Golden Brittlegill

Russula risigallina, long known in the literature as Russula lutea and sometimes as R. chamaeleontina, is a small, brightly coloured brittlegill of broadleaf woodland. Its most useful feature is not visible until the mushroom is set on paper: the spore deposit is a rich egg-yellow to deep ochre, among the darkest in the whole genus, and the mature gills take on the same warm colour.

The cap is a chameleon. Collections may be golden yellow, apricot, orange, salmon, rose-pink or a blend of these, and the same troop can contain fruit bodies of quite different hues. This variability generated a long list of synonyms and varietal names before spore colour was recognised as the more reliable guide.

It is a slight, thin-fleshed species compared with the heavy brittlegills of the same woods, with a fragile stipe and a cap that peels almost completely. In older specimens it develops a distinctly fruity odour, which combined with the yellow gills makes for a memorable find.

Cap

Small, 2-6 cm across, convex then flattened and finally slightly depressed. The surface is smooth and greasy when moist, matt when dry. Colour is warm and variable: golden yellow, apricot, orange, salmon-pink, rose or a mixture, often paler at the margin and deeper at the centre. The cuticle peels easily over most of the cap, and the thin margin becomes grooved with age.

Gills

Pale cream at first, then colouring strongly to a rich yellow-ochre as the spores mature — the deepest gill colour of any common small brittlegill. They are moderately spaced rather than crowded, adnexed, brittle, and sometimes forked near the stipe.

Stipe

Slender and fragile, 3-6 cm long and 0.6-1.5 cm thick, white and smooth, sometimes greying or browning faintly with age. It soon becomes stuffed and then hollow, and snaps cleanly. There is no ring or volva.

Flesh & spore print

The flesh is white, thin and unchanging when cut. Mature specimens develop a distinctly fruity odour. The spore print is a deep yellow to ochre, the key confirmatory character. Spores are broadly ellipsoid with tall isolated warts and few connecting lines.

The Golden Brittlegill is mycorrhizal with broadleaf trees, especially oak, beech, birch and hornbeam, and occasionally with lime or hazel. It grows on well-drained soils, often on chalk and limestone, and is typical of mature woodland, old coppice, woodland banks and grassy woodland rides.

Fruiting runs from July into October, generally in scattered small groups rather than large troops. The species is widespread across Europe and reported through temperate Asia; closely comparable yellow-spored small brittlegills occur in North American hardwood forest.

This is an ectomycorrhizal species. Its hyphae sheathe the fine roots of the host tree and penetrate between the outer root cells, forming an exchange surface across which soil nutrients — especially phosphorus and nitrogen bound in litter — move into the tree while photosynthetic sugars move into the fungus.

Its preference for base-rich, free-draining woodland soils places it in a community alongside other calcicole brittlegills, milkcaps and boletes. The small, thin-fleshed fruit bodies decay within a few days and are heavily used by fungus gnats and small beetles, whose movements also help disperse the deep-yellow spores through the litter layer.

The Ochre Brittlegill (Russula ochroleuca) is much larger and duller, a flat greenish-yellow to ochre, with a stouter greying stipe and a pale cream spore print rather than a deep yellow one. The Yellow Swamp Brittlegill (Russula claroflava) is a bright clean yellow but grows in wet birch bogs, is considerably larger, and its flesh greys strongly where cut.

Russula aurea, the Gilded Brittlegill, shares golden tones but is bigger, with distinctly yellow gill edges and a stipe flushed yellow, and it has a firmer build. Russula velenovskyi has a brick-red cap with a low central bump and a cream spore print. When cap colour is ambiguous, the deep yellow spore deposit is the decisive character for R. risigallina.