What are Tyloses?
Tyloses are balloon like structures produced by the xylem and ray parenchyma seen adjacent to the xylem vessels
After a period of activity the vessels are blocked by these structures and vessels become non-functional. The balloon like structures enter the lumen of the vessels through the pit cavities of it.
Later the walls become lignified and wood become rigid and durable. Tyloses are characteristic of some angiospemic woods.