world, on the migrations of the social plants, and the limit of the
height which their different tribes attain on the flanks of the
Cordilleras.

The natural sciences are connected by the same ties which link
together all the phenomena of nature. The classification of the
species, which must be considered as the fundamental part of
botany, and the study of which is rendered attractive and easy by
the introduction of natural methods, is to the geography of plants
what descriptive mineralogy is to the indication of the rocks
constituting the exterior crust of the globe. To comprehend the
laws observed in the position of these rocks, to determine the age
of their successive formations, and their identity in the most
distant regions, the geologist should be previously acquainted with
the simple fossils which compose the mass of mountains, and of
which the names and character are the object of oryctognostical
knowledge. It is the same with that part of the natural history of
the globe which treats of the relations plants have to each other,
to the soil whence they spring, or to the air which they inhale and
modify. The progress of the geography of plants depends in a great
measure on that of descriptive botany; and it would be injurious to
the advancement of science, to attempt rising to general ideas,
whilst neglecting the knowledge of particular facts.

I have been guided by these considerations in the course of my
inquiries; they were always present to my mind during the period of
my preparatory studies. When I began to read the numerous
narratives of travels, which compose so interesting a part of
modern literature, I regretted that travellers, the most
enlightened in the insulated branches of natural history, were