Fig. 9.3-5. Transverse section of pine wood (Pinus). If you have ever noticed “pitch” exuding from pine lumber or crystallized on the bark of a pine tree below a wound, this is the secretory structure that produces it. This is a transverse section of a resin canal in pine wood. This canal is one of many that run vertically in the wood (the surrounding box-shaped cells are tracheids cut in transverse section), and they interconnect with others that run radially outward through the rays (not shown here).