''Agaricus albolutescens'' is a moderate-sized, stocky-statured

mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is t ...

with a pleasant odor; it bruises slowly but persistently yellow. This character distinguishes it from other ''

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 ...

'' species, such as ''Agaricus xanthodermus'', a mildly toxic species which has a phenolic or medicinal odor, and bruises fleetingly yellow. Fieldmarks of ''Agaricus albolutescens'' include a tendency to discolor tawny-brown, rather than merely yellow, and chocolate-brown free gills. ''Agaricus silvicola'' is very similar but has a less dramatic bruising reaction, more yellowish than tawny, a normal rather than stocky stature, and slightly smaller spores. ''A. albolutescens'' and ''A. silvicola'' represent a single polymorphic species or a species complex.

Description

Pileus

The cap is 6–12 cm broad, and convex; it becomes planoconvex to planodepressed. The margin is incurved, then decurved, overlapping the gills. Occasionally, it is wavy and appendiculate from veil fragments. The surface is dry and white; when bruised, it turns tawny-brown. The context varies from 1.5 to 2.0 cm thick; it is firm and turns pale-peach when cut. When the flesh is dry, odor and taste is musty. ''Albolutescens'', in

botanical Latin Botanical Latin is a technical language based on New Latin, used for descriptions of botanical taxa. Until 2012, International Code of Botanical Nomenclature mandated Botanical Latin to be used for the descriptions of most new taxa. It is still the ...

, which has developed a much richer vocabulary of color words than the Romans had, signifies a yellowish white.

Lamellae Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal * ...

The gills are free, close, and, at first, pallid, though they then turn a pale pinkish-tan. As it ages, ''A. albsolutescens'' is dark chocolate-brown in color. The lamellulae are in five to six series.

Stipe

The stipe is 2.0-7.0 cm long, 1.5-3.0 cm thick, and more or less equal except for a bulbous base. In addition, it has a narrow, cottony central core. The surface of the apex is palled and finely striate, while the lower stipe can vary from glabrous to sparsely covered with whitish fibrils, occasionally sheathed with cottony-floccose veil remnants. Like 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 ...

, it yellows. 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 isolate ...

is layered. The surface underneath can be cottony or fibrillose. Sometimes, it fragments, leaving scattered cottony patches over a membranous-tomentose basement layer. The

annulus Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to: Human anatomy * ''Anulus fibrosus disci intervertebralis'', spinal structure * Annulus of Zinn, a.k.a. annular tendon or ''anulus tendineus com ...

is superior, thin, and initially erect, then pendulous.Arora, pg 331

Spores

Spores 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 ...

are 6.0-7.5 x 4.0-5.0 µm,

elliptical Elliptical may mean: * having the shape of an ellipse, or more broadly, any oval shape ** in botany, having an elliptic leaf shape ** of aircraft wings, having an elliptical planform * characterised by ellipsis (the omission of words), or by conc ...

, and inequilateral in profile. In addition, they are smooth, moderately thick-walled, and have an inconspicuous

hilar Hilum may refer to: * Hilum (anatomy), a part of an organ where structures such as blood vessels and nerves enter the body * Hilum (botany), a scar on a seed or spore created by detachment See also * Fovea (disambiguation), another term associat ...

appendage. Their

germ pore A germ pore is a small pore in the outer wall of a fungal spore through which the germ tube exits upon germination. It can be apical or eccentric in its location, and, on light microscopy, may be visualized as a lighter coloured area on the cell ...

is absent.

Taxonomy

The holotype of ''Agaricus albolutescens'' was collected at

Agate Beach, Oregon Agate Beach is an unincorporated community in Lincoln County, Oregon, United States. Agate Beach is named for the agates that are found on the beaches of the Pacific Ocean between Newport and Yaquina Head. Agate Beach post office was establish ...

by Gertrude S. Burlingham on November 21, 1937.

References

* ;Specific {{Taxonbar, from=Q4451218 Agaricus, albolutescens Fungi described in 1938