Most of the small wood cells in a tree run up and down (or vertically) in the stem, conducting fluids from the roots to the leaves. A few cells run in and out from the bark to the center of the stem (or horizontally or radially). These cells, that primarily store starches and sugars in the tree, are called ray cells or sometimes ray parenchyma cells. With a flatsawn piece of lumber, the ends of the ray cells (the ends appear like the cut ends of a handful of soda straws) are exposed on the face of the lumber and generally do not have too much of an effect on the appearance of the face: short vertical lines, if any effect. However, on quartersawn lumber, the sides of the ray cells are running parallel to the face. This side view creates an interesting pattern in many species of hardwood lumber, including maple, oak, sycamore and beech. This side view or appearance of the ray cells in quartersawn lumber is called ray fleck. In fact, the standard definition of quartersaw or riftsawn lumber for many species is that the ray fleck must be obvious.
Gene Wengert, aka The Wood Doctor, troubleshoots wood related problems, and explores lumber and veneer qualities and performance, species by species, in Wood Explorer, inside FDMC's Knowledge Center.
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