The Index to Plant Chromosome Numbers is a continuation of the series begun in 1956 by Marion S. Cave and colleagues at the University of California, Berkeley. Indexes prior to 1975 were published in Regnum Vegetabile, the book series of the International Association for Plant Taxonomy. The Index to Plant Chromosome Numbers project moved to the Missouri Botanical Garden, St. Louis in 1978.

Format and arrangement of major groups is for the most part identical to that in the last Index (1979-81).