Lactarius repraesentaneus
Lactarius repraesentaneus, commonly known as the purple-staining bearded milkcap, the northern bearded milkcap, or the northern milkcap, is a species of fungus in the family Russulaceae.
Distinguishing features of its fruit body include the large orange-yellow cap up to wide, cream to pale yellow gills, and a yellow coarsely-pitted stem that is up to long and thick. Cut fruit bodies ooze a white latex that will stain mushroom tissue lilac to purple.
The species has a northerly distribution, being found in temperate regions of North America and Europe. It is associated with spruce trees. The mushroom is poisonous, its consumption causing stomach aches. It has antibiotic activity against Staphylococcus aureus and contains chemicals that can modify the growth of plants.
Taxonomy
Lactarius repraesentaneus was first described by German mycologist Max Britzelmayr in 1885, based on material collected from Bavaria. The variety Lactarius scrobiculatus var. repraesentaneus, proposed by Killermann in 1933, is considered a synonym. Rolf Singer in 1942 defined the subspecies L. repraesentaneus ssp. speciosus to include fruit bodies with matted fibers arranged in concentric rings on the cap, in comparison with the nominate subspecies, where in young specimens the felt was evenly distributed on the cap surface, only becoming zonate at the cap margins in maturity.According to the classification proposed by Lexemuel Ray Hesler and Alexander H. Smith in their 1979 monograph of North American Lactarius species, L. repraesentaneus belongs in the stirps Speciosus of the section Aspideini, of the subgenus Piperites of genus Lactarius. Other species in stirps Speciosus include L. dispersus, L. subtorminosus, and L. speciosus, all of which have a hairy cap edge. Singer's 1986 classification of the Agaricales does not divide subsection Aspideini into stirpes, instead grouping Lactarius repraesentaneus with L. aspideus, L. uvidus, L. luridis, L. psammicola, and L. speciosus.
The mushroom is commonly known as the "northern bearded milkcap", the "northern milkcap", or the "purple-staining milkcap". The specific epithet repraesentaneus is Latin for "well-represented".
Description
The cap of L. repraesentaneus is wide, convex to broadly funnel-shaped. The margin is conspicuously bearded on young specimens. The cap surface is faintly zoned to azonate, with a thin layer of matted fibers, often becoming scurfy with age. It is dry to somewhat sticky, light yellow to orange-yellow, sometimes with rusty tints when older. The attachment of the gills to the stem is slightly decurrent—running slightly down the length of the stem. The gills are moderately broad, close to crowded, sometimes forked near the stem. Normally a cream to pale ochraceous color, they will stain dull lilac to purple when bruised.The stem is long, thick, nearly equal in width throughout or enlarged downward, hollow at maturity, sticky to dry, scrobiculate, pale yellow to orange-yellow, and stains dull lilac to purple. The flesh is firm, brittle, white, and will stain dull lilac to purple when cut. The odor is sometimes faintly fragrant or not distinctive, but when the mushroom is dry it smells intensely of soap. Its taste is mild to slightly acrid or somewhat bitter, and the flavor has been compared to sweet flag. The abundant amount of latex produced by the mushroom is white to cream, unchanging, staining all tissues dull lilac to purple. It tastes mild to slightly acrid or somewhat bitter. The spore print is yellowish.
A new form, Lactarius repraesentaneus f. immutabilis, was described from Le Sappey, in the Haute-Savoie department of southeastern France in 2011. It differs in the staining reaction of its injured flesh.
The spores are 8–12 by 6.5–9 μm, broadly ellipsoid to ellipsoid, ornamented with warts and ridges that do not form a reticulum, prominences up to 0.8 μm high, hyaline, and amyloid. The cap cuticle is an ixocutis—with the hyphae embedded in a slimy or gelatinized layer.