Pileus (mycology)

The pileus is the technical name for what is commonly known as the cap of a fungal fruiting body. It is particularly characteristic of agarics, boletes, and some polypores, tooth fungi, and ascocarps. Other sporocarp types have less clear differentiation between the pileus and the rest of the fruiting body. Sporocarps with a pileus typically have some type of hymenophore, such as lamellae, tubes, or teeth, on the underside of the pileus.

Classification
Pilei can be of various shapes: the most familiar being hemispherical or convex, with many of these becoming flat as they mature. Many well-known species have this shape, including the button mushroom, various Amanita species and boletes.

Some, such as the parasol mushroom, have distinct bosses or umbos and are described as umbonate. Many fungi, such as chanterelles have a funnel- or trumpet-shaped appearance, the pileus is termed infundibuliform.