Inosperma adaequatum
Mycologia 112(1): 101. 2020.
Common Name: none
Synonyms: Inocybe adaequata (Britzelm.) Saccardo; Inocybe jurana (Pat.) Saccardo
Cap 4.0-8.0 (9.0) broad, obtuse-conic to bell-shaped, eventually broadly-convex to nearly plane, often with a low umbo; margin incurved, then decurved, wavy, sometime rimose, at maturity occasionally upturned; surface radially appressed-fibrillose to minutely squamulose, pinkish-vinaceous at the disc, paler towards the margin, cap darkening to vinaceous-brown with age and handling; context firm, up to 10 mm thick at the disc, 2-3 mm at the margin, pallid, tinged pink when cut; odor and taste to faintly farinaceous.
Gills close, at first adnate, becoming notched to subdecurrent; color in youth, pale-buff, darkening to tobacco-brown, 5-10 mm broad; edges lighter than the faces, minutely fringed (use hand lens), lamellulae in three to four tiers.
Stipe 4.0-8.0 (10) cm long, 1.0-2.0 (3.0) cm thick, equal to narrowed below, sometimes with a basal bend, occasionally compressed, solid, fleshy-fibrous; surface of apex whitish, furfuraceous to fibrillose, the lower portion striate, flushed vinaceous, with scattered, loose, darker fibrils; context of base pinkish when cut; partial veil absent.
Spores 9.0-12.0 x 6.0-7.5 µm, smooth, moderately thick-walled, ellipsoid in face-view, similar in profile but inequilateral, i.e. with a flat and curved side, hilar appendage not conspicuous; spores dull-brown in deposit.
Under Quercus agrifolia (Coast liveoak) and possibly other oaks as well; fruiting shortly after the fall rains; infrequent, but probably more common than records indicate (see comments).
To be avoided; many Inocybe species contain the toxin muscarine.
This oak-loving species goes largely unnoticed because of its tendency to fruit partially buried in dirt and duff. It is an exception to the rule that all Inocybes s.l. are dull-brown, uninteresting, and difficult to identify. Known as Inocybe adaequata or Inocybe jurana in older field guides, Inosperma adaequatum, is recognized by a vinaceous-tinged, fibrillose cap, similarly colored stipe, and usually mild odor. Microscopically the absence of pleurocystidia and smooth rather than nodulose spores are important characters. Other reddish-hued Inocybes s.l. include Inocybe pudica, a diminutive species with a glabrous, whitish cap that in age becomes tinged pinkish-red; Inocybe godeyi, also small and white, reddening with age, but with a fibrillose cap, Inocybe fraudans (=I. pyriodora), with an ochre, fibrillose cap, occasionally red-tinged and strong odor of rotting pears or spicy-like as in matsutake, and Inocybe oblectabilis with a glabrous, reddish-brown to pinkish-brown cap and nodulose spores. Excluding the above, Inosperma adaequatum also bears a resemblance to several vinaceous-colored waxy caps, Hygrophorus erubescens, Hygrophorus purpurascens, and Hygrophorus russula. These, however, have white, not brown spores.
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