398 VEGETATION OF THE CARBONIFEROUS PERIOD 



gated round broken bits of vegetable matter (as fern leaves, stems or 

 cones) wbich served as nuclei. 



Now, thougb each of these points admits of some explanation when 

 taken independently, and some illustration from the action of an existing 

 vegetation upon soil, &c, it is very difficult to understand their com- 

 bined operation over so enormous a surface, for instance, as one of the 

 American coal-fields, and even more to account for their regular recur- 

 rence, according to some fixed law, in every successive coal-seam 

 throughout the whole carboniferous formation. These are problems of 

 the highest order and unsuited to this sketch, the remainder of which 

 shall refer to the plants themselves, and especially to those botanical 

 characters according to which the Coal Flora- has been grouped and 

 named, and to an illustration of these several points by a comparison of 

 them with what are afforded by recent plants. 



ON THE PROBABLE EXTENT OF THE FLORA OF THE COAL 

 FORMATION IN BRITAIN. 



No fewer than 300 species of plants have been enumerated as belong- 

 ing to the Coal Flora of Great Britain ; but whether this gives any 

 approximation either to what was the amount of their species at one 

 period, or even to all those which contribute to form the coal, it is im- 

 possible to say. It need hardly be observed, that a collection of the 

 fragments imbedded in our most recent deposits is no index to the 

 general mass of the vegetation, nor are the remains necessarily those 

 of the commonest plants, or even of such as would a priori be judged 

 the best suited for becoming fossilized. That hitherto unknown species 

 do exist in an available state for the botanist cannot be doubted : they 

 are of frequent occurrence ; but that these are not so numerous as might 

 be expected from the enormous magnitude of a coal-field, is evident, 

 from the great uniformity that prevails throughout the formation. It 

 may indeed be a query, whether the number of species still to be 

 discovered will equal in amount that of the so-called species, which 

 being founded on imperfect specimens, will ultimately prove to belong 

 to previously described forms. 



That the vegetation of the carboniferous period, whether confined to 

 the coal veins or not, was highly luxuriant, cannot be disputed. The 

 enormous bulk of carbon accumulated, and the prevalence of ferns 

 in all the fields, and the great size to which so many soft-tissued plants 

 attained, all prove this fact. A luxuriant vegetation is, however, no 

 index to a varied one ; and, as many of our modern woods and even 

 great arese of tropical forests consist of but a few species multiplied ad 

 infinitum, so may the forests of the carboniferous period have been com- 

 posed of but a few Sigillarice and Lepidodendrons, sheltering an under- 



