Hypoxylon carneum Petch.
Stromata effused on wood, more pulvinate on bark, widely to narrowly ellipsoid, 11-35 mm long x
3-15 mm broad x 0.4-0.5 mm thick; surface plane or irregular, with
inconspicuous perithecial mounds,dark purple (36), dark vinaceous (83), dark livid (80, when
young with white, pinkish or red brown effused margins; yellowish granules
beneath surface and between perithecia, giving a greyish lilac (100) colour
to the tissue beneath surface and between perithecia, with KOH-extractable
pigments dilute livid violet (79), absent in aged material; the tissue below the perithecial layer
inconspicuous to 200 µm thick, dark brown.
Perithecia spherical to obovoid, 200-300 µm diam x 250-350 µm
Ostioles lower than the stromatal surface, on mature stromata
surrounded by a ring of white substance 60 µm diam.
Asci 85-120 µm total length x 7-7.5 µm broad, the spore
bearing-parts 56-78 µm long, the stipes 25-55 µm long, with apical ring
discoid, amyloid, 0.8-1 µm high x 2.5-2.8 µm broad.
Ascospores light brown to brown, ellipsoid nearly equilateral,
8.8-11 x 4-4.8 µm (M = 9.8 x 4.6 µm), with straight germ slit
spore-length, at the centre of a darker band 1 µm broad; perispore
dehiscent in 10% KOH, smooth.
Anamorph in nature: white, velvety, at margins or on young
stromata. Conidiogenous cells hyaline, 10-20 x 2-3.5 µm; conidia
ellipsoid, hyaline, 3.5-4.8 x 2-3 µm. Conidiogenous structure is
Habitat: on wood or bark of branches and trunks of various hosts,
in contact with the soil in damp places. Recorded during this
study on Acer pseudoplatanus, Cornus sanguinea, Crataegus sp.,
Cydonia oblonga, Fraxinus excelsior, Malus sylvestris, Populus
tremula, Prunus spinosa, Salix atrocinerea, Salix caprea, Sorbus
torminalis, Tilia platyphyllos and Ulmus minor.
Known distribution: worldwide, reported from France (present study), New
Zealand, Sri Lanka, USA and Venezuela
(Ju & Rogers, 1996).
Specimens examined: FRANCE, Ariège (09): Rimont,
Las Muros, ruisseau de Peyrau, 12 Sept.1999, JF-99213, on Salix
caprea; Rimont, Las Muros, 27 Jun. 2000, JF-00103, on Ulmus
minor; Rimont, Las Muros, ruisseau de Peyrau, 22 Sept.2000,
JF-00209, on Ulmus minor; Rimont, Las Muros, 08 Feb.
2001, JF-01015, on Ulmus minor; Rimont, Las Muros, 06 Apr.
2001, JF-01061, on Sorbus torminalis. Haute Garonne (31): Montespan,
Le Pont, 17 Jun. 2002, JF-02107, on Ulmus sp. Pyrénées
Atlantiques (64): Mauléon, les Barthes de l'Hôpital Saint
Blaise, 27 Oct. 1998, JF-98180, on Salix atrocinerea.
Notes: Hypoxylon carneum is distinctive in having
small-sized effused stromata with a purplish tone, small-sized perithecia
surrounded by a greyish lilac tissue yielding dilute livid violet pigments in
10% KOH, and equilateral ascospores with the germ slit at the centre of a
darker band. This band is reported as dotted by
Ju and Rogers (1996) but
this feature is hardly visible under usual conditions. Another taxon with
similar stromatal colour and germ slit morphology is
H. vogesiacum (Pers.) Sacc.
which differs in having much larger ascospores 20-25 x 8-10 µm.
Hypoxylon carneum may be confused with small effused stromata of
H. perforatum and
Both H. fuscum and
differ in yielding olivaceous yellow pigments in 10%
KOH and in having larger inequilateral ascospores, while
is mainly different from H. carneum in having
orange or yellow brown granules yielding orange pigments in 10% KOH.
Hypoxylon carneum, which has not previously been reported from
Europe, is probably overlooked as it is easily confused with the common
and widespread above species. Its disjointed distribution probably reflects its
difficulty to be identifieded. In the field, a tangential section of
the stromatal surface readily shows the
greyish lilac tissue between the perithecia, which is diagnostic.
In their monograph,
Ju & Rogers (1996)
describe the stromata of
H. carneum with chestnut surface and yellowish brown to reddish
brown granules between perithecia without apparent KOH-extractable
On the other hand, the stromatal surface of the type collection
(Petch, 1924) is said to
be pinkish and the interperithecial tissue of pale red or
purple red hyphae, and that could more or less agree with our collections.
Unfortunately this type materiel is ruined by mercuric chloride used as
its stromatal features are no longer reliable and
KOH-extractable pigments were not reported.
Despite these differences, Professor J. D. Rogers identified three of
our collections as H. carneum (pers. comm.), relying on the
peculiar morphology of ascospore germ slit. This identification was
fully confirmed by comparison of HPLC profiles of type material from Sri Lanka
with material from France and other locations (Stadler, pers. comm.). HPLC
analyses reveal H. carneum stromata lack mitorubrin and other usual metabolites
of Hypoxylon, but contain BNT and yet unknown compounds
(Stadler, pers. comm.).