130 



MACLEAY SYSTEM OF 



ous isolated regions which enjoy a parity of climate and 

 other conditions, identical or the reverse ? The answei 

 is — that in such regions the vegetation bears a general 

 resemblance, but the species are nearly all different, and 

 'here is even, in a considerable measure, a diversity of fa- 

 milies. 



The general facts have been thus stated ; in the arctic 

 and antarctic regions, and in those parts of lower latitudes, 

 which from their elevation, possess the same cold climate, 

 there is always a similar or analogous vegetation, but few 

 species are common to the various situations. In like 

 manner, the intertropical vegetation of Asia, Africa, and 

 America, are specifically different, though generally simi- 

 lar. The southern region of America is equally diverse 

 from that of Africa, a country similar in clime, but sepa- 

 rated by a vast extent of ocean. The vegetation of Aus- 

 tralia, another region similarly placed in respect of clime, 

 is even more peculiar. These facts are the more remarka- 

 ble when we discover that, in most instances, the plants of 

 one region have thriven when transplanted to another of 

 parallel clime. This would show that parity of condi- 

 tion does not lead to a parity of productions so exact as to 

 include identity of species, or even genera. Besides the 

 various isolated regions here enumerated, there are some 

 others indicated by naturalists as exhibiting a vegetation 

 equally peculiar. Some of these are isolated by moun- 

 tains or the interposition of sandy wastes. For example, 

 the temperate region of the elder continent is divided 

 about the centre of Asia, and the east of that line is difFe- 

 ent from the west. So also is the same region divided in 

 North America by the Rocky Mountains. Abyssinia and 

 Nubia constitute another distinct botanical region. De 

 Candolle enumerates in all twenty well-marked portion* 

 of the earth's surface, which are peculiar with respect to 

 vegetation ; a number which would be greatly increased, 

 if remote islands and isolated mountain ranges were to be 

 included. 



When we come to the zoology, we find precisely similar 

 results, excepting that man (with, perhaps, some of the 

 less conspicuous forms of being) is universal, and tha: 

 several tribes, as the bear and dog, appear to have passed 

 by the land connexion from the arctic regions of the east- 

 ern to those of the western hemisphere. " With these ex- 

 ceptions," says Dr. Prichard, " and without ary others 



