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[Basidiomycota > Agaricales > Inocybaceae > Mallocybe . . . ] Mallocybe luteobasis by Michael Kuo, 7 May 2025 Mallocybe luteobasis is a recently-named inocybe found in the Midwestern and southeastern United States, in association with hardwoods in upland forests. It features a brown cap adorned with appressed, fibrillose scales, and a fibrillose-scaly stem. Fresh specimens often have a yellow, or at least yellowish, stem base, and most specimens feature yellow flesh inside the stem base (hence the epithet luteobasis). Under the microscope, Mallocybe luteobasis features smooth, ellipsoid spores that often have one side somewhat flattened, along with fingerlike to cylindric cheilocystidia. Mallocybe unicolor is very similar, and grows in the same kinds of forests, often at about the same time of year. Its cap is usually a little more reddish- or orangish-brown, with a granular-scaly (rather than fibrillose-scaly) surface. Microscopic features are also very similar, but the spores of Mallocybe unicolor are more narrow and the cheilocystidia are mostly cylindric with slightly swollen apices. Description: Ecology: Mycorrhizal; found in upland hardwood forests in association with oaks, beech, hickories, and blue beech; usually growing gregariously; summer; originally described from Illinois (Matheny et al. 2023), with additional collections cited from Indiana, Kansas, and Tennessee. The illustrated and described collections are from Illinois and Indiana. Cap: 1–5.5 cm; convex, becoming broadly convex to flat; dry; radially fibrillose-scaly with brown to reddish brown or orangish brown scales over a paler ground color; margin initially inrolled, later straightening. Gills: Attached to the stem by a tooth that runs down the stem's apex; close; short-gills frequent; pale yellowish in button-stage specimens when still covered by the veil, but later brownish and eventually brown, with yellowish edges; at first covered by an ephemeral, yellowish (sometimes whitish or brownish), cortina-like veil. Stem: 2.5–6 cm long; 4–10 mm thick; equal above a slightly tapered base; dry; bald and whitish at the apex; elsewhere covered with brown, fibrillose scales; sometimes featuring a vague ring zone; often yellowish near the base; basal mycelium yellowish to yellow when fresh, but sometimes fading to white. Flesh: Whitish to yellowish or watery brownish in the cap and upper stem; yellow in the stem base; not changing when sliced. Odor: Variable; sometimes not distinctive, but sometimes spermatic and/or foul. Chemical Reactions: KOH on cap surface gray to reddish black. Spore Print: Brown to orangish brown. Microscopic Features: Spores 8–10.5 x 5–6.5 µm; ellipsoid, often with one side somewhat flattened—or nearly amygdaliform; smooth; brownish yellow to golden in KOH; faintly brownish in Melzer's. Basidia 25–30 x 6–8 µm; clavate; 4-sterigmate. Cheilocystidia 35–60 x 2.5–7.5 µm; mostly cylindric but occasionally narrowly lageniform; flexuous; apices varying from merely rounded to subclavate, subcapitate, capitate, or subacute; smooth; thin-walled; septate; hyaline to yellowish in KOH. Pleurocystidia not found. Pileipellis a cutis; elements 5–10 µm wide, smooth or a little roughened, with brownish walls in KOH; clamp connections present. REFERENCES: P. B. Matheny & M. Kuo, 2023. (Matheny, 2018; Matheny et al., 2020; Matheny et al., 2023.) Herb. Kuo 07140307 (paratype), 07020703, 07180705 (holotype), 06211102 (paratype), 06071503 (paratype), 06081801, 06131801, 07292005 (paratype). This site contains no information about the edibility or toxicity of mushrooms. |
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Cite this page as: Kuo, M. (2025, May). Mallocybe luteobasis. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/mallocybe_luteobasis.html |