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Before the emergence of the radicle during the germination of Balanites aegyptiaca seeds, a sudden fall in both the oil and total sapogenin content occurred. Although the oil content fell continusouly, the total sapogenin content rose to a maximum in 5 days due to the biosynthesis of sapogenin by the germinating seedlings. The proportion of 25α- and 25β-sapogenin present remained fairly constant during the first 9 days of germination.

Infra-red spectrophotometric analysis showed 1 per cent total steroidal sapogenin in the root, 0·7 per cent in the stem bark and 1·2 per cent in the soft fruit wall of Balanites aegyptiaca Del., on a moisture-free basis. Elemental analysis of the sapogenin and its derivatives as well as mass, i.r. and NMR spectroscopy data show that the major sapogenin in these plant parts is yamogenin.

The main points may be briefly summarised. 1. 1. Laboratory and field experiments have shown that the fruit, bark and other parts of the tree Balanites aegyptiaca possess properties lethal to molluscs, bilharzial miracidia and cercaria, and the cercaria of animal trematodes. 2. 2. A simple technique is described, whereby strong emulsions of the fruit can be used for killing molluscs in water, without impairing the potability of the water. 3. 3. The use of the fruit as a substitute for chemicals will render the control of schistosomiasis in the Sudan more effective and less costly. 4. 4. Afforestation of the tree is recommended as an additional measure for the control of schistosomiasis.

Capparis decidua, Maytenus senegalensis and Balanites aegyptiaca do occur while trees of Prosopis cineraria are quite abundant. The economy of these sparsely populated areas is based on livestock production. Consequently the herbaceous primary production is of vital importance. The present work was undertaken to study the effects of grazing on the structure and productivity of the vegetation on three sites near Pilani. In this paper, the number of plant individuals and species, standing crop of above and underground biomass, standing dead vegetation, litter, plant pigments and the net vegetation production of the above and underground biomass have been assessed. DESCRIPTION OF THE STUDY SITES Areas were selected for study near Pilani (28023 N, 75?37 E) at an altitude of about 350 m. The sites were: I, sandy plains; II, hard ground; and III, stabilized dunes. Sites I and II lack trees and shrubs, while site III supports a thin scrub consisting of Capparis decidua, Balanites aegyptiaca, Lycium europaeum, Maytenus senegalensis and Prosopis cineraria. Herbaceous species, which are of common occurrence on more than one site, include annuals such as Dactyloctenium aegyptium, Eragrostis ciliaris, E. poaeoides, Tragus biflorus and Gisekia pharnaceoides while the perennials comprise Convolvulus microphyllus and Tephrosia purpurea. The rooting depth of annuals varies from 20-30 cm while that of perennials may be beyond 40 cm. However, the major portion of the dry matter of roots is found to lie within 25 cm of the soil surface. Study plots in sites I, II and III cover