Summary:
Subgenus Plinthogalus. The Lactarius fallax group with at least 2 difficult-to-distinguish species is a subgroup of the larger Lactarius lignyotus group. The latter group consists of several Lactarius species with a brown to nearly black, velvety cap. Other features of the Lactarius fallax group are the presence of a small umbo when young, white milk that stains wounded tissue dull reddish, gills that are crowded, narrow, and whitish, a dry stem colored like the cap or somewhat paler, a mild to slightly peppery taste, and growth on the ground or on rotten conifer wood. Different collections may have dark marginate gills or not, and in collections without visible marginate gills, pigmentation may still be seen with the microscope. The description is derived from Hesler(4) is for var. fallax, var. concolor being similar except that it lacks the marginate gills - the separation into two varieties is questionable: other species in the Lactarius lignyotus group have a variable marginate character in the gills. Stubbe(1) sequenced a limited sampling of collections of the Lactarius lignyotus group. The western North American collections grouped as Lactarius fallax sensu lato, with at least two species, Eurasian Lactarius lignyotus collections were close to each other, and eastern North American collections, known as Lactarius lignyotus, need a new name because Lactarius fallax is closer to Eurasian Lactarius lignyotus than eastern Lactarius aff. lignyotus are.

Cap:
2.5-7(9)cm across, convex to flat (often with an umbo) when young, often shallowly depressed when old; "evenly dark brown to nearly black, not zoned"; "dry and more or less velvety, often wrinkled toward the center", margin often scalloped, (Arora), (2.5)3-9(10)cm across, at first convex to flat with small papillate umbo, expanding to nearly flat when old or becoming shallowly depressed with or without umbo; dark sooty brown to blackish; dry, velvety, often rugulose [finely wrinkled] over disc, margin even to scalloped or crenate, (Hesler)

Flesh:
rather thin, brittle, whitish, staining dull reddish, (Arora), thin, brittle; whitish, staining pale vinaceous from milk, (Hesler), MILK white, usually copious, [not stated whether unchanging or turning dull reddish] but slowly staining wounded tissue dull reddish, (Arora), rather copious, milk-like, white, slowly staining the flesh and gills pale vinaceous, (Hesler), white, unchanging, staining the flesh light orange on exposure and gills light orange when cut, (Methven for var. fallax and var. concolor)

Gills:
adnate to slightly decurrent, crowded, narrow; white to creamy-buff; [edges dark in var. fallax and colored as faces in var. concolor], (Arora), adnate to short-decurrent, crowded, [described as close to crowded in var. concolor], narrow, none forking near stem, subgills in several or more tiers; white at first, creamy-buff when old, gradually staining vinaceous when injured (often in several hours if fruiting bodies old), edges brown like cap overall or in parts (but var. concolor has non-marginate edges), edges even, (Hesler)

Stem:
2.5-7cm x 0.5-1.5cm, "rather slender, more or less equal"; "colored like cap or somewhat paler; dry and unpolished or velvety", (Arora), 2.5-6cm x 0.8-1.5cm, equal or nearly so, solid; usually a paler brown than cap; "dry and unpolished to velvety", (Hesler)

Veil:
[none]

Odor:
not distinctive (Hesler)

Taste:
mild or slightly peppery (Arora), mild to faintly peppery (Hesler), not distinctive (Methven for var. fallax and var. concolor)

Microscopic spores:
spores 9-12 x 8-11 microns, more or less round, with amyloid warts and ridges, (Arora), spores 9-12 x 8.5-11.5 microns, 7.5-10 microns excluding ornamentation, round, ornamentation a broken to partial reticulum, prominences 0.8-2.0 microns high; basidia 4-spored, 38-60(75) x 10-14 microns, clavate, colorless in KOH; pleurocystidia: macrocystidia none, pleurocystidia scattered to rare, 2.5-5 microns wide, filamentose to fusoid-ventricose, cheilocystidia abundant, (13)32-50 x 3-7 microns, with dingy yellowish content to colorless in KOH, subfusoid, subcylindric, or flexuous [wavy], some pseudocystidia also present on edge; cap cuticle a trichoderm, the elements having the lower cells +/- inflated, but not forming a cellular layer, the pileocystidia forming a dense turf, "content homogeneous and brown in KOH", the cells 30-60(70) x 4-9 microns, (Hesler for var. fallax), spores 9-11(12) x (8.5)9-11 microns, excluding ornamentation 7.5-9 microns, round to nearly round, broken to partial reticulum, the elements variable in height (0.8-2 microns); basidia 4-spored, (42)55-75 x 10-14 microns; pleurocystidia: macrocystidia not observed, pseudocystidia scattered, refractive, filamentous, cheilocystidia 18-37 x 4-6 microns, colorless, subcylindric to subfusoid, blunt; cap cuticle "a modified trichoderm, the lower cells in the elements somewhat inflated", pileocystidia forming a dry turf, the cells 15-45 x 5-11 microns, "blunt, subfusoid to subcylindric, with brown homogeneous content in KOH", (Hesler for var. concolor)

Spore deposit:
yellowish (Arora, Hesler)

Notes:
Lactarius fallax is found at least WA, OR, ID, AK, and CA, (both varieties recorded in each case). There are collections for BC at the University of British Columbia and the Pacific Forestry Centre (both varieties). The collections sequenced by Stubbe(1) were from WA, ID, and CA.

EDIBILITY

unknown (Arora)