DOG'S MERCURY, a perennial herb of the family Euphor biaceae, mainly found in Europe and northern Africa. It has a creeping root and lance-shaped leaves and grows to a height of about one foot. The root contains certain colouring substances and is highly poisonous. The term is sometimes used to define Chenopodium which is cultivated as a pot-herb and commonly called mercury. Acalypha or three-sided mercury also belongs to this family. See also EUPHORBIACEAE.