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|gills on hymenium|
cap is convexor flat
|hymenium is free|
|stipe has a ring|
|spore print is brown|
|ecology is saprotrophic|
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.
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".
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. 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.
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 
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, 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. This species is rarely found in woodland.
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. 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 
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.
Bioactive properties 
See also 
- Nilsson, Sven & Persson, Olle (1977). Fungi of Northern Europe 2: Gill-Fungi. Penguin, New York. ISBN 0-14-063006-6.
- Fox RTV., R (2006). "Fungal foes in your garden: fairy ring mushrooms". Mycologist 20 (1): 36–37. doi:10.1016/j.mycol.2005.11.013.
- Richard Mabey (1972). Food For Free, a guide to the edible wild plants of Britain. Fontana/Collins.
- Grigson, Jane (1975). The Mushroom Feast. London: Penguin. ISBN 0-14-046273-2.
- Patrick Harding (2008). Mushroom Miscellany. Collins. ISBN 978-0-00-728464-1.
- Gray AM, Flatt PR (1998). "Insulin-releasing and insulin-like activity of Agaricus campestris (mushroom)". The Journal of Endocrinology 157 (2): 259–66. doi:10.1677/joe.0.1570259. PMID 9659289.