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Suillus luteus

Suillus luteus is a bolete fungus, and the type species of the genus Suillus. A common fungus native to Eurasia, from the British Isles to Korea, it has been introduced widely elsewhere, including North and South America, southern Africa, Australia and New Zealand. Commonly referred to as slippery jack or sticky bun in English-speaking countries, its names refer to the brown cap, which is characteristically slimy in wet conditions. The fungus, initially described as Boletus luteus by Carl Linnaeus in 1753, is now classified in a different family as well as genus. Suillus luteus is edible, though not as highly regarded as other bolete mushrooms, and is commonly prepared and eaten in soups, stews or fried dishes. The slime coating, however, may cause indigestion if not removed before eating.

The fungus grows in coniferous forests in its native range, and pine plantations in countries where it has become naturalized. It forms symbiotic ectomycorrhizal associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue. The fungus produces spore-bearing fruit bodies, often in large numbers, above ground in summer and autumn. The fruit body cap often has a distinctive conical shape before flattening with age, reaching up to 13 cm (5 in) in diameter. Like other boletes, it has tubes extending downward from the underside of the cap, rather than gills; spores escape at maturity through the tube openings, or pores. The pore surface is yellow, and covered by a membranous partial veil when young. The pale stipe, or stem, measures up to 10 cm (4 in) tall and 3 cm (1.2 in) thick and bears small dots near the top. Unlike most other boletes, it bears a distinctive membranous ring that is tinged brown to violet on the underside.

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