202 
THE FOSSIL FLORA. 
elusion, we are thus furnished with an additional argument against 
the common opinion of the origin 6( coal; if the vegetables had 
been washed from a distance, is it likely that the different kinds 
would have separated so completely, as to have produced the several 
varieties of coal, so distinct from each other ? often in layers, far too 
thick and continuous for us to suppose them to have originated, but 
from a multitude of plants of the same kind. However this may have 
been, we have little doubt of being able to pronounce, with tolerable 
accuracy, as the knowledge of the subject extends, what the plants 
were, the remains of which are of such incalculable value to us in 
the form of coal. 
It was at one time believed, that the remains of Dicotyledonous 
woods did not exist in the Carboniferous formation; but subsequent 
observation, aided by the power of the microscope, which has been 
applied with so much perseverance and effect, by our esteemed friend 
and fellow labourer, Mr. Witham, has enabled us to detect them in 
almost every quarry. Nevertheless, the great bulk of the vegetables, 
of what may emphatically be called the Carboniferous period, un¬ 
doubtedly have been of the genera Sigillaria, Lepidodendron, Cala- 
mites, Sigillaria, and Ferns. The more woody plants, on the con¬ 
trary, after being buried, were able to resist decay, until their fine 
tissue was completely filled up and sustained, by the gradual infiltra¬ 
tion of mineral matter. 
It is in consequence of the almost universal change into coal, which 
has taken place in plants of this period, that their internal organization 
is so obscure; but, fortunately for our science, individuals are some¬ 
times found uncompressed, and retaining the form of their internal 
organization in considerable perfection. 
Mr. Witham has thus, already, been able to detect the structure of 
a Lepidodendron, which was fortunately found by the Rev. C. G. V. 
Harcourt, and upon which we shall have to make some observations 
in the present volume. To this part of the subject we should wish to 
direct the attention of our friends, more particularly such as mav be 
resident in those Carboniferous districts where Calcareous Spar, and 
Sulphurct and Carbonate of Iron, abound; it is only where miner¬ 
alizing matter has been held in chemical solution in abundance, that 
we can expect to find the delicate and evanescent textures of the coal 
fossils preserved. By careful examination in such situations, and the 
aid of the microscope, the secret of their real nature will be revealed. 
