Slippery Jill

Appearance

The cap of ''S. salmonicolor'' is bluntly rounded or convex to nearly flattened, reaching a diameter of 3–9.5 cm. The cap surface is sticky to slimy when moist, but becomes shiny when dry. The cap color is variable, ranging from dingy yellow to yellowish-orange to ochraceous-salmon, cinnamon-brown or olive-brown to yellow-brown.

The flesh is pale orange-yellow to orange-buff or orange, and does not stain when exposed to air. The odor and taste are not distinctive. The pore surface on the underside of the cap is yellow to dingy yellow, or yellowish orange to salmon, darkening to brownish with age; it also does not stain when bruised. The pores are circular to angular, measuring 1–2 per mm and 8–10 mm deep.

The stem is 2.5–10 cm long, 6–16 mm thick, and either equal in width throughout or slightly enlarged in the lower portion. It is whitish to yellowish or pinkish-ochre, and has reddish-brown to dark brown glandular dots and smears on the surface. Glandular dots are made of clumps of pigmented cells, and, unlike reticulation or scabers, can be rubbed off with handling. The flesh is ochraceous to yellowish, often salmon-orange at the base of the stem. The partial veil that protects the developing gills is initially thick, baggy, and rubbery.

It often has a conspicuously thickened cottony roll of tissue at its base, and sometimes flares outward from the stem on the lower portion. It forms a gelatinous ring on the upper to middle part of the stem. The spore print is cinnamon-brown to brown. The surface of the cap, when applied with a drop of dilute potassium hydroxide or ammonia solution, will first turn a fleeting pink color, then dark red as the flesh collapses.

The spores are smooth, roughly ellipsoid in shape, inequilateral when viewed in profile, and measure 7.6–10 by 3–3.4 μm. They appear hyaline to yellowish in a dilute solution of KOH, and cinnamon to pale ochraceous when stained with Melzer's reagent. The basidia are somewhat collapsed, hyaline, and 5–6 μm thick. The cystidia are scattered, sometimes arranged in clusters, usually with an ochraceous-brown content, but occasionally hyaline.

They are club-shaped to somewhat cylindric and measure 34–60 by 10–13 μm. The cuticle of the cap is an ixotrichodermium—a cellular arrangement where the outermost hyphae are gelatinous and emerge roughly parallel, like hairs, perpendicular to the cap surface. These hyphae are hyaline and narrowly cylindric, measuring 1.4–3 μm in diameter. The stem surface is made of scattered bundles of caulocystidia that are brown or sometimes hyaline in KOH, club-shaped to subcylindrical bundles interspersed among hyaline cells. These bundles are underlain by a layer of gelatinous, hyaline, vertically oriented and parallel hyphae that are shaped like narrow cylinders. Clamp connections are absent from the hyphae.

Naming

First described as a member of the genus ''Boletus'' in 1874, the species acquired several synonyms, including ''Suillus pinorigidus'' and ''Suillus subluteus'', before it was assigned its current binomial name in 1983. It has not been determined with certainty whether ''S. salmonicolor'' is distinct from the species ''S. cothurnatus'', described by Rolf Singer in 1945.

Distribution

''Suillus salmonicolor'' occurs in a mycorrhizal association with various species of ''Pinus''. This is a mutualistic relationship in which the subterranean fungal mycelia creates a protective sheath around the rootlets of the tree and a network of hyphae that penetrates between the tree's epidermal and cortical cells. This association helps the plant absorb water and mineral nutrients; in exchange, the fungus receives a supply of carbohydrates produced by the plant's photosynthesis. Two-, three-, and five-needled pines have all been recorded to associate with ''S. salmonicolor''.

In North America, the fungus has been found growing with ''P. banksiana'', ''P. palustris'', ''P. resinosa'', ''P. rigida'', ''P. strobus'' and ''P. taeda''. In Kamchatka it has been found in association with ''P. pumila'', in the Philippines with ''P. kesiya'', and in southern India with ''P. patula''. The northern limit of its North American range is eastern Canada , and the southern limit is Nuevo León and near Nabogame in Temósachi Municipality, Chihuahua, Mexico.

''Suillus salmonicolor'' has been collected from the Dominican Republic in the Caribbean, Japan, Taiwan, and from Mpumalanga, South Africa. Because there are no native ''Pinus'' species in South Africa, the fungus is assumed to be an exotic species that has been introduced via pine plantations. It has also been introduced to Australia, where it is known from a single collection made in a plantation of Caribbean pine in Queensland, and has been found growing with Caribbean pine in Belize.

It is found in Hawaii under Slash Pine, including lawns where those trees are used in landscaping. ''S. salmonicolor'' is one of several ectomycorrhizal species that have "traveled the thousands of kilometers from a mainland to Hawaii in the roots and soil of introduced seedlings."