Cortex (botany)

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In botany, the cortex is the outer portion of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the pericycle. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells often acquire irregularly thickened cell walls, and are called collenchyma cells. Some of the outer cortical cells may contain chloroplasts. Its main function is the storage of starch; often, it also provides aeration of cells to allow respiration.