Agaricus of North America: 436. 2016.
Common Name: none
Misapplied name: Agaricus albolutescens Zeller
Cap (4.0) 6-12 (15) cm broad, convex, becoming plano-convex to plano-depressed; margin incurved, then decurved, overlapping the gills, occasionally wavy and appendiculate from veil fragments; surface dry, glabrous or with appressed fibrils, white to cream, bruising tawny-brown; context 1.5 to 2.0 cm thick, white, firm, tinged pale-peach when cut; odor and taste weakly of anise, musty when dry.
Gills free, close, at first pallid, then pale pinkish-tan, dark chocolate-brown in age, edges colored like the faces; lamellulae in five to six series.
Stipe 2.0-7.0 cm long, 1.5-3.0 cm thick, more or less equal except for a bulbous base, with a narrow, cottony central core; surface of apex pallid, finely striate; lower stipe variable, glabrous to sparsely covered with whitish fibrils, occasionally sheathed with cottony-floccose veil remnants, yellowing like the cap; partial veil two layered, the under-surface cottony-fibrillose, sometimes fragmenting leaving scattered cottony patches over a membranous-tomentose basement layer; annulus superior, thin, initially erect, then pendulous to appressed to the stipe.
Spores 6.0-7.5 x 4.0-5.0 µm, elliptical in face-view, similar in profile, inequilateral, smooth, moderately thick-walled, hilar appendage inconspicuous, germ pore absent.
Solitary, scattered, or in small groups under oaks at low elevations and in montane conifer woods; fruiting in the fall along the coast and in the spring in montane regions; occasional to common in wet seasons.
Edible and good.
Like other members of the Agaricus arvensis clan, Agaricus moronii has a pleasant anise odor and bruises slowly but persistently yellow, characters that distinguish it from Agaricus xanthodermus, a mildly toxic species which has a phenolic or medicinal odor, and bruises fleetingly yellow, i.e. fading usually within minutes. Fieldmarks of Agaricus moronii include a stocky stature, tendency to discolor tawny-brown, not merely yellow, and chocolate-brown free gills. Agaricus sylvicola is very similar but has a less dramatic bruising reaction, more yellowish than tawny, a normal rather than stocky stature, and slightly smaller spores. It is possible that Agaricus moronii and Agaricus silvicola represent a single polymorphic species or a species complex. Further study is needed to resolve this question.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Kerrigan, R.W. (1986). The Agaricales (Gilled Fungi) of California. 6. Agaricaceae. Mad River Press: Eureka, CA. 62 p.
Kerrigan, R.W. (2016). Agaricus of North America. New York Botanical Garden: Bronx, NY. 574 p. (Protologue)
Zeller, S.M. (1938). New or Noteworthy Agarics from the Pacific Coast States. Mycologia 30: 468-474.