Work on cotton taxonomy dates back to the 18^th century when Linneaus delineated the genus Gossypium and described the four cultivated species Gossypium arboreum L. and Gossypium herbaceum L. of the Old World and Gossypium barbadense L. and Gossypium hirsutum L. of the New World. Over the ensuing years many species of Gossypium were described by various workers. In the second decade of the 20^th century, chromosome numbers began to have impact upon the delineation of species in Gossypium, heralding in a more conservative approach to taxonomy and a diminishing number of species.