But most of the Algerian forests, already wasted in the time of the Romans, and again destroyed by the charcoal-burners, have been replaced by extensive tracts of brushwood and of smaller growths, such as the myrtle, arbutus, and bu-nafa, or thapsia garginica, formerly so famous in Cyrenaica under the name of silphium, and still highly prized in Algeria.
Above the maritime region and beyond the coast ranges, the changes in the character of the vegetation are due less to altitude than to the aspect of the land, and the proportion of moisture contained in the atmosphere. The olive, the characteristic tree of the scaboard and of the slopes facing the Mediterranean, scarcely reaches the upland plateaux, although it is still met on the Jebel Aures and in the oases at their foot. The cork-tree and Halep pine disappear at the same altitude as the olive, and no evergreen oaks are seen at a higher elevation
than 5,000 feet. In the Jurjura cedar forests flourish at between 3,300 and 4,000 feet, and this plant attains a higher altitude than any other species. The only tree that has adapted itself to the breezy and dry climate of the central plateaux, with their great extremes of temperature, is the betum (pistacia atlantica), which at a distance looks like an oak-tree. Here are also met a few tamarisks and arborescent species growing in the hollows, but no other trees or shrubs except those planted by the colonists round about the civil and military stations. The characteristic vegetation of the plateaux are coarse grasses, especially of the stipa family, which cover a space of about ten million acres altogether. Conspicuous amongst them are the well-known alfa, or rather halfa (stipa tenacissima), and the shi (artemisia herba alba), which occupies extensive tracts between the Marocco and the Nile deserts, and the dried leaf of which is used as a substitute for tobacco by the Arabs.
