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Geoglossum fallax E. J. Durand - Deceptive Earthtongue

Phylum: Ascomycota - Class: Leotiomycetes - Order: Helotiales - Family: geoglossaceae

Geoglossum fallax, France

Sometimes mistakenly recorded as Dead Man’s Fingers, Xylaria polymorpha, this sombre earthtongue is found mainly in mossy unimproved grassland, such as sensitively-managed old churchyards.

Distribution

Fairly common and widespread in Britain (including England, Wales and Scotland) and Ireland, Geoglossum fallax occurs also in many countries on mainland Europe, from Finland in the north to at least as far south as southern France. This earthtongue species is also known to occur in many parts of North America.

Taxonomic history

This sombre earthtongue was described in 1908 by American mycologist and botanist Elias Judah Durand (1870 - 1922), who gave it the scientific binomial name Geoglossum fallax which is still its generally-accepted name.

Synonyms of Geoglossum fallax include Geoglossum proximum S. Imai & Minakata, Geoglossum fallax var. proximum (S. Imai & Minakata) S. Imai, Geoglossum subpumilum S. Imai, and Geoglossum fallax var. subpumilum (S. Imai) S. Imai.

Etymology

The genus Geoglossum, set up by Christian Hendrik Persoon in 1794, is named from Geo- meaning earth and -glossum meaning tongue - hence fungi in this genus are referred to as earthtongues (or, as some authors prefer to write it, earth tongues). The specific epithet fallax is Latin and means deceptive.

Identification guide

Geoglossum fallax, North Wales, UK

Fruitbody

Stromata are blackish, club-like, comprising a longitudinally indented fertile section above a more or less cylindrical infertile stem. Individual tongues are 2 to 7cm tall. The dark-brown fertile section, shaped like a flattened club and often grooved, is 2-6mm thick and covers the upper third of the fruitbody; its surface is finely 'hairy' due to projecting asci. The stem is scaly, round, 1-2 mm in diameter, solid at the base but often hollow near the head. The flesh is light brown in the head section and blackish in the stem.

 

Asci

Cylindrical-clavate, 150 200 x 8-20µm; fairly thick walled; 8-spored, spores arranged in parallel.

 

Spores

Ascospores are narrowly fusiform or elongated cylindrical with tapered ends; smooth, 55-90 x 4-6µm; aseptate to 13-septate; initially hyaline, becoming brown as septa develop.

Spore print

Light brown.

 

Paraphyses

Paraphyses, often borne in separate clusters, are filiform, 3-4┬Ám in diameter and extend beyond the asci tips; often strongly curved or coiled at the apex; hyaline to pale brown; not closely septate; the apical cells are clavate to obovoid and comprise a chain of ovoid cells 4-6µm in diameter.

Odour/taste

Not distinctive.

Habitat & Ecological role

In mossy unimproved acidic grassland.

Season

August to November in Britain and Ireland.

Similar species

Xylaria polymorpha is an ascomycete of similar size. It grows on dead hardwood and its stromata (compound ascomycetous fruitbodies) are not usually laterally compressed or indented.

Trichoglossum hirsutum, commonly referred to as the Hairy Earthtongue, has a stem that is minutely hirsute rather than scaly.

Reference Sources

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

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 contribited by David Kelly.

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