A Meristem is a bundle of undifferentiated cells on a plant which, protruding in areas which will be the focal point of expansion via growth, are responsible for spawning the various complex specialized organs and structures which will constitute the mature organism. The meristem, being composed of undifferentiated or primitive cells characterized by their compactness, dense cytoplasm, minute vacuoles, and incompletely developed chloroplasts, is responsible for the origination of new tissues and continued growth, as differentiated plant cells are to specialized to spawn new tissues.Meristems are distinguished by their positioning on the plant. Apical meristems arbor at root and shoot tips, lateral meristems in the vascular and cork cambium(dividing tissues inserted between xylem and phloem layers), and intercalary meristems between internodes.The Apical Meristems are dubbed primary, as they are responsible for the production of the (the respective shoot and root apical meristems) stem and other above ground organs(incorporating reproductive structures), and roots.In apical dominance, the apical meristems will, through the excretion of the hormone auxin, inhibit partially or fully the growth of other meristems. This results in a clearly defined dominant trunk or stem with, depending on how complete the smothering effects of auxin are, lateral side branches such as is the case in trees. If the Apical meristem is damaged or severed, all suppressive effects are alleviated and branch meristem(s) will assume dominance, leading through time to certain branches looking as extensions of the main trunk/stem.The superior pinnacle of a common garden plant, the region in which lies the apical meristem, is featured in the shot above.