Editing Peristome (section)

==In mosses==
[[File:Dicranella varia sporogon.jpeg|left|thumb|Arthrodontous capsule of the [[moss]] ''Dicranella varia'']]
[[File:Bryum capillare peristome.jpg|thumb|upright|Peristome of ''[[Bryum capillare]]'']]
In [[moss]]es, 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 [[operculum (botany)|operculum]]) which falls off when the [[spore]]s inside are mature and thus ready to be dispersed.  The opening thus revealed is called the ''stoma'' (meaning "mouth") and is surrounded by one or two peristomes.  Each peristome is a ring of triangular "teeth" formed from the remnants of dead cells with thickened [[cell wall]]s.  There are usually 16 such teeth in a single peristome, separate from each other and able to both fold in to cover the stoma as well as fold back to open the stoma.  This articulation of the teeth is termed '''arthrodontous''' and is found in the moss subclass [[Bryopsida]].  In other groups of mosses, the capsule is either '''nematodontous''' with an attached operculum (as in the [[Polytrichopsida]]), or else splits open without operculum or teeth.

There are two subtypes of arthrodontous peristome.<ref>Edwards, S.R. (1984). "Homologies and inter-relationships of moss peristomes", pages 658–695 ''in'' R. M. Schuster (Ed.) ''New Manual of Bryology''. (Japan: The Hattori Botanical Laboratory). {{Listed Invalid ISBN|49381633045}}.</ref>  
# The first is termed '''haplolepidous''' and consists of a single circle of 16 peristome teeth.  
# 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.