Polygonaceae  

 ♦ Polygonaceae                

Perennial or annual herbs, shrubs, lianas, or trees, often with conspicuous swollen nodes. Woody species often with anomalous secondary growth; silica bodies and calcium oxalate crystals present in wood cells. Vessels with simple perforations; lateral pitting alternate; vestured pits mostly absent. Fibers with simple pits, mostly septate. Axial parenchyma scanty paratracheal or vasicentric. Rays from homogeneous to heterogeneous. Sieve-element plastids of S-type or (Triplaris, Ruprechtia, Coccoloba) Pfs-type (Behnke 1999). Leaves alternate, rarely opposite or verticillate, entire or rarely pinnatifid or palmately cleft, membranous to fleshy or leathery, sometimes articulated at the base; stipules interpetiolar, connate into a usually membranous or scarious sheath (ochrea) around the stem and completely or partly covering the nodes, reduced to a row of hairs or wanting in Eriogonoideae and in a few members of Polygonoideae. Stomata commonly anomocytic, sometimes anisocytic, diacytic, or paracytic. Flowers small, seldom solitary, mostly in various types of inflorescences, bisexual or less often unisexual and dioecious, actinomorphic, 3-merous or 5-merous, rarely 2-merous, apetalous. Sepals (2-)5 or 6, imbricate or quincuncial in bud, green and herbaceous to often colored and petaloid, more or less connate at the base or forming a short or long floral tube, persistent and sometimes enlarging in fruit. Stamens (3)5–8(9); filaments filiform, free or basally connate; anthers tetrasporangiate, versatile orbasifixed, opening longitudinally. Tapetum secretory. Microsporogenesis simultaneous. Pollen grains 3-celled or rarely 2-celled, mostly 3-colporate, rarely pantohexocolporate (Hong et al. 2005). A nectary disc present at the base of the ovary, which is annular as in Caryophyllaceae, or nectaries are placed between the bases of the filaments. Gynoecium of three or less often two, rarely four, carpels, with free or more or less connate stylodia; ovary superior, subtended by an annular (often lobed) glandular disc, unilocular, sometimes with vestigial partitions at the base. Ovule solitary, basal on more or less well-expressed stalk representing a reduced free-central placenta, orthotropous or rarely anatropous, bitegmic or sometimes more or less unitegmic through connation (Corner 1976), crassinucellate. Female gametophyte of Polygonum-type. Endosperm nuclear. Fruits nutlike, very often trigonous, sometimes closely subtended by the persistent calyx or enclosed in a fleshy floral tube. Seeds of medium size, straight; seed coat formed by the outer integument (testal); embryo straight or more often curved, well-differentiated, surrounded by a copious, starchy, and oily, horny.

1.1 ERIOGONOIDEAE
Leaves without well-defined stipules (ochrea lacking). Branching often sympodial.
Inflorescences cymose. Flowers always 3-merous.Anthraquinones probably lacking. — eriogoneae: Eriogonum, Hollisteria; pterostegieae: Pterostegia, Harfordia.

1.2 POLYGONOIDEAE.
Leaves with stipular sheaths (ochrea more or lessdeveloped). Branching monopodial. Inflorescences racemose with cymose partial infl orescences.Flowers3-merous, 2-merous, or 5-merous. Anthraquinones often present. – rumicieae: Rheum, Rumex, Emex; persicarieae: Persicaria, Antenoron, Bistorta,Aconogonon, Koenigia, Fagopyrum; polygoneae: Polygonum, Polygonella, Reynoutria, ,Oxygonum; atraphaxideae: Atraphaxis, Calligonum,; triplarideae: Gymnopodium; coccolobeae: Homalocladium.