What are the cell types that form the phloem? What are the main features of those cells?
The main cells that form the phloem are the sieve elements and the companion cells. The sieve elements form the vessel walls; they are living enucleated cells positioned in series forming the sieve tubes. Between successive vessel elements there are communicating pores. The companion cells are located outside and alongside the sieve tubes and they help in the absorption of the material to be transported.
