【来源】为苋科牛膝属植物牛膝 Achyranthes bidentata Blume的根。【形态特征】多年生草本,高0.7～1.2米。根粗壮,圆柱形,栽培品长可达1米以上,土黄色。茎直立,四棱形,分枝,节膨大如牛膝盖,故名“牛膝”,被柔毛。单叶对生,有柄;叶片膜质,椭圆形或椭圆状披针形,长5～12厘米,宽2～6厘米,先端渐尖,基部宽楔形,全缘,两面被柔毛。秋、冬开黄绿色花,穗状花序顶生或腋生,花后总梗延长,花序轴密被长柔毛,花开放后平展或下倾;苞片宽卵形,具芒。胞果矩圆形,长约2.5毫米。 [Source] is the root of Achyranthes bidentata Blume of Achyranthes Achyranthes. Morphological characteristics Perennial herb, 0.7-1.2 meters high. The roots are thick, cylindrical, and the length of cultivated products is up to 1 meter and the soil is yellow. Stems erect, four prisms, branches, section as big as cattle knees, hence the name “Achyranthes”, pubescent. Leaves single opposite, stalked; leaf blade membranous, elliptic or elliptic-lanceolate, 5 to 12 cm long, 2 to 6 cm wide, apex acuminate, base broadly cuneate, entire, puberulent on both surfaces. In autumn and winter, yellow-green flowers are opened, the spikes are topped or axillary, the post-anthesis stalks are extended, the inflorescence axis is densely villous, and the flowers open flattened or declined; bracts are broadly ovate and awned. The granules are oblong in shape and are about 2.5 mm long.