Double Seeds Take the Place of a Stone
In some cases the cavity left in the plum by the removal of the stone is filled by the development of a double seed. We have seen in other illustrations that the hereditary forces seem to be puzzled, if this expression be allowed, in determining how to deal with the altered conditions of the internal structure of a fruit that lacks the supporting stone at its center. One solution of the difficulty is shown in this picture.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 4