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Species Information
Summary: Features include a white to ocher-tinged cap that is dry and often areolate [cracked like dried mud], a fleeting ring, mild odor, growth in spring on cultivated or disturbed ground or in grass, light brown spore deposit, and spores 10-14 microns long. Agrocybe molesta (Lasch) Singer may be a better name for what has been known as Agrocybe dura in the Pacific Northwest. Kuo has addressed its place in the Agrocybe praecox species cluster (drawing on Flynn(1)), maintaining that it is the only one in the cluster that is a devoted decomposer of grass litter, and the only one with spores as long as 10-14 microns. While acknowledging that a microscope may be needed for definitive identification, Kuo says (italicizing Latin names), "To separate Agrocybe molesta (also known as Agrocybe dura) from Agrocybe praecox, field guides emphasize a suite of frustrating minor differences in physical features like the toughness of the stem, the tendency of the cap to crack in old age, the color of the cap, and the precise shade of brown displayed in the mature gills. But recent research has simplified things substantially for this species, allowing us to more or less ignore these differences and focus on the ecology: Agrocybe molesta is the only grass decomposer in the group, though it is variable in many of its physical features." (See also SIMILAR, and Agrocybe praecox group.)
Breitenbach(4) give distribution of Agrocybe dura as North America, Europe, Asia, North Africa. It is included in the Pacific Northwest key of Hermanson(1). There is a collection from OR at Oregon State University, one from BC at the University of British Columbia, and collections from WA, AK, and NC at the University of Washington.
Gills: adnate; pale brown to umber, (Phillips), adnate to sinuate, close, broad; whitish becoming more or less dark brown to purplish brown, (Hermanson); notched, 39-50 reaching stem, 3-7 subgills between each pair of gills, broad; "whitish when young, soon gray-brown to dark brown, sometimes with a lilac tinge"; edges white-floccose, (Breitenbach)
Stem: 4-10cm x 0.5-1.5cm, "equal, firm; white; smooth to fibrillose", (Phillips), 4-10cm x 0.5-1.5cm, equal; whitish becoming somewhat brownish; +/- pruinose at top, (Hermanson), 4-7(9)cm x 0.5-1.2cm, cylindric, top somewhat widened at times, base widened or narrowing, stuffed becoming hollow; whitish for a long time, later browning toward base; longitudinally fibrillose-floccose, may have white strands (rhizoids) at base, (Breitenbach)
Veil: "ring soon vanishing or left as tatters on cap margin", (Phillips), white, forming a thin, superior, fleeting ring or remains on the cap edge, (Hermanson), fleeting, whitish ring zone on upper third of stem (without a distinct membranous ring), margin hung with white veil remnants especially when young, (Breitenbach)
Odor: not distinctive (Phillips), mushroomy, (Hermanson), pleasant, barely farinaceous, (Breitenbach)
Taste: a little bitter, unpleasant, (Phillips), slightly bitter (Hermanson), mild, with a farinaceous hint, (Breitenbach), mild with an aftertaste (Miller)
Microscopic spores: spores 10-14 x 6.5-8 microns, truncate, (Phillips), 10-12 x 5-6 microns, truncate with germ pore; pleurocystidia 35-48 x 10-18 microns, ventricose-pedicellate [wider in middle with a small stalk], and apex broadly rounded, cheilocystidia similar, (Hermanson); spores 10.1-14.2 x 6.6-7.6 microns, elliptic, smooth, thick-walled, yellow-brown, with germ pore; basidia 4-spored, 35-45 x 10-12 microns, slenderly clavate, some with basal clamp; cheilocystidia 35-50 x 15-25 microns, vesicular, cylindric to broadly lageniform, pleurocystidia 35-45 x 20-25 microns, similar; cap cuticle "hymeniform, composed of clavate to pyriform cells 20-35 x 10-20 microns, with an encrusted, gelatinized layer above it which does not swell in KOH, clamps not seen", (Breitenbach)
Spore deposit: dull brown (Phillips), light brown (Hermanson), dark tobacco-brown (Breitenbach)
Habitat / Range
in fields, pastures, and wastelands, shrub borders, May to July, (Phillips), scattered to gregarious on lawns, waste grassland, pastures, gardens, shrub borders, roadsides, spring to fall, (Hermanson), gregarious to clustered, more rarely single "outside of forests, in gardens, fields, vineyards, dry and semi-dry lawns, on soil", spring-fall, (Breitenbach for Europe), cultivated and disturbed ground (Arora(1)), spring, summer, fall
Similar Species
A. praecox has less robust fruiting bodies, membranous pendant ring when young that disappears when old (as opposed to only a hint of a ring zone but distinct veil remnants on cap margin), and shorter spores. Agrocybe 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 above.
