M. De Candolle on Fossil Vegetables. 93 



tables existed simultaneously and uniformly in all countries ; or 

 whether, as at present, there were peculiar formations of plants 

 peculiar to certain regions, and natural groups confined to dis- 

 tricts of a limited extent, whilst others, on the contrary, were 

 spread over spaces of a vast extent ? 



In answering these questions, it is first of all necessary that 

 geologists should have thoroughly ascertained that similar or ana- 

 logous beds, which are situated in distant regions, were formed at 

 the same epochs on the surface of our globe. The circumstance 

 that certain strata of a similar nature are similarly placed, in 

 relation to each other, in America, for example, as well as in 

 Europe, unquestionably makes it probable that they were 

 formed at the same time, and in a corresponding manner. 

 When, moreover, they contain the same kinds of fossils, geo- 

 logists deduce from this circumstance a new proof of identity. 

 Not so, however, with the naturalist ; when, on the contrary, 

 inquiring whether, if the species are similar in cotemporaneous 

 or successive beds ; — were he to use this as proof, he would be 

 moving in a circle. 



Another difficulty arises from this circumstance, that vegeta- 

 ble fossils have hitherto been examined but in a very few coun- 

 tries, and even there in a very incomplete manner. Thus, 

 absolutely nothing can be concluded as to the geographical 

 distribution of vegetables belonging to the transition series, since 

 only fourteen species of this epoch are known, and thirteen of 

 these were collected in Europe, and the remaining one in North 

 America. In this point of view, it is manifest, we can only 

 compare epochs, a considerable number of whose species are 

 known, and which, moreover, have been collected in regions 

 which are very distant from one another. 



It is this consideration which confers a peculiar interest on the 

 258 species of the coal formation, which have been enumerated 

 by M. Brongniart : they have been obtained not in Europe 

 only, but also in North America, in New Holland, and in India. 



In examining M. Brongniart's table, and also the fossil flora 

 of England, we immodiatelv perceive that all the coal-mines in 

 Europe, and especially those of St Etienne in France, and those 

 of the north of England, those of Belgium and Bohemia, very 

 frequently present the same species of fossils. Nor is this very 



