122 Remarks on the Ancient Flora qftJie Earth. 



When we, however, proceed to compare the successive divi- 

 sion of plants in the different epochs of the earth's formation, 

 with their geographical distribution on the present surface of 

 the globe, it will not seem wonderful that the species observed 

 in the one district are partly found also in the other ; for it 

 is generally known that, in the present state of vegetation on the 

 earth's surface, there are single species which are preserved un-- 

 changed through every zone and climate. In the same manner 

 it is well known that the transitions of floras from one region to 

 another take place only by the gradual substitution of single 

 species by otliers more or less closely related to them, as well as 

 by the gradual decrease and disappearance of single families ; 

 while others increase in the universality of their distribution as 

 well as in the number of their species. 



The formations of old as well as modern epochs, in opposition 

 to the statements of M- Brongniart, afford us many instances of 

 the equal appearance of kindred species belonging to a former 

 age in different formations. We have already remarked, that 

 many of those coal formations, distinguished for their abun- 

 dant vegetation, can be shewn to be subordinate beds of old 

 red sandstone, while others, indeed, by far the greater num- 

 ber of them, such as the celebrated basins of England, Flanders, 

 Westphalia, and the Lower Rhine, belong entirely to the transi- 

 tion rocks ; and yet, among the vegetable remains of both forma- 

 tions, no permanent distinction has hitherto been discovered. 

 There are often enough the same Lepidodendra, SigillaricB, 

 and Calamites, the same kinds of Neuropteris, Pecopteris, of 

 Asterophylla, Annularia, Stigmaria, &c., which were known 

 to belong to the coal-pits of Manebach, Wetten, and Essen, 

 and also of Luttich, Namur, Valenciennes, Newcastle, Bath, 

 &c. * It farther seems as if the character of the vegetation of 



" The general view of the localities of the species of fossil plants describ- 

 ed by Sternberg in his " Tentamen Flora? PriniordiaUs," affords an inte- 

 resting contribution to the above important fact. One hundred and fifty 

 species (of which 138 are vascular cryptoganiia) are accurately described 

 and enumerated as belonging to the old coal formation in general. Of these 

 seventy-five species belong exclusively to the oldest formation, forty as ex- 

 clusively to the coal formation of the old red sandstone or rolhliegende, and 

 thiity.five species, about the fourth part of the whole, occur equally in both. 



