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Species Information
Summary: Features include a creamy to brownish or yellow brown cap that is smooth to cracked, pallid to light brown gills, whitish to brownish equal stem, thin membranous ring, farinaceous odor and taste, dark brown spore deposit, and growth in spring to early fall. There may be five species in this group in the Pacific Northwest, depending on how conservatively species are defined, and a dozen or so species around the world, (D. Miller, pers. comm.).
Agrocybe praecox is reported in Redhead(5) for BC. There are collections at the University of British Columbia for BC and at the University of Washington for WA, OR, ID, AK, CA, NY, and VA.
Cap: 2-6(8)cm across, rarely up to 14cm across, convex becoming flat or retaining obtuse central umbo, margin incurved at first; ivory to cream, often pale ochraceous to pale buff toward center, ivory or pale cream when dry; "smooth or lightly wrinkled or even cracking especially on drying", margin at first with a few white floccules of veil, (Watling), 3-10cm across, "convex to broadly umbonate; pale cream to buff or clay"; soft, smooth, sometimes cracking when dry, (Phillips), 3-9cm across, obtuse to convex becoming flat, or sometimes with a low broad umbo; cream to light brown at first then yellowish brown when old; bald, soft to touch, sometimes areolate [cracked like dried mud], (Hermanson), margin sometimes hung with a few whitish veil remnants, (Breitenbach)
Flesh: white in cap, grayish straw or buff in stem, (Watling), thin; white, (Phillips, Hermanson)
Gills: adnexed or adnate, with slight tooth, crowded, broad; "whitish to pale clay buff at first but soon umber or snuff brown", edges white; edges floccose, (Watling), "adnate, crowded; pallid then clay-brown", (Phillips), adnate to adnexed, close, broad; "pallid then light brown and finally dull dark brown", (Hermanson)
Stem: 4-11.9cm x 0.6-1cm, slender, equal or usually swollen toward base, stuffed; whitish throughout or tinged fawn or color of cap especially when old; mealy-striate at top, fibrillose streaky in lower part, "frequently attached to white, thin mycelial cords", (Watling), 3-10cm x 0.4-1cm, "equal; pale buff below ring, with white rhizomorphs at base", (Phillips), 3-10cm x 0.4-1.2cm, equal; whitish to pallid becoming brownish, with white rhizomorphs at base, often pruinose at top, (Hermanson)
Veil: white membranous apical ring, drooping with age, (Watling), ring membranous, high, often torn; white, (Phillips), submembranous often as patches (appendiculate) on edge of cap margin, disappearing when old, (Hermanson)
Odor: pleasant (Watling), farinaceous-mealy (Phillips) farinaceous (Hermanson), mild to fungoid (Miller)
Taste: mealy (Watling), farinaceous-mealy (Phillips) farinaceous (Hermanson), often has a somewhat bitter taste (Trudell)
Microscopic spores: spores 8.5-10 x 5-6 microns, elliptic in face view, slightly flattened on one side in side view, fulvous in water, hazel in alkali, germ pore large; basidia 4-spored, 25-30 x 6-7.5 microns, cylindric; pleurocystidia sparse, 45-65 x 15-20 microns, lageniform to fusiform, inflated below, head sometimes ampullaceous, cheilocystidia 20-30 x 10-15 microns, vesiculose to ventricose, colorless; cap cuticle "a hymeniform layer of subglobose, vesiculose to pyriform cells" 35-50 x 15-25 microns; stem cuticle "of parallel hyphae supporting vesiculose to lageniform cystidia at stem-apex"; veil of filamentous cylindric hyphae; clamp connections present, (Watling), spores 8-11 x 5-6 microns, truncate, (Phillips), spores 8-11 x 5-7 microns, truncate with apical germ pore; pleurocystidia present 38-50 x 10-18 microns, utriform, cheilocystidia similar, (Hermanson), spores 10-14 x 6.5-7.5 microns (Trudell)
Spore deposit: snuff brown (Watling), dark brown (Phillips, Hermanson), dark rich brown (Miller)
Habitat / Range
"on the ground in grassy or bare places, margins of fields and woods", spring and summer, often cespitose [in tufts] or in small troops, (Watling for Britain), "in wood chips, humus, and grass, in fields and woodlands", May to July, (Phillips) cespitose [in tufts] to gregarious or scattered, on humus, chip dirt, lawns, fields, roadsides, open woods, spring to early fall, (Hermanson), "very common in newly landscaped areas containing mulch or wood chips", occurring in spring or early summer, (Trudell), spring, summer, fall
Similar Species
Agrocybe dura [here considered to be Agrocybe molesta] has more robust fruiting bodies, and has only a hint of a ring zone, but there are distinct veil remnants on the cap margin, longer spores, and somewhat fatter cheilocystidia and pleurocystidia. A. dura "is easy to confuse with Agrocybe praecox... especially when the latter has a pale, areolate pileus. The two species can be definitely separated only microscopically, since A. dura always has spores distinctly > 10 microns long and cystidia which are vesicular to broadly lageniform. Macroscopically the two species can be separated by the fact that A. dura never has a pronounced membranous annulus but only a +/- well-defined annular zone with the veil remnants remaining attached to the pileal margin especially when young. In any case, an areolate cuticle is not a useful differentiating feature", (Breitenbach, Latin names italicized). See also NOTES section of Agrocybe molesta for a habitat differentiation. Agrocybe acericola has a dark yellow-brown cap and a persistent ring, and it is found on rotten logs and stumps or on buried wood, (Miller). Agrocybe smithii has larger spores and lacks a partial veil (Trudell). See also SIMILAR section of Stropharia coronilla.
