E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
{See also Small Agaricus Table} Section Minores. Features include 1) small size, 2) a whitish cap with fibrils or fibrillose scales that are at first pinkish (or can be yellowish brown at first according to some authors) and become brownish to grayish brown, 3) the tendency of the cap and stem to become deep yellow, 4) fragile flesh that may bruises yellow, 5) a slight fragile skirt-like ring, 6) an anise or almond odor, 7) growth in grass, 8) yellow reaction to KOH, and 9) small spores. It is also known as Agaricus micromegathus.

Murrill gives the distribution as New England (including VA, NJ) to TN, west to MI and TX. Hotson and Isaacs list it for WA, Phillips for OR, and Kerrigan(1) for CA. There are collections from BC deposited at University of British Columbia. But molecular confirmation is desirable. "Only one North American specimen (from California), with a light pink cap, has been ITS-sequenced; the sequence matched that from European sequences assigned to A. comtulus", (Kerrigan(3), with Latin name italicized).

Cap:
2-4cm across, "broadly convex to convex-truncate when young, becoming depressed centrally", when old nearly flat; dry, innately fibrillose, fibrils pinkish red, darkening to gray-brown or more dingy, forming appressed to slightly repent fine scales about 0.2cm long and 0.1-0.2cm wide, background whitish to buff, (Kerrigan), 4.5cm across approximately, convex, not umbonate; center brown, elsewhere pallid or whitish, staining deep yellow where bruised; innately fibrillose or with few minute appressed scales, (Hotson), 2-5(8)cm across, convex to flat; dry, "with silky fibrils or fibrillose scales (sometimes very sparse toward the margin)", "fibrils at first pinkish in one form, yellow-brown in another, but in both forms becoming brownish to grayish-brown in age on a whitish to buff background", "yellow to orange stains often developing in age or upon handling", (Arora), "fibrils pinkish-red, in age darkening to gray-brown or darker brown" and "streaked with tiny vinaceous-brown scales; surface bruises saffron yellow to ochraceous", (Chariton), cap exceeding gills markedly, 0.1-0.2cm, (Isaacs)

Flesh:
up to 0.4cm thick; white, unchanging or becoming yellowish, in stem white, to salmon orange when old, (Kerrigan), thick, white, unchanging, (but also notes all parts of sporophore staining deep saffron-yellow where bruised), (Hotson), thin, fragile; "white, unchanging or bruising yellowish", (Arora)

Gills:
free, close, up to 0.3cm broad, "greyish when young, soon pinkish" (quoted from Peck), finally dark blackish brown, (Kerrigan(1)), crowded, broad, thin; white for a long time, becoming pink then purplish gray, (Hotson), free at maturity, close; "pallid or grayish, then pinkish, finally chocolate-brown or darker", (Arora), finally chocolate brown or red-brown, (Chariton)

Stem:
2.5-3cm x 0.2-0.8cm, equal or very slightly bulbous, narrowly stuffed-hollow, cavity 0.05-0.1cm broad; white, becoming orangish when old or when bruised; finely fibrillose when young, bald when old, (Kerrigan(1)), about 4cm long and 0.8cm wide, short, stout, solid; white, staining deep yellow where bruised; bald, (Hotson), 2-6cm x 0.3-1cm, equal or slightly widened at base, "stuffed or hollow, fragile at maturity"; white or staining yellow to orange upon handling, especially in lower part, (Arora)

Veil:
veils sometimes appendiculate, more usually forming a pendant (to intermediate-type), subapical to supramedian white ring, flaring 0.2-0.4cm, partial veil white, loosely interwoven, universal veil a narrow denser zone on ring undersurface, soon becoming orangish, also leaving deciduous fibrils on stem, (Kerrigan(1)), ring "median or inferior, narrow, thin, simple, persistent, white", (Hotson), membranous, thin, "forming a fragile, superior to median ring" or disappearing, ring skirt-like or intermediate, (Arora)

Odor:
almond (Kerrigan(1)), distinctly sweet (anise-like or almondy), (Arora), pleasant (Phillips), pleasant, faintly of anise, (Kibby)

Taste:
pleasant (Phillips), nutty - almond-like (Isaacs)

Microscopic spores:
spores (3.8)4.6-4.9(5.6) x (3.0)3.5-3.8(4.1) microns, elliptic to broadly elliptic, dark brown, hilar appendix fairly prominent, germ pore not evident; basidia 4-spored, 21-25 x 5-7 microns, cylindroclavate, sterigmata 2-3 microns long; cheilocystidia not observed, gill margin fertile, (Kerrigan(1)), spores 5-6 x 4-4.5 microns, (Hotson), spores 4.5-5.5 x 3.5-4 microns, broadly elliptic, smooth, (Arora)

Spore deposit:
chocolate brown (Arora)