Paper presented at a meeting about involving farmers in the development of agricultural technology, Ouagadougou, Upper Volta, September 20-25, 1983., Pages 139-150 in Peter Matlon, Ronald Cantrell, David King and Michel Benoit-Cattin (eds), Coming full circle: farmers' participation in the development of technology. IDRC-189e, International Development Research Centre, Canada. 176 pages.