The worlds first trees

The Earliest Trees were Very Odd!

This article looks at cladoxylopsids, trees which appeared in the Middle Devonian (390 - 380 million years ago). If you wanted to design a tree you would not start with the cladoxylopsids! They are hollow and the xylem is not a continuous ring - it is a ring of individual parallel strands around the outside of the trunk. This leads to problems in growth - an expansion in tree diameter would lead to the insides detaching and the plant collapsing. Modern trees just have a new xylem layer forming on the outside.

This video explains all! And the cladoxylopsids were soon replaced by more sensible ways of being a tree.