There are 15 sugar estates in British Guiana on the coastal plain between the Essequibo and Courantyne Rivers. These are laid out in strips between the sea or estuary and the flooded savannas, divided into 2 by a central irrigation canal and separated from adjoining estates by drainage canals. The lay-out of each estate is identical, but the cane fields are laid out either on the Dutch or English systems or modifications derived from them. The practice of flood fallowing, long customary in British Guiana, improves the fertility and texture of the soil. Flooding is done by pumping in water from the middle-walk canal. The coastal sugar-cane soils are zoned into salt clays, heavy clays, normal clays, and pegassy clays, modified on the river estuaries by alluvium. There are 2 sites available for vegetation in flood fallows, i.e. cane banks and open water of variable depth. Four plant communities occur on these sites: swamp on heavy, normal and light clays, swamp on pegassy clay, semi-aquatic plants in shallow water, aquatic plants in deep water. The vegetation is largely detd. by depth of flooding, by maintenance of that depth and by soil type. Minor determining factors include flooding by blocks of fields, time lapse between cutting and flooding, and acidity of water in the middle-walk canal. The benefits derived from the vegetation of flood fallows are considered negligible. The flood fallows on heavy and normal clays are customary breeding sites of the malarial mosquito, those on light and pegassy clays exceptional. Customary sites can be distinguished from exceptional sites by indicator plants.