Summary:
Clade Heterophyllidia I. Russula aeruginea is characterized by a smooth green cap, pallid or brownish-spotted gills, a whitish stem that may stain pale brown at the base, and a pale yellow spore deposit (Arora).

Cap:
3-10cm across, center often depressed; "one color olive to grass green, more rarely olive brown or yellow green"; "viscid, drying shining smooth, margin striate", cap skin peeling, (Woo), 5-8.5cm across, when young cushion-shaped with depressed disc, later convex or flat with depressed disc, somewhat funnel-shaped when old; when young grayish olive green to olive gray, when mature these colors to grayish yellow green or moderate yellow green centrally and lighter marginally, sometimes suffused or spotted with pale orange yellow to light yellowish pink; slightly viscid or dry, glaucous or minutely velvety centrally, or bald overall, sometimes areolate-cracking in places, separable 1/3-1/2 radius, striate or tuberculate-striate 0.1-0.5cm from edge inward, (Shaffer), 3-9cm across, convex becoming flat or slightly depressed; dull green to dark green, sometimes with brown, gray, or yellowish tints or blotches; viscid when moist, margin often striate, (Arora), cap skin detachable 2/3 of the way to center (Lincoff(1))

Flesh:
firm; white, (Woo), 0.5-0.7cm thick in disc, firm-brittle at first, becoming soft brittle; sometimes tinged cap color close to surface, otherwise white, unchanging when cut, (Shaffer), brittle, white, (Arora), tends (at least in Europe) to turn gray on exposure to air, (Lincoff(1))

Gills:
crowded, forking at stem; white, yellowing when old, (Woo), adnexed, adnate, or subdecurrent, close, 0.5-0.8cm broad, equal, or unequal with subgills rare and usually approaching stem closely, rounded near margin, often forked at or near stem; "yellowish white, at times spotted-stained moderate yellowish brown"; interveined, entire, (Shaffer), adnate to adnexed or free, close, brittle; "white becoming pale yellowish, often with brownish stains", also referred to as "pallid or brownish-spotted", (Arora)

Stem:
white, sometimes with reddish spots at base, (Woo), 4-6cm x 0.8-1.9cm, equal or widening or narrowing downwards, stuffed becoming hollow; yellowish white, spotted-stained moderate yellow, moderate yellowish brown, or dark olive brown basally, but becoming only slightly dingy when bruised; dry, dull, felted-puberulent at top, otherwise bald, longitudinally rugulose, (Shaffer), 4-8cm x 1-2cm, equal or with tapered base; white or faintly yellow, base often with pale brown stains, (Arora)

Odor:
nondescript (Shaffer), pleasant (Lincoff(1))

Taste:
mild or slightly peppery when young (Woo), nondescript (Shaffer), mild or slightly hot (Rayner), mild (Arora), slightly peppery then sweet (Lincoff(1))

Microscopic spores:
spores 6-10 x 5.5-6.5 microns, ornamentation Patterson-Woo type B-2, (Woo), spores 6.2-8.3 x 5.1-6.8 microns, broadly elliptic, broadly ovate, broadly obovate, or nearly round, short-cylindric to bluntly conic warts and less common short ridges, all up to 0.3-0.8 microns high, the warts and ridges mostly isolated, but sometimes catenulate or with connectives, in some specimens forming a partial reticulum; basidia 4-spored, 31-57 x 6.8-10.7 microns; hymenial pseudocystidia abundant, usually arising in subhymenium, rarely in trama, projecting up to 45 microns beyond the basidioles, 41-102 x 7.9-12.9 microns, "subcylindric to clavate and then broadly rounded or appendiculate apically, or fusoid-clavate to fusiform or fusoid-ventricose with the neck sometimes capitellate or moniliform", (Shaffer), spores 6-10 x 5.5-6.5, many 8 x 5.5 microns, elliptic, some more or less pear-shaped, warts 0.1 microns or less high, with a few fine lines forming an incomplete reticulum, pleurocystidia 62-78 x 8-10 microns, "ventricose, apices capitate or rounded, banded", cheilocystidia 30-50 x 5-10 microns, "ventricose or narrowly clavate, rounded or mucronate, banded or empty", (Hesler for Sweden specimens), spores 6-9 x 5-7 microns, nearly round, amyloid warts and ridges, (Arora)

Spore deposit:
deep cream, Crawshay D-E, (Woo), pale orange yellow (Shaffer), "creamy to pale yellow or pale orange-yellow" (Arora)

Notes:
One collection was reported by Grund from WA. Thiers gives it for CA. Gamiet(2) reported it from BC. C. Roberts (pers. comm.) says it occurs on Vancouver Island. Cripps reported it from ID and MT. Shaffer examined collections from MI. 13 Ben Woo collections from the Pacific Northwest had sequences close to R. aeruginea (D. Miller, pers. comm.).

EDIBILITY

yes (Arora), slightly poisonous when raw (Lincoff(1))