Cap: 2-5 cm; conical to convex at first, becoming broadly convex to flat; smooth; dry; bright sulfur yellow to greenish yellow when fresh, sometimes yellowish orange when young, often with a darker center; the margin sometimes with small partial veil fragments.
Gills: Attached to the stem or pulling away from it; sulfur yellow, becoming olive or greenish yellow, eventually dusted with spores and therefore spotted purplish brown to blackish (see third illustration); close or crowded.
Stem: 5-12 cm long; 3-10 mm thick; more or less equal, or tapering to base, bright yellow to tawny, developing rusty brown stains from the base upwards; bright yellow partial veil present in buttons (see the bottom illustration), soon disappearing or leaving a ring zone near the top.
Flesh: Thin, yellow.
Odor and Taste: Odor not distinctive; taste bitter.
Spore Print: Purple brown.
Spores: 6-8 × 3.5-5 µ; elliptical; smooth; with a pore. Pleurocystidia ventricose to mucronate, often with a long neck; with refractive contents; to 42 × 11 µ. Cheilocystidia fusoid-ventricose; to 32 × 10 µ.
Note: Underside of cap glows dull to bright green under UV-A LED flashlights