198 



THE GEOLOGICAL HISTORY OP PLANTS. 



(birch) is represented by a few species, and specimens of 

 its peculiar bark are also common. Alnus (alder) ap- 

 pears in one species at least. The genus Platanus (Pig. 

 71), that of the plane-trees, represented at present by one 



Fig. 71. — Platamts nobilis, Newberry, variety baailobata. Laramie. 

 Much reduced. 



European and one American species, has several species 

 in the Cretaceous, though the plane-trees seem to culmi- 

 nate in the early part of the succeeding Eocene, where 

 there are several species with immense leaves. The large 



