1863.] 203 [Lesquereux. 



from the Lower to the Upper Devonian, but that at the close of the 

 Devonian, many species and some genera disappear. In the hower 

 Carboniferous, the flora is again poor, though retaining some of the 

 Devonian species, and it goes on increasing up to the period of the 

 Middle coal-measures, and this hy the addition of species quite dis- 

 tinct from those of the Devonian period^ Is not this acknowledging 

 a continual change in the vegetation of the coal epoch, from its be- 

 ginning to its end ? for we cannot admit of course that according to 

 the views of Professor Dawson, such a change has taken place in the 

 Lower Carboniferous, to stop at once at what he calls the Middle 

 coal-measures. And can we not then conclude that with careful and 

 long researches, at such places where the stratification is perfectly 

 well fixed, these changes of vegetation may be recognized in strata 

 of diiferent horizon, and thus used for comparison at other localities ? 

 The discussion concerning the true Garhoniftrous measures is, as 

 you say, tedious and useless, at least when it is made without com- 

 parison with what we have around us It is certain that the 



plants of the red shales (Vespertine or Ponent of Rogers), are differ- 

 ent from those of the coal-hearing measures. There is, indeed, a gap 

 in the vegetation between the Red shales and the Conglomerate, even 

 near their horizontal line of union at Pottsville, while in the West, 

 the true coal vegetation descends as low as the Upper Archimedes 

 limestone, or even lower. This anomaly is to my persuasion merely 

 apparent, or the result of causes without connection with the stratifi- 

 cation. The vegetation of the coal must be always considered as a 

 peculiar, and if I can say so, as a local one, born and continued under 

 peculiar influences, and thus without a necessary specific connection 

 with that of tbe open and dry land; a true peat or bog vegetation. 

 I have many times taken the trouble to compare the vegetation of 

 our peat bogs with that of the country at large, to show how the first 

 one would be insufficient to give us even a slight idea of the last. 

 Now the shales of the Old Red sandstone were evidently formed by 

 open extensive flats, alternately covered with water or left dry, and 

 thus, having a peculiar vegetation far different from that of the Bogs, 

 which were always under the influence of a continual internal and 

 external humidity. Compare, for example, the vegetation of the 

 flats of Holland around Groningue, with that of the peat bogs of the 

 same country, and seen just near the border of the same flats. There 

 is not a single species common to both formations. The same can 

 be said of our coast flats, and in New Jersey, you have the same 

 peculiar difference of vegetation near the shores ; the one covering 



