THE STORY TOLD BY FOSSIL PLANTS 



marked change through early Cretaceous time. The early 

 Cretaceous cycacis were essentially the familiar types of 

 later Jurassic time. They were abundant in genera, species, 

 and individuals, and they were quite as dominant an ele- 

 ment of the lower Cretaceous floras as they had been of 

 those of late Triassic and Jurassic time. Before the end 

 of the Lower Cretaceous epoch, however, most of these 

 plants had become extinct. In rocks laid down near the 

 end of that epoch we find preserved the first representatives 

 of the flowering plants (the angiosperms — that is, plants 

 having enclosed seeds, ,such as the walnuts, oaks, and 

 maples), and during Upper Cretaceous time these plants 

 gradually became predominant. 



Although the seas were widespread in early Mesozoic 

 time there were many large areas of land, but we know 

 nothing about the floras of these areas, which may have 

 been the scene of the evolution of the flowering plants. 

 Certainly during late Cretaceous time they spread con- 

 tinuously southward in Europe, North America, and Asia, 

 and almost everywhere the same forms occur, alike in 

 Bohemia, Alabama, or Sakhalin Island, localities suggest- 

 ing their northern" origin. During Upper Cretaceous time 

 they penetrated far into South America, reaching Argentina, 

 and they even reached Antartica (Graham Land). These 

 Upper Cretaceous floras invariably show a mingling of 

 temperate and tropical types, indicative of a humid warm- 

 temperate climate, and they all contain forms that are 

 to-day largely confined to the Southern Hemisphere. 

 Throughout Upper Cretaceous time new types continued to 

 appear and the stragglers from older floras gradually died 

 out, so that by the dawn of the Tertiary period most of the 

 archaic forms had become extinct. 



The flowering plants possess for us a profound interest, 



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