''Agaricus placomyces'' is a toxic

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, Ba ...

fungus of the genus

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 bi ...

. It is found in North America; the

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 ...

n populations formerly known by the same scientific name are nowadays known as '' A. moelleri'', while the present species may also be referred to as ''A. praeclaresquamosus''.

Description

''Agaricus placomyces'' has a

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 ...

that is 5–12 cm and varies from convex to broadly convex or nearly flat in age. In addition, the surface of the cap is dry and covered with brownish

fiber Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorpora ...

s and

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

, especially over the center. Underneath, the cap can be whitish under normal

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

s, or pinkish in wet weather. Covered with fine, appressed greyish-brown scales and concentrated at the disc, the cap is thick, slowly becoming vinaceous when injured; the odor smells of

phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...

. The flesh is white, and becomes yellow when placed in KOH. 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 ...

of this mushroom are free from the stem, crowded, and pale grayish-pink, turning brown in age. In addition, the stem is 6–15 cm long, 1–1.5 cm. thick and more or less equal, with an enlarged base (unlike typically ending in a small bulb like '' Agaricus pocillator''). Also, it is fairly smooth, white and bruising yellow, especially at the base, with a persistent

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 ...

, and the

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 isola ...

when still covering the gills developing brownish to yellowish droplets. At 8–15 cm long and 2–3.5 cm thick, the stipe is slightly enlarged at the base; the surface is white, and smooth above and below the ring. The veil of the stipe is

membranous A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...

, thick, white, and forms a persistent ring with a smooth upper and lower surface. The base of the stipe is typically yellow when bruised and smells of phenol. Agaricus

The spores are 4–6.0 x 3.5–4.5 µm, smooth, and elliptical; the

spore print 300px, Making a spore print of the mushroom ''Volvariella volvacea'' shown in composite: (photo lower half) mushroom cap laid on white and dark paper; (photo upper half) cap removed after 24 hours showing pinkish-tan spore print. A 3.5-centimeter ...

is blackish-brown.

Toxicity

''Agaricus placomyces'' contains toxins which cause gastrointestinal upset, as with other phenolic-odored ''Agaricus'' species. Some people reportedly may not be affected. The mushroom's taste is mild and its odor resembles phenol or coal tar.

Habitat

''Agaricus placomyces'' is

saprobic 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 ( ...

. In addition, it grows in groups under hardwoods and in mixed woods during summer and fall. It is generally found east of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...

and northern in distribution. Generally, it is solitary, living in either small groups, or clusters on disturbed ground under conifers. Unlike many other ''Agaricus'' species, it fruits from mid to late winter rather than during the late spring, summer and early fall.''Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi'' ; By David Arora, Edition: 2, illustrated; Published by Ten Speed Press, 1986; , page 329.

References

Sources

mushroomexpertrogermushrooms
{{Taxonbar, from=Q2669175 placomyces Fungi described in 1878 Fungi of North America Poisonous fungi Taxa named by Charles Horton Peck

Description

Toxicity

Habitat

See also

References

Sources