The caltrop (Tribulus terrestris) belongs to Zygophyllaceae (the Caltrop family). It is a perennial herb that is native to central and southern Japan, southern Asia, southern Europe, all over Africa, and Australia. This herb grows on seashore or inland arid places, and the stems radiate can reach from the crown to a diameter of about 10 cm to over 1 m, often branching. They are usually prostrate, forming flat patches. The leaves are opposite and pinnately compound with densely hairy leaflets. The lemon-yellow bloom from spring to fall. The fruits are thumbtack-like nutlets and a hazard to bicycle tires. The dried seeds are called "bai ji li" (疾黎子), and have been used as a traditional medicine for diuretic or diuresis in China.