What You Should Know
Lactarius uvidus is a European and North American "milk-cap" mushroom, of which the milk turns violet when the flesh is damaged. The fungi generally identified as L. uvidus are part of a complex of closely related species and varieties that are difficult to delimit definitively.
This cluster of species is found in deciduous and coniferous woods, with a preference towards acid soils. It has a wide distribution in Europe, North Africa, and North America, being fairly common in some regions but rare in others. It appears classified as vulnerable or endangered in the Danish and Dutch Red Lists of Fungi.
Lactarius uvidus is a slimy, purple-staining European species of Lactarius, found under birch, spruce, and willows.
Defining features include:
White milk that stains the gills and flesh lilac
A green reaction to KOH on the cap surface
Mild or somewhat bitter (but not strongly acrid) taste
A drab lilac cap that becomes darker with age
Other names: Purple Milk.
Lactarius uvidus Mushroom Identification
Mycorrhizal with quaking aspen, big-toothed aspen, and birch (also sometimes reported under conifers); growing alone or gregariously; summer and fall; fairly common in eastern North America from roughly the 41st parallel northward, but also reported from the southern Appalachian Mountains.
3-10 cm; broadly convex with an inrolled margin when young; becoming shallowly depressed, with an uplifted margin; slimy or sticky when fresh; bald; purplish to pale drab lilac, darkening with age and often becoming lilac brown or merely brownish when mature; without zones of color, or with faint zonations.
Broadly attached to the stem or beginning to run down it; close; white when young, becoming pale tan; staining and bruising purplish.
3-7 cm long; 1-1.5 cm thick; equal; smooth (very rarely with potholes); slimy or sticky when very fresh and young, but soon dry; whitish; often developing yellowish stains, especially near the base.
White; firm; staining lilac when sliced.
White, becoming creamy on exposure to air; staining all surfaces lilac.
Odor and Taste
Odor not distinctive; taste mild or somewhat bitter (never strongly acrid).
Cap surface green with KOH.
Spores 7.5-11 x 6.5-8.5 µ; broadly ellipsoid; ornamentation consisting of broad ridges extending 0.5-1 µ high; usually not forming a complete reticulum. Pleuromacrocystidia to about 80 x 10 µ; subcylindric to subventricose or fusiform. Cheilomacrocystidia similar. Pileipellis an ixocutis.
Lactarius quietus also has a buff cap, but it is found only under oaks and its milk does not turn lilac as it dries.
Lactarius uvidus Taxonomy and Etymology
This milkcap mushroom was first described in 1818 by the renowned Swedish mycologist Elias Magnus Fries who gave it the binomial scientific name Agaricus uvidus. Two decades later, in 1838, Fries transferred the species to its present genus, whereupon it became Lactarius uvidus, which is its currently accepted scientific name.
Synonyms of Lactarius uvidus include Agaricus lividorubescens Batsch, Agaricus livens J.F.Gmel., Agaricus uvidus Fr., Galorrheus uvidus (Fr.) P.Kumm., and Lactarius lividorubescens (Batsch) Burl.
The generic name Lactarius means producing milk (lactating) - a reference to the milky latex that is exuded from the gills of milkcap fungi when they are cut or torn. The specific epithet uvidus means damp or humid and is a reference to the habitat preference of this species.
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