If we comprehend, in one general view, the woody region which embraces the whole of South America, between the grassy plains of Venezuela (_los Llanos de Caracas_) and the Pampas of Buenos Ayres, lying between 8° north and 19° south latitude, we perceive that this connected _Hylæa_ of the tropical zone is unequalled in extent by any other on the surface of the earth. Its area is about twelve times that of Germany. Traversed in all directions by rivers, some of whose direct and indirect tributary streams (as well those of the second as of the first order) surpass the Danube and Rhine in the abundance of their waters, it owes the wonderful luxuriance of its vegetation to the twofold influence of great humidity and high temperature. In the temperate zone, particularly in Europe and Northern Asia, forests may be named from particular genera of trees which grow together as social plants (_plantæ sociales_), and form separate woods. In the Oak, Pine, and Birch forests of the northern regions, and in the Linden or Lime Woods of the eastern, there usually predominates only one species of Amentaceæ, Coniferæ or Tiliaceæ; while sometimes a single species of Piniferæ is intermixed with trees of deciduous foliage. Such uniformity of association is unknown in tropical forests. The excessive variety of their rich sylvan flora renders it vain to ask, of what do the primeval forests consist. Numberless families of plants are here crowded together; and even in small spaces, plants of the same species are rarely associated. Every day, and with every change of place, new forms present themselves to the traveller’s attention; often flowers, beyond his reach, although the shape of the leaf and the ramifications of the plant excite his curiosity.