THE WEST INDIAN SPECIES OF GOSSYPIUM OF VON ROHR AND RAFINESQUE

Summary In the 1780's J. P. B. von Rohr (1737–1793) intensively studied the cottons of the West Indies. His observations are recorded in a book that not only is a basic source of knowledge of the cottons of the 18th century, but which also provides the descriptions used by C. S. Rafinesque as the basis for 38 names of species and varieties in Gossypium . The present paper reports observations on 52 specimens of Gossypium collected by von Rohr and preserved in the Copenhagen Museum. From these specimens, lectotypes have been chosen for 12 of the Rafinesquian names (Table 2). The remaining names (Table 1) must thereupon be typified by the published descriptions. Lectotype species are also designated for the three subgenera of Gossypium published by Rafinesque (Table 3), the earliest available names in that rank. The presence of symptoms of the bacterial blight disease, caused by Xanthomonas malva‐cearum (E. F. Smith) Dows., on two of von Rohr's specimens, is noted as perhaps the earliest known occurrence of this disease. A review of the nomenclature of the kidney cottons is appended.