Mycologia 50: 46. 1958.
Common Name: none
Synonym: Tricholoma sclerotoideum Morse
Cap 1.0-3.0 (4.0) cm broad, convex, expanding to nearly plane, with or without a low umbo; margin when young sometimes sulcate-striate or wavy, tomentose, incurved, in age decurved to plane, occasionally raised; surface dry, dull, glabrous or with appressed fibrils, the latter unevenly tan-brown over a cream to pale-grey ground color; context white, firm, up to 4.0 mm thick, unchanging when cut; odor not distinctive; taste mild.
Gills adnate, broadly notched to subdecurrent, close, becoming subdistant at maturity, relatively broad, cream-buff to dull tan; lamellulae up to 2-seried.
Stipe 1.0-4.0 (6.0) cm tall, 4.0-8.0 mm thick, equal to clavate, solid, cream-colored; surface of apex fufuraceous, lower portion loosely covered with fibrils, sometimes inconspicuously pubescent, the base typically fused with other sporocarps, arising from a dirt-encrusted sclerotium; partial veil absent.
Spores 7.5 x 10.0 x 3.0-3.5 µm, ellipsoid to subfusoid (spindle-shaped), smooth, thin-walled, hilar appendage not conspicuous, inamyloid; spores creamy-yellow in deposit.
In cespitose clusters, rarely solitary, growing from the rotted remains of Helvella lacunosa; fruiting from mid to late winter.
An unusual fruiting habit, on the decayed remains of Helvella lacunosa, helps distinguish this small drab mushroom. The typically clustered fruitings grow from a sclerotium, a mass of partially differentiated tissue which includes stipe remnants of a Helvella lacunosa. These are best seen by sectioning a sclerotium. Members of the Collybia racemosa, C. tuberosa group also fruit on decayed mushrooms, but are smaller, less robust, fruit from a grain-sized sclerotium, and do not occur with Helvella lacunosa. Collybia racemosa is particularly distinctive in having a stipe with slender side branches. Also compare with Inocybe geophylla, a similar-sized, whitish mushroom sometimes found under Monterey pine (Pinus radiata) with Helvella lacunosa. The latter is separable by a spermatic odor, a dull-brown spore print, and a sparse fibrillose veil.
Bigelow, Howard E. (1982). North American Species of Clitocybe. Part I. J. Cramer: Vaduz, Liechtenstein. 280 p.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Morse, E.E. (1943). Study of a new Tricholoma. Mycologia 35: 573-581. (Protologue)
Trappe, J.M. (1972). Parasitism of Helvella lacunosa by Clitocybe sclerotoidea. Mycologia 64: 1337-1340.