Juglans spp.   Walnut   Juglandaceae

At least 21 species of walnut from the Mediterranean, East Asia, North America to the Andes produce edible, wrinkled hard nuts.  The ancient Romans likened the walnut, Juglans regia, to the human brain.  They saw the outer green husk as the scalp, and the hard shell that protects the kernel as the skull.  The paper-like partition between the two halves of the nut, the membrane and the nut itself, represented the two hemispheres of the cerebrum.  The hard shell is a medium on which Chinese carvers depict their lohans or holy men.