68 BERRY: MESOZOIC FLORA OF ATLANTIC COASTAL PLAIN 
That students in general have underestimated the contrast 
between Upper Cretaceous and Eocene floras is, I think, obvious. 
It is the fashion to picture the incoming of the angiosperms in 
Upper Cretaceous times as a sudden and overwhelming event 
which in Cenomanian times transformed the Mesozoic floras of 
ferns, cycadophytes and conifers into an essentially Cenozoic 
flora of broad-leafed modern forests. At the beginning of Lower 
‘Cretaceous time the floras, as might be predicated a priori, were 
essentially Jurassic in type. Only gradually do they become 
typically Cretaceous and those elements that give them a Creta- 
ceous facies linger in gradually diminishing numbers to the close of 
the Upper Cretaceous. -Floras as early as the Albian show a 
variety of dicotyledons and many still existing genera are recog- 
nized but the numerical representation of dicotyledons in the 
rocks tends to be illusory, and a large number of the Cretaceous 
dicotyledons are more or less synthetic types, if one is justified in 
drawing such conclusions from the evidence of foliage alone. 
The lower Eocene introduces us to floras of a decidedly different 
facies and ones that distinctly show a great Cenozoic moderni- 
zation, despite the difficulty of reflecting this in the current nomen- 
clature of paleobotany. Moreover when it comes to details the 
change is profound. If the Ripley flora be compared with the 
Wilcox flora of the same general region the two are seen to be 
almost totally unlike though living under apparently similar 
environmental conditions. Both are lowland coastal floras, both 
are warm temperate in type and yet they have no common species. 
A tyro would immediately recognize the one as Cretaceous and 
the other as Tertiary. The Cretaceous cycadophytes and conifers 
have disappeared in the interval between the two. The flowering 
plants are distinctly better differentiated and more modern. 
That these Eocene floras as well as the Upper Cretaceous dicoty- 
ledons had ancestors is no more pertinent than the fact that the 
Eocene mammals had ancestors, in fact the comparison is not 
inept since the evolution of the flowering plants was, I believe, 
the major factor that made possible the evolution of the mammals. 
It may be noted that of the genera identified in the Ripley 
flora thirty-five, or 51 per cent, are extinct. Most of these are 
sale gaat of angiosperms and therefore not as precise as 
