Lactarius rubrilacteus Hesler & A.H. Sm.

Barge, Edward G. & Cripps, Cathy L., 2016, New reports, phylogenetic analysis, and a key to Lactarius Pers. in the Greater Yellowstone Ecosystem informed by molecular data, MycoKeys 15, pp. 1-58 : 37

Taxon classification Fungi Russulales Russulaceae

19. Lactarius rubrilacteus Hesler & A.H. Sm. Figure 21

Description.

Pileus 45-90 mm in diameter, shallowly depressed–convex to broadly infundibuliform, smooth, viscid, zonate, light brown to orange–cream to yellow–orange to orange–brown to carrot to dingy orange, often with green stains; margin incurved when young becoming straight. Lamellae adnate to subdecurrent, crowded to subdistant, cream to pinkish cinnamon to dull pink, discoloring wine red and eventually green where damaged. Stipe 20-40 × 10-25 mm, equal to tapering toward the base, dry, smooth, at first with a light glaucous coating, ± scrobiculate, cream to dull pink to orange–cream, discoloring wine red and eventually green where damaged, solid, becoming hollow. Context white, immediately staining deep wine–red to burgundy. Latex scarce, wine red, staining tissue wine–red to burgundy and eventually green. Odor mild. Taste mild.

Basidiospores 7.5-9.5 × 5-7.5 µm, Q = 1.3-1.5, ellipsoid; ornamentation forming a partial reticulum. Pleuromacrocystidia 40-80 × 4-6 µm, sparse, fusoid; apex acute. Cheilomacrocystidia 30-65 × 6-9 µm, scattered, fusoid; apex acute.

Ecology and distribution.

In western North America with Pseudotsuga menziesii and Pinus . In the GYE this species occurs in foothills to low montane areas, near Pseudotsuga menziesii , spring and early summer.

Specimens examined.

U.S.A. MONTANA: Gallatin County, Bridger Range, Fairy Lake Road, under Pseudotsuga menziesii , 25 June 2013, EB13-040 ( MONT); Park County, Absaroka Mountains, George Lake Trailhead, under Pseudotsuga menziesii , 27 June 2014, EB900-14 ( MONT).

Discussion.

The European Lactarius sanguifluus (Paulet) Fr. is morphologically similar, however, its lamellae are typically more violet tinged and its stipe is often scrobiculate. Western North American members of the " Lactarius deliciosus " group can appear similar, however, their latex does not start out red as in Lactarius rubrilacteus . The western North American Lactarius barrowsii also has reddish latex, however, it features a whitish to straw colored pileus and ochraceous to pinkish orange lamellae.