horsetail (hôrs'tāl') Pronunciation Key
A member of a genus, Equisetum, of seedless vascular plants having a jointed hollow stem and narrow, sometimes much reduced leaves. Plants extremely similar to modern horsetails are known from fossils 300 million years old. The horsetails are the last surviving members of the phylum Sphenophyta, which dominated the forests of the Devonian and Carboniferous periods.
[hawrs-teyl] 
