightly urn-shaped, amyloid.
Ascospores 20-24.5 x 6.8-9.5 µm, ellipsoid-inequilateral with narrowly
rounded, slightly pinched ends, dark brown, with a straight germ slit spore-length on the less
convex side, with a slimy sheath on the flatenned side and the ends, 3-4 µm
wide on fresh material, soon disappearing.
Anamorph in nature: not seen.
Specimens examined: FRANCE: Ariège (09): Orlu,
Bois de Seys, 1700m, 03 Nov. 2004, JF-04250, leg. L. Gire, comm. G. Corriol,
on wood of Fagus sylvatica; Prades,
Forêt Domaniale, Bois de Font Frède,1100 m, 28 Sept. 1997, JF-97168, on wood of Fagus sylvatica;
Quérigut, Forêt de Bragues, refuge du Laurenti, 1600 m, 20 Aug. 2000, JF-00163,
on wood of Fagus sylvatica.
Notes: Rosellinia helvetica is a taxon erected by Petrini et
al. (1989), separated from other members of the R. mammaeformis complex
mainly through its conical-topped stromata embedded in a persistent subiculum.
However, as this subiculum is less developped than in members of subgenus
Rosellinia, and stromata smaller and less carbonaceous, it was kept in
subgenus Calomastia (Petrini, 1993).
Two of our collections are unfortunately in poor condition and lack asci
and fresh ascospores, therefore the ascospore slimy sheath was not checked.
However, the characteristic rather small stromata with a conical apex, embedded
in a persistent felty subiculum, combined with ascospore size and shape, and
host preference for Fagus in mountain forests allowed for a reliable identification.
The specimen JF-04250 is much more characteristic with its stromata deeply immersed
in the subiculum and ascospores with a conspicuous slimy sheath.
Aside its host preference for Fagus, one record on Salix viminalis
is reported by Petrini
et al. (1989). The known distribution of R. helvetica
is central Switzerland and central Pyrénées, but is likely to be extended to
additional mountain regions at least in Europe.