Trichomes are epidermal cells. Epidermis Tissue Mostly comprised of one cell thick layer of flat closely packed cells. They usually lack chloroplasts. Some plants produce Secondary Xylem or WOOD Xylem carries water and dissolved minerals upward from the roots of the plant. Xylem cells are dead at maturity.
Sieve cells are most primitive and found in non-flowering plants.
Long and tapered with overlapping ends. Sieve areas occur all over the surface. The sieve tube member and the companion cell arose from the same cell and are linked by many plasmodesmata.