Species of Citrus primitively had seeds, formed from the central post (i.e., axile placentation). These seeds may be sexual products or apomictic seeds with nucellar embryos. Mutants developed that lacked the ability to form sexual seeds, hence are seedless forms, and these were cloned via grafting. The fruit at the left is a seedless derivative of the seeded form to the right. There is a large difference in the thickness of the mesocarp, or albedo, of these two fruit forms.