Definitions for "Sapwood"
The alburnum, or part of the wood of any exogenous tree next to the bark, being that portion of the tree through which the sap flows most freely; -- distinguished from heartwood.
New wood surrounding the denser hardwood.
The outer, younger portion of a tree, usually distinguishable from the heartwood by its lighter color. Years ago, it was quite common to see sapwood (incorrectly referred to as "bark") on the exterior profiles of bagpipes. In those days the makers cut and sorted the wood from logs. The sapwood is the result of a maker using all the wood that he could.