12. Polygonum aviculare Linnaeus, Sp. Pl. 362. 1753; Hook. f., Fl. Brit. Ind. 5: 26. 1856; Boiss., Fl. Or. 4: 1036. 1879; Kom., Fl. URSS 5: 614. 1936; Kitamura, Fl. Afgh. 89. 1960; Pl. W. Pak. & Afgh. 44. 1964; Rech. f. & Schiman-Czeika in Rech. f., Fl. Iran. 56:79. 1968; RR.Stewart, l.c. 203.; Bhopal & Chaudhri, l.c. 81.; Hara, Enum. Fl. Nep. 178. 1983; Grierson & D.G.Long, l.c. 170; Munshi & Javeid, l.c. 54; Boulos, l.c. 28. (Fig.15, A-C).
Vern.: Kersu, Bannali.
Polygonum centinodum Lamk., Fl. Francies 3: 237. 1778; P. erectum Roth Beitr. Bot. 2: 131. 1783; P.heterophyllum Lindm. Svensk. Bot. Tidskr. 6: 960. 1912; P. aviculare var. heterophyllum (Lindm.) Munshi & Javeid, l.c. 55.
Suberect-erect, ascending or decumbent, glabrous annual herb, branched mostly from base. Leaves heterophyllous, lower larger on main branches, smaller on the lateral and upper branches, 0.8-2.5 x 0.25-1.0 cm, elliptic - lanceolate or ovate, acute, entire, dotted. Ochrea 0.75-1.25 cm long, bifid, silvery, membranous lacerate. Inflorescence solitary, axillary or 3-5 clusters. Flower 0.5-0.75 mm across, pedicel 0.5-0.75 (-1.0) mm. Ochrealae minute. Tepals 5, 1.5-2.0 x 0.5-1 mm, elliptic-lanceolate or ovate, obtuse-acute, entire. Stamens 5 (-4), filaments short, equal; anthers dorsifixed. Ovary 0.25-0.5 mm, ovate - circular, trigonous with 3 very short styles and capitate stigmas. Nuts 2-2.5 x 1.0-1.5 mm, ovate, trigonous, black, shining, striate.
Fl. Per.: March-September.
Type: Described from Europe, Hb. Linn. 510.23 (LINN).
Grows from plains to 3500 m, as a weed in area of cultivation, on waste ground, moist and shady areas; Distribution: Widely distributed in temperate and subtropical regions of both the hemispheres.
A cosmopolitan weed, usually number of sagregates from this highly variable taxon have been described as independent species on the basis of habit, heterophyllous and isophyllous leaves and the length of perianth tube. However, if large number of specimens are studied, the characters often break down in our region. We have presently maintained three species P. aviculare, P. arenastrum and P. olivascens on basis of habit and characters of leaves and nuts. Sometimes some intermediate are also found between P. aviculare and P.arenastrum. Experimental studies are needed to solve the problem.