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Page number:205 
Remarks (public):Cerrena unicolor was identified as the fungal symbiont of the wood wasp Tremex columba on Fagus grandifolia in eastern Canada by Stillwell (1964). This is the only known polypore symbiont of a wood wasp. Basidiocarps of C. unicolor are easy to recognize because of the hirsute pileus, the black line in the context and the labyrinthine hymenophore. 
Description type:Non-original description 
Description:Cerrena unicolor (Bull.:Fr.) Murr. - J. Mycol. 9:91, 1903. - Daedalea unicolor Bull.:Fr., Syst. Mycol. 1:336, 1821. - Boletus unicolor Bull. Herb. France p. 408, 1785.
Basidiocarps annual, sessile, effused-reflexed or rarely resupinate; pilei often in imbricate clusters. dimidiate, up to 10 cm wide; upper surface pale brownish to gray, hirsute to almost glabrous, often green due to algae, sulcate: pore surface ivory to pale huff on young specimens. becoming darker with age. the pores daedaleoid, variable, 3-4 per mm. in parts larger, dissepiments at first thick and tomentose. becoming thin and splitting; context duplex. up to 3 mm thick, corky, lower layer pale brownish, separated from soft, spongy, darker upper layer by a thin dark zone; tube layer continuous and concolorous with lower context, up to 1 cm thick.
Hyphal system trimitic; contextual generative hyphae thin-walled, with clamps, 2-4 µm in diam; skeletal contextual hyphae thick-walled, nonseptate, 2.5-5 µm in diam; binding hyphae thick-walled, nonseptate, much-branched, 2-4 µm in diam; tramal hyphae similar.
Cystidal hyphal ends in old hymenia and on dissepiments edges, clavate at the tips, with thickened walls that thin toward the apex. 2-3 µm in diameter and expanding to 46 µm at the tips. fusoid cystidioles present in the hymenium. thin-walled. 16-20 x 4-6 µm, with a basal clamp.
Basidia clavate, 4-sterigmate, 20-25 x 5-6 µm, with a basal clamp.
Basidiospores cylindric ellipsoid. hyaline, smooth, negative in Melzer's reagent, 5-7 x 2.5-4 µm.
Type of rot. White rot of dead hardwoods and also the cause of a stem canker of living hardwoods (Blanchette 1982).
Cultural characteristics. See Nobles 1948. 1958. 1965; Scalpers 1978. Sexuality. Heterothallic and bipolar (Nobles 1965).
Substrata. Dead wood of hardwoods like Acer. Aesculus, Alnus, Betula, Carpinus, Castanea, Cornus, Corylus, Fagus, Fraxinus, Malus, Populus, Quercus, Salix, Sorbus, Tilia and Ulmus, besides numerous exotic trees in park and gardens.
Distribution. Common and widely distributed in Europe from the Mediterranean to the North Cape area in Norway (70°N). Circumglobal in the Northern hemisphere and widespread in America and Asia.
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