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The big difference between our timber trees and the palm family (which includes about 4000 species of vines, shrubs, and trees) is that palm trees do not have a cambium layer. This thin layer in our timber trees is what forms bark on one side to waterproof and protect the tree and forms the water and food cells (xylem and phloem) on the other. This process is called "secondary thickening" and allows annual rings of wood to be formed.
On the other hand, the growth of the palm trees is sort of a top to bottom process called "primary thickening". The ever-green and ever-present leaves keep getting bigger and bigger. As they need more support and nourishment, new individual roots that look like the tendrils of a mop sprout and form random pipelines for food and water. These food and water cells (xylem and phloem and pith) are contained in "fibrovascular bundles" and are scattered haphazardly throughout the tree - not in consistent annual rings like our timber trees.
The rest of the stem is made of of fibrous material which gives the tree the support it needs plus elasticity -- we have all seen weather reports on the tube showing palm trees bending incredibly in hurricane force winds. A cross section of the palm's internal structure resembles a pepperoni pizza without the crust. The pepperonis might resemble the scattered "fibrovascular bundles" and are a little more concentrated on the outside of the pizza than in the center. The cheese would be the fibrous material that gives support and elasticity, but not wood.
© 2001 by David Mather. All rights reserved. No parts of this publication may be reproduced in any form or by any means without the written permission of the author.