Fig. 15.2-4. Tangential section of white pine wood. This high magnification shows a small ray only four cells tall (large, horizontal arrows). The cells are small and the walls appear bowed inward because almost the entire wall between each ray cell and the adjacent axial tracheid consists of a large circular bordered pit. The small, diagonal arrows point to circular bordered pits (more correctly, pairs of such pits) that connect adjacent axial tracheids. The ray cells are so small it would be easy to mistake one for a single circular bordered pit pair. Notice that the circular bordered pits are in the radial walls, the walls that come straight out at us as we look toward the center of the tree.