Page:American Journal of Sociology Volume 9.djvu/242

 228 THE AMERICAN JOURNAL OF SOCIOLOGY

original or acquired variations, but by reason also of their state of civilization. In regard to plants, the habitats extending from east to west are found principally among the numerous fami- lies of the north and under the mean degrees of latitude. On the contrary, the species whose habitat extends from north to south are found especially in the tropics. The families of the temperate and northern zone more often present the phenomena of habitats of very unequal diameter.

If we generalize these special distributions, we recognize three great lines along which the vegetable species propagate themselves or were formerly propagated : First, the countries around the arctic pole ; second, the zone of the Mediterranean, extending westward to the Canaries, the Azores, and Madeira ; eastward, to the Caucasus and Persia ; third, the great line of the Floridas, or from Texas to Montevideo. To these lines of main distribution one may add those of the mountains of Europe and the empire of Asia, those from California to Chili, and that from India to Senegal. In general, the configuration of the habitats of species appears to belong more to the physical and geo- graphical conditions than to the peculiar nature of these species. This static law will be more strongly affirmed among the ani- mals, and also among men, who form a single species.

The vegetal stations are localities uniting conditions peculiar to the fixation and to the development of each species. The environments that is to say, the indispensable supports to the existence of each^plant form the primary conditions for each station; thus fresh or salt water for the aquatic plants, the soil for the tuberous mushroom, certain vegetable species even for the parasitic plants, and the ordinary atmosphere for the great majority of species. Each one of these stations excludes the totality of the species of other stations. One should notice at once the fundamental distinction which separates, from this point of view, the varieties of the human species from the manifold vegetable species. The human varieties, though having distinct habitats appropriate to their special natures, are far from being as exclusive, and are becoming less and less exclusive, in refer- ence to each other.