L. Lesquereux on the Origin and Formation of Prairies. 29 
one Sumach, and one Walnut. If we consider the genera only, 
it is evident that this flora has the greatest analogy with ours; 
and if we could account for the transportation of seeds, it would 
perhaps seem reasonable to suppose that the change of ‘character 
of our vegetation, since the Tertiary period, might be explained 
by Prof. Winchell’s theory. Before conceding the value of this 
pootinbs however, we must Jook further to what we know 
the characters of the vegetation in our recent geological ages, 
The materials collected till now from the flora of Iceland as well 
as from our own are not sufficient to form a solid basis for argu- 
ment, but we must use them as they are 
In the lower Miocene (may be the Eocene ?) of the State of 
Mississippi, the most abundant remains of fossil plants ene vm 
cies of Calamopsis, an extinct genus of Palms. With 
and in about the same abundance, there are leaves of a Sabet 
resembling our Palmetto, and of Fig and Cinnamon trees. At 
a higher stage, in the red shales, which I consider as true Mio- 
ng we find still some leaves of. Fig, Cinnamon, and Sabal, wi: 
already those of Oak, Maple, apes Laurel, Olive, Magnolia 
and even Beech, whose species are related to, but not identical 
a species of our time. Higher still, in the chalk banks of 
mbus, Kentucky, we have leaves and fruits, whose relation 
is “still nearer to our a ets species. Some of them so much SO, 
that I have considered them as identical with ours.“ Passi 
higher up in the formations, we have, along the banks of the 
lower Ohio river, thick st rata of a compound of leaves and fruits 
mixed with alluvial clay ser formed in terraces. All the species 
of this formation are of our time and of our latitude. 
n the difference of forms between the plants of the lower 
fae and those of our sign we recognize a constant modi- 
we ascribe the last axa to a peculiar glacial agency, 
especially oe, to sustain the hypothesis, we should have n 
ur arborescent vegetation, exactly the same species thease 
cer 0 x Gp, t that em noted foie its 5 very. 
io efits are types of which no trace appears, in our. aceite 
vegeta 
~ ete Se ], xxvii, 364. Specimens of these fossil plants ona 
imajusrae some of them with species of our time, and 
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