Agrocybe putaminum

Appearance

Fruitbodies have a convex cap that later flattens out in maturity, sometimes developing a shallow umbo; the cap attains a diameter of 3–10 cm . Its color is initially dark brown, but fades to pale yellowish tan in age. The cap surface is smooth, matte, and is finely pruinose–as if coated with very fine flour. The gills, which have an adnate attachment to the stipe, are pale clay-brown in color, but later deepen to become dark brown after the spores mature. The gills are moderately crowded together, and are interspersed with lamellulae .

The cylindrical stipe of ''Agrocybe putaminum'' measures 5–8 cm long by 1–1.5 cm thick, and is thicker at both the apex and the club-shaped base. Initially stuffed with a cottony pith, the stipe eventually becomes hollow. It is the same color as the cap, and has a surface marked by thin raised ridges ; these ridges originate from mycelial cords. The flesh of the mushroom is white, up to 1.5 cm thick, and does not change color when cut or otherwise injured. Its odor is both farinaceous and fungal, while its taste is bitter, with a cucumber aftertaste. The mushrooms are not edible.

''Agrocybe putaminum'' produces a dark brown spore print. Spores are roughly elliptical, smooth, thick-walled with a germ pore, and measure 10–12 by 5–9 μm. The basidia are club-shaped, four-spored, and measure 25–30 by 10–15 μm. The stipe is covered in caulocystidia, which gives it a velvety texture.

Naming

The eastern North American species ''Agrocybe smithii'' is similar in appearance to ''A. putaminum''. It can be distinguished microscopically from the latter by the size and morphology of its cystidia , and the absence of pilocystidia. Another lookalike, ''A. hortensis'', lacks pleurocystidia and has broader cheilocystidia than ''A. putaminum''. Also, it can be distinguished from ''Agrocybe praecox'' macroscopically by the lacks of annulus and darkeing when handled.

Distribution

''Agrocybe putaminum'' is a saprobic species. Its fruitbodies grow on the ground in clusters or close groups, usually in woodchips, and so can be found in gardens, parks, and other areas that use this type of mulch. It is known to occur in western North American and Europe. The species used to be considered rare; after the initial report of its 1913 discovery in France, it was infrequently recorded again: in the Netherlands in 1958, Denmark in 1989, western Belgium and Italy in 1998, and India in 2003. The fungus has since become more common, and its range has spread along with the increasing use of woodchip mulch in ornamental flower beds. A 2007 report from central coastal California was the first North American record. It has been reported several times from Southwest Australia.

Habitat

''Agrocybe putaminum'' is a saprobic species. Its fruitbodies grow on the ground in clusters or close groups, usually in woodchips, and so can be found in gardens, parks, and other areas that use this type of mulch. It is known to occur in western North American and Europe. The species used to be considered rare; after the initial report of its 1913 discovery in France, it was infrequently recorded again: in the Netherlands in 1958, Denmark in 1989, western Belgium and Italy in 1998, and India in 2003. The fungus has since become more common, and its range has spread along with the increasing use of woodchip mulch in ornamental flower beds. A 2007 report from central coastal California was the first North American record. It has been reported several times from Southwest Australia.