The Palm-tree is, in Egypt, as in all the oases, the principal element of the arborescent vegetation. But you also meet there with the banana, the gum-tree, the orange, the jujube, the mulberry, the sycamore, and other tall trees, which were planted by command of Mehemet Ali, and have perfectly succeeded. The green banks of the river are diversified by coppices of acacias and tamarisks. In the Fayoum district bloom impervious hedges of cactus, and plantations of roses for the production of rosewater. Cereals yield four crops a-year; flax, hemp, indigo, cotton, the sugar-cane, prosper admirably; and under a climate where ice, snow, and hail are unknown, not a month but has its burden of flowers and fruits. Abundant crops of vegetables are raised, even as in those days when the Israelites in the wilderness bewailed "the cucumbers and the melons, the leeks, the onions, and the garlics" of Egypt. * * * * * M. Charles Martins classes the Oases of the Sahara under three heads, corresponding to his three sub-regions.[69] The oasis of the Table Lands is watered by a stream or a copious spring. That of the valleys of Erosion, by natural or artificial Artesian wells. That of the Sandy Desert wants water. In the latter the palm-trees are planted in conical cavities hollowed by the hand of man, that their roots may strike down to the subterranean reservoir which is to nourish them. Every oasis is composed, in the main, of date-palms, which seem to form a continuous forest; but in reality they are planted in rows, and in gardens separated from one another by walls of earth, which are pierced with an aperture to admit of the entrance of the irrigating rill into the enclosed square. The soil employed in the construction of the walls is removed from the paths, which are consequently below the surface, and can be employed for a double purpose; they facilitate circulation in the oases, and the waters, after having refreshed the gardens and revived the soil, discharge themselves into these hollow ways, whence they flow towards the chotts, or stagnate in swamps, which the lethargic Moslem never thinks of draining. From such hotbeds of infection issues the monster Fever every year, and slays its hundreds. In case of need, every oasis becomes a fortress. Each "square of flowery ground" is a redoubt; the assailant's bullet lodges in the earth wall, or if it pierces through, forms a new loophole in which the Arab plants his gun to aim at his enemy. The villages themselves are encircled with walls, flanked by towers, which remind the spectator of the picturesque fortifications of mediæval times. * * * * *