The Plant Sciences Card Catalog of the U.S. Department of Agriculture (USDA) Library was developed over a half century, and consists of three divisions: author catalog, plant pathology catalog, and subject catalog. Work on this catalog ceased on July 18, 1952 because of lack of funds. The plant science subject catalog (Botany Subject Index) is a card catalog with entries arranged alphabetically by subject and by scientific names, broken down into divisions and subdivisions of large subjects. Names of genera are arranged under the family, the family names appearing in their regular alphabetical place. Included also are references to literature on many subjects of interest to the botanist, such as textbooks arranged chronologically, voyages and travels, biographies, and geographical botany. It is world-wide in scope and contains references to botanical literature from earliest times as published books and in American and foreign serials of all kinds, journals, proceedings, bulletins, etc. The Bibliography of Agriculture, begun in 1942, includes the types of references covered by the plant science catalog. After the Plant Sciences Card Catalog was no longer updated, users of the Plant Sciences Catalog would have made use of this resource, which was updated monthly.