incurved

cap

(pl. caps)

Terms discussed: disk, effused-reflexed, incurved, inrolled, lacerate, lobed, margin (pl. margins), pileate, pileus (pl. pilei), resupinate, shelving, sterile margin

Image of Resupinatus applicatus from Christian Gottfried Daniel Nees von Esenbeck (1816 - 1817) Das System der Pilze und Schwämme

The pileus is the cap of the mushroom. A mushroom with a pileus is said to be pileate. A mushroom lacking a pileus, that is consisting of just a fertile surface with its back attached to or intergrown with the substrate, is said to be resupinate. Resupinate fungi usually grow on a substrate that is horizontal, like a fallen log.

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Photo of Polyporaceae by John Denk

Effused-reflexed is a term used to describe a mushroom on a vertical surface that is partially resupinate and partially pileate, as in the picture. The pileate portion of an effused-reflexed fruiting body is necessarily sessile. The part that's sticking out is sometimes called the reflexed portion, and the resupinate part is sometimes called the effused portion; I just call them (unless I forget) the pileate and resupinate parts of the cap.

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Image of Hygrophorus russula from Christian Gottfried Daniel Nees von Esenbeck (1816 - 1817) Das System der Pilze und Schwämme

The edge of the cap is called the margin, and the center of the top surface of the cap is called the disk (or disc). This specimen of Hygrophorus russula has a white margin, and the cuticle darkens considerably at the disk.

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Image of Clitocybe nebularis from A. M. Hussey (1847 - 1855) Illustrations of British mycology

In some species, the margin is inrolled, and this can be a helpful feature in identifying the mushroom. The term incurved is sometimes used in this sense.

Photo of Agaricus bitorquis by John Denk

If the margin extends beyond the gills or tubes, the mushroom is said to have a sterile margin.

Photo of Clitocybe nuda by Leon Shernoff

If the margin is wavy, it is called sinuate, just like a gill margin or attachment.

Image of Clitocybe dealbata from A. M. Hussey (1847 - 1855) Illustrations of British mycology

If the margin is looks like it has irregular, large, blunt, blobby extensions, it is said to be lobed. The margin of a mushroom often becomes lobed in age, as in this picture.

Image of Leptonia porphyrophaea from A. M. Hussey (1847 - 1855) Illustrations of British mycology

If the margin is broken up into many smaller, sharper protrusions that look like the cap has been torn slightly in order to make them, the margin is called lacerate. As with the lobed condition, a margin often becomes lacerate as the mushroom ages; but here it starts out quite young.

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