of four distinct lineages of gilled mushrooms, which led to the description of Multifurca as a new genus separated from Russula and the segregation of Lactifluus from Lactarius. Genera with closed fruitbodies within the family are form taxa instead of natural groups: Arcangeliella, Gastrolactarius, and Zelleromyces are phylogenetically part of Lactarius, while Cystangium, Elasmomyces, Gymnomyces, Macowanites, and Martellia belong to Russula. Nevertheless, some of these genus names are still in use, as many of the concerned species have not yet formally been synonymised with Lactarius or Russula. The crust-like genera Boidinia, Gloeopeniophorella, and Pseudoxenasma, formerly placed in the Corticiaceae or Gloeocystidiellaceae, are now classified in the Russulaceae and basal to the clade of mushroom-forming species described above. Studies have so far failed to clearly circumscribe and place these genera within the family. Boidinia in its current extent is polyphyletic, with some species not falling into the Russulaceae. Species diversity Altogether, the Russulaceae comprise around 1,900 accepted species. Russula is by far the largest genus with c. 1100 species, Lactarius has c. 550, Lactifluus c. 120, Boidinia 13, Multifurca 6, Gloeopeniophorella 6, and Pseudoxenasma 1 species. Closed-fruitbody species not yet synonymised with Lactarius or Russula (see above) account for some 150 species. New species in the Russulaceae continue to be described from various regions, such as the US, Guyana, Brazil, Patagonia, Togo, Sri Lanka, or Thailand. It has been estimated that the real number of Russula species in North America alone (currently around 400 described) might be as high as 2000. Cryptic species may increase true diversity: some morphologically well-defined species, especially in Lactifluus, have been shown to actually encompass several phylogenetic species. Description Macroscopic characteristics Three major types of fruitbodies occur in the Russulaceae: agaricoid and pleurotoid forms with a cap, gills, and a stipe; forms with closed (gasteroid) or partially closed (secotioid) fruitbodies, and corticioid, crust-like forms. The agaricoid species in Lactarius, Lactifluus, Multifurca, and Russula are readily distinguished from other gilled mushrooms by the consistency of their flesh, which is granular, brittle and breaks easily, somewhat like a piece of chalk. Russulaceae never have a volva, but a partial veil can be found in some tropical species. Gills are adnate to decurrent, and the colour of the spore print ranges from white to ochre or orange (with the brown-spored Lactarius chromospermus as an exception). Caps can be dull to very colourful, the latter especially in Russula; their size