Fig. 15.2-5a and b. Radial section of white pine wood. The lowest row of ray cells consists of ray tracheids. These can be difficult to pick out, and when examining them with your microscope, focus up and down frequently at high power to pick out details. Look for the circular bordered pits on the end walls (indicated by arrows here) as well as small circular bordered pits on the radial walls (the small white areas that are out of focus here).


   Above the row of ray tracheids are rows of ray parenchyma cells with large fenestriform (window-like) pits. The fenestriform pits are a type of cross-field pitting: pitting that interconnects ray cells with axial cells. The lower micrograph was refocused to bring the fenestriform pits into sharper view. You can see one or two fenestriform pits in each cell, the pits occupying almost the entire wall.