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 ag 
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 hgnin 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 
