Subgenus Russularia. Features include 1) a moist cap that is rusty red to dull chestnut when young, 2) unchanging milk that is milk-white in color and stains white paper yellow at least when young, 3) decurrent, close, narrow gills that are pale buff to pinkish or with a mauvy bloom, 4) a dry cap-colored stem with a velvety bloom when young, 5) slow, strong peppery taste when young (but mild when old), 6) a cream spore deposit, and 7) elliptic spores with amyloid ornamentation consisting of a broken to partial reticulum with additional warts and ridges. The American variant of L. hepaticus apparently has latex that shows less of a tendency to yellow on exposure to air, and to discolor cut surfaces yellow, than the type variant from Europe. Some Pacific Northwest species cited as Lactarius hepaticus below may be Lactarius atrobadius.
Material was cited from WA, ID, NS, CO, MA, ME, MI, NH, NM, UT, VT, WI, France, Netherlands, and Switzerland, (Hesler(4)). There are collections from BC labeled as this species at Pacific Forestry Centre and the University of British Columbia. There is a collection from OR labeled as this species at the University of Washington.
3-9cm across, "convex becoming flatter then depressed in the center, sometimes with a central papilla and a spreading or wavy margin crimped with tiny lobes; rusty red or dull chestnut, with papilla often darker; moist but not sticky, smooth, opaque," (Phillips), (3)4-9cm across, convex-depressed, margin more or less spreading when old; dark rusty red (about brick-red), when dried dark vinaceous brown to dull red and often with a darker central spot; moist when young, may be shiny and subviscid when mature, bald, opaque, not areolate or rimose and scarcely shining when old, (Hesler), the button have a particularly dark reddish color, becoming paler to dark red brown when mature (S. Gamiet, pers. comm.)
thin but brittle; pale, dingy pinkish buff, (Phillips), thin but brittle; pallid to pale sordid vinaceous buff, (Hesler), MILK "milk-white, unchanging, staining white paper yellow," (Phillips), milk-white, unchanging but when peppery readily staining white paper sulfur yellow, the stains persistent, the European version tends to turn yellow on exposure to air and stain cut surfaces yellow, but the American version shows less tendency to have these reactions, (Hesler)
"decurrent, close, narrow; pale buff to pinkish or with a mauvy bloom," (Phillips), decurrent, close, narrow; pallid becoming vinaceous pallid, slowly becoming dull vinaceous to +/- vinaceous red but whitish when dried, (Hesler)
4-9cm x 0.4-1cm, "solid; about the same color as the cap; dry, fragile, with a velvety bloom when young and hairy at the base", (Phillips), 4-9cm x (0.3)0.4-1cm, "about equal, solid, fragile"; +/- colored as cap; dry, pruinose when young, base somewhat strigose, the hairs drying whitish, (Hesler)
not distinctive (Phillips, Hesler)
spores 7.5-9 x 6-7 microns, "ornamented with large warts forming a partial reticulum", prominences 0.3-0.4 microns high, (Phillips), spores 7.5-9 x 6-7 microns, elliptic, "ornamentation a broken to partial reticulum with additional isolated warts and ridges", prominences 0.3-0.4 microns high; basidia 4-spored; pleurocystidia: macrocystidia 44-63 x 6-11 microns, "fusoid, pointed, content with refractive granules in some", pseudocystidia rare, 3-5 microns wide, filamentose, cheilocystidia about like macrocystidia but smaller (22-33 x 4-7 microns), gill trama "of interwoven hyphae, some inflated cells present, lactifers evident but not conspicuous"; cap cuticle "a short lax ixotrichoderm lacking a basal cellular layer but the hyphae irregularly arranged and many cells somewhat enlarged", elements of the ixotrichoderm 2-4 microns wide, "end cell often with a slight apical enlargement", a thin layer of slime evident in KOH and/or Melzer''s reagent; stem cuticle a cutis of cells somewhat refractive in KOH (the stem might be lubricous at times), (Hesler)
cream (Phillips), cream but thin deposit white, (Hesler)