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Species Information
Summary: Tricholoma myomyces is a member of the Tricholoma terreum group that includes small Tricholomas with fragile flesh and a dry, scaly or "furry" mouse-colored cap. Features of Tricholoma myomyces include 1) a dry, fibrillose to scaly cap that is dark drab gray to brownish gray or blackish gray, 2) pale gray flesh, 3) sinuate, close, broad, light gray gills, 4) a white to very pale gray stem that is silky-fibrillose with white or gray fibrils, 5) a fleeting, cobwebby cortina, 6) a mild odor and taste, 7) growth under conifers or on lawns, 8) a white spore deposit, and 9) narrowly elliptic, smooth, inamyloid spores. The online Species Fungorum, accessed November 16, 2014, considered it a synonym of Tricholoma terreum (Schaeff.) P. Kumm., but MycoBank, accessed the same date, maintained them separately - see SIMILAR section for possible differences. Heilmann-Clausen(1) doubted that T. myomyces as typically interpreted is a different species from T. terreum based on lack of congruence between proposed macro/micro-morphology differences and ITS phylogeny. Var. alboconicum was considered by Moser(1) to be T. inocybeoides, and both var. alboconicum and var. inocybeoides were considered by Leuthy(2) to be included in T. scalpturatum. Shanks(2) describes var. cystidiotum which differs from the type variety in having broadly clavate to spheropedunculate cheilocystidia (19-38 x 8.2-12.0 microns).
Ovrebo examined collections from ON, MI, MN, PA, WI, and Sweden, and indicated its presence in the Pacific Northwest in a private communication. The University of British Columbia has collections from BC. The University of Washington has collections from WA and AK. Oregon State University has collections from OR. The New York Botanical Garden has collections from ID. San Francisco State University has collections from WA, ID, and CA. It was reported by Kernaghan(1) from AB. Bessette(5) say it is widely distributed across northern N. America and show photographs from QC, CA, and NY.
Gills: "arcuate to sinuate, close, broad"; light gray, fading near stem when old, "very rarely discoloring with dull yellow spots", (Phillips), arcuate when young, sinuate when mature, often seceding when old, close, subgills numerous but not in distinct tiers, gills 0.2-0.8cm broad; "light gray to gray when young, when mature generally fading to nearly white near the stipe or occasionally remaining light gray overall, not discoloring or rarely with dull yellow spots"; edges entire, (Ovrebo)
Stem: 1.5-7cm x 0.5-1cm, generally rounded or abruptly tapered, solid or hollow; "white to pale gray; silky with white or gray hairs", (Phillips), 1.5-7cm x 0.5-1cm, equal or occasionally somewhat club-shaped, the base rounded or abruptly tapered, stem solid or hollow; white to very pale gray; silky-fibrillose and with white or grayish superficial fibrils projecting, (Ovrebo)
Veil: a cortina of white or gray hairs that leave a faint fleeting zone on stem, (Phillips), veil a cortina of white to grayish fibrils that at times leave a very fleeting zone of fibrils on central to upper part of stem, the reticulate fibrils on the cap surface likely also part of the veil and thus constituting a universal veil, (Ovrebo)
Odor: absent to nondescript (Ovrebo)
Taste: not distinctive (Bessette)
Microscopic spores: spores 6.7-11.4 x 3.8-5.7 microns, or more specifically 6.7-7.6 x 4.3-4.8 microns (4-spored form), 8.6-11.4 x 3.8-5.7 microns (2-spored form), narrowly elliptic, oblong, or oblong-ovate, in face view, in side view these shapes or slightly allantoid [curved-sausage-shaped], smooth, inamyloid, thin-walled, (Ovrebo, Phillips gives same spore measurements); basidia 25-33 x 6.7-7.6 microns for 2-spored and 4-spored variants, clavate, colorless; pleurocystidia and cheilocystidia absent [but see NOTES for var. cystidiotum]; cap cuticle hyphae 4.8-14 microns wide, interwoven to nearly erect over disc, radially appressed or agglutinated into recurved fascicles on margin, cylindric, smooth and thin-walled or roughened and thickened with colorless or brownish incrustations, colorless to light fuscous-black; hypodermium pseudoparenchymatous, cells 12.4-24 microns wide, broadly inflated to nearly isodiametric, smooth and thin-walled or roughened and thickened with fuscous-black incrustations, colorless or light fuscous; clamp connections absent, (Ovrebo)
Spore deposit: white (Phillips, Ovrebo)
Habitat / Range
"in groups or dense clusters under conifers in woods or on lawns", (Phillips), gregarious or in cespitose clusters under conifers, (Ovrebo)
Similar Species
Tricholoma terreum lacks the evanescent cobwebby cortina, and has different spores (Arora). T. terreum is described by Courtecuisse(1) as having blackish gray, fibrillose to innately streaky cap and not very close pale gray gills, and T. myomyces as having a dark mouse gray, fibrillose felted cap and fairly close whitish gills. T. terreum "is said by some mycologists to lack a cortina in the button stage" but increasingly the two are being synonymized by European mycologists (Bessette(5)). Tricholoma moseri "is small, has abundant tiny scales on a dark gray cap, pale gray gills, a white stalk, and relatively long narrow spores, lacks a cortina and pseudoparenchymatous hypodermium, and occurs primarily in the spring and early summer in the mountains of western North America" (Bessette(5)). Tricholoma scalpturatum tends to be paler, has a farinaceous odor and taste, has gills and stem that discolor yellow, and lacks a pseudoparenchymatous hypodermium, (Ovrebo(2)). T. scalpturatum tends to be paler, with scattered dark fibrils over a pale background, and has gills that discolor yellow, (Shanks). See also SIMILAR section of Tricholoma atrosquamosum var. atrosquamosum and Tricholoma triste.
