Common Mare's Tail
An illustration of a flowering branch of common mare's tail; a, flower before athesis; b, flower after athesis; c, fruit. The Common Mare's tail, Hippuris vulgaris, is a common aquatic plant of Eurasia and North America. The species is also sometimes called Horsetail, a name which is better reserved to the Horsetails of genus Equisetum. These are unrelated to the water plant, though there is some resemblance in appearance.