page_title: Russulaceae
section_title: Microscopic characteristics
hierarchical_section_title: Russulaceae / Description / Microscopic characteristics
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context_page_description: The Russulaceae are a diverse family of fungi in the order Russulales, with roughly 1,900 known species and a worldwide distribution. They comprise the brittlegills and the milk-caps, well-known mushroom-forming fungi that include some edible species. These gilled mushrooms are characterised by the brittle flesh of their fruitbodies.
  In addition to these typical agaricoid forms, the family contains species with fruitbodies that are laterally striped, closed, or crust-like. Molecular phylogenetics has demonstrated close affinities between species with very different fruitbody types and has discovered new, distinct lineages.
  An important group of root-symbiotic ectomycorrhizal fungi in forests and shrublands around the world includes Lactifluus, Multifurca, Russula, and Lactarius. The crust-forming genera Boidinia, Gloeopeniophorella, and Pseudoxenasma, all wood-decay fungi, have basal positions in the family.
context_section_description: All Russulaceae, including the corticioid species, are characterised by spherical to elliptic basidiospores with a faint to very distinct (e.g. warty, spiny, or crested) ornamentation that stains bluish-black with Melzer's reagent (an amyloid stain reaction). Basidia (spore-bearing cells) are usually club-shaped and four-spored. Russulaceae species do not have clamp connections.
  Characteristic cells with an oily content (gloeocystidia) are found in the hymenium. In Russulaceae, these show a positive colour reaction when treated with sulfoaldehydes (sulfovanillin is mostly used). They are also present in the hyphal sheath of ectomycorrhizal roots colonised by Russulaceae.
  The feature responsible for the brittle fruitbody structure in the mushroom-forming species are globular cells, called sphaerocytes or sphaerocysts, that compose the flesh (trama) alongside the usual hyphae. Sometimes, these cells are clustered, and the position and arrangement of these clusters differs among genera.
  Another particular trama cell type are lactiferous hyphae (also lactifers). These are hyphae carrying the "milk" or "latex" exuded by the milk-caps; they react positively with sulfoaldehydes, form an abundantly branched system in the trama and end as pseudocystidia in the hymenium. In general, only Lactarius, Lactifluus and Multifurca furcata possess lactifers. In Russula, similar hyphae can sometimes be observed in the trama, but these are not as abundantly branched as real lactifers and do not extend into the hymenium as pseudocystidia. This traditional distinction line between the "milk-caps" and Russula is however less evident in some tropical species presenting intermediate states.
caption: Spores of Lactarius rubidus, showing ornamentation with a blue, amyloid stain reaction that is typical for Russulaceae
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