What is the cavity found in vascular bundles of monocot stems called?

The cavity found in vascular bundles of monocot stems is called a lysigenous cavity or protoxylem lacuna. This cavity forms through the breakdown and dissolution of the first-formed xylem vessels (protoxylem) as the stem matures. As the plant grows and secondary xylem develops, these early-formed vessels become stretched and eventually disintegrate, leaving behind an empty space. This characteristic feature is commonly observed in monocot stems like maize, wheat, and bamboo. The presence of this cavity is one of the distinguishing anatomical features that helps identify monocot stems from dicot stems in botanical studies.