Suillus luteus . Suillus luteus is a bolete fungus common in its native Eurasia and widely introduced elsewhere. English names such as "slippery jack" refer to the brown cap, which is slimy in wet conditions. The mushrooms are edible, though not highly regarded, and are often eaten in soups, stews or fried dishes. The fungus grows in coniferous forests in its native range, and pine plantations where introduced. It forms symbiotic associations with living trees by enveloping the underground roots. The fungus produces spore-bearing mushrooms above ground in summer and autumn. The cap often has a distinctive conical shape before flattening with age. Instead of gills, the underside of the cap has pores with tubes extending downward that allow mature spores to escape. The pore surface is yellow, and covered by a membranous partial veil when young. The stalk is pale with small dots near the top. It bears a distinctive ring that is tinged brown to violet on the underside.