ABSTRACT
After an introduction in which he defines botanical geography and recalls its origins, de Candolle has three distinct sub-chapters in which he deals with the physical factors that influence the distribution of different plant species, stations, i.e., the milieu where they are found, and habitations, that is, the regions where they grow naturally.
Some plants are not able to grow in certain localities because they need “circumstances” which are not all found there. Furthermore, “the conditions for the existence of each species are not fixed, but allow some latitude between limits”. Thus, among the plants able to grow in a place, there are those that prosper more than the others and tend to eliminate them from the locality. Nevertheless, this dual action of physical causes and competition is not sufficient to explain all the observations recorded by botanical geography, as is shown, for example, by the difference in flora in the Old and New Worlds. In addition, there are certain endemic families and genres “for which all the species grow in a given country”.
All this shows that while “stations are related solely to physical causes currently at work”, in contrast “habitations might well have been partly determined by geological causes that are no longer existent”. De Candolle furthermore states that he will not take up the discussion of these obscure questions and explains that his article “is written based on the opinion that the species of organized beings are permanent”.
