ARS scientists maintain a wide variety of plants from all over the world as part of the U. S. National Arboretum Herbarium, a facility for research on the systematics, nomenclature, and history of cultivated plants. The herbarium contains about 600,000 specimens of 2,400 types of ornamentals, crop plants, weeds, and forest trees. The collection is worldwide in scope, and is noted for its extensive reference collection of the native flora of the United States and Canada. Formally organized in 1934, the herbarium serves as a national repository for voucher materials of wild and cultivated progenitors of various plants used for food, forage, industrial, and medicinal purposes. The collection has served to document germplasm materials as a permanent legacy of the history and development of American agriculture. Materials from the collection support ARS research on the nomenclature and taxonomy of cultivated plants, particularly those of economic importance. ARS also uses the collection to carry out 5,000 identifications annually as requested by government agencies, educational institutions, farmers, and other individuals and organizations.