It suffices to name the families of the Coniferæ and the Amentaceæ, which compose the greater portion of the Flora of our forests. Moreover, as Humboldt observes, in the Temperate Zone, particularly in Europe and the north of Asia, certain species of trees (_plantæ sociales_) grow together, and form of themselves forests which we may designate by their specific name. In the forests of oaks, firs, and birches which cover the countries of the North, in the forests of limes of the East, one unique species of Amentaceæ, Coniferæ, or Tiliaceæ generally prevails. This uniform society is foreign to the Tropical forests. The infinite variety of flowers which expand in these _Hylææ_ do not permit us to ask of what the virgin forests are composed. An innumerable quantity of different families stand side by side; even in the most confined spaces it is rare to see trees of the same nature re-united. Every day, as the traveller advances, he discovers new forms; oftentimes the outline of the leaf and the ramification of a tree attract his attention, without his being able to distinguish the flowers. There is yet another feature, more striking still, and more general than those previously mentioned, which broadly distinguishes the arborescent vegetation of the Tropics from that of northern climates. Here the plants, exposed annually to an often intense degree of cold which lasts for several months, experience a kind of suspension of their vital activity, cease to flower and to fructify, and entirely shed their foliage; the resinous species are the only exceptions to this rule. In the neighbourhood of the Equator, on the contrary, it is during the hottest, driest season that vegetation suffers; then the herbaceous plants and bushes of the plains die down; but the great trees of the virgin forests are hardly affected; their foliage incessantly renews itself; their branches are at all times loaded with fruits and flowers, and to the wayfarer's eyes they present the glorious spectacle of an eternal freshness, of a life which never wanes. Compared with these great points of difference, common to all the virgin forests of the Tropics, the peculiar features resulting from the botanical constitution which distinguishes more or less exactly one region from another, have, as the reader will understand, but a secondary importance. With the exception of a few countries which possess a Flora _sui generis_--such, for example, as Madagascar and Australia--the same aspects, the same general forms are almost everywhere reproduced.