66 
ELEMENTARY AGRICULTURE 
low branches. Thus if we desire long straight trunks for 
making boards and posts, it is desirable to have them 
growing in a close group or in woodlots. 
There are two distinct portions of the trunk in most 
trees, heartwood and sapwood. The portions are not 
very well marked in the holly, cypress, cottonwood, and 
others. The heartwood has a darker color and is used 
for making furniture and finished wood products. The 
sapwood is the growing portion on the outside of the tree. 
It is made of sap tubes, carrying water and soluble foods 
for the tree. 
Some valuable products come from this sap layer; as 
