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Agrocybe retigera

[ Basidiomycota > Agaricales > Strophariaceae > Agrocybe . . . ]

by Michael Kuo

Agrocybe retigera is a tropical and subtropical species from the Americas, characterized by its whitish colors, lack of a partial veil, and the way the surface of the cap is finely wrinkled and pocketed, especially toward the margin. Under the microscope, it features pleurocystidia and fairly large spores.

Agrocybe pediades is similar but generally more yellow, and its cap turns red with KOH; Agrocybe dura is also similar but has a partial veil that leaves a flimsy ring on the stem. Neither of these look-alikes develops the wrinkled and pocketed cap surface of Agrocybe retigera.

Thanks to Andy Methven for collecting, documenting, and facilitating study of Agrocybe retigera.


Ecology: Saprobic; growing alone, scattered, or gregariously in grass (lawns, meadows, fields) and in sandy areas; appearing year-round, but most likely to be seen in summer; originally described from Argentina; in North America distributed from the southeastern United States through Mexico; also found in the Caribbean, Central America, and South America. The illustrated and described collection is from North Carolina.

Cap: 1–4 cm; convex at first, becoming broadly convex or nearly flat, sometimes with a broad central bump; dry; finely wrinkled and pocketed near the margin or nearly overall; bald; whitish to dirty yellowish, especially over the center; the margin not lined.

Gills: Narrowly attached to the stem; close or nearly distant; short-gills frequent; whitish at first, becoming brownish and eventually brown.

Stem: 4–6 cm long and 3–5 mm thick; equal above a swollen base; bald; white; becoming hollow; basal mycelium white.

Flesh: White; unchanging when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: KOH on cap surface negative.

Microscopic Features: Spores 12–15 x 7–9 µm; more or less ellipsoid, with one end slightly flattened for a 1 µm pore; smooth; thick-walled; dull yellow-brown in KOH; brown in Melzer's. Basidia 35–38 x 7–9 µm; subclavate; 4-sterigmate. Cheilocystidia 30–45 x 7.5–22.5 µm; utriform to sphaeropedunculate; smooth; thin-walled; hyaline in KOH. Pleurocystidia 30–40 x 15–20 µm; mostly sphaeropedunculate or vesiculose; smooth; thin-walled; hyaline in KOH. Pileipellis hymeniform; terminal elements elements 10–30 µm wide; clavate to pyriform; hyaline to brownish in KOH.

REFERENCES: (C. L. Spegazzini, 1922) R. Singer, 1951. (Singer, 1977; Weber & Smith, 1985; Watling, 1992; Cortez & da Silveira, 2005; Niveiro et al., 2020.) Herb. Kuo 08232101.

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Agrocybe retigera

Agrocybe retigera

Agrocybe retigera

Agrocybe retigera

Agrocybe retigera

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Kuo, M. (2021, December). Agrocybe retigera. Retrieved from the MushroomExpert.Com Web site: