Vice-President’s Address. 219 
GENERAL REMARKS ON THE DISTRIBUTION OF THE 
FLORA OF THE CARBONIFEROUS FORMATION. 
I have already mentioned that in employing fossil plants 
for the purpose of ascertaining the groups, or divisions, of the 
Carboniferous formation that occur in Britain, and for the 
correlation of the isolated areas of these divisions that may lie 
in different parts of the country, I have not been guided by 
data afforded by the occurrence of any one species, but by 
the evidence derived from the examination of a general 
collection of the fossil plants from the rocks the age of 
which I wished to ascertain. 
It is true, so far as our present knowledge goes, that 
certain plants appear to be restricted to certain horizons ; 
but against the employment of such evidence as an infall- 
ible test of age, there is always the possibility of these 
species being yet found in other horizons. As examples of 
plants which appear to be restricted to one series of rocks, 
Calymmatotheca affinis, L. and H. sp., and Calymmatotheca 
bifida, L. and H. sp., may be mentioned. These have hitherto 
only been found in the Calciferous Sandstone Series, where 
in some localities they are plentiful. But even if isolated 
examples of these were found, say in the overlying Car- 
boniferous Limestone Series (= Yoredale Rocks), it would not 
alter their value as characteristic species of the Calciferous 
Sandstone Series. 
If, however, in forming our opinions of the age of rocks 
from the fossil plants they contain, we take a view of their 
flora as a whole, errors arising from false values being placed 
upon individual species are entirely eliminated. 
Nothing is more characteristic than the facies of a flora, 
a character which can only be observed when a representative 
collection of the whole flora of the series under consideration 
has been examined, and only under these conditions can the 
relative proportion of the species, another very important 
point, receive its proper value. 
1 I am aware that these species have been reported from other horizons, 
but it has only been through error of identification. 
