Butyriboletus regius: The Ultimate Mushroom Guide
About The Butyriboletus regius Mushroom
Butyriboletus regius (formerly Boletus regius) is a basidiomycete fungus of the genus Boletus. It has a pink cap, yellow flesh, and a reticulate pattern on the stem. Yellow pores age darker & bruise blue. Yellow cap flesh stains slowly & erratically. The cap sometimes has yellow or brown tones, especially near the margin. The stem sometimes has reddish tints, especially by the base.
This ectomycorrhizal mushroom is found singly or in very small groups under various kinds of oaks as well as Beech and Sweet Chestnut trees in calcareous regions. Rare in European countries, noticeably Italy, France, Spain and Portugal. B. regius is also known to occur in parts of North America and China.
Other names: Royal Bolete, Red-Capped Butter Bolete.
Butyriboletus regius Identification
Young caps of Butyriboletus regius are hemispherical and velvety, becoming smooth and often pitted or slightly wrinkled as the fruiting bodies mature. The cap surface is dark pink to red, sometimes with a yellowish or brownish tinge particularly near to the margin. Beneath the cap cuticle, the flesh is yellow and either does not blue or turns slightly pale blue when cut.
When fully expanded, the caps of the Royal Bolete range from 5 to 20cm in diameter, and the margin usually becomes wavy.
Tubes and Pores
The deep tubes (up to 2.5cm long) and angular pores of the Royal Bolete are yellow, darkening with age, and the tubes have adnate or slightly decurrent attachment to the stem. Pores spacing is typically 1mm. When bruised the pores of Royal Boletes found in Britain and Europe do not turn blue.
Mainly yellow but sometimes with red coloring, most often near the base, the stem is covered in a fine mesh network (reticulum) concolorous with the stem surface.
The stem surface does not blue significantly when bruised.
Variable in form but often slightly fusiform (barrel-shaped) or with a somewhat bulbous base, stems range from 3 to 5cm in diameter and are typically 5 to 12 cm long.
Narrowly ellipsoidal to fusiform, smooth, 10.5-16 x 3-5µm; hyaline (translucent).
Butyriboletus regius Look-Alikes
Much smaller and more gregarious bolete; it has a ruby-red cap but its stem is striate rather than reticulate.
Has dull pink to pinkish-brown cap, yellow blueing flesh, blueing tubes and pores, and spores of different sizes.
It may have similarly colored fruitbodies but it has blueing flesh and bitter taste.
Butyriboletus regius Taxonomy & Etymology
The Royal Bolete was first described in 1832 by the Bohemian mycologist Julius Vincenz von Krombholz (1782 - 1843), who called it Boletus regius, a most appropriate name that it retained until 2014, when Americans David Arora and Jonathan L. Frank transferred it to the new genus Butyriboletus, based largely on the results of molecular (DNA) analysis which has prompted a major revision of the family Boletaceae.
Butyriboletus regius has several synonyms, including Boletus regius Krombh., Boletus appendiculatus var. regius Konr., and Boletus subtomentosus ssp. cerasinus Martin.
The generic name Boletus comes from the Greek bolos, meaning 'lump of clay', while the butyri- prefix to the new genus means 'buttery'. The regal appearance of this large bolete is reflected in both its specific epithet and its common name, neither of which require any explanation.
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