Panaeolus castaneifolius

Panaeolus castaneifolius is a little brown mushroom which sometimes contains small amounts of the hallucinogen psilocybin.

Description
This is a little brown mushroom that grows in grass and has black spores. The cap is up to 4 cm across, dark gray to buff, campanulate when young and becoming to convex in age, and sometimes striated or wrinkled. The stem is 5 cm by 5 mm thick, hollow, brittle, pruinose and striated. The spores are black and slightly roughened, 13 x 8 micrometres.

This mushroom is often mistaken for Panaeolus foenisecii, and is distinguished by the dark purplish grayish blackish spore deposit and the gill color.