Pleurotus ostreatus
Champ. Jura. Vosg. 1: 112. 1872.
Common Name: oyster mushroom
Cap 5-25 cm broad, fan-shaped, broadly convex to sometimes nearly plane at maturity; margin lobed to wavy, especially when young; surface smooth, white to greyish-brown; flesh white, odor of anise.
Gills decurrent, white, yellowish in age; veil absent.
Stipe often absent, when present, short and thick: 0.5-3.0 cm long, 0.5-2.0 cm thick, eccentric or lateral with dense white hairs at the base.
Spores 7.5-9 x 3.5-4.5 µm, smooth, elliptical, nonamyloid. Spore print white.
Forming overlapping shelves or clusters on stumps and logs of hardwoods, uncommon on conifers, from early fall to mid- winter. Pleurotus ostreatus is a member of the "Fog Flora" fruiting sporadically along the coast during the summer.
Edible and very popular, although a few people are allergic to it.
Pleurotus ostreatus is believed to be a species complex. In the California, specimens can be found that vary from white and relatively thin-fleshed on oaks to thick fleshed, grey-brown shelves on cottonwood and willow. Whether these differences are environmentally induced or genetic is not clear, but most mycophagists prefer the large, thick-fleshed specimens collected from cottonwood.
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