Lactarius torminosus, commonly known as the woolly milkcap or the bearded milkcap, is a large species of agaric fungus. It was first described scientifically by Jacob Christian Schäffer in 1774 as an Agaricus, and later transferred to the genus Lactarius in 1821 by Samuel Frederick Gray. L. torminosus officially became the type species of Lactarius in 2011 after molecular studies prompted the taxonomic reshuffling of species between several Russulaceae genera. The caps are convex with a central depression, and attain a diameter of up to 10 cm (4 in). A blend of pink and ochre hues, the cap sometimes has concentric zones of alternating lighter and darker shades. The edge of the cap is rolled inward, and shaggy when young. On the underside of the cap are narrow flesh-colored gills that are crowded closely together. The cylindrical stem is a pale flesh color with a delicately downy surface and brittle flesh; it is up to 8 cm (3 in) long and 0.6–2 cm (1⁄4–3⁄4 in) thick. When cut or injured, the fruit bodies ooze a bitter white latex that does not change color upon exposure to air. The variety nordmanensis, in contrast, has latex that changes from white to yellow. Similar species like L. pubescens or L. villosus differ in morphology and coloration, as well as microscopic characteristics like spore shape and size. A common and widely distributed species, L. torminosus mushrooms form on the ground singly or in groups in mixed forests of both the Old World and North America. A mycorrhizal species, it associates with various trees, most commonly birch. The species is highly irritating to the digestive system when eaten raw. The toxins, also responsible for the strongly bitter or acrid taste, are destroyed by cooking. It is valued for its peppery flavor and eaten in Russia and Finland. Studies have identified several chemicals present in the mushrooms, including ergosterol and derivatives thereof, and the pungent-tasting velleral.
Taxonomy German naturalist Jacob Christian Schäffer was the first to describe the species, placing it in the genus Agaricus in 1774. Seven years later in 1781, Jean Bulliard described a species he called Agaricus necator and illustrated it in the first volume of his Herbier de la France; this name and the synonym Lactarius necator, resulting from Christian Hendrik Persoon's 1800 transfer to Lactarius, are both considered to refer to L. torminosus. Otto Kuntze, for his part chose to put it in Lactifluus, while Paul Kummer thought Galorrheus was the appropriate placement; until the recent resurrection of Lactifluus, both genera had been long considered to be unnecessary segregates of Lactarius. According to Index Fungorum, another synonym is Samuel Frederick Gray's Lactarius necans. Gray also gave the species its modern name when he transferred it to Lactarius in his 1821 Natural Arrangement of British Plants. According to Hesler and Smith's 1979 classification of the genus Lactarius, L. torminosus belongs to subgenus Piperites, section Piperites (in which it is the type species), subsection Piperites. Species in this subsection are characterized by having latex that does not turn yellow after exposure to air, and/or that does not stain the cut surface of the mushroom surface yellow. A 2004 phylogenetic analysis of European Lactarius species concluded that L. torminosus falls into a group that includes L. torminosulus, and that these two species are closely related to a group that includes L. tesquorum, L. scoticus, and L. pubescens. A multi-gene molecular analysis published in 2008 demonstrated that species then distributed in the genera Lactarius and Russula actually consisted of four distinct lineages. The subsequent reorganization of Russulaceae species—a taxonomic change needed to make Russula and Lactarius monophyletic—required that a new type species be defined for Lactarius, since the previous type, L. piperatus, belonged to the clade that will be transferred to genus Lactifluus. A proposal to conserve Lactarius with L. torminosus as the type was accepted by the Nomenclatural Committee for Fungi and passed at the 2011 International Botanical Congress. The change minimizes "taxonomic disruption", allowing most of the common and well-known Lactarius species to retain their names.
Etymology The specific epithet torminosus means "tormenting" or "causing colic", in reference to the gastrointestinal distress associated with consuming the raw mushroom. Early English vernacular names were Gray's "bellyach milk-stool" (1821), and James Edward Smith's "bearded pepper agaric" (1824). More recent common names include "shaggy milkcap", "powderpuff milkcap", "pink-fringed milkcap", "bearded milkcap", and the British Mycological Society-recommended "woolly milkcap".
Description
The cap is initially convex, but as it matures the center forms a depression and the outer edges rise until it assumes the shape of a shallow funnel; its final width is typically between 2 and 12 cm (3⁄4 and 4+3⁄4 in). The cap margin is strongly curled inward; when young, it is tomentose (covered with a thick matting of hairs), forming a veil-like structure that partly covers up the gills. This tomentum diminishes with age. The cap surface is at first similarly tomentose, but eventually, the hairs wear off, leaving the surface more or less smooth. The surface starts off somewhat sticky with clear concentric rings of darker shade (a zonate pattern); these rings, especially the outer ones, usually fade in maturity. The cap color is pinkish-orange to pale dull pink, becoming orange to whitish toward the margin as the pink gradually fades. The white to flesh-colored flesh is firm and brittle, but becomes flaccid in age. The latex that is produced when the mushroom tissue is cut or injured is white to cream, and does not change color with prolonged exposure to air, nor does it stain the gills. It has an acrid taste, with a slight to pungent odor.
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