Rosellinia mammaeformis (Pers.: Fr.) Ces. & De Not.
Stromata uniperitheciate, scattered to gregarious, rarely
fused in a 2-3-peritheciate stroma, dark brown to black, carbonaceous, hemispherical to
subglobose with usually flattened to rarely cupulate
top and broadly attached base, 0.7-1 mm diam x 0.6-0.9 mm high; subiculum absent
around mature stromata, a few immature stromata found growing on a cream white
hyphal mat of hyaline hyphae 2.5-3.5 Ám broad, heavily encrusted and then up
to 6 Ám broad.
Ostioles papillate, minutely to broadly conical.
Asci cylindrical, with apical apparatus cylindrical with a
at the apex, amyloid, 3.5-5 Ám high x 2.8-3.8 Ám broad.
Ascospores 17-21 x 6-7 Ám, ellipsoid-inequilateral,
brown, with ends darker and usually pinched, with a straight germ slit spore-length on the less convex side; a conspicuous
sheath present at both ends and on the flattened side.
Anamorph in nature: not seen.
Specimens examined: FRANCE: AriŔge (09): Les
Cabannes, route de Beille, 950 m., 24 Oct. 1996, JF-96149, on bark of Tilia
sp. Tarn (81): Escoussens, La BlancariÚe, 07 Feb. 2002, JF-02024,
on unidentified rotten wood.
Notes: Rosellinia mammaeformis was long
a name applied to taxa with different morphological and ecological features
that has been redefined by Petrini
et al. (1989), on the basis of examination of herbarium
material labelled under this name. They chose a lectotype, and showed that most
of material labelled R. mammaeformis should be better placed in a new
taxon they named R. britannica (see notes under this name).
Rosellinia mammaeformis and R. britannica
are very similar in external appearance, as they both have subglobose flat-topped
stromata and evanescent subiculum.They are primarily distinguished by ascospore
characters: ascospores of R. mammaeformis are shorter than those of R.
britannica ( 16-21 x 6-8 vs. 20-26 x 6-9 Ám) and exhibit a conspicuous slimy
sheath around the ends and along the flattened side, while in R. britannica
only the slimy caps at the ends are clearly visible. In addition ascal apical
apparati are significantly longer in R. britannica than in R. mammaeformis.
Petrini et al. (1989) report R. morthieri Fuckel, only known from
the type collection, as very similar to R. mammaeformis,
merely differing in slightly larger ascospores. They tentatively kept the name
R. morthieri, awaiting further collections and data.
Despite a systematic checking of Rosellinia specimens externally resembling
these two species, R. mammaeformis was only recorded twice, and
therefore can be considered much rarer than R. britannica, at least in
our region. Rosellinia mammaeformis has been recorded
on Corylus or Populus (lectotype), Fraxinus and Salix
The cream white hyphal mat associated with immature stromata in collection
JF-96149 is a puzzling feature which is not in agreement with the light brown
to brown subiculum reported by Petrini
et al. (1989). It is unclear whether it is an
immature member of Corticiaceae or something else.