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Lactarius argillaceifolius var. megacarpus
by Michael Kuo
This West-Coast mushroom is currently considered a variety of the eastern North American species Lactarius argillaceifolius, but its differences are substantial and it would not surprise me if DNA analysis were to reveal separate phylogenetic species--in which case the rules of taxonomy would dictate that the West-Coast mushroom become "Lactarius megacarpus."
Lactarius argillaceifolius var. megacarpus is a large, messy species of Lactarius associated with coast live oak and tanoak from southern Oregon to Baja California. Its cap, when fresh, is a dingy purplish color; its gills become dingy yellowish with age; and its off-white milk stains surfaces dingy brownish . . . in short, it's a dingy mushroom. Under the microscope it features partially reticulate, ellipsoid spores with low ornamentation.
Cap: 7-30 cm across when mature; convex, becoming flat with a central depression, or shallowly vase-shaped; drab lilac brown, fading to dirty buff; without zones; bald or minutely pocked and rugged; slimy when fresh.
Gills: Broadly attached to the stem; close or nearly distant; creamy whitish when young, but soon becoming dirty yellowish and, eventually, pale dingy cinnamon; stained slowly brownish to brown or brownish gray by the latex where damaged.
Stem: 6-20 cm long; 2-5 cm thick; more or less equal; whitish, discoloring to yellowish or brownish in age; dry or slightly sticky; bald; without potholes.
Flesh: Whitish; unchanging on exposure.
Milk: Off-white; unchanging when exposed; staining tissues brown to brownish.
Odor and Taste: Odor not distinctive; taste weakly to moderately acrid (especially the latex).
Spore Print: Whitish to very pale yellowish.
Chemical Reactions: KOH on cap surface yellow.
Microscopic Features: Spores 7-10.5 x 6.5-8 µ; broadly ellipsoid; ornamentation under 0.5 µ high, composed of warts and ridges that often form partial reticula. Pleuromacrocystidia fusiform; to about 100 µ long. Cheilomacrocystidia similar but usually shorter. Pileipellis an ixocutis or ixolattice.
Further Online Information:
Cite this page as:
Kuo, M. (2011, February). Lactarius argillaceifolius var. megacarpus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/lactarius_argillaceifolius_megacarpus.html