Tylopilus porphyrosporus (Fr. & Hök) A. H. Sm. & Thiers - Dusky Bolete

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

Distribution - Taxonomic History - Etymology - Identification - Culinary Notes - Reference Sources

With its purple-brown cap and stipe, Tylopilus porphyrosporus is a rather dull and sombre-looking bolete and not at all easy to spot, despite its large size. This summer and autumn species occurs under pines, often in dark woodland settings that add to the difficulty of spotting mushrooms with dark brown caps.

Distribution

This is a rare mushroom found in the UK, Ireland and parts of mainland Europe.

Taxonomic history

First described by Elias Magnus Fries and Fredrik Christopher Theodor Hök (1807 - 1877) in their thesis Boleti, Fungorum generis, illustratio in 1835, where it appeared under the scientific name Boletus porphyrosporus, the Dusky Bolete was transferred to the genus Porphyrellus 110 years later by the French mycologist Jean-Edouard Gilbert (1888 - 1954), and this was its generally-accepted scientific name until quite recently. The currently-accepted name Tylopilus porphyrosporus dates from a 1971 publication by American mycologists Alexander Hanchett Smith (1904 - 1986) and Harry Delbert Thiers (1919 - 2000).

Among the many synonyms of Tylopilus porphyrosporus (Fr. & Hök) A.H. Sm. & Thiers are Porphyrellus porphyrosporus (Fr. & Hök) E.-J. Gilbert, Krombholziella pseudoscaber (Secr. ex Singer), Boletus porphyrosporus Fr. & Hök, Phaeoporus porphyrosporus (Fr. & Hök) J. Bataille, and Porphyrellus pseudoscaber Secr. ex Singer.

Etymology

The Dusky Bolete gets its common name and its specific epithet from its dark purplish-brown colours.

The colours of the cap, stem and spores of the Dusky Bolete make it very easy to identify.

Identification Guide

Cap	This sombre mushroom has a dark brown cap with a noticeably paler margin. Initially convex, caps expand and sometimes become irregularly lobed. 6 to 15cm in diameter when fully expanded, the caps have soft buff flesh with a vinaceous tinge.
Tubes and Pores	The tubes and pores are greyish-yellow at first (as in the youngish specimen shown here) but, as the fruiting body begins releasing spores, the pores turn brown.  When cut or bruised, the tubes turn blue-green.
Stem	1 to 3cm in diameter and 5 to 12cm tall, the stems of this species are tobacco brown and slightly velvety to the touch when young, becoming smooth as the fruiting body matures. The stem flesh is buff, turning slightly blue-green near the apex when cut.
	Spores Ellipsoidal to subfusiform; smooth, thick-walled; 14-17.0 x 6.0-7.5µm. Spore print Vinaceous-brown.
Odour/taste	Unpleasant sour taste and odour.
Habitat & Ecological role	Under deciduous trees and in conifer forests.
Season	July to September in Britain and Ireland.
Similar species	The Bay Bolete, Imleria badia, is similar but with a shiny cap when fully developed; its tubes turn blue when bruised.

Culinary Notes

This mushroom is reported to have a sour taste, and it is best treated as inedible if not for that reason then for its rarity.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

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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