Agaricus micromegathus

Description

Agaricus micromegathus is a small grass mushroom. It is recognized by a cap with pinkish to purplish fibrils concentrated at the disc. With age, these become brownish and frequently tinged yellowish where handled. Habitat solitary to scattered, sometimes in arcs in the grass; fruiting in late summer in watered areas or soon after the fall rains; uncommon.

Mushroom Identification

1. 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 dingier, forming appressed to slightly repent fine scales about 0.2cm long and 0.1-0.2cm wide, background whitish to buff.

2. 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".

3. Gills

   Free, close, up to 0.3cm broad, grayish when young, soon pinkish, crowded, broad, thin; white for a long time, becoming pink then purplish gray, free at maturity, close.

4. 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.

5. 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 the stem.

6. Odor

   Almond, distinctly sweet (anise-like or almondy).

7. Taste

   Pleasant and nutty – almond-like.

8. Spore Print

   Chocolate brown.

9. Microscopic Features

   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.

Look-Alikes

1. Agaricus comptulus

   Another small, anise-odored species is found in grass, but it has a cream-colored cap. Like Agaricus micromegathus, it yellows slowly where injured.

2. Agaricus semotus

   Can be distinguished by somewhat larger size and habitat preference.

3. Agaricus diminutivus

   Is distinctive because of its unusually small size and slender stature. Except for gill color, it could easily be confused for species of Lepiota.

Photo sources:

Photo 1 - Author: leptonia (CC BY-NC 4.0)