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Page number:53 
Description type:Non-original description 
Description:Laetiporus sulphureus (Bull.:Fr.) Murrill, Mycologia 12: 11. 1920. Figs. 21-24.
Basidiomes shelving, dimidiate, up to 45 cm wide, 30 cm deep and 3 cm thick, laterally stipitate, sessile or with broad stipe attachment, upper surface of pileus and stipe bright salmon orange; context pale yellow, up to 3 cm thick, sometimes thicker at the stipe; pore surface lemon yellow to bright creamy yellow, 1-5 mm long, 2-4 per mm nearly circular at first, becoming more angular in age, decurrent on stipe to its attachment.
Pileus surface a tissue of compactly interwoven hyphae 30-50 µm thick. Hyphae up to 7 µm diam, but mostly collapsed, walls up to 1 µm, hyaline, smooth, septate, lacking clampconnections, grading rather abruptly into pileus context. Pileus context dimitic, composed of binding and generative hyphae. Binding hyphae 4-12 µm diam, hyaline, occasionally septate, lacking clamp connections, walls 1-3 µm thick, dissolving nearly completely in 2% KOH. Generative hyphae rarely apparent in the context. Pore trama dimitic, composed of skeletal and generative hyphae with more parallel organization than context. Skeletal hyphae, 4-6 µm diam, nearly parallel but some-what sinuous and undulating, occasionally septate, lacking clamp connections, walls 1-1.5 µm thick, dissolving nearly completely in 2% KOH. Generative hyphae nearly parallel in arrangement, 3-5 µm, diam, thin walled, hyaline, regularly septate, lacking clamps, remaining intact in 2% KOH. Subhymenium a densely compact tissue; hyphae tightly interwoven, frequently septate, thin walled, hyaline, septate, lacking clamps, giving rise to the hymenium elements. Hymenium of basidia only. Basidia pyriform, 15 x 7.5 µm, hyaline, thin walled, 4-sterigmate, lacking a basal clamp. Basidiospores broadly ovoid, 5.5-7 x (3.5-)4-5 µm, hyaline, thin walled, smooth, negative in Melzer's reagent.
Habitat: Laetiporus sulphureus occurs as a brown heart-rot of hardwood species (especially Quercus spp.) throughout the eastern USA except for in the states along the Gulf of Mexico where L. gilbertsonii is common. It fruits as shelving basidiomes on logs and on the trunks of living or dead trees, frequently as much as 10 feet or more above ground level and appears to differ in its function by causing a true heart-rot rather than a root-and butt-rot as caused by L. cincinnatus. Our observations indicate that the rot caused by L. cincinnatus is found in the roots and butt of the tree up to only 4-5 feet above ground level. The rot caused by L. sulphureus, while occurring as low as 3-4 feet in the trunk, is also found much higher in the tree.
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