In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry, and oak, the larger vessels or pores (as cross sections of vessels are called) are localised in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give strength and toughness to wood, while the vessels are a source of weakness.[citation needed]
What species of hardwood are hickory and mulberry trees? In what season do the growth-rings of ring-porous species form with larger vessels localized? In what season does the part of the growth-ring with smaller vessels form in ring-porous species? What fibers does the summer's section of growth-ring have more of? Along with strength, what property do wood fibers lend to wood?