Megacollybia platyphylla (Pers.) Kotl. & Pouzar - Whitelaced Shank

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

Megacollybia platyphylla - Whitelaced Shank

With a dark cap covering pallid gills, this is another tricky species to identify in situ, but its identity is at once betrayed if you excavate the base of the stem. The Whitelaced Shank has white... well, 'laces' is actually quite a good description for the stringy mycelial fibres that extend from the stem base for some considerable distance into the substrate timber or wood-rich humus of the forest floor. (In the picture in the 'Stem' identification characteristics, below, the white 'laces' are clearly visible.)

Distribution

In Britain and Ireland the Whitelaced Shank is widespread and common, particularly in the south. This woodland mushroom occurs also throughout most of mainland Europe and is also recorded in parts of Russia. This species was until recently thought to occur in parts of North America, but the USA specimens have now been shown to be non-co-specific with Megacollybia platyphylla and have been given species status.

Taxonomic history

This saprobic fungus was described scientifically in 1796 by Christiaan Hendrik Persoon, who established its basionym when he gave it the binomial scientific name Agaricus platyphyllus. (In the early years of fungal taxonomy most of the gilled mushrooms were included initially in the genus Agaricus, the contents of which has since largely been redistributed across several newer genera.) In 1972 Czech mycologists František Kotlaba and Zdeněk Pouzar reclassified this species as Megacollybia platyphylla, which is its currently-accepted scientific name.

Megacollybia platyphylla - Whitelaced Shank, a pale specimen

Synonyms of Megacollybia platyphylla include Agaricus grammocephalus Bull.Agaricus platyphyllus Pers.Agaricus repens Fr.Collybia platyphylla (Pers.) P. Kumm.Collybia grammocephala (Bull.) Quél.Agaricus tenuiceps Cooke & Massee, Tricholoma tenuiceps (Cooke & Massee) Massee, Tricholomopsis platyphylla (Pers.) Singer, and Oudemansiella platyphylla (Pers.) M.M. Moser.

This is the only species in the genus Megacollybia that is recorded from Britain, and it is the type species of that genus.

Etymology

The genus name Megacollybia come from Mega- meaning large, and -collybia meaning coins or coin-shaped, and so by implication these are larger than the coin-shaped fungi found in the genus Collybia.

Incidentally, several of the more common species that were for many years comfortably settled in the Collybia genus have recently been transferred to the genera Gymnopus and Rhodocollybia. See, for example, Gymnopus peronatus, the Wood Woollyfoot, and Rhodocollybia butyracea, Butter Cap (also commonly called Greasy Toughshank).

The specific epithet platyphylla comes from platy- meaning wide and -phylla meaning leaves (or gills in this case).

Identification guide

A young cap of Megacollybia platyphylla

Cap

6 to 14cm across; convex, not flattening completely but often developing a slight central depression with a small umbo; smooth and dry; various shades of grey-brown with radial streaks. In dry weather the caps of this mushroom sometimes split radially at the margins.

Gills of Megacollybia platyphylla

Gills

Sinuate or adnexed to stem; white, turning cream with age; crowded and very broad (platyphylla means literally 'broad leaves'). On older species the gills become irregularly wavy.

Cheilocystidia of Megacollybia platyphylla

Cheilocystidia

The gill-edge cystidia are clavate (club-shaped).

Stem and rhizomorphs, Megacollybia platyphylla

Stem

5 to 15cm long and 0.6 to 1cm dia.; base often rooting and with long white rhizomorphs (see left) attached; white, covered in grey-brown fibrils, paler at apex; no ring.

Spores of Megacollybia platyphylla

Spores

Broadly ellipsoidal, smooth, 7-9 x 4.5-6um; inamyloid.

Spore print

White.

Odour/taste

Not significant.

Habitat & Ecological role

Megacollybia platyphylla is a saprobic mushroom (feeding on rotting wood and other organic vegetation); it can occur either solitarily or in small groups on and near deciduous hardwood trunks, branches or woody debris (less commonly on conifer timber), or arising from the forest floor from from buried wood.

Season

June to November in Britain and Ireland.

Similar species

Melanoleuca polioleuca, the Common Cavalier, is similar but grows on soil rather than on wood;it has warty spores. (More than thirty species in the Melanoleuca genus are recorded from Britain and Ireland, and most have brownish caps and white gills; separating them is a task for specialists.)

Megacollybia platyphylla - Whitelaced Shank, a tufted group

Culinary notes

There are conflicting reports as to whether Megacollybia platyphylla is edible and reports that at least some people have been sick after eating it; I suggest, therefore, you consider them as for looking, not for cooking.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

Kuo, M. (2010). The genus Megacollybia, at MushroomExpert.Com

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

This page includes pictures kindly contributed by Simon Harding and Richard Shotbolt.

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