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Polygonaceae A. L. Jussieu
M. Qaiser
Herbs, shrubs, rarely trees or climbers. Stems often with swollen nodes. Leaves usually alternate, simple; stipules united forming a sheath around the stem (ochrea). Ochreae membranous, scarious, hyaline, fimbriate, lacerate, ciliate or sometimes entire at the mouth. Inflorescence of various types, basically a cyme often disposed in spikes, heads or panicles. Flowers bisexual, rarely unisexual, actinomorphic. Perianth biseriate, composed of 3, 4, 5 or 6 tepals which are united below, the inner sometimes enlarged or modified with hooks, spines, wings or tubercles, tepals often persistent, usually enlarged and membranous in fruit. Stamens 4-9(-16), uni or biseriate with nectar secreting glands at the base, pollen grains 3-4, colpate, 3-colporate, pantoporate or triporate. Carpels 2-3, syncarpous, ovary superior, unilocular, ovule 1, seemingly basal; styles 2-4 with capitate or fimbriate stigma. Fruit a biconvex or trigonous nut, often enclosed by the persistent perianth, shining, brown to black. Seed usually with a curved embryo.
A family of 55 genera and possibly over 1150 species, mostly distributed in temperate regions, particularly in the northern hemisphere. Represented in Pakistan by 19 genera and 103 species.
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| 1 |
Plants climbers or twiners. |
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(2) |
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Plants erect or scrambling. |
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(3) |
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| 2 (1) |
Plants climbing by tendrils. All perianth segments alike. |
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19 Antigonon |
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Plants twining. Inner 2 perianth segments thinner, flat, outer 3 cucculate, keeled or winged. |
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9 Fallopia |
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| 3 (1) |
Plants with flattened, thin jointed, ribbon-like phylloclades. |
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1 Homalocladium |
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Phylloclades absent. Stem cylindrical. |
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(4) |
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| 4 (3) |
Racemes very long (up to 40 cm). Styles hardened, persistent and hooked. |
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18 Antenoron |
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Racemes absent; if present, then seldom more than 10 cm long. Styles sometimes persistent but neither hardened nor hooked. |
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(5) |
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| 5 (4) |
Perianth 3-5 – partite. |
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(8) |
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Perianth 6 – partite. |
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(6) |
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| 6 (5) |
Outer perianth segments spiny in fruit. |
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14 Emex |
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Outer perianth segments though sometimes toothed or tuberculate but never spiny in fruit. |
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(7) |
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| 7 (6) |
Perianth segments in two whorls, inner segments accrescent, enveloping the triquetrous nuts. Stamens 6. Styles fimbriate. Nuts not winged. |
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13 Rumex |
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Perianth segments in one whorl, not accrescent. Stamens 7-9. Style very small and rounded. Nuts winged. |
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12 Rheum |
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| 8 (5) |
Stamens 12-18. Fruits usually covered with long and much branched setae. |
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17 Calligonum |
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Stamens 1-8. Fruits not as above. |
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(9) |
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| 9 (8) |
Flowers arranged in spiciform or capitate inflorescence. Nectaries usually present and conspicuous around the stamens. All stamens of the same size, usually not enlarged at the base. Tepal venation trifid. |
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(12) |
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Flowers in axillary clusters. Nectaries usually absent or inconspicuous around the stamens. Stamens usually enlarged and inflated at the base, inner larger. Tepal venation dendricular or anastomosing. |
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(10) |
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| 10 (9) |
Fruits winged. |
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15 Pteropyrum |
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Fruits not winged. |
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(11) |
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| 11 (10) |
Plants annual or perennial herbs, branches not ending into spines. Stamens usually less than 8. Fruits not enclosed by the perianth. |
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8 Polygonum |
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Plants shrubs, branches often ending into spines. Stamens 8. Fruit enclosed by the accrescent perianth. |
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16 Atraphaxis |
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| 12 (9) |
Perianth 4-partite, 2 outer segments smaller, becoming reflexed, inner 2, large erect. Stigma fimbriate. Nuts prominently winged. |
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11 Oxyria |
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Perianth 3-5 partite, if 4-partite then not as above. Stigma not fimbriate. Nuts not or very minutely winged. |
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(13) |
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| 13 (12) |
At least lower leaves deltoid. Perianth lobes almost free. Stamen filaments winged. Nuts 2-3 times longer than perianth lobes. |
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10 Fagopyrum |
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Leaves of various shapes but not deltoid. Perianth lobes fused up to ½ or more of their length. Stamen filaments not winged. Nuts equalling or shorter than perianth lobes. |
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(14) |
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| 14 (13) |
Flowers in dense to lax, clearly defined, spike-like or capitate inflorescence. |
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(15) |
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Flowers in diffused small clusters of large loose panicle-like inflorescences or terminal leafy flat topped corymb. |
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(16) |
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| 15 (14) |
Strongly rhizomatous perennial herbs. Basal leaves well developed, with prominent veins. Styles 3, free and elongate. Number of floral parts mostly constant. |
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7 Bistorta |
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Annual or rarely perennating by rooting branches.Leaves more evenly distributed along the stem, without prominent veins. Style 1, bifid or trifid. Number of floral parts often reduced. |
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4 Persicaria |
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| 16 (14) |
Nectaries confluent into the disc, associated with club shaped papillae. Perianth not fleshy in fruit. Pollen grains spinulose. |
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3 Koenigia |
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Nectaries free, fused with the inner stamens or confluent at the base. Papillae mostly absent, if present then cylindrical, pollen grains not spinulose. |
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(17) |
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| 17 (16) |
Leaves gradually narrowed towards base, ± hastate with 2 short, obtusish or rarely acute auricles; nuts black. |
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6 Knorringia |
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Leaves cuneate or rounded at base, always without auricles; nuts buff or brown. |
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(18) |
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| 18 (17) |
Styles very short, obconic several times shorter than the ovary, stigma very large. Pollen 3-colpate or 3-colporate. |
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2 Aconogonon |
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Styles columner, slightly shorter than the ovary; stigmas short. Pollen 6-colpate. |
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5 Rubrivena |
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List of lower taxa
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