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Rhizomarasmius pyrrhocephalus

[ Basidiomycetes > Agaricales > Physalacriaceae > Rhizomarasmius . . . ]

by Michael Kuo

This little marasmioid mushroom-like mushroom can almost be recognized without a microscope, if you are willing to subject it to intense scrutiny. Look for a combination of features: the orange to orangish brown cap; the tough stem that is dark brown or black, densely hairy, and usually deeply rooted and elongated; the white spore print; and the absence of a distinctive odor or taste. Microscopic characters (see below) will confirm identification.

Like a Chicago voter, Rhizomarasmius pyrrhocephalus shows up at the polls early and often; it is "one of the first agarics to appear in the spring and one of the last to cease fruiting in the fall" (Gilliam, 1975). Older sources treat this mushroom as a species of Marasmius, but DNA results (Moncalvo and collaborators, 2002) have upheld the suggestion of Petersen (2000) that it deserves separate treatment.


Ecology: Saprobic on leaf litter and woody debris in hardwood forests (especially oak-hickory woods); growing alone or gregariously; spring, summer, and fall; widely distributed east of the Rocky Mountains.

Cap: Up to 2.5 cm across; convex, becoming broadly convex or nearly flat; smooth or finely wrinkled; the margin often slightly lined; orange to yellowish orange, darkening with age to brownish orange or nearly brown.

Gills: Attached to the stem; close or nearly distant; whitish, becoming dingy or yellowish; sometimes developing brownish spots or discolorations.

Stem: 3-10 cm long; up to 2 mm thick; usually deeply rooted (up to 5 cm); more or less equal; dry; tough; densely velvety or hairy; dark reddish brown, brown, or nearly black (but paler initially and sometimes pale near the apex in age).

Flesh: Insubstantial; pale.

Odor and Taste: Taste not distinctive, or with a slightly bitter aftertaste; odor not distinctive.

Chemical Reactions: KOH negative on cap surface.

Spore Print: White.

Microscopic Features: Spores 6-10 x 3-4 µ; smooth; elliptical; inamyloid. Pleuro- and cheilocystidia variously shaped but often fusiform or capitate; 30-70 µ long. Pileipellis a hymeniform layer of variously shaped, smooth cells measuring 8-24 x 4-24 µ; inamyloid or with dextrinoid granular contents.

REFERENCES: Berkeley, 1847. (Kauffman, 1918; Gilliam, 1975; Petersen, 2000; Roody, 2003.) Herb. Kuo 04309501, 05260303, 06100302, 05030405, 05031102.

Marasmius pyrrhocephalus, Marasmius longipes, and Marasmius elongatipes are synonyms.

Marasmius sullivantii has a smooth stem that is usually paler in color and more fragile; its pileipellis has broom cells.


Rhizomarasmius pyrrhocephalus

Rhizomarasmius pyrrhocephalus

Rhizomarasmius pyrrhocephalus
Spore print

Rhizomarasmius pyrrhocephalus

Rhizomarasmius pyrrhocephalus

Rhizomarasmius pyrrhocephalus

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Kuo, M. (2008, May). Rhizomarasmius pyrrhocephalus. Retrieved from the MushroomExpert.Com Web site: