The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp (fungal fruiting body) that supports a spore-bearing surface, the hymenium. The hymenium (hymenophore

Hymenophore

A hymenophore refers to the hymenium-bearing structure of a fungal fruiting body. Hymenophores can be smooth surfaces, lamellae, folds, tubes, or teeth....

) may consist of lamellae, tubes, or teeth, on the underside of the pileus. A pileus is characteristic of agarics, boletes, some polypores, tooth fungi, and some ascomycetes.

Classification

Pilei can be of various shapes, and the shape can change over the course of the developmental cycle of a fungus. The most familiar pileus shape is hemispherical or convex. Convex pilei often continue to expand as they mature until they become flat. Many well-known species have a convex pileus, including the button mushroom

Button mushroom

Agaricus bisporus—known variously as the common mushroom, button mushroom, white mushroom, table mushroom, champignon mushroom, crimini mushroom, Swiss brown mushroom, Roman brown mushroom, Italian brown, Italian mushroom, cultivated mushroom, or when mature, the Portobello mushroom—is an edible...

, various Amanita

Amanita

The genus Amanita contains about 600 species of agarics including some of the most toxic known mushrooms found worldwide. This genus is responsible for approximately 95% of the fatalities resulting from mushroom poisoning, with the death cap accounting for about 50% on its own...

species and bolete

Bolete

A bolete is a type of fungal fruiting body characterized by the presence of a pileus that is clearly differentiated from the stipe, with a spongy surface of pores on the underside of the pileus...

s.

Some, such as the parasol mushroom

Parasol mushroom

The parasol mushroom is a basidiomycete fungus with a large, prominent fruiting body resembling a lady's parasol. It is a fairly common species on well-drained soils. It is found solitary or in groups and fairy rings in pastures and occasionally in woodland...

, have distinct bosses or umbos and are described as umbonate. An umbo

Umbo (mycology)

thumb|right|[[Cantharellula umbonata]] has an umbo.thumb|right|The cap of [[Psilocybe makarorae]] is acutely papillate.An umbo is a raised area in the center of a mushroom cap. Caps that possess this feature are called umbonate. Umbos that are sharply pointed are called acute, while those that are...

 is a knobby protrusion at the center of the cap. Some fungi, such as chanterelle

Chanterelle

Cantharellus cibarius, commonly known as the chanterelle, golden chanterelle or girolle, is a fungus. It is probably the best known species of the genus Cantharellus, if not the entire family of Cantharellaceae. It is orange or yellow, meaty and funnel-shaped...

s have a funnel- or trumpet

Trumpet

The trumpet is the musical instrument with the highest register in the brass family. Trumpets are among the oldest musical instruments, dating back to at least 1500 BCE. They are played by blowing air through closed lips, producing a "buzzing" sound which starts a standing wave vibration in the air...

-shaped appearance. In these cases the pileus is termed infundibuliform.

See also

• Lamella
• Stipe
  Stipe (mycology)
  thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
  
  
• Pileus area index
  Pileus area index
  The pileus area index is the technical name for the size of what is commonly known as the "cap" of a fungal fruiting body. It was coined by Asher Tarivona Mutsengi, a researcher at the University of Texas at Austin. It is particularly characteristic of agarics, boletes, and some polypores, tooth...