Agaricus campestris
Mycological characteristics
	gills on hymenium
	cap is convex or flat
	hymenium is free
	stipe has a ring
	spore print is brown
	ecology is saprotrophic
	edibility: choice

Agaricus campestris is commonly known as the field mushroom or, in North America, meadow mushroom. It is a widely eaten gilled mushroom closely related to the cultivated button mushroom Agaricus bisporus.

Taxonomy [edit]

This species was originally noted and named in 1753 by Carolus Linnaeus as Agaricus campestris. It was placed in the genus Psalliota by Lucien Quelet in 1872. Some variants have been isolated over the years, a few of which now have species status, for example, Agaricus bernardii Quel. (1878), Agaricus bisporus (J.E. Lange) Imbach (1946), Agaricus bitorquis (Quel.) Sacc. (1887), Agaricus cappellianus Hlavacek (1987), and Agaricus silvicola (Vittad.) Peck (1872).
Some were so similar they did not warrant even variant status, others have retained it e.g. Agaricus campestris var. equestris (F.H. Moller) Pilat (1951) is still valid, and presumably favors pasture where horses have been kept. Agaricus campestris var isabellinus (F.H. Moller) Pilat (1951), and Agaricus campestris var.radicatus, are possibly still valid too.
The specific epithet campestris is derived from the Latin campus "field".

Description [edit]

The cap is white, may have fine scales, and is 5 to 10 centimetres (2.0 to 3.9 in) in diameter; it is first hemispherical in shape before flattening out with maturity. The gills are initially pink, then red-brown and finally a dark brown, as is the spore print. The 3 to 10 centimetres (1.2 to 3.9 in) tall stipe is predominately white and bears a single thin ring.^[1] The taste is mild. The white flesh bruises slightly reddish, as opposed to yellow in the inedible (and somewhat toxic) Agaricus xanthodermus and similar species. The spores are 7–8 micrometres (0.00028–0.00031 in) by 4–5 micrometres (0.00016–0.00020 in), and ovate. Cheilocystidia are absent.
Similar species:
Amanita virosa (and similar, closely related species), the destroying angel (morbidly toxic).
Agaricus xanthodermus, the yellow stainer (causes gastrointestinal problems).
Agaricus arvensis, the horse mushroom (excellent edible).
White Clitocybe species, that also grow on lawns, and in grassy places (dangerous).

Distribution and habitat [edit]

Agaricus campestris is common in fields and grassy areas after rain from late summer onwards worldwide. It is often found on lawns in suburban areas. Appearing in small groups, in fairy rings,^[2] or solitary. Owing to the demise of horse drawn vehicles, and the subsequent decrease in the number of horses on pasture, the old 'white outs' of years gone by are becoming rare events.^[3] This species is rarely found in woodland.

Edibility [edit]

It is widely collected and eaten, even by those who would not normally eat wild mushrooms. This mushroom is not commercially cultivated on account of its fast maturing and short shelf-life.^[4] Culinary uses of the meadow mushroom include eating it sauteed or fried, in sauces, or even sliced raw and included in salads. In flavor and texture, this mushroom is almost identical to the white button mushroom available in grocery stores in the United States. Be sure to rinse well to dislodge any sand, and also watch out for small, white larvae which tunnel through the stems and caps. Among the similar species mentioned above, there have been cases (in fact the most common cause of fatal fungus poisoning in France) where the deadly toxic destroying angel (Amanita bisporigera) has been consumed by individuals who mistook it for this species. The edibility of specimens collected from lawns is uncertain because of possible contamination with pesticides or other chemicals.

Other uses [edit]

Research into fungal dressings for the treatment of ulcers, and bed sores, using fungal mycelial filaments, is ongoing. In the past, slices of A. campestris were applied to scalds, and burns in parts of Scotland.^[5]

Bioactive properties [edit]

Water extracts of A. campestris have been shown to enhance the secretion of insulin, and to have insulin-like effects on glucose metabolism in vitro, although the mechanism is not understood.^[6]

See also [edit]

Fungi portal

• List of Agaricus species

References [edit]

British Checklist
Index Fungorum

Agaricus bisporus—known variously when white as common mushroom, button mushroom, white mushroom, cultivated mushroom, table mushroom, champignon mushroom, cremini/crimini mushroom, when brown as Swiss brown mushroom, Roman brown mushroom, Italian brown, Italian mushroom, brown cap mushrooms, chestnut mushroom,^[2] and when mature as Portobello mushroom—is an edible basidiomycete mushroom native to grasslands in Europe and North America. Agaricus bisporus is cultivated in more than 70 countries^[3] and is one of the most commonly and widely consumed mushrooms in the world.

Agaricus bisporus
Mycological characteristics
	gills on hymenium
	cap is convex
	hymenium is free
	stipe has a ring
	spore print is brown
	ecology is saprotrophic
	edibility: choice

Taxonomy and naming [edit]

The common mushroom has a complicated taxonomic history. It was first described by English botanist Mordecai Cubitt Cooke in his 1871 Handbook of British Fungi, as a variety (var. hortensis) of Agaricus campestris.^[4][5] Danish mycologist Jakob Emanuel Lange later reviewed a cultivar specimen, and dubbed it Psalliota hortensis var. bispora in 1926.^[6] In 1938, it was promoted to species status and renamed Psalliota bispora.^[7] Emil Imbach imparted the species' current scientific name, Agaricus bisporus, after the genus Psalliota was renamed to Agaricus in 1946.^[3] The specific epithet bispora distinguishes the two-spored basidia from four-spored varieties.

Among English speakers, Agaricus bisporus is known by many names. A young specimen with a closed cap and either pale white or light brown flesh is known as a button mushroom or white mushroom. In strains with darker flesh, the immature mushroom is variously marketed as a cremini mushroom, baby portobello, baby bella, mini bella, portabellini, Roman mushroom, Italian mushroom, or brown mushroom. At this stage of maturation, the cap may also begin to open slightly. In maturity, it is called a portobello.^[8] The French name is champignon de Paris ("Paris mushroom").

The spellings "portobello", "portabella", and "portabello" are all used,^[9] but the first of these spellings is the most common.^{[citation needed]}

Description [edit]

The pileus or cap of the original wild species is a pale grey-brown in color, with broad, flat scales on a paler background and fading toward the margins. It is first hemispherical in shape before flattening out with maturity, and 5–10 cm (2–4 in) in diameter. The narrow, crowded gills are free and initially pink, then red-brown and finally a dark brown with a whitish edge from the cheilocystidia. The cylindrical stipe is up to 6 cm (2⅓ in) tall by 1–2 cm wide and bears a thick and narrow ring, which may be streaked on the upperside. The firm flesh is white though stains a pale pinkish-red on bruising.^[10][11] The spore print is dark brown. The spores are oval to round and measure around 4.5–5.5 x 5–7.5 μm, and the basidia usually two-spored, although two tetrasporic varieties have been described from the Mojave desert and the Mediterranean with predominantly heterothallic and homothallic lifestyles, respectively^[12][13]

Commonly found in fields and grassy areas after rain from late spring through to autumn worldwide, especially in association with manure. It is widely collected and eaten, even by those who would not normally experiment with mushrooming.^[11]

Similar species [edit]

The common mushroom could be confused with young specimens of the deadly poisonous destroying angel (Amanita sp.), but the latter can be distinguished by their volva or cup at the base of the mushroom and pure white gills (as opposed to pinkish or brown of Agaricus bisporus). Thus it is important to always clear away debris and examine the base of a mushroom, as well as cutting open young specimens to check the gills. Furthermore, the destroying angel grows in mossy woods and lives symbiotically with spruce.

A more common and less dangerous mistake is to confuse Agaricus bisporus with Agaricus xanthodermus, an inedible mushroom found worldwide in grassy areas. Agaricus xanthodermus has an odor reminiscent of phenol; its flesh turns yellow when bruised. This fungus causes nausea and vomiting in some people.

The poisonous European species Entoloma sinuatum has a passing resemblance but has yellowish gills turning pink and lacks a ring.

Cultivation [edit]

Agaricus bisporus being cultivated.

The earliest description of the commercial cultivation of Agaricus bisporus was made by French botanist Joseph Pitton de Tournefort in 1707.^[14] French agriculturist Olivier de Serres noted that transplanting mushroom mycelia would lead to more mushrooms. Originally, cultivation was unreliable as mushroom growers would watch for good flushes of mushrooms in fields before digging up the mycelium and replanting in beds of composted manure or inoculating 'bricks' of compressed litter, loam and manure. Spawn collected this way contained pathogens and crops would be commonly infected or not grow at all.^[15]

In 1893, sterilized, or pure culture, spawn was discovered and produced by the Pasteur Institute in Paris, for cultivation on composted horse manure.^[16] Today's commercial variety of the common mushroom was originally a light brown color. In 1926, a Pennsylvania mushroom farmer found a clump of common mushrooms with white caps in his mushroom bed. Like white bread it was seen as a more attractive food item and was very popular.^[17] As was done with the navel orange and Red Delicious apple, cultures were grown from the mutant individuals, and most of the cream-colored store mushrooms we see today are products of this chance natural mutation.

Agaricus bisporus is now cultivated in at least 70 countries around the world.^[3] Global production in the early 1990s was reported to be more than 1.5 million tons, worth more than US$ 2 billion.^[18]

Vitamin D [edit]

While Agaricus bisporus only contains 16 IU of vitamin D as ergocalciferol (vitamin D2), since they also contain high amounts of ergosterol, by brief exposure to UV light the ergocalciferol contents rise immensely.^[19][20][21]

Potential medicinal value [edit]

Agaricus bisporus also contains sodium, potassium, and phosphorus,^[22] conjugated linoleic acid^[23] and antioxidants.^[24] Protocatechuic acid and pyrocatechol are found in A. bisporus.^[25][26] A 2009 case control study of 2,018 women correlated a large decrease of breast cancer incidence in women who consumed mushrooms. Women in the study who consumed fresh mushrooms daily were 64% less likely to develop breast cancer, while those that combined a mushroom diet with regular green tea consumption reduced their risk of breast cancer by nearly 90%.^[27]

The table mushroom has also been shown to possess possible immune system enhancing properties. An in vitro study demonstrated the mushroom enhanced dendritic cell function.^[28][29]

Health risks [edit]

Some studies have revealed that raw A. bisporus - along with some other edible mushrooms - contain small amounts of carcinogenic hydrazine derivatives, including agaritine and gyromitrin.^[30][31] However, this research also noted that when cooked, these compounds were reduced significantly.^[32]

Agaricus bisporus gallery [edit]

• 

  Portobello mushrooms

• 

  Cross-section of a portobello cultivar

• 

  Ventral view of a portobello cultivar with a bisected stipe

• 

  Two Agaricus bisporus mushrooms which have fused together.

• 

See also [edit]

Fungi portal

• Effect of sunlight on mushrooms
• Fungiculture
• List of Agaricus species
• Medicinal mushrooms

Notes [edit]

References [edit]

• Benjamin, Denis R. (1995). Mushrooms: poisons and panaceas—a handbook for naturalists, mycologists and physicians. New York: WH Freeman and Company. ISBN 0-7167-2600-9. 
• Genders, Roy (1969). Mushroom Growing for Everyone. London: Faber. ISBN 0-571-08992-5. 
• Kuo, M. (January 2004). "Agaricus bisporus: The common mushroom". MushroomExpert.Com. 
• City of Hope Research [1]