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).