1. Polycnemum arvense Linnaeus, Sp. Pl. 1: 35. 1753.
多节草 duo jie cao
Herbs annual, 10-15 cm tall. Stem erect, covered with short, crisped hairs, branched from base; branches ascending or decumbent, nearly as long as main stem, somewhat glabrescent. Leaves obliquely ascending, rarely appressed to stem, subulate, 3-10 mm, subglabrous, base expanded, margin narrowly membranous below middle, apex mucronate, spinescent. Bracteoles triangular-lanceolate, near as long as perianth in fruit, keeled abaxially, apex long acuminate. Perianth segments imbricate, narrowly ovate-lanceolate, ca. 1 × 0.4 mm, slightly enlarged in fruit to 1.5 mm, membranous, slightly longitudinally ribbed, sparsely covered with crisped hairs abaxially, apex shortly acu-minate. Filaments filiform, ca. 1.5 mm; anthers shortly oblong, ca. 0.2 mm. Ovary broadly ovoid; style obscure; stigmas minute. Utricle enclosed in perianth, slightly compressed, broadly elliptic, ca. 1.1 × 1 mm; pericarp slightly thickened apically, easily separated from seed. Seed ovoid, laterally compressed, granulose sculptured. Fl. and fr. Jul-Aug.
Sandy soils, wastelands. Xinjiang [C and SW Asia, C and S Europe; occasionally naturalized in other regions].
Polycnemum, as well as the two other genera of tribe Polycnemeae (or subfam. Polycnemoideae), share some characters typical of Amaranthaceae, i.e., two bracteoles, membranous perianth segments, etc. Probably this tribe should be transferred to the Amaranthaceae.
This species is a good forage plant.