THE PENNSYLVANIAN PERIOD 



645 



series. The place of origin of the early Pennsylvania floras is not 

 known with certainty, but present evidence points to the land of 

 western Europe and eastern North America, connected by an Arctic 

 land bridge. 



Fig. 448. A group of fern fronds: a, Neuropteris auriculata, Brgt.; 6, .V. 

 angustifolia, Brgt.; c, N. vermicularis, Lx.; d, Odontopteris cornuta, Lx.; 

 e, Pecopteris unita, Brgt.; /, Dictyopteris rubelia, Lx.; g, Archceopteris 

 bochsiana, Goepp.; h, Sphenopteris splendens, Lx. 



The late Pennsylvania floras are not sharply separated from 

 the early ones on our continent, but the distinction is much greater 

 in Europe. The later Pennsylvanian floras indicate, on the whole, 

 less uniformity of climate than the earlier. 



The Filicales. Fern-like leaves surpass all other plant fossils in 

 number, but it is now known that most of them belonged to seed- 



