Mycena megaspora Kauffman - Rooting Bonnet

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

Mycena megaspora - Rooting, southern England

Many of the bonnet fungi are difficult to identify with confidence, but the dark cap of Mycena megaspora and its heath and peatland preferred habitat are a great help towards confident identification of this rarely recorded bonnet mushroom.

Unlike many of the bonnet mushrooms, Mycena megaspora does not require rotten wood as a substrate; it is at home in mossy peat bogs and on heathland with heather.

Mycena megaspora, New Forest

Distribution

This swarthy bonnet mushroom is quite a rare find in Britain and Ireland, perhaps partly because Sphagnum-rich bogs and burnt heathland habitats are not the favoured haunts of many mycologists and other fungus forayers, who tend to focus more on woodlands and low-nutrient grasslands which are easily accessible. The Rooting Bonnet is found in many other parts of mainland Europe, where it is generally reported to be either uncommon or rare. This species has also been recorded in the Pacific Northwest of America where its occurrence seems to be only occasional.

Mycena megaspora, New Forest, England

Taxonomic history

When in 1933 American mycologist Calvin H. Kauffman described this rare bonnet mushroom, he called it Mycena megaspora, which is still its generally-accepted scientific name.

In the past Mycena megaspora was sometimes referred to as Mycena dissimulabilis and Mycena permixta; another of its synonyms is Mycena uracea A. Pearson.

Etymology

The specific epithet megaspora comes from the prefix mega- meaning large and -spora referring to the spores. This bonnet mushroom certainly has huge spores compared with those of most other Mycena mushrooms.

As for the common name Rooting Bonnet, this is self explanatory: the stem bases of these bonnet mushrooms often penetrate deeply into their growing substrate.

Identification guide

Expanded cap of Mycena epipterygia

Cap

1.5 to 5cm in diameter when fully mature, the caps are conical to convex, markedly grooved and with a prominent central umbo; the surface is dark grey-brown with a very dark (sometimes almost black) centre; sometimes pruinose when very young. Diverticulate hyphae of the pileipellis are 2-3.5μm wide and are liberally covered with warts and/or relatively short outgrowths.

Stem

3-10cm long and 1-4mm in diameter; hollow; tough, with a long (to 10cm) tapered pseudorhiza (like a root). Stem apex pallid; the lower part darker sepia; surface faintly pruinose when young becoming smooth with age; often twisted with faint longitudinal striations. Cap and stem flesh pallid greyish brown.

Gills of Mycena epipterygia

Gills

Adnexed or slightly sinuate, the fairly distant interveined gills are grey and take on a slight pink tinge when fully mature.

Cheilocystidia of <em>Mycena megaspora</em>

Cheilocystidia

Cheilocystidia (cystidia on the gill edges) are 25-75μm tall and 6-17μm across; they are variously clavate, subcylindrical or irregularly shaped and covered with a variable number of fairly coarse outgrowths (medusa heads). Pleurocystidia (cystidia on the gill faces) are absent.

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Basidia of <em>Mycena megaspora</em>

Basidia

The clavate basidia are 30-50 x 10-15μm; two-spored and clampless or four-spored basidia with clamps.

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Sterigmata

Up to 10 μm long.

Spores of Mycena megaspora, Rooting Bonnet mushroom

Spores

Very variable in length; broadly ellipsoidal to cylindrical, smooth, 10-16 x 6-7.5µm; amyloid.

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Spore print

White.

Odour/taste

Slight odour of radish; taste not distinctive.

Habitat & Ecological role

Saprobic; on boggy ground, peat and in particular burnt heath, often among Sphagnum mosses rather than, as with many Mycena species, on rotten wood.

Season

Mid August to late November in Britain and Ireland.

Similar species

There are numerous bell-shaped fungi in the Mycena genus; however, the very dark, largish caps, rooting stem base, and particular growing habitats help to distinguish Mycena megaspora from many of the other darkish bonnet mushrooms.

Culinary Notes

These little mushrooms are not known to be edible and so I don't know whether they contain dangerous toxins; I therefore recommend that they should not be collected for eating.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

Penny Cullington, (Oct. 2013). British Mycenas - Brief Descriptions.

Giovanni Robich, (2003). Mycena d'Europa; Associazione Micologica Bresadola ; Vicenza : Fondazione Centro Studi Micologici.

British Mycological Society. 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.

Acknowledgements

Pictures and photomicrographs on this page are shown with the kind permission of David Kelly.

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