Major Groups > Polypores > Inonotus radiatus


Inonotus radiatus

[ Basidiomycetes > Hymenochaetales > Hymenochaetaceae > Inonotus . . . ]

by Michael Kuo

Inonotus radiatus is a fairly small annual polypore found on the deadwood of hardwoods, primarily in eastern North America. When young it has an attractive, yellowish, finely velvety cap--but it eventually becomes bald and darkens to brown or black. It is found above ground, on stumps and logs, which will help to separate it from some look-alikes. Ultimately, however, microscopic features (including ellipsoid spores that are pale in KOH, the absence of setal hyphae, and the presence of gorgeous, swollen hymenial setae) define the species.


Ecology: Saprobic on the deadwood of hardwoods (especially birches and alders but also on beech, maples, and other hardwoods); causing a soft white rot; annual; growing alone, gregariously, or in shelving clusters; summer and fall (or over winter in warm climates); fairly widely distributed from the Great Plains to the maritime provinces, and rare to occasional in the Pacific Northwest (primarily on alders).

Cap: Usually present and well developed, but sometimes present merely as a folded-over edge above a spreading pore surface; up to 7 cm across and 6 cm deep; semicircular to kidney-shaped; often arranged in shelves and sometimes fused laterally with other caps; usually convex to planoconvex; very finely velvety when young, becoming bald with age; yellowish to orangish at first, becoming yellowish brown and eventually darkening to dark brown or black; often zoned; the margin thin and often wrinkled.

Pore Surface: Yellowish brown when young, becoming brown; with 3-5 angular pores per mm; tubes to 8 mm deep.

Stem: Absent.

Flesh: Yellowish brown to reddish brown; corky; faintly zoned.

Chemical Reactions: Flesh black with KOH.

Spore Print: Yellowish to brownish.

Microscopic Features: Spores 5-6.5 x 3-4.5 µ; smooth; ellipsoid; hyaline to faintly yellowish in KOH; inamyloid or faintly dextrinoid. Hymenial setae scattered; to about 50 x 12 µ; fusoid; often with a swollen base. Setal hyphae absent. Hyphae thin- to thick-walled; 3-7 µ wide; simple-septate.

REFERENCES: (Sowerby, 1799) Karsten, 1881. (Fries, 1821; Saccardo, 1888; Overholts, 1953; Breitenbach & Kränzlin, 1986; Gilbertson & Ryvarden, 1986; Phillips, 1991/2005; Barron, 1999; McNeil, 2006.) Herb. Kuo 09240509.

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Inonotus radiatus

Inonotus radiatus

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Kuo, M. (2010, March). Inonotus radiatus. Retrieved from the MushroomExpert.Com Web site: