Fig. 15.1-1. Transverse section of wood of Ilex opaca (American holly, a dicot or hardwood) Each of the double-headed arrows on the left indicate an annual ring. The lower head of each arrow is near the earlywood, the upper head is near latewood (by common agreement, transverse sections of wood are shown with the younger rings near the top, as if the vascular cambium were somewhere above the top of the micrograph). The vertical red stripes are rays, and altogether they make up the ray system of wood. Between the rays are masses of fibers and vessels; these masses make up the axial system of wood. Even at this low magnification, it is possible to see significant detail in the vessels: they are present (so this cannot be a conifer), they are uniformly distributed within each annual ring (so this wood is diffuse porous), and all vessels are approximately the same size without any being extremely wide or narrow.