for and introduction of new crops. David Fairchild, Frank N. Meyer, and others introduced a broad range of new crops and genetic resources of existing crops (Cunningham, 1984; Hodge and Erlanson, 1956; Hyland, 1984; Klose, 1950; White et al., 1989). At the same time the plant introduction (PI) numbering system, still used by the NPGS, was established.

The section's Foreign Plant Introduction Office emphasized collecting. In the early 1930s, for example, H. G. MacMillan and C. O. Erlanson collected wild and primitive potatoes in Peru and Chile to obtain plants with genes for insect and disease resistance. Other plant hunters were in the West Indies searching for Sea Island cottons. R. Kent Beattie was completing a 5-year mission in China to collect chestnuts to replace the blight-stricken American chestnut. C. Westover and W. E. Whitehouse were searching for alfalfa in Russia as sources of resistance to bacterial wilt. Whitehouse then went on to Persia to collect melon, peach, apple, and pistachio germplasm. At the same time, W. J. Morse was making his now-famous contributions of thousands of wild and cultivated soybeans from China, Korea, and Japan.

The 1936 and 1937 editions of the USDA Yearbook of Agriculture recorded the genetic diversity of many crops of that time, but there were no nationally coordinated activities to preserve germplasm. In the 1940s the National Academy of Sciences' Committee on Plant and Animal Stocks expressed concern over the fate of the resources that formed the foundation for the world's crops. In a 1946 letter to Sir John Orr, the director general of the FAO, National Research Council Chairman Ross G. Harrison sought action by that organization and wrote the following (Harrison, 1946:1):

As improved varieties are introduced to production, large numbers of older, more diverse stocks disappear. A permanent loss of characters necessary for further improvement thus is likely to occur. As a safeguard to the welfare of all peoples, steps should be taken as soon as possible to collect and maintain the plant and animal materials likely to be of service in breeding.

In the summer of 1946 the 79th Congress passed Public Law 733; Title II of which is the Agricultural Marketing Act of 1946. This act provided the legal basis for establishing state-federal cooperation in managing crop and livestock genetic resources, and included an amendment to the earlier Bankhead-Jones Act of 1935 to support research (Title I). It also attempted to improve the marketing and distribution of agricultural products (Title II), and established a national advisory committee to the secretary of agriculture and the U.S. Department of Agriculture on matters of research and service authorized by the act (Title III).