Pseudosperma sororium
Mycologia 112(1): 94. 2020.
Basionym: Inocybe sororia Kauffman
Common Name: none
Cap 2.5-6.5 cm broad, conic, becoming bell-shaped, finally nearly plane with a distinct umbo, margin sometimes uplifted in age; surface dry, radially fibrillose to cracked, pale yellowish-buff, shading to a slightly darker disc, flesh thin, pallid to buff; odor of green corn.
Gills close, narrow, adnate, sometimes seceding, pallid to drab buff, becoming dull brown at maturity, edges lighter than the faces.
Stipe 4-10 cm tall, 0.3-0.8 cm thick, equal to slightly enlarged at the base, surface dry, fibrillose, pallid to concolorous with the cap; veil absent.
Spores 10-14 x 6-8 µm, elliptical, smooth. Spore print dull brown.
Solitary to scattered under hardwoods and conifers; in the San Francisco Bay Area it is common with Monterey pine; fruiting from late fall to mid-winter.
Toxic. Contains a clinically significant concentration of muscarine.
In a group known for small, drab, difficult to differentiate mushrooms, Pseudosperma sororium stands out because of its relatively large size and conic cap with a well developed umbo. Other important field characters are the radially fibrillose to cracked cap surface and the strong green corn odor obvious when the cap tissue is crushed.
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