THR ORIGIN OF THE FLORA OF ATLANTIC NORTH AMERICA. 313 
Magnolia, which recalls our M. grandiflora ; a Liriodendron, sole repre- 
sentative of our Tulip Tree; and a Sassafras, very like the living tree. 
** Most of these, it will be noticed, have their nearest or their only living 
representatives in the Atlantic States, aud when elsewhere, munly in 
Eastern Asia. Several of them, or of species like them, have been 
detected in our tertiary deposits west of of the Mississippi by Newberry 
our existing vegetation, its wide diffusion over the northern and more 
frigid zone, and its enforced migrations under changes of climate. 
“Supposing, then, that our existing vegetation, as a whole, is a con- 
tinuation of that of the tertiary period, may we conclude it absolutely 
originated then? Evidently not. ‘The preceding cretaceous period has 
y 
strobus ; a Liquidambar which well represents our Sweet Gum-tree ; Oaks 
analogous to living ones; leaves of a Plane-tree, which are also in the 
es 
of a Magnolia and Tulip Tree, and of ‘a Sassafras undistinguishable 
from our living species. I need not continue the enumeration. e 
hi qu very scrupulous 
investigator—has already announced, ‘That the essential types of our 
od, an ve come to us 
after passing, without notable changes, through the tertiary formations of 
inent,’ 
ccording to these views, as regards the plants at least, the adaptation 
to successive times and changed conditions has been maintained, not 
absolute renewals, but b gradual modifications. I, for one, cannot 
doubt that the present existing species are the lineal successors Va those 
that we can neither discern its 
nor reach its sources, whose onward flow is not less actual because 
too slow to be observed bv the ephemeree which hover over its surface or 
? 
Di 
are borne upon its bosom.’ 
