Introduction BPH Online is a fully indexed and searchable database documenting (as comprehensively as possible) periodicals published between 1665 and the present that have addressed the plant sciences. The scope of the database encompasses the larger disciplines of botanical literature (agriculture, agronomy, bacteriology, biology, ecology, floriculture, forestry, fruit growing, genetics and plant breeding, geography, horticulture, hydrobiology and limnology, microbiology and microscopy, palaeontology, pharmacology and pharmacognosy, plant pathology and vegetable crops) and includes approximately 34,000 title entries. With the ever-increasing wealth of digitization projects around the world, BHP Online remains consistently under heavy revision as new, and more thorough, information becomes available. There are also new publications, many of which are online only, which are indexed as they are discovered. Data are organized in a full-entry format. The entries are organized thusly: title (and occasionally a subtitle), place of publication, volume/numbering scheme, year or year range, the abbreviation, references concerned with superseded, preceded or continued titles, general notes, ISBN and HI number. The first print edition, B-P-H: Botanico-Periodicum-Huntianum, was published in 1968 and was edited by George H. M. Lawrence (1910–1978; director, 1960–1970), A. F. Günther Buchheim (1924–2007; fellow in bibliography, 1963–1965; bibliographer, 1965–1981), Gilbert S. Daniels (assistant director, 1967–1970; director, 1970–1977) and Helmut Dolezal (1912–1981; assistant bibliographer, 1965–1970; associate bibliographer, 1971–1975). It contained approximately 12,000 titles. A supplement, B-P-H/S: Botanico-Periodicum-Huntianum/Supplementum, followed in 1991, which was compiled and edited by Gavin D. R. Bridson (1936–2008; bibliographer, 1982–2008) with the assistance of Elizabeth R. Smith (1917–2005; assistant editor, 1966–2003). Despite slightly narrowing the scope of criteria for inclusion, it more than doubled the indexed titles and included many revisions to the initial work. BPH-2: Periodicals with Botanical Content was compiled by Bridson and published in 2004. It indexed over 33,000 titles. The current version of BPH exists only online, and it indexes approximately 34,000 titles. I extend my most sincere appreciation to the many who have offered insight into the improvement of BPH through the years. In particular, I would like to thank Dr. Robert W. Kiger and Dr. Kanchi N. Gandhi for their invaluable contributions to this project. all of the artists, individuals and organizations who have donated works to the collection over the years.