220 ESSAYS. 
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. 
CY CBUIZETOUS sce poe fe) ee ee geri 4 a 
Total, 33 genera, 85 species. 
Japan-Mandchurian, non-coniferous . 47 genera, 123 species. 
se coniferous a Pek, <p Rs 
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 
