Volvariella gloiocephala

The stubble rosegill, Volvariella gloiocephala (DC.) Boekhout & Enderle.
Credit: Jean-Pol Grandmont
Source: Wikipedia
Agaricus gloiocephalus DC.
in de Candolle & Lamarck, Fl. franç., Edn 3 (Paris) 5/6: 52 (1815)
Agaricus speciosus Fr.
Observ. mycol. (Havniae) 2: 1 (1818)
Amanita speciosa Fr.
Observ. mycol. (Havniae) 2: 1 (1818)
Volvaria gloiocephala (Fr.) Gillet
Hyménomycètes (Alençon): 388 (1876)
Volvaria speciosa (Fr.) P. Kumm.
Führ. Pilzk. (Zwickau): 99 (1871)
Volvaria speciosa var. gloiocephala (DC.) R. Heim, (1936)
Volvariella gloiocephala (DC.) Wasser
Ukr. bot. Zh. 45(6): 78 (1988) var. gloiocephala
Volvariella gloiocephala var. speciosa (Fr.) Bon
Docums Mycol. 22(no. 88): 40 (1993)
Volvariella speciosa (Fr.) Singer
Lilloa 22: 401 (1951) [1949]
Volvariella speciosa f. gloiocephala (DC.) Courtec.
Bull. Sem. Soc. Mycol. Nord 34: 16 (1984)
Volvariella speciosa (Fr.) Singer
Lilloa 22: 401 (1951) [1949] f. speciosa
Volvariella speciosa var. gloiocephala (DC.) Singer
Lilloa 22: 401 (1951) [1949]
Volvariella speciosa (Fr.) Singer
Lilloa 22: 401 (1951) [1949] var. speciosa
Stubble rosegill
Description
Cap: 5-14 cm diameter, white with a grayish-brown center; initially ovoid, becoming convex and finally more or less expanded, greasy or viscid when damp, otherwise smooth; flesh white and firm.
Gills: at first white, becoming light pink at maturity, free, broad, crowded.

Credit: Darvin DeShazer
Source: Mushroom Observer, licensed by-nc-sa2.5
Stem: 5-18 cm x 1-2.5 cm, white, smooth, tapering upwards, the base enclosed in a white or grayish volval sheath; flesh white and firm.
Odor: earthy
Taste: not distinctive.
Spores: pink, smooth, ellipsoid, non-amyloid, 13-18 x 8-10 µm.
Spore print: pale pink.
Edibility: edible, but beware of poisonous Amanita look-alikes (Amanitas have white spore prints).
Habitat: on grassy soil or on rich soil such as dung heaps, rotted straw, manured ground, compost heaps; summer to fall; infrequent.
Medicinal activity
Antitumor effects
Polysaccharides extracted from the mycelial culture of V. gloiocephala and administered intraperitoneally into white mice at a dosage of 300 mg/kg inhibited the growth of Sarcoma 180 and Ehrlich solid cancers by 90% and 80%, respectively (Ohtsuka et al., 1973).
Links
There's photos of the stubble rosegill from all angles at Biopix
Picture and description at CalPhotos (as Volvariella speciosa (Fries: Fries) Singer)
References
Boekhout T, Enderle M.
Typification of Volvariella gloiocephala (DC: Fr) Boekhout & Enderle.
Persoonia. 1996 16:249-51.
Ohtsuka S, Ueno S, Yoshikumi C, Hirose F, Ohmura Y, Wada T, Fujii T, Takahashi E.
Polysaccharides having an anticarcinogenic effect and a method of producing them from species of Basidiomycetes.
UK Patent 1331513, 26 September 1973.
Ouzouni PK, Riganakos KA.
Nutritional value and metal content profile of Greek wild edible fungi.
Acta Alimentaria. 2007 36(1):99-110.