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Agaricus porphyrocephalus

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

Taxonomy in Transition: ...  > Agaricales > Lepiotoid Clade (J&V, 1998)

by Michael Kuo

To be honest, I have real doubts about whether my collection really represents Agaricus porphyrocephalus--and about whether anyone's collection of "Agaricus porphyrocephalus" represents much more than a brownish, fibrillose form of Agaricus campestris. This is one area of Agaricus that has not seen as much contemporary taxonomic study as some other species groups in the genus (to my knowledge), and we are left with no choice but to rely on outdated taxonomies that emphasize subtle differences in visible and microscopic features.

Thus the presence of the brown fibrils, combined with the spore dimensions (see below) and the grass habitat, lead the illustrated collection to Agaricus porphyrocephalus. The similar Agaricus cupreobrunneus has larger spores and grows in bare soil in disturbed-ground settings or sandy areas. That said, perhaps we should remember that the closely related Agaricus bisporus can be cultivated to produce brownish and fibrillose mushrooms ("cremini")--and I should mention that the illustrated mushrooms were surrounded by smooth and white versions of Agaricus campestris, which proliferated in the vicinity. (No, I did not find any "intergrading" forms with partially brown or partially fibrillose caps.)

Description:

Ecology: Saprobic; growing alone, scattered, or gregariously in meadows, fields, lawns, and grassy areas; summer and fall; eastern North America.

Cap: 3-8 cm; convex to broadly convex; brownish underneath brown to purplish brown fibers and scales; dry; the margin sometimes adorned with hanging remnants of the partial veil.

Gills: Free from the stem; close or crowded; pink becoming brown and then dark chocolate brown in maturity; covered with a thin white partial veil when in the button stage.

Stem: 3-6 cm long; 1-2 cm thick; more or less equal, or tapering slightly to base (or slightly bulbous, according to European authors); with a quickly collapsing white ring; whitish to brownish; smooth or finely hairy.

Flesh: Whitish; not changing or changing to pinkish when sliced; not yellowing, even in the base of the stem.

Odor and Taste: Pleasant; not distinctive.

Chemical Reactions: Cap surface negative with KOH.

Spore Print: Dark chocolate brown.

Microscopic Features: Spores: 5-7 x 3-4.5 µ; elliptical.

REFERENCES: F.H. Møller, 1952. (Moser, 1978; Phillips, 1991/2005; Hansen & Knudsen, 1992; McNeil, 2006.) Herb. Kuo 10030503.

Further Online Information:

Agaricus porphyrocephalus at Roger's Mushrooms

 

Agaricus porphyrocephalus

Agaricus porphyrocephalus



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Cite this page as:

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