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Page number:172 
Description type:Non-original description 
Description:Rigidoporus microporus (Fr.) v. Ov. Figures 24-26, Plate 8 Ic. Fung. Malay. 5 (1924) 1-5; Ryvarden, Norw. J. Bot. 19 (1972) 236; Ryvarden and Johansen (1980) 545.
Polyporus microporus Fr. (1821).
Polyporus lignosus (KI.) Petch, Trans. Brit. mycol. Soc. 13 (1928)
245-253; Boedijn, Bull. Jard. bot. Buitenz. ser. III, 14 (1940) 385-6; Bose and Bakshi, Trans. Brit. mycol. Soc. 40 (1957) 456-460; Dennis (1970)110.
Fomes lignosus (KI.) Bres. (1912).
Rigidoporus lignosus (KI.) Imazeki, Bull. Gov. For. Exp. Stn. Tokyo, n. 57 (1952) 118; Wright and Deschamps, Rev. Invest, Agropec. INTA Buenos Aires ser. V, vol. XII n. 3 (1975) 159; Ryvarden, Mem. N.Y. bot. Gdn 28 (1976) 199-207.
Fruit-bodies with pileus -25 cm in radius, 40 cm wide, sessile, appla- nate, more or less ascending, bracket-shaped with a resupinate foot.
varying effuso-reflexed or wholly resupinate, always developing pilei on ascending surfaces, the pilei often imbricate or fusing into flanges, sometimes lobing and proliferating at the margin, rarely with a short stem-like base buried in crevices in the woody substratum; upper surface glabrous, faintly sulcate, often rather uneven, becoming rugose to tuberculate at the base, rich rufous orange or ferruginous bay brown with narrow crowded lighter zones, paler orange towards the margin, fading dull cinnamon to dull fawn brown with age, bleaching pallid white in strong light, weathering to drab woodcolour, drying rugulose with strongly incurved margin; margin obtuse to subacute, velutinate, white. Tubes -18(-70) mm long, 0.3-1.5 mm at 5 mm from the margin of the pileus, often with 2-3 indistinct layers, more rarely with up to 10 or so layers in old perennial subungulate pilei, rich orange buff to rufous cinnamon, discolouring in the older parts; pores 80-120 µm wide, or 130-170 µm, dissepiments 30-100 µm
thick, minute, waxy, entire, pinkish orange to brownish orange with a white bloom. Flesh 3-27 mm thick at the base of the pileus, 1.55.5 mm at 5 mm from the margin, corky felted, drying hard, pinkish buff to pale buff or nearly white, deeper coloured just above the tubes, without a crust. Smell sour.
On dead trunks and stumps in the forest and on dead bamboo stumps, also in the open, and as a root-parasite of rubber-trees (Hevea), developing white rhizomorphs and causing a white rot. Pantropical, lowland and montane -2000 m alt.
Spores 3-3.7 x 2.5-3 µm white, smooth, pip-shaped to subglobose, thin-walled, with vacuolate contents but sometimes with a guttula 0.51 µm wide, not dextrinoid. Basidia 9-14 x 4-5 µm, subclavate; sterigmata 4, 2-2.5 µm long. Cystidia 12-24 x 5-11 µm, ventricose, generally contracted into a short acute tip, in some collections subacute, rarely gradually tapered, with thin or slightly thickened walls especially'in the basal part, vacuolate, smooth, colourless, mostly near the poremouths, evanescent, not in the old tubes, but abundant. Extrahymenial setae and hyphal pegs none. Hyphae of the flesh subdimitic (dl), without clamps, 2-6 µm wide, occasionally dilated in places -8 µm wide, not encrusted, not dextrinoid; skeletal hyphae 4-6 µm wide, radiating, septate with cells 50-350 µm long, the walls thickened slightly -0.5 µm, sparingly branched or unbranched for lengths up to 1000 µm, the branches becoming generative or skeletal hyphae, not secondarily septate; generative hyphae 2-5 µm wide, thin-walled, freely branched, interweaving, with cells 15-150 µm; dissepiments dimitic with skeletal hyphae 3-4 µm wide agglutinated with pale yellow walls. Hymenium maturing in the young tubes when barely 50 µm long, compact, continuous, functioning for distances of 2-4 mm from the pore-mouths, not thickening, subhymenium slight. Surface of pileus with very oblique short-celled radiating hyphae, the cells 10-40 µm long with apical cells subclavate 4-7 µm wide, as a more or less decumbent palisade, the hyphal ends more erect at the base of the pileus as a very compact pile, but without a crust.
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