Standard Plum and Large Stone
Here we see another plum at a stage of development when the relation between the stone and the flesh of the fruit is still defective. In this case the stone, instead of decreasing in size, has grown larger. Mr. Burbank's next problem with this particular fruit was to retain the tendency to grow a large fruit, but to induce the stone to decrease in size. The problem was solved by further experiments in hybridizing and selection.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 4