INTRODUCTION. Ot 



plains each organic form attains the maximum of its develop- 

 ment Considerations of this nature, by their tendency to 

 generalization, impress a nobler character on the physical de- 

 scription of the globe, and enable us to understand how the 

 aspect of the scenery, that is to say, the impression produced 

 upon the mind by the physiognomy of the vegetation, depends 

 upon the local distribution, the number, and the luxuriance of 

 growth of the vegetable forms predominating in the general 

 mass. The catalogues of organized beings, to which was for- 

 merly given the pompous title of Systems of Nature, present 

 us with an adm jably connected arrangement by analogies of 

 structure, either in the perfected development of these beings, 

 or in the different phases which, in accordance with the views 

 of a spiral evolution, affect in vegetables the leaves, bracts, 

 calyx, corolla, and fructifying organs ; and in animals, with 

 more or less symmetrical regularity, the cellular and fibrous 

 tissues, and their perfect or but obscurely developed articula- 

 tions. But these pretended systems of nature, however ingen' 

 ious their mode of classification may be, do not show us or- 

 ganic beings as they are distributed in groups throughout our 

 planet, according to their different relations of latitude and 

 elevation above the level of the sea, and to climatic influences, 

 which are owing to general and often very remote causes. 

 The ultimate aim of physical geography is, however, as we 

 have already said, to recognize unity in the vast diversity of 

 phenomena, and by the exercise of thought and the combina- 

 tion of observations, to discern the constancy of phenomena 

 in the midst of apparent changes. In the exposition of the 

 terrestrial portion of the Cosmos, it will occasionally be neces- 

 sary to descend to very special facts ; but this will only be in 

 order to recall the connection existing between the actual dis- 

 tribution of organic beings over the globe, and the laws of the 

 ideal classification by natural families, analogy of internal or- 

 ganization, and progressive evolution. 



It follows from these discussions on the limits of the various 

 sciences, and more particularly from the distinction which must 

 necessarily be made between descriptive botany (morphology 

 of vegetables) and the geography of plants, that in the phys 

 ical history of the globe, the innumerable multitude of organ- 

 ized bodies which embellish creation are considered rather ac- 

 cording to zones of Iwbitation or stations, and to differently 

 inflected isothermal bands, than with reference to the princi- 

 ples of gradation in the development of internal organism. 

 Notwithstanding this, botany and zoology, which constitute 



