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The families of flowering plants

L. Watson and M.J. Dallwitz

Polygonaceae Juss.

Including Coccolobaceae Barkley, Eriogonaceae (Dum.) Meissner, Rumicineae (Rumicaceae) Dum.

Habit and leaf form. Herbs (commonly), or trees, or shrubs, or lianas. ‘Normal’ plants, or switch-plants; sometimes with the principal photosynthesizing function transferred to stems. Leaves well developed (usually), or much reduced. Plants autotrophic; green and photosynthesizing. With a basal aggregation of leaves (often), or without conspicuous aggregations of leaves. Self supporting, or climbing; when climbing, stem twiners, or tendril climbers; Polygonum twining clockwise. Helophytic, or mesophytic, or xerophytic. Leaves minute to large; alternate (nearly always), or opposite (Pterostegia); usually spiral; ‘herbaceous’, or membranous (when reduced); petiolate, or subsessile; sheathing. Leaf sheaths not tubular; with free margins. Leaves gland-dotted, or not gland-dotted; simple; sometimes almost peltate, or not peltate; epulvinate. Lamina entire; pinnately veined; cross-venulate; auriculate at the base, or cordate, or hastate, or sagittate, or attenuate to the base, or cuneate at the base, or rounded at the base. Leaves stipulate (usually), or exstipulate (Eriogoneae). Stipules when present, intrapetiolar; concrescent; ochreate; scaly. Lamina margins entire (or crisped), or crenate; revolute (when young). Leaf development not ‘graminaceous’.

General anatomy. Plants with ‘crystal sand’, or without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral (usually), or bifacial to centric (in at least 8 genera). Mucilaginous epidermis present, or absent. Stomata mainly confined to one surface (then usually abaxial, but adaxial on floating leaves of aquatics), or on both surfaces (commonly); anomocytic (mostly), or paracytic (e.g. in Oxytheca). Hairs of numerous kinds present (in the family); eglandular and glandular; unicellular and multicellular (long, unicellular non-glandular hairs present in all Eriogonoideae, absent from Coccoloboideae). Adaxial hypodermis present (occasionally), or absent. Minor leaf veins without phloem transfer cells (Polygonum, Rheum, Rumex).

Axial (stem, wood) anatomy. Cork cambium present; initially deep-seated, or initially superficial. Nodes penta-lacunar to multilacunar (mostly), or tri-lacunar (e.g., in climbing Polygonum and dioecious Rumex species). Primary vascular tissues at first comprising a ring of bundles, or in a cylinder, without separate bundles (i.e., soon becoming a continuous cylinder in woodier forms as secondary xylem develops); collateral (mostly), or bicollateral. Internal phloem probably nearly always absent. Cortical bundles present (sometimes, see illustration), or absent. Medullary bundles present (rather commonly, e.g. in Rumex, see illustration), or absent. Secondary thickening absent, or developing from a conventional cambial ring, or anomalous. The anomalous secondary thickening when present, via concentric cambia (variously resulting in interfascicular phloem strands in Emex, and semicircular groups of vascular bundles in the cortex of Caligonum spp.). Primary medullary rays wide.

The wood variously ring porous, or semi-ring porous, or diffuse porous. The vessels small (to very small), or medium (mostly); solitary and in radial multiples, or clustered. The vessel end-walls simple. The vessels with vestured pits; without spiral thickening. The axial xylem without fibre tracheids; with libriform fibres; including septate fibres (usually), or without septate fibres (in Calligonum and Eriogonum). The parenchyma sparse paratracheal. ‘Included’ phloem present, or absent. The wood partially storied (VP), or not storied.

Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious, or polygamomonoecious, or dioecious. Pollination anemophilous, or entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, axillary; often in fascicles. The ultimate inflorescence units cymose (but the main branching usually racemose). Inflorescences terminal, or axillary; racemes, corymbs, spikes and heads; with involucral bracts, or without involucral bracts; often conspicuously ochreolate. Flowers small; regular; 2 merous, or 3 merous, or 5 merous; cyclic to partially acyclic. When partially acyclic, the perianth acyclic and the androecium acyclic. Free hypanthium present, or absent. Hypogynous disk present (or represented by nectaries between the androecial members); annular.

Perianth ambiguously with distinct calyx and corolla, or sepaline, or petaline; 2–6; free to joined; 1 whorled, or 2 whorled (or spiralled); when biseriate, similar in the two whorls, or different in the two whorls; fleshy (sometimes), or non-fleshy; persistent; accrescent (often), or non-accrescent.

Androecium (2–)6(–9). Androecial members branched (e.g. Rheum), or unbranched; free of the perianth, or adnate (usually more or less perigynous); all equal, or markedly unequal; free of one another, or coherent (sometimes filaments basally connate); when cyclic, 2 whorled (3+3, or spiralled). Androecium exclusively of fertile stamens. Stamens (2–)6(–9); alternisepalous, or oppositisepalous. Anthers dorsifixed, or basifixed; versatile, or non-versatile; dehiscing via longitudinal slits; introrse, or extrorse and introrse, or latrorse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral. Anther wall initially with one middle layer; of the ‘monocot’ type. Pollen grains aperturate; 3–30 aperturate; colpate, or colporate, or foraminate, or rugate; 2-celled (rarely?), or 3-celled (in 5 genera).

Gynoecium (2–)3(–4) carpelled. Carpels isomerous with the perianth (when P cyclic). The pistil 1 celled (usually), or 3 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior. Ovary 1 locular (but rarely incompletely trilocellate by false septa). Locules secondarily divided by ‘false septa’ (rarely, incompletely), or without ‘false septa’. The ‘odd’ carpel posterior. Gynoecium stylate (sometimes only shortly). Styles (2–)3(–4); free to partially joined; apical. Stigmas (2–)3(–4); dry type; papillate, or non-papillate; Group II type. Placentation basal. Ovules in the single cavity 1; funicled, or sessile; ascending; non-arillate; orthotropous to anatropous; unitegmic to bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3 (becoming multinucleate in Rumex); not proliferating; ephemeral (often), or persistent. Synergids pear-shaped, or hooked (sometimes with filiform apparatus). Hypostase present, or absent. Endosperm formation nuclear. Embryogeny asterad.

Fruit non-fleshy; indehiscent; a nut (usually, usually trigonous or two-sided), or achene-like; enclosed in the fleshy hypanthium, or enclosed in the fleshy perianth, or without fleshy investment external to the original ovary; 1 seeded. Seeds endospermic. Endosperm ruminate (Coccoloba), or not ruminate; oily. Perisperm present to absent (‘more or less absent’). Seeds with starch. Cotyledons 2. Embryo achlorophyllous (5/14); straight to curved. The radicle lateral, or dorsal.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C3 and C4. C3 physiology recorded directly in Oxyria, Polygonum, Rheum, Rumex. C4 physiology recorded directly in Calligonum. Anatomy non-C4 type (Polygonum, Pteropyrum, Rumex), or C4 type (Calligonum). Sugars transported as sucrose (in Coccoloba, Ruprechtia, Triplaris). Not cyanogenic. Alkaloids present, or absent. Anthraquinones detected (6 genera); polyacetate derived. Arbutin absent. Iridoids not detected. Betalains absent (where sought). Saponins/sapogenins present, or absent. Proanthocyanidins present (usually), or absent; cyanidin, or delphinidin, or cyanidin and delphinidin. Flavonols present, or absent; quercetin, or kaempferol and quercetin, or kaempferol, quercetin, and myricetin. Ellagic acid absent (8 species, 4 genera). Aluminium accumulation not found. Plants accumulating free oxalates. Sieve-tube plastids S-type.

Geography, cytology. Frigid zone (a few), temperate (mainly), sub-tropical to tropical (a few). Widespread, but absent from Africa, tropical South ASmerica, West Indies, and Southeast Asia except New Guinea. X = 7–13.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Polygoniflorae (caryophylloid); Polygonales (close to Caryophyllales). Cronquist’s Subclass Caryophyllidae; Polygonales. APG III core angiosperms; core eudicot; Superorder Caryophyllanae. APG IV Order Caryophyllales.

Species about 800. Genera about 45; 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, Pteropyrum, Pterostegia, Rheum, Rumex, Ruprechtia, Stenogonum, Symmeria, Systenotheca, Triplaris.

Economic uses, etc. Foodstuffs from Fagopyrum (buckwheat) and Rheum (rhubarb); many noxious weeds, and some ornamentals.


Get you gone, you dwarf;
You minumus, of hindering knot-grass made
(‘Midsummer Night’s Dream’, iii., 2 - Polygonum aviculare. ‘Hindering’, from a superstition that drinking an infusion of the leaves and stems would stunt a boy’s growth)

By the lone quiet grave,
In the wild hedgerow the Knot grass is seen,
Down in the rural lane,
Or on the verdant plain,
Everywhere humble, and everywhere green
(Of Polygonum aviculare, quoted by Ann Pratt, ‘Wild Flowers’ (1857), unattributed)

Illustrations. • Le Maout and Decaisne: Rumex, Rheum. • Le Maout and Decaisne: Eriogonum, Fagopyrum, Koenigera, Muhlenbeckia. • Oxygonum sinuatum: Thonner. • Antigonon leptopus: Bot. Mag. 96 (1870). • Coccoloba cf. coronata: as C. virens, Bot. Reg. 1816, 1836. • Eriogonum compositum: Bot. Reg. 1774, 1836. • Eriogonum multiflorum: Hook. Ic. Pl. 3 (1840). • Fagopyrum esculentum (as Polygonum fagopyrum): Eng. Bot. 1226, 1868. • Fallopia dumetorum (as Polygonum dumetorum): Eng. Bot. 1228, 1868. • Oxyria digyna, as O. elatior: Hook. Ic. Pl. 5–6 (1842–3). • Oxyria digyna (as O. reniformis): Eng. Bot. 1225, 1868. • Polygonum affine: Bot. Mag. 106 (1880). • Polygonum tibeticum: Hook. Ic. Pl. 25 (1896). • Leptogonum domingense: Hook. Ic. Pl. 14 (1880–82). • Persicaria hydropiper, P. mite and P. maculosa (all as Polygonum): Eng. Bot. 1234, 1236 and 1237 (1868). • Persicaria lapathifolia, P. bistorta, P. vivipara (all as Polygonum): Eng. Bot. 1239, 1243, 1244 (1868). • Persicaria amphibia (as Polygonum, terrestrial and aquatic forms): Eng. Bot. 1241 and 1242, 1868. • Polygonum amplexicaule: Bot. Reg. 1839, 46. • P. rurivagum and Polygonum aviculare: Eng. Bot. 1229 and 1231, 1868. • Polygonum injucundum: Bot. Reg. 1250, 1829. • Polygonum maritimum: Eng. Bot. 1233, 1868. • Polygonum spp. (B. Ent. compilation). • Rheum nobile: Hooker’s Illustrations of Himalayan plants (1855). • Rumex acetosa and Rumex acetosella: Eng. Bot. 1223 and 1224, 1868. • Rumex conglomeratus, R. maritimus and R. sanguineus: Eng. Bot. 1210–1212, 1868. • Rumex crispus and Rumex hydrolappathum: Eng. Bot. 1218 and 1220, 1868. • Rumex sanguinus and Rumex maritimus: Eng. Bot. 1211 and 1212, 1868. • Rumex pulcher, R. obtusifolius and R. aff. conglomeratus (as R. pratensis): Eng. Bot. 1214–1216, 1868. • Rumex obtusifolius and R. aff. conglomeratus (as R. pratensis): Eng. Bot. 1214–1216, 1868. • Rumex spp. and Fagopyrum: B. Ent. compilation. • Rumex crispus: TS stem, with medullary vascular bundles (Solereder). • Calligonum comosum: TS stem, with cortical vascular bundles (Solereder, 1908).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.