The widely scattered places of sedentary occupation in the Sahara may take two forms: they may be oases in the midst of sandy desert, or they may be havens among the mountains. The desert oasis has its planted belt of date palms and plentiful supply of water, usually drawn from wells, sometimes from springs in open ditches. Under the shade of the palms are the irrigated gardens, where constant labour, at the seasons of cultivation, is demanded to flood the soil and nurse the plants to maturity in surroundings that would give no life without artificial aid. The gardens are sandy and small: a network of closely crowded allotments, each fenced with palm staves to hold in check the driving sand. By means of a regular system of irrigation channels the soil is fed with water at intervals each day; drawn to the surface by oxen, or by hand, at the expense of a good deal of patient labour. The consequent dampness and humidity breed malaria, which is, perhaps, a further reason for the importation of the negroid serf, who is, through hereditary environment, familiar with the destructive malady. Indeed, in this respect, at the time of rain it is common practice for many semi-nomadic masters to evacuate the oases altogether and roam far out into the more healthy desert, tending their flocks while leaving their serfs alone to look after the cultivation. The palms produce dates, which ripen in the autumn, and the gardens principally wheat, millet, tomatoes, and onions in sparing quantities. All the work of cultivation is done by hand. The dwellings of the desert oases have the character of towns, not villages. In a sense that designation may appear overdrawn, insomuch that many oases are no larger than the tiniest of villages, but against that should be set an environment that is so appallingly blank that any society of dwellings takes on the glamour of urban life. The market-places have their bazaars and their movement of people, the sandy streets are tolerably well laid out, while the clay-built buildings are compact and complete, and sometimes ornamental. But they are few and very widely scattered, and vary greatly in standard. Some are mere hovels, others towns in the full sense of the word; and these latter are chiefly in the Algerian Sahara near to Arab civilisation, though Bilma, Fachi, and like outstanding ports in the desert should on no account be overlooked. The sedentary havens among mountains such as Ahaggar and parts of Aïr are different from the desert oases. They are in character villages, and the life is entirely rural, as a place is rural that herds flocks about its doors and lives, for the most part, in grass-covered hutments.