LUMBER 



397 



wood is soft-grained; maple, birch, beech, and holly are 

 close-grained hardwoods; oak, chestnut, elm, and ash 

 are open-grained, light-colored hardwoods; black walnut, 

 cherry, ebony, mahogany, rosewood, maple, cedar, brazil- 

 wood, sat in wood, and boxwood r _- = ^^^-^____^___ 

 are dark-colored, decorative 

 woods and are used where beau- 

 ty and fine grain are desired. 



443. Chief Source of Com- 

 mercial Lumber. Most com- 

 mercial timber comes from 

 forest trees. Since trees de- 

 pend on the sunlight for their 

 growth, it follows that trees 

 growing in the open fields, as 

 do the shade trees, have a full 

 crown and a short trunk. They 

 yield, consequently, compara- 

 tively little lumber and even 

 that little is of a poor quality, 

 since it contains many knots. 



Trees grown in the forest, 

 where light enters only through 

 the top of the crowns of the 

 older trees, tend to grow tall and 

 straight in the struggle to the 

 light. As the crown develops, 

 the lower twigs and branches 

 die, because the light and heat of the sun are cut off while 

 the trunk is small in diameter and while the branches 

 themselves are small, Thus the planks of forest trees are 



FIG. 188. Balsam Fir Grown 

 in the Open. Notice the low 

 branches, the result of sun- 

 light on all sides. 



