Wood Fibres:

They are also called xylary fibres. Sclerenchyma fibres as­sociated with xylem are termed wood fibres. They possess very thick walls and few small pits. They originate from the derivatives of the cambium and have varied shapes. In wood fibres, known as libriform fibres, the wall is extremely thick and lumen is almost absent. Like the tracheids, wood bires are also dead and their main function is mechanical support.

Wood Parenchyma:

Parenchyma cells associated with xylem are called wood parenchyma. These are living cells and remain so, as long as the tissue in which they lie conducts water. The cells of wood parenchyma may be thin or thick walled have plenty of storage food and may help in conduction. In secondary xylem wood parencyma forms the rays which may help in radical conduction.