Cutaway views show inner workings of a tree.  Wood compartment at left includes parenchyma, or energy-storing cells; tracheids, or cellular tubes; and latewood cells.  At right, radial view shows "layers" and how compartments form.

This view shows what the tree looked like, with bark, when it was eight years old (A), 10 years old, (B), 12 years old (C), and 22 years old (D).

How a tree responds to a wound.  At left, microorganisms (green) in sapwood cause decay (brown).  At edges of infection, parenchymal cells make antimicrobial substances (red) to fight infection.  View at right shows the tree in a later season.  Internal defenses are winning.

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AMERICAN FORESTS JUNE 1986