Bordered Pits 20x

The pattern and types of pits are characteristic of particular species and useful for identifying different types of wood. Some have tyloses, balloonlike outgrowths of parenchyma cells that bulge through the circular bordered pits of vessel members and block water movement. The presence of tyloses in white oaks makes their wood watertight, which is why it is preferred in casks and shipbuilding to red oak, which lacks tyloses and does not hold water.