golden milkcap

The cap is 6–20 cm (2+1⁄2–8 in) wide, initially convex but becoming depressed to funnel-shaped in maturity. The cap margin is initially rolled inward, then becomes uplifted as the cap expands. The cap surface is sticky to slimy, and near the margin there are matted "hairs" beneath the slimy or sticky layer. The color of the cap surface is yellow-ochre, sometimes with concentric bands of lighter and darker shades; the color becomes paler near the margin. The gills are adnate (squarely attached to the stem) to decurrent (attached to and running down the length of the stem), narrow, and crowded closely together. Forked near the stem, the gills are initially whitish before becoming pale ochraceous-buff. There are many lamellulae—small gills that do not extend completely to the stem. The stem is 3–6 cm (1+1⁄4–2+1⁄4 in) long and 2–3 cm (3⁄4–1+1⁄4 in) thick, nearly equal in width throughout or tapered downward, dry, hard, coarsely pitted, and whitish to cream yellowish. It is initially solid, then becomes hollow with age. The flesh is thick, hard, whitish, and slowly stains pale yellow after the mushroom has been cut open. It has no distinctive odor, while the taste is immediately acrid. The latex is sparse, white on exposure to air, and unchanging or very slowly changing color to yellow. It stains cut flesh yellow, and tastes acrid. …

Lactarius alnicola is an ectomycorrhizal species, and engages in a mutualistic association with certain plant species. In this association, the hyphae of the fungus permeate large volumes of soil and obtain scarce elements, especially phosphorus—which is often limiting for plant growth—which they pass on to the plant in exchange for metabolic products of the plant's photosynthesis. The ectomycorrhizae that the fungus forms in association with Picea engelmannii have been shown to contain lactifers (latex-producing cells) and pigments similar to the fruit body. Fruit bodies of the fungus grow in groups on the ground under alders and conifers, usually appearing between July and October. It is a fairly common species in the western United States and Baja California. Additional collection locations in Mexico include Veracruz, Villarreal, and Tapia. A population in central and southern California is known to associate with oak trees. In the Rocky Mountains it is associated with the subalpine tree species Engelmann Spruce (Picea engelmannii), while at lower elevations it is commonly found with white spruce (Picea glauca). It is also known to associate with Ponderosa Pine (Pinus ponderosa) and Douglas-fir (genus Pseudotsuga). The mushroom has also been collected from Bageshwar, in the state of Uttarakhand, India.