Summary:
{See also Blackening Russulas Table.} Clade Compacta. Features include 1) large size, 2) a whitish slightly viscid cap that soon becomes gray or brown to black, the cap skin only partly separable, 3) flesh that turns red then black when cut, 4) distant (0.2-0.3cm apart), thick, pale straw or yellow young gills, 5) a whitish stem turning brown from the base and sometimes bruising red before becoming black, 6) a mild or slightly peppery taste, 7) a white spore deposit, and 8) relatively small spores with weak ornamentation. There was some question as to whether this species occurs in North America, but sequences of Pacific Northwest material match collections of Russula nigricans from the type area in Europe. The description of Russula dissimulans is similar but differentiated from Russula nigricans by Shaffer who found R. dissimulans in Washington, Oregon, Idaho, California, Michigan, North Carolina, and Vermont (see SIMILAR section of that species). Shaffer stated that Russula nigricans probably does not occur in the US, but Thiers found collections that matched the description very satisfactorily as well as frequent collections of Russula dissimulans.

Cap:
7-15(20)cm across, depressed in center; "whitish when young, soon sooty gray or dirty brown" and finally entirely black when old; "slightly viscid drying matte, often cracking into small areolae", not peeling, margin even, (Woo), 7-20cm across, convex when young, becoming flat and finally somewhat funnel-shaped; whitish when young, becoming gray or brown and finally almost black; slightly viscid when young, soon dry, matte, minutely felted, sometimes areolate-rimose when old, with cap skin partly separable and margin not striate, (Shaffer), almost inseparable, only in damp weather possible to peel about a third of it, (Pilat)

Flesh:
hard; "white, turning red when cut, then turning black", (Woo), rigid; "whitish, when cut becoming carrot red to indian red and then black", (Shaffer), "white, becoming blood red then gray to black", (Phillips), first pink and then black when cut (Pilat)

Gills:
distant, with regular subgills, thick; "pale straw or yellow, reddish when bruised", (Woo), emarginate or rounded adnate, distant, subgills intermixed, narrow to broad, up to 1.5cm, acute near margin, thick, 0.1-0.2cm thick, brittle; yellowish when young, finally colored as cap, when bruised becoming brick reddish and then dingy gray, (Shaffer), 60-90 reaching stem, 1-3(5) subgills between neighboring gills (Kranzlin)

Stem:
short, thick; "white turning brown from base, bruising red, then black", (Woo), 2-7cm x 1-4cm, equal or narrowing downward, solid, rigid; whitish, browning from base upward and finally colored as cap, when bruised seldom becoming brick reddish; bald, (Shaffer)

Odor:
earthy (Woo), none or slightly sweetish, (Shaffer), fruity, (Phillips), rank especially when aging (Schalkwijk-Barendsen), unpleasant earthy (Pilat), faintly unpleasant (Kranzlin)

Taste:
"mild or sometimes slightly peppery when young" (Woo), slightly peppery or mild, (Shaffer), slowly peppery (Phillips), usually mild, but when young may sometimes be slightly peppery or astringent, (Pilat), mild to somewhat peppery (Kranzlin)

Microscopic spores:
spores 7-8 x 6-7 microns, Patterson-Woo type D-1, (Woo), spores 6.3-7.9 x 5.3-6.8 microns, nearly round to broadly elliptic or oboval; ornamentation 0.1-0.3 microns high, of warts connected by fine lines, forming a sometimes broken, usually nearly complete to complete reticulum; basidia 4-spored, 40-49 x 7.3-9.3 microns, clavate; pleuropseudocystidia very abundant, arising in the subhymenium or outer trama, projecting not at all or only slightly, 43-61 x 4-7.3 microns, subcylindric to clavate, with apices rounded or capitate, sometimes curved or flexuous [wavy] basally, filled with refractive contents or partially empty, cheilopseudocystidia of same type as pleuropseudocystidia, (Shaffer), spores 7-8 x 6-7 microns, broadly elliptic, warts under 0.5 microns high, with partial reticulum, (Phillips), cap cuticle "115-116" microns thick, embedded in a gelatinous matrix, epicutis more or less interwoven, sometimes with free hyphal tips, pileocystidia absent, some hyphae with brown contents in KOH and with occasional nodulose enlargements, (Thiers), spores 6.4-8.5 x 5.4-6.6 microns, ornaments projecting up to 0.4 microns, "consisting of abundant, in part elongated warts and of ridges which form a nearly complete reticulum"; basidia (2)4-spored, 40-55 x 8-10 microns, clavate; pleurocystidia abundant, similar to cheilocystidia, 30-55 x 3.5-7 microns; cheilocystidia abundant, 50-65 x 3.5-7 microns, cylindric to clavate, with refractile contents; cap cuticle hairs 3-7 microns wide, +/- cylindric, "more rarely slightly tapered", some swollen up to 12 microns wide, with 1 to several septa, "most with vacuolar brown pigment"; no pileocystidia, (Kranzlin)

Spore deposit:
white, Crawshay A, (Woo), white (Shaffer)

Notes:
Russula nigricans reported by Grund for WA who calls it one of the largest and commonest mushrooms occurring in WA. Smith(6) says it is common in the Pacific Northwest though its occurrence in other areas of North America is apparently open to question. It was reported by Gamiet(1) for BC. Thiers included it for CA. There are collections at Oregon State University from OR and WA. However, Buyck collected and sequenced material in the Pacific Northwest that was a genetic match for Russula nigricans from the type area, (D. Miller, pers. comm.). Shaffer noted it for the United Kingdom (England), and France.

EDIBILITY

suspect (Phillips)