An apical meristem (embryonic tissue), or growing tip, is at the tip of a plant\'s stem or root. Its main function is to begin growth of new cells in young seedlings at the tips of roots and stems. Apical meristems contain several layers. Depending upon the type of plant, the number of layers varies. The tunica is the outermost layer with the innermost layers being the corpus. In monocots, the tunica regulate the physical characteristics of the leaf edge and margin. In dicots, layer two of the corpus regulate the characteristics of the edge of the leaf. All plant cells are formed from meristems. The tunica and corpus play a critical part in the physical appearance of a plant.