logwood, small, thorny tree ( Haematoxylon campechianum ) of the family Leguminosae (pulse family) native to tropical America and introduced into other tropical regions. The brown-red heartwood is the source of the dye haematoxylin and was exported to Europe as a major purple textile dye from the 16th cent. until the development of synthetic aniline dyes. It is still used more than are most natural dyes—as a histological stain, for ink, and as a special-purpose dye. Local names for the wood include campeachy wood and blackwood. The name logwood is sometimes applied to other similar woods. Logwood is classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Leguminosae.