Another Stoneless Plum Compromise
Here the cavity left by an eliminated stone is filled by enlarging the seed itself. This is not desirable from the standpoint of the horticulturist, but is one way over overcoming the defect of a large cavity within the fruit, which necessarily weakens the structure of the fruit itself. Further breeding experiments may reduce the size of the seed while increasing the pulp in such a way that no cavity will remain.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 4