The wealth of an oasis is computed by the number of its palm trees. All of them, however, are not fruitful; for the date is dioecious. It has its males and its females. The males have flowers furnished with stamens only, and form a closed-up, folded, grape-like ball, previous to the ripening of the pollen in an envelope called the spathe. The females, on the contrary, bear clusters of fruit also wrapped up in a spathe, but incapable of development until fecundated by the pollen or dust of the stamens. To multiply the date-trees, the Arabs do not sow the kernels of the fruits, though they germinate with extreme facility, for it is impossible to tell beforehand of what sex the tree will be; they prefer, therefore, to detach a slip from the trunk of a female tree, and this becomes fruitful at the expiry of eight years. The male trees blossom, says Mr. Tristram,[72] in the month of March, and about the same time the case containing the female buds begins to open. To impregnate these, a bunch of male flowers is carefully inserted and fastened in the calyx. Towards the beginning of July, when the fruit begins to swell, the bunches are tied to the neighbouring branches. The dates are ripe in October, at which time any premature rain is fatal to the crop, though the _roots_ require a daily watering. Not less injurious are east winds in March and April. The tree when it begins to bear is about seven feet high. Each year the lowest ring of leaves falls off, so that the age of a palm may be roughly computed from the notches on its stem. Its fruit begins to decline after a century, and the tree is then cut down for building purposes; but it will live for at least a couple of hundred years. Some trees produce as many as twenty bunches, but the average in a favourable season is from eight to ten bunches, each weighing from twelve to twenty pounds. Before the dates ripen, each proprietor is bound to set apart one tree in his garden, whose fruit is consecrated for the service of the mosque and the use of the poor. From the juice of the date the Arab obtains a sweet fermented liquor, called "laguni," of which he is inordinately fond. He makes an incision in the top of the tree, taking care to strike home to the centre. A funnel is attached, by which the sap flows into a vessel at the rate of about three quarts every morning for ten to sixteen days. The incision requires to be opened afresh daily. The cabbage, or soft pith and young unfolded leaves at the summit of the stem, in taste approaching the chestnut, is also eaten, but only when the tree has fallen or been felled, as the loss of its crown invariably destroys it. There are fifteen varieties of dates, of which the _dghetnour_ is considered the best for keeping, and three other kinds are preferred fresh.