Re: What is the cellular structure of wood?

-Xylem vessels: big dead cells where gross sap is transported from the 
roots to the plant organs.
-Tracheids: smaller dead cells, playing the same role.
These cells contain lignin in their walls, a kind of lipid which gives 
them a strong structure, because pressure is great inside these structures.
-Parenchyme cells, also dead, in contact with the vessels to regulate pH 
and content of the sap. These cells also store molecules produced by 
photosynthesis.
-"Wood" fibers: dead and very long cells containing lignin. These cells 
give a strong structure to wood. 80% of the wood is constituted by these 
cells.