Carboniferous Period. 325 
beds, is extremely limited, and appears scarcely to reach eight 
or ten. In other cases, and more generally in the middle and 
Superior beds, this number becomes more considerable, but I 
believe that it very rarely surpasses from thirty to forty spe- 
cies. We perceive that each of these small local and tempo- 
rary floras, which here give rise to a bed of coal, is extremely 
limited. We observe something of the same kind in our 
own day in the case of extensive forests, particularly such as 
are composed of Conifer, where one or two species of trees 
cover with their shade only four or five different phenoga- 
mous plants and a few mosses. 
But, in order to know whether these small floras, thus 
limited with regard to time and space, characterise so many 
special epochs in the vegetation of the globe, it is necessary 
to determine their succession in many of the principal coal- 
basins of Europe, and to notice if the nature of the vegetation 
is modified in the same manner in these different basins ; if, in 
a word, vegetation in different countries was everywhere the 
same at the same epoch, or if it was subjected to local varia- 
tions, analogous to those which now distinguish the vegeta- 
tion of a forest of Pinus sylvestris of Germany, of a forest of 
Abies taxifolia of the Vosges, Picea excelsa of the Jura, or 
Pinus pinaster of the Landes. 
Iam persuaded that this examination, if performed in a 
somewhat perfect manner, would shew that there are some 
general changes owing to the succession of the seasons, such 
as the predominance of certain genera, or of certain specific 
forms, combined with other differences altogether local, or to 
be ascribed to the influence of geographical position. 
It accordingly appears to me to be the result of many local 
observations, that the Lepidodendrons are more abundant in 
the ancient beds than in the superior beds of the greater part 
of the'coal-formations ; that the true Calamites are often in 
the same, condition ; that the Sigillarice would appear to pre- 
dominate in the middle and superior beds ; that the Astero- 
phyllites, and particularly the Annuaria, are found much 
more abundantly in the superior beds; that, it is the same 
with the Conifere ; and it is only in the superior beds of St 
