160 Distribution of the North American Flora, [March, 
plane, lime, hornbeam, hop-hornbeam, laurus, drospyros, poplar, 
birch, mulberry and horse-chestnut; together with about half 
that number of shrubs. 
The other example was afforded me by Goat island, which 
divides the great cataract of Niagara, and covers less ground 
than Kew Gardens. Here the vegetation was more boreal and 
less varied than in Missouri; but with Dr. Gray’s aid I counted 
thirty kinds of trees, of which three were oaks and three poplars, 
together with nearly twenty different shrubs. 
I know of no temperate region of the globe in which any 
approach to this aggregation of different trees and shrubs could 
be seen in such limited areas, and perhaps no tropical one could 
afford a parallel. 
No less remarkable is the composition of the flora of the East- 
ern States. Prof. Gray has shown that most of its genera are 
common to Europe and Asia, but that very many are all but con- 
fined to North-eastern Asia and Western America. This generic 
identity, however, gives but a faint idea of the close relationship 
between the East American and East Asiatic, especially the Jap- 
anese, floras, for there is further specific identity in about two 
hundred and thirty cases, and very close representation in upwards 
of three hundred and fifty ; and what is most curious is, that there 
are not a few very singular genera, of which only two species are 
known, one in East Asia, the other in East America; and in some 
of these instances the Asiatic species is a wide-spread plant in 
East Asia, whilst the American is an extremely scarce and local © 
plant in its country, which with other considerations render it con- 
ceivable that the Asiatic element in East America is a dying-out 
one. 
Leaving out of consideration the purely American genera of 
this flora, there remain the genera common to Europe, Asia and 
America; the genera confined to America and Asia; and the 
genera confined to America and Europe. I shall give an illus- 
tration of the proportions in which these occur by a reference to ` 
the principal trees and large shrubs only, their names being 
familiar to you, though the smaller shrubs and herbs afford 
infinitely more numerous and striking examples ; thus, of those 
common to the three northern continents, I find in America 
thirty-eight genera with about one hundred and fifty species; these 
include maples, ashes, hollies, elms, planes, oaks, chestnuts, nut, a 
