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Agaricus subrufescens

[ Basidiomycetes > Agaricales > Agaricaceae > Agaricus . . . ]

by Ron Meyers

A large compost pile in my yard has occasionally rewarded me with a good meal of Clitocybe nuda, the blewit. This year was no exception--but while I was collecting these mushrooms I noticed some large, brown, gilled mushrooms that were just a little too old for identification, although they were obviously some species of Agaricus. I noted that the stem stained yellow, and thought they might be Agaricus xanthodermus.

I was too late again for the second fruiting, but when the third appeared I found some fresh specimens, which keyed very quickly to Agaricus subrufescens. The only difference I found from David Arora’s description (1986) was the absence of an odor “strongly sweet (like almond extract).” I found the odor quite mild, but when cooked the mushroom had a very distinctive almond taste. The taste was quite pleasant, but my wife and I could not decide on the most appropriate use for an almond flavored mushroom. Perhaps it should be served with fruit, as it was not something we would want with our steak. Arora relates using it in cream of mushroom soup, which might be a better application.

The mushrooms kept for several days in my refrigerator. When I first collected them they were only lightly tanned on top. Shortly thereafter they turned darker tan and when I took them out of the refrigerator it was easy to see a reddish cast on the cap; the name subrufescens (becoming somewhat reddish) is very appropriate.

Description:

Ecology: Saprobic; growing scattered or in dense groups on rich humus, manure, and in particular on compost. While somewhat rare it seems to be widely distributed, reported from eastern North America as well as California, and often found in great quantities.

Cap: 7-25 cm; round, sometimes shaped like a marshmallow when young, becoming convex to nearly flat; surface dry, when young covered with fine matted fibrils which break up into tiny scales, except at the center; fibrils pallid, buff, pale brown, or pinkish-brown; scales becoming darker brown or reddish with age; background color white to pinkish-buff; sometimes yellowing with age or when bruised.

Gills: Free from the stem; close; whitish when young, becoming pinkish, then reddish brown, and eventually dark chocolate brown.

Stem: 5-15 cm long; 1-4 cm thick; equal or enlarged at base; with a thick membranous partial veil which has cottony patches on the underside and which forms a high, skirt-like ring; white to pinkish above the ring; smooth or with fibrils or scales below; base often staining yellow with age or when bruised (but the flesh inside does not stain bright yellow when cut); base often with mycelial threads attached.

Flesh: Thick; firm; white; bruising very slightly yellow or not at all.

Odor and Taste: Like almonds.

Chemical Reactions: Cap yellow with KOH.

Spore Print: Dark brown.

Microscopic Features: Spores 5.5-7.5 x 4-5 µ; elliptical; smooth; inamyloid. Pleurocystidia absent; cheilocystidia 10-15 x 4-5 µ; abundant; inflated.

REFERENCES: Peck, 1894. (Saccardo, 1895; Kauffman, 1918 [Psalliota subrufescens]; Smith, 1975; Freeman, 1979; Smith, Smith & Weber, 1979; Dilly, 1981; Arora, 1986; Kerrigan, 1986; Kerrigan, 2005.) Herb. Kuo 08250605.

Notes:   [from Michael Kuo]

Recent investigations support the idea that Agaricus subrufescens is a highly variable species, in both its outward and microscopic features. DNA evidence from Kerrigan (2005) suggests that South America's Agaricus blazei, as described by many authors, and Agaricus brasiliensis, are genetically identical to Agaricus subrufescens. The original description of Agaricus subrufescens, by Peck (1894), does not note any yellow bruising. However, Kerrigan points out that Peck studied specimens that were several days old, and had been sent to him; the actual collector wrote later that the mushroom had a "lemon tinted neck." Reports of Agaricus augustus from eastern North America may represent Agaricus subrufescens; it is unclear whether Agaricus augustus actually occurs east of the Rocky Mountains. It, too, has an almond odor and taste, large and blocky stature, and scales. However, it is usually darker brown, tends to have more prominent scales, grows more frequently in woods, and has significantly larger spores (7-10 x 4.5-5.5 µ).

Cited above: Kerrigan, R. W. (2005). Agaricus subrufescens, a cultivated edible and medicinal mushroom, and its synonyms. Mycologia 97: 12-24 [ Abstract ].

Further Online Information:

Agaricus subrufescens at Agaricales of the Hawaiian Islands
Agaricus augustus at Tom Volk's Fungi

 

Agaricus subrufescens

Agaricus subrufescens

Agaricus subrufescens

Agaricus subrufescens



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Cite this page as:

Meyers, R. (2005, September). Agaricus subrufescens. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/agaricus_subrufescens.html