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Ancient Vegetation of the Earth. 319 
But the study of the impressions of stems, leaves, and even 
fruit, which are in general contained, in so great quantities, in 
these rocks, proves not only the vegetable origin of this substance, 
but even enables us to determine the nature of the vegetables of 
which it has been formed, and which, consequently, at the period 
of such formation, occupied the surface of the earth. 
Among these vegetable imprints, the most frequent are those 
produced by the leaves of the Ferns ; yet these Ferns of the prim- 
itive world are not those which now grow in our climates ; for 
Europe, at this time, does not produce more than from thirty to 
forty species, while the same regions then nourished more than 
two hundred, all much more analogous to those now found be- 
tween the tropicks than to those of the temperate climates. 
In addition to the leaves of Ferns, the same earths contain 
trunks, the dimensions of which render them comparable to the 
most gigantick trees of our forests, while their form is wholly 
dissimilar ; and indeed all the ancient naturalists, struck with this 
dissimilarity, and yet desiring to find analogous productions still 
existent, referred them to arborescent vegetables, then imperfectly 
known, as the Bamboos, Palms, and the great Cactus, sometimes 
designated Torch-thistle. But a more attentive comparison of 
these products of the equinoctial regions with those trunks, the 
growth of the ancient world, suffices to dissipate all relations, 
which are founded only on some resemblances in the general as- 
pect, that have been attempted to be established between them ; 
and a more profound examination, either of these trunks or of the 
leaves which accompany them, readily shows that the vegetables 
which formed these primitive forests are not identical with any 
trees still found flourishing upon the eart 
The arborescent Ferns which, by the elegance and magnitude 
of their exteriour, now form one of the principal ornaments of the 
equatorial regions, are the only arborescent vegetables which are 
recognized, even in small number, among the trees of this antique 
vegetation. 
As to the other fossil stems, remains of these primitive forests 
of the ancient world, it is among the most humble vegetables of 
our epoch that we must seek their analogues. 
For instance, the Calamites, which attained from four to five 
métres (a little more than 13 to 16 feet) of height, and from one 
to two décimétres (not quite four to eight inches) of diameter, 
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