Boletus edulis Bull. : Fr.
Cap up to 20cm, hemispherical, then convex, flat convex or flat, more or less viscid, darker in the center, paler towards the margin, beige, pale brown, brown to dark brown, sometimes greyish, not blueing when bruised. Stipe club-shaped, cylindrical or sometimes tapering towards the base, bulbously swollen or rooting, white or whitish to pale brownish, with well defined network, not blueing when bruised. Flesh white, sometimes spotted brownish at the stipe base, rarely somewhat pinkish below the cap cuticle, unchanging when exposed to air. Tubes initially white, then cream, pale yellow to yellow with olivaceous tint, unchanging when exposed to air. Pores concolorous with the tubes, unchanging when bruised. Smell not distinctive. Taste not distinctive. Spores 12.0–19.5 × 4–7 μm, ratio 2.5–3.9. Pileipellis (the cap cuticle) trichodermium of interwoven septate, slightly gelatinized hyphae. Cells of the hyphae long cylindrical, not incrusted. Chemical reactions: hyphae of flesh in the stipe base inamyloid with Melzer’s solution.
Habitat. Coniferous, mixed and broadleaf forests, mycorrhizal with conifers – spruce (Picea), fir (Abies), pines (Pinus), or with deciduous trees – beech (Fagus) and birch (Betula).
Distribution. In Europe widespread, mostly mountain species in south.
Note. In the past there was a number of similar species recognized. Boletus betulicola (Vassilkov) Pilát & Dermek, growing with birch and having grayish cap, B. persoonii Bon with entirely white fruitbodies, and B. venturii Bon having yellow cap. Recent molecular research have proven that all three of them are very closely related with B. edulis, and that is why some authorities reduce all three taxa to mere forms of B. edulis. However, there is no consesus among the boletologists and some other authors still treat B. betulicola as a separate species (see Korhonen & al. 2009).
Bulliard's illustration accompanying the original description of Boletus edulis.