What is one of the many minute granules found in the protoplasm of vegetable cells. They are divided by their colors into three classes, chloroplastids, chromoplastids, and leucoplastids called?

plastid — (Bot.) One of the many minute granules found in the protoplasm of vegetable cells. They are divided by their colors into three classes, chloroplastids, chromoplastids, and leucoplastids. (Webster's 1913.)

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