Major Groups > Polypores > Inonotus dryadeus


Inonotus dryadeus

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

by Michael Kuo

"Hey everybody, wanna see a big butt rot fungus?"

Unfortunately, Inonotus dryadeus looks for all the world like what your non-mushroom friends would probably picture if you were to try discussing butt rot fungi with them. Always positioned at or near the base of the tree, Inonotus dryadeus has a lumpy, irregular cap with a finely velvety, dull yellow surface and a margin that exudes droplets of amber liquid when fresh and young. It has a buff pore surface that bruises and ages brown, composed of very tiny pores. Under the microscope, it features curved setae and subglobose spores.


Ecology: Parasitic on living oaks in eastern North America and, in the west, on true firs; causing a white butt rot and root rot; annual; growing alone, gregariously, or in shelving clusters; summer and fall (or over winter in warm climates); fairly widely distributed in North America but apparently absent in the Great Plains and Rocky Mountains.

Cap: Up to 40 cm across; semicircular, kidney-shaped, cushion-shaped, or irregular; usually convex; finely velvety, becoming bald with age; often lumpy; buff to dull yellow, becoming brown with age; often exuding drops of amber liquid when fresh, especially along the margin; the margin thick.

Pore Surface: Buff to yellowish when young, becoming brown; bruising slowly brown; exuding drops of amber liquid when fresh and young; with 4-6 circular to angular pores per mm; tubes to 2 cm deep.

Stem: Absent.

Flesh: Yellowish brown becoming reddish brown; soft, becoming leathery or corky; zoned.

Chemical Reactions: Flesh black with KOH.

Spore Print: Yellowish to brownish.

Microscopic Features: Spores 6-8 x 5-7 µ; smooth; subglobose; hyaline in KOH; dextrinoid. Setae usually present but sometimes very rare; to about 40 x 15 µ; usually curved. Contextual hyphae thin- to thick-walled; simple-septate.

REFERENCES: (Persoon, 1800) Murrill, 1908. (Fries, 1821; Saccardo, 1888; Overholts, 1953; Breitenbach & Kränzlin, 1986; Gilbertson & Ryvarden, 1986; Lincoff, 1992; Binion et al., 2008.) Herb. Kuo 09220802, 09010903.

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Inonotus dryadeus

Inonotus dryadeus

Inonotus dryadeus

Inonotus dryadeus

Inonotus dryadeus

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