220 ESSA YS. 



increased by further knowledge than are those of any of the 

 other regions. Properly to estimate the surpassing richness 

 of this Japan-Mandchurian forest, the comparative smallness 

 of geographical area must come in as an important consid- 

 eration. 



To complete the view, let it be noted that the division of 

 these forests into coniferous and non-coniferous is, for the 



European, non-coniferous 26 genera, 68 species. 



" coniferous 7 "17 " 



Total, 33 genera, 85 species. 



Japan-Mandchurian, non-coniferous . 47 genera, 123 species. 

 " " coniferous . . 19 " 45 " 



Total, 66 genera, 168 species. 



In other words, a narrow region in eastern Asia contains 

 twice as many genera and about twice as many species of in- 

 digenous trees as are possessed by all Europe ; and as to co- 

 niferous trees, the former has more genera than the latter has 

 species, and over twice and a half as many species. 



The only question about the relation of these four forest- 

 regions, as to their component species, which we can here 

 pause to answer, is to what extent they contain trees of iden- 

 tical species. If we took the shrubs, there would be a small 

 number, if the herbs a very considerable number, of species 

 common to the two New World and to the two Old World 

 areas respectively, at least to their northern portions, even 

 after excluding arctic-alpine plants. The same may be said, 

 in its degree, of the north European flora compared with the 

 Atlantic North American, of the northeast Asiatic compared 

 with the northern part of the Pacific North American, and 

 also in a peculiar way (which I have formerly pointed out 

 and shall have soon to mention) of the northeastern Asiatic 

 flora in its relations to the Atlantic North American. But 

 as to the forest trees there is very little community of species. 

 Yet this is not absolutely wanting. The Red Cedar (Juni- 

 perus Virginiana) among coniferous trees, and Populus 

 tremuloides among the deciduous, extend across the American 



