There are four categories of tissues: Meristematic Tissue, Ground Tissue, Dermal Tissue, and Vascular Tissue. Meristematic tissues, which originate at apical meristems (in dicots) produce cells that will specialize into the other types of tissues. Ground tissues are produced by the ground meristem and include paranchyma, sclerenchyma, and collenchyma. [It should be noted that these types of tissues can also be part of vascular bundles, in which case they are produced by either the procambium (primary growth) or the vascular cambium (secondary growth).] Dermal tissues include the epidermis, produced by the protoderm (primary growth), and cork, produced by the cork cambium (secondary growth). Dermal tissues form the outer-most surface of a plant. Vascular tissues are complex tissues comprised of many cell types, but are named for the conducting cells in the tissue. Xylem tissue is comprised of xylem cells, which conduct water and minerals, as well as parenchyma and sclerenchyma cells. Phloem tissue consists of phloem cells, which conduct sugars, and parenchyma and sclerenchyma cells.