THE FIRST FORESTS OF MODERN TYPE. 1S9 



Of the plants in this list, some, like the oaks, birches, willows, 

 and heaths, are common and familiar members of the tiora of 

 the northern hemisphere to-day, and even of the European 

 flora. Some, like the Magnolias, Myricas, and witch-hazels, are 

 characteristically American, and a few, like the Proteacese, are 

 now confined to the southern hemisphere. Some of these 

 families have dwindled since the Cretaceous time, so as to be 

 represented by very few species, or at least have not advanced, 

 while others have multiplied and prospered ; and on the whole 

 the flora of the northern hemisphere seems to have been as 

 rich in this early beginning of our modern forests as it is at 

 the present day. Lesquereux's results, with reference to the 

 American flora of the Dakota group, are very similar, and 

 present some surprising features of resemblance to modern 

 American forests, though he remarks that these Cretaceous 

 trees are generally characterised by the even or unserrated 

 edges of their leaves ; and the same remark seems to apply to 

 the oldest Cretaceous leaves of Europe. 



A very singular feature of the Cretaceous flora is the number 

 of species of some genera now represented by few or even a 

 single species; and this is the more remarkable when we 

 consider how few species, comparatively, of the older flora, are 

 known to us. For example, Lesquereux, though aware of the 

 great variability of the modem Sassafras of America, recog- 

 nises eight species of this genus in the Dakota Cretaceous, 

 one of which seems to be that still living in America, so that 

 it has continued unchanged, while the others have perished 

 (Fig. 155). Thus this genus culminates at once in the 

 Cretaceous, but continues still in one of its species. Again, 

 the tulip-tree, Liriodendron^ one of the most beautiful, unique, 

 and invariable of American trees, is represented by one sole 

 species in the present world. There seem to be no less than 

 four in the Dakota beds, and one species is found in the 

 Tertiary of Greenland as well as in that of Europe (Fig. 156). 

 There are probably four or five species of plane-tree {Piatanus) 



