FRUIT BODY 1–3cm across, rounded, irregularly rounded, to more elongate-ellipsoid, typically shorter than wide, firm, rubbery, surface smooth, shiny. Underside with a single or basal group of rhizomorphs. PERIDIUM dark cinnamon to dark red-brown, occasionally with darker blotches, developing black- ish brown stains when handled; black and shiny when dry. GLEBA firm, rubbery, sponge-like with tiny open locules. Whitish at first, soon yellowish, to olivaceous when mature, pale brown to olive on drying. Columella absent. STIPE absent. ODOR indistinct to fruity or cheesy. TASTE unknown. MICROSCOPY: Spores 5–6.5 (7) x 1.8–2.5 μm, cylindric to narrowly oblong, smooth, thin-walled, colorless singly, yellow-brown in mass in KOH; inamyloid, yellowish singly, slightly darker in mass, and typically with a false septum in Melzer’s reagent. Basidia 8-spored. Brachybasidioles hyaline, becoming thick-walled. Cystidia absent. Trama of interwoven, hyaline gelatinous hyphae. Subhymenium cellular, thick-walled. Peridium a single layer of interwoven, hyaline, thin-walled hyphae; pigment forming large rusty brown to fuscous brown balls in Melzer’s reagent. Clamp connections absent.
ECOLOGY: Typically hypogeous, more rarely emergent from duff. Ectomycor- rhizal, probably associated with multiple members of Pinaceae. Most sites have hemlock (Tsuga spp.) present, others have pine (Pinus spp.), fir (Abies spp.), or Douglas-fir (Pseudotsuga menziesii). Fruiting in fall, more rarely spring and summer.
SIMILAR SPECIES: Many Rhizopogon collections resemble this species and are notoriously hard to identify. Field identification is not possible for most species; microscopic features need to be observed. Studies have also shown that molecular sequences may be the only way to reliably distinguish species. The Rhizopogon parksii/villosulus group can be distinguished by its whitish to grayish peridium when young, overlaid with appressed dark fibrils, becoming dark brown to black- ish brown in age, typically staining bluish green when scraped, an inky KOH reaction and growth with Douglas-fir and Sitka Spruce (Picea sitchensis).