Agaricus augustus

According to Heinemann's (1978) popular division of Agaricus, A. augustus belongs to section Arvenses.{{cite book |author =Noordeloos M. E. |title=Volume 5 of Flora Agaricina Neerlandica: Critical Monographs on Families of Agarics and Boleti Occurring in the Netherlands |publisher=CRC Press |year=2001 |pages=44–45 |isbn=90-5410-495-3|url=https://books.google.com/books?id=YaBiXhgkfccC&q=bibliogroup:%22Flora+Agaricina+Neerlandica:+Critical+Monographs+on+Families+of+Agarics+and+Boleti+Occurring+in+the+Netherlands%22|access-date=2010-01-13}} The system proposed by Wasser (2002) classifies A. augustus within subgenus Flavoagaricus, section Majores, subsection Flavescentes.{{Cite journal|last=Lacheva |first=Maria |title=Genus Agaricus L. in Bulgaria–Taxonomy, Ecology, Chorology and Economic Importance (in Bulgarian) |journal=Agrarian University - Plovdiv |pages=18–19 |date=January 2006 |url=http://www.botanica.hit.bg/doc/AgaricusPhDthesis.pdf }}{{dead link|date=June 2017 |bot=InternetArchiveBot |fix-attempted=yes }} Moreover, there have been attempts to recognise distinct varieties, namely A. augustus var. augustus Fr., and A. augustus var. perrarus (Schulzer) Bon & Cappelli.

The specific epithet augustus is a Latin adjective meaning noble.

Agaricus augustus forms large and distinctive agarics. The cap shape is hemispherical during the so-called button stage, and then expands, becoming convex and finally flat, with a diameter from {{convert|8-30|cm|abbr=on|round=0.5}}.{{Cite book|last1=Davis|first1=R. Michael|url=https://www.worldcat.org/oclc/797915861|title=Field Guide to Mushrooms of Western North America|last2=Sommer|first2=Robert|last3=Menge|first3=John A.|publisher=University of California Press|year=2012|isbn=978-0-520-95360-4|location=Berkeley|pages=221–222|oclc=797915861}} The cap cuticle is dry, and densely covered with concentrically arranged, brown-coloured scales on a white to yellow background.{{Cite book |last=Audubon |title=Mushrooms of North America |publisher=Knopf |year=2023 |isbn=978-0-593-31998-7 |pages=542}}

The flesh is thick, firm and white and may discolour yellow when bruised. The gills are crowded and pallid at first, and turn pink then dark brown with maturity. The gills are not attached to the stem; they are free. Immature specimens bear a delicate white partial veil with darker-coloured warts, extending from the stem to the cap periphery.

The stem is clavate and {{convert|7-30|cm|abbr=on|round=0.5}} tall, and {{convert|2-6|cm|abbr=on|frac=4}} thick. In mature specimens, the partial veil is torn and left behind as a pendulous ring adorning the stem. Above the ring, the stem is white to yellow and smooth. Below, it is covered with numerous small scales.{{cite book|last1=Trudell|first1=Steve|url=https://books.google.com/books?id=WevHvt6Tr8kC|title=Mushrooms of the Pacific Northwest|last2=Ammirati|first2=Joe|publisher=Timber Press|year=2009|isbn=978-0-88192-935-5|series=Timber Press Field Guides|location=Portland, OR|pages=189}} Its flesh is thick, white and sometimes has a narrow central hollow. The stem base extends deeply into the substrate.

The mushroom's odour is strong and sweet, similar to almond extract, marzipan or maraschino cherry, due to the presence of benzaldehyde and benzyl alcohol.{{cite journal |journal= Mycologia |volume=82 | year=1990 |title= The Odor of Agaricus augustus |author1=Wood W. F. |author2= Watson R. L. |author3= Largent D. L. | doi=10.2307/3759861 |pages=276–278}}{{cite journal |doi=10.2307/3761770 |author =The Mycological Society of America |year=2002 |title=The anise-like odor of Clitocybe odora, Lentinellus cochleatus and Agaricus essettei |journal=Mycologia |volume=94 |issue=3 |pages=373–376|url=http://www.mycologia.org/cgi/content/full/94/3/373 |jstor=3761770 |pmid=21156507|url-access=subscription }} Its taste has been described as not distinctive. It shows a red positive Schaeffer's test reaction. The cap cuticle turns yellow when a 10% potassium hydroxide (KOH) solution is applied.{{r|Bas1988}}

File:Agaricus.augustus.spores.1000x.jpg

Under a microscope, the ellipsoid-shaped spores are seen characteristically large at 7–10 by 4.5–6.5 μm. The basidia are 4-spored. The spore mass is coloured chocolate-brown.{{r|Bas1988}}{{cite book | author = Michael Jordan | year = 1995 | title = The Encyclopedia of Fungi of Britain and Europe | publisher = David & Charles | isbn = 0-7153-0129-2|page=221}}

Toxic lookalikes include Amanitas which stain yellow when bruised or emit bad odor.{{cite book |last=Meuninck |first=Jim |title=Foraging Mushrooms Oregon: Finding, Identifying, and Preparing Edible Wild Mushrooms |date=2017 |publisher=Falcon Guides |isbn=978-1-4930-2669-2 |page=109}} Another similar-looking toxic species is Agaricus moelleri. Several other members of the genus are similar. Initially reported from North America, A. subrufescens produces smaller spores, sized 6–7.5 by 4–5 μm.

File:Agaricus augustus The Prince.JPG, Ayrshire]]

Agaricus augustus has a widespread distribution, occurring throughout Europe, North Africa, Asia, and North America. The mushroom is found in deciduous and coniferous woods and in gardens and by roadside verges. The fungus is saprotrophic and terrestrial; it acquires nutrients from decaying dead organic matter and its fruiting bodies occur on humus-rich soil. The species seems adapted to thriving near human activity, as it also emerges from disturbed ground.{{Cite book |last=Arora |first=David |author-link=David Arora |title=Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi |url=https://archive.org/details/arora-david-mushrooms-demystified-a-comprehensive-guide-to-the-fleshy-fungi-ten-speed-press-1986/page/337/mode/2up |date=1986 |publisher=Ten Speed Press |isbn=978-0-89815-170-1 |location=Berkeley, CA |orig-date=1979 |edition=2nd |pages=337-39}} In Europe, the species fruits in late summer and autumn. In North America, it is found from April to December.

A. augustus has been implicated in bioaccumulating the metal cadmium, with a quantity of 2.44 mg per kilogram of fresh weight as recorded in one Swiss study.{{cite journal |last=Neukom P. |year=2005 |title=Métaux toxiques dans les champignons comestibles. Danger pour la santé des consommateurs? |journal=Bulletin Suisse de Mycologie |language=fr |volume=15 |issue=4 |pages=170–171 |issn=0373-2959}} The same phenomenon is true for other edible species of Agaricus, namely A. arvensis, A. macrosporus and A. silvicola, though quantities may vary greatly depending on species, which part of the fruiting body is analysed, and the level of contamination of the substrate. Specimens collected near metal smelters and urban areas have a higher cadmium content. The hymenium contains the highest concentration of metal, followed by the rest of the cap, while the lower part of the stem contains the least.{{cite journal |author1=Kalač P. |author2=Svoboda L. |author3=Havlíčková B. |year=2004 |title=Contents of cadmium and mercury in edible mushrooms |journal=Journal of Applied Biomedicine |volume=2 |pages=15–20 |doi=10.32725/jab.2004.002 |issn=1214-0287 |doi-access=free}}

This mushroom is a choice edible{{cite book|author =Boa ER.|year=2006|title="Champignons Comestibles Sauvages" [Edible Wild Mushrooms]|page=141|publisher=Food and Agriculture Organization of the United Nations|isbn=92-5-205157-0|language=fr}} for most people. It is collected widely for consumption in Eurasia, Canada, the United States, and some parts of Mexico.

• List of Agaricus species

{{Reflist}}

• {{Commons-inline}}
• [http://botit.botany.wisc.edu/toms_fungi/aug2002.html Tom Volk's fungus of the month - Agaricus augustus]
• [https://web.archive.org/web/20120223190908/http://linnet.geog.ubc.ca/Atlas/AtlasFungi.aspx?sciname=Agaricus%20augustus Electronic Atlas of the Plants of British Columbia - Agaricus augustus]
• [http://www.mykoweb.com/CAF/species/Agaricus_augustus.html Mykoweb - Agaricus augustus]

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augustus

Category:Edible fungi

Category:Fungi of Europe

Category:Fungi of North America

Category:Fungi described in 1838

Category:Taxa named by Elias Magnus Fries

Category:Fungus species