Hybrids and Parents
At the left, a nut of the California black walnut (Juglans Californiaca), the staminate parent; in the center a nut of the eastern black walnut (Juglans nigra), the pistillate parent; at the right a nut of the Royal hybrid, all shown in natural size. It will be seen that the hybrid nut is fairly intermediate between the parent forms in its general appearance, but that it greatly surpasses either of them in size.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 11 Chapter 7