The History of Land PlantsCase 2: When do we find the first trees?
The first forests, the evolution of wood.
Where did the fossil wood Callixylon, a common fossil from the Devonian of Indiana, come from?
The first vascular plants were small herbs. Selection for greater height results from competition for light. Rows of water conduction cells (tracheids) form wood that allows the plant to get bigger. More water is available for the larger number of leaves. The thick walled tracheids also provide stronger tissue allowing taller stems.
The first trees are from a group called the progymnosperms and formed forests during the later Devonian. Callixylon is a plant fossil in Indiana that is from this group. These formed logs that floated into the seas covering Indiana (see the 900 pound Callixylon log in the main exhibit). Fossil leaves preserved without attachment to these woody stems have been called Archaeopteris.
Compare the fossil and the wood section. You can see the cells in rows and other structures in the wood. Woody trunks have been around for 390 million years.
Dr. David W. Taylor standing in front of 'First Trees' display case.
'First Trees' display To see close-ups of the specimens in this display, click here. Seed Plant: Boldly Growing Where No Plant Has Grown Before Monster Plants That Created Coal Flowering Plants: The New Revolution
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