POLYGONACEAE

'Polygonaceae' is a family of flowering plants also known as the "knotweed family" or "smartweed family". The name is based on the genus ''Polygonum''. Some well known members include ''Fagopyrum'' (buckwheat), ''Rumex'' (sorrel), ''Rheum'' (rhubarb), and ''Polygonum'' (knotgrass). The family is named for the shape of the seed; that of rhubarb, for example, has a triangular cross-section.
According to the database of the Royal Botanic Gardens, Kew, the family consists of 43 genera, totalling about 1100 species. Numerically the most important are ''Eriogonum'' (250 species), ''Polygonum'' (200 species), ''Rumex'' (200 species), ''Coccoloba'' (120 species), and ''Calligonum'' (80 species).
The family is present worldwide, but are most differentiated in temperate regions.

Contents

Taxonomy

Description

Selected genera

External links

Taxonomy

This family is very well-defined and is universally recognised, but its position has been less clear.
For example, in the Cronquist system, it was given its own order (Polygonales), but newer systems such as APG treat them as part of the Caryophyllales.
Polygonaceae can be divided in two subfamilies:

★ Polygonoideae, comprising about 28 genera and 800 species, are characterised by the lack of an involucre and the presence of ocreae. Important members are ''Polygonum'', ''Rumex'' and ''Calligonum''.

★ Eriogonoideae, with about 330 species, are exclusive to the New World and are characterised by the involucre, cymose inflorescence and lack of ocreae . Important members are ''Eriogonum'' and ''Coccoloba''.

Description

Most Polygonaceae are perennial herbaceous plants, but small shrubs (e.g. ''Coccoloba'') and climbers (e.g. ''Antipogon'') are also present.
'Leaves' of Polygonoideae have a peculiar pair of sheathing stipules known as 'ocreae'.

Selected genera

★ ''Afrobrunnichia''

★ ''Antigonon''

★ ''Aristocapsa''

★ ''Atraphaxis''

★ ''Brunnichia''

★ ''Calligonum''

★ ''Centrostegia''

★ ''Chorizanthe''

★ ''Coccoloba''

★ ''Dedeckera''

★ ''Dodecahema''

★ ''Emex''

★ ''Eriogonum''

★ ''Fagopyrum''

★ ''Fallopia''

★ ''Gilmania''

★ ''Goodmania''

★ ''Gymnopodium''

★ ''Harfordia''

★ ''Hollisteria''

★ ''Knorringia''

★ ''Koenigia''

★ ''Lastarriaea''

★ ''Leptogonum''

★ ''Muconea''

★ ''Muehlenbeckia''

★ ''Nemacaulis''

★ ''Neomillspaughia''

★ ''Oxygonum''

★ ''Oxyria''

★ ''Oxytheca''

★ ''Parapteropyrum''

★ ''Persicaria''

★ ''Podopterus''

★ ''Polygonella''

★ ''Polygonum'' or Knotweed

★ ''Pteropyrum''

★ ''Pterostegia''

★ ''Rheum''

★ ''Rumex''

★ ''Ruprechtia''

★ ''Stenogonum''

★ ''Symmeria''

★ ''Systenotheca''

★ ''Triplaris''

External links

★ Polygonaceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants: descriptions, illustrations, identification, information retrieval. http://delta-intkey.com