''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, Basid ...

fungus of the genus ''

Agaricus ''Agaricus'' is a genus of mushroom-forming fungi 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 ...

''. It is generally edible, but bioaccumulates the metal

cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

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 Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

adjective meaning noble.

Description

''Agaricus augustus'' forms large and distinctive

agaric An agaric () is a type of fungal 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. It is a type of mushroom (or toadstool) ...

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. The origin of the word "cap" comes from the Old French word "chapeau" which means "head co ...

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 Basidiomycota, basidiomycete fungus, fungi, typically agarics. ...

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

stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...

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

ring (The) Ring(s) 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 Arts, entertainment, and media Film and TV * ''The Ring'' (franchise), a ...

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 sweet, similar to almond extract,

marzipan Marzipan is a confectionery, confection consisting primarily of sugar and almond meal (ground almonds), sometimes augmented with almond oil or extract. It is often made into Confectionery, sweets; common uses are chocolate-covered marzipan and ...

maraschino cherry A maraschino cherry ( ) is a preserved, sweetened cherry, typically made from light-colored sweet cherries such as the Royal Ann, Rainier, or Gold varieties. In their modern form, the cherries are first preserved in a brine solution usually ...

, due to the presence of

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

and

benzyl alcohol Benzyl alcohol (also known as α-cresol) 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 a ...

. 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 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 utili ...

(KOH) solution is applied. Agaricus

Under a microscope, the ellipsoid-shaped

spores In biology, a spore is a unit of sexual (in fungi) 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 plant ...

are seen characteristically large at 7–10 by 4.5–6.5

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

. The

basidia A basidium (: basidia) is a microscopic spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. These bodies are also ...

are 4-spored. The spore mass is coloured chocolate-brown.

Similar species

Toxic lookalikes include '' Amanitas'' which stain yellow when bruised or emit bad odor. 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.

Distribution and habitat

''Agaricus augustus'' has a widespread distribution, occurring throughout Europe, North Africa, Asia, and North America. The 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 Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

and

conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

ous 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 ...

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 In ecology, a disturbance is a change in environmental conditions that causes a pronounced change in an ecosystem. Disturbances often act quickly and with great effect, to alter the physical structure or arrangement of biotic and abiotic element ...

. In Europe, the species fruits in late summer and autumn. In North America, it is found from April to December.

Potential toxicity

''A. augustus'' has been implicated in bioaccumulating the metal

, 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 oth ...

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

Uses

This mushroom is a choice edible for most people. It is collected widely for consumption in Eurasia, Canada, the United States, and some parts of Mexico.

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 Gaius Julius Caesar Augustus (born Gaius Octavius; 23 September 63 BC – 19 August AD 14), also known as Octavian (), was the founder of the Roman Empire, who reigned as the first Roman emperor from 27 BC until his death in A ...

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