242 THE PLANT LIFE OF MARYLAND 



Along the cliffs themselves, there are alternating bands of more 

 or less poor soil formed by the varying proportions of undecomposed 

 rock and humus. Upon the poorer exposures such plants as Sedum 

 ternatum occur, with Saxifriga virgiwiensis, Veronica officinalis, 

 Mitchella repens, with Dryopteris achrostichoides, Botrychium vir- 

 ginianum, and Adiantum pedatum as the soil ferns, Polypodiurn 

 vulgare, and Camptosorpus rhizopliyllus as the rock-inhabiting 

 forms. Celastrus scandens was here noted, and the following 

 species not common elsewhere were recorded : 



Adicea pumila 

 Circaea lutetiana 

 Hypopitis hypopitis 

 Washingtonia claytoni 

 Parietaria pennsyl va n ica 

 H omalocenchrus virginicus 

 Anychia canadensis 

 Lippia lanceolata. 



In the area more closely adjacent to the Potomac, there were in 

 addition to those just mentioned: Mollugo verticillata, Euphorbia 

 nutans, Scirpus americana, Cephalanthus occidentalis and Asclepias 

 pulchra. In the shallows of the river, where the earth was exposed 

 at low-water periods, or was just below the surface under the or- 

 dinary conditions, the Water Willow (Di/iullirra americana) grows 

 in considerable abundance. 



Elk Ridge. 



While considering the conditions along the Potomac, it will be 

 simplest to include the next point of botanical interest, and then 

 to follow the forest along the Blue Eidge to the upper end at Pen 

 Mar. A ridge somewhat separated from the main elevation crosses 

 the Potomac just east of Harpers Ferry, and forms . the gorge 

 through w T hich the combined flow of the Shenandoah and the Poto- 

 mac passes eastward. Elk Eidge is the Maryland termination of 

 the Blue Eidge mountain in Virginia which extends for a few- 

 miles northward from the river, much as the Catoctin ridge ends 



