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Rubinoboletus rubinus (W.G. Sm.) Pilàt & Dermek - Crimson Bolete

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Boletales - Family: Boletaceae

Rubinoboletus rubinus

With its beautiful carmine-red pores and upper stem, this is surely one of the most striking of all the boletes that occur in Britain.

Distribution

A rare find in southern and central Britain, Rubinoboletus rubinus occurs in many parts of mainland Europe including Poland, France and Italy; its range is thought to extend into western Asia.

Taxonomic history

This species was originally named and described in 1868 by English mycologist Worthington George Smith (1835-1917) who gave it the binomial scientific name Chalciporus rubinus. Some authorities still hold this to be the most appropriate name; however, the name used here, Rubinoboletus rubinus, reflects the fact that in microscopic details this bolete is very different from Chalciporus species. The name Rubinoboletus rubinus dates from a 1969 publication by Czech mycologist Albert Pilàt (1903-1974) and Slovak mycologist Aurel Dermek (1925-1989).

Synonyms of Rubinoboletus rubinus include Boletus rubinus W.G. Sm., Chalciporus rubinus (W.G. Sm.) Singer, Suillus rubinus (W.G. Sm.) Kuntze, and Xerocomus rubinus (W.G. Sm.) A. Pearson.

Etymology

The generic name Boletus comes ​​from the Greek bolos, meaning 'lump of clay', while the specific epithet rubinus comes from Latin and refers to the ruby-red colouring of pores and stem.

Identification guide

Cap of Chalciporus piperatus

Cap

3 to 8cm across, initially hemispherical and eventually becoming almost flat; smooth or slightly tomentose; dry, often becoming slightly sticky or greasy in wet weather; yellowish orange to reddish brown. The cap flesh is yellow with a pinkish region immediately beneath the cap cuticle.

Cap cuticle of Rubinoboletus rubinus

Cap cuticle

A tangled trichodermium of broad (typically 15µm diameter) hyphae.

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Pores of Rubinoboletus rubinus

Tubes and Pores

The shortly-decurrent ochre tubes become more pink towards their termination in irregularly angular carmine pores that do not change colour significantly when bruised.

Stem cross section, Rubinoboletus rubinus

Stem

2 to 5cm tall and 0.5 to 1.5cm in diameter; surface bright carmine; cylindrical, usually tapering in slightly towards a yellowish base. Stem flesh whitish near cap, becoming bright yellow towards the base.

Spores of Rubinoboletus rubinus

Spores

Broadly ellipsoidal, smooth, 5.5-8.5 x 4-5.5µm.

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Spore print

Pale reddish brown to ochre.

Odour/taste

Odour pleasant but not distinctive; taste mild (distinguishing it from Chalciporus piperatus whose spores are hot and very peppery).

Habitat & Ecological role

Mycorrhizal, found in oak woodland as well as under Beech in Britain but also recorded under Hornbeam trees in some parts of mainland Europe.

Season

Summer and autumn.

Similar species

Chalciporus piperatus is similar in macroscopic appearance but its spores are fusiform rather than broadly ellipsoidal.

Culinary Notes

This very rare bolete - it is reported to be on the Red List of at least seven countries - is also quite insubstantial and therefore fruitbodies should not be gathered except when necessary for research purposes.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

British Boletes, with keys to species, Geoffrey Kibby (self published) 3rd Edition 2012

Roy Watling & Hills, A.E. 2005. Boletes and their allies (revised and enlarged edition), - in: Henderson, D.M., Orton, P.D. & Watling, R. [eds]. British Fungus Flora. Agarics and boleti. Vol. 1. Royal Botanic Garden, Edinburgh.

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.

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