EXOGENOUS SERIES BROADLEAF WOODS. 91 



XXBlack Cotton wood. Populus trichocarpa Torr. and Gr. 

 Nomenclature. (Sudworth.) 



Black Cottonwood (Oreg., Cottonwood (Oreg,, Cal.). 



Cal.). Balm Cottonwood (Cal.). 



Balsam Cottonwood, Balm 



(Oreg.). 

 Locality. 



Pacific coast region, Alaska to California. 

 Features of Tree. 



A large tree sometimes one hundred and fifty feet in height and 

 four to six feet in diameter. 



Color, Appearance, or Grain of Wood. 



Heartwood light dull brown, sapwood nearly white, compact 

 structure. 



Structural Qualities of Wood. 

 Light, soft, weak. 



X Representative Uses of Wood. 

 Staves, woodenware (local). 



Weight of Seasoned Wood in Pounds per Cubic Foot. 



2 3- 

 Modulus of Elasticity. 



1,580,000. 

 Modulus of Rupture. 



8400. 



Remarks. 



Largest deciduous tree of Puget Sound district (Sargent). 



The Cottonwood, Tacmahac, Balsam, Balsampoplar, or Balm of 

 Gilead (Populus balsamiferd) grows from Hudson Bay and Alaska 

 south to Oregon and New England. It is a large upright tree, some- 

 times five or more feet in diameter. It is distinctly a northern species. 

 It has whitish trunk, drooping catkins and other poplar characteristics. 

 The very light, soft, white wood has been used in paper making. 

 The gummy exudations on the twigs of this and related species have 

 been substituted for other medicinal balsams. The Balm of Gilead 

 (Populus balsamifera candicans) is cultivated in New England. 



Professor Bessey believes that cottonwood timber culture would be remunera- 

 tive in many parts of the middle west even for fuel. Cottonwoods have attained 

 to sizes large enough for saw logs in twenty years. (Pinchot, U. S. Forestry 

 Circular No. 27). 



