Fig. 15.3-5a and b. Tangential section of American hornbeam (Carpinus caroliniana). This is an unusual type of ray called an aggregate ray: it is a mixture of many ray cells and a few axial cells. On the right side, it is bounded by fibers and a vessel; the left side too is bounded by fibers but the edge of the micrograph hides them. In addition to being extremely wide, aggregate rays are also typically very tall.

            Notice the angular, cube-shaped crystals (arrows). Crystals are not extremely common in wood, but not particularly rare either. They are shown at higher magnification in the lower micrograph.