Horsetail is an unusual plant with a hollow, jointed stem. The stem is usually grooved. It contains silica, which is an abrasive material (see Silica ). The horsetail is sometimes called scouring rush because it was once used to polish metal.
Horsetails are nonseed plants that are related to ferns. They do not bear flowers or fruit. Horsetails reproduce by means of both spores and sex cells. The spores are contained in small cones at the tips of the stem or its branches, or sometimes on a separate stalk. The plant releases the spores, which germinate in damp places and grow into tiny plants. These plants produce male and female sex cells that unite and develop into mature horsetails.
Horsetails were much more common during the Paleozoic Era, which ended about 250 million years ago. During that time, some horsetails grew to be large trees. Today, most horsetails are small.
