xylem vessels are long, tube-like structures formed from cells joined end to end
on xylem vessels there are no end walls, making an uninterrupted tub that allows water to pass up through the middle easy
the xylem is made up from dead cells so contain no cytoplasm
the cell walls are thickened with a woody substance called lignin, helps support the walls and stops them collapsing inwards
lignin can be deposited in xylem walls in different ways e.g. in a spiral or distinct rings
being in these patterns allows flexibility and prevents the stem breaking
as the cell gets older the amount of lignin increases
water and mineral ions move into and out the vessels through small pits in the walls where there's no lignin . this is how other types of cells are supplied with water
