Page:Africa by Élisée Reclus, Volume 1.djvu/30

 and the distribution of its inhabitants has also been determined almost exclusively by the climatic conditions, depending everywhere on the abundance of rain and vegetation. In its flora and fauna, as well as its climate and geology, North Africa belongs to the zone of transition between Europe and Asia. The apparent unity imparted to the continent by its compact form is not realised when we examine in detail the phenomena of life. Cyrenaica and the whole Mauritanian seaboard on the slope of the Atlas range belong to the vegetable domain of the Mediterranean, in which are also comprised Spain, Provence, Italy, the Balkan peninsula, the shores of Asia Minor, and Syria. The zone of the Sahara, which stretches under the Tropic of Cancer across the continent, is continued in Arabia to the Persian Gulf, and even through some of their rarer species embraces the Baluchistan coast, Thar, the Rann, and the Kathyawar peninsula in India. Lastly, the floras of Yemen and Hadraraaut resemble those of Sudan, the narrow Red Sea having been easily traversed by African species.

For the whole continent, the characteristic vegetable zone is that of Sudan and the equatorial regions, which stretches from sea to sea, and from desert to desert, between the Atlantic and Indian Oceans, between the Sahara and Kalahari. Speaking broadly, it is much poorer in distinct species than the other tropical regions, such as India and the Sunda Islands, and even than some sub-tropical lands, such as Asia Minor. Nevertheless certain central districts in Africa possess a remarkable variety of plants, as for instance, the territory watered by the Diur, not far from the dividing line between the Nile and Congo basins. Here Schweinfurth collected in five months nearly seven hundred flowering species, which it would be impossible to do in the richest European lands.

Most of the African tropical domain is exposed to the periodical rains, with long intervening periods of dryness. Hence arborescent vegetation nowhere displays greater exuberance and vigour than on the plains between the Congo and Nile, where the streams often disappear amid dense masses of foliage, and in the neighbourhood of the Bight of Benin, which enjoys far more humidity than the interior. A large extent of the zone of the Sudan is occupied by prairies, although some tracts are so overgrown with graminaceous and other herbs that animals refuse to penetrate into them. In the Nile marsh lands, certain andropogonous varieties have non-woody stalks over twenty feet high, affording to the giraffe cover from the hunter. The various graminaceous plants of Central Africa are not intermingled like those of the European fields, and tracts several hundred square miles in extent are sometimes occupied by a single species.

Thorny plants are relatively very abundant in the forests of the Sudan, and after clearances the trees appear not to spring up so rapidly in this zone as in South America. Varieties of the palm family are ten times more numerous in Asia and America than in Africa, which has consequently a wider range for its prevailing species. The equatorial regions of other continents have scarcely any cocoa-nut