Common Name: Cypress Agaricus
Cap 8-20 cm broad, convex, expanding to nearly plane, in age the disc sometimes slightly depressed; margin incurved, decurved at maturity; surface at first pallid to cream-buff, especially when developing below ground, soon becoming appressed fibrillose-squamose, light brown, hazel-brown, dull chestnut-brown, occasionally lilac-brown, darker in age, at times developing orange-brown, rufescent areas; context thick, very firm, white, slowly turning vinaceous when cut or bruised; odor, of "mushrooms," taste mild.
Gills free, close, moderately broad, dingy-pink when young, bruising reddish-brown slowly, dark chocolate-brown at maturity.
Stipe 9-19 cm long, 3-5 cm thick, equal to clavate, the core stuffed; surface dry, white with scattered fibrils at the apex, smooth to patchy fibrillose below, discoloring dingy brownish-red to ochraceous at the base; partial veil white, membranous, thick, elastic, upper surface wrinkled to striate, lower surface more or less smooth, occasionally cracked and forming patches, but not cottony-floccose, sometimes yellowing in age or when bruised, forming a superior, pendulous annulus at maturity, blackish from adhering spores and typically collapsing against the stipe.
Spores 5-6.5 x 4-5 µm, elliptical, smooth; spore print dark-brown.
Scattered to clustered under Monterey Cypress (Cupressus macrocarpa); fruiting from mid to late winter.
Edible and choice.
Agaricus lilaceps is among the largest and best edible Agaricus species in our area. Unfortunately, it is also the least common. We know it from only 4 sites under cypress along the San Mateo coast and are indebted to Mark Haley of the MSSF for pointing these out. It should be noted that Agaricus lilaceps is more common further south, especially in the Monterey Bay area, and is said to also occur on the campus of Stanford University under eucalyptus. Aside from size, Agaricus lilaceps is characterized by a robust stature, the stipe often club-shaped and well buried in the substrate, a cap with hazel-brown to dull-brown, appressed-fibrils/squamules, and a thick, white veil which sometimes becomes yellowish. The species epithet refers to the cap ornamentation of some specimens that may become lilac-brown. Related red-staining, cypress-inhabiting species include Agaricus pattersonae and A. fusco-fibrillosus. Agaricus pattersonae is very similar and takes practice to tell from A. lilaceps. The cap scales of Agaricus pattersonae are typically smaller, usually not as appressed, thus the underlying, pallid ground color is more apparent; in addition, the lower surface of the partial veil is more likely to develop pale brown patches, and never yellows; finally the stipe is more likely to have brown scaly rings at the base. A. fusco-fibrillosus is the most frequently encountered of the red-staining Agaricus species under cypress. It is smaller and less robust than A. pattersonae and has an appressed-fibrillose-squamose brown cap similar to A. lilaceps. Also distinctive is an annulus with a pale-brown margin and conspicuous scaly, pale-brown rings at the stipe base.