Lactarius xanthogalactus

[ Basidiomycetes > Russulales > Russulaceae > Lactarius . . . ]

by Michael Kuo

This West-Coast milky cap was identified by Charles Peck in 1907, on the basis of material sent to him in New York by a California collector, Miss A. M. Patterson, who found the mushroom under live oak on the Stanford campus. It has a brownish orange cap, gills that do not develop reddish stains with maturity, and milk that turns yellow on exposure to air--though there has been some confusion over this last item, since Peck recorded the milk as "yellow." However, mycologists have decided that Miss Patterson must have missed the fact that the milk is white at first, since the color change can happen in as little as two or three seconds.

Lactarius vinaceorufescens of eastern North America is similar--and western field guides used its name to describe Lactarius xanthogalactus for many years, despite the efforts of Patterson and Peck. However, as Andrew Methven points out in his monograph of Lactarius in California, Lactarius vinaceorufescens is associated with conifers, and develops reddish stains and discolorations.

Lactarius xanthogalactus should not be eaten; it may be poisonous.

Description:

Ecology: Mycorrhizal with Coast Live Oak (perhaps also with Tanoak); growing alone, scattered, or gregariously; fall and winter; on the West Coast.

Cap: 2-8 cm; convex, becoming flat or shallowly vase-shaped; moist or thinly slimy; smooth or streaked with appressed fibers; without zones of color, or with faint zones of texture; grayish orange, becoming brownish orange.

Gills: Attached to the stem or running slightly down it; close or nearly distant; pale yellowish to pale orange; not developing stains or discolorations; not staining from the milk.

Stem: 2-8 cm long; up to 2 cm thick; pale orange; more or less equal; smooth; without pot-holes; often with whitish or orangish fuzz at the base.

Flesh: White, turning quickly yellow when sliced.

Milk: White, turning quickly yellow on exposure to air; staining tissues yellow.

Odor and Taste: Odor not distinctive; taste mild or slightly acrid.

Spore Print: Yellowish.

Chemical Reactions: KOH on cap yellow.

Microscopic Features: Spores 7-8.5 x 6-7 µ; broadly elliptical; ornamentation with prominences to 0.5 µ high; connectors forming partial reticula.

REFERENCES: Peck, 1907. (Arora, 1986 [as L. vinaceorufescens]; Methven, 1997; Wood & Stevens, 2004). Herb. Kuo 01130501.

Further Online Information:

Lactarius xanthogalactus at MykoWeb

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Cite this page as:

Kuo, M. (2005, March). Lactarius xanthogalactus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/lactarius_xanthogalactus.html