Bloody Brittlegill

Russula sanguinaria

"Russula sanguinaria", commonly known as the bloody brittlegill or rosey russula, is a strikingly coloured mushroom of the genus "Russula", which has the common name of brittlegills. It is bright blood-red, inedible, and grows in association with coniferous trees. It was previously widely known as "Russula sanguinea".
Red stemmed Russula A bit ratty, but rather distinctive, with it's very red stem Fall,Geotagged,Russula sanguinaria,United States

Appearance

The robust cap grows up to 10 cm in diameter. At first it is convex, but later flattens, and sometimes becomes saucer-shaped when mature. It is bright blood-red, or rose coloured at first, fading slightly with age, and often having paler areas. The cap skin peels at the margin only. The stem is firmly robust, occasionally white, but more commonly flushed with the cap colour. It is streaked vertically, and tends to turn greyish pink with age. The cream to pale ochre gills are adnate to slightly decurrent, narrow and forking. The spore print is also cream to pale ochre. The flesh is white, somewhat hot and peppery, and sometimes bitter on the tongue, with a faint fruity smell.

Naming

*"Russula helodes" is macroscopically identical, but tends to favour sphagnum moss in coniferous forests, and is much rarer.
⤷ "Russula emetica" Pers. grows in the same habitat, and has a bright red cap. It almost never has a coloured stipe, and is very crumbly and fragile.
Most of the other common bright red "Russula" species grow with deciduous trees.

Habitat

"Russula sanguinaria" appears in summer and autumn. It is widespread in the northern temperate zones, and is mycorrhizal with softwood trees, often "Pinus" in coniferous woodland, on sandy soils.

References:

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Taxonomy
KingdomFungi
DivisionBasidiomycota
ClassAgaricomycetes
OrderRussulales
FamilyRussulaceae
GenusRussula
SpeciesR. sanguinaria