What is the function of the xylem? phloem? vascular cmabium? epidermis?

The Xylem transports water from roots to leaves. 
The Phloem transports organic nutrients usually from leaves to roots. 
The Vascular cambium divides to produce new xylem cells toward the inside of the vascular cambium and new phloem cells toward the outside. 
The Epidermis Covers the plant but is replaced by cork (periderm) in the stems and roots of woody plants.