Psilocybe semilanceata, commonly known as the
liberty cap, is a
psychedelic (or "magic") mushroom that contains the
psychoactive compounds
psilocybin,
baeocystin and
phenylethylamine. Of the world's
psilocybin mushrooms, it is both one of the most widely distributed in nature, and one of the most
potent. The mushrooms have a distinctive conical to bell-shaped
cap, up to in diameter, with a small
nipple-like protrusion on the top. They are yellow to brown, covered with radial grooves when moist, and fade to a lighter color as they mature. Their
stipes tend to be slender and long, and the same color or slightly lighter than the cap. The
gill attachment to the stipe is adnexed (narrowly attached), and they are initially
cream-colored before tinting purple as the
spores mature. The spores are dark purplish-brown in
mass,
ellipsoid in shape, and measure 10.5–15 by 6.5–8.5
micrometres.