Timbuktu or to study. By 1300, the population increased to 10,000 and kept increasing until it reached about 50,000 in the 1500s. There is insufficient rainfall in the Timbuktu region for purely rain-fed agriculture and crops are therefore irrigated using water from the River Niger. The main agricultural crop is rice. African floating rice ("Oryza glaberrima") has traditionally been grown in regions near the river that are inundated during the annual flood. Seed is sown at the beginning of the rainy season (June–July) so that when the flood water arrives plants are already in height. The plants grow up to in
Rissoina oryza Rissoina oryza Rissoina oryza is a species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoinidae. The height of the small, white shell attains 2 mm. The shell has an oblong-ovate shape. It is solid, smooth, and shining, The spire is moderately elevated, and rather rapidly tapering. The apex is obtuse. The 6-7 whorls are flatly convex. The body whoprl is rather large, and slightly compressed beneath. The suture is faintly impressed and broadly margined beneath. The rather large aperture is oblique and has a sub-ovate shape. The thick peristome is dilated. The columella is