Rosellinia mammaeformis

              

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JF96149

JF02024

JF02024

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JF02024

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JF02024

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 marked rim 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 slimy 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 (Petrini et al.,1989).

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.