Trial field key to the species of AGARICUS in the Pacific Northwest

Prepared for the Pacific Northwest Key Council
by Laverne R. Chariton (North Idaho Mycological Association)
January 1992, Revised June 1997
Copyright © 1992, 1997, 2003 Pacific Northwest Key Council

Reformatted by Ian Gibson April 2003

 

 

TABLE OF CONTENTS

 Introduction

 Acknowledgements

 Key to Species

       Section A: Group 100 - Unchanging species

       Section B: Group 200 - Red stainers species

       Section C: Group 300 - Yellow stainers species

 References

 Glossary

 Index

 

INTRODUCTION

The genus Agaricus, referred to in older publications as Psalliota, is made up of a group of mostly medium sized to large saprophytic (living on dead organic matter) mushrooms, with variations in color of the pileus from white to almost black or sometimes shades of yellow, pink, brown, red to violet. The cap surfaces have appressed hyphae, radially arranged, and under varying conditions may appear glabrous, fibrillose, squamous, or areolate. They have chocolate-brown to purple brown spores, gills that are free from the stem, close, pallid to pinkish when young then colored by the spores to chocolate-brown to blackish brown at maturity. The stem is central, separates easily from the cap, and is fleshy, except in the Minores (the little guys, whose stems are thin and sometimes fragile). Flesh color is pure white or whitish unless otherwise noted. The stem may be solid, stuffed or hollow. An Agaricus will always have a ring on the stem. If evanescent, there will still be evidence that a ring had been there, such as a zone on the stipe or fragments clinging to the pileus edge. If the ring is thin, silky or cottony, it may be termed "single", meaning there would be no veil patches on the underside. When the ring is composed of two clearly visible layers of tissue , it is called "double". In some cases the under layer will have separated into colored patches on the underside of the upper layer. These rings may be skirt-like (pendant), intermediate (sub-peronate), or sheath-like (peronate).

In species identification the spore size is significant also. A microscope will give that answer.

Staining reactions should especially be noted in fresh specimens by cutting or rubbing the flesh of the cap and stalk, and in the extreme base of the stem. Some species are unchanging with rubbing or cutting. Others are rufescent (red to orange or vinaceous). Many are lutescent (yellow, yellow-orange or ochraceous) when bruised or cut, although some take as long as 15-30 minutes to stain. If chemicals are used to check the staining reaction, be sure to discard that tissue so it will not be ingested.

Odor should be noted in fresh specimens by cutting or crushing a portion of the cap tissue and the base of the stipe. Those species that emit an unpleasant odor (phenol, creosote, ink or bleach) seem to poison the majority of people who eat them. Usually there is a correlation between the intensity of lutescence and the strength of the odor. The brighter the yellow stain the stronger it smells. Any of the species that smell bad are likely to produce vomiting and diarrhea, the worst culprit being A. xanthoderma, called "the sickener". This unpleasant odor becomes more pronounced on cooking. The pleasant smelling Agaricus will be sweet, like anise or almond extract, sometimes mild, at times almost absent.

Many species grow in grassy areas, others will fruit near trees or in woodlands. Many species look very similar to others, and many are variable in size, shape and color.

The species listed in this trial key are those on record as having been collected in Washington, Oregon, North Idaho and Northern California.

 

 

ACKNOWLEDGEMENTS

In the spring of the year 1968 a friend, Elsie Coulter, who lived in Hayden Lake, called me and said "I ate my first morel today". My response to that was "What is a morel?" Elsie and I and others were lucky enough to be among the charter members of the North Idaho Mycological Association that year.

We have learned a lot since then, and have had an interesting hobby and a very rewarding way of life. Perhaps this project will in some small way give back to others help such as I received along the way from those more knowledgeable than I.

I owe unlimited gratitude to our teacher, mentor and friend, Kit Scates Barnhart. I also wish to thank Harley Barnhart for lending me his European publication written by A. Cappelli, which had the excellent color plates of so many Agaricus species. I am grateful also for being able to use the printed material of William (Bill) Isaacs, Richard Kerrigan, David Arora and others.

I also wish to include the fellow members of the Pacific Northwest Key Council who have encourage me and make helpful suggestions along the way.

 

KEY TO SPECIES

SECTIONS:

A. Flesh or surface not changing on cutting or bruising (allow 15-30 minutes); and surface not changing with age

B. Flesh or surface changing to red or red-brown

C. Flesh or surface changing to yellow or ochraceous when cut or bruised, or with age

 

 

SECTION A: GROUP 100 - UNCHANGING SPECIES

101a Cap large, 10-25 (35) cm.

................................................................................A. crocodilinus v. crocodilinus

  CAP dry; white or tinged "cinnamon-buff" over disc; surface sometimes cracking, causing it to resemble the skin of a crocodile, usually on exposure to sun; flesh firm, thick, unchanging. ODOR mildly almond. GILLS broad, ventricose, crowded, not pink at any time, pale when young, dark purple-brown at maturity. STEM 10-15 cm long, 2-4 cm thick; easily obliterated scales below ring; white, red-brown with age. RING double, membranous; white. HABITAT always in the open. EDIBLE. Agaricus sp

 

101b Cap smaller, less than 10 cm (mature specimens)

 

102a Stem with double ring

Agaricus sp
 

102b Stem with single ring

Agaricus sp

 

103a Stem equal, short, stout and smooth (see 204a)

................................................................................A. bitorquis

  CAP 5-25 cm; margin inrolled; white to gray or buff; kidskin smooth; flesh dry, firm, unchanging or slightly reddening after cutting, sometimes tough. ODOR not pronounced. TASTE mild. GILLS close, pallid at first, grayish-lavender then dark-blackish brown. STEM 4-18 cm x 1.2-3.8 cm; firm and solid, surface white; flesh of stem slowly, finally rufescent. RING two rings on stem, the upper edge free or flaring, the lower flaring upward. HABITAT urban, on hard packed ground, along roadsides, even pushing up asphalt. EDIBLE and good. Agaricus sp

 

103bStem bulbous, with or without scales

104a Stem clavate or with slight bulb, smooth

................................................................................A. integer nom. prov.

  CAP 8-15.5 cm broad; white at first then buff to light ochraceous, then pinkish gray. ODOR slightly unpleasant almond. GILLS white in button then grayish-pink. STEM 9-11 cm x 3 cm; smooth, white. RING double, cogwheel. HABITAT open grassy places, sometimes in moss. EDIBLE. Agaricus sp

 

104b Stem bulbous at base with pointed scales in rings

................................................................................A. nivescens v. nivescens

  CAP 7-12 (25) cm; shiny white then tan, bruises ochraceous; dry, silky smooth; flesh white, unchanging, thick, firm. ODOR almond. GILLS white, then pale gray to brownish-lilac, then chocolate-brown. STEM 8-9 cm x 1.5-2.5 cm; stipe as long as the width of the cap; solid; white. RING double, thick, flaring; triangular felty patches on the underside; white. CHEMICAL yellows with KOH (see 311a). HABITAT pastures, in grassy places; fall. MICROSTRUCTURES spores 5.9-7 x 4.7-5.3 um. REMARKS If ochraceous bruising is noted, this should key to 311a (A. osecanus may be the same species.) A parkensis has broadly umbonate lustrous silvery cap with brownish disc, grows near trees (Robinia, Quercus), and could key here if cap not much changed with age (see 312b). Agaricus sp

 

105a (102b) Cap white. Gills bright pink in button

................................................................................A. campestris

  CAP sometimes at maturity a dingy tan, disc brown. ODOR mild almond. GILLS pink at first, finally blackish-brown. STEM 3-11 cm x 0.5-1 cm thick; tapering to a point at base; white. RING single, evanescent, white. CHEMICAL not yellowing with KOH. HABITAT always in open areas; spring & fall East of the Cascades. EDIBLE and choice. Agaricus sp

 

105b Cap with colored fibrils (wine-brown, gray-vinaceous, cinnamon-buff, or with orange pigment). Gills usually pale pink, gray or white in button

106a Cap medium, fibrils purple-brown to wine-brown. Stipe with white wooly substance below ring (see 203a)

................................................................................A. subrutilescens

  CAP 7-13(20) cm; dry, white with large brown scales, becoming more reddish-brown (purple-brown) on whitish ground. ODOR fruity/spicy. GILLS at first pallid, then pink, then blackish-brown. STEM 8-17 cm long, 2-3 cm thick; equal to clavate; white, except apex initially pink, base aging brownish. RING subapical, rarely median; pendant, thin; white. CHEMICAL turns green slowly with KOH on pileus; not reddening, not yellowing, gills only rufescent. HABITAT sylvan, conifers or mixed hardwoods. EDIBLE delicious, but has been known to cause severe gastric upsets in some people. Agaricus sp

 

106b Cap medium or small, fibrils gray-vinaceous, cinnamon-buff, or with orangish pigment. Stipe white or flushed brownish

107a Cap medium; fibrils with orangish pigment (see 316a)

................................................................................A. smithii

  CAP 8-13 cm; dry; yellowing with age. ODOR almond-like. GILLS close; dull pinkish, then grayish, finally blackish-brown. STEM 7-15 cm x 1-1.5 cm above, 2-4 cm at abruptly bulbous base; white-yellowish at base; stuffed-hollow with age; deciduous fibrils over lower stipe; base with yellowish mycelial strands. RING subapical to supramedian; ample; pendant; white; cogwheel with tawny points. SPORES dark brown; ellipsoid. HABITAT, DISTRIBUTION mixed conifers; October to November (January); CA to OR. Agaricus sp

 

107bCap small, fibrils gray-vinaceous or cinnamon-buff. Stipe white or flushed brownish

108aCap with gray vinaceous fibrils. Stipe white, floccose above and below ring.

................................................................................A. lamellodistans nom. prov.

  CAP 3-6.5 cm; dry; scaly; flesh unchanging. ODOR odorless. GILLS white at first becoming rosy-pink, finally dark vinaceous-brown. Deeply rounded at stipe, abruptly pointed at cap margin. STEM 2.5-4 cm x 2-2.5 cm thick at apex; equal or tapering to a point at base; white, then rosy-pink, finally light brown. RING median; appressed to stipe as a broad band. HABITAT in grass under pine.  

 

108bCap with cinnamon buff fibrils, stipe smooth, flushed vinaceous-fawn to brown at base

................................................................................A. subsolidipes nom. prov.

  CAP 6-8 cm broad; fibrillose, creamy ground with darker scales; flesh unchanging. ODOR faint but disagreeable. GILLS pallid, then pink, finally chocolate-brown. STEM 5-7 cm x 1.8-2.3 cm; base narrowed, white, unchanging. RING superior; thin, narrow; occasionally with double edge; white. HABITAT on lawns. Agaricus sp

 

 

SECTION B. GROUP 200 - RED STAINERS SPECIES

201aFlesh changing quickly to red or red-brown when bruised or cut

201bFlesh changing slowly finally to red

202aCap white, then flushed dingy gray, smooth

................................................................................A. benesii

  CAP 2.5-8 cm broad; dry; margin floccose-tomentose; disc maroon; flesh stains on pileus and flesh of stipe. ODOR fruity/spicy. GILLS pale to gray-flesh in button, darkening to reddish-brown. STEM 4.5-13 cm x 1-1.5 cm; bulbous or slightly clavate; going quickly red in the upper 1/3 when cut; surface silky above ring, numerous white squamules below; basal region buff to pinky-cinnamon. RING pendant, flaring; white. HABITAT conifers and/or pine. EDIBLE. Agaricus sp

 

202bCap with red-brown overlapping scales

................................................................................A. haemorrhoidarius

  CAP large, up to 12 cm broad; appears smooth at first, breaking into scales on nearly white ground; flesh thick, firm, stains quickly cherry-red when cut. ODOR faint. GILLS white, then flesh-pink, or gray-pink. STEM 7-13 cm x 1-2 cm; equal, with narrow flattened bulb; floccose-squamose on lower half. RING pendant, persistent. HABITAT under conifers. EDIBLE and good. Agaricus sp

 

203a (201b) Stem white, densely wooly below ring (see 106a)

................................................................................A. subrutilescens

203b Stem dingy brown, smooth or possibly with fibrils

204a Stem with two rings, sheathing from below upward (see 103a)

................................................................................A. bitorquis

(formerly A. rodmani)

 

204b Stem with one ring, thick or thin on edge

205a Stature tall and slender

................................................................................A. annae

  CAP small, usually under 6 cm; surface appressed fibrillose; stains slowly red. ODOR none. STEM 7-9 cm x 1-1.5 cm; stains orange-red when cut. RING single; brown. HABITAT usually with cypress. (Has been found in the Hayden Lake, Idaho area under mixed conifers. Rare.) Agaricus sp

 

205b Stature blocky, length of stem equal to cap width

206a Stem equal, smooth streaked brown

................................................................................A. bisporus

  CAP 4-16 cm; with broad red-brown to cinnamon-brown scales. ODOR fruity spicy. GILLS pink when young, blackish brown at maturity. STEM Lighter zone above ring. RING narrow; felty; single; undersurface with wide toothed flaps that separate from the surface and point down the stem; white. HABITAT cultivated, or manure rich ground. (The wild brown variety has been collected in Post Falls and Rathdrum in Kootenai County, Idaho.) EDIBLE. Agaricus sp

 

206b Stem bulbous or club-shaped, white to dingy brown

207a Stem smooth, bulbous

................................................................................A. silvaticus

  CAP 5-10 cm; dry; smooth; nut-brown (tawny olive/fawn); scales on lighter ground; fleshfirm, thick, turns red-brown when cut, especially outer layer at stem top and just above the gills. GILLS whitish, then pale pink, then dark chocolate-brown. STEM 6-10 cm x 2-2.5 cm; white, tinged pinkish or dingy brown with age. RING sheathing striate above; white squamules under, turning gray finally. CHEMICAL not yellowing with KOH. HABITAT mixed conifer woods. Agaricus sp

 

207b Stem with fibrils, clavate

208a Stem somewhat clavate, white, densely fibrillose below ring

................................................................................A. flavitingens

  CAP 4-10 cm; dry with sordid yellow-brown fibrils; flesh stains vinaceous-pink when cut or bruised. ODOR none. TASTE nutty. GILLS pink, then dark sordid purple brown. STEM silky above the ring. RING single, thin; pallid. HABITAT with Western Red Cedar, Douglas Fir, maple and alder. Agaricus sp

 

208b Stem massively clavate, with light brown fibrils in zones

................................................................................A. lilaceps

  CAP 7-25 cm; dry; smooth with pale brown to cinnamon brown fibrils. ODOR fruity/spicy. GILLS pallid, then pale pink, then becoming reddish-brown or purple brown. STEM 5-22 cm x 3-6(9) cm; not truly scaly. RING superior; skirt-like pendant; under-surface white or yellow. CHEMICAL cuticular hyphae bright yellow with KOH. HABITAT with cypress or other trees. EDIBLE and choice. REMARKS Not as broad as A. crocodilinus, not as a tall as A. augustus, but much denser.

 

Agaricus sp

 

 

SECTION C: GROUP 300 - YELLOW STAINERS SPECIES

301a Odor unpleasant (phenolic, creosote, ink or bleach)

301b Odor and/or taste of almonds or anise, sometimes mild or none

302aCap smooth, white when young, cracking with age. Quickly staining bright yellow on all parts

................................................................................A. xanthoderma

  CAP 5-15 cm; darkens to brown; flesh spongy. ODOR strong, unpleasant, phenolic. TASTE unpleasant, phenolic. GILLS pale at first, then deep brown. STEM 5-12 cm x 1-2.5 cm; chrome yellow at base when cut; subbulbous. RING pendant with cottony underside, thick, flaring. CHEMICAL bright yellow with KOH. HABITAT lawns, at edges of paths, in gardens, at edges of woods; August to December. POISONOUS (Can cause sweating, nausea, and severe stomach cramps.) Agaricus sp

 

302b Cap with colored fibrils. Stem yellows only at top or base

303a Cap with honey-brown, red-brown, or cinnamon-brown fibrils. Stem top staining yellow when cut

................................................................................A. helodes nom. prov.

  CAP 4-12 cm broad; dry. ODOR unpleasant, phenolic. TASTE mild almond. GILLS pallid, then wine-pink. STEM 7-15 cm x 0.5 to 1-1.5 cm; surface silken-shining at apex; lower surface with scattered loose fibrils of shining white. RING superior; flaring; upper surface striate, undersurface cottony; not truly double. CHEMICAL bright yellow with 3% KOH. HABITAT conifers, needle duff. Agaricus sp

 

303b Cap with fawn-brown or silver-gray fibrils. Stem base yellowing when cut

304a Cap with fawn-brown fibrils on pale to buff ground

................................................................................A. hondensis

  CAP 4-15 cm; with fawn-brown fibrils on pale to buff ground; smooth at first. ODOR creosote or phenol; unpleasant. TASTE metallic. GILLS white in buttons, then pinkish, finally lilac-gray to reddish-brown or chocolate-brown. STEM 6-15 cm x 0.5-2.5 cm; smooth, without scales; equal or slightly bulbous to massively bulbous (up to 4 cm thick). RING thick, felt-like, flaring. CHEMICAL bright yellow with 3% KOH. HABITAT low elevation, conifer duff. POISONOUS. REMARKS A handsome forest mushroom but can cause serious gastro-intestinal distress. It is a lookalike to A. haemorrhoidarius, the edible one with reddening flesh and pleasant odor. Agaricus sp

 

304bCap with silver-gray to gray brown fibrils

305a Cap with silver-gray to gray-brown fibrils on lighter ground

................................................................................A. praeclaresquamosus

(A. meleagris is a synonym.)

  CAP 5-20 cm; with silver-gray to gray-brown fibrils on lighter ground; flesh bruising bright yellow in base of stem, pinkish with age. ODOR unpleasant, phenolic, ink-like, (especially when cooked). GILLS pale gray to pink, then chocolate-brown. STEM 7-18 cm x 1-3 cm; equal to clavate; smooth; white to reddish-brown. RING thick, felt-like, flabby; cogwheel; white. CHEMICAL cap surface yellowing with KOH. HABITAT conifer forest edges or lawns; September to December. POISONOUS. Agaricus sp

 

305b Cap with inrolled margin, yellowing or with bicolor flesh

306a Cap white with gray-brown fibrils. Gills pallid in button stage

................................................................................A. californicus

  CAP 3-9(12) cm; at first marshmallow shaped expanding to broadly convex, plane or broadly umbonate; dry, smooth, white to silvery-gray with gray-brown center then red-brown; flesh thick, white, unchanging or yellowing slightly when bruised. ODOR faintly phenolic. GILLS pinkish-brown after veil breaks; chocolate-brown at maturity. STEM 3-8(12) cm x 0.5-1(1.5) cm; equal; smooth; white; often crooked. RING persistent; superior or median; skirtlike. HABITAT found in lawns, gardens and woods; year round in California. Mildly POISONOUS. Agaricus sp

 

306bCap with cinnamon-brown fibrils. Gills grayish

................................................................................A. crassistipus

  CAP 9-20 cm; margin abruptly inrolled; dry; rich, dark cinnamon brown squamules against flesh colored ground; darker on disc; pileal surface turning yellow slowly when bruised. ODOR phenolic. GILLS pale grayish to gray-vinaceous then dark reddish-brown. STEM smooth and silken above annulus; two band-like zones of concentric scales below; white, soon flushed grayish flesh color, where bruised becoming yellow then rufescent, the yellow mostly in the upper portion of the stipe, the rufescence in the stipe base and the cap. RING median to inferior, thick, recumbent, smooth, striate, white. HABIT, HABITAT gregarious to subcespitose; in grass under Douglas Fir to Western Red Cedar. September through November.  

 

307a (301b) Stature large. Cap usually more than 10 cm

307b Stature small to medium. Usually 10 cm or less

308a Cap white, or creamy (yellow or tan at maturity); smooth or warty, cracking with age

308b Cap with yellow-brown, orange-brown, or dark-brown fibrils or scales

309a Stem lacking scales. Cap 15-20 cm

................................................................................A. crocodilinus v. mutabilis

  CAP thick; convex; white to dull tan with small appressed scales; flesh bright yellow where bruised. ODOR burnt almond or wet straw. GILLS tinged wine-pink at first, then dark brown. STEM lacking scales. RING median to superior, flaring, thick. HABITAT pastures or fields. Agaricus sp

 

309b Stem base scaly or woolly below annulus, at least when very young, and cap usually smaller

310aStem with rings of minute scales; growing in grass or woods

310b Stem woolly (sometimes only sparsely ringed with wooly substance in button stage)

311aStem spindle shaped with scales in rings below double annulus, in grassy places

................................................................................A. osecanus

  CAP 7-14 cm; white with minute squamules; tawny with age; flesh yellowing slightly or not. ODOR faintly sweet almond. GILLS pale, then grayish, then dark chocolate-brown. STEM 4-8(10) cm x 1.5-3.5 cm at base; solid. RING white. CHEMICAL cap yellowing with KOH. HABITAT in grassy places. EDIBLE best in button stage as mature specimens sometimes have a musty odor. REMARKS Kerrigan says A. nivescens may be the same species, and it would key here if it bruises ochraceous. Agaricus sp

 

311bStem slightly clavate or equal to slightly bulbous; silky above and/or finely floccose below annulus, in woods or near trees

312aCap white, turns lemon yellow on bruising

................................................................................A. excellens

  CAP 10-15 cm; silky; beautifully white, then with sulfur yellow tinge; margin with dentate border. ODOR faintly almond. GILLS flesh color, then blackish-brown. STEM 10-14 cm x 3-4 cm; slightly clavate; white; silky at apex; flesh in lower part of stem pinkish. RING pendulous, thick at edge; white. HABITAT in woods; August to October; infrequent. Agaricus sp

 

312b Cap silvery white to lustrous grayish

................................................................................A. parkensis

  CAP 6-10 (15) cm; with broad umbo; fibrils lustrous forming concentric zones; cap buff with age; flesh unchanging. ODOR & TASTE almond. STEM 9-12 x 1.5-2 cm above, 1.5-2.5 cm below; equal to slightly bulbous; unchanging, stuffed hollow; smooth, silky above, finely floccose below. RING supramedian, pendant; cogwheel; white. CHEMICAL flesh pale yellow with KOH. HABIT, HABITAT gregarious; near trees, associated with locust (Robinia) and oak. Agaricus sp

 

313a(310b) Stem equal or slightly enlarged at base

................................................................................A. arvensis

  CAP (7)10-20 cm; white, then yellowish to buff; dry glabrous; stains or bruises yellow when young; ages yellowish. ODOR sweet almond (some say bitter almond when young), often musty with age. TASTE sweet, excellent. GILLS white, rarely pink, later grayish, finally dark blackish-brown. STEM 10-17 cm x 2-3 cm; small cottony scales midway to base in button stage. RING double, broadly flaring; cogwheel; white or tinged yellow with cottony patches on underside. CHEMICAL cap surface yellowing with KOH. HABITAT grasslands. EDIBLE for most people but causes gastric upset in some people. REMARKS There are two forms in the Pacific Northwest. Mainland: Tall and slender with thin pliant ring that bruises yellowish if rubbed hard. Islands: Squat with thick ring, bruises quickly. Agaricus sp

 

313b Stem with marginate/rounded bulb

................................................................................A. coepiochraceus nom. prov.

  CAP 7.5-15.5 cm; margin inrolled when young, nearly plane at maturity; creamy yellow, becoming ochraceous; dry; smooth at disc; appressed fibrils at margin. ODOR faintly to distinctly almond; disagreeable on staining. TASTE almond. GILLS pallid, gray-flesh color at first, then cinnamon-drab, then dark brown. STEM 7-16 cm x 2.5-4.5 cm; silken, creamy at apex; base cottony, mustard yellow where bruised. RING double, pendant, flaring, thick, cogwheel. CHEMICAL bright yellow with KOH. HABITAT Beaches. REMARKS Similar to A. excellens and the tall slender form of A. arvensis, differing in the ochraceous color, marginate bulb stipe base and beach habitat; bruises honey-yellow. Agaricus sp

 

314a (308b) Stem glabrous to silky

................................................................................A. cervinifolius

  CAP 10-20 cm broad; hemispheroid; dark brown appressed scales; yellowish when bruised; flesh thick at disc, thin at margin. ODOR & TASTE pleasant. GILLS pale vinaceous-fawn, then fawn to cinnamon-drab, finally dark purple-brown. STEM 8-16 cm x 2-3 cm; slightly bulbous; whitish gray to mouse-gray when older, bruising reddish-brown when handled. RING superior, collar-like; white, stained brownish where bruised. HABITAT at margins of conifer forests or horse pastures in November in Oregon; infrequent.  

 

314b Stem floccose or scaly

315a Stem rarely enlarged at base, up to 30-35 cm long

................................................................................A. augustus

  CAP 8-32 cm; marshmallow shaped in button; with abundant dark-brown scales on whitish to yellowish ground, sometimes brown-yellow where bruised or cut; flesh thick, meaty. ODOR fragrant almond-anise. GILLS pallid, briefly flesh color, later gray-brown, then blackish-brown. STEM 1-4 cm thick, equal; smooth above, floccose but not truly scaly below, tinged brownish. RING subapical, double, pendant, flaring, white with thick patches of pointed tips on underside. CHEMICAL immediately bright yellow with KOH. HABITAT in duff under conifers, in trash heaps and disturbed soil. EDIBLE and choice, but causes gastric upset in some people. Agaricus sp

 

315b Stem equal above bulbous base, usually not over 15 cm long

316a Stem smooth above ring, deciduous fibrils below (see 107a)

................................................................................A. smithii

  CAP 8-13 cm; with orangish cuticular pigment; abruptly bulbous stipe base; yellows with age. Look-alike A. subrufescens is usually smaller, with pinkish buff cap, rather stocky stature, and smaller spores (5.3-7.5 x 4.1-4.9 um as opposed to 6.4-9.8 x 4.5-6.4 um for A. smithii and 6.8-10.5 x 4.5-6.8 um for A. augustus).  

 

316bStem with buff wooly patches in rings below double annulus with blunt edge

................................................................................A. elwhaensis nom. prov.

  CAP 12-35 cm; many dark-brown scales on pale ground; disc appressed; fibrillose; just under cuticle stains bright yellow, then orange. ODOR & TASTE mild almond. GILLS pale then grayish-wine. STEM 15 cm x 2 cm thick; equal above large submarginate bulb, tapering to short blunt soil insertion. RING superior, flaring; buff colored; upper surface satiny, lower surface felty; broken into areolate patches near margin. HABITAT in needle duff under Douglas Fir. EDIBLE. Agaricus sp

 

317a (307b) Cap medium: 6-10 cm

317b Cap small: 6 cm or less

318a Cap with appressed scales; buff

................................................................................A. tenuiannulatus nom. prov.

  CAP 8-12 cm; smooth; apex cracked with age; scales remaining appressed for life; button cushion shaped; slowly bruising ochraceous. ODOR slightly unpleasant almond. TASTE good. GILLS grayish in button then gray-brown. STEM 4-7 cm x 1-2.5 cm; white streaked yellowish with age; silky, smooth; slowly changing to pale ochre when handled or bruised; slight club at base. RING single; felty; fragile, evanescent. CHEMICAL cap surface yellows with KOH. HABITAT in lawns, cultivated areas. EDIBLE. REMARKS A. subrufescens sometimes larger, with distinct almond odor, strongly sweet or taste of green nuts; smaller spores than A. augustus. Agaricus sp

 

318b Cap smooth and white

319aStem minutely fibrillose to floccose below ring, robust. Cap stains quickly amber then yellow with age

................................................................................A. albolutescens

  CAP 9.5-10.5 cm; margin incurved when young; silken, smooth; white then tan; flesh where rubbed or cut turning intensely yellow. ODOR & TASTE pleasant almond-anise; older specimens disagreeable, like wet straw. GILLS grayish to grayish-rose, then reddish-brown. STEM 11-18 cm x 1.5-2 cm; base massively bulbous; satiny above annulus; white becoming tan in spots, yellow where bruised. (Thicker stipe than A. silvicola.). RING superior, double, flaring; undersurface areolate-patched; white, then buff. HABITAT in dense conifer woods. EDIBLE and choice, but some people adversely affected. Agaricus sp

 

319b Stem smooth or floccose, stature slender or average. Cap staining slowly amber or yellow

320a Stem smooth with abrupt bulb at base

................................................................................A. silvicola

(A. abruptibulbus is a synonym.)

  CAP 5-6 cm; shiny, white, soon sulphur yellow, dark lemon yellow on bruising. ODOR anise. GILLS long pale, then pinkish buff, then dark, finally blackish-brown. STEM 6-8 cm x 1-1.5 cm; with mycelial strands attached; hollow; white, sometimes reddish above ring; lemon yellow when bruised. RING superior, pendulous; white; with or without white or yellowish scales. HABITAT in dense conifer forests. EDIBLE with caution. (Be sure there is no volva, and that the gills are not white in mature specimens. The deadly Amanitas can be very similar in size, shape, and color.) Agaricus sp

 

320bStem smooth or floccose, equal or tapered

321a Stem about 7 cm long, smooth, equal. Staining violet at base

................................................................................A. fugaciovelus nom. prov.

  CAP 7-9 cm; dry; white, then amber-white, finally lemon yellow. ODOR not notable. GILLS soon rosy pink, then slate-violet, finally brownish-drab. STEM 7cm x 1.5-2 cm; smooth, white, staining yellow near ring. RING lacking entirely when partial veil remnants adhere to pileal margin. When there is a ring, it is superior, narrow, flaring, with thick floccose-silky edge and stains intensely yellow. HABITAT In needles under cedar. REMARKS Similar to A. coepiochraceus but lacks the flat marginate stipe base, has different coloring, and lacks the thick, persistent annulus of that species. Agaricus sp

 

321b Stem 5.5 cm or less, floccose toward base, tapered, unchanging on cutting

................................................................................A. campestris v. lutescens nom. prov.

  CAP 3.5-5.5 cm; smooth white, with distinct yellow staining when bruised. ODOR pleasant or none. GILLS broad, white, then pink, finally vinaceous-brown. STEM equal or tapered; satiny above, floccose toward base; white; flesh of stipe unchanging on cutting. RING single; thin, evanescent. HABITAT Artemesia-Agropyron shrub-steppe and Salix communities of Grant County, WA. REMARKS Very similar to A. equestris, differing as to color change, and the broad gills, and A. equestris yellows only at maturity. Agaricus sp

 

322a (317b) Stem base with small bulb and small volva; rare

................................................................................A. involucratus nom. prov.

  CAP 3.5 cm; smooth, suede-like; dingy white; dry; flesh thick and firm, yellowing slightly where bruised. ODOR inodorous. GILLS dingy, pale salmon-pink. STEM 3.5-4 cm long x 1.2-1.3 cm thick with 1.5 cm bulb at base. RING thin, membranous, sheathed both up and down; brown. HABITAT in bare soil. EDIBILITY not recommended as edible because of resemblance to the poisonous Amanita species. Agaricus sp

 

322b Stem base various, lacking a volva

 

323a Growing in grassy areas (lawns, meadows, etc.)

323b Growing in forested or wooded areas

324a Cap at first convex; white when young then buff with a few brownish squamules, brown-yellow on bruising; gills brown-pink when young

................................................................................A. comptulus

  CAP 2-5 cm broad; sometimes with universal veil remnants on margin; white young then buff with a few brownish squamules; creamy yellow to ochraceous where bruised. ODOR faintly almond-anise. GILLS at first pink, then reddish-brown to blackish brown with age. STEM 3-4 cm x 0.5-0.7 cm; whitish, yellowing slightly at base; equal. RING pendulous; thin, flaring. CHEMICAL quickly bright yellow with 15% KOH. HABITAT always in grass; infrequent. EDIBLE. Agaricus sp

 

324bCap at first pulvinate (disc flattened), with fibrils pinkish-red, in age darkening to gray-brown or darker brown; sometimes bruises yellowish, gills "grayish when young, soon pinkish" (Peck)

................................................................................A. micromegathus

  CAP 2-6 cm broad; streaked with tiny vinaceous-brown scales; surface bruises saffron yellow to ochraceous; flesh thin and fragile; unchanging or bruising yellowish. ODOR sweet almond-anise. GILLS grayish then pinkish, finally chocolate-brown or red-brown. STEM 2.5-3 cm x 0.2-0.8 cm; equal or thickened at base; fibrillose; white. RING single; cottony and delicate. CHEMICAL is bright-yellow with 3-15% KOH. HABITAT in grass, open fields. EDIBLE. REMARKS A. peckii nom. prov. has larger spores, tastes nutty and is negative with KOH. Agaricus sp

 

325a (323b) Cap diameter less than 3 cm; gills very narrow ( 1 mm broad); rare

................................................................................A. gracilifolius nom. prov.

  CAP usually 2 cm; rosy-lilac between brown umbo and whitish margin. GILLS subdistant; pink then grayish violaceous pink. STEM 3.5 cm x 0.3 cm; equal or with slightly thickened base; white on yellowish ground. RING superior, ample; white to pallid. CHEMICAL Cheilocystidia brownish yellow with KOH. HABITAT on leaf mold. Agaricus sp

 

325b Cap diameter more than 3 cm; gills broader than 1 mm

326a Stature comparatively tall & slender (stem diameter less than 4 mm but length 1.5-2.5 x cap diameter)

326b Stature more average (stem diameter more than 4 mm and length approximately equal to cap diameter)

327a Cap umbonate-mammillate (with breast & nipple shape); (hyphae of annulus lacking orange inclusions when dried material is mounted in KOH); rare

................................................................................A. comptuloides

  CAP 3-4 cm; with pinkish-brown umbo, surface rosy-isabelline; slightly fibrillose. ODOR not noted. GILLS in age blackish-brown. STEM 7 cm x 0.4-0.5 cm thick; smooth; white then yellow where handled or in age; pinkish above ring. RING pendant; white, scant. HABITAT in mixed evergreen litter. Agaricus sp

 

327b Cap not umbonate; (hyphae of annulus filled with orange inclusions when mounted in KOH); frequent

................................................................................A. diminutivus

  CAP 2.5-4 cm; with amethyst-gray fibrils, purplish-pink at disc with appressed pink or rosy-red scales, yellowing where bruised; margin incurved. ODOR pleasant almond. GILLS grayish-pink at first then reddish-black. STEM 3-5 cm x 0.1-0.3 (0.4) cm thick; smooth; equal to slightly rounded-bulbous base becoming yellowish. RING superior; white, apricot-orange on drying or with age. CHEMICAL lamellar section intensely dark yellow with 3% KOH. HABITAT under conifers. REMARKS Look-alike A. hotsoni has spores with evident truncate distal end. Rare. Agaricus sp

 

328a(326b) Stem clavate; cap creating fibrillose appearance until very mature; background color white, bruising yellow, aging drab and bruising orange; frequent

................................................................................A. semotus

  CAP 2-5 cm; silky, fibrils reddish-brown, rosy-grayish at disc and margin; buttons convex to semi-cylindrical; flesh brittle. ODOR & TASTE distinct anise. GILLS grayish-wine, pruinose. STEM 5-7.5 cm long x 0.5-0.7 cm thick. RING single, flaring, evanescent. CHEMICAL bright yellow with KOH. HABITAT under conifers or mixed trees, under oak. EDIBLE. Agaricus sp

 

328b Stem equal to a rounded bulbous base; fibrils grouped in small batches to create slightly squamulose look; background color of margin light grayish, bruises ochraceous

................................................................................A. purpurellus

  CAP 4-4.5 cm; wine red at disc; buttons cushion shaped. ODOR daintily fragrant anise. GILLS pale grayish-wine then reddish. STEM 3.5-7 cm x 0.5 cm thick; white or pallid, often staining yellowish; sometimes slightly tufted at base. RING single, thin, evanescent; white. CHEMICAL yellow with KOH. HABITAT open woods. EDIBLE but may be confused with species of Inocybe, most of which are poisonous. REMARKS A. amethystina and A. purpurellus are considered part of the A. diminutivus group because of their petite size, red to purplish cap color, and woodland habitat. Both yellow with KOH. Agaricus sp

 

REFERENCES

  1. Arora, David. 1986 Mushrooms Demystified Second Edition. Ten Speed Press, Berkeley.
  2. Isaacs, Bill Forgust. 1963. A Survey of Agaricus in Washington, Oregon, and California. Thesis for Master of Science, University of Washington.
  3. Kerrigan, Richard W. 1986. The Agaricales (Gilled Fungi) of California. 6. Agaricaceae. Mad River Press. Eureka, California.

 

GLOSSARY

annulus - ring or collar or tissue on stipe formed by ruptured veil

appressed - flattened down (ironed down)

areolate - cap surface marked with cracks

clavate - like a caveman's club

concentric - having teeth or pointed projections

conifer - cone bearing

dentate - having rings or zones

disc - center of the cap

dry - cap or stalk neither viscid or hygrophanous

evanescent - soon disappearing

fibril - thin threadlike fiber

fibrillose - cottony or wooly

hygrophanous - watery appearance when moist, opaque when dry

hyphae (plural) threadlike fungal cells

marginate - having a distinct margin

membranous - thin and pliant

ochraceous - yellow-orange with a brownish tinge

pendant - hanging down, skirt-like

pruinose - looking as if finely powdered

pulvinate - disc flattened, cushion shaped

recumbent - hangs down, rests on surface from which it extends

rufescent - becomes reddish

scabrous - roughened by short projecting scales

squamous - furnished with scales, scaly

striate - ridged, marked with lines or grooves

terete - cylindrical and usually tapering at both ends

tomentose - covered with hairs

truncate - larger portion ending as if cut off, having the end square

ventricose - markedly swollen or inflated

vinaceous - the color of wine

 

INDEX

 

 GENUS AND SPECIES KEY ENTRIES
   
 AGARICUS L.  
    A. abruptibulbus (see A. silvicola)  
    A. albolutescens Zeller 319a
    A. annae Pilát 205a
    A. arvensis Schaeffer 313a
    A. augustus Fr. 315a
    A. benesii (Pilát) Singer 202a
    A. bisporus (Lange) Imlach 206a
       = A. brunnescens Peck  
    A. bitorquis (Quélet) Sacc. 103a, 204a
       = A. rodmani Peck  
    A. brunnescens (see A. bisporus)  
    A. californicus Peck 306a
    A. campestris Fr. 105a
    A. campestris v. lutescens nom. prov. Isaacs 321b
    A. cervinifolius (Zeller) Hotson 314a
    A. coepiochraceus nom. prov. Isaacs 313b
    A. comptuloides Murrill 327a
    A. comptulus Fr. 324a
    A. crassistipus nom. prov. Isaacs 306b
    A. crocodilinus Murrill v. crocodilinus 101a
    A. crocodilinus v. mutabilis nom. prov. Isaacs 309a
    A. diminutivus Peck 327b 327b
    A. elwhaensis nom. prov. A.H.Sm. 316b
    A. excellens (Moeller) Moeller 312a
    A. flavitingens Murrill 208a
    A. fugaciovelus nom. prov. Isaacs 321a
    A. gracilifolius nom. prov. Isaacs 325a
    A. haemorrhoidarius Schulz. apud Kalchbr. 202b
    A. helodes nom. prov. Isaacs 303a
    A. hondensis Murrill 304a
    A. hotsoni. nom. prov. Isaacs 327b
    A. integer nom. prov. 104a
    A. involucratus nom. prov. Isaacs 322a
    A. lamellodistans nom. prov. Isaacs 108a
    A. lilaceps Zeller 208b
    A. meleagris (see A. praeclaresquamosus)  
    A. micromegathus Peck 324b
    A. nivescens v. nivescens (Moeller) Moeller 104b, 311a
    A. nivescens v. parkensis (Moeller) Moeller (See A. parkensis)  
    A. osecanus Pilát 104b, 311a
    A. parkensis (Moeller) Kerrigan 104b, 312b
    A. peckii nom. prov. Isaacs 324b 324b
    A. praeclaresquamosus Freeman 305a
       = A. meleagris (J. Schaeffer) Imlach  
    A. purpurellus (Moeller) Moeller 328b 328b
    A. rodmani v. rodmani (see A. bitorquis)  
    A. semotus Fr. 328a
    A. silvaticus Schaeff.: Fr. 207a
    A. silvicola (Vitt.) Peck 320a
       = A. abruptibulbus Peck  
    A. smithii Kerrigan 107a, 316a
    A. subrufescens Peck 316a, 318a
    A. subrutilescens Kauffman 106a, 203a
    A. subsolidipes nom. prov. Isaacs 108b
    A. sylvaticus (see A. silvaticus)  
    A. sylvicola (see A. silvicola)  
    A. tenuiannulatus nom. prov. 318a
    A. xanthoderma 302a 302a

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