tlie Earth at different Epoc^is, <Sfc. SB5 



The examination of the particular floras of each epoch of for- 

 mation, having shewn us that we might group several of them 

 together, and establish more extended periods, during which the 

 earth appears to have possessed a vegetation, if not absolutely 

 similar, at least analogous, it remains for us to compare the floras 

 of these periods, and to examine what are the characters by which 

 they are distinguished. 



The tables appended to this memoir make known the vegeta- 

 bles hitherto found in the different formations belonging to the 

 same period of vegetation. These vegetables are referred, with 

 all the strictness which their state of preservation admits, to the 

 genera, families and classes to which they have belonged ; and 

 we shall now make known the principal results elicited from their 

 examination. 



In the first period, which corresponds to the coal deposits, we 

 see that of the six classes which we have admitted in the vege- 

 table kingdom, only two existed. They are the vascular Cryp- 

 togamic plants, comprehending the Filices, Equisetaceae, Lyco- 

 podia, &c., and the Monocotyledones, containing a small num- 

 ber of plants which appear to resemble the palms and arbores- 

 cent liliaceae *. 



There remain, moreover, about twenty plants whose position 

 is uncertain. 



Thus, at the epoch in question, we find no evident trace of 

 dicotyledonous plants, or Conifera? or Cycadeae. The class 

 which has almost of itself composed this flora, is that of the vas- 

 cular cryptogamic plants ; and, in fact, of 260 species disco- 

 vered in this terrain, 220 belong to that class. 



But these vegetables, although evidently ranking in the fa- 

 milies of Equisetaceae, Filices, and Lycopodiaceae, differ from the 

 species, and frequently even from the genera at present existing 

 in several points of their organisation, and especially in their gi- 

 gantic size. All the researches which I have made for some 

 years back, confirm the approximations which I have made be- 

 tween the Calamitcs and Equiseta, the Sigillarise and the stems 

 of the tree Ferns, the Lepidodendra and the Lycopodiaccse ; 



• In the present memoir we pass over the marine plants, which be- 

 long to another order of vegetation, and speak exclusively of those which 

 grew on the uncovered parts of the earth's surface. 



