''Agaricus augustus'', known commonly as the prince, is a

basidiomycete Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Agaricus ''Agaricus'' is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom (''Agaricus bisp ...

''.

Taxonomy

According to Heinemann's (1978) popular division of ''Agaricus'', ''A. augustus'' belongs to section ''Arvenses''. The system proposed by Wasser (2002) classifies ''A. augustus'' within subgenus ''Flavoagaricus'', section ''Majores'', subsection ''Flavescentes''. 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.

Description

The fruiting bodies of ''Agaricus augustus'' are large and distinctive

agaric An agaric () is a type of fungus fruiting body characterized by the presence of a pileus (cap) that is clearly differentiated from the stipe (stalk), with lamellae (gills) on the underside of the pileus. In the UK, agarics are called "mushrooms ...

s. The

cap A cap is a flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3200 BC. Caps typically have a visor, or no brim at all. They are popular in casual and informal se ...

shape is hemispherical during the so-called button stage, and then expands, becoming convex and finally flat, with a diameter from . The cap cuticle is dry, and densely covered with concentrically arranged, brown-coloured scales on a white to yellow background. The flesh is thick, firm and white and may discolour yellow when bruised. The

gills A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

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 In mycology, a partial veil (also called an inner veil, to differentiate it from the "outer", or universal veil) is a temporary structure of tissue found on the fruiting bodies of some basidiomycete fungi, typically agarics. Its role is to isolate ...

with darker-coloured warts, extending from the stem to the cap periphery. The

stem Stem or STEM may refer to: Plant structures * Plant stem, a plant's aboveground axis, made of vascular tissue, off which leaves and flowers hang * Stipe (botany), a stalk to support some other structure * Stipe (mycology), the stem of a mushro ...

is clavate and tall, and thick. In mature specimens, the partial veil is torn and left behind as a pendulous

ring Ring may refer to: * Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry * To make a sound with a bell, and the sound made by a bell :(hence) to initiate a telephone connection Arts, entertainment and media Film and ...

adorning the stem. Above the ring, the stem is white to yellow and smooth. Below, it is covered with numerous small scales. 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 nutty, of

anise Anise (; '), also called aniseed or rarely anix is a flowering plant in the family Apiaceae native to Eurasia. The flavor and aroma of its seeds have similarities with some other spices and herbs, such as star anise, fennel, licorice, and ta ...

almond The almond (''Prunus amygdalus'', syn. ''Prunus dulcis'') is a species of tree native to Iran and surrounding countries, including the Levant. The almond is also the name of the edible and widely cultivated seed of this tree. Within the genus ...

s, which can be associated with the presence of

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor. ...

and

benzyl alcohol Benzyl alcohol is an aromatic alcohol with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn" (not to be confused with "Bz" which is used for benzoyl), thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid w ...

. Its taste has been described as not distinctive. Under a microscope, the ellipsoid-shaped

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s are seen characteristically large at 7–10 by 4.5–6.5 μm. The

basidia A basidium () is a microscopic sporangium (a spore-producing structure) found on the hymenophore of fruiting bodies of basidiomycete fungi which are also called tertiary mycelium, developed from secondary mycelium. Tertiary mycelium is highly-c ...

are 4-spored. The spore mass is coloured chocolate-brown. A species initially reported from North America, '' A. subrufescens'' closely resembles ''A. augustus'' in appearance. However, ''A. subrufescens'' produces smaller spores, sized 6–7.5 by 4–5 µm.

Identification

''Agaricus augustus'' shows a red positive Schaeffer's test reaction. The cap cuticle turns yellow when a 10%

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

solution is applied. Toxic lookalikes include '' Amanitas'' which stain yellow when bruised or emit bad odor. Another similar-looking toxic species is ''

Agaricus moelleri ''Agaricus moelleri'', also known as the inky mushroom, or dark scaled mushroom, is a large mushroom of the genus ''Agaricus''. It appears occasionally in most kinds of woodland, during late summer, in northern temperate zones. Taxonomy For man ...

''.

Habitat

''Agaricus augustus'' has a widespread distribution, occurring throughout Europe, North America, North Africa and Asia. This mushroom is found in

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

and

coniferous Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extant ...

woods and in gardens and by roadside verges. The fungus is

saprotrophic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi (f ...

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, for it also emerges from disturbed ground.Google Books
/ref> In Europe, ''A. augustus'' fruits in late summer and autumn.

Edibility

This mushroom is a choice

edible An edible item is any item that is safe for humans to eat. "Edible" is differentiated from "eatable" because it does not indicate how an item tastes, only whether it is fit to be eaten. Nonpoisonous items found in nature – such as some mushroo ...

, and is collected widely for consumption in

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago a ...

, the United States, Canada and some parts of Mexico. ''A. augustus'' has been implicated in specifically bioaccumulating the metal

cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

, with a quantity of 2.44 mg per kilogram of fresh weight as recorded in one Swiss study. 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 The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some ...

contains the highest concentration of metal, followed by the rest of the cap, while the lower part of the stem contains the least.

References

External links

*
Tom Volk's fungus of the month - ''Agaricus augustus''

Electronic Atlas of the Plants of British Columbia - ''Agaricus augustus''

{{Taxonbar, from=Q267538

augustus Caesar Augustus (born Gaius Octavius; 23 September 63 BC – 19 August AD 14), also known as Octavian, was the first Roman emperor; he reigned from 27 BC until his death in AD 14. He is known for being the founder of the Roman Pri ...

Edible fungi Fungi of Europe Fungi of North America Fungi described in 1838 Taxa named by Elias Magnus Fries