Naematoloma fasciculare: Hypholoma fasciculare
Cap 2-7 cm broad, convex, expanding to nearly plane in age, sometimes with a broad low umbo; margin incurved when young, wavy if clustered, often slightly appendiculate with veil fragments; surface smooth, moist, disc yellow-orange to tawny-orange, shading to a lighter margin, overlapped caps often patchy purple-brown from shed spores; flesh pale yellow, thin; odor not distinctive; taste bitter.
Gills adnate, crowded, narrow, yellow becoming sulphur-green, in age dingy, olive-brown from maturing spores.
Stipe 2-9 cm tall, 0.4-1.5 cm thick, equal or tapering downward, hollow, often twisted, pale yellow with brown fibrils, bruising brown on handling; partial veil evanescent, usually leaving sparse fragments on the cap margin but sometimes forming a superior fibrillose annular zone.
Spores 6.5-8 x 3.5-4.5 µm, elliptical, smooth, with an apical pore; spore print purple-brown.
Gregarious to clustered on hardwood/conifer logs or stumps, sometimes in grass from buried wood; fruiting from late fall to mid-winter.
Probably poisonous. Opinion is divided on the toxicity of this species, but since it is extremely bitter, the question is purely academic.
Hypholoma fasciculare is often abundant in Bay Area woodlands forming bright yellow clusters on both hardwood and conifer wood. The sulphur-green gills, slightly appendiculate cap margin in young specimens, and bitter taste are important field characters. A close cousin, Hypholoma capnoides, is not as common in our area. It lacks the sulphur-green gills and bitter taste.