Irpex lacteus

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Ecology: Saprobic; spreading across the bottoms and sides of fallen hardwood logs (occasionally on the wood of conifers); annual; causing a white rot of the sapwood and rarely the heartwood; occasionally reported as parasitic on the living wood of cherry trees; appearing year-round; widely distributed in North America but rare or absent in the Southwest.

Fruiting Body: A spreading patch of whitish pore surface with 2-3 pores per mm, soon becoming tooth-like rather than poroid, except near the margin; developing shelflike edges or even caps when growing on the sides of logs; caps when present kidney-shaped to irregular, with a whitish to grayish (often zoned), velvety to hairy upper surface; flesh thin, whitish, and tough; without a stem.

Chemical Reactions: All parts brownish orange with KOH.

Spore Print: White.

Microscopic Features: Spores 5-7 x 2-3 ; smooth; elliptical to subcylindric; hyaline in KOH; inamyloid. Cystidia conspicuous; abundant to scattered; 50-110 x 5-10 ; encrusted apically or over nearly the whole length. Thin-walled generative hyphae frequently branching; 2-4 wide. Thick-walled skeletal hyphae rarely branching; 2.5-6 wide. Clamp connections absent.

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