52 THE BOOK OF FORESTRY 



composition of wood for example the distillation of 

 resin from the Georgia pine. Others must have woods 

 with fiber of great length. The spruce of our North- 

 ern forests for instance is not only in great demand as 

 a paper wood on account of the length of its fiber but 

 also because its resonance makes it excellent material 

 for violin backs and piano sounding boards. The violin 

 makers of Europe will pay large sums for old spruce 

 beams and joists in a house that is being torn down, as 

 the well-seasoned wood is just what they need. 



Gross Structure. On cutting down a mature tree a 

 marked difference is noted in the hue of the wood. In 

 the center is a dark-colored core which is called the 

 heartwood, while around the outside is a ring of lighter 

 softer wood called the sapwood. The dark color of heart- 

 wood is due to the presence of certain materials like tan- 

 nin, resin, etc., and its greater durability is also due to 

 the presence of these substances. When wood changes 

 from sap to heartwood additional amounts of wood sub- 

 stance called lignin are deposited upon the cell walls, 

 making the heartwood stronger as well as darker and 

 more durable. On account of its greater moisture content 

 the sapwood is much more subject to decay and is less 

 desirable as a rule. Hickory and maple are practically 

 the only species in which the sapwood is preferred to 

 wood from the heart. The heartwood is dead physically 

 and its principal use is to support the tree. The sap- 

 wood, however, is very much alive because it contains 

 the vessels which transmit the raw sap from the roots to 

 the leaves. This relation between heartwood and sap- 

 wood can be clearly proven by examining many hollow 

 old pasture trees. Old veterans may be found which 

 are nothing but shells in which the heartwood has 

 practically rotted out, leaving a hollow cylinder several 



