Agaricus section Minores - click to expand

The smallest ones, often <5 cm. All these species stain yellow (perhaps orange), often with the colour strengthening over time. They have a sweet almond scent. KOH reaction yellow.

Species mentioned: Agaricus comtulus, micromegathus, kerriganii, semotus, diminutivus, purpurellus, dulcidulus, jacobi, comptuloides, friesianus

Agaricus comtulus EU (= A. micromegathus NY/MI?) - in grass with a bald cap. Agaricus micromegathus, with a pinkish fibrillose cap, may not be a separate species, as Rick examined a collection from CA that has the same ITS DNA sequence as A. comtulus, and we reproduced that result in WA. As you'll see below, it's not uncommon for more than one species to have the same ITS sequence and still be separate species, but in this case, the pinkish fibrils are the only difference that can be found, so perhaps they are just forms of the same species.

Agaricus kerriganii EU (=A. semotus) - possibly the largest of the small forest speices. A relatively stocky species, it can be up to 7 cm across, large for this section, and supposedly the stem will be less than twice as long as the width of the cap (although I haven't verified this). Some of the little known species below might also be stocky, so be careful of making an ID. It may also have a small bulb on the bottom of the stem and visible rhizomorphs. It used to be called Agaricus semotus but there was confusion over what that species really was, so that name was abandoned and it was renamed in honour of Rick.

Agaricus comtulus © Lauren Ré,     Agaricus 'micromegathus' © Daniel Winkler,     Agaricus kerriganii © Fred Rhoades

Agaricus diminutivus group - slender species found in forests (not grass) are common here as a group, but a confusing mess at the moment. Sometimes the fibers on the cap might be purple, even strikingly so, but that does not seem to indicate one particular species. We do not know what east coast Agaricus diminutivus really is, so we don't know if we have that species here or not. These species do not actually make a group, since they are scattered throughout the /Minores, and we need more collections of all them for further study, especially purple collections.

Agaricus purpurellus EU and Agaricus dulcidulus EU - purple species from the EU reported from the PNW, but so far none of our local sequences of purple collections match EU sequences of those species (which may be the same thing), so it is doubtful that they occur here. The purple collections we've sequenced so far are not these species.

Agaricus jacobi EU -  my collection had a lot of brown fibrils on a cap that was uniformly dark brown. A. jacobi was never suspected from North America until I found one in my front yard near Seattle, an almost exact genetic match to the Spanish type sequence.

Agaricus comptuloides WA - perhaps with a more pronounced umbo, this Seattle species is definitely found here, but we're not sure what it is. In the absence of a type sequence, we have the sequence of a specimen from Everett WA that Rick studied and thinks is a good candidate for what this species is, and it is close genetically to the newer European species Agaricus friesianus. I have a sequence of a collection with an umbo from near Mt. Rainier in WA that is 4 bp and 2 indels from the type sequence of A. friesianus so maybe that's the same thing as what Rick studied. Then we found a matching WA collection, although neither are prominently umbonate. If these collections are not A. comptuloides, we have to figure out what it really is and what these 2 collections really are. We need more umbonate collections.

Agaricus friesianus EU (=A. gracilifolius n.p.?) - Bill Isaacs started to describe a very small (<2 cm broad) A. comptuloides like mushroom (with umbo). A decades old collection by his UW professor, Dan Stuntz, with that name, has an ITS1 sequence almost the same as A. friesianus (differing by 1 bp and in 1 ambiguous location), very close to the sequence that may be A. comptuloides, as expected. A. friesianus is not described that small, so I don't know if our local collection should be called A. friesianus or if we should resurrect the name A. gracilifolius and formally describe it. Then a Spokane WA collection sequenced only 1 bp different in ITS2 than the type of A. friesianus.

Agaricus 'friesianus PNW09' - one WA collection has a sequence 2 bp different from A. friesianus' type sequence, and even further from A. comptuloides and A. gracilifolius. It was an extremely small probably immature mushroom.

Agaricus 'diminutivus PNW02' - may or may not be purple, found in WA and OR. PNW05, below, is known from a single purplish collection in OR.

Agaricus 'diminutivus PNW03' - found once in WA in hardwood leaf litter. Not much is known about it. The only collection had a reddish brown dark disc and paler cap rim.

Agaricus 'diminutivus PNW04' - found once in southern OR and twice in southern WA under conifers. Not much is known about it. The species seems pale and rather stocky.

Agaricus 'diminutivus PNW05' - our single collection from OR was purplish, like PNW02 can be. It is not known if this species will always have purple in it.

California has an additional species (like something I call A. diminutivus #1), and we probably have more that I've missed so far, since so far almost every collection I sequence seems to turn out to be a new species.

Agaricus jacobi © Danny Miller and Alan Rockefeller (2 images from CO),     A. comptuloides © NAMA & the Field Museum of Natural History, and Yi-Min Wang (2 images)

Agaricus 'diminutivus PNW02' © Buck McAdoo, normal form © Sava Krstic & Richard Tullis, and purple form © NAMA and the Field Museum of Natural History

Agaricus 'diminutivus PNW03' © NAMA and the Field Museum of Natural History,     A. 'diminutivus PNW04' © Jonathan Frank and Michael Beug,     A. 'diminutivus PNW05' © Leah Bendlin

Agaricus section Arvenses - click to expand

Larger, typically at least 10 cm at maturity (and up to 20 cm or more), but otherwise similar to section Minores: they also may stain yellow (perhaps orange) usually slowly, sometimes not at all at first, but similarly, the colour will strengthen over time. They always with a sweet almond scent that can be teased out of them at least if the flesh is crushed. KOH reaction yellow.

Species mentioned: Agaricus augustus, smithii, smithianus, subrufescens, arvensis, nivescens, osecanus, parkensis, fissuratus, coepiochraceus, crocodilinus, excellens, albolutescens, moronii, summensis, albiceps, sylvicola, macrocarpus, abruptibulbus, mesocarpus, gemellatus, didymus, sandianus

Highly pigmented, with lots of warm brown fibrils or scales

Agaricus augustus EU - this European mushroom has a very scaly cap (and usually scaly stem), and is often found in urban areas (like gardens or disturbed areas). We have found a couple of collections from BC and WA that are 2 bp different than the others and one WA collection that is 3 bp and 2 indels different. There is normally not a lot of genetic variation in Agaricus species, so we need more studies to see if we have more than one related species here. Is it significant that the stem is not scaly in some collections?

Agaricus smithianus CA (=Agaricus smithii CA) - similar, the cap and stem are usually fibrous to somewhat scaly and with even stronger orange tones than A. augustus. It is found under spruce and pine, large but slender, with a bulbous stem. This coastal California described mushroom is rare here except possibly in southern Oregon. There was an older mushroom named Agaricus smithii from England described in 1836, but that was not published with any sort of description to say what it could be, so Rick has used the name for this species. Then just to be safe he changed the name to A. smithianus so there is no confusion anymore.

Agaricus subrufescens NY - small sized scales on the cap and somewhat scaly on the stem, this east coast species is rare in CA and may extend up to the PNW in urban areas (gardens or compost, etc).

Agaricus augustus complex © Steve Trudell,     unsequenced A. smithii © Noah Siegel,     unsequenced possible A. subrufescens © Ben Woo

Agaricus sandianus NM - this montane species doesn't have scales that are as dark or highly contrasted as the previous species, but has tan scales on a white background. The stem may have a bulb, and there are subtle scales on the stem too. This NM species has recently discovered DNA from a Manning Park, BC collection and from Idaho.

Agaricus sandianus © Joe Matanzas

Whitish caps usually in grass habitats (hard to identify if not)

Agaricus arvensis EU -  uncommon European species, slightly yellowing. Its synonyms are A. nivescens, A. osecanus, and A. parkensis. It may be found near spruce, possibly without grass, complicating its identification.

Agaricus fissuratus EU (=A. coepiochraceus n.p.?) - Rick figured out that most collections named A. arvensis in the PNW were actually a different lookalike species, A. fissuratus. The differences are subtle - it yellows a little stronger, is not quite as large, the cap may be slightly fibrillose and the stem may be slightly bulbous. The best way to differentiate them is that the spores are significantly larger. Back in the 60s, Bill Isaacs started to describe A. coepiochraceus, a mushroom that was much like A. arvensis but with those same differences, known from beaches. We sequenced a decades old collection labelled A. coepiochraceus by Kit Scates (co-founder of the PNW Key Council) and it did indeed turn out to be A. fissuratus. My guess is that they are the same and Bill did not know of A. fissuratus because it was poorly understood at the time.

Agaricus crocodilinus CA (=A. excellens?) - this sometimes giant California species (up to 40 cm), more often has cracked skin when dry than the otherwise similar A. arvensis and has the largest spores. It used to be common in CA and up here in the PNW but has disappeared in the last decade and now seems to be rare, although it was found again in WA in the spring of 2022. It doesn't really turn yellow. Rick is of the opinion that the newer European Agaricus excellens is just this species and not distinct.

Agaricus arvensis © Christian Schwarz,     A. fissuratus © Fred Stevens,     A. crocodilinus © Kit Scates Barnhart (best separated by spore size)?

Whitish caps in forests, not grass - yellow staining is quicker and brighter than the subsequent species

Agaricus albolutescens OR - coastal Oregon species probably also uncommonly found near the coast in WA and BC, white cap, stocky. The ITS DNA is very similar to the A. mesocarpus group of species in the next section (as little as 2 bp different).

Agaricus moronii UT - montane Utah species also found uncommonly in the mountains of OR and WA, white cap, stocky. Best told apart by location.

Agaricus summensis CA - is reported from both the coast and in the mountains, but is not quite as stocky (it's large, but taller). It has many brown fibers on the white cap, unlike the other two species, and a clavate stem that often eventually tapers if you dig up the whole thing. It is a rare new discovery from Snoqualmie Pass. We only have montane sequences, but none from the type area of coastal California, which we should get to verify for sure that ours is the same species as in coastal CA.

Agaricus albiceps China - one ID sequence matches the Chinese type sequence very well. It was found in a grassy/deep duff area near edge of conifer woodlands.

Agaricus albolutescens © Christian Schwarz,     A. moronii © Noah Siegel,     A. summensis © Danny Miller,     A. albiceps © Krista Willmorth

Whitish caps in forests, not grass - yellow staining is duller and slow but definite or difficult to detect

Which species occur here and how to differentiate them is not well understood, and more collections of any of them would be valuable. Until recently, finds of all six of these were being called A. sylvicola, which ironically has not been confirmed from the PNW.

Agaricus cf. sylvicola EU - white, mostly bald cap, stem bulb or not. Agaricus sylvicola itself of Europe is only confirmed in California but not for the PNW. The many reports of it here have so far all turned out to be one of the below species. However, the pictured specimen has a sequence that differs from A. sylvicola only in 8 ambiguous locations, from A. PNW10 (RWK2283) in 8 ambiguous locations plus one indel, and from the type sequence of A. moronii in 9 ambiguous locations plus 1 indel. Without a stem bulb (unlike PNW10) and without strong cap pigment (unlike A. moronii) it morphologically most resembles A. sylvicola whose sequence it slightly more closely matches (no indel difference). I showed this to Rick Kerrigan and he guesses it is a hybrid "fling with a very distant relative", which he had observed in Europe and the Rockies but not on this coast before. I wonder if this will ever be found again, and we still need proof that A. sylvicola is in the PNW.

Agaricus macrocarpus EU - a European, usually larger white species (stem often >2.5 cm thick at maturity) with a slight stem bulb and not really turning yellow at all. This is a rare new discovery for the PNW where the DNA has been found twice in Victoria, where it was mistaken for A. sylvicola, which it is very difficult to tell apart from. We don't have a type sequence, so these sequences are Rick's best guess as to what probably represents this species.

Agaricus abruptibulbus NY - east coast species also found here, white cap, strong stem bulb, slow but definite yellowing on the cap of a brassy colour. Also very much like A. sylvicola.

Agaricus PNW10 (RWK2283) NM - a little known discovery near Seattle, rather large and stocky, and similar to A. abruptibulbus with a stem bulb but probably not yellowing or only slightly. The only other collection ever made was in NM.

Agaricus mesocarpus CO/gemellatus UT - montane species described from the US SW, very similar to A. sylvicola, but their white caps have appressed fibers that become more apparent as they stain yellow making them stand out in contrast to the balder cap of A. sylvicola and allies. Both type sequences have the same ITS DNA (and an almost identical sequence to A. didymus which may differ only in ambiguous locations). A. mesocarpus and A. gemellatus can be told apart by spore size so Rick is keeping them separate for now. Our three collections are a recent discovery for the PNW from near Mt. Rainier in WA, in the cascades of BC near the American border, and also near Seattle (the latter notably not a montane habitat). A microscopic analysis has not been done to identify which of the two species our three collections might be (or to determine if they are all the same or if we have both species here). Fascinatingly, the secotioid mushroom Agaricus inapertus (Endoptychum depressum) has the same ITS DNA as well, and it looks very, very different.

Agaricus cf. sylvicola © Danny Miller,     A. macrocarpus © A and O Ceska,     A. abruptibulbus © Danny Miller,     A. PNW10 (RWK2283) © Daniel Donato Antone and iNaturalist user keiradeluna

Agaricus mesocarpus/gemellatus group © Danny Miller

Agaricus section Xanthodermati - click to expand

These species stain yellow to orange (quickly or slowly) with the colour fading in time, and have a creosote/phenolic odor (unpleasant like science lab chemicals). You may have to crush the stem base flesh to detect the odor. Also try sniffing where the gills meet the stem. KOH reaction yellow. These species are poisonous.

Species mentioned: Agaricus xanthodermus, buckmacadooi, deardorffensis, moelleri, praeclarasquamosus, hondensis, subrufescentoides, cervinifolius, californicus

Agaricus xanthodermus EU - The fastest staining yellow species, not just in this section, but of all. Smoothed white capped specimens and grey fibrillose capped specimens have the same DNA and are the same species, with the difference suspected to be environmental (it may be especially susceptible to sun-scalding). It is a European species formerly found uncommonly here, but perhaps becoming more common.

Agaricus 'cervinifolius PNW06' - Known from a single sequenced WA collection under mixed conifers, cottonwood and vine maple near Leavenworth, with no matching ITS DNA anywhere in the world. Its closest relative is A. subrufescentoides. A. 'cervinifolius PNW06' has a mostly smooth whitish cap and a weak phenolic odor, but unlike A. xanthodermus, it only stains weakly and slowly yellow, if at all. It is a lookalike of Agaricus californicus, which has not yet been found in the PNW. I believe its identity is Agaricus cervinifolius OR, a little known Agaricus that has long been a mystery. It has tiny, scattered, dark scales on the cap just like the description (a different kind of scale than A. californicus has), and everything else about it is a good match, except that Zeller did not detect the phenolic odor (which may be very faint unless crushed). I will try to prove this theory by getting the type sequenced.

Agaricus xanthodermus (white form) © Daniel Winkler, (grey fibrillose form) © Kit Scates Barnhart,     A. 'cervinifolius PNW06' © Sandra Ruffner

Agaricus buckmacadooi WA - Mostly dark grey or cold grey-brown tones in the scales, can get quite large (25 cm).

Agaricus deardorffensis CA - Sometimes greyer and not as brown as the previous species, and not quite as large. Other times, almost exactly the same. Until recently, both this and A. buckmacadooi went under the name Agaricus moelleri or Agaricus praeclarasquamosus, which is a similar looking but different European mushroom. These two are so similar we never even noticed there were 2 different species until recently.

Agaricus buckmacadooi © Buck McAdoo,     A. deardorffensis © Christian Schwarz

Agaricus hondensis CA - pale reddish brown scales (more colour than the previous two), that are not too dark (but may be dark when young). In fact, it may be almost pure white, in which case the slow (at best) yellow staining separates it from Agaricus xanthodermus. Stocky appearance, cap often > 10 cm and very thick felty ring.

Agaricus subrufescentoides WA - very similar, usually with similarly coloured but darker red-brown scales, a ring that is not as thick and felty, and a fruitbody not as large or stocky as as the more neutral grey-brown Agaricus buckmacadooi (this one is often <10 cm).

Agaricus hondensis © Fred Stevens, (white capped form) © Buck McAdoo,     A. subrefescentoides © Buck McAdoo

Agaricus section Sanguinolenti - click to expand

Strong and/or quick red staining reaction. Normal mushroom odor. No KOH reaction. The one strong red stainer that doesn't belong here smells briny and is very squat (stem shorter than the cap width and almost as wide). These species are not well known yet in the PNW, and much is left to learn. Save any that you find.

Species mentioned: Agaricus thujae, haemorrhoidarius, sylvaticus subsp occidentalis, albosanguineus, benesii, bivelatoides

Agaricus thujae WA - A newly described species from WA under cedar. Slender, dark brown scaly cap, with veil remnants on the cap margin and scales on the lower stem.

Agaricus thujae © Richard Morrison

Agaricus cf 'haemorrhoidarius' EU - this is a name that has been used for a sturdy mushroom with a dark brown cap and smooth stem. Two WA collections match the description well according to Rick. However, A. haemorrhoidarius is a confusing name that is being abandoned, so whatever this is will likely need a new name of its own.

Agaricus cf 'haemorrhoidarius' © Richard Morrison

Agaricus sylvaticus EU subsp occidentalis UT - A small species (caps <5 cm across) with a pale cap (white to tan) and scaly stem. The staining is said to be pinkish-red or orangish-red. It has been found near Seattle with ITS DNA matching the UT type. This is a western subspecies of the European A. sylvaticus. One OR collection had a sequence equally distant from the EU type subspecies and our local western subspecies (only 1 bp different from each, they are very close together). I'm not sure what to make of that, but I think it makes more sense to think of them as geographically isolated subspecies or the same thing rather than considering that both subspecies may occur here.

Agaricus sylvaticus subsp occidentalis © Daniel Winkler

Agaricus albosanguineus WA/benesii EU - Do we have one species here or two?

Agaricus albosanguineus WA is sturdy mushroom with a thick, smooth stem. The staining is supposedly a more pure deep red. Despite the name 'albo' the cap may be white or brown (which will cause confusion with the darker brown A. cf 'haemorrhoidarius' when brown and the smaller A. sylvaticus subsp occidentalis when white). It was described from WA, but our attempt to sequence the type failed, so we need new collections.

Agaricus benesii of Europe is a more recent, similar species that is thought by many to be the same thing, although its stem is reportedly scaly below the ring. It also is reported as either white or brown capped in different areas. We have sequences of brown capped versions from California and Alberta, and white capped versions from Europe that match well. We need local white capped collections of this and smooth stemmed A. albosanguineus to see if they are all the same. If so, A. albosanguineus is the older name and would have priority, even though everybody is using the name A. benesii right now. Whatever they are, they are rare in the PNW.

unsequenced possible Agaricus benesii © Christian Schwarz

Agaricus cf annae EU - One Bill Isaacs (see below under Little Known Agaricus) collection from Idaho from the 60's had  than any other red-stainer, >8x4u (all the others are <6x4u). Bill tentatively identified it as A. annae, noting that the description did not really match. We need to find more large spored collections and find out what it really is.

Agaricus bivelatoides WA - the type is from WA under redwoods. It is slender with a long stem and a smooth, silver-tan broadly umbonate cap and a widening stem base with small spores (<6x4u) like most of the species in this section. It is a little known species and it is only a hypothesis that it represents a species in this section, so we need collections and sequences. No reliable photo yet.

Agaricus section Chitonioides - click to expand

A quick or strong red staining reaction, stem almost as thick as the cap is wide and very short (very squat mushroom) that grows in salty areas and smells briny itself. Inrolled cap margin. KOH negative.

Species mentioned: Agaricus bernardii

Agaricus section Bivelares - click to expand

A slow red reaction (if at all). Normal mushroom odor. The ring sometimes sheathes upwards and then outwards instead of down and out, but is always well developed (unlike the similar section Agaricus) and they usually grow in compost or disturbed areas, not deep in forests (unlike the similar /Subrutilescentes). KOH negative.

Species mentioned: Agaricus bitorquis, bisporus

Agaricus bitorquis EU - We need local samples of this mushroom to prove it matches EU sequences, but it's an ecological and microscopic match, and there are matching sequences from elsewhere in NA, probably even California, so it's very likely that's our species too. White cap, very squat, tapering stem, in hard packed, disturbed soil. Little red staining. 5-20cm or so. The thick veil is so sheathing that it can look like a volva on the bottom of the stem.

unsequenced Agaricus bitorquis from CA © Michael Wood

Agaricus bisporus EU - This is the famous European cultivated store bought button, crimini and portobello mushroom (they are all the same species, made to grow different sizes based on their environment and how much room they are given to grow). It is uncommonly found in the wild in compost or gardens. White or brownish cap, stem not as thick, tapered nor with as developed a veil as A. bitorquis. Little red staining. 5-15cm or so. Best recognized microscopically by only having 2 spores per basidium, because it's hard to recognize in the field as you don't expect to find it in the wild.

Agaricus bisporus © Fred Stevens

Agaricus section Subrutilescentes - click to expand

No staining reaction. Normal mushroom odor. KOH green. Well developed ring. Found deep in forests under conifers with dark vinaceous brown scaly caps.

Species mentioned: Agaricus subrutilescens, thiersii

Agaricus subrutilescens OR - With a shaggy stem <1.5cm wide. Up to 15cm across. Described from Oregon under various conifers.

Agaricus thiersii CA - A similar larger species (stem > 1.5cm) with a bald lower stem, described from California under pine but found rarely so far in OR, WA and BC as well.

unsequenced Agaricus subrutilescens © Steve Trudell,     A. thiersii © Susie Holmes

Agaricus section Agaricus - click to expand

No staining reaction (rarely slightly orange). Normal mushroom odor. KOH negative. The stem often tapers and the veil leaves tissue hanging off the edge of the cap but not much of a ring compared to the other subgenera. Usually found in grass.

Species mentioned: Agaricus campestris, porphyrocephalus, porphyrocephalus var pallidus, braendlei, argenteus, aristocratus, altipes, chionodermus

Agaricus campestris group - The mushrooms matching this description (mostly white) found in the PNW are mostly not the European Agaricus campestris like everyone currently believes. That species was previously only known from the Rockies in the west. So the $64,000 question is, which species do we have and how many? We need more collections of everything in this section to figure things out.

Agaricus campestris EU - the most recent sequence (as of this writing) finally found the real A. campestris, after four lookalikes were found first. An aged specimen from Victoria, BC of this smoothish, whitish capped species had browned a lot, and the photos are too small judge how fibrillose the cap was. Our sequence differs by 4 bp and 1 indel from the Spanish type sequence, but Rick says even in Europe this species has variation in ITS, so this could be the real thing. We need fresher collections.

Agaricus porphyrocephalus var pallidus PN - I think that many collections of supposed Agaricus campestris in the PNW have actually been this. This supposedly rare mushroom resembles A. campestris (smoothish, whitish cap) but the spores are much smaller, so it's surprising that the mistake has gone on so long. I don't think anybody knew there were alternatives to A. campestris, so they just never verified the spores. It has been found in WA and OR so far.

Agaricus campestris © James Holkko (2 images),     Agaricus porphyrocephalus var pallidus © Bitty Roy

Agaricus porphyrocephalus var porphyrocephalus EU - This brown fibrillose-scaly capped variety is consistently slightly genetically different. It may stain a bit orange, which confused me for a while. I found this variety a few times in WA and these are the first reports and DNA records on the west coast. No fibrillose brown capped section Agaricus species have ever been reported from the PNW. This was either overlooked before, or a recent introduction. Now that we're looking for it, it's been spotted a few years in a row, so it's probably not rare. Like var. pallidus, it has much smaller spores than any of the other species in this group.

A. porphyrocephalus var porphyrocephalus © Danny Miller

Agaricus PNW07 - three times in 2014 and 2015, this new species was found in places with grass near Eugene, OR. It is yet another brownish fibrillose capped species. It seems to be in between - less scaly than A. porphyrocephalus var. porphyrocephalus and a little more coloured and fibrillose than A. braendlei subsp. annettae, below. The most remarkable thing to me is that there were no known brown fibrillose/scaly capped "meadow mushrooms" in the PNW until recently, and in the past couple of years we've found a half dozen species. This species is currently being described and will soon have a name.

Agaricus braendlei - This species has two subspecies, a white capped one (the "normal" one, type DC) and a tan, subtly fibrillose capped variety (subsp. annettae type CA). The white capped subspecies, with similar sized spores as A. campestris, is probably one of the species mistaken for A. campestris in the past. I don't see any significant ITS differences between the two varieties, so I don't know how genetically significant the cap colour is. This species was previously called Agaricus argenteus, but that name was invalid because an older mushroom already had that name. So it was renamed A. braendlei after the person who attempted to call it A. argenteus.

Agaricus PNW07 © Bitty Roy (2 images)

Agaricus braendlei © Mariah Cady (2 images) and Danny Miller

Agaricus 'aristocratus PNW08' - This sister species to the European A. aristocratus is 8 bp different. It was found once in eastern WA. The white cap and lower stem are usually fibrillose/scaly instead of smooth.

Agaricus cf altipes EU - This white capped species grows in forests instead of grass with a long stem, but otherwise has the slightly tapering stem and poorly developed ring of this section (although the one in this photo appears to have a pretty good ring). We have one WA sequence, and NM and AK sequences, but no EU sequences to compare to to see if this is in fact that species, as Rick assumes. These photos of the WA collection don't really match the description, though, unlike a couple of NM collections which do match the description well. This collection is still a mystery.

Agaricus cf altipes © Richard Morrison

Agaricus cf chionodermus EU - DNA that Rick thinks is this species has been found so far in Boreal BC, AB, AK and CO, but not the PNW. We have no EU sequences to verify the ID.

Secotioid and Little Known Agaricus - click to expand

Species mentioned: Agaricus deserticola, inapertus, zelleri. Secotium texense. Longula texensis. Endoptychum depressum. Gyrophragmium. Agaricus cervinifolius, chionodermus, flavitingens, lilaceps, coepiochraceus, crassistipus, crocodilinus var mutabilis, fugaciovelus, gracilifolius, helodes, hotsonii, integer, involucratus, lamellodistans, subsolidipes, tennuiannulatus, brevistipes, elwhaensis

Secotioid species

Agaricus deserticola TX - this secotioid mushroom appears to be in its own section, or at least its in none of the above. Formerly Secotium texense and Longula texensis. We need collections from OR where it has been reported to check that it is the real thing, described from Texas. We also need DNA of var. major described from California to see if it is actually different.

Agaricus inapertus ID/OR - has the same ITS DNA as the "normal" species Agaricus mesocarpus and Agaricus didymus. It grows rarely in the mountains, partially underground. Its former name is Endoptychum depressum, back when secotioid mushrooms and truffles got their own genera.

Gyrophragmium - there are reports of this genus in the PNW, but it genetically represents a species of Agaricus, perhaps Agaricus zelleri, as species in this genus are not distinct enough to deserve their own genus. Save any collections you find.

Agaricus deserticola © Michael Wood,     A. inapertus © Steve Trudell

Little known species

Agaricus cervinifolius OR and Agaricus chionodermus EU - have already been discussed above

Agaricus flavitingens WA - section Arvenses, the type is from WA, but we may never know what it is as the Murrill type has turned to powder. A Smith collection labeled as this had the wrong spore size, so it probably wasn't A. flavitingens. So what was it? We'll probably never know that either, so this represents two mysteries.

Agaricus lilaceps CA - section Nigrobrunnescentes from CA was rumoured once from ID, but we need a modern collection to prove it is actually here.

Bill Isaacs

Bill Isaacs did a master's thesis on Agaricus at the University of Washington in Seattle in 1963. He described dozens of new Agaricus, but not validly published, and deposited his type collections at the Burke Museum at UW. When I tried to find them, I discovered most of them were missing, and he must have taken them with him to Michigan when he moved there without officially de-accessioning them from the Burke. When we tried to find them in Michigan, we discovered they were missing from there too. He must have taken them with him again somewhere during a subsequent move and we have lost most of them. The few we did try to sequence failed to sequence. We may never know what the following really represent, although it is expected that some or many of them would be duplicates of existing species that varied only slightly.

A. coepiochraceus (see above), A. crassistipus, A. crocodilinus var mutabilis, A. fugaciovelus, A. gracilifolius (see above), A. helodes, A. hotsonii, A. integer, A. involucratus, A. lamellodistans, A. subsolidipes, A. tennuiannulatus.

MycoMatch (MatchMaker) has all the data that is known about them. If you ever think you have found one, please save it.

Alex Smith collected a mushroom he thought could have been Isaacs' A. brevistipes n.p. It is not the type, but it was deposited in the Burke as A. brevistipes, although A. campestris was found to be written on the collection box itself. That sequence was successful, but it was simply the store bought crimini mushroom A. bisporus. Perhaps this is a footnote to give some evidence to the fact that at least some Isaacs' species are not actually novel species, but perhaps it doesn't mean anything in itself.

Agaricus elwhaensis n.p. - a Smith provisional name for a very large species much like Agaricus augustus but with a very scaly and bulbous stem. We don't have a sequence of Smith's original collection, but we do have an ITS1 sequence of one collection with this name that sequenced very close to A. augusutus except with a chunk of 10 nucleotides missing in ITS1. We should search for it again.