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Pakistan | Family List | Pakistan V. 205

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.


1 Plants climbers or twiners.   (2)
+ Plants erect or scrambling.   (3)
       
2 (1) Plants climbing by tendrils. All perianth segments alike.   19 Antigonon
+ Plants twining. Inner 2 perianth segments thinner, flat, outer 3 cucculate, keeled or winged.   9 Fallopia
       
3 (1) Plants with flattened, thin jointed, ribbon-like phylloclades.   1 Homalocladium
+ Phylloclades absent. Stem cylindrical.   (4)
       
4 (3) Racemes very long (up to 40 cm). Styles hardened, persistent and hooked.   18 Antenoron
+ Racemes absent; if present, then seldom more than 10 cm long. Styles sometimes persistent but neither hardened nor hooked.   (5)
       
5 (4) Perianth 3-5 – partite.   (8)
+ Perianth 6 – partite.   (6)
       
6 (5) Outer perianth segments spiny in fruit.   14 Emex
+ Outer perianth segments though sometimes toothed or tuberculate but never spiny in fruit.   (7)
       
7 (6) Perianth segments in two whorls, inner segments accrescent, enveloping the triquetrous nuts. Stamens 6. Styles fimbriate. Nuts not winged.   13 Rumex
+ Perianth segments in one whorl, not accrescent. Stamens 7-9. Style very small and rounded. Nuts winged.   12 Rheum
       
8 (5) Stamens 12-18. Fruits usually covered with long and much branched setae.   17 Calligonum
+ Stamens 1-8. Fruits not as above.   (9)
       
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.   (12)
+ 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.   (10)
       
10 (9) Fruits winged.   15 Pteropyrum
+ Fruits not winged.   (11)
       
11 (10) Plants annual or perennial herbs, branches not ending into spines. Stamens usually less than 8. Fruits not enclosed by the perianth.   8 Polygonum
+ Plants shrubs, branches often ending into spines. Stamens 8. Fruit enclosed by the accrescent perianth.   16 Atraphaxis
       
12 (9) Perianth 4-partite, 2 outer segments smaller, becoming reflexed, inner 2, large erect. Stigma fimbriate. Nuts prominently winged.   11 Oxyria
+ Perianth 3-5 partite, if 4-partite then not as above. Stigma not fimbriate. Nuts not or very minutely winged.   (13)
       
13 (12) At least lower leaves deltoid. Perianth lobes almost free. Stamen filaments winged. Nuts 2-3 times longer than perianth lobes.   10 Fagopyrum
+ 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.   (14)
       
14 (13) Flowers in dense to lax, clearly defined, spike-like or capitate inflorescence.   (15)
+ Flowers in diffused small clusters of large loose panicle-like inflorescences or terminal leafy flat topped corymb.   (16)
       
15 (14) Strongly rhizomatous perennial herbs. Basal leaves well developed, with prominent veins. Styles 3, free and elongate. Number of floral parts mostly constant.   7 Bistorta
+ 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.   4 Persicaria
       
16 (14) Nectaries confluent into the disc, associated with club shaped papillae. Perianth not fleshy in fruit. Pollen grains spinulose.   3 Koenigia
+ Nectaries free, fused with the inner stamens or confluent at the base. Papillae mostly absent, if present then cylindrical, pollen grains not spinulose.   (17)
       
17 (16) Leaves gradually narrowed towards base, ± hastate with 2 short, obtusish or rarely acute auricles; nuts black.   6 Knorringia
+ Leaves cuneate or rounded at base, always without auricles; nuts buff or brown.   (18)
       
18 (17) Styles very short, obconic several times shorter than the ovary, stigma very large. Pollen 3-colpate or 3-colporate.   2 Aconogonon
+ Styles columner, slightly shorter than the ovary; stigmas short. Pollen 6-colpate.   5 Rubrivena

  • List of lower taxa


     

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