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Species Information
Summary: Features include 1) a viscid cap that is pale yellow with a slightly darker disc, becoming "Isabella color" to olivaceous in aging, the disk tinged orange at times, 2) close, broad gills that are whitish initially but soon violaceous brown, 3) a stem that is somewhat fibrillose to somewhat scaly below the membranous to fibrillose ragged fleeting ring, and 4) growth in moist areas under alder and Populus. Arora gives this as (=Stropharia magnivelaris?), but Smith, in his 1941 report of S. magnivelaris from Washington, pointed out that the veil was atypical for S. magnivelaris Peck, and in 1979 he placed these specimens in S. riparia Smith. The description is derived from Smith(18) except where indicated.
It has been found in the Rocky Mountains and the Pacific Northwest including WA, (Smith(18)). It has been reported from BC (Kroeger(1)). There are collections from BC and OR at the University of British Columbia. There are collections from WA, AK, and CO at the University of Washington. It has also been found in California according to Desjardin(6), but says it is almost indistinguishable from the European Leratiomyces percevalii. According to Siegel(2) the common tan Leratiomyces found on wood chips in the Redwood Coast of California is Leratiomyces percevalii. Leratiomyces riparia was originally described from Washington. Although some collections at the University of British Columbia labeled as this species are probably Leratiomyces percevalii, collections from Meager Mountain (Pebble Creek) and Manning Park (Beaver Pond) would be this species with alders in riparian areas, (P. Kroeger, pers. comm.).
Gills: broadly adnate and usually with decurrent tooth, becoming depressed around stem when mature, close, broad: 0.5-0.7cm; whitish when young, soon violaceous brown; edges even
Stem: 6-9(12)cm x 0.4-1(1.2)cm, equal or slightly widened in upper or lower part, hollow; white or whitish (pallid) but when old sordid brownish near base; somewhat fibrillose to somewhat scaly below ring, bald above
Veil: ring submembranous [somewhat membranous] or merely fibrillose," whitish, usually very ragged and soon vanishing"
Microscopic spores: spores 11-14(15) x 6-8 microns, elliptic to subovate, smooth, dark yellowish brown in KOH, truncate from apical to subapical germ pore; basidia 4-spored, 28-34 x 8-9 microns, colorless in KOH; pleurocystidia none, cheilocystidia "abundant and forming a sterile band on the gill edge", 20-40 x 4-7 microns, colorless in KOH, "clavate when young but soon filamentose and flexuous"; gill trama of interwoven hyphae 6-12 microns wide, colorless in KOH; cap cuticle a thin ixocutis; clamp connections present
Spore deposit: [presumably near violaceous brown]
Habitat / Range
single to gregarious or subcespitose [more or less in tufts] under Alnus (alder) and species of Populus (cottonwood and small-toothed aspen), "in moist places such as seepage areas and along streams, spring and fall", (Smith(18)), common during wet periods in summer (Smith(6))
Similar Species
Stropharia ambigua is similar but Leratiomyces riparius has 1) a slightly smaller and slimmer stature (stem less than 1cm thick), 2) a thinner more kleenex-like veil that often leaves remnants on the cap near the margin rather than dangling from the margin itself, 3) a stem surface that is not nearly as shaggy, and 4) a cap shape more likely to be slightly umbonate, (Arora). See also SIMILAR section of Leratiomyces magnivelaris, Leratiomyces percevalii, Stropharia coronilla, and (regarding Leratiomyces percevalii) Leratiomyces ceres.
Smith(18) (colors in quotation marks from Ridgway(1)), Smith(6), Smith(19), Arora(1), Kroeger(1), Desjardin(6)*, Siegel(2), Marrone(1)* References for the fungi
