Tetraena mongolica Maxim.is the only member of the genusTetraenathat belongs to the family Zy-gophyllaceae.It is characterized by the following features:small deciduous shrubs,30~50 cmtall,muchbranched;leaves paripinnate,opposite on current year branches,and fascicled on old branches;leaflets 2,sessile,on an extremely short leaf rachis,oblanceolate,5~7 mmlong,2~3 mm broad,entire,densely cov-ered with appressed T-shaped hairs,apex acute;flowers bisexual,solitary or 1~2 on a short shoot;sepals4…