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Summary: Section Arvenses. Agaricus augustus is distinguished by 1) large size, 2) a yellow staining cap with fibrils or scales that are dark brown to warm brown or tawny brown, 3) gills that are pallid, sometimes briefly pinkish, and then grayish brown and chocolate brown from spores, 4) a stem that is smooth in its upper part and shaggy with white or brown-tipped scales in its lower part, 5) a prominent skirt-like ring, 6) an almond odor, and 7) growth in disturbed soil. Agaricus perrarus Schulz. is given as a synonym by Breitenbach(4) and other European authors, but A.H. Smith showed that the material he named A. perrarus was different and this material has been renamed Agaricus smithii Kerrigan. |The odor of A. augustus is due to benzaldehyde which can be perceived as anise by some or as the usual almond odor (Wood(1)). |A. augustus is common in the Pacific Northwest.
It has been found in BC, WA, OR, and CA. There are collections from BC at the University of British Columbia and from WA, OR, and VA at the University of Washington. Lincoff(2) says it is found from BC to CA, in the Rocky Mountains, and reportedly in eastern North America. Breitenbach(4) give the distribution as North America, Europe, Asia, and North Africa.
Cap: 7-30(40)cm across, "usually marshmallow-shaped but sometimes convex", expanding to flat or with an uplifted margin; "covered with numerous dark brown to warm brown or tawny-brown fibrils or fibrillose scales" on a white background that usually becomes yellowish, buff, or ocher when old, "giving an overall golden tone to many mature specimens", center often darker; may bruise yellow when rubbed, especially when young; dry, "surface sometimes breaking up into warts in dry weather", (Arora), 8-32cm across, at first nearly spherical or more cylindric, then convex to broadly convex, finally flat to uplifted, margin sometimes wavy; at first medium brown, later darker brown, or dark brown when old, on whitish background, sometimes becoming bright yellow when bruised or cut, often tawny when old, typically yellowish to orange after drying; dry, appressed-fibrillose becoming appressed-fibrillose-squamulose when mature, scales about 0.5cm long, with pointed tips, "or alternatively forming large patches of fibrils", or sometimes areolate [cracked like dried mud] if dried out, (Kerrigan)
Flesh: thick, firm, white, (Arora), up to 3cm thick, firm when young; white, sometimes becoming yellow near cuticle after exposure, in stem white, occasionally yellowish somewhat near cuticle or base when cut, (Kerrigan)
Gills: free when mature, close; pallid, sometimes briefly pinkish, finally turning grayish brown, eventually chocolate brown to blackish brown, (Arora), free, close, up to 2cm broad; pallid when young, occasionally briefly pink, later grayish brown, finally dark blackish brown, with pallid margin, (Kerrigan(1))
Stem: 8-35cm x 1-4(6)cm, equal or widening slightly downward, rather tough, fibrous, base usually deep in ground; "white but often aging or bruising yellowish"; "smooth above the ring, sheathed with white or brown-tipped scales below (but these often wearing away in age)", (Arora), 10-35cm x 1-4cm, equal, rarely widened in lower part, stuffed-hollow, somewhat fibrous, base deeply rooted; white, sometimes briefly pink near top after veil rupture, becoming pale yellowish when old; bald in upper part, under humid conditions completely covered in lower part with erect floccose squamules [woolly-cottony fine scales], (Kerrigan(1))
Veil: "membranous, with white to brown cottony patches on underside (but these sometimes disappearing)", forming a large, ample, superior, skirt-like ring, (Arora), "veils forming a thick, broadly flaring, pendant, subapical to supramedian, white annulus", partial veil smooth above, 0.1-0.2cm thick, universal veil a loosely interwoven, floccose-rimose layer, with a zone of thicker (about 0.2-0.3cm thick) patches near ring margin, or sometimes appendiculate [hanging] on cap margin, patches white to colored as cap, universal veil also leaving "a continuous covering of deciduous, white or brown-tipped, pointed, fibrillose-floccose squamules" below ring, (Kerrigan(1)), double, thick patches of pointed tips on underside, (Chariton)
Odor: "sweet (like almond extract), especially when young", (Arora), of almonds (Kerrigan(1)), pleasant, of almonds, (Phillips), anise (Hotson), anise or almonds (Miller)
Taste: pleasant, of almonds, (Phillips), mild (Miller)
Microscopic spores: spores 7.5-10 x 5-6 microns, elliptic, smooth, (Arora), spores (6.8)7.7-9.4(10.5) x (4.5)5.1-6.0(6.8) microns, elliptic approaching elongate, dark brown, hilar appendix prominent, germ pore not evident; basidia 4-spored, 18-22 x 9-10 microns, clavate to broadly clavate; cheilocystidia abundant, continuous, 6-30 x 6-22 microns, mostly elongate, sometimes shorter, to nearly spherical, short-catenulate, (Kerrigan(1)), basidia predominantly tetrasporic (Kerrigan(3))
Spore deposit: chocolate brown (Arora)
Habitat / Range
single or in groups or clumps on ground in woods, but usually near roads and paths, in clearings, and other places where soil disturbed, sometimes in flower beds, composted areas, under trees in towns, in arboretums, etc., (Arora), single to gregarious or cespitose [in tufts], in litter under Sequoia, Picea (spruce), Tsuga (hemlock), or occasionally Quercus (oak), or under planted Cupressus (cypress) or Pinus (pine), usually near roads or paths, or rarely in lawns near trees, fruiting year round, (Kerrigan(1) for California), spring, summer, or fall, (Miller)
Agaricus moelleri group has grayer cap fibrils, a smoother stem and smells like phenol, (Arora). Agaricus subrufescens is usually rather stocky and has a minutely scaly, pallid to pinkish buff cap, (Kerrigan(1)). A. subrufescens is paler than A. augustus, and has a smoother stem and smaller spores, (Arora). Agaricus smithii is "very slender, with an orangish cuticular pigment and an abruptly bulbous stipe base", (Kerrigan(1)). Agaricus julius Kerrigan is a large mushroom that grows at high elevations in the western interior mountain ranges (Sangre de Cristo Range and Rocky Mountains), NM, CO, and northward into AK. It has been called "The Prince" in Colorado. As that English name suggests it is most similar to Agaricus augustus, but has larger spores measuring (6.6)8.2-8.7(10.3) x (6.0)6.3-6.6(7.1) microns and can have a more rounded, fleshier cap. (Kerrigan(3)). A less similar but also large mushroom sometimes found at high altitudes or latitudes is Agaricus summensis Kerrigan. "The large size, tall stature, thick, clavate stipe with pointed base, and pronounced yellow-orange discolorations are the main field characters." It has the most obviously fibrillose cap surface among related species. It was described from coastal CA, but appears to be very similar to sequenced specimens from UT, CO, and AK. (Kerrigan(3)). See also SIMILAR section of Agaricus crocodilinus, Agaricus ''elwhaensis'', Agaricus ''tenuiannulatus'', and Agaricus xanthodermus.
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:
2023-12-01 4:50:56 AM
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