During the formation of leaves and elongation of stem, some cells 'left behind' from shoot apical meristem, constitute the axillary bud. The meristem which occurs between mature tissues is known as intercalary meristem. Both apical meristems and intercalary meristems are primary meristems because they appear early in life of a plant. Following divisions of cells in both primary and as well as secondary meristems, the newly formed cells become structurally and functionally specialised and lose the ability to divide. Primary permanent tissues develop from primary meristems through the process of differentiation, while secondary permanent tissues develop from secondary meristems through redifferentiation.

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