¹ Wrigley, C., ‘Speculations on the economic prehistory of Africa’, Journal of African History (1960), I, 2, 289–203 (197).Google Scholar

² Murdock, G. P., Africa; its peoples and their culture history (New York, 1959), 71, 223, and 245.Google Scholar

³ Richards, P. W., The Tropical Rain Forest (1952).Google Scholar

⁴ Keay, R. W. J., Vegetation map of Africa south of the Tropic of Cancer (1959) (explanatory notes).Google Scholar

⁵ In this context ‘harmattan’ refers to the occurrence of air of unusually low relative humidity and associated with dust composed of very fine particles frequently giving the appearance of mist or fog.Google Scholar

⁶ Wrigley, op. cit., 197.Google Scholar

⁷ Ibid.

⁸ Murdock, op. cit., 69.Google Scholar

⁹ Dalziel, J. M., The useful plants of West Tropical Africa (London, 1937), 488–93.Google Scholar

¹⁰ Amongst the Yoruba D. esculenta is known sa ‘ishu alubosa’, the onion yam, i.e. introduced after the onion, which itself was introduced by the Hausa (alubosa = Hausa albasa = Arabic al basala).Google Scholar

¹¹ Miège, J., ‘L'importanceéconomique des ignames en Côte d'Ivoire. Repartition des cultures et principales variétés’, Revue internat. de Bot. Ap. et d'Agric. Trap. (1952), XXXII, 144–55.Google Scholar

¹² Keay op. cit., and Outline of Nigerian Vegetation (2nd edition, 1953).Google Scholar

¹³ In Leaba in northern Nupe near the northern limit of yam cultivation the yam is harvested once only, i.e. seed yams cannot be produced. Nadel, S. F., A Black Byzantium (1946), 220.Google Scholar

¹⁴ See Irvine, F. R., A text book of West African agriculture (1934), 119–34.Google Scholar

¹⁵ Guinea corn or sorghum is described by Murdock as a staple only amongst the Nupe of ‘Southern Nigerians’, whereas it is a staple of the Oyo Yoruba, closely associated with yam cultivation for which it frequently provides a trellis.Google Scholar

¹⁶ Miège, J., ‘Les cultures vivrières en Afrique occidental’, Les Cahiers d'Outre-Mer (1954), VII, 25–50. The suggestion has been made that the limit once lay farther to the east since yams are claimed to have replaced rice as a staple in Ghana in the seventeenth century.Google ScholarMeyerowitz, E. L. R., The Sacred State of the Akan (1951), 46–8.Google Scholar

¹⁷ Portères, R., ‘Linguistique et migrations du riz dans l'Ouest africain’, Farm and Forest (1946);Google Scholar‘Les riz flottants de l'espèce O. sativa L. et leurs possibilités d'exploitation en Afrique’, L'Agronomie Tropicale (1946), 1, 467–503.Google Scholar‘Le système de riziculture par franges univariétales et l'occupation des fonds par les riz flottants dans l'Ouest africain’, R.I.B.A. (1949), XXIX, 553–63;Google Scholar‘Vieilles agricultures de l'Afrique intertropical’, L'Agronomie Tropicale (1950), V, 489–507;Google Scholar‘Historique sur les premiers échantillons d'Oryza glaberrinia St. recueillis en Afrique’, Journ. d'Agric. Trop. et de Bot. Ap. (1955), II, 35–7;Google Scholar‘Un problème d'ethno-botanique: relations entre le riz flottant du Rio Nunez et l'origine medi-nigerienne des Baga de Ia Guinée Française’, J.A.T.B.A. (1955), II, 538–42.Google Scholar

¹⁸ Portères, R., ‘L'introduction du maïls en Afrique’, J.A.T.B.A. (1955), II, 221–31;Google Scholar‘Les appellations des céréales en Afrique’, J.A.T.B.A. (1959), vi, 68–105, 189–233, 290–339 (invaluable general paper on all the important cereals of Africa).Google ScholarAdandé, A., ‘Le maïs et sea usages dans le Bas-Dahomey’, Bull. de l'I.F.A.N. (1953), xv, 220–82.Google Scholar

¹⁹ A useful article on Digitaria is: Portères, R., ‘Les céréales mineures du genre Digitaria en Afrique et en Europe’, J.A.T.B.A. (1953), II, 349–86 and 477–510.Google Scholar

²⁰ Taro or eddoes, Colocasia esculentum, has been long established, but to some extent has been replaced by Xanthosoma sagittifolium—possibly introduced into Ghana from the West Indies in 5843, Dalziel, op cit., 484.Google Scholar

²¹ The Coleus spp. are not ‘forest-zone crops’ (Wrigley, op. cit., 198), but generally mature in five or six months and are restricted to the savannahs.Google Scholar

²² The argument for the introduction of yams into the rain forest from the savannahs has been made in the Leverhulme Trust, the West African Commission, 1938–9, 1943, 56–59, and supported by Wrigley, op. cit., 198. One may note that Yoruba legend suggests movement of cultivators in the opposite direction, although it may refer to a period when agriculture was already well established. For the early planting of kola see Chevalier, A., and Perrot, E., Les kolas and les noix de kola (1911).Google Scholar

²³ Forde, C. D., ‘The Cultural Map of West Africa’, Trans. New York Acad. of Sciences (1955), Series II. Murdock, op. cit., 207ff.Google Scholar