1 In mosses 2 In pitcher plants 3 In fungi 4 In shelled gastropods 5 References 6 External links
Arthrodontous capsule of the moss Dicranella varia
Peristoma of Bryum capillare
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 operculum) which falls off when the spores 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 walls. 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.
The first is termed haplolepidous and consists of a single circle of
16 peristome teeth.
The second type is the diplolepidous peristome fround 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
In pitcher plants
Diagram showing the location of the peristome on a
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
In shelled gastropods
The ventral surface of a shell of Cepaea nemoralis. The peristome is thickened and dark in an adult snail.
Main article: Lip (gastropod) 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. References
^ 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).
^ Pegler, D.N. et al. 1995. British Puffballs,
v t e
Aperture Apex Body whorl Callus Columella Lip Lira Nacre Periostracum Peristome Planispiral Plait Protoconch Sculpture Selenizone Siphonal canal Siphonal notch Spire Stromboid notch Suture Umbilicus Valve Varix Whorl
Other hard parts
Clausilium Love dart Operculum Pearl Radula
External soft parts
Caryophyllidia Caudal mucous pit Cerata Cnidosac Mantle Mentum Notum Parapodium Pneumostome Rhinophore Semper's organ Siphon Suprapedal gland
Internal soft parts
Circulatory system of gastropods Crop Ctenidium Digestive system of gastropods Diverticula Excretory system of gastropods Gastric shield Hancock's organ Hepatopancreas Hypobranchial gland Nephridium Nervous system of gastropods Nidamental gland Odontophore Oesophageal pouch Osphradium Reproductive system of gastropods Respiratory system of gastropods Sensory organs of gastropods
Epiphragm Pseudofeces Torsion Circumesophageal nerve ring Trochophore Tyrian pu