This chapter uses historical data on patents and registrations of new plant varieties to examine the effects of the Plant Patent Act on biological innovation. Evidence on a later Act, the Plant Variety Protection Act (PVPA) of 1970, is mixed. The PVPA complemented the PPA by extending IPRs to plants that reproduce “sexually” through seeds, such as wheat, soybeans, or cotton. Survey results suggest that it encouraged research expenditures and “stimulated the development of new varieties of wheat and soybeans.” Most of these increases in research investments, however, came from the public sector, and there is little evidence that crops, and specifically wheat, performed better after 1970. For cotton, on the other hand, changes in acreage and in the variety of cotton crops suggest a positive effect of IPRs.