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Page number:377 
Remarks (public):The species is easy to recognize because of the hirsute to tomentose, zonate pileus and the lamellate hymenophore. 
Description type:Non-original description 
Description:Lenzites betulinus (L.:Fr.) Fr. - Epicr. p. 405. 1838. - Daedalea betulina L.:Fr.. Syst. Mycol. 1:333, 1821. - Agaricus betulinus L.. Spec. Plant. p. 1176. 1753.
Basidiocarps annual, single to a few together. pileate, dimidiate to semicircular or broadly attached with a partly resupinate, effused part. 1-5 x 2-8 x 0.3-2.0 cm. margin even to lobed or incised, corky and coriaceous; upper surface tomentose to hirsute in concentric, partly sulcate zones, at first white, later grayish to cream. old specimens often with a greenish tint because of algae in the tomentum; hymenophore lenzitoid with thin radial lamellae, new lamellae arising toward the margin by dichotomous forking of old ones, but also individually between older ones, when young and along the margin straight. 10-15 per cm measured tangentially. about 100-200 µm thick, in older parts and when dry, mostly undulating or flexuous. thus, the distance between individual lamellae may very considerably, at first white, later cream to ochraceous, lamellae up to 12 mm deep at the base; context thin, 1-2 mm thick, tough-fibrous, white, distinctly paler than the lamellae.
Hyphal system trimitic, generative hyphae hyaline, with clamps, in the subhymenium 2-4 µm in diam. thin-walled, in the context rather scattered, somewhat thick-walled to thin-walled. up to 5 in diam; skeletal hyphae solid to thick-walled, hyaline. nonseptate, 3-7 µm in diam, totally dominating in the tomentum, almost solid, at least in old specimens. in the trama with a more distinct lumen; binding hyphae very common in both the context and trama. hyaline. thick-walled to solid, tortuous and much branched. up to 10 µm in diam (in KOH), in the context with thin and whip like branches, in the trama with stouter branches and below the subhymenium with straight, thick-walled. swordlike branches. more or less parallel, partly pointing into the lower part of the hymenium, but in fertile specimens never above the dense palisade of basidia.
Cystidia none, but in collapsed hymenia the swordlike branches of the binding hyphae may easily be mistaken for thick-walled cystidia unless a careful examination is undertaken.
Basidia clavate. 4-sterigmate, 20-25 x 6-7 µm. with a basal clamp.
Basidiospores cylindrical, often slightly curved. hyaline, smooth, thin-walled, negative in Melzer's reagent, 5-6 x 2-3 µm.
Type of rot. White rot of dead hardwoods.
Cultural characteristics. See Nobles 1948. 1958. 1965; Stalpers 1978. Sexuality. Heterothallic and tetrapolar.
Substrata. On dead hardwoods, most commonly on Betula species, but also found on Acer. Alms. Carpinus, Corylus, Fagus, Fraxinus, Juglans, Prunus, Quercus, Salty, Sorbus, Tilia and Ulmus, rarely on conifers like Cedrus and Picea. In the tropics and on other continents on numerous other hosts.
Distribution. Scattered throughout Europe and the boreal forest zone. Cosmopolitan species, but much rarer in the tropical zones than in the temperate-boreal regions.
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