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Hypoxylon perforatum (Schwein.: Fr.) Fr.
Stromata pulvinate or effused-pulvinate on bark, effused on
wood, with inconspicuous to very conspicuous perithecial mounds, frequently
wrinkled between perithecial mounds, 2-25 mm long x 2-8 mm broad x 0.5-1(-2.5)
mm thick; surface dark brick (60), sepia (63), umber (9) to brown vinaceous (84) or
dark vinaceous (82); dull yellow granules beneath surface, with
KOH-extractable pigments amber (47) to ochreous (44) or greenish yellow (16); the tissue
beneath the perithecial layer dark brown, inconspicuous or up to 2mm
thick.
Perithecia spherical to obovoid, 250-300 (400) µm diam x 300-400
µm high.
Ostioles lower than the stromatal surface, conspicuously
surrounded by a ring of white substance 60-120 µm diam on mature
stromata.
Asci 80-128 µm total length x 6-8 µm broad, the spore
bearing-parts 51-80 µm long, the stipes 24-51 µm long, with apical ring
discoid, amyloid, 0.8-1.5 high x 2-2.8 µm broad.
Ascospores brown to dark brown, ellipsoid-inequilateral, often
crescent-shaped, 9.7-11.5 x 4.7-5.3 µm (M = 10.9 x 4.9 µm), with straight
germ slit spore-length; perispore dehiscent in 10% KOH, smooth.
Anamorph in nature: vinaceous buff (86) to greyish sepia (106), velvety,
on young stromata or at margins. Conidiogenous structure
Virgariella-like, pale brown, smooth. Conidiogenous cells hyaline,
11-17 x 2.5-3.5 µm. Conidia broadly ellipsoid, 3.5-4.8 x 2.8-3.5 µm.
Habitat: on bark or wood of various trees or shrubs,
frequently found on branches that are not in contact with the soil. Very common
on Fraxinus excelsior and Ulmus minor, also collected on
Acer campestre, Coriaria myrtifolia, Cornus sanguinea, Corylus
avellana, Cydonia oblonga, Eucalyptus sp., Fagus sylvatica,
Frangula alnus, Juglans regia, Ligustrum vulgare, Mespilus germanica, Populus
tremula, Prunus domesticus, Prunus padus, Prunus spinosa, Quercus ilex,
Rhamnus catharticus, Robinia pseudoacacia, Rosa canina,
Salix caprea, Sarothamnus scoparia, Sorbus torminalis.
Known distribution : worldwide.
Specimens examined: FRANCE, Ariège (09): Rimont,
Las Muros, 12 Sept. 1996, JF-96093, on Fraxinus excelsior;
Rimont, Las Muros, 11 Nov. 1996, JF-96160, on Acer campestre;
Rimont, Las Muros, 20 Dec. 1996, JF-96182, on Sorbus
torminalis; Rimont, Las Muros, 19 Jul. 1997, JF-97101, on
Populus tremula; Rimont, Las Muros, 26 Jul. 2000, JF-00128, on
Populus tremula; Rimont, Las Muros, 02 Sept. 2000, JF-00181,
on Fraxinus excelsior; Rimont, Las Muros, 17 Jun. 2001,
JF-01113, on Cornus sanguinea; Saint Quirc, Forêt communale,
03 Dec. 2000, JF-00257, on Eucalyptus sp.
Notes Hypoxylon perforatum has long been considered to be a synonym of
H. rubiginosum
(Miller, 1961),
which, indeed, looks very similar. Later,
Petrini and Müller (1986)
proposed the varietal rank, as
H. rubiginosum var. perforatum, on account of its short-stipitate asci.
More recently
Ju and Rogers (1996)
considered it a distinct species, on
account of its different KOH-extractable pigments and different anamorph.
In the field, H. perforatum is usually distinguished by its
ostioles conspicuously encircled with a white substance but,
unfortunately, young stromata lack this distinctive feature. Moreover this
ostiolar feature may be encountered in several other taxa having similar
stromatal colour, i. e.,
H. carneum,
H. fuscum,
H. intermedium,
H. petriniae and
H. rubiginosum.
Hypoxylon carneum
differs in having livid violet KOH-extractable pigments,
H. petriniaeand
H. rubiginosum in
having orange KOH-extractable pigments.
H. fuscum and
H. intermedium
both have similar yellow pigments in KOH to those
of H. perforatum, but both have larger ascospores. The yellow
pigments observed in H. perforatum are due to hypomiltin, a recently
described new azaphilone, which is also present in H. intermedium
(Hellwig et al., 2004),
associated in both species
to orsellinic acid. Although pigments of H. fuscum obtained in KOH are
similar, they are due to very different compounds
(Mühlbauer et al.,2002 and
Quang et al., 2003).
In our area, H. perforatum is the more frequently encountered
species of Hypoxylon and undoubtedly the more plurivorous
one.
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