Gymnopilus luteofolius

Gymnopilus luteofolius, also known as Yellow-Gilled Gymnopilus is a large and widely distributed mushroom which grows in dense clusters on dead hardwoods and conifers. It has a rusty orange spore print and a bitter taste. It contains the hallucinogen psilocybin.

In Japan this mushroom is called waraitake, which translates to "laughing mushroom". This mushroom is often mistaken for Gymnopilus ventricosus, which contains no psilocybin.

Description
The cap ranges from 7 to 42 cm across, is convex, and is bright orange, orangish brown, or reddish brown with a dry scaly surface. The cap margin is inrolled well into maturity. The flesh is yellow and the gills are crowded, yellow to orange, and adnate to subdecurrent. The stem is dusted with rusty orange spores and has a cottony partial veil, and often narrows near the base.