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Remarks (internal):Perenniporia medulla-panis is characterized by a white pore surface, 4-5-(6) pores per mm, narrow, hyaline, non-dextrinoid, arboriform vegetative hyphae, but with frequently an amyloid reaction in the lumen, and small, dextrinoid basidiospores, (4.2)-4.5-5.5-(6.0) x (3.2)-3.5-4.5-(6.0) µm. This combination of characters is unique within Perenniporia, and defines the species well, as previously noted by Niemelä & al. (1992). Perenniporia amylodextrinoidea Gilb. & Ryvarden also presents an amyloid reaction of the vegetative hyphae, but it differs by having strongly amyloid wall (not the inner side or the lumen) and more ellipsoid, narrower basidiospores, 4.5-5.5-(6.0) x 3.0-3.5-(4) µm wide (Gilbertson & Ryvarden, 1987). The latter species is only known from a few collections in Southern United States (Gilbertson & Ryvarden, 1987). Perenniporia narymica (Pilát) Pouzar (= Perenniporia amylohypha Ryvarden & Gilb.) was characterized also by having slightly amyloid skeletal hyphae (Gilbertson & Ryvarden, 1987). However, this species does not belong to Perenniporia; it differs by having non-branched skeletal hyphae and thin-walled, ellipsoid basidiospores (Bernicchia, 1990, Gilbertson & Ryvarden, 1987, Ryvarden & Gilbertson, 1994) and may belong in Diplomitoporus (see below).
The previously used concept of P. medulla-panis (Bondartseva, 1998, Domanski, 1972, Donk, 1967, Gilbertson & Ryvarden, 1987, Ryvarden, 1978, Ryvarden & Gilbertson, 1994, Ryvarden & Johansen, 1980) was broad and included two species in Europe, as demonstrated by the examination of specimens of Persoon, Bresadola, Fries, and other collections from various herbaria (see above discussion). The situation is still more complicated when one includes other areas e.g. North America, Australia, or the tropical areas, where more taxa are represented under the name P. medulla-panis (C. Decock, pers. obs.).
As presently defined, P. medulla-panis is known only from Europe (ranging from Italy to Norway, eastward to Russia). However, its precise geographic distribution remains largely unknown. As well, details of its ecological requirements are largely fragmentary. The species seems to occur preferably (but not exclusively) on dead wood of Quercus and Ryvarden and Gilbertson (1994) reported it in North Europe up to the limit of the Quercus range. Perenniporia medulla-panis sensu auctores has been reported in literature on many other hosts (Ryvarden & Gilbertson, 1994).
The literature contains descriptions of the cultural features and the sexual behaviour of P. medulla-panis (Baxter, 1940, David & Malençon, 1978, Stalpers, 1978, Flott & Gilbertson, 1991). However, it is not known if these cultures belong to P. medulla-panis s.s. as described here or to P. medulla-panis sensu auctores. The P. medulla-panis cultures used by David & Malençon (1978) to determine the sexual behaviour of the species probably belong to P. meridionalis. The identities of the North American cultures (Baxter, 1940, Flott & Gilbertson, 1991) are uncertain. A revision of these cultures and of the original herbarium specimens from whence they were isolated is necessary to ascertain their identity.
The literature contains several presumed synonyms of Perenniporia medulla-panis (Ryvarden, 1991). None of them except Polyporus xylostromatis Fuckel are based on European materials and thus far, only this latter name is accepted here as a synonym of P. medulla-panis.
Description type:Non-original description 
Description:Perenniporia medulla-panis (Jacq. : Fr.) Donk, Persoonia 5: 76. 1967. Figs. 1,2, 9-15. = Boletus medulla-panis Jacq., Misc. Austriaca 1: 141. t. 11. 1778 (basionym) = Poria medulla-panis (Jacq.) Pers., Neues Mag. Bot. 1: 109. 1794 = Polyporus medulla-panis Jacq. : Fr., Syst. Mycol. 1: 380. 1821 = Poria medullaris Gray, Nat. Arrang. Br. Pl.: 640. 1821, nom. illeg. = Physisporus medulla-panis (Jacq. : Fr.) Chevall., Flore Générale des Environs de Paris 1: 262. 1826
Lectotype (see Donk, 1960: 266): [icon in] Jacq., Misc. Austriaca 1: t. 11. 1778 - Epitype (designated here): Norway: Vestfold NL 77, Guldkronen ved Jarlsberg hoveg˴rd, on wood of Quercus, 01 Aug. 1971, L. Ryvarden 7587 (O); isoepitype (MUCL 43250); crDNA 5.8S, ITS1 & 2, and partial 28S sequence available at MUCL.
= Polyporus xylostromatis Fuckel, Jb. Nassau. Ver. Naturk. 27-28: 86. 1872 = Poria xylostromatis (Fuckel) Cooke, Grevillea 16: 111. 1886 - Lectotype (designated here): Austria: Bachweg, spring, on old trunk of Quercus / Betula, Fuckel (NY)
Basidiome (annual to) perennial, resupinate, becoming widely effused, adnate, rigid, individual pieces observed up to 120 x 60 mm, (1)-2-20 mm thick. Margin narrow, thin to slightly rounded, concolorous with the pore surface. Pore surface homogeneous, white when fresh, drying white to pale cream-coloured, cream-coloured (4A3) to pale corky, or pale greyish orange (5(A-B)3) to greyish orange (5B5) on bruising, rarely with pale yellow to pale orange area, discolouring to dark brown to black (6F6) in old pore surface. Pores round to angular, ellipsoid, elongated on oblique part, 4-5-(6) per mm, (100)-125-198-(225) µm diam. (av. = 159 µm). Dissepiments entire, smooth, (35)-40-102-(180), (av. = 73 µm). Tubes layers single to stratified, up to 7-8 layers, 2-20 mm thick, elongated on oblique part, individual layers 1-3 mm thick, the entire tube with a (hard) corky consistency, a fibrous texture, the youngest layers white, creamy, discolouring to pale greyish orange (pale corky) to greyish orange up to light brown (cinnamon) in the older layers. Subiculum absent or strongly reduced to a thin, soft, flexible, fibrous sheet (“xylostromata”), white to cream, greyish orange to pale brown, also present in the substrate.
Hyphal system dimitic, both in the subiculum and the trama of the tubes. Generative hyphae hyaline, thin-walled, clamped, 1.5-3.0 µm diam. Vegetative hyphae mainly as arboriform skeletobinding hyphae, hyaline, non-dextrinoid, but with a variable amyloid reaction in the lumen or close to the inner side of the wall, more conspicuous at the branching points, cyanophilous, non-swelling in KOH. Subiculum (xylostromata) composed of densely packed vegetative hyphae, hyaline, sparingly branched. Trama of the tubes with arboriform skeletal hyphae, composed of an unbranched basal stalk, clamped at the basal septum, straight to sinuous or geniculated, then often with lateral aborted processes, thick-walled, but not solid, (30)-54-142-(165) µm long (av. = 91 µm), slightly widening from 1.7-2.3 µm (av. = 2.0 µm) wide at the basal septum up to 1.8-2.5 µm wide (av. = 2.2 µm) at the branching point, branches straight to sinuous, 1.2-1.7-(2.0) µm wide, (av. = 1.5 µm), slightly narrowing at the thin-walled apices.
Basidia clavate to slightly pedunculate, with a clamp at the basal septum, 15-17 x 7.8-10 µm, with four sterigmata. Basidioles similar, without sterigmata. Cystidioles few, hyphal-like to slightly clavate, slightly fusoid, or slightly ventricose, occasionally slightly apically mamillate, clamped at the basal septum, 14.3-25.0 x 4.4-6.3 µm (av. = 17.7 x 5.2 µm). Basidiospores ellipsoid to broadly ovoid to subglobose, apically truncate, with an apiculus, thick-walled, with an apical germ pore, 0-1 guttate, hyaline, (non-) to mostly strongly dextrinoid, cyanophilous, (4.2)-4.5-5.5-(6.0) x (3.2)-3.5-4.5-(6.0) µm, R = (1.0)-1.1-1.4-(1.6), (av. = 4.9 x 3.9 µm, av.R = 1.3). Chlamydospores absent.
Type of rot: a white rot.
Cultural features: unknown (see remarks)
Sexuality: Most probably heterothallic tetrapolar (see below)
Substrate: dead wood of deciduous tree, with a marked preference for Quercus.
Distribution: Europe.
Specimens examined:
Lectotype & Epitype (see above)
Taxon name: