564 PHYSICAL GEOGRAPHY. 



southern parts of Africa can be compared to that of New Holland. In the same latitudes 

 we find innumerable legions of heaths and Protece, which include many shrubs remarkable 

 for their graceful and delicate forms, adorning the otherwise barren soil of either climate. 

 But in all the places we have visited, and above all on the western side of New Holland, 

 we do not find, in the great masses of vegetation, either the majesty of the virgin forests 

 of the New World, or the variety and elegance of those of Asia, or the delicacy and 

 freshness of the woods of our temperate countries of Europe. The vegetation is gene- 

 rally gloomy and sad. It has the aspect of our evergreens or heaths. The plants are for 

 the most part woody : the leaves of nearly all are linear, lanceolated, small, coriaceous, 

 and spinescent. This contexture of vegetable productions is the effect of the aridity of 

 the soil and the dryness of the climate. It is without doubt to these same causes that the 

 rarity of cryptogamous and herbaceous plants is owing. The grasses, which elsewhere 

 are generally soft and flexible, participate in the stiffness of the other vegetables. The 

 greater part of the plants of New Holland belong to new genera ; and those included in 

 the genera already known are of new species." Analogy, with still stronger diversity, 

 marks the vegetation of most contrasted districts at some considerable distance from each 

 other ; but the analogy is striking between the flora of contiguous countries, not divided 

 by arid deserts or high mountain chains. Thus England does not possess fifty species of 

 plants which are not found in France ; and the opposite shores of the Mediterranean have 

 a kindred flora. On the other hand, there are scarcely any species to be met with in 

 Senegal that are common to the north coast of Africa, the Great Desert dividing the two 

 regions ; and Mr. Darwin, upon crossing the Andes of Chili, was struck with the marked 

 difference of the vegetation in the valleys on each side, though the climate, as well as the 

 kind of soil, was nearly the same, and the difference of longitude very trifling. 



The preceding facts are obviously fatal to the Linnaean hypothesis respecting vegetable 

 distribution that the originals of all the species of plants had their primary habitation 

 in one spot, from which central region they have been diffused by natural agencies over 

 the face of the globe. In order to provide that diversity of climate necessary to support 

 in the same place arctic and tropical forms, Linnaeus imagined the common birthplace of 

 plants to have been a high mountain tract in a warm region, the various necessary tem- 

 peratures being found at different heights from the base to the summit. This has been 

 justly called a scheme more allied to poetry or fiction than to a serious investigation of 

 the phenomena of nature. The ascertained condition of the vegetable kingdom is utterly 

 irreconcilable with it. A second theory rejects the idea of a local centre, and places the 

 original distribution of plants under the government of soil and climate: but this is 

 scarcely more tenable than the former hypothesis, on account of totally different genera 

 and species occurring under the same physical conditions. A third theory is an expan- 

 sion of the Linnaaan. It recognises every species or tribe as emanating from a primitive 

 centre, each centre being the seat of a certain number of species, these primary habi- 

 tations being in different parts of the earth. This hypothesis is most in harmony with 

 facts. It accounts for the different botanical regions into which the surface of the earth 

 may be mapped out ; for the diversities of species under the same parallels of latitude ; 

 while the natural transporting agencies of Linnaeus remain in full force, to disperse each 

 species to a distance from its primal seat, and to intermingle the floras of different dis- 

 tricts, not separated by insurmountable physical barriers to migration. Dr. Prichard, 

 after examining the subject with great research and care, thus states the conclusion: 

 " It appears, then, that the phenomena connected with the distribution of plants are only 

 reconcilable with one hypothesis, or rather they lead us clearly to one inference, namely, 

 that the vegetable creation was originally divided into a limited number of provinces. 

 Each country had its particular tribes, which at first existed not elsewhere. This conclu- 



