FLORA. 205 



coal formation. We have designated under the name of 

 Ursien stage the first sub-division of this period ; with 

 this coincides the appearance of the most ancient terres- 

 trial vegetation sufficiently rich to give us an idea of the 

 appearance presented by the vegetation at this primitive 

 epoch. This flora was perhaps in fact spread across the 

 northern hemisphere, both in the old and in the new 

 continent from 47 to 74 or 75 of northern latitude ; 

 and everywhere it shows the same character. Everywhere 

 appeared the calamites radiatus which covered with its 

 high columnar stems the marshy lowlands, whilst it great 

 rhizomes penetrated everywhere into the boggy soil. 

 Everywhere also made themselves to be seen associated 

 with them the wonderful Knorria, the Lepidodendron, 

 with stems ramified dichotomously, and leaves united in a 

 compressed plume. The Cyclostigma which we find both 

 in the south of Ireland and in Bear Island, are also rarely 

 awanting in the bosom of the layers formed on an emerged 

 soil ; and these plants must have composed in^ part the 

 forests under the shade of which the Cardiopteris and 

 Palaeopteris stretched their stout fronds. 



'This flora comprised already a pretty considerable 

 number of species ; and many of them showed themselves 

 at the same time in regions so remote from one another, 

 that their repeated presence warrants us to suspect the 

 existence of a vast continent, stretching out both into the 

 temperate and the arctic zone. The Russian carboniferous 

 region prolonged itself probably to Bear Island ; and the 

 vegetation of this island would then have made an integral 

 part of the lower carboniferous flora of Russia, of which it 

 would mark the continuation towards the north the proof 

 that the Ursien stage must have been formed along the 

 coasts of a great continent, resulting from the presence of 

 fresh water animals, and pondal shells, and nervopters, 

 which could not have lived but in a land sufficiently con- 

 siderable to contain lakes and to give birth to rivers. 



' What was the duration of this period ? That is a 

 point which one would fain determine! Then began a 



