( 72 ) 



On the Chronological Exposition of the Periods of Vegetation, 

 and the different Floras which have succeeded each other on 

 the Earth^s Surface, According to the views of M. Brong- 



NIART. 



{Continued from p. 330 of Volume 48.) 



" II. Permian Period. — The nature of the vegetables which 

 appear peculiar to this epoch, is far from being determined 

 in a positive manner ; for the few localities where the fossils 

 we consider as belonging to it, have hitherto been found, are 

 not perhaps really of a formation very identical and truly con- 

 temporaneous. For it may be asked, whether the bituminous 

 and copper slates of the county of Mansfield, classed by all 

 geologists with the zechstein, and the sandstone of Russia, 

 placed by M. M. Murchison and Verneuil in their Permian 

 formation, are really contemporaneous ? Finally, is there 

 greater reason for classifying the slates of Lodeve, considered 

 by M. M. Dufresnoy and Elie de Beaumont as depending on 

 the variegated sandstone, but so different from the same 

 sandstone of the Vosges in its flora, in this period, which 

 would thus be a kind of passage from the coal period, so well 

 characterised, to the vosgian or variegated sandstone, which 

 differs from it in so decided a manner ? 



On account of these doubts, M. Brongniart indicates these 

 three floras separately; 1*/, The Flora of the bituminous slates 

 of Thuringia, composed of algae, ferns, and coniferse ; 2d, 

 The Flora of the Permian sandstones of Russia, which com- 

 prehends ferns, equisetaceae, lycopodiaceae, and nceggerathiae ; 

 Zd, The Flora of the slates of Lodeve, which is compose dof 

 ferns, asterophyllitese, and coniferse. 



" We perceive that there are great specific differences be- 

 tween the plants of these localities, and that hitherto no 

 species common to them has been found. Must we ascribe 

 these differences to the influence of the great diversity of 

 geographical position, or is there, besides, a difference in the 

 period of their origin among these formations ? The only 

 character which tends to bring these two latter Floras near 



