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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 µm diam x 380-600 µm
high.
Ostioles lower than the stromatal surface, infrequently slightly
higher, surrounded by a ring of white substance 60-70 µm diam.
Asci 190-240 µm total length x 11-19 µm broad, the spore
bearing-parts 95-176 µm long, the stipes 60-105 µm long, with apical ring
amyloid, 1.5-2 µm high x 3.5-4.8 µm broad.
Ascospores brown, ellipsoid-inequilateral, 18-29 x 8-11.5 µm (M
= 22.3 x 9.8 µm), 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 µm. Conidia olivaceous, broadly
ellipsoid, 3.5-4 x 2.5-3 µm.
Habitat: on rotten decorticated wood. Type collection is on
Acer pseudoplatanus
(Petrini & Müller, 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, Ariège (09): Orlu,
Réserve nationale d'Orlu, Jasse de Justiniac, 1280 m elev., banks of
Oriège, 29 Jul. 2001, JF-01152, on Ulmus montana; same location, 28
Sept. 2001, JF-01212, on Ulmus montana. Pyrénées
Atlantiques (64): Saint Just, Ibarre, Gorges de la Bidouze, 05
Apr. 1989, FC 5286-1, leg J. Vivant, on Ulmus montana.
Hautes Pyrénées (65): Saint Lary, Loudenvielle, Vallée
d'Aure, 28 Apr. 2002, JF-02077, leg. P. Valet, on Ulmus sp.
SWITZERLAND: Graubünden, 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 µm 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 µm 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.
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