Juglans nigra According to legend, when the gods walked upon the earth, they lived on walnuts; hence the name Juglans or Jovis glans, Jupiter"s nut. The tree has been cultivated in Europe since Roman times for its nuts; these yield an important oil containing essential fatty acids, such as alfa -linolenic, that are vital for healthy cell function and prostaglandin development. The white walnut, or butternut (J. cinerea), from eastern North America is a useful laxative. Black walnut bark helps relieve constipation and is useful against fungal and parasitic infections. It is used to expel, rather than kill, worms during the normal course of laxative-induced cleansing of the body. It may also help to eliminate warts, which are growths caused by viruses.