Agaricus macrosporus

Description
Mushroom Identification
Look-Alikes
History
Synonyms

Description

This small group of Macro Mushrooms were found on a grassy roadside verge, not far from some fields and a small wooded area. They’re also found in similar environments such as pastures, woodland edges and grassy woodland clearings.

Unfortunately, maggots can spot this mushroom as well and almost all the Macro mushrooms are maggot ridden.

Agaricus macrosporus is a great edible species to use in any recipe that calls for a large cultivated mushroom (Portobello). It excels in risotto dishes and omelets, and makes delicious soups and sauces to eat with meat.

Common names: Macro Mushroom.

Mushroom Identification

Cap

Initially spherical, expanding, becoming planoconvex, eventually flattened, without involute edges, surface radially fibrous or scaly at maturity, initially white, but becomes light ochre and yellows easily. When mature, the cap can reach a diameter of 10 to 25 cm. When bruised, the cap surface slowly turns yellow, most noticeably towards the margin.
Gills

Pale grayish-pink when young, dense, free, somewhat wavy gills later turning dark brown or purple-brown with age. The gill edges are slightly paler than the gill faces.
Stem

2-4 cm in diameter and 7-13 cm long, fusiform to cylindrical, slightly rod-shaped at the base, drooping membranous rings, and gear-like patterns on the underside. Above the ring, the stem surface is smooth, while below, it is surrounded by white or brownish scales in a rather irregular snakeskin-like pattern. When cut, the flesh of the stem will turn light brown, most notably at the base of the stem.
Spores

Ellipsoidal, smooth, 8.5-12.3 x 5.2-6.9µm.
Spore print

Brown.
Odor and Taste

The odor has an almond flavor, but as the fruitbody ages its smell becomes increasingly ammoniacal (or like urine). The taste is mushroomly.
Habitat

Saprobic; commonly seen in small groups in permanent pastures, grassy roadside verges, woodland edges, and in grassy woodland clearings.

Look-Alikes

Agaricus augustus

Does not have the pure white cap in young specimens.
Agaricus arvensis

Has a similar white cap, but turns a more yellowish tint as it matures. Its spores are much smaller than those of Agaricus urinascens and it doesn't smell as bad as it ages.
Agaricus osecanus

Similar, but with smaller spores; it also smells like crushed almonds when ripe.

History

This thoroughly modern fungal species was scientifically described in 1938 by the Danish mycologist Frits Hansen Møller (1887 - 1962) and the German mycologist Julius Schäffer (1882 - 1944), when it was given the binomial name Psalliota urinascens.

The scientific name Agaricus urinascens comes from a 1949 paper by German-born American Rolf Singer (published in 1951).

The specific epithet urinascens means "the gradual acquisition of a urine-like odor", while the common English name Macro Mushroom refers to the enormous size of the spores of these fungi.