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International Plant Names Index

Alternate Title:
Index Kewensis

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Database available without restriction Database available without restriction

The International Plant Names Index (IPNI) is a database of the names and associated basic bibliographical details of all seed plants, ferns and fern allies. Its goal is to eliminate the need for repeated reference to primary sources for basic bibliographic information about plant names. The data are freely available and are gradually being standardized and checked. IPNI will be a dynamic resource, depending on direct contributions by all members of the botanical community.

IPNI is the product of a collaboration between The Royal Botanic Gardens, Kew, The Harvard University Herbaria, and the Australian National Herbarium

One part of the database is the Index Kewensis (IK).  It is maintained by the Royal Botanic Gardens, Kew and its aim was to register all formal botanical names for seed plants, at the rank of species and genus. Later, it also started to include names of families and of taxa below the rank of species.

It was started in 1885, with regular supplements issued on newly published names. A digitalized version of the IK has been integrated in IPNI (, so that it can be consulted online: its entries are recognizable by the letters "(IK)".

Since 1885, the Royal Botanic Gardens, Kew, has been indexing names of seed plants at the level of genus and species published since 1753, and of all ranks from family downward since supplement 16, and making them available in a series of bound volumes, the Index Kewensis. Charles Darwin provided funds for the initial indexing effort which attempted to capture all names back to 1753. Darwin realized the great need for a list of plant names with bibliographic details of where they were originally published and, since then, generations of biologists and systematists have found the Index Kewensis an indispensable resource for botanical research. The original two volumes of Index Kewensis contained nearly 400,000 names. Some 6,000 additional names are added annually and hard-copy supplements are published at 5-yearly intervals. The most recent supplement was the twentieth which was published in 1996. Since 1971, records of infraspecific names of plants have also been included in this index and since 1997 details of type specimens have been recorded. The whole Index Kewensis, now totalling over one million records, has been available in electronic form to staff and visitors at Kew for many years. However, until the launch of IPNI, the only widely available digital format for this data was CD-ROM. Most volumes of Index Kewensis are still available as hard copy.

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  • Environmental Science
  • Biology

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