pileus

[ pahy-lee-uhs, pil-ee- ]

noun

, plural pi·le·i [pahy, -lee-ahy, pil, -ee-ahy] pi·le·us

1. Mycology. the horizontal portion of a mushroom, bearing gills, tubes, etc., on its underside; a cap.
2. Zoology.
   1. the umbrella or bell of a jellyfish.
   2. pileum.
3. Also called cap cloud, Meteorology. a small, thin cloud just above or attached to a growing cumulus cloud.
4. a felt skullcap worn by the ancient Romans and Greeks.

pileus

/ ˈpɪl-; ˈpaɪlɪəs /

noun

1. the upper cap-shaped part of a mushroom or similar spore-producing body

pileus

/ pī′lē-əs /

, Plural pilei pī′lē-ī′

1. The umbrellalike fruiting structure forming the top of a fleshy fungus. It is supported by the stipe. The cap of a mushroom is a pileus.

Word History and Origins

Origin of pileus¹

1750–60; < New Latin, special use of Latin pīleus skullcap; akin to Greek pîlos felt, felt cap

Word History and Origins

Origin of pileus¹

C18 (botanical use): New Latin, from Latin: felt cap

Example Sentences

The reverse features two daggers on either side of a cap known as a pileus.

From New York Times

A cumulus, for example, might just be a cumulus; or it might be a cumulus fractus, if its edges are tattered; or a cumulus pileus, if a smaller cloud appears over it like a hood.

From New York Times

The larger species of fungi, such as the Agaricini and Polyporei, &c., are prepared for the herbarium by cutting a slice out of the centre of the plant so as to show the outline of the cap or pileus, the attachment of the gills, and the character of the interior of the stem.

From Project Gutenberg

The remaining portions of the pileus are then lightly pressed, as well as the central slices, between bibulous paper until dry, and the whole is then “poisoned,” and gummed on a sheet of paper in such a manner as to show the under surface of the one and the upper surface of the other half of the pileus on the same sheet.

From Project Gutenberg

A “map” of the spores should be taken by separating a pileus and placing it flat on a piece of thin paper for a few hours when the spores will fall and leave a nature print of the arrangement of the gills which may be fixed by gumming the other side of the paper.

From Project Gutenberg