Equisetaceae
An order of interesting crypto-gams, which takes its name from the genus Equisetum, the only one the order contains. There are about twenty-five species, chiefly found in temperate Northern regions; a few are sub-tropical. One of the latter group (E. Martii), recently introduced to Kew from Brazil, attains, in its native habitats, the enormous height of 30ft. "Dutch Rushes," used for scouring and polishing, are the stems of E. hyemale; their roughness is due to a deposit of siliceous particles in the epidermis.