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Agaricus porphyrocephalus var. pallidus

[ Basidiomycota > Agaricales > Agaricaceae > Agaricus . . . ]

by Michael Kuo

Here's another mushroom you and your field guide have been calling "Agaricus campestris." It's white, squat, and grows in grass—and it features flimsy veils and gills that are pink when young. In short, you won't be able to distinguish it from other members of the campestris group without a microscope; its spores, at about 6 x 4.5 µm, are shorter than those of look-alikes.

Although its DNA indicates this mushroom is v-e-e-e-ry close to Agaricus porphyrocephalus (only three ITS base pairs separate it), its cap is not fibrillose and brown; Agaricus guru Richard Kerrigan (2016) designated it as a pale variety, Agaricus porphyrocephalus var. pallidus, rather than as a separate species. I have found var. pallidus growing within a few yards of the typical variety.


Ecology: Saprobic; growing alone, scattered, or gregariously in meadows, fields, lawns, and grassy areas; fall; possibly widespread in North America (recorded from Pennsylvania to Colorado). The illustrated and described collections are from Illinois.

Cap: 4–10 cm; convex, becoming broadly convex; dry; white; finely appressed-fibrillose or nearly bald; the young margin often adorned with hanging whitish remnants of the partial veil; in wet weather sometimes staining a little pinkish.

Gills: Free from the stem; close; short-gills frequent; pink at first, maturing to dark brown; covered with a thin white partial veil when in the button stage.

Stem: 4–6 cm long; 1–2 cm thick; more or less equal above a tapered base; with a quickly collapsing whitish ring; whitish; bald or finely fibrillose.

Flesh: Whitish; not changing when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: KOH negative on cap surface.

Spore Print: Dark brown.

Microscopic Features: Spores: 5–6.5 x 3.5–4.5 µm; ellipsoid; smooth; thick-walled; brown in KOH. Basidia 4-sterigmate. Pleurocystidia not found. Cheilocystidia not found. Pileipellis a cutis; elements 5–7.5 µm wide, smooth, hyaline to yellowish in KOH.

REFERENCES: Kerrigan, 2016. Herb. Kuo 09260501, 10030504.

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Agaricus porphyrocephalus var pallidus

Agaricus porphyrocephalus var pallidus

<Agaricus porphyrocephalus var pallidus

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Kuo, M. (2018, April). Agaricus porphyrocephalus var. pallidus. Retrieved from the MushroomExpert.Com Web site: