Horsetail
Horsetail, or Scouring Rush, a genus of perennial flowerless herbs. There are about 25 species, chiefly in Europe, Asia, and North America. The stems are hollow, grooved, and jointed. The leaves at each joint serve as a sheath enclosing the base of the section above it. Horsetail spores are borne in conelike spikes. Because its rough stems contain silica, horsetail was once used for scouring utensils.
Horsetails make up the division Sphenophyta. There is only one genus, Equisetum.