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Page number:300 
Remarks (public):Usually there is no difficulty in recognizing this species because of the orange colour, the often large size of the basidiocarps, and the virtual restriction to oak and chestnut. During drying the basidiocarps become darker and shrink severely, especially the tubes. H. croceus and Tyromyces fissilis have been put in a separate genus, Aurantioporus Murr., because of the dense agglutinated tubes in dried specimens, the monomitic hyphal system, and the broadly ellipsoid spores. However, we feel that the striking colour and a reaction in KOH justify the inclusion of H. croceus in Hapalopilus. In this flora, species with distinctly coloured basidiocarps have generally been kept in separate genera such as Pycnoporus and Pyrofomes although little is known about the phylogenetic significance of the compounds responsible for the colours. 
Description type:Non-original description 
Description:Hapalopilus croceus (Pers.:Fr.) Bond. & Sing. - Ann Mycol. 39:52, 1921. - Boletus croceus Pers., Obs. Mycol. 1:87, 1796. - Polyporus croceus Pers.:Fr.. Syst. Mycol. 1:364, 1821. - Observ. Mycol. 1:129, 1815. Basidiocarps annual, sessile, pileate, broadly attached, up to 20 cm wide x 6 x 15 cm, soft and watery when fresh, shrinking considerably under drying and finally hard and resinous; taste slightly bitter; pileus surface at first bright orange and finely velutinate to pubescent, later more brownish orange and smooth to scrupose with tufts of agglutinated hyphae, red to carmine when touched with KOH; pore surface bright reddish-orange when fresh. brownish when dry, pores angular, 2-3 per mm; context bright orange, spongiose and watery when fresh, when dried darker orange to brownish,
resinous and hard. but distinctly paler than the tubes. up to 3 cm thick at the base; tube layer concolorous with pore surface. when dry as soaked with resinous substances, up to 12 mm thick.
Hyphal system monomitic; generative hyphae hyaline. thin-walled. with clamps. throughout the basidiocarp often covered with grains, crystals. and granules of a golden substance. and hyphae often densely agglutinated in this substance, moderately branched. in the context forming some agglutinated cordons of hyphae imbedded in a looser matrix of more branched hyphae, up to 4 µm in diam; in the trama more irregularly organized and up to 6 µm in diam.
Cystidia or other sterile hymenial elements absent.
Basidia clayate. 4-sterigmate, 18-30 x 7-10 µm. with a basal clamp.
Basidiospores broadly ellipsoid. hyaline. thin-walled, smooth. negative in Melzer's reagent. 4-7 x 3-4.5 µm.
Type of rot. White rot in heartwood of living hardwoods.
Cultural characteristics. See Davidson et al. 1942; Cerny 1966; David 1969.
Sexuality. Unknown.
Substrata. In Europe preferably on Quercus species, rarely on Castanea. Distribution. Rare species but widespread and seemingly following the genus Quercus except at its northern range. Known chiefly from central and southern Europe. north to southern part of Sweden. Not seen since 1880 in Norway and since 1937 in Denmark and by all probability extinct in both countries. Circum-meriodinal in the warm parts of the north temperate zone.
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