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Species Information
Summary: Features include 1) cushion-shaped fruitbodies on willow wood, 2) fruitbody color purplish gray becoming black, the surface with conspicuous perithecial mounds, 3) dull reddish brown granules beneath the surface and between perithecia, with KOH-extractable pigments greenish olivaceous, and 4) spores that are elliptic, nearly equilateral, and brown, with a continuous to discontinuous germ slit much less than spore-length, and with dotted ornamentation on the entire epispore. Miller, J.H.(1) considered H. macrosporum P. Karst. to be a synonym of H. mammatum (Wahlenb.) P. Karst. [== Entoleuca mammata (Wahlenb.) J.D. Rogers & Y.-M. Ju].
Hypoxylon macrosporum has been found in BC, WY, Russia, and Switzerland, (Ju).
Fruiting body: stromata [fruitbodies] 0.3-6cm x 0.2-1.5cm and 0.05-0.15cm thick; effused-pulvinate to pulvinate [cushion-shaped], surface purplish gray, becoming black when old; "with conspicuous perithecial mounds, usually with cracks along the valley of perithecial mounds"; "dull reddish brown granules immediately beneath surface and between perithecia, with KOH-extractable pigments greenish olivaceous"; the tissue below the perithecial layer grayish brown, inconspicuous to conspicuous, up to 0.1cm thick; perithecia spherical to obovoid, ostioles slightly higher than or at the same level as the surface, (Ju)
Microscopic: SPORES 22-31 x (7.5) 8.5-11 microns, elliptic, "nearly equilateral, with narrowly rounded ends, sometimes with one or both ends broadened", "brown to dark brown, unicellular", "with straight, continuous to discontinuous germ slit much less than spore-length", "perispore indehiscent in 10% KOH", epispore smooth, finely dotted beneath epispore; ASCUS 190-260 x 13-16 microns in total, spore-bearing part 130-180 microns long, the stem 50-90 mm long, with apical ring lightly blueing in Melzer''s reagent, discoid, 0.18-0.2 microns high and 0.5-0.6 microns broad; PERITHECIUM 100-400 microns in diameter and 300-400 microns high, spherical to obovoid, (Ju)
Habitat / Range
generally associated with Salix (willow) in glaciated areas, (Ju)
Similar Species
"Hypoxylon macrosporum differs from H. vogesiacum in having greenish stromatal pigments, in having darker, larger, more inequilateral ascospores, in having a less than spore-length germ slit, and in having dotted ornamentation on the entire ascospore epispore", (Ju).
