CAP 2–6cm across, obtusely conic when young, becoming broadly bell-shaped, with a broad to pointed umbo. Margin inrolled when young, becom- ing down-curved to even, or wavy in age. Surface smooth, glutinous to viscid, hygrophanous. Yellowish brown when young, typically darker on disc, becoming orange-brown, dark reddish brown or blackish brown. GILLS narrowly attached, crowded, narrow. Pale yellowish to pale pinkish white at first, developing cinnamon color, becoming dingy yellow-brown in age. STIPE 4–7 (10) cm long above ground, up to 25 cm overall, 0.4-1.2 cm thick at apex, equal, pseudorhiza tapering down- wards to a fused point. Surface smooth, dry to lubricous. Pale pinkish tan to orange buff at apex, cinnamon to orang lower, becoming dark orange-brown from base up in age. Pseudorhiza salmon-colored. FLESH thin, cartilaginous, buff. Stipe hollow, cartilaginous rind concolorous with exterior. ODOR indistinct, slightly floral, or slightly farinaceous in age. TASTE indistinct to slightly bitter when young. SPORE DEPOSIT yellowish brown. MICROSCOPY: Spores 7.2–9.5 × 4.5–5.6 μm, averaging 8.5 × 5 μm, ovate in face view, lemon-shaped with eccentric, short apiculus and central 1 μm long beak in side view, roughened-warty, pale rusty brown in KOH, non-dextrinoid in Melzer’s reagent. Basidia 26–34 x 5–6.5 μm, 4-spored. Cheilocystidia lageniform to capitulate-tibiiform, base ~20 μm long, ~5 μm wide, necks ~3 μm wide, thick-walled. Pleurocystidia absent. Cap cuticle a two-layered ixocutis; upper layer 100–300 μm thick, radially aligned, uplifted, narrow hyaline hyphae, 1–3 μm wide; embedded in a gelatinous matrix. Lower layer with wider (4–15 μm) thick-walled, gelatinized hyphae with brownish to brownish orange walls in KOH. Clamp connections absent.
ECOLOGY: Ectomycorrhizal with conifers and possibly Tanoak. California sites have Douglas-fir (Pseudotsuga menziesii), Grand Fir, (Abies grandis), Western Hemlock (Tsuga heterophylla), and Tanoak (Notholithocarpus densiflorus). This species may be restricted to mature and old-growth forests. Fruiting in small to large clusters in soil, typically in areas with thick duff. Fruiting in fall.
SIMILAR SPECIES: Phaeocollybia gregaria has a golden-tan to brown, conical to bell-shaped cap, smoky white to pale cinnamon gills, a tall, slender rooting stipe with an ivory to tan apex and orange base. Microscopically, it has variably clavate, thin-walled cheilocystidia, and large spores (9.6 × 5.7 μm). Phaeocollybia spadicea has a darker brown to gray-brown cap that develops vinaceous tones in age; it also has darker gills, slightly smaller spores (8 × 5 μm), and tibiiform to lageniform cheilocystidia with narrow, thick-walled necks.