Structures of the fungi in this genus in common with members of the family Boletaceae including the presence of a cylindrical stipe, fleshy pileus, soft context and tubular hymenium. Pileus surface viscid to glutinose and glabrous, slimy and sticky when moist or dry and fibrillose-squamulose, the fibrils or scales superimposed above a gelatinized layer, more rarely innate, detersile or not, sometimes with appendiculate remnants. Microscopically an ixotrichodermium or a trichodermium, or also a two-layered cuticle consisting of an upper trichodermal and a lower gelatinous layer.
Context white or pale yellow, unchanging or staining pale reddish or turninggreenish-blue by autooxidation. Hymenophore adnate to adnexed, sometimes decurrent, whitish, grey, yellow, orange or pale cinnamon brown, seldom bruising bluish or greenish. Pores small to wide, occasionally boletinoid. Stipe solid, dry or glutinous, veil present or absent, often forming an annulus or merely a velar appendiculation on the margin of the pileus, typically with but also without glandular dots or smears. Bilateral hymenophoral trama boletoid. Spores smooth, elongate, short fusoid, usually cinnamon brown or chocolate brown in mass, sometimes with olivaceous tinge. Hymenial cystidia rather large and mostly covered by a colored incrustation, usually clustered, with amorphous brown pigmentation at the base. Clamp connections absent.
Distributed mostly in the northern temperate hemisphere and southward into the tropics to the southern limit of Pinaceae. Some species introduced adventitiously with pine trees in pine plantations outside of the indigenous area of Pinaceae; thus frequently occurring with transplanted Pinaceae. Species in the genus associated especially with members of the genera Pinus, Larix and Pseudotsuga, but also known with Betula spp. and Salicaceae; most species obligately mycorrhizal (SINGER 1986, ŠUTARA 1987 a, 2005, KLOFAC 2007, HALLING 2013); the strict affiliation to accompanying trees often overestimated (KRETZER & al. 1996, WU & al. 2000).