Perhaps the most distinctive feature of the bald cypress is the presence of knees. Cypress knees are cone-shaped structures that grow vertically from the lateral roots of the tree where the roots are at the soil/sediment surface. Knees were once thought to provide the roots with oxygen an adaptive strategy under flooded circumstances. Later, experiments showed that there was little exchange of oxygen between roots and knees. Furthermore, trees that had knees removed continued to thrive under continued submergence. The most likely function of the knees, it seems is to provide stability in the swamp substrate.