Fig. 7.1-6. Transverse section of pine wood (Pinus). All cells in this micrograph are tracheids. You can not tell that from simply looking at this section, but rather by knowing that it is a sample of pine, which has lacks both vessels and fibers. The three arrows indicate circular bordered pits; any cell with bordered pits will be a tracheary element, not a fiber. If this were an unknown sample, you could search for perforations -- if these were vessels, a perforation should be visible somewhere (although in transverse section, it might be difficult to recognize). An important clue that these are tracheids and not vessels is that they are all so similar in diameter -- they are uniformly large in the earlywood and uniformly smaller in the latewood. Vessels typically are present in several sizes, and are virtually always associated with other cells that are smaller than they. The uniformity here, along with the circular bordered pits, indicates that these are tracheids.