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Hymenopellis megalospora

[ Basidiomycota > Agaricales > Physalacriaceae > Hymenopellis . . . ]

by Michael Kuo

To the naked eye, Hymenopellis megalospora is a dead ringer for several other xeruloid mushrooms, including Hymenopellis incognita and pale, small forms of Hymenopellis furfuracea. This means you will probably need a microscope, the ability to conduct mating studies in a mycological laboratory, or equipment for DNA studies in order to identify it with certainty--unless you are willing to dry and preserve your specimen for a few years; Hymenopellis megalospora appears to be the only North American xeruloid mushroom species that develops bright orange gills when stored in a herbarium. However, the orange color takes a few years to develop, and apparently fades to yellow within about 50 years (see Redhead and collaborators 1987 for details).

The easiest course is to study Hymenopellis megalospora with a microscope. Its large spores are decidedly lemon-shaped, and feature finely dimpled surfaces; its cheilocystidia have swollen, capitate ends; and its pileipellis features hyaline, thin-walled pileocystidia.

Xerula megalospora is a synonym. Older field guides often combined Hymenopellis megalospora with what have since been designated as separate species of Hymenopellis, in treatments of "Collybia radicata," "Oudemansiella radicata," and "Xerula radicata."


Ecology: Saprobic on the deadwood of hardwoods; occasionally growing directly from very well decayed logs and stumps, but more commonly attached to buried deadwood near stumps, appearing terrestrial; late spring through fall; widely distributed east of the Rocky Mountains. The illustrated and described collections are from Illinois.

Cap: 2-5 cm; bell-shaped to sub-conic when young, becoming broadly bell-shaped to broadly convex or nearly flat in age; bald; sometimes somewhat radially wrinkled; sticky to greasy when young, but soon dry; color variable, ranging from dark grayish brown to dull yellowish brown--or buff to nearly white, with or without a darker center.

Gills: Attached to the stem by means of a notch and a tiny tooth that runs down the stem; distant or nearly so (occasionally close); white; short-gills frequent.

Stem: 4-16 cm long above ground; 0.5-1.5 cm thick; tapering to apex; bald, or finely fibrillose with brownish fibrils that break up in age to form stripes and chevrons; white; with a short, quickly tapering tap root extending up to 4 cm underground; the root staining reddish brown.

Flesh: White; thin; unchanging when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: KOH on cap surface negative.

Dried Specimens: Gills of dried specimens become bright orange after several years in storage.

Spore Print: White.

Microscopic Features: Spores 15-21 x 8-12 µ; limoniform to amygdaliform at maturity; finely dimpled or pitted; inamyloid; hyaline in KOH. Hymenial elements of herbarium specimens often with pinkish orange to orange contents in KOH. Pleurocystidia widely cylindric to subutriform; thin-walled; hyaline; smooth; 70-110 x 10-22 µ. Cheilocystidia usually capitate to subcapitate but sometimes clavate or fusiform; up to 80 x 15 µ. Pileipellis hymeniform and somewhat gelatinized; pileocystidia frequent, thin-walled, hyaline, up to 90 x 30 µ.

REFERENCES: (Clements, 1896) R. H. Petersen, 2010. (Redhead, Ginns & Shoemaker, 1987; Phillips, 1991/2005; Petersen & Methven, 1994; Barron, 1999; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Petersen & Hughes, 2010; Kuo & Methven, 2014.) Herb. Kuo 05169505, 05160801, 06070802, 06270806, 07120805, 07200802.

This website contains no information about the edibility or toxicity of mushrooms.


Hymenopellis megalospora

Hymenopellis megalospora

Hymenopellis megalospora

Hymenopellis megalospora

Hymenopellis megalospora
Dried specimen after 20 years

Hymenopellis megalosporaSpores (units x 2.5)

Hymenopellis megalosporaPleurocystidia

Hymenopellis megalosporaCheilocystidia

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Kuo, M. (2014, November). Hymenopellis megalospora. Retrieved from the MushroomExpert.Com Web site: