EQUISETUM

[eq.ui.se.tum] n, pl -se.tums or -se.ta [NL, fr. L equisaetum horsetail plant, fr. equus horse + saeta bristle] (1830): any of a genus (Equisetum) of lower tracheophytes comprising perennial plants that spread by creeping rhizomes and have leaves reduced to nodal sheaths on the hollow jointed ribbed shoots--called also horsetail, scouring rush