Hei Dou

Glycine max, the soybean, is an erect to suberect annual herb of the Fabaceae family domesticated in East Asia for several millennia and now the world's most important leguminous crop. The plant typically grows fifty to one hundred fifty centimeters tall with a branching stem clothed in stiff brown or grey hairs. Leaves are alternate, pinnately trifoliolate with broadly ovate to elliptic leaflets, the lateral pair usually larger than the terminal; stipules and stipels are present. Small white, pink, or pale purple papilionaceous flowers are borne in short axillary racemes during summer, self-pollinated, and quickly give way to densely pubescent pods two to seven centimeters long, each containing one to four nearly spherical to ellipsoid seeds. The black-seeded varieties known in Chinese as Hei Dou are the type used for the medicinal preparation.