Agaricus species 01

[ Basidiomycetes > Agaricales > Agaricaceae > Agaricus . . . ]

by Michael Kuo

I find this little Agaricus in grassy edgewoods and disturbed ground in oak-hickory woods in central Illinois, in July and August. It has a pale yellowish brown cap that is covered with tiny fibers and scales, a (proportionally) tall and slender stem that features a thin white ring, and flesh that does not change color when sliced. Its odor is not distinctive. The cap surface turns yellow when a drop of KOH is applied.

It is reminiscent of a miniature Agaricus subrufescens, but its small size and lack of a strong almondy odor distinguish it. The species does not have a name--yet. But it has recently also been collected in Pennsylvania and in France (Kerrigan and Guinberteau, pers. com.), and a name is forthcoming.

The mushroom described and illustrated here is edible, though not particularly good. It is featured in my book 100 Edible Mushrooms (2007), where John David Moore gives it an edibility rating of "fair."

Description:

Ecology: Presumably saprobic; growing alone or gregariously in grassy areas at the edges of oak-hickory forests--or along paths, in disturbed-ground or grassy settings within woods; July, August, and September; Coles County, Illinois.

Cap: 3-8 cm; blocky at first, before the veil ruptures; becoming broadly convex to planoconvex; dry; whitish to pale brownish underneath golden brown to brown, pressed-down fibers that separate with maturity and become aggregated into small scales over the disc; not bruising on the margin when rubbed repeatedly.

Gills: Free from the stem; close or crowded; short-gills frequent; white when young, going through a pink stage before eventually becoming dark chocolate brown; covered when in the button stage with a whitish partial veil.

Stem: 5-7 cm long; 6-10 mm thick; more or less equal; with or without a slight basal bulb; dry; smooth or finely hairy; with a fragile, skirtlike, whitish ring that occasionally disappears; whitish; not bruising or bruising faintly brownish on handling.

Flesh: White; not changing when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: Cap surface negative to weakly yellow with KOH.

Spore Print: Dark chocolate brown.

Microscopic Features: Spores: 6-8 x 3.5-5 µ; elliptical; smooth. Cheilocystidia scattered and infrequent; up to 24 x 12 µ; clavate to subfusoid.

REFERENCES: Herb. Kuo 07250302, 08280401, 08200504, 09230501, 09280503.

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Kuo, M. (2007, October). Agaricus species 01. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/agaricus_sp 01.html