270 THE PLANT LIFE OF MARYLAND 



Phlox subulata 

 Claytonia virginica 

 Hepatica hepatica 

 Bicuculla canadensis 

 Chelidonium majus 

 Syndesmon thalictroides 

 Asarum canadensis 

 Capnoides flavulum 

 Epigaea repens 

 Aquilegia canadensis. 



The sandstone is coarse, and while the exposed summit is very- 

 dry and unfavorable to general vegetation, on the slopes, especially 

 where there is an accumulation of talus, coarse and fine mixed to- 

 gether, there is a good cover of vegetation. The finer material grad- 

 ually weathers to soil, and the spaces between the rocks catch the 

 leaves and debris from the larger plants, to add fertility to the more 

 sandy portion. Percolating moisture supplies and maintains the 

 water supply on the lower slopes, which it cannot conserve on the 

 exposed top. 



Summary. 



The area of the Upper Midland Province may for convenience 

 in review be divided into (1) Parr's Ridge, (2) the Limestone Val- 

 leys, (3) the Sandstone Ridges and (4) the Shale Ridges, and on 

 this basis the points of the discussion may be summarized. 



Tbe boundary line between the Upper and the Lower District of 

 the Midland Zone lies in the first Ridge discussed in the foregoing 

 pages, but as Parrs Ridge offers nothing strikingly different in re- 

 spect to soil and vegetation from the conditions to the east, and in 

 the other portion of the Midland Province of which it is properly 

 the topographic boundary, its bearing upon tbe Upper Province may 

 be given in a few words. 



Parr's Ridge Area. — Along the eastern boundary of the Upper 

 Province the soils are derived to a large degree from the decomposi- 

 tion of the rocks of volcanic or granite types with occasional valleys 

 in limestone. The vegetation which is characteristic of this area is 



