124 THE OLDER MESOZOIC FLOEA OF VIRGINIA. 



dence of the fossil plants, the Mesozoic of North Carolina is of the same 

 age with that of Virginia. 



If we compare the plants common to North Carolina and Virginia 

 with the plants peculiar to each State, certain facts become prominent. 

 The North Carolina strata are much l-icher in conifers than those from 

 Virginia, both in the number of individuals and in species. This is, I 

 think, due to the accidents of preservation. Most of the North Carolina 

 plants come from a horizon where the strata indicate disturbances of level, 

 abundant sedimentation, and the ingress of rivers. It will be noted that 

 by far the richest flora is that found in the blue shales intercalated in the 

 upper conglomerates, or No. 5 of the series of beds. These shales were 

 accumulated in pauses of the more violent action which produced the con- 

 glomerates, and would of course be very favorable for the reception and 

 preservation of plants swept off the higher parts of the land, where conifers 

 would grow. We have no plants in the Virginia Mesozoic from this horizon. 



Another fact worthy of note is the great rarity of plants from the coal- 

 bearing portion of the North Carolina Mesozoic, while nearly all of the 

 plants from the Virginia Mesozoic come from the strata associated immedi- 

 ately with the coal. While the vertical distance apart of the horizons 

 yielding plants in the two States is perhaps not sufficient to cause any con- 

 siderable change in the flora, the conditions that prevailed when the strata 

 of the two horizons were laid down were undoubtedly different, and easily 

 account for the differences that prevail in the kinds of plants preserved in 

 the two States. The North Carolina plants come, with three or four excep- 

 tions, from the upper strata which were accumulated, as above stated, in 

 waters no doubt in an unquiet state and loaded with sediment. We find, 

 then, in these strata comparatively few ferns, but many conifers and oycads, 

 plants that did not grow in the marshy grounds of the lakes, or on their 

 swampy shores, but were to be found on higher ground, and hence had to 

 be transported some distance in order to reach the sediment that preserved 

 them. On the other hand, the Virginia plants all come from the horizon of 

 the coal where the sediment was slowly accumulated, and where the waters 

 were still and received few remains of plants besides those that grew in the 

 mud and on low or marshy grounds. We find accordingly in the Virginia 



