Three hundred million years ago plants of the genus Sphenophyta or Articulates , were represented by tree-like plants known as Calamites. They grew to heights of 30 feet or more.

Today, the sphenophytes consist of only one genus, Equisetum, with about thirty living species known worldwide, the tallest of which seldom achieve heights over 6 feet.

Sphenophyta are distinguished by their straight stems with branches or leaves arranged in regular whorls.

Equisetum are known as horsetails, foxtails, or scouring rushes -- the latter name being derived from the fact that Equisetum stores granules of silica within its cells, making it
an effective tool for scrubbing pots and polishing wood.