448 X. GENERAL REMARKS. 



become altered ; the floras undergoing greater propor- 

 tionate changes from, east to west, or from west to east. 



The specific differences are- numerous, and usually 

 much ill excess over the identities, when the floras of the 

 two opposite coasts of an intervening ocean are compared 

 together, as those of Europe and America. The same 

 holds true also when the floras of the contrary sides of a 

 wide continent, very dissimilar in climate, are compared 

 together ; those of Europe and China, for example. But 

 even on those dissevered coasts, or those distant lands 

 and dissimilar climates, where only a smaller number of 

 the species are found to be identical, there is still usually 

 much resemblance between the floras of corresponding 

 latitudes, through an ordinal and generic identity, al- 

 though not become (rather, perhaps, not continuing) so 

 close as to be deemed sjiecific identity. 



Britain is not an exception to the prevailing rule of 

 change or difference longitudinally ; although this island 

 by itself is a longitudinal fragment of the globe too 

 small and narrow to show much difference in its native 

 flora on the two sides of the island. And the floral dif- 

 ferences which do appear are perhaps chiefly attributable 

 to oceanic influences, and to the oblique position of the 

 island with relation to the continent of Euroj)e. The 

 largely prevailing identity of the western and eastern 

 species has been already repeatedlj'^ mentioned. It has 

 been shown in the summary of distribution, by the 

 paucity of small lines, instead of the letters ' w e.' And 

 in the latter portion of the census of species it became 

 apparent that the non-correspondence between those of 

 the west and east was slight comparatively with the total 

 number. According to the table on page 364, the nume- 

 rical values of the western and eastern floras are summed 

 up thus : — 



