THE OLDER MESOZOIC FLORA OF VIRGINIA. 



BY WILLI AM M. FONTAINE. 



PART I. 



THE GEOLOGY OF THE MESOZOIC AREAS. 



The occurrence of the plants forming the flora of the older Mesozoic 

 beds of Virginia cannot be made intelligible without some account of the 

 strata that contain them. I shall give of the geology of the several Meso- 

 zoic areas only so much as will be necessary to show the characteristics of 

 the occurrence of the fossil plants found in them. 



The Mesozoic beds of Virginia are all situated east of the Blue Ridge, 

 and most of them are found within the terrane of the crystalline Azoic 

 rocks. They lie on the eroded and upturned Azoic strata, and are formed 

 out of the material yielded by them. Two series of Mesozoic beds must 

 be distinguished from each other. 



The older Mesozoic strata, those that contain the plants that form the 

 subject of this memoir, although very variable, yet have many features in 

 common that easily enable us to group them together. They now lie in 

 long narrow strips isolated from each other, and seem to have been depos- 

 ited in fresh, or at most, brackish water. Some of these areas were, at some 

 period in their history, in the form of marshes, or had such a character as 

 to permit the growth of an abundant vegetation and the accumulation of 

 considerable amounts of coal. In Virginia coal is found only in those areas 

 that lie farthest east. 



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