The periderm must constantly change to accomodate growth of the trunk and branches. It repeatedly makes new phellogen and sloughs off the old, cracked layers of cork. Hardwood Hardwood is derived from dicotyledonous angiosperms. Most dicotyledonous plants have vessels or short water conducting cells that conduct water through openings in the ends of the cells. See the picture on page 548.
Hardwoods have tracheids, vessels, fibers, ray tracheids, and xylem parenchyma.
Lignin is a polymeric phenylpropanoid material that helps to stiffen the plant. Softwood Softwood is derived from gymnosperms. The xylem of gymnosperms is composed mostly of tracheids. Gymnosperms do not have vessels. They have tracheids, resin canals, but no true fibers or vessels.