Russula albonigra
Description
Russula albonigra is a species of fungi in the family Russulaceae. The cap is convex to infundibuliform, whitish, sticky. The stipe is dusky, or white above, pale gray-ochreous towards the base. The gills are decurrent, crowded, thick, unequal, connected by veins, dusky whitish or yellowish. The flesh is white, turns black or sooty. The taste is somewhat bitter and unpleasant to mild. Habitat solitary to gregarious in duff under conifers; fruiting from fall through winter in mixed conifer or hardwood-conifer forests along the north coast and the Sierra foothills.
First described by the mycologist Julius Vincenz von Krombholz in 1838, its specific epithet comes from Latin albus and niger, which mean white and black.
Edible but low food quality. Used after 15 minutes of boiling, boiled, fried, and salting.
Mushroom Identification
Cap
5 - 10 cm in diameter, first convex, with a twisted edge, later spread, concave-spread, with a thick smooth edge. The surface of the cap is smooth, dry, matte, sticky in wet weather, white, brownish, dirty-white-brown, lighter whitish at the edges, black when dry. In young specimens in places of contact turns black.
Gills
The plates are narrow, thick, of various lengths, initially white, whitish, creamy, blacken in maturity, blacken in places of damage.
Stem
3 - 7 cm high, 1.5 - 2.5 cm in diameter, cylindrical, smooth, dense, initially white, black with age, black in places of contact.
Flesh
The flesh is dense, firm, brittle, white, black on the cut, odorless, and with a slightly pungent taste. Reaction with FeSO4 (iron sulphate) turns the flesh green.
Spores
7.7-9 * 5.7-6.7 microns, elliptical, elongated, finely warty.
Spore Print
White.
Look-Alikes
Russula atrata
Also forms robust white fruitbodies that soon turn black and lack a red staining phase; however, R. atrata has a thicker gelatinous pileipellis, which can be distinguished only through microscopic analyses.
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Has a viscid cap: it may redden slightly before turning smoky brown or grayish black.
Russula dissimulans, Russula densifolia, and Russula nigricans
Redden before blackening.
Synonyms
Agaricus alboniger Krombh., 1845
Russula nigricans var. albonigra (Krombh.) Cooke & Quél., 1878
Russula adusta var. albonigra (Krombh.) Massee, 189
Photo sources:
Photo 1 - Author: Jerzy Opioła (CC BY-SA 3.0)
Photo 2 - Author: Jerzy Opioła (CC BY-SA 3.0)
Photo 3 - Author: Ron Pastorino (Ronpast) (CC BY-SA 3.0)
Photo 4 - Author: Wilhelm Zimmerling PAR (CC BY-SA 4.0)