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Polygonaceae
A large family including 首乌属[1],山蓼属 [2],沙拐枣属[3] 虎杖屬 e.g. Fallopia japonica (sive reynoutria japonica[4])Fagopyrum Fallopia sachalinensis [5]
description
Knotweeds are a family of the order of centrosperms[6][7], herbs, a few shrubs, with nodular stems, some of which are twining, and mostly alternate, simple leaves with rolled edges in the bud position, the stem of which forms a stem-enclosing sheath at the base, which continues at the top into a sheath-shaped stipule called a ochrea . The flowers, which may be complete or unisexual, are often two or three in number, are solitary or in clusters or whorls and are usually united in spikes, racemes or panicles. The perigone is goblet- or corolla-like and consists of 4-6 free or fused leaves at the base, of which the three inner leaves are usually larger and which usually remain attached to the fruit or enlarge. The stamens are inserted at the base of the perigone, present in the same number as the perigone leaves or in pairs or in threes in front of the outer ones, standing singly in front of the inner ones. The upper, unifoliate ovary consists of 2 or 3 fused carpels and is provided with as many styles or sessile, head- or brush-shaped stigmas; it contains a single basal, orthotropic seed bud. The fruit is a lenticularly compressed or three-, rarely four-sided caryopsis or achene, which is covered by the often enlarged, variously formed perigone.The seed has the same shape as the fruit, a membranous husk, a mealy endosperm and a straight seedling, either on the side or in the center of the endosperm, with linear or leaf-like and curved cotyledons.Cf. Meissner's monograph in De Candolles “Prodromus”, vol. 14. There are about 700 species, which are distributed over all parts of the world and occur in the largest numbers in the northern temperate zone.Their green parts are often used as fodder and food, especially by Rumex and Polygonum species. Because of the flour-rich seeds, some species of Polygonum (Fagopyrum) are cultivated like cereals. The roots of several species of the genus Rheum (rhubarb) provide important medicinal substances [8]
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