Presented below is a photomicrograph of plant cell bordered pits, structures that allow fluids to pass from one cell to another. This digital image was captured with the DXM 1200 ACT-1 control software in single-image acquisition mode utilizing apodized phase contrast illumination.

Bordered pits are structures found in the conductive tissues of many plants that allow for fluids to pass from one cell to another. The tracheids, which transport liquids, are dead cells; their contents decomposed, they are essentially empty. Simple pits are areas of the tracheid cell wall so thin that nutrient rich solutions can pass through them, to be dispersed throughout the plant. Bordered pits have the secondary cell wall extending over the pit with a small hole in the secondary cell wall that allows the water to pass through. When looking at a bordered pit under the microscope, it has the appearance of a donut. The hole of the donut is the pore and the outer ring of the donut is the margin of the bordered pit.

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.