236 THE PLANT LIFE OF MARYLAND 



the top, except where fire has aided the dry sandstone soil in pro- 

 ducing an arid type of covering. The higher slopes have been sub- 

 ject to forest fires at repeated intervals, and must of the stands of 

 timber are marred by the fire-killed trees in various degrees of 

 decay. 



A natural passage-way over the main ridge is found at Braddock 

 Heights and the forest in that region is slightly different from 

 those areas previously mentioned. The following species were 

 noted in the fresh cover at this point: Quercus macrocarpa, Celtis 

 occidentalis, Acer rubrum, Diospyros virginica, and for the first 

 time in the mountain area Quercus marylandica. The elevation of 

 the mountain at this point begins to diminish quite rapidly, and 

 near Jefferson has become very much reduced, allowing the plants 

 from the lower ground to come into the area of the Catoctin ridges. 

 The Elm appears to be a tree of this character, being found so far 

 along the high grounds only where they are rapidly merging into 

 the more level areas. 



Point of Rocks. — Catoctin Mountain is cut through at Point of 

 Rocks by the Potomac River, practically terminating there, although 

 it continues into Virginia as a hill with decreasing elevation. At 

 Point of Rocks, the igneous rocks are exposed, and constitute the 

 ''bastard granite" at that point. The rocks above the canal near 

 the tunnel have clumps of Woodsia obtusa, Aquilegia canadensis. 

 Hi in 7/ era americana and Saxifraga virginienstSj and at the base 

 Vincetoxicum hirsutum is occasional. Upon the top of the tunnel 

 hill the following species were noted : 



/ 'linns americana 

 Uhnus fulva 

 Corn us florida 

 (Jin reus rubra 

 Eobinia pseudaccai ia 

 Pinus virginiana 

 Quercus alba 

 Quercus velutina 

 < 'ercis canadensis. 



and many of the plants already mentioned in the discussion. 



