Name: Agaricus campestris
Citation: [as ‘campester’], Sp. pl. 2: 1173 (1753)
Synonym(s): Agaricus campestris L. var. campestris
Deprecated Synonym(s): Psalliota campestris (L.) Quél., Agaricus campestris var. fuscopilosellus F.H. Møller, Agaricus campestris var. squamulosus (Rea) Pilát, Fungus campestris (L.) Kuntze, Pluteus campestris (L.) Fr., Pratella campestris (L.) Gray, Psalliota campestris var. squamulosa Rea, Psalliota flocculosa Rea, Agaricus compestris, Agaricus campestris L.: Fr.
Fr., Syst. mycol. 1: 281 (1821)
CAP: 4-11(15)cm across, convex or dome-shaped for a long time, then often becoming flat; “pure white, or sometimes with a few grayish to brown or cinnamon-buff fibrils or fibrillose scales”; dry, smooth or silky-fibrillose, margin extending beyond gills, “often hung with veil remnants”1, (2)3-7(10)cm across, obtuse to convex, expanding to broadly convex to flat or at times the disc slightly depressed when old; pure white in one form but becoming pinkish to vinaceous brown or finally dull purplish brown when old at least over marginal area, “in a second form the fibrils more or less cinnamon-brown even on buttons and retaining these colors” (but with the flesh gradually darkening as in the white form); dry, innately fibrillose to appressed silky-fibrillose, nearly bald at first, “the fibrils often loosening and becoming aggregated into appressed scales, the scales either white or becoming cinnamon to reddish brown”, disc sometimes areolate [cracked like mud] and margin torn into imbricate [shingled] scales from the splitting of the cuticle and flesh6.
FLESH: thick; white, not bruising but sometimes staining brownish or reddish when old or in wet weather (especially just above the gills)1, soft to rather firm; “white to pallid vinaceous or finally darker”6.
GILLS: free at maturity, close; pale pink in button stage, then bright pink becoming purple-brown to chocolate brown and finally blackish brown with spores1, free, crowded, narrow, 0.5-0.6cm broad, usually not reaching the margin of the cap; pallid pink, becoming bright pink before veil breaks, dark purplish brown when old; edges even6.
STEM: 2-6(10)cm x 1-2.5cm, usually with a tapered base, firm, stuffed or hollow; white; smooth above the veil, often with a few fibrils below1, 2-4(6)cm x 1-1.5cm, “equal, subventricose or narrowed at base, stuffed and becoming hollow, white and silky above the ring but soon tinged pink and finally sordid vinaceous brown, below the annulus more or less white-fibrillose, glabrescent, white at first but finally discoloring to dull vinaceous brown”6.
VEIL: “thin, somewhat cottony, white, forming a thin ring on stalk or leaving remnants on cap margin or disappearing entirely; ring rarely well-formed, intermediate (sometimes flaring) or rarely skirtlike, median to superior”1, ring thin, single, membranous but often torn and frequently fleeting, sometimes most of veil adhering to cap margin6.
CHEMICAL REACTIONS: not yellowing with KOH1
MICROSCOPIC: spores 6.5-8.5 × 4-5.5 microns, elliptic, smooth, basidia mostly 4-spored1, spores 6-7.5 × 4.5-5 microns, elliptic to subovoid, smooth, dark chocolate brown in KOH; basidia both 4-spored and 2-spored in a given cap (the former abundant, the latter rare), 20-24 × 7-8 microns, colorless in KOH; pleurocystidia none, cheilocystidia basidia-like or an occasional cystidium greatly enlarged (up to 20 microns broad); no clamp connections6.
Created: 2007-01-09 21:04:00 PST (-0800) by Nathan Wilson (nathan)
Last modified: 2011-03-15 11:03:29 PDT (-0700) by Erlon (Herbert Baker)
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