Agaricus porphyrocephalus F. H. Møller

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Agaricaceae

Agaricus porphyrocephalus

Agaricus porphyrocephalus is a rare find, maybe because it is difficult to distinguish between a brownish Field Mushroom Agaricus campestris and the brownish (perhaps with a purple tinge as the scientific name suggests) Agaricus porphyrocephalus. Most authorities appear to accept that this is not merely a form of variety of Agaricus campestris but a unique species; however, the macroscopic and microscopic differences are not great, and so it would be easy to confuse these grassland mushrooms.

Agaricus porphyrocephalus

Distribution

Rarely found in Britain, and not yet (mid May 2014) formally recorded from Ireland, Agaricus porphyrocephalus is reported to occur also in parts of North America.

Taxonomic history

When it was first described, in 1950, by Danish mycologist Frits Hansen Møller (1887 - 1962), this mushroom was given the scientific name Psalliota porphyrocephalus. The Psalliota genus is now defunct, and Møller transferred this species to the genus Agaricus in 1952, thereby establishing its currently-accepted scientific name Agaricus porphyrocephalus.

Psalliota porphyrea F.H. Møller is the only synonym of Agaricus porphyrocephalus that I am aware of. (If you know of other synonyms please do let me know.)

Etymology

The specific epithet porphyrocephalus means 'with a purple head' - a reference to the purplish-brown cap scales..

Identification guide

Cap of Agaricus porphyrocephalus

Cap

Initially hemispherical, becoming broadly convex, the whitish caps are covered with fine purplish-brown radial fibrils. Diameter at maturity ranges from 4 to 6cm.

Gills of Agaricus porphyrocephalus

Gills

Pink at first, the free crowded gills turn brown as the fruitbody matures.

Stem of Agaricus porphyrocephalus

Stem

3 to 4.5cm tall and 1 to 2cm in diameter, the white stems are smooth above the narrow, ring-like remnants of the partial veil. Stems are cylindrical or slightly swollen centrally and then taper towards a narrower base.

The flesh of this mushroom turns slightly pinkish when cut.

Spores of Agaricus porphrocephalus

Spores

Ovoid or broadly ellipsoidal, 5.5-7 x 3-4.5µm.

Show larger image

Spore print

Deep chocolate brown.

Odour/taste

Faintly mushroomy but not distinctive.

Habitat & Ecological role

Saprobic, in neutral or acidic grassland, most particularly heathland and moorland.

Season

July to October in Britain.

Similar species

The Prince Agaricus augustus is similar but much larger and has somewhat larger spores; its cut flesh smells like bitter almonds.

Culinary Notes

Because of its rarity the edibility of this mushroom is in doubt, and so it should be treated as suspect and should not be gathered for eating.

Agaricus porphyrocephalus mature specimens

Reference Sources

The genus Agaricus in Britain, 3rd Edition, self-published, Geoffrey Kibby 2011

BMS List of English Names for Fungi

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

Acknowledgement

This page includes pictures kindly contributed by David Kelly.

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