THE STORY TOLD BY FOSSIL PLANTS 



Lower Cretaceous plants are found in the rocks of all 

 the continents, and they are particularly abundant in North 

 America and Europe. The two most extensive Lower 

 Cretaceous floras are those preserved in the Potomac group 

 of rocks of Maryland and Virginia and those of the rocks 

 of the opposite side of the Atlantic, in southern Portugal. 

 Comparisons of these floras shed light on the place of origin 

 and the migrations of the various types. A third large 



%i2!^^^ 



Fig. 8. — Restoration of Wielandiella, one of the best known 

 branched cycads of the older Mesozoic. (After Nathorst.) 



Lower Cretaceous flora is that of the so-called Wealden of 

 England, Belgium, and Germany. Other floras of this age 

 are found in South Africa and eastern Asia, as well as in 

 Spitzbergen, Australia, New Zealand, and Greenland. 



Although the known floras of the Lower Cretaceous epoch 

 necessarily represent only a small percentage of the species 

 that clothed the earth during that time, they furnish some 

 suggestive data concerning the march of vegetation during 



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