Entoloma atromadidum A. M. Ainsw. & B. Douglas

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

Distribution - Taxonomic History - Etymology - Identification - Culinary Notes - Reference Sources

This largish (for an Entoloma) mushroom is a rare find in Britain and Ireland, and microscopic study of spores is necessary to seprate it from other macroscopically similar bluish pinkgills.

Distribution

Entoloma madidum is a rare find in Britain. This pinkgill probably occurs also in parts of mainland Europe, but at the time of writing this article (early 2020) I know of no credible records outside Britain.

Taxonomic history

This species was separated from other big blue Entoloma species by DNA studies, the results of which were published in 2018 by British mycologists Martyn Ainsworth and Brian Douglas, who gave it the name Entoloma atromadidum. No synonyms exist for this name.

Etymology

The generic name Entoloma comes from ancient Greek words entos- meaning inner, and -lóma, meaning a fringe or a hem. It is a reference to the inrolled margins of many of the mushrooms in this genus.

The specific epithet atromadidum means a blackish form of E. madidum, which in turn is derived from Latin and means moist or wet.

Identification guide

	Cap 3 to 10cm across; initially sticky then dry and matt; convex to umbonate with an inrolled margin, becoming plano convex with a slight umbo and a wavy down-turned margin, often splitting; developing silky radial fibrils and radial groves or rivules towards the margin; cap flesh firm and white, sometimes with grey-blue streaks.
	Gills Sinuate, almost free; moderately crowded; edge usually irregularly serrulate; white with a faint blue tinge near the cap margin when young (left).
	The gills become pink at maturity (left). Basidia Clavate, 28.8-50.0 x 8.8-11.2μm; mainly 4-spored, with basal clamps.
	Stem Cylindrical, sometimes tapering at base, longitudinally coarsely fibrillose, sometimes semi-reticulate; up to 5.5cm long and up to 1.5cm in diameter; colour as cap or somewhat paler but fading to white or yellowish buff at the base; no stem ring. Stem flesh white, sometimes mottled blue-grey.
	Spores Angular, mostly pentagonal or hexagonal in side view, subglobose, 6.2-8.3 x 6.4-8.0μm; Qav=1.0; inamyloid. Show larger image Spores of Entoloma atromadidum  X  Spore print Pink.
Odour/taste	Mealy (like wet flour).
Habitat & Ecological role	Solitary or in groups in unimproved grassland.
Season	Fruiting in summer and autumn in Britain and Ireland.
Similar species	This mushroom may be poisonous; it could be confused with Entoloma bloxamii, which has somewhat larger spores, or with other big bluish mushrooms in the Entoloma genus.

Culinary Notes

Entoloma atromadidum is very rare and should not be gathered except for scientific study. Its edibility is suspect and it has no culinary value.

Reference Sources

Fascinated by Fungi, 2nd Edition, Pat O'Reilly 2016, reprinted by Coch-y-bonddu Books in 2022.

Entoloma atromadidum A.M. Ainsw. & B. Douglas, in Ainsworth, Douglas & Suz, Field Mycology 19(1): 9 (2018) - British Mycological Society.

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.

Acknowledgements

This page includes pictures kindly contributed by Simon Harding.

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