What is Fern Allies - Equisetum ?

The earliest land plants are thought to have evolved from green algal ancestors, since they share many features. Both green algae and plants have the green photosynthetic pigments chlorophyll a and b, and the yellow-orange accessory pigment beta-carotene. They both have cell walls composed of cellulose; they both store starch as their energy source; and they both produce cell plates in the latter stages of mitosis. The fern allies are thought to be early forms of vascular plants that reproduce by means other than seeds. One of these groups is the Equisetum, or horsetails. Horsetails feature stems that are jointed with whorls of scales that grow from and surround each joint, or node. They also produce distinctive cone-like reproductive structures called strobili at the tips of the stems.

Some species of Equisetum used to be called "scouring rushes," because colonists would use these plants as pot scrubs. They discovered that horsetails were abrasive, and thus could be put to practical use. This abrasive quality is due to the presence of silica in their cell walls.