J44- 



THE PLANT WORLD. 



HEMLOCK BLUFF, POTOMAC RIVER. 



forming narrow and sometimes long bottoms, which are often eroded 

 and gullied by the overflowing waters when man has interfered with 

 the forest growth. The Potomac is continually infringing on this 

 Virginia shore, hence the rocks and bluffs; while the opposite Mary- 

 land side is but lightly swept. 



This rugged character of the southern bank and the absence of 

 good roads has permitted the perpetuation of the natural conditions, 

 though some of the larger trees have succumbed to the axe, and the 

 gold hunter has invaded its retreats. Above the freshet line the 

 slopes are thickly strewn with broken rocks, the talus of ancient cliffs 

 which have partially disappeared. These rocks are thickly covered 

 with mould and mosses, and often covered with flowering plants, rare 

 or otherwise unusual about Washington. These characteristics indi- 

 cate that little change has occurred since the white man first began 

 to influence the topography of the country, 300 years ago. A mile or 

 more back of the bluffs the country is rolling and quite thickly studded 

 with farms and woods. 



The northern exposure of these bluffs and their arboreal vegeta- 

 tion, the numerous side streams and deep, often rocky gorges, and 

 the cool, deep waters of the Potomac, permit here the survival in 

 large numbers of species of the more boreal animals and plants which 

 cannot elsewhere, about Washington, find a congenial habitat of as 

 large extent. This narrow strip of boreal territory is really an exten- 

 sion of the flora and fauna of the Alleghany mountains, its existence 



