12. Alternanthera Forsskål, Fl. Aegypt.-Arab. 28. 1775.
莲子草属 lian zi cao shu
Herbs annual or perennial, ascending or creeping; stem much branched. Leaves opposite, margin entire. Flowers perfect, in sessile or peduncled heads, solitary in axils of bracts. Bracts and bracteoles persistent, membranous. Tepals 5, often unequal, membranous. Stamens 2-5; filaments connate into a tube or a cup at base; anthers 1-loculed; pseudostaminodes entire, dentate, or laciniate. Ovary globose or ovoid; ovule 1, pendulous; style short or long; stigma capitate. Utricles globose or ovoid, indehiscent, falling off with perianth. Seeds lenticular, vertical.
About 200 species: mainly in North and South America, widely naturalized elsewhere; five species (four introduced) in China.
Alternanthera purpurea Y. T. Chang & M. J. Lai (Landscape Architecture [Taipei]  (4): 125. 1990, not Pynaert, 1879) was described from Taiwan. We have seen no specimens of this taxon and are therefore unable to treat it in this account. Further revisionary study is necessary.