The Index Kewensis was first published in two volumes between 1893 and 185, and its five-yearly supplements have long been established as a standard work of reference. The Index lists the place of publication of new and changed names of seed-bearing plants. Until 1970, only the ranks of genus and species were included. Since 1971, all ranks from family downwards have been listed. The closing date for this supplement was the end of December 1990. Also included is a list of the new generic names from the main body arranged in alphabetical order under family headings. The Index Kewensis is the most authoritative and comprehensive work of its kind, and is the indispensable reference for botanists conducting pure and applied research.