for consumption, caution is of vital importance to avoid confusion with the dangerously poisonous Amanita phalloides (better known as the death cap), a mushroom that can be most easily identified by its volva and ring. The nutritional components of R. virescens mushrooms have been characterized. Fresh mushrooms contain about 92.5% moisture. A sample of dried mushroom (100 g dw) has 365 kcal (1527 kilojoules). Carbohydrates make up the bulk of the fruit bodies, comprising 62% of the dry weight; 11.1% of the carbohydrates are sugars, the large majority of which (10.9%) is mannitol. The total lipid, or crude fat, content makes up 1.85% of the dry matter of the mushroom. The proportion of fatty acids (expressed as a percentage of total fatty acids) are 28.78% saturated, 41.51% monounsaturated, and 29.71% polyunsaturated. The most prevalent fatty acids include: palmitic acid, 17.3% of total fatty acids; stearic acid, 7.16%; oleic acid, 40.27%; and linoleic acid, 29.18%. Several bioactive compounds are present in the mushroom. One hundred grams (dry weight) contains 49.3 micrograms (µg) of tocopherols (20.0 µg alpha, 21.3 µg beta, and 8.0 µg gamma) and 0.19 milligrams (mg) of the carotenoid pigment lycopene. There are 4.46 g of organic acids per 100 g of dry mushrooms, including oxalic acid (0.78 g), malic acid (2.71 g), citric acid (0.55 g), and fumaric acid (0.23 g). Mushrooms have 22.6 mg/100 g dw of the phenolic compound 4-hydroxybenzoic acid, and 15.8 mg/100 g dw of cinnamic acid. Habitat and distribution Russula virescens can be found fruiting on soil in both deciduous forests and mixed forests, forming ectomycorrhizal symbiotic relationships with a variety of trees, including oaks (Quercus), European beech (Fagus sylvatica), and aspen (Populus tremula). Preliminary investigations suggest that the fungus also associates with at least ten species of Dipterocarpaceae, an important tree family prevalent in the tropical lowland forests of Southeast Asia. Fruit bodies may appear singly or in groups, reappear in the same spots year after year, and are not common. In Europe, fruiting occurs mainly during the months of summer to early autumn. A Mexican study of the seasonal occurrence of several common mushroom species in subtropical forests in Xalapa showed that the fruiting period of R. virescens occurred in April, before the onset of the rainy season. The distribution of R. virescens in North America is subject to debate, where a number of similar species such as R. parvovirescens and