Russulaceae

Russulaceae is a family of fungi in the order Russulales. Its species have typically friable, chalk-like stalks, that break with a distinct crack, like a carrot but with porous flesh (see below). Microscopically, the cells are not all long thin hyphae, which would provide strength and more fibrous appearance when broken. Instead the flesh contains also many large spherical cells ('sphaerocysts'), which give rise to the macroscopic consistency.

Genera
There are only two genera:


 * The genus Russula, sometimes known as Brittlegills, comprises around 160 species, the majority of which are quite difficult to identify. They have splitting gills and do not exude a milky substance at cut surfaces, contrarily to the genus Lactarius. There are several edible species (Russula vesca, Russula virescens or Russula aurata).


 * The genus Lactarius, or Milk-caps, characterized by caps and stalks that exude a milky substance ("latex") when pressed or cut and lactiferous, gloeoplerous hyphae, is a large genus of mycorrhizal fungi. When cut, the mushroom exudes a kind of milky liquid. This liquid is may be orange, red, lilac, white or yellow, and may develop its final colour only after exposure to air. Certain ones, such as L. deliciosus are edible and delicious, very much appreciated in Mediterranean areas.

Distinctive flesh consistency
An important characteristic to distinguish the Russulaceae from other types of mushrooms is the consistency of the stipe. In Russula and Lactarius, this breaks like the flesh of an apple, whilst in most other families it only breaks into fibres. The pictures compare the broken stipe of a Lactarius vellereus, with that of Suillus variegatus, a member of the Boletaceae.

Parasites
Members of both Lactarius and Russula are subject to parasitization by the Lobster mushroom (Hypomyces lactifluorum). This ascomycete replaces the flesh of the host mushroom, rendering it into a choice edible, though it can be peppery if the host is a species like Lactarius piperatus. 