Peristome

Peristome (from the

In mosses

In mosses, the peristome is a specialized structure in the sporangium that allows for gradual spore discharge, instead of releasing them all at once.

Most mosses produce a capsule with a lid (the

There are two subtypes of arthrodontous peristome.^[1]

1. The first is termed haplolepidous and consists of a single circle of 16 peristome teeth.
2. The second type is the diplolepidous peristome found in subclass Bryidae. In this type, there are two rings of peristome teeth—an inner endostome (short for endoperistome) and an exostome. The endostome is a more delicate membrane, and its teeth are aligned between the teeth of the exostome. There are a few mosses in the Bryopsida that have no peristome in their capsules. These mosses still undergo the same cell division patterns in capsule development, but the teeth do not fully develop.

In pitcher plants

In pitcher plants, the peristome is a reflexed ring (or partial ring) of tissue that surrounds the entrance to the digestive tube in these plants. It often (for example in Cephalotus and Nepenthes) possesses sharp, overhanging 'teeth' which aid in prey retention. It is often studded with nectar secreting glands, hence its popular name, nectar roll.

In fungi

The

In shelled gastropods

The peristome is the margin of the aperture of a gastropod shell. It is the edge of the lip of the shell. This part is sometimes reflected (turned back) or thickened once the snail reaches adult size, and these qualities of the peristome can be diagnostic features of the shell which may aid in identification of the species.

In other invertebrates

The peristome is any of the structures or sets of parts that surround the mouth or invertebrates such as echinoderms or earthworms.^[3]

References