Russula virescens is a basidiomycete mushroom of the genus Russula, and is commonly known as the green-cracking russula, the quilted green russula, or the green brittlegill. It can be recognized by its distinctive pale green cap that measures up to in diameter, the surface of which is covered with darker green angular patches. It has crowded white gills, and a firm, white stipe that is up to tall and thick. Considered to be one of the best edible mushrooms of the genus Russula, it is especially popular in Spain and China. With a taste that is described variously as mild, nutty, fruity, or sweet, it is cooked by grilling, frying, sautéeing, or eaten raw. Mushrooms are rich in carbohydrates and proteins, with a low fat content. The species was described as new to science in 1774 by Jacob Christian Schaeffer. Its distribution encompasses Asia, North Africa, Europe, and Central America. Its presence in North America has not been clarified, due to confusion with the similar species Russula parvovirescens and R. crustosa. R. virescens fruits singly or scattered on the ground in both deciduous and mixed forests, forming mycorrhizal associations with broadleaf trees such as oak, European beech, and aspen. In Asia, it associates with several species of tropical lowland rainforest trees of the family Dipterocarpaceae. R. virescens has a ribonuclease enzyme with a biochemistry unique among edible mushrooms. It also has biologically active polysaccharides, and a laccase enzyme that can break down several dyes used in the laboratory and in the textile industry. Taxonomy Russula virescens was first described by German polymath Jacob Christian Schaeffer in 1774 as Agaricus virescens. The species was subsequently transferred to the genus Russula by Elias Fries in 1836. According to the nomenclatural authority MycoBank, Russula furcata var. aeruginosa (published by Christian Hendrik Persoon in 1796) and Agaricus caseosus (published by Karl Friedrich Wilhelm Wallroth in 1883) are synonyms of Russula virescens. The variety albidocitrina, defined by Claude Casimir Gillet in 1876, is no longer considered to have independent taxonomic significance. According to Rolf Singer's 1986 classification of Russula, R. virescens is the type species of subsection Virescentinae in section Rigidae, a grouping of mushrooms characterized by a cap surface that breaks into patches of bran-like (furfuraceous) particles. In a molecular phylogenetic analysis of European Russula, R. virescens formed a clade with R. mustelina; these two species were sister to a clade containing R. amoenicolor