Agaricus augustus
Encyclopedia
Agaricus augustus, known commonly as the prince, is a basidiomycete fungus
of the genus
Agaricus
.
s. The cap
shape is hemispherical during the so-called button stage, and then expands, becoming convex and finally flat, with a diameter of up to 22 cm. The cap cuticle is dry, 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 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 up to 20 cm tall, and 4 cm 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. 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
or almond
s which can be associated with the presence of benzaldehyde
and benzyl alcohol
. Its taste has been described as not distinctive.
Under a microscope, the ellipsoid-shaped spore
s 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.
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.
test reaction. The cap cuticle turns yellow when a 10% potassium hydroxide
solution is applied.
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, for it also emerges from disturbed ground. In Europe, A. augustus fruits in late summer and autumn.
, the USA, Canada
and some parts of Mexico
. Agaricus augustus has been implicated in specifically bioaccumulating
the metal cadmium
, 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
contains the highest concentration of metal, followed by the rest of the cap, while the lower part of the stem contains the least.
Fungus
A fungus is a member of a large 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, Fungi, which is separate from plants, animals, and bacteria...
of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Agaricus
Agaricus
Agaricus is a large and important genus of mushrooms containing both edible and poisonous species, with possibly over 300 members worldwide...
.
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 agaricAgaric
An agaric is a type of fungal fruiting body characterized by the presence of a pileus that is clearly differentiated from the stipe , with lamellae on the underside of the pileus. "Agaric" can also refer to a basidiomycete species characterized by an agaric-type fruiting body...
s. The cap
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
shape is hemispherical during the so-called button stage, and then expands, becoming convex and finally flat, with a diameter of up to 22 cm. The cap cuticle is dry, 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 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
Partial veil
thumb|150px|right|Developmental stages of [[Agaricus campestris]] showing the role and evolution of a partial veilPartial veil is a mycological term used to describe a temporary structure of tissue found on the fruiting bodies of some basidiomycete fungi, typically agarics...
with darker-coloured warts, extending from the stem to the cap periphery.
The stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
is clavate up to 20 cm tall, and 4 cm thick. In mature specimens the partial veil is torn and left behind as a pendulous ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
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
Anise , Pimpinella anisum, also called aniseed, is a flowering plant in the family Apiaceae native to the eastern Mediterranean region and Southwest Asia. Its flavor resembles that of liquorice, fennel, and tarragon.- Biology :...
or almond
Almond
The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...
s which can be associated with the presence of benzaldehyde
Benzaldehyde
Benzaldehyde 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. This colorless liquid has a characteristic pleasant almond-like odor...
and benzyl alcohol
Benzyl alcohol
Benzyl alcohol is an organic compound with the formula C6H5CH2OH. The benzyl group is often abbreviated "Bn", thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is a useful solvent due to its polarity, low toxicity, and low vapor...
. Its taste has been described as not distinctive.
Under a microscope, the ellipsoid-shaped spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s are seen characteristically large at 7–10 by 4.5–6.5 μm. The basidia
Basidium
thumb|right|500px|Schematic showing a basidiomycete mushroom, gill structure, and spore-bearing basidia on the gill margins.A basidium is a microscopic, spore-producing structure found on the hymenophore of fruiting bodies of basidiomycete fungi. The presence of basidia is one of the main...
are 4-spored. The spore mass
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
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.
Chemical tests
Agaricus augustus shows a red positive Schaeffer'sJacob Christian Schäffer
Jakob or Jacob Christian Gottlieb Schäffer or Schäffern was a German dean, professor, botanist, mycologist, entomologist, ornithologist and inventor.-Biography:...
test reaction. The cap cuticle turns yellow when a 10% potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
solution is applied.
Habitat
Agaricus augustus has a widespread distribution, occurring throughout Europe, North America, North Africa and Asia. This mushroom is found in deciduousDeciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
and coniferous woods and in gardens and by roadside verges. The fungus is saprotrophic
Saprotrophic nutrition
Saprotrophic nutrition is a process of chemoheterotrophic extra-cellular digestion involved in the processing of dead or decayed organic matter that occurs in saprotrophs or heterotrophs, and is most often associated with fungi, for example Mucor and Rhizopus...
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. In Europe, A. augustus fruits in late summer and autumn.
Edibility
This mushroom is edible. It is collected widely for consumption in EurasiaEurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
, the USA, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and some parts of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Agaricus augustus has been implicated in specifically bioaccumulating
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
the metal cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
, 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
Agaricus arvensis
Agaricus arvensis, commonly known as the Horse Mushroom, is a mushroom of the genus Agaricus.-Taxonomy:Described as Agaricus arvensis by Jacob Christian Schaeffer in 1762, and given numerous binomial descriptions since. Its present name arvensis means 'of the field'.-Description:The cap is similar...
, A. macrosporus
Agaricus macrosporus
Agaricus macrosporus is a rare, edible mushroom found from June at wood fringes and in meadows.-Description:The white cap is hemispherical and white when young, but later flattens out up to 25 cm in diameter and becomes yellowish or tan. Its flesh is very thick. The gills are pinkish grey when...
and A. silvicola
Agaricus silvicola
Agaricus silvicola, also known as the Wood Mushroom is a species of Agaricus mushroom related to the button mushroom.- Description :...
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
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 cells develop into sterile cells called cystidia or...
contains the highest concentration of metal, followed by the rest of the cap, while the lower part of the stem contains the least.