Horsetail

Horsetail, primitive plant (genus Equisetum) related to the fern that once dominated the plant world and was important in the formation of coal. One fossil horsetail was 100 ft (30 m) high, but living species are rarely more than 2 to 3 feet (0.6 to 0.9 m) high. Each horsetail plant lasts several years. It has an underground stem that sends up hollow vertical stems each year. Each vertical stem is jointed and at each joint there is a ring of small leaves. The plant is coated with gritty silica, thus it has been called scouring rush and has been used for cleaning pans. Some horsetails have 2 kinds of stems. The first bears a spore-producing organ at the tip. The spores are released and drift away to produce small sexual plants as in ferns. These stems then die down and are replaced by taller green stems that last all season.