Euepixylon udum (Pers.: Fr.) Laess°e & Spooner.
For synonyms, see Laess°e & Spooner, 1994.
Stromata immersed to half-erumpent, usually multiperitheciate, linear
1.5-10 mm long, often coalescent and forming broader patches; stromatal surface
dark brown to black, when young with an ochreous-white powdery coating,
forming a clypeoid carbonaceous layer 60-120 Ám thick extending deeply into
the substrate. Perithecia subglobose to obovoid, 0.5-0.9 (-1.1) mm diam
x 0.7-1.1 mm high. Ostioles papillate, broadly conical, black.
Asci short-stipitate, with discoid amyloid apical ring 1.5-2 Ám high x 4-5
Ám broad. Ascospores brown, ellipsoid nearly equilateral, 23-32 x 9-12.5
Ám, with a poroid ellipsoid germ slit 5-7 Ám long x 2-3 Ám broad, on the more
convex side when ascospores are inequilateral; immature ascospores with a fugacious
and inconspicuous hyaline rounded cellular appendage 2 x 2 Ám.
Specimens examined: FRANCE: AriŔge (09):
Rimont, Las Muros, 14 Nov. 1996, JF-96165, on Acer campestre;
Rimont, Las Muros, 12 Jan.
1997, JF-97010, on rotten wood of Quercus robur; Rimont, Las Muros,
ruisseau de Peyrau, 25 Sept. 2001, JF-01204, on rotten wood of Corylus avellana;
Rimont, Las Muros, ruisseau de Peyrau,15 Aug. 2002, JF-02140, on rotten wood
of Quercus robur; Rimont, Grillou, 13 Nov. 2002, JF-02215, on rotten
wood of Quercus robur.
Notes: Euepixylon udum is not uncommon but rarely reported,
owing to its inconspicuous stromata that are easily overlooked. Moreover, it
is easily confused with Nemania confluens (Tode: Fr.) Laess°e & Spooner
which is macroscopically similar in having a few perithecia more or less immersed
under a black clypeoid stromatal crust extending into the substrate. Nemania
confluens differs from E. udum in having shorter ascospores with
more narrowly rounded ends and a straight germ slit spore-length.
Euepixylon udum is so far known from Europe
(Petrini and MŘller, 1986;
Granmo et al., 1999,
Laess°e et al., 2000), and constantly grows on decorticated
rotten sapwood, mostly of Quercus, but also found on Corylus and
once on Acer campestre.