Amanita phalloides

Amanita phalloides /æməˈnaɪtə fəˈlɔɪdiːz/, commonly known as the death cap, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Widely distributed across Europe, but now sprouting in other parts of the world, A. phalloides forms ectomycorrhizas with various broadleaved trees. In some cases, the death cap has been introduced to new regions with the cultivation of non-native species of oak, chestnut, and pine. The large fruiting bodies (mushrooms) appear in summer and autumn; the caps are generally greenish in colour with a white stipe and gills. Cap colour is variable, including white forms (see Taxonomy below), and thus not a reliable identifier. These toxic mushrooms resemble several edible species (most notably Caesar's mushroom and the straw mushroom) commonly consumed by humans, increasing the risk of accidental poisoning. Amatoxins, the class of toxins found in these mushrooms, are thermostable: they resist changes due to heat, so their toxic effects are not reduced by cooking. A. phalloides is one of the most poisonous of all known toadstools. It is estimated that as little as half a mushroom contains enough toxin to kill an adult human. It has been involved in the majority of human deaths from mushroom poisoning, possibly including the deaths of Roman Emperor Claudius in AD 54 and Holy Roman Emperor Charles VI in 1740. It has been the subject of much research, and many of its biologically active agents have been isolated. The principal toxic constituent is α-amanitin, which damages the liver and kidneys, causing hepatic and renal failure that can be fatal. The death cap is named in Latin as such in the correspondence between the English physician Thomas Browne and Christopher Merrett. Also, this infamous toadstool was described by French botanist Sébastien Vaillant in 1727, who gave a succinct phrase name 'Fungus phalloides, annulatus, sordide virescens, et patulus' - a recognizable name for the fungus today. Though the scientific name phalloides means 'phallus-shaped', it is unclear whether it is named for its resemblance to a literal phallus or the stinkhorn mushrooms Phallus.In 1821, Elias Magnus Fries described it as Agaricus phalloides, but included all white amanitas within its description. Finally in 1833, Johann Heinrich Friedrich Link settled on the name Amanita phalloides, after Persoon had named it Amanita viridis 30 years earlier. Although Louis Secretan's use of the name Amanita phalloides predates Link's, it has been rejected for nomenclatural purposes because Secretan's works did not use binomial nomenclature consistently; some taxonomists have, however, disagreed with this opinion. Amanita phalloides is the type species of Amanita section Phalloideae, a group that contains all of the deadly poisonous Amanita species thus far identified. Most notable of these are the species known as destroying angels, namely Amanita virosa and Amanita bisporigera, as well as the fool's mushroom (A. verna). The term 'destroying angel' has been applied to A. phalloides at times, but 'death cap' is by far the most common vernacular name used in English. Other common names also listed include 'stinking amanita' and 'deadly amanita'. A rarely appearing, all-white form was initially described A. phalloides f. alba by Max Britzelmayr, though its status has been unclear. It is often found growing amid normally colored death caps. It has been described, in 2004, as a distinct variety and includes what was termed A. verna var. tarda. The true Amanita verna fruits in spring and turns yellow with KOH solution, whereas A. phalloides never does. The death cap has a large and imposing epigeous (aboveground) fruiting body (basidiocarp), usually with a pileus (cap) from 5 to 15 cm (2 to 6 in) across, initially rounded and hemispherical, but flattening with age. The color of the cap can be pale-, yellowish-, or olive-green, often paler toward the margins and often paler after rain. The cap surface is sticky when wet and easily peeled, a troublesome feature, as that is allegedly a feature of edible fungi. The remains of the partial veil are seen as a skirtlike, floppy annulus usually about 1.0 to 1.5 cm (0.39 to 0.59 in) below the cap. The crowded white lamellae (gills) are free. The stipe is white with a scattering of grayish-olive scales and is 8 to 15 cm (3 to 6 in) long and 1 to 2 centimetres (3⁄8 to 3⁄4 in) thick, with a swollen, ragged, sac-like white volva (base). As the volva, which may be hidden by leaf litter, is a distinctive and diagnostic feature, it is important to remove some debris to check for it. The smell has been described as initially faint and honey-sweet, but strengthening over time to become overpowering, sickly-sweet and objectionable. Young specimens first emerge from the ground resembling a white egg covered by a universal veil, which then breaks, leaving the volva as a remnant. The spore print is white, a common feature of Amanita. The transparent spores are globular to egg-shaped, measure 8–10 μm (0.3–0.4 mil) long, and stain blue with iodine. The gills, in contrast, stain pallid lilac or pink with concentrated sulfuric acid.