The tuber begins its growth with the swelling of the seedling hypocotyl. Later, the cavities are formed when cork-generating meristems arise in the inner parenchymatous tissue forming a cork-like wall, cutting off carious shaped and sized enclosures.
This passage describes the process of tuber development, highlighting the role of the hypocotyl and the formation of cork-generating meristems within the parenchyma tissue to seal off cavities.