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Geastrum elegans Fr. - Elegant Earthstar

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Geastrales - Family: Geastraceae

Geastrum elegans, Elegant Earthstar

Initially looking like a round stone lying partly buried in the soil, the outer peridium (skin) splits into 6 to 8 pointed rays that fold back neatly beneath the inner spore sac, raising it up from the ground. The Elegant Earthstar usually fruits in small groups and occasionally in lines or partial fairy rings; these pale little fungi are easily overlooked in habitat that is often littered with small pale snail shells.

Geastrum elegans - Elegant Earthstar, Ynyslas Dunes, Wales

Distribution

The Elegant Earthstar is the rarest of more than 15 earthstar species known to occur in Britain. It has been recorded in the Isles of Scilly and in Norfolk (where, unfortunately, it has not been seen in recent years) and West Wales. The specimens shown on this page were seen at Ynyslas (part of Dyfi National Nature Reserve), on the coastal sand-dune system midway between Aberystwyth and Machynlleth. Elsewhere this species is a rare find in several central and southern European countries including Italy and The Netherlands.

Taxonomic history

The currently-accepted scientific name of this earthstar dates from an 1842 publication by Italian mycologist Carlo Vittadini (1800 - 1865), although he used the old genus name Geaster. Earlier, it had been described as Geastrum badium by Christiaan Hendrik Persoon, and so you may see references to this species using that synonym.

Etymology

Geastrum, the generic name, comes from Geo- meaning earth, and -astrum meaning a star, and so literally Geastrum means earth star. The specific epithet elegans is also from Latin and of course means elegant.

Identification guide

Top view of Geastrum elegans

Fruitbody

6 to 8 brown outer rays are usually recurved beneath the sessile (unstalked) papery whitish spore sac, which is 0.5 to 1cm in diameter, more or less globose and with a finely pruinose (floury) surface. The outer diameter (when the rays are recurved at maturity) is 1.2 to 3.5cm.

 

Top view of Geastrum elegans

Underside features

Only a minority of Earthstar species have a nest-like cup attached to the ends of their rays, and there is no such feature in Geastrum elegans; instead it holds on to soil and debris as the rays fold beneath the fruitbody and raise it from its substrate, In the centre of this patch of debris there is a small whitish bare patch or scar; this is where the fruitbody has broken free of its mycelium.

Peristome of Geastrum elegans

Peristome

The peristome is a conical beak 1.5 to 3 mm long with between 14 and 20 ridges narrowing to a small apical hole via which the mature spores emerge. There is no clear ridge delineating the base of the peridiole - a feature which helps distinguish Geastrum elegans from other somewhat similar species such as Geastrum schmidelii.

Spores, Geastrum elegans

Spores

Globose, minutely warty, 4.8 - 5.7µm in diameter (excluding the blunt warts which are 0.4 - 0.6µm tall).

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Spore mass

Pale brown to yellowish brown.

Capillatum, Geastrum elegans

Capillitum

The capillitial hyphae are smooth, thick walled, 3-7µm in diameter and taper slghty to rounded ends.

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Odour/taste

Not significant.

Habitat & Ecological role

Found in chalk-rich sandy soil - in Britain, usually on short-sward vegetated and mossy coastal dunes.

Season

Autumn and winter.

Similar species

Geastrum fimbriatum is similar but usually has a larger spore sac; its peristome is not ridged.

Several other Geastrum species are of the same general form, and confident identification requires experience.

Culinary Notes

Geastrum elegans is very rare in Britain and a Biodiversity Action Plan species that should not be gathered. In common with other earthstars, it is an inedible fungus and of no culinary value.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

Pegler, D.N., Laessoe, T. & Spooner, B.M (1995). British Puffballs, Earthstars and Stinkhorns. Royal Botanic Gardens, Kew.

Sunhede, Stellan (1989) Geastraceae (Basidiomycotina) - morphology, ecology, and systematics with special emphasis on the North European species; Synopsis fungorum, Volume 1, Oslo, Norway

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.

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