Brawny bolete

A species of Imperator

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.