Solid but empty

The xylem in conifers is composed of elongated cells called tracheids, which represent over 90% of the volume of the wood. When you look at it up close, this seemingly uniform wood is made up almost entirely of empty ducts!

The tiny tracheids are no more than a few millimetres long and range in diameter from one-tenth to one-hundredth of a millimetre. So there can be tens, if not hundreds, of thousands of tracheids in a single cubic centimetre of wood – about the size of the tip of your baby finger. These minuscule workers co-operate to transport water from the roots to the leaves. They are joined by tiny pits that allow the water to move from one cell to the next as it travels toward the tree's crown.