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

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

Entoloma atromadinum, young wet specimen

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.

Entoloma atromadidum

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.

Entoloma atromadidum under a Hawthorn tree

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 of Entoloma atromadidum

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 of Entoloma atromadidum

Gills

Sinuate, almost free; moderately crowded; edge usually irregularly serrulate; white with a faint blue tinge near the cap margin, becoming pink at maturity.

Basidia

Clavate, 28.8-50.0 x 8.8-11.2μm; mainly 4-spored, with basal clamps.

Stem of Entoloma atromadidum

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.

Spore of Entoloma atromadidum

Spores

Angular, mostly pentagonal or hexagonal in side view, subglobose, 6.2-8.3 x 6.4-8.0μm; Qav=1.0; inamyloid.

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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, Pat O'Reilly 2016.

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 and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

Acknowledgements

This page includes pictures kindly contributed by Simon Harding.

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