The genus Sorghum Moench is subdivided into sections Chaeotosorghum, Heterosorghum, Parasorghum, Stiposorghum and Sorghum. Section Sorghum includes two rhizomatous species, S. halepense (L.) Pers. (2n = 40) and S. propinquum (Kunth) Hitchcock (2n = 20), as well as the annual S. bicolor (L.) Moench (2n = 20). Sorghum bicolor is divided into subspecies bicolor to include all domesticated grain sorghums, subspecies drummondii (Steud.) de Wet comb. nov. to include stabilized derivatives of hybridization among grain sorghums and their closest wild relatives and subspecies arundinaceum (Desv.) de Wet et Harlan to include the wild progenitors of grain sorghums. Four ecotypes of subspecies arundinaceum are recognized: race aethiopicum of the arid African Sahel, race virgatum of northeastern Africa, race arundinaceum of the African tropical forest, and race verticilliflorum of the African Savanna. The numerous, usually recognized grain sorghums are divided among five basic races, bicolor, caudatum, durra, guinea and kafir, and ten hybrid races that each combine characteristics of at least two of these basic races. Races of grain sorghum are morphologically distinct, and they maintain their unity of type through spacial and ethnological isolation. SORGHUM Moench is a heterogeneous genus. The following sections are usually recognized: Stiposorghum, Parasorghum, Sorghum, Heterosorghum and Chaetosorghum (Garber, 1950). Stiposorghum and Parasorghum are characterized by distinct rings of hairs at each culm node, with the awns of Stiposorghum over 65 mm long and those of Parasorghum substantially shorter. The culm nodes are glabrous or hairy in Sorghum, Chaetosorghum and Heterosorghum, but never do the hairs form a nodal ring. The pedicellate spikelets are reduced to subequal glumes in Heterosorghum and unequal glumes in Chaetosorghum. Section Sorghum is characterized by better developed pedicellate spikelets that are often male fertile but almost always female sterile. Sessile spikelets in the genus Sorghum are

Systematics and evolution of Sorghum sect. Sorghum (Gramineae)

The horticultural strategies of traditional tropical agriculturists center on the preservation of harvest security. In addition to cultivating simultaneously numerous species of crops, traditional tropical farmers also plant multiple varieties of each crop. These cultivars are frequently distinguished on the basis of color, ranging from white to yellow to red to purple. In addition to varying in appearance and taste and in resistance to environmental stresses, the color-based varieties often differ in length of growing season. By practicing multicolored, intraspecific polyculture, the traditional tropical farmer either provides himself several opportunities to secure a complete single harvest and/or staggers his harvest throughout the year and thus, in either case, preserves his lifestyle. Acceptance of Green Revolution technologies by traditional tropical farmers would accelerate if they were offered multiple, high-yielding varieties of staple food crops of varying color and maturation periods.

Harvest Security and Intraspecific Diversity in Traditional Tropical Agriculture

Special paper: systematics and evolution of sorghum sect. sorghum (gramineae)

This essay explores ground common to ecology and politics. It addresses the question to what extent and in what ways are ecological ideas political ideas. The discussion, divided into five man sections, endeavors to steer a course between the pitfalls of environmental determinism on the one hand and economic reductionism on the other. The first section deals with the link between population processes and land use. Explanations stressing population increase as the driving force behind agricultural change are contrasted with arguments in which demographic fluctuations are treated as responses to economic imperatives. An example of the second kind of approach is Meillassoux's attempt to reconstruct the demographic dynamic of a precapitalist, lineage, mode of production. This is but one of a number of attempts to construct models of “natural economy” as starting points for discussions of the penetration of African agriculture by capitalism. Against the assumptions on which such models are based it is argued here, and in later sections of the paper, that the demographic and ecological processes subsumed under the category “natural economy” (or alternatively, “precapitalist subsistence production”) are more plausibly viewed as products of capitalism and colonialism. An example from southern Nigeria in the early colonial period is used to suggest that the kind of evidence on which Meillassoux's reconstruction is based is a complex ideological by-product of factional politics in an economy dominated by merchant capital. The second section of the paper focuses on the topic of the ecology of disease in Africa. Special attention is paid to John Ford's (1971) work on the ecology of trypanosomiasis. Critical of colonial scientific orthodoxy, and of colonialism itself (properly treated as a factor in the spread of sleeping sickness in Africa in the twentieth century), Ford's book has received some attention from Africanists in the social sciences and humanities. It is probably fair to say, however, that the originality of the book's ecological argument has yet to have its full impact on such readers. This is the justification for substantial summary of one of Ford's case studies. The significance of this case study is that is illustrates the ecological complexity characteristic of trypanosomiasis, and of a number of other African epidemic diseases, and the importance of local knowledge and initiative in adapting to such diseases.

Ecological Change and the Politics of African Land Use

There is a wide variety of wetland environments in West Africa. They include various kinds of floodplains (for example those of the Senegal, Niger and Logone-Chari system), larger inland deltas and lacustrine wetlands (notably Lake Chad and the Niger Inland Delta in Mali), and coastal and delta environments (for example the deltas of the Senegal, Niger and Volta Rivers, the Basse Casamance or the Banc d'Arguin in Mauritania). Most of them support substantial communities of people, who depend on their natural resources and the ecology and hydrological patterns that maintain them. Indigenous systems of water resource management include agriculture (including flood cropping, notably of rice, flood recession cropping and various kinds of irrigation at various scales), fishing and pastoralism. In the Sahel in particular, wetlands provide a vital element in the resources available to people not only within but well beyond their immediate boundaries. Many of these wetlands also support internationally important populations of wild species, those in the Sahel, for example, providing important links in the Palaearctic-African bird migration flyway. Water resource development projects can have serious implications for the ecology and economy of wetlands in West Africa, and great care is needed to ensure that development projects do not cause real economic costs that outweigh potential economic benefits.

Indigenous use of wetlands and sustainable development in West Africa

The hydrology of the central delta of the Niger River is extremely complex, but the local cultivators have developed a remarkably sophisticated agriculture in order to deal with it. Crops, varieties and cultural practices are sensitively adjusted to variations in the height of the flood, soil texture, storage hazards, bird damage, nutritional needs and food preferences.

Jean Pasquereau

Papers

Décrue agriculture in Mali