Biscogniauxia dennisii

              

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JF99190

JF99190

JFM9928

JF99190

JF96074

JF99190

JF99190

JFM9928

JF99190

Biscogniauxia dennisii (Pouzar) Pouzar.

Stromata orbicular to irregularly ellipsoid, 5-20 mm long x 5-12 mm wide x 2-3.5 mm thick, plane to slightly cupulate with raised margins, restricted at the centre where connected to the underlying wood; surface shiny black, carbonaceous, covered when immature by an outer stromatal layer which is externallyochreous and dry, and internally grey, gelified, pseudoparenchymatous; tissue beneath the perithecia 1.5-2 mm thick, of slightly whitened cortical host tissue mixed with dark fungal tissue.

Perithecia long tubular, 0.3 mm diam x 1.5 mm high.

Ostioles coarsely papillate.

Asci short-stipitate, with apical ring discoid, amyloid.

Ascospores blackish brown, 14-18 x 8.8-12.5 µm, broadly ellipsoid, with straight germ slit spore-length.

Specimens examined: FRANCE: Ariège (09): Rimont, Las Muros, 02 Jun. 1996, JF-96074, on Ulmus minor; same location, 18 Aug. 1999, JF-99190, on Ulmus minor. Haute Garonne (31): Martres- Tolosane, le Moulin, 27 Apr. 2002, JF-02087, on Ulmus minor.

Notes: similar stromata with raised margins and coarsely papillate ostioles are encountered in two other species: B. querna and B. repanda. The distinction between these two taxa and B. dennisii relies on ascospore size and morphology. In B. querna and B. repanda, ascospores have a circular germ slit while it is unilateral in B. dennisii; ascospores of B. repanda are smaller than those of B. dennisii, while those of B. querna are more globose and flattened. Moreover, B. repanda is mostly found on Sorbus aucuparia and has a hemiboreal to boreal distribution, while B. dennisii is plurivorous with a predominant occurrence on Ulmus and Quercus, and is found in temperate areas. Biscogniauxia querna is known from only one collection on Quercus (Pouzar, 1986). Biscogniauxia dennisii is so far known from central Europe (Pouzar, 1977, 1986) and southern Europe ( Candoussau, 1986).