Also known as horsetails.
The fossil record of the Equisetophyta dates back to the upper Devonian, with a peak in abundance and diversification during the Carboniferous.
Today, Equisetum is the sole extant genus, with approximately 15 species, that are divided into two subgenera, Equisetum and Hippochaete. Equisetum has an underground rhizome from which adventitious roots and an upright, photosynthetic stem with whorls of microphylls grow.
General description of this family of terrestrial, herbaceous, homosporous vascular plants, comprising a single genus with about 15 species. Includes photos of several Equisetum species. www.botany.hawaii.edu/faculty/carr/equiset.htm
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