British North American Plants. 19 
perate type, but that the relations of land and water were 
such as to allow migration between Europe and America. 
Is it unreasonable to suppose that the land then sufficiently 
elevated above the sea to connect the old world with the 
” 
new, may have been in a similar position in Pliocene or ~ 
Post-Pliocene times, and have afforded the facilities then 
needed for the intermingling of the flora still existing at the 
present day on the two continents ? 
Pre-GuactaL Drirr PLANts. 
It is interesting to find that in the pre-glacial drift which 
is thought to be either Pliocene or Pleistocene, and which 
is spread over a considerable portion of the Middle and 
Southern States, paleobotanists believe they have recog- 
nized three of the existing trees of these States—Magnolia 
_ glauca, L., Liquidambar styracifua, L., and Quercus imbri- 
caria, Mx. These species do not range as far as Canada, 
AGE OF THE CANADIAN Fora. 
The relative ages of the species which comprise the Cana- 
dian flora form matters rather of speculation, and yet, from 
the foregoing pages, it will be seen that there are some data 
on which to found opinions. The conclusions may be thus 
summarized :—The species of whose presence iu the Kocene 
there is fossil evidence, are the oldest known representatives 
_of the existing flora, Next to these in age, as species, are 
the plants common to Europe and America, for they were 
apparently already well distributed at the time of the depo- 
sition of the Leda clays. It is probable that many of the 
Arctic species, which are now limited to America, are 
equally old, but, jast as many plants now have but limited 
ranges, they had not in these older times found their way 
beyond the American continent. The American species, 
not also European in range, but which are denizens of 
Japan, may be contemporaneous with these Americo- 
European species, or even earlier in origin. Two of the 
plants now common to Japan and America date back to 
the Laramie times. The plants confined in range to British 
