Ever green: Pine trees, which can grow for thousands of years, are the oldest living trees. But scientists are learning that palms can be even older—at least at the cellular level. A recent American Journal of Botany paper explains that conventional trees experience a secondary growth phase—replacing functional tissues with younger cells—but palm trees do not. The individual cells in a palm, seen in this micrograph of the genus Veitchia, endure throughout the tree's life span, which can range from 100 to 740 years.

This 1.5-millimeter-wide cross section of a vascular bundle (green and red center) is responsible for transporting water, minerals and nutrients through the trunk. Thousands of these bundles are found in every level of the palm and continuously work to sustain its growth.