''Xerocomus subtomentosus'', commonly known as suede bolete, brown and yellow bolete , boring brown bolete or yellow-cracked bolete, is a species of

bolete {{refimprove, date=July 2020 A bolete is a type of mushroom, or fungal fruiting body. It can be identified thanks to a unique mushroom cap. The cap is clearly different from the stem. On the underside of the cap there is usually a spongy surf ...

fungus in the family

Boletaceae The Boletaceae are a family of mushroom-forming fungi, primarily characterised by small pores on the spore-bearing hymenial surface (at the underside of the mushroom), instead of gills as are found in most agarics. Nearly as widely distributed ...

. The fungus was initially described by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...

in 1753 and known for many years as ''Boletus subtomentosus''. It is

edible An edible item is any item that is safe for humans to eat. "Edible" is differentiated from "eatable" because it does not indicate how an item tastes, only whether it is fit to be eaten. Nonpoisonous items found in nature – such as some mushroo ...

, though not as highly regarded as other bolete mushrooms. It occurs throughout Eurasia, North America and Australia and grows with a wide range of hardwood and conifer trees. It forms symbiotic ectomycorrhizal associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue. The fungus produces spore-bearing

fruit bodies The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cyc ...

. The olive to tan fruit body cap is up to in diameter and has a distinctive velvety surface. Like other boletes, it has tubes extending downward from the underside of the cap, rather than

gills A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

; spores escape at maturity through the tube openings, or pores. The pore surface is yellow and bruises blue. The stipe, or stem, measures up to 8 cm (3 in) tall and thick.

Taxonomy

''Xerocomus subtomentosus'' was first described in 1753 by the father of taxonomy

as ''Boletus subtomentosus''. The starting date of fungal

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

had been set as January 1, 1821, to coincide with the date of the works of the 'father of mycology', Swedish naturalist Elias Magnus Fries, which meant that the name required sanction by Fries (indicated in the name by a colon) to be considered valid, as Linnaeus' work preceded this date. It was thus written ''Boletus subtomentosus'' L.:Fr. However, a 1987 revision of the

International Code of Botanical Nomenclature The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...

set the starting date at May 1, 1753, the date of publication of Linnaeus' seminal work, the '' Species Plantarum''. Hence the name no longer requires the ratification of Fries' authority. French mycologist

Lucien Quélet Lucien Quélet in 1869 Lucien Quélet (14 July 1832 – 25 August 1899) was a French naturalist and mycologist. Quélet discovered several species of fungi and was the founder of the Société mycologique de France, a society devoted to mycolo ...

had classified a number of ''

Boletus ''Boletus'' is a genus of mushroom-producing fungi, comprising over 100 species. The genus ''Boletus'' was originally broadly defined and described by Carl Linnaeus in 1753, essentially containing all fungi with hymenial pores instead of ...

'' species in the genus ''Xerocomus'', with ''Xerocomus subtomentosus'' made the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

. The genus name is derived from the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

''Xeros'' "dry" and ''kome'' "hair", and refers to the velvety surface of the cap. This classification was disputed, with many authorities not recognising the genus and continuing to use ''Boletus subtomentosus''; however genetic analysis published in 2013 confirmed the distinctness of this species and its close relatives from the core group of fungi in the genus ''Boletus'' ( sensu stricto). ''Xerocomus subtomentosus'' and relatives, including '' Phylloporus pelletieri'', form a clade known informally as the "/Xerocomus Clade" within a larger group (informally called hypoboletus) in the suborder

Boletineae The Boletineae are a suborder of the fungal order Boletales. Families in the Boletineae include the Boletaceae and the Paxillaceae. Taxa *Paxillaceae **'' Alpova'' **'' Austrogaster'' **'' Gyrodon'' **'' Hydnomerulius'' **'' Meiorganum'' **'' ...

. Other clades within the group include the ''

Aureoboletus ''Aureoboletus'' is a genus of bolete fungi in the family Boletaceae. It was circumscribed by Czech mycologist Zdeněk Pouzar in 1957. A taxonomic monograph was published in 2010 by Wolfgang Klofac. Species Species from Index Fungorum ''Inde ...

'' and '' Hemileccinum'' clades, as well as species currently designated ''Boletus'' (though they are not closely related to ''

Boletus edulis ''Boletus edulis'' (English: cep, penny bun, porcino or porcini) is a basidiomycete fungus, and the type species of the genus ''Boletus''. Widely distributed in the Northern Hemisphere across Europe, Asia, and North America, it does not occu ...

'') and three species currently designated ''

Boletellus ''Boletellus'' is a genus of fungi in the family Boletaceae. The genus has a widespread distribution, especially in subtropical regions, and contains about 50 species. The genus was first described by American mycologist William Alphonso Murrill i ...

'' (though they are unlikely to be close relatives of the type species, '' Boletellus ananas''). The clade containing the hypoboletus group and the '' Royoungia'' clade is sister to the anaxoboletus group (containing the genera ''

Tylopilus ''Tylopilus'' is a genus of over 100 species of mycorrhizal bolete fungi separated from ''Boletus''. Its best known member is the bitter bolete (''Tylopilus felleus''), the only species found in Europe. More species are found in North America, s ...

'' sensu stricto, '' Strobilomyces'', '' Xanthoconium'', '' Porphyrellus'', '' Xerocomellus'', ''Boletus'' sensu stricto, and species that require new generic names (e.g., '' Boletus badius'') and the leccinoid group (comprising the genera '' Leccinellum'', ''

Leccinum ''Leccinum'' is a genus of fungi in the family Boletaceae. It was the name given first to a series of fungi within the genus ''Boletus'', then erected as a new genus last century. Their main distinguishing feature is the small, rigid projections ...

'', '' Spongiforma'', and the species '' Retiboletus griseus''). As ''X. subtomentosus'' is the type species of the genus, it and close relatives remain ''Xerocomus'' as other members are placed in different genera. Its specific name ''subtomentosus'' is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

"finely haired", referring to its cap. Mushroom author David Arora nicknamed the mushroom the ''boring brown bolete'' from its lack of taste and appeal. Other vernacular names include "yellow-cracked bolete", "suede bolete", and "brown and yellow bolete".

Description

The pale olive or tan

cap A cap is a flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3200 BC. Caps typically have a visor, or no brim at all. They are popular in casual and informal se ...

is initially convex before flattening, and measures or sometimes up to in diameter with a velvety tan surface. Occasionally the cap slits revealing yellow flesh beneath. The

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...

of the cap is very hard to remove. The pores underneath the cap are yellow, and bruise blue or green before fading somewhat. The stipe lacks a

ring Ring may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell :(hence) to initiate a telephone connection Arts, entertainment and media Film and ...

and is up to tall by wide. The

spore print 300px, Making a spore print of the mushroom ''Volvariella volvacea'' shown in composite: (photo lower half) mushroom cap laid on white and dark paper; (photo upper half) cap removed after 24 hours showing pinkish-tan spore print. A 3.5-centimeter ...

is olive-brown. A drop of

ammonium hydroxide Ammonia solution, also known as ammonia water, ammonium hydroxide, ammoniacal liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH3(aq). Although ...

on the cap instantly produces a

mahogany red Mahogany is a reddish-brown color. It is approximately the color of the wood mahogany. However, the wood itself, like most woods, is not uniformly the same color and is not recognized as a color by most. The first recorded use of ''mahogany'' a ...

reaction, which distinguishes it from some other similar species of the genus. The

flesh Flesh is any aggregation of soft tissues of an organism. Various multicellular organisms have soft tissues that may be called "flesh". In mammals, including humans, ''flesh'' encompasses muscles, fats and other loose connective tissues, but ...

is white and has little taste or smell.

Similar species

The rare European species '' Xerocomus silwoodensis'', described as new to science in 2007, is similar in appearance to ''X. subtomentosus''. It can be distinguished from the latter in the field by the darker reddish-brown tones of the cap and its preference for associating with '' Populus'' trees. It has white flesh that becomes yellow-tinged on exposure to air. '' Xerocomus chrysonemus'' has bright yellow flesh and mycelium. '' Xerocomus ferrugineus'' is found under conifers and also has yellow mycelium. Also somewhat similar are ''

Boletus chrysenteron ''Xerocomellus chrysenteron'', formerly known as ''Boletus chrysenteron'' or ''Xerocomus chrysenteron'', is a small, edible, wild mushroom in the family Boletaceae. These mushrooms have tubes and pores instead of gills beneath their caps. It i ...

'', ''B. citriniporus'', and ''B. edulis''.

Distribution and habitat

''Xerocomus subtomentosus'' occurs in autumn in forests throughout

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

, North America and Australia and forming a

mycorrhizal A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the pla ...

relationship with a wide range of hardwood and conifer trees. It has been recorded from the vicinity of

Tangier Tangier ( ; ; ar, طنجة, Ṭanja) is a city in northwestern Morocco. It is on the Moroccan coast at the western entrance to the Strait of Gibraltar, where the Mediterranean Sea meets the Atlantic Ocean off Cape Spartel. The town is the capi ...

in Morocco, growing under cork oak (''

Quercus suber ''Quercus suber'', commonly called the cork oak, is a medium-sized, evergreen oak tree in the section ''Quercus'' sect. ''Cerris''. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the core ...

''). It is associated with

bilberry Bilberries (), or sometimes European blueberries, are a primarily Eurasian species of low-growing shrubs in the genus ''Vaccinium'' (family Ericaceae), bearing edible, dark blue berries. The species most often referred to is '' Vaccinium myrtill ...

and other evergreen shrubs of the heath family

Ericaceae The Ericaceae are a family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with c.4250 known species spread across 124 genera, making it th ...

. ''Xerocomus subtomentosus'' is found in subarctic areas of western Greenland, where it is common and grows in association with white birch (''

Betula pubescens ''Betula pubescens'' (syn. ''Betula alba''), commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of deciduous tree, native and abundant throughout northern Europe and northern Asia ...

'').

Edibility

''Xerocomus subtomentosus'' is

, although not highly regarded. Its mild taste makes it suitable for mixed mushroom dishes. An

elemental analysis Elemental analysis is a process where a sample of some material (e.g., soil, waste or drinking water, bodily fluids, minerals, chemical compounds) is analyzed for its elemental and sometimes isotopic composition. Elemental analysis can be qualita ...

of specimens collected from Notec Forest in western Poland determined the mushrooms to have abundant amounts of

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

, and

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

, with mean values of 46000, 8400, and 1100 milligramme/kilogramme dry weight, respectively, in the caps. The levels of the toxic metals

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

, mercury, and

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

in the mushrooms "did not pose a threat to a consumer's health".

References

External links

* {{Taxonbar, from=Q198817 Edible fungi Boletaceae Fungi described in 1753 Fungi of Australia Fungi of Europe Fungi of North America Taxa named by Carl Linnaeus