Cypress knee, mystery of nature

The bald cypress is most often found growing in swamps, wetlands and along rivers and streams. The tree is noted for producing valuable lumber that is more resistant to rot than most other woods.

It is an unusual deciduous conifer tree. It has needlelike leaves that drop in autumn and it bears seeds in cone-like pods similar to evergreen trees, such as the eastern red cedar. But the tree also holds claim to a mystery -- Why does it grow vertical extensions called "knees" from the topside of its roots?

It was once believed that the knees delivered oxygen or other necessary nutrients from the air since the roots are usually under water. This idea has been discredited by scientists who cut off all the knees from several trees and discovered that the trees did not die. I personally planted a small 1 1/2-foot-tall bald cypress under water in a pond where it remained fully submerged for two years before it successfully broke the surface and is still alive and growing today after five years.

Another more apt but improbable, assumption is the knees help the roots provide stability to the tree. Maybe the answer lies millions of years in the past.