heartwood, the central, woody core of a tree, no longer serving for the conduction of water and dissolved minerals; heartwood is usually denser and darker in color than the outer sapwood . Before the synthesis of aniline dyes, the heartwood of several tropical trees (sold collectively under the commercial name brazilwood ) was used to produce blue, purple, and red dyes. As a tree becomes older, the heartwood increases in diameter, whereas the sapwood remains about the same thickness. See wood .
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