Earth Science and Natural Science Articles - How to Identify Petrified Wood

How to Identify Fossil (Petrified) Wood - Page 3 of 5
By Ed Strauss, Washington (photos and content)

When you examine your specimen it may instead look like this:

Figure 3
Fossil wood magnified

Figure 4
Fossil wood magnified

These two specimens represent flowering trees or angiosperms. Oak, sycamore, walnut, maple and willow are common names of trees that fit this category. The second specimen (figure 4) is a specimen that shows about 2 seasonal growth rings; the first specimen (figure 3) has about 1 ring. These micro photographs are taken at the same magnification as the conifers. Right away you can see that these flower bearing trees look different than those cone bearing trees. The large circles in the angiosperm specimens are called vessels. They have a similar function as tracheids in the trees physiology. In the second specimen (figure 4) the vessels are not very round. That is characteristic of certain types of wood, but not others.

Both of these angiosperm specimens have large bright lines running from top to bottom in the photograph. These are groups of another kind of cells called parenchyma. The groups of parenchyma cells that appear as bright lines in the photos are called rays. Rays are groups of cells that go from the center of the tree to the bark. Among other things they can store nutrients for the tree. When you are looking down on the stump (end grain) rays appear as lines of cells that run from the center of the tree towards the bark across the growth ring boundaries. The previous two conifer specimens (figure 1 and figure 2) have rays, they are the lines between the rows of tracheids. Notice that some rows are brighter, that is a ray that is two cells wide instead of the usual one cell wide. Compared with the two flowering tree examples (figure 3 and figure 4) the conifers have tiny (very narrow) rays. Both of these angiosperm specimens have some rays that are from 10 - 20 cells wide. The first flower bearing tree specimen (figure 3) has rays of two sizes the one big wide multiseriate (composed of many cells) ray and many small rays only one cell wide. This characteristic is found in the Beech family (which contains the oaks) as well as other families, but is a feature that is not common. The angiosperm specimen (figure 4) does not have rays of two sizes, it has rays of all sizes (widths). Notice also that the rays flare out or get a little wider as they passes the growth ring boundary. These are called noded or distended rays. They are characteristic of the Sycamore family as well as other families, but it is not a common feature among all trees.

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