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Lactarius xanthogalactus

by Michael Kuo, 31 January 2024

This West-Coast milky cap is found in coastal forests, usually in association with coast live oak. Defining features include the faintly zoned, reddish brown to orangish brown cap, the lack of potholes on the stem surface and, especially, the milk, which is white as exuded but quickly turns yellow when exposed to air.

Lactarius alnicola is a similar species found in the same coastal forests as Lactarius xanthogalactus; however, the milk of Lactarius alnicola turns only slightly yellow (if at all), its taste is quickly and excuciatingly acrid, and its stem usually features at least some potholes. In eastern North America, Lactarius vinaceorufescens is a similar species associated with eastern white pine.

Description:

Ecology: Mycorrhizal with coast live oak, and possibly with Douglas-fir (Horton et al. 1999); growing alone or gregariously; fall and winter; originally described from the Stanford University campus; distributed primarily in coastal California. The illustrated and described collections are from Santa Cruz and San Mateo counties.

Cap: 5–12 cm; convex with an incurved margin when young, becoming shallowly vase-shaped, with the margin uplifted; sticky when young, but soon merely moist, or dry; bald; orangish brown to reddish brown, often with vague concentric zones of color.

Gills: Beginning to run down the stem; close; short-gills frequent; pale yellowish at first, becoming orangish to dull brownish orange.

Stem: 2–7 cm long; 1–1.5 cm thick; equal; bald; without potholes; colored like the cap; hollowing with age; basal mycelium white to yellowish.

Flesh: White; stained yellow by the milk when sliced.

Milk: White as exuded but quickly yellow.

Odor and Taste: Odor not distinctive; taste not distinctive, or faintly acrid.

Microscopic Features: Spores 6–8 x 5–7 µm; ellipsoid; ornamentation consisting of amyloid ridges and warts under 0.5 µm high, forming partial reticula. Hymenial macrocystidia 45–70 x 7–11 µm; fusiform, occasionally with an apical constriction and a knob; smooth; thin-walled; hyaline in KOH. Pileipellis an ixocutis.

REFERENCES: C. H. Peck, 1907. (Hesler & Smith, 1979; Methven, 1997; Horton et al., 1999; Redecker et al., 2001; Bessette et al., 2009; Desjardin, Wood & Stevens, 2015; Siegel & Schwarz, 2016.) Herb. Kuo 01122404.

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Spores

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Kuo, M. (2024, January). Lactarius xanthogalactus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/lactarius_xanthogalactus.html