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Summary: Section Bivelares. Agaricus bitorquis is characterized by large size, short stout stature, whitish cap with kid leather surface, strongly inrolled cap margin, firm, unchanging flesh, band-like or sheathing ring, mild odor, fondness for hardpacked soil, and chocolate brown spore deposit. Kerrigan(3) says (with Latin words italicized) about red-staining "Marijke Nauta of the Netherlands has written to say that red-staining examples of A. bitorquis are not uncommon in her experience. However, I rarely encounter pronounced rufescence in this species in North America, and colleagues in other parts of Europe agree. A faint rufescence, or none, is more common."
It is found at least in WA but is not common. Kerrigan(1) lists for CA, Vellinga(5) lists for MI, and Phillips says it is found throughout most of North America. Breitenbach(4) give distribution as North America, Europe, and North Africa. Collections from BC are deposited at the University of British Columbia.
Cap: 4-18cm or more across, broadly convex becoming flat or with slight central depression, "margin inrolled when young, often extending beyond gills"; "white or whitish but often dirty", "not bruising yellow but sometimes discoloring sordid yellowish to tan in old age"; dry, smooth or sometimes cracking into scales, (Arora), 5-25cm across, convex with strongly inrolled margin becoming broadly convex, finally flat to uplifted; white to buff, rarely becoming faintly yellow when bruised; dry, bald or shallowly laciniate [as if cut into delicate bands] (Kerrigan), 5-10cm across, convex to flat with inrolled margin; white to dull ivory; dry, smooth, (Phillips), surface smooth like kid-leather (Chariton)
Flesh: thick, very firm; "white, not staining when bruised (but may discolor slightly)", (Arora), up to 3cm thick, firm; white, unchanging, (Kerrigan), thick; white to pale flesh-colored when cut, (Phillips), slowly staining red-brown when cut (Kibby)
Gills: free or nearly free, close; pallid, soon becoming grayish pink, then deep reddish brown to chocolate brown, finally blackish brown, (Arora), free, close, up to 1cm broad; pallid at first, finally dark blackish brown, without intervening pink stage, (Kerrigan(1)), "free, crowded, very narrow; pale pink then brown", (Phillips), pallid, soon becoming grayish lavender, then dark blackish brown, (Chariton)
Stem: 2-10(18)cm x 1-3(4)cm, "equal or slightly thicker below, but often with a narrowed or pointed base", very firm, solid; white, no scales, (Arora), 4-18cm x 1.2-3.8cm, firm, solid; white, bald above the veils, (Kerrigan(1)), 5-10cm x 1.5-2.5cm, narrowing at base; white; with a double ring, (Phillips)
Veil: "membranous, white, thick, forming a prominent, persistent, more or less median (or even basal) ring", ring band-like (upper edge free or flaring and lower edge free) or sheath-like (like a volva with only the upper edge free), (Arora), veils forming a volvate peronate sheath, more or less appressed to stem, upper limb flaring or not, sometimes with 0.1-0.3cm striate pad, lower veil boundary or limb usually not observed, in eastern North America and Europe tends not to be volvate, (Kerrigan(1)), "double ring stretched to form almost a volvalike structure at times", (Phillips), "two rings on stem, the upper edge free or flaring, the lower flared upward ", (Chariton), illustration shows a band-like ring with upper edge free and lower edge also visible, and a sheath with an upper edge below the first ring, (Kibby)
Odor: mild (Arora, Kerrigan(1)), pleasant (Phillips), pleasant, faintly almond, (Miller)
Taste: mild (Kerrigan(1), Isaacs), pleasant (Phillips), nutty (Schalkwijk-Barendsen)
Microscopic spores: spores 5-7 x 4-5.5 microns, broadly elliptic, smooth, (Arora), spores (4.5)5.8-6.0(8.3) x (4.1)4.5-5.1(6.0) microns, broadly elliptic, dark brown, hilar appendix not prominent, germ pore not evident; basidia 19-30 x 6-7.5 microns, clavate to cylindroclavate; cheilocystidia forming a continuous band, 19-30 x 6-7.5 microns, cylindric to cylindroclavate, 1-septate or not, (Kerrigan(1)), spores 5-6.5 x 4-5 microns, nearly round, (Phillips), basidia 4-spored in one collection, 4-spored or occasionally 2-spored in another, (Isaacs), basidia (2)4-spored (Breitenbach)
Spore deposit: chocolate brown (Arora), deep brown (Phillips)
Habitat / Range
single, scattered, or in groups or rows "on road shoulders, in hard-packed soil, along sidewalks, around playgrounds, and in other disturbed areas; often fruiting underground", (Arora), single to gregarious "in soil where organic matter has been incorporated, or in hard-packed soils, or along roadsides and foundations etc.", (Kerrigan(1)), "especially along roadsides, paths, in parks and towns, often in bare soil or gravel, even pushing up asphalt", July to October, (Phillips), spring, summer, fall, winter, (Miller)
A. bernardii has flesh that turns reddish, strong briny odor and contorted cheilocystidia, (Kerrigan(1)). Agaricus bitorquis is like A. campestris, but A. bitorquis lacks truly rose-colored gills, has a different ring, and has smaller spores.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2020. E-Flora BC:
Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for
Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2023-03-31 10:02:05 AM
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