INTRODUCTION TO SOCIOLOGY 231
Pampas of South America, in order that the uniformity may appear." This uniformity in the same conditions appears to us in a striking manner in the structure and life of human popu- lations.
One other static vegetable law is that the average area of species is the greater as their average height is less. Thus the domain of mosses and lichens is excessively extended. We know that civilizations little advanced, and uniform, can occupy immense spaces, as in Africa, and in America during the Indian period.
It seems, however, that there is no correlation between the human static and the vegetable law according to which the average area of the species of a single family diminishes in proportion as one travels from the arctic pole to the southern extremities of continents a law which is pretty applicable to the general average area of the species.
The regions farthest separated from others by seas or deserts are, in general, those which offer most to the special species ; for example, the Cape of Good Hope and Australia. We have noted the same law in connection with our observations con- cerning the influence of general geography and orography upon the formation of races and nationalities.
Among the phanerogamic species, whose area is, however, the greatest by reason of their perfect organization, none extends itself over the entire surface of the globe ; none, notably, is found directly under the equator (at least in the plains) , and at the opposite extremities of the continents, towards the two poles. In fact, the same mass of physical environment, through its extent and its natural variations, opposes an obstacle in such a way that the vegetable line forms a single and uniform empire. The sea itself constitutes a peculiar botanic region, where, besides extensive and powerful kingdoms, there are in the small islands most distant from other lands some very small specific areas, some very minute principalities.
Outside of these limits, more or less special, the plant king- dom has some general impassable limits. It does not extend above 5,000 meters in the Cordilleras, 2,700 in the Alps and,
