DISEASES IN PLANTS. 381 
For our purpose it will be sufficient to know, 
that such immense changes took place in our globe, 
and necessarily had a powerful influence upon the 
vegetable world. In northern countries, where the 
cold is so great that no trees can grow, and a few 
small shrubs with difliculty shoot forth, we find 
whole strata and beds of coal, which, as we cer- 
tainly know, are vegetable productions. In those 
countries, therefore, forests certainly were once in 
abundance, where now there are none. In the same 
manner, bones of the elephant and rhinoceros are 
dug up, though these animals could not now live in 
our cold climate. We find in our slate clay, im- 
pressions of filices, seeds, and palmae, which do 
not occur in our country. About Wettin, near Halle, 
(in Upper Saxony), a great number of those im- 
pressions in slate elay are found, in which the spe- 
cies of several filices can be recognized, which at 
“present grow all in the West Indies only. Of some 
impressions the originals have not yet been detected. 
Tt would be superfluous to mention here the great 
number of shells which we find, without knowing 
the recent species. 
It is only in flat countries: and upon floetz moun- 
tains, where these respectable remnants of past times 
are met with, and never in primitive rocks. But 
not only are the products of warm climates with us 
often found buried in the deepest ground, bones 
of animals of the coldest regions are likewise found. 
And the products of both countries are often mixed 
together. Hence we cannot say that the warm cli- 
mate once was extended farther to the north; that 
our 
