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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. The outer cortical cells often acquire irregularly thickened cell walls, cand are called collenchyma cells. Some of the outer cortical cells may contain chloroplasts.

In zoology, a cortex is the superficial layer of an organ. Organs with well-defined cortical layers include kidneys, adrenal glands, ovaries, the thymus, and portions of the brain. Of these, the brain's cerebral cortex is the most familiar; it is rich in neurons and is the site of most sophisticated neural processing.

There is no common origin or structure between the various cortexes, their only commonality is that they are distinctive layers at the surfaces of the organs involved.

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