5 
from some difference existing previous to deposition, and 
that difference is most likely to have been originally in the 
nature of the plants of whose remains the coal beds consist."* 
Having proved this point, our next one for consideration 
is that of the geographical distribution of species ; for there 
is one circumstance observable in the flora of the carbon- 
iferous period which is very remarkable, as apparently 
indicating an universality of vegetation, or that in former 
ages the range of the species of plants was far more 
extensive than at the present day. Dr. Hooker observes, 
" It appears that an uniformity once existed in the vegeta- 
tion throughout the extra tropical countries of the northern 
hemisphere, to which there is now no parallel ; and this 
was so, whether we consider the coal plants as representing 
all the flora of the period, or a part only, consisting of 
some widely distributed forms that characterised certain 
local conditions." If we compare the floras of modern 
Europe and America we find them essentially unlike, while 
if we examine the floras of the coal fields of these two 
distant regions, we are instantly struck with the remarkable 
fact, that not only nearly all the genera, but many of the 
species, are precisely the same. Even in Melville Island, 
deep in the Arctic regions, plants, identical with those in 
the coal formation of Britain, are said to have been found. 
Sir C. Lyell, in describing the coal-fields of Nova Scotia 
and Cape Breton, says, " Out of forty-eight species, without 
enumerating the different varieties of Stigmaria, there are 
no less than thirty-seven which have been identified, of 
which twenty-two are identical with British coal plants ; 
four or five may be considered as varieties of British types ; 
and two appear to be identified with European species not 
yet discovered in Britain ; and the greater part of the 
remaining eleven might, perhaps, have been found to agree 
* Fossil Flora, vol. ii., pp. 25, 26. 
