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Species Information
Summary: The most conspicuous features are the radially elongated, relatively thick-walled pores and the pronounced umbo that typically develops at the base. Other features include a relatively large, bracket-like, approximately semicircular fruitbody with a tough texture, a bumpy-wavy surface that is whitish to ocher or green from algae, a whitish to gray-ocher pore surface, and microscopic characters including elliptic-cylindric spores and a trimitic hyphal system. Domanski(1) described five forms from Eurasia. Forma gibbosa has dimidiate fruitbodies 1-4cm thick, with the white to yellowish upper surface velvety, chamois-like or tomentose (usually bald when old), and pores "more or less rectangular or elongated, radially arranged, sometimes labyrinthine". Forma tenuis has a thinner fruitbody with tubes often confluent and merging into almost gill-like structures. Forma hirsuta is "of moderate size, with a thin margin and zonate surface, covered with dense gray hairs" (resembling those of Trametes hirsuta). Forma kalchbrenneri has a velvety to almost bald surface, zonate with belts either throughout or near the margin, and grayish-ochraceous, light- or rufous-cinnamon in color. Forma amurensis (east Asia) has an azonate or weakly zonate upper surface that is white (cream to grayish when dry), tubes 0.5-1cm long, with thinner walls than forma gibbosa and smaller (0.5 millimeters diameter), circular or angular, radially arranged pores.
Distribution includes BC, WA, and OR (Ginns), WI (Neuman), QC, PA, southeastern United States, (Kout), Denmark, Norway, Sweden, United Kingdom to USSR where beech grows, (Ryvarden(2)), Europe, China, Siberia, (Domanski), and Japan (Ryvarden(3)).
Cap: up to 20cm along substrate, projecting up to 15cm, 1-4cm thick at attachment, bracket-like, semicircular plate-like, broadly attached, margin sharp, undulating, often crenate [scalloped]; whitish when young, then ocherish to yellow-brownish, also green from algae, margin whitish to brown; cap surface "tuberculate-undulating, sometimes zoned, with distinct umbo where attached, here and there with proliferations", finely velutinous [velvety] to tomentose, becoming bald, (Breitenbach), up to 12cm along the substrate and projecting up to 12cm, 1-4cm thick at base, "pileate, applanate, broadly attached to dimidiate, semicircular to slightly elongated"; white to cream, when old ochraceous to grayish "in broad sulcate zones"; at first finely adpressed velutinate [velvety] to tomentose, becoming bald in zones, "margin sharp and even", (Ryvarden(2)), up to 15cm both along wood and projecting from it, 1-4cm thick at base, "pileate, applanate, sessile to dimidiate, usually semicircular in outline", tough and coriaceous, upper surface at first tomentose to bald, usually in zones, when old bald; "at first white, then cream to ochraceous or discoloured pale brown to olivaceous in spots and isolated areas, often greenish at the base due to algae"; margin sharp, (Ryvarden(3)), 8-10(12)cm x 5-12(20)cm x 1-4(8)cm, upper surface mostly flat, rather distinctly zonate, densely pubescent to velvety, sometimes tomentose or even strigose, finally bald, "white, grayish, yellowish, white-avellaneous or ferruginous-cinnamon, at the base sometimes olive-celadon or even greenish owing to the development of algae among hairs", margin "even, obtuse, later thin, sometimes rufous-brown"; hairs from surface 1-2cm x 0.01-0.05cm, (Domanski)
Flesh: very tough and elastic; white to cream-colored, (Breitenbach), up to 3cm thick at base, "tough and slightly succulent when fresh, bony hard when dry"; white to cream, (Ryvarden(2)), "white, dense, tough-fibrous, azonate", (Ryvarden(3)), in the central part up to 3cm thick, at the margin about 0.2-0.3cm, homogeneous, white, when fresh coriaceous [leathery] and succulent, "after drying light and corky", (Domanski)
Pores: 1-2 per millimeter, pore length up to 4 millimeters; pores elongated, almost lamellate [gill-like] toward margin; whitish to cream, when old gray-ocher; tubes 0.5-1(1.5)cm long, with thick partitions, (Breitenbach), 1-2 per millimeter measured tangentially, 0.1-0.5cm long measured radially, "radially elongated, slightly so at the margin, more distinctly towards the base and in some specimens partly sinuous, lamellate to labyrinthine"; white, cream, or pale straw-colored; tubes the same color, up to 1.5cm deep, "mostly unstratified, but sometimes a distinct stratification may occur", (Ryvarden(2)), 1-2 per millimeter tangentially, 0.1-0.5 microns radially, "distinctly radially elongated, angular with entire dissepiments, in parts splitting up with age and becoming partly sinuous, labyrinthine to lamellate"; "white to pale cream or straw-coloured in old specimens"; tube layer up to 2cm deep, coloured as pore surface, (Ryvarden(3)), "mostly longitudinal, radially arranged, nearer the margin circular or rounded", at the base in some places labyrinthine [maze-like] or even merging into gills, 0.04-0.08 x 0.04-0.2cm in diameter (1-2 per millimeter), pore surface white or grayish white, when dry cream; tubes in one layer 0.3-0.6(1.5)cm thick, whitish or straw yellow, (Domanski), pores "linear, short, and narrow, usually straight, sometimes slightly sinuous", and again, apparently describing his own collections "pores are large, narrow, unequal and more or less sinuous", young pores near growing margin small, but become larger and sinuous when old, (Neuman)
Stem: none, broadly attached
Odor: like Heterobasidion annosum [which the authors describe as "strongly fungoid"], (Breitenbach)
Taste: somewhat bitter (Breitenbach)
Microscopic: spores 4-5.5 x 2-2.5 microns, elliptic-cylindric, smooth, inamyloid, colorless, sometimes with droplets; basidia 4-spored, 15-22 x 5-8 microns, clavate, with basal clamp connection; cystidia not seen; hyphal system trimitic, generative hyphae 2.5-4.5 microns wide, septa with clamp connections, skeletal hyphae 5-6 microns wide, thick-walled, binding hyphae 2-3 microns wide, branched, thick-walled, (Breitenbach), spores 4-5 x 2-2.5 microns, cylindric to oblong-elliptic and often slightly bent, smooth, inamyloid, colorless, thin-walled; hyphal system trimitic: generative hyphae 2-4 microns wide, colorless, thin-walled, with clamp connections, skeletal hyphae "dominating in the fruitbody", 3-6 microns wide, thick-walled to almost solid, binding hyphae 2-5 microns wide, "mostly restricted to the trama, scarce and scattered in the context, tortuous and strongly branched, more rarely with long unbranched segments", (Ryvarden(2)), basidia 14-18 x 3-5 microns; cystidia absent, fusoid cystidioles present, 13-19 x 4-5 microns; generative hyphae 2-4 microns wide, branched, colorless, thin-walled, with clamp connections, skeletal hyphae 4-9 microns wide, thick-walled to subsolid, colorless, nonseptate, binding hyphae 2-4 microns wide, tortuous, thick-walled to solid, colorless, intermediate forms exist between binding and skeletal hyphae, (Ryvarden(3))
Spore Deposit: white (Buczacki)
Habitat / Range
single to gregarious and imbricate [shingled], on dead hardwood, especially on stumps of Fagus (beech), causes white soft-rots, (Breitenbach), annual, on hardwood, in north Europe especially beech, (Ryvarden(2)), annual; in Europe on dead wood of hardwoods, particularly Carpinus, Fagus, less often Alnus, Populus or Betula, "annual, but rather durable and sometimes hibernating", (Domanski), usually imbricate (Bernicchia), sporulating in late spring (Phillips), most common (in Europe) on Fagus, but also recorded from other hardwoods, including Acer, Aesculus, Ailanthus, Alnus, Betula, Castanea, Corylus, Crataegus, Eucalyptus, Fraxinus, Juglans, Malus, Morus, Platanus, Populus, Prunus, Pyrus, Rhamnus, Quercus, Salix, Sorbus, Tilia, and Ulmus, once recorded on Picea; preference for Fagus strict in northern part of its European range, less so in southern Europe; causes white rot of Fagus, rarely in other hardwoods, (Ryvarden(3)), may be seen year round (Bacon), all year (Buczacki)
Similar Species
Lenzites elegans (Trametes elegans) (southernmost states and Mississippi basin) is typically much flatter, and even the very large fruitbodies are not more than 1cm thick. The pores are more irregular, in parts distinctly gill-like or even tooth-like. For Trametes gibbosa, triquetrous fruitbodies up to 5-10cm thick at the base and small pores (3-4 per millimeter) regularly elongated in radial direction to 0.2-0.3cm are typical. However, both species are variable in these characters - very flat specimens of T. gibbosa with nearly gill-like tubes in parts of the fruitbody occur quite frequently. The surface of the cap in Trametes gibbosa is hirsute in zones with individual hairs visible with the naked eye or through a 10X lens, but the cap in Lenzites elegans is tomentose with no distinct hairs through a 10X lens. (Kout)
