Woolly Milkcap

Appearance

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 . The cap margin is strongly curled inward; when young, it is tomentose , 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 ; 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.

The gills are subdecurrent , close to crowded together, narrow, and sometimes forked near the stem. Their color is whitish, becoming pink-tinged, turning pale tan with age. The adult stem is 1.5–8 cm long, 0.6–2 cm thick, fragile, more or less equal in width throughout, and cylindrical or narrowed at the base. Its surface is dry, and either smooth to pruinose . The color ranges from pale light pink to yellowish-tinged or slightly pinkish orange to orange white, sometimes spotted. The interior of the stem is firm, beige white, and filled with a soft pith, but it eventually becomes hollow. Occasionally, white mycelium is visible at the base of the stem where it meets the ground.

The fruit body formation of ''L. torminosus'' is pileostipitocarpic. In this type of development, the hymenium forms early on the underside of the cap and upper stem of the mushroom primordium. As the cap enlarges, the margin, made of flaring filamentous hyphae that grow outward and downward, tends to curve inward, eventually forming a flap of tissue roughly parallel to the stem surface. As further development takes place, these hyphae make contact with and adhere to the hymenial surface of the stem, covering basidia and macrocystidia already present. The junction between the two tissues produces a cavity that provides some temporary protection to the basidia, although they are already fertile when the cap margin starts to grow.The spore print of ''L. torminosus'' is cream to pale yellow, and the spores 8–10.2 by 5.8–6.6 μm, roughly spherical to broadly elliptical in side view, and hyaline . Only the ornamentation on their surface is amyloid; it is partially reticulate with interrupted ridges roughly 0.5–0.7 μm high, and a few isolated warts. Spores have a conspicuous apiculus, demarcating where it was once attached to the basidia via the sterigma. The basidia are four-spored, hyaline and club-shaped to cylindrical, measuring 30–47.7 by 7.3–8.2 μm.

Pleurocystidia are only present in the form of macrocystidia embedded and originating in the hymenium and just below it, they reach 40.3–80.0 by 5.1–9.5 μm. Macrocystidia are abundant in the hymenium. Characterized by their spindle-shaped to ventricose form that gradually tapers in width, they have granular hyaline contents. Gill edge cystidia are smaller: 30–52 by 4.5–8.0 μm. The cap cuticle is made of gelatinized, interwoven hyphae arranged more or less parallel to the cap surface ; the thin-walled, threadlike hyphae of this layer are 2.5–7.3 μm wide.

Naming

The woolly cap margin, pinkish tones in the cap, acrid latex, and association with birch are reliable field characteristics to help identify ''L. torminosus''. However, there are several hairy ''Lactarius'' species with which it is often confused, and sometimes examination of microscopic characteristics is necessary to distinguish between them. The closely related ''L. torminosulus'' is a dwarf version of ''L. torminosus'', an arctic species associated with the birches ''Betula nana'' or ''B. glandulosa''. Immature fruit bodies of ''L. scrobiculatus'' resemble ''L. torminosus'', but they have a white latex that soon turns yellow upon exposure to air, and their stems have shiny depressed spots. The caps of the poorly known species ''L. cilicioides'' are not zonate, and its spores are smaller. ''L. pubescens'' is physically quite similar, but can be distinguished by its paler color and smaller spores . ''L. controversus'' has a cap margin that is not as hairy, whitish to cream-colored gills, and larger spores measuring 7.5–10 by 6–7.5 μm. ''L. mairei'' has a coloration similar to ''L. torminosus'', but is rarer and typically found associated with oak trees on calcareous soil. Known only from North Carolina and western Canada, ''L. subtorminosus'' was named for its similarity to ''L. torminosus''. It can be distinguished by its mild-tasting latex and smaller, roughly spherical spores measuring 5.5–7 by 5.5–6.5 μm.

Distribution

''Lactarius torminosus'' is a mycorrhizal species, and as such plays an important role in facilitating nutrient and water uptake by trees. It grows in association with birch and hemlock in mixed forests. It is also known to grow in urban settings when birch trees are nearby. A field study in Scotland concluded that the species is more likely to be present in older than in younger birch woodlands. Fruit bodies grow on the ground, scattered or grouped together. They are a component of the diet of the red squirrel, and serve as breeding sites for some fungus-feeding flies in the Drosophilidae and Mycetophilidae families. ''Lactarius torminosus'' mushrooms may be parasitized by the mold ''Hypomyces lithuanicus'', which produces a cream-ochre to cinnamon-colored granular or velvety growth of mycelium on the surfaces of the gills and causes them to be deformed.

The species is found in northern temperate and boreal climates, penetrating sometimes into subarctic regions. It has been recorded from North Africa, northern Asia, Europe, and is common in North America, where it sometimes grows with aspen . The North American distribution extends north into the Yukon and Alaska and south to Mexico.

Habitat

''Lactarius torminosus'' is a mycorrhizal species, and as such plays an important role in facilitating nutrient and water uptake by trees. It grows in association with birch and hemlock in mixed forests. It is also known to grow in urban settings when birch trees are nearby. A field study in Scotland concluded that the species is more likely to be present in older than in younger birch woodlands. Fruit bodies grow on the ground, scattered or grouped together. They are a component of the diet of the red squirrel, and serve as breeding sites for some fungus-feeding flies in the Drosophilidae and Mycetophilidae families. ''Lactarius torminosus'' mushrooms may be parasitized by the mold ''Hypomyces lithuanicus'', which produces a cream-ochre to cinnamon-colored granular or velvety growth of mycelium on the surfaces of the gills and causes them to be deformed.

The species is found in northern temperate and boreal climates, penetrating sometimes into subarctic regions. It has been recorded from North Africa, northern Asia, Europe, and is common in North America, where it sometimes grows with aspen . The North American distribution extends north into the Yukon and Alaska and south to Mexico.

Defense

"Its taste is biting, worse than Cayenne pepper.... Unless he possessed a stomach built for the purpose, the man who touched such food as this would have a singularly bad time before him."
Jean-Henri Fabre

The intensely peppery taste of the raw mushroom can blister the tongue if sampled in excess. Some authors have reported the species as outright poisonous, or causing "mild to fatal gastroenteritis". In a 1930 publication, Hans Steidle reported that although the mushroom was not toxic to "unicellular and cold-blooded organisms" when ingested, the liquid extract and the pressed juice of the fruit bodies, when injected under the skin of a frog, resulted in disturbed breathing, paralysis, and eventually death. Symptoms that are typically experienced after consuming raw mushrooms include nausea, vomiting, and severe diarrhea that starts about one hour after ingestion. This combination can lead to dehydration, muscle spasms, and circulatory collapse. The gastroenteritis will usually resolve without treatment in a couple of days.

Despite these reports of toxicity, ''L. torminosus'' mushrooms are prepared in Finland, Russia, and other northern and eastern European countries by parboiling, soaking in brine for several days, or pickling, after which it is valued for its peppery taste. In Norway, it is roasted and added to coffee. Mushrooms are harvested for commercial sale in Finland. The nutrient composition of Finnish specimens has been analyzed and found to contain the following components : protein, 17.2%; phosphorus, 0.46%; calcium, 0.12%; magnesium, 0.088%; potassium, 2.97%; sodium 0.011%.