Summary:
Clade Ingratula II. Russula crassotunicata is characterized by 1) small to medium size, 2) a white to cream cap with a thick separable cap skin, 3) gills that tend to stain brown, 4) a white stem that develops brown spots and has a mealy surface, 5) a bitter peppery taste; and 6) a white spore deposit.

Cap:
4-8cm across, white or cream; with a thick, translucent, rubbery cuticle (cap skin) that may crack in dry weather, peels over half, margin even, (Woo), 4-8cm across, "convex, soon narrowly depressed in center, eventually somewhat flattened and expanding"; white; dry, or viscid and drying very rapidly, with thick and almost leathery cuticle [cap skin], with finely innately fibrillose brown punctation, scurfy, but at first perfectly smooth, eventually finely areolate [cracked like dried mud], margin smooth, peeling thickly over one half of radius, (Singer), 3-8cm across, when young deeply pulvinate [cushion-shaped] with the margin curved in, then convex with depressed disc, irregularly somewhat funnel-shaped when old; white, yellowish white, pale orange yellow, or pale yellow, becoming stained moderate yellowish brown to light olive brown; viscid when moist but soon dry, felted, eventually cracking in various patterns, not striate or only obscurely striate 0.1-0.2cm from edge inward, cap skin rubbery and thick, almost completely separable, (Shaffer), 3-8cm across, "deep convex then expanded with depressed disc; white to yellowish white or pale buff, staining yellowish brown; viscid when moist, usually dry and felty", cap skin thick and rubbery, almost totally separable, (Phillips)

Flesh:
firm, elastic; white, staining brownish, (Woo), rather firm; white, with an inclination to stain brownish, (Singer), moderately thick ( 0.4-0.8cm thick at disc), firm-brittle (hard and tough when dried); "white or yellowish white, slowly staining moderate yellowish brown, light olive brown, or dark grayish yellowish brown when cut", (Shaffer), "firm; white, staining when cut", (Phillips)

Gills:
white, bruising brown, (Woo), subdistant, medium broad, narrowed toward both ends, subintermixed to almost alternating; white more or less stained brownish by bruising, (Singer), adnexed to adnate, subdistant to distant, equal or unequal with subgills rare to common, subacute [somewhat acute] near margin, interveined, occasionally forking near stem; pale orange yellow when young, becoming pale yellow, slowly staining like the cap flesh when injured; edges entire, (Shaffer), "adnate, quite distant, narrow; pale yellow, staining yellow-brown when injured", (Phillips)

Stem:
white, spotting brown; with a fine mealy surface texture, (Woo), 3-3.3cm x 0.9-1.15cm, rather short, more or less equal, but sometimes widening or narrowing downward, hollow, rather firm; white, becoming brown spotted; "finely but distinctly roughened subfurfuraceous in a horizontally banded pattern, or anyhow not longitudinally rugulose as in the majority of the Russulas", never quite smooth, (Singer), 3.5-5cm x 0.9-2cm, equal, or widening to the base, solid then stuffed, firm-brittle; white or yellowish white, staining like the cap flesh when injured; dry, dull, puberulent [downy] to furfuraceous overall when young, sometimes becoming bald basally, longitudinally rugulose [wrinkled], (Shaffer), 3.5-5cm x 0.9-2cm, "equal, solid then spongy; white, staining yellow-brown, dry, dull, almost velvety", (Phillips)

Odor:
faintly fungoid (Woo), of trimethylamine (Singer), Lycoperdon puffball-like or coconut-like, (Shaffer, Phillips)

Taste:
bitter and peppery (Woo), bitterish and slightly burning after a while in the throat, never quite mild when fresh, (Singer), slight peppery-bitter or nondescript, gills peppery, (Shaffer), peppery to burning, (Phillips), peppery, often bitter, unpleasant, (Thiers)

Microscopic spores:
spores 9-10 x 7.5-8 microns, ornamentation Patterson-Woo type A-2, B-2, (Woo), spores 8.5-11.5 x 7.0-9.3 microns, usually broadly elliptic to broadly obovate, occasionally elliptic or nearly round, mostly isolated, cylindric to bluntly conic or clavate warts up to 0.6-1.2 microns high "and sometimes also a few connectives, which may be attached to only one wart", "never forming even a partial reticulum"; basidia 4-spored, 37-62 x 7.9-14.7 microns, clavate; hymenial pseudocystidia abundant, 49-102 x 5.7-12.4 microns, subcylindric, fusiform, or clavate, often capitellate or appendiculate, otherwise rounded to acute apically, SV+, usually projecting up to 45 microns beyond basidioles, (Shaffer), spores 8.5-11.5 x 7-9 microns, warts up to 1.2 microns high, isolated, (Phillips), cap cuticle up to 500 microns thick; "epicutis very tough, gelatinous, elastic, differentiated as a layer of interwoven hyphae when young", tangled to loosely interwoven when old, "with scattered free hyphal tips and well differentiated pileocystidia, some hyphal tips SV+", (Thiers)

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

Notes:
Shaffer and Singer both examined collections from WA and MI. Russula crassotunicata is included for CA in Thiers(3). It occurs on Vancouver Island in BC (C. Roberts, pers. comm.) and there are collections from BC at the University of British Columbia. The University of Washington has collections from WA, OR, and AK.

EDIBILITY

not recommended (Phillips)