Stem: equal or flexuous, usually with several joined at base, similarly coloured to the cap, fibrillose streaky or with some fibrils from the veil stretching from the cap to the stem in young specimens.
Gills: sinuate and crowded, at first sulphur-yellow then olive-green, but finally with a flush of purple-brown.
Flesh: with rather strong and unpleasant smell, yellow throughout.
Spore-print: purple-brown.
Spores: medium-sized, ellipsoid or ovoid, smooth, purple-brown and less than 10 µm in length (6-8 × 4 µm).
Marginal cystidia: flasked-shaped, short, cylindric and hyaline.
Facial cystidia: more swollen than marginal cystidia and with silvery contents which yellow in solutions containing ammonia.
Habitat & Distribution: The sulphur-tuft grows in dense clusters on and around old stumps of broad-leaved trees, and can be found throughout the year; it also grows on conifers, but less frequently.
General Information: It may be recognised by the greenish tint of the immature gills and of the young cap. H. capnoides (Fries) Kummer grows on the wood of coniferous trees and has a much more ochraceous brown cap and stem than the sulphur-tuft and slightly larger spores—7-8 × 4-5 µm. H. sublateritium (Fries) Quélet grows on hardwoods but is bigger than H. fasciculare and has a brick-coloured cap and very sturdy stem (spores 6-7 × 3-4 µm).
Illustrations: F 37b; Hvass 176; LH 147; NB 1415; WD 762.