Agaricus agrocyboides

The fruiting body has a cap 4–6 cm wide that is at first broadly bell-shaped, later expanding and developing a low central bump (an umbo) with a slight depression at the top. Its surface is pale ochraceous-brown, a little pinker toward the margin and more ochraceous at the centre, and is covered with fine fibrils and small, rather indistinct scales of the same colour. The stipe is slender, 6–8 cm long and 5–7 mm thick, hollow, and gradually widens toward the base, which reaches about 12 mm across. Above the ring it is white and fibrillose; below the ring it is dotted with small ochraceous scales and stains ochre when handled. The ring is white, broad, membranous, and fragile, with a torn edge. The gills are crowded, free from the stipe, and up to about 5 mm broad; they become progressively darker with age, and the spore print is brown. The flesh is firm and white, but turns brownish when cut, with a more reddish-brown tint in the stipe.^[2]

Microscopically, the spores are comparatively small, elongated to ellipsoid, and measure 5.2–6.6 by 3.2–3.8 μm. They lack a germ pore. The gill edges bear abundant, broadly pear-shaped cheilocystidia measuring 30–40 by 11–22 μm. The cap surface is made up of long cylindrical hyphae with abundant yellow and orange-brown deposits between them. On dried material, the Schaeffer reaction was recorded as a strong fire-red colour.^[2]

This species is known only from Panzi in present-day South Kivu, Democratic Republic of the Congo, then part of the Belgian Congo. The type was collected in December 1954, and a second collection was made there in January 1955. It was found growing singly or in small groups of two or three on soil in an old Coffea arabica plantation, so the species appears, at least from the early available records, to be associated with cultivated ground rather than forest habitat.^[2]