Russula albonigra is a member of the Russula

Russula

Around 750 worldwide species of mycorrhizal mushrooms compose the genus Russula. They are typically common, fairly large, and brightly colored - making them one of the most recognizable genera among mycologists and mushroom collectors...

genus, all of which are collectively known as brittlegills.

Taxonomy

First described by the mycologist Julius Vincenz von Krombholz

Julius Vincenz von Krombholz

Julius Vincenz von Krombholz was a physician and mycologist born in Oberpolitz , northern Bohemia....

 in 1838, its specific epithet comes from Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 albus and niger, which mean white and black.

Description

The cap

Pileus (mycology)

The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...

 is convex to infundibuliform, whitish, sticky. The stipe

Stipe (mycology)

thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...

 is dusky, or white above, pale grey-ochreous towards the base. The gills are decurrent

Decurrent

Decurrent is a term used in botany and mycology to describe plant or fungal parts that extend downward.In botany, the term is most often applied to leaf blades that partly wrap or have wings around the stem or petiole and extend down along the stem...

, crowded, thick, unequal, connected by veins, dusky whitish or yellowish.The flesh

Trama (mycology)

In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....

is white, turns black or sooty. The taste is somewhat bitter and unpleasant to mild.