288 The Cottonwoods : The Ailanthus. 



tonwood," appears to belong to this species, and the superior quali- 

 ties claimed for it appear to be due to the soil and to the density of its 

 growth. Isolated trees are generally more thrifty, and therefore 

 have more sap-wood, and are more difficult to split. When grown 

 in the interior of a grove they are often less tough, and the quality 

 of the wood is generally more dense and durable. 



1170. COTTONWOOD OF THE PACIFIC COAST (Populus tricJiocarpa) . 

 This tree grows to the height of 30 to 50 feet from San Diego north- 

 ward. In Washington Territory it is found from 60 to 100 feet 

 high, and from 2 to 6 feet in diameter. In British Columbia it is 

 found chiefly in the valleys of streams and on the banks of rivers 

 throughout the whole Province, and north-eastward in the Peace river 

 district. It is used by the Indians of the interior in making their 

 canoes. 



1171. A variety (P. augustifoliti) is found in the Rocky Moun- 

 tains, and the P. balsamifera and P. monilifera, with several varie- 

 ties somewhat uncertain as to their classification are also found, all 

 bearing the name of " cotton wood." The Populus Fremontii grows 

 to a large tree. 



1172. ANGULAR-STEMMED COTTONWOOD (Populus angulata). 

 This is one of the cottonwoods of the Mississippi river and its trib- 

 utaries, and is distinguished by its angular stems, and the absence 

 of resinous and aromatic buds. The wood is soft, but of rapid 

 growth. It does not extend up the Mississippi river beyond Lake 

 Pepin. 



1173. BALM OF GILEAD POPLAR (Populus candicans). This is a 

 tree of very rapid growth, easily cultivated, and well adapted for 

 planting as a shade tree. Its leaves give out a slight balsamic odor, 

 aiid it has been recommended to plant groves of this tree along the 

 borders of marshes, to intercept the malaria arising from such local- 

 ities. A narrow-leaved variety, commonly called " cottonwood " or 

 " willow-leaved poplar," occurs from Colorado and New Mexico to 

 Washington Territory and Oregon, being the prevalent species in 

 Nevada and Utah. 



THE AILANTHUS. 



1174. The Ailanthus glandulosa, or " tree of heaven," is a native 

 of China, but has a wide range of adaptation to soils and climates, 

 enduring heat and drouth very well, and thriving upon soils where 

 many other kinds of wood fail. It grows rapidly, and is very apt 



