TREE SPECIES. 29 



White hickory {Hicoria alba). This is the most common hickory. It is fre- 

 quent on rich warm soil at a low elevation, where it becomes a large tree, 

 sometimes 110 feet in height and 36 inches in diameter. The hard, tough wood is 

 preferred to that of the other species for mechanical uses. It seeds and repro- 

 duces freely, and young trees are common in culled woods at low altitudes. 

 This and the other species are largely used for fuel. 



Red-heart hickory {Hicoria odorata). The red-heart hickory reaches 120 feet 

 in height and 30 inches in diameter, and is one of the most common species. In 

 the Southern Appalachians it is second in value and importance only to the white 

 hickory. It prefers rich, warm soil at low elevations. It seeds often and in abun- 

 dance, and reproduction is good. 



Pignut {Hicoria glabra). The pignut is a slender tree, exceptionally 100 feet 

 in height. It generally grows on dry soil, and is not common. The timber is 

 inferior to that of the red-heart hickory. 



Hairy pignut {Hicoria glabra hirsutd). ^This tree is like the preceding in 

 size and in the character of its timber, but is not so common. 



Sand hickory {Hicoria villosa). The sand hickory is a small, uncommon tree, 

 yielding a wood similar to that of the pignut. It grows on sandy soil along 

 streams and on dr}^ ridges at low elevations. 



Black willow {Salix nigra). The black willow is a small tree reaching a 

 height of 50 feet, and is common along streams below an elevation of 3,000 feet. 

 The wood is not used, but the tree is important, as its tough roots serve to 

 protect from erosion the banks of the streams along which the trees grow. 



Silkly willoio {Salix sericea). The silky willow is from 20 to 30 feet in 

 height, with a straight stem. It is common along streams and in wet meadows 

 below an altitude of 4,000 feet. It is too small to furnish useful wood, but as a 

 protection against the erosion of the banks of small streams it is of more 

 importance than the black willow. It seeds abundantly and reproduces freely. 



Large-tooth aspen {Popuhis grandidentata). This is a slender tree reaching a 

 height of 50 feet. It is not common and the wood is not used. 



Balm of Gilead {Poptdus baUamifera candicans). Balm of Gilead has been 

 extensively planted along streams, where it makes an excellent soil binder and 

 protects the banks against washing. It is also useful in building up low areas 

 along streams which are subject to flooding, as the deposit of earth around its 

 stems during freshets does not injure the tree. The collection and sale of the 

 large resinous buds, which are used medicinally, is an industry of some import- 

 ance. It is a tree of rapid growth, and soon reaches a height of 50 feet. The 

 wood is light, soft, and not durable. 



River birch {Betula nigra). The river birch reaches a height of 70 feet and 



