a type of reaction wood formed on the lower sides of branches and leaning or crooked stems of coniferous trees, characterized by heavily lignified tracheids that are rounded in cross-section and bear spiral cell wall checks —note 1. zones of compression wood typically have denser and darker cell walls than the surrounding tissue, and an abnormally high longitudinal shrinkage tending to cause distortion and splitting during drying —note 2. compression wood has lower quality with shorter tracheids, less cellulose, more lignin, and higher longitudinal shrinkage —see tension wood This definition last updated 07/28/2008