Hypoxylon vogesiacum

              

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JF01152

JF01152

JF01152

JF01152

JF01212

JF01152

JF01152

JF01212


Hypoxylon vogesiacum (Pers.) Sacc.

Stromata effused-pulvinate, with inconspicuous perithecial mounds, 2-30 mm long x 1.5-8 mm broad x 0.5-1 mm thick; surface vinaceous purple (101) to dark livid (80), with a whitish pruina and then greyish lilac (100), eventually blackish when aged, usually wrinkled between perithecial mounds; yellowish to pale brown granules beneath surface with KOH-extractable pigments livid violet (79) to pale purplish grey (127), absent in aged material; the tissue below the perithecial layer brown, up to 0.5 mm thick.

Perithecia spherical to obovoid, 320-500 m diam x 380-600 m high.

Ostioles lower than the stromatal surface, infrequently slightly higher, surrounded by a ring of white substance 60-70 m diam.

Asci 190-240 m total length x 11-19 m broad, the spore bearing-parts 95-176 m long, the stipes 60-105 m long, with apical ring amyloid, 1.5-2 m high x 3.5-4.8 m broad.

Ascospores brown, ellipsoid-inequilateral, 18-29 x 8-11.5 m (M = 22.3 x 9.8 m), with straight germ slit spore-length; perispore indehiscent in 10% KOH, smooth.

Anamorph in nature: ochreous (44) to fulvous (43), velvety, on young stromata. Conidiogenous structure Nodulisporium-like, hyaline to pale brown, smooth. Conidiogenous cells 14-30 x 2 m. Conidia olivaceous, broadly ellipsoid, 3.5-4 x 2.5-3 m.

Habitat: on rotten decorticated wood. Type collection is on Acer pseudoplatanus (Petrini & Mller, 1986). In northern Europe it is found mainly on Ulmus sp. but also recorded on various deciduous hosts (Granmo et al., 1989).

Known distribution: Europe, North America, Asia, considered hemiboreal by Granmo et al. (1989).

Specimens examined: FRANCE, Arige (09): Orlu, Rserve nationale d'Orlu, Jasse de Justiniac, 1280 m elev., banks of Orige, 29 Jul. 2001, JF-01152, on Ulmus montana; same location, 28 Sept. 2001, JF-01212, on Ulmus montana. Pyrnes Atlantiques (64): Saint Just, Ibarre, Gorges de la Bidouze, 05 Apr. 1989, FC 5286-1, leg J. Vivant, on Ulmus montana. Hautes Pyrnes (65): Saint Lary, Loudenvielle, Valle d'Aure, 28 Apr. 2002, JF-02077, leg. P. Valet, on Ulmus sp. SWITZERLAND: Graubnden, Station Untervaz, Oberau, 22 Sept. 1983, FC-5237-1-b, on unidentified wood.

Notes: Hypoxylon vogesiacum is similar to H. macrosporum in several respects (see notes under H. macrosporum). The distinction between the two taxa is based mainly upon the olivaceous brown KOH-extractable pigments and the short germ slit and dotted epispore of ascospores of H. macrosporum, while H. vogesiacum lacks KOH-extractable pigments and its ascospores have a spore-length germ slit at the centre of a dotted band (Ju & Rogers, 1996).

All other Hypoxylon taxa with purplish stromata that could be confused with H. vogesiacum (i.e., H. carneum, H. fuscopurpureum, H. fuscum, H. macrocarpum, H. perforatum, H. petriniae) have much shorter ascospores, averaging less than 15 m long.

The specimens that we studied share with H. vogesiacum as described by Ju & Rogers (1996) similar purplish and pruinose stromatal surface, and ascospores averaging more than 20 m long, with a spore-length germ slit. They differ from the typical H. vogesiacum in producing livid violet to grey pigments in KOH and in having slightly larger ascospores lacking a dotted or darker band along the germ slit.

Professor J. D. Rogers, who studied the specimen JF-01212, thinks that it might represent an intermediate form between H. vogesiacum and H. macrosporum (pers. comm.). As, in addition, dehiscence of perispore is variable among different collections (Ju & Rogers, 1996), H. vogesiacum appears to be a problematic taxon which needs more records from various locations and more investigation.

HPLC analyses should shed some light on a possible heterogeneity within this species and affinities with H. carneum.