78 M. Brongniart on the different Floras which 



neral changes due to the succession of time, such as the predo- 

 minance of certain genera or certain specific forms, combined 

 with other diiferences altogether local, or due to an influence of 

 the geographical position. 



Thus it appears to me to result from many local observations, 

 that the Lepidodendra would be more abundant in the old strata 

 than in the upper layers of most of the coal-measures ; that the 

 true Calamites would often be in the same position ; that the 

 Siffillaria would appear to predominate in the middle and upper 

 layers ; that the same would be true of the Coniferge ; and it is 

 only indeed in the upper layers of St. Etienne, Autun, &c., that 

 their branches are found, at least in France. 



But these facts, which I indicate with much reserve, from ob- 

 servations which I have made in different coal basins of France, 

 the more require to be generalized by observations gathered in 

 other localities, that the position of the layers is often enveloped 

 in much obscurity, and differently determined by the most di- 

 stinguished geologists. 



Thus the enumeration of the genera with the approximative 

 indication of the number of species, which will presently be given, 

 represents the totality of the plants which have flourished on the 

 whole surface of the globe explored by geologists, during the 

 long series of ages which the coal period comprehends, and not 

 the vegetables which grew at the same time and in the same 

 place. 



It will be noticed, also, that the necessity of distinguishing 

 frequently, as diflerent genera and species, the different organs 

 of an identical plant, sometimes apparently augments the number 

 of species of a family, the number of species of which it would only 

 be requisite, in this case, to determine by the study of the organ 

 occurring most frequently and presenting the clearest specific 

 differences. 



Flora of the Carboniferous Period. 



A. Marine Vegetation (peculiar to 

 the transition formations). 



Alg^. 



Chondrites 2 



Amansites 3 



B. Vegetation of the land or fresh 



water . 



Amphlgenous Cryptogamla. 

 HvPOXYLEfiE. 



Excipuhtes 1 



Hymenomycbtesv 

 Polyporites 1 



Acrogenous Cryptogamia. 

 FlLICES. 



* Fronds. 



Cyclopteris 6 



Nephropteris 4 



Neuropteris 32 



Odontopteris 10 



Dictyopteris 3 



Sagenopteris 1 



