E. W. Berry — Pleistocene Plants. 223 



fessedly of untested value, however, and too much reliance 

 cannot be placed on them. 



Prof. Holden has called my attention to a small lake known 

 locally as the duck pond about a mile northeast of the fossil 

 plant locality on Big Pond Ridge, which occupies a similar 

 position with relation to the underlying Cambrian. As lime- 

 stones are present in the Cambrian shales this pond may be a 

 solution pond, and this suggests a similar character and origin 

 for the Pleistocene leaf-bearing lens. The fact that these 

 Pleistocene shales dip 20° indicates a late solution of under- 

 lying calcareous beds. 



The attitude of the area relative to sea-level in the Pleis- 

 tocene is unknown — doubtless this region shared more or less 

 in the oscillations known to have occurred in the coastal plain, 

 and it is possible that an area of depression, when the waters 

 of the Atlantic advanced inland over the Virginia coastal plain 

 and converted the country immediately east of the Fall line 

 belt into a region of estuaries, may have been a factor in the 

 spread of the coastal plain vegetation through the water gap 

 of the James River into the Shenandoah Valley. The alterna- 

 tive view, equally speculative, is that these elements of the 

 present coastal plain flora were normally present in the Great 

 Valley at this early period. Of the two the former seems the 

 most probable. 



Regarding climatic factors that may be legitimately deduced 

 from these fossil plants, it is obvious from their present dis- 

 tribution that the mean temperature was higher at Buena 

 Vista at this stage of the Pleistocene than it is now. While 

 temperature is less of a factor in the details of plant distribution 

 than has been commonly supposed, as Livingstone and Shreve 

 have recently pointed out (Johns Hopkins Univ. Circ, 1912, 

 No. 2, p. 19), the grouping of these fossil species in the exist- 

 ing flora in somewhat warmer areas is evident, since the more 

 important moisture conditions (rainfall, humidity, etc.) as well 

 as edaphic factors are not the same for the cypress, Spanish oak 

 and arboreal vaccinium. The presence of the cypress at Buena 

 Vista probably indicates a Pleistocene cypress bay or pond. 



At the same time there is every reason to believe that the 

 rainfall and humidity were both greater than they are at the 

 present time along the western flank of the Blue Ridge. The 

 presence of these, in the main more southern, species would 

 indicate that the time was a late Interglacial period, but we' 

 know too little of the relation of vegetation to the continental 

 ice sheets to the northward to be able to draw any legitimate 

 conclusions on this point, and the deposits may well be post- 

 glacial since the evidence for a mild climate immediately fol- 

 lowing the Wisconsin ice sheet is becoming- established on a 



r> 



tinner footing with each additional fragment of evidence. 



■& 



Johns Hopkins University, Baltimore, Md. 



