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Inocybe subradiata

by Michael Kuo, 19 September 2026

Inocybe subradiata is a small species of Inocybe found under oaks east of the Great Plains. It features a dark brown cap that soon develops radial fissures, and a stem surface that is very finely lined above a small basal bulb. The lines on the stem extend from the apex to the base, and are composed of aggregations of pruina, individually invisible to the naked eye but easily seen under the microscope as caulocystidia.

Further identifying features for Inocybe subradiata include its lack of a distinctive odor and its spores, which are nodulose, featuring fairly small and well spaced nodules.

Description:

Ecology: Mycorrhizal with oaks; growing gregariously; summer and fall; originally described from Florida (Murrill 1945); possibly widely distributed in the Midwestern and southeastern United States. The illustrated and described collections are from Illinois.

Cap: 2–3 cm; broadly conic at first, becoming broadly convex with a central bump; dry; bald or finely fibrillose; dark brown; splitting radially, especially in the marginal half.

Gills: Narrowly attached to the stem, becoming nearly free from it; close; short-gills occasional; whitish at first, becoming dull brown.

Stem: 20–50 cm long; 1.5–3 mm thick; equal above a small basal bulb that features a rimmed upper edge; dry; pruinose in fine longitudinal lines extending the entire length of the stem; brownish; basal mycelium white.

Flesh: Insubstantial; whitish; not changing when sliced.

Odor: Not distinctive.

Chemical Reactions: KOH negative on cap surface.

Microscopic Features: Spores 8–10 x 5–7 µm including nodules; nodulose; nodules 1–1.5 µm long, small and well spaced; dull golden in KOH. Hymenial cystidia 40–70 x 12–18 µm; lageniform; smooth, but developing apical crystals; walls 2–3 µm thick; hyaline to yellowish in KOH. Pileipellis a cutis; elements 2–5 µm wide, smooth, brownish yellow in KOH. Caulocystidia present in sections taken from the lower portion of the stipe; 45–100 x 10–22 µm; narrowly lageniform; smooth, but developing apical crystals; walls 2–3 µm thick; hyaline to yellowish in KOH. Clamp connections present.

REFERENCES: W. A. Murrill, 1945. (Murrill, 1945; Matheny, 2023.) Herb. Kuo 07120301, 07201605.

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Spores

Pleurocystidium

Caulocystidia

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Kuo, M. (2026, September). Inocybe subradiata. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/inocybe_subradiata.html