Polygonaceae Juss.
Including Coccolobaceae Barkley, Eriogonaceae (Dum.) Meissner, Rumicineae (Rumicaceae) Dum.
Habit and leaf form. Herbs (commonly), or trees, or shrubs, or lianas; non-laticiferous and without coloured juice. ‘Normal’ plants, or switch-plants; sometimes with the principal photosynthesizing function transferred to stems. Leaves well developed (usually), or much reduced. Plants with roots. With a basal aggregation of leaves (often), or with neither basal nor terminal 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 at the base, or cuneate at the base, or rounded at the base. Leaves stipulate (usually), or exstipulate (Eriogoneae). Stipules intrapetiolar; concrescent; ochreate; scaly. Lamina margins entire (or crisped), or crenate; revolute (when young). Leaves without a persistent basal meristem.
General anatomy. Plants with ‘crystal sand’, or without ‘crystal sand’.
Leaf anatomy. Mucilaginous epidermis present, or absent. Stomata anomocytic (mostly), or paracytic (e.g. Oxytheca).
Adaxial hypodermis present (occasionally), or absent. Lamina dorsiventral, or isobilateral, or centric. Minor leaf veins without phloem transfer cells (Polygonum, Rheum, Rumex).
Stem anatomy. Cork cambium present; initially deep-seated, or superficial. Nodes penta-lacunar to multilacunar. Medullary bundles present, or absent. Internal phloem probably absent. Secondary thickening absent, or developing from a conventional cambial ring, or anomalous; when anomalous, via concentric cambia. ‘Included’ phloem present, or absent. Xylem with vessels. Vessel end-walls simple. Vessels with vestured pits. Wood partially storied (VP), or not storied; parenchyma sparse paratracheal. Sieve-tube plastids S-type.
Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious, or polygamomonoecious, or dioecious. Anemophilous, or entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, axillary; often in fascicles. The terminal inflorescence unit cymose (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 nectaries present 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.
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 (though 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; 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, biochemistry. Not cyanogenic. Alkaloids present, or absent. Iridoids not detected. Arthroquinones detected (6 genera); polyacetate derived. 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). Arbutin absent. Betalains absent. Saponins/sapogenins present, or absent. Aluminium accumulation not found. Plants accumulating free oxalates. Sugars transported as sucrose (in Coccoloba, Ruprechtia, Triplaris). 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).
Geography, cytology. Frigid zone (a few), or temperate (mainly), or 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 (1998) Eudicot; core Eudicot; neither Rosid nor Asterid; 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.
Illustrations. • Polygonum. • Rumex, Fagopyrum. • Technical details (Rumex, Rheum, Fagopyrum). • Technical details (Oxygonum).
Quotations
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)
Cite this publication as: ‘L. Watson and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 14th December 2000. http://biodiversity.uno.edu/delta/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Watson and Dallwitz (1991) should also be cited (see References).
