page_title: Imperator torosus
section_title: Description
hierarchical_section_title: Imperator torosus / Description
caption_attribution_description: English: Boletus torosus Deutsch: Ochsen-Röhrling (Boletus torosus)
context_page_description: Imperator torosus, commonly known as the brawny bolete, is a species of bolete fungus in the family Boletaceae. It is native to southern Europe east to the Caucasus and Israel. It is generally associated with deciduous trees such as hornbeam, oak and beech in warm, dry locales. Although generally rare in Europe, it appears to be relatively common in Hungary. Appearing in summer and autumn on chalky soils, the stocky fruit bodies have an ochre cap up to 20 cm across, yellow pores on the cap underside, and a wine-red to brown or blackish stipe up to 6–15 cm long by 3–6 cm wide. The pale yellow flesh changes to different colours when broken or bruised depending on age; younger mushrooms become reddish, and older ones additionally take on bluish tones.
  Elias Magnus Fries and Christopher Theodor Hök first described this species as Boletus torosus in 1835, a name by which it came to be known for many years. Modern molecular phylogenetics shows that it is only distantly related to Boletus edulis—the type species of Boletus—and it was duly placed in the new genus Imperator in 2015.
  Eating raw mushrooms of this species leads to vomiting and diarrhea.
context_section_description: Quite heavy compared with other mushrooms of similar size, the stocky fruit body contains relatively high amounts of chitin. Holding the brawny bolete has been described as "having a stone in your hand". The cap is 6–20 cm (2.4–7.9 in) in diameter. Hemispherical when young, it extends and flattens into a convex and finally a flattish shape, sometimes forming a slight depression in the centre. Initially curled downward and inward, the cap margin gradually turns outward, eventually flattening in maturity, and sometimes protruding beyond the pored undersurface. The surface texture starts slightly velvety, but becomes smoother and hairless with age; in moist weather, the cap is slightly sticky. Changing over time, the colour of the cap is initially vivid yellow or golden yellow, then ochre, then darkening in age to brown. However, if the cap cuticle is bruised, or even touched, there are sudden changes in the colour that depend on the age of the mushroom: young, yellow caps become cherry-red, while ochre-brown cap tissue bruises to reddish-purple. These colour changes soon give way to bluish or greyish tones, which, when combined, give the cap a variegated appearance.
  The pores on the cap underside are round and small, the sulfur-yellow colour of the pore surface becoming less intense with age. The squat stipe measures 6–15 cm (2.4–5.9 in) long by 3–6 cm (1.2–2.4 in) thick. Egg-shaped when young, it lengthens somewhat as the mushroom grows, but is still bulbous in maturity; a mature stipe is typically a little shorter than the diameter of the cap. It is initially roughly the same colour as the cap, but as it matures, develops a wine-red colouration near the base and a dirty brown to bluish-black colouration elsewhere. The surface has a mesh-like pattern (reticulation) that has a colour development similar to that of the cap: initially yellow, then purplish, and finally dark brown. The flesh is thick and hard. It is yellow, except for the stipe base where it is deep red or dark brownish in older mushrooms. The pores, stipe and flesh turn greenish-blue with bruising or cutting. The smell is unpleasant, but the taste is mild.
  The spore print is olive-brown. The smooth oval spores measure 12–15 by 5–6 μm, and sometimes have an internal oil drop. Basidia (spore-bearing cells) are club-shaped, four-spored, and measure 22–34 by 8–9 μm. The fusiform (fuse-shaped) cystidia are colourless with oil droplets, and have dimensions of 40–50 by 7–8 μm. Cap cuticle tissue is in the form of a trichoderm, where the outermost hyphae emerge roughly parallel, like hairs, perpendicular to the cap surface. These cylindrical, interwoven hyphae contain septa.
caption: The base of the thick stipe is wine-red coloured.
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