CHAPTER IV. 



THE CARBONIFEROUS FLORA CULMINATION OF THE 

 ACROGENS FORMATION OF COAL. 



ASCENDING from the Erian to the Carboniferous sys- 

 tem, so called because it contains the greatest deposits of 

 anthracite and bituminous coal, we are still within the 

 limits of the Palaeozoic period. We are still within the 

 reign of the gigantic club-mosses, cordaites, and taxine 

 pines. At the close of the Erian there had been over 

 the whole northern hemisphere great changes of level, 

 accompanied by active volcanic phenomena, and under 

 these influences the land flora seems to have much dimin- 

 ished. At length all the old Erian species had become 

 extinct, and their place was supplied by a meagre group 

 of lycopods, ferns, and pines of different species from 

 those of the preceding Erian. This is the flora of the 

 Lower Carboniferous series, the Tweedian of England, 

 the Horton series of Nova Scotia, the lower coal-meas- 

 ures of Virginia, the culm of Germany. But the land 

 again subsided, and the period of the marine limestone 

 of the Lower Carboniferous was introduced. In this the 

 older flora disappeared, and when the land emerged we 

 find it covered with the rich flora of the coal-formation 

 proper, in which the great tribes of the lycopods and 

 cordaites attained their maxima, and the ferns were con- 

 tinued as before, though under new generic and specific 

 forms. 



