Geastrum fimbriatum

Description

Geastrum fimbriatum is an inedible species of mushroom belonging to the genus Geastrum, or earthstar fungi. The species has a widespread distribution and is found in Asia, Europe, and the Americas. It is distinguished from other earthstars by the delicate fibers that line the circular pore at the top of its spore sac.

Common names: Fringed Earthstar, Sessile Earthstar.

Mushroom Identification

1. Fruitbody

   5 to 9 creamy-white outer rays are recurved beneath the unstalked papery grey spore sac, which is finely downy. The outer diameter (across the rays) is 2.5 to 5cm.

2. Spore Sac

   Subspherical (an oblate spheroid), the spore sac is 1 to 2.2cm in diameter, ochraceous-cream, becoming greyer with age. The apical pore is fibrous but not striate.

3. Spores

   Globose, minutely warty, 2.9-3.5µm in diameter (excluding warts).

4. Spore Mass

   Brown.

5. Odor

   Not significant.

6. Habitat & Ecological Role

   Mainly found in leaf-litter-rich soil in deciduous and mixed woodland, often on chalk-rich soil.

7. Season

   Fruiting in the autumn; long-lasting, and sometimes remaining intact through the winter months.

Look-Alikes

1. Geastrum saccatum

   This mushroom is larger – up to 5 cm (2.0 in) across – and has a clearly delimited ring-like area around the pore opening.

2. Geastrum rufescens

   Has reddish tones that are absent from G. fimbriatum.

History

The species was described in 1829 by the great Swedish mycologist Elias Magnus Fries, who established its basionym when he gave it the binomial name Geastrum fimbriatum. The species had been recognized much earlier, of course - for example in 1801 Christiaan Hendrik Persoon had described this earthstar under an invalid (already used) specific epithet.

Synonyms of Geastrum fimbriatum include Geastrum rufescens var. minor Pers., Lycoperdon sessile Sowerby, Geastrum tunicatum Vittad., and Geastrum sessile (Sowerby) Pouzar.

Geastrum, the generic name, comes from Geo- meaning earth, and -astrum meaning a star, and so literally Geastrum means earth star. The specific epithet fimbriatum is Latin and means fibrous or fringed - a reference to the fringed opening of the peristome (spore sac); the English word fimbriate is also used to indicate how the ends of a flower petal such as a pink (of the family Caryophyllaceae) are split into two or more divisions. The synonymous specific epithet sessile by which this earthstar was until recently more commonly known means sessile (the Latin and English spellings being identical), in other words sitting down.

Photo sources:

Photo 1 - Author: Ra'ike (see also: de:Benutzer:Ra'ike) (CC BY-SA 3.0)

Photo 2 - Author: Luis Fernández García (CC BY-SA 2.5)

Photo 3 - Author: Liz Popich (Lizzie) (CC BY-SA 3.0)

Photo 4 - Author: Luis Fernández García (CC BY-SA 2.5)

Photo 5 - Author: Dwergenpaartje (CC BY-SA 4.0)