As of 2018, this genus is divided into 6
subgenera and more than 20
sections: are found in a variety of often rather
arid habitats, and typically have a smooth white to scaly light brown cap. The flesh, when bruised, usually turns distinctly yellow to pinkish in particular on the cap, while the end of the stalk may remain white; a marked yellow stain is caused by applying KOH. Their sweetish smell of almond extract or
marzipan due to
benzaldehyde and derived compounds distinguishes them from the section
Xanthodermatei, as does a bright dark-orange to brownish-red coloration in Schäffer's test. Many members of this subgenus are highly regarded as food, and even medically beneficial, but at least some are known to accumulate
cadmium and other highly toxic chemicals from the environment, and may not always be safe to eat. Peck 1873'' Fr. 1836/1838'' '
Subgenus Minores''''' :A group of buff-white to reddish-brown species. Often delicate and slender, the typical members of this subgenus do not resemble the larger
Agaricus species at a casual glance, but have the same telltale chocolate-brown gills at spore maturity. Their flesh has a barely noticeable to pronounced sweetish smell, typically
almond-like, turns yellowish to brownish-red when cut or bruised at least in the lower stalk, yellow to orange with KOH, and orange to red in Schäffer's test. Species such as
A. aridicola (formerly known as
Gyrophragmium dunalii),
A. colpeteii,
A. columellatus (formerly
Araneosa columellata),
A. diminutivus,
A. dulcidulus,
A. lamelliperditus,
A. luteomaculatus,
A. porphyrizon,
A. semotus and
A. xantholepis are included here, but delimitation to and indeed distinctness from subgenus
Flavoagaricus is a long-standing controversy. Unlike these however, subgenus
Minores contains no choice edible species, and may even include some slightly poisonous ones; most are simply too small to make collecting them for food worthwhile, and their edibility is unknown. • '
Section Leucocarpi''''' :Includes
A. leucocarpus. • '
Section Minores''''' :Includes
A. comtulus and
A. huijsmanii. • '
Section Pantropicales''''' :Includes
A. candidolutescens and an undescribed relative. • '
Section Duploannulatae'''
(also known as section Bivelares or Hortenses'') :Traditionally often included in section
Agaricus as subsection
Bitorques, it seems to belong to a much younger radiation. It unites robust species, usually with a thick, almost fleshy ring, which inhabit diverse but often nutrient-rich locations. Some are well-known edibles; as they are frequently found along roads and in similar polluted places, they may not be safe to eat if collected from the wild. Their flesh is rather firm, white, with no characteristic smell, in some species turning markedly reddish when bruised or cut (though this may soon fade again), and generally changing color barely if at all after application of KOH or Schäffer's test. Based on DNA analysis of
ITS1, ITS2, and
5.8S sequences, the studied species of this section could be divided into six distinct clades, four of which correspond to well-known species from the
temperate Northern Hemisphere:
A. bisporus,
A. bitorquis (and the doubtfully distinct
A. edulis),
A. cupressicola and
A. vaporarius. The other two clades comprise the
A. devoniensis (including
A. subperonatus) and
A. subfloccosus (including
A. agrinferus)
species complexes. Additional members of this section not included in that study are
A. cappellianus,
A. cupressophilus,
A. subsubensis,
A. taeniatus,
A. tlaxcalensis, and at least one undescribed species. The section forms a single
clade based on analysis of ITS1+2. They are either bright white all over, or have a cap densely flecked with brownish scales or tufts of fibers. The ring is usually large but thin and veil-like. Most inhabit woodland, and in general they have a more or less pronounced unpleasant smell of
phenolic compounds such as
hydroquinone. As food, they should all be avoided, because even though they are occasionally reported to be eaten without ill effect, the chemicals they contain give them a acrid, metallic taste, especially when cooked, and are liable to cause severe gastrointestinal upset. Their flesh at least in the lower stalk turns pale yellow to intensely reddish-ochre when bruised or cut; more characteristic however is the a bright yellow reaction with KOH while Schäffer's test is negative. Apart from
A. xanthodermus, the core group of this section contains species such as
A. atrodiscus,
A. californicus,
A. endoxanthus and the doubtfully distinct
A. rotalis,
A. fuscopunctatus,
A. iodosmus,
A. laskibarii,
A. microvolvatulus,
A. menieri,
A. moelleri,
A. murinocephalus,
A. parvitigrinus,
A. placomyces,
A. pocillator,
A. pseudopratensis,
A. tibetensis,
A. tollocanensis,
A. tytthocarpus,
A. xanthodermulus,
A. xanthosarcus, as well as at least 4 undescribed species, and possibly
A. cervinifolius and the doubtfully distinct
A. infidus. Whether such species as
A. bisporiticus,
A. nigrogracilis and
A. pilatianus are more closely related to the mostly
Eurasian core group, or to the more basal lineage here separated as section
Hondenses, requires clarification. ''(F.H.Møller & Jul.Schäff. 1938) Hlaváček 1949 ex Pilát/Singer 1951 '
Subgenus Spissicaules''''' :The flesh of members of this subgenus tends to turn more or less pronouncedly yellowish in the lower stalk, where the skin is often rough and scaly, and reddish in the cap. They typically resemble the darker members of subgenus
Flavoagaricus, with a sweet smell and mild taste; like that subgenus,
Spissicaules belongs to the smaller of the two main groups of the genus, but they form entirely different branch therein. While some species are held to be edible, others are considered unappetizing or even slightly poisonous. Also includes
A. lanipes and
A. maskae, which probably belong to section
Rarolentes or
Spissicaules, and possibly also
A. bresadolanus and its doubtfully distinct relatives
A. radicatus/
romagnesii. • '
Section Amoeni''''' :Includes
A. amoenus and
A. gratolens. • '
Section Rarolentes''''' :Includes
A. albosquamosus and
A. leucolepidotus. • '
Section Spissicaules''''' (
Hainem.)
Kerrigan :Includes species such as
A. leucotrichus/
litoralis (of which
A. spissicaulis is a synonym, but see also Geml
et al. 2004 but since then,
molecular phylogenetic studies have revalidated several disputed species, as well as resolved some
species complexes, and aided in discovery and description of a wide range of mostly tropical species that were formerly unknown to science. As of 2020, the genus is believed to contain no fewer than 400 species, and possibly many more. The
medicinal mushroom known in Japan as
Echigoshirayukidake was initially also thought to be an
Agaricus, either a subspecies of
Agaricus "blazei" (i.e.
A. subrufescens), or a new species. It was eventually identified as
sclerotium of the crust-forming bark fungus
Ceraceomyces tessulatus, which is not particularly closely related to
Agaricus. Several
secotioid (
puffball-like) fungi have in recent times be recognized as highly aberrant members of
Agaricus, and are now included here. These typically inhabit
deserts where few fungiand even fewer of the familiar cap-and-stalk mushroom shapegrow. Another desert species,
A. zelleri, was erroneously placed in the present genus and is now known as
Gyrophragmium californicum. In addition, the scientific names
Agaricus and – even more so –
Psalliota were historically often used as a "
wastebasket taxon" for any and all similar mushrooms, regardless of their actual relationships. Species either confirmed or suspected to belong into this genus include: •
Agaricus abramsii •
Agaricus abruptibulbus – abruptly-bulbous agaricus, flat-bulb mushroom (disputed) •
Agaricus aestivalis •
Agaricus agrinferus (disputed) •
Agaricus alabamensis •
Agaricus albolutescens (disputed) •
Agaricus alligator •
Agaricus amicosus •
Agaricus angusticystidiatus •
Agaricus annae •
Agaricus arorae •
Agaricus arvensis – horse mushroom •
Agaricus augustus – the prince •
Agaricus aurantioviolaceus •
Agaricus benesii •
Agaricus bernardii – salt-loving mushroom •
Agaricus bisporus – cultivated/button/portobello mushroom (includes
A.brunnescens) •
Agaricus bitorquis – pavement mushroom, banded agaric •
Agaricus braendlei •
Agaricus bresadolanus •
Agaricus brunneofibrillosus (formerly in
A.fuscofibrillosus) •
Agaricus californicus – California agaricus •
Agaricus campestris – field/meadow mushroom •
Agaricus columellatus (formerly in
Araneosa) •
Agaricus cupreobrunneus – brown field mushroom •
Agaricus deserticola G.Moreno, Esqueda & Lizárraga (2010) – gasteroid agaricus (formerly in
Longula) •
Agaricus dulcidulus – rosy wood mushroom (sometimes in
A.semotus) •
Agaricus excellens (disputed) •
Agaricus freirei •
Agaricus hondensis – felt-ringed agaricus •
Agaricus impudicus – tufted wood mushroom •
Agaricus inapertus (formerly in
Endoptychum) •
Agaricus julius •
Agaricus lanatoniger •
Agaricus langei (=
A.fuscofibrillosus) •
Agaricus lilaceps – giant cypress agaricus •
Agaricus litoralis – coastal mushroom (includes
A.spissicaulis) •
Agaricus macrosporus (disputed) •
Agaricus moelleri – inky/dark-scaled mushroom (formerly in
A.placomyces, includes
A.meleagris) •
Agaricus nebularum •
Agaricus pattersoniae •
Agaricus perobscurus – American princess •
Agaricus phaeolepidotus •
Agaricus pilatianus •
Agaricus placomyces (includes
A.praeclaresquamosus) •
Agaricus pocillator •
Agaricus santacatalinensis •
Agaricus semotus •
Agaricus silvaticus – scaly/blushing wood mushroom, pinewood mushroom (=
A.sylvaticus, includes
A.haemorrhoidarius) •
Agaricus silvicola – wood mushroom (=
A.sylvicola) •
Agaricus subrufescens (includes
A.rufotegulis, often confused with
A.blazei and
A.brasiliensis) – almond mushroom, royal sun agaricus, and various fanciful names •
Agaricus subrutilescens – wine-colored agaricus •
Agaricus taeniatus •
Agaricus urinascens •
Agaricus xanthodermus – yellow-staining mushroom == Description ==